Analyte-induced SERS hot spots for dramatically improving the ability to distinguish different concentrations of chemical solutions

Background

Surface-enhanced Raman scattering (SERS) is commonly used for material detection but usually exhibits low sensitivity to concentration changes. Here, we propose a novel method based on analyte-induced hot spots to enhance its sensitivity.

Methods

SERS substrates were prepared by thermally depositing silver onto glass slides, followed by plasma treatment in a mixed atmosphere of air and oxygen. This treatment altered the silver morphology, increasing the separation between Ag nanoparticles (AgNPs) and initially inhibiting hot spot formation. Consequently, the substrates exhibited low SERS efficiency due to limited hot spot development. Interestingly, upon introducing an aqueous analyte onto the substrate, AgNP aggregation occurred, leading to the formation of numerous hot spots that showed a positive correlation with analyte concentration. This positive correlation significantly enhanced SERS sensitivity to concentration variations.

Significant findings

The proposed technique effectively distinguishes adenine analytes, demonstrating a twofold difference across a concentration range of 2 × 10⁻⁶ to 2 × 10⁻⁴ M, supported by non-overlapping error bars in the SERS signals. Our research introduces an innovative method that utilizes analyte-induced hot spots to significantly enhance SERS effectiveness in distinguishing between different concentrations of chemical solutions. This advancement represents a significant step forward in achieving precise quantitative SERS detection.