Synthesis And Optical Properties Of Low Density Porous Gold Nanoparticles

Nanoporous gold has attracted a tremendous attention because of their novelproperties, such as large surface area, high porosity, better mechanical properties, etc.Nanoporous gold (Au) has many potential applications in many fields, for example,surface enhancement raman spectroscopy (SERS)、catalysis、sensor and so on. In thispaper, nanoporous Au film was fabricated by using dealloying method, and then its opticalproperties were systematically studied.Firstly, silver (Ag) nanoparticles, silver coated gold (Ag@Au) nanoparticles andgold-silver (Au_xAg_y) alloy nanoparticels were synthesized by using a modified Frensmethod. These nanoparticles were characterized by using Field emission scanning electronmicroscopy (FSEM), Transmission Electron Microscope (TEM) and UV-Vis spectrometer(UV). The results showed that the diameter of Ag nanoparticles increased with increasingthe amount of silver nitrate. The diameter of Ag nanoparticles decreased with increasingthe amount of the reducing agent. There is no evidence change of Ag nanoparticlesdiameter with the increased of the reaction time. Our results also showed that theabsorption peak of the Au_xAg_yalloy had an obvious red shift with the increased of the Aumolar ratio.Secondly, the prepared Au_xAg_yalloy nanoparticles were assembled on the siliconsubstrate by using titration method. Au_xAg_yalloy film was obtained by sintering process.The film was observed on FSEM, X-ray powder diffraction (XRD) and energy dispersiveX-ray detector (EDX). The effect of the Au molar ratio and the sintering temperature onthe film structure was systematically researched.Finally, in order to fabricate the nanoporous Au, the different alloy films includingAu_xAg_yfilm and the hybrid film of Au/Ag nanoparticles were successfully dealloyed witha certain concentration of nitric acid solution. FSEM and EDX were used to characterizethe nanoporous Au. The results showed that the nanoporous Au prepared by the Au_xAg_yfilm had a smooth surface and a special high porosity. The nanoporous Au prepared byanother method had a smooth surface and low porosity. The effect of dealloying time and heat treatment on the nanoporous Au was also studied. In this paper the complexnanoporous Au was first fabricated by using our simple method.