Colloidal Synthesis of Wurtzite Cu₂ZnSnS₄ Nanorods and Their Perpendicular Assembly

The quaternary copper chalcogenide Cu₂ZnSnS₄ is an important emerging material for the development of low-cost and sustainable solar cells. Here we report a facile solution synthesis of stoichiometric Cu₂ZnSnS₄ in size-controlled nanorod form (11 nm × 35 nm). The monodisperse nanorods have a band gap of 1.43 eV and can be assembled into perpendicularly aligned arrays by controlled evaporation from solution

Investigations into the Electrochemical, Surface, and Electrocatalytic Properties of the Surface-Immobilized Polyoxometalate, TBA₃K[SiW₁₀O₃₆(PhPO)₂]

Surface anchoring of an organic functionalized POM, TBA₃K­[SiW₁₀O₃₆(PhPO)₂] was carried out by two methods, the layer-by-layer (LBL) assembly technique by employing a pentaerythritol-based ruthenium­(II) metallodendrimer as a cationic moiety and also by entrapping the POM in a conducting polypyrrole film. The redox behavior of the constructed films was studied by using cyclic voltammetry and electrochemical impedance spectroscopy. The surface morphologies of the constructed multilayers were examined by scanning electron microscopy and atomic force microscopy. X-ray photoelectron spectroscopy was conducted to confirm the elements present within the fabricated films. The multilayer assembly was also investigated for its catalytic efficiency towards the reduction of nitrite

Biomineralization Mechanism of Gold by Zygomycete Fungi Rhizopous oryzae

In recent years, there has been significant progress in the biological synthesis of nanomaterials. However, the molecular mechanism of gold biomineralization in microorganisms of industrial relevance remains largely unexplored. Here we describe the biosynthesis mechanism of gold nanoparticles (AuNPs) in the fungus Rhizopus oryzae. Reduction of AuCl₄^– [Au(III)] to nanoparticulate Au⁰ (AuNPs) occurs in both the cell wall and cytoplasmic region of R. oryzae. The average size of the as-synthesized AuNPs is ∼15 nm. The biomineralization occurs through adsorption, initial reduction to Au(I), followed by complexation [Au(I) complexes], and final reduction to Au⁰. Subtoxic concentrations (up to 130 μM) of AuCl₄^– in the growth medium increase growth of R. oryzae and induce two stress response proteins while simultaneously down-regulating two other proteins. The induction increases mycelial growth, protein yield, and AuNP biosynthesis. At higher Au(III) concentrations (>130 μM), both mycelial and protein yield decrease and damages to the cellular ultrastructure are observed, likely due to the toxic effect of Au(III). Protein profile analysis also confirms the gold toxicity on R. oryzae at high concentrations. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis shows that two proteins of 45 and 42 kDa participate in gold reduction, while an 80 kDa protein serves as a capping agent in AuNP biosynthesis

Selective Phase Transformation of Wurtzite Cu₂ZnSn(SSe)₄ (CZTSSe) Nanocrystals into Zinc-Blende and Kesterite Phases by Solution and Solid State Transformations

A wide range of physical properties from optoelectronic (e.g., band gap) to structural (e.g., hardness) can be affected without changing the composition of a solid but just by altering the crystal phase. Here, we report a selective structural phase transition of metastable wurtzite CZTSSe nanocrystals into more stable phases such as zinc blende and kesterite using solution and solid state transformations, respectively. The phase transformation pathways are selective, with the wurtzite to zinc-blende transition not occurring because of thermal annealing or the wurtzite to kesterite transition because of solution transformation. We show the importance of both ligand chemistry and temperature to lowering the barrier for rapid conversion from one phase to another in this system. The phase transitions are accompanied by changes in the band gap with values for each calculated by cyclic voltammetry

High Density Growth of Indium seeded Silicon Nanowires in the Vapor phase of a High Boiling Point Solvent

Herein, we describe the growth of Si nanowires (NWs) in the vapor phase of an organic solvent medium on various substrates (Si, glass, and stainless steel) upon which an indium layer was evaporated. Variation of the reaction time allowed NW length and density to be controlled. The NWs grew via a predominantly root-seeded mechanism with discrete In catalyst seeds formed from the evaporated layer. The NWs and substrates were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The suitability of the indium seeded wires as anode components in Li batteries was probed using cyclic voltammetric (CV) measurements. The route represents a versatile, glassware-based method for the formation of Si NWs directly on a variety of substrates

Silver-Modified η‑Al₂O₃ Catalyst for DME Production

Herein, an in situ DRIFT technique was used to study the reaction mechanism of methanol dehydration to dimethyl ether (DME). Moreover, the effect of silver loading on the catalytic performance of η-Al₂O₃ was examined in a fixed bed reactor under the reaction conditions where the temperature ranged from 180 to 300 °C with a WHSV = 48.4 h^–1. It was observed that the optimum Ag loading was found to be 10% Ag/η-Al₂O₃ with this novel catalyst also showing a high degree of stability under steady-state conditions, and this is attributed to the enhancement in both the surface Lewis acidity and the hydrophobicity

Silver-Modified η‑Al₂O₃ Catalyst for DME Production

Herein, an in situ DRIFT technique was used to study the reaction mechanism of methanol dehydration to dimethyl ether (DME). Moreover, the effect of silver loading on the catalytic performance of η-Al₂O₃ was examined in a fixed bed reactor under the reaction conditions where the temperature ranged from 180 to 300 °C with a WHSV = 48.4 h^–1. It was observed that the optimum Ag loading was found to be 10% Ag/η-Al₂O₃ with this novel catalyst also showing a high degree of stability under steady-state conditions, and this is attributed to the enhancement in both the surface Lewis acidity and the hydrophobicity

Surface Immobilization of a Tetra-Ruthenium Substituted Polyoxometalate Water Oxidation Catalyst Through the Employment of Conducting Polypyrrole and the Layer-by-Layer (LBL) Technique

A tetra Ru-substituted polyoxometalate Na₁₀[{Ru₄O₄(OH)₂(H₂O)₄}­(γ-SiW₁₀O₃₆)₂] (Ru₄POM) has been successfully immobilised onto glassy carbon electrodes and indium tin oxide (ITO) coated glass slides through the employment of a conducting polypyrrole matrix and the layer-by-layer (LBL) technique. The resulting Ru₄POM doped polypyrrole films showed stable redox behavior associated with the Ru centres within the Ru₄POM, whereas, the POM’s tungsten-oxo redox centres were not accessible. The films showed pH dependent redox behavior within the pH range 2–5 whilst exhibiting excellent stability towards redox cycling. The layer-by-layer assembly was constructed onto poly­(diallyldimethylammonium chloride) (PDDA) modified carbon electrodes by alternate depositions of Ru₄POM and a Ru­(II) metallodendrimer. The resulting Ru₄POM assemblies showed stable redox behavior for the redox processes associated with Ru₄POM in the pH range 2–5. The charge transfer resistance of the LBL films was calculated through AC-Impedance. Surface characterization of both the polymer and LBL Ru₄POM films was carried out using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Initial investigations into the ability of the Ru₄POM LBL films to electrocatalytically oxidise water at pH 7 have also been conducted