Core/Shell Composite of Self-Assembled Hierarchical Bismuth Oxide/Europium Doped Gadolinium Oxide for Scintillating Dete
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1207-N07-25
Core/Shell Composite of Self-Assembled Hierarchical Bismuth Oxide/Europium Doped Gadolinium Oxide for Scintillating Detection Teng-Kuan Tseng*, Jihun Choi, Mark Davidson and Paul H. Holloway Department of Materials Science and Engineering, MICROFABRITECH University of Florida, Gainesville, FL 32611-6400, USA
ABSTRACT A novel three dimensional (3D) self-assembled hierarchical bismuth oxide was prepared via a sol-gel synthesis with the aid of capping agent of polyethylene glycol-8000 (PEG-8000) at 85 ℃ in 45 min. The morphology evolution was studied versus reaction time and interpreted in terms of growth mechanisms. The as-grown 3D hierarchical flower-like bismuth oxide was crystalline cubic gamma-phase. The morphology and crystal phase of these 3D cubic gammaphase bismuth oxide flowers were not changed with heating up to 600 ℃. The flower-like morphology was attributed to modification of the growth kinetics from the PEG-OH bond bridging with bismuth ions. Europium doped gadolinium oxide shell were further deposited on the bismuth oxide cores through sol-gel synthesis exhibiting good photoluminescence characteristics at 610 and 622 nm under the excitation at 280 nm.
INTRODUCTION Luminescent rare-earth nanocrystals and colloidal quantum dots incorporated with dopants have aroused great interests due to their applications in various fields, i.e. display and solid-state lightening, scintillator detector, and biologic diagnosis [1-3]. Gadolinium oxide exhibits good luminescent properties when doped with rare-earth ions. The characteristics of the luminescent and paramagnetic multifunctional properties lead to a number of possible applications such as neutron capture therapy targets and bimolecular detection [4-6]. Moreover, this oxide phosphor is a potential scintillation detector material due to its short luminescent decay lifetime, large atomic number and density, low afterglow, large light output and low hygroscopicity [7]. The detection efficiency or γ-ray stopping power depends on the density and the thickness of the detector materials. To produce high detection efficiency of the scintillation materials, a core/shell composite with high atomic number bismuth oxide and superior luminescent europium doped gadolinium oxide is employed. For bismuth oxide core material, a number of synthetic approaches have been applied to fabricate bismuth oxide in the form of spheres or one-dimensional structure, such as flame spray pyrolysis (FSP), chemical vapor deposition (CVD), hydrothermal synthesis, electrospinning and microemulsion methods [8-10]. Bismuth oxide is a complex system with four different polymorphic forms which are denoted by α- (monoclinic), β- (tetragonal), γ- (body centered cubic) and δ-Bi2O3 (face centered cubic). The α and δ phases are the stable phases at room temperature and high temperature between 730 ℃ to the melting point at 824 ℃, respectively. Self-assembled one- or two-dimensional (1D or 2D) nano- or micro-structures have been produced in a variety of materials by different synthesis meth
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