Evaporation-induced self-assembly of silver nanospheres and gold nanorods on a super-hydrophobic substrate for SERS applications.

Surface-enhanced Raman scattering (SERS) has drawn attention for broad applications. We successfully fabricated highly effective SERS structures via evaporation-induced self-assembly of blend nanoparticles containing sliver nanospheres (Ag NSs) and gold nanorods (Au NRs) on a super-hydrophobic (SH) substrate. On the SH substrate, the droplets of the mixed aqueous solution of silver nanospheres (Ag NSs), gold nanorods (Au NRs), and probe molecules can preserve their spherical shape during the evaporation process, and the probe molecules (R6G) are confined into extremely small areas after solvent removal due to hydrophobicity-enhanced concentration effects. The Raman enhancement effect of the blend nanoparticles with 40 vol% Ag NSs is far higher than that of the other samples. The structure of the aggregated Ag NSs on the film-like Au NRs greatly enhances the SERS effect of Ag NSs, which is optimal for the blend system with 40 vol% Ag NSs. The SERS structure also displays excellent signal reproducibility (RSD < 10%) and low detection limits (0.5 nM). Thus, this work offers a simple and efficient strategy to fabricate a highly effective SERS structure with broad applications in environmental science, analytical chemistry, etc.