J. Madhavan

Synthesis, growth and characterization of new borate-mixed crystals of type (NH4)1-xKxB5O8.

New borate-mixed crystals of type (NH4)1-x KxB5O8 were grown from aqueous solution by slow solvent evaporation method. The mixed crystals were confirmed by atomic absorption studies (AAS) and characterized by X-ray diffractometry (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman), optical absorption and solubility studies. The second harmonic generation efficiencies of the parent and mixed crystals were studied and compared with that of KDP.

Growth, thermal, dielectric and mechanical properties of L-phenylalanine–benzoic acid: A nonlinear optical single crystal

An efficient amino acid family nonlinear optical single crystal L-phenylalanine-benzoic acid (LPB) was conveniently grown by slow evaporation technique at room temperature. The crystal system and the lattice parameters were analyzed by single crystal X-ray diffraction studies. The grown crystal has excellent transmission in the entire visible region and its lower cut-off wavelength was found to be 248 nm. The SHG efficiency of the grown crystal was found to be 1.6 times higher than that of KDP crystal. The Laser damage threshold value of LPB has been found to be 6.5 GW/cm(2). The sample was thermally stable up to 134°C. Microhardness, dielectric and AC/DC conductivity measurements were made along (001) plane and reported for the first time. Microhardness studies revealed that the sample belongs to hard nature. Frequency dependent dielectric constant was measured for different temperatures and found maximum dielectric constant of 14 for 363 K. Photoconductivity studies of LPB divulged its negative photoconducting nature.

Effect of samarium (Sm3+) doping on structural, optical properties and photocatalytic activity of titanium dioxide nanoparticles

ABSTRACT The current work reports the hydrothermal preparation of pure TiO2 and Sm3+ ion-doped TiO2 nanoparticles and the influence of samarium ion doping in the TiO2 host lattice. The as-synthesized both pure and Sm3+-doped TiO2 nano samples were extensively characterized by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX) and UV–VIS spectroscopy. XRD pattern reveals the crystalline size and phase of the nanoparticles and the formation of spherical morphology was confirmed by HR-TEM observation. The incorporation of Sm in TiO2 is confirmed by EDX. The optical properties of TiO2 and Sm3+:TiO2 nanoparticles have been studied using diffuse reflectance spectroscopy analysis. The addition of the dopant ion markedly increases the bandgap from 3.39 to 3.46 eV. The photocatalytic activity of the crystalline as-synthesized nanoparticles was examined for the degradation of Rhodamine B induced by UV irradiation and the degradation efficiency is also reported.

Transparent ZnO–PVA binary composite for UV-A photo detector: optical, electrical and thermal properties followed by laser induced fluorescence

A compatible high performance UV-A sensor has been developed using poly(vinyl alcohol) (PVA)/ZnO membrane on an ITO substrate. The current challenges on UV-A photo detector have been overcome with the optimized performance of the binary composition through combining the wide-range of UV-A light photo-response, high sensitivity and quick response. This paper presents the electrical and optical properties of ZnO/PVA nanocomposites. It deals with the experimental correlation between complex optical conductivity and complex dielectric function. The ZnO filler is addressed to the modification in the band-structure, thermal properties and molecular orbital electron density. The defect states formation and laser induced fluorescence of composites were also investigated for the first time.

Hollow ZnSnO 3 Crystallites: Structural, Electrical and Optical Properties

Zinc stannate (ZnSnO3) hollow cubic crystallites were successfully synthesized by hydrothermal reaction at 120 °C. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) studies were employed to characterize the structure and morphology of the as-synthesized ZnSnO3 crystallites and it is found that ZnSnO3 exhibits almost uniform cubic structure. The FT-IR analysis confirmed the functional groups. Dielectric constant and dielectric loss were found to decrease with increase in frequency. UV and Photoluminescence spectra analysis were also performed.

Theoretical and Experimental studies on nonlinear optical L-phenylalaninium maleate

Good quality single crystals of L-phenylalaninium maleate (LPM) were grown successfully by slow evaporation technique. The grown crystal was subjected to powder X-ray diffraction study at room temperature. From the powder XRD studies it was observed that the crystal belongs to monoclinic crystal system having non-centrosymmetry with P21 space group. Quantum chemical Density functional theoretical (DFT) computations were performed and the optimized structure parameters of LPM molecule calculated by DFT (B3LYP) level with 6-31G (d,p) basis set were obtained. The optical absorption spectrum is used to study various linear optical parameters as a function of incident photon energy. It is found that LPM is a suitable material for NLO applications. HOMO-LUMO calculations were performed and the energy band gap was obtained.