http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/171 Thu, 30 Oct 2025 06:50:50 GMT 2025-10-30T06:50:50Z 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 Sun, 01 Mar 2015 00:00:00 GMT http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1010 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. Thu, 30 Mar 2023 00:00:00 GMT http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1006 2023-03-30T00:00:00Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1004 Title: Asymmetric Michael addition using sugar derived organocatalysts Authors: Vanlaldinpuia, K Abstract: Sugars are low-molecular-weight carbohydrates which consist of polyhydroxyl and carbonyl (aldehyde or ketone) functional groups. Different types of compounds derived from sugars have been used extensively as powerful and effective catalysts for asymmetric synthesis. They are readily available at a reasonable price, easily prepared, no metal contamination and are inert towards moisture and air. They are highly functionalized and have well defined stereogenic centres. Most of them are employed as chiral ligands in metal based asymmetric catalysis and are used for various asymmetric transformations. Different compounds derived from sugars have also been used recently as organocatalysts for asymmetric synthesis. The present article provides some of the organocatalysts used for asymmetric synthesis Mon, 07 Aug 2017 00:00:00 GMT http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1004 2017-08-07T00:00:00Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1003 Title: Monofunctional primary amine: A new class of organocatalyst for asymmetric Aldol reaction Authors: Vanlaldinpuia, K Abstract: A new class of organocatalysts involving a primary amine as the only functional group is developed for catalytic asymmetric aldol reaction of cyclohexanone/cyclopentanone with various aryl aldehydes in the presence of benzoic acid as an additive at −10◦C. In an unexpected observation, the primary amine catalyzed reactions gave excellent yield and good to excellent stereoselectivity, while secondary amines were found to have little or no reactivity under similar reaction conditions. Fri, 13 Jan 2017 00:00:00 GMT http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1003 2017-01-13T00:00:00Z