Controlling Equilibrium Morphologies of Bimetallic Nanostructures Using Thermal Dewetting via Phase-Field Modeling

Herein, we report a computational model for the morphological evolution of bimetallic nanostructures in a thermal dewetting process, with a phase-field framework and superior optical, physical, and chemical properties compared to those of conventional nanostructures. The quantitative analysis of the simulation results revealed nano-cap, nano-ring, and nano-island equilibrium morphologies of the deposited material in thermal dewetting, and the morphologies depended on the gap between the spherical patterns on the substrate, size of the substrate, and deposition thickness. We studied the variations in the equilibrium morphologies of the nanostructures with the changes in the shape of the substrate pattern and the thickness of the deposited material. The method described herein can be used to control the properties of bimetallic nanostructures by altering their equilibrium morphologies using thermal dewetting.

Synthesis of Palladium and Copper Nanoparticles Supported on TiO2 for Oxidation Solvent-Free Aerobic Oxidation of Benzyl Alcohol

The use of metal oxides as supports for palladium and copper (Pd–Cu) nanoalloys constitutes a new horizon for improving new active catalysts in very important reactions. From the literatures, Pd-based bimetallic nanostructures have great properties and active catalytic performance. In this work, nanostructures of titanium dioxide (TiO2) were used as supports for Pd–Cu nanoparticles catalysts. Palladium and copper were deposited on these supports using the sol-immobilisation method. The composite nanoalloys were characterized using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The catalyst was evaluated for the oxidation of benzyl alcohol. The effect of the Cu–Pd ratio using sol-immobilization methods supported on TiO2 was investigated. The results show that monometallic Cu/TiO2 was observed to have a low activity. However, as soon as the catalyst contained any palladium, the activity increased with a significant increase in the selectivity towards isomerization products. The influence of support and temperature were investigated. Furthermore, the catalyst reusability was also tested for oxidation of benzyl alcohol reactions, by repeatedly performing the same reaction using the recovered catalyst. The Pd–Cu/TiO2 catalyst displayed better reusability even after several reactions

Directional color routing assisted by switchable Fano resonance in bimetallic metagrating

Great progress in nanophotonics has been demonstrated in tailoring the impinging beams. The physics behind those intriguing effects is to a large extent governed by the parameter of the optical phase. While, simple nanostructures usually suffer from fundamental limitations on their efficiency in wave transformation, especially in the transmission system, associated with their inadequate phase accumulation, challenge their implementation in practical application. Here, we describe a transparent nanostructure built from a pair of partially overlapped gold and aluminum semi-nanoshells that show almost π phase accumulation through material-dependent plasmon resonances. Combined with an optical slab waveguide, the bimetallic metagratings exhibit prominent directional color routing properties in transmission light, which result from switchable Fano resonances between plasmon resonances of bimetallic nanostructures and ±1 order waveguide diffraction modes at two opposite oblique incidences due to sufficient phase shift provided by the asymmetric and bimetallic plasmon resonators. Both theoretical and experimental results show that the Fano-resonance-assisted color routing exhibits a relatively broadband tuning range (∼150 nm with an efficiency of up to 50%) and a color routing efficiency of up to 70% at the central wavelength of λ = 600 nm.