Directional growth of Ag nanorod from polymeric silver cyanide: A potential substrate for concentration dependent SERS signal enhancement leading to melamine detection

Abstract

Attention has been directed to prepare exclusive one-dimensional silver nanostructure from the linear inorganic polymer AgCN. Successive color change from yellow to orange, to red and finally to green reflects the evolution of high yielding Ag nanorods (NRs) from well-known -[Ag-CN]- chains of polymeric AgCN at room temperature. The parental 1D morphology of AgCN is retained within the as-synthesized Ag NRs. So we could successfully exploit the Ag NR for surface-enhanced Raman scattering (SERS) studies for sensing a popular milk adulterant melamine down to picomolar level. We observed interesting concentration dependent selective SERS band enhancement of melamine. The enhanced ~1327cm−1 SERS signal intensity at lower concentration (10−9 and 10−12M) of melamine speaks for the preferential participation of –C–N of melamine molecule with Ag surface. On the other hand, ‘–NH2’ group together with ring ‘N’ participation of melamine molecule onto Ag surface suggested an adsorptive stance at higher (10−3–10−7M) concentration range. Thus the binding modes of the molecule at the Ag surface justify its fluxional behavior.