Collaborative Research: Probing Reconfigurable Nanoparticle Biointerfaces using Catalysis

迈阿密大学的Marc Knecht教授和纽约州立大学石溪分校的Anatoly I. Frenkel教授在化学系的大分子、超分子和纳米化学（MSN）项目的支持下，开发了生物分子键合纳米颗粒，用于独特的催化应用。纳米粒子是一种难以置信的小尺寸材料，比人类一根头发的宽度还小1000倍。为了防止这些颗粒不受控制地聚集成更大的结构，小分子被化学地束缚在颗粒表面。这些分子，也被称为配体，使纳米颗粒稳定地悬浮在溶液中，从而可以研究从收集太阳能到化学催化等广泛应用的材料特性。虽然这些配体非常重要，但它们通常被锁定在单一构象中，从而限制了纳米颗粒的性能。在这个项目中，Knecht教授和Frenkel教授正在利用生物学灵感和分子设计来开发生物配体，这种配体在受到特定波长或颜色的光照射时可以改变其结构。当这些生物分子被用来稳定金属纳米粒子时，它们可以在与材料结合时改变它们的排列，从而获得两种不同的构象并增强单一材料的潜在性能。这些构象差异和材料性质的变化正在使用催化和先进的光谱学方法进行研究，为材料设计提供了大量细节。Knecht教授和Frenkel教授还鼓励本科生将这项研究与入门级教育相结合，以鼓励学生从事与科学相关的研究和职业。此外，实施大一、大二通识、有机课程、实验课程调整方案，提高化学本科学生的保有率。胶体金属纳米颗粒通常使用表面钝化配体构建，这些配体与无机表面紧密结合，将其锁定为单一构型。通过能够远程驱动颗粒表面的界面结构以采用不同的构象，可以根据需要调整材料的性能。Knecht教授和Frenkel教授假设，基于肽的纳米颗粒钝化剂可以通过外部刺激远程可逆地重新配置，以采用两种不同的配置来按需控制材料性能。这种能力是通过将光开关集成到肽结构中来实现的。由于生物分子与纳米颗粒表面的结合，光开关异构化状态的变化可以通过肽的构象进行传播。这种能力正在使用催化剂作为配体结构构象的表面探针进行检查，其中反应速率的差异是可观察到的。这些差异正被用来实现开/关催化反应性，这对于多步反应可能很重要。此外，作为本研究的一部分，纳米颗粒的先进的、原位的和操作的x射线光谱分析被用来识别粒子表面结构的变化，作为光开关和催化之前、期间和之后配体构象的函数。最后，研究了纳米颗粒组成、大小和形状的影响，以调节基于光开关的肽结构差异水平，从而增强对颗粒催化性能的控制。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。

Professor Marc Knecht of the University of Miami and Professor Anatoly I. Frenkel of SUNY at Stony Brook are supported by the Macromolecular, Supramolecular and Nanochemistry (MSN) Program of the Division of Chemistry to develop biomolecule-bonded nanoparticles for unique applications in catalysis. Nanoparticles are incredibly small-sized materials that are 1000 times smaller than the width of one strand of human hair. To prevent these particles from uncontrollably aggregating to larger structures, small molecules are chemically bound to the particle surface. These molecules, also called ligands, keep the nanoparticles stably suspended in solution, allowing for studies of the material properties for wide ranging applications from harvesting solar energy to chemical catalysis. While these ligands are incredibly important, they are typically locked in a single conformation, thus limiting the properties of a nanoparticle. In this project, Professors Knecht and Frenkel are using biological inspiration and molecular design to develop biological ligands that can change their structure when irradiated with light of a certain wavelength or color. When these biomolecules are used to stabilize metal nanoparticles, they can change their arrangement when bound to the material, thus accessing two different conformations and enhancing the potential properties of a single material. These conformation differences and the changes to the material properties are being studied using catalysis and advanced spectroscopy methods, providing great detail to aid in material design. Professors Knecht and Frenkel are also engaging undergraduate students with the integration of this research with education at the entry level to encourage students into science related studies and careers. In addition, plans are implemented to realign the Freshman and Sophomore general and organic courses and laboratories to improve the chemistry undergraduate students' retention ratio. Colloidal metal nanoparticles are typically constructed using surface passivating ligands that are rigidly bound to the inorganic surface, locking them into a single configuration. By having the ability to remotely actuate the interfacial structure on the particle surface to adopt different conformations, the properties of the materials could be tuned on demand. Professors Knecht and Frenkel hypothesize that peptide-based nanoparticle passivants can be remotely and reversibly reconfigured via external stimuli to adopt two different configurations for on demand material property control. Such capabilities are achievable through the integration of a photoswitch into the peptide structure. Changes in the photoswitch isomerization state can be propagated through the peptide conformation due to the binding between the biomolecule and the nanoparticle surface. This capability is being examined using catalysis as a surface probe of the ligand structural conformation, where differences in reaction rates are observable. These differences are being exploited to achieve on/off catalytic reactivity, which could be important for multistep reactions. Furthermore, as part of this study, advanced, in situ and operando X-ray spectroscopic analysis of the nanoparticles are being used to identify changes in particle surface structure as a function of ligand conformation before, during, and after photoswitching and catalysis. Finally, the effects of the nanoparticle composition, size, and shape are being studied to modulate the level of photoswitch-based peptide structural differences for enhanced control over the particle catalytic properties.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.