Influences of Composition on Electroless Deposition of Silver Nanoparticles on Glass Substrates for Surface-Enhanced Raman Scattering Measurements

A silver-mirror reaction was used to prepare active substrates for surface-enhanced Raman scattering (SERS). Glass plates were surface treated with a thin layer of silver nanoparticles (Ag-NPs). The factors influencing the performance of the SERS substrates were systematically studied. Factors included concentrations, species of complexing agents, and reducing agents. p-Nitrothiophenol (pNTP) was used to test the surfaces with Ag-NPs, with the observed signals used to compare the performance resulting from different reducing and complexing agents. The morphologies of the Ag-NPs formed by different reaction conditions were also examined by scanning electron microscope (SEM) and correlated with the SERS signals. Reducing agents included formaldehyde, sodium tartrate, and several carbohydrates. The results indicate that the use of glucose as a reducing agent produced the most suitable Ag-NPs for SERS measurements. Complexing agents of ammonia and ethyl amine offered the best performances. The optimal concentration of complexing agent was found to be approximately six times the concentration of silver ions. With a reaction time of 2 min, the optimized concentrations of glucose and silver nitrate were 0.5 M and 50 mM, respectively. In general, the enhancement factor was on the order of 10(5) to 10(6) for the substrates prepared in this work.