Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences , Beijing, 100190, People's Republic of China.
ACS Nano. 2013 Sep 24;7(9):7573-82. doi: 10.1021/nn402889h. Epub 2013 Aug 19.
The size, shape, and crystallinity of organic nanostructures play an important role in their physical properties and are mainly determined by the self-assembling kinetics of molecular components often involving the solvent conditions. Here, we reported a kinetically controlled self-assembly of C60 assisted by the solvent carbon bisulfide (CS2) into single-crystal ultrathin microribbons of 2C60·3CS2, upon mixing the poor solvent isopropyl alcohol with a C60/CS2 stock solution. Surface energy calculations reveal that these microribbons represent a kinetically favored high-energy state as compared with the thermodynamically stable shape of prismatic rods. High-resolution transmission electron microscopy observations clarify that association of CS2 at the nucleation stage helps to guide and rigidify the formation of π-π stacking 1D chains of C60 through the surrounding CS2 cage-like structures, which further act as glue, boosting lateral assembly of as-formed 1D chains into untrathin 2D microribbon single crystals. Precise control over the thickness, width, and length of 2C60·3CS2 microribbons was achieved by manipulation of the growth kinetics through adjusting the solvent conditions. Upon heating to 120 °C, sublimation of CS2 components results in fcc C60 microribbons. We found that both microribbons of solvated monoclinic 2C60·3CS2 and pure fcc C60 exhibit highly sensitive photoconductivity properties with a spectral response range covering UV to visible. The highest on/off ratio of two-terminal photodetectors based on single ribbons reaches around 250, while the responsitivity is about 75.3 A W(-1) in the UV region and 90.4 A W(-1) in the visible region.
有机纳米结构的大小、形状和结晶度对其物理性质起着重要作用，主要由分子组件的自组装动力学决定，这通常涉及溶剂条件。在这里，我们报道了 C60 在溶剂二硫化碳 (CS2) 的辅助下通过动力学控制自组装，形成 2C60·3CS2 的单晶超薄微带，方法是将不良溶剂异丙醇与 C60/CS2 储备溶液混合。表面能计算表明，与热力学稳定的棱柱形棒相比，这些微带代表了一种动力学上有利的高能状态。高分辨率透射电子显微镜观察表明，在成核阶段 CS2 的缔合有助于通过周围 CS2 笼状结构引导和刚性化 C60 的π-π堆叠一维链的形成，这进一步充当了胶，促进了所形成的一维链的横向组装成超薄 2D 微带单晶。通过控制溶剂条件来调节生长动力学，可以精确控制 2C60·3CS2 微带的厚度、宽度和长度。加热至 120°C 时，CS2 成分升华得到 fcc C60 微带。我们发现，溶剂化的单斜 2C60·3CS2 和纯 fcc C60 的微带都表现出对光高度敏感的光电导性能，光谱响应范围涵盖紫外至可见光。基于单个微带的两端光电探测器的最高开/关比约为 250，而在紫外区域的响应度约为 75.3 A W(-1)，在可见区域的响应度约为 90.4 A W(-1)。
