TY - JOUR A1 - Pellegrino, Francesco A1 - Ortel, Erik A1 - Mielke, Johannes A1 - Schmidt, R. A1 - Maurino, V. A1 - Hodoroaba, Vasile-Dan T1 - Customizing New Titanium Dioxide Nanoparticles with Controlled Particle Size and Shape Distribution: A Feasibility Study Toward Reference Materials for Quality Assurance of Nonspherical Nanoparticle Characterization JF - Advanced Engineering Materials N2 - An overview is given on the synthesis of TiO2 nanoparticles with well-defined nonspherical shapes (platelet like, bipyramidal, and elongated), with the focus on controlled, reproducible synthesis, as a key requirement for the production of reference materials with homogeneous and stable properties. Particularly with regard to the nanoparticle shapes, there is a high need of certified materials, solely one material of this type being commercially available since a few months (elongated TiO2). Further, measurement approaches with electron microscopy as the golden method to tackle the nanoparticle shape are developed to determine accurately the size and shape distribution for such nonspherical particles. A prerequisite for accurate and easy (i.e., automated) image analysis is the sample preparation, which ideally must ensure a deposition of the nanoparticles from liquid suspension onto a substrate such that the particles do not overlap, are solvent-free, and have a high deposition density. Challenges in the Synthesis of perfectly monodispersed and solvent-free TiO2 nanoparticles of platelet and acicular shapes are highlighted as well as successful measurement approaches on how to extract from 2D projection electron micrographs the most accurate spatial information, that is, true 3D size, for example, of the bipyramidal nanoparticles with different geometrical orientations on a substrate. KW - Nanoparticles KW - Titanium dioxide KW - Reference materials KW - Standardisation KW - Particle size and shape distribution PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538849 DO - https://doi.org/10.1002/adem.202101347 VL - 24 IS - 6 SP - 1 EP - 10 PB - Wiley-VCH AN - OPUS4-53884 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hodoroaba, Vasile-Dan A1 - Cios, G. A1 - Tokarski, T. A1 - Mansfeld, Ulrich A1 - Ortel, Erik A1 - Mielke, Johannes A1 - Pellegrino, F. A1 - Maurino, V. T1 - Towards 3D Understanding of Non-spherical Nanoparticles by Transmission Kikuchi Diffraction (TKD) for Improved Particle Size Distribution by Electron Microscopy JF - Microscopy and Microanalysis N2 - 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. KW - Nanoparticles KW - Transmission Kikuchi Diffraction (TKD) KW - Electron microscopy KW - TiO2 KW - 3D PY - 2020 DO - https://doi.org/10.1017/S1431927620013999 VL - 26 IS - S2 SP - 260 EP - 261 PB - Cambridge University Press CY - Cambridge, UK AN - OPUS4-51772 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pellegrino, F. A1 - Isopescu, R. A1 - Pellutiè, L. A1 - Sordello, F. A1 - Rossi, A. M. A1 - Ortel, Erik A1 - Martra, G. A1 - Hodoroaba, Vasile-Dan A1 - Maurino, V. T1 - Machine learning approach for elucidating and predicting the role of synthesis parameters on the shape and size of TiO2 nanoparticles JF - Scientific Reports N2 - 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. KW - Machine learning KW - Nanoparticles KW - Titanium dioxide KW - Size KW - Shape KW - Synthesis PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-515084 DO - https://doi.org/10.1038/s41598-020-75967-w VL - 10 IS - 1 SP - 18910 PB - Springer Nature AN - OPUS4-51508 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hodoroaba, Vasile-Dan A1 - Rades, Steffi A1 - Borghetti, P. A1 - Ortel, Erik A1 - Wirth, Thomas A1 - Garcia, S. A1 - Gómez, E. A1 - Blanco, M. A1 - Alberto, G. A1 - Martra, G. T1 - Organic surface modification and analysis of titania nanoparticles for self‐assembly in multiple layers JF - Surface and Interface Analysis N2 - The characteristics of TiO2 coatings can greatly influence their final performance in large‐scale applications. In the present study, self‐assembly of TiO2 nanoparticles (NPs) in multiple layers was selected as a deposition procedure on various substrates. For this, the main prerequisite constitutes the surface modification of both NPs and substrate with, for example, silane coupling agents. A set of functionalized TiO2 NPs has been produced by reaction with either (3‐aminopropyl)triethoxysilane (APTES) or (3‐aminopropyl)phosphonic acid (APPA) to functionalize the NP surface with free amino‐groups. Then, the complementary functionalized NP set can be obtained from an aliquot of the first one, through the conversion of free surface amino groups to aldehydes by reaction with glutaraldehyde (GA). Several types of TiO2 NPs differing in size, shape, and specific surface area have been functionalized. Fourier‐transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), SEM/ energy‐dispersive X‐ray spectroscopy (EDS), XPS, Auger electron spectroscopy (AES), and Time‐of‐Flight (ToF)‐SIMS analyses have been carried out to evaluate the degree of functionalization, all the analytical methods employed demonstrating successful functionalization of TiO2 NP surface with APTES or APPA and GA. KW - TiO2 KW - Nanoparticles KW - Surface functionalization KW - Layer-by-layer deposition KW - Surface chemical analysis PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-508601 DO - https://doi.org/10.1002/sia.6842 SN - 1096-9918 VL - 52 IS - 12 SP - 829 EP - 834 PB - John Wiley & Sons Ltd AN - OPUS4-50860 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rades, Steffi A1 - Borghetti, P. A1 - Ortel, Erik A1 - Wirth, Thomas A1 - Blanco, M. A1 - Gómez, E. A1 - Martinez, A. A1 - Jupille, J. A1 - Martra, G. A1 - Hodoroaba, Vasile-Dan T1 - Control of functionalization of supports for subsequent assembly of titania nanoparticle films JF - Surface and Interface Analysis N2 - For self‐assembling of TiO2 nanoparticles in multiple layers by layer‐by‐layer deposition to be applied to TiO2 thin films with defined and homogeneous thickness for large‐scale applications, the proper functionalization of substrate surface is a prerequisite to guarantee sufficient adhesion. The substrates selected and tested in the present paper were conductive, fluorine‐doped tin oxide (FTO) glass, nonconductive silica glass, and titanium alloy. The current study focusses on the analytical control of the stepwise functionalization of the substrates with 3‐aminopropyltriethoxysilane and glutaraldehyde (GA) for both the FTO glass and silica glass and with 3‐aminepropyl phosphonic acid and GA for Ti alloy. The analyses have been conducted by means of surface sensitive methods, X‐ray photoelectron spectroscopy, Auger electron spectroscopy, and time‐of‐flight secondary ions mass spectrometry. Chemical composition of surface of functionalized substrates shows differences in the degree and type of modification in dependence on substrate. It could be demonstrated that the best functionalized substrates were the conductive FTO glasses. The analysis of the functionalized Ti substrates has revealed that the surface coverage with 3‐aminepropyl phosphonic acid and GA molecules is an inhomogeneous one, and further optimization of the two‐step functionalization on the Ti alloy substrate is necessary. KW - Nanoparticles KW - Surface functionalization KW - TiO2 KW - SEM/EDX KW - Auger Electron Spectroscopy KW - ToF-SIMS KW - Thin films PY - 2018 DO - https://doi.org/10.1002/sia.6398 SN - 0142-2421 SN - 1096-9918 VL - 50 IS - 11 SP - 1200 EP - 1206 PB - John Wiley & Sons, Ltd. AN - OPUS4-46406 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 JF - Crystal Growth & Design 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 - Rades, Steffi A1 - Hodoroaba, Vasile-Dan A1 - Ortel, Erik A1 - Wirth, Thomas A1 - Borghetti, P. A1 - Garcia, S. A1 - Gómez, E. A1 - Blanco, M. A1 - Alberto, Gabriele A1 - Martra, G. T1 - Organic surface modification and analysis of titania nanoparticles for self-assembly in multiple layers JF - Microscopy and Microanalysis N2 - Parameters of TiO2 coatings can greatly influence their final performance in largescale applications such as photocatalytic measurements, orthopedic and/or dental prostheses, cell cultures, and dye-sensitized solar cells. From different film deposition procedures, self-assembly of TiO2 NPs in multiple layers was selected for systematic characterization. EDX, AES and ToF-SIMS analysis have been carried out in order to evaluate the functionalization of several types of TiO2 NPs differing in size, shape and surface area. KW - TiO2 KW - Nanoparticles KW - Surface modification KW - Functionalization PY - 2017 UR - https://www.cambridge.org/core/journals/microscopy-and-microanalysis/article/organic-surface-modification-and-analysis-of-titania-nanoparticles-for-selfassembly-in-multiple-layers/66776A4CA7FD059CE39041A99A922D90 DO - https://doi.org/10.1017/S1431927617010029 SN - 1431-9276 SN - 1435-8115 VL - 23 IS - S1 (July) SP - 1872 EP - 1873 PB - Cambridge University Press CY - New York, NY, U.S.A. AN - OPUS4-42457 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 JF - Microscopy and Microanalysis 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 - Wollschläger, Nicole A1 - Palasse, L. A1 - Häusler, Ines A1 - Dirscherl, K. A1 - Oswald, F. A1 - Narbey, S. A1 - Ortel, Erik A1 - Hodoroaba, Vasile-Dan T1 - Characterization of the inner structure of porous TiO2 nanoparticle films in dye sensitive solar cells (DSSC) by focused ion beam (FIB) tomography and transmission Kikuchi diffraction (TKD) in the scanning electron microscope (SEM) JF - Materials Characterization N2 - A combined methodical approach is tested for the first time with respect to the characterization of the inner structure of porous TiO2 layers infiltrated with ruthenium molecular sensitizer as typically used in modern dye sensitized solar cells (DSSC). Their performance is directly linked to the surface area ‘offered’ by the pore Network to the dye. The micrometer thick layer employed was manufactured by screen-printing of a starting TiO2 powder constituted of shape-controlled, bipyramidal anatase nanoparticles (NPs) 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). While the first method results in the visualization of the 3D pore network within the TiO2 layer, the second one can be successfully applied to analyze the crystal orientation of grains (i.e. NPs in our case) in nanometer resolution. Moreover, 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 - Transmission Kikuchi diffraction KW - Focused ion beam tomography KW - Titanium dioxide KW - Nanoparticles KW - Porosity KW - Particle size KW - DSSC PY - 2017 DO - https://doi.org/10.1016/j.matchar.2017.06.030 SN - 1044-5803 SN - 1873-4189 VL - 131 SP - 39 EP - 48 PB - Elsevier AN - OPUS4-40875 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 JF - Applied Catalysis B: Environmental 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 -