Optical properties of SiO2 opal crystals decorated with silver nanoparticles

SiO 2 opal crystals decorated with silver nanoparticles (AgNPs) have been successfully fabricated. SEM analysis revealed that the SiO 2 opals have an ordered region of 25–30 μm 2 , and AgNPs are located into the gaps between the SiO 2 nanospheres. The effect of the plasmons of AgNPs on the photoluminescence of SiO 2 opal crystals were investigated. Under excitation of a 325 nm laser, we observed the quenching of the intrinsic defect emission in SiO 2 as the concentration of AgNPs increased. The cause of the observed photoluminescence behavior is attributed to the interaction between surface plasmon induced by AgNPs and photoluminescence centers in SiO 2 opal crystals. Then, we utilized SiO 2 opals crystals decorated with AgNPs as a SERS substrate. The final enhancement factor of the Raman shift was 1.64 × 10 7 , enabling the trace detection limit for a case of malachite green to be as low as 0.05 ppm, with a relative standard deviation of less than 1.75 %. This outcome suggests the potential for direct application of the prepared substrates in ultra-fast chemical analysis. • Under 325 nm excitation, the photoluminescence bands with peaks at 400 nm were quenched more rapidly than those with peaks at 440 nm and 500 nm with raising AgNPs concentration. • The surface plasmon resonance absorption band of AgNPs is overlapped with the emission of SiO 2 opal crystals and the photoluminescence changes are assigned to the interaction between plasmons and optical centers. • The detection limit achieved by novel SERS substrates is 0.05 ppm for malachite green. The enhancement factor reaches above 1.6 × 10 7 . Relative standard deviation (RSD) of less than 1.75 %.