Abstract: Organic modification and surface functionalization of nanomaterials offers wide spectrum of materials which can be employed for several applications. Using this tool we have developed high performance recyclable nanocatalysts for several reactions such as transesterification, hydrogenation and oxidation. Using magnetic nanoparticles as a core, a few magnetically recoverable nanomaterials were also prepared. With suitable modifications these materials could be utilised for asymmetric synthesis as well as for drug delivery. Due to their interaction with magnetic field such hybrid nanomaterials can provide a strong platform for magnetic tumor targeting.
Abstract: We have investigated dynamical conductivity of graphene based systems; Single Layer Graphene (SLG), Bilayer Graphene (BLG) and Single Layer Gapped Graphene (SLGG), at zero and finite temperatures by taking into the account screening effects within the Random Phase Approximation (RPA). Rσq,ω and Rσq,ω show peaks that correspond to single particle excitations (SPE) and collective excitations (CE) respectively. In SLG, SPE positions are observed at ωħ≈0.5εf,εf∧1.5εf for q0.5kf,kf∧1.5kf respectively for all values of temperature. The peak height increases with increasing electron momentum and temperature. We noticed that for finite momentumq0.5kf∧kf, the peak height is maximum for T=0K and minimum for T=0.5Tf while that for T=Tf is intermediate. We also noticed that Rσq,ω peaks are blue shifted at high temperature for all graphene systems. In case of BLG, Landau undamped peak has been observed at T=0 for finite momentumq=0.3kf which becomes smooth at T=0.5Tf∧Tf. For q=0.8kf, Landau damped plasmon peaks have also been observed for all values of temperature. No major changes are observed in case of SLGG, with respect to SPE and CE peaks positions and heights specifically due to small change in band gap value incorporated here.
Abstract: Size-controlled silver nanoparticles are prepared at two different heating time duration (30 and 60min) under conventional heating at 80 ̊C in an aqueous solution of silver nitrate (AgNO3) as a precursor and trisodium citrate (C6H5O7Na3.2H2O) as a reducing agent under continuous stirring. The size and size distribution of the resulting silver nanoparticles prepared under conventional heating are strongly dependent on the duration of heating. As the heating duration is increased, aggregation and grain growth is observed. When duration of heating was 60min a distinct increase in the particles size was observed that lead to shift in the plasmon band as confirmed by UV-Vis absorption spectroscopy. TEM images shows that silver nanoparticles are nearly spherical in shape and their sizes are ranging between 2-42 nm and their cubic structure was confirmed by X-ray diffractogram. From X-ray diffractogram we calculated crystallite size using Scherrer’s equation which comes out to about 36nm and that determined from Hall-Williamson plot turns out to be 19nm.
Abstract: In the present study, two different PVA-PEO nanocomposite blend polymer electrolyte systems viz., System-I: [(PVA)(42.5):(PEO)(42.5):(AgNO3)(5):(PEG)(10):(Al2O3)(x)] and System-II: [(PVA)(47):(PEO)(47):(LiCF3SO3)(9):(EC)(6):(Al2O3)(x)] are prepared using solution cast technique for various Al2O3 nanofiller amounts ranging from 2 to 10 wt%. The influence of Al2O3 concentration on the transport properties of the electrolytes of both these systems is closely inspected. Here, the ionic transport number (ti) measurements of the blend specimens are carried out using ‘dc Polarization Technique’.
Abstract: A newly proposed pseudopotential has been put forwardwith a novel scheme of determining potential parameters. Based on the criteria that the (i) potential and its first derivative are continuous at the core radius,(ii) exponential decay of columbic tail outside the core and, (iii) non-singular character with finite derivative at r→0; a pseudopotential is designed. Of the total five parameters, only two parameters are independently tuned to cohesive properties at ambient (T = 0 K and zero-pressure) condition, while the remaining three parameters are computed consistently following above mentioned criteria. However in the present study, we have examined the atomic transport properties of liquid phase for the case of aluminum. Results for velocity autocorrelation function (VACF), cosine power spectrum and mean square displacement are evaluated and compared with available MD results. From the computed results for diffusion co-efficient at various temperatures, activation energy is also calculated. Good agreement for diffusion co-efficient and activation energy with experimental findings confirm the transferability of pseudopotential even in the liquid phase.
Abstract: We present the calculation of structural properties for liquid Ga at different temperatures using pseudopotential theory. The temperature dependence of structure factor has been determined using the hard-sphere Percus-Yevick approximation which is characterized by single parameter hard sphere diameter or equivalently packing fraction. The temperature dependent hard-sphere diameter σ (T) is estimated using criterion from the calculated effective pair potential. The modified empty-core pseudopotential due to Hasegawa et al. (J. Non-Cryst. Solids. 117/118 (1990) 300), which is valid for all electrons and contains the repulsive delta function to achieve the necessary s-pseudisation is used for electron–ion interaction. The temperature effects have been studied via dimensionless damping term and potential parameter in the pair potential. Finally, the predicted results for structure factor, pair correlation function and coordination numbers have been compared with recent available data, and a good agreement has been achieved.
Abstract: The electron mobility is calculated for h-BN nanosheets (h-BNNSs) and graphene with and without doping of manganese at high electric fields via acoustical deformation potential (ADP) scattering mechanism and piezoelectric scattering (Polar Acoustical Phonon (PAP) mechanism at low temperatures. Calculation includes the variation of electron Fermi energy and effective mass with high electric fields and with variation of Mn concentrations. Comparison of mobility in both the cases of with and without doping is carried out. It is observed that the net electron mobility due to both ADP and PAP mechanisms in graphene is much larger than that for h-BNNS for both the cases of with and without doping of manganese at low temperatures.
Abstract: A theoretical study of first order pressure induced structural phase transition, mechanical and thermal properties of YBi and ScBi compounds have been investigated using the modified inter-ionic potential theory (MIPT), which parametrically includes the effect of coulomb screening. The calculated results of phase transition pressure of ScBi and YBi are agree well with the available theoretical data. We have also reported the second order elastic constants and Debye temperature of these compounds. Our calculated values of second order elastic constant C11, C12 and C44 are 128.4, 29.5, 30.2 GPa and 123.1, 29.7, 30.3 GPa for ScBi and YBi compounds respectively. These results are in good agreement with available theoretical data. We have also estimated Debye temperatures (θD) are 80K, 86K, for ScBi and YBi compounds respectively.
Abstract: In polar semiconductor materials, LO phonons produce a macroscopic electric field, which interacts with the electrons. This coupling of long range is known as Frohlich interaction. Due to the interaction of an electron with LO phonons, a quasi-particle is formed known as polaron. The strength of this coupling is expressed by a dimensionless Frohlich coupling constant. Due to the polar coupling to LO phonons, the carriers lose their initial kinetic energy to the lattice by a very efficient relaxation mechanism in III-V bulk semiconductors. Therefore it would be interesting to examine the effect of Frohlich coupling constant on the operational characteristics of optical parametric interaction in compound semiconductor medium. Using hydrodynamic model and coupled mode theory, a theoretical model is developed to determine threshold pump field for the onset of parametric process. For the sake of numerical estimations, data of ZnS and GaAs have been used. These prominent materials are assumed to be shined by a 10.6 μm CO2 laser so that nonlinearity could be induced in the medium. It is found that material having lower coupling constant is beneficial for a cost effective parametric interaction. It is hoped that result of this paper may be useful for various industrial applications.