Single Molecule Science centre

Morpholinium perchlorate, an organic nonlinear optical material was synthesized and the crystals were grown by the slow evaporation solution growth technique. Single crystal X-ray diffraction study revealed that the grown crystal belongs to orthorhombic system with space group of P2 1 2 1 2 1 . The structure of the compound was also confirmed by 1 H NMR studies. The Fourier transform infrared analysis was used to identify the various functional groups present in the title compound. The UV-visible absorption spectrum was recorded to study the optical transmittance in the range from 200 to 1100 nm. The optical band gap, reflectance, refractive index (n), extinction coefficient and electric susceptibility were calculated using transmittance data. The mechanical stability of the grown crystal was studied by Vickers′s micro hardness test. The PL spectrum of the title compound shows red emission at 648 nm.

LiInSe 2 polycrystalline material was successfully synthesized from melt and temperature oscillation method (MTOM). The crystalline phase was confirmed by powder X-ray diffraction pattern. Crack free LiInSe 2 single crystal of size 12 mm diameter and 32 mm length was grown using two zone tubular resistive heated furnace by modified vertical Bridgman-Stockbarger method with steady ampoule rotation. The grown LiInSe 2 crystal was subjected to single crystal XRD, inductively coupled plasmaoptical emission spectroscopy (ICP-OES), positron annihilation spectroscopy (PAS), Hall effect and dielectric measurements. Single crystal XRD measurement confirms the orthorhombic crystal system. ICP-OES analysis gives the crystal composition as Li 0.81 In 1.01 Se 2.18 . The average lifetime 278.03 ps in PAS measurements corresponds to vacancy clusters present in LiInSe 2 crystal. Hall effect measurement confirms the n-type semiconductor nature. The dielectric permittivity and dielectric loss were obtained to be 9.8 and 0.108 respectively by capacitance measurements at room temperature for the frequency of 2 MHz.

4-dimethylaminopyridinium salicylate monohydrate (DMAPSA) was synthesized and its crystal structure was determined using single crystal X-ray diffraction analysis. From the crystal structure analysis it can be inferred that the crystal belongs to monoclinic system with space group of P2 1 /n. Investigation has been carried out to assign the vibrational frequencies of the grown crystals by FTIR spectral studies. 1 H and 13 C FT-NMR has been recorded to elucidate the molecular structure. The molecular mass of DMAPSA has been measured using mass spectroscopic analysis. The thermal stability and thermal decomposition of DMAPSA have been investigated by means of thermogravimetric analysis and differential thermal analysis. The melting point of crystal was observed as 172°C by melting point apparatus. Fluorescence spectra were taken for the excitation wavelength of 240 nm.

Undoped, fluorine doped and antimony doped tin oxide films are prepared on quartz plates by Spray pyrolysis technique. The films grown at the optimum substrate temperature with different doping levels have been chosen for this study. Optical properties of these films are investigated in the entire UV-Visible -IR region (0.2 -10 µm). The observed absorption edge lies at 3.65 eV for undoped tin oxide and on doping it shifts towards higher energies, which is due to the Moss -Burstein effect. For fluorine doping depending upon the fluorine concentration, the absorption edge lies in the range 3.9 -4.14 eV and for antimony doping it lies in the range 3.82 -4.1 eV. In the undoped tin oxide films the direct allowed transition occurs at 4.02 eV and indirect allowed transition occurs at 2.43 eV, whereas for fluorine doped tin oxide and antimony doped tin oxide films, the direct allowed transitions occur in the range 4.18 -4.28 and 4.13 -4.22 eV respectively and the indirect allowed transitions occur in the range 2.63 -2.73 and 2.54 -2.65 eV respectively. Optical properties near the plasma edge have been analyzed using Drude's theory. The dependence of effective mass on carrier concentration has been explained on the basis of nonparabolicity of the conduction band. The shift in the fermi energy, calculated on the basis of energy dependent effective mass, is consistent with the measured shift in the absorption edge.

The nucleation thermodynamics of RbTiOXO 4 (where X= P or As) family crystals crystallizing from high temperature solution using the phosphate and tungstate solvents have been studied. Using the regular solution model and classical nucleation theory the nucleation thermodynamical parameters like interfacial energy, chemical potential, free energy change, critical energy barrier and radius of critical nucleus have been calculated which leads to b etter understanding of the nucleation process. Comparative study has also been made to investigate the metastable zone width of the above family crystals grown from different fluxes.

a b s t r a c t <0 0 1> directed good quality potassium dihydrogen phosphate (KDP) single crystal has been grown by SankaranarayananeRamasamy (SR) method with the vision to improve the crystalline perfection and efficiency. A seed crystal of diameter 25 Â 15 Â 3 mm 3 was mounted in the ampoule, where the diameter of the ampoule was much bigger than the seed. The size of the crystal grown was 30 Â 20 Â 60 mm 3 . The obtained transparency for the crystal grown by SR method is 93% and by conventional method is 85% in the entire visible region. The HRXRD analysis indicates that the crystalline perfections of the crystals are excellent without having any very internal structural grain boundaries. The obtained FWHM for conventional method grown crystal is 12 arc s and for SR method is 6 arc s. Low dielectric loss indicates that the <0 0 1> directed crystal contains minimum defects. Higher mechanical stability was observed in SR method grown KDP compared to the other. Laser damage threshold value has been determined using Nd:YAG laser operating at 1064 nm. The optical transmission study and the powder SHG measurement show the suitability of the ingot for nonlinear optical applications.

Polycrystalline material of Na 0.5 Bi 0.5 TiO 3 -BaTiO 3 (abbreviated as NBBT) was synthesised by solid state reaction technique. NBBT single crystal with reasonable size has been successfully grown by spontaneous nucleation technique. The X-ray diffraction results confirmed that the crystal system of as grown NBBT was cubic at room temperature. The unit cell parameters of as-grown NBBT crystal are a ¼b ¼ c¼ 4.07 Å; V¼ 68 Å 3 . The composition of as-grown NBBT was analyzed by Energy Dispersive X-ray analysis (EDS). Differential Scanning Calorimetry (DSC) revealed the thermal behavior of the grown NBBT crystal. The temperature dependence of dielectric constant was measured and the Curie temperature was found to be 310 1C for NBBT crystal. The dielectric data fitted with Curie-Weiss law shows that the gamma value of the as-grown NBBT crystal is 1.46, which also confirms the relaxor behavior.

Single crystals of potassium acid phthalate (KAP), a semi-organic compound, have been grown at an average growth rate of 4 mm/day from aqueous solution by using the uniaxial crystal growth method of Sankaranarayanan-Ramasamy (SR). Transparent, cylindrical KAP crystal of size 70 mm length and 15 mm diameter was grown. The grown crystals were characterized by etching and UV-vis NIR analysis. HRXRD analysis indicates that the crystalline perfection of SR method-grown KAP is good. The KAP crystals grown by SR method have 9% higher transmittance than conventional method-grown crystal. The microhardness test was carried out on the (0 1 0) face and a load-dependent hardness was observed. TG-DTA evaluated the thermal properties of the grown crystal. KAP was found to be thermally stable up to 290 1C. The dielectric constant and dielectric loss of the crystal were studied as function of frequency and temperature.

The single crystals of tetra glycine barium chloride (TGBC), a semi-organic material, were grown by the solvent evaporation technique from an aqueous solution of glycine and barium chloride at ambient temperature. Good optical quality single crystals of size 11 Â 13 Â 7 mm 3 were grown in a period of 2 weeks. Powder X-ray diffraction (XRD) and Fourier transform infrared transmission (FTIR) have confirmed the formation of the new crystal. The grown crystals were characterized by single-crystal XRD analysis to study the crystal structure. The crystalline perfection was evaluated by high-resolution X-ray diffractometry (HRXRD). From this analysis we found that the quality of the crystal was quite good. The full-width at half-maximum (FWHM) of the diffraction curves is 8.5 arcsec, which is very close to that expected from the plane wave dynamical theory of XRD showing that the crystalline perfection is excellent. UV-Vis-NIR spectrum was recorded to study the optical transparency of the grown crystals. Thermal properties of the crystal have been investigated using thermo gravimetric (TG), differential thermal analysis (DTA). The mechanical strength of the crystal is estimated by Vicker's hardness test. r

Transparent single crystals of glycine phosphite were grown by Sankaranarayanan-Ramasamy (SR) method and conventional slow evaporation solution technique (SEST) which had the sizes of 100 mm in length, 30 mm diameter and 10 Â 11 Â 8 mm 3 . The conventional slow evaporation and Sankaranarayanan-Ramasamy method grown glycine phosphite single crystals were characterized using laser damage threshold, chemical etching, Vickers microhardness, UV-vis-NIR and dielectric analysis. The laser damage threshold value was higher in SR method grown GPI crystal as against conventional method grown crystal. The SR method grown GPI has higher hardness and also higher transmittance compared to conventional method grown crystal. The chemical etching and dielectric loss measurements indicate that the crystal grown by SR method has low density of defects and low value of dielectric loss compared to conventional method grown GPI crystal.

Single crystal of dimethylammonium picrate (DMAP) was successfully grown for the first time by the slow evaporation method with dimensions 25 Â 15 Â 10 mm 3 . 1 H NMR was recorded to elucidate the molecular structure. The cell parameters were determined from single crystal X-ray diffraction studies. The crystal has eight developed facets with major ones (0 0 1) and (0 0 À 1). The structural perfection of the grown crystals has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. Fourier transform infrared (FTIR) spectral studies have been performed to identify the functional groups. Thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study its thermal properties. Powder test with Nd:YAG laser radiation shows second harmonic generation. The proton donor (-OH) group and proton acceptor amine (-NH) group in the DMAP structure provide infrastructure to introduce the charge asymmetry. The optical transmittance window and the lower cutoff wavelength of the DMAP have been identified by UV-vis-NIR studies. The laser induced surface damage threshold for the grown crystal was measured using Nd:YAG laser. The dielectric properties of DMAP from 323 to 373 K were investigated by the impedance analysis. The microhardness test was carried out and the load dependent hardness was measured.

Crack free LiInSe 2 single crystal with bottom dimension of 8 mm diameter and 10 mm length and top dimension of 12 mm diameter and 22 mm length was grown using modified vertical Bridgman-Stockbarger method with steady ampoule rotation. The grown LiInSe 2 crystal was characterized by X-ray diffraction pattern, Rutherford backscattering spectroscopy (RBS) analysis, Thermogravimetric-Differential thermal (TG-DTA) analysis, optical transmission and microhardness measurements. X-ray diffraction pattern gives the orientation of the crystal as 〈002〉. RBS analysis confirms that the composition of the grown crystal is Li 0.8 In 1.16 Se 2.04 . TG-DTA analysis confirms that the melting point of the grown crystal is 897.5 1C. Optical behavior has been assessed by ultraviolet-visible-near infrared spectroscopy and Fourier transform infrared analysis. LiInSe 2 optical band gap energy is 2.72 eV and the cut off wavelength is 450 nm. Mechanical behavior has been studied using Vickers Microhardness measurements.

Diglycine zinc chloride, a semi-organic nonlinear optical crystal was grown by conventional slow evaporation and Sankaranarayanan-Ramasamy method. By employing this unidirectional method, diglycine zinc chloride single crystals of diameters 10, 30 and length up to 60 mm were grown. The growth conditions have been optimized. A maximum growth rate of 1.5 mm per day was realized. A comparative damage threshold analysis made on the diglycine zinc chloride crystals by conventional and unidirectional method shows that the crystal grown by Sankaranarayanan-Ramasamy method has higher damage threshold. The conventional and Sankaranarayanan-Ramasamy method grown diglycine zinc chloride crystals were also characterized by chemical etching, UV-vis analysis, dielectric constant, dielectric loss, Vicker's microhardness analysis and the results were compared. The present study indicates that the crystal quality of Sankaranarayanan-Ramasamy method grown diglycine zinc chloride is good compared to conventional slow evaporation method grown crystal.

Ammonium malate, an organic nonlinear optical single crystal, has been grown to a dimension of 50 mm length and 20 mm diameter by uniaxial solution-crystallization method of Sankaranarayanan-Ramasamy (SR). The growth conditions and experimental details of the grown crystals have been presented. The crystalline perfection of the grown crystals has been evaluated by high-resolution X-ray diffraction technique and the results reveal that the crystal quality of SR grown crystal is better than the conventional method grown crystal. The growth features in SR grown crystal have been analyzed by chemical etching technique and well-defined triangular etch hillocks have been observed. The mechanical property of the grown crystal has been analyzed by Vickers microhardness method and it reveals that the grown crystal is moderately harder material. Ammonium malate crystal possesses lower cut off wavelength at 230 nm. It enables good optical transmission of the second harmonic generation of Nd:YAG laser and other applications in the blue-violet region. The second harmonic generation of the grown crystal has been confirmed by the Kurtz powder technique.

Pure and antimony doped tin oxide thin films were deposited on glass and quartz plates by spray pyrolysis method. Structural, electrical and optical properties of these films were studied by varying the substrate temperature and antimony concentration. The best electro-optic properties obtained were, resistivity as low as 9;10\ cm and average transmission of 80% in the visible region, at the substrate temperature of 400°C with the antimony concentration of 9 at%. While doping, change in preferred orientation was observed from [1 1 0] to [2 0 0]. The optical investigation showed that, depending upon the doping concentration, the antimony doped films had direct allowed transitions in the range 4.13-4.22 eV and indirect allowed transitions in the range 2.54-2.65 eV.

Dicalcium phosphate dihydrate (DCPD) was crystallized by single diffusion method under physiological pH, in the presence of cobalt and malic acid. The morphology, composition and microstructure of the grown crystals were analyzed using EDTA titration, UV-Visible, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), atomic absorption spectroscopy (AAS) and scanning electron microscopy (SEM). These analyses showed that the grown crystals were Co 2+ -doped DCPD. The temperature has influenced the dopant entry into DCPD crystals, but the dopant content and temperature were having not much influence on the crystal morphology. In pathological crystallization, the size and morphology are very important since they decide the mode of treatment to adopt. The morphological changes arise when the growth assay is doped with cobalt and malic acid. The effect of malic acid on the crystallization was highly specific, adsorbing on certain crystal faces during growth and producing different morphologies. At higher concentration, the morphology showed a feature frequently encountered in biomineralization, the orientational ordering in [0 0 1], leading to elongated crystals. r