Discovery and Development of Novel Nanochemical Processes to Enhance the Effect of X-rays

加州大学戴维斯分校的郭挺教授在化学系的大分子、超分子和纳米化学（MSN）项目的支持下研究x射线纳米化学，x射线纳米化学被定义为创建和发现纳米化学过程来增强x射线的效果。在这项工作中，化学、光刻和微流体制备的纳米组件被合成和创建，以分离、优化和重组单个增强机制。具体来说，本文研究了纳米材料对x射线吸收引起的局部能量沉积的物理增强，纳米材料的催化性能引起的化学增强，以及两者的有效结合。x射线效应的增强导致许多过程的产率增加，包括x射线触发的水中精确能量沉积、水中特定活性氧的产生、键形成反应（如羟基化和聚合）和键裂解反应（如核基的氧化导致DNA链断裂）。许多这些过程可以用来探测增强的幅度。创建了三个示例性纳米系统来研究(1)如何控制x射线照射下活性氧与纳米结构之间的电荷转移过程，这是最大化化学增强的关键；(2)如何通过控制纳米结构的形状来测量和最大化物理增强；(3)如何将化学和物理增强机制结合起来而不造成它们之间的破坏性干扰。后者有时是自然发生的。在理想的情况下，高达1000倍的组合增强，以适当设计的羟基化和聚合反应的产量被设想。光学光谱和电子自旋共振光谱被用来协助这一探索。x射线纳米化学是通过引入定制纳米材料来放大x射线诱导效应的新兴研究课题。与任何新领域一样，在了解该领域的真正潜力之前，还存在许多严峻的挑战。这项由MSN资助的工作仔细研究了新定义的概念，如不同类型的增强，并探索将这些增强结合起来的新机制，以实现前所未有的增强。所提出的研究努力试图巩固和扩大这一新领域的知识基础。这些基础研究的结果可能对几类技术产生变革性影响，例如，癌症诊断和治疗、从核废料到液体燃料的能量转换、辐射传感和检测，以及在持续本底电离辐射照射下纳米材料潜在生态效应的修复。第一代科学家的教育，包括女性和少数族裔研究生和本科生在这个新领域的前沿工作，旨在创造一个劳动力，帮助定义x射线纳米化学的未来。本工作开发和使用的仪器和研究平台新颖、价格低廉，可为国内大多数研究实验室所采用。

Professor Ting Guo of the University of California at Davis is supported by the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program in the Division of Chemistry to study X-ray Nanochemistry, which is defined as creating and discovering nanochemical processes to enhance the effects of X-rays. In this proposed work, chemically, lithographically, and microfluidically prepared nanoassemblies are synthesized and created to isolate, optimize and recombine individual enhancement mechanisms. Specifically, physical enhancement of localized energy deposition resulting from X-ray absorption by nanomaterials, chemical enhancement enabled by catalytic properties of nanomaterials, and the effective combination of the two are investigated in this work. The enhancement to the X-ray effects results in increase in the yield of many processes including X-ray triggered precision energy deposition in water, generation of a specific reactive oxygen species in water, bond formation reactions such as hydroxylation and polymerization, and bond cleavage reactions, e.g.,oxidation of nucleoabses leading to DNA strand breaks. Many of these processes can be used to probe the magnitude of enhancement. Three exemplary nanosystems are created to study (1) how to control charge transfer processes between reactive oxygen species and the nanostructures under X-ray irradiation, which is critical to the maximization of chemical enhancement, (2) how to measure and maximize physical enhancement through controlling the shape of nanostructures, and (3) how to combine the chemical and physical enhancement mechanisms without causing destructive interference between them, the latter sometimes occuring naturally. In ideal circumstances, up to 1,000 times combined enhancement to the yield of properly-designed hydroxylation and polymerization reactions is envisioned. Optical spectroscopy and electron spin resonance spectroscopy are being used to assist this exploration.X-ray nanochemistry is a new research topic in which X-ray-induced effects are magnified by introducing customized nanomaterials. Like any new field, many stiff challenges remain before the true potential of the field is known. The work supported by this MSN grant scrutinizes newly defined concepts such as different types of enhancement and explores new mechanisms to combine these to achieve unprecedented enhancements. The proposed research endeavors attempt to solidify and expand the knowledge basis of this new field. The outcomes of these fundamental investigations may have transformative impacts on several categories of technology, for example, cancer diagnosis and treatment, energy conversion from nuclear wastes to liquid fuels, radiation sensing and detection, and remediation of potential ecological effects of nanomaterials under constant irradiation of background ionizing radiation. Education of the first generation scientists including women and underrepresented minority graduate and undergraduate students working on the forefront of this new field is directed at creating a workforce that helps define the future of X-ray nanochemistry. The instrumentation and research platform developed and employed in this work are new and inexpensive, and can be adopted by the majority of research laboratories in the country.