Colloidal BaZrS3 chalcogenide perovskite nanocrystals for thin film device fabrication

The theoretical optoelectronic properties of chalcogenide perovskites (e.g., BaZrS3) are as good as those of halide perovskites (e.g., CH3NH3PbI3). But the fabrication of optoelectronic devices is rarely reported, mainly because researchers still do not know how to prepare good quality thin films of chalcogenide perovskites. Here, we report colloidal BaZrS3 nanocrystals (NCs, 40-60 nm) and their solution processed thin film transistors. BaZrS3 NCs are first prepared using a solid-state synthesis route, and the subsequent surface modifications lead to a colloidal dispersion of NCs in both polar N-methyl-2-pyrrolidinone and non-polar chloroform solvents. The NCs exhibit good thermal (15-673 K) and aqueous stability. Colloidal BaZrS3 NCs in chloroform are then used to make field effect transistors showing ambipolar properties with a hole mobility of 0.059 cm(2) V-1 s(-1) and an electron mobility of 0.017 cm(2) V-1 s(-1). This report of solution processed chalcogenide perovskite thin films with reasonable carrier mobility and optical absorption and emission is expected to pave the way for future optoelectronic devices of chalcogenide perovskites.11Nsciescopu

Curcumin-Based Pyrazoline Analogues As Selective Inhibitors Of Human Monoamine Oxidase A

A series of 2-methoxy-4-(5-phenyl-4,5-dihydro-1H-pyrazol-3-yl)phenol (pyrazoline) derivatives (2-6) have been synthesized and tested for human monoamine oxidase (hMAO) inhibitory activity. The most active derivative (2) behaved as a competitive hMAO-A inhibitor, with an inhibition constant value of 0.08 M and a strong hMAO-A selectivity (K-i(hMAO-B)/K-i(hMAO-A) > 1751). In addition, 2 exhibited little to no cytotoxic effects up to a 25 M concentration and provided the best blood-brain barrier permeability among the derivatives synthesized. Molecular dynamics simulations revealed that a chlorine substituent at the para-position of the phenyl ring in 2 enabled a - stacking interaction with Tyr407 and Tyr444 that resulted in the formation of an aromatic sandwich structure. Consequently, this tight-binding aromatic cage culminated in a dramatically reduced active site volume that is believed to be the origin of the observed selectivity between the hMAO-A and hMAO-B isozymes. Removal of the chlorine from 2 disrupted the favorable intermolecular interactions and resulted in a selectivity change towards hMAO-B

Unlocking the Potential of Single Atoms Loaded Geobacter Hybrid Catalyst as Bifunctional Electrocatalyst for Water Splitting

Single-atom metal (SA-M) catalysts with high dispersion of active metal sites allow maximum atomic utilization. However, conventional synthesis of SA-M catalysts involves high-temperature treatments, leading to a low yield with random distribution of atoms. Herein, a facile method to synthesize SA-M catalysts (M = Fe, Ir, Pt, Ru, Cu, or Pd) in a single step at ambient temperature, using the extracellular electron transfer capability of Geobacter sulfurreducens (GS), is presented. Interestingly, the SA-M is coordinated to three nitrogen (N) atoms adopting an MN3 on the surface of GS. Dry samples of SA-Ir@GS without further heat treatments show exceptionally high activity for OER when compared to benchmark IrO2 catalyst and comparable HER activity to commercial 10 wt.% Pt/C. The SA-Ir@GS electrocatalyst exhibits the best water‐splitting performance compared to other SA-M@GS, showing a low applied potential of 1.65 V to achieve 10 mA cm−2 in 1.0 M KOH solution with cycling over 5 h. The density functional calculations reveal that the large adsorption energy of H2O and moderate adsorption energies of reactants and reaction intermediates for SA-Ir@GS favorably improve its activity. This nature-based facile synthesis method of SA-M at room temperature provides a versatile platform for the preparation of other transition metal SA-M catalysts for various energy-related applications by merely altering the metal precursors. <br /

A Convenient Route for Au@Ti–SiO₂ Nanocatalyst Synthesis and Its Application for Room Temperature CO Oxidation

Small gold nanoparticles of size less than 5 nm encapsulated inside titanium modified silica shell have been reported. Here, a modified sol–gel method, which is a one-step process, produces Au@Ti–SiO₂ nanocatalyst with a good control of titanium loading. With a titanium loading of 0.9 and 2.2 wt % in silica, unprecedented low temperature activity (full conversion) is observed for this catalyst for CO oxidation reaction compared to Au@SiO₂ catalyst. A combination of optimum sized gold nanoparticles with a large amount of oxygen vacancies created due to Ti incorporation in silica matrix is considered to be the reason for this enhanced catalytic activity. The size of gold nanoparticles is maintained even after high temperature pretreatments, which show the benefit of encapsulation. The effect of the various pretreatments on the catalytic activity has also been reported

Anisotropic phenanthroline-based ruthenium polymers grafted on a titanium metal-organic framework for efficient photocatalytic hydrogen evolution

Combining conjugated polymers with transition-metal-based metal-organic frameworks offers an opportunity to produce efficient photocatalytic materials. Here, exposed active sites and efficient charge transfer lead to hydrogen evolution rates of up to 2438 µmol g−1 h−1 for composites of anisotropic phenanthroline-based ruthenium polymers grafted on titanium-based MOFs

Size-Induced Structural Phase Transition at ∼6.0 nm from Mixed fcc–hcp to Purely fcc Structure in Monodispersed Nickel Nanoparticles

We have investigated the core issue of atomic lattices in monodispersed Ni nanoparticles (NPs) of sizes 3.8–10.1 nm using detailed analysis of X-ray diffraction, synchrotron radiation X-ray absorption spectroscopy, and magnetization data. This has revealed the very remarkable coexistence of atomic face-centered cubic (fcc) and hexagonal closed-packed (hcp) lattices in samples with particle size ≤ 6.0 nm with the prevalence of only fcc phase beyond this. They are also associated with reduced coordination number, modified electronic structure, and surface atom coordination with ligands. Magnetization data furthermore reveal the coexistence of ferromagnetism and superparamagnetism at 300 K. Considered to be due to dominant roles of ligands, they are likely to open up far-reaching implications to their future applications

Nitrogen Doping in Oxygen-Deficient Ca₂Fe₂O₅: A Strategy for Efficient Oxygen Reduction Oxide Catalysts

Oxygen reduction reaction (ORR) is increasingly being studied in oxide systems due to advantages ranging from cost effectiveness to desirable kinetics. Oxygen-deficient oxides like brownmillerites are known to enhance ORR activity by providing oxygen adsorption sites. In parallel, nitrogen and iron doping in carbon materials, and consequent presence of catalytically active complex species like C–Fe–N, is also suggested to be good strategies for designing ORR-active catalysts. A combination of these features in N-doped Fe containing brownmillerite can be envisaged to present synergistic effects to improve the activity. This is conceptualized in this report through enhanced activity of N-doped Ca₂Fe₂O₅ brownmillerite when compared to its oxide parents. N doping is demonstrated by neutron diffraction, UV–vis spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Electrical conductivity is also found to be enhanced by N doping, which influences the activity. Electrochemical characterization by cyclic voltammetry, rotating disc electrode, and rotating ring disk electrode (RRDE) indicates an improved oxygen reduction activity in N-doped brownmillerite, with a 10 mV positive shift in the onset potential. RRDE measurements show that the compound exhibits 4-electron reduction pathways with lower H₂O₂ production in the N-doped system; also, the N-doped sample exhibited better stability. The observations will enable better design of ORR catalysts that are stable and cost-effective