Highly uniform core/shell structures AuR/Ag and AuR/Ag@BSA with various shell thicknesses for surface-enhanced Raman scattering

This work indicates the synthesis of uniform core/shell nanostructures (AuR/Ag) with different thicknesses of Ag shell by the double seed method. This method consists of two self-sufficient progresses, one seed for the formation of gold nanorods (AuRs) and one for the formation of the Ag shell for the gold nanorods to form the AuR/Ag. Acid ascorbic (L-AA) acts as a weak reducing agent and hexadecyltrimethylammonium chloride (CTAC) acts as a surfactant for Ag shell. The formation and growth of the Ag shell were carefully investigated by changing the reaction factors such as temperature, time, and concentration of AgNO₃. The greater the concentration of AgNO₃ shelling precursor, the thicker the shell and therefore the more high-energy vibrational modes appear in the near-ultraviolet region. In survey of surface-enhanced Raman scattering effect of AuRs and AuR/Ag with Rhodamine B (RB) detector, the results show that AuR/Ag has the ability to enhance Raman signal much better than AuRs. At the same time, the thicker the Ag shell, the better the Raman signal enhancement ability.