Atanu Naskar

Synthesis, characterization and antibacterial activity of Ag incorporated ZnO–graphene nanocomposites

The present work reports on the successful one-pot surfactant-free in situ synthesis of silver incorporated ZnO–chemically converted graphene (CCG) nanocomposites (AZG) by adopting a low temperature solution technique from zinc acetate dihydrate, silver nitrate and graphene oxide, and the varying silver content (up to 20% Ag with respect to Zn) in the precursors. X-ray diffraction and transmission electron microscopy studies confirmed the presence of Ag and ZnO nanoparticles (NPs), distributed uniformly with CCG. FTIR, Raman, UV-visible and X-ray photoelectron spectroscopic analyses confirmed the existence of interaction between CCG with the inorganic moieties (ZnO/Zn2+ and Ag NPs) of the AZG samples. In vitro cytotoxicity and quantitative cell viability of the human ovarian teratocarcinoma cell line (PA1) was studied up to a maximum sample concentration of 200 μg ml−1. Antibacterial activity was also measured on E. coli and S. aureus to confirm the efficiency of the nanocomposite, especially for killing bacterial cells without any major effect on the surrounding cells. Among the nanocomposites, the 10% Ag incorporated sample at a 6.25 μg ml−1 dose showed excellent antibacterial activity with negligible cytotoxicity. This simple strategy could be applied in the synthesis of Ag incorporated different metal oxide–CCG nanohybrids for antibacterial applications.

Low temperature synthesis of graphene hybridized surface defective hierarchical core–shell structured ZnO hollow microspheres with long-term stable and enhanced photoelectrochemical activity

The present work reports on successful in situ synthesis of chemically converted graphene (CCG) hybridized, surface defective core–shell structured ZnO hollow microspheres (ZG-CSHM) from a surfactant/template free precursor by adopting a low temperature solution method. This special architecture has been synthesized as an intermediate product between solid and hollow microspheres via Ostwald ripening process by optimizing the reaction time, as observed by field emission scanning and transmission electron microscopic studies. The samples have also been characterized by X-ray photoelectron, FTIR and Raman spectral as well as X-ray diffraction analyses. From textural property measurement by BET N2 adsorption–desorption isotherms, it is seen that the ZG-CSHM possesses an enhanced specific surface area with narrow distribution of mesopores. Relatively higher photoelectrochemical activity with long term stability of ZG-CSHM is found compare to pristine core–shell structured ZnO hollow microspheres. The synergic effect of graphene hybridization and the presence of surface defects of ZnO nanoparticles in the mesoporous sample can play the key roles in advancing its photoelectrochemical activity. The surface defects can prolong the recombination rate of photogenerated charge carriers and the high surface area with narrow sized mesopore distribution can provide large number of active sites, make electrolyte diffusion and mass transportation easier. The ZG-CSHM sample also shows an improved photocurrent density compare to solid and hollow microspheres. Moreover, the existence of chemically interacted CCG with ZnO inhibits the photocorrosion, resulted long-term stable photoelectrochemical activity of ZG-CSHM. This facile process can create an avenue for synthesis of core–shell structured microspheres from different metal oxide semiconductors for improving their photoelectrochemical activity.

ZnO–graphene–polyaniline nanoflowers: solution synthesis, formation mechanism and electrochemical activity

Three dimensional hierarchical inorganic–organic hybrid nanoflowers of conducting ZnO–chemically converted graphene–polyaniline nanocomposite have been successfully synthesized at low temperature from surfactant-free precursor solution and studied their formation mechanism. The nanocomposite with hierarchical architecture shows an enhanced electrochemical activity, illustrating a promise for application in electrochemical devices.

Protein adsorption capability of zinc ferrite nanoparticles formed by a low-temperature solution-based process

We report successful synthesis of zinc ferrite nanoparticles (ZFs) by a facile low-temperature (90xa0°C) solution-based process from ferric nitrate nonahydrate and zinc nitrate hexahydrate precursors in presence of hydrazine hydrate. X-ray diffraction analysis and transmission electron microscopy confirmedxa0the presence of ZFs, which were further characterized by Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric measurements for identification of characteristic chemical bond vibrations and thermal weight loss behavior, respectively. Measurements of magnetic properties at room temperature revealed that the sample showed quite high saturation magnetization (22.0xa0emu/g at ~19,200xa0G), implying the presence of less impurities/surface defects in the ZFs. The material also showed zero coercivity as a soft-magnetic material. The protein adsorption performance of the ZFs was checked using bovine serum albumin (BSA) as model protein. Excellent protein adsorption capacity of 210xa0mg/g (close to the value of 218.81xa0mg/g calculated using the Langmuir model) for BSA concentration of 0.3xa0mg/mL was obtained at optimized solution pH of 5. This simple process could be adopted for synthesis of different magnetic nanomaterials for use in biomedical applications.

Anti-biofilm activity and food packaging application of room temperature solution process based polyethylene glycol capped Ag-ZnO-graphene nanocomposite

Present work reports on synthesis and anti-biofilm activity as well as food packaging application of Ag-ZnO-reduce graphene oxide (rGO)-polyethylene glycol (PEG) (AZGP) nanocomposites via adopting room temperature solution process by varying silver nitrate content (up to 0.1u202fM) with fixed content of graphene oxide and PEG used in the precursors. Presence of Ag and ZnO nanoparticles (NPs) distributed uniformly over rGO nanosheets has been confirmed by X-ray diffraction and transmission electron microscopic analyses whereas FTIR, Raman, UV-Visible and X-ray photoelectron spectral studies have been performed to confirm the existence of chemical interaction/complexation that happened between the available oxygen functionalities of rGO and PEG with the inorganic moieties (Ag-ZnO/Zn2+) of AZGP samples. A formation mechanism of AZGP nanocomposite is proposed based on the experimental results. Anti-biofilm activity has been studied on Staphylococcus aureus and Pseudomonas aeruginosa bacteria to confirm the efficiency of the nanocomposites for killing the bacterial cells. It is found that 0.05u202fM silver nitrate based AZGP nanocomposite at 31.25u202fμg/mL sample dosage shows about 95% inhibition activity towards the biofilm formation as well as eradication of preformed biofilm. Also, agar based AZGP film has been fabricated and characterized by X-ray diffraction study for the purpose of food packaging application. Textural analysis of agar based film shows an enhanced film tensile strength. The film also shows an excellent antimicrobial activity even after keeping it for a prolong period of about 90u202fdays. This cost effective simple synthesis strategy can make an avenue for development of Ag incorporated other biocompatible metal oxide based rGO-PEG nanocomposites for potential food packaging application.

One pot low temperature synthesis of graphene coupled Gd-doped ZnFe2O4 nanocomposite for effective removal of antibiotic levofloxacin drug

AbstractNanocomposites of reduced graphene oxide (rGO) coupled gadolinium doped ZnFe2O4 (GZFG) have been successfully one pot in-situ synthesized adopting low temperature solution process from zinc nitrate, iron nitrate, gadolinium acetate and graphene oxide with varying concentrations of gadolinium (upto 10% Gd with respect to Zn) in the precursor medium. X-ray diffraction and transmission electron microscopy studies confirm the presence of single phase cubic spinel structure of ZnFe2O4 that uniformly distributed over the rGO layers. With increasing Gd doping concentration in precursor medium, the average crystallite size of ZnFe2O4 diminishes gradually from ~11 to ~5.5u2009nm. Raman and X-ray photoelectron spectral analyses confirm an existence of interaction between rGO and ZnFe2O4 in GZFG samples. Using antibiotic levofloxacin in water, the drug removal capacity (DRC) of GZFG has been performed by optimization of parameters such as gadolinium doping concentration in precursor medium, solution pH, etc. However, the gadolinium doping leads to an improvement in DRC of the nanocomposite and the 5% Gd doped sample shows about 86% DRC at the optimized condition. This simple strategy can be utilized in the synthesis of rGO coupled Gd doped other metal oxide nanocomposites for DRC application.n

Nano gold-coated surface patterned mesoporous titanium tin oxide sol–gel thin film: fabrication, optical and photoelectrochemical properties

AbstractNano noble metal coating on surface patterned mesoporous semiconductor thin film can play an important role in enhancing visible light harvesting efficiency (LHE) towards improvement in photoelectrochemical (PEC) activity of the material. In this work, one-dimensional (1D) and two-dimensional (2D) mesoscale surface patterns have been created on sol–gel-based titanium tin oxide (TSO) nanostructured thin film on pure silica/indium tin oxide-coated glass by soft lithography. The TSO film matrix is observed to be mesoporous and semicrystalline as evidenced from the structural characterization by transmission electron microscopy and measurement of atmospheric ellipso-porosimetry, respectively. The 2D patterned film exhibits maximum LHE value in visible wavelength region. Further film surface modification has been carried out by depositing nano Au coating onto the bare patterned TSO films by a low temperature solution technique. Under visible light, a significant improvement in PEC activity is found and the gold-coated patterned 2D film shows higher visible LHE as well as >2.7 times higher photocurrent density than bare 2D film. This facile fabrication strategy can create an avenue toward improvement in LHE vis-à-vis the PEC activity of mesoporous mixed metal oxide semiconductor thin film.n HighlightsFabricated 1D/2D patterned mesoporous tin titanium oxide sol–gel thin films.Deposited nano Au onto the patterned films.Au-coated 2D patterned film showed better visible light harvesting efficiency.The 2D patterned film exhibited an improved photoelectrochemical activity.