Research On The Formation Mechanism Of Gold Nanoparticles In PVP System

The use of PVP as protecting agent in the preparation of metal nanoparticles dates back to the late seventies,and it has been employed since then in countless reports. During the past decade,PVP has been demonstrated to be one of the most versatile polymers,capable of complexing and stabilizing Ag,Au,Pt,Pd,and Cu nanoparticles, among others,but also with certain activity as a reducing agent,and definitely influencing the final particle size and morphology.1.A templateless,surfactantless,wet-chemical approach is proposed to direct fabricate gold nanostructures by just using 1-vinyl-2-pyrrolidone.The shape and size of gold nanoparticles could be easy controlled via simply changing experiment parameters.The possible growth process is proposed by arresting the growth at a series of intermediate morphology stages during the shape evolution of gold nanostructures.2.The proposed formation mechanism was investigated by using DLVO theory to calculate the V_elec and V_vdW of the gold nanoparticles reduced at initial stage.The contribution of 1-vinyl-2-pyrrolidone's to the synthesis of gold nanoparticles with controllable shapes was also considered.3.The importance of the solvent in the synthetic process was stressed,since different results were obtained when the DMF was used as the reaction solvent in the presence of various EG concentration in the PVP system.A possible factor is solvent effect.The different adsorption properties of DMF and EG on different gold facets would induce various shapes and gold nanoparticles.Different reducing ability of Au³⁺ by DMF and EG may also affect the product shapes.4.We also investigate that the copolymer PVP-co-PAA act both as a capping agent and reducing agent,which providing a variety of surface functionalities.The copolymer has two distinct moieties including pyrrolidone as stabilizer which selectivily interacts with the different crystallographic facets and polyacrylic acid for reduction and additional functionalization.5.A simple method for one-step ultralsonication synthesis of monodispersed cystine-capped gold nanoparticles in aqueous solution at room temperature has been developed.Cysteine was used as reducing agent in reaction processing.The thiol group of cysteine undergoes dimerization to form cystine via the oxidation of two thiol groups.The cystine is combined with the surface of gold nanoparticles due to the interaction between S and Au.