Preparation and surface-enhanced Raman scattering properties of GO/Ag/Ta₂O₅ composite substrates

The composite substrate composed of precious metal, semiconductor and graphene has not only high sensitivity and uniform Raman signal but also stable chemical properties, which is one of the important topics in the field of surface-enhanced Raman scattering (SERS). In this paper, a sandwich SERS substrate based on tantalum oxide (Ta₂O₅) is designed and fabricated. The substrate has high sensitivity, stable performance and high quantification capability. The composite substrate can achieve a high sensitivity Raman detection of crystal violet (CV) with a detection limit of 10^-11 M and an enhancement factor of 1.5 × 10⁹. This is the result of the synergistic effect of electromagnetic enhancement and chemical enhancement, in which the chemical enhancement is the cooperative charge transfer in the system composed of probe molecules, silver nanoparticles (AgNPs) and Ta₂O₅, and the electromagnetic enhancement comes from the strong local surface plasmon resonance between the adjacent AgNPs. After exposing the composite substrate to the air for one month, the Raman signal did not weaken, indicating that the performance of the composite substrate is stable. In addition, there is an excellent linear relationship between the intensity of Raman characteristic peak and the concentration of probe molecules, which proves that the composite substrate has high quantification capability. In practical application, the composite SERS substrate can be used to detect harmful malachite green quickly and sensitively and has a broad application prospect in the field of food safety and chemical analysis.