Fabrication of Ag nanoaggregates/SiO2 yolk–shell nanoprobes for surface-enhanced Raman scattering

Surface-enhanced Raman scattering (SERS) has received much attention due to ultra-high sensitivity in detection of biological and chemical analytes. When SERS is used as tagging probe, several strong points such as high sensitivity and multiplexing capability can resolved several key issues with current optical tagging materials. Our group has reported synthesis of silica-coated silver nanoparticles (NPs) embedded silica NPs (SERS Dots) for bio-applications. Here, we designed and synthesized a new type of hollow-shell type SERS active NP (yolk–shell SERS Dots), which are aggregated silver NPs with a hollow silica nanostructure. The yolk–shell SERS Dots were prepared by adding NaBH4 to SERS Dots, resulting in the prepared NPs exhibiting 2.3 times stronger SERS signals due to aggregation of silver NPs inside the silica shells and generating several hot spots among those silver NPs. Moreover, biotin-conjugated yolk–shell type SERS dots successfully bound streptavidin-Cy5 to demonstrate the potential of yolk–shell SERS dots for bio-detection. These yolk–shell SERS Dots have great potential for bio-imaging and drug delivery applications.

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