Mkwawa University College of Education

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Browsing Mkwawa University College of Education by Author "Aryal, Pabitra"

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    Fabrication and investigation of the effects of various gadolinium compounds on Ce3+-activated phosphate glasses for scintillation applications
    (Elsevier, 2022-07) Ntarisa, Amos Vincent; Saha, Sudipta; Nguyen, Duy Quang; Kim, HongJoo; Wantana, N; Pandey, Indra Raj; Aryal, Pabitra; Kothan, Suchart; Kaewkhao, Jakrapong
    Ce3+-activated phosphate-based glasses were fabricated for scintillation purposes following melt-quenching technique. Chemical compositions of the glasses were designed in mol. % ratio with formula (62P2O5:20Li2CO3:10X:5Al2O3:3CeBr3 where X Gd2O3/GdF3/GdCl3/GdBr3/GdI3). The amorphous structure of the glasses was verified by the powder X-ray diffraction measurements. Fourier-transform infrared (FTIR) measurements were carried out to study the structural properties of the fabricated glass samples. X-ray-induced luminescence and photoluminescence (PL) spectra were used to investigate the luminescence properties of the glasses. A broad PL excitation band was found for all prepared glasses that refers to Gd3+ and Ce3+ characteristic transitions. GdI3 containing glass sample provided the optimum emission under X-ray and UV (308 nm) excitations peaking at 347 and 341 nm, respectively. The scintillation property of the GdI3 containing glass was studied under 5.5 MeV α-particle from 241Am radiation source and a clear alpha peak was observed with energy resolution of 35.3%. The shortest decay component of the glass sample was observed to be 27.9 ns, 30.7 ns and 29.12 ns under the α-particles, γ-ray, and 266 nm pulsed laser excitations, respectively. In conclusion, the GdI3 prepared glass sample can be used for α -particles detection.
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    Luminescence and scintillation properties of Ce3+-doped P2O5-Li2CO3-GdBr3-Al2O3 glasses
    (Elsevier, 2021-09-01) Ntarisa, Amos Vincent; Saha, Sudipta; Aryal, Pabitra; Kim, HongJoo; Khan, Arshad; Nguyen, Duy Quang; Pandey, Indra Raj; Kaewkhao, Jakrapong; Kothan, Suchart
    A series of glass samples were fabricated with the composition of (65-x)P2O5:20Li2CO3:10GdBr3:5Al2O3:xCeBr3 (where, x = 0.5,1,2,3,4). The powder X-ray diffraction measurements were performed to verify the amorphous structure of the prepared glass samples. Energy-dispersive X-ray spectroscopy showed an interesting phenomenon of oxygen bridging eliminating Br (Bromine) from the initial compounds. The luminescence characteristics of the samples were studied using X-rays and UV–Vis excitations. Characteristics Ce3+ emission was observed at 350 nm including energy transfer from 4f energy state of Gd3+ to 5d energy band of Ce3+. The fast decay component was observed as 37 ns, 42 ns, and 44 ns for the UV, α-particles, and γ-ray excitations, respectively. The intermediate and slow components were observed for α-particles, and γ-rays excitations indicating Gd3+ to Ce3+ energy transfer and 4f-4f transitions of Gd3+ -ions accordingly. The scintillation property was studied with α-particles using a 241Am source.
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    Mn2+ doping inside glass substrate utilizing metal ion beam implantation technique
    (Elsevier, 2022-07) Hwang, YongSeok; Aryal, Pabitra; Kim, HongJoo; Ntarisa, Amos Vincent; Saha, Sudipta; Kim, Chorong; Kothan, Suchart; Kaewkhao, Jakrapong
    The Korea multi-purpose accelerator complex (KOMAC) has been providing metal ion beam services such as Cr+, Fe+, Co+, Cu+, Mg+ and Ni+ using a modified Bernas ion source for diverse users. In this study, metal ion implantation facilitated by KOMAC has been utilized to implant Mn+ ions into a glass substrate. First, phosphate glass substrate doped with CeBr3 was fabricated following melt-quenching technique and then Mn+ ion beam was irradiated with flounces of 5 × 1016 ions/cm2. The irradiated sample was heat-treated at 400 °C, and characterized by absorption, excitation, and emission spectra. The presence of Mn2+ and the existence of energy transfer from Ce3+ to Mn2+ were explored by characteristic emission and excitation spectra. The emission intensity of Mn2+ was significantly higher when excited by Ce3+ excitation than Mn2+.
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    Novel technique for simultaneous detecting three naturally occurring radon isotopes (222Rn, 220Rn and 219Rn)
    (Elsevier, 2022-11) Ntarisa, Amos Vincent; Kim, HongJoo; Aryal, Pabitra; Nguyen, Duy Quang; Saha, Sudipta
    Radon inspection is becoming increasingly prevalent due to its negative effects on human health. After cigarette smoking, radon is the second leading cause of lung cancer due to its internal dosage through respiration. In this study, we employed a novel liquid scintillation technique to simultaneously detect three naturally occurring radon isotopes (222Rn, 220Rn and 219Rn). The detection method utilises the delayed coincidence technique and the pulse shape discrimination implemented by digital charge comparison. Furthermore, a Monte Carlo simulation was performed to obtain the gamma response functions of the detector using standard 22Na, 60Co and 137Cs gamma sources. Additionally, the detector resolution and energy calibration parameters were determined by comparing the measured and simulated light output distributions. For the measurement, radon gas from the atmosphere was infused into 700 mL of Ultima Gold AB for 48 h. We determined that the minimum detectable activities of 222Rn (238U decay chain), 220Rn (232Th decay chain) and 219Rn (235U decay chain) were 1.7, 1.0 and 1.2 mBq/l, respectively. The proposed novel technique offers a potential application for detecting all three naturally occurring radon isotopes in water samples.
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    Rapid and convenient crystallization of quantum dot CsPbBr3 inside a phosphate glass matrix
    (Elsevier, 2022-06-15) Aryal, Pabitra; Kim, HongJoo; Saha, Sudipta; Cho, Jaeyoung; Ntarisa, Amos Vincent; Kothan, Suchart; Kaewkhao, Jakrapong
    Although inorganic halide perovskite quantum dots (QDs) have promising photophysical properties and a wide range of applications, they suffer from some issues such as poor water and thermal stabilities. Here, we developed a simple strategy to embedded CsPbBr3 QDs in a glass matrix by adopting conventional melt-quenching technique. We systematically presented the modified glass melting and quenching technique for the direct crystallization of CsPbBr3 QDs inside a glass matrix. Crystallization of the QDs took place during the cooling of the quenched hot glass melt. The effect of the concentration of Cs2CO3, PbBr2 and NaBr on the formation of CsPbBr3 QDs size was also identified. The glasses containing CsPbBr3-embedded QDs showed photoluminescence emission stability without any alteration in their emission peaks and full-width at half-maximum for at least six months under ambient conditions. Our results provide new insights into rapid and convenient crystallization of QDs inside the protective glass matrix. The technique can be utilized to fabricate several rare earth ions co-doped QDs glasses for various color tunable lighting optical devices application.
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    Synthesis and characterization of CeF3‒doped (74.5-x)P2O5:20Li2O:5Al2O3:x(GdF3, LaF3 and YF3) glasses
    (Elsevier, 2021-12) Aryal, Pabitra; Saha, Sudipta; Kim, HongJoo; Kang, SJ; Ntarisa, Amos Vincent; Angnanon, A; Kaewkhao, Jakrapong
    Glasses have a wide variety of applications in different types of devices, including solid-state lasers, fiber-optic amplifiers, medical imaging, radiation dosimeter, solar cells, neutron imaging, and scintillators. Among several rare-earth (RE) ions, Ce3+ exhibits short decay time and offers promising scintillation when it is doped in a transparent glass matrix. The objective of this study was to investigate the energy transfer from Gd3+, La3+, and Y3+ ions to Ce3+ ion in 64.5P2O5:20Li2O:5Al2O3 glass matrix while considering an enhancement in its scintillation efficiency. Four glass samples doped with CeF3 alone and co-doped with GdF3, LaF3, and YF3 were fabricated. Broad photoluminescence and radio-luminescence emissions peaking near to 340 and 350 nm were found when excited by 310 nm and X-ray, respectively, for all the glasses. A photoluminescence emission quenching was found in LaF3 co-doped glass. A strong energy transfer from Gd3+ to Ce3+ was noticed while the GdF3 co-doped glass was excited by X-ray, 275 nm (from Gd3+), and 310 nm (from Ce3+) excitations. The Gd3+ co-doped glass consisted of a 37 ns decay constant under the 266 nm laser excitation. The thermoluminescence analysis showed two glow curves centered at 210 °C and 345 °C, respectively, after X-ray irradiation. Considering the efficient energy transfer from Gd3+ to Ce3+ ions and short lifetime of Ce3+ emission, the glass composition of the above formula having Gd3+ and Li+ with Ce3+ ions appeared to be a promising candidate in the search of good promising scintillating glasses with fast fluorescence decay time.