TY - JOUR A1 - Wollschläger, Nicole A1 - Häusler, Ines A1 - Ortel, Erik A1 - Hodoroaba, Vasile-Dan A1 - Palasse, L. A1 - Dirscherl, K. T1 - Characterization of porous, TiO2 nanoparticle films using on-axis TKD in SEM – a new nano-analysis tool for a large-scale application N2 - A combined methodical approach is tested with respect to the characterization of the inner structure of porous TiO2 layers as typically used in modern dye sensitized solar cells (DSSC). Their performance is directly linked to the surface area of the pore network. The micrometer thick layer employed was manufactured by screen-printing of a starting TiO2 powder constituted of shape-controlled, bipyramidal anatase nanoparticles on FTO/glass substrates. The analytical methods exploited in our study are Focused Ion Beam (FIB) slicing followed by 3D reconstruction as well as the new approach transmission Kikuchi diffraction (TKD) technology in the scanning electron microscope (SEM). Size and shape distribution of the TiO2 NPs within the layer can be extracted. SEM in transmission mode and atomic force microscopy (AFM) have been used to verify the dimensional data obtained by the new combined methodical approach. Its analytical benefits but also the challenges and limitations are highlighted. KW - TiO2 KW - TKD KW - Particle size distribution KW - Nanoparticles KW - Porous film PY - 2017 UR - https://www.cambridge.org/core/services/aop-cambridge-core/content/view/8A8B29335A2F4D0CB6922F6F5A19C5DC/S1431927617003397a.pdf/characterization_of_porous_tio2_nanoparticle_films_using_onaxis_tkd_in_sem_a_new_nanoanalysis_tool_for_a_largescale_application.pdf DO - https://doi.org/10.1017/S1431927617003397 VL - 23 IS - S1 (July) SP - 542 EP - 543 PB - Cambridge University Press CY - New York, NY, U.S.A. AN - OPUS4-41924 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lavric, V. A1 - Isopescu, R. A1 - Maurino, V. A1 - Pellegrino, F. A1 - Pellutiè, L. A1 - Ortel, Erik A1 - Hodoroaba, Vasile-Dan T1 - A new model for nano-TiO2 crystal birth and growth in hydrothermal treatment using an oriented attachment approach N2 - The synthesis of TiO2 was studied in an original hydrothermal process that uses triethanolamine titanium complex Ti(TeoaH)2 as a Ti precursor and triethanolamine (TeoaH3) as a shape controller to obtain bipyramidal anatase nanoparticles. Backed-up by experimental evidence, i.e., time profiles for Ti(IV) species concentrations together with crystal shape and particle size distributions measured by dynamic light scattering and electron microscopy, a mathematical model was built. The model includes chemical reactions responsible for TiO2 generation in solution and the subsequent anatase nucleation and crystal growth. The oriented attachment mechanism was adopted to explain the build-up of crystals with equilibrium anatase structure (Wulff structure) and time-varying shape factor. This complex mathematical model was solved writing and validating an in-house software using the Matlab (Natick, MA, USA) environment. The process was simulated for a batch time of 50 h, and the results, in terms of main species concentration and crystal size distributions, are in rather good agreement with the experimental measurements. KW - Nanoparticles KW - TiO2 KW - SEM/EDX KW - Modelling KW - Crystal growth PY - 2017 UR - http://pubs.acs.org/doi/pdf/10.1021/acs.cgd.7b00302 DO - https://doi.org/10.1021/acs.cgd.7b00302 SN - 1528-7483 SN - 1528-7505 VL - 17 IS - 11 SP - 5640 EP - 5651 PB - ACS Publications AN - OPUS4-42724 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wohlleben, W. A1 - Mielke, Johannes A1 - Bianchin, A. A1 - Ghanem, A. A1 - Freiberger, H. A1 - Rauscher, H. A1 - Gemeinert, Marion A1 - Hodoroaba, Vasile-Dan T1 - Reliable nanomaterial classification of powders using the volume-specific surface area method N2 - The volume-specific surface area (VSSA) of a particulate material is one of two apparently very different metrics recommended by the European Commission for a definition of "nanomaterial" for regulatory purposes: specifically, the VSSA metric may classify nanomaterials and non-nanomaterials differently than the median size in number metrics, depending on the chemical composition, size, polydispersity, shape, porosity, and aggregation of the particles in the powder. Here we evaluate the extent of agreement between classification by electron microscopy (EM) and classification by VSSA on a large set of diverse particulate substances that represent all the anticipated challenges except mixtures of different substances. EM and VSSA are determined in multiple labs to assess also the level of reproducibility. Based on the results obtained on highly characterized benchmark materials from the NanoDefine EU FP7 project, we derive a tiered screening strategy for the purpose of implementing the definition of nanomaterials. We finally apply the Screening strategy to further industrial materials, which were classified correctly and left only borderline cases for EM. On platelet-shaped nanomaterials, VSSA is essential to prevent false-negative classification by EM. On porous materials, approaches involving extended Adsorption isotherms prevent false positive classification by VSSA. We find no false negatives by VSSA, neither in Tier 1 nor in Tier 2, despite real-world industrial polydispersity and diverse composition, shape, and coatings. The VSSA screening strategy is recommended for inclusion in a technical guidance for the implementation of the definition. KW - Nanomaterial KW - Nanomaterial classification KW - Regulation KW - VSSA KW - Size measurement KW - Particle size PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-391450 DO - https://doi.org/10.1007/s11051-017-3741-x SN - 1388-0764 SN - 1572-896X VL - 19 IS - 2 SP - Article 61, 1 EP - 16 PB - Springer Nature AN - OPUS4-39145 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Grulke, E. A. A1 - Yamamoto, K. A1 - Kumagai, K. A1 - Häusler, Ines A1 - Österle, Werner A1 - Ortel, Erik A1 - Hodoroaba, Vasile-Dan A1 - Brown, S. C. A1 - Chan, C. A1 - Zheng, J. A1 - Yamamoto, K. A1 - Yashiki, K. A1 - Song, N. W. A1 - Kim, Y. H. A1 - Stefaniak, A. B. A1 - Schwegler-Berry, D. A1 - Coleman, V. A. A1 - Jämting, Å. K. A1 - Herrmann, J. A1 - Arakawa, T. A1 - Burchett, W. W. A1 - Lambert, J. W. A1 - Stromberg, A. J. T1 - Size and shape distributions of primary crystallites in titania aggregates N2 - The primary crystallite size of titania powder relates to its properties in a number of applications. Transmission electron microscopy was used in this interlaboratory comparison (ILC) to measure primary crystallite size and shape distributions for a commercial aggregated titania powder. Data of four size descriptors and two shape descriptors were evaluated across nine laboratories. Data repeatability and reproducibility was evaluated by analysis of variance. One-third of the laboratory pairs had similar size descriptor data, but 83% of the pairs had similar aspect ratio data. Scale descriptor distributions were generally unimodal and were well-described by lognormal reference models. Shape descriptor distributions were multi-modal but data visualization plots demonstrated that the Weibull distribution was preferred to the normal distribution. For the equivalent circular diameter size descriptor, measurement uncertainties of the lognormal distribution scale and width parameters were 9.5% and 22%, respectively. For the aspect ratio shape descriptor, the measurement uncertainties of the Weibull distribution scale and width parameters were 7.0% and 26%, respectively. Both measurement uncertainty estimates and data visualizations should be used to analyze size and shape distributions of particles on the nanoscale. KW - Measurement uncertainty KW - Size distribution KW - Shape distribution KW - TEM KW - Titania PY - 2017 DO - https://doi.org/10.1016/j.apt.2017.03.027 SN - 0921-8831 VL - 28 IS - 7 SP - 1647 EP - 1659 PB - Elsevier B.V. AN - OPUS4-40478 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pellegrino, F. A1 - Pellutiè, L. A1 - Sordello, F. A1 - Minero, C. A1 - Ortel, Erik A1 - Hodoroaba, Vasile-Dan A1 - Maurino, V. T1 - Influence of agglomeration and aggregation on the photocatalytic activity of TiO2 nanoparticles N2 - Particle aggregation and agglomeration influence the optical properties of materials and therefore theirability to absorb and scatter the incoming radiation, also affecting their photocatalytic activity. Wehave studied the correlation between aggregation and photocatalytic activity for titanium dioxide bymeans of experimental measurements of extinction and photocatalytic activity and calculations of theiroptical properties (extinction, absorption and scattering cross-sections). This approach can be adoptedto quantitatively assess the quantum yields of the heterogeneous photocatalytic systems. The study wasperformed on TiO2PC105 Cristal ACTiVTM, made of aggregated (and agglomerated) primary particles of anatase. The size of the aggregates has been reduced with ultra-sonication. Aqueous suspensions of the obtained materials were characterized by measuring the optical properties (UV–vis extinction), the sizing properties (DLS) and the photocatalytic activity (degradation of phenol under standard con-ditions). The extinction and absorption spectra of the suspensions were derived from the calculatedcoefficients, considering also the size distributions measured with DLS, and revealed that light absorptionis maximized when particle aggregation and agglomeration are avoided, while diffusion of the incomingradiation dominates when large aggregates and agglomerates are present. The present paper represents a valuable approach to the accurate and reproducible measurement of the photocatalytic activity ofTiO2nanoparticles suspensions, thus allowing a more reliable comparison of the properties of different materials. KW - Titanium dioxide KW - Nanoparticles KW - Agglomeration/aggregation KW - Photocatalysis KW - Quantum yield PY - 2017 DO - https://doi.org/10.1016/j.apcatb.2017.05.046 SN - 0926-3373 SN - 1873-3883 VL - 216 SP - 80 EP - 87 PB - Elsevier B.V. AN - OPUS4-40477 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mielke, Johannes A1 - Dohányosová, P. A1 - Müller, P. A1 - Lopez, S. A1 - Hodoroaba, Vasile-Dan T1 - Electrospray as a sample preparation tool for electron microscopic investigations: Toward quantitative evaluation of nanoparticles N2 - The potential of electrospray deposition, for the controlled preparation of particles for imaging in electron microscopes, is evaluated on various materials: from mono-modal suspensions of spherical particles to multimodal suspensions and to real-world industrial materials. It is shown that agglomeration is reduced substantially on the sample carrier, compared with conventional sample preparation techniques. For the first time, it is possible to assess the number concentration of a tri-modal polystyrene suspension by electron microscopy, due to the high deposition efficiency of the electrospray. We discovered that some suspension stabilizing surfactants form artifact particles during electrospraying. These can be avoided by optimizing the sprayed suspension. KW - Electrospray deposition KW - Nanoparticles KW - SEM KW - TEM KW - Sample preparation PY - 2017 UR - https://www.cambridge.org/core/journals/microscopy-and-microanalysis/article/electrospray-as-a-sample-preparation-tool-for-electron-microscopic-investigations-toward-quantitative-evaluation-of-nanoparticles/483B212FF290B7EC001A212A19E4E72A DO - https://doi.org/10.1017/S1431927617010145 SN - 1435-8115 SN - 1431-9276 VL - 23 IS - S1 (July) SP - 1896 EP - 1897 PB - Cambridge University Press CY - New York, NY, U.S.A. AN - OPUS4-42453 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rosu, Dana-Maria A1 - Ortel, Erik A1 - Hodoroaba, Vasile-Dan A1 - Kraehnert, R. A1 - Hertwig, Andreas ED - Hertwig, Andreas ED - Hinrichs, K. ED - Beck, Uwe ED - Esser, N. T1 - Ellipsometric porosimetry on pore-controlled TiO2 layers N2 - The practical performance of surface coatings in applications like catalysis, water splitting or batteries depends critically on the coating materials’ porosity. Determining the porosity in a fast and nondestructive way is still an unsolved problem for industrial thin-films technology. As a contribution to calibrated, non-destructive, optical layer characterisation, we present a multi-method comparison study on porous TiO2 films deposited by sol-gel synthesis on Si wafers. The ellipsometric data were collected on a range of samples with different TiO2 layer thickness and different porosity values. These samples were produced by templated sol-gel synthesis resulting in layers with a well-defined pore size and pore density. The ellipsometry measurement data were analysed by means of a Bruggeman effective medium approximation (BEMA), with the aim to determine the mixture ratio of void and matrix material by a multi-sample analysis strategy. This analysis yielded porosities and layer thicknesses for all samples as well as the dielectric function for the matrix material. Following the idea of multi-method techniques in metrology, the data was referenced to imaging by electron microscopy (SEM) and to a new EPMA (electron probe microanalysis) porosity approach for thin film analysis. This work might lead to a better metrological understanding of optical porosimetry and also to better-qualified characterisation methods for nano-porous layer systems. 1. IntroductionPorous materials, especially porous thin films play an importantrole in chemical and physical technology in every case where thecontact area between two media has to be maximised. From cataly-sis to photochemistry and photovoltaics, the applications of porouslayer materials are diverse and numerous [1–6].The accurate and non-destructive characterisation of porousfilms for layered systems poses a challenge. This applies especiallyfor the key parameter of porous films, their porosity, i.e. the mix-ing ratio between the Matrix of the film (host material) and thepore volume which is empty or filled with a fluid medium (inclu-sions). This parameter influences most of the physical and chemicalproperties of a porous thin film and is therefore essential for theunderstanding as well as the optimisation of this class of materials. T2 - International Conference on Spectroscopic Ellipsometry (ICSE-7) CY - Berlin, Germany DA - 06.06.2016 KW - Spectroscopic ellipsometry KW - Porous materials KW - Porosimetry KW - Multi-sample analysis KW - Thin film metrology PY - 2017 DO - https://doi.org/10.1016/j.apsusc.2016.11.055 SN - 0169-4332 SN - 1873-5584 VL - 421 IS - Part B SP - 487 EP - 493 PB - Elsevier B.V. AN - OPUS4-42517 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan T1 - Analysis of TiO2 nanoparticles – Various activities at BAM N2 - The presentation goes into the characterization of TiO2 engineered nanoparticles within EU/FP7 SETNanoMetro Project and the nanomaterial classification according to the EC definition tested within EU/FP7 NanoDefine Project. Further, ISO/TC 229/JWG 2 activities related on ISO standards in development and inter-laboratory comparisons on measurement of nanoparticle size and shape distribution by SEM and TEM are discussed. T2 - Seminar CY - PTB Braunschweig, Germany DA - 23.03.2017 KW - Nanoparticles KW - Electron microscopy KW - Nanomaterial KW - Standardization KW - Inter-laboratory comparison PY - 2017 AN - OPUS4-39527 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan T1 - Analysis of fluorine traces in TiO2 nanoplatelets by SEM/EDX, AES and TOF-SIMS N2 - Hydrothermal synthesis of anatase TiO2 nanosheets with a high fraction of exposed {001} facets and related high photocatalytic activity - as an alternative to bipyramidal anatase TiO2 nanoparticles mainly exposing the {101} facets. The scope of the material preparation work is the thermal reduction of residual fluorides from HF (capping agent) induced during the synthesis of TiO2 nanosheets by calcination at 873K. The analytical task consists of detection and localization of fluorine present at the surface and/or in the bulk of TiO2 nanosheets before and after calcination by SEM/EDX, Auger electron spectroscopy and ToF-SIMS. T2 - Microscopy & Microanalysis 2017 Meeting CY - St. Louis, MO, USA DA - 06.08.2017 KW - Nanoplatelets KW - Fluorine KW - SEM/EDX KW - Auger electron spectroscopy KW - ToF-SIMS KW - TiO2 PY - 2017 AN - OPUS4-41579 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan T1 - Electrospray as a sample preparation tool for electron microscopy: Toward quantitative evaluation of nanoparticles N2 - Electrospray ionization constitutes a promising deposition technique for high-resolution imaging. Particle distribution on TEM grids takes place homogeneously and no losses occur. Suspension must be appropriate (stabilizer may induce artefacts). ESI parameters need to be optimized for each material. T2 - Final NanoDefine Outreach Event: Classification of nanomaterials according to the EU definition CY - Brüssel, Belgium DA - 19.09.2017 KW - Electrospray deposition KW - Electron microscopy KW - Nanoparticles PY - 2017 UR - http://www.nanodefine.eu/index.php/nanodefine-meetings/125-final-outreach-event-2017 AN - OPUS4-42508 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -