State Key Laboratory of Physical Chemistry of Solid Surfaces and Key Laboratory of Analytical Sciences, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
Nat Commun. 2011;2:305. doi: 10.1038/ncomms1310.
The conductance of single-molecule junctions may be governed by the structure of the molecule in the gap or by the way it bonds with the leads, and the information contained in a Raman spectrum is ideal for examining both. Here we demonstrate that molecule-to-surface bonding may be characterized during electron transport by 'fishing-mode' tip-enhanced Raman spectroscopy (FM-TERS). This technique allows mutually verifiable single-molecule conductance and Raman signals with single-molecule contributions to be acquired simultaneously at room temperature. Density functional theory calculations reveal that the most significant spectral change seen for a gold-4,4'-bipyridine-gold junction results from the deformation of the pyridine ring in contact with the drain electrode at high voltage, and these calculations suggest that a stronger bonding interaction between the molecule and the drain may account for the nonlinear dependence of conductance on bias voltage. FM-TERS will lead to a better understanding of electron-transport processes in molecular junctions.
单分子结的电导可能由间隙中分子的结构或其与引线的键合方式决定，而拉曼光谱中包含的信息非常适合同时检查这两个方面。在这里，我们证明了在电子输运过程中，通过“钓鱼模式”针尖增强拉曼光谱（FM-TERS）可以对分子到表面的键合进行表征。该技术允许在室温下同时获得相互验证的单分子电导和拉曼信号，并且单分子的贡献也可被检测到。密度泛函理论计算表明，对于金-4,4'-联吡啶-金结，在高电压下与漏极接触的吡啶环的变形导致了最显著的光谱变化，并且这些计算表明，分子和漏极之间更强的键合相互作用可能导致电导对偏压的非线性依赖性。FM-TERS 将有助于更好地理解分子结中的电子输运过程。
