Collaborative Research: Degradation Mechanism of Cyanotoxins Using Novel Visible Light-Activated Titania (TiO2) Photocatlysts

合作研究：利用新型可见光激活二氧化钛(TiO2光催化剂)降解氰基毒素的机理智力价值：世界各地河口和淡水水系中蓝藻(Cyano-Habs)有害藻华的增加是一个主要的全球性问题。蓝藻产生和释放多种具有极高毒性的蓝藻毒素(即肝毒素、皮肤毒素、神经毒素)。作为或可能作为饮用水供应来源的水生系统中存在高浓度有害氰基毒素，这对人类和环境健康构成严重威胁。传统的水处理技术不能完全有效地去除这些剧毒的自然产生的有毒有机化合物，迫切需要开发新的技术来有效地去除水中的氰基毒素。这项提案是根据美国-爱尔兰研发计划提交的，旨在开发一种太阳能驱动的高级氧化技术(AOT)，作为解决水中氰化物污染问题的可行方案。光催化是一种AOT，它利用光激活的半导体来驱动水中的氧化还原过程，导致有机污染物的破坏和微生物的灭活。二氧化钛(TiO2光催化剂)是最适合水处理的光催化剂，但它需要紫外光激发，这意味着只能利用4%的太阳光谱。开发可见光活性(VLA)光催化剂材料将是朝着有效利用太阳能处理受污染的水迈出的重要一步。非金属掺杂的可见光活化(VLA)二氧化钛材料特别有前景，因为它们是强大的可见光吸收材料，容易敏化活性氧物种(ROS)的形成，而ROS是已知的降解有毒有机污染物的物质。目前，有机底物在辐照VLA-二氧化钛存在下的化学性质还不是很清楚。知识库中的这一差距是一个严重的问题，因为它阻碍了这些系统在水处理应用中的优化。这项美国-爱尔兰跨国合作研究的目的是阐明可见光辐射或太阳光激活的VLA二氧化钛催化降解水中氰基毒素的机制，包括来自美国的两所大学(一所是少数族裔机构)、一所北爱尔兰的大学和一所爱尔兰共和国的理工学院的科学家和工程师。中心假设是，VLA二氧化钛的照射产生了降解氰基毒素的ROS，这种反应活性可以很容易地通过改变材料的性质和光催化条件来调节。在强大的初步证据和聚集的研究人员的广泛经验的指导下，这一假设将通过追求三个具体目标来验证：(1)合成、表征和优化新型VLA TiO2光催化剂，用于破坏水中的氰化毒素；(2)研究VLA TiO2光催化剂的光电化学响应；(3)确定在氰化毒素存在的情况下VLA TiO2光催化剂产生的ROS的形成、去向和反应性，确定氰化毒素降解的动力学，评估氧化产物的生物活性，并确定利用可见光或太阳光活化的VLA TiO2光催化剂降解氰基毒素的反应中间体和反应途径。这项提议的工作是原创性的，因为它专注于新材料的制备和光化学，这些材料的性质很容易被改变。这项拟议的研究具有重要意义，因为它有望提供制定合理战略所需的机械知识，以优化太阳能驱动的光催化水处理过程。广泛影响：研究活动将通过汇集由本科生、研究生、博士后研究人员和PI组成的研究团队，直接促进发现和理解，同时促进教学、培训和学习。该研究计划强调代表人数不足的群体参与国际层面的科学项目。此外，本科生和研究生将受益于严格的跨学科轮换实验室培训，从而丰富课程。该项目还将为学生研究人员提供在海外接受科学培训的机会，从而促进合作实验室之间的思想交流。除此之外，研究结果还将用于加州大学、FIU、UU和CREST-DIT的本科生和研究生授课课程(例如纳米技术模块)。总体而言，拟议的活动预计将加强相关研究所之间的合作，因此，这些活动与美国国家科学基金会S国际合作研究目标以及美国、爱尔兰共和国和北爱尔兰最近达成的纳米技术创新协议非常一致。这项研究的更广泛的社会影响包括加强可持续发展和缩小人类生态足迹。从这些研究中获得的知识将指导利用可再生能源开发新的水处理方法。这些见解的应用将加快相关纳米技术在解决环境问题方面的实施，并推动用于太阳能收集的光电化学系统和光催化材料在其他环境应用中的发展，如空气净化、消毒和传感。

Collaborative Research: Degradation Mechanism of Cyanotoxins UsingNovel Visible Light-Activated Titania (TiO2) PhotocatalystsIntellectual merit: The increase of harmful algal blooms by cyanobacteria (Cyano-HABs) in estuaries and freshwater aquatic systems around the world is a major global problem. Cyano-HABs produce and release a variety of cyanobacterial toxins (cyanotoxins) (i.e., hepatotoxins, dermatotoxins, neurotoxins)with extremely high toxicity. The presence of high concentrations of harmful cyanotoxins in aquatic systems that serve or could potentially serve as sources of drinking water supply is a serious threat to human andenvironmental health. Conventional water treatment technologies are not wholly effective for the removal of these highly toxic naturally occurring toxic organic compounds and there is a critical need to develop new technologies which can effectively remove cyanotoxins from water. This proposal, submitted under the USIreland R&D initiative, aims to develop a solar driven advanced oxidation technology (AOT) as a viable solution to the problem of cyanotoxin contamination in water. Photocatalysis is an AOT which utilizes light-activatedsemiconductors to drive redox processes in water, leading to the destruction of organic pollutants and the inactivation of microorganisms. Titanium dioxide (TiO2) is the most suitable photocatalyst for water treatment; however, it requires UV excitation meaning that only 4% of the solar spectrum can be utilized.The development of visible light active (VLA) photocatalyst materials would be a major step forward towards the effective utilization of solar energy for the treatment of polluted water. Non-metal doped visible light activated (VLA) TiO2 materials are especially promising because they are strong visible-light absorbers and readily sensitize the formation of reactive oxygen species (ROS), which are known to degrade toxic organic pollutants. At present, the chemistry of organic substrates in the presence of irradiated VLA TiO2 is not well understood. This gap in the knowledge base is a critical problem, because it prevents the optimization of these systems for water treatment applications. The objective of this United States-Ireland trans-nationalcollaborative study, involving scientists and engineers from two universities in the United States (one being a minority institution), one University from Northern Ireland and one Institute of Technology from the Republic of Ireland, is to elucidate the mechanism of cyanotoxin degradation in water catalyzed by VLA TiO2 activated by visible light radiation or solar light. The central hypothesis is that irradiation of VLA TiO2 produces ROS that degrade cyanotoxins and that this reactivity can be readily modulated by varying the properties of the materials and the photocatalysis conditions. Guided by strong preliminary evidence and the extensive experience of the assembled researchers, this hypothesis will be tested by pursuing three specific objectives:(1) Synthesize, characterize and optimize new VLA TiO2 photocatalysts that will be evaluated for the destruction of cyanotoxins in water, (2) Investigate the photoelectrochemical response of VLA TiO2 photocatalysts, and (3) Determine the formation, fate, and reactivity of ROS generated during irradiation of VLA TiO2 in the presence of cyanotoxins, determine kinetics of cyanotoxin degradation, evaluate the biological activity of the oxidation products, and determine reaction intermediates and reaction pathways ofcyanotoxin degradation using VLA TiO2 photocatalyst activated by visible light radiation or solar light. The proposed work is original because it focuses on the preparation and photochemistry of new materials whose properties are readily modified. The proposed research is significant because it is expected to provide the mechanistic knowledge that is necessary for the development of rational strategies for optimizing solar-driven photocatalytic processes for water treatment.Broader impact: The research activities will directly advance discovery and understanding while promoting teaching, training and learning by bringing together a research team composed of undergraduate students, graduate students, postdoctoral researchers and the PIs. The research plan emphasizes participation of under-represented groups in scientific projects of international dimensions. In addition,undergraduate and graduate students will benefit from rigorous cross-disciplinary rotational laboratory training, thereby enriching the curriculum. The project will also offer opportunities to the student researchers to receive scientific training overseas, thereby facilitating exchange of ideas between the collaborating laboratories. In addition to this, the results of the research will be utilized for undergraduate and postgraduate taught courses (e.g. module in nanotechnology) in UC, FIU, UU, and CREST-DIT. Overall, the proposed activities are expected to strengthen co-operation between the institutes involved, and therefore,these activities are well aligned with the NSF?s international collaboration research objectives and the recent nanotechnology innovation agreement between the U.S., Republic of Ireland and Northern Ireland. The broader societal impacts of this research include enhancing sustainable development and shrinking the human ecological footprint. The knowledge obtained from these studies will guide the development of new water treatment methodologies using renewable energy. Application of these insights will accelerate the implementation of related nanotechnologies in addressing environmental problems, as well as advance the development of photoelectrochemical systems for solar energy harvesting and photocatalytic materials in other environmental applications such as air purification, disinfection and sensing.