title: Reducing strength prevailing at root surface of plants promotes reduction of Ag+ and generation of Ag(0)/Ag2O nanoparticles exogenously in aqueous phase.
abstract: Potential of root system of plants from wide range of families to effectively reduce membrane impermeable ferricyanide to ferrocyanide and blue coloured 2,6-dichlorophenol indophenol (DCPIP) to colourless DCPIPH2 both under non-sterile and sterile conditions, revealed prevalence of immense reducing strength at root surface. As generation of silver nanoparticles (NPs) from Ag+ involves reduction, present investigations were carried to evaluate if reducing strength prevailing at surface of root system can be exploited for reduction of Ag+ and exogenous generation of silver-NPs. Root system of intact plants of 16 species from 11 diverse families of angiosperms turned clear colorless AgNO3 solutions, turbid brown. Absorption spectra of these turbid brown solutions showed silver-NPs specific surface plasmon resonance peak. Transmission electron microscope coupled with energy dispersive X-ray confirmed the presence of distinct NPs in the range of 5-50 nm containing Ag. Selected area electron diffraction and powder X-ray diffraction patterns of the silver NPs showed Bragg reflections, characteristic of crystalline face-centered cubic structure of Ag(0) and cubic structure of Ag2O. Root system of intact plants raised under sterile conditions also generated Ag(0)/Ag2O-NPs under strict sterile conditions in a manner similar to that recorded under non-sterile conditions. This revealed the inbuilt potential of root system to generate Ag(0)/Ag2O-NPs independent of any microorganism. Roots of intact plants reduced triphenyltetrazolium to triphenylformazon and impermeable ferricyanide to ferrocyanide, suggesting involvement of plasma membrane bound dehydrogenases in reduction of Ag+ and formation of Ag(0)/Ag2O-NPs. Root enzyme extract reduced triphenyltetrazolium to triphenylformazon and Ag+ to Ag(0) in presence of NADH, clearly establishing potential of dehydrogenases to reduce Ag+ to Ag(0), which generate Ag(0)/Ag2O-NPs. Findings presented in this manuscript put forth a novel, simple, economically viable and green protocol for synthesis of silver-NPs under ambient conditions in aqueous phase, using root system of intact plants.
authors.affiliation: Department of Environmental Studies, University of Delhi, Delhi, India.
authors.forename: Peddisetty
authors.initials: P
authors.lastname: Pardha-Saradhi
authors.affiliation: Department of Environmental Studies, University of Delhi, Delhi, India; Department of Botany, University of Delhi, Delhi, India.
authors.forename: Gupta
authors.initials: G
authors.lastname: Yamal
authors.affiliation: Department of Petroleum Engineering & Earth Sciences, University of Petroleum and Energy Studies, Dehradun, Uttarakhand, India.
authors.forename: Tanuj
authors.initials: T
authors.lastname: Peddisetty
authors.affiliation: Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India.
authors.forename: Peddisetty
authors.initials: P
authors.lastname: Sharmila
authors.affiliation: Department of Environmental Studies, University of Delhi, Delhi, India.
authors.forename: Shilpi
authors.initials: S
authors.lastname: Nagar
authors.affiliation: Department of Chemistry, University of Delhi, Delhi, India.
authors.forename: Jyoti
authors.initials: J
authors.lastname: Singh
authors.affiliation: Department of Chemistry, University of Delhi, Delhi, India.
authors.forename: Rajamani
authors.initials: R
authors.lastname: Nagarajan
authors.affiliation: Department of Botany, University of Delhi, Delhi, India.
authors.forename: Kottapalli S
authors.initials: KS
authors.lastname: Rao
mesh_terms: D019684:Magnoliopsida / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D018517:Plant Roots / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D018030:Silver Compounds / Q000737:chemistry*
chemical_list: D010087:Oxides; D018030:Silver Compounds; D012834:Silver; C040225:disilver oxide