Shujiang Liu

Bio-synthesis participated mechanism of mesoporous LiFePO4/C nanocomposite microspheres for lithium ion battery

In this paper we report a bio-synthesis route towards controllable mesoporous LiFePO4/C nanocomposite microspheres (MP-LFP/C-NC-MS). During the synthesis bakers yeast cells were used as both structure templates and a carbon source. Then we clarify the bio-deposited and biomolecular self-assembly mechanisms of iron phosphate by means of the Langmuir biosorption isotherms of the yeast biomass in iron ion solution and by applying the model of heterogeneous nucleation of iron phosphate in a yeast cell. The MP-LFP/C-NC-MS show a uniform size distribution (4.76 μm), high tap density (1.74 g cm−3) and a large specific surface area (203 m2 g−1). The microsphere is composed of densely aggregated nanoparticles and interconnected nanopores. The open mesoporous structure allows lithium ions to easily penetrate into the spheres, while a thorough coating of the biocarbon network on the surface of the LiFePO4 nanoparticles facilitates lithium ion and electron diffusion. The MP-LFP/C-NC-MS have a high discharge capacity of about 158.5 mA h g−1 at a current density of 0.1 C, discharge capacity of 122 mA h g−1 at 10 C, and high capacity retention rate. Therefore the mesoporous microspheres are an ideal type of cathode-active materials for making high-power Li-ion batteries.

Direct immobilization of glucose oxidase in magnetic mesoporous bioactive glasses

Direct immobilization of enzymes on the bioactive glasses is conceptually a completely new strategy. We find that the Fe2O3-CaO-SiO2-P2O5 magnetic mesoporous bioactive glass (MMBG) is an ideal immobilization matrix for glucose oxidase (GOD). Its unique chemical surface properties and open mesopores enhance the catalytic activity of directly immobilized GOD. In this paper, MMBG was synthesized using the sol-gel approach and polyethylene glycol (PEG) as template at 700 °C. GOD molecules were spontaneously entrapped inside the open mesoporous structure and onto the surface of MMBG via iron ion binding, their activity was not impaired. The substrates and products can access and diffuse freely through the open mesoporous structure in MMBG. This study is focused on understanding the formation mechanism of MMBG, the immobilized mechanism of GOD and the magnetic separation mechanism of MMBG from the reaction medium. The MMBG can be utilized in the design of a solid support for any enzyme for bioconversion, bioremediation, and biosensors.