Quantum dots of CdS and Ni-doped CdS were synthesized through chemical precipitation method using a high-boiling solvent. Nanocrystallinity of the as prepared nanostructure is confirmed using X-ray diffraction (XRD). The mean crystal size obtained by full-width half maxima (FWHM) analysis is 3.33 nm for CdS, 3.37 nm for CdS:Ni (2 mM) and 3.39 nm for CdS:Ni (4 mM). The electrical conductivity data reveal semiconducting behaviour of both pure CdS and Ni-doped CdS nano-crystals. The optical absorption analysis conducted in UV-vis range 200-900 nm reveals the transparency of these nanocrystals in entire visible range but not in ultraviolet range. The results based on optical analysis yield band gap values as 2.65 eV for CdS, 2.59 eV for CdS:Ni (2 mM) and 2.53 eV for CdS:Ni (4 mM) nanoparticles. This implies that pure CdS and Ni doped CdS are blue shifted with respect to the bulk CdS (2.42 eV); however, Nickel doped CdS nanocrystals are red shifted with respect to pure CdS nanocrystals.

Results of dielectric and thermal studies on strontium tartrate pentahydrate crystals are described. The value of dielectric constant is shown to be independent of temperature till 360 K at all the frequencies (110-700 kHz) of the applied a.c. field. It increases abruptly achieving a peak value of 25⋅5 at 100 kHz; the peak value being strongly dependent on frequency. In the temperature range, 87 < T < 117°C, the value of ε′ falls suggesting a transition at around 100°C or so. The dielectric constant, ε′, of the material is shown to be frequency dependent but temperature independent in the pre-or post-T c range 87 < T < 117°C, suggesting that the contribution towards polarization may be due to ionic or space charge polarization which gets eliminated at higher frequencies. The ferroelectric transition is supported by the results of thermoanalytical studies. It is explained that crystallographic change due to polymorphic phase transition may be occurring in the material, besides the change due to loss of water molecules, which leads to the dielectric anomaly at around 100°C. Coats-Redfern approximation method is applied for obtaining non-isothermal kinetic parameters leading to calculation of activation energies corresponding to three decomposition stages of material in the temperature ranging from 379-1113 K.

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Growth of pure-, sodium-and lithium-doped potassium hydrogen tartrate single crystals by gel technique is reported. Growth conditions conducive for the growth of single crystals are worked out. The crystals are characterized by using powder XRD, SEM, FTIR, AES, EDAX, CH analysis and thermoanalytical techniques. The stoichiometric composition for the grown crystals are established asDoping of sodium and lithium in the pure potassium hydrogen tartrate single crystals is found to influence the size, perfection, morphology, crystal structure and the thermal stability of crystals.

Chemical precipitation method using a highboiling solvent is used to synthesize ZnS and Ba-doped ZnS quantum dots. The presence of organic ligands in the prepared nanostructures is verified using Fourier transform infra-red spectroscopic studies. The samples have been analysed using X-ray diffraction analysis confirming nanocrystallinity of the as-prepared quantum dots (QD). The mean crystal size obtained by full width half maxima analysis is 3.2 nm for ZnS and 3.9, 4.2 nm for ZnS:Ba (2, 4 mM). TEM micrographs also reveal nanosized particles of ZnS and Ba-doped ZnS. An optical absorption study conducted in UV-Vis range 150-600 nm reveals the transparency of these quantum dots in entire visible range but not in ultraviolet range. The results based on optical analysis yield band gap values as 4.88 eV for ZnS and 4.69, 4.43 eV for ZnS:Ba (2, 4 mM) quantum dots. Impedance analysis of the samples was carried out to reveal the variation of impedance with frequency at room temperature. These results show the capacitive admittance associated with the quantum dots and hence nanostructure ZnS and Ba-doped ZnS can have potential applications in electronics as nano-tuned devices in which resonant frequency can be adjusted by controlling the size and shape of the quantum dots.