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.
