Surface-enhanced Raman spectroscopy studies of orderly arranged silica nanospheres-synthesis, characterization and dye detection

Silica nanospheres have been explored much for drug delivery, photocatalysis, sensors and energy storage applications. It also acts as a template for Surface-Enhanced Raman Spectroscopy (SERS) substrates. Uniform nanostructures at low cost with high reproducibility are the major challenges in SERS substrate fabrication. In the present work, silica nanospheres were synthesized using stober method and deposited on to glass slides using Vertical deposition techniques. Different size/thickness of Silver (Ag) nanoparticles were deposited onto silica thin films using sputter deposition technique. The monodispersity of silica nanospheres and size of silver nanoparticles (10 nm, 20 nm and 30 nm) were confirmed by FESEM analysis. The structural properties were confirmed through XRD. UV–Vis analysis revealed that the plasmonic properties of Ag@SiO2 give high surface plasmons for 30 nm thickness of silver. The binding energy of Ag@SiO2 confirmed through XPS spectrum. The fabricated SERS substrates were used to detect Rhodamine 6G (R6G), Methylene blue (MB), Methylene violet (MV) and Methyl orange dyes as an analyte molecule with a limit of detection at about 10−11 mol/L. The addition of SiO2 nanospheres decreases the Ag oxidation rate and increases their stability. The maximum enhancement factor (1.5 × 107) achieved for 30nm thickness of Ag@SiO2. The results and technique establish the potential applications and reproducible SERS substrate.