Highly sensitive, reproducible, and stable SERS sensors based on well-controlled silver nanoparticle-decorated silicon nanowire building blocks

Abstract

Surface-enhanced Raman scattering (SERS), as a powerful analytical tool, has attracted great interest in the development of chemical and biological sensors because of its ultrahigh sensitivity and amenability to molecular fingerprinting. However, practical applications with current SERS sensors based on colloidal metal nanoparticles (NPs) or a rough metal film remain great challenges, due to the poor stability and low reproducibility. Here, we report a facile strategy to prepare highly sensitive SERS sensors with excellent reproducibility and stability based on uniform and well-controlled silver NP-decorated silicon nanowire (AgNP@SiNW) building blocks. In this strategy, uniform, size- and interparticle distance-controlled AgNPs are deposited on SiNWs, yielding abundant hot spots. A single AgNP@SiNW exhibits ultrahigh sensitivity with an enhancement factor of 4.12 × 10⁹, spot-to-spot and wire-to-wire reproducibility, and good stability in an aqueous environment. Furthermore, sensors fabricated with this AgNP@SiNW building block have diverse applications that are demonstrated with a single NW for microscopic detection of a low concentration of carbaryl (0.01 mg mL⁻¹) residues on a cucumber surface with 1 s acquisition time and an assembled thin film sensor for label-free, real-time detection of E. coli in drinking water. This combination of prominent SERS performances, highly efficient detection, and accessibility in multiple sample matrices indicates that our facile SERS sensor fabrication strategy has the potential to increase the applicability of the SERS technique in the real world.