Controlled Synthesis Of Gold Nanoparticles And Their Electrochemical Application

Gold nanoparticles are particularly important because their stability and fascinating optical properties can be tuned through control over particles size,shape, composition and morphology.It is believed that large-scale size-and shape-controlled metal nanoparicles will be conveniently produced through further optimization of these synthetic processes and expected to find intriguing applications in field such as cataysis,biosensor,recording media,and optics.The main goal of the present work is to develop a simple and effective hydrothermal method based on a polyol process and synthesize gold nanparticles with controllable size and shape.The synthesis was realized by the reduction of HAuCl₄ with ethylene glycol(EG)in the presence of poly(vinyl pyrrolidone)(PVP)as a capping agent under hydrothermal condition.Their morphology,size,structure and optical properties were characterized systemically by TEM,HRTEM,SEM,XRD, SAED,EDS and UV-vis spectroscopy.The growth mechanism of the gold nanoparticles with different shapes wasdiscussed.The major results of the thesis are outlined as follows:1.High yield,well-defined gold nanocrystals with shape of icosahedron were synthesized by the rapid reduction of gold precursors with ethylene glycol(EG)in presence of poly(vinyl pyrrolidone)(PVP)under hydrothermal condition for 1 h.Au icosahedron is one of multiple twinned particles(MTPs)which has 20 faces,each were enclosed by {111} facet.2.The truncated icosahedra have been prepared for the first time by prolonging the reaction time to 4 h.The XRD,SEM,TEM and Uv-vis technologies confirm the high shape difference between icosahedral gold nanocrystals and their truncated forms.3.The growth of truncated icosahedra could be induced and maintained through interplay of following processes:the～50 nm multiple twinned seeds were generated; shape and size focused by Ostwald ripening,then oxidativly etched and preferentially grew on the {100} face.Oxidative etching plays an important role in the formation of gold nanocrystals on hydrothermal condition.The gold nanocrystals with various shapes have been obtained by changing the concentration of hydrogen tetrachloroaurate (HAuCl₄)and poly(vinyl porridone)(PVP),the reaction time and the other experiment parameters.4.Gold clusters have been electrodeposited on a glassy carbon electrode by scanning the potential from 0.7 V to 0.0 V(vs.SCE)in a solution of 0.5 mM KAuCl₄ and 1.0 M KCl.The nanogold-modified glassy carbon electrode shows excellent sensitivity and selectivity for epirubicin dection.The detection limit is 1.0×10^-8mol/L.