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Abstract: In this paper, reduced graphite oxide (RGO) was prepared using thiourea dioxide as reductant and polyvinylpyrrolidone (PVP) as stabilizer. Thiourea dioxide, a cheap and nontoxic industrialized material, was demonstrated to be an efficient reducing agent for graphite oxide (GO) in this paper. Ultraviolet and visible (UV–vis) spectroscopy results revealed that the reduction of GO could be readily achieved in 10min, a reaction time which is much shorter than those required in common reduction reactions. The procedures of reduction including the by-products are all nontoxic, thus it is absolutely environmentally friendly. To the best of our knowledge, this is the first time that thiourea dioxide was successfully used to prepare RGO. Moreover, the stabilizer, PVP, which could be easily absorbed onto the surface of RGO, provided RGO with good water and organic solvents solubility, with low conductivity though. However, by controlling the content of PVP, RGO with balanced solubility and conductivity can be obtained. The resultant RGO could be used as nanofillers to prepare conductive materials and biomaterials with potential applications as electrical devices or biosensors. [Copyright &y& Elsevier]

Abstract: Ultrasonication is often used to disperse nano-particles in aqueous solution. However, a good dispersion of nano-particles in aqueous solution is not always achieved, due to the fact that incoming ultrasonicwaves in liquid are usually reflected and damped at the gas/liquid interface. In this work, we report a so-called wet-grinding assisted ultrasonication (GU) method, in which wet-grinding of multi-walled carbon nanotubes (MWCNTs) in chitosan solution is carried out before ultrasonication. The dispersions of MWCNTs were characterized by visual comparison, UV/vis spectroscopy, and scanning electron microscopy (SEM). The results demonstrate that the dispersion quality of chitosan/MWCNT suspension prepared by wet-grinding assisted ultrasonication is much better than that by ultrasonication or wet-grinding alone. It was found that wet-grinding could improve the water wettability of MWCNTs and eliminate the barrier of air layer around MWCNTs to ultrasonicwaves. Meanwhile, the composite from the chitosan/MWCNTs suspension prepared by GU method has an obvious improvement in mechanical property compared to pure chitosan. This simple method for integrating MWCNTs and biocompatible chitosan into a homogeneous dispersion may have great potential application in biotechnology, such as preparing composite materials for medicine, bio-fiber, biosensor, antibacterial coating, and cell cultivation. [Copyright &y& Elsevier]