Siby Joseph

Microwave assisted facile green synthesis of silver and gold nanocatalysts using the leaf extract of Aerva lanata.

Herein, we report a simple microwave assisted method for the green synthesis of silver and gold nanoparticles by the reduction of aqueous metal salt solutions using leaf extract of the medicinal plant Aerva lanata. UV-vis., FTIR, XRD, and HR-TEM studies were conducted to assure the formation of nanoparticles. XRD studies clearly confirmed the crystalline nature of the synthesized nanoparticles. From the HR-TEM images, the silver nanoparticles (AgNPs) were found to be more or less spherical and gold nanoparticles (AuNPs) were observed to be of different morphology with an average diameter of 18.62nm for silver and 17.97nm for gold nanoparticles. In order to evaluate the effect of microwave heating upon rate of formation, the synthesis was also conducted under ambient condition without the assistance of microwave radiation and the former method was found to be much faster than the later. The synthesized nanoparticles were used as nanocatalysts in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4.

Indigofera tinctoria leaf extract mediated green synthesis of silver and gold nanoparticles and assessment of their anticancer, antimicrobial, antioxidant and catalytic properties

Abstract This study reports the synthesis of noble metal nanoparticles, namely silver and gold from their respective salt by leaf extract of a medicinal plant Indigofera tinctoria. This leaf extract plays a dual role as stabilizing and reducing agent for the formation of nanoparticles. The synthesized silver and gold nanoparticles were characterized by UV-vis. spectroscopy, FTIR spectroscopy, XRD, TEM, EDX and AFM analysis. All these techniques confirm the formation of crystalline nanoparticles. The cytotoxic effect of I. tinctoria leaf extract and the nanoparticles were studied on lung cancer cell line A549. It was shown that the cell viability decreases with increasing concentration and nanoparticles has more toxic effect on cancer cell than the pure leaf extract. IC50 value of I. tinctoria leaf extract, AuNP and AgNP respectively, are 71.92 ± 0.76 μg/ml, 59.33 ± 0.57 μg/ml and 56.62 ± 0.86 μg/ml. Antimicrobial activities were tested against both bacterial and fungal strains by agar well diffusion method. The synthesized nanoparticles show high antimicrobial activities towards all tested microbial strains with varying degree. The antioxidant activities of synthesized nanoparticles were analysed by using DPPH method and found that nanoparticles show higher antioxidant activities than the leaf extract. Outstanding catalytic activities of nanoparticles were demonstrated by employing the reduction reactions of o/p-niroanilines by NaBH4.

Microwave assisted green synthesis of silver nanoparticles using leaf extract of elephantopus scaber and its environmental and biological applications

Abstract The fabrication of spherical silver nanoparticles using the phytoreducing agent Elephantopus scaber is reported here. Irradiation of the reaction mixture under a domestic microwave oven enabled the formation of stable silver nanoparticles and was confirmed by UV-vis spectral portrait. Chemical components inherent in the aqueous leaf extract which reduces the monovalent silver were identified by FT-IR spectroscopy. The crystal structure of the synthesized nanoparticles was established as face centred cube by the powder XRD analysis. The TEM images suggest an average particle size of 37.86 nm to the silver nanoparticles. The prepared silver nanocatalysts can successfully reduce various organic nitro compounds, namely, 4-nitrophenol, 2-nitroaniline and 4-nitroaniline. The environmental pollution caused by dyes like eosin Y is effectively wiped off within a short span of time using the prepared nanocatalysts. The free radical quenching efficacy of the plant extract and the silver nanoparticles were checked by employing DPPH assay bestowing ascorbic acid reference. The potential of the nanoparticles as antimicrobials against six human disease causing pathogens were tested through the well diffusion pathway. The newly developed silver nanoparticles produced IC50 value 15.68 ± 0.15 μg/mL on human skin carcinoma cells, A375 and 65.49 ± 0.40 μg/mL on fibroblast cells, L929 when the cytotoxicity is studied employing MTT assay. Elephantopus scaber showed IC50 value 50.55 ± 0.17 μg/mL against A375 cells. Graphical Abstract

Microwave-assisted facile green synthesis of silver nanoparticles and spectroscopic investigation of the catalytic activity

Silver nanoparticles have been successfully synthesized in aqueous medium by a green, rapid and cost-efficient synthetic approach based on microwave irradiation. In this study, iota-carrageenan (I-carrageenan) is used both as reducing and stabilizing agent. The formation of nanoparticles is determined using UV–vis, Fourier transform infrared (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray (EDX) and high-resolution-transmission electron microscopic (HR-TEM) analysis. Transmission electron microscopic (TEM) images show that the nanoparticles are of spherical shape with an average diameter of 18.2 nm. I-carrageenan-stabilized silver nanoparticles show outstanding catalytic activity for the reduction of 4-nitrophenol in the presence of NaBH4 in aqueous medium. The reaction follows pseudo-first-order kinetics and the reaction rate increases with the increase in amount of the catalyst. The study of the temperature dependence of reaction rate gives activation energy of 42.81 kJ mol−1. The synthesized silver nanoparticles are anticipated to be a promising material for pollution abatement.

Microwave Assisted Biosynthesis of Silver Nanoparticles Using the Rhizome Extract of Alpinia galanga and Evaluation of Their Catalytic and Antimicrobial Activities

Biomediated methods are considered to be a safer alternative to conventional physicochemical methods for the fabrication of nanomaterials due to their eco-friendly nature. In the present study, silver nanoparticles (AgNPs) were synthesized by microwave irradiation using aqueous rhizome extract of the medicinal plant Alpinia galanga. The nanoparticles were also synthesized under ambient condition without the assistance of microwave radiation and the former method was found to be much faster than the latter. The silver nanoparticles were characterized by UV-vis., FTIR, XRD, and HR-TEM analysis. UV-vis. spectroscopic studies provided ample evidences for the formation of nanoparticles. The FTIR spectrum confirmed the presence of plant phytochemicals as stabilizing agent around the AgNPs. XRD and HR-TEM analyses clearly proved the crystalline nature of the nanoparticles. From the TEM images, the nanoparticles were found to be roughly spherical in shape with an average diameter of 20.82 ± 1.8 nm. The nanoparticles showed outstanding catalytic activity for the reduction of methyl orange by NaBH4. The AgNPs were also evaluated for their antimicrobial activity by well diffusion method against S. aureus, B. subtilis, V. cholera, S. paratyphi, and A. niger. They were found to be highly toxic against all the tested pathogenic strains.

YTTRIUM AND LANTHANIDE IODIDE COMPLEXES OF N, N'-BIS(4-ANTIPYRYLMETHYLIDENE)ETHYLENEDIAMINE

Abstract Complexes of yttrium and lanthanide iodides with N,N′-bis(4-antipyrylmethylidene)ethylenediamine (BAME) having the general formula [Ln(BAME)3I]I2 (where Ln=Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er) have been synthesised and characterised by elemental analyses, molar conductance in non-aqueous solvents, electronic, infrared and proton NMR spectra as well as thermogravimetric analyses. BAME acts as a neutral bidentate ligand coordinating through both azomethine nitrogen atoms. One of the iodide ions is coordinated. A coordination number of 7 may be assigned to the metal ion in these complexes. The covalency parameters evaluated from the solid state electronic spectra suggest weak covalent character of the metal-ligand bond. The TG data of the lanthanum complex indicate that the complex is stable up to about 145°C and undergoes decomposition in two stages forming lanthanum oxide as the final product.

Synthesis and characterization of multifunctional gold and silver nanoparticles using leaf extract of Naregamia alata and their applications in the catalysis and control of mastitis

Phytoreduced nanoparticles have multi-functionalities due to their sustainable origin and biocompatible nature. Herein, we report the synthesis and characterization of silver and gold nanoparticles using leaf extract from the herb Naregamia alata. Microwave radiation from a domestic microwave oven, a non-classical source of energy, is used to perform the reduction of the metal ion precursors. The spherical silver nanoparticles have an average diameter of 18.05 ± 4.73 nm, and the poly-shaped gold nanoparticles exhibit an average size of 27.92 ± 9.19 nm. The X-ray powder diffraction patterns indicate different crystal planes, namely the (111), (200), (220) and (311) planes of fcc nanosilver and nanogold. The actions of six major mastitis pathogens are inhibited by the antimicrobial power of the silver and gold nanoparticles. Colored pollutants from the paper, printing and textile industries such as eosin Y and methyl red are degraded without light irradiation using the catalytic power of the synthesized noble metal nanoparticles. Furthermore, the reduction of the organic compound 4-nitrophenol by NaBH4 in the presence of the nanocatalysts increases the laboratory value of the present study.

Yttrium and Lanthanide Nitrate Complexes of 4-Formyl-2, 3-Dimethyl-1-Phenyl-3-Pyrazolin-5-One

Abstract Complexes of yttrium and lanthanide nitrates with 4-formyl-2, 3-dimethyl-1-phenyl-3-pyrazolin-5-one (FDPP) having the general formula [Ln(FDPP)2(NO3)2]NO3, where Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er have been synthesised and characterised by elemental analyses, molar conductance in non-aqueous solvents, electronic, infrared and proton NMR spectra as well as thermogravimetric analyses. FDPP acts as a neutral monodentate ligand, coordinating through the ring carbonyl oxygen and two of the nitrate ions are coordinated in a bidentate manner. A. coordination number of six may be assigned to the metal ion in these complexes. The covalency parameters evaluated from the solid state electronic spectra suggest weak covalent character of the metal-ligand bond. The TG data of the lanthanide complexes indicate that the complexes are stable up to about 170°C. and undergo decomposition in two stages forming the respective anhydrous lanthanide oxide as the final product.

Green synthesis of silver nanoparticles using Nervalia zeylanica leaf extract and evaluation of their antioxidant, catalytic, and antimicrobial potentials

ABSTRACT Here we report a simple, one-pot, inexpensive, and eco-friendly method for the synthesis of silver nanoparticles. The leaf extract of a medicinal plant Nervalia zeylanica was used as reducing and stabilizing agent for the synthesis of nanoparticles by microwave-assisted strategy. The nanoparticles show characteristic surface plasmon peak at 468 nm in UV–vis absorption spectrum. The involvement of phytochemicals in the reduction and stabilization of nanoparticles was confirmed by FTIR analysis. Using X-ray diffraction analysis, the crystalline nature of the nanoparticles was demonstrated. Transmission electron microscopic analysis shows that the nanoparticles were in spherical shape with average particle size of 34.2 nm. The antioxidant studies were performed by the 1,1-diphenyl-2-picryl hydrazyl method. The nanoparticles show excellent scavenging activities than the leaf extract. The IC50 values of silver nanoparticles and the leaf extract, respectively, were 15.20 and 92.83 µg mL−1. The catalytic activities of synthesized nanoparticles were examined by using them in the reduction of organic dyes. The nanoparticles show excellent catalytic activities and follow pseudo-first-order kinetics. The antimicrobial activities of nanoparticles were analyzed by an agar well diffusion method against six microbial strains and found that the nanoparticles were highly toxic against all the tested microbial strains.

Eco-friendly synthesis of silver and gold nanoparticles with enhanced antimicrobial, antioxidant, and catalytic activities

The present work is emphasised on the bio-fabrication of silver and gold nanoparticles in a single step by a microwave-assisted method using the leaf extract of Synedrella nodiflora as both reducing and stabilising agent. The synthesised nanoparticles are highly stable and show surface plasmon resonance peak at 413 and 535 nm, respectively, for silver and gold nanoparticles in UV-Vis spectrum. The functional group responsible for the reduction of metal ions were obtained from Fourier transform infrared spectroscopy. The crystalline nature of nanoparticles with face-centred cubic geometry was confirmed by the X-ray diffraction and selected area electron diffraction patterns. The morphology and sizes of the silver and gold nanoparticles were obtained from transmission electron microscopy images. The nanoparticles exhibit effective antimicrobial activities against various pathogenic strains. These antimicrobial properties were analysed by employing agar well diffusion method. The nanoparticles show significant antioxidant properties, and it was determined using 2, 2-diphenyl-1-picrylhydrazyl assay. The nanoparticles also show potent catalytic activity in the degradation of anthropogenic pollutant dyes Congo red and eosin Y by excess NaBH4. Thus, the current study demonstrates the potential use of S. nodiflora as a reducing and stabilising agent for the synthesis of silver and gold nanoparticles and their relevance in the field of biomedicine and catalysis.