Capillarity-constructed reversible hot spots for molecular trapping inside silver nanorod arrays light up ultrahigh SERS enhancement

Abstract

SERS hot spots with outstanding enhancement ability can spontaneously form in a reversible and reproducible way by the self-approach of flexible silver nanorods driven by the capillary force of solvent evaporation, and at the same time the target analytes can be trapped in the top-closed silver nanorods in the solvent evaporation process. The Raman intensity of the top-closed vs. top-opened nanorod arrays was a factor of 100–1000 higher for SERS reporters such as p-aminothiophenol or crystal violet. Furthermore, triplicate measurements on long nanorod arrays at the same position show a variation of the Raman intensity <10%, demonstrating a good reproducibility of the enhancement. Moreover, we found that the self-approach is highly dependent on the nanorod length and the molecules with different adsorptivity have different SERS performance in the solvent evaporation process. This solvent evaporation-controlled self-approach is an extremely simple and efficient strategy for the spontaneous formation of Raman hot spots with outstanding enhancement ability. These characteristics promise a generic platform for molecule trapping and SERS sensing with high sensitivity and reproducibility, which can help to transform SERS into a practical analytical technique.