Preparation And Properties Of Au NPs/ Graphene Hybrid

Graphene is applied in the field of semiconductor, electrochemical sensor and substrate material for nano-particles due to its large specific surface area and high conductivity. And Au nanoparticles (Au NPs) have high catalytic activity and good biocompatibility, showing a promising prospect in organic catalysis, biosensing and surface enhanced raman scattering. The hybrid of these two materiasl can produce synergisitic effect, which will improve the properties of catalytic and sensing better. In recent years, researches are focused on the hybrid of these two materials.Oxidation-reduction method and chemical vapor deposition (CVD) method were adopted to synthesize 2D graphene and 3D graphene respectively. And it used seed-mediated method to grow Au NPs. All samples were characterized by SEM, TEM and Raman spectrometer.Then in situ reduction method was used to synthesize Au NPs/2D graphene hybrid for catalyzing 4-nitrophenol (4-NP) reduction. Electrophoretic deposition method and hydrothermal method were used to synthesize Au NPs/3D graphene hybrid as electrochemical sensor for detecting H2O2 in low concentration. The catalytic and sensing properties of Au NPs/graphene hybrid were tested by UV-vis spectrophotometer and electrochemical workstation and the main results are as follows:(1) The graphene synthesized by oxidation-reduction method and CVD method have large specific surface area and can be the ideal substrate for nano-particles. Beside, CVD graphene has high conductivity. Au NPs were made by seed-mediated method and its size is 20-25nm. It has spherical shape and good stability in water.(2)Au NPs/2D graphene hybrid was synthesized by in situ reduction method. Au NPs are capped on graphene uniformly with a high coverage rate. It is a high efficient catalyst for 4-NP reduction. And with the increase of catalyst amount, catalytic rate increased. When adding 0.1ml,0.15ml and 0.2ml catalyst, the kinetics constants are as high as 0.717min-1,1.21 min-1 and 2.511min-1 respectively, much higher than adding single Au NPs of same molar weight. And after holding the catalyst at～4℃ for 40 days, when adding 0.1ml,0.15ml and 0.2ml catalyst again, the kinetics constants are as high as 0.361mm-1,0.691 min-1 and 1.444mm-1 respectively, exhibiting an excellent and stable catalytic activity.(3)Au NPs/3D graphene hybrid was synthesized by electrophoretic deposition method and deposited under different voltages. It is found that when the voltage is 6V, it get the best results, with Au NPs covered densely and uniformly on the graphene. And it also has the best electrochemical sensing properties for detecting H2O2, with a detection limit of 5μM, a detect range from 5μM to 395μM and a response time within 3s. Hydrothermal method could get Au NPs/3D graphene hybrid with Au NPs size between 100-200nm. The detection limit is 0.5mM and response time is 10s, and because of the low cost and simple process, it is suitable for detecting H2O2 in millimolar level.