Tailoring Single-Walled Carbon Nanotubes with Structure-Selective Photochemistry

威廉·马什·赖斯大学的罗伯特·B·魏斯曼教授在化学系大分子、超分子和纳米化学计划的支持下，开发了利用特定波长的激光光源控制和操纵单壁碳纳米管的光学和化学性质的新方法。碳纳米管是一类令人兴奋的纳米材料，因其独特的物理化学性质和许多潜在的现实应用而在技术上具有重要意义，包括在能源、医疗保健和环境方面的应用。目前的碳纳米管制备方法导致了具有多种结构形式和性质的混合物。为了获得适合特定应用的样品，通常需要对这些混合组分进行分离和分选。该项目选择性地改变目标纳米管物种的表面化学，使它们能够比目前可能的更容易和可伸缩性地物理分离。其目的是产生具有量身定制的光学性质和组成的样品，使人们能够更深入地了解碳纳米管反应、与光的相互作用以及潜在的实际应用。除了对学生进行纳米材料高级光谱学和分析化学方面的培训外，高中教师和一名专业视觉艺术家也参与了这个项目。教师们被招待在实验室进行暑期研究，从而获得知识和视角来丰富他们的教学。这位艺术家正在将荧光碳纳米管融入他的作品中，以吸引和教育公众关于纳米技术的知识。在这个项目中，短波红外波长的光学跃迁被用作控制单壁碳纳米管混合物的组成的工具。用特定短波红外波长的激光照射含有许多不同直径和手性的纳米管的样品，以选择性地激发样品中目标纳米管的S11跃迁。在适当的反应物存在下，这些被激发的纳米管成为化学官能化的。由此得到的选择性功能化的纳米管结构显示出改变的物理化学性质和抑制的荧光产量。通过这种方式，样品发射光谱的目标部分被“切割”出来，以生成适合于基础研究和应用开发的定制光谱配置文件。使用双水相分离或受控离心法等方法对样品进行后续处理，可将功能化的目标结构与样品的其余部分分离。然后使用热和化学方法使分离的组分去官能化，以恢复物理分离的结构的原始形式。最终目标是产生具有定制光学性质和组成的结构分类的碳纳米管样品。这些研究是为了更深入地了解碳纳米管光谱学、光过程和反应。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Professor Robert B. Weisman of William Marsh Rice University is supported by the Macromolecular, Supramolecular and Nanochemistry Program of the Division of Chemistry to develop new methods to control and manipulate the optical and chemical properties of single-wall carbon nanotubes using laser light sources of specific wavelengths. Carbon nanotubes are an exciting class of nanomaterials that are technologically important for their unique physical and chemical properties and their many potential real-world applications, including uses in energy, health care, and the environment. Current carbon nanotube preparation methods result in mixtures with many structural forms and properties. Separation and sorting of these mixed components are often needed to obtain samples suitable for specific applications. The project selectively alters the surface chemistry of targeted nanotube species to allow them to be physically separated with greater ease and scalability than is currently possible. The aim is to generate samples with tailored optical properties and compositions, enabling advanced and deeper understanding of carbon nanotube reactions, interactions with light, and potential practical applications. In addition to training students in the advanced spectroscopy and analytical chemistry of nanomaterials, high school teachers and a professional visual artist are involved in the project. The teachers are hosted in the laboratory to conduct summer research, thereby gaining knowledge and perspective to enrich their teaching. The artist is incorporating fluorescent carbon nanotubes into his artwork to engage and educate the public about nanotechnology.In this project, optical transitions at short-wave infrared wavelengths are used as a tool to control the composition of single-wall carbon nanotube mixtures. Samples containing nanotubes of many different diameters and chiralities are irradiated with lasers at specific short-wave infrared wavelengths chosen to selectively excite the S11 transitions of targeted nanotubes within the sample. In the presence of appropriate reactants, those excited nanotubes become chemically functionalized. The resulting selectively functionalized nanotube structures exhibit altered physico-chemical properties and suppressed fluorescence yields. In this way, targeted portions of the sample's emission spectrum are "carved out" to generate customized spectral profiles suited for use in basic research and applications development. Subsequent processing of the sample using methods such as aqueous two-phase partitioning or controlled centrifugation isolates the functionalized targeted structure from the rest of the sample. The isolated fraction is then defunctionalized using thermal and chemical methods to recover the physically separated structure in its pristine form. The ultimate goal is to generate structurally sorted carbon nanotube samples with tailored optical properties and compositions. These are investigated to arrive at a deeper understanding of carbon nanotube spectroscopy, photo-processes, and reactions.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.