Impact of Nano- and Micro-Sized Chromium(III) Particles on Cytotoxicity and Gene Expression Profiles Related to Genomic Stability in Human Keratinocytes and Alveolar Epithelial Cells

Exposure to Cr(VI) compounds has been consistently associated with genotoxicity and carcinogenicity, whereas Cr(III) is far less toxic, due to its poor cellular uptake. However, contradictory results have been published in relation to particulate Cr$_2$O_3$. The aim of the present study was to investigate whether Cr(III) particles exerted properties comparable to water soluble Cr(III) or to Cr(VI), including two nano-sized and one micro-sized particles. The morphology and size distribution were determined by TEM, while the oxidation state was analyzed by XPS. Chromium release was quantified via AAS, and colorimetrically differentiated between Cr(VI) and Cr(III). Furthermore, the toxicological fingerprints of the Cr$_2$O_3$ particles were established using high-throughput RT-qPCR and then compared to water-soluble Cr(VI) and Cr(III) in A549 and HaCaT cells. Regarding the Cr$_2$O_3$ particles, two out of three exerted only minor or no toxicity, and the gene expression profiles were comparable to Cr(III). However, one particle under investigation released considerable amounts of Cr(VI), and also resembled the toxicity profiles of Cr(VI); this was also evident in the altered gene expression related to DNA damage signaling, oxidative stress response, inflammation, and cell death pathways. Even though the highest toxicity was found in the case of the smallest particle, size did not appear to be the decisive parameter, but rather the purity of the Cr(III) particles with respect to Cr(VI) content

Tuning the optical properties of 2D monolayer silver-bismuth bromide double perovskite by halide substitution

: Silver-bismuth double perovskites are promising replacement materials for lead-based ones in photovoltaic (PV) devices due to the lower toxicity and enhanced stability to environmental factors. In addition, they might even be more suitable for indoor PV, due to the size of their bandgap better matching white LEDs emission. Unfortunately, their optoelectronic performance does not reach that of the lead-based counterparts, because of the indirect nature of the band gap and the high exciton binding energy. One strategy to improve the electronic properties is the dimensional reduction from the 3D to the 2D perovskite structure, which features a direct band gap, as it has been reported for 2D monolayer derivates of Cs2AgBiBr6obtained by substituting Cs+cations with bulky alkylammonium cations. However, a similar dimensional reduction also brings to a band gap opening, limiting light absorption in the visible. In this work, we report on the achievement of a bathochromic shift in the absorption features of a butylammonium-based silver-bismuth bromide monolayer double perovskite through doping with iodide and study the optical properties and stability of the resulting thin films in environmental conditions. These species might constitute the starting point to design future sustainable materials to implement as active components in indoor photovoltaic devices used to power the IoT

Influence of NCM Particle Cracking on Kinetics of Lithium-Ion Batteries with Liquid or Solid Electrolyte

In liquid electrolyte-type lithium-ion batteries, Nickel-rich NCM (Li$_{1+x }$(Ni$_{1−y−z}$Co$_{ y}$Mnz)$_{1−x}$O$_{2}$) as cathode active material allows for high discharge capacities and good material utilization, while solid-state batteries perform worse despite the past efforts in improving solid electrolyte conductivity and stability. In this work, we identify major reasons for this discrepancy by investigating the lithium transport kinetics in NCM-811 as typical Ni-rich material. During the first charge of battery half-cells, cracks form and are filled by the liquid electrolyte distributing inside the secondary particles of NCM. This drastically improves both the lithium chemical diffusion and charge transfer kinetics by increasing the electrochemically active surface area and reducing the effective particle size. Solid-state batteries are not affected by these cracks because of the mechanical rigidity of solid electrolytes. Hence, secondary particle cracking improves the initial charge and discharge kinetics of NCM in liquid electrolytes, while it degrades the corresponding kinetics in solid electrolytes. Accounting for these kinetic limitations by combining galvanostatic and potentiostatic discharge, we show that Coulombic efficiencies of about 89% at discharge capacities of about 173 mAh g$_{1+x }$NCM$^{-1}$ can be reached in solid-state battery half-cells with LiNi$_{0.8}$Co$_{0.1}$Mn$_{0.1}$O$_{2}$ as cathode active material and Li$_{6}$PS$_{5}$Cl as solid electrolyte

Halide ion influence on the formation of nickel nanoparticles and their conversion into hollow nickel phosphide and sulphide nanocrystals

A dependence of the formation of tri-n-octylphosphine-capped Ni nanocrystals on the presence of halide ions during their synthesis is shown. For the application-oriented synthesis of Ni particles, this information can be crucial. Furthermore, Ni nanoparticles can be converted to nickel phosphide or sulphide by heating them up in the presence of a phosphorus or sulphur source, resulting in either solid or hollow nanocrystals, formed via the nanoscale Kirkendall effect, depending on the synthesis route. By adjusting the Ni crystallite size in the initial nanoparticles via the halide ion concentration the cavity size of the resulting hollow nanocrystals can be tuned, which is otherwise impossible to realise for particles of a similar total diameter by using this process. The synthesised hollow Ni3S2 nanocrystals exhibit a much sharper localised surface plasmon resonance (LSPR) band than all previously presented particles of this material, which is known to show molar extinction coefficients at the LSPR maximum similar to Au. This narrow linewidth could be explained by the nanoparticles’ high crystallinity resulting from the Kirkendall process and is interesting for various possible optical applications such as surface-enhanced Raman spectroscopy owing to the low cost of the involved materials compared to the widely used noble metals

Functionalization of Ti-40Nb implant material with strontium by reactive sputtering

Background: Surface functionalization of orthopedic implants with pharmaceutically active agents is a modern approach to enhance osseointegration in systemically altered bone. A local release of strontium, a verified bone building therapeutic agent, at the fracture site would diminish side effects, which could occur otherwise by oral administration. Strontium surface functionalization of specially designed titanium-niobium (Ti-40Nb) implant alloy would provide an advanced implant system that is mechanically adapted to altered bone with the ability to stimulate bone formation. Methods: Strontium-containing coatings were prepared by reactive sputtering of strontium chloride (SrCl2) in a self-constructed capacitively coupled radio frequency (RF) plasma reactor. Film morphology, structure and composition were investigated by scanning electron microscopy (SEM), time of flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). High-resolution transmission electron microscopy (HR-TEM) was used for the investigation of thickness and growth direction of the product layer. TEM lamellae were prepared using the focused ion beam (FIB) technique. Bioactivity of the surface coatings was tested by cultivation of primary human osteoblasts and subsequent analysis of cell morphology, viability, proliferation and differentiation. The results are correlated with the amount of strontium that is released from the coating in biomedical buffer solution, quantified by inductively coupled plasma mass spectrometry (ICP-MS). Results: Dense coatings, consisting of SrOxCly, of more than 100 nm thickness and columnar structure, were prepared. TEM images of cross sections clearly show an incoherent but well-structured interface between coating and substrate without any cracks. Sr2+ is released from the SrOxCly coating into physiological solution as proven by ICP-MS analysis. Cell culture studies showed excellent biocompatibility of the functionalized alloy. Conclusions: Ti-40Nb alloy, a potential orthopedic implant material for osteoporosis patients, could be successfully plasma coated with a dense SrOxCly film. The material performed well in in vitro tests. Nevertheless, the Sr2+ release must be optimized in future work to meet the requirements of an effective drug delivery system

Kinetics and Pore Formation of the Sodium Metal Anode on NASICON‐Type Na3.4_{3.4} Zr2_2Si2.4_{2.4}P0.6_{0.6}O12_{12} for Sodium Solid‐State Batteries

In recent years, many efforts have been made to introduce reversible alkali metal anodes using solid electrolytes in order to increase the energy density of next-generation batteries. In this respect, Na$_{3.4}$Zr$_2$Si$_{2.4}$P$_{0.6}$O$_{12}$ is a promising solid electrolyte for solid-state sodium batteries, due to its high ionic conductivity and apparent stability versus sodium metal. The formation of a kinetically stable interphase in contact with sodium metal is revealed by time-resolved impedance analysis, in situ X-ray photoelectron spectroscopy, and transmission electron microscopy. Based on pressure- and temperature-dependent impedance analyses, it is concluded that the Na|Na$_{3.4}$Zr$_2$Si$_{2.4}$P$_{0.6}$O$_{12}$ interface kinetics is dominated by current constriction rather than by charge transfer. Cross-sections of the interface after anodic dissolution at various mechanical loads visualize the formed pore structure due to the accumulation of vacancies near the interface. The temporal evolution of the pore morphology after anodic dissolution is monitored by time-resolved impedance analysis. Equilibration of the interface is observed even under extremely low external mechanical load, which is attributed to fast vacancy diffusion in sodium metal, while equilibration is faster and mainly caused by creep at increased external load. The presented information provides useful insights into a more profound evaluation of the sodium metal anode in solid-state batteries

Kinetics and Pore Formation of the Sodium Metal Anode on NASICON‐Type Na₃.₄Zr₂Si₂.₄P₀.₆O₁₂ for Sodium Solid‐State Batteries

In recent years, many efforts have been made to introduce reversible alkali metal anodes using solid electrolytes in order to increase the energy density of next‐generation batteries. In this respect, Na₃.₄Zr₂Si₂.₄P₀.₆O₁₂ is a promising solid electrolyte for solid‐state sodium batteries, due to its high ionic conductivity and apparent stability versus sodium metal. The formation of a kinetically stable interphase in contact with sodium metal is revealed by time‐resolved impedance analysis, in situ X‐ray photoelectron spectroscopy, and transmission electron microscopy. Based on pressure‐ and temperature‐dependent impedance analyses, it is concluded that the Na|Na₃.₄Zr₂Si₂.₄P₀.₆O₁₂interface kinetics is dominated by current constriction rather than by charge transfer. Cross‐sections of the interface after anodic dissolution at various mechanical loads visualize the formed pore structure due to the accumulation of vacancies near the interface. The temporal evolution of the pore morphology after anodic dissolution is monitored by time‐resolved impedance analysis. Equilibration of the interface is observed even under extremely low external mechanical load, which is attributed to fast vacancy diffusion in sodium metal, while equilibration is faster and mainly caused by creep at increased external load. The presented information provides useful insights into a more profound evaluation of the sodium metal anode in solid‐state batteries

Bound exciton luminescence in Zinc Oxide

Im Rahmen dieser Dissertation wurden exzitonische Rekombinationen einer Vielzahl von ZnO-Proben untersucht. Bei den untersuchten Proben handelte es sich um kommerziell erhältliche Einkristalle, mit verschiedenen Elementen implantierte und anschließend ausgeheilte Einkristalle sowie epitaktisch mittels CVD gewachsene Dünnschichten auf verschiedenen Substratmaterialien. Das Spektrum der bekannten Rekombinationen konnte dabei um einige weitere Rekombinationslinien ergänzt werden. An Einkristallen der Firma Cermet konnten durch temperaturabhängige Messungen gebundene Exzitonen identifiziert werden, deren beteiligtes Loch aus dem B-Valenzband stammt. Die gebundenen B-Exzitonen konnten den in den Einkristallen auftretenden an neutrale Donatoren gebundenen A-Exzitonen zugeordnet werden, dabei wurde ein Abstand von etwa 4,5 meV zwischen A- und B-Exziton gemessen. Außerdem konnten zu den an neutrale Donatoren gebundenen A-Exzitonen die zugehörigen an ionisierte Donatoren gebundenen A-Exzitonen gemessen werden. Die Korrelation von an neutrale Donatoren gebundenen Exzitonen mit an ionisierte Donatoren gebundenen Exzitonen konnte außerdem an einer Reihe unterschiedlich dotierter ZnO-Proben belegt werden, in denen einzelne Rekombinationslinien in der Intensität deutlich hervortraten. Außerdem konnten die an ionisierte Donatoren gebundenen Exzitonen in magneto-PL-Messungen als solche identifiziert werden. Somit konnte eine Zuordnung der an ionisierte Donatoren gebundenen Exzitonen zu den an neutrale Donatoren gebundenen Exzitonen gemacht werden. Es konnte ein Zusammenhang zwischen an ionisierte und neutrale Donatoren gebundenen Exzitonen gefunden werden, mit dem auch für nicht explizit untersuchte Rekombinationslinien Zuordnungen vorgenommen werden, die in einer Tabelle zusammengestellt sind. Für diese Rekombinationslinien ergibt sich ein linearer Zusammenhang zwischen Donatorbindungsenergie und der jeweiligen Lokalisierungsenergie. Darüber hinaus wurde in homoepitaktisch gewachsenen ZnO-Dünnschichten eine exzitonische Rekombination identifiziert, bei der ein Exziton an einer komplexen donatorartigen Störstelle lokalisiert ist und ein vierfach aufgespaltenes Linienspektrum erzeugt. Der Zusammenhang dieser Rekombinationslinien X1 bis X4 bei 3,3618, 3,3621, 3,3636 und 3,3639 eV konnte durch temperaturabhängige Messungen untermauert werden. Neben diesen erfolgreichen Identifizierungen haben die zahlreichen Messungen im Rahmen dieser Arbeit aber auch immer wieder neue Fragen und neue Rekombinationslinien hervorgebracht, deren Identifizierung nachfolgenden Arbeiten vorbehalten bleiben muss. Die bekannten, identifizierten und noch nicht identifizierten Rekombinationslinien sind ebenfalls in einer Tabelle zusammengestellt