M. Senthil Pandian

Growth and characterization of semi-organic third order nonlinear optical (NLO) potassium 3,5-dinitrobenzoate (KDNB) single crystals

The semi-organic single crystal of potassium 3,5-dinitrobenzoate (KDNB) was successfully grown by slow evaporation solution technique (SEST) at room temperature. The lattice parameters of the grown KDNB crystal were confirmed by single crystal X-ray diffraction. The functional groups of the KDNB crystal were confirmed by Fourier transform infrared (FTIR) spectroscopy analysis. The optical quality of the grown crystal was identified by UV-Vis NIR spectral analysis. The grown crystal has good optical transparency in the range of 410–1100 nm. In the photoluminescence spectrum, sharp broad emission peaks were observed, which indicate violet and blue emission. The photoconductivity study reveals that the grown crystal has a negative photoconductive nature. The thermal behaviour of the crystal has been investigated by thermogravimetric and differential thermal analysis (TG-DTA). Vickers microhardness analysis was carried out to identify the mechanical stability of the grown crystal and the indentation size effect (ISE) was explained satisfactorily by Hays–Kendalls approach and proportional specimen resistance model [PSRM]. A chemical etching study was carried out and the etch pit density (EPD) was calculated. Laser damage threshold (LDT) energy has been measured by using a Nd:YAG laser (1064 nm). The dielectric permittivity and dielectric loss as a function of frequency were measured for the grown crystal. The solid state properties such as plasma energy, Penn gap and Fermi energy were evaluated for the KDNB crystal using the empirical relation. These estimated values were utilized to report the electronic polarizability. This matches well to the value calculated from Clausius–Mossotti relation, Lorentz–Lorentz equation, optical band gap energy and coupled dipole method (CDM). The third-order nonlinear optical properties such as refractive index (n2), absorption co-efficient (β) and susceptibility (χ(3)) were studied using Z-scan technique at 632.8 nm of He–Ne laser.

Sol–gel synthesized mesoporous anatase titanium dioxide nanoparticles for dye sensitized solar cell (DSSC) applications

Hierarchically structured titanium dioxide nanoparticles were successfully synthesized by the sol–gel method. The synthesized nanoparticles were subjected to powder X-ray diffraction, UV–Vis DRS spectroscopy, Brunauer–Emmett–Teller method, Barrett–Joyner–Halenda analysis, field emission scanning electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray analysis. The powder X-ray diffraction pattern shows that the obtained particles are of anatase phase with good crystallite nature. The nitrogen adsorption and desorption isotherms show that the prepared material has surface area of 31.71 m2 g−1 and the pore size distribution analysis shows the average pore diameters of mesoporous TiO2 nanostructures to be 7.1 and 9.3 nm. The UV–Vis DRS spectrum shows that the TiO2 nanoparticles are having absorption in the ultraviolet region. The optical band gap of the nanoparticles is 3.2 eV. The morphological studies show the morphology of the particles as spherical in shape. The elemental compositions of TiO2 nanoparticles were confirmed by energy-dispersive X-ray spectrum analysis. The conversion efficiency of the solar cell was 3.415% with open-circuit voltage (Voc), short-circuit current (Jsc) and fill factor (FF) of 0.607 V, 13.206 mA cm−2 and 42.56%, respectively.

Bulk growth of organic non-linear optical (NLO) L-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) single crystals by Sankaranarayanan–Ramasamy (SR) method

Abstract Organic non-linear optical single crystals of L-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) are grown by Sankaranarayanan–Ramasamy (SR) method and slow evaporation solution technique (SEST) with the sizes of about 45 mm length, 15 mm diameter and 6 × 5 × 5 mm3, respectively. The grown crystals were characterised by single crystal X-ray diffraction to determine the crystallographic unit cell parameter values. The etch pit density of SEST and SR method grown LAPP crystals have been calculated using chemical etching analysis. The mechanical and optical properties of the SEST and SR method grown LAPP crystals are studied using Vickers microhardness and UV–vis NIR measurement, respectively. Laser damage threshold analysis has been made on cut and polished SEST and SR method grown LAPP crystal of 5 mm thickness. Photoconductivity study of LAPP crystal grown by SEST and SR method reveals positive photoconductivity nature. The thermal properties of the grown crystal were carried out by thermogravimetric and differential thermal analysis. The second-harmonic generation efficiency of LAPP crystal was determined using powder Kurtz–Perry technique and it was found to be 2.3 times that of standard potassium dihydrogen phosphate material.

Synthesis, crystal growth, physicochemical properties and quantum chemical investigations of a D–π–A type organic single crystal: 2-amino-5-nitropyridinium p-phenolsulfonate (2A5NPP) for nonlinear optical (NLO) applications

Efficient organic nonlinear optical (NLO) 2-amino-5-nitropyridinium p-phenolsulfonate (2A5NPP) single crystals have been grown by slow cooling method using methanol as a solvent. Single crystal X-ray diffraction (SXRD) analysis revealed the unit cell parameters of the grown crystal. The morphology of the grown crystal was identified by single crystal XRD analysis as well. The crystallinity of the title crystal was studied by powder X-ray diffraction (PXRD) analysis. The presence of functional groups was determined by FTIR spectral analysis. The optical transmittance revealed that the grown crystal is transparent in the visible and NIR region with a lower cutoff wavelength of 408 nm. The chemical etching analysis showed that the grown crystal has a lower etch pit density (EPD). The title compound is thermally stable up to 200 °C, as assessed by thermogravimetric (TG) and differential thermal analysis (DTA). The photocurrent (Ip) and dark current (Id) values were found to be 5.3 × 10−11 A and 3.3 × 10−11 A at 50 V, respectively, by photoconductivity analysis. A dielectric study was carried out to find the distribution of charges within the crystal. Theoretical calculations were performed using the B3LYP/6-311++G(d,p) level basis set. The structural parameters of 2A5NPP were studied using the DFT method and the calculated results were compared with the experimental values. The charge transfer characteristic of the title compound was studied by frontier molecular orbital (FMO) analysis. The first-order hyperpolarizability of the 2A5NPP molecule was found to be 2.9 × 10−29 e.s.u, which is 37 times higher compared to the reference urea molecule. The Mulliken charge of the obtained molecule was theoretically analyzed. Hydrogen bonding of the obtained molecule was confirmed by NBO analysis. The Kurtz–Perry powder technique was used to evaluate the second harmonic generation (SHG) efficiency of the title crystal and it was found to be 22 times that of the reference KDP material.

Crystal growth, structural, optical, thermal and dielectric studies of non-linear optical 2-amino-5-nitropyridinium nitrate (2A5NPN) single crystals

Abstract Single crystals of 2-amino-5-nitropyridinium nitrate (2A5NPN), semiorganic non-linear optical crystals have been grown by conventional slow evaporation solution technique using water as solvent. Optically good quality crystal having dimension up to 10 × 10 × 10 mm3 was grown. The single-crystal X-ray diffraction (XRD) studies confirm that 2A5NPN crystallises in monoclinic crystal system with the space group P21/n and the morphology of the grown crystal was identified. The powder XRD pattern of the grown crystal was recorded. Fourier transform infrared (FTIR) measurement was carried out to identify the various functional groups present in the compound. The optical property of the grown crystal was analysed using UV–Visible Near Infrared analysis. The thermal stability of the compound was ascertained using thermogravimetric and differential scanning calorimetric analysis. The etch pit density of the grown crystal was calculated by chemical etching analysis using dimethyl sulphoxide as an etchant. The frequency and temperature dependent dielectric constant and dielectric loss of the grown crystal was analysed. The photoluminescence analysis was carried out.

Growth of organic non-linear optical 4-Hydroxy L-Proline (HLP) single crystal by conventional solution method and its structural, vibrational, optical and mechanical characterisations

Good quality and transparent organic non-linear optical crystal 4-Hydroxy L-Proline (HLP) was grown by slow evaporation solution technique (SEST), which has the size of 10 × 5 × 5 mm3. The crystal system was identified and lattice parameters were measured by single-crystal X-ray diffraction. Functional groups of HLP are identified by FTIR spectrum measurement. The optical quality of the grown crystal was measured by UV–vis–NIR analysis. The mechanical stability of the grown HLP crystal was tested by Vickers microhardness analysis and the work hardening co-efficient value was also calculated. The dielectric constant and loss studies were carried out at various temperature to establish the dielectric nature of the HLP crystal. The frequency and temperature response of the dielectric property of the crystal was measured. The second order non-linear optical (NLO) property of the crystal was confirmed by powder Kurtz-Perry technique.

The effect of different π-bridge configuration on bi-anchored triphenylamine and phenyl modified triphenylamine based dyes for dye sensitized solar cell (DSSC) application: A theoretical approach

Twenty eight bi-anchored triphenylamine (TH-1 to TH-14) and phenyl modified triphenylamine (PH-TH-1 to PH-TH-14) based metal free organic dyes are designed for DSSC application. The electronic effect of different π-bridge configurations in donor-π-bridge-acceptor (D-π-A)2 structure was theoretically simulated and verified using density functional theory (DFT) and time dependent density functional theory (TD-DFT). The triphenylamine and phenyl modified triphenylamine groups are used as donor and cyanoacrylic acid group is used as acceptor. Thiophene and cyanovinyl groups are used as π-bridge. The ground state molecular structure was optimized by density functional theory and the electronic absorption spectra were calculated by time dependent density functional theory. The light harvesting efficiency (LHE), dye regeneration energy (ΔGreg) and electron injection energy (ΔGinject) are determined by computational examination. It is observed that, when the number of π-bridge increases, the band gap of the dye decreases. Also the absorption maximum and molar extinction coefficient of the dyes are increased. Theoretical result shows that the thiophene-cyanovinyl and thiophene-thiophene-cyanovinyl-cyanovinyl configurations give broader and red shifted absorption spectrum compared to other configurations. Also the results of phenyl modified triphenylamine (PH-TH) dyes clearly show better absorption and dye regeneration energy compared to TH dyes.

Growth of organic nonlinear optical (NLO) ammonium D,L-tartrate (AMT) single crystal by conventional and unidirectional method and its characterization

Abstract High-quality, transparent uniaxial ammonium D,L-tartrate (AMT) single crystal having dimension of 15 mm diameter and 60 mm length was grown by Sankaranarayanan–Ramasamy (SR) method with a growth rate of 1 mm per day. Single-crystal X-ray diffraction was carried out to confirm the AMT crystals. The presence of functional groups of crystallized AMT molecules were identified by FTIR spectral analysis. The dislocation density of the AMT crystals grown by slow evaporation solution technique (SEST) and SR method were characterized using chemical etching analysis. A comparative laser damage threshold analysis was made on the AMT crystals grown by conventional and SR method which shows that the crystal grown by SR method has higher damage threshold. The SR method grown AMT crystal has higher microhardness and also higher optical transmittance compared to conventional method grown crystal. The thermal properties of the SEST and SR method grown AMT crystals were measured by photoacoustic spectrum analysis. The second harmonic generation efficiency of AMT was determined using the powder Kurtz–Perry technique.

Synthesis of 2-cyano 3-(4 dimethylaminophenyl) prop 2-enoic acid dye derived from 4-dimethylaminobenzaldehyde and methyl cyanoacetate and its properties

2-Cyano 3-(4-dimethylaminophenyl) prop 2-enoic acid was synthesized by the condensation of 4-dimehylaminobenzaldehyde and methyl cyanoacetate followed by purification with column chromatography. 1H Nuclear Magnetic Resonance, 13C Nuclear Magnetic Resonance, and Fourier Transform Infrared studies revealed the structure. The electronic properties of the molecules were analysed by ultraviolet–visible absorption spectroscopy. Cyclic voltammetric analysis of the compound was influenced by scan rate. Thermal analysis of the compound was undertaken using TG-DTA.

Nanorods and nanoparticles of titanium dioxide and their use in dye sensitized solar cells

Mesoporous TiO2 nanorods/nanorods were successfully synthesized by hydrothermal process at 170 °C for 72 hr. The powder X-ray diffraction pattern shows large fraction of anatase phase with good crystalline behavior of the prepared materials. The specific surface area and pore volume of the synthesized material are about 84.83 m2/g and 0.1316 cc/g respectively. The morphological results show that the TiO2 nanorods had diameter of ~ 25 nm and the length of ~ 80 nm. The nanoparticles have 20 nm in size. The current-voltage curve shows that the synthesized TiO2 nanostructure results in 36.7 % higher solar cell efficiency than commercial P25.