Sneha Mohan

Completely green synthesis of dextrose reduced silver nanoparticles, its antimicrobial and sensing properties

We herein report the green synthesis of highly monodispersed, water soluble, stable and smaller sized dextrose reduced gelatin capped-silver nanoparticles (Ag-NPs) via an eco-friendly, completely green method. The synthesis involves the use of silver nitrate, gelatin, dextrose and water as the silver precursor, stabilizing agent, reducing agent and solvent respectively. By varying the reaction time, the temporal evolution of the growth, optical, antimicrobial and sensing properties of the as-synthesised Ag-NPs were investigated. The nanoparticles were characterized using UV-vis absorption spectroscopy, Fourier transform infra-red spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HR-TEM). The absorption maxima of the as-synthesized materials at different reaction time showed characteristic silver surface plasmon resonance (SPR) peak. The as-synthesised Ag-NPs show better antibacterial efficacy than the antibiotics; ciproflaxin and imipenem against Pseudomonas aeruginosa with minimum inhibition concentration (MIC) of 6 μg/mL, and better efficacy than imipenem against Escherichia coli with MIC of 10 μg/mL. The minimum bactericidal concentration (MBC) of the as-synthesised Ag-NPs is 12.5 μg/mL. The sensitivity of the dextrose reduced gelatin-capped Ag-NPs towards hydrogen peroxide indicated that the sensor has a very good sensitivity and a linear response over wide concentration range of 10(-1)-10(-6)M H2O2.

Facile synthesis of transparent and fluorescent epoxy–CdSe–CdS–ZnS core–multi shell polymer nanocomposites

A facile and environmentally benign approach for the synthesis of highly transparent and fluorescent CdSe–CdS–ZnS core–multi-shell polymer nanocomposites is presented. The CdSe–CdS–ZnS core–multi-shell quantum dots (QDs) were prepared via a continual precursor injection and phosphine free method in paraffin liquid and oleic acid without a protective atmosphere. The as-prepared core–multi-shell QDs were dispersed directly in an epoxy polymer matrix via a melt mixing technique. The QDs showed better dispersibility and good optical properties in the epoxy matrix. The transmission electron microscopy (TEM) images showed that the as-synthesized QDs are small, spherical and are well dispersed inside the polymer matrix without any change in morphology. It was found that the nanocomposite filled with yellow-emitting QDs had more transparency compared to the neat epoxy. The luminescence of the neat polymer shifted from the blue region to the yellow region in the nanocomposite. The fluorescent lifetime analysis of the as-prepared core–multi shell and the polymer nanocomposite showed a decrease compared to the core while the tensile measurements showed an increase in the tensile properties of the nanocomposite in comparison with the neat polymer.

Size tunable synthesis of HDA and TOPO capped ZnSe nanoparticles via a facile aqueous/thermolysis hybrid solution route

We herein report the synthesis of hexadecylamine (HDA) and trioctylphosphine (TOPO) capped ZnSe nanoparticles (NPs) via a simple and environmentally benign aqueous/thermolysis hybrid solution route. The synthesis involves the use of cheap and less toxic precursors as starting materials. By varying the reaction temperature, monomer concentration, capping group and zinc precursor we systematically studied the size, optical and structural properties of the as-synthesised NPs. The NPs were characterised using UV–Vis absorption and photoluminescence spectroscopy, transmission electron microscopy, high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). All the particles exhibited strong quantum confinement with respect to the bulk ZnSe. The absorption and emission maxima of the TOPO-capped ZnSe NPs are blue-shifted, as compared to the HDA-capped NPs synthesized at the same temperature and monomer concentration. The use of Zn(CH3COO)2 as the precursor resulted in a smaller NPs with no evidence of trap emission. The HRTEM confirm the crystallinity of the material while the XRD results indicated that the capping group has no pronounced effect on the phase and crystalline structure of the as-synthesised ZnSe NPs.

Biosynthesis of silver nanoparticles from Acacia mearnsii De Wild stem bark and its antinociceptive properties

ABSTRACT The biosynthesis of silver nanoparticles (Ag-NPs) using the hydrosol extract of the dry stem bark of Acacia mearnsii as reducing and capping agents, and their antinociceptive properties are hereby reported. By varying the temperature and reaction time, the temporal evolution of the optical and morphological properties of the as-synthesized material was investigated. The NPs were characterized by UV–visible absorption spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS) and x-ray diffractometry (XRD) The optical analyses show that the position of the maximum surface plasmon resonance (SPR) peak is red-shifted as the reaction temperature decreased. The TEM micrographs show that the as-synthesized Ag-NPs are spherical while the X-ray diffraction shows that the material is highly crystalline with face-centered cubic structures. The anti-inflammatory efficacy, analyzed by the formalin model, indicates that the as-synthesized Ag-NPs are very effective, with an inhibition rate of about 76%. GRAPHICAL ABSTRACT

Completely green synthesis of silver nanoparticle decorated MWCNT and its antibacterial and catalytic properties

Abstract We herein report a simple large scale green synthesis route for the synthesis of silver nanoparticle (Ag-NP) multi walled carbon nanotubes (MWCNTs) hybrid nanocomposite (Ag-MWCNTs). The as-synthesized hybrid nanocomposite were characterized using UV-Vis absorption spectroscopy, Fourier transform infra-red spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction analysis (XRD) and high resolution transmission electron microscopy (HR-TEM). Raman spectroscopy analysis showed an increase in the D/G ratio of Ag-MWCNTs hybrid nanocomposites when compare with that of functionalized MWCNTs (F-MWCNTs) attributed to the presence of Ag-NPs on the surface of the F-MWCNTs. The as-synthesized Ag-MWCNTs nanocomposites showed strong antibacterial efficacy against Escherichia coli compared to the Ag-NPs and MWCNTs. The catalytic potential of the Ag-MWCNTs hybrid nanocomposite was investigated for the first time by studying the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride at 299 K at various reaction times. The reaction follows first order kinetics with a rate constant of 5.18×10−1 s−1. It is believed that, the large scale synthesis of such hybrid nanocomposites via simple method using non-toxic reagent will not only enhance its antibacterial efficacy, durability and biocompatibility, it will also minimize its biotoxcity and environmental impacts.

Synthesis of Silver Nanoparticles Using Buchu Plant Extracts and Their Analgesic Properties

We herein report for the first time the synthesis and analgesic properties of silver nanoparticles (Ag-NPs) using buchu plant extract. The as-synthesised Ag-NPs at different temperatures were characterised by UV-Vis spectroscopy, Fourier transform infra-red spectroscopy (FTIR) and transmission transform microscopy (TEM) to confirm the formation of silver nanoparticles. Phytochemical screening of the ethanolic extract revealed the presence of glycosides, proteins, tannins, alkaloids, flavonoids and saponins. The absorption spectra showed that the synthesis is temperature and time dependent. The TEM analysis showed that the as-synthesised Ag-NPs are polydispersed and spherical in shape with average particle diameter of 19.95 ± 7.76 nm while the FTIR results confirmed the reduction and capping of the as-synthesised Ag-NPs by the phytochemicals present in the ethanolic extract. The analgesic study indicated that the combined effect of the plant extract and Ag-NPs is more effective in pain management than both the aspirin drug and the extract alone.