Smartphone colorimetry for rapid environmental monitoring: Detecting Ni2+ using EDTA and mercapto succinic acid functionalized silver nanoparticles

Abstract

Keeping the importance of devising a simple, fast, low-cost, and precise method in view for the determination of the targeted analytes in an environmental sample, this work exploited synthesized silver nanoparticles (AgNPs) along with mercapto succinic acid (MSA) and ethylenediamine tetraacetate (EDTA) as probes for detecting Ni²⁺ ions. The effectiveness of these probes as Ni²⁺ sensors was validated using the digital image colorimetry (DIC) method. The prepared AgNPs had an average particle size of 14.68 nm and demonstrated good stability for up to 2 months. The addition of Ni²⁺ ions to colloidal AgNPs induced particle aggregation through metal–ligand coordination, which led to a color change in the solutions from yellow (λ_max 402 nm) to blue (λ_max 620 nm) and an increase in the Euclidean distance (Δd) value. Furthermore, the modified AgNPs were able to detect Ni²⁺ in the concentration range of 10–300 µM with a very low detection limit of 3.30 µM for the spectrophotometric method and 3.57 µM for the DIC method. The probe showed high selectivity for Ni²⁺ against eleven other potential interfering ions. The resulting sensor showed good performance in detecting Ni²⁺ ions in Code river and tap water with an accuracy of 97.43–106.85 %. Our findings provide a simple and rapid method for routine monitoring of the presence of heavy metals in environmental samples.