Green synthesis of silver nanoparticles using cauliflower waste and their multifaceted applications in photocatalytic degradation of methylene blue dye and Hg2+ biosensing

Abstract

Green synthesis of silver nanoparticles (AgNPs) using plant extracts has emerged as a viable environment-friendly method. The aim of the study was to biosynthesize AgNPs using cauliflower (Brassica oleracea var. botrytis) waste extract and further test their potential applications in photocatalytic degradation of methylene blue (MB) dye and Hg 2+ biosensing. Optimum extract concentration, AgNO 3 concentration, pH and temperature required for biosynthesis of stable AgNPs were determined by UV-visible spectroscopy. FT-IR, XRD, SEM, TEM, SAED, XPS and BET analysis were performed for characterizing AgNPs. MB dye degradation using AgNPs was determined by analyzing the intensity of dye absorption maxima at 664 nm. Specificity and sensitivity of biosynthesized AgNPs for Hg 2+ ions were studied for assessing their biosensing 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 contained necessary functional groups that facilitated biosynthesis of AgNPs. XRD, SEM, TEM, SAED, XPS results confirmed the formation of AgNPs. BET analysis showed that AgNPs had an average size of 35.08 nm and surface area of 19.22 m 2 /g. Maximum MB dye degradation percentage of 97.57% was obtained at 150 min without any significant silver leaching thereby, signifying notable photocatalytic property of AgNPs. Biosensing studies showed that AgNPs were specifically able to detect up to 0.1 mg/l Hg 2+ ions. In summary, cauliflower waste served as a useful source of reducing agents for biosynthesizing AgNPs with promising environmental applications.

Sustainable-green synthesis of silver nanoparticles using safflower (Carthamus tinctorius L.) waste extract and its antibacterial activity

“…This phenomenon was also observed and corroborated in the micrographs obtained by TEM of the silver nanoparticles. Other authors have also mentioned the facility of agri-food waste extracts for the synthesis of silver nanoparticles, and their subsequent capping and stabilization by molecules present to extract [ 40 , 41 , 42 ].…”

A hybrid lipid membrane coating “shape-locks” silver nanoparticles to prevent surface oxidation and silver ion dissolution

“…is indicative of Cl À ion oxidation of Ag 0 to Ag + ions. 55,59 Citrate capping agents offer no protection to Cl À oxidation of the AgNPs. The triangular and spherical Ag-Cit-SOA-PC without thiols underwent slower surface oxidation and Ag + ion dissolution.…”

“…47,48 Although these synthetic methods have produced AgNPs shaped as spheres, 49 cubes, 50 bipyramids, 51 stars, 52 nanoprisms, 53 triangular plates 53 these methods are energy-intensive, the size and shape distributions are not always homogenous, and chemicals used can be toxic. Consequently, this has given rise to alternative green synthetic approaches employing biological entities such as microorganisms 10,12,54,55 and plant extracts 4, [56][57][58][59][60][61][62][63] to replace more complex syntheses of AgNPs free from toxic capping agents and hazardous byproducts.…”

Green Synthesis of Ag Nanoparticles for Plasmon-Assisted Photocatalytic Degradation of Methylene Blue

“…Ag NPs possess lower loss and higher quality plasmon resonance than other metal NPs, under LSPR hot electrons transfer from Ag NPs to oxygen absorbed on the Ag NPs, which result in a negatively charged state of the oxygen-absorbed Ag nanostructure, and the hot electrons enhanced the catalytic oxidation reaction of plasmonic Ag NPs [43]. Green synthesized Ag NPs has been proven efficient for the degradation of MB under full spectrum sunlight [44], the calculated percentage of degradation efficiency was 95.3% after 72 h sunlight irradiation, but the photocatalytic degradation under visible light still remains unexplored. In this study, the visible light sensitized photocatalytic activity of synthesized Ag NPs was evaluated by degradation of MB under a sunlight simulator with a UV filter cut-off at 450 nm.…”