Photochemically-induced electronic switching in carbon nanotubes

本项目的中心目标是制造和研究纳米线，这些纳米线能够分别在高导电性和低导电性两种状态之间进行可逆切换。电子开关将在单壁碳纳米管（SWCNT）内基于光诱导反应实现，所述光诱导反应降低管的π共轭系统的延伸，从而降低其导电性。为了获得能够重复可逆开关的稳定装置，单壁碳纳米管将被封闭在由蒽衍生物组成的紧凑的表面活性剂壳中。选择这种类型的化合物是因为初步实验揭示了蒽与SWCNT的光诱导环加成的可能性，这可以通过热活化来逆转。蒽基表面活性剂的化学结构将被优化，以实现与SWCNT的石墨烯层的足够强的π相互作用，结合良好平衡的疏水/亲水特性。将进行透射电子显微镜、荧光光谱和原子力显微镜以确定SWCNT上两亲物的分子排列和SWCNT/复合物对水溶液的稳定性，两者都是pH值、不同离子的存在、温度以及光照射的函数。的单壁碳纳米管/表面活性剂复合物的电子结构进行比较之前和之后的光照射详细的电荷传输测量，扫描隧道光谱和空间高分辨拉曼光谱。由于在所有三种方法中，将检查相同的单个SWCNT，因此获得的数据将允许对辐射效应进行明确的解释。将采用相同类型的调查，以确定是否可以热诱导或通过较短波长的照射实现的逆反应，包括环回复到起始构型。此外，将进行热循环或光循环研究，以研究器械的长期稳定性。

The central goal of the present project is the fabrication and investigation of nanowires that are able to undergo a reversible switch between two states of high and low electrical conductivity, respectively. The electronic switch shall be realised within single-wall carbon nanotubes (SWCNT) on the basis of light-induced reactions that decrease the extension of the pi-conjugated system of the tubes and hence their conductivity. To obtain stable devices capable of repeated reversible switches, the SWCNTs will be enclosed in a compact surfactant shell consisting of an anthracene derivative. This type of compound is chosen since preliminary experiments revealed the possibility of photo-induced cycloaddition of anthracene to SWCNTs, which can be reversed by thermal activation. The chemical structure of the anthracene-based surfactants will be optimised to achieve sufficiently strong pi-interaction with the graphene layer of the SWCNTs, combined with a well-balanced hydrophobic/hydrophilic character.Transmission electron microscopy, fluorescence spectroscopy, and atomic force microscopy will be performed to determine the molecular arrangement of the amphiphiles on the SWCNT and the stability of the SWCNT/complexes against aqueous solutions, both as a function of pH value, the presence of different ions, temperature, as well as photo-irradiation. The electronic structure of the SWCNT/surfactant complexes will be compared before and after photo-irradiation by detailed charge transport measurements, scanning tunnelling spectroscopy and spatially high-resolved Raman spectroscopy. Since in all three methods the same individual SWCNTs will be examined, the obtained data will allow an unequivocal interpretation of the radiation effect. The same types of investigation will be employed to determine whether the back reaction, consisting of cycloreversion to the starting configuration, can be thermally induced or achieved via irradiation with a shorter wavelength. In addition, thermal- or photo-cycling studies will be carried out to investigate the long term stability of the devices.