LEAPS-MPS: Harnessing materials from nature: from biomaterials to metal oxides

人们普遍认为，自从第一批动植物出现在地球上以来，大自然一直在完善它的材料。因此，大自然给了我们一些最好和最独特的材料的灵感，比如壁虎脚、鲨鱼皮和荷叶。仿生材料试图通过模仿天然材料的结构来利用这数亿年的进化。不幸的是，天然材料通常很难或不可能在我们的实验室中复制，因为每种新的生物材料通常需要一种新的，量身定制的策略来将其复制为人造材料。这样的策略，如果存在的话，通常是相当复杂的，限制了可能的材料组成，使它们难以扩大规模。“碳复制”天然材料的过程将是一个完美的解决方案。本项目将研究利用化学方法将天然材料矿化成金属氧化物的过程。通过将天然材料样品转化为具有相同结构但成分不同的金属氧化物样品，这种矿化过程可以用于仿生材料的快速原型制作。它还可用于将农业和林业工业的生物质原料和生物废弃物转化为催化、储能和转化、吸附、传感和光学应用的新型增值材料。该项目还整合了一项全面计划，以增加代表性不足群体对STEM的参与，并增加来自工业界和学术界代表性不足群体的领导者和榜样的数量。该计划将高中和社区外展活动与对高中生、本科生和研究生的培训和指导结合起来。第2部分：技术概述非水解溶胶-凝胶（NHSG）矿化证明了天然纤维素材料转化为具有结构保留的金属氧化物。然而，我们目前缺乏对固体材料如何完成这一过程的理解，以及它是否可以应用于其他天然材料。本研究计划的总体目标是了解纤维素的NHSG矿化机制及其与其他天然材料的相容性。中心假设是NHSG矿化与其他多糖和富氧聚合物兼容，如果它们可以被溶剂膨胀，并且具有适当类型和数量的氧基团。强调提出的研究的基本原理是，产生的理解将解开将天然材料转化为具有定制成分的金属氧化物的一般策略。PI计划通过追求以下具体目标来实现总体目标：(1)阐明纤维素材料的NHSG矿化机制；(2)阐明NHSG矿化与其他聚合物材料的相容性。为了完成具体目标#1，PI将使用精心设计的纤维素材料，通过横断面扫描电子显微镜和能量色散x射线光谱的元素映射来研究转化过程。具体目标2将通过测试NHSG矿化中具有广泛化学和结构特性的常见天然聚合物来完成，以了解聚合物材料实现有效转化的要求。该项目还将支持对研究生、本科生和高中生的培训。高中学生将参加一个为期8周的暑期研究项目，在此期间他们将进行研究并接受指导，以使他们能够继续接受STEM教育。总体而言，该项目将支持至少一名女性、一名未被充分代表的少数族裔学生和两名弱势学生参与STEM。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARYIt is widely appreciated that nature has been perfecting its materials since the first plants and animals appeared on Earth. Thus, nature gives us inspiration for some of the best and most unique materials, such as gecko feet, shark skin, and lotus leaves. Biomimetic materials try to capitalize on these hundreds of millions of years of evolution by mimicking the structures of natural materials. Unfortunately, natural materials are often difficult or impossible to reproduce in our laboratories since each new biomaterial generally requires a new, tailored strategy to reproduce it as a man-made material. Such strategies, if exist, are often quite intricate, limiting the possible material compositions and making them difficult to scale up. A process for "carbon copying" natural materials would be a perfect solution. This project will study a process of mineralization of natural materials into metal oxides using chemistry. Such mineralization process can then be used for quick prototyping of biomimetic materials by converting samples of natural materials into metal oxide samples with the same structure but varied compositions. It can also be used to convert feedstock of biomass and biowaste from agricultural and forestry industries into new, value-added, materials for catalysis, energy storage and conversion, adsorption, sensing, and optical applications. The project also integrates a comprehensive plan for increasing participation of underrepresented groups in STEM and the numbers of leaders and role models from underrepresented groups in industry and academia. This plan combines high-school and community outreach activities with training and mentoring of high school, undergraduate, and graduate students.PART 2: TECHNICAL SUMMARYNon-hydrolytic sol-gel (NHSG) mineralization demonstrated conversion of natural cellulosic materials into metal oxides with structure retention. However, we currently lack the understanding of how this process is completed for solid materials and if it can be applied to other natural materials. The overall objective of this research proposal is to understand the mechanism of NHSG mineralization of cellulose and its compatibility with other natural materials. The central hypothesis is that NHSG mineralization is compatible with other polysaccharides and oxygen-rich polymers if they can be swelled by the solvent and have an appropriate type and amount of oxygen groups. The rationale that underlines the proposed research is that the generated understanding will unlock a general strategy for converting natural materials into metal oxides with tailored composition. PI plans to achieve the overall objective by pursuing the following specific objectives: (1) elucidate mechanism of NHSG mineralization for cellulosic materials and (2) elucidate compatibility of NHSG mineralization with other polymeric materials. To complete Specific Objective #1, PI will use carefully designed cellulose materials to study the conversion process with cross-sectional scanning electron microscopy coupled with elemental mapping via energy-dispersive X-ray spectroscopy. Specific Objective #2 will be completed by testing common natural polymers with broad range of chemical and structural properties in NHSG mineralization to understand requirements for polymeric materials to achieve effective conversion. The project will also support training of graduate, undergraduate, and high school students. High school students will be hosted for an 8-week summer research project where they will conduct research and receive mentoring to empower them to continue into STEM education. Overall, the project will support participation of at least one woman, one underrepresented minority student, and two disadvantaged students in STEM.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.