Sonochemical-assisted eco-friendly synthesis of silver nanoparticles (AgNPs) using avocado seed extract: Naked-eye selective colorimetric recognition of Hg2+ions in aqueous medium

An easy and cost-effective protocol for colorimetric detection of potentially hazardous Hg2+ ions was devel-oped through sonochemical-assisted eco-friendly synthesized silver nanoparticles (AgNPs). The AgNPs were prepared using the aqueous extract of avocado (AV) seed at room temperature. UV-visible spec-troscopy revealed the formation of AV-AgNPs with a narrow surface plasmon resonance (SPR) band at 417 nm. FTIR analysis exposed the capping and stabilisation of phytoconstituents on the surface of AV-AgNPs. The average particle size was determined using a DLS profile to be 119 nm. FE-SEM images were revealed the spherical morphology of AV-AgNPs. In EDX spectra, AV-AgNPs exhibited a characteristic peak of Ag at ti 3 keV. Further, the unmodified AV-AgNPs were evaluated for colorimetric detection of different metal ions in aqueous medium. Surprisingly, these unmodified AV-AgNPs showed a good colorimetric selective sensing response towards Hg2+ ions. The colour of AV-AgNPs was changed from brown to colour-less and accompanying the disappearance of the SPR band with blue shift. There was no distinct colour change and disappearance of SPR band for the other investigated metal ions. The detection limit of AV-AgNPs probe towards Hg2+ was 3.0 x 10-4 M. The redox reaction between AgNPs and Hg2+ ions could be the basis for a selective sensing mechanism. The AV-AgNPs probe showed a good linear response in the range of 25-200 lM towards Hg2+ with R2 value 0.9914. The exceptional performance of unmodified green synthesized AV-AgNPs suggested a very promising probe for on-site detection of Hg2+ in water sample.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

A protocol for colorimetric detection of potentially hazardous Hg2+ ions was developed using sonochemical-assisted eco-friendly synthesized silver nanoparticles (AgNPs) prepared with avocado seed extract. The AgNPs showed good selective sensing response towards Hg2+ ions with a color change and disappearance of the surface plasmon resonance (SPR) band. The unmodified green synthesized AV-AgNPs exhibited promising potential for on-site detection of Hg2+ in water samples.