Quantitative Photophysics of Photoluminescent and Scintillating Nanoparticles

量子点(QD)是直径在~2~5 nm的半导体材料(如Cd，Cd Se)的荧光晶体。这还不到典型活细胞直径的千分之一。量子点被活性分子覆盖，使它们在水或其他溶液中保持稳定的悬浮液。量子点的能量和反应性--由材料、封端剂和尺寸决定--决定了量子点向溶液中的其他分子转移电子或从溶液中的其他分子接受电子的能力。这种电子转移对于各种应用和问题都是非常重要的。不必要的电子转移会损害或杀死生物组织。由于它发生在纳米级，损伤可能发生在细胞内部，包括细胞核。另一方面，电子转移可以用来杀死不需要的细胞，如癌细胞或细菌。将电子从量子点转移到其他材料也使量子点可以用作太阳能电池的材料，尽管目前对这一过程还不够了解，无法创造出高效率的材料。 在我们最近的工作中，我们使用了一个数学模型来描述量子点在给电子分子存在时的荧光性质。这个模型有助于描述量子点的荧光和电子转移的机制，也提供了对单个量子点中出现的熄灭-开启“闪烁”的洞察。我们这项提议的目标是扩展和发展这个模型，以提供量子点荧光和闪烁的一般定量光物理描述，特别强调水中暴露在电子供体分子中的量子点。我们还将扩展到研究其他类型的纳米颗粒，例如那些在X射线而不是可见光照明下发光的纳米颗粒(放射发光纳米颗粒)。 这项研究将为所有在生物医学或替代能源应用中从事纳米粒子光物理工作的科学家提供一个有用的框架。我们实验室的长期目标是利用这些结果创造基于纳米颗粒的抗菌和抗癌药物。这些药物将专门针对癌症或病原体，因此对健康细胞的毒性比许多化疗药物低。

Quantum dots (QDs) are fluorescent crystals of semiconductor materials (such as cadmium selenide, CdSe) that range from ~ 2 to 5 nm in diameter. This is less than 1/1000th the diameter of a typical living cell. QDs are capped with active molecules that enable them to remain in a stable suspension in water or other solutions. The energy and reactivity of QDs--determined by the material, capping agent, and size--determine the ability of a QD to transfer electrons to, or accept electrons from, other molecules in the solution. This electron transfer is very important for a large variety of applications and problems. Unwanted electron transfer can damage or kill biological tissue. Since it happens on the nanoscale, damage can occur deep inside cells, including the nucleus. On the other hand, electron transfer can be used to kill unwanted cells, such as cancer cells or bacteria. Transferring of electrons from QDs to other materials also allows QDs to be used as materials for solar cells, although currently the process is not well-enough understood to create high-efficiency materials. In our recent work we used a mathematical model to describe the fluorescence properties of QDs in the presence of electron-donating molecules. This model helped describe the mechanisms of QD fluorescence and electron transfer, and also provided insight into the off-on "blinking" seen in individual QDs. Our goals for this proposal are to extend and develop this model to provide a general quantitative photophysical description of QD fluorescence and blinking, with a particular emphasis on QDs in water exposed to electron-donating molecules. We will also expand to study other types of nanoparticles, such as those that emit luminescence under X-ray instead of visible light illumination (radioluminescent nanoparticles). This research will provide a framework useful to all scientists working with nanoparticle photophysics in biomedical or alternative energy applications. Our laboratory's long-term goals are to use these results to create anti-bacterial and anti-cancer agents based upon nanoparticles. These agents will be specifically targeted to the cancer or pathogen, and so show lower toxicity to healthy cells than many chemotherapy drugs.