a b s t r a c tGd 2 O 3 :Eu 3+ (4 mol%) nanophosphor co-doped with Li + ions have been synthesized by low-temperature solution combustion technique in a short time. Powder X-ray diffractometer (PXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV-VIS and photoluminescence (PL) techniques have been employed to characterize the synthesized nanoparticles. It is found that the lattice of Gd 2 O 3 :Eu 3+ phosphor transforms from monoclinic to cubic as the Li + -ions are doped. Upon 254 nm excitation, the phosphor showed characteristic luminescence 5 D 0 → 7 F J (J = 0-4) of the Eu 3+ ions. The electronic transition located at 626 nm ( 5 D 0 → 7 F 2 ) of Eu 3+ ions was stronger than the magnetic dipole transition located at 595 nm ( 5 D 0 → 7 F 1 ). Furthermore, the effects of the Li + co-doping as well as calcinations temperature on the PL properties have been studied. The results show that incorporation of Li + ions in Gd 2 O 3 :Eu 3+ lattice could induce a remarkable improvement of their PL intensity. The emission intensity was observed to be enhanced four times than that of with out Li + -doped Gd 2 O 3 :Eu 3+ .
Gd(2)O(3) nanoparticles (27-60 nm) have been synthesized by the low temperature solution combustion method using citric acid, urea, glycine and oxalyl dihydrazide (ODH) as fuels in a short time. The structural and luminescence properties have been carried out using powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), Raman, UV-Vis, photoluminescence (PL) and thermoluminescence (TL) techniques. The optical band gap values were estimated for as formed and 800 °C calcined samples. The band gap values in as-formed and calcined samples were found to be in the range 4.89-5.59 eV. It is observed that, the band gap values are lower for as-formed products and it has been attributed to high degree of structural defects. However, in calcined samples, structure becomes more order with reduced structure defects. Upon 270 nm excitation, deep blue UV-band at ~390nm along with blue (420-482 nm), green (532 nm) and red emission (612 nm) was observed. The 390 nm emission peak may be attributed to recombination of delocalized electron close to the conduction band with a single charged state of surface oxygen vacancy. TL measurements were carried out on Gd(2)O(3) prepared by different fuels by irradiating with γ-rays (1 kGy). A well resolved glow peak at 230 °C was observed for all the samples. It is observed that TL intensity is found to be higher in for urea fuel when compared to others. From TL glow curves the kinetic parameters were estimated using Chen's peak shape method and results are discussed in detail.
Effective atomic numbers' (Z(eff)) effective electron density (N(el)) for human organs and tissues have been computed in the energy region of 1 keV to 100 GeV using WinXCOM. The computed data of Z(eff) and N(el) are tabulated. The computed values are compared with previous results. The computed data of Z(eff)and N(el)for almost all tissues (34 tissues of different human organs) in the given energy range are not available in literature and find application in radiotherapy and dosimetry.
a b s t r a c tThe G-P fitting method has been used to compute the exposure build-up factor of teeth [enamel outer surface (EOS), enamel middle (EM), enamel dentin junction towards enamel (EDJE), enamel dentin junction towards dentin (EDJD), dentin middle (DM) and dentin inner surface (DIS)] for a wide energy range (0.015-15 MeV) up to the penetration depth of 40 mean free paths. The dependence of exposure build-up factor on incident photon energy, penetration depth, electron density and effective atomic number has also been studied. The computed exposure build-up factor is useful to estimate the relative dose distribution in different regions of teeth.
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