TY - JOUR A1 - Ankli, P. P. A1 - Abdelwahab, A. A. A1 - Logachov, A. A1 - Bugiel, R. A1 - Drobne, D. A1 - Novak, S. A1 - Kranjc, E. A1 - Saje, S. A1 - Pellegrino, F. A1 - Alladio, E. A1 - Sordello, F. A1 - Corrao, E. A1 - Hodoroaba, Vasile-Dan A1 - Radnik, Jörg A1 - Mrkwitschka, Paul A1 - Madbouly, Loay Akmaal A1 - Akdemir, Yücel A1 - Gulumian, M. A1 - Wepener, V. A1 - Andraos, C. A1 - Boodhia, K. A1 - Jones, E. A1 - Doolin, A. A1 - Leuchtenberg, K. A1 - Valsami Jones, E. A1 - Rocca, C. A1 - Ibrahim, B. A1 - Singh, D. A1 - Chakraborty, S. A1 - Jurkschat, K. A1 - Johnston, C. A1 - Van Der Zande, M. A1 - Fernandez, D. A1 - Queipo, P. A1 - Clifford, C. A1 - Hardy, B. T1 - Knowledge Infrastructure supporting image-based characterisation of 2D graphene materials N2 - As part of the European Horizon ACCORDs project, advanced methods are being developed for the image-based characterisation of 2D nanomaterials. Given the complexity of this task, robust nd wellorganised data management is critical to ensuring high-quality outcomes. To support this, we have established a knowledge infrastructure that serves as the central repository for protocols, images and experimental data which are stored in a standardised, harmonised manner and in accordance with the FAIR principles – Findable, Accessible, Interoperable and Reusable and open science. This machine-readable framework enables the systematic and computationally automated correlation of image features with experimental descriptors, facilitating accurate material characterisation and transparent reporting which is all integrated in the ACCORDs KI. KW - Graphene-related 2D materials (GR2M) KW - 2D materials KW - Knowledge infrastructure KW - Characterisation PY - 2025 DO - https://doi.org/10.1016/j.toxlet.2025.07.660 SN - 0378-4274 VL - 411 SP - S281 EP - S282 PB - Elsevier B.V. AN - OPUS4-65061 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mrkwitschka, Paul A1 - Sahre, Mario A1 - Zurutuza, Amaia A1 - Radnik, Jörg A1 - Hodoroaba, Vasile-Dan T1 - Standardized Chemical Composition Analysis of Graphene Oxide Flakes with SEM/EDS and XPS Works Reliably N2 - Suspensions of graphene-related 2D materials (GR2M) are broadly used for further applications like printable electronics. The reliable quantification of the composition of graphene-related 2D materials as liquid suspensions is still a challenging task, which can hinder the commercialisation of the products. Specific parameters to be measured are defined, e.g. the oxygen-to-carbon (O/C) concentration ratio, the trace metal impurities, or the functional groups present, but reference protocols are still missing. One of the central methods for the quantification is X-ray photoelectron spectroscopy (XPS) as a rather expensive method. Therefore, the development of cheaper alternatives is highly desired. One attractive alternative of XPS is energy-dispersive spectroscopy (EDS) which is usually coupled with scanning electron microscopy (SEM). This combination is one of the most widely used methods in analytical laboratories. In this contribution the results of a systematic study on the capability of SEM/EDS to reliably quantify the O/C ratio in a well-defined and well-characterized graphene oxide material are presented. The robustness of the SEM/EDS results obtained at various measurement conditions (various excitation energies) is tested by comparing the results to the established XPS analysis, which has been carried out on the same samples. It is demonstrated that for samples prepared by drop-casting on a substrate, both surface-sensitive XPS analysis and bulk-characterising EDS result in very similar elemental composition of oxygen and carbon for thick spots. Further, the effect of untight deposited material enabling co-analysis of the (silicon) substrate, is evaluated for both methods, XPS and EDS. The last results clearly show the influence of the substrate on the analysis of the results and stressed out the importance of the sample preparation. KW - EDS KW - Light elements KW - XPS/HAXPES KW - Graphene oxide KW - Quantification KW - Standardisation PY - 2025 DO - https://doi.org/10.1093/mam/ozaf048.267 VL - 31 IS - 7 SP - 531 EP - 532 PB - Oxford Aacademic AN - OPUS4-63792 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mrkwitschka, Paul T1 - Standardized Chemical Characterisation of Graphene Oxide Flakes by X-Ray Photoelectron Spectroscopy and Energy-Dispersive X-Ray Spectroscopy N2 - Reliable quantification of the chemical composition of graphene-related 2D materials as powders and liquid suspensions is a challenging task. Analytical methods such as XPS, ICP-MS, TGA and FTIR are recommended to be used in ongoing projects at standardisation bodies. The specific parameters to be measured are also defined, e.g. the oxygen-to-carbon (O/C) concentration ratio, the trace metal impurities, or the functional groups present [1]. In this contribution, for the first time, the results of a systematic study on the capability of SEM/EDS to reliably quantify the O/C ratio in a well-defined and well-characterized graphene oxide material [2] are presented. It is expected that the quantitative EDS analysis of light elements emitting characteristic X-ray lines below 1 keV to be provided with significantly larger measurement uncertainties than the analysis of elements with an atomic number of 11 (Na) or above [3]. The robustness of the SEM/EDS results obtained at various measurement conditions (various excitation energies) is tested by comparing the results to the established XPS analysis [4], which has been carried out on the same samples. A crucial step in sample preparation from liquid suspension with graphene oxides flakes onto a substrate for analysis with both XPS and EDS. It is demonstrated that if a closed and enough thick drop-cast deposited spot is succeeded to be deposited on a substrate, both surface-sensitive XPS analysis and bulk-characterising EDS result in very similar elemental composition of oxygen and carbon. Hence, theoretical, expected O/C atomic ratio values for pure graphene oxide of ~0.5 [1] are achieved (with both methods), see Figure 1. Further, the effect of untight deposited material enabling co-analysis of the (silicon) substrate, is evaluated for both methods, XPS and EDS. To note that all the EDS results in this study have been quantified standardless. The results of this study demonstrate the reliability of the reference measurement protocol for SEM/EDS to be introduced into ISO/DTS 23359, including the dedicated sample preparation, particularly for the cases when the concentration of the GO flakes in stock liquid suspension is low. Further, also the consideration of this GO material as one of the very few available as a commercial material on the market as the very first GO reference material with regard to its morphology as well as chemical composition. Both the standard measurement procedure and the candidate reference material will immensely contribute to characterise reliably the chemical composition of graphene-related 2D materials with SEM/EDS as one of the most widely used methods in analytical laboratories T2 - EMAS 2025 Workshop CY - Mataró, Spain DA - 11.05.2025 KW - Advanced Materials KW - Graphene KW - Chemical Quantification KW - EDX KW - XPS PY - 2025 AN - OPUS4-64082 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mrkwitschka, Paul T1 - Wire-print procedure for accurate morphological and Chemical characterization of graphene-related 2D-materials N2 - One of the biggest challenges in the physico-chemical characterization of particulate nanomaterials pertains to the sample preparation. Particularly the imaging methods require suitable deposition of the sample on a substrate. ‘Suitable’ sample preparation of a particulate (nano)material on a substrate means to make visible the constituent particles to a microscopy technique able to analyze the nanoscale (AFM, SEM, TEM, etc). The particles deposited on a substrate either directly as a powder or from liquid suspension must be ideally isolated (de-agglomerated), without particle losses, homogeneously distributed in a high density of particles per substrate area for efficient analysis, with good statistics of the counted particles. Various sample preparation approaches to meet the latter requirements have been reported in the literature, e.g. electrospray, substrate surface treatment, embedding the particulate material and polishing the cross-section, or addition of ligands to the suspended nanostructures to enhance their hydrophilicity [1], [2], [3], [4]. In this study we have systematically tested the efficacy of a new deposition procedure for graphene-related 2D materials (GR2M’s) from liquid suspension onto a substrate for quantitative analysis of their size and shape distribution with electron microscopy. The technique is an extension of the conventional drop-casting method, and we have designated it “wire-print” deposition. It consists of two steps, first one being usual drop-casting on a copper substrate and second one involving a thin copper wire with a sub-mm diameter being dipped into the deposited droplet and retracted with a corresponding half-spherical droplet attached on its tip and final deposition of this entire nL-amount of suspension onto e.g. a silicon wafer for microscopical, detailed analysis. The result of 11 series of such a wire-print deposition for a graphene-based ink is shown in Figure 1 (labeled A-L), where various conditions (treatment of the starting suspension) have been experimented with a repetition of up to 10 times per condition, all together 86 spots on a silicon wafer of 10 mm x 10 mm. The result of one series of 8 repeated wire-print depositions is shown in Figure 2, where the deposited spots are visualized with SEM. Note the weak presence of coffee-rings, irregular spot shape, and presence of agglomerates. The results for the measured flake size distribution expressed as ECD (equivalent circular diameter) are represented in Fig. 3 for all the eight depositions. Both the mean value of the 8 ECD distributions and the total number of flakes deposited in each spot show a variance in the range of 17% and 22%, respectively, see Table 1. In the context of accurate analysis of such challenging complex materials these numbers can be considered as excellent and demonstrate the high benefit of the wire-print deposition for accurate morphological measurements on GR2M’s. T2 - Microscopy and Microanalysis 2025 CY - Salt Lake City, UTAH, USA DA - 27.07.2025 KW - Sample preparation KW - Graphene KW - Electron Microscopy KW - Morphology PY - 2025 AN - OPUS4-64083 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rossi, Andrea A1 - Corrao, Elena A1 - Alladio, Eugenio A1 - Drobne, Damjana A1 - Hodoroaba, Vasile-Dan A1 - Jurkschat, Kerstin A1 - Kononenko, Veno A1 - Madbouly, Loay Akmal A1 - Mrkwitschka, Paul A1 - Yasamin, Nakhli A1 - Novak, Sara A1 - Radnik, Jörg A1 - Saje, Špela A1 - Santalucia, Rosangela A1 - Sordello, Fabrizio A1 - Pellegrino, Francesco T1 - Multivariate optimization and characterization of graphene oxide via design of experiments and chemometric analysis N2 - Controlling the structure and properties of graphene oxide (GO) remains a challenge due to the poor reproducibility of conventional synthetic protocols and limited understanding of parameter-property relationships. In this study, we present an integrated analytical framework that combines Design of Experiments (DoE) with chemometric modelling to systematically assess the effects of eight synthesis variables on GO’s physicochemical and functional features. A Plackett–Burman experimental design enabled efficient screening of synthesis conditions, while comprehensive characterization (spanning UV–Vis spectroscopy, XPS, SEM–EDX, TEM–EDX, and XRD) was coupled with multivariate tools (Principal Component Analysis and Multiple Linear Regression) to identify statistically significant correlations between synthetic inputs and material responses. Notably, we demonstrate that UV–Vis spectra can serve as a robust proxy for oxidation state, offering a rapid and accessible alternative to surface-sensitive methods. The approach yields a predictive analytical toolkit for guiding GO synthesis and highlights a generalizable strategy for the rational design of flat nanomaterials. This work supports reproducible, resource-efficient material development aligned with Safe and Sustainable by Design (SSbD) principles. KW - Graphene oxide KW - 2D-materials KW - Design of Experiment KW - Synthesis KW - Chemometric analysis PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-652576 DO - https://doi.org/10.1016/j.flatc.2025.100988 SN - 2452-2627 VL - 55 SP - 1 EP - 9 PB - Elsevier B.V. AN - OPUS4-65257 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Abram, Sarah-Luise A1 - Mrkwitschka, Paul A1 - Thünemann, Andreas A1 - Radnik, Jörg A1 - Häusler, I. A1 - Bresch, Harald A1 - Hodoroaba, Vasile-Dan A1 - Resch-Genger, Ute T1 - Iron Oxide Nanocubes as a New Certified Reference Material for Nanoparticle Size Measurements N2 - The rational design and increasing industrial use of nanomaterials require a reliable characterization of their physicochemical key properties like size, size distribution, shape, and surface chemistry. This calls for nanoscale reference materials (nanoRMs) for the validation and standardization of commonly used characterization methods closely matching real-world nonspherical nano-objects. This encouraged us to develop a nonspherical nanoRM of very small size consisting of 8 nm iron oxide nanocubes (BAM-N012) to complement spherical gold, silica, and polymer nanoRMs. In the following, the development and production of this nanoRM are highlighted including the characterization by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) as complementary methods for size and shape parameters, homogeneity and stability studies, and calculation of a complete uncertainty budget of the size features. The determination of the nanocubes’ edge length by TEM and SAXS allows a method comparison. In addition, SAXS measurements can also provide the mean particle number density and the mass concentration. The certified size parameters, area equivalent circular diameter and square edge length, determined by TEM with a relative expanded uncertainty below 9%, are metrologically traceable to a natural constant for length, the very precisely known (111) lattice spacing of silicon. Cubic BAM-N012 qualifies as a certified nanoRM for estimating the precision and trueness, validation, and quality assurance of particle size and shape measurements with electron microscopy and SAXS as well as other sizing methods suitable for nanomaterials. The production of this new iron oxide nanocube RM presents an important achievement for the nanomaterial community, nanomaterial manufacturers, and regulators. KW - Certification KW - SAXS KW - Homogeneity KW - Nano KW - Particle KW - Iron oxide KW - Quality assurance KW - Reference material KW - Size KW - Electron microscopy KW - Stability KW - Shape PY - 2023 DO - https://doi.org/10.1021/acs.analchem.3c00749 SN - 0003-2700 VL - 95 IS - 33 SP - 12223 EP - 12231 PB - American Chemical Society CY - Columbus, Ohio AN - OPUS4-58176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mrkwitschka, Paul T1 - Correlative analysis with electron microscopy applied in different operating modes (SEM, STEM-in-SEM and TEM) for the accurate morphological characterisation of non-spherical fine nanoparticles N2 - Electron microscopy applied in different operating modes, e.g., SEM, TEM or STEM-in-SEM, is the gold standard method to investigate the exact size and shape of individual nanoparticles. However, when fine nanoparticles with a non-monodisperse size distribution and non-spherical shapes are analysed, achieving an accurate result is challenging. Deviations in size measurements of more than 10% may occur. Understanding of the contrasts and sensitivities characteristic to the individual operating modes of an electron microscope is key in interpreting and evaluating quantitatively the measurement uncertainties needed for an eventual certification of specific nanoparticles via traceable results. Further, beyond the pure measurement, the other components in the analysis workflow with significant impact on the overall measurement uncertainties are the sample preparation and the image segmentation. In the present study the same areas of selected iron oxide fine nanoparticles (<25 nm) as reference nanomaterial (candidate) prepared on substrate for electron microscopy imaging are analysed correlatively with SEM, STEM-in-SEM and TEM with respect to their size and shape distribution. Individual significant measurement uncertainties are discussed, e.g., the sensitivity of secondary electron detectors of InLens-type to the surface morphology, particularly to the presence of an ultrathin organic coating or signal saturation effects on the particle edges, to electron beam exposure, to surface contamination, or the selection of the threshold for image segmentation. Another goal of this study is to establish a basis of analysis conditions which shall guarantee accurate results when both manual and particularly (semi-)automated segmentation approaches are applied. Advantages as well as limitations of the use of different electron microscopy operating modes, applied individually and correlatively, are highlighted. T2 - E-MRS 2024 Spring Meeting CY - Strasbourg, France DA - 27.05.2024 KW - Nanoparticles KW - Electron Microscopy KW - Metrology KW - Imaging KW - Reference materials PY - 2024 AN - OPUS4-60436 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mrkwitschka, Paul A1 - Hodoroaba, Vasile-Dan T1 - Understanding Correlative Electron Microscopy Imaging with SEM, STEM in SEM and TEM for the Accurate Characterization of Size and Shape of FeOx Nanoparticles N2 - The recently certified reference material (CRM) BAM-N012 as cubical iron oxide FeOx nanoparticles (NPs) of 8 nm area equivalent square edge length (ESL) and the RM candidate BAM-N013 as nearly spherical NPs of 22 nm size were analyzed in detail by electron microscopy (EM). For the metrological characterization with SEM, STEM in SEM and TEM, the understanding of the imaging contrasts and sensitivities, and the correct interpretation of the (art)effects which are inherent to each detection mode is necessary. The same sample areas with NPs deposited on a TEM grid were analyzed by two SEM acquisition modes, i. e. SE InLens and STEM in SEM using a dedicated transmission sample holder, and further, correlatively, analyzed with TEM. With increasing kV, SE InLens shows increasing particle size (unless overcharging at the particle boundaries is filtered), as a known effect. For STEM-in-SEM the particle size decreases significantly and individual particles are identified easier (at 2 kV only a few single particles can be detected automatically). ❑ Documentation of the sample preparation and measurement conditions (including optimization process) is important for reproducibility. ❑ Plasma cleaning, analysis in the transmission mode at SEM is recommended for FeOx NPs. ❑ Selection of the threshold algorithm can significantly alter the reported ECD. T2 - Microscopy and Microanalysis 2024 CY - Cleveland, OH, USA DA - 28.07.2024 KW - Nanoparticles KW - Electron microscopy KW - Iron oxide KW - Reference materials KW - Correlative microscopy KW - Size and shape distribution PY - 2024 AN - OPUS4-60806 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mrkwitschka, Paul T1 - Understanding Correlative Electron Microscopy Imaging with SEM, STEM-in-SEM and TEM for the Accurate Characterization of Size and Shape of FeOx Nanoparticles N2 - The recently certified reference material (CRM) BAM-N012 as cubical iron oxide FeOx nanoparticles (NPs) of 8 nm area equivalent square edge length (ESL) and the RM candidate BAM-N013 as nearly spherical NPs of 22 nm size were analyzed in detail by electron microscopy (EM). For the metrological characterization with SEM, STEM in SEM and TEM, the understanding of the imaging contrasts and sensitivities, and the correct interpretation of the (art)effects which are inherent to each detection mode is necessary. The same sample areas with NPs deposited on a TEM grid were analyzed by two SEM acquisition modes, i. e. SE InLens and STEM in SEM using a dedicated transmission sample holder, and further, correlatively, analyzed with TEM. With increasing kV, SE InLens shows increasing particle size (unless overcharging at the particle boundaries is filtered), as a known effect. For STEM-in-SEM the particle size decreases significantly and individual particles are identified easier (at 2 kV only a few single particles can be detected automatically). ❑ Documentation of the sample preparation and measurement conditions (including optimization process) is important for reproducibility. ❑ Plasma cleaning, analysis in the transmission mode at SEM is recommended for FeOx NPs. ❑ Selection of the threshold algorithm can significantly alter the reported ECD. T2 - SALSA Make and Measure 2024: Interfaces CY - Berlin, Germany DA - 11.09.2024 KW - Correlative microscopy KW - Electron microscopy KW - Iron oxide KW - Nanoparticles KW - Reference materials KW - Size and shape distribution PY - 2024 AN - OPUS4-62347 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mrkwitschka, Paul T1 - Understanding Correlative Electron Microscopy Imaging with SEM, STEM in SEM and TEM for the Accurate Characterization of Size and Shape of FeOx Nanoparticles N2 - The recently certified reference material (CRM) BAM-N012 as cubical iron oxide FeOx nanoparticles (NPs) of 8 nm area equivalent square edge length (ESL) and the RM candidate BAM-N013 as nearly spherical NPs of 22 nm size were analyzed in detail by electron microscopy (EM). For the metrological characterization with SEM, STEM in SEM and TEM, the understanding of the imaging contrasts and sensitivities, and the correct interpretation of the (art)effects which are inherent to each detection mode is necessary. The same sample areas with NPs deposited on a TEM grid were analyzed by two SEM acquisition modes, i. e. SE InLens and STEM in SEM using a dedicated transmission sample holder, and further, correlatively, analyzed with TEM. With increasing kV, SE InLens shows increasing particle size (unless overcharging at the particle boundaries is filtered), as a known effect. For STEM-in-SEM the particle size decreases significantly and individual particles are identified easier (at 2 kV only a few single particles can be detected automatically). ❑ Documentation of the sample preparation and measurement conditions (including optimization process) is important for reproducibility. ❑ Plasma cleaning, analysis in the transmission mode at SEM is recommended for FeOx NPs. ❑ Selection of the threshold algorithm can significantly alter the reported ECD T2 - 2. Treffen des DGE-Arbeitskreises SEM CY - Stuttgart, Germany DA - 26.09.2024 KW - Correlative microscopy KW - Electron microscopy KW - Iron oxide KW - Nanoparticles KW - Reference materials KW - Size and shape distribution PY - 2024 AN - OPUS4-62349 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ankli, P.P. A1 - Ali, A. A1 - Hodzic, S. A1 - Logachov, A. A1 - Maciejczuk, K. A1 - Milochiv, A. A1 - Hardy, S. A1 - Hardy, B. A1 - Novak, S. A1 - Kranjc, E. A1 - Kononenko, V. A1 - Saje, S. A1 - Hodoroaba, Vasile-Dan A1 - Radnik, Jörg A1 - Akmal, Loay A1 - Mrkwitschka, Paul A1 - Pellegrino, F. A1 - Rossi, A. A1 - Alladio, E. A1 - Sordello, F. A1 - Gulumian, M. A1 - Valsami-Jones, E. A1 - Andraos, C. A1 - Wepener, V. A1 - Jurkschat, K. A1 - Jones, E. A1 - Singh, D. A1 - Ibrahim, B. A1 - van der Zande, M. A1 - Fernandez-Poulussen, D. A1 - Queipo, P. A1 - Drobne, D. T1 - Data management for image-based characterisation of 2D nano-materials N2 - The ACCORDs project, funded through Horizon Europe, is pioneering a novel approach to investigate Graphene Family Materials (GFMs) through image analysis. Our aim is to unveil how these materials might influence health and the environment. To achieve this, we are developing a platform designed for the easy retrieval, access, sharing, and utilisation of GFM data and the coordination between biological and physico-chemical data formats. Integral to this platform is an OMERO-based library for image storage, alongside data collection forms and image analysis tools. Efforts are underway to streamline the process for researchers to upload and disseminate their findings, manage information within a database and navigate the data with ease. Adhering to REMBI guidelines, which set the standard for annotating biological images with metadata, we ensure our data collection is comprehensive and adheres to established best practices. Initially, we are employing thresholding and basic machine learning techniques for image segmentation, laying the groundwork for advanced analysis through deep learning to gain more profound insights. Upon completion, the project will deliver a comprehensive platform facilitating efficient data and image management concerning GFMs. This platform will enable the straightforward discovery and use of protocols and results, all organised in accordance with the FAIR principles – Findable, Accessible, Interoperable, and Reusable. This initiative is poised to significantly impact materials science, enhancing our comprehension of the safety and environmental implications of 2D materials. KW - Graphene KW - Image analysis KW - Data management PY - 2024 DO - https://doi.org/10.1016/j.toxlet.2024.07.655 VL - 399 SP - S271 PB - Elsevier B.V. AN - OPUS4-61011 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Rossi, Andrea A1 - Alladio, Eugenio A1 - Drobne, Damjana A1 - Hodoroaba, Vasile-Dan A1 - Jurkschat, Kerstin A1 - Kononenko, Veno A1 - Madbouly, Loay Akmal A1 - Mrkwitschka, Paul A1 - Novak, Sara A1 - Radnik, Jörg A1 - Saje, Špela A1 - Santalucia, Rosangela A1 - Sordello, Fabrizio A1 - Pellegrino, Francesco T1 - Publisher correction: Development of a one-pot synthesis of rGO in water by optimizing Tour’s method parameters N2 - This is a publisher's correction to the original article "Development of a one-pot synthesis of rGO in water by optimizing Tour’s method parameters" that was published online on 27th September 2024 in "Scientific reports" (DOI: 10.1038/s41598-024-73606-2). PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-617590 DO - https://doi.org/10.1038/s41598-024-77468-6 SN - 2045-2322 VL - 14 IS - 1 SP - 1 PB - Springer Nature CY - London AN - OPUS4-61759 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mrkwitschka, Paul T1 - Towards automated analysis of the lateral dimensions of graphene oxide flakes N2 - Graphene and graphene-oxide (GO) are advanced materials which – similar to other graphene-related 2D materials (GR-2M) - are already used for instance in catalysis processes, biomedical applications, in inks and resins, or as composite materials for the aviation industry. The lateral/structural characterization of graphene oxide (GO) flakes is a challenging task, with steps like sample preparation, representative image selection and exact determination of the particle size distribution of well-defined size and shape descriptors being crucial for an accurate analysis. To ensure that safe-by-design principles are met within the various application fields, the commercial material must be thoroughly characterized and specified through well-known and standardized procedures. GO flakes with different degrees of complexity were selected to assess the requirements for an accurate evaluation of their physico-chemical properties. These samples show inherent features with complex nanoscale characteristics such as porosity and edge roughness; further, the lateral size (quantified via equivalent circular diameter (ECD), minimum Feret and maximum Feret) of isolated and overlapping particles deposited on a substrate span over several orders of magnitude (nano to micron scale). The samples showed different degrees of agglomeration (and possible aggregation) with sizes ranging between submicron to a few tens of micrometers. One focus is the automated segmentation and evaluation of images obtained by electron microscopy. The GO samples appear translucent with well-defined contrast between single and overlapping flakes both with the secondary electron detector of type InLens as well as with SEM in the transmission mode (STEM) utilizing a dedicated sample holder. To this end it is of utmost importance for the accurate image segmentation to carefully select thresholds both manually and through semi-automatic approaches using well-known threshold algorithms such as “IsoData” and pre-defined segmentation applications such as the ParticleSizer software package. Further specific challenges in identifying and extracting key features of selected graphene oxide flakes are being discussed and approaches towards accurate and representative characterization are presented. T2 - E-MRS 2024 Spring Meeting CY - Strasbourg, France DA - 27.05.2024 KW - Graphene /-oxide KW - Morphology KW - Electron microscopy KW - Imaging KW - Advanced materials PY - 2024 AN - OPUS4-60435 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mrkwitschka, Paul A1 - Mühlbauer, Michaela A1 - Rossi, Andrea A1 - Pellegrino, Francesco A1 - Zurutuza, Amaia A1 - Radnik, Jörg A1 - Meier, Florian A1 - Hodoroaba, Vasile-Dan T1 - Morphological Analysis of Graphene Oxide by Scanning Electron Microscopy and Correlative Field-flow Fractionation Coupled with Multi-angle Light Scattering N2 - In this paper graphene related 2D materials (GR2M) arre investigated by centrifugal field flow fractioning (CF3) and SEM. Three materials were selected as case studies (CS): graphene „HD-G (CS I), graphene oxide UniTo“ (CS II), and graphene oxide „Graphenea“ (CS III). For CS I particles were evaluated as constituent particles in agglomerates, for the other two materials only isolated (non aggregated/agglomerated) flakes were considered for determination of the area equivalent circular diameter (ECD). Size analysis of all three materials was carried out by CF3 coupled with MALS (Multi-Angle Light Scattering). For evaluation, it was found that the data obtained was best suited to a disc model. Results are in good agreement when compared to the sizes obtained before CF3 analysis. CS II material is too heterogenous to accurately determine flake size by imaging. CF3 coupled with MALS enables to assess fractions within the highly heterogenous material of CS II. Imaging of the material in CS III after CF3 measurement indicates that the procedure is non-destructive. This could not be verified for the CS‘s I & II As a next step we plan to analyse the fractionated samples by imaging them within a SEM wet-cell. KW - 2D Materials KW - SEM KW - Centrifugal field flow fractionation (CF3) KW - Imaging KW - Size distribution PY - 2025 DO - https://doi.org/10.1093/mam/ozaf048.222 VL - 31 IS - 7 SP - 442 EP - 443 PB - Oxford Academic AN - OPUS4-63804 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mrkwitschka, Paul A1 - Abram, Sarah-Luise A1 - Thünemann, Andreas A1 - Rühle, Bastian A1 - Radnik, Jörg A1 - Bresch, Harald A1 - Resch-Genger, Ute A1 - Hodoroaba, Vasile-Dan T1 - The Role of Electron Microscopy in the Development of Monodisperse Cubic Iron Oxide Nanoparticles as Certified Reference Material for Size and Shape N2 - BAM is currently building up a platform of novel nanoRMs relying on iron oxide nanoparticles of different shape, size and surface chemistry. Iron oxide was chosen as a core material because of its relevance to the material and life sciences. As a first candidate of this series, we present cubic iron oxide nanoparticles with a nominal edge length of 8 nm. These particles were synthesized by thermal decomposition of iron oleate in high boiling organic solvents adapting well-known literature procedures. After dilution to a concentration suitable for electron microscopy (TEM and SEM) as well as for small-angle X-ray scattering (SAXS) measurements, the candidate nanoRM was bottled and assessed for homogeneity and stability by both methods following the guidelines of ISO 17034 and ISO Guide 35. The particle sizes obtained by both STEM-in-SEM and TEM are in excellent agreement with a minimum Feret of 8.3 nm ± 0.7 nm. The aspect ratio (AR) of the iron oxide cubes were extracted from the images as the ratio of minimum Feret to Feret resulting in an AR of 1.18 for TEM to 1.25 for SEM. Alternatively, a rectangular bounding box was fitted originating from the minimum Feret and the longest distance through the particle in perpendicular direction. This led to AR values of 1.05 for TEM and 1.12 for SEM, respectively. The results confirm the almost ideal cubic shape. KW - Reference nanoparticles KW - Iron oxide KW - Cubical shape KW - Electron microscopy KW - SAXS KW - Nano CRM KW - Size PY - 2022 DO - https://doi.org/10.1017/S1431927622003610 SN - 1435-8115 VL - 28 IS - Suppl. 1 SP - 802 EP - 805 PB - Cambridge University Press AN - OPUS4-55599 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mrkwitschka, Paul T1 - The Role of Electron Microscopy in the Development of Monodisperse Cubic Iron Oxide Nanoparticles as CRM for Size and Shape N2 - Due to their unique physico-chemical properties, nanoparticles are well established in research and industrial applications. A reliable characterization of their size, shape, and size distribution is not only mandatory to fully understand and exploit their potential and develop reproducible syntheses, but also to manage environmental and health risks related to their exposure and for regulatory requirements. To validate and standardize methods for the accurate and reliable particle size determination nanoscale reference materials (nanoRMs) are necessary. However, there is only a very small number of nanoRMs for particle size offered by key distributors such as the National Institute of Standards and Technology (NIST) and the Joint Research Centre (JRC) and, moreover, few provide certified values. In addition, these materials are currently restricted to polymers, silica, titanium dioxide, gold and silver, which have a spherical shape except for titania nanorods. To expand this list with other relevant nanomaterials of different shapes and elemental composition, that can be used for more than one sizing technique, we are currently building up a platform of novel nanoRMs relying on iron oxide nanoparticles of different shape, size and surface chemistry. Iron oxide was chosen as a core material because of its relevance for the material and life sciences. T2 - Microscopy and Microanalysis 2022 CY - Online meeting DA - 31.07.2022 KW - Certified Referencematerial KW - Cubical Iron Oxide KW - Nanoparticles KW - Electron Microscopy KW - Small-Angle X-ray Scattering PY - 2022 AN - OPUS4-57035 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mrkwitschka, Paul A1 - Sahre, Mario A1 - Corrao, Elena A1 - Pellegrino, Francesco A1 - Hodoroaba, Vasile-Dan T1 - Wire-Print as a Sample Preparation Procedure Suitable for Accurate Morphological Characterization of Constituent Particles for Graphene-Related 2D-Materials N2 - In this study we have systematically tested the efficacy of a new deposition procedure for graphene-related 2D materials (GR2M’s) from liquid suspension onto a substrate for quantitative analysis of their size and shape distribution with electron microscopy. The technique is an extension of the conventional drop-casting method, and we have designated it “wire-print” deposition. It consists of two steps, first one being usual drop-casting on a copper substrate and second one involving a thin copper wire with a sub-mm diameter being dipped into the deposited droplet and retracted with a corresponding half-spherical droplet attached on its tip and final deposition of this entire nL-amount of suspension onto e.g. a silicon wafer for microscopical, detailed analysis. 11 series of such a wire-print deposition for a graphene-based ink have been considered, whereby various conditions (treatment of the starting suspension) have been experimented with a repetition of up to 10 times per condition, all together 86 spots on a silicon wafer of 10 mm x 10 mm. The evaluation of one series of 8 repeated wire-print depositions reveal that the deposited spots are visualized with SEM. The weak presence of coffee-rings, irregular spot shape, and presence of agglomerates should be noticed. Both the mean value of the 8 ECD distributions and the total number of flakes deposited in each spot show a variance in the range of 17% and 22%, respectively. In the context of accurate analysis of such challenging complex materials these numbers can be considered as excellent and demonstrate the high benefit of the wire-print deposition for accurate morphological measurements on GR2M’s. KW - Sample preparation KW - Imaging KW - 2D materials KW - Morphology KW - Size distribution PY - 2025 DO - https://doi.org/10.1093/mam/ozaf048.219 VL - 31 IS - 7 SP - 436 EP - 437 PB - Oxford Academic AN - OPUS4-63821 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mrkwitschka, Paul A1 - Rühle, Bastian A1 - Kuchenbecker, Petra A1 - Löhmann, Oliver A1 - Lindemann, Franziska A1 - Hodoroaba, Vasile-Dan T1 - Embedding and cross-sectioning as a sample preparation procedure for accurate and representative size and shape measurement of nanopowders N2 - Reliable measurement of the size of polydisperse, complex-shaped commercial nanopowders is a difficult but necessary task, e.g., for regulatory requirements and toxicity risk assessment. Suitable methods exist for the accurate characterization of the size of non-aggregated, stabilized, spherical and monodisperse nanoparticles. In contrast, industrial nanoscale powders usually require dedicated sample preparation procedures developed for the analysis method of choice. These nano-powders tend to agglomerate and/or aggregate, a behavior which in combination with an innate broad particle size distribution and irregular shape often significantly alters the achievable accuracy of the measured size parameters. The present study systematically tests two commercially available nanoscale powders using different sample preparation methods for correlative analysis by scanning electron microscopy, dynamic light scattering, Brunauer–Emmet–Teller method and differential mobility analysis. One focus was set on the sample preparation by embedding nanoparticles in carbon-based hot-mounting resin. Literature on this topic is scarce and the accuracy of the data extracted from cross sections of these particles is unclearly stated. In this paper systematic simulations on the deviation of the size parameters of well-defined series of nanoparticles with different shapes from the nominal value were carried out and the contributing factors are discussed. KW - Nanopowder KW - Electron microscopy KW - Sample preparation KW - Cross-sectioning KW - Cerium oxide KW - Zinc oxide PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-593289 DO - https://doi.org/10.1038/s41598-023-51094-0 SN - 2045-2322 VL - 14 SP - 1 EP - 10 PB - Springer Nature CY - London AN - OPUS4-59328 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mrkwitschka, Paul A1 - Mieller, Björn A1 - Rabe, Torsten A1 - Markötter, Henning ED - Petzow, G. ED - Mücklich, F. T1 - Machine learning assisted characterization of a Low Temperature Cofired Ceramic (LTCC) module measured by synchrotron computed tomography N2 - The 5G technology promises real time data transmission for industrial processes, autonomous driving, virtual and augmented reality, E-health applications and many more. The Low Temperature Co-fired Ceramics (LTCC) technology is well suited for the manufacturing of microelectronic components for such applications. Still, improvement of the technology such as further miniaturization is required. This study focuses on the characterization of inner metallization of LTCC multilayer modules, especially on the vertical interconnect access (VIA). Critical considerations for this characterization are delamination, pore clustering in and at the edge of the VIA, deformation, and stacking offset. A LTCC multilayer consisting of a glassy crystalline matrix with silver based VIAs was investigated by synchrotron x-ray tomography (CT). The aim of this study is to propose a multitude of structural characteristic values to maximize the information gained from the available dataset. Data analysis has been done with the open source software ImageJ as well as several additional plugins. The high-resolution CT data was evaluated through 2D slices for accessibility reasons. The segmentation of all 2000 slices to assess the different regions e.g. pores, silver and glass ceramic was done by a supervised machine learning algorithm. A quantitative evaluation of shape, deformation, and porosity of the VIA with respect to its dimensions is presented and the suitability of the characterization approach is assessed. T2 - 54. Metallographie Taagung CY - Online meeting DA - 16.09.2020 KW - Machine Learning KW - LTCC KW - Synchrotron Tomography PY - 2020 SN - 978-3-88355-422-8 VL - 54 SP - 136 EP - 141 PB - Deutsche Gesellschaft für Materialkunde e.V CY - Sankt Augustin AN - OPUS4-51298 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mrkwitschka, Paul T1 - Machine learning assisted characterization of a Low Temperature Co-fired Ceramic (LTCC) module measured by synchrotron computed tomography. N2 - The 5G technology promises real time data transmission for industrial processes, autonomous driving, virtual and augmented reality, E-health applications and many more. The Low Temperature Co-fired Ceramics (LTCC) technology is well suited for the manufacturing of microelectronic components for such applications. Still, improvement of the technology such as further miniaturization is required. This study focuses on the characterization of inner metallization of LTCC multilayer modules, especially on the vertical interconnect access (VIA). Critical considerations for this characterization are delamination, pore clustering in and at the edge of the VIA, deformation, and stacking offset. A LTCC multilayer consisting of a glassy crystalline matrix with silver based VIAs was investigated by synchrotron x-ray tomography (CT). The aim of this study is to propose a multitude of structural characteristic values to maximize the information gained from the available dataset. Data analysis has been done with the open source software ImageJ as well as several additional plugins. The high-resolution CT data was evaluated through 2D slices for accessibility reasons. The segmentation of all 2000 slices to assess the different regions e.g. pores, silver and glass ceramic was done by a supervised machine learning algorithm. A quantitative evaluation of shape, deformation, and porosity of the VIA with respect to its dimensions is presented and the suitability of the characterization approach is assessed. T2 - 54. Metallographie Tagung CY - Online meeting DA - 16.09.2020 KW - Machine Learning KW - LTCC KW - Synchrotron Tomography PY - 2020 AN - OPUS4-51299 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bresch, Sophie A1 - Mieller, Björn A1 - Mrkwitschka, Paul A1 - Moos, R. A1 - Rabe, Torsten T1 - Glass-ceramic composites as insulation material for thermoelectric oxide multilayer generators N2 - Thermoelectric generators can be used as energy harvesters for sensor applications. Adapting the ceramic multilayer technology, their production can be highly automated. In such multilayer thermoelectric generators, the electrical insulation material, which separates the thermoelectric legs, is crucial for the performance of the device. The insulationmaterial should be adapted to the thermoelectric regarding its averaged coefficient of thermal expansion α and its sintering temperature while maintaining a high resistivity. In this study, starting from theoretical calculations, a glass-ceramic Composite material adapted for multilayer generators fromcalciummanganate and Calcium cobaltite is developed. The material is optimized towards an α of 11 × 10−6 K−1 (20–500◦C), a sintering temperature of 900◦C, and a high resistivity up to 800◦C. Calculated and measured α are in good agreement. The chosen glass-ceramic composite with 45 vol.% quartz has a resistivity of 1 × 107 Ωcm and an open porosity of <3%. Sintered multilayer samples from tape-cast thermoelectric oxides and screen-printed insulation show only small reaction layers. It can be concluded that glass-ceramic composites are a well-suited material class for insulation layers as their physical properties can be tuned by varying glass composition or dispersion phases. KW - Electrical insulators KW - Glass-ceramics KW - Multilayers KW - Thermal expansion PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538898 DO - https://doi.org/10.1111/jace.18235 SN - 0002-7820 SP - 1 EP - 10 PB - Wiley Online Library AN - OPUS4-53889 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mrkwitschka, Paul A1 - Abram, Sarah-Luise A1 - Rühle, Bastian A1 - Hodoroaba, Vasile-Dan T1 - Understanding Correlative Electron Microscopy Imaging with SEM, STEM-in-SEM and TEM for the Accurate Characterization of Size and Shape of Iron Oxide Nanoparticles N2 - The recently certified reference material (CRM) BAM-N012 as cubical iron oxide FeOx nanoparticles (NPs) of 8 nm area equivalent square edge length (ESL) and the RM candidate BAM-N013 as nearly spherical NPs of 22 nm size were analyzed in detail by electron microscopy (EM). For the metrological characterization with SEM, STEM in SEM and TEM, the understanding of the imaging contrasts and sensitivities, and the correct interpretation of the (art)effects which are inherent to each detection mode is necessary. The same sample areas with NPs deposited on a TEM grid were analyzed by two SEM acquisition modes, i. e. SE InLens and STEM in SEM using a dedicated transmission sample holder, and further, correlatively, analyzed with TEM. With increasing kV, SE InLens shows increasing particle size (unless overcharging at the particle boundaries is filtered), as a known effect. For STEM-in-SEM the particle size decreases significantly and individual particles are identified easier (at 2 kV only a few single particles can be detected automatically). ❑ Documentation of the sample preparation and measurement conditions (including optimization process) is important for reproducibility. ❑ Plasma cleaning, analysis in the transmission mode at SEM is recommended for FeOx NPs. ❑ Selection of the threshold algorithm can significantly alter the reported ECD. KW - Nanoparticles KW - Iron oxide KW - Electron microscopy KW - Reference materials KW - Particle size distribution KW - Imaging PY - 2024 DO - https://doi.org/10.1093/mam/ozae044.339 VL - 30 IS - Supplement_1 SP - 710 EP - 711 PB - Oxford University Press (OUP) AN - OPUS4-61007 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -