Effects of Gamma Irradiation on Optical Properties of Colloidal Nanocrystals
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1038-O09-05
Effects of Gamma Irradiation on Optical Properties of Colloidal Nanocrystals Nathan J. Withers1, Krishnaprasad Sankar1, Brian A. Akins1, Tosifa A. Memon1, Jiangjiang Gu1,2, Tingyi Gu1,2, Shin T. Bowers1,3, Melisa R. Greenberg1,4, Gennady A. Smolyakov1, Robert D. Busch5, and Marek Osinski1 1 Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, NM, 87106-4343 2 School of Electronic, Information, and Electrical Engineering, Shanghai Jiao Tong University, Shanghai, China, People's Republic of 3 Division of Engineering, Brown University, Box 0424, Providence, RI, 02912 4 CVI Laser, LLC, 200 Dorado Pl. SE, Albuquerque, NM, 87123 5 Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM, 87131 ABSTRACT The effects of 137Cs gamma irradiation on photoluminescence properties, such as spectra, light output, and lifetime, of several types of colloidal nanocrystals have been investigated. Irradiation-induced damage testing was performed on CdSe/ZnS, LaF3:Eu, LaF3:Ce, ZnO, and PbI2 nanocrystals synthesized on a Schlenk line using appropriate solvents and precursors. Optical degradation of the nanocrystals was evaluated based on the measured dependence of their photoluminescence intensity on the irradiation dose. Radiation hardness varies significantly between various nanocrystalline material systems. INTRODUCTION Colloidal nanocrystals (CNCs) have attracted tremendous interest over the last few years for a wide range of applications. So far, however, their potential has generally eluded the nuclear detector community. Yet, compared to currently used scintillating particles of the micrometer size or large-size single crystals, NCs offer the prospect of significantly improved performance. Due to three-dimensional confinement and much better overlap of electron and hole wavefunctions, the optical transitions are expected to be more efficient and much faster than in bulk scintillators, which should eliminate the major problem of relatively slow response of scintillator detectors. So far, only scintillation of commercial CdSe/ZnS core/shell quantum dots under α [1,2] and γ-ray irradiation [3] has been reported, with no attempt to assess possible degradation effects of long-term exposure. CNCs are semiconductor single crystals of ~3-100 nm size, synthesized by chemical processes. Due to their small size, the crystals exhibit enhanced quantum mechanical effects, such as size-dependent emission, room-temperature (RT) excitonic features, decrease in carrier lifetime, and dominance of surface effects. CNCs are being researched for a wide range of biomedical applications [4,5], to produce fast efficient phosphors for light emitting diodes [6,7], and as active elements in photovoltaic devices [8]. Detection of nuclear radiation by its conversion to UV or visible light can be another attractive application of CNCs. Practical importance of a scintillator material is determined by considering characteristics such as efficiency of converting a γ photon to UV/
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