Colorimetric sensor for copper and lead using silver nanoparticles functionalized with fluoresceinamine isomer I

Chemical sensing of heavy metals in aqueous environments offers significant advantages, including a rapid and cost-effective method for estimating their concentrations. In this study, silver nanoparticles (AgNPs) were functionalized with fluoresceinamine (FLA) to detect Cu²⁺and Pb²⁺in water. Cysteamine (Cyt) was subsequently added to detect these metals with the naked eye. UV–Vis and fluorescence spectroscopy were conducted to determine the limits of detection (LODs) of each method. All AgNPs were characterized using transmission electron microscopy and Fourier transform infrared spectroscopy. The lower LODs using Cu²⁺and Pb²⁺ were 4.40 × 10⁻⁶ and 1.15 × 10⁻⁶ M for UV–Vis titration and 6.53 × 10⁻⁶ and 1.39 × 10⁻⁶ M for fluorescence, respectively. The recovery percentage for the spectroscopic methods was high at 87 %. Subsequently, cellulose paper sensors were impregnated with AgNPs-FLA and AgNPs-FLA-Cyt to analyze both cations with a limit of quantification (LOQ) of 10⁻³ M. The cellulose paper sensors were characterized using drop shape analysis and fluorescence. These findings demonstrate the potential of colorimetric sensors composed of AgNPs-fluorophores for the rapid estimation of the concentration of specific heavy metals in solution using UV–Vis and fluorescence spectroscopy. Further, the incorporation of an additional molecule, such as Cyt, linked to AgNPs-fluorophores enabled detection with the naked eye, offering potential utility in water analysis for mining industries characterized by high concentrations of contaminants.