6 Materialchemie
Filtern
Erscheinungsjahr
- 2020 (284) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (158)
- Vortrag (73)
- Posterpräsentation (17)
- Beitrag zu einem Sammelband (10)
- Sonstiges (6)
- Forschungsdatensatz (5)
- Handbuch (4)
- Zeitschriftenheft (Herausgeberschaft für das komplette Heft) (4)
- Beitrag zu einem Tagungsband (3)
- Sammelband (Herausgeberschaft für den kompletten Band) (2)
Schlagworte
- Nanoparticles (41)
- Electron microscopy (14)
- Laser-induced periodic surface structures (LIPSS) (14)
- SAXS (12)
- XPS (12)
- Nanoparticle (11)
- BAMline (10)
- MALDI-TOF MS (10)
- Mechanochemistry (10)
- Particle size distribution (10)
Organisationseinheit der BAM
- 6 Materialchemie (284)
- 6.3 Strukturanalytik (84)
- 6.1 Oberflächen- und Dünnschichtanalyse (81)
- 6.6 Physik und chemische Analytik der Polymere (50)
- 6.2 Material- und Oberflächentechnologien (39)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (30)
- 1 Analytische Chemie; Referenzmaterialien (15)
- 6.7 Materialsynthese und Design (14)
- 5 Werkstofftechnik (12)
- 4 Material und Umwelt (9)
Paper des Monats
- ja (3)
Eingeladener Vortrag
- nein (73)
Functional materials for energy conversion are important technology drivers needed for the implementation of low carbon energy. Therefore, researchers commonly focus on improving the intrinsic properties of a functional material. However, for applications, the extrinsic properties are at least as important as the intrinsic ones. Consequently, it is important to investigate and understand the external and internal structure of semi-finished products and especially defect dependent properties. The extrinsic properties may change during application and the life cycle of the material as well as through processing and molding steps. Our studies show how X-ray tomographic (XCT) investigations can contribute to structure investigations in composites and massive samples using the example of magnetic materials for energy conversion.
Various applications for artificial intelligence in the context of spectroscopy will be presented. in particular, examples from BAMline will be presented. After a short introduction to synchrotron radiation, artificial intelligence algorithms for the quantification of X-ray fluorescence measurement are discussed. In the second example, information retrieval by natural language processing is discussed.
Synchrotron radiation sources with their unique properties in terms of intensity, polarization and adjustability offer a wide range of possibilities in materials research. A basic introduction about the creation and special properties of synchrotron radiation will be given. Examples of current work at BAMline, the high-energy measuring facility of the Federal Institute for Materials Research and Testing at the synchrotron BESSY, are used to illustrate the possibilities and limitations of existing measuring methods.
In this talk, the features of X-ray fluorescence analysis with synchrotron radiation will be presented. First, the basics of the origin of synchrotron radiation and X-ray fluorescence analysis and the experimental setup will be discussed. Then, examples of trace element detection, micrometer resolution, and application of the X-ray color camera will be shown.
Gold ist eines der sieben schon im Altertum bekannten Metalle und wurde wg. seines Glanzes und seiner Seltenheit von alters her als Tauschmittel und zur Herstellung von Schmuck benutzt. Außerdem ist es einfach bearbeitbar und weitestgehend gegen chemische Einflüsse resistent. Die Untersuchungen von Gold mit synchrotronstrahlungsangeregter Röntgenfluoreszenzanalyse sind zerstörungsfrei und geben Auskunft über die in der untersuchten Probe vorhandenen chemischen Elemente. Bei den hier vorgestellten Untersuchungen an der BAMline stehen Fragestellungen wie Herkunft, Herstellungsverfahren und Zusammengehörigkeit von Goldfunden im Vordergrund. Die verschiedenen Fragestellungen werden an einer Reihe von Beispielen erläutert die vom Wikingerschatz aus Hiddensee über die Himmelsscheibe von Nebra bis hin zu Funden aus Ägypten langen. Der Fund von Bernstorf wird ausführlich diskutiert.
Various applications for artificial intelligence in the context of spectroscopy will be presented. in particular, examples from bamline will be featured. After a short introduction to synchrotron radiation, artificial intelligence algorithms for the quantification of X-ray fluorescence measurement are discussed. In the second example, information retrieval by natural language processing is reviewed. As a last example the reconstruction of measurements with the X-ray color camera and coded apertures is presented.
Trace elements are chemical elements whose concentration in a material is very low. The exact definition depends on the application and varies for example between 100 micrograms per gram in analytical chemistry and 1000 micrograms per gram in geology. The ability to detect trace elements fast and quantitatively is of great importance in many areas of science and technology. With its high brilliance and flexibility in the excitation conditions, synchrotron radiation is an ideal tool for detecting traces even in small sample quantities. In this contribution I will report about the use of X-ray fluorescence(XRF)for qualitative and quantitative element sensitiveanalysis. In addition to the fundamentals of XRF and its quantification methods, the advantages and problems of different geometries like e.g. microXRF, Total Reflection X-ray Fluorescence (TXRF)or Double Dispersive XRF (D²XRF) will be discussed. Practical examples from BAMline from the research fields of medicine, geology and archaeometry will complete the lecture.
In this work, we describe the use of artificial neural networks for the quantification of X-ray fluorescence measurements. The training data were generated using Monte Carlo simulation, which avoided the use of adapted reference materials. The extension of the available data set by means of an ANN to generate additional data was demonstrated. Particular emphasis was put on the comparability of simulated and experimental data and how the influence of deviations can be reduced. The search for the optimal hyperparameter, manual and automatic, is also described. For the presented case, we were able to train a network with a mean absolute error of 0.1 weight percent for the synthetic data and 0.7 weight percent for a set of experimental data obtained with certified reference materials.
The hexapeptide hIAPP22–27 (NFGAIL) is known as a crucial amyloid core sequence of the human islet amyloid polypeptide (hIAPP) whose aggregates can be used to better understand the wild‐type hIAPP′s toxicity to β‐cell death. In amyloid research, the role of hydrophobic and aromatic‐aromatic interactions as potential driving forces during the aggregation process is controversially discussed not only in case of NFGAIL, but also for amyloidogenic peptides in general. We have used halogenation of the aromatic residue as a strategy to modulate hydrophobic and aromatic‐aromatic interactions and prepared a library of NFGAIL variants containing fluorinated and iodinated phenylalanine analogues. We used thioflavin T staining, transmission electron microscopy (TEM) and small‐angle X‐ray scattering (SAXS) to study the impact of side‐chain halogenation on NFGAIL amyloid formation kinetics. Our data revealed a synergy between aggregation behavior and hydrophobicity of the phenylalanine residue. This study introduces systematic fluorination as a toolbox to further investigate the nature of the amyloid self‐assembly process.
This is the repository of all experimental raw data used in the Scientific Reports publication "Specific adsorption sites and conditions derived by thermal decomposition of activated carbons and adsorbed carbamazepine" by Daniel Dittmann, Paul Eisentraut, Caroline Goedecke, Yosri Wiesner, Martin Jekel, Aki Sebastian Ruhl, and Ulrike Braun.
It includes
- overview_measurements.xlsx and overview_measurements.ods containing a list of all TGA experiments (TGA, TGA-FTIR, TED-GC-MS, and ramp-kinetics)
- TED-GC-MS.zip containing gas chromatography-mass spectrometry experimtent files for the Chemstation and OpenChrom
- TGA.zip containing thermogravimetric analyses raw data on evolved gas analyses experiments (TGA-FTIR and TED-GC-MS)
- TGA_kinetics.zip containing thermogravimetric analyses raw data on decomposition kinetic experiments (ramp-kinetics)
- TGA-FTIR.zip containing Fourier-transform infrared spectroscopy series files for OMNIC
- XRF.zip containing x-ray flourescence data on elemental composition
Dataset and Jupyter worksheet interpreting the (results from) small- and wide-angle scattering data from a series of boehmite/epoxy nanocomposites. Accompanies the publication "Competition of nanoparticle-induced mobilization and immobilization effects on segmental dynamics of an epoxy-based nanocomposite", by Paulina Szymoniak, Brian R. Pauw, Xintong Qu, and Andreas Schönhals.
Datasets are in three-column ascii (processed and azimuthally averaged data) from a Xenocs NanoInXider SW instrument. Monte-Carlo analyses were performed using McSAS 1.3.1, other analyses are in the Python 3.7 worksheet. Graphics and result tables are output by the worksheet.
This dataset is a complete set of raw, processed and analyzed data, complete with Jupiter notebooks, associated with the manuscript mentioned in the title.
In the manuscript, we provide a "systems architecture"-like overview and detailed discussions of the methodological and instrumental components that, together, comprise the "MOUSE" project (Methodology Optimization for Ultrafine Structure Exploration). Through this project, we aim to provide a comprehensive methodology for obtaining the highest quality X-ray scattering information (at small and wide angles) from measurements on materials science samples.
The Dark Side of Science
(2020)
Development and characterization of starch film and the incorporation of silver nanoparticles
(2020)
Starch is one of the biopolymers being used for bioplastic synthesis. For production, starch can be combined with different plasticizers, starches from different plant sources and even with nanomaterials to improve or to add film properties. The challenge of adding these, e.g. in the form of silver nanoparticles (AgNp) is to determine the concentration so as to avoid impairing the properties of the film, agglomeration or altering the visual characteristics of the film. In this study, a starch film synthesis route and the incorporation of silver nanoparticles has been proposed in order not to alter the properties of the film while maintaining the transparency and a clear colour of the starch film. The results showed that the proposed synthesis route is promising, efficient, reproducible, fast and the film has good mechanical properties.
The image designed by Natalia Cano Murillo and colleagues shows the cross section of a ternary composite (boehmite/polycarbonate/epoxy, 80μm x 80μm). The surface was measured by AFM kelvin probe microscopy, yielding the surface potential which is shown as 3D‐surface and contour lines. The sample was further subjected to AFM force spectroscopy with a lateral resolution of 1μm², yielding the local Young's modulus, projected in false colors on the 3D surface. The ternary system, containing boehmite nanoparticles, shows a broad distribution of modulus, desirable for optimized macroscopic mechanical properties, such as high stiffness as well as toughness.
Tuning and controlling the solid-state photophysical properties of organic luminophore are very important to develop next-generation organic luminescent materials. With the aim of discovering new functional luminescent materials, new cocrystals of 9-anthracene carboxylic acid (ACA) were prepared with two different dipyridine coformers: 1,2-bis(4-pyridyl)ethylene and 1,2-bis(4-pyridyl)ethane. The cocrystals were successfully obtained by both mechanochemical approaches and conventional solvent crystallization. The newly obtained crystalline solids were characterized thoroughly using a combination of single crystal X-ray diffraction, powder X-ray diffraction, Fourier-transform infrared spectroscopy, differential thermal analysis, and thermogravimetric analysis. Structural analysis revealed that the cocrystals are isostructural, exhibiting two-fold interpenetrated hydrogen bonded networks. While the O–H···N hydrogen bonds adopts a primary role in the stabilization of the cocrystal phases, the C–H···O hydrogen bonding interactions appear to play a significant role in guiding the three-dimensional assembly. Both π···π and C–H···π interactions assist in stabilizing the interpenetrated structure. The photoluminescence properties of both the starting materials and cocrystals were examined in their solid states. All the cocrystals display tunable photophysical properties as compared to pure ACA. Density functional theory simulations suggest that the modified optical properties result from charge transfers between the ACA and coformer molecules in each case. This study demonstrates the potential of crystal engineering to design solid-state luminescence switching materials through cocrystallization.
Amorphous calcium carbonate (ACC) is an important precursor in the biomineralization of crystalline CaCO3. In nature, it serves as a storage material or as a permanent structural element, whose lifetime is regulated by an organic matrix. The relevance of ACC in materials science is primarily related to our understanding of CaCO3 crystallization pathways and CaCO3/(bio)polymer nanocomposites. ACC can be synthesized by liquid–liquid phase separation, and it is typically stabilized with macromolecules. We have prepared ACC by milling calcite in a planetary ball mill. Phosphate “impurities” were added in the form of monetite (CaHPO4) to substitute the carbonate anions, thereby stabilizing ACC by substitutional disorder. The phosphate anions do not simply replace the carbonate anions. They undergo shear-driven acid/base and condensation reactions, where stoichiometric (10%) phosphate contents are required for the amorphization to be complete. The phosphate anions generate a strained network that hinders ACC recrystallization kinetically. The amorphization reaction and the structure of BM-ACC were studied by quantitative Fourier transform infrared spectroscopy and solid state 31P, 13C, and 1H magic angle spinning nuclear magnetic resonance spectroscopy, which are highly sensitive to symmetry changes of the local environment. In the first—and fast—reaction step, the CO32– anions are protonated by the HPO42– groups. The formation of unprecedented hydrogen carbonate (HCO3–) and orthophosphate anions appears to be the driving force of the reaction, because the phosphate group has a higher Coulomb energy and the tetrahedral PO43– unit can fill space more efficiently. In a competing second—and slow—reaction step, pyrophosphate anions are formed in a condensation reaction. No pyrophosphates are formed at higher carbonate contents. High strain leads to such a large energy barrier that any reaction is suppressed. Our findings aid in the understanding of the mechanochemical amorphization of calcium carbonate and emphasize the effect of impurities for the stabilization of the amorphous phases in general. Our approach allowed the synthesis of new amorphous alkaline earth defect variants containing the unique HCO3– anion. Our approach outlines a general strategy to obtain new amorphous solids for a variety of carbonate/phosphate systems that offer promise as biomaterials for bone regeneration.
n this work, three new pharmaceutical hydrated salts of ciprofloxacin with selected derivatives of benzoic acid, namely 4-hydroxybenzoic acid, 4-aminobenzoic acid and gallic acid, were obtained and systematically investigated by several solid-state analytical techniques. In situ Raman spectroscopy was applied to elucidate the alternative pathways of the solid forms' formation under mechanochemical conditions. Crystal structure analysis and a CSD survey allowed us to establish a distinct supramolecular motif formed by infinite columnar stacks of ciprofloxacin dimers arranged in the “head-to-tail” manner. An alternative “head-to-head” packing arrangement was only observed in the crystal of the hydrated ciprofloxacin salt with 4-aminobenzoic acid. In addition, the pH-solubility behavior of the solid forms was thoroughly investigated. Furthermore, a distinct structure–property relationship between the specific features of the supramolecular organization of the hydrated salts and their solubility was observed and discussed.
Im Vortrag wird ein Messfiltertiegel als Zusatztool für die TED-GC/MS vorgestellt, welcher für die Probenaufbereitung von kleinen Partikelfrachten oder kleinen Partikelgrößen genutzt werden kann. Er ist Filtereinheit und Messtiegel in einem, wodurch Verluste bei der Überführung der Probe in das Messgefäß sowie Kontaminationen vermindert werden. Das beispiel ist hier die Filtration von Flaschenwasser mit anschließender Detektion mit der TED-GC/MS.
Controlling thickness and tightness of surface passivation shells is crucial for many applications of core–shell nanoparticles (NP). Usually, to determine shell thickness, core and core/shell particle are measured individually requiring the availability of both nanoobjects. This is often not fulfilled for functional nanomaterials such as many photoluminescent semiconductor quantum dots (QD) used for bioimaging, solid state lighting, and display technologies as the core does not show the applicationrelevant functionality like a high photoluminescence (PL) quantum yield, calling for a whole nanoobject approach. By combining high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS), a novel whole nanoobject approach is developed representatively for an ultrabright oleic acid-stabilized, thick shell CdSe/CdS QD with a PL quantum yield close to unity. The size of this spectroscopically assessed QD, is in the range of the information depth of usual laboratory XPS. Information on particle size and monodispersity were validated with dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) and compared to data derived from optical measurements. In addition to demonstrating the potential of this novel whole nanoobject approach for determining architectures of small nanoparticles, the presented results also highlight challenges faced by different sizing and structural analysis methods and method-inherent uncertainties.
Based on practical examples of analysis with Electron Microscopy and Energy-Dispersive X-ray Spectroscopy, the minimum information requirements for reliable and reproducible nanomaterial characterization data such as particle size and shape distribution and elemental analysis are presented and discussed.
In this contribution different ways are explored with the aim to generate suitable training data for ‘non-ideal’ samples using various approaches, e.g., computer-generated images or unsupervised learning algorithms such as generative adversarial networks (GANs). We used these data to train simple CNNs to produce segmentation masks of SEM images and tested the trained networks on real SEM images of complex nanoparticle samples. The novel use of CNN for the automated analysis of the size of nanoparticles of complex shape and with a high degree of agglomeration has proved to be a promising tool for the evaluation of particle size distribution on a large number of constituent particles. Further development and validation of the preliminary model, respectively larger training and validation data sets are necessary.
In this paper one refined approach is applied to determine the exact orientation of bipyramidal TiO2 nanoparticles prepared with good dispersion as almost isolated particles on a carbon TEM grid. The advantages of the recently developed high-throughput Transmission Kikuchi Diffraction (TKD) are used to identify quickly and reliably the geometrical orientation of the crystalline TiO2 nanoparticle bipyramids (anatase) on a statistically relevant number of particles.
The present study addresses the capability of measurement of relative particle number concentration by scanning electron microscopy for model bimodal silica and gold samples prepared in the frame of the European research project “nPSize - Improved traceability chain of nanoparticle size measurements” as candidate reference nanoparticles.
Background, Motivation and Objective
Nanomaterials are at the core of some of the 21st century’s most promising technologies. In order to utilize and rationally design materials at the nanoscale the reliable characterization of their physico-chemical properties is highly important. Furthermore, the European Commission has taken measures via the REACH Regulations to control the classification of nanomaterials. REACH Annexes which entered into force in January 2020 require manufacturers to register nanomaterials that are traded in larger quantities (at least 1 ton). Every powder or dispersion where 50% (number distribution) of the constituent particles have sizes ≤ 100 nm in at least one dimension are defined as a nanomaterial. This creates a need for both industrial manufacturers and research and analytical service facilities to reliably characterize potential nanomaterials. Currently, BAM is working on developing reference nanoparticles, which shall expand the scarce list of worldwide available nano reference materials certified for particle size distribution, but also targeting other key parameters such as shape, structure (including porosity) and functional properties. Thus, candidate materials are considered to complement the already available spherical and monodisperse silica, Au and polystyrene reference nanoparticles, e.g. iron oxide and titanium oxide, with an average atomic number between those of silica and gold. Particularly for the imaging by electron microscopies, new nanoparticles of well-defined size in the range of 10 nm are decisive for the accurate particle segmentation by setting precise thresholds.
Statement of Contribution/Methods
Synthesis: Highly monodisperse iron oxide nanoparticles can be synthesized in large quantities by thermal decomposition of iron oleate or iron acetylacetonate precursors in high boiling solvents such as octadecene or dioctyl ether in the presence of oleic acid and oleylamine as capping agents.
Scanning Electron Microscope: An SEM of type Supra 40 from Zeiss has been used including the dedicated measurement mode transmission in SEM (STEM-in-SEM) with a superior material contrast for the nanoparticle analysis. The software package ImageJ has been used for the analysis of the STEM-in-SEM images and to determine the particle size distribution.
Dynamic Light scattering (DLS): Particles in suspension were measured in comparison by means of Zetasizer Nano (Malvern Panalytical; cumulants analysis) and NanoFlex (Microtrac; frequency power spectrum).
Results/Discussion
In this study iron oxide nanoparticles synthesized at BAM and pre-characterized by DLS, SEM (including the transmission mode STEM-in-SEM) are presented. The particles are spherical and highly monodisperse with sizes slightly larger than 10 nm.
Zur Validierung und Harmonisierung von verschiedenen Methoden in der Mikroplastik-Analytik werden polymere Referenzmaterialien benötigt. In diesem Vortrag wird dargestellt, was bisher an der BAM zu Referenzmaterialien für die Mikroplastik-Analytik entwickelt wurde, wo es hingehen soll und ein Überblick über bisher gelaufene Vergleichsuntersuchungen gebracht.
Insights into the In Vitro Formation of Apatite from Mg‐Stabilized Amorphous Calcium Carbonate
(2020)
A protein‐free formation of bone‐like apatite from amorphous precursors through ball‐milling is reported. Mg2+ ions are crucial to achieve full amorphization of CaCO3. Mg2+ incorporation generates defects which strongly retard a recrystallization of ball‐milled Mg‐doped amorphous calcium carbonate (BM‐aMCC), which promotes the growth of osteoblastic and endothelial cells in simulated body fluid and has no effect on endothelial cell gene expression. Ex situ snapshots of the processes revealed the reaction mechanisms. For low Mg contents (<30%) a two phase system consisting of Mg‐doped amorphous calcium carbonate (ACC) and calcite “impurities” was formed. For high (>40%) Mg2+ contents, BM‐aMCC follows a different crystallization path via magnesian calcite and monohydrocalcite to aragonite. While pure ACC crystallizes rapidly to calcite in aqueous media, Mg‐doped ACC forms in the presence of phosphate ions bone‐like hydroxycarbonate apatite (dahllite), a carbonate apatite with carbonate substitution in both type A (OH−) and type B (PO43−) sites, which grows on calcite “impurities” via heterogeneous nucleation. This process produces an endotoxin‐free material and makes BM‐aMCC an excellent “ion storage buffer” that promotes cell growth by stimulating cell viability and metabolism with promising applications in the treatment of bone defects and bone degenerative diseases.
Current time-resolved in situ approaches limit the scope of mechanochemical investigations possible. Here we develop a new, general approach to simultaneously follow the evolution of bulk atomic and electronic structure during a mechanochemical synthesis. This is achieved by coupling two complementary synchrotron-based X-ray methods: X-ray absorption spectroscopy (XAS) and X-ray diffraction. We apply this method to investigate the bottom-up mechanosynthesis of technologically important Au micro and nanoparticles in the presence of three different reducing agents, hydroquinone, sodium citrate, and NaBH4. Moreover, we show how XAS offers new insight into the early stage generation of growth species (e.g. monomers and clusters), which lead to the subsequent formation of nanoparticles. These processes are beyond the detection capabilities of diffraction methods. This combined X-ray approach paves the way to new directions in mechanochemical research of advanced electronic materials.
Control over the bottom up synthesis of metal nanoparticles (NP) depends on many experimental factors, including the choice of stabilising and reducing agents. By selectively manipulating these species, it is possible to control NP characteristics through solution-phase synthesis strategies. It is not known, however, whether NPs produced from mechanochemical syntheses are governed by the same rules. Using the Au NPs mechanosynthesis as a model system, we investigate how a series of common reducing agents affect both the reduction kinetics and size of Au NPs. It is shown that the relative effects of reducing agents on mechanochemical NP synthesis differ significantly from their role in analogous solution-phase reactions. Hence, strategies developed for control over NP growth in solution are not directly transferrable to environmentally benign mechanochemical approaches. This work demonstrates a clear need for dedicated, systematic studies on NP mechanosynthesis.
Methods and materials are presented here, which enable the manufacturing of fine structures using a 3D-printing method known as two-photon polymerization (2PP). As traditional photolithography methods for structuring ceramic slurries do not function with 2PP, due to light scattering on ceramic particles, a novel water-based photoresist with high ceramic loading of extremely well dispersed ceramic nano particles was developed. This photoresist is basically a ceramic slurry containing a photocurable agent and a photoinitiator to be crosslinkable with the 780 nm wavelength femtosecond laser light source of the 2PP machine. It is demonstrated that it is possible to gain a highly transparent and low viscous slurry suitable for 2PP processing. This work shows the development of the slurry, first printing results and the post-printing processes required to form three dimensional ceramic microstructures consisting of alumina toughened zirconia (ATZ).
The present study investigates the possibility of improving the selective oxidation of methane to formaldehyde over V-SBA-15 catalysts in two different ways. In a classical approach of catalyst optimization, the in situ synthesis of V-SBA-15 catalysts was optimized with regard to the applied pH value. Among the set of catalysts synthesized, a higher amount of incorporated vanadium, a higher content of polymeric VOx species as well as a less ordered structure of the support material were observed by increasing the pH values from 2.0 to 3.0. An optimum in performance during the selective oxidation of methane to formaldehyde with respect to activity and selectivity was found over V-SBA-15 prepared at a pH value of 2.5. With this knowledge, we have now evaluated the possibilities of reaction control using this catalyst. Specifically, artificial neural network modelling was applied after the collection of 232 training samples for obtaining insight into the influence of different reaction parameters (temperature; gas hourly space velocity (GHSV); and concentration of O2, N2 and H2O) onto methane conversion and selectivity towards formaldehyde.
This optimization of reaction conditions resulted in an outstanding high space-time yield of 13.6 kgCH2O∙kgcat∙h−1
Rund ein Jahr haben DIN und DKE in einem gemeinsamen Projekt mit dem Bundesministerium für Wirtschaft und Energie und zusammen mit ca. 300 Fachleuten aus Wirtschaft, Wissenschaft, öffentlicher Hand und Zivilgesellschaft an der Normungsroadmap Künstliche Intelligenz gearbeitet. Eine hochrangige Steuerungsgruppe unter dem Vorsitz von Prof. Wolfgang Wahlster hat die Erarbeitung koordiniert und begleitet.
Ziel der Roadmap ist die frühzeitige Entwicklung eines Handlungsrahmens für die Normung und Standardisierung, der die internationale Wettbewerbsfähigkeit der deutschen Wirtschaft unterstützt und europäische Wertmaßstäbe auf die internationale Ebene hebt.(...)
The present study investigates early stages of ZIF-8 crystallization up to 5 minutes post mixing of precursor solutions. Dispersive X-ray Absorption Spectroscopy (DXAS) provides a refined understanding of the evolution of the coordination environment during ZIF-8 crystallization. Linear Combination Fiting (LCF) suggests tetrakis(1-methylimidazole)zinc2+ to be a suitable and stable mononuclear structure analogue for some early stage ZIF-8 intermediates. Our results pave the way for more detailed studies on physico-chemical aspects of ZIF-8 crystallization to better control tailoring ZIF-8 materials for specific applications.
A major source of capacity fade of the common vanadium redox flow battery (VRFB) is the vanadium ion transport through the separator. However, different transport models disagree significantly in the diffusion coefficient for the different V species and the influence of different transport mechanisms. The underlying hypothesis of this work is that reactions inside the membrane are partly responsible for these discrepancies. Accordingly, it was investigated if redox reactions inside the nanoscopic water body of Nafion 117 can occur. X-ray absorption near edge structure spectroscopy (XANES) was used to distinguish between the different V species inside hydrated Nafion 117 and novel PVDF-based membranes. It was validated that the speciation of vanadium can be performed using the pre-edge peak energy and intensity. The experiments were performed as follows: strips of the membrane were exposed from one site to a V3+ solution (green) and from the other site to a VO2+ solution (yellow). The ions could diffuse into the membrane from both sides. A change of color of the membrane strip was observed. The blue color in the middle of the strip indicated that VO2+ was formed where V3+ and VO2+ got in contact. Using XANES this reaction inside Nafion was proven.
In this work, we present various promising sample preparation procedures aiming to avoid drying artifacts and guarantee homogeneously distributed NP samples for imaging techniques like TEM, SEM or AFM. This involves retarded drying in an environment of high relative humidity as well as spin coating or freeze drying of the sample on the substrate.
Depending on the type of the NPs, different techniques are successful in obtaining homogenous sample deposition. Simple drying at ambient conditions often results in heavily agglomerated NPs densely packed in coffee ring traces. Retardation of the drying speed in an environment of high relative humidity, however, yields homogeneous NP deposition in the case of bimodal SiO2 and bimodal gold NP’s. In contrast, a sample of bipyramidal TiO2, heavily agglomerated when commonly dried, is successfully dispersed by spin coating the suspension on the substrate. The analysis of the particle size distribution of the bimodal silica and gold samples yielded number ratios resembling the nominal number ratios. The reliable measurement of the NP concentration of polydisperse samples by electron microscopy, even if relative, is new and of special relevance because up to now only the size of the particles, i.e. the abscissa of the PSD, can be measured reliably.
Various promising sample preparation procedures aiming to avoid drying artifacts and guarantee homogeneously distributed NP samples for imaging techniques like TEM, SEM or AFM are presented. This involves retarded drying in an environment of high relative humidity as well as spin coating or freeze drying of the sample on the substrate.
Depending on the type of the NPs, different techniques are successful in obtaining homogenous sample deposition. Simple drying at ambient conditions often results in heavily agglomerated NPs densely packed in coffee ring traces. Retardation of the drying speed in an environment of high relative humidity, however, yields homogeneous NP deposition in the case of bimodal SiO2 and bimodal gold NP’s. In contrast, a sample of bipyramidal TiO2, heavily agglomerated when commonly dried, is successfully dispersed by spin coating the suspension on the substrate.
The analysis of the particle size distribution of the bimodal silica and gold samples yielded number ratios resembling the nominal number ratios. The reliable measurement of the NP concentration of polydisperse samples by electron microscopy, even if relative, is new and of special relevance because up to now only the size of the particles, i.e. the abscissa of the PSD, can be measured reliably.
Data quality is a vast term, which comprises the completeness, relevance (adequacy), and reliability of data. So far, many attempts to assure data quality have been pursued, and evaluation criteria for data quality have been established. One relatively novel but already well-known aspect of data quality refers to the concept of data FAIRness, which states that data should be: findable, accessible, interoperable and re-usable. In order to find, use, and access data, a user has to be guided properly. Such guidelines already exist for regulators and the scientific community. However, a ‘simple’ non-academic user from general society is very unlikely to be able to access or understand such data. Our objective in the H2020 project NANORIGO is to help and guide all types of users (i.e., scientists, regulators, industry workers, citizens, etc.) to access and make use of high-quality data and information from available and suitable data repositories in order to increase the transparency of and trust in nanotechnology.
A series of different nanoparticle suspensions (Gold, Latex, and SiO2 in varying concentrations) were microprinted onto TEM grids in a 4 x 4 array in the concentration range 7x10^8 to 1x10^11 NP/mL and imaged with SEM and TSEM. Concentrations and printing conditions (temperature, relative humidity) were varied in order to minimize the coffee ring effect.
Blueprint for a sustainable new European Centre to support safe innovation for nanotechnology
(2020)
This paper presents the blueprint for the operation of a sustainable and permanent European Centre of collaborating reference laboratories and research centres, to establish a one-stop shop for a wide variety of nanosafety related services, and to provide a central contact point for questions about nanosafety in Europe. The Centre aims to harmonise service provision, and bring novel risk assessment and management approaches closer to practice.
You Ask – ACEnano Replies
(2020)
The workshop starts with introductory information about the workshop and the H2020 project ACEnano, followed by two expert round tables, focussing on how the project could address regulator and industry needs, respectively. This is be followed by parallel sessions on tools (based on preferences expressed by those registered to attend, see “Questions”) and finally a question-and-answer session with the attendees.
The experts invited in Round Table 1 have been prepared to answer to questions related to obstacles and advantages for stakeholders such as SMEs to use the ACEnano approaches/tools. Standardisation needs are discussed.
There is growing interest in quantifying microplastics in environmental samples. This application note presents a thermal extraction desorption-gas chromatography/mass spectrometry (TED-GC/MS) method that is well suited to automation and increased sample throughput. The method is also able to detect all particle sizes in the sample as long as the limit of detection (LOD) is reached and allows analysis of larger samples of 15 to 25 mg or more. Samples were decomposed by thermogravimetric analysis (TGA), and the gaseous decomposition products were trapped on a solid-phase sorbent, followed by thermal desorption‑gas chromatography/mass spectrometry (TD-GC/MS) using an Agilent 5977B GC/MSD coupled to an Agilent 7890B GC. Target microplastic particle (MP) polymers were identified in environmental samples including surface water, finished compost, house dust, and drinking water. Quantification of MP polymers in environmental samples provided LODs of 0.06 to 2.2 μg, allowing the detection of MPs in trace amounts with sample weights of up to 1 g. Method repeatability was adequate for reliable quantification with RSDs of approximately 6 to 12%.
Microplastic particles are currently detected in almost all environmental compartments. The results of detection vary widely, as a multitude of very different methods are used with very different requirements for analytical validity.
In this work four thermoanalytical methods are compared and their advantages and limitations are discussed. One of them is thermal extraction-desorption gas chromatography mass spectrometry (TED-GC/MS), an analysis method for microplastic detection that has become established in recent years. In addition, thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy (TGA-FTIR) and mass spectrometry (TGA-MS) were applied, two methods that are less common in this field but are still used in other research areas. Finally, microscale combustion calorimeter (MCC) was applied, a method not yet used for microplastic detection.
The presented results are taken from a recently published interlaboratory comparison test by Becker et al. (2020). Here a reference material consisting of suspended matter and specified added polymer masses was examined, and only the results of the recoveries were presented. In the present paper, however, the results for the individual polymers are discussed in detail and individual perspectives for all instruments are shown.
It was found that TED-GC/MS is the most suitable method for samples with unknown matrix and unknown, variable kinds and contents of microplastic. TGA-FTIR is a robust method for samples with known matrix and with defined kinds of microplastic. TGA-MS may offer a solution for the detection of PVC particles in the future. MCC can be used as a very fast and simple screening method for the identification of a potential microplastic load of standard polymers in unknown samples.
Nanoparticles (NP) have become important materials for a variety of chemical technologies. The enhance surface-area-to-volume ratio of NPs is very high, making them excellent for use as catalyst, in analytical assays, and for antimicrobial applications.
Nickel NPs have exhibited immense potential as important catalyst for the Sabatier reaction, i.e. converting waste to energy via transformation of CO2 into CH4, and could replace the rare earth elements such as Ru, PT, or Rh. In this work we describe the solvothermal synthesis of monometallic and bimetallic nickel nanoparticles.
Monodisperse monometallic Ni nanoparticles were synthesized using Oleylamin as solvent and reducing agent. The nanoparticles were investigated using small angle scattering (SAXS), scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX), showing that the catalytically active sites are accessible. However, Ni has a high propensity to undergo oxidation, and becoming deactivated by coke formation. Hence, we further explore the preparation of bimetallic NPs, where a second metal is added to stabilize the Ni.
Bimetallic Cu-Ni NPs were synthesized by simultaneous solvothermal reduction. These bimetallic NPs exhibit excellent catalytic properties are promising candidates to be used as catalysts for efficient energy storage.
A brief introduction to the efforts we have done in our lab towards AI/ML analysis of SAXS data. For this, we need to extend the data with an extensive, structured hierarchy of metadata and associated data. A practical look into the information stored in our files, and the organization of the files in a data catalog is presented.
Biofouling is a major challenge in the application of textiles, biosensors, and biomedical implants. In the current work, a straightforward method for the solvent-free polymerization of antifouling dendritic polyglycerol (dPG) from mussel-inspired dendritic polyglycerol (MI-dPG) coatings on hydrophilic titanium dioxide (TiO2) and hydrophobic polydimethylsiloxane (PDMS) is reported. Surface characterization is performed by static water contact angle (CA) measurements, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Significant lower CA values are obtained after dPG grafting from MI-dPG-coated TiO2 and MI-dPG coated PDMS. Furthermore, XPS shows a time-dependent increase of the CO bond content upon dPG grafting from MI-dPG-coated TiO2 and MI-dPG-coated PDMS. Analysis of the surface morphology by SEM shows a clear time-dependent increase in the surface roughness upon dPG grafting from MI-dPG-coated TiO2 and MIdPG-coated PDMS. When the viability of two adhesive cell types is studied via LIVE/DEAD staining, a strong reduction in the cell density is observed after the dPG grafting from MI-dPG-coated TiO2 and MI-dPG-coated PDMS (a decrease of >95% in all cases). The combined results show that biocompatible but highly cell-repelling surfaces are efficiently constructed via the grafting of dPG from MI-dPG-coated TiO2 and MI-dPG-coated PDMS.
We report the results of a Versailles Project on Advanced Materials and Standards interlaboratory study on the intensity scale calibration of x-ray photoelectron spectrometers using low-density polyethylene (LDPE) as an alternative material to gold, silver, and copper. An improved set of LDPE reference spectra, corrected for different instrument geometries using a quartz-monochromated Al Kα x-ray source, was developed using data provided by participants in this study. Using
these new reference spectra, a transmission function was calculated for each dataset that participants provided. When compared to a similar calibration procedure using the NPL reference spectra for gold, the LDPE intensity calibration method achieves an absolute offset of ∼3.0% and a systematic deviation of ±6.5% on average across all participants. For spectra recorded at high pass energies (≥90 eV), values of absolute offset and systematic deviation are ∼5.8% and ±5.7%, respectively, whereas for spectra collected at lower pass energies (<90 eV), values of absolute offset and systematic deviation are ∼4.9% and ±8.8%, respectively; low pass energy spectra perform worse than the global average, in terms of systematic deviations, due to diminished count rates and signal-to-noise ratio. Differences in absolute offset are attributed to the surface roughness of the LDPE induced by sample preparation. We further assess the usability of LDPE as a secondary reference material and comment on its performance in the presence of issues such as variable dark noise, x-ray warm up times, inaccuracy at low count rates, and underlying spectrometer problems. In response to participant feedback and the results of the study, we provide an updated LDPE intensity calibration protocol to address the issues highlighted in the interlaboratory study. We also comment on the lack of implementation of a consistent and traceable intensity calibration method across the community of x-ray photoelectron spectroscopy (XPS) users and, therefore, propose a route to achieving this with the assistance of instrument manufacturers, metrology laboratories, and experts leading to an international standard for XPS intensity scale calibration.
In the face of rising energy demand and the impending climate change the development of a sustainable, fossil-free fuel and chemical production is of global importance. One possible goal is the development of electrochemical conversion processes using catalysts. Porous materials play an important role in such energy applications. The key to the development of improved catalysts is a better understanding of the relations between their performance, stability and physico-chemical properties. However, the complex morphology of such catalysts constitutes a challenge even for modern analytical techniques. Spectroscopic ellipsometry (SE) is a versatile method for studying material properties by using appropriate models (e.g. film thickness, optical and electronic properties). The fact that the material properties cannot be taken directly from the measured spectra, the developed models have to be validated. In a first step, the model for the ellipsometric fit studies of a calcination series of mesoporous iridium oxide films (300 – 600 °C) was investigated and validated with respect to their material properties. Moreover, the electronic structures of the catalysts reveal a direct correlation with electrochemical activities. The development of an environmental cell offers the possibility of investigations under real conditions. This will allow changes in the optical and electronic properties during the electrocatalytic oxygen evolution reaction.
Efficient water electrolysis requires highly active electrodes. The activity of corresponding catalytic coatings strongly depends on material properties such as film thickness, crystallinity, electrical conductivity, and chemical surface speciation. Measuring these properties with high accuracy in vacuum-free and nondestructive methods facilitates the elucidation of structure−activity relationships in realistic environments. Here, we report a novel approach to analyze the optical and electrical properties of highly active oxygen evolution reaction (OER) catalysts via spectroscopic ellipsometry (SE). Using a series of differently calcined, mesoporous, templated iridium oxide films as an example, we assess the film thickness, porosity, electrical resistivity, electron concentration, electron mobility, and interband and intraband transition energies by modeling of the optical spectra. Independently performed analyses using scanning electron microscopy, energy-dispersive X-ray spectroscopy, ellipsometric porosimetry, X-ray reflectometry, and absorption spectroscopy indicate a high accuracy of the deduced material properties. A comparison of the derived analytical data from SE, resonant photoemission spectroscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy with activity measurements of the OER suggests that the intrinsic activity of iridium oxides scales with a shift of the Ir 5d t2g sub-level and an increase of p−d interband transition energies caused by a transition of μ1-OH to μ3-O species.
The European legislation has responded to the wide use of nanomaterials in our daily life and defined the term “nanoform” in the Annexes to the REACH (Registration, Evaluation, Authorization of Chemicals) Regulation. Now specific information of the nanomaterials is required from the companies when registering the appropriate materials in a dossier.
In the context of REACH eleven physicochemical properties were considered as relevant, of which the following six are essential for registration of nanoforms (priority properties): chemical composition, crystallinity, particle size, particle shape, chemical nature of the surface (“surface chemistry”), and specific surface area (SSA). A key role is the reliable, reproduceable and traceable character of the data of these priority properties.
In this context, we want to discuss which ‘analytical’ information is exactly required to fulfill these conditions. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and X-ray Photoelectron Spectroscopy (XPS) were chosen as the most popular surface analytical methods. Both methods allow a detailed understanding of the surface chemistry with an information depth below ten nanometers. As a rather bulk method for the analysis of nanoforms, Electron Probe Microanalysis (EPMA) in the version with energy dispersive X-ray spectroscopy (EDS) is considered for the quick identification of the main chemical elements present in the sample. Furthermore, Scanning Electron Microscopy (SEM) results are discussed which provide results on particle size and shape. Thus, four of the six priority properties can be obtained with these methods.
We studied the dissolution behavior of β NaYF4:Yb(20%), Er(2%) UCNP of two different sizes in biologically relevant media i.e., water (neutral pH), phosphate buffered saline (PBS), and Dulbecco’s modified Eagle medium (DMEM) at different temperatures and particle concentrations. Special emphasis was dedicated to assess the influence of different surface functionalizations, particularly the potential of mesoporous and microporous silica shells of different thicknesses for UCNP stabilization and protection. Dissolution was quantified electrochemically using a fluoride ion selective electrode (ISE) and by inductively coupled plasma optical emission spectrometry (ICP OES). In addition, dissolution was monitored fluorometrically. These experiments revealed that a thick microporous silica shell drastically decreased dissolution. Our results also underline the critical influence of the chemical composition of the aqueous environment on UCNP dissolution. In DMEM, we observed the formation of a layer of adsorbed molecules on the UCNP surface that protected the UCNP from dissolution and enhanced their fluorescence. Examination of this layer by X ray photoelectron spectroscopy (XPS) and mass spectrometry (MS) suggested that mainly phenylalanine, lysine, and glucose are adsorbed from DMEM. These findings should be considered in the future for cellular toxicity studies with UCNP and other nanoparticles and the design of new biocompatible surface coatings.
MISTRAL-Müller-Matrix-basierte Identifizierung von Inhomogenitäten und strukturellen Anomalien
(2020)
Mit abbildender Ellipsometrie (imaging ellipsometry: IE) können Nanometer-Beschichtungen/ Degradationen visualisiert und bezüglich Brechungsindex n, Extinktionskoeffizient k und Schichtdicke d charakterisiert werden. Materialseitig werden lokal Homogenität und Isotropie innerhalb eines/mehrerer Bildpunkte (field of analysis: FOA) und messtechnisch global die Ebenheit der Proben bezüglich aller Bildpunkte des Messfeldes vorausgesetzt. Für die Müller-Matrix-basierte abbildende Ellipsometrie (MM-IE), die den optischen Response anisotroper Materialien in jedem Bildpunkt über die bis zu 16 Müller-Matrix-Elemente erfasst, ist dies von besonderer Relevanz. Reale Substrate sind aber oft nicht eben, können lokal Noppen/Mulden (im FOA) aufweisen oder sind global konvex/ konkav im möglichen Messfeld (field of view: FOV) gekrümmt. Diese lokalen/globalen strukturellen Anomalien des Substrats werden schon für die IE messtechnisch/modellseitig oft nicht beherrscht und sind für die MM-IE in der Wirkung auf die MM-Elemente unbekannt. Diese Defizite sollen messtechnisch bzw. modellmäßig behoben und somit die Messung lokal/global gekrümmter Oberflächen ermöglicht werden (MM-CSIE, CS curved surface).
The technological advances in lasers enabled the wide application of laser-induced breakdown spectroscopy (LIBS) as a powerful analytical means for elemental analyses. Rather than commonly used lasers that operate at several to several-tens of Hz, the high repetition rate ones that operate at tens of kHz showed superior analytical advantages while implying unique excitation pathways. Specifically, the production of excited atomic hydrogen and oxygen, which can serve as internal standards, is quite different from that in commonly reported double-pulse LIBS. In this part of the work, it was found that the atomic emitters stemming from water are not related to cavitation bubbles. Moreover, the emitter productions of dissolved species, e.g., Na+, and water-related species, e.g., H-α, are two distinctive mechanisms. Towards analytical applications of the high repetition-rate system, the fundamental investigation can provide important guidelines to address real-life challenges. In this part of the work, the high repetition-rate regime of operation is explored from a more kinetic perspective.
In recent years, laser-induced breakdown spectroscopy (LIBS) has gained significant attention as a means for simple elemental analyses. The suitability of LIBS for contactless analysis allows it to be a perfect candidate for underwater applications. While the majority of LIBS systems still rely upon sub-kHz pulsed lasers, this contribution introduces 10s-kHz low pulse-energy lasers into underwater LIBS to improve the throughput and statistical validity. Interestingly, the spectral component significantly changed above a critical laser repetition-rate threshold. Spectral lines of atomic hydrogen and oxygen stemming from water become visible beyond a ∼10 kHz repetition rate. This observation suggests a different plasma dynamic compared to low repetition rates. When the pulse-to-pulse interval becomes sufficiently short, a cumulative effect begins to be significant. Apparently, the new phenomena occur on a timescale corresponding to a threshold rate of ∼10 kHz, i.e. ∼100 μs. Analytically, the high repetition rates result in improved statistical validity and throughput. More plasma events per unit time allowed the use of low efficiency Echelle spectrometers without compromising on the analytical performance. Meanwhile, the presence of H I and O I out of the water (as the matrix) also offers internal standardization in underwater elemental analysis. Since the laser fluence was on the lower edge of the plasma threshold, an additional ultrasound source was introduced to induce external perturbation, which significantly improved the plasma formation stability. A huge advantage of LIBS is the possibility of detecting almost all elements within a sample simultaneously. Throughout the periodic table, chlorine is one of the most challenging elements. Consequently, Ca2+ and Na+ were used as samples to demonstrate the capability of this high repetition-rate LIBS platform. As an ambitious benchmark for our system, chlorine detection in water was also discussed.
This paper reports a systematic study into the effect of different biomass-derived precursors on the structure and porosity of carbons prepared via catalytic graphitization. Glucose, starch and cellulose are combined with iron nitrate and heated under a nitrogen atmosphere to produce Fe3C nanoparticles, which catalyze the conversion of amorphous carbon to graphitic nanostructures. The choice of organic precursor provides a means of controlling the catalyst particle size, which has a direct effect on the porosity of the material. Cellulose and glucose produce mesoporous carbons, while starch produces a mixture of micro- and mesopores under the same conditions and proceeds via a much slower graphitization step, generating a mixture of graphitic nanostructures and turbostratic carbon. Porous carbons are critical to energy applications such as batteries and electrocatalytic processes. For These applications, a simple and sustainable route to those carbons is essential. Therefore, the ability to control the precise structure of a biomass-derived carbon simply through the choice of precursor will enable the production of a new generation of energy materials.
Stone deterioration is the result of a complex interaction of external physical, chemical and biological forces with the mineralogical-petrophysical properties of the stone. With a better understanding of how these properties are linked to material behavior and durability, more effective measures for stone conservation can be developed. Studying these interactions in tuff is particularly complex due to the naturally high heterogeneity of tuff rocks.
The first aim of a current research project is to combine the results of recent and older studies on tuff deterioration. Furthermore, the literature overview is complemented by our own investigation of Weibern and Ettringen tuff, with a focus on pore structure characteristics.
The main outcomes of the EMPIR project nPSize are presented and the suitability of the new capabilities (e.g. reference materials, measurement procedures, VAMAS inter-laboratory comparisons) to be standardized and implemented in accredited analytical laboratories is discussed. Complementation and/or filling gaps of published and ongoing standardisation projects on size, shape and number concentration measurements under ISO/TC 229/JWG 2 are offered.
It is a well-known story that copolymers beside their molar mass distribution (MMD) can exhibit a functionality type distribution (FTD), a copolymer composition distribution (CCD), a monomer sequence distribution (MSD) and additionally different topologies within one sample. Small, often isobaric heterogeneities in topology or microstructure can usually not be simply separated chromatographically or distinguished by any common detector. Nowadays a wide range of different analytical separation techniques and multi-detection possibilities are available. The challenge consists in a clever combination of these techniques with a specific approach of data analysis. In this presentation different liquid chromatographic separation modes were combined with Electrospray Time-of-Flight mass spectrometry.
The online coupling allows the analysis of reconstructed ion chromatograms (RIC) of each degree of polymerization. While a complete separation often cannot be achieved, the derived retention times and peak widths lead to information on the existence and dispersity of heterogeneities in microstructure or topology, that are otherwise inaccessible This method is suitable to detect small differences in e. g. branching, topology, monomer sequence or tacticity and could potentially be used in production control of oligomeric products or other routinely done analyses to quickly indicate deviations from set parameters. Based on a variety of examples e.g. the topology elucidation of branched EO-PO copolymers, the possibilities and limitations of this approach were demonstrated.
The increasing enrichment of water bodies and soils with plastic waste leads to the accumulation of microscopic plastic particles, so-called microplastics (MP). There is an urgent need for analytical methods that help to identify and quantify MP. At present, mainly thermo-analytical and microscopic methods such as micro-infrared spectroscopy or micro-Raman are used for this purpose. The latter are usually tied to time-consuming sample enrichment and preparation, only small sample quantities (micrograms) can be examined and the evaluation of the obtained spectra can be demanding. In the context of this presentation, two approaches are presented which, via the multi-variate analysis of spectroscopic data, allow i) a new methodological approach to screening MP in contaminated soils and ii) an alternative evaluation of large (micro)-spectroscopic data sets.
First, a NIR spectroscopic method is presented which allows MP consisting of polyethylene, polyethylene terephthalate, polypropylene and polystyrene to be detected in the range of up to 0.5 mass percent. Due to short measurement times and robust technology, this approach has the potential, in contrast to thermo-analytical and micro-spectroscopic methods, to examine larger sample quantities with minimal pre-treatment.
The second approach deals with the evaluation of large data sets, as typically obtained as a result of micro-FTIR using modern FPA detectors. The micro-FTIR technique is based on the spectral recording, imaging and subsequent identification of vibration bands typical of synthetic polymers. The image data sets are large and contain spectra of numerous particles of natural and synthetic origin. Exploratory multivariate data analysis has been tested to complement existing approaches based on e.g. spectrum library searches. The core concept used was dimensionality reduction. The results not only represent an orthogonal method for checking the results obtained by an automated library search, but also revealed a group of spectra that were not recorded in the existing spectrum libraries.
X-ray imaging methods are used in many fields of research, as they allow a non-destructive Investigation of the elemental content of various samples. As for every imaging method, for X-ray imaging the optics are of crucial importance. However, these optics can be very expensive and laborious to build, as the requirements on surface roughness and precision are extremely high. Angles of reflection and refraction are often in the range of a few mrad, making a compact design hard to achieve. In this work we present a possibility to simplify X-ray imaging. We have adapted the coded aperture method, a high energy radiation imaging method that has its origins in astrophysics, to full field X-ray fluorescence imaging. In coded aperture imaging, an object is projected through a known mask, the coded aperture, onto an area sensitive detector. The resulting image consists of overlapping projections of the object and a reconstruction step is necessary to obtain the information from the recorded image. We recorded fluorescence images of different samples with an energy-dispersive 2D detector (pnCCD) and investigated different reconstruction methods. With a small coded aperture with 12 holes we could significantly increase the count rate compared to measurements with a straight polycapillary optic. We show that the reconstruction of two different samples is possible with a deconvolution approach, an iterative algorithm and a neural network. These results demonstrate that X-ray fluorescence imaging with coded apertures has the potential to deliver good results without scanning and with an improved count rate, so that measurement times can be shortened compared to established methods.
The aim of the work presented was the evaluation of corrosion resistance
of various materials in geothermal Waters as a base to create a catalogue of suitable materials for applications in (not only) German geothermal power plants.
Users shall be enabled to have a basis for designing such facilities. High alloyed corrosion resistant alloys are suitable and do not cause copper or lead deposition. They shall be chosen for future design of the piping system, either in massive or in cladded form, if crevices formation with non-metallic materials can be prevented!
In the present work a series of design rules are developed in order to tune the morphology of TiO2 nanoparticles through hydrothermal process. Through a careful experimental design, the influence of relevant process parameters on the synthesis outcome are studied, reaching to the develop predictive models by using Machine Learning methods. The models, after the validation and training, are able to predict with high accuracy the synthesis outcome in terms of nanoparticle size, polydispersity and aspect ratio. Furthermore, they are implemented by reverse engineering approach to do the inverse process, i.e. obtain the optimal synthesis parameters given a specific product characteristic. For the first time, it is presented a synthesis method that allows continuous and precise control of NPs morphology with the possibility to tune the aspect ratio over a large range from 1.4 (perfect truncated bipyramids) to 6 (elongated nanoparticles) and the length from 20 to 140 nm.
A detailed calorimetric and dielectric study on two epoxy-based nanocomposite system was performed employing bisphenol A diglycidyl ether (DGEBA) cured with diethylenetriamine (DETA) and methyl tetrahydrophtalic acid anhydride (MTHPA) aas the polymer matrix and taurine-modified MgAL layered double hydroxide (T-LDH) and boehmite as nanofiller. The molecular dynamics investigation revealed an intrinsic structural heterogeneity of the epoxy materials. Moreover the polymer/particle interphase was qualitatively and quantitavely investigated.
This presentation is structured in two parts: i) Hybrid metrology by combining SEM with AFM (N. Feltin) and ii) hybridization and corelative microscopy by SEM, STEM-in-SEM, TEM, EDS, Auger Electron Microscopy, TKD and more (D. Hodoroaba).
The first part is focused on the metrological part of the hybrid measurement SEM-AFM, the second part offers some further possibilities of correlative microscopy of nanoparticles based on practical examples.
For the first time, structure−electrochemical relationships of thin films of a plasma-polymerized acrylic acid/carbon dioxide AA/CO2 (75/25%) copolymer modified by implanted silver nanoparticles are discussed. The pulsed plasma polymerization of AA/CO2 was utilized and adjusted to obtain a maximal amount of COOH Groups forming an almost uncross-linked polymer structure. The prepared polymer layer is rinsed by a silver nitrate solution to impregnate Ag+ ions. This step is followed by its reduction of Ag+ with NaBH4 as a chemical route in comparison to the reduction by sunlight as an ecofriendly photoreduction method. The chemical composition and morphology of the topmost surface layer of the AA/CO2 polymer thin film were investigated by X-ray photoelectron spectroscopy and atomic force microscopy. Moreover, the molecular mobility, conductivity, and thermal stability of the polymer layer were analyzed using broadband dielectric spectroscopy. The dielectric properties of the AA/
CO2 polymer thin film were studied in the presence of Ag+ ions or Ag0. It was found that a cross-linked polymer layer with a smooth surface and high conductivity was obtained in the presence of Ag+/ Ag0.
The aim of this study is to develop nanometer-thin epoxy-based films on aluminium alloy AA2024-T3 as a model coating system for high resolution corrosion studies. Spin coating was used for the layer-by-layer (LbL) deposition of poly-(ethylenimine) (PEI) and poly([o-cresyl glycidyl ether]-co-formaldehyde) (CNER) bilayers. The film chemistry and the cross-linking process were characterized by means of Fourier-transform infrared spectroscopy (FTIR).
Ellipsometric data confirmed the linear increase of film thickness. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) results indicate the improvement of the film barrier properties with increasing film thickness. Mapping of the topography and the volta potential was performed by means of scanning Kelvin probe force microscopy (SKPFM).
The results indicate the presence of a homogeneous film structure, while the intermetallic phases can still be identified below the coating. The SKPFM Analysis confirmed that the model films are suitable for investigation of corrosion processes at the coating/metal interface.
To simulate the movement of the macroscopic magnetic moment in ferromagnetic systems under the influence of elevated temperatures, the stochastic version of the Landau-Lifshitz (LL) or the Landau-Lifshitz-Gilbert equation with a spin density of one per unit cell has to be used.
To apply the stochastic LL to micromagnetic simulations, where the spin density per unit cell is generally higher, a conversion has to be performed. OOMMF sample files MIF) are provided which can be used to determine the Curie temperature for the classical bulk magnets, iron, nickel and cobalt.
These files contain cell models for TOPAS/Geant4 and the inclusion of nano particles in particle scattering simulations. A simple spherical cell with nanoparticles can be generated in a fast manner. The user has the option to include the following organelles: nucleus, mitochondria, cell membrane. Additionally nanoparticles can be included in the cytosol and at the surface of the nucleus and/or the mitochondria.
The C++ classes in this repository extend the functionality of the TOPAS (http://www.topasmc.org/) Monte-Carlo program, which is itself a wrapper of the Geant4 MCS Toolkit (http://geant4.org). The sourcecode together with examples and scorers are provided.
"If you use this extension please cite the following literature:
Hahn, M.B., Zutta Villate, J.M. "Combined cell and nanoparticle models for TOPAS to study radiation dose enhancement in cell organelles." Sci Rep 11, 6721 (2021).
https://doi.org/10.1038/s41598-021-85964-2 "
Fluorides are well-known as wood preservatives. One of the limitations of fluoride-based wood preservatives is their high leachability. Alternative to current fluoride salts such as NaF used in wood protection are low water-soluble fluorides. However, impregnation of low water-soluble fluorides into wood poses a challenge. To address this challenge, low water-soluble fluorides like calcium fluoride (CaF2) and magnesium fluoride (MgF2) were synthesized as nanoparticles via the fluorolytic sol−gel synthesis and then impregnated into wood specimens. In this study, the toxicity of nano metal fluorides was assessed by termite mortality, mass loss and visual analysis of treated specimens after eight weeks of exposure to termites, Coptotermes formosanus. Nano metal fluorides with sol concentrations of 0.5 M and higher were found to be effective against termites resulting in 100% termite mortality and significantly inhibited termite feeding. Among the formulations tested, the least damage was found for specimens treated with combinations of CaF2 and MgF2 with an average mass loss less than 1% and visual rating of “1”. These results demonstrate the efficacy of low water-soluble nano metal fluorides to protect wood from termite attack.
Eine umfangreich ausgestaltete Trinkwasseraufbereitung als Multibarrieren-System ist notwendig, wenn das Rohwasser direkt aus Fließgewässern entnommen wird (z. B. für das Mülheimer Verfahren). Eine der Barrieren wird, als gezielte Behandlungs- oder Sicherheitsstufe, oft als Filter mit granulierter Aktivkohle (GAK-Filter) realisiert. Ihre Standzeit kann bei geringer Wasserbelastung (DOC < 2 mg/L), z. B. bei der Landeswasserversorgung Langenau, bis zu 5 Jahre betragen. Bei Rohwasser mit höherem Organikgehalt (DOC > 7 mg/L), wie bei der Nordwasser in Rostock, wird hingegen mindestens alle drei Jahre die GAK in den Filterkolonnen ausgetauscht.
Die Rest-Adsorptionskapazität der GAK kann durch verschiedene Verfahren abgeschätzt werden, ist aber nach wie vor Gegenstand aktueller Forschung. Die weitergehende Charakterisierung der beladenen GAK kann hierbei helfen.
Auf dem Poster sollen erste Ergebnisse zu den in Langenau und Rostock eingesetzten Aktivkohlen präsentiert werden. Hierzu wurden die frischen und nach unterschiedlichen Laufzeiten beladenen GAK untersucht. Die Zusammensetzung der Anorganik und der adsorbierten Organik, welche mittels Zersetzungs¬gasanalyse charakterisiert wurde, zeigt deutliche Unterschiede. Bspw. nimmt der Calcium-Gehalt der GAK in Langenau kontinuierlich zu, wohingegen dieser in den Proben aus Rostock mit zunehmender Laufzeit zurückgeht. Umgekehrt verhält es sich mit der Organik: Die GAK aus Rostock zeigen Hinweise auf biologische Besiedelung, während diese in Langenau trotz längerer Filterlaufzeit auszubleiben scheint.
This paper reports the formation of zinc phosphate nanoparticles from the artificial digestion of zinc chloride. Initially, the formation of amorphous primary particles with a mean radius of 1.1 nm is observed, alongside the formation of larger, protein stabilized aggregates. These aggregates, with a radius of gyration of 37 nm, are observed after 5 minutes of exposure to artificial saliva and are shown to be colloidally stable for a minimum time of two weeks. The initially formed primary particles are thought to consist of amorphous zinc phosphate, which is then transformed into crystalline Zn3(PO4)2·4H2O over the course of two weeks. Our results demonstrate that the interaction of inorganic salts with bodily fluids can induce the formation of de novo nanoparticles, which in turn, provides insights into how zinc‐enriched foods may also facilitate the formation of nanoparticles upon contact with saliva. As such, this may be considered as an undesirable (bio)mineralization.
In this work the flexural rigidity of individual large diameter multi-walled carbon nanotubes (MWCNTs) was investigated. The bending modulus were obtained by detecting the resonance frequencies of mechanically excited cantilevered carbon nanotubes using the so-called dynamic scanning electron microscopy technique, and applying the Euler–Bernoulli beam theory. For the nanotubes studied, we determined a modulus of up to 160 GPa. This agrees with values reported by other authors for MWCNTs produced by catalytic chemical vapor deposition, however, it is 6-8 times smaller than values reported for single and multi-walled carbon nanotubes produced by arc-discharge synthesis. Toxicological studies with carbon nanotubes have been showing that inhaled airborne nanofibers that reach the deep airways of the respiratory system may lead to serious, asbestos-like lung diseases. These studies suggested that their toxicity critically depends on the fiber flexural rigidity, with high rigidity causing cell lesions. To complement the correlation between observed toxicological effects and fiber rigidities, reliable and routinely applicable measurement techniques for the flexural rigidity of nanofibers are required.
Small-area/spot photoelectron spectroscopy (SAXPS) is a powerful tool for the investigation of small surface features like microstructures of electronic devices, sensors or other functional surfaces. For evaluating the quality of such microstructures, it is crucial to know whether a small signal in a spectrum is an unwanted contamination of the field of view (FoV), defined by the instrument settings, or it originated from outside. The aperture has a major influence on the signal-contribution from the outside. For the evaluation of the FoV, we determined the Au4f intensities measured with the center of the FoV aligned with the center of the spot and normalized to the Au4f intensity determined on the Au-film. With this test specimen, it was possible to characterize the FoV: The signal-contribution from the outside is reduceable down to lower than 50 %, when the aperture is 30 % of the structure dimension for our Kratos AXIS Ultra DLD system.
Surface nanostructuring enables the manipulation of many essential surface properties. With the recent rapid advancements in laser technology, a contactless large‐area processing at rates of up to m2 s−1 becomes feasible that allows new industrial applications in medicine, optics, tribology, biology, etc. On the other hand, the last two decades enable extremely successful and intense research in the field of so‐called laser‐induced periodic surface structures (LIPSS, ripples). Different types of these structures featuring periods of hundreds of nanometers only—far beyond the optical diffraction limit—up to several micrometers are easily manufactured in a single‐step process and can be widely controlled by a proper choice of the laser processing conditions. From a theoretical point of view, however, a vivid and very controversial debate emerges, whether LIPSS originate from electromagnetic effects or are caused by matter reorganization. This article aims to close a gap in the available literature on LIPSS by reviewing the currently existent theories of LIPSS along with their numerical implementations and by providing a comparison and critical assessment of these approaches.
Small-area/spot photoelectron spectroscopy (SAXPS) is a powerful tool for the investigation of small surface features like microstructures of electronic devices, sensors or other functional surfaces. For evaluating the quality of such microstructures, it is crucial to know whether a small signal in a spectrum is an unwanted contamination of the field of view (FoV), defined by the instrument settings, or it originated from outside. The aperture has a major influence on the signal-contribution from the outside. For the evaluation of the FoV, we determined the Au4f intensities measured with the center of the FoV aligned with the center of the spot and normalized to the Au4f intensity determined on the Au-film. With this test specimen, it was possible to characterize the FoV: The signal-contribution from the outside is reduceable down to lower than 50 %, when the aperture is 30 % of the structure dimension for our Kratos AXIS Ultra DLD system.
In a recent publication the authors have presented theoretical and experimental results indicating that the Jacobson–Stockmayer (JS) theory does not provide a correct description of reversible polycondensations for all polymers and for high conversions (e.g. polycondensation in bulk). In this context reversibility means that all condensation step whether resulting in chain growth or in cyclization are reversible and thus, part of an equilibrium. The first two sections of that paper were focused on the demonstration that small, and above all, large cycles can be formed by end-to-end (ete) cyclization in reversible like in irreversible polycondensations. A significant contribution of ete-cyclization to the course of reversible polycondensations was denied by J + S apparently as a contribution to Florýs dogma, that the end groups of long polymer chains will never meet.
Hydrogen economy is a central aspect of future energy supply, as hydrogen can be used as energy storage and fuel. In order tomake water electrolysis efficient, the limiting oxygen evolution reaction (OER) needs to be optimized. Therefore, C-based composite materials containing earth-abundant Fe and Mn were synthesized, characterized and tested in the OER. For pyrolysis temperatures above 700°C N-rich multi-walled carbon nanotubes (MWCNT) are obtained. Inside the tubes Fe3C particles are formed, Fe and Mn oxides are incorporated in the carbon matrix and metal spinel nanoparticles cover the outer surface. The best catalyst prepared at 800°C achieves a low overpotential of 389 mV (at 10 mA/cm2) and high stability (22.6 h). From electrochemical measurements and characterization it can be concluded that the high activity is mainly provided by MWCNT, Fe3C and the metal oxides in the conductive carbon matrix. The metal spinel nanoparticles in
contrast protect the MWCNT from oxidation and thereby contribute to the high stability.
Imaging and small-spot (small area) XPS have become increasingly important components of surface chemical analysis during the last three decades, and its use is growing. Some ambiguity in the use of terminology, understanding of concepts, and lack of appropriate reference materials leads to confusing and not always reproducible data. In this paper, it is shown that by using existing knowledge, appropriate test specimens, and standardized approaches, problems of comparability and such reproducibility issues recently observed for XPS data reported in the scientific literature can be overcome. The standardized methods of ISO 18516:2019, (i) the straight-edge, (ii) the narrow-line, and (iii) the grating method, can be used to characterize and compare the lateral resolution achieved by imaging XPS instruments and are described by reporting examples. The respective measurements are made using new test specimens. When running an XPS instrument in the small-spot (small area) mode for a quantitative analysis of a feature of interest, the question arises as to what contribution to the intensity originates from outside the analysis area. A valid measurement approach to control the intensity from outside the nominal analysis area is also described. As always, the relevant resolution depends on the specific question that needs to be addressed. The strengths and limitations of methods defining resolution are indicated.
The effect of the presence of Fe(III) during the cultivation on the electrochemical activity and corrosion behaviour of dissimilatory iron reducing bacteria Shewanella putrefaciens was studied by means of ex situ and in situ X-ray absorption near-edge spectroscopy (XANES). Stainless steel AISI 304 and thin iron films were studied as substrates. XANES analysis indicated an accelerated iron dissolution and growth of an oxide/hydroxide film for the culture grown with Fe(III) in comparison to the culture grown in absence of Fe(III). Electrochemical Analysis indicated that the biofilm resulted in acceleration of the general corrosion but provides protection against local corrosion.
Electrical conductivity and multiple glassy dynamics of crow-ether based columnar liquid crystals
(2020)
The phase behavior of two unsymmetrical triphenylene crown ether-based columnar liquid crystals (CLCs) bearing different lengths of alkyl chains, KAL465 and KAL468, was investigated using differential scanning calorimetry (DSC). A plastic crystalline (Cry), columnar liquid crystalline (Colh) and an isotropic phase were observed along with two glass transitions in the Cry phase. The molecular mobility of the KAL compounds was further studied by a combination of broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques. By the BDS investigations, three dielectric active relaxation processes were observed for both samples. At low temperatures, a γ-process in the Cry state was detected and is assigned to the localized fluctuations taking place in the alkyl chains. An α2-process takes place at higher temperatures in the Cry phase. An α3 process was found in the Colh mesophase. The advanced calorimetric techniques consist of fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS) employing temperature modulated DSC and FSC (TMDSC and TMFSC). The advanced calorimetric investigations revealed that besides the α2 process in agreement with BDS, a second dynamic glass transition (α1-process) is present which is not observed by dielectric spectroscopy. The results are in good agreement with the glass transitions detected by DSC for this process. The temperature dependences of the relaxation rates of the α1 , α2 and α3 processes are all different. Therefore, different molecular assignments for the relaxation processes are proposed. In addition to the relaxation processes, a conductivity contribution was explored by BDS for both KAL compounds. The conductivity contribution appears in both Cry and Colh phases, where the conductivity increases by ca. one order of magnitude at phase transition from the crystalline to the hexagonal phase.
The structure and composition of polycarbonate polydimethylsiloxane copolymer (PC-co-PDMS) was investigated by applying various analytical approaches including chromatographic separation methods, spectrometric, and spectroscopic detection techniques. In particular, size exclusion chromatography (SEC) and liquid adsorption chromatography operating at different conditions (e.g. using gradient solvent systems) were used to achieve separations according to molar mass and functionality distribution. The coupling of both techniques resulted in fingerprint two-dimensional plots, which could be used to easily compare different copolymer batches. Matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry was applied for structural investigations. The different ionization behavior of both comonomers, however, strongly limited the applicability of this technique. In contrast to that, Fourier-transform Infrared (FTIR) spectroscopy could be used to quantify the amount of PDMS in the copolymer at different points in the chromatogram. The resulting methodology was capable of distinguishing PC-co-PDMS copolymer from PC homopolymer chains present in the material.
The progress in activities on Microbeam Analysis under VAMAS/TWA 37 is reviewed. Particularly the liaison with the new projects within the ISO technical committee TC 202 is presented and discussed with respect to the possibility of identifying and launching related VAMAS projects. Need of more promotion for the engagement of more participants from industry and academia at national, European and international level is highlighted. Also, the competition with the other technical working areas (on 'nano' or materials-related) is critically discussed.
Nanotechnology and lasers are among the most successful and active fields of research and technology that have boomed during the past two decades. Many improvements are based on the controlled manufacturing of nanostructures that enable tailored material functionalization for a wide range of industrial applications, electronics, medicine, etc., and have already found entry into our daily life. One appealing approach for manufacturing such nanostructures in a flexible, robust, rapid, and contactless one-step process is based on the generation of laser-induced periodic surface structures (LIPSS). This Perspectives article analyzes the footprint of the research area of LIPSS on the basis of a detailed literature search, provides a brief overview on its current trends, describes the European funding strategies within the Horizon 2020 programme, and outlines promising future directions.
Gold nanocubes with a monodispersed size distribution (edge = 55 nm) deposited on a silicon wafer. These tiny uniform cubes were produced as reference nanoparticles within the EMPIR project nPSize - Improved traceability chain of nanoparticle size measurements. SEM image acquired at 10 kV with an in-lens secondary electron detector. Image colored in ImageJ using LUT “Orange hot.” Published in Microscopy and Microanalysis 25(S2) (2019) 2328.
Gold nanocubes with a monodispersed size distribution (edge = 55 nm) deposited on a silicon wafer. These tiny uniform cubes were produced as reference nanoparticles in the frame of the European project nPSize - Improved traceability chain of nanoparticle size measurements. SEM Image acquired at 10 kV with an in-lens secondary electron detector. Image colored in ImageJ using LUT “Orange hot.” Published in Microscopy and Microanalysis 25(S2) (2019) 2328.
Laser-induced periodic surface structures (LIPSS) are a universal phenomenon and can be generated on almost any material by irradiation with linearly polarized radiation. This chapter reviews the current state in the field of LIPSS, which are formed in a “self-ordered” way and are often accompanying materials processing applications. LIPSS can be produced in a single-stage process and enable surface nanostructuring and, in turn, adaption of optical, mechanical, and chemical surface properties. Typically, they feature a structural size ranging from several micrometers down to less than 100 nm and show a clear correlation with the polarization direction of the light used for their generation. Various types of LIPSS are classified, relevant control parameters are identified, and their material-specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics. Finally, technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.
3D coherence scanning interferometry (CSI) is an optical, non-contact and rapide measurement technique using a defined bandwidth of white light at normal incidence. Based on this operational principle, white light interference microscopy (WLIM) provides three-dimensional surface topometry data up to a resolution of 0.4 μm lateral and 0.1 nm vertical. Three operating modi, i.e. surface, films and advanced films, enable measurements of step heights, roughness, wear volume, cone angle, surface pattern and layer thickness of transparent coatings.
The determination of layer thickness by WLIM requires the knowledge of optical constants, i.e.the refractive index n and the extinction coefficient k. For technical surfaces, data base values - if available at all - have to be determined or validated by spectroscopic ellipsometry (SE). From this oblique incidence technique both optical constants and layer thickness can be derived based on a model for at least semi-transparent coatings. For different layer thicknesses, a
comparison is made between WLIM and SE. Measurement uncertainty is
discussed for both topometric features and layer thickness for different use cases.
Traceability to SI system is ensured by certified standards (PTB/NIST) within a DAkkS DIN EN ISO/IEC 17025:2018 accredited lab.
Biofilm formation in industrial or medical settings is usually unwanted and leads to serious health problems and high costs. Inhibition of initial bacterial adhesion prevents biofilm formation and is, therefore, a major mechanism of antimicrobial action of surfaces. Surface topography largely influences the interaction between bacteria and surfaces which makes topography an ideal base for antifouling strategies and eco-friendly alternatives to chemical surface modifications. Femtosecond laser-processing was used to fabricate sub-micrometric surface structures on silicon and stainless steel for the development of antifouling topographies on technical materials.
Amphiphilic polymer nanogels (NGs) are promising drug delivery vehicles that extend the application of conventional hydrophilic NGs to hydrophobic cargoes. By randomly introducing hydrophobic groups into a hydrophilic polymer network, loading and release profiles as well as surface characteristics of these colloids can be tuned. However, very little is known about the underlying internal structure of such complex colloidal architectures. Of special interest is the question how the amphiphilic network composition influences the internal morphology and the “fuzzy” surface structure. To shine light into the influence of varying network amphiphilicity on these structural features, we investigated a small library of water-swollen amphiphilic NGs using small-angle X-ray scattering (SAXS). It was found that overall hydrophilic NGs, consisting of pure poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA), display a disordered internal structure as indicated by the absence of a SAXS peak. In contrast, a SAXS peak is present for amphiphilic NGs with various amounts of incorporated hydrophobic groups such as cholesteryl (CHOLA) or dodecyl (DODA). The internal composition of the NGs is considered structurally homologous to microgels. Application of the Teubner–Strey model reveals that hydrophilic PHPMA NGs have a disordered internal structure (positive amphiphilicity factor) while CHOLA and DODA samples have an ordered internal structure (negative amphiphilicity factor). From the SAXS data it can be derived that the internal structure of the amphiphilic NGs consists of regularly alternating hydrophilic and hydrophobic domains with repeat distances of 3.45–5.83 nm.
A new metallosilicate based on yttrium was synthesized and characterized by XRD, FT-IR, 29Si MAS-NMR, and 89Y MAS-NMR. The mixed framework of the material was confirmed by the detection of distinct chemical shift groups using 29Si MAS-NMR (at -82 to -87 ppm, -91 to -94 ppm, -96 to -102 ppm, and -105 to -108 ppm), as well as four distinct chemical shifts in the 89Y MAS-NMR spectrum (at -89, -142, -160, and -220 ppm). Adsorption and kinetic analyses indicated the potential of the new material for the removal of lead and cadmium from aqueous media. The adsorption results for lead indicated that dynamic equilibrium was reached after five hours, with total lead removal of around 94 %, while for cadmium it was reached in the first hour, with total Cadmium removal of around 74 %. The adsorptions of lead and cadmium were modeled using pseudo-first order (PFO) and pseudo-second order (PSO) kinetic models. Although both models provided high R2 values (0.9903 and 0.9980, respectively), the PSO model presented a much lower χ2 red value (4.41×10−4), compared to the PFO model (2.12×10−3), which indicated that the rate-limiting step was probably due to the chemisorption of lead from the solution onto the yttrium-based metallosilicate.
Understanding the correlation between the morphological and functional properties of particulate materials is crucial across all fields of physical and natural sciences. This manuscript reports on the investigation of the effect of polyethylene glycol (PEG) employed as a capping Agent in the synthesis of SrTiO3 crystals. The crucial influence of PEG on both the shape and size of the strontium titanate particles is revealed, highlighting the effect on the photocurrents measured under
UV–Vis irradiation.
We present an approach towards the in situ solid state NMR monitoring of mechanochemical reactions in a ball mill. A miniaturized vibration ball mill is integrated into the measuring coil of a home-built solid state NMR probe, allowing for static solid state NMR measurements during the mechanochemical reaction within the vessel. The setup allows to quantitatively follow the product evolution of a prototypical mechanochemical reaction, the formation of zinc phenylphosphonate from zinc acetate and phenylphosphonic acid. MAS NMR investigations on the final reaction mixture confirmed a reaction yield of 89% in a typical example. Thus, NMR spectroscopy may in the future provide complementary information about reaction mechanisms of mechanochemical reactions and team up with other analytical methods which have been employed to follow reactions in situ, such as Raman spectroscopy or X-ray diffraction.
Lanthanides (Ln) are critical raw materials, however, their mining and purification have a considerable negative environmental impact and sustainable recycling and separation strategies for these elements are needed. In this study, the precipitation and solubility behavior of Ln complexes with pyrroloquinoline quinone (PQQ), the cofactor of recently discovered lanthanide (Ln) dependent methanol dehydrogenase (MDH) enzymes, is presented. In this context, the molecular structure of a biorelevant europium PQQ complex was for the first time elucidated outside a protein environment. The complex crystallizes as an inversion symmetric dimer, Eu2PQQ2, with binding of Eu in the biologically relevant pocket of PQQ. LnPQQ and Ln1Ln2PQQ complexes were characterized by using inductively coupled plasma mass spectrometry (ICP‐MS), infrared (IR) spectroscopy, 151Eu‐Mössbauer spectroscopy, X‐ray total scattering, and extended X‐ray absorption fine structure (EXAFS). It is shown that a natural enzymatic cofactor is capable to achieve separation by precipitation of the notoriously similar, and thus difficult to separate, lanthanides to some extent.
Tire and road wear particles (TRWPs) are heteroagglomerates of tire rubber and other particles deposited on the road surface and one of the main contributors to non-exhaust emissions of automobile traffic. In this study, samples from road environments were analyzed for their TRWP contents and concentra- tions of eight organic tire constituents. TRWP concentrations were determined by quantifying Zn in the density fraction < 1.9 g/cm ³and by thermal extraction desorption-gas chromatography-mass spectrometry (TED-GC/MS) and the concentrations ranged from 3.7 to 480 mg TRWP/g. Strong and statistically signif- icant correlations with TRWPs were found for 2-hydroxybenzothiazole and 2-aminobenzothiazole, indi- cating that these substances may be suitable markers of TRWPs. The mass distribution of TRWPs in road dust suggests that the main mass fraction formed on roads consists of coarse particles ( > 100 μm). Data for a sedimentation basin indicate that the fine fraction ( < 50 μm) is preferentially transported by road runoffinto receiving waters. The size distribution and density data of TRWP gathered by three different quantitation approaches also suggest that aging of TRWPs leads to changes in their particle density. An improved understanding of the dynamics of TRWP properties is essential to assess the distribution and dissipation of this contaminant of emerging concern in the environment.
Sufficient adhesion/tensile strength are basic requirements for any coating/composite material. For coatings, adhesive strength in N/mm2 is of Major interest for various applications such as decorative and water-repellent coatings on wood (paints and varnishes), optical coatings on glass and polymers (reflectors and filters), electrical coatings on semiconductors, glass and polymers (conducting and bondable layers), mechanical coatings on metals and polymers (wear-reduction, scratch-resistance) and adhesion-promoting layers. For composite materials, tensile strength in N/mm2 is also a key quantity for carbon fiber reinforced composites (CFC), laminates and adhesive-bonded joints. Centrifugal adhesion testing (CAT) transfers the single-sample tensile test from a tensile or universal testing machine into an analytical centrifuge as multiple-sample test of up to eight test pieces. The one-sided sample support instead of a two-sided sample clamping and the absence of mounting- and testing-correlated shear forces provides fast and reliable results both for adhesive strength and bonding strength by means of bonded test stamps. For bonding strength, the evaluation of failure pattern from microscopic inspection is required in order to determine the failure pattern according to ISO 10365 such as adhesive failure (AF), delamination failure (DF) and cohesive failure (CF). Hence, one test run by CAT-technology provides either statistics or ranking of up to eight samples at once. For adhesive strength of coatings, a variety of examples is discussed such as ALD-Al203 layers as adhesion promoters, evaporated Ag-layers on N-BK7 glass, sputtered Cr- and Al-layers on Borofloat 33 glass, evaporated Au-films on N-BK7 glass and sputtered SiO2 -layers on CR39 Polymer. Provided adhesive or bonding strength are high enough, the substrate or the joining part may also fail.
The concept of direct mass-spectrometric analysis, especially exploited by ambient desorption/ionization (ADI) methods, provides numerous means for convenient sample analysis. While many simple and versatile ionization sources have been developed, challenges lay in achieving efficient sample introduction. In previous work, a sample introduction method employing direct current corona discharge (CD) coupled to a surface acoustic wave nebulization (SAWN) device enhanced sampling performance for both polar and nonpolar analytes by up to 4 orders of magnitude. In fact, the SAWN-CD method generated a multiply charged peptide ion signal comparable to that of conventional ESI. Unfortunately, the high cost of the SAWN devices themselves limits their accessibility. Herein, we report on an analogous implementation of CD with an inexpensive ultrasonic nebulizer (USN) on the basis of a commercial room humidifier demonstrating equivalent exemplary performance. We subsequently compare the two methods of SAWN-CD and USN-CD in a screening application of milk for the detection of two antibiotic drugs, ciprofloxacin and ampicillin. Finally, we further investigate the relative softness of these CD-coupled acoustic nebulization methods in comparison to that of ESI using a survival yield study of the thermometer ion nitrobenzylpyridinium.