Green synthesis of silver nanoparticles using cauliflower waste and their multifaceted applications in photocatalytic degradation of methylene blue dye and Hg~(2+) biosensing

摘要

Green synthesis of silver nanoparticles (AgNPs) using plant extracts has emerged as a viable environment-friendlymethod. The aim of the study was to biosynthesize AgNPs using cauliflower (Brassica oleracea var. botrytis) waste extractand further test their potential applications in photocatalytic degradation of methylene blue (MB) dye and Hg~(2+)biosensing.Optimum extract concentration, AgNO_3concentration, pH and temperature required for biosynthesis of stableAgNPs were determined by UV–visible spectroscopy. FT-IR, XRD, SEM, TEM, SAED, XPS and BET analysis were performedfor characterizing AgNPs. MB dye degradation using AgNPs was determined by analyzing the intensity of dye absorptionmaxima at 664 nm. Specificity and sensitivity of biosynthesized AgNPs for Hg~(2+)ions were studied for assessing theirbiosensing abilities. Optimum conditions needed for biosynthesis of stable AgNPs were observed to be 3 ml extract,0.5 mM AgNO_3,pH 8.5 and microwave-assisted heating at 600 W for 5 min. FT-IR analysis showed that the extract containednecessary functional groups that facilitated biosynthesis of AgNPs. XRD, SEM, TEM, SAED, XPS results confirmedthe formation of AgNPs. BET analysis showed that AgNPs had an average size of 35.08 nm and surface area of 19.22 m2/g.Maximum MB dye degradation percentage of 97.57% was obtained at 150 min without any significant silver leachingthereby, signifying notable photocatalytic property of AgNPs. Biosensing studies showed that AgNPs were specificallyable to detect up to 0.1 mg/l Hg~(2+)ions. In summary, cauliflower waste served as a useful source of reducing agents forbiosynthesizing AgNPs with promising environmental applications.