title: Light Mediated Generation of Silver Nanoparticles by Spinach Thylakoids/Chloroplasts.
abstract: The unique potential of chloroplasts/thylakoids to harness light energy to transport electrons from H2O to various entities was exploited for reduction of Ag+ to generate nanoparticles (NPs). Spinach thylakoids/chloroplasts turned AgNO3 solutions brown in light, but not in dark. Besides showing Ag-NPs specific surface plasmon resonance band, these brown solutions showed presence of 5-30 nm crystalline NPs composed of Ag. Powder X-ray diffraction (PXRD) analysis revealed that Ag-NPs were biphasic composed of face-centered cubic Ag0 and cubic Ag2O. X-ray photoelectron spectroscopy (XPS) data further corroborated the presence of Ag2O in Ag-NPs. Limited formation of Ag-NPs in dark and increased generation of Ag0/Ag2O-NPs with increase in light intensity (photon flux density) by thylakoids/chloroplasts, established the role of light-harvesting photosynthetic machinery in generation of Ag0/Ag2O-NPs. Potential of thylakoids/chloroplasts to generate Ag-NPs from Ag+ on exposure to red and blue wavelength regions of visible light of electromagnetic spectrum, further confirmed the involvement of photosynthetic electron transport in reduction of Ag+ and generation of Ag-NPs. While light energy mediated photosynthetic electron transport donates energized electrons extracted from H2O to Ag+ to form Ag0-NPs, O2 released as a by-product during photolysis of H2O oxidizes Ag0 to form Ag2O-NPs. Our findings furnish a novel, simple, economic and green method that can be exploited for commercial production of Ag0/Ag2O-NPs.
authors.affiliation: Department of Environmental Studies, University of Delhi, Delhi, India.
authors.forename: Nisha
authors.initials: N
authors.lastname: Shabnam
authors.affiliation: Department of Chemistry, Indian Institute of Technology Delhi, New Delhi, India.
authors.forename: P
authors.initials: P
authors.lastname: Sharmila
authors.affiliation: Department of Energy and Environmental System Engineering, University of Seoul, Seoul, Korea.
authors.forename: Hyunook
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Environmental Studies, University of Delhi, Delhi, India.
authors.forename: P
authors.initials: P
authors.lastname: Pardha-Saradhi
mesh_terms: D002736:Chloroplasts / Q000378:metabolism*; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D012834:Silver / Q000737:chemistry*; D018724:Spinacia oleracea / Q000378:metabolism*; D020524:Thylakoids / Q000378:metabolism*
chemical_list: D012834:Silver