http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/183 Assistant Professor, PUC Campus, Aizawl 2026-04-29T11:22:38Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1010 Title: Effect of annealing on the luminescence properties of YVO4:Dy3+ phosphor on co-doping Pb2+ ions Authors: Devi, Ch Victory Abstract: Pb2+ co-doped YVO4:Dy3+ phosphors have been synthesized at a relatively low temperature of 120 C via ethylene glycol route. The samples are further annealed at 500 and 900 C. The prepared samples were characterized by XRD, SEM, spectra energy dispersive analysis of X-ray (EDAX) and photoluminescence spectroscopy. XRD patterns of all samples are well indexed with single tetragonal phase of YVO4. The emission intensity of Dy3+ is significantly enhanced on co-doping Pb2+ ions. The highest emission is obtained at 7 at.% Pb2+ for 900 C annealed samples. Both emission intensity and decay lifetime increases on annealing the samples from 500 to 900 C. On co-doping Pb2+ into YVO4:Dy3+ phosphors, the emission color falls near the white region and then shift towards yellow region on annealing from 500 to 900 C thereby indicating that annealing temperature play a role on tuning the color of the phosphors. As well as the emission color of the phosphors remain the same even on changing the excitation wavelengths from 280 nm, which would serve as potential phosphors for white emission in LED applications 2015-03-01T00:00:00Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1006 Title: Luminescence properties of Ln3+ doped BaMoO4 (Ln3+ = Sm3+ and Dy3+) phosphors under UV excitation Authors: Devi, Ch Victory Abstract: Ln3+ doped BaMoO4 (Ln 3+ = Sm3+ and Dy3+) nanoparticles have been synthesized successfully using ethylene glycol as a solvent. All the prepared samples are well indexed into the pure scheelite-type tetragonal structure of BaMoO4, the doping of trivalent ions (Ln3+) in to the bivalent host ions (Ba2+) sites of the BaMoO4 do not change the pure tetragonal structure of BaMoO4 although there is a charge difference between Ba2+ and Ln3+. The SEM image of the prepared BaMoO4 samples shows a number of uniform shuttle-like nanocrystalline with protrusion in the middle. The doping of Ln3+ ions do not change the morphology of the BaMoO4. The photoluminescence study has been carried in detail by measuring the excitation and emission spectra of the prepared samples. The excitation spectrum consists of a broad band with a maximum at about 268 nm thereby demonstrating the transfer of energy from MoO2- 4 groups to the doped Ln3+ ions. Yellow emission is dominated over blue in case of Dy3+ doped BaMoO4 and in Sm3+ doped BaMoO4 red emission dominated over other lights under UV excitation. The luminescence intensity is highest at 10 at.% Ln3+ under the UV excitation. Under this UV excitation BaMoO4: Sm3+ exhibits strong orange-red and BaMoO4:Dy3+ greenish-yellow emissions. Excitation of Dy3+ in thin film of BaMoO4 emits an intense yellow color which could be applicable in the field of biological assays and biological fluorescence labeling. 2023-03-30T00:00:00Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/618 Title: Binding interaction of Trivalent Praseodymium with Calf Thymus DNA: A Comparative Study Authors: Devi Victory, CH Abstract: The interaction of trivalent praseodymium ion with Calf-Thymus DNA (CT-DNA) has been studied by employing absorption spectroscopy involving 4f-4f transitions. The absorption spectra of Pr(III) exhibits hyperchromism without shifting in wavelength on increasing the amount of CT-DNA thereby inducing the subsequent changes in the oscillator strengths of different 4f-4f bands. The other spectral parameters namely Slator-Condon, nephelauxetic ratio, bonding and covalency parameters were also determined to correlate with the binding of calf-thymus DNA to Pr(III). The binding constant, Kb has been determined and found to be 5.18 x102 M-1. The viscosity of rod-liked DNA was found to be decreased on addition of Pr(III). The absorption and viscosity measurement result suggest the non-intercalative mode of binding between trivalent praseodymium and Calf-thymus DNA. Thermodynamic parameters determined from relevant absorption data further revealed the appearance of hydrophobic interaction in addition to electrostatic mode of binding on negatively charged DNA phosphate backbone that occurs along external DNA double helix. 2013-01-31T00:00:00Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/617 Title: 4f-4f absorption spectral study for the interaction of Pr(III) and Nd(III) with uracil in presence and absence of Ca(II): A Model on the use of Ln(III) as probes at Ca(II) binding sites in biological systems. Authors: Devi Victory, CH Abstract: A bioinorganic approach into the problem of the isomorphous substitution of calcium(II) by lanthanide(III) ions in biological system is explored through absorption difference and comparative absorption spectroscopy involving 4f-4f transitions. The interaction of Pr(III) and Nd(III) with uracil induced substantial changes in the intensities of 4f-4f bands and their perturbation was reflected through oscillator strength and Judd-Ofelt intensity (Tλ) parameters. Intensification of these bands became more prominent in presence of Ca(II) thereby suggesting that the changes in the oscillator strengths of different 4f-4f bands and Judd-Ofelt intensity (Tλ) parameters can be followed to predict in vivo intracellular complexation of uracil with Ca(II) in vitro as both Pr(III) and Nd(III) have unique similarity in their coordination with Ca(II). 2015-05-31T00:00:00Z