Investigations are reported on the x-ray scintillation and imaging application of CdTe quantum dots ͑QDs͒ and their polymer nanocomposites. Aqueous CdTe QDs with emissions ranging between 510 and 680 nm were prepared and incorporated into polyvinyl alcohol or polymethyl methacrylate polymer matrices. The x-ray luminescent properties were evaluated and a resolution of 5 lines/mm was obtained from the nanocomposite films. Additionally, the fast decay time, nonafterglow, and superior spectral match to conventional charge coupled devices, show that CdTe QD nanocomposites have high promise for x-ray imaging applications. © 2011 American Institute of Physics. ͓doi:10.1063/1.3589366͔High-performance x-ray phosphor screens are a key device component for applications such as x-ray crystallography and mammography. For example, the current generation of charge coupled devices ͑CCDs͒ based x-ray crystallography detectors are mosaic arrays of individual modules, each consisting of a phosphor screen, to convert incident x-rays to light, a fiber-optic taper to couple the light into a CCD sensor, and the CCD, which converts the light into an electronically readable format. 1,2 However, these x-ray detectors are still not as fast, sensitive, efficient, or have high enough resolution as required by some applications and existing limitations restricts their usefulness in many biological and medical applications. In order to improve the performance of these detectors, x-ray phosphor screens with excellent properties including: high stopping power, high spatial resolution, very fast decay times, minimum afterglow, detector spectral match, and excellent x-ray conversion efficiency are required.In this letter, CdTe quantum dot ͑QD͒ based polymer nanocomposites were studied for x-ray scintillation and imaging applications. QD nanomaterials can be advantageous for x-ray applications compared to traditional phosphors. Current x-ray phosphor screens are made using micron-sized powder phosphors such as Gd 2 O 2 S : Tb, ZnSe:Cu,Cl, or CsI:Tl, which are efficient and bright x-ray converters. 3 They provide good results with regards to efficiency ͑ratio of visible light output to x-ray absorption͒, stopping power ͑x-ray absorption efficiency͒, and time response ͑decay time and afterglow͒. However, large-sized phosphor particles give rise to a great deal of scatter, which limits their spatial resolution ͑minimum distinguishable features in the image͒. There is ample theoretical argument to suggest that nanometer-sized particles, such as QDs, in a transparent polymer-matrix screen will exhibit significantly higher spatial resolution than micron-sized phosphor particles. 4,5 In addition, the fast decay time and nonafterglow features of QDs will ensure faster time response than that of existing powder phosphors. Also, QDs can be made from high-Z and high density compounds such as CdTe, CdHgTe, PbSe, and PbTe to increase stopping power relative to that of low-Z and less-dense phosphor materials. Moreover, the narrow emission band of QDs can be tun...
We report the development of new nanophosphor structures based on the Mn-doped ZnSeS material system to enhance the color properties, luminosity and efficiency of white LEDs. These structures have been demonstrated for phosphor-based white LED applications utilizing both blue and UV LED systems. Bandgap tuning for near UV (405 nm) and blue (460 nm) excitations are reported. Using various optimization procedures, we have produced ZnSe:Mn nanoparticles with an external quantum yield greater than 80%.
Transparent glass-ceramic containing rare-earth doped halide nanocrystals exhibits enhanced luminescence performance. In this study, a glass-ceramic with Tb doped gadolinium fluoride nanocrystals embedded in an aluminosilicate glass matrix is investigated for X-ray imaging applications. The nanocrystalline glass-ceramic scintillator was prepared by a melt-quench method followed by an anneal. The GdF3:Tb nanocrystals precipitated within the oxide glass matrix during the processing and their luminescence and scintillation properties were investigated. In this nanocomposite scintillator system, the incorporation of high atomic number Gd compound into the glass matrix increases the X-ray stopping power of the glass scintillator, and effective energy transfer between Gd3+ and Tb3+ ions in the nanocrystals enhances the scintillation efficiency.
An efficient ZnTe: O x-ray powder phosphor was prepared by a dry synthesis process using gaseous doping and etching medias. The x-ray luminescent properties were evaluated and compared to standard commercial phosphors exhibited an x-ray luminescent efficiency equivalent to 76% of Gd 2 O 2 S : Tb and an equal resolution of 2.5 lines/ mm. In addition, the fast decay time, low afterglow, and superior spectral match to conventional charge-coupled devices-indicate that ZnTe: O is a very promising phosphor candidate for x-ray imaging applications.
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