Mohit Rawat

Enhanced catalytic reduction of 4-nitrophenol and congo red dye By silver nanoparticles prepared from Azadirachta indica leaf extract under direct sunlight exposure

ABSTRACT The manuscript reports an efficient approach for the synthesis of biogenic silver (Ag) nanoparticles from Azadirachta indica leaf extract-mediated reduction of silver nitrate under solar radiation at mild temperature conditions for nanoparticles (NPs) preparation. Spectroscopic and electron microscopic characterization studies revealed the formation of stable and monodisperse Ag NPs with sharp absorption band at 438 nm and average diameter of 10–15 nm. Catalytic potential of the NPs was descriptively investigated for the reduction of 4-nitrophenol to 4-aminophenol in alkaline medium. Apparent rate constant () values were determined to be 0.014, 0.0238, 0.0338, 0.063, and 0.0794 at 5, 10, 15, 20, 40, and 50 µL Ag NPs volume, respectively, thereby depicting linear relationship between the variables under study. Catalytic reduction of Congo red dye was achieved within 2 h, thus validating the efficacy of Ag NPs as a photocatalyst. The NPs also exhibited linear increment in antibacterial activity on cultured Escherichia coli plates with increasing volumes. These catalytic capabilities firmly advocate the applications of Ag NPs in purification of polluted water by the removal of toxic and contaminant materials and harmful/pathogenic bacteria.

Amphiphilic carbon dots derived by cationic surfactant for selective and sensitive detection of metal ions

Carbon Dots (CDs) the kind of recently exposed fluorescent nanomaterials have become increasingly popular in the precedent decade due to their distinctive physical and optical properties. Relating to above recognition for the first time we present the synthesis of CDs by cationic surfactant, Cetylpyridinium Bromide (CPB). Due to good carbon content amphiphilicity, and existence of heteroaromatic π system, CPB reveals three advantageous properties including a good carbon source, stabilizing agent, and contributing fluorophore in the CDs system. The as prepared CDs synthesized by hydrothermal technique reveals excellent fluorescent properties having strong green emission at 525 nm when excited over 470 nm. The FTIR results showed the presence of CC, CO, NH, CH and OH bonds. The presence of hydrophilic groups such as carboxyl and hydroxyl groups present on the surface confer them water solubility. The HRTEM results revealed the size of prepared CDs to be in the range of 7-10 nm. The XPS spectrum confirms the presence of Carbon, Oxygen and Nitrogen, suggesting that the CDs have good purity and very little impurities. Latterly CDs were used for the selective and sensitive detection towards Fe2+ ions. Also the as prepared CDs were utilized for real sample analysis.

Plant leaves mediated synthesis of semiconductor ZnO nanoparticles and its application for seed germination

Green synthesis of nanoparticles is a simple, eco-friendly and cost-effective approach which might cover the way for researchers across the globe to explore the potential of different herbs to synthesize nanoparticles. In this regard, the present work focus on the green synthesis of zinc oxide nanoparticles usingan aqueous extract of Azadirachtaindicaleaves. The extract was used as the biological reduction agent for synthesizing zinc oxide nanoparticles from zinc acetate. Synthesis conditions were optimized for maximal and narrow size range synthesis of zinc oxide nanoparticles. The resultant nanopowder was characterized using various analytical techniques, such as UV-Visible spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffraction Spectroscopy (XRD), Field Emission Scanning Electron Microscopy(FESEM) withEnergy Dispersive X-ray Spectroscopy (EDX). The characterization resultsconfirm thecrystalline nature of green synthesized Zinc Oxide nanoparticles (ZnO-NPs) with spherical morphology and the averagesize of ∼50 nm. UV-Visible absorbance peak was centered near 363 nm for the reduction of zinc acetate to the ZnO nanoparticles. It was observed that the linear increment of the root and shoot length of mung bean (Vigna radiata) seeds with the concentration of ZnO NPs.Green synthesis of nanoparticles is a simple, eco-friendly and cost-effective approach which might cover the way for researchers across the globe to explore the potential of different herbs to synthesize nanoparticles. In this regard, the present work focus on the green synthesis of zinc oxide nanoparticles usingan aqueous extract of Azadirachtaindicaleaves. The extract was used as the biological reduction agent for synthesizing zinc oxide nanoparticles from zinc acetate. Synthesis conditions were optimized for maximal and narrow size range synthesis of zinc oxide nanoparticles. The resultant nanopowder was characterized using various analytical techniques, such as UV-Visible spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffraction Spectroscopy (XRD), Field Emission Scanning Electron Microscopy(FESEM) withEnergy Dispersive X-ray Spectroscopy (EDX). The characterization resultsconfirm thecrystalline nature of green synthesized Zinc Oxide nanoparticles (ZnO-NPs) with spherical morphol...

A uncanny potential of plants for metal nanoparticles synthesis

In this era, metal nanoparticles have captivated researchers because of their impending applications in numerous fields such as biomedical, catalysis, electronics etc.1–4 The properties of nanoparticles can be tuned by their size, synthesis process, reaction parameters, which make them the special candidate for every field. Generally, these nanoparticles are synthesized by two methods top down and bottom up. The top-down suggests the nanoparticles preparation by lithographic techniques, ball milling, etching, sputtering, etc. The most effective approach for the synthesis of nanoparticles is the bottom-up methods, in which nanoparticles are grown from simpler molecules and size or shape of nanoparticles can be controlled or modulated by changing the concentration of chemicals and reaction condition (temperature, pH etc.).5

Low Temperature Synthesis of Elongated Triangular Bipyramidal ZnO Nanostructures for Photocatalytic Activity

The manuscript reports wet chemical assisted low temperature synthesis of CTAB stabilized elongated triangular bipyramidal shape nanostructures of ZnO for photocatalytic degradation of methyle blue (MB) and congo red (CR) dyes. Physiochemical characterization has been carried out by X-ray diffraction, scanning electron microscope, transmission electron microscope and UV-visible spectroscope. Pure wurtzite structure of ZnO with crystallite size ~56 nm has been confirmed from X-ray study. Well dispersed particles with elongated triangular bipyramidal morphology have been observed through SEM. Fine resolved particles with varied aspect ratios ~80 X 200 ± 10 nm have been depicted by TEM images. UV-visible absorption analysis confirms the energy band gap of 3.43 eV for synthesized ZnO particles. Molecular composition and functional groups of CTAB were confirmed by FTIR spectroscopy. The potential applicability of the particles for photocatalytic degradation of MB and CR as standard analytical dyes was studied. Time bound study under UV irradiated source depicted more than 95% degradation of both dyes in separate experiments.

Biogenic ZnO nanoparticles: a study of blueshift of optical band gap and photocatalytic degradation of reactive yellow 186 dye under direct sunlight

Abstract Synthesis of nanoparticles (NPs) using plant extracts has been suggested as an environmentally friendly alternative to chemical synthesis of semiconductor NPs. In the present study, ZnO NPs were synthesized by a simple and cost-effective method using Coriandrum sativum leaf extract and zinc acetate as precursors. The as-synthesized ZnO NPs were characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) analysis. The results confirmed the formation of ZnO NPs with a wurtzite structure, spherical shape and average particle size of 24 nm. The photocatalytic degradation of reactive yellow 186 (RY 186) dye was carried out under direct sunlight irradiation and its degradation efficiency and apparent rate constant (K’app) of reaction were calculated to be 93.38%, and 0.0019 min−1, respectively. The optical band gap value of the as-synthesized ZnO NPs was found to be 3.4 eV, which indicates the presence of blueshift. Owing to the presence of blueshift and a wide band gap of synthesized biogenic ZnO NPs, the overall absorption of sunlight irradiation will be enhanced, which leads to higher degradation efficiency of the dye. The current study thus highlights the optical band gap properties of biogenic ZnO NPs and their significance as a heterogeneous catalyst for the purification of polluted water.

Graphene: from synthesis to engineering to biosensor applications

Graphene is a fascinating material of recent origin whose first isolation was being made possible through micromechanical cleavage of a graphite crystal. Owing to its fascinating properties, graphene has garnered significant attention in the research community for multiple applications. A number of methods have been employed for the synthesis of single-layer and multi-layer graphene. The extraordinary properties of graphene such as its Hall effect at room temperature, high surface area, tunable bandgap, high charge mobility and excellent electrical, conducting and thermal properties allow for the development of sensors of various types and also opened the doors for its use in nanoelectronics, supercapacitors and batteries. Biological aspects of graphene have also been investigated with particular emphasis on its toxicity and drug delivery. In this review, many of the salient aspects of graphene, such as from synthesis to its applications, primarily focusing on sensor applications which are of current interest, are covered.

Synthesis of Cu and Ce co-doped ZnO nanoparticles: crystallographic, optical, molecular, morphological and magnetic studies

Abstract In the present research work, crystallographic, optical, molecular, morphological and magnetic properties of Zn1-xCuxO (ZnCu) and Zn1-x-yCeyCuxO (ZnCeCu) nanoparticles have been investigated. Polyvinyl alcohol (PVA) coated ZnCu and ZnCeCu nanoparticles have been synthesized by chemical sol-gel method and thoroughly studied using various characterization techniques. X-ray diffraction pattern indicates the wurtzite structure of the synthesized ZnCu and ZnCeCu particles. Transmission electron microscopy analysis shows that the synthesized ZnCu and ZnCeCu particles are of spherical shape, having average sizes of 27 nm and 23 nm, respectively. The incorporation of Cu and Ce in the ZnO lattice has been confirmed through Fourier transform infrared spectroscopy. Room temperature photoluminescence spectra of the ZnO doped with Cu and co-doped Ce display two emission bands, predominant ultra-violet near-band edge emission at 409.9 nm (3 eV) and a weak green-yellow emission at 432.65 nm (2.27 eV). Room temperature magnetic study confirms the diamagnetic behavior of ZnCu and ferromagnetic behavior of ZnCeCu.

Facile Synthesis of CuO Semiconductor Nanorods for Time Dependent Study of Dye Degradation and Bioremediation Applications

The manuscript reports facile one step synthesis of CuO semiconductor nanorods by sol-gel aaproach for photocatalytic and bioremediation applications. Spectroscopic characterization along with X-ray diffractometry and electron microscopy studies confirmed the formation of nanorods with 12 to 14 nm diameter and 50-100 nm length. As synthesized nanorods were subjected to photocatalytic degradation of dyes viz. Methylene Orange (MO), Methylene Blue (MB), Eriochrome Black T (ET) and Congo Red (CR) in a time bound study. Comparative analysis of the data depicted that time taken for degradation of equal amount of CR was more compared to the other three dyes owing to its high molecular weight and lower diffusion rate in aqueous medium. Subsequently, the antibacterial properties of the nanorods were investigated against the gram negative Escherichia coli and gram positive Bacillus bacteria. Zone of clearance was observed in disk diffusion assays, thereby confirming the antibacterial characteristics of the nanorods. These nanorods thus hold great promise as a simple, selective and a sensitive analytical platform for the effective bio-monitoring and photocatalyst for dye degradation.

Band gap and FTIR studies for copper-zinc sol-gel glasses

Sol-gel technique was used for synthesis of Calcium phosphorous Borosilicate (CaO-SiO2-B2O3-P2O5-CuO-ZnO) glasses by varying composition of Copper oxide and Zinc oxide. Sol-gel route uses organic precursors which provide better homogeneity and uniform particle size compared to melt quenched glass. Four different glass stoichiometries were characterised using UV-visible spectroscopy and Fourier transforms infra-red spectroscopy (FTIR). Infra-red spectrum of transmittance of powdered glass samples is obtained by FTIR which measure the transmittance of wavelength in them and it also determines the presence of different functional group. Band gap has been obtained using UV-visible spectroscopy for all the glasses so as to study the effect of increasing ZnO content in glass composition. The change in band gap with ZnO content is indication of the change in number of non-bridging oxygen’s (NBO).