A Highly Selective and Sensitive Nano-Silver sol Sensor for Hg²⁺ and Fe³⁺: Green Preparation and Mechanism

The development of highly selective and highly sensitive nanometer colorimetric chemical sensors is an urgent requirement in the immediate detection of heavy metal ions. In this work, silver-nanoparticle (Ag NPs)-based chemosensors were prepared by a simple and green method, in which the silver nitrate, carboxymethyl cellulose sodium (CMS) and Polyvinylpyrrolidone (PVP), and glucose are used as the silver source, double stabilizer and green reductant, respectively. The obtained colloidal CMS/PVP-Ag NPs showed a high dispersibility and stability, and creating a high selectivity and sensitivity to detect Hg²⁺ and Fe³⁺ with remarkable and rapid color variation. Low limits of detection (LOD) of 7.1 nM (0-20 μM) and 15.2 nM (20-100 μM) for Hg²⁺ and 3.6 nM for Fe³⁺ were achieved. More importantly, the CMS/PVP-Ag NPs has a high sensitivity even in a complex system with multiple heavy ions, the result of the practical ability to detect Hg²⁺ and Fe³⁺ in tap water and seawater reached a rational range of 98.33~104.2% (Hg²⁺) and 98.85~104.80% (Fe³⁺), indicating the great potential of the as-prepared nanocomposites colorimetric chemosensor for practical applications.