Raman enhancement properties of Ag nano-islands with SiO2 microsphere arrays prepared by self-assembly technology and the thin-film annealing method

Combining self-assembly technology and the thin-film annealing method, annealed Ag nano-islands (Ag NIs) with SiO2 microsphere (MS) arrays were prepared as surface-enhanced Raman scattering (SERS) substrate in this paper. A "top-binding" model was established to analyze the effect of SiO2 MS at different annealing temperatures and different Ag film thickness. The corresponding comparative analysis with and without MS templates have been carried on. We simulated the electric field enhancement, coupling enhancement spectrum and the optical focus function of SiO2 MS. Characterization and experiments showed that the use of a SiO2 MS array as a dewetting template can well regulate the size and morphology of Ag NIs. Among them, SiO2 MS-Ag-20 can achieve the most uniform particle size at an annealing temperature of 873.15 K. According to the UV-Vis absorption spectrum, it had an active SERS analytical enhancement factor (AEF) of ∼3.91×105 and good SERS reproducibility (relative standard deviation, RSD = 0.113) for R6G when the wavelength was 532 nm.