Xiang Chu

Facile synthesis of ultrafine cobalt oxide nanoparticles for high-performance supercapacitors

The ultrafine Co3O4 nanoparticles are successfully prepared by a novel solvothermal-precipitation approach which exploits the supernatant liquid of Co3O4 nanoflake micropheres synthesized by solvothermal method before. Interestingly, the water is only employed to obtain the ultrafine nanoparticles in supernatant liquid which was usually thrown away before. The microstructure measurement results of the as-grown samples present the homogeneous disperse ultrafine Co3O4 nanoparticles with the size of around 5-10nm. The corresponding synthesis mechanism of the ultrafine Co3O4 nanoparticles is proposed. More importantly, these ultrafine Co3O4 nanoparticles obtained at 250°C show the highest specific capacitance of 523.0Fg-1 at 0.5Ag-1, 2.6 times that of Co3O4 nanoflake micropheres due to the quantum size effect. Meanwhile, the sample annealed under 350°C possesses the best cycling stability with capacitance retention of 104.9% after 1500 cycles. These results unambiguously demonstrate that this work not only provides a novel, facile, and eco-friendly approach to prepare high-performance Co3O4 nanoparticles electrode materials for supercapacitors but also develops a widely used method for the preparation of other materials on a large scale.

Visible and near-infrared luminescent properties of Pr3+ doped strontium molybdate thin films by a facile polymer-assisted deposition process

Quartz substrate supported Praseodymium (Pr) doped strontium molybdate (SrMoO4) thin films with good uniformity and outstanding fluorescent properties are successfully fabricated via a facile polymer-assisted deposition (PAD) method. In combination with the strong chelating effect of water-soluble polymer on metal cations, the free cations without chelating are effectively ruled out but the remaining chelating metal cations are employed for the highly uniform and accurate stoichiometry luminescent SrMoO4: Pr thin films, layer-by-layer mounting on the common quartz substrates. More importantly, the excellent release of stress from polymer during the growth process of epitaxial thin film can effectively overcome the mismatch between thin film and common quartz substrate and then guarantee the quality of thin film. Under the ultraviolet (UV) light excitation, the samples show high luminescence intensity both in visible and near-infrared (NIR) regions peaked at 646 nm and 1037 nm, mainly ascribing to the transitions of 3P0 → 3F2 and 1G4 → 3H4 of Pr3+ ions. The luminescent properties can be tailored by optimizing the number of spin-coated layers and doping concentrations. The maximum emission occurs at 4 mol% of Pr3+ dopant, and it exhibits an impressive high photoluminescence quantum yield (QY) of up to 86.12%. These results evidently demonstrate the present PAD method is a useful prototype for preparing high performance luminescent thin films even on the cheap quartz substrate.