Analytische Chemie
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Eingeladener Vortrag
- nein (193)
Measuring the moisture state of screeds is critical for floorers in order to prevent structural damages of bottom coverings. Typically destructive tests are carried out on small samples delivering only punctual information. We tested several non-destructive testing methods in terms of sensitivity in the critical low moisture range and observed substantially different drying behavior for the two tested cement based and calcium-sulphate based screed samples. Our findings are supported by moisture gradient measurements using the nuclear magnetic resonance technique.
Polymers, such as polystyrene, have been successfully analyzed with matrix-assisted laser desorption/ionization (MALDI) through the addition of e.g. copper or silver salts. This method is often used to establish the polydispersity index of polymer blends.
However, the mechanism of cation addition and the possible interactions between the added salts and the chosen target material are still points of interest. Therefore, the addition of several trifluoroacetate salts to a mixture of polystyrene and matrix
on a range of different target plate materials was systematically investigated, revealing several new interesting aspects of MALDI.
Polystyrene (Mw 1,920 Da) was mixed with a range of trifluoroacetate salts (Li, Na, K, Cs, Ba, Cr, Pd, Cu, Ag, Zn, Al and In, as well as
trifluoroacetic acid) and analyzed with MALDI using 2
-[2E-3-4-tert-butylphenyl)-
2-
methylprop-2-enylidene]ma
lononitrile DCTB) as matrix on different target plate materials (chrome, copper, silver, gold, Ti90/Al6/V4, Inconel® 625, Zinc and stain
less steel) to evaluate the occurrence of redox-reactions.
Polystyrene/salt/matrix solutions were deposited through pneumatic-assisted spraying on microscope slide
-shaped target plate insets of varying material, which, secured with copper tape, fitted a milled out structure from the original target plate. Spectra, obtained on a Bruker Autoflex I MALDI-Time
-of-Flight mass spectrometer, were processed with MATLAB to obtain polystyrene-and matrix
-adduct ion signal intensities for direct comparison between chosen conditions.
The resulting spectra shed light on the MALDI adduct formation process and the cation-polystyrene interactions. It was found
that the following cation
-polystyrene adducts were formed on stainless steel: Al, Li, Na, Cu and Ag, where the yield was found to depend on the sample layer thickness and possibly the cation’s ability to form a complex with either one or two of polystyrene’s phenyl rings, based on the ligand-field and the valence bond theory. With the exception of Al, these salts also formed adducts
and in case of Cu and Ag also sandwich adducts with DCTB. Some alkali salts (e.g. potassium) formed clusters rather than interacting with polystyrene or DCTB, which can be explained with the HSAB theory. Application of TFA salts on a copper surface
led to copper cation formation, resulting in DCTB and polystyrene copper-adduct formation. The same effect occurred for silver substrate. In the absence of copper or silver salts, it is therefore still possible to form their respective adducts by choosing the proper alternative salt (e.g. Li, Cs, Ba, Cr) in combination with either a silver or a copper substrate surface. Incubation tests with copper beads in various salt solutions, before matrix and polystyrene addition, support that copper ions are not generated during the deposition process before the MALDI experiment is carried out, except when trifluoroacetic acid, indium and aluminium
trifluoroacetate are used. For all other salts used on a copper plate, it can therefore be concluded that these copper cation forming redox-reactions are enabled by the input of laser photon energy. Furthermore, it was discovered that copper beads can successfully sequester polystyrene from the sample mixture, indicating the strong bonding of polystyrene to the copper surface.
These findings support that the redox-reactions occur (almost) instantaneously with laser pulse impact at the sample-coated substrate surface.
Determination of tributyltin in whole water matrices under the European water framework directive
(2016)
Monitoring of water quality is important to control water pollution. Contamination of the aquatic systemhas a large effect on human health and the environment. Under the European Water Framework Directive(WFD) 2000/60/EC and the related directive on environmental quality standards (EQS) in the field of waterpolicy 2008/105/EC, the need for sensitive reference methods was highlighted. Since tributyltin (TBT) isone of the WFD listed priority substances a method was developed which is capable to qualify and quantifythe pollutant at the required low WFD EQS of 0.2 ng L⁻¹ in whole water bodies, i.e. in non-filtered watersamples with dissolved organic carbon and suspended particulate matter. Therefore special attention waspaid on the interaction of TBT with the suspended particulate matter and humic substances to obtain acomplete representation of the pollution in surface waters. Different water samples were investigatedvarying the content of organic dissolved and suspended matter. Quantification was performed usingspecies-specific isotope dilution (SSID) and gas chromatography with inductively coupled plasma massspectrometry (GC-ICP-MS). Different sample treatment strategies were evaluated and compared. Theprocess of internal standard addition was investigated and optimized, hence the equilibrium betweeninternal standards and matrix is of primary importance to perform accurate SSID. Samples spiked at EQSlevel were analyzed with a recovery between 95 and 105 %. Additionally real surface water samples wereinvestigated and the TBT concentration for the whole water body was determined and compared withconventional routine analysis method.
Cellular effects of Al-, Ti- and Zn-containing nanomaterials on intestinal cell lines in vitro
(2016)
Aluminium-, titanium- and zinc-containing chemicals are highly abundant in food, food contact materials and consumer products. Physical and chemical conversion might lead to a certain amount of nanoscaled particles that can be taken up by the gastrointestinal tract. Nanospecific effects such as higher reactivity, increased surface or altered uptake can increase hazardous potential for human health. The aim of this study as part of the european SolNanoTOX project is to characterize toxicological effects of Al-, Zn- and Ti-containing nanomaterials on intestinal cell lines.
While toxicological potential of zinc species has been well studied, little is known about the effects of aluminium- and titanium-species. We have performed toxicological experiments on the human intestinal cell line Caco-2 for numerous endpoints: Cellular ATP and glutathione levels, apoptosis, necrosis, vesicular uptake, oxidative stress, growth rate and cell cycle modification. While zinc-containing controls showed toxic responses, our utilized aluminium- (elementary Al, γ-Al2O3) and titanium-species (TiO2, rutile) did not. Nevertheless, we detected some differences between both different aluminium nanoparticle species and aluminium ions with regard to cell viability. We also provide strong evidence for particle-specific uptake of aluminium and titanium in the intestinal cell line Caco-2.
In summary, among the different tested endpoints, Al- and Ti-containing nanomaterials did not show any toxicity in intestinal cell lines in vitro. Nevertheless, this absence of effect was not due to an absence of exposure, since particle-specific uptake was reported. Metal particle uptake over a long time might therefore be relevant for risk assessment of aluminium- and titanium-containing food products.
Although aluminium is one of the most common elements in the biosphere, little is known about its impact on human health. Since aluminium derivatives are highly abundant in food its oral uptake route is of toxicological relevance. Recently aluminium-containing nanomaterials are considered to be linked to cancer and neurodegenerative disorders. Within the frame of the european SolNanoTOX project, we therefore investigated the toxicological effects of Al-containing species in different intestinal cell lines that represent the first biological barrier for food components prior to systemic distribution.
In our in vitro digestion system, nanomaterials have been exposed to different physiological, chemical and biochemical conditions characteristic for saliva, gastric juice and the intestinal fluid. In vitro toxicity assays and cellular impedance measurements demonstrated the absence of cytotoxic effects of nanoparticles during a period of 48h after incubation. This was also observed after the digestion procedure. In contrast, aluminium ions from high concentrations of AlCl3 showed larger effects on cell viability after the digestion procedure.
In summary, the toxicological potential of aluminium-containing nanoparticles and ions to healthy intestinal cells appears to be low. Artificial digestion of these particles does not increase their toxic potential. Only for high doses of ionic aluminium, an increase of toxicity after artificial digestion was observed. Hence, we suggest that the release of Al ions from nanoparticles may lead to toxicity. Due to these observations, other cellular effects of Al-containing nanomaterials are required to be investigated.
Aluminium and its chemical derivatives are highly abundant in food, food contact materials and consumer products. Up to now little is known about its derivatization and uptake during digestion and its impact on human health. As part of the SolNanoTOX project, different aluminium species were investigated during an artificial digestion process that mimics the saliva, the stomach and the intestine regarding pH-values, duration time, chemical environment and enzymatic composition.
Two different nanomaterials (Al, Al2O3) and a soluble ionic AlCl3 control were digested and investigated by different analytical methods regarding core radius, hydrodynamic diameter, agglomeration and dissolution behavior in biological media.
The fate of nanoparticles during typical pH-values of saliva, gastric and intestinal juice was studied with dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and ICP-MS in the single particle mode. After disappearance at pH 2 the nanoparticles were detected again in the intestinal fluid, as measured by DLS. During all artificial digestion stages Al nanoparticles had a constant average SAXS radius. In contrast, the radii of Al2O3 nanoparticles changed concentration-dependently. Highest radii were observed in the stomach fluid while intestinal fluid was found to cause full recovery of the primary particles. Dissolution of digested nanoparticles in cell culture media showed a bimodal size distribution of primary particles and aggregates.
In summary, simulation of the gastrointestinal tract, mainly the change of pH settings, has provided evidence that the bioavailability of Al is likely to increase during the passage of the gut after oral uptake of aluminium-containing food products.
One of the crucial characteristics of functionalized thin films is their porosity (i.e., the ratio between the pore volume and the volume of the whole film). Due to the very low amount of material per coated area corresponding to thin films, it is a challenge for analytics to measure the film porosity. In this work, we present an Approach to determine the porosity of thin films by means of electron probe microanalysis (EPMA) either by wavelength-dispersive X-ray spectrometry (WDX) or by energy-dispersive X-ray spectrometry (EDX) with a scanning electron microscope (SEM). The procedure is based on the calculation of the film mass deposition from electron-excited X-ray spectra. The
mass deposition is converted into film density by division of measured film thickness.
Finally, the film porosity is calculated from the measured film density and the density of bulk, nonporous film material. The general applicability of the procedure to determine the
porosity is demonstrated on thin templated mesoporous TiO₂
films, dip-coated on silicon
wafer, with controlled porosity in the range of 15 to 50%. The high accuracy of the mass deposition as determined from X-ray spectra was validated with independent methods (ICP-OES and weighing). Furthermore, for the validation of the porosity results, ellipsometry, interference fringes method (IFM), and focused ion beam (FIB) cross sectioning were employed as independent techniques. Hence, the approach proposed
in the present study is proven to be suited as a new analytical tool for accurate and relatively fast determination of the porosity of thin films.
Ionic liquids (ILs) are proposed as simple and efficient test materials to evaluate the performance of energy dispersive X-ray spectrometers (EDS) in the low energy range below 1 keV. By only one measurement, C Kα, N Kα, O Kα, and F Kα X-ray lines can be excited. Additionally, the S Kα line at 2.3 keV and, particularly, the S L series at 149 eV complete the picture with X-ray lines offered by the selected ILs. The well-known (certifiable) elemental composition of the ILs selected in the present study can be used to check the accuracy of results produced with the available EDS quantification routines in the low energy range, simultaneously, for several low atomic number elements. A comparison with other reference materials in use for testing the performance of EDS in the low energy range is included.
Waste disposal of carbon nanotube (CNT) containing products is expected to be the most important pathway for release of CNTs into the environment. In the present work, the use of radiolabelled CNTs (14C-CNT) for polycarbonate polymer nanocomposites with 1 wt% 14C-CNT content allowed for the first time to quantify and differentiate the CNT release according to the type of impact along the materials' ageing history. After an initial exposure of the nanocomposite by solar-like irradiation, further environmental impacts were applied to composite material. They aimed at mimicking disposal site conditions that may induce further ageing effects and CNT release. This study included shaking in water, rapid temperature changes, soaking in humic acid solution as well as waste water effluent, and, finally, gentle mechanical abrasion. All ageing impacts were applied sequentially, both on pristine (control) and on solar-irradiated nanocomposites. All experiments were accompanied by absolute quantification of radioactive release as well as chemical and morphological analyses of the nanocomposite surfaces using infra-red (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The morphological analysis showed that spectral irradiation can uncover CNT networks on the outer nanocomposite surface layers by polymer degradation. After having subjected the solar-irradiated nanocomposite to all studied disposal site effect, the total radioactive release was quantified to amount to 64 mg CNT/m2, whereas only 0.8 mg CNT/m2 were found for the un-irradiated control sample. Solar degradation of polymers was thus found to significantly increase the propensity of the studied polymer nanocomposites to release CNTs during ageing effects at the product's end-of-life typical for disposal sites.
In recent years, elemental imaging of biological samples using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is gaining in importance. Recent improvements regarding spatial resolution (down to 1 µm) and washout time make LA-ICP-MS particularly interesting for single cell analysis.
Many current nanomaterials can serve as contrast agents in cellular or tissue imaging, drug delivery vehicles or therapeutics, whereas others can cause toxic effects. In order to evaluate nano-bio interactions, the number of nanoparticles (NPs) inside cells as well as their localisation within cellular substructures is of particular interest.
LA-ICP-MS was used to study the NP pathway from uptake, via intracellular processing up to cell division. Fibroblast cells were incubated with different metallic NPs under varying experimental conditions. For LA analysis the cells were fixed with formaldehyde and dried.
Our results show that LA-ICP-MS is able to localise NP aggregates within cellular substructures. The NPs accumulate in the perinuclear region in the course of intracellular processing, e.g. multivesicular fusion and endosomal maturation, but do not enter the nucleus [1, 2]. A strong dependence of NP uptake on concentration and incubation time was found. Additionally, the number of NPs internalized by individual cells was determined and variations within the cell population became visible.
A new laser ablation system providing a short washout time (50 ms) together with small spot sizes (< 4 µm) and high repetition rates allows high spatial resolution applications. First results of cell imaging will be shown.
The findings demonstrate the potential of LA-ICP-MS providing insight into NP uptake and intracellular distribution dependent on experimental parameters.
In the last decade the utilization of silver nanoparticles in consumer related products is enhanced. Therefore, many studies focus on investigations regarding their toxicological potential. This includes investigations concerning uptake, distribution and excretion of the particles. So far, little attention was paid to changes of physical and chemical properties in the human body. During processes like digestion, the question arises whether they can pass this barrier in a nanoscale form. In this study we analytically monitored the changes in the size distribution of colloidal silver during an artificial digestion process with the help of small angle x-ray scattering (SAXS). Therefore, we synthesized polyacrylic acid stabilized ultra-small silver nanoparticles with a radius of 3 nm and a size distribution width of 18%. The artificial digestion process mimics the gastro-intestinal passage and simulates the oral, gastric and small intestinal conditions. Additionally, food components like oil, starch, glucose and skimmed milk powder are used to provide a preferably realistic environment.
In absence of any food components the low pH initiates aggregation of the particles in the stomach. However, the particles unexpectedly stabilize in a defined cluster form with a mean radius of 12 nm. By the use of the food components oil and starch we observed that the particles are dispersed again. Now we found a bimodal size distribution of primary particles and aggregates. In contrast to that, with skimmed milk powder only a slight aggregation occurs in the stomach. In the gastric tract the particle distribution is stabilized at a mean volume weighted radius of 5 nm. Hence, skimmed milk powder acts as a colloidal stabilizer. For comparison we also used silver nitrate as a control substance. Surprisingly, we observed a formation of nanoparticles already in the saliva. During the digestion process the distribution narrows and finally in the intestine it shows a stable distribution with a mean volume weighted radius of 3 nm and a small fraction of aggregates. These results indicate that the silver nanoparticles can pass the digestion process in a nanoscale form but undergo a transformation in the size distribution. However, even from pure silver nitrate nanoparticle formation can be observed. This sketches a complex mechanism in which not only food components but also silver ions cause changes in nanoparticle size and aggregation.
Over the course of the last decades, concrete construction has significantly changed from mass application towards sophisticated more innovative, future oriented, and performance based materials technology. Today concrete no longer consists of cement, water, and aggregates, but can be enhanced significantly by using supplementary additions and chemical admixtures. Advancements in admixtures eventually facilitated the development of new concrete types such as self-compacting concrete (SCC) and high performance concrete (HPC) by uncoupling the workability from the water-cement ratio (w/c).
While for traditional concrete types the major mixture parameter for the workability and strength were the w/c and the grading of the aggregates, for SCC and HPC the performance parameters are more complicated and the performance depends highly on the powder components. This makes the system more sophisticated and in parallel more prone to scatter during the production. The complexity and difficulty to predict the effects of changes in the process and mixture makes it very difficult to identify the right potentials for savings.
Chemical admixtures like superplasticisers or stabilising agents are of ever increasing importance for modern concrete technology. They liberate the workability of concrete from its dependency on water content, and thus, open the gate towards innovative and future oriented concrete technologies such as selfcompacting concrete. Meanwhile admixtures have become common practice in concrete technology, but the understanding of these highly complex polymers in the entire concrete system lags far behind their application. Due to its complex time-dependent, multi-phase and multi-scale behaviour, flowable concrete systems are highly complicated and cannot be described comprehensively by simple models. It is therefore extremely challenging to identify the relevant parameters that predominantly control flow phenomena on different size scales, since these may occur on any scale between the nano scale (e.g. superplasticizer adsorption) and macro scale (e.g. grading of the aggregates). The present study discusses fundamental mechanisms at the interface between particle or hydrate surfaces and the fluid phase at a very early stage of concrete formation, and links these effects to macroscopic flow phenomena. Methods are discussed that appear promising interdisciplinary tools for enhancement of the understanding of the relevant interactions that are responsible for the macroscopic flow of flowable concrete.
Interactions between waste paper sludge ashes and superplasticizers based on polycarboxylates
(2016)
In many industrial nations, about two third of the paper demand is covered by recovered paper. A major process step within the treatment of waste paper is the de-inking. It is a floating process yielding paper sludge as a waste product. About 50 % of this residue is used as a fuel. In several cases it is burnt at temperature of about 850 °C and thereafter the accrued ashes are collected in the flue gas filter. During the combustion, kaolinite and calcium oxide generate gehlenite and larnite. Calcite is the main component of waste paper sludge ash (PA).The chemical and mineralogical composition of PA suggests using it as a supplementary cementitious material.
In modern construction materials technology, workability aspects gain importance, since for most modern materials the rheology and compaction ability are relevant for the operation at a hardened state. It was observed that PA significantly increases the water demand of powder systems, which can cause serious problems during the casting of mineral binder systems containing PA. It is therefore obvious that binder systems containing PA might demand for the use of superplasticizers. Superplasticizers are polymers with anionic backbone that cause electrostatic and steric repulsion effects upon adsorption on surfaces of particles and hydration phases.
In this paper interactions between superplasticizers and waste paper sludge ashes are discussed and analysed. Based on observations of changes in the zeta potential and the dispersion of the particle system, the influence of the charge density of superplasticizers is observed and time dependent effects are demonstrated.
South Africa and recently Nigeria are the only net exporter of cement in Africa, yet cements are imported into the country mainly on the basis of price competitiveness. This poses potential for scatter in the properties of the cements in the South African market as pricing seems to be the only determining factor that affects Portland cements imported. A survey of cements of grade 42.5N in the South African cement market was carried out to identify major players in the industry. The identified cements, which included four locally produced and one imported cement were then analysed for both chemical composition and physical properties in line with the Eurocode EN 196. Tests carried out include loss on ignition, chloride content, sulphate content, specific surface (Blaine), standard consistence, initial setting time, final setting time, soundness and flexural and compressive strength at 2, 7 and 28 days. The testing program was initiated as part of on-going Africa-wide cement testing competency program in partnership with BAM and PTB in Germany. The performance of the identified cements from the different local manufacturers and the imported cement were analysed and are presented in this paper. These results reveal some similarities and differences in the properties. Particularly of interest is the marked difference in the 28 days compressive strength of the cements. This paper shows that there is need for further tests across the cement industry as some of the cements failed to meet certain requirement as set by EN 196. The paper also recommends the use of proficiency testing schemes in the cement industry of the country to ensure the cement laboratories are providing results of high quality and at the same time act as a check to make sure these laboratories are not failing to meet standard requirements.
Chemical admixtures like superplasticisers or stabilising agents are of ever increasing importance for modern concrete technology. They liberate the workability of concrete from its dependency on water content, and thus, open the gate towards innovative and future oriented concrete technologies such as self-compacting concrete.
Today, admixture addition has become common practice in concrete technology, but the understanding of their highly complex mode of operation is extremely difficult and demands for understanding of processes within the range between nanometres and centimetres.
Due to its complex time-dependent, multi-phase and multi-scale behaviour, flowable concrete systems are highly complicated and cannot be described comprehensively by simple models. It is therefore extremely challenging to identify the relevant parameters that predominantly control flow phenomena on different size scales, since these may occur on any scale between the nano scale (e.g. superplasticizer adsorption) and macro scale (e.g. grading of the aggregates). The present study discusses fundamental mechanisms at the interface between particle or hydrate surfaces and the fluid phase at a very early stage of concrete formation, and links these effects to macroscopic flow phenomena. Methods are discussed that appear promising interdisciplinary tools for enhancement of the understanding of the relevant interactions that are responsible for the macroscopic flow of flowable concrete.
Control chart systems are commonly used in quality management systems to keep production processes stable. The most efficient control chart systems are cumulated sums (cusum), which look at the deviations from a target value. Cusum charts react more rapidly on systematic changes in processes than other charts such as Shewhart charts, which look at the process values. The cusum method is often applied for compressive strength but it is particularly suitable if counteractions be taken immediately, like in the case of fresh concrete properties.
The present study shows that regardless of the manipulation, a steady slump flow can be achieved only by adding supplementary superplasticizer in case of loss of flow and adding stabilising agent (ST) in case of increased flow if the V-mask indicates a systematic change. A reference SCC was artificially manipulated in order to achieve either increased or reduced flowability. Arithmetic mean values and standard deviations were determined experimentally without and after taking counteractions. These parameters were used for case studies of steady SCC productions based on normally distributed random values. For the indication of a systematic change, a standard V-mask was used.
The results point out that productions with applied cusum methods were capable of keeping the slump flow deviation from the target in the order of magnitude of about 1% despite drastic manipulations, while productions without applied cusum method deviated up to 14% and more from the target slump flow value.
Chemical admixtures like superplasticisers or stabilising agents are of ever increasing importance for modern concrete technology. They liberate the workability of concrete from its dependency on water content, and thus, open the gate towards innovative and future oriented concrete technologies such as self-compacting concrete. Today, admixture addition has become common practice in concrete technology, but the understanding of their highly complex mode of operation is extremely difficult and demands for understanding of processes within the range between nanometres and centimetres. Due to its complex time-dependent, multi-phase and multi-scale behaviour, flowable concrete systems are highly complicated and cannot be described comprehensively by simple models. It is therefore extremely challenging to identify the relevant parameters that predominantly control flow phenomena on different size scales, since these may occur on any scale between the nano scale (e.g. superplasticizer adsorption) and macro scale (e.g. grading of the aggregates). The present study discusses fundamental mechanisms at the interface between particle or hydrate surfaces and the fluid phase at a very early stage of concrete formation, and links these effects to macroscopic flow phenomena. Methods are discussed that appear promising interdisciplinary tools for enhancement of the understanding of the relevant interactions that are responsible for the macroscopic flow of flowable concrete.
Research on carbohydrate based interactions with proteins, nucleic acids or antibodies has gained increased interest in the last years especially in clinical diagnosis or drug development. The efficiency of diagnostic interfaces depends upon the number of probe molecules, e.g. carbohydrates. The control of surface parameters as density and distribution of immobilized carbohydrates is essential for a reliable interaction with protein analytes. A controlled production of biomolecular interfaces can be reached by a stepwise quality control during buildup of these biointerfaces.
Here, ß-amino-cyclodextrin molecules were attached to amine-reactive silicon oxide surfaces via click chemistry to construct a model biosensor surface. The amount of surface bound carbohydrates was determined indirectly after chemical derivatization with 4-(trifluoromethyl)-benzylamine (TFMBA). Moreover, these surfaces were used to form host-guest complexes of ferrocene (guest) and β-cyclodextrin (host) moieties to mimic the target binding (sensing) of the model biosensor. Surface chemical analysis of all steps during biosensor construction was performed using X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Our approach widens the possibilities to generate switchable surfaces based on ß-Cyclodextrin surfaces for biosensor applications.
In respect of modern approaches in material sciences and highly increased requirements on materials on safety relevant components, quality management and non-destructive testing reclaims a steadily increased meaning. The destructive meaning of measuring the degree of purity is defined in DIN EN 10247 through metallurgical investigations, especially microsections. For and comparable, but non-destructive testing due ultrasonic testing, the material the SEP 1927 is a well-defined industry standard. A novel and alternative way of reference block construction was focused by this work. The proposed amendments, regarding the manufactoring and machining, are less time and cost consuming. Verified by measurements the presented reference block fits the same acoustical characteristics and the requirements of the guideline.
In respect of modern approaches in material sciences and highly increased
requirements on materials on safety relevant components, quality management
and non-destructive testing reclaims a steadily increased meaning. The
destructive meaning of measuring the degree of purity is defined in DIN EN 10247
through metallurgical investigations, especially microsections.
For and comparable, but non-destructive testing due ultrasonic testing, the material
the SEP 1927 is a well-defined industry standard. A novel and alternative way
of reference block construction was focused by this work. The proposed amendments,
regarding the manufacturing and machining, are less time and cost consuming.
Verified by measurements the presented reference block fits the same acoustical
characteristics and the requirements of the guideline.
In this study, a new direct functionalization method of silicon nitride (Si3N4) using azidation and click chemistry is presented. First, amino groups (NHx) were created on a Si3N4 substrate by fluoride etching. These NHx-terminated Si3N4 surfaces were analyzed by chemical derivatization X-ray photoelectron spectroscopy (CD-XPS) with 4-trifluoromethylbenzaldehyde (TFBA) and a derivatization yield of 20% was concluded. In the second step freshly prepared NHx surfaces were transformed into azides which were used immediately in a click reaction with halogenated alkynes. The presented combination of amination, azidation and click reaction is a promising alternative for common silane-based Si3N4 functionalization methods.
Eight different screed types are tested including two different sample heights of 35 and 70 mm. The moisture of the four cement based and four sulphate based screeds are monitored during hydration and evaporation. All samples are stored in a climatic chamber at 23° C and 50 % relative humidity. Embedded sensors like temperature arrays, humidity sensor arrays, and multi-ring electrodes are embedded in the samples to yield a detailed moisture evolution with high depth resolution. Furthermore, nuclear magnetic resonance is used to quantify the water content at different depths. This multi-sensor approach allows a comprehensive monitoring of the moisture and its gradient in the different screed samples. This yields a deeper insight into the hydration, moisture convection, and diffusion processes.
Pollen represent one major cause for human allergic diseases. Currently the characterization and identification of pollen is time-consuming since it mainly relies on the microscopic determination of the genus-specific pollen morphology. A variety of new analytical approaches, like Raman - and fluorescence spectroscopy have been proposed in order to develop fast and reliable pollen identification. Recently matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was initially applied for the rapid investigation of such complex biological samples. Taxonomic differences and relations of single pollen grains could be identified.
Both commercially available lyophilized pollen and fresh pollen acquired from biological samples collected in parks and in the Botanical Garden Berlin in the years 2013-2015 were investigated. The samples were prepared by formic acid extraction in the gas phase and spotted with HCCA matrix. A variety of new approaches, like a newly developed MALDI target with micrometer sample spots sizes, were tested for their suitability. The obtained mass spectral data were investigated by principal component analysis (PCA).
The applicability of MALDI-TOF mass spectrometry for the classification of pollen according to their taxonomic relationships was proven. Specifically, chemical differences in the mass spectra at the levels of plant order, genus and in many cases even of species could be identified. Based on these results, further investigations have been undertaken to optimize the sample preparation for the classification of single pollen grains in mixtures of pollens. A novel MALDI-target design was developed to enhance the phenotypic information of pollens in their mass spectra. The combination of mass spectral patterns and multivariate statistics provide a powerful tool for the investigation of structural correlations within mixtures. The results can be used to improve the reconstruction of taxonomic relations of single species in various mixtures and might be useful for the development of a fast routine method to identify pollen based on mass spectrometry.
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and high-resolution scanning electron microscopy are well-acknowledged tools in materials characterization. The ability to map chemical species on the surface of an investigated sample with often low mass detection limits makes ToF-SIMS an essential tool in fields where many question marks concerning Degradation processes and damage mechanisms exist. The aim of this paper is to describe the power of data fusion of ToF-SIMS and high-resolution scanning electron microscopy results employing computational methods for multivariate data Analysis such as principal component analysis. As a case study the investigation of hydrogen distribution in an artificially charged Duplex stainless steel microstructure is presented aiming on a better understanding of hydrogen embrittlement.
To quantify the moisture in concrete, RFID based humidity sensors are embedded. Passive high frequency, ultra-high frequency RFID tags as well as active Bluetooth sensors are tested. After concreting, all sensors measure the corresponding relative humidity to monitor the concrete moisture. Two case studies are performed, embedding in an existing construction, i.e. the duraBASt test bridge, and embedding in cement based mortar in the laboratory. As basis for robust and long-life sensors in alkaline concrete, different casing materials are tested. Furthermore, signal strength measurements and their sensitivity to different moisture levels are performed.
To quantify the moisture in concrete, RFID based humidity sensors are embedded. Passive high frequency, ultra-high frequency RFID tags as well as active Bluetooth sensors are tested. After concreting, all sensors measure the corresponding relative humidity to monitor the concrete moisture. Two case studies are performed, embedding in an existing construction, i.e. the duraBASt test bridge, and embedding in cement based mortar in the laboratory. As basis for robust and long-life sensors in alkaline concrete, different casing materials are tested. Furthermore, signal strength measurements and their sensitivity to different moisture levels are performed.
Eight different screed types are tested including two different sample heights of 35 and 70 mm. The moisture of the four cement based and four sulphate based screeds are monitored during hydration and evaporation. All samples are stored in a climatic chamber at 23◦ C and 50 % relative humidity. Embedded sensors like temperature arrays, humidity sensor arrays, and multi-ring electrodes are embedded in the samples to yield a detailed moisture evolution with high depth resolution. Furthermore, nuclear magnetic resonance is used to quantify the water content at different depths. This multi-sensor approach allows a comprehensive monitoring of the moisture and its gradient in the different screed samples. This yields a deeper insight into the hydration, moisture convection, and diffusion processes.
The photocatalytic degradation of three indoor air relevant volatile organic compounds (VOC), namely toluene, butylacetate (BuAc) and limonene was investigated both under UV and visible light using modified TiO2 as photcatalyst. The new materials feature a high reactivity under UV light and, compared to pure TiO2, a significantly enhanced reactivity under blue light irradiation for the decomposition of BuAc (up to 39% degradation).
Coulometric sensors are applied for trace humidity measurements in various technical gases. The use of this sensor type is demanded in some standards by the European Pharmacopoeia for medical gases. Coulometric sensors allow the measurement of water vapour in gases such as e.g. air, Cl2, H2, N2, N2O, CH4 between the concentration ranging from 0.1 to 2,500 µmol∙mol-1 which corresponds to frost point temperature -90 °C to -10 °C, respectively.
The sensing principle is based on Faraday’s law of electrolysis whereby water is decomposed to hydrogen and oxygen. The sensor signal is the measured electrical current which is proportional to the mass of water that is absorbed on the hygroscopic phosphorous pentoxide layer. The signal is dependent on the gas flow at a given voltage, gas pressure and temperature.
The sensors need to be calibrated to measure the accurate signal for humidity in air. However, the signal is dependent on the type of gas matrix. This dependency has not been quantified so far. Therefore, the impact of reactive gases such as hydrogen and nitrous oxide on the calibration curve was investigated. Furthermore, a possible rationale in relation to the interaction of water with the gas matrix and its impact on the electrode reactions is suggested.
The experimental setup consists of a gas supply, dryer, humidifier, test chamber and reference hygrometer. The test gas is generated by mixing the dry and the wet gas flow. First the carrier gas is dried by an activated carbon filter and then split into two flows. One flow is dried again with a molecular sieve. The other flow is humidified by passing it through a bubbler filled with pure water. After this, the rate of both flows is controlled by mass flow controllers and then mixed with the test gas. A calibrated precision chilled mirror dew-point hygrometer is used as a reference instrument.
The coulometric sensors were exposed to different humidified gases and the sensor signal was recorded till a constant value was obtained. Calibration curves were calculated for the frost point temperature in the range of about -70 °C to -10 °C according to the equation, tf = A + B∙ln(I), (I is the electrolysis current and A, B are constants) followed with a linear regression fit.
Comparison of the results of air and nitrogen showed no significant differences. In contrast, there are remarkable differences for humidified hydrogen and nitrous oxide, respectively.
The difference might be due to increased recombination of hydrogen with the produced oxygen to form new water molecules in humidified hydrogen.
In conclusion, coulometric trace humidity sensor is a robust hygrometer for various technical applications. However it needs to be calibrated for the specific gas matrix.
Currently established and projected regulatory frameworks require the classification of materials (whether nano or non-nano) as specified by respective definitions, most of which are based on the size of the constituent particles. This brings up the question if currently available techniques for particle size determination are capable of reliably classifying materials that potentially fall under these definitions.
In this study, a wide variety of characterisation techniques, including counting, fractionating, and spectroscopic techniques, has been applied to the same set of materials under harmonised conditions.
The selected materials comprised well-defined Quality control materials (spherical, monodisperse) as well as industrial materials of complex shapes and considerable polydispersity. As a result, each technique could be evaluated with respect to the determination of the number-weighted median size. Recommendations on the most appropriate and efficient use of techniques for different types of material are given.
Analytical routines for a comprehensive in-depth morphological, structural, and chemical characterization of functionalized TiO2 films by using different state-of-the-art analytical techniques are presented and discussed with the main objective to identify potential reference TiO2 coating parameters able to be certified at a later stage. TiO2 films fabricated by two different synthetic procedures as representative for two main large-scale applications were selected: (i) pulsed d.c. magnetron sputtering for photocatalytic applications and (ii) screen printing from preformed anatase nanoparticles. The screen-printed films were further loaded with a sensitizing dye for application as a dye-sensitized solar cell. Film properties such as microstructure and crystallographic texture of pulsed d.c. magnetron sputtering synthesized films were systematically studied by means of scanning nanobeam electron diffraction in a transmission electron microscope and the surface and inner morphology by scanning electron microscopy. The dye distribution over the depth of screen-printed TiO2 layers was analyzed before and after dye-loading by means of energy dispersive X-ray spectroscopy at scanning electronmicroscope, Auger electron spectroscopy and time-of-flight secondary ion mass spectrometry. The long-term goal of the present study is the improvement of quality of the TiO2 film parameters as measured by using different types of reference TiO2 coatings having specific parameters certified.
In situ investigations using PXRD coupled with Raman spectroscopy permit the evaluation of the formation pathways of milling reactions. The liquid-assisted grinding cocrystallisation of theophylline with benzamide leading to polymorphic compounds was investigated. The dipole moment of the solvent used in the synthesis determines the structure of the polymorphic product. A detailed investigation allows determining the kinetically and thermodynamically favored product. In situ observations of the formation pathway during the grinding process of both polymorphs show that the thermodynamically favored cocrystal is formed in a two-step mechanism with the kinetic cocrystal as intermediate. The evaluation of the mechanochemical formation pathways reveals the importance of in situ investigations for an in depth understanding of mechanochemical synthesis mechanisms. Our study demonstrates that the choice of the solvent in the LAG synthesis is decisive for the controlled formation of a desired polymorphic final product.
A portable device for calibration of trace humidity sensors and an adopted calibration procedure have been developed. The calibration device is based on humidity generation by permeating water through polymeric membrane tubes. Water vapour transmission rates for various polymers were experimentally determined in order to select the most suitable polymeric material. The developed trace humidity generator consists of a gas-flow polymeric hose immersed in a water reservoir thermostated by a sensorcontrolled heater. Mole fractions of water vapour between 1 µmol/ molˉ¹ and 350 µmol/molˉ¹ (equivalent to frost-point temperatures from -76 °C to -31 °C) were generated by varying either the operating temperature or gas flow. The operating temperature can be varied from 20 °C to 60 °C and kept stable within 0.1 K. Uncertainty analysis indicated that the trace humidity generator produces gas flows of constant humidity amounts with a relative expanded uncertainty less than 3.4% (k = 2) of the generated value.
Supernatants from a fermentation process of Pichia pastoris were investigated by Raman spectroscopy. Using partial least squares regression, the principal substrates glycerol and methanol could be predicted, however not the expressed protein. To gain further insight, a priori prepared calibration samples were studied by vibrational-, UV/Vis-, and fluorescence spectroscopy. For the quantification of glycerol and methanol, Raman spectroscopy was identified as the most sensitive technique, and superior to near-infrared spectroscopy, but not for protein contents below 1 g L–1. Both UV/Vis absorption and fluorescence spectroscopy are well suited for the quantification of protein, however, best results were obtained with UV/Vis absorption.
Most ambient sample introduction and ionization techniques for native mass spectrometry are highly selective for polar agents. To achieve a more general sensitivity for a wider range of target analytes, a novel laser ablation dielectric barrier discharge (LA DBD) ionization scheme was developed. The Approach employs a two-step mechanism with subsequent sample desorption and post-ionization. Effective Ablation was achieved by the second harmonic output (λ = 532 nm) of a diode pumped Nd:YVO₄ laser operating at a high-repetition rate of several kHz and pulse energies below 100 μJ. The ejected analytecontaining aerosol was consecutively vaporized and ionized in the afterglow of a DBD plasma jet.
Depending on their proton affinity the superexcited Helium species in this afterglow produced analyte ions as protonated and ammoniated species, as well as radical cations. The optimization procedure could corroborate underlying conceptual consideration on the ablation, desorption and ionization mechanisms.
A successful detection of a variety of target molecules could be shown from the pharmaceutical ibuprofen, urea, the amino acids L-arginine, L-lysine, the polymer polyethylene glycol, the organometallic compound ferrocene and the technical mixture wild mint oil. For a reliable evaluation of the introduced detection procedure spectra from the naturally abundant alkaloid capsaicin in dried capsicum fruits were recorded.
X-ray powder diffraction (XRD) patterns of the high-temperature (HT) cristobalite form of SiO2 and its isoelectronic AlPO4 analogue are essentially influenced by the dynamic disorder of these crystal structures. The nature of this disorder and of the phase transition between the α- and β-form has been the subject of intensive research during the last four decades [1]. By 1989 it became possible to stabilize the HT-form of cristobalite SiO2 at room temperature in laboratory and engineering ceramic industries by applying solid solution forming techniques [2]. However, for the HT-form of cristobalite AlPO4 nothing similar has been known until 2014 when it was discovered that nanocrystalline and stacking-disordered β-cristobalite AlPO4 is the major component of the fly ash of a large incineration facility operated by the waste water treatment authorities of Frankfurt/M. [3]. Previous comprehensive investigations of this fly ash failed to interpret its complex XRD pattern – presumably mainly due to the lack of a matching experimental digital pattern in the Powder Diffraction Database. The present paper reports on a synthesis route that facilitates the crystallization of nanocrystalline and stacking-disordered β-cristobalite AlPO4 that is free of crystalline impurity phases and long-term stable at ambient. Its room temperature XRD pattern is presented with parameters traced back to certified reference materials.
[1] Yuan F. and Huang L., Phys. Rev, B, 2012, 85, 134114. [2] Perrotta J.A., Grubbs D.K., Martin E.S., Dando N.R., McKinstry H.A. and Huang C.-Y., J. Am. Ceram. Soc., 1989, 72, 441. [3] Peplinski B., Adam C., Adamczyk B., Müller R., Michaelis M., Krahl Th. and Emmerling F., Powder Diffraction Journal, 2015, 30, 2, Supp. 1, S31.
Paper-based SERS test strips
(2016)
For the non-destructive chemical analysis of organic compounds, several different methods such as NMR, UV-vis absorption, IR, Raman, or fluorescence spectroscopy are available. However, all available methods have some restrictions such as the necessity of a large sample amount, interferences in the presence of water, or overlapping signals from the analytes or matrix. Surface enhanced Raman scattering (SERS) allows to observe analytes directly without labelling in low concentrations in aqueous solutions and to identify them by their spectral fingerprint. Therefore, in this work we use SERS as a detection method for different analytes in low concentrations in combination with paper-based test strips as SERS substrates and for sample preparation.
We present a spray method for the preparation of SERS test stripes.[1] With this spray method, nanoparticle solution was deposited on cellulose and glass fibre paper as SERS substrate. The prepared paper-based test strips were tested with classical SERS reporter molecules, e.g. rhodamine 6G, 4-aminothiophenol, and adenine. For the quantification of analytes, highly reproducible signal intensities are necessary, which can be realized with the test strips in acceptable quality. Moreover, employing intensity vs concentration calibration for the analytes, data analysis revealed a behaviour that was best described by a Langmuir isotherm, stressing the strong distance dependence of the SERS effect.
For an easier identification of analytes in a mixture of compounds, the paper-based test strips were functionalised with hydrophobic barriers by wax printing. With these microfluidic paper-based analytical devices (µPAD) the sample mixture can be separated by the chromatographic effects of the paper and the different analytes can be separately detected and identified by SERS.
[1] A. Bolz, U. Panne, K. Rurack, M. Buurman, Glass fibre paper-based test strips for sensitive SERS sensing, Anal. Methods, 2016, 8, 1313-1318.
A comprehensive characterization of plasma modified polymer surfaces or plasma-polymerized thin films needs access to parameters as
- concentration of saturated/unsaturated carbon species (e.g. aromaticity) or other double bonds as C=N or C=O,
- branching, and
- losses of crystallinty or other degrees of structural order.
Furthermore the complex ageing phenomena of plasma modified polymers/plasma-polymers and the measurement of an in-depth distribution of chemical species are challenges for the analyst. The talk will display selected examples where such challenges have been met by using advanced methods of surface chemical analyses as Photoelectron Spectroscopy with variable excitation energy (“SyncXPS”), X-ray Absorption Spectroscopy (NEXAFS) at C, N and O K-edges and Time-of-Flight Secondary Mass Spectroscopy (ToF-SIMS) combined with Principal Component analysis (PCA).
In Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy X-Ray photons are used to excite tightly bound core electrons to low-lying unoccupied orbitals of the system. This technique offers insight into the electronic structure of the system as well as useful structural information. In this work, we apply NEXAFS to two kinds of imidazolium based ionic liquids ([CnC₁im]⁺[NTf₂]⁻ and [C₄C₁im]⁺[I]⁻). A combination of measurements and quantum chemical calculations of C K and N K NEXAFS resonances is presented. The simulations, based on the transition potential density functional theory method (TP-DFT), reproduce all characteristic features observed by the experiment. Furthermore, a detailed assignment of resonance features to excitation centers (carbon or nitrogen atoms) leads to a consistent interpretation of the spectra.
In this study, a new reliable, economic, and environmentally-friendly one-step synthesis is established to obtain carbon nanodots (CNDs) with well-defined and reproducible photoluminescence (PL) properties via the microwave-assisted hydrothermal treatment of starch and Tris-acetate-EDTA (TAE) buffer as carbon sources. Three kinds of CNDs are prepared using different sets of above mentioned starting materials. The as-synthesized CNDs: C-CND (starch only), N-CND 1 (starch in TAE) and N-CND 2 (TAE only) exhibit highly homogenous PL and are ready to use without need for further purification.
The CNDs are stable over a long period of time (>1 year) either in solution or as freeze-dried powder. Depending on starting material, CNDs with PL quantum yield (PLQY) ranging from less than 1% up to 28% are obtained. The influence of the precursor concentration, reaction time and type of additives on the optical properties (UV-Vis absorption, PL emission spectrum and PLQY) is carefully investigated, providing insight into the chemical processes that occur during CND formation. Remarkably, upon freeze-drying the initially brown CND-solution turns into a non-fluorescent white/slightly Brown powder which recovers PL in aqueous solution and can potentially be applied as fluorescent marker in bio-imaging, as a reduction agent or as a photocatalyst.
Novel air-coupled ultrasonic transducer combining the thermoacoustic with the piezoelectric effect
(2016)
In recent years, there has been an increasing industrial demand for one-sided inspection of various structures by means of air-coupled ultrasonic technique. Lightweight structures based on carbon-fibre-reinforced polymers may have very complex shapes, making air-coupled transmission difficult or even impossible. The inspection of concrete structures is another example where one-sided inspection is required.
To address these challenges a new type of transducer for air-coupled pulse-echo inspection was developed, which unites two principles: thermoacoustic emission and piezoelectric reception. The thermoacoustic emitter is a titanium electrode with a thickness of several tens of nanometer. This electrode was deposited onto charged cellular polypropylene, which serves as a piezoelectric receiver. The thermoacoustic transmission is based on a transformation of the thermal energy of an electrically heated electrode into the acoustic energy of an ultrasonic wave. Thermoacoustic emitters provide resonance-free behaviour and thus extremely broadband pulses. Charged cellular polypropylene is piezoelectric due to the polarization of its cells and it is well matched to air, with a Young modulus in the order of magnitude of MPa. In this contribution we present some pulse-echo measurements with the first prototypes of the combined thermoacoustic-piezoelectric transducer.
Novel air-coupled ultrasonic transducer combining the thermoacoustic with the piezoelectric effect
(2016)
In recent years, there has been an increasing industrial demand for one-sided inspection of various structures by means of air-coupled ultrasonic technique. Lightweight structures based on carbon-fibre-reinforced polymers may have very complex shapes, making air-coupled transmission difficult or even impossible. The inspection of concrete structures is another example where one-sided inspection is required.
To address these challenges a new type of transducer for air-coupled pulse-echo inspection was developed, which unites two principles: thermoacoustic emission and piezoelectric reception. The thermoacoustic emitter is a titanium electrode with a thickness of several tens of nanometer. This electrode was deposited onto charged cellular polypropylene, which serves as a piezoelectric receiver. The thermoacoustic transmission is based on a transformation of the thermal energy of an electrically heated electrode into the acoustic energy of an ultrasonic wave. Thermoacoustic emitters provide resonance-free behaviour and thus extremely broadband pulses. Charged cellular polypropylene is piezoelectric due to the polarization of its cells and it is well matched to air, with a Young modulus in the order of magnitude of MPa. In this contribution we present some pulse-echo measurements with the first prototypes of the combined thermoacoustic-piezoelectric transducer.
Immunoassays are analytical methods used to track both clinical and environmental parameters. Antibodies or other proteins with similar recognizing activity, are employed, often immobilized onto a modified surface. Addressable microarrays are based on single-stranded DNA oligonucleotides which are normally used to detect aptamers or relevant gene sequences. The use of antibody-oligonucleotide conjugates allows non-directed antibody immobilization from an immunoassay to be converted into DNA hybridization events on the array. Consequently, the diagnostics platform is multiplexed and addressable. Figure 1 is a model representation of the whole biosensor construct. In brief, a surface is coated with streptavidin, and decorated with biotin-modified oligonucleotides of a controlled size and known sequence. These oligonucleotides on the surface also contain a furan motif, which upon irradiation and in the presence of a photosensitizer, is oxidized via single oxygen to a reactive intermediate which crosslinks the immediate opposing base when hybridized with its complementary strand [1].
Antibody-oligonucleotides conjugates still display several concerns due to their heterogeneicity, difficulty of characterization and high price [2]. The being the case, we aim at developing stable, robust, reproducible and well characterized quimeras for the application on te above described immunoarray. Mild chemical conditions are crucial for the antibody stability, therefore bivalent crosslinkers have been employed [2]. Even though the use of these bilinkers is standard for other substrate conjugation (i.e., enzymes, drug payloads, etc.), there is no literature available on the conjugation of small oligonucleotides (< 30 mer) to antibodies using this method. Several protein-nucleic acid conjugates have been therefore developed, and successfully characterized using MALDI-ToF and gel electrophoresis techniques.
A round robin test on flash thermography was organized within the scope of a standardization research project. This test gives information on reliability, comparability and efficiency of different testing situations. Data recorded on metal and CFRP test specimens with flat bottom holes (FBH) were analysed by evaluating the detectability and by calculating the signal-to-noise ratio (SNR) of the defect signatures as a function of defect parameters. For the investigation of the influence of material properties on the spatial resolution as well as on penetration depth, test specimens made of steel and copper with crossed notches and a notch ramp were constructed and investigated. Here, the minimum resolvable notch distance and the maximum detectable depth of the ramp were analysed.
A round robin test on flash thermography was organized within the scope of a standardization research project. This test gives information on reliability, comparability and efficiency of different testing situations. Data recorded on metal and CFRP test specimens with flat bottom holes (FBH) were analysed by evaluating the detectability and by calculating the signal-to-noise ratio (SNR) of the defect signatures as a function of defect parameters. For the investigation of the influence of material properties on the spatial resolution as well as on penetration depth, test specimens made of steel and copper with crossed notches and a notch ramp were constructed and investigated. Here, the minimum resolvable notch distance and the maximum detectable depth of the ramp were analysed.
Sulfamethoxazol (SMX),a sulfonamide, is a widely used bacteriostatic antibiotic and therefore a promising marker for the entry of anthropogenic Pollution in the environment. SMX is frequently found in wastewater and surface water. This study presents the production of high affinity and selective polyclonal antibodies for SMX and the development and Evaluation of a direct competitive enzyme-linked immunosorbent assay(ELISA)for the quantification of SMX in environmental watersamples. The crystal structures of the cross-reacting compounds sulfamethizole, N4-acetyl-SMX andsuccinimidyl-SMX were determined by x-ray diffraction aiming to explain their high cross-reactivity. These crystal structures are described for the first time. The quantification range of the ELISA is 0.82–63 µg/L. To verify our results, the SMX concentration in 20 environmental samples,including wastewater and surfacewater,was determined by ELISA and tandem mass spectrometry(MS/MS).A good Agreement of the measured SMX concentrations was found with average recoveries of 97–113%for the results of ELISA compared to LC-MS/MS.
We have compared the performance of the typical Darr and CM moisture testing techniques, which are destructive with several non-destructive testing techniques on two types of floor screeds. In case of cement based screeds these destructive tests failed to deliver reliable results. Moreover, our measurements indicate significantly different drying and moisture transport behavior for the investigated cement based and calcium-sulphate based screeds. Whereas we have strong with depth decreasing moisture gradients in the CT material, we observe in the penetrated volumes of our ndt methods basically no clear moisture gradient in the CA samples. The findings with ndt methods could be supported by moisture gradient studies with nuclear magnetic resonance measurements.
A robust and sensitive method for the detection of the explosive trinitrotoluene (TNT) was developed. The detection limit was determined to be around 0.5 µg/L. The fast signal response of less than 1 minute shows that this approach is suitable for security and other time-critcal applications. In addition, the very low cross-reactivity highly reduces the number of false-positives in relation to competing techniques, including sniffer dogs. Due to the multianalyte ability of the SAW system, several explosives might be detected in parallel.
Microstrain distributions were acquired in functional thin films by high-resolution X-ray microdiffraction measurements, using polycrystalline CuInSe2 thin films as a model system. This technique not only provides spatial resolutions at the submicrometre scale but also allows for analysis of thin films buried within a complete solar-cell stack. The microstrain values within individual CuInSe2 grains were determined to be of the order of 10^-4. These values confirmed corresponding microstrain distribution maps obtained on the same CuInSe2 layer by electron backscatter diffraction and Raman microspectroscopy.
Raman microspectroscopic imaging was just recently introduced into the analysis of cement stone. Here, we demonstrate this approach on 19th-century Roman and Portland cement mortars and extend it to gypsum-based samples originating from a medieval stucco sculpture (high-burnt gypsum) and a stucco ornament prefabricated at the beginning of the 20th century (plaster of Paris). Furthermore, the distributions of dolomite and Calcite were mapped in an accessory mineral grain with approx. 500 nm lateral Resolution demonstrating the ability for studying alteration processes such as dedolomitisation. As we would like to make this approach accessible to other researchers, we discuss its present status, advantages, limitations and pitfalls.
Injection of poly(methyl methacrylate) cements, one standard Treatment for osteoporotic vertebral body fractures, may lead to critical loads and subsequent fractures in adjacent vertebral bodies. Biodegradable calcium phosphate cements (CPC) with bioinductive growth factors may be an alternative, since they have a Young’s modulus comparable to that of cancellous bone. Non-destructive tests with μCT and quantitative Image evaluation are used to assess new bone growth and material resorption following intravertebral injection of CPC. Immediate deep-freezing of excised bone prevents shrinkage or tissue disintegration and the samples have to be kept frozen for all following steps, including transport, μCT measurements, and subsequent biomechanical tests. Here we will report on a set-up to preserve the frozen state of the material and allow stable long-term serial μCT measurements. In addition, the image processing technique for the evaluation of bone growth and selected results on subsequently carried out compressive strength tests will be presented.
A model is presented that employs a unified approach for
simulating the photon energy spectra for transmission and direct
beam targets composed of arbitrary homogeneous materials. In order
to achieve this, a detailed model of electron transport within the
target is employed. The validity of the developed model is shown
through comparisons with Monte Carlo simulations as well as
measurements for a number of different configurations.
Modelling becomes more and more important in modern NDE. It is increasingly used to optimize techniques for complex applications, to support the preparation of written procedures, and for education purposes. To describe the complete chain of RT, the model includes simulating all necessary properties of X- or Gamma-ray sources, the interaction of photons with material with special attention to scattered radiation, the detection process, and the complete geometrical RT setup handling arbitrary parts or constructions. Depending on the given inspection problem and the influencing factors that should be addressed by the simulation, an appropriate physical model has to be chosen to describe the underlying interaction mechanisms. The simulator aRTist combines analytical and Monte Carlo methods to efficiently model the radiation transport such that transmission as well as scatter techniques can be modelled. In this contribution we focus on Monte Carlo simulation of scatter contribution within aRTist. Examples for RT/tomographic applications and back-scatter techniques are presented to demonstrate the usability of the presented simulation tool for a broad range of radiological applications.
Aiming at the development of validated protocols
for protein conjugation of nanomaterials and the determination
of protein labeling densities, we systematically assessed
the conjugation of the model protein streptavidin (SAv) to
100-, 500-, and 1000-nm-sized polystyrene and silica nanoparticles
and dye-encoded polymer particles with two
established conjugation chemistries, based upon achievable
coupling efficiencies and labeling densities. Bioconjugation
reactions compared included EDC/sulfo NHS ester chemistry
for direct binding of the SAv to carboxyl groups at the particle
surface and maleimide-thiol chemistry in conjunction with
heterobifunctional PEG linkers and aminated nanoparticles
(NPs). Quantification of the total and functional amounts of
SAv on these nanomaterials and unreacted SAv in solution
was performed with the BCA assay and the biotin–FITC
(BF) titration, relying on different signal generation principles,
which are thus prone to different interferences. Our results
revealed a clear influence of the conjugation chemistry on
the amount of NP crosslinking, yet under optimized reaction
conditions, EDC/sulfo NHS ester chemistry and the attachment
via heterobifunctional PEG linkers led to comparably
efficient SAv coupling and good labeling densities. Particle
size can obviously affect protein labeling densities and
particularly protein functionality, especially for larger
particles. For unstained nanoparticles, direct bioconjugation
seems to be the most efficient strategy, whereas for dyeencoded
nanoparticles, PEG linkers are to be favored for the
prevention of dye–protein interactions which can affect
protein functionality specifically in the case of direct SAv
binding. Moreover, an influence of particle size on achievable
protein labeling densities and protein functionality could be
demonstrated.
Modeling of the photon-electron cascade process in multicomponent objects of complex geometrical structure by use of hybrid supercomputers is considered. An approach to computing the cascade processes is developed. The approach has three key properties allowing the effective use of heterogeneous structure of computers for solving the tasks of radiation transport in complex multi-scale geometries. Firstly, two different discreet geometrical description of an object being under radiation is used: triangulated model for photon transport and voxel model for elec-tron transport. Secondly, small parameter of the problem is explicitly taking into ac-count for modeling surface effects (for instance, electron emission). Thirdly, the ef-fective calculation decomposition between CPU and GPU is developed for signifi-cant increasing the speed of calculations of processes in question. Modeling of ex-periment on researching the bremsstrahlung generated by electron beam in Ta target is carried out. Comparison of computing and experimental results shows satisfactory consent.
In this contribution, we discuss the influence of scattered radiation on materials’ effective attenuation coefficients at higher X-ray energies. The selected X-ray spectra for the dual-energy experiments correspond to 3 MV and 7.5 MV acceleration potential of the used betatron. Experiments were performed on a test phantom containing step wedges of different low- and high-Z materials. We evaluated the ratio between low- and high-energy X-ray attenuation coefficients quantitatively based on simulated poly-energetic high-energy X-ray source spectra and the detector sensitivity using the “analytical Radiographic Testing inspection simulation tool” (aRTist) developed at BAM. Furthermore, the influence of scattered radiation is evaluated using an efficient Monte-Carlo simulation. The simulation results are compared quantitatively with experimental investigations. Finally, important applications of the proposed technique in the context of aviation security are discussed.
X-ray backscatter imaging is a well established NDT technique to inspect complex objects using only a single-sided access. In difference to conventional transmission X-ray radiography, the X-ray backscatter imaging utilizes the scattered radiation caused by the Compton scattering effect. In order to achieve high backscatter intensities from a test object, it is necessary to optimize the backscatter system parameters namely the angle between source and slit camera, the slit collimator system, the shielding between source and scatter camera, and the type of detector. In addition, the scatter phenomena in to the investigated object need to be understood.
In this contribution, we present a Monte Carlo model McRay which considers all relevant single and multiple interactions of photons and electrons. This model can be used to simulate back scatter techniques. It allows not only calculating the scatter image for a given experimental setup but also registering the spectrum of the detected scattered photons. Both aspects are important to understand the imaging process, to interpret the results, and to optimize the backscatter camera investigated here. Additionally experimental results will be presented and compared with simulations.
Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent disconti-nuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. Otherwise, planar discontinuities like cracks in plastics or delaminated lay-ers in composites can be abstracted as layers located at any angle in relation to the outer sample surface direction. A tomogram from the scanned sample can then be reconstructed in case the interactions of electromagnetic pulses with the existing in-herent interfaces are detectable and a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielec-tric properties.
A short description of both the SAFT – and Optical Layer algorithm for the recon-struction of the inherent structure is initially given. Measurements on representative samples with a variety of artificially produced small and large scale. Reconstructed tomograms are presented to discuss and evaluate the benefits and limits of the two different reconstruction approaches.
For non-destructive testing (NDT) appropriate reference blocks are required in order to verify and calibrate a testing procedure. At BAM a special electric discharge machining (EDM) system has been developed which is able to manufacture artificial defects having a width down to 30 μm.
Especially in the case of austenitic materials conventional EDM leads to a transformation of austenite to martensite. The martensite transformation causes a higher sensitivity of electromagnetic NDT methods (e. g. eddy current testing) at the artificial defects compared to natural defects of same size. The EDM system developed at BAM uses very low energy to avoid this material transformation. A side effect of the low-energy EDM is a lower surface roughness compared to conventional EDM.
The artificial defects manufactured at BAM are measured optically and delivered with a certificate.
A comparison of artificial defects shows the influence of material transformation on NDT and how differently the quality of the artificial defects can be.
For non-destructive testing (NDT) appropriate reference blocks are required in order to verify and calibrate a testing procedure. At BAM a special electric discharge machining (EDM) system has been developed which is able to manufacture artificial defects having a width down to 30 μm.
Especially in the case of austenitic materials conventional EDM leads to a transformation of austenite to martensite. The martensite transformation causes a higher sensitivity of electromagnetic NDT methods (e. g. eddy current testing) at the artificial defects compared to natural defects of same size. The EDM system developed at BAM uses very low energy to avoid this material transformation. A side effect of the low-energy EDM is a lower surface roughness compared to conventional EDM. The artificial defects manufactured at BAM are measured optically and delivered with a certificate. A comparison of artificial defects shows the influence of material transformation on NDT and how differently the quality of the artificial defects can be.
One essential step on the way towards accurate quantitative simulation of radiographic testing is an accurate description of the utilized energy spectrum of X-ray photons. For use in general purpose simulation tools, the spectra of X-ray tubes have to be described by a model covering at least the intended range of applications. This range includes transmission tubes as well as direct beam tubes with varying angles of incidence and emission, for a number of typical target materials. In radiographic testing acceleration voltages frequently reach up to 450 kV for direct beam targets and up to 225 kV for transmission targets, with even higher voltages available or being developed. Currently used models are unable to cover the whole range of configurations.
Here a model is presented that employs a unified approach for simulating the photon energy spectra for transmission and direct beam targets composed of arbi-trary homogeneous materials. In order to achieve this, a detailed model of electron transport within the target is employed. The validity of the developed model is shown through comparisons with Monte Carlo simulations as well as measurements for a number of different configurations.
Modeling of the photon-electron cascade progress in multicomponent objects of complex geometrical structure by use of hybrid supercomputers is considered. An approach to computing the cascade processes is developed. The approach has three key properties allowing the effective use of heterogeneous structure of computers for solving the tasks of radiation transport in complex multi-scale geometries. Firstly, two different discreet geometrical description of an object being under radiation is used: triangulated model for photon transport and voxel model for electron transport. Secondly, small parameter of the problem is explicitly taking into account for modeling surface effects (for instance, electron emission). Thirdly, the effective calculation decomposition between CPU and GPU is developed for significant increasing the speed of calculations of processes in question. Modeling of experiment on researching the bremsstrahlung generated by electron beam in Ta target is carried out. Comparison of computing and experimental results shows satisfactory consent.
In this contribution, we discuss the influence of scattered radiation on materials’ effective attenuation coefficients at higher X-ray energies. The selected X-ray spectra for the dual-energy experiments correspond to 3 MV and 7.5 MV acceleration potential of the used betatron. Experiments were performed on a test phantom containing step wedges of different low- and high-Z materials. We evaluated the ratio between low- and high-energy X-ray attenuation coefficients quantitatively based on simulated poly-energetic high-energy X-ray source spectra and the detector sensitivity using the “analytical Radiographic Testing inspection simulation tool” (aRTist) developed at BAM. Furthermore, the influence of scattered radiation is evaluated using an efficient Monte-Carlo simulation. The simulation results are compared quantitatively with experimental investigations. Finally, important applications of the proposed technique in the context of aviation security are discussed.
X-ray backscatter imaging is a well established NDT technique to inspect complex objects using only a single-sided access. In difference to conventional transmission X-ray radiography, the X-ray backscatter imaging utilizes the scattered radiation caused by the Compton scattering effect. In order to achieve high backscatter intensities from a test object, it is necessary to optimize the backscatter system parameters namely the angle between source and slit camera, the slit collimator system, the shielding between source and scatter camera, and the type of detector. In addition, the scatter phenomena in to the investigated object need to be understood.
In this contribution, we present a Monte Carlo model McRay which considers all relevant single and multiple interactions of photons and electrons. This model can be used to simulate back scatter techniques. It allows not only calculating the scatter image for a given experimental setup but also registering the spectrum of the detected scattered photons. Both aspects are important to understand the imaging process, to interpret the results, and to optimize the backscatter camera investigated here. Additionally experimental results will be presented and compared with simulations.
Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities.
A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. Otherwise, planar discontinuities like cracks in plastics or delaminated layers in composites can be abstracted as layers located at any angle in relation to the outer sample surface direction. A tomogram from the scanned sample can then be reconstructed in case the interactions of electromagnetic pulses with the existing inherent interfaces are detectable and a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric properties.
A short description of both the SAFT – and Optical Layer algorithm for the reconstruction of the inherent structure is initially given. Measurements on representative samples with a variety of artificially produced small and large scale. Reconstructed tomograms are presented to discuss and evaluate the benefits and limits of the two different reconstruction approaches.
Modelling becomes more and more important in modern NDE. It is increasingly used to optimize techniques for complex applications, to support the preparation of written procedures, and for education purposes. To describe the complete chain of RT, the model includes simulating all necessary properties of X- or Gamma-ray sources, the interaction of photons with material with special attention to scattered radiation, the detection process, and the complete geometrical RT setup handling arbitrary parts or constructions. Depending on the given inspection problem and the influencing factors that should be addressed by the simulation, an appropriate physical model has to be chosen to describe the underlying interaction mechanisms. The simulator aRTist combines analytical and Monte Carlo methods to efficiently model the radiation transport such that transmission as well as scatter techniques can be modelled. In this contribution we Focus on Monte Carlo Simulation of scatter contribution within aRTist. Examples for RT/tomographic applications and back-scatter techniques are presented to demonstrate the usability of the presented simulation tool for a broad range of radiological applications.
For the last 20 years active thermography has developed into a standard method in non-destructive material testing. It has become possible to detect defects such as cracks, voids, or even material inhomogeneities. Until now, it is still difficult to quantify subsurface or hidden defects in size due to the diffusive nature of heat flow within a solid. Facing this issue, lockin thermography and other photothermal techniques have been established. They are based on exciting a sample periodically (e.g. with a halogen lamp), causing a controlled periodical heat flow and thereby representing strongly damped thermal waves. These techniques make use of interference and reflection of thermal waves which allow enhancing depth resolution.
So far, only the temporal component of the light source was modified to achieve a defined vertical heat flow – In contrast, we propose a novel technique in which we are able to control both: time and space. This technique enables us to exploit the possibilities of coherent thermal wave shaping. We achieve that by combining a spatial light modulator (SLM) with a high power laser. This approach allows us to launch a set of individually controlled and fully coherent high energy thermal waves into the sample volume. That means, we intentionally use wave propagation throughout the sample’s material in both - vertical and lateral direction.
As one possible application, we use a thermal waves’ interference effect of two phase shifted wave patterns to detect the position of hidden defects. The wave patterns are positioned with a certain distance and a 180° phase shift to each other creating an amplitude depletion zone right in the middle of the two patterns. When a defect is brought unsymmetrically into the depletion zone, the lateral heat flow is disturbed. If the sample is now moved through the depletion zone, a defect can be easily characterized. Exciting periodically while controlling simultaneously phase and amplitude enables us to have a defined thermal wave propagation throughout the sample which means thermal waves can be controlled almost like acoustical or optical waves. This offers the opportunity to transfer known technologies from wave shaping techniques to thermography methods.
For the last 20 years active thermography has developed into a standard method in non-destructive material testing. It has become possible to detect defects such as cracks, voids, or even material inhomogeneities. Until now, it is still difficult to quantify subsurface or hidden defects in size due to the diffusive nature of heat flow within a solid. Facing this issue, lockin thermography and other photothermal techniques have been established. They are based on exciting a sample periodically (e.g. with a halogen lamp), causing a controlled periodical heat flow and thereby representing strongly damped thermal waves. These techniques make use of interference and reflection of thermal waves which allow enhancing depth resolution.
So far, only the temporal component of the light source was modified to achieve a defined vertical heat flow – In contrast, we propose a novel technique in which we are able to control both: time and space. This technique enables us to exploit the possibilities of coherent thermal wave shaping. We achieve that by combining a spatial light modulator (SLM) with a high power laser. This approach allows us to launch a set of individually controlled and fully coherent high energy thermal waves into the sample volume. That means, we intentionally use wave propagation throughout the sample’s material in both - vertical and lateral direction. As one possible application, we use a thermal waves’ interference effect of two phase shifted wave patterns to detect the position of hidden defects. The wave patterns are positioned with a certain distance and a 180° phase shift to each other creating an amplitude depletion zone right in the middle of the two patterns. When a defect is brought unsymmetrically into the depletion zone, the lateral heat flow is disturbed. If the sample is now moved through the depletion zone, a defect can be easily characterized. Exciting periodically while controlling simultaneously phase and amplitude enables us to have a defined thermal wave propagation throughout the sample which means thermal waves can be controlled almost like acoustical or optical waves. This offers the opportunity to transfer known technologies from wave shaping techniques to thermography methods.
Applications of fibre reinforced plastic (FRP) composites in modern industries are increasing due to their considerable advantages such as light weight and excellent mechanical properties. Accordingly, importance of operational safety of modern structures made of advanced composites by ensuring the material quality has led to increasing demands for development of non-destructive evaluation (NDE) systems. In the context of a European project entitled “Validated Inspection Techniques for Composites in Energy Applications” (VITCEA), the aim is to develop and validate traceable procedures for novel NDE techniques with contrasting damage detection capabilities in energy related applications such as wind and marine turbine blades, nacelles, oil and gas flexible risers. Accordingly, VITCEA focuses on optimization of ultrasonic tests (UTs) for quantitative defect detection and quality characterization of FRP structures. In this context, the present study describes the ultrasound field in heterogeneous composite materials. The theoretical predictions are compared with simulation results obtained from CIVA a software package dedicated to NDT simulations based on the asymptotic ray theory.
Recent developments in Förster resonance energy transfer (FRET) diagnostics using quantum dots
(2016)
The exceptional photophysical properties and the nanometric dimensions of colloidal semiconductor quantum dots (QD) have strongly attracted the bioanalytical community over the last approximately 20 y. In particular, the integration of QDs in the analysis of biological components and interactions, and the related diagnostics using Förster resonance energy transfer (FRET), have allowed researchers to significantly improve and diversify fluorescence-based biosensing. In this TRENDS article, we review some recent developments in QD-FRET biosensing that have implemented this technology in electronic consumer products, multiplexed analysis, and detection without light excitation for diagnostic applications. In selected examples of smartphone-based imaging, single- and multistep FRET, steady-state and time-resolved spectroscopy, and bio/chemiluminescence detection of QDs used as both FRET donors and acceptors, we highlight the advantages of QD-based FRET biosensing for multiplexed and sensitive diagnostics.
Excelling in brevity but lacking in applicability, the 2011 EU nanomaterial definition has become a source of anguish for scientists and industry alike. Repeated pleas and discussions with our own envoy have demonstrated the strength of their resolve: this definition is unlikely to change. Manufacturers of many materials (cosmetics, pigments, foodstuffs, etc.) will have to characterise and label all their products accordingly, a task still impossible for lack of a clear metrological approach towards this goal. Therefore, the onus has fallen on the scientists to come up with a practicable measurement technique allowing inexpensive classification covering large swathes of the material landscape. Small-angle X-ray Scattering (SAXS) probes the size range in question, and can - with due care - deliver a bulk-averaged volume-weighted size distribution. Like any other real-world measurement method, however, it is not (and can never be) a universal solution. This presentation will clarify the SAXS technique, provide several application examples for nanomaterial characterisation, and will detail the limitations and pitfalls that accompany its abilities. At the end of this presentation, you will have the information to judge whether the technique is amenable to your materials or not.
In recent years, elemental imaging of biological samples using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is gaining in importance. Latest improvements regarding spatial resolution (down to 1 µm) and washout time make LA-ICP-MS particularly interesting for single cell analysis.
Many current nanomaterials can serve as contrast agents in cellular or tissue imaging, drug delivery vehicles or therapeutics, whereas others can cause toxic effects. In order to evaluate nano-bio interactions, the number of nanoparticles (NPs) inside cells as well as their localisation within cellular substructures is of particular interest.
LA-ICP-MS was used to study the NP pathway from uptake, via intracellular processing up to cell division. Fibroblast cells were incubated with different metallic NPs under varying experimental conditions. For LA analysis the cells were fixed with formaldehyde and dried.
Our results show that LA-ICP-MS is able to localise NP aggregates within cellular substructures. The NPs accumulate in the perinuclear region in the course of intracellular processing, e.g. multivesicular fusion and endosomal maturation, but do not enter the nucleus [1, 2]. A strong dependence of NP uptake on concentration and incubation time was found. Additionally, the number of NPs internalized by individual cells was determined and variations within the cell population became visible.
A new laser ablation system providing a short washout time (50 ms) together with small spot sizes (< 4 µm) and high repetition rates allows high spatial resolution applications. First results of cell imaging will be shown.
The findings demonstrate the potential of LA-ICP-MS enabling insight into NP uptake and intracellular distribution dependent on experimental parameters.
Imuno-histochemical staining (IHC) of cancer biomarker on tissue sections is one of the most important analytical techniques for cancer diagnosis although standardization and quality management is tedious and differ significantly from clinic to clinic. Combining established IHC staining strategies with modern quantitative methods would increase it`s potential. We used element mass spectrometry (ICP-MS) and a new ink-jet printed internal standardization approach in combination with IHC staining. The printing strategy was utilized to improve elemental image resolution and reproducibility of paraffin embedded breast cancer tissue sections in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) after conventional IHC staining as a model system to investigate the new capabilities of this technique.
Thermoresponsive polymers have shown great potential in applications such as bioseparation, drug delivery and diagnostic. Only few thermoresponsive polymers that present an upper critical solution temperature (UCST) in a relevant temperature range, i.e. phase separate from solution upon cooling, have been reported so far. Moreover, the most studied UCST type polymers namely polybetaines are difficult to use under physiological conditions, which significantly restricts their potential applications. Therefore, UCST polymers with sharp and robust phase transition in physiological conditions (in the presence of salts, ions etc.) are highly needed in order to extend the range of applications of this class of polymers. Herein, a robust UCST-type copolymer of acrylamide (AAm) and acrylonitrile (AN) (poly(AAm-co-AN)) was prepared by reversible addition fragmentation chain transfer (RAFT) polymerization and its thermo-induced aggregation behavior in aqueous media was studied. At temperature below the UCST, the copolymer chains were aggregated together. The aggregate size was found to be larger with increasing AN contents and became smaller upon dilution of the copolymer solutions. While above the UCST, the copolymer chains were expanded and weekly associated in solution. The association between the copolymer chains formed smaller aggregates with increasing the AN contents or the dilution of the solutions. A model is proposed to explain such aggregation-association behavior of the Fig. 1.
Figure 1. Schematic illustration of the proposed thermos-induced aggregation behavior of the poly(AAm-co-AN) in aqueous solution.
Imuno-histochemical staining (IHC) of cancer biomarker on tissue sections is one of the most important analytical techniques for cancer diagnosis although standardization and quality management is tedious and differ significantly from clinic to clinic. Combining established IHC staining strategies with modern quantitative methods would increase it`s potential. We used element mass spectrometry (ICP-MS) and a new ink-jet printed internal standardization approach in combination with IHC staining. The printing strategy was utilized to improve elemental image resolution and reproducibility of paraffin embedded breast cancer tissue sections in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) after conventional IHC staining as a model system to investigate the new capabilities of this technique.
The laser-induced breakdown spectroscopy (LIBS) is a fast method to provide multi-elemental analysis of any sample. At the Federal Institute for Materials Research and Testing (BAM) the LIBS technique is applied on building materials to measure ingress profiles of harmful species like chloride and alkalis. The ingress depth and the quantitative amount is important for the evaluation of the potential for damage processes like the alkali-silica reaction or chloride-induced corrosion. Concrete as an example is a highly heterogeneous material with 1/7 cement (major component CaO) and 6/7 aggregates (SiO2) with different grain sizes. Due to a scanning procedure a two dimensional element distribution of a concrete surface can be measured. In order to have an automated Separation method to evaluate heterogeneous materials, different cluster algorithm have been tested. Best results have been achieved with the Expectation-Maximization-Algorithm (EM-Algorithm).
The motivation to examine the influence of friction on surfaces of energetic materials (EM) has diverse backgrounds. On the one hand the very old hot spot theory predicts, that the size of such hot spot could be in the range of a molecule. The initiation of an EM could start by mechanical excitation, i.e. friction, and continues driven by an exothermal chemical reaction. Following such phenomena on the molecular scale with an imaging method such as AFM should enable us to separate several steps of ignition, if there are any. The experiments showed that HMX mainly undergoes a plastic deformation without further consequences. TNP however showed self healing in the wear track after scratching and simultaneously the destruction of a crystal edge outside the wear track. Additionally nanoparticles appear, tribologists call this "third body formation", which are proven to have a different chemical composition as the original TNP. The self healing effect on the surface is verified with experiments on self diffusion of TNP molecules to and fro the free edges of the crystal. The conclusion is that the formation of a hot spot can be shown to consist of several subsequent steps, separated temporally and locally. The goal to excite the thermal decomposition of a whole TNP crystal (nanoexplosion) was yet not reached due to unfavourable conditions related to thermal conductivity and build-up of pressure.
qNMR provides the most universally applicable form of direct purity determination without need for reference materials of impurities or the calculation of response factors but only exhibiting suitable NMR properties. The development of CRMs addressing qNMR specific measurement issues will give analysts compounds ideally suited for the analytical method and also provide full characterisation of qNMR related parameters to enable more realistic uncertainty budgets. These materials will give users the tools to exploit qNMR more easily and enable them to speed up analytical method development and reduce the time and financial burden of multiple analytical testing.
The nature of the bound water in solids with hydrogen-bonded networks depends not only on temperature and pressure but also on the nature of the constituents. The collapse and reorientation of these network structures determines the stability of hydrated solids and transitions to other crystalline or amorphous phases. Here, we study the mechanochemically induced loss of bound water in Co₃(PO₄)₂·8H₂O and compare this process to the behavior under hydrostatic pressure.
The associated phase transition and its kinetics were monitored by X-ray powder diffraction with Synchrotron radiation and quantitative IR spectroscopy. High shearing forces are responsible for the degradation of the hydrogen-bonded network and the concomitant crystalline–amorphous transformation. UV/Vis spectroscopy, extended X-ray absorption spectroscopy (EXAFS), and X-ray absorption near-edge spectroscopy (XANES) provided information about the short-range order in the amorphous solid, and thermal analysis revealed its composition and showed that the moderate charge densities of the Co²⁺ and PO₄³⁻ ions, which make the hydration enthalpy comparable to the binding energy of the counteranions, and the Formation of hydrogen-bonded networks favor multistage crystallization processes associated with the release and uptake of coordinated water. The changes of the Co²⁺ coordination induce a color change from pink to blue; therefore, Co₃(PO₄)₂·8H₂O can be used as an overheat temperature indicator.
Self-assembling biomolecules provide attractive templates for the preparation of metallic nanostructures. However, the intuitive transfer of the “outer shape” of the assembled macromolecules to the final metallic particle depends on the intermolecular forces among the biomolecules which compete with interactions between template molecules and the metal during metallization. The shape of the bio-template may thus be more dynamic than generally assumed. Here, we have studied the metallization of phospholipid nanodiscs which are discoidal particles of ~10 nm diameter containing a lipid bilayer ~5 nm thick. Using negatively charged lipids, electrostatic adsorption of amine-coated Au nanoparticles was achieved and followed by electroless gold deposition. Whereas Au nanoparticle adsorption preserves the shape of the bio-template, metallization proceeds via invasion of Au into the hydrophobic core of the nanodisc. Thereby, the lipidic phase induces a lateral growth that increases the diameter but not the original thickness of the template. Infrared spectroscopy reveals lipid expansion and suggests the existence of internal gaps in the metallized nanodiscs, which is confirmed by surface-enhanced Raman scattering from the encapsulated lipids. Interference of metallic growth with non-covalent interactions can thus become itself a shape-determining factor in the metallization of particularly soft and structurally anisotropic biomaterials.
When modeling the propagation of elastic guided waves in plates or cylinders, Finite Element based numerical methods such as the Scaled Boundary Finite Element Method (SBFEM) or the Semi-Analytical Finite Element (SAFE) Method lead to an eigenvalue problem to be solved at each frequency. For the particular case of shear horizontal modes in a homogeneous plate or torsional modes in a homogeneous cylinder, the problem can be drastically simplified. The eigenvalues become simple functions of the frequency, while the eigenvectors are constant. The current contribution discusses how this behavior is represented in the numerical formulation and derives the expressions for the eigenvalues and eigenvectors as well as the dynamic stiffness matrix of infinite elastic waveguides.
We describe a fast and effective synthesis for molecular metal phosphonates. Isomorphic compounds [M(II)(HO₃PPh)₂(H₂O₃PPh)₂(H₂O)₂] (M = Mn (1), Co (2), Ni (3); Ph = C₆H₅) were obtained by grinding. The complexes are mononuclear compounds containing neutral and monodeprotonated phenylphosphonic acid and water as ligands. The crystal structures were determined using powder X-ray diffraction (PXRD) data and validated by extended X-ray absorption fine structure (EXAFS) data. Combined synchrotron XRD measurements and Raman spectroscopy were conducted for investigating the reactions in situ. Based on these data, the intermediates were characterized and the formation mechanism was derived.
Fluorescence imaging microscopy is an essential tool in biomedical research. Meanwhile, various fluorescent probes are available for the staining of cells, cell membranes, and organelles. Though, to monitor intracellular processes and dysfunctions, probes that respond to ubiquitous chemical parameters determining the cellular function such as pH, pO2, and Ca2+ are required. This review is focused on the progress in the design, fabrication, and application of photoluminescent nanoprobes for sensing and imaging of pH in living cells. The advantages of using nanoprobes carrying fluorescent pHindicators compared to single molecule probes are discussed as well as their limitations due to the mostly lysosomal uptake by cells. Particular attention is paid to ratiometric dual wavelength nanosensors that enable intrinsic referenced measurements. Referencing and proper calibration procedures are basic prerequisites to carry out reliable quantitative pH determinations in complex samples such as living cells. A variety of examples will be presented that highlight the diverseness of nanocarrier materials (polymers, micelles, silica, quantum dots, carbon dots, gold, photon upconversion nanocrystals, or bacteriophages), fluorescent pH indicators for the weak acidic range, and referenced sensing mechanisms, that have been applied intracellularly up to now.
Optical constants of harmful and highly energetic liquids for application to THz screening systems
(2016)
The far-infrared (IR) optical constants of a set of hazardous and flammable liquids have been obtained by means of spectroscopic ellipsometry in attenuated total reflection configuration over a broad spectral range. Such liquids recently became of considerable concern for transportation security measures worldwide. Their optical identification at check-in gates can only become possible if the characteristic spectra are already known. The refractive indices and the extinction coefficients reported here contribute to a spectroscopic data base in the far-IR and terahertz (THz) spectral regions and may support modeling the performance of THz screening systems on liquids for airports and other security sensitive areas. Examples of several container material/liquid systems are discussed. From the measured optical constants typical THz waveforms are calculated and discussed.
Silver nanoparticles (Ag NPs) are widely used in consumer products due to their excellent antibacterial properties. Their broad application has led to a variety of recent regulation on their use and labelling. Thus, a highly specific analytical method for their characterization and quantification is needed.
Due to their large separation range, field-flow fractionation (FFF) techniques are repeatedly applied for the analysis of NP. Limitations of FFF include quantification, sample loss and insufficient recovery rates. Another challenge can be non-ideal elution behavior of particles in complex and unknown matrices.
The possible sources for sample losses of Ag NP have been studied using an asymmetric flow FFF (AF4) in combination with inductively coupled plasma mass spectrometry (ICP-MS). The influence of different parameters, for example the sample concentration, on the recovery rates and sample loss has been investigated. Using laser ablation ICP-MS, the Ag deposition on the membrane was located and quantified. Our results identified ionic silver as the main sources of sample loss. These results can be useful for further method improvement.
However, when a Ag NP sample containing an unknown complex matrix is analyzed, FFF method optimization is challenging as the sample might show a shift in the retention times and lower recovery rates. In this case, ICP-MS experiment in the single particle mode (sp-ICP-MS) can be a useful addition to the FFF measurement. Here, upon assumption of spherical particles, the geometric diameters can be calculated. This fast and easy approach can be helpful in order to interpret the FFF fractograms and advice the FFF method optimization process.
A combined analysis of EXAFS and Raman spectra is applied for the study of
InxGa1-xN alloys with 0.3<x<0.5. Alloying causes relaxation of the selection rules resulting in
Raman spectra that resemble the vibrational density of states. On the other hand, theoretical
simulation of the Raman spectra using the Equation of Motion routine of FEFF8 provides the
vibrational component of the Debye-Waller factor (DWF). The static disorder component of
the DWFs was obtained by fitting the Ga and In K-edge EXAFS spectra. The analysis revealed
that the nearest neighbor distances of the 1st and 2nd shell deviate from the values predicted by
the law of Vegard and the virtual crystal approximation. The static disorder in the first nearest
neighboring shell (In-N and Ga-N) is null whereas in the cation-cation neighboring shells the
static component is generally smaller than the vibrational.
Recent technical developments of NMR instruments such as in acquisition electronics and probe design allow detection limits of components in liquid mixtures in the lower ppm range (approx.. 5–10 ppm amount of substance). The major advantage of quantitative NMR spectroscopy (qNMR) is that it is a direct ratio method of analysis without the need of calibration. This means that the signal for a specific NMR-active nucleus (e.g., a proton) in an analyte can be compared and quantified by reference to a different nucleus of a separate compound, comparable to a counting of spins in the active volume of the spectrometer.
Technical mixtures can be investigated online directly next to a process setup by using flow probes. This makes it a promising method for process analytical applications, especially during process development in laboratory and pilot plant scale. With the growing market of Benchtop devices based on permanent magnets nowadays an integration of NMR spectroscopy in an industrial environment becomes reasonable.
A special application of qNMR in technical mixtures is the observation in the gas phase, which is rarely applied compared to liquid and solid NMR studies. Because of the low density it results in a reduced sensitivity, which can be improved by applying pressure. Therefore a high-pressure NMR setup was developed based on a commercially available NMR tube made of zirconia. This is currently tested up to 20 MPa, but can be extended up to 100 MPa with regard to pressure rating of its components. This work shows results of gas-phase application on natural-gas like reference gas mixtures produced at BAM, as well as investigations on liquefied gas mixtures with high accuracy provided in piston cylinders.
Besides that amine gas treatment and hydroformylation in a microemulsion represent two other examples of applications in process analytical technology. These show the potential of combination of online NMR spectroscopy with other spectroscopic methods, especially during model development for data evaluation.
The successful mechanochemical syntheses of three cadmium phenylphosphonates indicates that mechanochemistry is ideally suited for synthesizing metal phosphonates. With this powerful synthesis tool it is possible to synthesize rapidly and efficiently both known and novel phosphonates. The Crystal structures of the two new compounds, and, were solved from PXRD data. They contain monodeprotonated phenylphosphonate and neutral phenylphosphonic acid ligands. The synthesis pathways of all three compounds were investigated in situ. A diffusion mechanism is corroborated by our findings.
Intermediates could be detected and identified. The kinetically favored product (3) could always be detected during the syntheses. The thermodynamic stability of the compounds and the stoichiometric ratio of the starting materials are the two directing factors for the synthesis of the final products.
Online NMR spectroscopy is an excellent tool to study complex reacting multicomponent mixtures and gain process insight and understanding. For online studies under process conditions, flow NMR probes can be used in a wide range of temperature and pressure. This paper compiles the most important aspects towards quantitative process NMR spectroscopy in complex multicomponent mixtures and provides examples. After NMR spectroscopy is introduced as an online method and for technical samples without sample preparation in deuterated solvents, influences of the residence time distribution, pre-magnetization, and cell design are discussed. NMR acquisition and processing parameters as well as data preparation methods are presented and the most practical data analysis strategies are introduced.
The lasing effect is demonstrated in laser plasmas induced on various metal targets and pumped by a laser tuned in resonance with a strong optical transition of a metal. The intense, polarized and lowdivergent radiation is emitted from a longitudinally pumped plasma plume in forward and backward directions with respect to the pump beam. Lasing occurs only within duration of the pumping pulse. The effect is found for elements of 13th and 14th groups and for Ca, Ti, Zr, Fe and Ni. The Einstein coefficients for spontaneous emission of all lasing transitions are higher than 10⁷ s⁻¹. For some elements like Al and In, a three-level lasing scheme is realized. For others, like Tl, both three- and four-level lasing schemes are realized. It is found that the longitudinal pump geometry is more efficient than the transversal one.
A boron dipyrromethene (BDP) unit and its monostyryl derivative (MSBDP) were introduced at the axial positions of a silicon(IV) phthalocyanine (SiPc) core. The absorption spectrum of this compound virtually covered the entire visible region (300-700 nm) and could be interpreted as a superposition of the spectra of individual components. The intramolecular photoinduced energy and charge transfer processes of this triad were studied using steady-state and time-resolved spectroscopic methods in polar and nonpolar solvents. Upon BDP-part excitation, a fast and highly efficient excitation energy transfer (EET) occurred resulting in strong quenching of its fluorescence and the formation of the first excited singlet state of SiPc or MSBDP. It was found that both EET and charge transfer (CT) processes competed with each other in the depopulation of the first excited singlet state of the MSBDP moiety. The former strongly superseded CT in nonpolar toluene, whereas the latter was dominant in a polar environment. Direct or indirect (via EET) excitation of the SiPc-part of the triad was followed by CT yielding the charge-separated (CS) species BDP-SiPc center dot--MSBDP center dot+. The energy gap between the CS state and the S-1-state of the SiPc moiety was found to be only 0.06 eV in toluene, which facilitated the back CT process and resulted in the appearance of thermally activated delayed fluorescence. With increasing solvent polarity, the energy of the CS state reduced resulting in the disappearance of the delayed fluorescence in CHCl3, tetrahydrofuran or N,N-dimethylformamide. The charge recombination rate, k(CR), was very fast in polar DMF (3.3 x 10(10) s(-1)), whereas this process was two-orders of magnitude slower in nonpolar toluene (k(CR) = 4.0 x 10(8) s(-1)).
The folding of single-stranded telomeric DNA into guanine (G) quadruplexes is a conformational change that plays a major role in sensing and drug targeting. The telomeric DNA can be placed on DNA origami nanostructures to make the folding process extremely selective for K+ ions even in the presence of high Na+ concentrations. Here, we demonstrate that the K+-selective G-quadruplex formation is reversible when using a cryptand to remove K+ from the G-quadruplex. We present a full characterization of the reversible switching between single-stranded telomeric DNA and G-quadruplex structures using Förster resonance energy transfer (FRET) between the dyes fluorescein (FAM) and cyanine3 (Cy3). When attached to the DNA origami platform, the G-quadruplex switch can be incorporated into more complex photonic networks, which is demonstrated for a three-color and a four-color FRET cascade from FAM over Cy3 and Cy5 to IRDye700 with G-quadruplex-Cy3 acting as a switchable transmitter.
Typically, mycotoxigenic moulds and consequently small percentages of extremely contaminated portions (“hot spots”) are randomly distributed in a cereal lot. Therefore, an efficient sampling procedure for mycotoxin analysis represents a complex challenge for operators involving invasive and cost intensive steps. Establishing an in situ analysis of mycotoxins from the homogeneous gas-phase above cereal crops instead of analysing random samples could address this difficult issue. During studies for microbial volatile organic compounds (MVOCs) indicating an infection with Fusarium, trichodiene was identified as a unique biosynthesis intermediate of trichothecenes - one of the largest groups of the mycotoxin family. The sesquiterpene trichodiene is the only volatile biogenic precursor of the trichothecenes, thus, early and fast in situ detection of this biomarker might be of interest for a potential trichothecene infestation. However, there is no commercial trichodiene standard available needed for the quantification of trichodiene in cereal grains.
The aim of the current project is to develop a fast, easy-to-handle and non-invasive gas-phase quantification of trichodiene in the field. Therefore, trichodiene was prepared by total synthesis based on a tandem orthoester Claisen rearrangement - oxidation - Robinson annulation strategy providing the racemic natural product in 9 steps and 8 % overall yield. Its structure was fully elucidated by NMR and MS. With the reference standard in hand, a protocol was established for the quantitative headspace analysis of trichodiene above crop spikes by GC/MS in the < 10 µg/kg range. Besides a sample survey and a trichodiene - trichothecene correlation study, it is aimed to transfer the validated analytical method from the laboratory into a field-portable analytical system.
The fast and reliable in situ detection of trichodiene as a volatile biomarker for trichothecene mycotoxins will contribute to a reduction of food production/analysis costs and to an improvement of food safety.
A monitoring method is introduced that creates twodimensional (2D) maps of the soil gas distribution. The method combines linear gas sensing technology for in-situ monitoring of gases in soil with the mapping capabilities of Computed Tomography (CT) to reconstruct spatial and temporal resolved gas distribution maps. A weighted iterative algebraic reconstruction method based on Maximum Likelihood with Expectation Maximization (MLEM) in combination with a source-by-source reconstruction approach is introduced that works with a sparse setup of orthogonally-aligned linear gas sensors. The reconstruction method successfully reduces artifact production, especially when multiple gas sources are present, allowing the discrimination between true and non-existing so-called ghost source locations. Experimental validation by controlled field experiments indicates the high potential of the proposed method for rapid gas leak localization and quantification with respect to Pipeline or underground gas storage issues.
The growing interest in artificial bioorganic Interfaces as a platform for applications in emerging Areas as personalized medicine, clinical diagnostics, biosensing, biofilms, prevention of biofouling, and other fields of bioengineering is the origin of a need for in Detail multitechnique characterizations of such layers and interfaces. The in-depth analysis of biointerfaces is of special interest as the properties of functional bioorganic coatings can be dramatically affected by in-depth variations of composition.
In worst cases, the functionality of a device produced using such coatings can be substantially reduced or even fully lost.
In this book many practical hints are given and analytical problems are discussed by the authors from their own experiences. A critical assessment of the methods is given, which is most important for decision makers to select a good combination of complementary methods to solve practical analytical problems.
Surface-enhanced Raman scattering (SERS) exploits the enhancement of electromagnetic fields in close vicinity of plasmonic nanostructures. The nanometer-scale spatial arrangement of plasmonic metal nanoparticles and analyte molecules has a significant effect on the observed signal enhancements and represents a great challenge in this technique. Especially interesting effects are expected for complex gold nanolenses (AuNLs), consisting of three or more differently-sized AuNPs. We use DNA origami to assemble AuNLs with 10, 20 and 60 nm AuNPs, arranged in three different geometries. Using correlated AFM and Raman spectroscopy, and probing single AuNLs, we systematically examined the SERS properties of the three different assemblies.