Search

2D vanadium-doped tungsten oxide (V-doped WO3) inverse opal (IO) monolayer film was successfully fabricated on ITO glass by simply doping vanadium ions within pre-synthesized 2D WO3 IO. The new material exhibited a large-area highly ordered porous array with featured structural colors. The obtained 2D V-doped WO3 IO film showed an improved electrochromic response in near infrared (NIR) region with a high optical contrast as 24.2% at 1100 nm wavelength, much higher than that of crystallized m-WO3 IO film (18.1%), or amorphous WO3 IO composite film (6.4%). Such advanced property could be attributed to the successful doping of vanadium, resulting in enhanced absorption owing to oxygen vacancies defect-inductive effect, and greatly improved the electrochromic response in the NIR region. Further, the V-doped WO3 IO film also featured with an excellent cyclic stability with the capacity retention of (75.2%) after 30 cycles, comparable to crystallized m-WO3 IO film (78.0%). As contrast to it, the amorphous WO3 IO film was found destroyed even after 10 cycles. [ABSTRACT FROM AUTHOR]

Spinel ferrites have potential applications as gas sensors, catalysts, microwave absorbers, and they can be used for information storage systems, rechargeable lithium batteries and medical diagnostics. Alkaline steaming-assisted conversion, a new strategy, was first developed for the synthesis of pure NiFe2O4 spinel nanoparticles, and its mechanism is discussed. Ammonia, ethylenediamine, and mixtures of both were used as steaming vapor to convert the dry powder of a stoichiometric mixture of FeCl3·6H2O and NiCl2·6H2O into NiFe2O4. In this system, ethylenediamine cooperates with ammonia in the alkaline steaming vapor to convert the Ni and Fe precursors into NiFe2O4 nanoparticles. Pure NiFe2O4 nanoparticles were only obtained by the combination of alkaline ammonia and ethylenediamine. The results show that the purity of the product depends on the concentration of ethylenediamine. The crystallization and the magnetization of these NiFe2O4 nanoparticles depend on the processing temperature and duration of the steaming process. The alkaline-steaming assisted conversion strategy was further successfully extended to the synthesis of pure CoFe2O4 nanoparticles, demonstrating a broad application possibility. [ABSTRACT FROM AUTHOR]

The open-layered structure of Vanadium pentoxide (V2O5) has triggered significant interest in exploring its energy-related application as lithium (Li) intercalation cathode material. Various methods are extensively studied to improve the Li diffusion using thin films or nanoarchitecture. In this work, high-quality two-dimensional (2D) inverse opal α-V2O5 films were synthesized via a modified 'dynamic hard template' infiltration strategy using sacrificial polystyrene spheres (PS, a diameter of 530 nm) photonic crystal as a template. The new material exhibited an excellent porous array with featured structural colors in a large area. The electrochromic behavior was explored by combining bandgap and electrochemical characterization. On the one hand, the intercalation/deintercalation of Li+ played an important role in the bandgap (Eg), and thereafter on the visible range transmittance through changing the film's stoichiometry and the valence of vanadium ions. On the other hand, the asymmetry of the lattice due to the disordered distribution of Li+ within the V2O5 interlayer and/or the formation of an irreversible phase explained the change in transmittance with voltage. [ABSTRACT FROM AUTHOR]