Colorimetric and plasmonic detection of Hg2+ in water by biogenic Ag nanoparticles synthesized with Opuntia joconostle.

[Display omitted] • Silver nanoparticles (AgNPs) were biosynthesized using Opuntia joconostle fruit. • No infusion was required for the formation of AgNPs with mean diameter of 17.7 nm. • AgNPs detect colorimetrically and selectively Hg2+ ion in aqueous solution. • Functionalization of AgNPs is not required for sensing Hg2+ ion even in tap water. Silver nanoparticles (AgNPs) have been synthesized, for the first time, using the pulp of Opuntia joconostle fruit as reducing reagent of Ag+ ions. The reported method is wholly green, since no temperature or infusion preparation were required. AgNPs with a 428 nm plasmon absorbance, a quasi-spherical morphology, a mean size of 17.7 nm, and an FCC crystal structure were obtained. These biogenic AgNPs, without further chemical functionalization, could sense easily (naked eye) and selectively the presence of Hg2+ ions in aqueous solution and in tap water. [ABSTRACT FROM AUTHOR]