Green Synthesis Of Gold-alginate Nanocomposites And Optical Applications

Gold nanoparticles have excellent optical properties、stability、biocompatibility and good physical and chemical properties, also have excellent properties such as Surface Plasmon Resonance(SPR)、fluorescence and so on. These properties make gold nanoparticle has a wide range of applications such as catalysis and environmental testing. It is an important task to explore a simple and efficient method for the synthesis and its use. In this paper, we mainly carried out the following three aspects of the Au NPs/SA composite material:(1)Gold nanoparticles(Au NPs) were synthesized by reducing chloroauric acid with sodium alginate(SA). Here, SA acts as reducing as well as stabilizing agent. The maximum absorption wavelengths at 522-543 nm of colloidal Au NPs/SA solutions were measured by UV–vis spectroscopy. The size and size distribution of Au NPs were determined from HR-TEM images. The influence of various factors on the size of Au NPs particularly the concentration of Au3+ and SA, and dose rate、PH of the solution、temperature and the reaction time were also investigated. The colloidal Au NPs/SA solution was fairly stable more than 4 months under storage at ambient condition.(2)Use calcium alginate gel prepared Au NPs/CA microspheres. The resulting Au NPs/CA beads function as an effcient heterogeneous catalyst in reducing decoloration of azo-dye model compounds,especially in acid orange 7(AO7) and reactive orange 5(RO5) with the presence of sodium borohydride. The reaction rate constants, estimatedbased on the reduction reactions followed pseudo-first-order kinetics, suggest the high catalytic activity and stability of the Au NPs/CA beads.(3)The fluorescence properties of Au NPs/SA were explored. The experimental results show that the Au NPs/SA has the strongest fluorescence characteristics at the excitation wavelength of Ex=360nm, and the maximum emission wavelength is Em=415nm. The concentration of Cr(VI) was analyzed quantitatively by using the fluorescence characteristics of Au NPs/SA. The fluorescence intensity decreased with the increase of Cr(VI) concentration, and the fluorescence analysis method for the determination of Cr(VI) was established. In this system, the concentration of Cr(VI) in the range of 0.01 u M to 0.09 u M with F/F0 has a good linear relationship(R=0.9919), the detection limit of the method(S/N=3) is 0.005 u M.