Detection and quantification of Cu2+ ion using gold nanoparticles via Smartphone-based digital imaging colorimetry technique

Abstract

Heavy metals are the main pollutants in the environment because of their toxic effects on human health. One of the heavy metals in drinking water is copper ion (Cu2+). In this study, gold nanoparticles (AuNPs) were used to detect Cu2+ using a smartphone via the digital image colorimetry (DIC) method. The synthesis of AuNPs was carried out by chemical reduction method from HAuCl4 solution with sodium citrate as a reducing agent. The formation of AuNPs was confirmed using UV–vis spectroscopy, TEM, XRD, and FTIR. AuNPs (45 mM) which had a wine red color selectively changed color to blue after the addition of Cu2+ ions. The color change of AuNPs was monitored using a smartphone and validated with a UV–vis spectrophotometer. Particle size analysis concluded that the presence of Cu2+ ions could cause AuNPs to agglomerate, making the particle size larger. The standard curve for Cu2+ ions shows good linear results in the concentration range of 15–90 mM using the DIC method. The accuracy of the proposed DIC was tested by checking the actual concentration and an accuracy of 97.6% was obtained. This method also shows good results for sensitivity and selectivity, with a detection limit of 8.3 mM.