CBET: Upconversion Enhanced Visible Light Sensitization of Semiconductor Photocatalysts for Environmental Application

CBET 1335934Jaehong KimYale University半导体光催化剂作为一种可持续的技术选择在环境方面的应用在过去几十年里受到了极大的关注，并取得了一些显著的商业成功。但挑战仍然存在，这与它对太阳光谱中丰富的更长波长、更低能量的光的光敏化效率相对较低有关。该项目将开发一种高度创新的方法，以提高基于半导体的光催化过程的可见光敏感性。这项研究旨在通过一种基于三重-三重湮灭(TTA)机制的被称为上转换(UC)的独特的光致发光过程来操纵光来放大其频率。通过TTA-UC过程，两个波长较高的光子被组合在一起，转化为波长较低的单光子；这些上转换的光子随后被用于敏化光催化剂，并产生有效降解污染物和灭活水中微生物的活性氧物种(ROS)。研究人员将使用一对有机增感剂和接受剂，实现高效的可见光到可见光或蓝色到UVA的上转换。研究人员将选择各种发色团对，将它们封装到微胶囊中，并将它们与选定的半导体光催化剂偶联。我们将通过各种光致发光、光催化实验和仪器分析来定量评估这个新体系的性质，包括量子产率、激发光谱和发射光谱、能量传递过程的动力学(时间分辨光谱)和ROS的产生。材料合成和系统开发将专门针对污染物降解和水中微生物灭活以及使用后的分离和回收进行测试。确保获得廉价和清洁的水源是本世纪最大的全球挑战之一。先进的材料技术，例如本项目开发的技术，提供了跨越传统基础设施密集型技术的机会，以便在工业化国家和发展中国家开发更可持续的方法，只要成本效益得到保证，并避免不必要的附带影响。这个项目有很大的潜力来开发基于太阳能的技术，有效地收集太阳能光谱中的低能量部分，否则在任何现有的基于光催化剂的过程中都会浪费掉。研究人员预计，UC/光催化剂具有更高的太阳能利用效率和易于分离的能力，可以很容易地在各种环境工程实践中实现，包括太阳能光催化消毒(例如，使用太阳能聚光器)、高级氧化和光催化。该项目旨在通过有效地整合上转换、材料合成、半导体光催化、环境微污染物控制和消毒等光物理来实现这一目标。

CBET 1335934Jaehong KimYale UniversityEnvironmental application of semiconductor photocatalysts as a sustainable technology option has received significant attention over the past few decades with some notable commercial successes. But challenges still remain and are related to its relatively low efficiency of photosensitization by longer-wavelength, lower-energy light that is abundant in the solar spectrum. This project will develop a highly innovative approach of enhancing the visible light susceptibility of semiconductor-based photocatalytic process. This research aims at manipulating light to amplify its frequency via a unique photoluminescence process called upconversion (UC) based on a triplet-triplet annihilation (TTA) mechanism. Through the TTA-UC process, two photons of higher wavelength, which are otherwise wasted, are combined and converted to a single photon with lower wavelength; these upconverted photons are subsequently used to sensitize photocatalysts and to produce reactive oxygen species (ROS) that effectively degrade pollutants and inactivate microorganisms in water. Researchers will employ a pair of organic sensitizers and acceptors that enable a highly efficient visible to visible or blue to UVA upconversion. Researchers will select various chromophore pairs, encapsulate them into microcapsules, and couple them with selected semiconductor photocatalysts. Various photoluminescence and photocatalytic experiments and instrumental analyses will be performed to quantitatively evaluate the properties of this new system including quantum yield, excitation and emission spectra, kinetics of energy transfer process (time-resolved spectra), and ROS production. The material synthesis and system development will be specifically targeted and tested for contaminant degradation and microbial inactivation in water as well as separation and recovery after use.Ensuring access to inexpensive and clean sources of water is one of the greatest global challenges of this century. Advanced materials technology, such as the one developed in this project, offers opportunities to leapfrog over traditional infrastructure-intensive technologies to develop more sustainable approaches in both industrialized and developing countries, as long as cost efficacy is assured and unnecessary collateral impacts are avoided. This project has a great potential to develop solar-based technology that efficiently harvests lower-energy portions of the solar spectrum which is otherwise wasted in any existing photocatalyst-based processes. Researchers expect that UC/photocatalysts with improved solar energy utilization efficiency and capability for easy separation can be readily implemented in various environmental engineering practices including solar photocatalytic disinfection (e.g., implemented using a solar concentrator), advanced oxidation, and photocatalysis. The project aims at achieving this goal through effective integration the photophysics of upconversion, material synthesis, semiconductor photocatalysis, environmental micropollutant control, and disinfection.