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Surface adaptation prompted enhanced photo and thermoluminescence properties of Dy3þ doped wollastonite nanophosphor

2020-05-28T09:30:30Z

Title: Surface adaptation prompted enhanced photo and thermoluminescence properties of Dy3þ doped wollastonite nanophosphor Authors: Nijalingappa, TB.,; Veeraiah, MK.,; Darshan, GP.,; Kavyashree, D.,; Sharma, SC.,; Premkumar, HB.,; Nagabhushana, H Abstract: The novel CaSiO3:Dy3þ (1–11 mol %) nanophosphors synthesized via simple solution combustion route and covered with silica (SiO2) by the St€ober method are reported in the present work. The X ray diffraction analysis verifies the phase purity of the synthesized samples. The diffraction peaks observed in the recorded powder x-ray diffraction patterns are in good relation with those known for the CaSiO3 structure. The photoluminescence and thermoluminescence properties of SiO2@CaSiO3:Dy3þ (3 mol %) nanophosphors were extensively investigated. The 3-fold enhancement in the photoluminescence intensity of nanophosphors after surface coating was observed, that may be due to light diffraction and multiplied by shell SiO2. The utility of the prepared samples in white light emitting diodes was confirmed by studying photometric properties. The thermoluminescence study of the samples with different γ-ray doses showed good linearity up to 4 kGy and, thereafter, the sub-linear behavior was noticed. The variation in the thermoluminescence intensity arises as a consequence of competition between different trapping centers. The aforementioned results signify that the present material was highly useful for display and dosimetry applications.

NUV light-induced visible green emissions of Erbium-doped hierarchical Bi2Zr2O7 structures

2020-02-27T12:56:53Z

Title: NUV light-induced visible green emissions of Erbium-doped hierarchical Bi2Zr2O7 structures Authors: Rajashekharaiah, AS., Darshan, G.P.; Basavaraj, R B., Naik, Yashwanth V.; Kavyashree, D., Sharma, SC.; Nagabhushana, H. Abstract: We reported a facile strategy to synthesis of Er3+ doped Bi2Zr2O7 nanophosphors via hydrothermal route using Aloe Vera gel as a bio - surfactant. The photoluminescence spectra exhibit intense peaks centered at ~524, 547 and 660 nm, which were attributed to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ ions, respectively. The highest photoluminescence intensity was achieved in 5 mol % of Er3+ ions. The electric dipolequadrupole (d-q) interaction was responsible for the concentration quenching. The fluorescence intensity ratio technique was utilized for optical thermometric properties of the nanophosphors in the temperature range of 303–463 K. At lower temperature (282 K) the relative sensor sensitivity of the optimized nanophosphor was found to be ~0.0621 K−1. Thermoluminescence glow curves of 5 mol % Er3+ ions doped nanophosphor irradiated with γ-rays showed two peaks at ~120 and 203 °C. A thermoluminescence glow peak at ~120 °C showed good linearity with dose, simple glow curve structure, minimal fading and good reproducibility. The above results clearly showed that the optimized nanophosphor is quite useful in WLED's, TL dosimetry and optical thermometry applications.

Shape controllable ultrasound assisted fabrication of CaZrO3:Dy3+ hierarchical structures for display, dosimetry and advanced forensic applications

2020-02-27T12:57:56Z

Title: Shape controllable ultrasound assisted fabrication of CaZrO3:Dy3+ hierarchical structures for display, dosimetry and advanced forensic applications Authors: Navami, D., Darshan, G.P.; Basavaraj, R B., Sharma, S.C.; Kavyashree, D. Venkatachalaiah,KN.; Nagabhushana, H. Abstract: Herein, we report hierarchical arrow-like structures of CaZrO3:Dy3+ (1-11 mol %) are prepared by sonochemical route using bio template as a surfactant. High purity and crystallinity of the product was obtained in sonochemical route when compared to conventional methods. Morphological results showed arrow-like structures which are highly reliant on many experimental parameters such as, sonication time, bio-template concentration, sonication power, pH and surfactant to water ratio. The photoluminescence emission spectra consist of sharp peaks at ~ 481 nm (blue), 575 nm (yellow) and 665 nm (red), which ascribed to 4F9/2→6H15/2, 4F9/2→6H13/2 and 4F9/2→6H11/2 transitions of Dy3+ ions, respectively. The decrement in the photoluminescence emission intensity after 7 mol % of Dy3+ ion concentration was clearly noticed, which may due to concentration quenching. The photometric properties of the prepared samples showed intense white emission with high color purity. Thermoluminescence glow curves of CaZrO3:Dy3+ (7 mol %) showed broad and intense peak at ~ 143 o C at a warming rate of 2 oCs-1. Thermoluminescence profile reveals the linear dependence with dose, least fading and highly reproducible. The optimized powders are employed to image the latent fingerprints with higher resolution on various porous, non-porous and semi-porous surfaces. The aforementioned results clearly indicate that the optimized hierarchical structures are effectively used in radiation dosimetry, display devices and advanced forensic applications.

Micro Structural Parameters of Silver Nano Particles Using Whole Pattern Fitting Technique

2019-01-13T09:08:47Z

Title: Micro Structural Parameters of Silver Nano Particles Using Whole Pattern Fitting Technique Authors: Mahesh, S. S.; Prashanth, K. S.; Ananda, S.; Nandaprakash, M. B.; Somashekar, R. Abstract: Silver Nano particles are synthesized by Conventional method of biosynthesis of silver nano particles using extract of Parthenium hysterophorus. The synthesized Nano particles were subjected to XRD and SEM analysis for the characterization process for estimating the size of crystalline particle and figure out the morphology. The as-prepared powders are all nano-sized ( nm) and the same is confirmed by broadening of the X-ray diffraction peaks and Scanning electron microscopy. XRD results show that Crystallite area decreases with increasing concentration. The crystallite size (), lattice strain (g in %), stacking faults (αd) and twin faults (β) determined by whole powder pattern fitting technique, developed by us.We have studied the microcrystalline parameters from XRD. Activation energy has been computed for these systems.