A two-step temperature-raising process to gold nanoplates with optical and surface enhanced Raman spectrum properties

Abstract

Gold nanoplates in high yields have been successfully achieved via a two-step temperature-raising process through the reduction of hydrogen tetrachloroaurate in diethylene glycol in the presence of cetyltrimethylammonium bromide (CTAB) and poly vinyl pyrrolidone (PVP) at 180–200 °C for 35 min. X-Ray diffraction measurements showed that the gold samples are pure face-centered cubic (fcc) phase with a preferred orientation of <111> direction. Scanning and transmission electron microscopies demonstrated that the samples are trigonal and hexagonal plates and the selected area electron diffraction pattern indicated that the main plane of the product is the (111) plane. The reaction parameters of temperature, time, and quantity of CTAB and PVP were studied and it is found that they play important roles in the morphology and size of the product, and the two-step temperature-raising process advances the yield of gold nanoplates up to 90%. The UV-vis-NIR spectroscopic investigation demonstrated that the gold nanoplates have a strong adsorption band in the near-infrared region (∼800 nm). Meanwhile, the surface enhanced Raman spectrum property of Rhodamine 6G on the gold nanoplates was also investigated and the Raman scattering of Rhodamine 6G has been enhanced with an enhancement factor of ∼1 × 10⁵.