Quantitative determination of melamine in milk by surface-enhanced Raman scattering technique based on high surface roughness silver nanosheets assembled by nanowires

High surface roughness silver nanosheets assembled by nanowires with high surface-enhanced Raman scattering (SERS) capability were prepared and used to detection the melamine in liquid milk. The nanosheets were prepared by a solid-state ionics method under the direct current electric field (DECF) using silver ions conductor RbAg4I5 films and vacuum thermal evaporation method. The surface morphology and surface roughness of the prepared silver nanosheets are significantly different upon a change in the impressed current intensity. The growth mechanism of silver nanosheets was related to the irregular electrode interface and the apical growth advantage. When the current intensity was 1 mu A and 7 mu A, the fractal dimension of silver nanosheets was 1.62 and 1.70, the diameters of nanowires ranged from 50 to 110 nm and 80 to 180 nm, and many densely arranged regularly arranged silver nanoparticles lie in the prepared nanosheets, respectively. The result shows that there were more silver nanostructures and surface roughness under 7 mu A DCEF. The treatment procedure of the liquid milk required only addition of acetic acid and centrifugation. The detection concentration of melamine by this method is low as 10(-9) mol/L, which is far below the strictest safety limits required in US and China. With its facile material synthesis, simple sample pretreatment and low detection concentration, this high surface roughness silver nanowire sheets shows a strong potential detection tool in the field of food safety.