R. Sankar

Preparation and characterization of rare earth (Pr, Nd) doped ZnO nanoparticles

Pr and Nd doped ZnO nanoparticles are prepared by simple chemical route and precursors used are ZnCl<inf>2</inf> and NaOH. From XRD patterns, the particles size are found to be 15, 16, 17 nm for 1 wt%, 2 wt% and 3 wt% of Pr doped ZnO nanoparticles respectively and 17,18, 19 nm for 1 wt%, 2 wt% and 3 wt% of Nd doped ZnO nanoparticles respectively. Absorption studies are carried out from 200 to 800 nm. The ZnO cut off wavelength of both the Pr and Nd doped are found near 346 nm. Pr³⁺ absorption peaks are found at 446, 463 and 589 nm and these correspond to transitions from the ground state of ³H<inf>4</inf> to ³P<inf>2</inf>, ³P<inf>1</inf> and ¹D<inf>2</inf> and Nd³⁺ absorption peaks are found at 520, 578, 738 and 799 nm and these correspond to transitions from the ground state of ⁴I<inf>9/2</inf> to ⁴G<inf>7/2</inf>, ⁴G<inf>5/2</inf> + ²G<inf>7/2</inf>, ⁴S<inf>3/2</inf> + ⁴F<inf>7/2</inf>, ⁴F<inf>5/2</inf> + ²H<inf>9/2</inf>. Photoluminescence studies of the sample are also made and excitation wavelength was 325 nm. Emission bands characteristic of Pr³⁺ are observed at 450, 469, 482 and 493 nm for samples, which corresponds to ³H<inf>4</inf>−>³P<inf>2</inf>, ¹I<inf>6</inf>−>³H<inf>4</inf>, ³P<inf>1</inf>−>³H<inf>4</inf> and ³P<inf>0</inf>−>³H<inf>4</inf> transitions, respectively. Emission bands characteristic of Nd³⁺ are observed at 450, 473, 480 and 530 nm for samples, which corresponds to ²P<inf>3/2</inf> −> ⁴I<inf>13/2</inf>, ²P<inf>3/2</inf>−>⁴I<inf>15/2</inf>, ²P<inf>1/2</inf>−>⁴I<inf>11/2</inf> and ⁴G<inf>7/2</inf>−>⁴I<inf>9/2</inf> transitions, respectively. FTIR spectra show the Zn-O stretching at 535 cm⁻¹ for the Pr doped and at 544 cm⁻¹ for Nd doped ZnO nanoparticles. High resolution SEM images are taken and morphology of the particles was reported.

GROWTH AND CHARACTERIZATION OF A NEW SEMI-ORGANIC NON-LINEAR OPTICAL CRYSTAL L-ARGININE HYDROCHLOROFLUORIDE MONOHYDRATE (LAHClF)

A new non-linear optical mixed crystal of L-arginine hydrochlorofluoride monohydrate (LAHClF) has been grown by temperature lowering solution growth technique. The single crystal X-ray diffraction studies show that the LAHClF belongs to monoclinic crystal system. The optical transmittance of the crystal was studied by UV–Visible–NIR spectroscopy. Fourier transform infrared spectroscopy and thermal analysis were performed to study the molecular vibrations and thermal behavior of the crystals, respectively. The second harmonic generation intensity and laser damage threshold of the LAHClF crystal were measured. The mechanical strength of the material was determined by the Vickers hardness method.