Didenko Vladimir V, Moore Valerie C, Baskin David S, Smalley Richard E
Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030, USA.
Nano Lett. 2005 Aug;5(8):1563-7. doi: 10.1021/nl050840h.
Manipulating optical properties of single-walled nanotubes (SWNTs) is necessary for the development of nanoscale optical devices and probes for biomedical research. In life sciences it will make possible the direct observation of SWNTs inside living cells using optical microscopes. In the nanotechnology field it will enable the development of nanosensors with fluorescent reporting. However, the direct fluorescent labeling of SWNTs is obstructed by their strong light quenching qualities. Besides, chemical functionalization of SWNTs needed for the covalent attachment of fluorescent dyes could change favorable properties of nanotubes. Here we report that optical properties of SWNTs can be manipulated without their covalent modification by wrapping them with fluorescently labeled polymer poly(vinylpyrrolidone) (PVP-1300). Fluorescent PVP-1300 forms a monomolecular approximately 2.5 nm thick layer coiling around individual SWNTs and nanotube bundles. PVP casing is fluorescent although it is only several nanometers thick. This makes individual SWNTs observable by a fluorescent microscope. The spare polymer strands left over after wrapping around the relatively shorter nanotubes form junctions between SWNTs tying them together into new configurations, primarily Y- and psi-type junctions. The ability to use a single fluorescent polymer strand to fasten nanotubes together can be useful in assembly of nanotube-made devices. In PVP-covered SWNTs multiple fluorophores are attached to each single nanotube making them unique composite fluorophores attractive as parts of biological fluorescent probes and in the development of the new materials in photonics and nanotechnology.
操纵单壁纳米管（SWNTs）的光学性质对于纳米级光学器件的开发以及生物医学研究用探针而言是必要的。在生命科学领域，这将使利用光学显微镜直接观察活细胞内的单壁纳米管成为可能。在纳米技术领域，这将推动具有荧光报告功能的纳米传感器的开发。然而，单壁纳米管的强光猝灭特性阻碍了其直接荧光标记。此外，用于荧光染料共价连接所需的单壁纳米管化学功能化可能会改变纳米管的有利特性。在此我们报告，通过用荧光标记的聚合物聚乙烯吡咯烷酮（PVP - 1300）包裹单壁纳米管，可以在不进行共价修饰的情况下操纵其光学性质。荧光PVP - 1300形成一层约2.5纳米厚的单分子层，围绕单个单壁纳米管和纳米管束盘绕。尽管PVP外壳只有几纳米厚，但它具有荧光性。这使得单个单壁纳米管能够通过荧光显微镜观察到。在包裹相对较短的纳米管后剩余的多余聚合物链在单壁纳米管之间形成连接点，将它们连接成新的构型，主要是Y型和ψ型连接点。利用单条荧光聚合物链将纳米管连接在一起的能力在纳米管制成的器件组装中可能会很有用。在PVP覆盖的单壁纳米管中，多个荧光团附着在每个单纳米管上，使其成为独特的复合荧光团，作为生物荧光探针的组成部分以及在光子学和纳米技术新材料的开发中具有吸引力。
