Effects of Surface-Adsorbed Biomolecules and Geomolecules on the Photoreactivity of Metal Oxide Nanomaterials

近年来，人们发现并开发了在太阳光照射(光反应或光催化)下降解有机污染物的新型纳米材料。这种独特的光反应性使其在各种水处理技术中的应用具有吸引力。另一方面，这一特性也可能与纳米材料在自然环境中的毒理危害相关。预测纳米材料的光反应性在水环境中是具有挑战性的，因为纳米材料的表面可能被生物分子和天然有机物的复杂混合物所覆盖。这些复杂的表面涂层与辐照的纳米材料的相互作用以及由此对纳米材料的有效光反应活性的影响尚不清楚。另一个挑战是将涂层效应推广到目前正在研究的各种光催化纳米材料上。光催化纳米材料的例子包括被紫外光激活的二氧化钛，以及新型可见光活性纳米材料，如氧化钼，它可以提高水处理应用的可行性。这项研究将研究复杂表面涂层形成的机理及其对各种金属氧化物纳米材料光反应性的影响。本研究开发的基本知识和模型将有助于开发有效和安全的环境应用光催化纳米材料，并减轻行业和监管机构大规模测试纳米材料的负担。这项研究的结果将通过休斯顿大学和当地博物馆联合开展的名为“揭开纳米材料世界面纱”的项目向公众传播。该计划旨在让K-12学生，特别是来自代表性不足的群体的学生，进入科学和工程领域。这项研究还将纳入高中教师动手模块，向休斯顿地区的高中生传播知识，展示纳米技术对社会的影响，并招募教师进行纳米技术领域的研究。最后，研究结果将被纳入休斯顿大学关于水质和环境建模的本科生和研究生环境工程课程。这项研究的首要目标是开发一个模型，能够预测表面涂层对各种光催化金属氧化物纳米材料的光反应性的影响，包括二氧化钛和氧化钼。涂层的效果被假设为可以从表面涂层的组成中预测，这将决定涂层与光反应纳米材料相互作用的类型和程度。这项研究将结合新的方法和分析工具，以实现对涂层效应的机理理解，包括(1)直接表征和控制生物分子和天然有机物的非均相混合物在光催化纳米材料上的表面涂层形成，(2)验证和改进互补的生物和化学分析以量化光反应活性，以及(3)应用原位光谱方法来识别和监测特定涂层成分在纳米材料表面的反应。这项研究中获得的详细的表面化学和反应性数据最终将被用来开发定量模型，表达有机表面涂层改善纳米材料有效光反应性的基本机制。

Recently, new nanomaterials that can degrade organic pollutants under sunlight irradiation (photoreaction or photocatalysis) have been identified and developed. This unique photoreactivity makes them attractive for applications in diverse water treatment technologies. On the other hand, this property can also correlate to the toxicological hazard of nanomaterials in natural environments. Predicting nanomaterial photoreactivity is challenging in aqueous environments since the surface of the nanomaterial can become coated with a complex mixture of biomolecules and natural organic matter. The interactions of these complex surface coatings with the irradiated nanomaterial and the resulting impact on the effective photoreactivity of the nanomaterial are not yet well understood. A further challenge is to generalize the coating effects across a variety of photocatalytic nanomaterials currently being investigated. Examples of photocatalytic nanomaterials include titanium dioxide, which is activated by ultraviolet light, and novel visible light active nanomaterials, such as molybdenum oxide that could show improved viability for water treatment applications. This research will investigate the mechanisms underlying the formation of complex surface coatings and their effects on the photoreactivity of various metal oxide nanomaterials. The fundamental knowledge and models developed in this research will facilitate the development of effective and safe photocatalytic nanomaterials for environmental applications and alleviate the burden on industry and regulatory agencies for large-scale testing of nanomaterials. The results of this research will be disseminated to the public through a joint program between the University of Houston and local museums called "Unveiling the World of Nanomaterials." This program aims to expose and recruit K-12 students, particularly from underrepresented groups, to careers in science and engineering. This research will also be incorporated into hands-on modules for high school teachers to disseminate knowledge to high school students in the Houston area, demonstrate impacts of nanotechnology on society, and recruit teachers to conduct research in the field of nanotechnology. Finally, the results will be incorporated into undergraduate and graduate environmental engineering courses on water quality and environmental modeling at the University of Houston. The overarching goal of this research is to develop a model that is capable of predicting the effects of surface coatings on photoreactivity across a variety of photocatalytic, metal oxide nanomaterials, including titanium dioxide and molybdenum oxide. The effect of the coating is hypothesized to be predictable from the composition of the surface coating, which will dictate the type and extent of coating interactions with the photoreactive nanomaterials. Novel approaches and analytical tools will be incorporated in this research to enable a mechanistic understanding of the coating effects, including (1) direct characterization and control of surface coating formation onto photocatalytic nanomaterials from heterogeneous mixtures of biomolecules and natural organic matter, (2) validation and refinement of complementary biological and chemical assays to quantify photoreactivity, and (3) application of in situ spectroscopic methods to identify and monitor the reactions of specific coating components on the nanomaterial surface. The detailed surface chemistry and reactivity data obtained in this research will ultimately be used to develop quantitative models expressing the fundamental mechanisms by which organic surface coatings modify the effective photoreactivity of nanomaterials.