Broadening the Photoluminescence Excitation Spectral Bandwidth of YVO4:Eu3+ Nanoparticles via a Novel Core-Shell and Hybridization Approach

For many optoelectronic applications, it is desirable for the lanthanide-doped phosphors to have broad excitation spectrum. The excitation mechanism of the lanthanide-doped YVO₄, a high quantum efficient lasing material, primarily originates from the energy transfer process from the host VO₄³⁻ complexes to the lanthanide ions, which has an excitation spectral bandwidth range of 230–330 nm. For applications in silicon solar cells, such phosphors can convert ultraviolet light to visible light for more efficient power generation, but this spectral range is still not broad enough to cover the entire ultraviolet spectrum of solar light. In this work, a novel core-shell and inorganic–organic hybridization strategy has been employed to fabricate Eu³⁺-doped YVO₄ nanoparticles to broaden their photoluminescence excitation spectral bandwidth to the range of 230–415 nm, covering the entire ultraviolet spectrum of solar light and enabling their potential applications in silicon solar cells.

La0.8Sr0.2MnO3-Based Perovskite Nanoparticles with the A-Site Deficiency as High Performance Bifunctional Oxygen Catalyst in Alkaline Solution

Perovskite (La_0.8Sr_0.2)_1-xMn_1-xIr_xO₃ (x = 0 (LSM) and 0.05 (LSMI)) nanoparticles with particle size of 20-50 nm are prepared by the polymer-assisted chemical solution method and demonstrated as high performance bifunctional oxygen catalyst in alkaline solution. As compared with LSM, LSMI with the A-site deficiency and the B-site iridium (Ir)-doping has a larger lattice, lower valence state of transition metal, and weaker metal-OH bonding; therefore, it increases the concentration of oxygen vacancy and enhances both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). LSMI exhibits superior ORR performance with only 30 mV onset potential difference from the commercial Pt/C catalyst and significant enhancement in electrocatalytic activity in the OER process, resulting in the best oxygen electrode material among all the reported perovskite oxides. LSMI also exhibits high durability for both ORR (only 18 mV negative shift for the half-wave potential compared with the initial ORR) and OER process with 10% decay. The electrochemical results indicate that the A-site deficiency and Ir-doping in perovskite oxides could be promising catalysts for the applications in fuel cells, metal-air batteries, and solar fuel synthesis.

Evaporation-Driven Deposition of WO₃ Thin Films from Organic-Additive-Free Aqueous Solutions by Low-Speed Dip Coating and Their Photoelectrochemical Properties

We prepared tungsten trioxide (WO3) photoelectrode films from organic-additive-free aqueous solutions by a low-speed dip-coating technique. The evaporation-driven deposition of the solutes occurred at the meniscus during low-speed dip coating, resulting in the formation of coating layer on the substrate. Homogeneous WO3 precursor films were obtained from (NH4)10W12O41·5H2O aqueous solutions and found to be crystallized to monoclinic WO3 films by the heat treatment at 400-700 °C. All the films showed a photoanodic response irrespective of the heat treatment temperature, where a good photoelectrochemical stability was observed for those heated over 500 °C. The highest photoanodic performance was observed for the WO3 film heated at 700 °C, where the IPCE (incident photon-to-current efficiency) was 36.2% and 4.6% at 300 and 400 nm, respectively.

The facile preparation of a carbon coated Bi2O3nanoparticle/nitrogen-doped reduced graphene oxide hybrid as a high-performance anode material for lithium-ion batteries

A hybrid of carbon coated Bi₂O₃nanoparticles distributed on nitrogen-doped reduced graphene oxide is prepared by facile thermal treatment processes.

Preparation of metal oxide thin films from organic-additive-free aqueous solutions by low-speed dip-coating

Transparent, crack-free SnO₂ and TiO₂ precursor films were obtained from organic-additive-free aqueous solutions by low-speed dip-coating. The precursor films were crystallized to SnO₂ and TiO₂ by the heat treatment at 700 °C for 10 min in air.

Two-dimensional V2O5 sheet network as electrode for lithium-ion batteries

Two-dimensional V2O5 and manganese-doped V2O5 sheet network were synthesized by a one-step polymer-assisted chemical solution method and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal-gravimetric analysis, and galvanostatic discharge-charge analysis. The V2O5 particles were covered with thin carbon layers, which remained after decomposition of the polymer, forming a network-like sheet structure. This V2O5 network exhibits a high capacity of about 300 and 600 mA·h/g at a current density of 100 mA/g when it was used as a cathode and anode, respectively. After doping with 5% molar ratio of manganese, the capacity of the cathode increases from 99 to 165 mA·h/g at a current density of 1 A/g (∼3 C). This unique network structure provides an interconnected transportation pathway for lithium ions. Improvement of electrochemical performance after doping manganese could be attributed to the enhancement of electronic conductivity.

Bismuth Oxide: A New Lithium-Ion Battery Anode

Bismuth oxide directly grown on nickel foam (p-Bi₂O₃/Ni) was prepared by a facile polymer-assisted solution approach and was used directly as a lithium-ion battery anode for the first time. The Bi₂O₃ particles were covered with thin carbon layers, forming network-like sheets on the surface of the Ni foam. The binder-free p-Bi₂O₃/Ni shows superior electrochemical properties with a capacity of 668 mAh/g at a current density of 800 mA/g, which is much higher than that of commercial Bi₂O₃ powder (c-Bi₂O₃) and Bi₂O₃ powder prepared by the polymer-assisted solution method (p-Bi₂O₃). The good performance of p-Bi₂O₃/Ni can be attributed to higher volumetric utilization efficiency, better connection of active materials to the current collector, and shorter lithium ion diffusion path.

Chemical solution deposition of epitaxial metal-oxide nanocomposite thin films

Epitaixial metal-oxide nanocomposite films, which possess interesting multifunctionality, have found applications in a wide range of devices. However, such films are typically produced by using high-vacuum equipment, like pulse-laser deposition, molecular-beam epitaxy, and chemical vapor deposition. As an alternative approach, chemical solution methods are not only cost-effective but also offer several advantages, including large surface coating, good control over stoichiometry, and the possible use of dopants. Therefore, in this Personal Account, we review the chemistry behind several of the main solution-based approaches, that is, sol-gel techniques, metal-organic decomposition, chelation, polymer-assisted deposition, and hydrothermal methods, including the seminal works that have been reported so far, to demonstrate the advantages and disadvantages of these different routes.

Preparation of Mesoporous Silica-Supported Palladium Catalysts for Biofuel Upgrade

We report the preparation of two hydrocracking catalysts Pd/CoMoO4/silica and Pd/CNTs/CoMoO4/silica (CNTs, carbon nanotubes). The structure, morphologies, composition, and thermal stability of catalysts were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), and thermogravimetric analysis (TGA). The catalyst activity was measured in a Parr reactor with camelina fatty acid methyl esters (FAMEs) as the feed. The analysis shows that the palladium nanoparticles have been incorporated onto mesoporous silica in Pd/CoMoO4/silica or on the CNTs surface in Pd/CNTs/CoMoO4/silica catalysts. The different combinations of metals and supports have selective control cracking on heavy hydrocarbons.