Single crystalline silver nanoparticles have been synthesized by thermal decomposition of silver oxalate in water and in ethylene glycol. Polyvinyl alcohol (PVA) was employed as a capping agent. The particles were spherical in shape with size below 10 nm. The chemical reduction of silver oxalate by PVA was also observed. Increase of the polymer concentration led to a decrease in the size of Ag particles. Ag nanoparticle was not formed in the absence of PVA. Antibacterial activity of the Ag colloid was studied by disc diffusion method.

S. Navaladian

Balasubramanian Viswanathan

Ram Prasad Viswanath

Thirukkallam Kanthadai Varadarajan

Escherichia coli

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IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Nanoscale Research Letters

Nanoparticles exhibit unique properties that enable them to find potential applications in various fields. Accordingly, significant research attention is being given to the development of novel strategies for the synthesis of nanoparticles. Among these, biological route of nanoparticle synthesis has been portrayed as an efficient, low-cost and environmental friendly technique. Biological materials such as bacteria, fungi, yeast, algae and plant have been reported to possess high bioreduction ability to synthesize various size and shape of metallic nanoparticles. Of these biomaterials, this review focuses on plant-mediated biosynthesis of metallic nanoparticles. The biomolecules present in the plants such as terpenoids, flavones, ketones, aldehydes, proteins, amino acids, vitamins, alkaloids, tannins, phenolics, saponins, and polysaccharides play a vital role in reduction of metals. A systematic comparison of literature, based on the bioreduction capacity of various plant biomass/extract towards various metals under different experimental conditions, is also provided. Various instrumental techniques utilized to characterize nanoparticles are also discussed. Finally, this review also highlights the application of biosynthesized nanoparticles in different fields such as medicine, agriculture, catalytic, cosmetic and food. Thus, this article reviews the achievements and current status of plant-mediated biosynthesis, and hopes to provide insights into this exciting research frontier. © 2017 Published by Elsevier Ltd.

Journal of Environmental Chemical Engineering

Plant-mediated biosynthesis of metallic nanoparticles: A review of literature, factors affecting synthesis, characterization techniques and applications

Potassium-birnessite (K-OL-1) samples of different morphologies (nanowire networks, nanoparticles and mesoporous hierarchical nanowire networks) and textural properties were synthesized from KMnO4 by using oxalate-reduction method under ambient conditions. Cryptomelane (K-OMS-2) samples of similar morphologies were synthesized by the calcination of birnessite samples. The synthesized MnO2 samples were characterized by XRD, TGA, DTA, SEM, TEM, nitrogen adsorption-desorption and ICP-OES analyses. One each of the birnessite and the cryptomelane samples showed mesoporous nature (pore size ∼50 Å and 66 Å respectively). The pH of the reaction medium has been found to have a key role in the properties of the resulting MnO2 samples. Electrochemical studies of MnO 2-carbon black composites were performed in 0.1 M aqueous Na 2SO4 solution using cyclic voltammetry and galvanostatic charge-discharge cycling. One of the birnessite samples with nanowire network morphology and a BET surface area of 202 m2 g-1 exhibited a high capacitance value of 234 F g-1. Electrochemical studies revealed that the specific capacitance values of the studied MnO2 materials have a direct relationship with their BET surface area values. Birnessite samples have exhibited better capacitance behavior and values than their cryptomelane derivatives. The effect of the morphology has also been reflected in the values of the specific capacitance. This journal is © the Partner Organisations 2014.

RSC Advances

A facile, morphology-controlled synthesis of potassium-containing manganese oxide nanostructures for electrochemical supercapacitor application

Worm-like nanorods and nanospheres of silver have been synthesized by photochemical decomposition of silver oxalate in water by UV irradiation in the presence of CTAB and PVP, respectively. No external seeds have been employed for the synthesis of Ag nanorods. The synthesized Ag colloids have been characterized by UV-visible spectra, powder XRD, HRTEM, and selected area electron diffraction (SAED). Ag nanospheres of average size around 2 nm have been obtained in the presence of PVP. XRD and TEM analyses revealed that top and basal planes of nanorods are bound with {111} facets. Williamson-Hall plot has revealed the presence of defects in the Ag nanospheres and nanorods. Formation of defective Ag nanocrystals is attributed to the heating effect of UV-visible irradiation.

Fabrication of worm-like nanorods and ultrafine nanospheres of silver via solid-state photochemical decomposition

Palladium nanoparticles of average size around 8 nm have been synthesized rapidly by UV irradiation of mixture of palladium chloride and potassium oxalate solutions. A rod-shaped palladium oxalate complex has been observed as an intermediate. In the absence of potassium oxalate, no Pd nanoparticles have been observed. The synthesized Pd nanoparticles have been characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selective area electron diffraction and energy dispersive analysis by X-rays (EDAX) analyses. XRD analysis indicates the preferential orientation of catalytically activeticles. A plausible mechanism has been proposed for the formation of anisotropic Pd nanoparticles.

A rapid synthesis of oriented palladium nanoparticles by UV irradiation

Anisotropic silver nanoparticles (NPs) have been synthesized rapidly using microwave irradiation by the decomposition of silver oxalate in a glycol medium using polyvinyl pyrolidone (PVP) as the capping agent. The obtained Ag nanoparticles have been characterized by UV-visible spectroscopy, powder x-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) studies. Anisotropic Ag nanoparticles of average size around 30 nm have been observed in the case of microwave irradiation for 75 s whereas spherical particles of a size around 5-6 nm are formed for 60 s of irradiation. The texture coefficient and particle size calculated from XRD patterns of anisotropic nanoparticles reveal the preferential orientation of (111) facets in the Ag sample. Ethylene glycol is found to be a more suitable medium than diethylene glycol. A plausible mechanism has been proposed for the formation of anisotropic Ag nanoparticles from silver oxalate. © IOP Publishing Ltd.

Journal	Nanoscale Research Letters
ISSN	19317573
Open Access	Yes