Pb-Qdot Direct Gamma Detectors

描述(申请人提供)：分子成像系统(例如，PET、伽马相机)需要电子密度材料来有效地检测高能伽马射线。提高探测器中电子密度的传统解决方案是用高原子序数材料(如溴化镧)制造闪烁体。高质量的电子密度闪烁体往往很昂贵，因为很难提供高透明度和一致性的晶球。闪烁体还具有需要光电探测器(例如，光电倍增管)将可见光转换成电信号的缺点，进一步增加了体积和成本。直接探测固态设备比闪烁体具有更好的能量分辨率，因为在从伽马射线到电信号的转换过程中减少了步骤。有几种固态材料具有优异的能量分辨率(例如CZT-镉碲化锌)，但对PET系统中使用的伽马射线的阻挡能力较低，而且相对昂贵。尽管其他半导体电子致密化合物(如PbS、PbSe)具有高阻挡能力，但由于这些化合物的不利电子性质(例如，低载流子迁移率寿命产品和/或窄带隙)，设计使用它们的直接探测器件一直是一个挑战。低载流子迁移率-寿命产品导致任何实际厚度的探测器的能量分辨率较差。窄的带隙导致低的电阻率，从而导致高的泄漏电流。纳米技术可以为受限材料(例如量子点)提供与相同化合物的块状配方显著不同的电子特性。这种微调电子特性的能力在光伏领域引起了强烈的兴趣。这一提议建立在一个小组所做的大量工作的基础上，该小组将量子结构嵌入到半导体塑料中，形成具有良好的迁移率寿命和带隙特性的导电聚合物施主-受主大块异质结。幸运的是，从我们的观点来看，量子点可以由低成本、高原子序数的化合物(如硫化铅)构成。我们建议探索使用廉价的电子密度高的量子点/聚合物复合材料作为X射线和伽马射线探测器。公共卫生相关性：分子成像系统(PET和核医学)已整合到癌症诊断和治疗中。这些分子成像系统使用昂贵的探测器材料，以便有效地收集辐射。我们建议使用纳米技术方法来制造新型辐射探测器材料，以降低分子成像系统的成本和尺寸，并降低患者的辐射暴露。

DESCRIPTION (provided by applicant): Molecular imaging systems (e.g., PET, gamma cameras) require electron-dense materials to effectively detect high-energy gamma rays. The traditional solution to increasing electron density in detectors has been to fabricate scintillators out of high-atomic-number materials (e.g., lanthanum bromide). High quality electron-dense scintillators tend to be expensive, due to difficulties in delivering crystal boules of high transparency and uniformity. Scintillators also have the disadvantage of requiring photodetectors (e.g., photomultipliers) to convert visible light into electrical signals, further adding to bulk and expense. Direct-detecting solid-state devices have better energy resolution than scintillators because of the reduced number of steps in the conversion process from gamma-rays to electrical signal. Several solid-state materials are available with excellent energy resolutions (e.g., CZT - cadmium zinc telluride), but have low stopping power for gamma-rays used in PET systems, and are relatively expensive. Although other semiconducting electron-dense compounds are available with high stopping power (i.e. PbS, PbSe), it has been challenging to design direct-detecting devices using them, because of unfavorable electronic properties of these compounds (e.g., low carrier mobility- lifetime product and/or narrow band-gap). Low carrier mobility-lifetime product results in poor energy resolution for detector of any practical thickness. Narrow band-gaps result in low resistivity, and consequently in high leakage current. Nanotechnology can provide confined materials (e.g., quantum dots) with electronic properties that significantly differ from those of the bulk formulations of the same compounds. This ability to fine-tune electronic properties has generated strong interest within the photovoltaic community. This proposal builds on the substantial work generated by one group that has embedded quantum structures in semiconducting plastics, forming conducting polymer donor- acceptor bulk heterojunctions with favorable mobility-lifetime and band-gap characteristics. Fortuitously from our point of view, quantum dots can be constructed of inexpensive compounds with high atomic number (e.g., lead sulfide). We propose to explore the use of inexpensive electron-dense quantum dot/polymer composites as x-ray and gamma-ray detectors. PUBLIC HEALTH RELEVANCE: Molecular imaging systems (PET and nuclear medicine) have become integrated into cancer diagnosis and treatment. These molecular imaging systems employ expensive detector materials in order to efficiently collect radiation. We propose the use of nanotechnology methods to fabricate novel radiation detector materials that will reduce cost and size of molecular imaging systems, and lower patients' radiation exposures.