Fabrication of a bowl-shaped silver cavity substrate for SERS-based immunoassay

In this study, a metal sandwich substrate bridged by an immunocomplex has been created for a surface enhanced Raman scattering (SERS)-based immunoassay. The bottom bowl-shaped silver cavity thin film layer was prepared by electrodeposition using a closely packed monolayer of 700 nm diameter polystyrene spheres as a template. The reflection spectra of the films were recorded as a function of film thickness, and then correlated with SERS enhancement using p-aminothiophenol as the probe molecule. The results demonstrate that SERS enhancement can be maximized when both the frequency of the incident laser and Raman scattering approach the resonance frequency of the localized surface plasmon resonance, providing a guideline for the fabrication and further application of these nanocavity arrays. The second layer of silver was introduced by the interactions between the immunocomplexes in the middle layer of the sandwich architecture and the silver nanoparticles. The proposed structure was used to perform the SERS-based immunoassay. The labeled protein can be detected over a wide concentration range and the detection limit of TRITC and Atto610 labeled proteins were 50 and 5 pg mL(-1), respectively. The results demonstrate that the new SERS substrate is suitable for the quantitative identification of biomolecules.