Bifunctional quantum dot-decorated Ag@SiO2 nanostructures for simultaneous immunoassays of surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF).

Bifunctional nanostructured ensembles of quantum dot (QD)-decorated Ag@SiO2 nanoparticles embedded with Raman reporters p-aminothiophenol (PATP) were intentionally prepared for simultaneous immunoassays of surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF). The maximum SEF intensity was optimized with a silica shell spacer of about 9 nm. The SERS sensitivity was significantly improved due to the large Raman scattering cross-section of the coupling reaction product of PATP, generated on the Ag cores upon irradiation of laser during the SERS measurements. The antibody-immobilized QD-decorated Ag/PATP@SiO2 nanocomposites were used for antigen immunoassays using SERS and SEF with high sensitivity. This progress demonstrates the crucial role of rational design/control of multifunctional nanostructures in biodetection and bioimaging.