V.B. Taxak

Synthesis, structural and optical properties of SrZrO3：Eu3＋phosphor

Abstract Eu 3+ activated Sr 1− x Eu x ZrO 3 ( x =0.01−0.04) phosphor with perovskite structure was successfully synthesized by using combustion method. The structure, morphology and optical properties of the material were characterized by X-ray diffraction, scanning electron microscopy and fluorescence spectrometry. The XRD results indicated that crystals of SrZrO 3 :Eu 3+ belongs to tetragonal perovskite system. The phosphor could be effectively excited by UV light and the emission spectra results indicated that reddish-orange luminescence of SrZrO 3 :Eu 3+ due to magnetic dipole transition 5 D 0 → 7 F 1 at 593 nm was dominant. Thus, the prepared phosphor showed remarkable luminescent properties which find applications in field emission display (FED) and plasma display panel (PDP) devices.

Luminescent Properties of ZnS:Eu2+ Nanocrystals

Europium-activated ZnS nanocrystals were synthesized by a low temperature tartaric acid assisted sol-gel method. The emission peak of Eu due to the 4f5d →4f 7 transitions at 480nm was observed in the emission spectra on excitation at 260nm. Scanning electron microscopy (SEM) investigations were carried out to understand surface morphological features and the particle size of the nanocrystals. The uniformity of phase of Eu doped ZnS nanocrystals was checked by X-ray diffraction (XRD) technique. In addition, the dependence of the luminescence intensity on Eu concentrations of the nanocrystals has also been discussed. The particle size of the nanocrystals was found to be 28nm.

Synthesis, photoluminescence and biological properties of terbium(III) complexes with hydroxyketone and nitrogen containing heterocyclic ligands.

The ternary terbium(III) complexes [Tb(HDAP)3⋅biq], [Tb(HDAP)3⋅dmph] and [Tb(HDAP)3⋅bathophen] were prepared by using methoxy substituted hydroxyketone ligand HDAP (2-hydroxy-4,6-dimethoxyacetophenone) and an ancillary ligand 2,2-biquinoline or 5,6-dimethyl-1,10-phenanthroline or bathophenanthroline respectively. The ligand and synthesized complexes were characterised based on elemental analysis, FT-IR and (1)H NMR. Thermal behaviour of the synthesized complexes illustrates the general decomposition patterns of the complexes by thermogravimetric analysis. Photophysical properties such as excitation spectra, emission spectra and luminescence decay curves of the complexes were investigated in detail. The main green emitting peak at 548nm can be attributed to (5)D4→(7)F5 of Tb(3+) ion. Thus, these complexes might be used to make a bright green light-emitting diode for display purpose. In addition the in vitro antibacterial activities of HDAP and its Tb(III) complexes against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and antifungal activities against Candida albicans and Aspergillus niger are reported. The Tb(3+) complexes were found to be more potent antimicrobial agent as compared to the ligand. Among all these complexes, [Tb(HDAP)3⋅bathophen] exhibited excellent antimicrobial activity which proves its potential usefulness as an antimicrobial agent. Furthermore, in vitro antioxidant activity tests were carried out by using DPPH method which indicates that the complexes have considerable antioxidant activity when compared with the standard ascorbic acid.

Photoluminescent properties of Tb3+ doped GdSrAl3O7 nanophosphor using solution combustions synthesis

AbstractA color tunable terbium doped GdSrAl3O7 nanophosphor has been synthesized at low temperature using solution combustion synthesis. The photoluminescent properties of nanophosphors have been explored by analyzing their excitation and emission spectra alongwith their decay curves. The emission spectra exhibit dominating green light at 544 nm due to 5D4→7F5 transition of Tb3+ ions in GdSrAl3O7 on excitation by UV light of 239 nm. Furthermore, the luminescence in Gd(1−x)SrAl3O7: xTb3+nanophosphors shifted from blue to green color by properly tuning the concentration of terbium ions. Decay curves indicate that non-radiative cross-relaxation is primarily responsible for concentration quenching phenomenon in the GdSrAl3O7 host. X-ray diffraction (XRD) analysis confirmed that single tetragonal phased nanophosphor could be readily obtained at low temperature 550°C. The smooth surfaced nanocrystals with particle size of 45 - 50 nm have also been examined by transmission electron microscopy (TEM). All these features augmented the probability of GdSrAl3O7: Tb3+ nanophosphor for potential applications in optical devices.

Citric Acid Assisted Sol-Gel Synthesis and Photoluminescence Characteristics of CaAl1.8Y0.2-xO4:xTb Nanoparticles

In recent years, rare earth ions-activated nanostructure materials have been attracting much interest due to the excellent luminescence and potential applications in luminescent devices and display equipment, such as lighting, field emission display (FED), cathode ray tubes (CRT), and plasma display panels (PDP) resolution[1-6]. In the present time, field emission display (FEDs) , plasma display panels (PDPs) are attracting deal of attention as new display technology . Scientist have undertaken investigations of the influence of particle size on the optical and electronic properties of nanocrystal materials of rare earth oxides [7-8]. The origion of nanoparticle research can be said to be in study of colloids ,their synthesis and characteristics. The quantum confinement and major changes observed in other properties have been the subject of intense research .The surface and interface of nanocrystal play an important role in the optical and electronic properties . Many phosphors have been made in nanophase by employing different techniques .