Mangesh Kokate

Bioinspired synthesis of highly stabilized silver nanoparticles using Ocimum tenuiflorum leaf extract and their antibacterial activity

Biosynthesis of nanoparticles is under exploration due to wide biomedical applications and research interest in nanotechnology. We herein reports bioinspired synthesis of silver nanoparticles with the aid of novel, non toxic ecofriendly biological material namely Ocimum tenuiflorum leaf extract. It acts as reducing as well as stabilizing agent. An intense surface plasmon resonance band at ∼450 nm in the UV-visible spectrum clearly reveals the formation of silver nanoparticles. The photoluminescence spectrum was recorded to study excitation and emission. TEM and PSD by dynamic light scattering studies showed that size of silver nanoparticles to be in range 25-40 nm. Face centered cubic structure of silver nanoparticles are confirmed by SAED pattern. The charge on synthesized silver nanoparticles was determined by zeta potential. The colloidal solution of silver nanoparticles were found to exhibit high antibacterial activity against three different strains of bacteria Escherichia coli (Gram negative), Corney bacterium (gram positive), Bacillus substilus (spore forming).

Preparation of N doped TiO2 via microwave-assisted method and its photocatalytic activity for degradation of Malathion

We report herein, nitrogen doped TiO2 nanostructure synthesized by simple microwave assisted method, where ammonia was used as hydrolyzing agent. The synthesized nanomaterials were characterized by means of X-ray diffraction (XRD) which demonstrated that N-doped TiO2 is in anatase phase with average crystallite size of 10nm. Doping of N into the lattice of TiO2 was supported by X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared spectroscopy (FT-IR), CHNS analysis, energy dispersive spectroscopy (EDS). The diffuse reflectance spectroscopy (DRS) showed shifting of absorption edge toward the visible region. Thermogravimetric-differential thermal analysis (TGA-DTA) points out N-doped TiO2 nanoparticles are thermally stable. In order to achieve maximum degradation efficiency, the effect of catalyst loading, pH and light sources (UV and sunlight) were studied. A maximum 97% degradation efficiency was achieved under optimized conditions. A 80% reduction in the chemical oxygen demand (COD) was observed after 150min that indicated mineralization of Malathion. The cytotoxicological studies indicate that photocatalytically degraded products were less toxic as compared to Malathion.

One pot synthesis of magnetite–silica nanocomposites: applications as tags, entrapment matrix and in water purification

We report herein a novel one pot single step synthesis of magnetite–silica nanocomposites. The concept of co-precipitation of iron(II) and iron(III) salts by a base has been used. The main process differentiator is the use of an alkaline solution of sodium silicate instead of a base. This unique modification helps not only in the formation of iron oxide (due to alkaline conditions) but also introduces silica in the reaction to form a magnetite–silica nanocomposite. Having a silica surface is advantageous, in that it stabilizes the silica particles, makes them biocompatible and gives opportunity to further modify and tag functional groups via the well established silica surface chemistry. Furthermore, the process also yields porous silica, which increases the overall surface area of the nanocomposite. The nanocomposite samples have been characterized by a host of techniques, such as UV-vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy dispersive analysis using X-rays (EDAX), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), zeta potential measurements, dynamic light scattering and magnetic measurements. The utility of these high-surface area nanocomposites for different applications such as tagging (attachment of fluorophores Rhodamine, Rh B), entrapment matrix (zinc loading) and removal of arsenic for water purification has been explored.

One-pot synthesis of PVA-capped silver nanoparticles their characterization and biomedical application

The rapid one-pot synthesis of silver nanoparticles (SNPs) at room temperature by using hydrazine hydrate as reducing agent and polyvinyl alcohol as stabilizing agent is reported. The SNPs were characterized with UV-visible (UV-Vis) spectroscopy, x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The synthesized silver nanoparticle shows surface plasmon resonance at 410?nm. The XRD reveals face-centered cubic (FCC) structure of SNPs. FE-SEM, AFM and TEM show that nanoparticles have spherical morphology with diameters in the range of 10?60?nm. The antimicrobial activity of synthesized hybrid material against strains of four different bacteria (Bacillus cereus, Escherichia coli, Staphylococus aureus, Proteus vulgaris), that are commonly found in hospitals has been studied. The results indicate that such particles have potential applications in biotechnology and biomedical science.

Synthesis and enhancement of photocatalytic activities of ZnO by silver nanoparticles

Herein, we reports synthesis, characterization and photocatalytic degradation of Rhodamine B under natural sunlight using zinc oxide and Ag-ZnO composite. Zinc oxide nanoparticles were prepared by simple wet chemical method using ethanol-water mixture. Ag-ZnO composite was prepared in two steps by dispersing synthesized ZnO in silver nitrate solution and subsequently reducing it with Ocimum tenuiflorum leaves extract as bioreducing agent. The synthesized bare zinc oxide and Ag-ZnO composite was characterized by various techniques like XRD, DRS, FE-SEM, TEM, SAED, PSD, Zeta potentials, etc. Zinc oxide being wide band gap material can absorbs UV light from solar spectrum which is only 5% so is not efficient material for dye degradation under sunlight. The absorption of visible light was increased by preparing the Ag-ZnO composite. The enhancement in photocatalytic activities of Ag-ZnO composite was observed than bare ZnO. This enhancement is due to shift of absorption edge of ZnO in visible region and decrease in band gap.