Preparation And Characterization Of Silver-gold Core-shell Nanoparticles And Their Potential Bioanalytical Application

With the development of nano science and technology, recently the research interests of scientists have been increasingly focused on the preparation, properties and application of nanoparticles. Core-shell composite nanoparticle has a novel, regular and assemble structure. It is a more advanced composite nanostructure. Core-shell composite nanoparticles possess better properties than single nanomaterial, and have a lot of new applications.In this study, a new method was developed to synthesize nanosilver and Ag/Au core-shell hydrosol. nanosilver colloid was prepared by chemical reduction of AgNO3 using gallic acid in the present of micro amount of nanogold produced by reducing micro amounts of HAuCl4 in the solution. The formed gold nanoparticles were acted as catalyzer to promote the reductive reaction and prepare the bright yellow nanosilver colloid. The as-prepared silver nanoparticles were monodisperse, regular and stable with their mean diameter of about 18 nm. Then the as-prepared silver nanoparticles are used as crystal seed to prepare a series of Ag/Au core-shell nanoparticles with different Ag/Au mole ratio in the presence of chloroauric acid and gallic acid. Several primary influence factors were optimized.The prepared Ag/Au core-shell nanoparticles was used as a probe for the quantitative detection of human serum albumin (HSA) by the method of resonance light scattering (RLS). HSA can be combined with electronegative Ag/Au core-shell nanoparticles by electrostatic interaction to form congeries. The formed congeries can enhance the RLS intensity of nanoparticles markedly and quickly. In optimum conditions, there was a linear relationship between enhanced RLS intensity and the concentration of HSA. The linear regress equation is mensurated in the linear range of 0.01-0.35 mg/L. The proposed RLS method has been used for the detection of protein in human serum, and the results were in good coincidence with those obtained in the Coomassie Brilliant Blue G-250 assay.The prepared Ag/Au core-shell nanoparticles were bound with oligonucleotide molecules labeled by a thiol group at one end by Au-S covalent bond, so that the nanoparticle probes with oligonucleotide molecules were prepared. The two completely complementary nanoparticle probes were hybridized, which leads nanoparticles to congregate. Experemental results showd that the as prepared Ag/Au core-shell nanoparticles have been used successfully to develop a new colorimetry to recognize and ascertain detect DNA sequences.Human IgG was attached on the surface of Ag/Au core-shell nanoparticles by surface tension to form the probe of Ag/Au core-shell nanoparticles, meanwhile the human IgG was used to qualitative detection goat anti-human IgG by the method of immunoassay. When there was goat anti-human IgG in blood serum, the composites were formed owing to the immunoreaction between antigen and antibody. The formed composites made the maximum absorption wavelength of the probes Einstein shift. The method can be used for rapidly qualitative detection of antigen or antibody.