Preparation Of Gold Nanoparticles And Its Application In Evaluation Of Antioxidant Capacity Of Flower Tea

The gold nanoparticles have been used widely in many fields due to its characteristics such as unique optical,electrical properties,good biocompatibility,and so forth.The unique properties and applications of gold nanoparticles depend on their size and morphology.In this paper,gold nanorods were prepared by gallic acid reduction and seeding growth approach.The antioxidant capacity of scented tea was investigated.The results were compared with the gold nanoparticles growth method and the traditional DPPH method in this paper.The major contributions are as follows:1.Gold nanorods were prepared by a seeding growth approach with gallic acid as reducing agent and characterized by UV-Vis and TEM.The effects of the reaction time,the amount of silver nitrate,the amount of gallic acid and the amount of CTAB on the the morphology of gold nanorods were investigated.The results show that the shape of gold nanorods is changed from bone-like to homogeneous rod-like,the longitudinal surface plasmon resonance peak is red-shifted and the aspect ratio of gold nanorods is increased gradually with increasing reaction time.The longitudinal surface plasmon resonance peak of gold nanorods is red-shifted and aspect ratio of gold nanorods is increased gradually by increasing the amount of AgNO3 or gallic acid.The decreasing of the concentration of CTAB is hardly to formation of gold nanorods.In addition,compared to method of the ascorbic acid as reducing agent,the reaction process using gallic acid as a reducing agent is slower and the range of aspect ratio of gold nanorods is wider and the morphology of gold nanorods is controlled easily.2.The antioxidation capacity of scented tea was evaluated by gold nanorods.The longitudinal surface plasmon resonance peak of gold nanorods blue-shifted gradually when gold nanorods oxidized by H2O2.The antioxidants in scented tea can eliminate partial H2O2 and prevent the blue-shift of the longitudinal surface plasmon resonance peak of gold nanorods.The antioxidation capacity of scented tea was evaluated by detecting the restraining levels of the blue-shift of longitudinal surface plasmon resonance peak of gold nanorods in this paper.The order of the antioxidant capacity of five kinds of scented tea is lophantherum gracile brongn,rose,lavender,hawthorn and lotus leaf.3.The antioxidant capacity of scented tea was evaluated through gold nanoparticles growth method.The antioxidants in scented tea promoted the growth of gold nanoparticles,and the evaluation of the antioxidant capacity of scented tea achieved by investigating the growth of gold nanoparticles.The results show that lophantherum gracile brorign has the strongest antioxidant capacity during five kinds of scented tea,and follows by rose,lavender,hawthorn and lotus leaf.The order of the antioxidant capacity of five kinds of scented tea detected and verified by the traditional DPPH method,is consistent with detected by gold nanorods method and gold nanoparticles growth method.