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).
Optically transparent single crystals of 2-amino 4-methylpyridinium salicylate were successfully grown by slow evaporation solution growth technique at room temperature. The grown crystal was characterized by various characterization techniques such as single crystal X-ray diffraction, Fourier transform infrared microscopy, optical, dielectric and Z-scan studies. The presence of various functional groups was identified by Fourier transform infrared technique. UV-Vis-NIR studies implied the absence of absorption in the visible region. Dielectric studies were carried out in the frequency range from 50 Hz to 5 MHz. Thermogravimetric/differential thermal analysis and nuclear magnetic resonance spectra studies were also performed for the grown crystal. Nonlinear refractive index, absorption coefficient and third order nonlinear optical susceptibility of the crystals were evaluated by Z-scan studies.
L. Chandra, J. Chandrasekaran, K. Perumal, B. Babu and V. Jayaramakrishnan
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.
S. Balaprabhakaran, J. Chandrasekaran, B. Babu, R. Thirumurugan and K. Anitha
Hexamethylenetetramine succinate was synthesized and good quality single crystals with the size of 14 mm × 6 mm × 4 mm were grown by the slow evaporation solution growth technique at room temperature. The single crystal XRD revealed that the grown crystal belongs to the monoclinic system with the space group of P21/c. The presence of functional groups in the crystal was identified using FT-IR technique. The optical behavior was examined through UV-Vis-NIR studies. The photoconductivity study exhibited the positive photoconductivity nature of the grown crystal. Microhardness studies revealed the soft nature of the crystal. The nonlinear refractive index (n2), nonlinear absorption coefficient (β) and third order nonlinear optical susceptibility χ(3) of the crystals were measured by Z-scan studies.
A. Mahudeswaran, A. Jeeva, J. Chandrasekaran and P.S. Vijayanand
In this article, we report the synthesis and characterization of silver dispersed poly(m-toluidine-co-2-bromoaniline) copolymer synthesized by chemical oxidative polymerization method. The synthesized copolymer composites were subjected to different analytical characterization methods, such as FT-IR, UV, XRD, SEM, photoluminescence and electrical conductivity studies. All the polymer samples are found to be soluble in common organic solvents. UV absorption spectra show a red shift when silver nanoparticles are dispersed in the copolymer. The characteristic peaks observed in FT-IR spectra confirm the formation of the copolymer. XRD pattern reveals the crystalline nature of the copolymer composites and sharp peaks in the spectra confirm the presence of silver particles. The silver nanoparticles change the surface morphology in the form of perfect encapsulation. The electrical conductivity of the polymer composites is found to vary from 10−4 S/cm to 10−6 S/cm. PL study reveals the charge transfer between the copolymer and the silver particles.
B. Babu, J. Chandrasekaran, S. Balaprabhakaran and P. Ilayabarathi
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.