Temperature derived morphological engineering in gold nanoparticles for colorimetric sensing of chromium ions in...

The controlled synthesis of the nanomaterials is imperative to develop efficient sensing probes. Herein, we report a simple, selective, and sensitive colorimetric sensor for Cr(III) detection based on citrate-capped gold nanoparticles (AuNPs) synthesized under varying temperature conditions. Using a one-step synthesis approach, five types of citrate capped AuNPs (AuNPs-I to AuNPs-V) were prepared at 4, 25, 37, 50, and 100 °C synthesis temperature, respectively. Upon addition of Cr(III), the developed AuNPs displayed color change (from red to blue) and a red shift in the localized surface plasmon resonance (LSPR) peak due to nanoparticle aggregation. The AuNPs aggregation is driven by strong Cr(III)-citrate interactions, where each Cr(III) ion coordinates with two citrate molecules to disrupt their colloidal stability. Among the developed AuNPs variants, AuNPs-I demonstrated the highest sensitivity, with a detection limit of 38.04 ppb. Notably, all the developed probes exhibited excellent selectivity for Cr(III) over other metal ions. Moreover, the practical applicability of the probes was accessed by evaluating their performance on tap water and grape juice.