Converting Visible Light to UVC: Lanthanide Upconversion Nano-Phosphors for Light-Activated Biocidal Surface Development

将可见光转换为 UVC：用于光激活杀菌表面开发的镧系元素上转换纳米荧光粉

• 批准号: 1033866
• 负责人: Jaehong Kim
• 金额: $ 31.89万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-01-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1033866&HistoricalAwards=false
• 关键词: Converting; Visible; Light; UVC; Lanthanide

Lanthanide-doped upconversion phosphor (UCP) materials can absorb one or more low-energy photons and subsequently emit one higher-energy, lower-wavelength photon via a unique photoluminescence process called upconversion. UCP nanocrystals that are capable of converting IR radiation to visible light have seen intensive research in the past decade and have already begun to emerge in solar energy and biomedical applications. We herein recognize the great potential for exploiting UCP nanocrystals - that are engineered to convert ordinary visible light into germicidal ultraviolet radiation - in creating highly innovative biocidal surface technologies, i.e., surfaces that inactivate microorganisms when exposed to visible light.Hypothesis. While a handful of visible-to-UV upconversion materials already exist in the literature, their conversion efficiencies are considered too low for practical biocidal applications. However, based on the recent advances made in IR-to-visible light upconversion technology, they hypothesize that (i) sophisticated material design will lead to higher, more practical upconversion efficiencies and enable UV-emission under low-power sunlight or ambient indoorlight conditions; and (ii) such improvements can be achieved through careful selection of lanthanide dopant combinations, low vibrational host matrices, and nano-structural optimization.They further hypothesize that surfaces coated with carefully engineered nanocrystalline UV-emitting phosphors will exhibit biocidal effects, providing an effective, cost-efficient, and sustainable alternative to current antimicrobial surfaces for the deterrence of pathogen transfer.Objectives. The primary focus of the proposed research is to explore fundamental nanophosphor design strategies that result in efficient upconversion of broadband visible light into UV photons in the germicidal range and, consequently, effective biocidal action when coated onto surfaces.Approach. Upconversion nanocrystals will be synthesized via sol-gel decomposition and hydrothermal techniques with varying lanthanide dopant combinations, host crystals and nanostructural modifications. The efficiency and mechanisms of energy transfer processes will be gauged using a custom-built high-energy laser photoluminescence spectroscopy. Materials will be characterized using X-ray diffraction analysis, transmission electron microscopy, etc. Biocidal efficacy and biofilm inhibition will be determined via kinetic viability assays and scanning confocal laser microscopy, respectively, using various test microorganisms.Intellectual Merits. The idea of engineering upconversion nanophosphors for light-activated biocidal surface development has never been explored in the literature. The proposed study will provide fundamental, first-step knowledge in UV-emitting upconversion nanophosphor synthesis strategies, material characterization, and environmental technology applicability. This researchwill also answer fundamental questions regarding: (i) similarities and differences between the well-understood IR-to-visible upconversion and visible-to-UV upconversion processes; and (ii)design aspects that promote the conversion of a broad range of excitation wavelengths.Broader Impacts. The advancement of light conversion materials is a critical forefront in sustainable and green technology, as it allows utilization of renewable energy as well as, in this case, decreased reliance on continuous chemical application. Surfaces which can inherently remain pathogen free are a long sought-after tool for inhibiting pathogen transfer in hospitals,food industry, and public areas, while we additionally envision application to solar water disinfection kits for the developing world. Educating undergraduate and graduate students is an integral part of the proposed project and will provide participating students with exceptional interdisciplinary and collaborative learning experiences in applied solid-state physics/chemistry,material science, nanotechnology, and environmental engineering. The project will also leverage an existing high school student summer internship program.

掺杂镧系元素的上转换磷光体（UCP）材料可以吸收一个或多个低能光子，随后通过称为上转换的独特光致发光过程发射一个较高能量、较低波长的光子。能够将红外辐射转换为可见光的UCP纳米晶体在过去十年中得到了深入的研究，并且已经开始出现在太阳能和生物医学应用中。我们在此认识到利用UCP纳米晶体的巨大潜力-其被设计成将普通可见光转化为杀菌紫外线辐射-在创建高度创新的生物杀灭表面技术中，即，当暴露在可见光下时微生物的表面。虽然在文献中已经存在少数可见光-UV上转换材料，但是它们的转换效率对于实际的生物杀灭应用而言被认为太低。然而，基于IR到可见光上转换技术的最新进展，他们假设（i）复杂的材料设计将导致更高、更实用的上转换效率，并在低功率阳光或环境室内光条件下实现UV发射;和（ii）通过仔细选择镧系元素掺杂剂组合，低振动主体基质，他们进一步假设涂覆有精心设计的纳米晶UV发射磷光体的表面将表现出杀生物效果，为当前的抗微生物表面提供有效、具有成本效益和可持续的替代方案，以阻止病原体转移。拟议研究的主要重点是探索基本的纳米荧光粉设计策略，这些策略可以将宽带可见光有效地上转换为杀菌范围内的UV光子，从而在涂覆到表面上时发挥有效的杀菌作用。上转换纳米晶体将通过溶胶-凝胶分解和水热技术与不同的镧系元素掺杂剂组合，主体晶体和纳米结构修饰合成。能量转移过程的效率和机制将使用定制的高能激光光致发光光谱仪进行测量。将使用X射线衍射分析、透射电子显微镜等对材料进行表征。将使用各种测试微生物，分别通过动力学活力测定和扫描共聚焦激光显微镜测定杀生物功效和生物膜抑制。工程上转换纳米荧光粉用于光激活的杀生物表面开发的想法在文献中从未被探索过。拟议的研究将提供基本的，第一步的知识，在紫外线发射上转换纳米荧光粉的合成策略，材料表征和环境技术的适用性。这项研究还将回答以下基本问题：（i）众所周知的IR到可见光上转换和可见光到UV上转换过程之间的相似性和差异;以及（ii）促进宽范围激发波长转换的设计方面。光转换材料的进步是可持续和绿色技术的关键前沿，因为它允许利用可再生能源，并且在这种情况下，减少对连续化学应用的依赖。可以保持无病原体的表面是长期以来在医院，食品工业和公共场所抑制病原体转移的工具，同时我们还设想将其应用于发展中国家的太阳能水消毒套件。教育本科生和研究生是拟议项目的一个组成部分，并将为参与学生提供应用固态物理/化学，材料科学，纳米技术和环境工程方面的特殊跨学科和协作学习经验。该项目还将利用现有的高中生暑期实习计划。