In situ and room-temperature synthesis of ultra-long Ag nanoparticles-decorated Ag molybdate nanowires as high-sensitivity SERS substrates

We report on room-temperature synthesis of Ag nanoparticles (NPs) decorated silver molybdate nanowires (SMNs) using a solution-based chemical reaction method. We show that Ag_x Mo_y O_z (Ag₂ Mo₂ O₇ , Ag₂ MoO₄ and Ag₆ Mo₁₀ O₃₃) nanomaterials can be selectively synthesized by altering the pH value of the reaction media in the presence of silicotungstic acid at room temperature. This reaction process uses isopropyl alcohol as a free radical scavenger and occurs over a short reaction time compared to the traditional hydrothermal method. Moreover, we demonstrate that under UV-light illumination of different periods, Ag NPs of controllable distribution densities are formed in situ on the surface of SMNs in tungstosilicate acid environment. We show that the SERS sensitivity of such Ag NP-SMN complex depends on the distribution density of Ag NPs, with the best structure capable of detecting the p-aminothiophenol at a concentration as low as 1.0 × 10^-11 M. The same substrate is further used to enhance the Raman signal from 2-mercaptopyridine from which a quantitative relationship between the analyte concentration and its corresponding Raman intensity can be established.