Sanjay S. Kolekar

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).

Hydrothermal synthesis of rutile TiO2 nanoflowers using Brønsted Acidic Ionic Liquid [BAIL]: Synthesis, characterization and growth mechanism

Herein we report a facile method to synthesize rutile TiO2 nanoflowers (TNF) comprising a bunch of aligned nanorods with uniform size and shape via a hydrothermal method in Bronsted Acidic Ionic Liquid [BAIL] room temperature ionic liquid (RTIL). This method has some advantages: the process is simple and single step; the reaction can be performed under low temperature. The TNFs are highly crystalline and free of aggregation.

Extraction of pesticides, dioxin-like PCBs and PAHs in water based commodities using liquid–liquid microextraction and analysis by gas chromatography–mass spectrometry

Water based samples such as flavored drinks, juices and drinking water may contain contaminants at ultra trace level belonging to different chemical classes. A novel, simple, low-cost and fast method was developed and validated for trace residue extraction of pesticides, dioxin-like PCBs and PAHs from water and water based samples followed by analysis through gas chromatography (GC) coupled with time-of-flight mass spectrometry (ToFMS). The extraction solvent type, volume; sample volume and other extraction conditions were optimized. This was achieved by extracting 10 mL sample with 250 μL chloroform by vortexing (1 min, standing time of 2 min) followed by centrifugation (6000 rpm, 5 min). The bottom organic layer (200 μL) was pipetted out, evaporated to near dryness and reconstituted in 20 μL of ethyl acetate+cyclohexane (1:9) mixture resulting in an enrichment factor of 400. The recoveries of all compounds were within 76-120% (±10%) with the method detection limit (MDL) ranging from 1 to 250 ng/L depending on the analyte response. The MDLs were 400 times lower than the instrument quantification limits that ranged from 0.4 to 100 ng/mL. The method was further validated in water based drinks (e.g. apple, lemon, pineapple, orange, grape and pomegranate juice). For the juices with suspended pulp, the extraction was carried out with 400 μL chloroform. The extract was analyzed by GC-ToFMS at both 1D and GC×GC modes to chromatographically separate closely eluting interfering compounds the effect of which could not be minimized otherwise. The resulting peak table was filtered to identify a range of compounds belonging to specific classes viz. polycyclic aromatic hydrocarbons, chlorinated, brominated, and nitro compounds. User developed scripts were employed on the basis of identification of the molecular ion and isotope clusters or other spectral characteristics. The method performed satisfactorily in analyzing both incurred as well as market samples.

Low cost flexible 3-D aligned and cross-linked efficient ZnFe2O4 nano-flakes electrode on stainless steel mesh for asymmetric supercapacitors

A simple and economic approach for growth of 3-D aligned and cross-linked ZnFe2O4 nano-flakes on a flexible stainless steel mesh (FSSM) substrate (300 mesh) using a rotational chemical bath deposition technique for fabricating efficient asymmetric supercapacitors is reported. The prepared ZnFe2O4 nano-flake thin film (ZnFe2O4/FSSM-300) as an anode in combination with Ni(OH)2/FSSM-300 as a cathode was used as an asymmetric supercapacitor. Furthermore, ZnFe2O4 nano-flakes were also grown on FSSM with a different mesh and designated as ZnFe2O4/FSSM-200, ZnFe2O4/FSSM-250 and ZnFe2O4/FSSM-300 for investigating the effect of mesh size on the morphology formation and their electrochemical performance. Amongst the samples, ZnFe2O4/FSSM-300 exhibited excellent supercapacitive properties, such as a higher specific capacitance (1625 F g−1 at 1 mA cm−2) and excellent cycle stability (8000 cycles, 97% retention), which was marginally higher than ZnFe2O4/FSSM-250 (545 F g−1 at 1 mA cm−2, 70% retention), ZnFe2O4/FSSM-200 (241 F g−1 at 1 mA cm−2, 56% retention) and other earlier reported ferrites. In addition, the fabricated asymmetric pseudocapacitor device delivered better performance with high specific capacitance (118 F g−1 at 5 mA cm−2), excellent cycle stability (8000 cycles, 83% capacitance retention) and high energy density (42 W h kg−1) even at higher power density (5 kW kg−1).

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.

Dissipation and distribution behavior of azoxystrobin, carbendazim, and difenoconazole in pomegranate fruits.

The dissipation behavior and degradation kinetics of azoxystrobin, carbendazim, and difenoconazole in pomegranate are reported. Twenty fruits/hectare (5 kg) were collected at random, ensuring sample-to-sample relative standard deviation (RSD) within 20-25%. Each fruit was cut into eight equal portions, and two diagonal pieces per fruit were drawn and combined to constitute the laboratory sample, resulting in RSDs <6% (n = 6). Crushed sample (15 g) was extracted with 10 mL of ethyl acetate (+ 10 g Na(2)SO(4)), cleaned by dispersive solid phase extraction on primary secondary amine (25 mg) and C(18) (25 mg), and measured by liquid chromatography tandem mass spectrometry. The limit of quantification was ≤0.0025 μg g(-1) for all the three fungicides, with calibration linearity in the concentration range of 0.001-0.025 μg mL(-1) (r(2) ≥ 0.999). The recoveries of each chemical were 75-110% at 0.0025, 0.005, and 0.010 μg g(-1) with intralaboratory Horwitz ratio <0.32 at 0.0025 μg g(-1). Variable matrix effects were recorded in different fruit parts viz rind, albedo, membrane, and arils, which could be correlated to their biochemical constituents as evidenced from accurate mass measurements on a Q-ToF LC-MS. The residues of carbendazim and difenoconazole were confined within the outer rind of pomegranate; however, azoxystrobin penetrated into the inner fruit parts. The dissipation of azoxystrobin, carbendazim, and difenoconazole followed first + first order kinetics at both standard and double doses, with preharvest intervals being 9, 60, and 26 days at standard dose. At double dose, the preharvest intervals extended to 20.5, 100, and 60 days, respectively.

Mechanochemical growth of a porous ZnFe2O4 nano-flake thin film as an electrode for supercapacitor application

Herein, we are reporting a simple, economic, easy to handle, scalable and reproducible mechanochemical i.e. rotational chemical bath deposition (R-CBD) approach for the synthesis of well adhered nano-flake ZnFe2O4 thin films (NFs-ZnFe2O4) with uniform morphology on a stainless steel (SS) substrate, in comparison with nano-grain ZnFe2O4 thin films (NGs-ZnFe2O4) prepared using a conventional CBD approach. The influence of rotation on the evolution of the nano-flake morphology in NFs-ZnFe2O4 is also investigated. The porous NFs-ZnFe2O4 thin films demonstrated excellent pseudocapacitor properties with higher specific capacitance of 768 F g−1 at high current density of 5 mA cm−2, stability upto 5000 cycles (88% retention), higher energy density (106 W h kg−1) and power density (18 kW kg−1) compared to NGs-ZnFe2O4. The results were also found to be higher than those reported earlier for MFe2O4 based systems.

Fabrication of Cu2ZnSnS4 thin film solar cell using single step electrodeposition method

Cu2ZnSnS4 (CZTS) thin films were deposited onto Mo-coated and tin-doped indium oxide (ITO) coated glass substrates by using single step electrodeposition technique followed by annealing in N2 + H2S atmosphere. Subsequently, they were applied to the fabrication of thin film solar cells. Upon annealing, the amorphous nature of as-deposited precursor film changes into polycrystalline kesterite crystal structure with uniform and densely packed surface morphology. Energy dispersive X-ray spectroscopy (EDS) study reveals that the deposited thin films are nearly stoichiometric. Optical absorption study shows the band gap energy of as-deposited CZTS thin films is 2.7 eV whereas, after annealing, it is found to be 1.53 eV. The solar cell fabricated with CZTS absorber layer, showed the best conversion efficiency (η) 1.21% for 0.44 cm2 with open-circuit voltage (Voc) = 315 mV, short-circuit current density (Jsc) = 12.27 mA/cm2 and fill factor (FF) = 0.31.

Ag:BiVO4 dendritic hybrid-architecture for high energy density symmetric supercapacitors

We demonstrate the fabrication of Ag:BiVO4 with a dendritic architecture by a template free hydrothermal method. Then, symmetric cells based on Ag:BiVO4 electrodes were assembled which exhibit an extended voltage window of up to 1.6 V with an excellent energy density of 2.63 mW h cm−3 (38.43 W h kg−1) and a power density of 558 mW cm−3 (8.1 kW kg−1).

Removal of Bi (III) with Adsorption Technique Using Coconut Shell Activated Carbon

Abstract In present study, we report the preparation of coconut shell activated carbon as adsorbent and its application for Bi (III) removal from aqueous solutions. The developed adsorbent was characterized with scanning electron microscope (SEM), Fourier Transform Infrared (FTIR), C, H, N, S analyzer, and BET surface area analyzer. The parameters examined include agitation time, initial concentration of Bi (III), adsorbent dose and temperature. The maximum adsorption of Bi (III) (98.72%) was observed at 250 mg·L−1 of Bi (III) and adsorbent dose of 0.7 g when agitation was at 160 r·min−1 for 240 min at (299±2) K. The thermodynamic parameters such as Gibbs free energy (ΔGθ), enthalpy (ΔHθ) and entropy (ΔSθ) were evaluated. For the isotherm models applied to adsorption study, the Langmuir isotherm model fits better than the Freundlich isotherm. The maximum adsorption capacity from the Langmuir isotherm was 54.35 mg·g−1 of Bi (III). The kinetic study of the adsorption shows that the pseudo second order model is more appropriate than the pseudo first order model. The result shows that, coconut shell activated carbon is an effective adsorbent to remove Bi (III) from aqueous solutions with good adsorption capacity.