R. Mohan

Effect of Iodic Acid Dopant on the Growth and Structural, Optical, and Electrical Properties of L-Arginine Phosphate Single Crystals

Effect of iodic acid on the growth and properties of L-arginine phosphate (LAP) single crystals has been studied. The presence of iodic acid in the LAP crystals is confirmed by inductively coupled plasma mass spectrometry (ICP-MS) analysis. The unit cell parameters for pure and iodic acid doped LAP crystals have been estimated using powder X-ray diffraction (XRD) analysis. UV-Visible transmittance spectral studies revealed the transmittance percentage and cut-off wavelengths of pure and doped LAP crystals. Powder second harmonic generation measurement has been carried out for the grown LAP crystals. The dielectric behavior of the grown crystals was analyzed for different frequencies at room temperature.

Low-temperature synthesis of hexamethylenetetramine-stabilised ZnS nanoparticles and its photocatalytic properties

ZnS nanoparticles have been synthesised at low temperature by short reaction (80°C for 2 h) via wet chemical route. The nanoparticles were stabilised using hexamethylenetetramine (HMTA) as surfactant in aqueous solution. The average particle size calculated from X-ray diffraction studies was about 4 nm with cubic zincblende structure. The presence of HMTA in the synthesised ZnS nanoparticles was confirmed by FTIR studies. A significant blue shift was observed in the optical absorption band edge for the ZnS nanoparticles as compared to the bulk, indicating a strong quantum confinement. The room temperature photoluminescence (PL) spectrum showed a broad green emission peak at around 502 nm. The photocatalytic property of HMTA-stabilised ZnS nanoparticles were investigated on the decolourisation of methylene blue aqueous solution under UV light irradiation.

Growth, optical and thermal studies of pure and thiourea doped ammonium pentaborate nonlinear optical single crystals

Abstract Single crystals of pure and thiourea doped ammonium pentaborate have been successfully grown by slow solvent evaporation technique. The growth conditions and surface morphology of pure and thiourea doped single crystals of APBO are optimised and the grown crystals are confirmed by X-ray diffraction. The crystals are characterised by Fourier transform infrared spectroscopy and UV-vis-NIR spectral techniques. The grown crystals of pure and thiourea doped APBO are subjected to thermal studies. The thermogravimetry and derivative thermogravimetry studies confirm that the decomposition of pure and doped crystals takes place in three different stages making them suitable for device fabrication for frequency conversion applications. The second harmonic generation of the crystals are confirmed by Nd∶YAG pulsed laser employing Kurtz powder technique and the influence of thiourea is also discussed. The Vicker microhardness test was carried out on the grown crystals to study the mechanical strength therein the Vicker’s hardness number (Hv) and Work hardening coefficient (n) were calculated.

CONTROLLED SYNTHESIS AND CHARACTERIZATION OF CERIUM-DOPED ZnS NANOPARTICLES IN HMTA MATRIX

Cerium-doped ZnS nanoparticles have been synthesized through hydrothermal method. The nanoparticles were stabilized using hexamethylenetetramine (HMTA) as surfactant in aqueous solution. The average particle size of the prepared samples is about 2 nm. The structure of the as-prepared ZnS nanoparticles is cubic (zinc blende) as demonstrated by X-ray powder diffraction (XRD) and selected area electron diffraction (SAED) analysis. TEM results showed that the synthesized nanoparticles were uniformly dispersed in the HMTA matrix without aggregation. The UV–Vis absorption spectra of the prepared ZnS nanoparticles show a considerable blueshift in the absorption band edge compared to bulk ZnS indicating a strong quantum confinement effect. Formation of HMTA-capped ZnS nanoparticles was confirmed by FTIR studies. Photoluminescence studies showed that the relative emission intensity of Ce3+-doped ZnS nanoparticles is higher than that of undoped ZnS nanoparticles, which is due to the enhancement of radiative recombination in the luminescence process. The PL spectra showed two emission peaks at around 420 nm and 442 nm, which may be attributed to deep-trap emission or defect-related emission of ZnS and presence of various surface states.

Enhanced third-order nonlinear optical properties of high purity ZnS nanoparticles

This paper reports on the preparation of high purity ZnS nanoparticles by a facile single step solvent-free route via thermal decomposition of zinc acetate dihydrate and thiourea in air atmosphere. The third-order optical nonlinearity of the prepared ZnS nanoparticles were measured by Z-scan technique using continuous wave 532-nm diode pumped Nd:YAG laser. From nonlinear optical (NLO) measurements, the prepared ZnS nanoparticles possess negative nonlinearity i.e., self-defocusing. Open aperture Z-scan measurement shows saturable absorption within the medium. These results show that the prepared ZnS nanoparticles are promising candidate for various potential applications in the field of nonlinear optics.

Spectral, electrical and thermal properties of electron-irradiated L-threonine single crystals

Electrons of energy 6 MeV have been irradiated on L-threonine single crystals. Crystals irradiated at various electron fluences were subjected to various techniques such as Fourier transform infrared spectroscopy, dielectric and Kurtz–Perry powder second harmonic generation analyses. Differential scanning calorimetry measurement has also been carried out to test the thermal stability of the irradiated samples. The results have been discussed in detail.

Swift ion irradiation effects on L-threonine amino acid single crystals

Single crystals of L-threonine were subjected to 50 MeV Li3+ ion irradiation at various ion fluences. Radiation induced changes in the structural, electrical, thermal and optical properties of the crystals have been studied in detail. The ion fluence dependence on these properties has also been discussed. Surface modifications in the crystals have been explored through atomic force microscopy. It has also been observed that the powder second-harmonic generation efficiency of irradiated L-threonine varies with the ion fluence studied.

Crystal growth, morphology, spectrographic characterization and thermal properties of Glycine Barium Bromo Chloride crystals

Glycine Barium Bromo Chloride material was purified by repeated recrystallization. Single crystal was grown by the slow evaporation solution technique (SEST). The presence of functional groups in the grown crystals was confirmed by Fourier transform infrared spectrum analysis. Thermal properties of the crystals were investigated using thermogravimetric (TG) and differential thermal analyses (DTA). The dielectric studies were carried out to identify the phase transition temperature and the dielectric constant was found. The transparency of crystal was tested using UV-visible spectra. Single crystal X-ray diffraction study has been carried out to find the crystal system and unit cell parameters.

Growth and characterization of potassium acid phthalte for third order NLO applications

Nonlinear optical crystals of potassium acid phthalate (COOK C6H4 COOH)-KAP were grown from aqueous solution. Transparent crystals of size (21×17×4) mm3 with well defined morphology were grown from slow cooling techniques. The grown crystals were characterized by single crystal X-ray diffraction. The crystal structure of Potassium Acid Phthalate C8H5K+O4 was orthorhombic with the following unit-cell dimensions at 298(2) K; a = 9.5970(3) A; b = 13.2869(5) A; c = 6.4643(3) A; α = 90°; β = 90°; γ = 90°; with a space group PCa21. Spectral analysis were carried out to investigate confirm its presence of various functional groups and to study the optical absorption properties. Third order nonliner studies have also been studied by Z-scan techniques. Nonlinear absorption and nonlinear refractive index were found out and the third order bulk susceptibility of compound was also estimated. The results have been discussed in detail.

200 MeV Ag15+ ion beam irradiation effects on spray deposited 5 wt% ‘Li’ doped V2O5 thin film

Lithium 5 wt% doped V2O5 thin film was deposited onto ITO substrate by spray pyrolysis technique. The substrate temperature was kept at 450 °C. 200 MeV Ag15+ ion beams at a fluence of 5×1012 ions/cm2 was irradiated on 5 wt% ‘Li’ doped V2O5 film of thickness 1367 nm. The XRD pattern confirms that the pristine film is non stoichiometry with orthorhombic structure and upon irradiation the crystallinity decreased and an obvious textured growth along (020) plane is induced. Raman peak observed at 917 cm−1 is due to oxygen deficiency. Upon irradiation, the optical transparency and band gap of the film decreased. Electrical transport property study shows that the resistivity increased by one order for the irradiated film.