Single Molecule Dynamics at a Mechanically Controllable Break Junction in Solution at Room Temperature
Single Molecule Dynamics at a Mechanically Controllable Break Junction in Solution at Room Temperature
复制标题
DOI：
10.1021/ja307821u
复制
发表时间：
2013-01-23
影响因子：
15
通讯作者：
Murakoshi, Kei
中科院分区：
文献类型：
--
作者：
Konishi, Tatsuya;Kiguchi, Manabu;Murakoshi, Kei
对单分子结的几何和电子结构动力学的原位观测对于分子电子学的进一步发展具有重要意义。然而，由于灵敏度的限制，单分子结的观察是困难的。在这里，我们报告的表面增强拉曼散射（SEAS）的一个单一的4，4 '-联吡啶分子的条件下，在原位电流在纳米间隙中，通过使用纳米制造的，机械可控的断裂结（MCBJ）电极。当在室温下吸附在溶液中的金属纳米电极上形成单分子结时，统计分析表明，4，4 '-联吡啶的非完全对称B（1）和B（2）模式相对于在固体或水溶液中观察到的相同模式强烈增强。Sers强度，能量（波数），和选择性的拉曼振动带，是符合电流波动的显着变化提供信息的不同状态的电子和几何结构的单分子结，即使在室温下发生的大的热波动。通过B（1）和B（2）模式转换，我们观察到4，4 '-联吡啶在Au纳米间隙中垂直和倾斜构型之间的运动动力学。通过观察分子结的拉曼模能量的增加和电导的降低，还观察到分子的倾斜角略有增加。
The in situ observation of geometrical and electronic structural dynamics of a single molecule junction is critically important in order to further progress in molecular electronics. Observations of single molecular junctions are difficult, however, because of sensitivity limits. Here, we report surface-enhanced Raman scattering (SEAS) of a single 4,4'-bipyridine molecule under conditions of in situ current flow in a nanogap, by using nano-fabricated, mechanically controllable break junction (MCBJ) electrodes. When adsorbed at room temperature on metal nanoelectrodes in solution to form a single molecule junction, statistical analysis showed that nontotally symmetric b(1) and b(2) modes of 4,4'-bipyridine were strongly enhanced relative to observations of the same modes in solid or aqueous solutions. Significant changes in SERS intensity, energy (wavenumber), and selectivity of Raman vibrational bands that are coincident with current fluctuations provide information on distinct states of electronic and geometrical structure of the single molecule junction, even under large thermal fluctuations occurring at room temperature. We observed the dynamics of 4,4'-bipyridine motion between vertical and tilting configurations in the Au nanogap via b(1) and b(2) mode switching. A slight increase in the tilting angle of the molecule was also observed by noting the increase in the energies of Raman modes and the decrease in conductance of the molecular junction.