P. Sagayaraj

Growth and characterisation of l-arginine diphosphate crystal

Good optical quality single crystals of l-arginine diphosphate C6H20N4O10P2 (abbreviated as LADP) having dimensions up to 30 � 6 � 4m m 3 are reported. The crystals have been grown by slow solvent evaporation at a constant temperature of 301C from its aqueous solution. The grown single crystals were characterised by employing UV-VIS spectrum, FTIR, DTA, TGA and X-ray diffraction methods. r 2002 Elsevier Science B.V. All rights reserved.

L-Phenylalanine L-phenylalaninium bromide – a new nonlinear optical material

L-Phenylalanine L-phenylalaninium bromide (LPLPB), an amino acid non-centrosymmetric crystal having a large second harmonic generation (SHG) efficiency, being 4.5 times that of KH2PO4 (KDP), has been successfully grown using a slow evaporation method employing a temperature gradient technique. The structure of the grown crystal was solved and refined by single-crystal X-ray diffraction, and this demonstrates that it belongs to a monoclinic system with the space group P21. The confirmation of its functional groups was recorded using Fourier transform infrared spectroscopy. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to study its thermal properties. The optical behaviour was examined and its optical constants were determined by UV-vis analysis. Dielectric spectroscopy reveals the dielectric nature of the grown crystal. The mechanical strength of the grown LPLPB was estimated by microhardness studies, and the Youngs modulus of the grown LPLPB was calculated to be 3.310 × 1010 N m−2.

Growth and characterization of pure and doped potassium pentaborate (KB5) single crystals

Single crystals of pure and Mg + ,B a + ,C a + and Cu + doped potassium pentaborate (KB5) have been grown by low temperature solution growth technique. The growth conditions and surface morphology of pure and doped single crystals of KB5 are optimized and the grown crystals are confirmed by XRD. The pure and doped crystals of KB5 are subjected to TGA and DSC studies. Using the TGA and DSC curves, the enthalpies, decomposition temperature (Td) and weight loss are measured and the results are analysed and discussed. The influence of the presence of added dopants on the microhardness behaviour of Mg + ,B a + ,C a + and Cu + doped KB5 crystals are also studied and discussed. The SHG of the pure and doped samples of KB5 is confirmed by Nd:YAG pulsed laser employing the Kurtz powder technique.

Synthesis, growth and characterization of new borate-mixed crystals of type (NH4)1-xKxB5O8.

New borate-mixed crystals of type (NH4)1-x KxB5O8 were grown from aqueous solution by slow solvent evaporation method. The mixed crystals were confirmed by atomic absorption studies (AAS) and characterized by X-ray diffractometry (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman), optical absorption and solubility studies. The second harmonic generation efficiencies of the parent and mixed crystals were studied and compared with that of KDP.

Growth and Optical Studies of a Novel Organometallic Complex NLO Crystal: Tetrathiourea Cadmium(II) Tetrathiocyanato Zinc(II)

Tetrathiourea cadmium(II) tetrathiocyanato Zinc(II) (TCTZ) single crystals were grown in acetone-water mixture solvent using slow solvent evaporation technique and their optical property was studied for the first time. Both thiourea and thiocyanate ligands were combined with the transition metal ions Cd2+ and Zn2+. The nonlinear optical (NLO) efficiency of TCTZ crystal was tested and measured using Kurtz and Perry technique. The dielectric behavior of the sample was also studied.

Study of Optical, Electrical, and Magnetic Properties of Tetrakis Thiourea Nickel Chloride Single Crystals

Dark green transparent crystals of nickel thiourea chloride of dimension 8 × 4 × 3 mm3 are grown in a period of 45 days. Single crystal X-ray diffractometer (XRD) shows that the crystal belongs to body centered tetragonal symmetry class I4. The UV-Vis-NIR spectrum establishes the transmission range to be 300 nm to 2500 nm, with a sharp absorption peak at the red end of the visible region. Photoconductivity and dielectric studies are carried out and reported for the first time. The sample exhibits negative photoconductivity. The dielectric constant and dielectric loss decrease with increase in frequency. The magnetic moment was measured to be 2.9941 μ B .

Growth and physicochemical properties of L-phenylalaninium maleate: a novel nonlinear optical crystal.

Single crystals of novel organic nonlinear optical material, L-phenylalaninium maleate (LPM) having dimensions up to 10 × 6 × 6 mm(3) were grown by slow evaporation solution growth technique at room temperature. The grown crystals were confirmed by single crystal X-ray diffraction studies and the various functional groups were identified by FT-IR spectroscopic analysis. The optical properties were studied by optical absorption, second harmonic generation (SHG), photoconductivity and photoluminescence (PL) studies and reported for the first time. The optical band gap energy and SHG efficiency were found to be 4.85 eV and 1.5 times higher than KDP crystals. Negative photoconducting nature was confirmed by photoconductivity studies. Photoluminescence studies confirm the suitability of the sample for blue and green radiations. The title compound was also subjected to TG/DTA analysis and dielectric studies. Layer like growth pattern was analyzed by SEM micrograph.

Influence of oleic acid on the nucleation and growth of 4-N,N-dimethylamino-4-N-methyl-stilbazoliumtosylate (DAST) crystals

A simple method to control the nucleation and morphology of (4-N,N-dimethylamino-4-N-methyl-stilbazoliumtosylate) DAST crystals is explored. At equal concentrations of oleic acid and DAST in methanol, pure DAST crystals with an irregular hexagonal shape are obtained by a solvent evaporation method. The influence of oleic acid on facilitating the growth in specific faces is investigated. The purity of the grown crystal is investigated by powder XRD, NMR and Raman spectroscopy analyses. As a major improvement, we present a method where a preference for the growth of one of the desired faces (010) in the final morphology of the DAST crystal is possible which would be attractive for terahertz generation and detection studies.

A cost effective approach for developing substrate stable TiO2 nanotube arrays with tuned morphology: a comprehensive study on the role of H2O2 and anodization potential

A rapid growth rate of vertically grown and ‘substrate-stable’ titania (TiO2) nanotubes with self-organized nanotubular structures is realized in an electrolyte consisting of ethylene glycol (EG) and ammonium fluoride (NH4F) at various concentrations of hydrogen peroxide (H2O2). We have explored the possible growth of ordered TiO2 nanotubes in the electrolyte with four different concentrations of H2O2 (3, 5, 10 and 15 vol%) at six different applied potentials (30, 40, 50, 60, 70 and 80 V), where self-organized TiO2 nanotube arrays with the maximum tube length of 28 μm have been attained within 3 h of anodization in the electrolyte containing 10 vol% H2O2 at 60 V. The porosity of the synthesized nanotube samples is found to vary with the concentration of H2O2 and the applied potential. The samples were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD).

Growth, linear and nonlinear optical properties of a DSSS crystal

N,N-Dimethylamino-N′-methylstilbazolium p-styrenesulphonate (DSSS), a stilbazolium derivative is synthesized by employing the modified counter anion approach. The growth mechanism of DSSS in the methanol–water solvent system is investigated by using the isothermal evaporation method and defects reveal that a layered growth mechanism is adopted by DSSS. The morphology control of the crystal based on supersaturation is further investigated. Powder XRD analysis confirms that DSSS crystallizes in the monoclinic system with the Cc space group. The diffuse reflectance spectrum proved that DSSS is optically similar to N,N-dimethylamino-N′-methylstilbazolium p-toluenesulphonate (DAST). Important optical properties like the absorption coefficient, refractive index and dielectric constant are investigated in order to identify whether DSSS satisfies the requirements of being a Terahertz generating material. Second harmonic generation is found to be similar to that of DAST.