J. Chandrasekaran

Investigation on growth, structure and characterization of succinate salt of 8-hydroxyquinoline: an organic NLO crystal.

8-Hydroxyquinolinium succinate (8-HQSU) has been synthesized and single crystals were grown from ethanol solvent by employing the technique of slow evaporation at room temperature. The structure of the grown crystal has been elucidated by single crystal X-ray diffraction analysis. It reveals that 8-HQSU crystallizes in monoclinic system with non-centro symmetric space group P2(1). FTIR, 1H and 13C NMR spectral investigations have been carried out to identify the vibrational modes of various functional groups and placement of proton and carbon in the 8-HQSU compound, respectively. UV-vis-NIR transmission spectrum shows the cutoff wavelength around 357 nm. In addition, a photoluminescence spectral analysis was carried out for 8-HQSU crystals. The thermal properties of crystals were evaluated from TGA and DTA techniques and the crystal was found to be stable up to 145°C. The dielectric studies show that the dielectric constant and dielectric loss decrease exponentially with frequency at different temperatures. Photoconductivity studies were carried out on the grown crystals it reveals the positive photo conducting nature. Powder second harmonic generation property of the crystal was confirmed by Kurtz and Perry powder SHG technique and it is found to be 1.3 times greater than that of KDP.

Synthesis, crystal growth and physiochemical characterization of organic NLO crystal: L-ornithinium dipicrate (LODP).

L-ornithinium dipicrate (LODP) has been synthesized and good quality single crystals were grown by slow evaporation method at room temperature. Single crystal XRD confirms that the grown crystal belongs to the monoclinic system with the noncentrosymmetric space group P21. Powder X-ray diffraction study confirms the crystalline nature of the compound. FTIR spectral analysis confirms the functional group in the synthesized compound. Thermogravimetric and differential thermal analyses reveal the thermal stability of the crystal. The optical absorption spectrum shows the absence of absorption between 475 nm and 800 nm. The dielectric measurements were carried out to estimate the dielectric parameters of the grown crystal in the frequency range from 50 Hz to 5 MHz at various temperatures. The second harmonic property has been investigated by Kurtz-Perry powder technique. The relative SHG efficiency of LODP is found to be 14.57 times greater than that of the reference material KDP.

Growth and characterization of hexamethylenetetramine crystals grown from solution

Organic nonlinear optical single crystals of hexamethylenetetramine (HMT; 10 × 10 × 5 mm3) were prepared by crystallization from methanol solution. The grown crystals were subjected to various characterization techniques such as single crystal XRD, powder XRD, UV-Vis and electrical studies. Single crystal XRD analysis confirmed the crystalline structure of the grown crystals. Their crystalline nature was also confirmed by powder XRD technique. The optical transmittance property was identified from UV-Vis spectrum. Dielectric measurements were performed as a function of frequency at different temperatures. DC conductivity and photoconductivity studies were also carried out for the crystal. The powder second harmonic generation efficiency (SHG) of the crystal was measured using Nd:YAG laser and the efficiency was found to be two times greater than that of potassium dihydrogen phosphate (KDP).

Optical, structural and electrical properties of pure and urea doped KDP crystals

Single crystals of good optical quality, made of potassium dihydrogen phosphate (KDP) doped with urea were grown by slow evaporation solution growth technique at a constant temperature of 35 °C. Optical absorption and dielectric properties were studied for pure and urea doped KDP crystals. Using powder XRD studies, crystalline nature of pure and urea doped KDP crystals was confirmed. AC conductivity was measured for the grown crystals. DC electrical conductivity and photoconductivity studies were carried out for pure and urea doped KDP crystals and the differences caused by the dopant were also discussed.

Growth, physicochemical and quantum chemical investigations on 2-amino 5-chloropyridinium 4-carboxybutanoate – an organic crystal for biological and optoelectronic device applications

Optically transparent organic single crystals of 2-amino 5-chloropyridinium 4-carboxybutanoate (2A5C4C) with sizes of 7 × 4 × 2 mm3 were grown by a slow evaporation solution growth technique at room temperature using methanol solvent. The lattice parameter values of the crystals were evaluated by single crystal XRD; the results confirmed that 2A5C4C crystal belongs to the orthorhombic system with cell parameters of a = 5.1858 A, b = 14.501 A and c = 15.963 A. The crystalline phases and quality of the grown crystals were ascertained by powder XRD and high resolution XRD (HRXRD) studies, respectively. The crystal structure and various functional groups present in 2A5C4C were confirmed by 1H, 13C NMR and FTIR analysis. The optical absorption, transmittance and lower cutoff wavelength were identified by UV-Vis-NIR studies. The optical band gap was estimated from the Tauc plot and was found to be about 3.68 eV. The charge transport mechanism and photoconducting nature of 2A5C4C were analyzed using dielectric and photoconductivity studies, and the obtained results were compared with previously reported values. In order to analyze the thermal and mechanical stability properties of the 2A5C4C crystal, TG/DTA and Vickers microhardness studies were performed. The laser-induced surface damage threshold values for the grown crystal were measured using a Nd:YAG laser. Powder SHG analysis was also carried out for powder samples using the Kurtz and Perry powder second harmonic generation (SHG) technique; the results were compared with KDP as a reference. The theoretical molecular electrostatic potential, HOMO–LUMO, natural bonding orbital analysis (NBO) and first hyperpolarizability values of the 2A5C4C molecule were calculated and discussed in detail. Moreover, the hydrogen bonded charge transfer crystal was screened for its pharmacological antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2) radicals.

Investigation on optical, electrical and etching properties of 2-aminopyridinium 4-aminobenzoate: A phase matchable organic single crystal for optoelectronic device applications

Abstract NLO active 2-aminopyridinium 4-aminobenzoate (APAB) single crystals were successfully grown by the standard slow evaporation technique. The crystallinity of the grown crystals was analyzed through X-ray diffraction (XRD) measurements. Fourier transform infrared (FT-IR) spectroscopic studies were also performed for the identification of different modes present in the compound. The UV-Vis absorption and transmittance spectra were recorded for the grown crystal and the optical band gap was calculated. Birefringence and etching studies were also carried out. The dielectric study showed that the dielectric constant decreased with an increase in frequency. The photoconductivity study revealed its positive photoconducting nature. Theoretical HOMO LUMO investigations were also made for the crystal. The relative SHG efficiency of the material was investigated by the Kurtz and Perry powder technique. The phase matching property of the crystal was studied through the SHG dependence of average particle sizes.

Characterization of WMoO3 Thin Films and its n-WMoO3/p-Si Junction Diodes Via JNS Pyrolysis Technique

Abstract The jet nebulizer sprayed tungsten doped molybdenum trioxide (WMoO3) thin films and its P-N junction diode parameters have been studied for different doping concentrations (0, 3, 6 and 9 wt.%) of tungsten (W). The prepared films were studied by XRD, SEM, EDX, UV and I-V. The structural analyses of XRD and SEM revealed that the WMoO3 films depicted the orthorhombic structure in polycrystalline nature and showed the sub-microsized plate and flake-like structures on the surface. The presence of the elements such as W, Mo and O in the WMoO3 films prepared by jet nebulizer spray (JNS) pyrolysis technique was confirmed by the EDX spectra. From UV-vis analysis, the absorbance decreases up to 3 wt.% of WMoO3 then increases. 3 wt.% WMoO3 film exhibited the minimum band gap energy. The electrical property from I-V represents that the maximum average conductivity obtained as 5.70169×10−12 S/cm for 3 wt.% WMoO3 film. From the I-V measurements in darkness and under the illumination, the different diode parameters of ideality factor (n), barrier height (Φb) and sheet resistance (Rs) of n-WMoO3/p-Si were examined using J-V, Cheung’s and Norde methods.

Structural, morphological, optical and electrical properties of PANI: Mo13O33 composite prepared by in-situ chemical oxidative method—application to p–n junction diode

Polyaniline (PANI) composites were prepared with PANI and molybdenum oxide by in-situ chemical oxidative method. The prepared samples were characterized through FT-IR, XRD, UV–Vis, and SEM with EDS techniques. Electrical studies were also carried out for the pure PANI and composite samples. The presence of functional groups PANI: Mo13O33 composite is confirmed through related FT-IR spectra. Molybdenum oxide particles incorporated with PANI matrix is confirmed through the XRD analysis. The UV–Vis spectra reveal that the bandgap values of the composite samples are inversely proportional to weight percentage of molybdenum oxide. SEM images show the formation of rock shape and plate like images in Pure PANI and molybdenum oxide, respectively. The EDS spectra clearly show the presence of C, N, O and Mo in the prepared composite samples. The electrical conductivity results show the semiconducting nature of pure PANI and composite samples. From I–V characterization, it is observed that the p-PANI: Mo13O33/n-Si composite samples have non-linearity behavior in forward bias condition. Among the composite samples, PANI: Mo13O33 (20%) shows better non-linearity behavior owing to the presence of rectifying effect.

Experimental and Computational Perspectives on Bis(Creatininium) Succinate: An Efficient Organic Nonlinear Optical Material

Abstract In this work, combined experimental and computational investigations of a promising organic nonlinear optical (NLO) material, bis(creatininium) succinate (BCS), are reported. The optical quality single crystals of BCS were grown with the dimensions of 12×2×2 mm3. Single crystal X-ray diffraction analysis reveals that BCS crystallized in the orthorhombic system with non-centrosymmetric (NCS) space group F2dd. Vibrational modes of various BCS functional groups were confirmed by using FTIR and FT-Raman spectrum. UV-Vis-NIR spectrum shows that BCS crystal has low near-UV cut-off wavelength at 261 nm and optical transparency window in the visible and near-IR (261–1100 nm) region. Photoconductivity study has been carried out magnificently for grown crystals. The nonlinear optical property such as nonlinear refractive index (n2) and nonlinear absorption coefficient (β) have been investigated by z-scan technique. Density functional theory (DFT) studies were carried out to probe Mulliken charge analysis, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP) mapping and first order hyperpolarizability (β) for the optimized molecular structure. Experimental and computed vibrations were correlated well. All these characterization results endorse BCS as a suitable NLO candidate and are discussed in this work.

The Structural, Optical and Electrical Properties of Spin Coated WO 3 Thin Films Using Organic Acids

Tungsten trioxide (WO3) thin films were prepared incorporating various organic acid additives by the sol-gel spin coating technique. They were characterized by X-ray diffraction (XRD), UV-Visible analysis, scanning electron microscopy (SEM) and dc electrical conductivity. From XRD, the crystal phase, average grain size and structural parameters of WO3 thin films were found to vary owing to different water dissolved organic acid additives. The variation of optical conductivity and band gap energy was calculated from the UV-Visible analysis. The SEM studies revealed that the organic acids influenced the surface morphology of the microsized plates of tungsten oxides. The electrical conductivity at various temperatures correlated with the average grain size of the nanocrystallites of WO3 thin films.