Visual colorimetric sensing of copper ions based on reproducible gelatin functionalized silver nanoparticles and gelatin hydrogels

• Gelatin functionalized AgNPs and AgNPs loaded gelatin hydrogels were prepared and characterized.
• Solution and solid (hydrogels) phase selective colorimetric detection of Cu2+ has been studied.
• AgNPs loaded gelatin hydrogels were reproduced by EDTA.
• The level of copper ion obtained using our method was in good agreement with those from AAS.
• Results are promising for environmental applications.

In this study, we have investigated the colorimetric sensing of heavy metal ions, especially copper ions (Cu2+) for multiple analyses using gelatin functionalized silver nanoparticles (AgNPs) and AgNPs loaded gelatin hydrogels. Gelatin functionalized AgNPs were prepared by chemical reduction of silver nitrate. The gelatin functionalized AgNPs showed concentration dependent color variation (yellow to green color) in the range from 1 × 10−8 to 1 × 10−4 M with lower detection limit of 1 × 10−7 M under optimal condition on interaction with Cu2+ ions. The selectivity response of AgNPs to various metal ions has been evaluated and found that the present method is highly selective for Cu2+ owing to agglomeration of gelatin functionalized AgNPs and formation of complex between Cu2+ and amino group of gelatin. Similarly, studies have been carried out using AgNPs loaded gelatin hydrogels for the detection of Cu2+. The regeneration of AgNPs and hydrogels was carried out by using ethylenediaminetetraacetic acid (EDTA). The sensor response of real sample was evaluated with pond water and the sensitivity values are in good agreement with the value obtained by atomic absorption spectroscopy (AAS) analysis. To the best of our knowledge, the proposed sensor system is new and shows promising result for simple and low-cost sensing of Cu2+ which may be explored for pollution monitoring applications.

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