Studies on the Growth, Optical, Thermal and Physical Properties of an Efficient Second Order Nonlinear Optical Organic Crystal: 2-Amino-5-Chloropyridinium- Trifluoroacetate for Optoelectronic and Photonic Device Applications

The novel organic single crystal 2-amino-5-chloropyridinium-trifluoroacetate (2A5CTFA) has been synthesized andgrown successfully using methanol as solvent by continuous slow evaporation technique. The X-ray diffraction resultsreveals that the crystal 2-amino-5-chloropyridinium-trifluoroacetate crystallizes into monoclinic crystal system with the noncentrosymmetricspace group Pc. The vibrational spectrum of the sample by FTIR and FT-RAMAN study confirms thecharacteristic functional groups of the 2A5CTFA crystal. The optical absorption spectrum shows 85% of transmittance inthe entire UV-Vis-NIR region with cut-off wavelength at 345 nm. The crystal has a thermal stability of 137° C without anymajor weight loss in the TG curve. The photoluminescence spectrum of the crystal has a prominent violet emission peakcentered at 388 nm. The dielectric behavior of the crystal measured with various frequencies at different temperaturesreveals the normal behavior for optical materials. The second order NLO effect from the crystal is confirmed by theemission of green signal from the crystal upon tested with the aid of Kurtz powder analysis using Nd:YAG laser. The laserinduced surface damage threshold value of the crystal is found to be 1.05 GW/cm2. Overall, the outlined properties of thegrown crystal makes it suitable for opto-electronic and nonlinear optical device applications

Estimation of daily surface ozone using periodic and stochastic modeling in Chennai region

This study deals with the modeling and forecasting of surface ozone time series in an urban area. First, an analysis of the systematic components (periodicity and stochastic components) was performed. Subsequently, prediction model for the daily surface ozone series was developed. In the recent past years there was no permanent measurement of surface ozone data in this site, so we measured surface ozone during period from June 2011 to September 2012 at the urban site Chennai the capital of Tamil Nadu, India. Daily cumulative ozone data series was obtained by using hourly instantaneous data. The data series is free of trend were found using Mann-Kendall test. The periodicity of ozone data was analyzed using Fourier Transform method. Stochastic components of ozone data are assumed as residues between observed ozone data and values computed from periodic model. Stochastic model presented in this research is basically a 3rd order autoregressive model. The developed models were validated using correlation coefficient between the model predicted values and observed values. This result suggests that this approach is a promising way to forecast daily surface ozone with sufficient accuracy

Estimation of daily surface ozone using periodic and stochastic modeling in Chennai region

293-302The present study deals with the modeling and forecasting of surface ozone time series in an urban area. First, an analysis of the systematic components (periodicity and stochastic components) was performed. Subsequently, prediction model for the daily surface ozone series was developed. In the recent years, there was no permanent measurement of surface ozone at this site, so surface ozone was measured from June 2011 to September 2012 at the urban site Koyembedu, Chennai (the capital of Tamil Nadu), India. Daily cumulative ozone data series was obtained by hourly instantaneous data. It was found, using Mann-Kendall test, that the data series is free of trend. The periodicity of ozone data was analyzed using Fourier Transform method. Stochastic components of ozone data are assumed as residues between observed ozone data and values computed from periodic model. Stochastic model presented in this research is basically a 3rd order autoregressive model. The developed models were validated using correlation coefficient between the predicted values and measured values. The spectrums of series exhibit 100 days period of daily surface ozone and implies that the pattern in the series is repeated every 100 days. The correlation coefficient (R) of this model delivers 0.810 and can provide mean bias error (MBE) = 0.85, and root mean square error (RMSE)=0.83. The result suggests that this approach is good for estimating daily surface ozone with sufficient accuracy

Crystal structure, DFT study, Hirshfeld analysis and optical third order nonlinear properties of new 1-naphthylaminium hydrogen fumarate salt

This study reports the crystal structure and its supramolecular framework, quantum chemical calculations and nonlinear optical properties of 1-naphthylaminium hydrogen fumarate salt. The supramolecular self-assembly of fumarate anions and 1-naphthylaminium cation of the salt is primarily stabilized by N-H…O, O-H…O and C-H…O interactions. The construction of strong hydrogen bonds such as N-H…O and O-H…O produces two-dimensional corrugated sheet parallel to (010) plane, which resembles a supramolecular grid type architecture in the crystal structure. Two weak C-H…O interactions interlink the parallel (010) supramolecular sheet generating a three-dimensional molecular network. The molecular stability of the experimentally determined structure is theoretically optimized by DFT quantum chemical calculations using 6-31G(++) basis set. The relative molecular interaction-based charge distribution and the chemical reactivity of the titled salt were identified using electrostatic potential contouring and HOMO-LUMO maps. The crystal structure is subjected to Hirshfeld surface analysis to gain better understanding on the intermolecular interactions exhibited by the molecules. The optical nonlinearities of the titled salt are examined using Z-scan experimentation, the optical nonlinear refractive index and optical nonlinear absorption coefficient is estimated by closed and open aperture Z-scan methods. The observed nonlinear values are quite comparable to the conventional optical nonlinear values

Growth, structural, optical, thermal and dielectric properties of a novel semi-organic nonlinear optical crystal: Dichloro-diglycine zinc II

Dichloro-diglycine zinc II (DCDGZ II), a semi-organic nonlinear optical material has been synthesized and single crystals were grown from the aqueous solution up to dimensions 20×10×3 mm3. The title compound, DCDGZ II (C4H10Cl2N2O4Zn·H2O) crystallizes into monoclinic structure with the space group of C2/c. The unit-cell parameters were found to be a=14.4191(7), b=6.9180(2), c=12.9452(6) Å and Z=4. In the crystal structure, DCDGZ II layer is building up alternatingly with layers of water in which the zinc ions lie on a twofold axis. Theoretical calculations for polarizability, which are useful for device fabrication were made using Clausius–Mosotti equation and Penn analysis and the results were compared. Fourier transform infrared (FTIR) spectroscopic studies were performed for the identification of the different functional groups presented in the compound. The UV–vis–NIR absorption spectrum reveals that the lower UV cut-off wavelength is 240 nm. The optical band gap of the crystal was estimated as 2.2 eV. The surface morphology, thermal behaviour, dielectric properties have been studied using SEM, TG/DTA and LCR HITESTER analyzer. The nonlinear optical property of the crystal was also confirmed using Kurtz powder technique

Studies on the Growth, Optical, Thermal and Physical Properties of an Efficient Second Order Nonlinear Optical Organic Crystal: 2-Amino-5-Chloropyridinium- Trifluoroacetate for Optoelectronic and Photonic Device Applications

763-772The novel organic single crystal 2-amino-5-chloropyridinium-trifluoroacetate (2A5CTFA) has been synthesized and grown successfully using methanol as solvent by continuous slow evaporation technique. The X-ray diffraction results reveals that the crystal 2-amino-5-chloropyridinium-trifluoroacetate crystallizes into monoclinic crystal system with the noncentrosymmetric space group Pc. The vibrational spectrum of the sample by FTIR and FT-RAMAN study confirms the characteristic functional groups of the 2A5CTFA crystal. The optical absorption spectrum shows 85% of transmittance in the entire UV-Vis-NIR region with cut-off wavelength at 345 nm. The crystal has a thermal stability of 137° C without any major weight loss in the TG curve. The photoluminescence spectrum of the crystal has a prominent violet emission peak centered at 388 nm. The dielectric behavior of the crystal measured with various frequencies at different temperatures reveals the normal behavior for optical materials. The second order NLO effect from the crystal is confirmed by the emission of green signal from the crystal upon tested with the aid of Kurtz powder analysis using Nd:YAG laser. The laser induced surface damage threshold value of the crystal is found to be 1.05 GW/cm2. Overall, the outlined properties of the grown crystal makes it suitable for opto-electronic and nonlinear optical device applications

Synthesis, structural and optical characterisation of cadmium sulphide nanoparticles

448-452Cadmium sulphide nanoparticles of uniform size have been synthesized at room temperature via wet chemical precipitation method using cadmium chloride and sodium sulphide with methanol as capping agent. The microstructure and morphology of the synthesized CdS nanoparticles have been characterized by X-ray diffraction and scanning electron microscopy analysis. XRD pattern reveals that as-synthesized CdS nanoparticles exhibit both sphalerite and wurtzite phases. The size of the particles calculated by Debye Scherrer formula according to the XRD spectra has been found to be about 13-17 nm. X-ray peak broadening analysis has been used to calculate the crystalline size and lattice strain by the Williamson-Hall (W-H) plot. The optical properties of the sample have been studied by UV-Visible and photoluminescence spectroscopy. The existence of blue shift in UV-visible spectroscopy reveals the quantum confinement effect of CdS nanoparticles. The photoluminescence spectrum shows two broad bands centered at 422 and 538 nm

Growth and microhardness studies of mixed crystals of (NH₄)₂SbF₅-K₂SbF₅

260-263Mixed crystals of (NH4)2SbF5-K2SbF5 , an electro-optic material have been grown by isothermal evaporation technique. Powder X-ray diffraction method has been used for structural identification and determination of lattice parameters. Load dependent microhardness measurements on this crystal reveal the mechanical behaviour of the material. The work hardening co-efficient and the yield strength of the material were found to be 11.66 and 2.058 Mpa, respectively