Rapid and Sensitive Detection of Malachite Green and Melamine with Silver Film over Nanospheres by Surface-Enhanced Raman Scattering

Silver film over nanospheres (AgFON) have been prepared by depositing Ag thin film onto the self-assembled monolayer arrays of polystyrene nanospheres with vacuum magnetron sputtering method. The surface morphologies and optical properties have been characterized by using scanning electron microscope (SEM) and ultraviolet-visible near-infrared (UV-Vis-NIR) spectrophotometer. AgFON was used as substrate to detect the surface-enhanced Raman scattering (SERS) spectra of malachite green (MG) and melamine (MA). It was found that the AgFON substrate presented outstanding performance that the Raman enhancement factor was calculated to be as large as 9.76 x 10(12). The minimum limit for MG was down to 10(-8) mol/L with a good linear response range from 10(-4) to 10(-8) mol/L. In addition, this substrate showed excellent ability to recognize MA molecules with a detection limit of 0.1 mg/L. A good linearity (r = 0.9887) was obtained in the concentration range of 2-100 mg/L. Furthermore, the AgFON substrate exhibited good uniformity with a relative standard deviation (RSD) of 9.01 % and good reproducibility with RSD of 8.60 %.