Browsing by Author "Khandaker, M.U."

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Carbon Rich Media for Luminescence-Based Surface Dosimetry and Study of Associated Surface Defects
(Elsevier, 2023-09-15) Lam, S.E.; Bradley, D.A.; Nawi, S.N. Mat; Khandaker, M.U.; Sani, S.F. Abdul
The present study continues research into the utilisation of carbonaceous media for medical radiation dosimetry, focusing on the effects of surface area-to-volume ratio and carbon content on structural interaction alterations and dosimetric properties in sheet- and bead-type graphitic materials (with the respective carbon content of ∼98 wt% and ∼90 wt%). Using 60Co gamma-rays and doses from 0.5 Gy to 20 Gy, the study has been made of the response of commercially available graphite in the form of 0.1 mm, 0.2 mm, 0.3 mm and 0.5 mm thick sheets, also of activated carbon beads. Confocal Raman and photoluminescence spectroscopy have been employed, examining radiation-induced structural interaction alterations. Dose-dependent variation in the Raman intensity ratio ID/IG relates to the varying dominance of defect generation and dose-driven defect annealing. Of the various thickness graphite sheets, the 0.1 mm thick medium possesses the greatest surface area-to-volume ratio. Perhaps unsurprisingly, it also exhibits the greatest thermoluminescence (TL) yield compared to that of the other carbonaceous sheet foils used herein. Moreover, the second greatest mass-normalised TL yield has been observed to be that of the porous beads, reflected in the greater defect density (ID/IG > 2) when compared to the other media, due in part to their inherent feature of large internal surface area. Considering the challenge posed in matching skin thickness with skin dose, the near tissue equivalent graphite sheets show particular promise as a skin dosimeter, sensitive as a function of depth.
Molecular disruptions in PTFE as the basis of a therapy-level skin dosimeter
(2024-10-24) Bradley, D.A.; Lam, S.E.; Taheri, A.; Mat Nawi, S.N.; Khandaker, M.U.; Abdul Sani, S.F.; Ung, N.M.; Alkhorayef, Mohammed
75 μm thick PTFE tape attracts interest, forming the basis of a potential skin dosimeter capable of utilization in radiotherapeutic external beam applications. The medium is readily available, for instance in the form of ordinary plumber's tape as used herein, typically of 12 mm width mounted on a spool. A60Co (mean energy 1.25 MeV) irradiator has been used to deliver doses in the range 0.1- to 10 Gy, with disrupted molecular bonds inspected via Raman spectrometry. The peak of greatest magnitude, at a wavenumber of ∼734 cm−1, corresponds to the difluoromethylene (CF2) symmetric stretching mode. Reduction in the peak intensity is seen to occur over the range 0.1- to 5 Gy, covering the values of skin dose typically arising in a single fractionated radiotherapeutic treatment. Results from these preliminary investigations point to a technique offering viability for radiotherapy skin dosimetry, utilizing a soft, low atomic number medium of particularly low-cost, also available in hypoallergenic form.
Studies of OSLProperties of Alkali- and Rare Earth-Doped BEO Based Novel Dosimeters for Applications in External Beam Radiotherapy
(Elsevier, 2023-11-15) Abusaid, W.; Altunal, V.; Guckan, V.; Khandaker, M.U.; Yegingil, Z.
This study aims to assess the feasibility of a novel Beryllium Oxide (BeO) based ceramics to be used as optically stimulated luminescence (OSL) dosimeters for monitoring of high-energy beams used in radiotherapy. The BeO ceramic dosimeters doped with alkali and rare earth metals (BeO:Na5%,Ce0.005%,Tb0.05%, BeO:Na5%,Ce0.01%,Er0.01%, and BeO:Na5%,Ce0.01%,Dy0.01%) were fabricated in pellet forms, and their luminescence responses were measured at the virtual water phantom interfaces for various field sizes of a 6 MV flattening filter-free photon beam of Varian LINAC. The OSL dosimeter's performance has been confirmed their practical usefulness as in vivo dosimeters in radiotherapy clinics. The provided dose estimates were validated using varying X-ray energies and doses, typically employed for actual medical radiotherapy systems. Our results indicated that the studied dosimeters rendered an almost linear response in the dose range of 0.05 Gy–20 Gy delivered from the 6 MV X-ray beam. Fading of the stored OSL was found to be less than 5% after a short storage period. The dependencies of OSL responses concerning beam energy, dose rate, irradiation angle, depth, and field size are all found to be supportive of the successful utilization of the BeO OSLDs in clinical environments.
The efficacy of rare-earth doped V2O5 photocatalyst for removal of pollutants from industrial wastewater
(Scopus, 2024-01) Kabir, M.H.; Hossain, M.Z.; Jalil, M.A.; Ghosh, S.; Hossain, M.M.; Ali, M.A.; Khandaker, M.U.; Jana, D.; Rahman, M.M.; Hossain, M.K.; Chowdhury, J.; Kazi, Mohsin
Photocatalysis is regarded as one of the most environmentally benign methods of mitigating the effects of textile wastewater. Despite the fact that various semiconducting metal oxides are used in photocatalysis, their performance is still insufficient. In this study, the hydrothermal method was used to synthesize rare-earth (RE) elements [Holmium (Ho) and Ytterbium (Yb)] doped vanadium pentoxide (V2O5) to improve its photocatalytic efficiency. The effect of RE ions on the photocatalytic efficiency of doped V2O5 has also been analyzed from both the experimental and first-principle density functional theory (DFT) methods. The stable orthorhombic crystal structure of doped V2O5 is confirmed by the X-ray diffraction with no secondary phase, and high-stressed conditions are generated for the 3 mol.%. The crystallite size, strain, and dislocation density are calculated to perceive the doping effect on the bare V2O5. The optical characteristics have been measured using UV–vis spectroscopy. The absorptions are found to be increased with increasing doping concentrations; however, the bandgap remains in the visible range. The photocatalytic properties are examined for the bare compound with varying pH, with the highest efficiency exhibited for pH 7. Moreover, it is observed that the RE ions significantly impact the catalytic behavior of V2O5. The degradation efficiency is improved by 93 % and 95 % for the 3 mol.% of Ho and Yb-doped V2O5 samples within 2 h, respectively, and the mechanism behind these extraordinary efficiencies has been explained thoroughly.
Thermoluminescence characterization of flooring tiles from Malaysia for potential use in retrospective dosimetry
(Scopus, 2024-08) Nawi, S.N. Mat; Khandaker, M.U.; Sani, S.F. Abdul; Lam, S.E.; N.A.I., H. Osman; Ishak, Md; Saidur, R.; Bradley, D.A.
In the event of natural disasters or technical malfunctions at nuclear sites, the surrounding media, including individuals, may be subject to unforeseen radiation exposure. Thus, it is not possible to determine the precise level of radiation exposure that each person has received in this scenario. To handle such a problem, the use of retrospective dosimetry can offer an accurate evaluation of the radiation dose acquired as a result of such incidents. This information enables the development of suitable remedial actions. Normally, in the region that has been impacted, several artifacts can serve as natural dosimeters. The study involved the utilization of locally available seven different brands of flooring tiles in Malaysia for the possibility of being used in retrospective dosimetry through exposures to 60Co gamma-rays within a range of 10–200 Gy. To understand the luminescence features of this material, a convenient thermoluminescence (TL) technique has been employed. The dosimetric features of the samples were investigated, including their effective atomic numbers (Zeff), reproducibility, glow curve, dose response, sensitivity, linearity index, energy dependency and fading, which is representative of the usual TL method. Additionally, by analyzing the glow curves of the irradiated samples together with the peak shape method and the initial rise methods, several kinetic parameters, including the kinetic orders (b), activation energy (E) or trap depth, frequency factor (s) or escape probability, and trap lifetime (τ) were calculated. Different kinds of tiles exhibit distinct scenarios in terms of kinetic characteristics. T1 sample exhibits the highest degree of sensitivity and a highly linear dose response among the tile samples that were evaluated. Also, T1, T3, and T5 samples show minimal loss of TL intensity (∼38–39%) one year after irradiation, making them ideal for use as a retrospective dosimeter.
Thermoluminescence Characterization of Flooring Tiles From Malaysia for Potential Use in Retrospective Dosimetry
(Elsevier, 2024-08-15) Nawi, S.N. Mat; Khandaker, M.U.; Sani, S.F. Abdul; Lam, S.E.; Osman, H.; Ishak, N.A.I. Md; Saidur, R.; Bradley, D.A.
In the event of natural disasters or technical malfunctions at nuclear sites, the surrounding media, including individuals, may be subject to unforeseen radiation exposure. Thus, it is not possible to determine the precise level of radiation exposure that each person has received in this scenario. To handle such a problem, the use of retrospective dosimetry can offer an accurate evaluation of the radiation dose acquired as a result of such incidents. This information enables the development of suitable remedial actions. Normally, in the region that has been impacted, several artifacts can serve as natural dosimeters. The study involved the utilization of locally available seven different brands of flooring tiles in Malaysia for the possibility of being used in retrospective dosimetry through exposures to 60Co gamma-rays within a range of 10–200 Gy. To understand the luminescence features of this material, a convenient thermoluminescence (TL) technique has been employed. The dosimetric features of the samples were investigated, including their effective atomic numbers (Zeff), reproducibility, glow curve, dose response, sensitivity, linearity index, energy dependency and fading, which is representative of the usual TL method. Additionally, by analyzing the glow curves of the irradiated samples together with the peak shape method and the initial rise methods, several kinetic parameters, including the kinetic orders (b), activation energy (E) or trap depth, frequency factor (s) or escape probability, and trap lifetime (τ) were calculated. Different kinds of tiles exhibit distinct scenarios in terms of kinetic characteristics. T1 sample exhibits the highest degree of sensitivity and a highly linear dose response among the tile samples that were evaluated. Also, T1, T3, and T5 samples show minimal loss of TL intensity (∼38–39%) one year after irradiation, making them ideal for use as a retrospective dosimeter.