Facile synthesis of a highly SERS active nanosilver sol using microwaves and its application in the detection of E. coli using Victoria blue B as a molecular probe

Abstract

A rapid and green microwave procedure was developed to synthesize highly surface-enhanced Raman scattering (SERS) active silver nanoparticles (AgNPs), using diethanolamine as a reducing agent, that had a surface plasmon resonance (SPR) absorption peak at 444 nm and a resonance Rayleigh scattering (RRS) peak at 450 nm, and a new SERS enhancement mechanism was proposed for the AgNPs–NaCl–AgNO₃ system. Bacteria, which were stained using Victoria blue B (VBB), possess the characteristics of a SERS molecular probe in the AgNP sol substrate, with a strong SERS peak at 1611 cm⁻¹ and a peak intensity linear to E. coli concentration in the range of 5 × 10⁶ to 3 × 10⁹ colony forming units per mL (cfu mL⁻¹). This new, simple, rapid and sensitive SERS quantitative analysis method was used for detecting E. coli in real samples.