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Tamrakar R.K.,Bhilai Institute of Technology | Bisen D.P.,Pandit Ravishankar Shukla University | Upadhyay K.,Shri Shankaracharya Vidyalaya
Luminescence | Year: 2015

Erbium-doped nano-sized Gd2O3 phosphor was prepared by a solution combustion method in the presence of urea as a fuel. The phosphor was characterized by X-ray diffractometry (XRD), Fourier transform infra-red spectroscopy, energy dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM). The results of the XRD shows that the phosphor has a monoclinic phase, which was further confirmed by the TEM results. Particle size was calculated by the Debye-Scherrer formula. The erbium-doped Gd2O3 nanophosphor was revealed to have good down-conversion (DC) properties and the intensity of phosphor could be modified by annealing. The effects of annealing at 900°C on the particle size and luminescence properties were studied and compared with freshly prepared Gd2O3:Er3+ nanoparticles. The average particle sizes were calculated as 8 and 20 nm for the freshly prepared samples and samples annealed at 900°C for 1 h, respectively. The results show that both freshly prepared and annealed Gd2O3:Er3+ have monoclinic structure. © 2014 John Wiley Sons, Ltd. Source


Tamrakar R.K.,Bhilai Institute of Technology | Bisen D.P.,Pandit Ravishankar Shukla University | Brahme N.,Pandit Ravishankar Shukla University | Sahu I.P.,Pandit Ravishankar Shukla University | Upadhyay K.,Shri Shankaracharya Vidyalaya
Optik | Year: 2015

Cubic phase Gd2O3:Er3+ (1%) phosphor was synthesized by the solid-state reaction method. The structural properties of the Gd2O3:Er3+ phosphor was studied by using X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM). Particle size was calculated by Debye Scherrer formula. The XRD patterns reveal that this phosphor has cubic crystal structure and particle size of 47 nm. TL glow curve and kinetic parameter of Er3+ doped Gd2O3 phosphor was recorded with the help of TLD reader. In photoluminescence, major emission peaks found at 420, 461, 467, 472, 476, 545, 551, 555 and 578 at 965 nm excitation. The thermouminescence (TL) glow curve study gives useful information of traps. © 2015 Elsevier GmbH. Source


Tamrakar R.K.,Bhilai Institute of Technology | Bisen D.P.,Pandit Ravishankar Shukla University | Upadhyay K.,Shri Shankaracharya Vidyalaya | Sahu I.P.,Pandit Ravishankar Shukla University
Journal of Physical Chemistry C | Year: 2015

Er3+/Yb3+-codoped Gd2O3 phosphors have been synthesized by combustion method and solid-state reaction method. The prepared phosphors were compared for their structural, morphological, and optical properties. The phosphor prepared by combustion method is of monoclinic phase, whereas the phosphor formed by solid-state reaction method is of cubic phase. The structural properties were carried out by PXRD analysis. The crystallinity and morphology of the prepared phosphors were evaluated by SEM and TEM analysis, and the parameters are in good relation to PXRD results. All of the phosphors prepared by both of the methods are found to be in the nanometer range. The particle size is higher in the phosphor prepared by solid-state reaction method. The upconversion spectra of the phosphor were compared under 980 nm excitation. The luminescence behavior was studied as a function of activator and sensitizer concentrations and excitation power. © 2015 American Chemical Society. Source


Tamrakar R.K.,Bhilai Institute of Technology | Bisen D.P.,Pandit Ravishankar Shukla University | Upadhyay K.,Shri Shankaracharya Vidyalaya | Bramhe N.,Pandit Ravishankar Shukla University
Superlattices and Microstructures | Year: 2015

Monoclinic and cubic Gd2O3 phosphor co doped with Er3+ and Yb3+ were prepared by using combustion synthesis and solid state reaction methods. The emission spectra were recorded as the function of Er3+ concentration, Yb3+ concentration, and also as the function of excitation wave length. The optical properties and the morphologies of the phosphors prepared by both the methods have been compared. Average crystal size for the phosphors yielded by both the synthesis routes were in nanometer range, which were confirmed by using XRD, TEM and SEM technique. The morphological studies shows that the phosphors prepared by solid state reaction method is more homogenous and the particle size of these phosphors are larger than the phosphor synthesized by combustion synthesis method. The luminescence intensity of the phosphor prepared by solid state reaction method is more than the phosphor prepared by combustion synthesis method at a particular excitation. ©2015 Elsevier Ltd. All rights reserved. Source


Upadhyay K.,Shri Shankaracharya Vidyalaya | Asthana A.,Government Vytpg Autonomous College | Tamrakar R.K.,Bhilai Institute of Technology
Research on Chemical Intermediates | Year: 2015

A simple, sensitive, extractive spectrophotometric method for determination of α-methyldopa in both pure form and in pharmaceutical formulations is described. The method is based on the reaction of diazotized p-aminoacetophenone with α-methyldopa in basic medium to yield an orange-yellow-coloured product having an absorption maximum at 440 nm. The orange-coloured species was extracted in isopentanol. The coloured species obeyed Beer's law in the range of 0.05-0.5 μg/mL. The molar absorptivity as obtained from Beer's law data was found to be 0.3736 × 106 L mol-1 cm-1, while Sandell's sensitivity was found to be 0.00064 μg cm-2. Common excipients did not interfere with the proposed method. The result obtained by the proposed method compares favorably with other reported methods. The proposed method offers the advantages of simplicity and higher sensitivity over the other existing methods. © 2014 Springer Science+Business Media. Source

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