Jian Ping Gao

A pH and Electric Responsive Graphene Oxide Based Composite Hydrogel

The pH and electric responsive composite hydrogels were prepared by in situ polymerization in the presence of graphene oxide (GO). Their structure and properties were characterized by scanning electron microscopy, Raman microscopy and mechanical testing. The results indicate that the GO is evenly dispersed in the composite hydrogels and the mechanical properties of the GO based composite hydrogels are significantly improved. Most importantly, the composite hydrogels were responsive to external stimuli such as pH and electric field.

Graphene Oxide Reduced and Dispersed by Polysaccharide

An green method to reduce graphene oxide (RGO) was developed by using polysaccharide as both a reducing agent and a stabilizing agent. The RGO was characterized and the factors that affect the reduction of graphene oxide (GO) were explored to obtain optimum reaction conditions. Analysis shows that GO can be reduced at a comparatively low temperature by polysaccharide and forms a stable RGO aqueous dispersion owing to the dispersion of polysaccharide. This approach provides a new green method for GO reduction that has great value for graphene applications.

Study on the Catalytic Activity of Graphene Oxide

Graphene oxide (GO), an oxygen-rich carbonaceous layered material, is produced by the strong oxidation of graphite. The GO aqueous suspension is very stable and can be fabricated to porous GO aerogels by a green method, unidirectional freeze-drying technology. GO shows catalytic activities in both solution and solid state. It can also act as reductant or oxidant depending on the reaction patterns. The product of the reaction was analyzed and the component change of the graphene oxide (GO) was monitored by x-ray photoelectron spectrometer, scanning electron microscopy and transmission electron microscopy. The results confirm that GO not only acts as the reactant in the reaction, but also as the catalyst to catalyze the reaction.

Graphene Oxide Containing Composite Hydrogel Fabricated by Freeze/Thaw Method

Graphene oxide (GO) was used as inorganic fillers to enhance the mechanic properties of graphene oxide/poly(vinyl alcohol) composite hydrogels that were prepared by freeze/thaw method. The structure and properties of the composite hydrogels were characterized. Since GO was well dispersed in polymer matrix, the composite hydrogels showed an outstanding mechanical improvement. Significant increase in Youngs modulus and compressive strength was achieved, indicating a good load transfer between fillers and matrix.

Polyaniline Hybrid with Inverse Opal Structure for Fabrication of Thermoelectric Materials

The colloidal crystal template or opal with a closed-packed face centered cubic (fcc) lattice was prepared from monodisperse polystyrene (PS) microspheres by gravity sedimentation, and it was used for the fabrication of polyaniline hybrid with inverse opal structure. The template provided void space for the infiltration of Bi2Te3 and monomer that was then in situ polymerized to polyaniline. The opal composite was then soaked in toluene for completely removing PS microspheres to form porous polyaniline hybrid with inverse opal structure. The PS microspheres were replaced by air microspheres, which interconnected each other through the windows on the polyaniline hybrid wall. Both the wall and the air void constitute continuous phases. The polyaniline hybrid with inverse opal structure was observed with scanning electronic microscopy.

Stable Reduced Graphene Oxide Suspension Modified by PAMAM

Poly (amidoanime) (PAMAM) dendrimers contain numerous amino-terminal groups and are highly hydrophilic. These terminal groups make PAMAM molecules adsorbed onto graphene oxide (GO) nanosheets through electrostatic action with oxygen containing groups on graphene oxide nanosheets. The PAMAM molecules react with GO, and form stable aqueous suspension of modified reduced graphene oxide (RGO).

Fabrication of Stable PVA/PVP Hydrogels

PVA hydrogel has been used in the field of cartilage replacement in recent year. In order to improve the water-keeping ability of PVA gel and mechanical property, PVP was introduced into PVA and crosslinked by adding ammonium persulfate to form a composite gel. The crosslinkage of the gel was identified, and the effect of PVP and ammonium persulfate amount on the composite gel was studied. The crosslinkage, the degree of swelling and the compress stress of the composite gels have been tested. UV analysis was used to investigate the release of PVP from the composite gels. The dried composite gels were put into water to investigate the degree and velocity of the rehydration of different composite gels.

Fabrication of Calcium Sulfate/Tri-Calcium Phosphate Composite Bone Fillers through Molding Method

Calcium sulfate/tri-calcium phosphate (CaSO4/TCP) composite bone fillers were fabricated through molding method. Their structure and properties were characterized by infrared spectroscope, scanning electronic spectroscope, x-ray diffraction and degradation test. The results show that TCP crystals were attached to the CaSO4 crystals and prevented the growing of sulfate crystals. So their size is shorter than that of CaSO4 crystals prepared from pure CaSO4 semihydrate, and some even had defect. The resorption rate of CaSO4 bone fillers was decreased when TCP was incorporated.

Graphene Based Ultrahin Composite Films Prepared by Layer-by-Layer Electrostatic Assembly and Spinning Coating

Ultra thin graphene oxide (GO)/polyvinyl alcohol and graphene-polyvinyl alcohol/gelatin composite films were fabricated by electrostatic layer-by-layer assembly and spinning coating methods. The assembling and coating process were traced with UV-visible absorption spectroscopy and the morphology of the formed ultra thin films was observed under scanning electron microscopy. The results show that the adsorption value of the GO based composite films linearly increased as the number of layers increased. The ultra thin graphene oxide/polyvinyl alcohol and graphene-polyvinyl alcohol/gelatin composite films have layered structure with high tensile strength because of the incorporation of GO. These strong ultra thin films have potential applications in coating, sensor and electrochemical devices.

Controlled Drug Release from Biodegradable Bone Fillers

Plaster of Pairs is a common used implanting material. However, its rapid degradation or drug releasing rate as a bone filler or drug carrier does not meet the requirement of clinic application. In this paper, plaster of Pairs bone fillers loaded with drug was prepared and their degradation and the drug release period were adjusted by coating their surface with polymers. The results show that the structure of coatings can effectively control the degradation period of the bone fillers, and consequently the drug release rate.