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      Volume 35, Issue 7

      December 2012,   pages  1039-1239

    • Development, characterization, sintering, dielectric and optical properties of NdBa2ZrO5.5 nanocrystals

      V Ratheesh Kumar P R S Wariar R Pazhani J K Thomas R Jose J Koshy

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      Nanocrystalline NdBa2ZrO5.5 has been successfully synthesized through a single step auto-ignition combustion route for the first time. X-ray diffraction and Fourier transform infrared spectroscopy revealed that the combustion product is phase pure and has an ordered cubic perovskite structure. The phase transitions and thermal stability of the nanopowder were investigated by differential thermal and thermogravimetric analyses. Transmission electron microscopy results indicated that the particle sizes are 20–30 nm. Selected area electron diffraction pattern has shown that as-prepared powder is polycrystalline in nature. The optical absorption spectra analysis confirmed that the material falls to the semiconducting range with a bandgap of ∼3.69 eV and therefore, could be used as transparent wide bandgap semiconductor. The relative density of the sintered sample is ∼96% at 1510 °C for 2 h. The surface morphology of the sintered pellet has been studied by scanning electron microscopy and the average grain size observed is ∼0.7 𝜇m. Dielectric constant (𝜀r) of NdBa2ZrO5.5 at 5 MHz is 29.6 and loss factor (tan 𝛿) is 4 × 10-2 at room temperature.

    • A comparative study on heat dissipation, morphological and magnetic properties of hyperthermia suitable nanoparticles prepared by co-precipitation and hydrothermal methods

      Md Shariful Islam Yoshihumi Kusumoto Junichi Kurawaki Md Abdulla-Al-Mamun Hirotaka Manaka

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      Magnetite (Fe3O4) nanoparticles were prepared by co-precipitation and hydrothermal methods and their phase transfer was done successfully to compare their performances in different aspects. Synthesized nanoparticles were characterized for XRD, FE–SEM, TEM, UV-Vis absorption (reflectance) spectra, magnetic hysteresis loops and a.c. magnetic field induced hyperthermia. The magnetic nanoparticles prepared by the co-precipitation method show superior performances in respect of heat dissipation capability, saturation of magnetization values and particle size when compared to those prepared by the hydrothermal method.

    • First principles results of structural and electronic properties of ZnS clusters

      D L Lalsare Anjali Kshirsagar

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      We present results of the study of Zn𝑛S𝑛 (1 ≤ 𝑛 ≤ 9) clusters, using the density functional formalism and projector augmented wave method within the generalized gradient approximation. Along with the structural and electronic properties, nature of bonding and overall stability of clusters has been studied.

    • Polymer–clay nanocomposites via chemical grafting of polyacrylonitrile onto cloisite 20A

      YAGOUB MANSOORI Khadijeh Roojaei Mohammad Reza Zamanloo Gholamhassan Imanzadeh

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      The synthesis and characterization of polyacrylonitrile (PAN) nanocomposites through grafting the polymer onto organophilic montmorillonite have been reported. Cloisite 20A reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinylmoiety. Because the reaction liberates HCl, it was performed in the presence of sodium hydrogen carbonate to prevent the exchange of quaternary alkylammonium cations with H+ ions. Only the silanol groups on the edge of the clay reacted with vinyltrichlorosilane. The radical polymerization of the product with acrylonitrile (AN) as a vinyl monomer leads to chemical grafting of polyacrylonitrile onto montmorillonite surface. The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhlet extraction. Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy. The prepared nanocomposite materials and grafted nanoparticles were studied by XRD and TEM. Exfoliated nanocomposites were obtained for 0.5–7 wt% clay content. The nanocomposites were studied by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMTA).

    • Anticorrosives, encapsulates, catalytic supports and other novel nanostructured materials

      Genoveva Hernández-Padrón Laura S Acosta-Torres Fernando Rojas-González Víctor M Castaño

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      A phenolic-formaldehydic resin (PFR) of the Novolac-type and modified through the attachment of carboxylic end groups (MPR), is used to tailor the morphological and optical properties of sol–gel synthesized silica materials. Silica microparticles are produced from alkoxide precursors in the presence of PFR or MPR resins, leading to a final material consisting of SiO2 globules entangled inside a polymerized resin matrix. Under appropriate experimental conditions, chemical bonds can be established between the SiO2 silanol surface groups and the MPR carboxylic chains, to render SiO2/MPR core-shell-type compounds. The presence of PFR or MPR resins during the sol–gel production of silica microspheres allows to control:

      1. the sizes of final SiO2 particles and

      2. the transparency or opacity properties of the final hybrid products.

      In this way, either opaque or transparent solid substrates can be obtained, depending on the amounts of reactants used to prepare the hybrid specimens. Solid MPR and SiO2/MPR samples were characterized by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy to determine chemical and textural properties of the hybrid substrates. Under appropriate experimental conditions, chemical bonds could be established between the SiO2 silanol surface groups and the MPR carboxylic chains, to render SiO2/MPR core-shell-type compounds.

    • Chemically ordered face-centred tetragonal Fe–Pt nanoparticles embedded SiO2 films

      Sourav Pramanik Goutam De

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      Chemically ordered face-centred tetragonal (fct) Fe–Pt alloy nanoparticles (NPs) embedded SiO2 films were synthesized on glass substrate by in situ hybrid sol–gel approach followed by heating at 450–900 °C in air and reducing (10% H2–90% Ar) atmospheres. Heat treatment of Fe/Pt co-doped films in air caused generation of Pt NPs first. At this stage, Fe remained in ionic state covalently bonded with silica network. Further heat treatment at 800–900 °C in reducing atmosphere facilitated the formation of uniformly dispersed fct Fe–Pt alloy NPs in amorphous SiO2 film matrix. The generated alloy composition was estimated by grazing incidence X-ray diffraction and TEM analysis to be Fe0.42Pt0.58 which is close to the nominal value.

    • Characterization of amorphous hydrogenated carbon films deposited by MFPUMST at different ratios of mixed gases

      Haiyang Dai Changyong Zhan Hui Jiang Ningkang Huang

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      Amorphous hydrogenated carbon films (𝑎-C:H) on 𝑝-type (100) silicon wafers were prepared with a middle frequency pulsed unbalanced magnetron sputtering technique (MFPUMST) at different ratios of methane–argon gases. The band characteristics, mechanical properties as well as refractive index were measured by Raman spectra, X-ray photoelectron spectroscopy (XPS), nano-indentation tests and spectroscopic ellipsometry. It is found that the 𝑠𝑝3 fraction increases with increasing Ar concentration in the range of 17–50%, and then decreases when Ar concentration exceeds 50%. The nano-indentation tests reveal that nano-hardness and elastic modulus of the films increase with increasing Ar concentration in the range of 17–50%, while decreases with increasing Ar concentration from 50% to 86%. The variations in the nano-hardness and the elastic modulus could be interpreted due to different 𝑠𝑝3 fractions in the prepared 𝑎-C:H films. The variation of refractive index with wavelength have the same tendency for the 𝑎-C:H films prepared at different Ar concentrations, they decrease with increasing wavelength from 600 to 1700 nm. For certain wavelengths within 600–1700 nm, refractive index has the highest value at the Ar concentration of 50%, and it is smaller at the Ar concentration of 86% than at 17%. The results given above indicate that ratio of mixed gases has a strong influence on bonding configuration and properties of 𝑎-C:H films during deposition. The related mechanism is discussed in this paper.

    • Electroless plating and magnetic properties of Co–Zn–P coating on short carbon fibres

      Xinghua Su Chengwen Qiang

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      A layer of Co–Zn–P alloys was coated on short carbon fibre (CFs) surfaces using electroless plating method. The influence of the concentration of Co2+ and Zn2+ and reaction time on the plating rate were measured by comparing the relative mass gain rate of Co–Zn–P-coated fibres with uncoated carbon fibres prepared under different conditions. The materials characterizations were analysed by field emission scanning electron microscopy, X-ray diffraction and energy dispersive spectroscope. The magnetic properties of Co–Zn–P/CFs composites prepared in different Zn2+ concentration baths were measured by the vibrating sample magnetometer. The best processing parameters of electroless plating of Co–Zn–P coating on short carbon fibres were obtained.

    • Effect of surface modification of Grewia optiva fibres on their physicochemical and thermal properties

      Amar S Singha Ashvinder K Rana

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      This paper deals with the surface modification of Grewia optiva fibre through benzoylation and graft copolymerization process. Benzoylation of Grewia optiva fibre has been carried out on mercerized fibre with varying concentrations of benzoyl chloride solution. Graft copolymerization of acrylonitrile (AN) onto Grewia optiva fibre was carried out with ceric ammonium nitrate as the redox initiator in aqueous medium under the influence of microwave radiation. Raw, graft copolymerized and benzoylated fibres were subjected to evaluation of some of their properties like swelling behaviour, moisture absorbance and chemical resistance behaviour. It has been observed that 5% benzoyl chloride treated and graft copolymerized Grewia optiva show more resistance towards moisture, water and chemicals when compared with that of raw fibre. Further morphological, structural changes, thermal stability and crystallinity of raw, graft copolymerized, pretreated and benzoylated fibres have also been studied by SEM, FTIR, TGA and XRD techniques.

    • Large resonant third-order optical nonlinearity of thin film containing J-like aggregates of a bis[4-(𝑁-dibutylamino)phenyl]squarylium dye

      Zhongyu Li Song Xu Lin Zhu Kazuo Kasatani

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      The third-order optical nonlinearity and response of thin film containing J-like aggregates of a bis[4-(𝑁-dibutylamino)phenyl]squarylium dye were measured by degenerate four-wave mixing (DFWM) technique under resonant conditions. The temporal profile of DFWM signal was obtained with a time resolution of 0.3 ps (FWHM), and was found to consist of at least two components, i.e. the coherent instantaneous nonlinear response (electronic response) and the slow response due to the excited state population grating. The effective 𝜒(3) value of thin squarylium dye film was evaluated to be as high as 1.1 × 10-7 esu, and the figure of merit of third-order nonlinearity 𝐹(𝐹 = 𝜒(3)/𝛼), was calculated to be about 2.1 × 10-13 esu cm.

    • Influence of bowl shaped substrate holder on growth of polymeric DLC film in a microwave plasma CVD reactor

      Sambita Sahoo S K Pradhan Venkateswarlu Bhavanasi Swati S Pradhan S N Sarangi P K Barhai

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      The properties of diamond like carbon (DLC) films grown in modified microwave plasma CVD reactor is presented in this paper. By using bowl shaped steel substrate holder in a MW plasma CVD reactor (without ECR), films have been grown at relatively high pressure (20Torr) and at low temperature (without heating). The input microwave power was about 300W. Earlier, under the same growth conditions, no deposition was achieved when flat molybdenum/steel substrate holders were used. In this study, two different designs of bowl shaped steel substrate holder at different bias have been experimented. Raman spectra confirm the DLC characteristics of the films. FTIR results indicate that the carbon is bonded in the 𝑠𝑝3 form with hydrogen, and this characteristic is more pronounced when smaller holder is used. UV-visible spectra show high visible transmittance (∼85%) for films grown in both the holders. The nanoindentation hardness of the films have a wide range, about 4–16GPa. Field emission scanning electron microscope (FESEM) images reveal that the films have featureless and smooth surface morphology. These films are polymeric in nature with moderately high hardness, which may be useful as anti-scratch and anti-corrosive coatings.

    • Characterization of carboxy methylcellulose doped with DTAB as new types of biopolymer electrolytes

      A S Samsudin M I N Isa

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      The investigation of new solid biopolymer electrolyte (BEs) system based on carboxy methylcellulose (CMC) is creating opportunity for new types of electrochemical devices, which may themselves, in turn, revolutionize many industrial areas. Biodegradable carboxy methylcellulose (CMC) doped with dodecyltrimethyl ammonium bromide (DTAB) as BEs were prepared via solution-casting method. Upon addition of 35 wt. % of DTAB, highest ionic conductivity of 7.72 × 10-4 Scm-1 was achieved due to its higher amorphous region compared to other samples prepared. This result had been further proven in FTIR study. Temperature dependence relationship obeys the Arrhenius rule from which the activation energy, 𝐸a, for ionic conductivity and activation energy for relaxation process, 𝐸𝜏, were evaluated. The divergent values between 𝐸a for ionic conductivity and relaxation process 𝐸𝜏 shows that the ions hop by jumping over a potential barrier.

    • Synthesis and characterization of carboxymethyl chitosan hydrogel: Application as site specific delivery for lercanidipine hydrochloride

      Subhash S Vaghani Madhabhai M Patel C S Satish Kandarp M Patel N P Jivani

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      In the present study, carboxymethylchitosan (CMCS) was prepared from chitosan, crosslinked with glutaraldehyde and evaluated in vitro as a potential carrier for site specific drug delivery of lercanidipine hydrochloride (LERH). LERH was incorporated at the time of crosslinking of CMCS. The chitosan was evaluated for its degree of deacetylation (𝐷𝐷) and average molecular weight, which were found to be 84.6% and 3.5 × 104 Da, respectively. The degree of substitution on prepared CMCS was found to be 0.68. All hydrogel formulations showed more than 86% and 77% yield and drug loading, respectively. The swelling behaviour of prepared hydrogels were checked in different pH values, 1.2, 6.8 and 7.4, indicated pH responsive swelling characteristic with very less swelling at pH 1.2 and quick swelling at pH 6.8 followed by linear swelling at pH 7.4 with slight increase. In vitro release profile was carried out at the same conditions as in swelling and drug release was found to be dependent on swelling of hydrogels and showed biphasic release pattern with non-fickian diffusion kinetics at higher pH. The carboxymethylation of chitosan, entrapment of drug and its interaction in prepared hydrogels were checked by FTIR, 1H-NMR, DSC and 𝑝-XRD studies, which confirmed formation of CMCS from chitosan and absence of any significant chemical change in LERH after being entrapped in crosslinked hydrogel formulations. The surface morphology of formulation 𝑆6 was checked before and after dissolution, revealed open channel like pores formation after dissolution.

    • Effect of surface modification and hybridization on dynamic mechanical properties of Roystonea regia/glass–epoxy composites

      Govardhan Goud R N Rao

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      The paper evaluates effect of fibre surface modification and hybridization on dynamic mechanical properties of Roystonea regia/epoxy composites. Surface modification involved alkali and silane treatments. Alkali treatment proved to be more effective on dynamic mechanical properties as compared to silane treatment. Storage and loss modulus values increased after treatments with simultaneous decrease in tan 𝛿 values. Roystonea regia and glass fibres were used together with varying proportions as reinforcement in epoxy matrix to study the hybridization effect on dynamic mechanical properties. Storage and loss modulus values increased with increase in glass fibre content whereas tan 𝛿 values were found to decrease. Scanning electron microscopy of tensile fractured surfaces was carried out to study the interface adhesion of different composites.

    • Effect of pMDI isocyanate additive on mechanical and thermal properties of Kenaf fibre reinforced thermoplastic polyurethane composites

      Y A El-Shekeil S M Sapuan K Abdan E S Zainudin O M Al-Shuja’a

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      The effect of polymeric methylene diphenyl diisocyanate (pMDI) on mechanical and thermal properties of Kenaf fibre (KF) reinforced thermoplastic polyurethane (TPU) composites was studied. Various percentages viz. 2%, 4% and 6%, were studied. The composites were characterized by using tensile testing, thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR). It was noticed that the addition of pMDI 2%, 4%and 6% did not induce a better tensile nor thermal properties.

    • A novel wound dressing material — fibrin–chitosan–sodium alginate composite sheet

      M Pandima Devi M Sekar M Chamundeswari A Moorthy G Krithiga N Selva Murugan T P Sastry

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      The present study describes preparation and characterization of fibrin–chitosan–sodium alginate composite (F–C–SA) in sheet form. F–C–SA composite was prepared and characterized for its physicochemical properties like water absorption capacity, surface morphology, FTIR spectra and mechanical properties. The optimum quantities of fibrin, chitosan and sodium alginate to get better mechanical properties to composite were determined. FTIR spectrum confirmed the interaction between amino groups of chitosan, fibrin and sodium alginate and SEM studies revealed composite nature of the material.

    • Dielectric behaviour of sodium and potassium doped magnesium titanate

      Vishnu Shanker Santosh Kumar T Surendar

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      Pure phase of magnesium titanate (MgTiO3) was obtained at 1100°C by both the conventional solid-state method as well as by the flux method starting from hexahydrated magnesium nitrate and titanium dioxide as the reactants. MgTiO3 doped with Na or K was also prepared by the solid-state route. Na and K doped compositions led to monophasic MgTiO3 below 5 mol% dopant concentration while biphasic mixture of MgTiO3 (major phase) and MgTi2O5 (minor phase) were obtained at higher dopant concentration. The dielectric constant and dielectric loss of MgTiO3 were found to be almost the same irrespective of the preparative method. MgTiO3 doped with 5 mol % of Na and K ions displayed optimum dielectric properties.

    • Photochemical events during photosensitization of colloidal ZnO nanoparticles by riboflavin

      E Vaishnavi R Renganathan

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      The photosensitization of colloidal ZnO nanoparticles with riboflavin (RF) was investigated using absorption, fluorescence spectroscopic measurements and time resolved fluorescence measurements. Riboflavin adsorbed strongly on the surface of ZnO nanoparticles. Apparent association constant was obtained from the fluorescence quenching measurements. The free energy change, 𝛥𝐺et, for electron transfer process has been calculated by applying Rehm Weller equation.

    • Chemically deposited TiO2/CdS bilayer system for photoelectrochemical properties

      P R Deshmukh U M Patil K V Gurav S B Kulkarni C D Lokhande

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      In the present investigation, TiO2, CdS and TiO2/CdS bilayer system have been deposited on the fluorine doped tin oxide (FTO) coated glass substrate by chemical methods. Nanograined TiO2 was deposited on FTO coated glass substrates by successive ionic layers adsorption and reaction (SILAR) method. Chemical bath deposition (CBD)method was employed to deposit CdS thin film on pre-deposited TiO2 film. A further study has beenmade for structural, surface morphological, optical and photoelectrochemical (PEC) properties of FTO/TiO2, FTO/CdS and FTO/TiO2/CdS bilayers system. PEC behaviour of FTO/TiO2/CdS bilayers was studied and compared with FTO/CdS single system. FTO/TiO2/CdS bilayers system showed improved performance of PEC properties over individual FTO/CdS thin films.

    • Synthesis of vanadium oxides 5 wt.%VO2–M𝑥O𝑦 by sol–gel process and application in cyclohexene epoxidation

      S El-Korso I Rekkab A Choukchou-Braham S Bedrane L Pirault-Roy C Kappenstein

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      A series of SiO2, Al2O3 and TiO2 mixed vanadium materials have been prepared from inorganic precursors via the sol–gel process and subsequently dried, calcined and reduced at elevated temperatures. Structural characterization of these materials was carried out by X-ray diffraction (XRD), N2 adsorption at 77 K, thermal analysis (TGA/DTA), UV-vis diffused reflectance spectroscopy (DR UV-vis) and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX). Their catalytic activities in the epoxidation of cyclohexene with TBHP as oxidant were also examined. Results of XRD and DR UV-visible diffused revealed that VO2 species are predominant in all samples and no formation of V2O5 was detected. Experimental results indicated that the VO2–SiO2 catalysts performed excellently for the epoxidation of cyclohexene by tertiobutyl hydroperoxide.

    • Amino acid-assisted synthesis of strontium hydroxyapatite bone cement by a soft solution freezing method

      D Gopi S Nithiya L Kavitha J M F Ferreira

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      Among many cations that can substitute for calcium in the structure of hydroxyapatite, strontium provokes an increasing interest because of its beneficial effect on bone formation and prevention of bone resorption. Strontium-incorporated calcium phosphates show potential in biomedical application, particularly the doped strontium may help in new bone formation. We have synthesized strontium hydroxyapatite powders at 2 °C by a soft solution freezing method using glycine as the template. The structural and morphological characterizations were carried out on the as obtained powders using Fourier transform infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy techniques. Strontium was quantitatively incorporated into hydroxyapatite where its substitution for calcium provoked a linear shift of the infrared absorption bands of the hydroxyl and phosphate groups. The strontium substituted bone cement has potential for use in orthopaedic surgeries. The present study shows that the addition of glycine plays an important role in reducing the particle size of strontium hydroxyapatite which could be used for biomedical applications.

    • Biosynthesis of silver nanoparticles by marine bacterium, Idiomarina sp. PR58-8

      Sachin Seshadri Anupama Prakash Meenal Kowshik

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      Metal-tolerant microorganisms have been exploited in recent years to synthesize nanoparticles due to their potential to offer better size control through peptide binding and compartmentalization. In this paper, we report the intracellular synthesis of silver nanoparticles (SNPs) by the highly silver-tolerant marine bacterium, Idiomarina sp. PR58-8 on exposure to 5mM silver nitrate. SNPs were characterized by UV-visible spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). UV-visible absorption scan of a 48 h culture exposed to 5mM silver nitrate revealed a broad peak at 450nm indicative of the surface plasmon resonance of SNPs. XRD analysis confirmed the presence of elemental silver and the crystallite size was calculated to be 25nm using Scherrer formula. The average particle size as per TEM analysis was found to be 26 nm. Metal stress is known to induce the production of non-protein thiols (NP–SHs) which sequester metal ions. In this study, the production of NP–SHs was followed from 6–48 h, wherein it was observed that the NP–SH levels in the silver-exposed culture were consistently higher (261% on an average) than in the unexposed culture.

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