CaCO3/TiO2 Nanoparticles Based Dye Sensitized Solar Cell

In this communication,the synthesis and structural,morphological,optical,and photo-electrochemical properties of TiO_2 and CaCO_3/TiO_2 nanoparticles as well as their applications in dye sensitized solar cells(DSSCs),have been reported.In an X-ray diffraction pattern of CaCO_3/TiO_2 nanoparticles,the peak at 29.41°of CaCO_3 has been detected,demonstrating its coating on the surface of TiO_2,which is further verified using high resolution-transmission electron microscopy,energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy.The strong quenching in photoluminescence emission,in the case of CaCO_3/TiO_2nanoparticles,has been attributed to the decrease in recombination rate of photo-generated electron—hole pairs.In the case of UV—visible reflectance spectra,the absorption edge for CaCO_3/TiO_2 nanoparticles has slightly been found to be blue-shifted as compared to bare TiO_2 nanoparticles,which corresponds to an increase in energy band gap of the former.The dye desorption studies reveal that CaCO_3/TiO_2 electrodes adsorbed more dye than the bare TiO_2 electrode.CaCO_3/TiO_2 based DSSC show improved photoelectrochemical properties compared to the bare TiO_2 based DSSC as CaCO_3 coating on TiO_2 forms an energy barrier,and,consequently suppressing the charge recombination,and,thus,improving the overall energy conversion efficiency(η) from 0.46%to 1.44%under the illumination of simulated light of 100 mW/cm~2.     

Optical and magnetic properties of Fe-doped CdS dilute magnetic semiconducting nanorods

Solvothermal technique has been used for the synthesis of Fe-doped CdS nanorods (Cd_1?xFe_xS) with (x = 0.0, 0.3, 0.5, 1.0, 1.5). Structural analysis carried out using X-ray diffraction reveals the formation of defect-free hexagonal phase of the CdS nanorods. Energy dispersive X-ray analysis confirms the presence of elements Cd, Fe and S in their stoichiometric ratio. Blue shift in the band gap, as compared to the bulk CdS, has been observed in UV–visible spectra. The decrease in the intensity of the photoluminescence peaks confirms the quenching of spectra upon Fe doping. Transmission electron microscopy, high-resolution transmission electron microscopy and selected area diffraction studies confirm the polycrystalline nature as well as growth of CdS nanorods along (112) plane. Magnetic study confirms the ferromagnetic nature of the synthesized nanorods. Magnetic saturation has been found to be 0.187, 0.300, 0.450, 0.675, 0.600 emu g^?1, respectively, for undoped, 3, 5, 10, and 15 % Fe-doped CdS.     

Synthesis and evaluation of ciprofloxacin-loaded carboxymethyl tamarind kernel polysaccharide nanoparticles

Nanotechnology is currently employed as a tool to fight more efficiently against human pathogens. Nanoparticles can be prepared from a variety of materials such as protein, biodegradable polymers and synthetic polymers. Tamarindus indica Linn. or tamarind is one of the most important biodegradable polymer. In the present study, chemically modified polymer of tamarind ‘carboxymethyl tamarind kernel polysaccharide’ (CMTKP) is used for the synthesis of nanoparticulate formulation. Antibacterial activity of CMTKP was analysed which was then enhanced by incorporating a flouroquinolone antibiotic, ciprofloxacin to it. Ciprofloxacin-loaded CMTKP nanoparticles were synthesised via ionotropic gelation technique. Nanosuspension so formed was lyophilised by addition of a cryoprotectant. Nanoparticles obtained were characterised for its particle size, morphology and stability. Interaction studies were confirmed by Fourier transform infrared spectroscopy (FT-IR). Antibacterial activities of ciprofloxacin, CMTKP and ciprofloxacin-loaded CMTKP nanoparticles were tested against two Gram negative and positive bacteria. The antibacterial assay results revealed greatest zone of inhibition by ciprofloxacin-loaded CMTKP nanoparticles in Micrococcus luteus. Toxicity analysis of the prepared formulation was carried out on vero cell lines via resazurin assay which revealed its minimum toxicity.     

Synthesis,structural, thermal and optical studies of rare earth coordinated complex: Tb(Sal)3Phen

Complexes of salicylic acid (Sal) and 1,10-phenanthroline (Phen) were synthesized coordinated with terbium ion (Tb³⁺) in crystalline phases. The structural characterizations of the lanthanide complex were made using FT-IR, NMR (¹H and ¹³C) and XRD techniques. These measurements confirm the formation of Tb(Sal)₃Phen complex structure. The thermal aspects of the complex were examined using DTA and TGA techniques. An enhancement in luminescence intensity of Tb³⁺ ion bands were observed in Tb(Sal)₃Phen complex as compared to TbCl₃ crystals on 355 nm laser excitation. Enhancement is reported due to the efficient energy transfer process from Sal to Tb³⁺ ions. This is also confirmed by the time resolved photoluminescence spectroscopy with increase in lifetime of Tb³⁺ ions due to encapsulation in Sal/Phen network. Our system in itself can be a deserving candidate for luminescent solar collector material when coupled with solar cells.     

Anti-oxidant activity and total phenolic content of some Asian vegetables

The anti-oxidant activity of extracts from 36 vegetables was evaluated by using a model system consisting of β-carotene and linoleic acid. The total phenolics of the extracts was determined spectrophotometrically according to the Folin–Ciocalteau procedure and ranged from 34 to 400 mg (100 g)⁻¹ on a fresh weight basis. Mint, aonla, black carrots, chenopodium, fenugreek, kachnar and ginger had high phenolic contents. The anti-oxidant activity expressed as per percent inhibition of oxidation ranged from a high of 92% in turmeric extracts to a low of 12.8% in long melon. Other vegetables found to have high anti-oxidant activity (>70%) were kachnar, aonla, ginger, fenugreek, mint, beetroot, black carrots, Brussels sprouts, broccoli, lotus stem, yam, coriander and tomato. Anti-oxidant activity correlated significantly and positively with total phenolics ( r ²=0.6578, P  < 0.05). The results indicate that vegetables containing high phenolics may provide a source of dietary anti-oxidants.     

Modification of Tefzel film through graft copolymerization

The graft copolymerization of styrene (st) and methacrylonitrile (MAN) onto Tefzel film in aqueous media by the preirradiation method has been studied. In order to follow the effect of preswelling of the backbone polymer, grafting was attempted onto preirradiated Tefzel film and monomer preswollen, preirradiated Tefzel film. Optimum conditions pertaining to maximum percentage of grafting of st and MAN have been evaluated. Grafting onto preswollen, preirradiated Tefzel film displayed better results. The effect of different alcohols of increasing chain length on the percentage of grafting of st and MAN was also studied. Graft copolymerization of st showed an increase, while grafting with MAN exhibited a decrease, in the percentage of grafting in the presence of alcohols as compared to that obtained in the aqueous medium. Characterization of the graft copolymers was made by IR and thermogravimetric studies. Tefzel‐graft‐polystyrene showed improved thermal stability while the MAN grafted onto preswollen, preirradiated Tefzel film produced graft copolymer with poor thermal stability. Copyright © 2004 Society of Chemical Industry     

Enzyme‐catalyzed regioselective synthesis of sugar esters and related compounds

In this review, a comprehensive and illustrative survey is made of the regioselective synthesis of esters of sugars and related compounds using lipases. The main emphasis has been given to the screening and use of commercially available lipases for the enzymatic esterification of neutral monosaccharides, disaccharides, sugar alcohols and their selected ether and ester derivatives. The effect of solvents and solubilizing agents in improving the yields of the resultant sugar fatty acid esters has been incorporated. Further, solvent‐free esterification with molten fatty acids, use of ionic liquids and microwave radiations for improvement in the methodology have also been discussed. Copyright © 2006 Society of Chemical Industry