Dokument-ID Dokumenttyp Autoren/innen Persönliche Herausgeber/innen Haupttitel Abstract Auflage Verlagsort Verlag Herausgeber (Institution) Erscheinungsjahr Titel des übergeordneten Werkes Jahrgang/Band ISBN Veranstaltung Veranstaltungsort Beginndatum der Veranstaltung Enddatum der Veranstaltung Ausgabe/Heft Erste Seite Letzte Seite URN DOI Lizenz Datum der Freischaltung OPUS4-55207 Zeitschriftenartikel Clark, P.C.J; Andresen, Elina; Sear, M. J.; Favaro, M.; Girardi, L.; van de Krol, R.; Resch-Genger, Ute; Starr, D.E. Quantification of the Activator and Sensitizer Ion Distributions in NaYF4:Yb3+, Er3+ Upconverting Nanoparticles Via Depth-Profiling with Tender X-Ray Photoemission The spatial distribution and concentration of lanthanide activator and sensitizer dopant ions are of key importance for the luminescence color and efficiency of upconverting nanoparticles (UCNPs). Quantifying dopant ion distributions and intermixing, and correlating them with synthesis methods require suitable analytical techniques. Here, X-ray photoelectron spectroscopy depth-profiling with tender X-rays (2000-6000 eV), providing probe depths ideally matched to UCNP sizes, is used to measure the depth-dependent concentration ratios of Er3+ to Yb3+, [Er3+]/[Yb3+], in three types of UCNPs prepared using different reagents and synthesis methods. This is combined with data simulations and inductively coupled plasma-optical emission spectroscopy (ICP-OES) measurements of the lanthanide ion concentrations to construct models of the UCNPs' dopant ion distributions. The UCNP sizes and architectures are chosen to demonstrate the potential of this approach. Core-only UCNPs synthesized with XCl3·6H2O precursors (β-phase) exhibit a homogeneous distribution of lanthanide ions, but a slightly surface-enhanced [Er3+]/[Yb3+] is observed for UCNPs prepared with trifluroacetate precursors (α-phase). Examination of Yb-core@Er-shell UCNPs reveals a co-doped, intermixed region between the single-doped core and shell. The impact of these different dopant ion distributions on the UCNP's optical properties is discussed to highlight their importance for UCNP functionality and the design of efficient UCNPs. Weinheim, Germany Wiley-VCH-Verlag 2022 Small 1 13 urn:nbn:de:kobv:b43-552075 10.1002/smll.202107976 https://creativecommons.org/licenses/by/4.0/deed.de 2022-07-07 OPUS4-55189 Zeitschriftenartikel Bresch, Harald; Hodoroaba, Vasile-Dan; Schmidt, Alexandra; Rasmussen, K.; Rauscher, H. Counting Small Particles in Electron Microscopy Images — Proposal for Rules and Their Application in Practice Electron microscopy (EM) is the gold standard for the characterisation of the morphology (size and shape) of nanoparticles. Visual observation of objects under examination is always a necessary first step in the characterisation process. Several questions arise when undertaking to identify and count particles to measure their size and shape distribution. In addition to challenges with the dispersion and identification of the particles, more than one protocol for counting particles is in use. This paper focuses on precise rules for the counting of particles in EM micrographs, as this influences the measurement accuracy of the number of particles, thus implicitly affecting the size values of the counted particles. We review and compare four different, commonly used methods for counting, which we then apply in case studies. The impact of the selected counting rule on the obtained final particle size distribution is highlighted. One main aim of this analysis is to support the application of a specific, well-defined counting approach in accordance with regulatory requirements to contribute to achieving more reliable and reproducible results. It is also useful for the new harmonised measurement procedures for determining the particle size and particle size distribution of nanomaterials. Basel MDPI 2022 Nanomaterials 12 13 2238 urn:nbn:de:kobv:b43-551891 10.3390/nano12132238 https://creativecommons.org/licenses/by/4.0/deed.de 2022-07-06 OPUS4-54468 Zeitschriftenartikel Bastos, V.; Oskoei, P.; Andresen, Elina; Saleh, Maysoon I.; Rühle, Bastian; Resch-Genger, Ute; Oliveira, H. Stability, dissolution, and cytotoxicity of NaYF4‑upconversion nanoparticles with different coatings Upconversion nanoparticles (UCNPs) have attracted considerable attention owing to their unique photophysical properties. Their utilization in biomedical applications depends on the understanding of their transformations under physiological conditions and their potential toxicity. In this study, NaYF4: Yb,Er UCNPs, widely used for luminescence and photophysical studies, were modified with a set of four different coordinatively bound surface ligands, i.e., citrate, alendronate (AA), ethylendiamine tetra(methylene phosphonate) (EDTMP), and poly(maleic anhydride-alt-1-octadecene) (PMAO), as well as silica coatings with two different thicknesses. Subsequently, the aging-induced release of fluoride ions in water and cell culture media and their cytotoxic profile to human keratinocytes were assessed in parallel to the cytotoxic evaluation of the ligands, sodium fluoride and the lanthanide ions. The cytotoxicity studies of UCNPs with different surface modifications demonstrated the good biocompatibility of EDTMP-UCNPs and PMAO-UCNPs, which is in line with the low amount of fluoride ions released from these samples. An efficient prevention of UCNP dissolution and release of cytotoxic ions, as well as low cytotoxicity was also observed for UCNPs with a sufficiently thick silica shell. Overall, our results provide new insights into the understanding of the contribution of surface chemistry to the stability, dissolution behavior, and cytotoxicity of UCNPs. Altogether, the results obtained are highly important for future applications of UCNPs in the life sciences and bioimaging studies. London Springer Nature 2022 Scientific reports 12 1 13 urn:nbn:de:kobv:b43-544681 10.1038/s41598-022-07630-5 https://creativecommons.org/licenses/by/4.0/deed.de 2022-03-14 OPUS4-54358 Zeitschriftenartikel Le Guevel, X.; Wegner, Karl David; Würth, Christian; Baulin, V. A.; Musnier, B.; Josserand, V.; Resch-Genger, Ute; Koll, J-C Tailoring the SWIR emission of gold nanoclusters by surface ligand rigidification and their application in 3D bioimaging The influence of solvent polarity and surface ligand rigidification on the SWIR emission profile of gold nanoclusters with an anistropic surface was investigated. A strong enhancement of the SWIR emission band at 1200 nm was observed when measuring in different local environments: in solution, in polymer composites, and in solids. SWIR in vivo imaging of mice assisted by deep learning after intravenous administration of these gold nanoclusters provides high definition pseudo-3D views of vascular blood vessels. RSC 2022 Chemical Communications 58 18 2967 2970 urn:nbn:de:kobv:b43-543582 10.1039/D1CC06737K https://creativecommons.org/licenses/by/4.0/deed.de 2022-02-16 OPUS4-53719 Zeitschriftenartikel Ahiboz, D.; Andresen, Elina; Manley, P.; Resch-Genger, Ute; Würth, Christian; Becker, C. Metasurface-Enhanced Photon Upconversion upon 1550 nm Excitation Photon upconversion upon 1550 nm excitation is of high relevance for applications in the third biological excitation window, for photovoltaics beyond current limitations, and enables appealing options in the field of glass Fiber telecommunications. Trivalent doped erbium ions (Er3+) are the material of choice for 1550 nm excited upconversion, however, they suffer from a low absorption cross-section and a low brightness. Therefore, the ability of Silicon metasurfaces to provide greatly enhanced electrical near-fields is employed to enable efficient photon upconversion even at low external Illumination conditions. Hexagonally shaped β-NaYF4:Er3+ nanoparticles are placed on large-area silicon metasurfaces designed to convert near-infrared (1550 nm) to visible light. More than 2400-fold enhanced photon upconversion luminescence is achieved by using this metasurface instead of a planar substrate. With the aid of optical simulations based on the finite-element method, this result is attributed to the coupling of the excitation source with metasurface resonances at appropriate incident angles. Analysis of the excitation power density dependence of upconversion luminescence and red-to-green-emission ratios enables the estimation of nanoscale near-field enhancement on the metasurface. The findings permit the significant reduction of required external excitation intensities for photon upconversion of 1550 nm light, opening perspectives in biophotonics, telecommunication, and photovoltaics. Wiley-VCH-GmbH 2021 Advanced Science News 9 24 2101285 urn:nbn:de:kobv:b43-537193 10.1002/adom.202101285. https://creativecommons.org/licenses/by/4.0/deed.de 2021-11-10 OPUS4-54093 Beitrag zu einem Tagungsband Krietsch, Arne; Reyes Rodriguez, M.; Kristen, A.; Kadoke, D.; Abbas, Z.; Krause, U. Ignition temperatures and flame velocities of metallic nanomaterials The production of materials with dimensions in the nanometre range has continued to increase in recent years. In order to ensure safety when handling these products, the hazard potential of such innovative materials must be known. While several studies have already investigated the effects of explosions (such as maximum explosion pressure and maximum pressure rise) of powders with primary particles in the nanometre range, little is known about the ignition temperatures and flame velocities. Therefore, the minimum ignition temperature (MIT) of metallic nano powders (aluminium, iron, copper and zinc) was determined experimentally in a so called Godbert-Greenwald (GG) oven. Furthermore, the flame velocities were determined in a vertical tube. In order to better classify the test results, the tested samples were characterised in detail and the lower explosion limits of the tested dust samples were determined. Values for the burning velocity of aluminium nano powders are higher compared to values of micrometre powders (from literature). While MIT of nanometre aluminium powders is within the range of micrometre samples, MIT of zinc and copper nano powders is lower than values reported in literature for respective micrometre samples. Physikalisch-Technische Bundesanstalt 2021 Proceedings of the 13th Symposium International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions 13th Symposium International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions (ISHPMIE) Online meeting 27.07.2021 31.07.2021 591 605 urn:nbn:de:kobv:b43-540930 10.7795/810.20200724 https://creativecommons.org/licenses/by-nd/4.0/deed.de 2021-12-20 OPUS4-53531 Zeitschriftenartikel Grauel, Bettina; Würth, Christian; Homann, C.; Krukewitt, Lisa; Andresen, Elina; Roik, Janina; Recknagel, Sebastian; Haase, M.; Resch-Genger, Ute Volume and surface effects on two-photonic and three-photonic processes in dry co-doped upconversion nanocrystals Despite considerable advances in synthesizing high-quality core/shell upconversion (UC) nanocrystals (NC; UCNC) and UCNC photophysics, the application of near-infrared (NIR)-excitable lanthanide-doped UCNC in the life and material sciences is still hampered by the relatively low upconversion luminescence (UCL) of UCNC of small size or thin protecting shell. To obtain deeper insights into energy transfer and surface quenching processes involving Yb3+ and Er3+ ions, we examined energy loss processes in differently sized solid core NaYF4 nanocrystals doped with either Yb3+ (YbNC; 20% Yb3+) or Er3+ (ErNC; 2% Er3+) and co-doped with Yb3+ and Er3+ (YbErNC; 20% Yb3+ and 2% Er3+) without a surface protection shell and coated with a thin and a thick NaYF4 shell in comparison to single and co-doped bulk materials. Luminescence studies at 375 nm excitation demonstrate backenergy transfer (BET) from the 4G11/2 state of Er3+ to the 2F5/2 state of Yb3+, through which the red Er3+ 4F9/2 state is efficiently populated. Excitation power density (P)-dependent steady state and time-resolved photoluminescence measurements at different excitation and emission wavelengths enable to separate surface-related and volume-related effects for two-photonic and threephotonic processes involved in UCL and indicate a different influence of surface passivation on the green and red Er3+ emission. The intensity and lifetime of the latter respond particularly to an increase in volume of the active UCNC core. We provide a threedimensional random walk model to describe these effects that can be used in the future to predict the UCL behavior of UCNC. Springer 2022 NanoResearch 15 3 2362 2373 urn:nbn:de:kobv:b43-535317 10.1007/s12274-021-3727-y https://creativecommons.org/licenses/by/4.0/deed.de 2021-10-18 OPUS4-53359 Zeitschriftenartikel Geißler, Daniel; Nirmalananthan-Budau, Nithiya; Scholtz, Lena; Tavernaro, Isabella; Resch-Genger, Ute Analyzing the surface of functional nanomaterials — how to quantify the total and derivatizable number of functional groups and ligands Functional nanomaterials (NM) of different size, shape, chemical composition, and surface chemistry are of increasing relevance for many key technologies of the twenty-first century. This includes polymer and silica or silica-coated nanoparticles (NP) with covalently bound surface groups, semiconductor quantum dots (QD), metal and metal oxide NP, and lanthanide-based NP with coordinatively or electrostatically bound ligands, as well as surface-coated nanostructures like micellar encapsulated NP. The surface chemistry can significantly affect the physicochemical properties of NM, their charge, their processability and performance, as well as their impact on human health and the environment. Thus, analytical methods for the characterization of NM surface chemistry regarding chemical identification, quantification, and accessibility of functional groups (FG) and surface ligands bearing such FG are of increasing importance for quality control of NM synthesis up to nanosafety. Here, we provide an overview of analytical methods for FG analysis and quantification with special emphasis on bioanalytically relevant FG broadly utilized for the covalent attachment of biomolecules like proteins, peptides, and oligonucleotides and address methodand material-related challenges and limitations. Analytical techniques reviewed include electrochemical titration methods, optical assays, nuclear magnetic resonance and vibrational spectroscopy, as well as X-ray based and thermal analysis methods, covering the last 5-10 years. Criteria for method classification and evaluation include the need for a signal-generating label, provision of either the total or derivatizable number of FG, need for expensive instrumentation, and suitability for process and production control during NM synthesis and functionalization. Springer Nature 2021 Microchimica Acta 188 10 1 28 urn:nbn:de:kobv:b43-533597 10.1007/s00604-021-04960-5 https://creativecommons.org/licenses/by/4.0/deed.de 2021-09-23 OPUS4-38947 Forschungsbericht Hodoroaba, Vasile-Dan; Mielke, Johannes Techniques evaluation report for selection of characterisation methods This report is the result of a comprehensive study on the available CMs which come potentially in question for the reliable analysis of the number based size distribution of a nanomaterial according to the EC recommendation for a definition of nanomaterial. Based on the performance criteria already established in NanoDefine the potential CMs are evaluated according to studies available in the literature as well as following the expertise of the NanoDefine consortium partners. The specific advantages and disadvantages of each method with respect to its applicability to the scope of NanoDefine are particularly highlighted. An CM evaluation table is produced so that the mostly suited CMs with respect to the EC definition can be grouped and recommended to the corresponding NanoDefine work packages for further specific development (improvement and adaption), or for direct validation and standardisation, respectively. The actual evaluation report including the recommended CMs will be revised and, if necessary, eventually updated at the mid time of the project. The update will be jointly discussed in the NanoDefine consortium on the basis of the results of testing the methods on the NanoDefine real world materials. Wageningen, The Netherlands The NanoDefine Consortium 2015 D3.1, 1 57 urn:nbn:de:kobv:b43-389473 http://www.gesetze-im-internet.de/urhg/index.html 2017-01-13 OPUS4-38982 Forschungsbericht Hodoroaba, Vasile-Dan; Mielke, Johannes Templates for nanomaterial characterisation of tier 1 and tier 2 measurement methods The EU FP7 NanoDefine project was launched in November 2013 and will run until October 2017. The Project is dedicated to support the implementation of the EU Recommendation on the Definition of Nanomaterial by the provision of the required analytical tools and respective guidance. Main goal is to develop a novel tiered approach consisting of (i) rapid and cost-efficient screening methods and (ii) confirmatory measurement methods. The "NanoDefiner" eTool will guide potential end-users, such as concerned industries and regulatory bodies as well as enforcement and contract laboratories, to reliably classify if a material is nano or not. To achieve this objective, a comprehensive inter-laboratory evaluation of the performance of current characterisation techniques, instruments and software is performed. Instruments, software and methods are further developed. Their capacity to reliably measure the size of particulates in the size range 1-100 nm and above (according to the EU definition) is validated. Technical reports on project results are published to reach out to relevant stakeholders, such as policy makers, regulators, industries and the wider scientific community, to present and discuss our goals and results, to ensure a continuous exchange of views, needs and experiences obtained from different fields of expertise and application, and to finally integrate the resulting feedback into our ongoing work on the size-related classification of nanomaterials. Wageningen, The Netherlands The NanoDefine Consortium The NanoDefine Consortium 2014 1 74 urn:nbn:de:kobv:b43-389827 http://www.gesetze-im-internet.de/urhg/index.html 2017-01-18