Biogenic nanosilver incorporated reverse osmosis membrane for antibacterial and antifungal activities against selected pathogenic strains: An enhanced eco-friendly water disinfection approach

Reverse osmosis (RO) membranes have been used extensively in water desalination plants, waste water treatment in industries, agricultural farms and drinking water production applications. The objective of this work is to impart antibacterial and antifungal activities to commercially available RO membrane used in water purification systems by incorporating biogenic silver nanoparticles (AgNPs) synthesized using Rosa indica wichuriana hybrid leaf extract. The morphology and surface topography of uncoated and AgNPs-coated RO membrane were studied using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Elemental composition of the AgNPs-coated RO membrane was analyzed by energy-dispersive X-ray spectroscopy (EDAX). The functional groups were identified by Fourier Transform Infrared spectroscopy (FT-IR). Hydrophilicity of the uncoated and AgNPs-coated RO membrane was analyzed using water contact angle measurements. The thermal properties were studied by thermogravimetric analysis (TGA). The AgNPs incorporated RO membrane exhibited good antibacterial and antifungal activities against pathogenic bacterial strains such as E. coli, S. aureus, M. luteus, K. pneumoniae, and P. aeruginosa and fungal strains such as Candida tropicalis, C. krusei, C. glabrata, and C. albicans.

Synthesis of benzimidazole-grafted graphene oxide/multi-walled carbon nanotubes composite for supercapacitance application

We are reporting the fabrication, characterizations and supercapacitance performance of benzimidazole-grafted graphene oxide/multi-walled carbon nanotubes (BI-GO/MWCNTs) composite. The synthesis of BI-GO materials involves cyclization reaction of carboxylic groups on GO among the hydroxyl and amino groups on o-phenylenediamine. The BI-GO/MWCNTs composite has been fabricated via in situ reduction of BI-GO using hydrazine in presence of MWCNTs. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) have been used to characterize its surface and elemental composition. The uniform dispersion of MWCNTs with BI-GO helps to improve the charge transfer reaction during electrochemical process. The specific capacitance of BI-GO/MWCNTs composite is 275 and 460 F/g at 200 and 5 mV/s scan rate in 1 mol/L aqueous solution of H2SO4. This BI-GO/MWCNTs composite has shown 224 F/g capacitance after 1300 cycles at 200 mV/s scan rate, which represents its good electrochemical stability. (C) 2014 Elsevier B.V. All rights reserved.

Graphene Oxide-MnFe2O4 Magnetic Nanohybrids for Efficient Removal of Lead and Arsenic from Water

We show that the hybrids of single-layer graphene oxide with manganese ferrite magnetic nanoparticles have the best adsorption properties for efficient removal of Pb(II), As(III), and As(V) from contaminated water. The nanohybrids prepared by coprecipitation technique were characterized using atomic force and scanning electron microscopies, Fourier transformed infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and surface area measurements. Magnetic character of the nanohybrids was ascertained by a vibrating sample magnetometer. Batch experiments were carried out to quantify the adsorption kinetics and adsorption capacities of the nanohybrids and compared with the bare nanoparticles of MnFe2O4. The adsorption data from our experiments fit the Langmuir isotherm, yielding the maximum adsorption capacity higher than the reported values so far. Temperature-dependent adsorption studies have been done to estimate the free energy and enthalpy of adsorption. Reusability, ease of magnetic separation, high removal efficiency, high surface area, and fast kinetics make these nanohybrids very attractive candidates for low-cost adsorbents for the effective coremoval of heavy metals from contaminated water.

Formulation of nanotized curcumin and demonstration of its antimalarial efficacy

Aim: The present study was conducted to overcome the disadvantages associated with the poor water solubility and low bioavailability of curcumin by synthesizing nanotized curcumin and demonstrating its efficacy in treating malaria. Materials and methods: Nanotized curcumin was prepared by a modified emulsion-diffusion-evaporation method and was characterized by means of transmission electron microscopy, atomic force microscopy, dynamic light scattering, Zetasizer, Fourier transform infrared spectroscopy, and differential thermal analysis. The novelty of the prepared nanoformulation lies in the fact that it was devoid of any polymeric matrices used in conventional carriers. The antimalarial efficacy of the prepared nanotized curcumin was then checked both in vitro and in vivo. Results: The nanopreparation was found to be non-toxic and had a particle size distribution of 20-50 nm along with improved aqueous dispersibility and an entrapment efficiency of 45%. Nanotized curcumin (half maximal inhibitory concentration IC50]: 0.5 mu M) was also found to be ten-fold more effective for growth inhibition of Plasmodium falciparum in vitro as compared to its native counterpart (IC50: 5 mu M). Oral bioavailability of nanotized curcumin was found to be superior to that of its native counterpart. Moreover, when Plasmodium berghei-infected mice were orally treated with nanotized curcumin, it prolonged their survival by more than 2 months with complete clearance of parasites in comparison to the untreated animals, which survived for 8 days only. Conclusion: Nanotized curcumin holds a considerable promise in therapeutics as demonstrated here for treating malaria as a test system.

Mixture of Fuels Approach for the Synthesis of SrFeO3-delta Nanocatalyst and Its Impact on the Catalytic Reduction of Nitrobenzene

A modified solution combustion approach was applied in the synthesis of nanosize SrFeO3-delta (SFO) using single as well as mixture of citric acid, oxalic acid, and glycine as fuels with corresponding metal nitrates as precursors. The synthesized and calcined powders were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis and derivative thermogravimetric analysis (TG-DTG), scanning electron microscopy, transmission electron microscopy, N-2 physisorption methods, and acidic strength by n-butyl amine titration methods. The FT-IR spectra show the lower-frequency band at 599 cm(-1) corresponds to metal-oxygen bond (possible Fe-O stretching frequencies) vibrations for the perovskite-structure compound. TG-DTG confirms the formation temperature of SFO ranging between 850-900 degrees C. XRD results reveal that the use of mixture of fuels in the preparation has effect on the crystallite size of the resultant compound. The average particle size of the samples prepared from single fuels as determined from XRD was similar to 50-35 nm, whereas for samples obtained from mixture of fuels, particles with a size of 30-25 nm were obtained. Specifically, the combination of mixture of fuels for the synthesis of SFO catalysts prevents agglomeration of the particles, which in turn leads to decrease in crystallite size and increase in the surface area of the catalysts. It was also observed that the present approach also impacted the catalytic activity of the SFO in the catalytic reduction of nitrobenzene to azoxybenzene.

Reduced graphene oxide-titania based platform for label-free biosensor

A label-free biosensor has been fabricated using a reduced graphene oxide (RGO) and anatase titania (ant-TiO2) nanocomposite, electrophoretically deposited onto an indium tin oxide coated glass substrate. The RGO-ant-TiO2 nanocomposite has been functionalized with protein (horseradish peroxidase) conjugated antibodies for the specific recognition and detection of Vibrio cholerae. The presence of Ab-Vc on the RGO-ant-TiO2 nanocomposite has been confirmed using electron microscopy, Fourier transform infrared spectroscopy and electrochemical techniques. Electrochemical studies relating to the fabricated Ab-Vc/RGO-ant-TiO2/ITO immunoelectrode have been conducted to investigate the binding kinetics. This immunosensor exhibits improved biosensing properties in the detection of Vibrio cholerae, with a sensitivity of 18.17 x 10(6) F mol(-1) L-1 m(-2) in the detection range of 0.12-5.4 nmol L-1, and a low detection limit of 0.12 nmol L-1. The association (k(a)), dissociation (k(d)) and equilibrium rate constants have been estimated to be 0.07 nM, 0.002 nM and 0.41 nM, respectively. This Ab-Vc/RGO-ant-TiO2/ITO immunoelectrode could be a suitable platform for the development of compact diagnostic devices.

Sensitive detection of C-reactive protein using optical fiber Bragg gratings

An accurate and highly sensitive sensor platform has been demonstrated for the detection of C-reactive protein (CRP) using optical fiber Bragg gratings (FBGs). The CRP detection has been carried out by monitoring the shift in Bragg wavelength (Delta lambda(B)) of an etched FBG (eFBG) coated with an anti-CRP antibody (aCRP)-graphene oxide (GO) complex. The complex is characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. A limit of detection of 0.01 mg/L has been achieved with a linear range of detection from 0.01 mg/L to 100 mg/L which includes clinical range of CRP. The eFBG sensor coated with only aCRP (without GO) show much less sensitivity than that of aCRP-GO complex coated eFBG. The eFBG sensors show high specificity to CRP even in the presence of other interfering factors such as urea, creatinine and glucose. The affinity constant of similar to 1.1 x 10(10) M-1 has been extracted from the data of normalized shift (Delta lambda(B)/lambda(B)) as a function of CRP concentration. (C) 2014 Elsevier B.V. All rights reserved.

Properties of the chalcogenide-carbon nano tubes and graphene composite materials

Composite can deliver more than the individual elemental property of the material. Specifically chalcogenide- multi walled carbon nano tubes and chalcogenide- bilayer graphene composite materials could be interesting for the investigation, which have been less covered by the investigators. We describe micro structural properties of Se55Te25Ge20, Se55Te25Ge20 + 0.025% multi walled carbon nano tubes and Se55Te25Ge20 + 0.025% bilayer graphene materials. This gives realization of the alloying constituents inclusion/or diffusion inside the multi walled carbon nano tubes and bilayer graphene under the homogeneous parent alloy configuration. Raman spectroscopy, X-ray photoelectron spectroscopy, UV/Visible spectroscopy and Fourier transmission infrared spectroscopy have also been carried out under the discussion. A considerable core energy levels peak shifts have been noticed for the composite materials by the X-ray photoelectron spectroscopy. The optical energy band gaps are measured to be varied in between 1.2 and 1.3 eV. In comparison to parent (Se55Te25Ge20) alloy a higher infrared transmission has been observed for the composite materials. Subsequently, variation in physical properties has been explained on the basis of bond formation in solids. (C) 2014 Elsevier B. V. All rights reserved.

Modification of crosslinked chitosan membrane using NaY zeolite for pervaporation separation of water-isopropanol mixtures

The blocked diisocyanate crosslinked chitosan membrane was modified by incorporating different mass% of NaY zeolite. The physico-chemical properties of resulting composite membranes were studied using Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The mechanical properties of the membranes were studied using universal testing machine (UTM). After measuring the equilibrium swelling, membranes were subjected to pervaporation for separation of water-isopropanol mixtures. Both flux and selectivity were increased with increasing NaY zeolite content in the membranes. The membrane containing 40 mass% of NaY zeolite exhibited the highest separation selectivity of 11,241 with a flux of 11.37 x 10(-2) kg/m(2) h for 10 mass% of water in the feed. The total flux and flux of water are almost overlapping each other, suggesting that these membranes could be effectively used to break the azeotropic point of water-isopropanol mixture. From the temperature dependent diffusion and permeation values, the Arrhenius activation parameters were estimated. All the composite membranes exhibited lower activation energy compared to crosslinked membrane, indicating that the permeants require less energy during the process because of molecular sieving action attributed to the presence of sodalite and super cages in the framework of Nay zeolite. The Henry's mode of sorption dominates the process, giving an endothermic contribution. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Photo induced effects on the optical properties of As20Sb20S60 thin films

The thermally evaporated As20Sb20S60 amorphous film of 800 nm thickness was subjected to light exposure for photo induced studies. The as-prepared and illuminated thin films were studied by X-ray diffraction, Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectroscopy and Raman spectroscopy. The optical band gap was reduced due to photo induced effects along with the increase in disorder. These optical properties changes are due to the change of homopolar bond densities. The core level peak shifting in XPS spectra and Raman shift supports the optical changes happening in the film due to light exposure.

Effect of the nature of a transition metal dopant in BaTiO3 perovskite on the catalytic reduction of nitrobenzene

In the present study, we have synthesized Fe, Co and Ni doped BaTiO3 catalyst by a wet chemical synthesis method using oxalic acid as a chelating agent. The concentration of the metal dopant varies from 0 to 5 mol% in the catalysts. The physical and chemical properties of doped BaTiO3 catalysts were studied using various analytical methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), BET surface area and Transmission electron microscopy (TEM). The acidic strength of the catalysts was measured using a n-butylamine potentiometric titration method. The bulk BaTiO3 catalyst exhibits a tetragonal phase with the P4mm space group. A structural transition from tetrahedral to cubic phase was observed for Fe, Co and Ni doped BaTiO3 catalysts with an increase in doped metal concentration from 1 to 5 mol%. The particle sizes of the catalysts were calculated from TEM images and are in the range of 30-80 nm. All the catalysts were tested for the catalytic reduction of nitrobenzene to azoxybenzene. The BaTiO3 catalyst was found to be highly active and less selective compared to the doped catalysts which are active and highly selective towards azoxybenzene. The increase in selectivity towards azoxybenzene is due to an increase in acidic strength and reduction ability of the doped metal. It was also observed that the nature of the metal dopant and their content at the B-site has an impact on the catalytic reduction of nitrobenzene. The Co doped BaTiO3 catalyst showed better activity with only 0.5 mol% doping than Fe and Ni doped BaTiO3 catalysts with maximum nitrobenzene conversion of 91% with 78% selectivity to azoxybenzene. An optimum Fe loading of 2.5 mol% in BaTiO3 is required to achieve 100% conversion with 93% selectivity whereas Ni with 5 mol% showed a conversion of 93% and a azoxybenzene selectivity of 84%.

Inter molecular azide-diisocyanate coupling: new insights for energetic solid propellants

Hydroxyl terminated azide binders can undergo a spurious reaction with diisocyanates to form tetrazoline-5-one via an inter molecular 1,3-dipolar cycloaddition reaction apart from urethane/allophanate groups which has been overlooked. This has serious implications on solid propellants. The computed activation barrier using density functional theory (DFT) for urethane formation reaction is 28.4 kJ mol(-1) and that for tetrazoline-5-one formation reaction is 108.0 kJ mol(-1). DFT studies reveal that the rate limiting step of the reaction is 1,3-dipolar cycloaddition between azide and isocyanate. A dual cure was observed in the temperature ranges 42-77 degrees C and 78-146 degrees C by differential scanning calorimetry (DSC) and rheological studies, confirming multiple reactions. Tetrazoline-5-one formation was confirmed by Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance spectroscopy (NMR).

Effect of Coldfog on the Corona Induced Degradation of Silicone Rubber Samples

Corona is an unavoidable phenomena in high voltage power transmission system, in spite of suitably designed insulator accessories and transmission line hardware. It is a proven fact that the continuous occurrence of corona can subject the polymeric insulator to a severe degradation. Further, moisture in the air has a positive influence on the corona activity. This paper presents the methodology to evaluate the corona performance of the silicone rubber housing material with simultaneous application of cold fog. Analysis conducted after corona treatment by the Fourier Transform Infrared Spectroscopy (FTIR) present an interesting results showing a higher hydroxylation of sample surface under the moisture application than in the normal condition for both AC and DC excitation. FTIR spectrum also indicates the presence of nitric acid on the treated surface with coldfog application. Results obtained from SEM analysis are also presented.

Contrasting Effects of Graphene Oxide and Poly(ethylenimine) on the Polymorphism in Poly(vinylidene fluoride)

The nature of interaction between a heteronucleating agent (graphene oxide, GO) and a strongly polar macromolecule (poly(ethylenimine), PEI) with poly(vinylidene fluoride) (PVDF) influencing the crystalline structure and morphology has been systematically investigated in this work. PEI interacts with PVDF via ion-dipole interaction, which helps in lowering the free energy barrier for nucleation thereby promoting faster crystallization. In contrast, besides interacting with PVDF, GO also promotes heteronucleation in PVDF. We observed that both GO and PEI have very different effects on the overall crystalline morphology of PVDF. For instance, the neat PVDF showed a mixture of both alpha and beta phases when cooled from the melt. However, incorporation of 0.1 wt % GO resulted in phase transformation from the stable alpha-phase to polar beta-polymorph in PVDF. In contrast, PEI, which also resulted in faster crystallization in PVDF predominantly, resulted in the stable alpha- phase. Various techniques like Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry were employed to confirm the phase transformations in PVDF. PEI was further grafted onto GO nanosheets to understand the combined effects of both GO and PEI on the polymorphism in PVDF. The PVDF/PEI-GO composite showed a mixture of phases, predominantly rich in a. These phenomenal effects were further analyzed and corroborated with the specific interaction between GO and PEI with PVDF using X-ray photon scattering (XPS) and NMR. In addition, the dielectric permittivity increased significantly in the presence of GO and PEI in the composites. For instance, PVDF/PEI-GO showed the highest permittivity of 39 at 100 Hz.

Effect of laser irradiation on the optical properties of As40Sb15Se45 chalcogenide thin films

The exposure with band gap light of thermally evaporated As40Sb15Se45 amorphous film of 800 nm thickness, were found to be accompanied by optical changes. The as-prepared and illuminated thin films were studied by X-ray diffraction, Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectroscopy and Raman spectroscopy. The optical band gap was reduced due to photo induced effects along with the increase in disorder. These optical properties changes are due to the change of homopolar bond densities. The core level peak shifting in XPS spectra and Raman shift supports the optical changes happening in the film due to light exposure.