Biologically green synthesized silver nanoparticles as a facile and rapid label-free colorimetric probe for determination of Cu2+ in water samples.

A highly sensitive and cost-effective colorimetric sensing platform for the selective trace analysis of Cu2+ ions was developed based on the accelerated etching of Riboflavin stabilized silver nanoparticles (R/AgNPs). The R/AgNPs were prepared from the Cucumis melo juice by a green chemistry approach. The bio-synthesized AgNPs were studied by UV-Vis spectroscopy and showed an intense absorption band at 404nm that were further confirmed by FTIR and EDS analysis. Simultaneous presence of Cu2+ and thiosulfate decreased the absorption intensity of green synthesized AgNPs which resulted in sensitive and selective determination of Cu2+. The selectivity of R/AgNPs detection system for Cu2+ was excellent. Furthermore, the method offered a wide linear detection range from 5nM to 100nM with a detection limit of 1.12nM. Surprisingly, it was a quick approach and the decolorization of the R/AgNPs solutions occurred only within 5min. Our results clearly indicate these R/AgNPs could be used as an efficient probe for the colorimetric sensing of Cu2+ in environmental water samples.