Sensitive and selective SERS probe for trivalent chromium detection using citrate attached gold nanoparticles

Abstract

In this article, we have demonstrated a sensitive and selective surface enhanced Raman spectroscopy (SERS) probe, based on citrate-capped gold nanoparticles (AuNPs), for trivalent chromium (Cr³⁺) detection. After introducing Tween 20 to a solution of citrate-capped AuNPs, the as-prepared Tween 20/citrate–AuNP probe could recognize Cr³⁺ at a 50 × 10⁻⁹ M level in an aqueous medium at a pH of 6.0. Tween 20 can stabilize the citrate-capped AuNPs against conditions of high ionic strength. Due to the chelation between Cr³⁺ and citrate ions, AuNPs undergo aggregation. As a result, it formed several hot spots and provided a significant enhancement of the Raman signal intensity through electromagnetic (EM) field enhancements. A detailed mechanism for tremendous SERS intensity change had been discussed. The selectivity of this system toward Cr³⁺ was 400-fold, remarkably greater than other metal ions.