Nanoparticle Precursor into Polycrystalline Bi₂Fe₄O₉: An Evolutionary Investigation of Structural, Morphological, Optical, and Vibrational Properties

Mullite-type Bi₂Fe₄O₉ was synthesized using a polyol-mediated method. X-ray powder diffraction (XRD) revealed that the as-synthesized sample is nanocrystalline. It transformed into a rhombohedral perovskite-type BiFeO₃ followed by a second transformation into mullite-type Bi₂Fe₄O₉ during heating. Each structural feature, from as-synthesized into crystalline phase, was monitored through temperature-dependent XRD in situ. The locally resolved high resolution transmission electron micrographs revealed that the surface of some heated samples is covered by 4–13 nm sized particles which were identified from the lattice fringes as crystalline Bi₂Fe₄O₉. XRD and Raman spectra demonstrate that the nucleation of both BiFeO₃ and Bi₂Fe₄O₉ might simultaneously commence; however, their growth and ratios are dependent on temperature. The diffuse UV/vis reflectance spectra showed fundamental absorption edges between 1.80(1) and 2.75(3) eV. A comparative study between the “derivation of absorption spectrum fitting method” (DASF) and the Tauc method suggests Bi₂Fe₄O₉ to be a direct band gap semiconductor

Correction to Ultrathin Au-Alloy Nanowires at the Liquid–Liquid Interface

Correction to Ultrathin Au-Alloy Nanowires at the Liquid–Liquid Interfac

Ultrathin Au-Alloy Nanowires at the Liquid–Liquid Interface

Ultrathin bimetallic nanowires are of importance and interest for applications in electronic devices such as sensors and heterogeneous catalysts. In this work, we have designed a new, highly reproducible and generalized wet chemical method to synthesize uniform and monodispersed Au-based alloy (AuCu, AuPd, and AuPt) nanowires with tunable composition using microwave-assisted reduction at the liquid–liquid interface. These ultrathin alloy nanowires are below 4 nm in diameter and about 2 μm long. Detailed microstructural characterization shows that the wires have an face centred cubic (FCC) crystal structure, and they have low-energy twin-boundary and stacking-fault defects along the growth direction. The wires exhibit remarkable thermal and mechanical stability that is critical for important applications. The alloy wires exhibit excellent electrocatalytic activity for methanol oxidation in an alkaline medium

Ultrasmooth Ru(0001) Films as Templates for Ceria Nanoarchitectures

Single crystalline magnetron sputter-deposited Ru(0001) epitaxial thin films on c-plane sapphire were prepared and used as a template for reactive CeO₂ growth. Low-energy electron microscopy and diffraction, as well as transmission electron microscopy and atomic force microscopy, experiments were performed to investigate the crystallinity and morphology of the prepared films. Multiple cycles of Ar⁺ sputtering and high-temperature annealing produces films of exceptional surface quality. High-temperature reactive ceria growth leads to perfectly aligned triangular single-crystalline CeO₂(111) islands of extraordinary morphological and structural homogeneity. At the chosen growth conditions, ceria nucleation takes place only at V-shaped surface defects on the otherwise atomically flat Ru terraces, opening up the possibility to influence the nucleation by introducing artificial surface defects using standard etching techniques. Due to their high crystallinity and extraordinary surface quality, these substrates present a low-cost alternative to Ru single crystals for model studies in heterogeneous catalysis and also allow for the use of destructive investigation techniques and irreversible surface modifications