Pokhrel, Suman
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Pokhrel, Suman
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Pokhrel, Suman
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Item-typ:Veröffentlichung, Rare-Earth-Doped Y4Al2O9 Nanoparticles for Stable Light-Converting Phosphors(American Chemical Society, 2019-12-24); ; ; ; The ternary mixed metal oxides with high specific surface area are industrially important for sensors, catalysis, energy storage, and optoelectronics. However, synthesis of such metal oxides is always challenging, especially when multicomponent mixtures occur due to very narrow formation temperature windows. Flame spray pyrolysis is one of the best known techniques which enable formation of pure phases optimizing the temperature profile via control over the fuel/oxidizer ratio. Here, Y4Al2O9 (monoclinic phase of yttrium aluminum oxide, also known as YAM) and Y4–xEuxAl2O9 (x = 0.05–1.0) were strategically synthesized with specific precursor–solvent chemistry. While the hydrated yttrium nitrate with 28.2% water was unsuitable for the formation of crystalline Y4Al2O9 particles, the use of organic precursor–solvent combinations (Y/Al 2:1) resulted in 16 nm phase pure, highly crystalline Y4Al2O9 particles. All the materials were characterized by using X-ray diffraction with Rietveld refinement, Raman spectroscopy, and transmission electron microscopy. To develop a stable light-converting phosphor, the Y4Al2O9 host was doped with Eu to investigate the photoluminescence properties of Y4–xEuxAl2O9 (x = 0.05–1.0). The results indicated increased photoluminescence intensity with increasing Eu3+ concentration up to x = 0.5, i.e., Y3.5Eu0.5Al2O9, and a subsequent drop or decrease in intensity for x ≥ 0.7. Hence, Y3.5Eu0.5Al2O9 is proposed for a potential light-converting phosphor.Wissenschaftlicher ArtikelBand:3Heft:116 11 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, The impact of metal doping on fumed silica structure and amino acid thermal condensation catalytic properties(Springer, 2021-08-18); ; ; ; Fumed silica nanoparticles (FSN) are one of the most common synthetic forms of silica, but prolonged exposure leads to cell toxicity and apoptosis due to reactive oxygen species (ROS) generation and cell membrane perturbation resulting from hydrogen bonding and electrostatic interactions. Increasing attention is being put on synthesizing FSN material that is safer both for workers involved in large-scale industrial production, and consumers coming in contact with FSN additives. In the present work, we explore the molecular structural differences and efficacy of Al- and Ti-metal-doped FSN which has previously been shown to reduce toxicity effects of FSN. We use a combination of 29Si and 27Al solid-state magic angle spinning (MAS) NMR, Raman spectroscopy, and thermogravimetric analysis (TGA) to probe the surface and bulk structure and quantify the adsorption capacity and reactivity of the metal-doped FSN with respect to amino acid thermal condensation. Alanine was selected as the amino acid of choice for its simplicity and ubiquity in biochemical reactions. The results indicate that metal doping has a modest impact on the fumed silica molecular structure with a small decrease in amino acid adsorption capacity and thermal condensation reactivity as a function of increased metal doping.Wissenschaftlicher ArtikelBand:5644 72 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Redox Activity and Nano–Bio Interactions Determine the Skin Injury Potential of Co3O4-Based Metal Oxide Nanoparticles toward Zebrafish(American chemical society, 2020-03-19); ; ; ; Redox-active metal oxide nanoparticles show varying oxidizing capacities and injury potentials toward biological systems. Here, two metal oxide libraries including transition-metal-doped Co3O4 and PdO-Co3O4 with strong chemical contacts were design-synthesized and used to investigate their biological injury potential and mechanisms using zebrafish as a model organism. Among different dopants, Cu significantly increased the oxidizing capacity of Co3O4. An increased amount of PdO resulted in higher density of heterojunctions, which also led to higher oxidizing capacity. The oxidizing capacity of these nanoparticles was positively correlated with higher mortality of dechorionated embryos and severe larval skin injury upon exposure. Using transgenic zebrafish Tg(LysC:eGFP), we show in real time that the redox-active nanoparticles induced skin injury and activated the infiltration of immune cells. Such inflammatory response was confirmed by the increased mRNA expression level of Nrf2a, HO-1, IL-1β, and IL-6 genes. Although the exposure to the nanoparticles alone was not lethal, the skin injury did lower the tolerance level against other environmental contaminants. More importantly, after withdrawing from the nanoparticle exposure, larvae with skin injury could recover within 24 h in uncontaminated medium, indicating such injury was transient and recoverable.Wissenschaftlicher ArtikelBand:14Heft:433 37 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, HCHO Sensing Mechanism of In4Sn3O12 Revealed by DRIFTS and DFT(American Chemical Society, 2023-05-25); ; ; ; The combination of operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy measurement and Density Functional Theory calculation reveals the counterintuitive HCHO sensing mechanism of In4Sn3O12. It is merely partial oxidation of HCHO into formate (or HCOOH) with medium activation energy (0.43–0.68 eV) and sufficient electron donation effect that is responsible for the sensor signal at the optimum temperature of 200 °C. The Sn (3a)-connected O is the active site and plays key roles in both HCHO adsorption and partial oxidation.Wissenschaftlicher ArtikelBand:127Heft:2249 70 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Electrochemical Behavior of Single CuO Nanoparticles: Implications for the Assessment of their Environmental Fate(Wiley, 2018-07-17); ; ; ; The electrochemical behavior of copper oxide nanoparticles is investigated at both the single particle and at the ensemble level in neutral aqueous solutions through the electrode-particle collision method and cyclic voltammetry, respectively. The influence of Cl− and NO3− anions on the electrochemical processes occurring at the nanoparticles is further evaluated. The electroactivity of CuO nanoparticles is found to differ between the two types of experiments. At the single-particle scale, the reduction of the CuO nanoparticles proceeds to a higher extent in the presence of chloride ion than of nitrate ion containing solutions. However, at the multiparticle scale the CuO reduction proceeds to the same extent regardless of the type of anions present in solution. The implications for assessing realistically the environmental fate and therefore the toxicity of metal-based nanoparticles in general, and copper-based nanoparticles in particular, are discussed.Wissenschaftlicher ArtikelBand:14Heft:3294 117