Photoconductivity of solids

Novel report on γ-glycine crystal yielding high second harmonic generation efficiency

Peroxymonosulfate (PMS) is being extensively investigated as an eco-friendly oxidant and various activation methods of PMS have been investigated. Here we demonstrated a new method of catalytic PMS activation, which employed amino acids as both a visible light sensitizer and a substrate to be degraded. Although PMS and amino acids do not absorb any visible light, the surface adsorption of amino acids on titania formed charge-transfer complexes that absorb visible light (λ > 420 nm). Serine and histidine were employed as main target amino acids and their surface complexes on TiO2 were characterized by various spectroscopic methods The ligand-to-metal charge transfer between amino acids and TiO2 enabled the absorption of visible light and the subsequent electron transfer catalytically activated PMS with generating sulfate radicals which were detected by electron paramagnetic resonance analysis. Based on various scavenger tests, amino acids seem to be degraded mainly by sulfate radical (radical pathway) and by a non-radical pathway (PMS serving primarily as an electron acceptor) to some extent. Amino acids were degraded with producing ammonium as a sole nitrogenous product in this process, whereas most advanced oxidation processes of amino acid generate not only ammonium but also nitrate and nitrite. The visible light-induced charge transfer characteristics of the amino acid-TiO2 complexes were demonstrated by the photoelectrochemical characterizations and the time-resolved laser spectroscopic analysis.

Visible light-induced catalytic activation of peroxymonosulfate using heterogeneous surface complexes of amino acids on TiO2

Semi-organic nonlinear optical (NLO) 2-amino-5-nitropyridinium bromide (2A5NPBr) single crystals have been grown by slow evaporation solution technique (SEST) with the growth period of 60 days. The single-crystal XRD analysis confirms the unit cell parameters of the grown crystal. The crystallinity of grown 2A5NPBr was analyzed by powder X-ray diffraction (PXRD) measurement. The presence of functional groups of 2A5NPBr crystal was confirmed by Fourier transform infrared (FTIR) spectrum analysis. The optical transmittance of the grown crystal was analyzed by UV–Vis–NIR analysis. It shows good transparency in the visible and NIR region and it is favorable for nonlinear optical (NLO) device applications. The chemical etching study was carried out and it reveals that the grown crystal has less dislocation density. The photoconductivity study reveals that the grown crystal possesses positive photoconductive nature. The thermal stability of the crystal has been investigated by thermogravimetric (TG) and differential thermal analysis (DTA). The dielectric constant and dielectric loss as a function of frequency were measured. The electronic polarizability (α) of 2A5NPBr molecule has been calculated theoretically by different ways such as Penn analysis, Clausius–Mossotti relation, Lorentz–Lorenz equation, optical bandgap, and coupled dipole method (CDM). The obtained values of electronic polarizability (α) are in good agreement with each other. Laser damage threshold (LDT) of 2A5NPBr crystal has been measured using Nd:YAG laser with the wavelength of 1064 nm. Third-order nonlinear optical property of the grown crystal was studied by Z-scan technique using He–Ne laser of wavelength 632.8 nm.

Crystal growth and characterization of semi-organic 2-amino-5-nitropyridinium bromide (2A5NPBr) single crystals for third-order nonlinear optical (NLO) applications

The compound preparation, crystallization, spectroscopic characterizations and third order nonlinear optical properties of an organometallic nonlinear optical cesium hydrogen tartrate (CT) single crystal is reported. The title compound was crystallized in orthorhombic crystal system with noncentrosymmetric space group P212121. The functional group and their vibrational states were analyzed by FTIR spectroscopy. The optical band gap was found to be 5.98 eV. The recorded photoluminescence was evident for inter-band defect energy levels in the title crystal. The calculated CIE coordinates on RGB color gamut shows the blue light emitting capacity of CT crystal. Nonlinear optical properties of the title material under continues wave and pulsed laser excitation is reported for the first time. The intensity dependent refractive index (n2), absorption coefficient (β) and third order nonlinear optical susceptibility (χ(3)) of CT under continues wave excitation were found to be 0.569 × 10−8 (cm2W−1), 0.265 × 10−4 (cmW−1) and 8.78 × 10−7 (esu) respectively. The variation of β was studied under pulsed excitation with varying peak intensities. The values were found to be 0.72 × 10−10 (mW−1), 0.68 × 10−10 (m/W−1) and 0.64 × 10−10 (mW−1) for peak intensities of 0.61 × 10−12 (Wm−2), 1.23 × 10−12 (Wm−2) and 2.46 × 10−12 (Wm−2) respectively which confirms the presence of effective two photon absorption in CT. The optical limiting threshold at three intensities mentioned above were found to be 1.36 × 10−12 (Wm−2), 1.55 × 10−12 (Wm−2) and 1.79 × 10−12 (Wm−2) respectively. The value of Meyer’s index (n) by Vickers micro hardness test was found to be 3.74 and it shows CT crystal belongs to soft material category. The thermogravimetric analysis showed that the CT crystal is thermally stable up to 215 °C. The dielectric constant (e), dielectric loss (tan δ), AC and DC conductivity as a function of frequency and temperature were studied. The superior mechanical, thermal and dielectric properties with intensity tunable optical nonlinearity of cesium hydrogen tartrate single crystal promotes it as a promising candidate for optical limiting application.

Intensity tunable optical limiting behavior of an organometallic cesium hydrogen tartrate single crystal

Nonlinear optical single crystal of organic amino acid L-Serine (LS) was grown by slow evaporation technique. Solubility study of the compound was measured and metastable zone width was found. Single crystal X-ray diffraction study was carried out for the grown crystal. The linear and nonlinear optical properties of the crystal were confirmed by UV-Vis analysis and powder SHG tester. FT-IR spectrum was recorded and functional groups were analyzed. Vickers’ microhardness studies showed the mechanical strength of the grown crystal. Laser damage threshold value of the crystal was calculated. Photoconductivity studies reveal the conductivity of the crystal.

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Structural, Linear, and Nonlinear Optical and Mechanical Properties of New Organic L-Serine Crystal

Single crystals of pure and Lanthanum doped L-Alanine Tartrate were grown by slow evaporation method. The cell parameters were determined using single crystal X-ray diffraction method. To improve the physical properties of the LAT crystal, Lanthanum dopant was added by 2 mol%. ICP studies confirm the presence of Lanthanum in the grown LAT crystal. Transparency range of the crystal was determined using UV-VIS-NIR spectrophotometer. The functional groups of pure and doped LAT crystals were analyzed by FT-IR spectroscopy. Using Vickers microhardness tester, mechanical strength of the material was found. Dielectric studies of pure and doped LAT single crystals were carried out. The doped LAT crystal is found to have efficiency higher than that of pure LAT crystal.

https://downloads.hindawi.com/archive/2013/613092.pdf

Growth and Characterization of Pure and Doped L-Alanine Tartrate Single Crystals

Single crystals of L-serine phosphate (LSP) were grown by slow evaporation technique. The optical studies reveal the transparency of the crystal in the entire visible region. Grown crystal was subjected to single crystal XRD diffraction technique. Thermal studies of LSP confirm the thermal stability of the crystal and it is stable up to 210°C. The functional groups and optical behaviour of the crystal were identified from FT-IR and UV-Vis analysis. The crystals were also characterized by microhardness and photoconductivity to determine the mechanical strength and the optical conductivity. Laser damage threshold and nonlinear optical activity of the grown crystal were confirmed by Q-switched Nd : YAG laser beam.

/pdf/optical-thermal-and-mechanical-properties-of-l-serine-2i178rio1v.pdf

Optical, Thermal, and Mechanical Properties of L-Serine Phosphate, a Semiorganic Enhanced NLO Single Crystal

L-Serine Acetate (LSA) single crystal was successfully grown by slow solvent evaporation technique. Cell parameters are determined by single crystal X-ray diffraction study. Various functional groups presented in the crystal were confirmed by FT-IR Analysis. The transmission of the crystal was found by UV analysis and band gap energy of the grown crystal was also calculated. Dielectric constant and dielectric loss of the crystal was determined using dielectric studies. Hardness studies were employed to characterize the mechanical strength of the grown crystal. Nonlinear optical property has been studied by Kurtz Perry technique. The second harmonic generation conversion efficiency of the grown crystal shows the suitability of the grown crystal for frequency conversion applications.Due to a publication oversight, the PDF file of this article was accidentally substituted by a PDF file containing a different article. The PDF file of the correct article was published on June 12, 2013. AIP Publishing would like to apologize to the authors and editors for any inconvenience this may have caused.

K. Rajesh

Papers

Structural, Linear, and Nonlinear Optical and Mechanical Properties of New Organic L-Serine Crystal

Growth and Characterization of Pure and Doped L-Alanine Tartrate Single Crystals

Optical, Thermal, and Mechanical Properties of L-Serine Phosphate, a Semiorganic Enhanced NLO Single Crystal

Growth, optical, mechanical and electrical properties of L-serine acetate: A promising semiorganic nonlinear optical crystal

Growth and characterization of l-histidinium 2-nitrobenzoate [LH2NB(I)]—A promising non linear optical single crystal