Fabrication of SERS composite substrates using Ag nanotriangles-modified SiO photonic crystal and the application of malachite green detection.

A novel surface-enhanced Raman scattering (SERS) composite substrates on the basis of Ag triangular nanoplates(Ag TNPs)-modified SiO photonic crystals (PC) is fabricated and applied to the SERS detection of malachite green (MG). It consists of uniformly arranged Ag TNP@SiO, a new PC. Notably, Ag TNP are uniformly aligned on the SiO surface, forming a three-dimensional high-density hotspot nanostructure. With the tip "hot spots" of Ag TNPs, Bragg diffraction of SiO and coupling enhancement between Ag TNPs and SiO, the SERS enhancement of this composite substrates was multiplied. The effect on the SERS of Ag TNP@SiO composite substrate was systematically optimized by tuning Ag TNP size, size of SiO microspheres, coverage of Ag TNPs on SiO and fabrication method of Ag TNPs and PC. Moreover, the uniform of SERS composite substrates and Raman signal was dramatically increased by the method of vertical deposition. Eventually, the SERS composite substrates were employed in MG detection. Its broad detection range of 1 pM-1 μM and low limit of detection (LOD) of 0.49 pM indicated acceptable sensitivity and repeatability. This work illustrates the promising applicability in food safety analysis based on SERS composite substrates composed by Ag TNP@SiO with numerous SERS enhancements and excellent stability.