Fluorine-Doped SnO₂@Graphene Porous Composite for High Capacity Lithium-Ion Batteries

For the first time, a composite of fluorine-doped SnO₂ and reduced graphene oxide (F-SnO₂@RGO) was synthesized using a cheap F-containing Sn source, Sn­(BF₄)₂, through a hydrothermal process. X-ray photoelectron spectroscopy and X-ray diffraction results identified that F was doped in the unit cells of the SnO₂ nanocrystals, instead of only on the surfaces of the nanoparticles. F doping of SnO₂ led to more uniform and higher loading of the F-SnO₂ nanoparticles on the surfaces of RGO sheets, as well as enhanced electron transportation and Li ion diffusion in the composite. As a result, the F-SnO₂@RGO composite exhibited a remarkably high specific capacity (1277 mA h g^–1 after 100 cycles), a long-term cycling stability, and excellent high-rate capacity at large charge/discharge current densities as anode material for lithium ion batteries. The outstanding performance of the F-SnO₂@RGO composite electrode could be ascribed to the combined features of the composite electrode that dealt with both the electrode dynamics (enhanced electron transportation and Li ion diffusion due to F doping) and the electrode structure (uniform decoration of the F-SnO₂ nanoparticles on the surfaces of RGO sheets and the three-dimensional porous structures of the F-SnO₂@RGO composite)

Enhanced Photothermal Bactericidal Activity of the Reduced Graphene Oxide Modified by Cationic Water-Soluble Conjugated Polymer

Surface modification of graphene is extremely important for applications. Here, we report a grafting-through method for grafting water-soluble polythiophenes onto reduced graphene oxide (RGO) sheets. As a result of tailoring of the side chains of the polythiophenes, the modified RGO sheets, that is, RGO-<i>g</i>-P3TOPA and RGO-<i>g</i>-P3TOPS, are positively and negatively charged, respectively. The grafted water-soluble polythiophenes provide the modified RGO sheets with good dispersibility in water and high photothermal conversion efficiencies (ca. 88%). Notably, the positively charged RGO-<i>g</i>-P3TOPA exhibits unprecedentedly excellent photothermal bactericidal activity, because the electrostatic attractions between RGO-<i>g</i>-P3TOPA and <i>Escherichia coli</i> (<i>E. coli</i>) bind them together, facilitating direct heat conduction through their interfaces: the minimum concentration of RGO-<i>g</i>-P3TOPA that kills 100% of <i>E. coli</i> is 2.5 μg mL^–1, which is only 1/16th of that required for RGO-<i>g</i>-P3TOPS to exhibit a similar bactericidal activity. The direct heat conduction mechanism is supported by zeta-potential measurements and photothermal heating tests, in which the achieved temperature of the RGO-<i>g</i>-P3TOPA suspension (2.5 μg mL^–1, 32 °C) that kills 100% of <i>E. coli</i> is found to be much lower than the thermoablation threshold of bacteria. Therefore, this research demonstrates a novel and superior method that combines photothermal heating effect and electrostatic attractions to efficiently kill bacteria