Analytische Chemie
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Introduction: Laser Induced Breakdown Spectroscopy (LIBS) is an atomic emission analytical technique, wide spreading in laboratories and industries. One way to dramatically increase its analytical results is to deposit metal NPs on the sample surface, resulting in an better version called Nanoparticle Enhanced LIBS (NELIBS). In order to better know and use this technique, the evolution of the plasma has been studied with Tomography.
Clinoptilolite is a natural, medium pore size, zeolite. It contains a 2-deminsional pore system containing of oxygen-8- membered and oxygen-10-membered rings. It is one of the most abundant natural zeolites. Clinoptilolite has a crystalline structure showing unique ion exchange and sorption properties. It is mainly used as ion exchanger and adsorbent for removal of toxic elements and compounds from the environment. The use of natural zeolite as spent catalysts may open new perspectives in the chemical use of heavy feed feedstock by chemical conversion. Natural zeolites are not expensive, widely available and environment friendly. Clinoptilolite is the most abundant natural zeolite. Although clinoptilolite is a potential acid catalyst, reports on its application in catalysis are limited so far.
This contribution deals with the modification of the acidity of the natural zeolite clinoptilolite, the characterization of the acid sites and the catalytic activity in the Brønsted acid catalyzed acetalization of benzaldehyde with butandiol-1,3. The samples were acidified by via ammonium-ion exchange followed by calcination and acid treatment. The obtained catalysts were characterized by XRD regarding crystallinity and phase composition. The morphology was studied by TEM images The acidity was studied by ammonia-TPD measurements and 1H solid state MAS NMR as well as REDOR experiments. Structure and structural changes caused by applied modifications were studied by 27Al- and 29Si MAS NMR measurements and thermal analysis.
The ion experiments show that a part of the cations of clinoptilolite readily exchange with ammonium ions and protons from HCl treatment. The NMR results give first hints for a relation of the catalytic conversion with the presence of 5-fold coordinated aluminum. The results will be discussed in terms of a collaborative action of Brønsted acid sites and 5-fold coordinated aluminum.
1. Introduction
Catalytic processing of heavy feedstock can meet the increased demand of energy up to a great extent. It requires the application of acidic catalysts like zeolites. However, the used synthetic catalysts are difficult to recover and reuse and are mostly spent. The use of natural zeolite as spent catalysts may open new perspectives in the chemical use of heavy feed feedstock by chemical conversion. Natural zeolites are not expensive, widely available and environment friendly. Clinoptilolite is a natural, most abundant medium pore size zeolite, consisting of 2-deminsional pore system containing of oxygen-8- membered and oxygen-10-membered rings.Although clinoptilolite is porous and can be acidified by ion exchange or acid treatment. Samples were characterized by XRD regarding crystallinity and phase composition. The acidity was studied by ammonia-TPD measurements and 1H solid state MAS NMR as well as REDOR experiments. Structure and structural changes caused by applied modifications were studied by 27Al- and 29Si MAS NMR measurements and thermal analysis.
2. Experimental Part
The ion exchange behaviour of natural zeolite tuff contained ca. 90 ma. % of clinoptilite was studied in 0.1 and 0.5 M ammonium nitrate solution and for comparison with HCl solution of similar concentration. The activation temperature was varied between 300-600°C.The catalytic test was performed using ca. 0.2 g of the catalyst and ca.10g of the aldehyde and alcohol using toluene as solvent and under reflux. Reaction water was removed via a by-pass.
3. Results and discussion
The experiments show that a part of the cations of clinoptilolite readily exchange with ammonium ions and protons supplied by acid treatment. Substitution of the compensating cations by NH4+ followed by calcination and HCl treatment does not produce structural changes in the original material, but it opens the channels and increases acidity and thermal stability. Calcination at higher temperature and exchange with concentrated acid has a more severe impact on the clinoptilolite structure dealumination as indicated by the appearance of 5- and 6-fold coordinated aluminum. Catalytic activity of sample is related to the surface acidity. The presence of acidic protons of medium to strong strength is confirmed by ammonia-TPD and proton NMR measurements.
4. Conclusions
Acidic natural clinoptilolite catalysts prepared via ammonium exchange followed by calcination and acid treatment shows a positive influence on acidity and porosity. Modification creates hierarchical micro-nano porosity. The specific surface area varies between ca. 45 m2/g and 245 m2/g.
Ever since increasing a reaction’s yield while shortening the reaction time is the main objective in synthesis optimization. Microwave reactors meet these demands. In literature however their usage is under discussion due to claims of the existence of non-thermal effects resulting from the microwave radiation. Especially for nano-material syntheses it is of crucial importance to be aware of influences on the reaction pathway. Therefore, we compare ultra-small silver nanoparticles with mean radii of 3 nm, synthesized via conventional and microwave heating. We employed a versatile one-pot polyol synthesis of poly(acrylic acid) (PAA) stabilized silver nanoparticles, which display superior catalytic properties. No microwave specific effects in terms of particle size distribution characteristics, as derived by small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS), are revealed. Due to the microwave reactor’s characteristics of a closed system, syntheses can be carried out at temperatures beyond the solvent’s boiling point. Particle formation was accelerated by a factor of 30 by increasing the reaction temperature from 200 °C to 250 °C. The particle growth process follows a cluster coalescence mechanism. A post-synthetic incubation step at 250 °C induces a further growth of the particles while the size distribution broadens. Thus, utilization of microwave reactors enables an enormous decrease of the reaction time as well as the opportunity of tuning the particles’ size. Possibly, decomposition of the stabilizing ligand at elevated temperatures results in reduced yields. A temperature of 250 °C and a corresponding reaction time of 30 s represent a compromise between short reaction times and high yields.
The damage caused by ionizing radiation to biomolecules, especially DNA, is the reason to treat cancer via radiation therapy. A better understanding of the molecular processes and the quantification of the various damaging mechanisms is the prerequisit to develope efficient therapies. Hereby the understanding of the processes involved in the damage to DNA are of key interest due to its central role in reproduction and mutation. Due to the high amount of water in biological tissue, most of the damage is caused by the secondary particles produced by the interaction of the IR with water. Thereby a multitude of species are produced, e.g. kinetic low energy electrons, prehydrated electrons, OH-radicals and ions. The quantification of the contribution to DNA damage of the various species is of interest. Here we present an experimental approach to disentangle their relative DNA strand break yield. Plasmid DNA is irradiated in water with electrons under the presence of different scavengers. With the presented method it will be possible to reveal the relative contributions of OH-radicals, low energy electrons and prehydrated electrons to the DNA single and double strand break yield.
Synchrotron X-ray refraction radiography (SXRR) is proven to identify different kinds of defects in Ti-Al6-V4 samples produces by selective laser melting. Namely, these defect types are empty pores and unprocessed powder, which are characteristic to the regions above and below the optimal laser energy density, respectively. Furthermore, SXRR detects small defects below the spatial resolution.
Fluorescence based sensing is a versatile approach for the trace analysis outside of the laboratory, requiring suitable sensor materials and their integration into sensing devices. The versatility of fluorophores as probes, especially in terms of the possibility to tailor their optical as well as their recognition properties by synthetic modifications in a wide range, renders them a superior active component for the preparation of optical sensor devices. Recent works at BAM in this field include, for example, the detection of nerve gas agents, illustrating impressively the aforementioned benefits of fluorophores in optical sensing applications.
In the interdisciplinary approach presented here, we target hazardous gases such as ammonia, benzene, and hydrogen sulfide, next to others, which pose a major threat to human health and environmental safety and for which the availability of a sensitive and reliable detection method is highly desirable.
The dyes presented follow a “turn-on” fluorescence schematic which allows for the selective and sensitive detection of the respective gaseous analyte. The immobilization of the probe in polymeric matrices is then the next step toward the fabrication of a prototype device for molecular sensing.
Development of certified reference material and analytical method for zearalenone in edible oil
(2017)
Quality and safety of food products require their reliable analysis. Contaminants, in particular mycotoxins, are key-components for food safety. About 25 % of the world's food crops are contaminated with mycotoxins posing a severe health risk to humans. In order to strengthen food safety and consumer protection the European Commission (EC) set maximum levels for priority mycotoxins in certain foods for human consumption. In 2013, the EC and CEN (European Committee for Standardization) started an initiative to standardize analytical methods for mycotoxins in food which gained increasing relevance, e.g. zearalenone (ZEN). ZEN, an estrogenic mycotoxin produced by several Fusarium species, contaminates cereal crops worldwide. Due to its lipophilic nature ZEN is often found in edible oils (particularly in maize germ oils) derived from contaminated plants. Therefore, an European maximum level of 400 µg/kg is currently in force. To perform reliable food analysis a sustainable metrological infrastructure is of major importance enabling the quantification of priority mycotoxins (here: ZEN). To achieve this goal, an integrated approach is needed targeted at the development of validated analytical methods and certified reference materials (CRM).
A highly selective method for ZEN in edible oils will be presented, based on solid phase extraction (SPE) using hydrazine-functionalized particles. This method was developed for manual application using commercial SPE cartridges as well as for automated SPE-HPLC online coupling. While ZEN is covalently coupled to the solid phase by means of a hydrazone bond, undesired matrix components can be removed very efficiently. Finally, ZEN is decoupled from the solid phase, leading to highly purified extracts which are measured by HPLC-FLD.
The development of the first European Reference Material (ERM®) for ZEN in maize germ oil (ERM®-BC715) will be presented and discussed. This ERM®-project underpins the urgent need for mycotoxin-CRMs to support food safety and public health.
Development of analytical method and certified reference material for zearalenone in edible oils
(2017)
Quality and safety of food products require their reliable analysis. Contaminants, in particular mycotoxins, are key-components for food safety. About 25 % of the world's food crops are contaminated with mycotoxins posing a severe health risk to humans. In order to strengthen food safety and consumer protection the European Commission (EC) set maximum levels for priority mycotoxins in certain foods for human consumption. In 2013, the EC and CEN (European Committee for Standardization) started an initiative to standardize analytical methods for mycotoxins in food which gained increasing relevance, e.g. zearalenone (ZEN).[1] ZEN, an estrogenic mycotoxin produced by several Fusarium species, contaminates cereal crops worldwide. Due to its lipophilic nature ZEN is often found in edible oils (particularly in maize germ oils) derived from contaminated plants. Therefore, an European maximum level of 400 µg/kg is currently in force.[2] To perform reliable food analysis a sustainable metrological infrastructure is of major importance enabling the quantification of priority mycotoxins (here: ZEN). To achieve this goal an integrated approach is needed targeted at the development of validated analytical methods and certified reference materials (CRM).
A highly selective method for ZEN in edible oils will be presented, based on solid phase extraction (SPE) using hydrazine-functionalized particles. This method was developed for manual application using commercial SPE cartridges as well as for automated SPE-HPLC online coupling. While ZEN is covalently coupled to the solid phase by means of a hydrazone bond, undesired matrix components can be removed very efficiently. Finally, ZEN is decoupled from the solid phase, leading to highly purified extracts which are measured by HPLC-FLD.
The development of the first European Reference Material (ERM®) for ZEN in maize germ oil (ERM®-BC715) will be presented and discussed. This ERM®-project underpins the urgent need for mycotoxin-CRMs to support food safety and public health.
[1] European Commission (EC) Mandate M/520 (2013) for standardisation addressed to CEN for methods of analysis for mycotoxins in food. [2] Commission Regulation (EC) No 1126/2007 amending Regulation (EC) No 1881/2006 setting maximum levels for certain contaminants in foodstuffs as regards Fusarium toxins in maize and maize products.
Pollution through emission of toxic gases is an increasing problem for the environment. It affects similarly agricultural, industrial and urban areas. In future, environmental emissions in ambient air must be monitored at even lower concentrations as nowadays. One environmental relevant compound is ammonia and its conversion product ammonium that have strong negative impact on human health and ecosystems. Most ammonia measurements in ambient air are performed in the range below 1000 nmol·mol-1 and thus there is a need for reliable traceable ammonia gas standards and in addition in situ analytical procedures for monitoring (in ambient air to avoid that thresholds are exceeded). Therefore, the use of reference materials is necessary for development accompanying test or for calibration, e. g. of structure-integrated sensors and mobile multi-gas sensors.
The developed gas standard generator produces gas mixtures that comply with the metrological traceability for ammonia gas standards in the desired environmentally relevant measurement range. The method is based on the permeation of ammonia through a membrane at constant temperature and pressure. The resulting ammonia penetrant gas flow is then mixed with a carrier gas flow to generate a gas standard flow of known concentration. The dynamic rage is enlarged by using a two dilution steps. Depending on the permeation rate, generable molar fractions are possible in the range nmol·mol-1 to a few µmol·mol-1. We present the design of an ammonia gas standard generator and first results of the characterisation of its individual components supporting the uncertainty assessment according to GUM for stable gas concentrations in this range. The relative uncertainty of the generated ammonia gas standard is smaller than 4 % (k = 2).
A scanning transmission x-ray microscopy (STXM) based methodology is introduced for determining the dimensions (shell thickness, core and total diameter) of core-shell nanoparticles which exhibit a strong x-ray absorption contrast and a well-defined interface between core and shell material. A low radiation dosage during data acquisition and, therefore, less x-ray beam induced damage of the sample is achieved by recording STXM images only at two predetermined energies of maximum absorption contrast, instead of recording a stack of images across the whole absorption edge. A model core-shell nanoparticle, polytetrafluoroethylene (PTFE) cores with polystyrene (PS) shell, is used for demonstration. Near edge x-ray absorption fine structure (NEXAFS) spectroscopy confirms the significant difference in x-ray absorption behavior between PTFE and PS. Additionally, due to the insolubility of styrene in PTFE a well-defined interface between particle core and shell is expected. In order to validate the STXM results, both the naked PTFE cores as well as the complete core-shell nanoparticles are examined by scanning electron microscopy (SEM). The introduced STXM based methodology yields particle dimensions in good agreement with the SEM results (deviation equal or less than 10%) and provides additional information such as the position of the particle core which cannot be extracted from a SEM micrograph.
LIBS (laser-induced breakdown spectroscopy) is known as a fast and simultaneous multi-element analysis with little or no sample preparation. In the last few years there has been a growing interest in applications of LIBS in the field of agriculture. As part of the National Research Strategy BioEconomy 2030 the German Federal Ministry of Education and Research (BMBF) started an innovation programme called BonaRes. BonaRes consists of ten interdisciplinary research project associations which are dealing with soil as a sustainable resource for the bio-economy. One of these research projects is I4S (intelligence for soil) which has the goal to develop an integrated system for site-specific soil fertility management. This system includes a sensor platform, which contains different sensors, like XRF, VIS-NIR, Gamma and LIBS. The main task of LIBS measurements in this project is the real time determination of the elemental contents of nutrients in soils, like calcium, magnesium, potassium. For this purpose, a special setup has been designed. The sample uptake operates with the help of a rotatable sample plate which circulates with different velocities to simulate the application on the field. To provide a higher intensity and a better reproducibility of the obtained signal, a double-pulse Nd:YAG laser was used. In order to minimize dust formation from the soil during the operation of the laser, a dust removal by suction has been integrated. When using relative methods such as LIBS, a suitable calibration curve is needed for absolute quantification. With the help of 16 certified reference soils, calibration curves for different elements were initially calculated and used for the quantification of seven soil samples from different testing grounds in Germany. The complex matrix of soils, as well as the influence of moisture and grain size in soils makes the absolute quantification by LIBS challenging. To overcome these influences, a calibration curve based on multivariate analysis (partial least square regression) was generated.
The identification of external paint layers on medieval stained glass windows in Lincoln Cathedral is not only of interest for art historians but is also important for the development of conservation proposals. For the gradual reduction and removal of corrosion layers conservators have to take care to preserve any remaining paint layers which are hidden underneath these corrosion and weathering crusts.
An important aspect of micro or nano particles development is the understanding and control of the particle structure, as it can be determining for particle’s final function, and it affects among other things potential further surface functionalisation/modification.
This work shows the capability of resonant mass measurements (RMM) to measure the mass and density of micron sized particles. The technology utilizes a suspended MEMS microchannel resonator, through which individual particles transit across the resonator altering the resonant frequency, which is then detected using an optical-based method. Changes in frequency observed when a particle enters the microchannel resonator are proportional to the buoyant mass of the particle, and can be translated into mass, size or surface area. RMM therefore allows particle concentration to be determined as well as particle mass in a single measurement.
Furthermore, a method for estimating the density distribution of particles from RMM measurements has been developed. This uses the convolution of the buoyant mass distribution of the particles obtained when suspended in different fluids.
By combining the data from the density and mass determinations, small mass shifts arising from applying a coating to a particle can be estimated, and the resulting shell thicknesses calculated. These methods have been applied to silica coated and uncoated polystyrene latex particles.
RMM shows that it can be used to measure, and distinguish between, silica shell thicknesses that are in the order of 10s of nanometres on hybrid micron-sized particles
In micro or nano particles development it is important to understand and control the particle structure, as it affects among other things the potential further surface functionalisation/modification possible.
This work shows the capability of resonant mass measurements (RMM) to measure the mass and density of micron sized particles. The technology utilizes a suspended MEMS microchannel resonator, through which individual particles transit across the resonator altering the resonant frequency, which is then detected using an optical-based method. Changes in frequency observed when a particle enters the microchannel resonator are proportional to the buoyant mass of the particle, and can be translated into mass, size or surface area. RMM therefore allows particle concentration to be determined as well as particle mass in a single measurement.
Furthermore, a method for estimating the density distribution of particles from RMM measurements has been developed. This uses the convolution of the buoyant mass distribution of the particles obtained when suspended in different fluids.
By combining the data from the density and mass determinations, small mass shifts arising from applying a coating to a particle can be estimated, and the resulting shell thicknesses calculated. These methods have been applied to silica coated and uncoated polystyrene latex particles.
RMM shows that it can be used to measure, and distinguish between, silica shell thicknesses that are in the order of 10 to 55 nanometres on hybrid micron-sized particles. RMM can also determine the shell density.
Aluminum is the third most abundant element in the earth crust and therefore ubiquitously detectable in the environment. Mostly found in the form of derivatives such as silicates or oxides, it also occurs as metallic aluminum for example as colorant in sweets or in aluminum foil.
With regard to potential toxicological effects, the different solubility of metallic aluminum nanoparticles compared to Al2O3 is of high relevance. Formation of ions may facilitate the crossing of blood-tissue barriers. Distribution towards other organs and subsequent re-formation of particulate aluminum due to milieu changes might occur. Therefore, the determination of solubility is required for proper risk assessment. Inductively coupled plasma mass spectrometry (ICP-MS) allows determination of aluminum with a detection limit of about 6 ppb. It could be proven that dissolution and solubility of metallic aluminum is significantly different when compared to Al2O3.
Using ICP-MS in the single particle mode, a significant change in the behavior of both aluminum species was detected after undergoing the artificial digestion. Nearly unchanged in the saliva, particles show dissolution and high agglomeration during the gastric state before deagglomerating again in the intestine.
Further analysis by time-of-flight secondary ion mass spectrometry (ToF-SIMS) revealed the uptake of both aluminum forms by proliferating and differentiated Caco-2 cells. For both particle forms different ions could be detected. Several aluminum-amino acid complex-derived ions from serine and valine were identified. In the case of Al2O3, Al2O2+, AlOH+, AlH2O+ and Al[(H2O)6]3+ were the main ions found co-localizing within treated cells.
LIBS (laser-induced breakdown spectroscopy) is known as a fast and simultaneous multi-element analysis with little or no sample preparation. Because of that, over the last few years there has been a growing interest in applications of LIBS in the field of agriculture.
As part of the National Research Strategy BioEconomy 2030 the German Federal Ministry of Education and Research (BMBF) started an innovation programme called BonaRes. BonaRes consists of ten interdisciplinary research project as-sociations which are dealing with soil as a sustainable resource for the bio-economy. One of these research projects is I4S (intelligence for soil) which has the goal to develop an integrated system for site-specific soil fertility management. This system includes a sensor platform, which contains different sensors, like XRF, VIS-NIR, Gamma and LIBS. The main task of LIBS measurements in this project is the real time determination of the elemental contents of major and minor nutrients in soils, like calcium, magnesium, potassium. For this purpose, a special setup has been designed. The sample uptake operates with the help of a rotatable sample plate, on which the loose soil sample can be placed in form of a track. The sample plate circulates with different velocities to simulate the application on the field. To provide a higher intensity and a better re-producibility of the obtained signal, a double-pulse Nd:YAG laser (1064 nm) was used. In order to minimize dust formation from the soil during the operation of the laser, a dust removal by suction has been integrated When using relative methods such as LIBS, a suitable calibration curve is needed for absolute quantification. Within the I4S project a large number of soil samples from different testing grounds with known data of chemical composition, texture etc. is available. For the first calibration curves seven soil samples from different grounds in Germany were prepared as reference materials and four certified reference materials from China and Canada were purchased. With the help of these reference materials, calibration curves for different elements were initially calculated based on internal standard addi-tion. Copper was used as internal standard because of its low concentration in soils. The complex matrix of soils, as well as the influence of moisture and grain size in soils makes the absolute quantification by LIBS challenging. To overcome these influences, a calibration curve based on multivariate analysis was generated. Therefore, baseline correction on the second derivative with a Savitzky-Golay filter was followed by a partial least squares regression (PLSR). Multivariate analysis leads to noise reduction and neglection of interfering signals. Therefore, a better correlation between signal intensity and nutrient concentration is observed and a robust calibration curve is obtained.
The recent developments of inovative compact NMR spectrometers are therefore remarkable due to their possible application in process analytical technology (PAT) in an industrial environment without high maintenance requirements. spectroscopic methods, NMR spectroscopy offers some unique features for online reaction monitoring. However, those benefits have not been exploited for PAT applications so far. Within the CONSENS Project, the challenge to adapt a commercially available benchtop NMR spectrometer to the full requirements of an automated chemical production environment was tackled successfully. was provided in an explosion proof housing and involves a compact NMR spectrometer together with an automated data acquisition and evaluation unit, flow control, as well as data communication.
Monitoring chemical reactions is the key to process control. Today, mainly optical online methods are applied, which are calibration intensive. NMR spectroscopy has a high potential for direct loop process control while cutting the calibration and validation needs to an minimum and thus exhibiting short set-up times. Compact NMR instruments make NMR spectroscopy accessible in industrial and harsh environments for advanced process monitoring and control.
Intensified continuous processes are in focus of current research. Flexible (modular) chemical plants can produce different products using the same equipment with short down-times between campaigns and quick introduction of new products to the market. In continuous flow processes online sensor data and tight closed-loop control of the product quality are mandatory. Data analysis techniques are available but currently mostly used for off-line data analysis to detect the causes of variations in the product quality.
This is addressed within the EU’s Research Project CONSENS by the development and integration of a smart NMR module for process monitoring. The presented NMR module is provided in a mobile explosion proof housing and involves a compact spectrometer together with an acquisition unit and a programmable logic controller for automated data preparation (phasing, baseline correction), and evaluation. Such “smart sensors” provide the basis for the future project “Industrie 4.0”, and Industrial Internet of Things (IIoT), along with current requirements to process control, model based control, or soft sensing. The module transforms the acquired online spectra of various technically relevant reactions to either conventional 4‒20 mA signals as well as WiFi based OPC-UA communication protocols, which enables NMR-based advanced process control and funny discussions with plant managers along with automation and safety engineers.
Monitoring chemical reactions is the key to chemical process control. Today, mainly optical online methods are applied. NMR spectroscopy has a high potential for direct loop process control. Compact NMR instruments based on permanent magnets are robust and inexpensive analysers, which feature advantages like low maintenance, ease of use, and cryogen-free operation. Instruments for online NMR measurements equipped with a flow-through cell, possessing a good signal-to-noise-ratio, robustness, and meeting the requirements for integration into industrial plants (i.e., explosion safety and fully automated data analysis) are currently not available off the rack.
Intensified continuous processes are in focus of current research. Flexible (modular) chemical plants can produce different products using the same equipment with short down-times between campaigns and quick introduction of new products to the market. In continuous flow processes online sensor data and tight closed-loop control of the product quality are mandatory. Otherwise there is a huge risk of producing large amounts of out-of-spec (OOS) products. This is addressed in the European Union’s Research Project CONSENS by development and integration of smart sensor modules for process monitoring and control within such modular plant setups.
The presented NMR module is provided in an explosion proof housing with a module size of 57 x 57 x 85 cm and involves a compact 43.5 MHz NMR spectrometer together with an acquisition unit and a programmable logic controller for automated data preparation (phasing, baseline correction) and evaluation. Indirect Hard Modeling (IHM) was selected for data analysis of the low-field NMR spectra. A set-up for monitoring continuous reactions in a thermostated 1/8” tubular reactor using automated syringe pumps was used to validate the IHM models by using high-field NMR spectroscopy as analytical reference method.
Ferritic steels with chromium contents up to 13 wt% are used as materials for power plant components as boiler materials (< 2 wt% Cr) and super heater tubes (> 9 wt% Cr). These materials are subject to aggressive corrosion caused by hot gases such as CO2, H2O, O2 and SO2. Especially SO2 causes fatal corrosion even as a minor component. To examine sulfurous corrosion mechanisms, experiments with pure SO2 were conducted. A proper analysis of the material changes requires phase identification and quantification with a high lateral resolution within the corrosion scale.
Deposition of Redox-switchable rotaxanes on surfaces
Nature has created molecular machines which can perform a variety of different tasks. They exhibit defined operational pathways and order, resulting in directed macroscopic effects. Within the last decades researchers have been developing numerous artificial molecular machines which are so far mostly operating in solution. However, this represents a major obstacle for the generation of a macroscopic output, due to the random orientation of molecules in solution. As a general approach to this problem, interfaces have been used to generate ordered arrays of functional molecules.
Recently, we developed a new class of redox-switchable crown ether/ammonium-based [2]- and [3]rotaxanes which incorporate redox-active tetrathiafulvalene and naphthalene diimide units in their wheels resulting in emergent optoelectronic properties. Electrochemical stimuli influence the interactions between the two macrocycles of [3]rotaxanes and induce conformational changes.
In a proof-of-principle study [2]pseudorotaxanes were deposited on gold surfaces by “click”-reaction to azide-terminated self-assembled monolayers to generate ordered arrays of redox-active rotaxanes on-surface. X-ray photoelectron spectroscopy (XPS) confirms the successful deposition of a rotaxane monolayer, though angle-resolved near-edge X-ray absorption fine structure spectroscopy (NEXAFS) exhibits poor order of the rotaxanes.
Following, new terpyridine-stoppered rotaxanes will be synthesised opening a pathway for the deposition of [2]- and [3]rotaxanes in a layer-by-layer metal-mediated self-assembly procedure. This approach would allow for a programmed sequence of different rotaxanes in multilayers. Electrochemical on-surface switching will be investigated by angle-resolved NEXAFS spectroscopy, XPS, cyclic voltammetry and UV/Vis spectroscopy.
A more detailed understanding of the electron-transfer between the surface and the different rotaxane layers as well as of the on-surface switching could give rise to potential applications like optoelectric data-storage devices or potential-driven molecular motors.
Mycotoxins cause a variety of mold-related health risks which makes it necessary to further examine their metabolic pathways in human and other mammals. Beside standard in vitro assays with liver cell microsomes an increasing interest in new and rapid simulation techniques are playing a growing role in mycotoxin research.
Herein, the coupling of electrochemistry with liquid chromatography and mass spectrometry (EC/LC/MS) is presented as fast and simple method to investigate the oxidative fate of mycotoxins. For this case study, two food relevant mycotoxins (zearalenone and citrinin) were selected. Experiments were performed by using an electrochemical flow through cell integrated in the flow path of the autosampler of the chromatographic system. The reaction mixture was separated by a RP-C18 column and analyzed by a single quadrupole MS (Figure 1). Oxidation products were generated by applying potentials of 400, 800, 1200 and 1600 mV vs Pd/H2 using a glassy carbon working electrode. Different oxidation reactions like hydroxylation, dehydrogenation and dimerization lead to a diverse product pattern of the investigated mycotoxins.
In a comparative study, electrochemical generated reaction products were compared with metabolites produced by human and rat liver microsomes in vitro. The obtained data show that EC/LC/MS is a versatile and promising tool in mycotoxin research to support metabolic investigations of known and unknown mycotoxins.
Tandem MS experiments allow the fast acquisition of spectral datasets with enormous size and unprecedented content of information. The most commonly used method is undoubtedly collision induced dissociation (CID). The relatively young technical adaptation of CID to modern day Orbitrap experiments needs a higher confinement voltage and has accordingly been named higher-energy collisional dissociation HCD. Despite the name the absolute value of transferred energy per collision in HCD is lower than in CID. Since for many proteins CID and HCD result in comparable fragmentation patterns the two techniques are often treated as interchangeable. This approach is, however, not without pitfalls as other classes of biomolecules often exhibit strongly pronounced fragmentation specificity. As an example, MS/MS experiments on several 4-mer oligonucleotides were conducted employing both collision methods and the results were thoroughly compared. It is apparent that not only the total fragment yield but also the identity of the observed fragments differ significantly between the two methods.
Bacterial biofilms represent a ubiquitous form of microbial life on Earth. Due to an evolved armory of protean biological responses to external stimuli, bacteria are able to adhere to, colonize and thrive on virtually all surfaces, whether natural or synthetic, even in challenging environmental conditions. In addition to significant health risks, biofilms are among the salient contributors to the deterioration of metals and their alloys, thereby causing safety risks for technical equipment. Hence, understanding the interaction mechanisms of electroactive sessile bacteria with metal surfaces is vital for facilitating the development of efficient control strategies and novel anti-fouling surfaces in various industries and technologies.
The present study focusses on a combined spectroelectrochemical approach, melding methods of surface enhanced Raman spectroscopy (SERS) and electrochemical techniques, to investigate the chemical characteristics and redox activities of electroactive bacteria during the initial stages of biofilm formation. Gold has been selected as a model substrate due to its inert character, considerably high surface enhancement factor, as well as its capability to allow surface chemistry modifications and substrate polarization in order to precisely control the surface charge. Square wave voltammetry (SWV) and cyclic voltammetry (CV) studies have been performed for quantitative determination of flavin concentration and electrochemical impedance spectroscopy (EIS) has been utilized to study the changes in electrochemical processes within biofilms during different stages of growth. Shewanella sp. have been chosen as microorganisms within this work due to their versatile exoelectrogenic respiratory behavior and their distinct ability to reduce metals via extracellular electron transfer mechanisms involving self-secreted electron shuttle redox molecules such as flavins. To further explicate the process of diffusion of flavins within biofilms, a model system has been developed to simulate the structural features of the bacterial extracellular polymeric substances typically found in biofilms. This has been achieved by creating hydrogel films comprised of calcium-cross-linked alginate. The results demonstrate an interplay of factors contributing to the initial phases of bacterial settlement and biofilm formation as a function of environmental parameters. Furthermore, the results allow insight into the diffusion of flavins, much like they would in a natural biofilm, and how their redox behavior affects the biofilm development.
Discotic liquid crystals (DLC) filled into cylindrical nanopores exhibit a liquid crystalline phase with their molecules arranged in hexagonal columns. The columns orient perpendicular (radially) or parallel (axially) with respect to the pore axis depending on surface anchoring conditions and pore size. Axially oriented columns enable the fabrication of organic nanowires utilizing the high conductivity in the stacking direction due to overlapping π-electrons. This leads to interesting applications in e.g. organic semiconductorbased devices. The molecular ordering of the liquid crystalline columns can be probed by temperature dependent optical retardation measurements supplemented by X-ray diffraction sensitive to the translational order.
We investigated the DLC 2, 3, 6, 7, 10, 11 - hexakis [hexyloxy] triphenylene (HAT6) embedded in nanoporous alumina and silica membranes as function of the pore diameter (12 nm - 180 nm). Due to their hydrophilic nature porous membranes enforce face-on anchoring leading to a radial orientation. To obtain edge-on anchoring conditions, and thus favoring axial orientation, the silica membrane surface is chemically modified. The optical retardation measurements show that the columns orient radially in these membranes independent of the anchoring conditions. Interestingly, a quantized phase transition of each molecular layer is found indicated by a distinct increase of the optical orientation. Additionally, an axial orientation of HAT6 filled into alumina membranes with a pore diameter of 25 nm is achieved. A Landau-de Gennes ansatz semi-quantitatively describes the phase transition behavior observed. X-ray diffraction experiments performed at the 3rd generation synchrotron radiation source PETRA III at DESY giving detailed information about the translational order support these findings. Summarizing, this study shows the existence of a phase transition in the molecular range as well as the suitability of the membrane with 25 nm pores as a template for preparing organic nanowires.
This presentation introduces a novel robotic platform for aerial remote gas sensing. Spectroscopic measurement methods for remote sensing of selected gases lend themselves for use on mini-copters, which offer a number of advantages for inspection and surveillance. No direct contact with the target gas is needed and thus the influence of the aerial platform on the measured gas plume can be kept to a minimum. This allows to overcome one of the major issues with gas-sensitive mini-copters. On the other hand, remote gas sensors, most prominently Tunable Diode Laser Absorption Spectroscopy (TDLAS) sensors have been too bulky given the payload and energy restrictions of mini-copters. Here, we introduce and present the Unmanned Aerial Vehicle for Remote Gas Sensing (UAV-REGAS), which combines a novel lightweight TDLAS sensor with a 3-axis aerial stabilization gimbal for aiming on a versatile hexacopter. The proposed system can be deployed in scenarios that cannot be addressed by currently available robots and thus constitutes a significant step forward for the field of Mobile Robot Olfaction (MRO). It enables tomographic reconstruction of gas plumes and a localization of gas sources. We also present first results showing the gas sensing and aiming capabilities under realistic conditions.
Bridge monitoring using embedded ultrasonics First results from the BLEIB reference structure
(2017)
The BLEIB reference structure The structure is a two-span, 24 m long inverse u-shaped post-tensioned concrete beam. Fibre optic sensing cables, RFID sensors and ultrasonic transducers are permanently embedded. Other sensing techniques (vibrational, optical, ultrasonic, mechanical) are applied externally. Tension can be adjusted. Loads can be placed at arbitrary locations. Limited damage is introduced to one span. The BLEIB reference structure is located at BAM‘s test site in Horstwalde, south of Berlin. Ultrasonic transducer before concreting.
Embedded ultrasonic transducers 14 piezo transducers have been embedded before concreting. They are located in five sections, two close to the centers of both spans respectively and one above the central bearing.
Load experiment and data evaluation In a first experiment load 2 (weight 2 t) was moved three times along the southern (right) span. The tension forces were modified as well.
Ultrasonic transmission measurements were repeated over time and evaluated using Coda Wave Interferomerry (CWI), which determines correlation coefficients and relative velocity changes as subtle indicators for loads and other changes in the material.
Seismic wave velocities are related to elastic moduli and other properties and can serve as indicators for changes in the material. They are conventionally determined by active measurements. Using ideas from seismic interferometry Determination from stacked cross-correlations of registrations of man- made and natural noise (“passive seimics“) is an effective alternative, as these data might be available from vibration monitoring anyway. The validity of this approach is demonstrated by a simple experiment based on recordings of man made noise using accelerometers at the reference structure. The s-wave (or more probable. guided wave) velocity was determined to be 2100 m/s in both active and passive experiments.
Seismic wave velocities are related to elastic moduli and other properties and can serve as indicators for changes in the material. They are conventionally determined by active measurements. Using ideas from seismic interferometry determination from stacked cross-correlations of registrations of man-made and natural noise (“passive seimics“) is an effective alternative, as these data might be available from vibration monitoring anyway. The validity of this approach is demonstrated by a simple experiment based on recordings of man made noise using accelerometers at the reference structure. The s-wave (or more probable. guided wave) velocity was determined to be 2100 m/s in both active and passive experiments.
Oxidative stress is produced by an imbalance between free radical production and biological system's ability to detoxify the reactive intermediates and repair the resulting damage. In the human eye the main causes of oxidative stress are the daily exposure to sunlight, chemical insults and the special microenvironment with abundant photo-sensitizers. For this reason, oxidative stress has been associated several ocular diseases, like aged-related macular degeneration (AMD). On the other hand, Metallothioneins (MTs) are a family of low molecular weight (6–7 kDa), cysteine-rich (30%) and metal-binding proteins. The cysteine residues can bind metal atoms such as zinc, copper, and cadmium via thiolate bonds. These proteins have a wide range of functions including defense against oxidative damage, intracellular storage and transport and metabolism of metal ions. The antioxidant properties of MTs reside in their capacity to capture and neutralize free radicals by binding and transferring zinc ions in a redox-dependent fashion, forming the antioxidant system Zinc-Metalothionein (Zn-MT).
Highly sensitive analytical tools are required to study the relationship between Zn and MTs in sections from ocular tissues. These methodologies should permit the simultaneous localization (bioimaging) of metals and proteins. Laser ablation (LA) coupled to ICP-MS has shown a huge potential for bioimaging studies in biological tissues. In addition, the use of metal nanoclusters (NCs) as elemental tags will provide signal amplification, compared with other tags traditionally employed (e.g. polymeric tags). To this end, antibodies with gold nanoclusters (AuNCs) will be used in combination with LA-ICP-MS for the detection of different metallothioneins (MT 1/2 and 3) directly into the ocular tissue sections.
- Methods:
The AuNCs synthesized were bioconjugated with an Anti-MT 1/2 antibody and with Anti-MT 3 antibody. Next, using ocular tissue sections (5 microns thick) from different donors the immunoassays were performed. After the immunoassay protocol, imaging studies were carried out by LA-ICP-MS as well as by fluorescence (confocal microscope) in order to compare both methodologies.
- Results:
The MTs (measuring the Au signal) and the coordinated metals distribution (Zn and Cu) were successfully carried out in human ocular tissues, including sclera, choroid, retina and retinal pigment epithelium regions. The image patterns found in ocular tissues were in agreement with those reported by conventional immunohistochemistry.
- Conclusions:
It is possible to know the distribution of MT proteins and different coordinated metals using bioconjugated AuNCs and LA-ICP-MS. Proposed analytical tools could help to better understand the roles of the antioxidant system Zinc-Metalothionein in the eye.
Assessment and validation of various flow cell designs for quantitative online NMR spectroscopy
(2017)
Compact nuclear magnetic resonance (NMR) instruments make NMR spectroscopy and relaxometry accessible in industrial and harsh environments for reaction and process control. Robust field integration of NMR systems have to face explosion protection or integration into process control systems with short set-up times. This paves the way for industrial automation in real process environments.
The design of failsafe, temperature and pressure resistant flow through cells along with their NMR-specific requirements is an essential cornerstone to enter industrial production plants and fulfill explosion safety requirements. NMR-specific requirements aim at full quantitative pre-magnetization and acquisition with maximum sensitivity while reducing sample transfer times and dwell-times. All parameters are individually dependent on the applied NMR instrument. Luckily, an increasing number of applications are reported together with an increasing variety of commercial equipment. However, these contributions have to be reviewed thoroughly.
The performance of sample flow cells commonly used in online analytics and especially for low-field NMR spectroscopy was experimentally and theoretically investigated by 1H-NMR experiments and numerical simulations. Here, we demonstrate and discuss an automated test method to determine the critical parameters of flow through cells for quantitative online NMR spectroscopy. The setup is based on randomized setpoints of flow rates in order to reduce temperature related effects. Five flow cells and tubings were assessed and compared for high-field as well as low-field NMR spectrometers.
Knowledge about feeding behavior is essential to determine trophic interactions and reconstruct predator-prey relationships in modern and past foodwebs. Traditionally, nitrogen isotopes (δ15N) of collagen are used to quantify the ingestion of animal protein, however collagen usually does not preserve over geological time scales. To infer the diet of extinct vertebrates from fossil material more resistant dietary proxies such as Ca and Mg isotopes are needed, which are major elements in the bioapatite of bones and teeth. Magnesium is a bio-essential element that replaces calcium in the bioapatite lattice and bone and enamel δ26Mg values of extant mammals increase systematically along the foodchain [1, 2].
The existing δ26Mg data, however, is scarce, in particular with respect to carnivores, thus still limiting the capability of this dietary proxy to reliably determine trophic differences between plant- and animal-feeders. To better constrain trophic-level effects recorded in Mg isotopes, we analyzed δ26Mg of bioapatite from modern mammals with a focus on faunivores, both carnivores and as yet unexplored insectivores.
The trophic level effect of δ26Mg is influenced by the geological substrate which causes isotope variability in δ26Mg of faunal remains between different ecosystems [1, 2]. Therefore, as first-order proxy for sample provenance and to assess potential influences of the bedrock substrate of the animals´ habitats on δ26Mg of bones and teeth, we measured the 87Sr/86Sr on the same specimens. This information will enable us to refine trophic level effects and determine whether δ26Mg can be used to distinguish different faunivores isotopically. This will be of paramount importance for dietary reconstructions of trophic niches in fossil foodwebs.
[1] Martin et al. (2014) Geochmica Cosmochimica Acta 130, 12-20. [2] Martin et al. (2015) Proceedings of the National Academy of Sciences 112, 430-435.
Qualitative reference materials (RM) cover a wide range of the overall RM market. Proficiency testing providers attract up to a thousand of participants in PT schemes purely oriented on qualitative results. The RM used for these kinds of PT are poorly regulated, nevertheless with a more and more general acceptance of accreditation in the field of RM production and PT provision, there is an ever increasing interest in assessing producers and providers according to rules already well accepted in the field of quantitative analysis.
The basic governing document, ISO 17034:2016, is written in a form that, at least for the overwhelming majority of requirements, may be applied to both qualitative and quantitative RM. However, problems remain. In particular, the expression of uncertainty of a purely qualitative result is still unresolved, and under discussion, the latter now lasting already dozens of years.
Some handles would be needed. In the poster, existing approaches and some pragmatic, new ways to tackle the problem are displayed and discussed.
Anomalous surface composition in thin films of a poly(vinyl methyl ether) / polystyrene blend
(2017)
Highly surface-sensitive X-ray photoelectron spectroscopy at HE-SGM beamline revealed in the outermost region (< 2nm) of thin films (15 -65 nm) of PVME/PS blends a relative high amount of PS, whereas in slightly deeper regions PVME was enriched. Such enrichment of PVME in the whole near-surface region was proposed in former investigations based on conventional XPS studies.
Hepcidin-25 has attracted much attention ever since its discovery in 2001. It is widely recognized that this liver produced peptide hormone plays a major role in the regulation of iron levels in mammals and can reveal important clinical information about several pathological states in patients suffering from iron-related disorders.
With the aim to tackle the current difficulties in hepcidin quantification and improve the status of this promising biomarker in the clinical field, we developed a rapid and robust analytical strategy for the quantification of hepcidin-25 in human samples based on HPLC-MS/MS (QqQ) to be implemented in routine laboratories. The novelty of the method is the use of special HPLC vials to avoid adsorptive losses due to the basic character of the peptide that causes interaction with the silanol groups of the vial’s glass surface. Up to 90% decrease in the MS/MS signal was observed, when commercial HPLC vials were used, while vials treated with 3-(2-aminoethylamino)propylmethyl-dimethoxysilane or 1H,1H,2H,2H-perfluorooctyltriethoxysilane, leading to no significant losses in the dynamic range of physiological hepcidin-25 mean serum levels (10-20 µg/L).
Careful analytical validation was performed for determining the reproducibility, repeatability, limit of quantification (0.5 µg/L) and linearity (0.5-40 µg/L) of the method. Serum samples from 9 healthy volunteers were analyzed with a median hepcidin-25 level of 3.3 µg/L, comparable to results reported in the literature.
The synthesis of TiO2 nanoplatelets with fluorine-containing reactants is carried out using Ti (IV) butoxide as precursor and concentrated HF as shape controller, the final product requires a working up in order to eliminate or at least to reduce the amount of residual fluorides, which is realized here by well-defined thermal treatment.
Qualitative investigation of the bulk elemental composition by means of EDX of TiO2 nanoparticles (NPs) has identified fluorine in case of the as-synthesized samples. EDX spectra of thermally treated products exhibit either a fluorine content close to the limit of detection. The latter holds also true for the reference sample, TiO2 NPs of bipyramidal shape and prepared by a different synthesis route. For differentiation whether fluorine is present in the bulk or at the surface of the TiO2 nanoplatelets, top-surface sensitive AES and ToF-SIMS has been applied. Secondary ions of fluorine are detected in ToF-SIMS spectra of all samples, but could be roughly quantified by measurement of same reference sample as for EDX, namely TiO2 nano-bipyramids. This revealed that the amount of fluorine within1 nm depth beneath the surface is reduced in the thermally treated specimen compared to the raw product down to a content about as low as in the reference sample. AES allows analyzing analysis of the first few nanometers from the top-surface of individual NPs by point analysis. An F KLL peak has been detected at the surface of samples of as-prepared TiO2 nanoplatelets under optimized measurement conditions, but was not detectable after their calcination, which is in agreement with ToF-SIMS results. Moreover, high resolution AES on single TiO2 nanoplatelets elucidated that the surface atomic layers surrounding the TiO2 nanopaltelet contain fluorides before thermal treatment of the NPs.
Hydrothermal synthesis of anatase TiO2 nanosheets with a high fraction of exposed {001} facets and related high photocatalytic activity - as an alternative to bipyramidal anatase TiO2 nanoparticles mainly exposing the {101} facets. The scope of the material preparation work is the thermal reduction of residual fluorides from HF (capping agent) induced during the synthesis of TiO2 nanosheets by calcination at 873K. The analytical task consists of detection and localization of fluorine present at the surface and/or in the bulk of TiO2 nanosheets before and after calcination by SEM/EDX, Auger electron spectroscopy and ToF-SIMS.
The ambient air quality around residential areas is influenced by industrial objects, including industrial sewage, livestock farming and landfill sites. These sites are generating malodours or toxic gases involving degradation of ambient air quality, which may constitute a risk in human health if maximum emission limits are exceeded. Therefore, appropriate tools allowing detection of harmful or bad odorous, subsequently contributing to a reduction of odour nuisance are greatly needed. The aim of this study was to demonstrate the capability of an electronic nose E-nose to discriminate various gas samples collected from six different sites from the agglomeration of Meknès city corresponding to municipal landfill, in the city at 2 km of landfill, industrial estate wastewater, traffic road, and sheep breeding. The investigations were carried out with an E-nose system based on an array of six-commercial MQ sensors. Further, a pattern recognition technique known as Principal Component Analysis (PCA), Linear Discriminent Analysis (LDA), and Support Vector Machines (SVMs) was implemented to study the discrimination capability of the sensor array. PCA results demonstrate excellent discriminating ability of the dataset with a score of 99.47 %. Additionally, another measurement database containing 12 air atmospheric samples was projected on the previously built PCA model to check the stability of the E-nose. The LDA was applied to the same dataset and showed a good discrimination between the ambient air samples of the six sites. Furthermore, SVMs technique was also used to build a classifier and reached a score of 100 % success rate in the recognition of the analysed samples. The obtained results of six areas demonstrate the increasing interests and the applicability of E-noses for ambient air quality classification of six areas caused by emitted decomposed organic matters.
Leaking methane (CH4) from infrastructures, such as pipelines and landfills, is critical for the environment but can also pose a safety risk. To enable a fast detection and localization of these kind of leaks, we developed a novel robotic platform for aerial remote gas sensing. Spectroscopic measurement methods for remote sensing of selected gases lend themselves for use on mini-copters, which offer a number of advantages for inspection and surveillance over traditional methods. No direct contact with the target gas is needed and thus the influence of the aerial platform on the measured gas plume can be kept to a minimum. This allows to overcome one of the major issues with gas-sensitive mini-copters. On the other hand, remote gas sensors, most prominently Tunable Diode Laser Absorption Spectroscopy (TDLAS) sensors have been too bulky given the payload and energy restrictions of mini-copters. Here, we present the Unmanned Aerial Vehicle for Remote Gas Sensing (UAV-REGAS), which combines a novel lightweight TDLAS sensor with a 3-axis aerial stabilization gimbal for aiming on a versatile hexacopter. The proposed system can be deployed in scenarios that cannot be addressed by currently available robots and thus constitutes a significant step forward for the field of Mobile Robot Olfaction (MRO). It enables tomographic reconstruction of gas plumes and a localization of gas sources. We also present first results showing its performance under realistic conditions.
Leaking methane (CH4) from infrastructures, such as pipelines and landfills, is critical for the environment but can also pose a safety risk. To enable a fast detection and localization of these kind of leaks, we developed a novel robotic platform for aerial remote gas sensing. Spectroscopic measurement methods for remote sensing of selected gases lend themselves for use on mini-copters, which offer a number of advantages for inspection and surveillance over traditional methods. No direct contact with the target gas is needed and thus the influence of the aerial platform on the measured gas plume can be kept to a minimum. This allows to overcome one of the major issues with gas-sensitive mini-copters. On the other hand, remote gas sensors, most prominently Tunable Diode Laser Absorption Spectroscopy (TDLAS) sensors have been too bulky given the payload and energy restrictions of mini-copters. Here, we present the Unmanned Aerial Vehicle for Remote Gas Sensing (UAV-REGAS), which combines a novel lightweight TDLAS sensor with a 3-axis aerial stabilization gimbal for aiming on a versatile hexacopter. The proposed system can be deployed in scenarios that cannot be addressed by currently available robots and thus constitutes a significant step forward for the field of Mobile Robot Olfaction (MRO). It enables tomographic reconstruction of gas plumes and a localization of gas sources. We also present first results showing its performance under realistic conditions.
Innovation is the catalyst for the technology of the future. It is important to develop new and better technologies that can continuously monitor the environmental impact, e.g., for air quality control or emission detection. In the recently at BAM developed Universal Pump Sensor Control (UPSC3) module, different components and sensors are fused. The combination of the individual components makes the UPSC3 module an excellent monitoring and reference system for the development and characterization of gas specific sensors. Measurements over long periods are possible, for mixed gas loads or for certain gas measurements. The system is part of a mobile sensor network of several sensor units, which can also be used as standalone systems.
The motivation and objective of this research is to develop gas sensors based on fluorescence detection with range of ppm / ppb. For this task a reference system is required, which contains volatile organic compound (VOC) sensors for reference data from different scenarios. The integrated multi-sensor unit can measure different gases through the integrated 3-fold VOC sensor, which can be adapted to the addressed scenario. . The system-integrated flow control, with pump and flow sensor, allows the gas molecules to be transported directly to the VOC sensor. The entire measurement is permanently stored on an integrated memory card. If the previously determined limit range is exceeded, an alarm is generated. The system is an important tool towards further developments in the field of gas sensors and is primarily used for the validation of chemically based gas sensors.
Pollutants of low molecular weight, such as drug residues, are in the focus of water quality assessment: some of them, like carbamazepine are only partially degraded in wastewater treatment plants. Thus, these pollutants can serve as marker substances for elimination efficiencies. Monitoring water quality demands for selective, high-throughput and multi-target analytical methods. Immunoassays, such as ELISA, offer the possibility to be highly sensitive and selective due to the specific recognition by high affinity of target molecules to antibodies (Abs). Batch-wise processing in microtiter plates allows for the necessary high-throughput, however only a single analyte can be determined within one measurement.
To overcome these disadvantages, we developed a four-plex microbead-based flow cytometric assay, which is adaptable for the microtiter plate format. The modular and self-prepared bead support consists of polystyrene-core/silica-shell particles. While, the polystyrene core is used for encoding, by introducing different amounts of fluorescent dyes, the silica shell creates a solid support for the immunoassay: The target analytes, three drugs, carbamazepine, diclofenac and caffeine and the fecal marker isolithocholic acid are coupled covalently to the surface via NHS chemistry to amino groups on the surface.
For determination of the pollutants, a mixture of specific Abs is incubated with the samples, to bind competitively on the “anchor” molecules on the surface of the beads or the analyte in solution. Bound antibodies are then visualized via fluorescent dye-labelled secondary Abs. Flow-cytometry allows for decoding of the beads and signal read-out, without washing the system. In order to decrease non-specific binding, we investigated different types of surface modifications, finding, that a PEG-based surface is suitable to support our immunoassay format. For maximum sensitivity, a design-of-experiment approach was chosen for optimization of the assay parameters. The resulting immunoassay is appropriate to quantify the pollutants in the low μg/L-range.
Besides their plasticizing effect, superplasticizers (SPs) are known to retard the hydration of inorganic systems such as cement. Despite their frequent use, the understanding of these highly complex systems is still limited and the relevant parameters, which control the interaction between SPs, and cement components and reaction products are in the focus of ongoing research activities.[1] Optical methods have been successfully used for the analysis and monitoring of the interactions between a broad variety of nanoscale and molecular systems like nanoparticles of various chemical composition and different types of organic ligands or biomolecules. The potential of these methods to study processes at the interface between (hydrated) particles and the fluid phase at a very early stage of concrete formation could reveal possible mechanisms of interaction.
This investigation focuses on the study of organic/inorganic mixtures consisting of cement (CEM) and cement phases (C3S and C3A) in the presence of polycarboxylate ether and organic dyes in aqueous solution (particularly alkali resistant dyes) at a water to powder ratio of 1. Diffuse reflectance as well as steady state and time resolved fluorescence spectroscopy of the above mentioned mixtures were evaluated. Based upon changes of the intensity of the reflectance and fluorescence signal and spectral changes of the dye, acting as optical reporter, a model for the interactions of dye, PCE and cement (including different cement phases) was derived which describes the very first stage of cement hydration.
The EC recommendation for the definition of nanomaterial [2011/696/EU] requires the quantitative size determination of constituent particles in samples down to 1 nm. Accordingly, a material is a nanomaterial if 50 % or more of the particles are in the size range 1-100 nm. The fact that engineered nanomaterials already exist in many industrial and consumer products challenges the development of measurement methods to reliably identify, characterize and quantify their occurrence as substance and in various matrices.
The EU FP7 NanoDefine project [www.nanodefine.eu] has addressed this challenge by developing a robust, readily implementable and cost-effective measurement strategy to obtain quantitative particle size distributions and to distinguish between nano and non-nano materials according to the EU definition. Based on a comprehensive evaluation of existing methodologies and intra- and inter-lab comparisons, validated measurement methods and instrument calibration procedures have been established to reliably measure the size of particles within 1-100 nm, and beyond, including different shapes, coatings and chemical compositions in industrial materials and consumer products. Case studies prove their applicability for various sectors, including food, pigments and cosmetics.
Main outcome is the establishment of an integrated tiered approach including rapid screening (tier 1) and confirmatory methods (tier 2), and a user manual to guide end-users, such as manufacturers, in selecting appropriate methods. Another main product is the “NanoDefiner” e-Tool allowing the standardised / semi-automated selection of appropriate methods for material classification according to the EU definition. Results also contribute to standardization efforts, such as CEN TC 352 or ISO TC 229.
Laser ablation with inductively coupled plasma is still more used in life science as biology and biomedicine and the utilization of metals and proteins determination simultaneously is also growing up. We have developed a new strategy of labeling of antibody (it can specific binds to proteins) by nanoparticles and quantum dots which is composed of thousands of atoms and thus increases the sensitivity enormously and of course decreases the Limit of detection, compare to lanthanoids labeling. The ability of successfully tagged antibodies bound to Antigen (protein) was proved by dot blot on membrane imaged by LA-ICP-MS.
Most crucial for components of complex shape or heterogeneous micro structure, precise control of sintering has decisive influence on dimensional accuracy, mechanical integrity and reliability of sintered components. In these cases, only in situ 3D high-temperature shape screening during shrinkage would allow revealing temporary sinter warpage and hereby caused potential defects. Against this background, nokra Optische Prüftechnik und Automation GmbH, HTM Reetz GmbH and BAM developed a testing device for in situ 3D shape screening for ceramic and glass-ceramic tapes up to 1000°C by means of high-temperature laser profilometry. The local repeatability of the sample-sensor distance (sample height profile) is 10 µm at 1000°C. Current work is focused on dropping these restrictions in sample shape and temperature. In a second testing device, currently being in development, samples up to 5 cm x 5 cm x 5 cm can be measured at temperatures up to 1500°C.The presentation illustrates the current state of this work and possible applications of the method.
Graphene derivatives have shown great promise in the field of pathogen binding and sensing. Due to their diverse applications, they show a variety of activities that range from bacterial adhesion to bacterial resistance. Therefore, domination of the graphene-pathogen interactions is highly relevant for producing 2D platforms with the desired applications. In order to gain control over the interactions between graphene and biosystems, mechanisms should be fully understood. The surface functionality of graphene is one of the most important factors that dominates its interactions with biosystems and pathogens. Covalent functionalization is a robust method through which functionality, chemical structure, and subsequently physicochemical properties of graphene are abundantly manipulated. A critical issue for preparing graphene-based 2D materials with a defined surface structure, however, is controlling the functionalization in terms of number, position, and type of functional groups.
Graphene and its derivatives have recently attracted much attention for sensing and deactivating pathogens. However, mechanism of multivalent interactions at the graphene-pathogen interface are not fully understood. Since different physicochemical parameters of graphene play a role at this interface, control over graphene’s structure is necessary to study the mechanism of these interactions. In this work, zwitterionic graphene nanomaterials (ZGNMs) were synthesized with defined isoelectric points and exposure, in terms of polymer coverage and functionality. Then, the switchable interactions of ZGNMs with E. coli were investigated to study the validity of the generally proposed “trapping” mechanism for inactivating pathogens by functionalized graphene derivatives. The ZGNMs were able to controllably trap and release E. coli by crossing their isoelectric points.