NER: Catalytic formation of nanostructured ceramics by a bio-mimetic and environmentally friendly approach

国家科学基金会-主动纳米结构和纳米系统（ANN）（NSF 06-595）纳米尺度探索性研究（NER）提案编号：CBET-0708054主要研究者：Adamson，Douglas附属机构： 普林斯顿大学提案标题：NER：纳米结构陶瓷的催化形成通过仿生和环境友好的方法纳米结构陶瓷的催化形成通过仿生和环境友好的方法纳米结构陶瓷的催化形成数百万年来，自然界已经能够制造出具有精确细节和纳米级控制的陶瓷结构。鲍鱼壳的强度和硅藻中发现的复杂设计是生物体在环境温度下接近中性pH值的条件下产生高度有序的陶瓷材料的两个例子。在人造材料的情况下，不仅缺乏精确的纳米结构，形成陶瓷所需的条件涉及极端的pH值和/或高温。这些条件在成本和环境影响方面是有害的，并且可能妨碍许多有机结构导向剂的使用以及可包括在多孔陶瓷基质中的催化剂的掺入。一种合成系统，可以模仿自然的能力，在温和的条件下产生良好的有序陶瓷在纳米尺度将发现在结构材料，催化和过滤技术的应用范围。我们集中精力研究的自然系统是在海洋海绵Tethya aurantia中发现的蛋白质Silicatein。这种海绵产生由占骨针重量75%的二氧化硅外壳和含有蛋白质混合物的核心组成的二氧化硅骨针。在核心中发现的蛋白质中，70%是硅酸盐。我们关注该蛋白有两个原因：第一，蛋白质的结构已经确定，第二，其催化机制已经阐明。这些研究表明，硅酸盐具有催化正硅酸乙酯（TEOS）水解的能力。水解的硅烷的随后缩合是快速的，并导致二氧化硅的形成。利用这种机制，相对稳定的TEOS可以在室温下和近中性pH下快速转化为silca。我们最近开发了一种合成的，非肽基聚合物，模拟蛋白质Silicatein的催化功能。通过将在蛋白质的催化活性中显示关键的官能团的类似物并入纯合成聚合物中，我们已经证明了在非肽嵌段共聚物中的催化功能。这项工作已经在一份手稿中描述，目前正在考虑由美国化学学会杂志。我们已经通过多种分析和化学方法证明了我们的聚合物在TEOS缩合方面的催化性质。基于我们成功的催化示范，我们将利用嵌段共聚物催化剂的两亲性，在近中性pH和环境温度下形成纳米结构陶瓷。这项工作的高风险因素是使用这种聚合物来模板陶瓷与纳米级的功能和陶瓷的结合，而不是二氧化硅，这两个都没有以前证明。因此，我们将创建一个模拟自然系统的合成系统，其中纳米级模板剂也是催化剂。这笔赠款的更广泛影响包括在环境友好的条件下创造新材料，提高催化效率，生产新的纳米结构陶瓷，并创造新的结构材料。它还将允许将温度或pH敏感材料结合到多孔陶瓷基质中。此外，这笔赠款将支持PI参与外展计划，其中包括本科生研究经验（REU）计划，普林斯顿大学材料学院（CAMA）针对代表性不足的少数民族高中生，以及自由科学中心的常驻科学家计划。该补助金还包括一名本科生的研究活动。将尽一切努力吸引女性或少数民族学生，并向他们介绍尖端研究。这项工作的智力影响是双重的。能够模仿生物过程是真正理解它的最佳途径之一。因此，我们在一个完全合成的系统中复制自然过程的努力将导致对自然过程的更深入理解。其次，在合成纳米级有序陶瓷的过程中，我们将增加对自组装两亲系统的理解，以及如何固定和利用所形成的结构。

National Science Foundation - Active Nanostructure and Nanosystems (ANN) (NSF 06-595)Nanoscale Exploratory Research (NER)Proposal Number: CBET-0708054Principal Investigator: Adamson, DouglasAffiliation: Princeton UniversityProposal Title: NER: Catalytic formation of nanostructured ceramics by a bio-mimetic and environmentally friendly approachNER:Catalytic formation of nanostructured ceramics by a bio-mimetic andenvironmentally friendly approachFor millions of years nature has been able to make ceramic structures with precise detail and control at the nanoscale. The strength of the abalone shell and the intricate designs found in diatoms are two examples of organisms producing highly ordered ceramic materials under conditions of near-neutral pH at ambient temperatures. In the case of man-made materials, not only is the precise nano-structure lacking, the conditions required to form ceramics involve extremes of pH and/or high temperatures. These conditions are detrimental in terms of cost and environmental impact, and may preclude the use of many organic structure-directing agents as well as the incorporation of catalysts that could be included in a porous ceramic matrix. A synthetic system that can mimic the ability of nature to produce well ordered ceramics at the nano-scale under mild conditions would find applications ranging in structural materials, catalysis, and filtration technologies. The natural system on which we have focused our efforts is the protein Silicatein, found in the marine sponge Tethya aurantia. This sponge creates silica spicules that are composed of a silica outer casing comprising 75% of the spicule weight and a core containing a mixture of proteins. Of the protein found in the core, 70% is Silicatein. We focused on this protein for two reasons: first, the structure of the protein had been determined and second, the mechanism of its catalysis had been elucidated. These studies revealed that Silicatein has the ability to catalyze the hydrolysis of tetraethoxysilane (TEOS). The subsequent condensation of the hydrolyzed silane is rapid and results in the formation of silca. Exploiting this mechanism, the relatively stable TEOS can be quickly converted to silca at room temperature and under near neutral pH. We have recently developed a synthetic, non-peptide based polymer that mimics the catalytic function of the protein Silicatein. By incorporating analogs of the functional groups shown to be critical in the catalytic activity of the protein into a purely synthetic polymer, we have demonstrated catalytic function in a non-peptide block copolymer. This work has been described in a manuscript currently under consideration by the Journal of the American Chemical Society. We have demonstrated by numerous analytical and chemical methods the catalytic nature of our polymer with respect to TEOS condensation. Building on our successful demonstration of catalysis, we will exploit the amphiphilic nature of our block copolymer catalyst to form nano-structured ceramics under near-neutral pH and ambient temperatures. The high-risk element of this work is the use of this polymer to template ceramics with nanoscale features and the incorporation of ceramics other than silica, neither of which has been previously demonstrated. We thus will create a synthetic system that mimics the natural system in which a nanoscale templating agent is also a catalyst. The broader impacts of this grant include the creation of new materials that increase the efficiency of catalysis, produce new nanostructured ceramics, and create new structural materials, under environmentally benign conditions. It will also allow for the incorporation of temperature or pH sensitive materials into a porous ceramic matrix. Additionally, this grant will support the PI's involvement in outreach programs that include a Research Experience for Undergraduates (REU) program, Princeton University Materials Academy (PUMA) targeted at underrepresented minority high school students, and the Scientist in Residence program at the Liberty Science Center. This grant also includes research activities for an undergraduate student. Every effort will be made to attract a female or minority student and introduce them to cutting edge research. The intellectual impact of this work is two-fold. Being able to mimic a biological process is one of the best ways to truly understand it. Thus our efforts to reproduce what nature does in a completely synthetic system will lead to a deeper understanding of the natural process. Secondly, in synthesizing a ceramic ordered at the nano-scale, we will increase our understanding of self-assembled amphiphilic systems and how the structures formed can be immobilized and exploited.