Conformation, and Charge Tunneling through Molecules in SAMs
Conformation, and Charge Tunneling through Molecules in SAMs
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DOI：
10.1021/jacs.0c12571
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发表时间：
2021-02-23
影响因子：
15
通讯作者：
Whitesides, George M.
中科院分区：
文献类型：
--
作者：
Belding, Lee;Root, Samuel E.;Whitesides, George M.
本文证明了自组装单层（sam）分子的分子构象（除了组成和结构外）影响通过自组装单层（sam）的电荷隧穿（CT）速率，在AuTS/S(CH2)(2)(CONRR2)-R-1//Ga2O3/EGaIn形式的分子结中，R-1和R-2是不同长度的烷基链。选择链R-1和R-2的长度来影响分子在单分子层中的构象和构象均匀性。分子的构象影响单层的厚度（即隧道势垒宽度）及其在+/- 1.0 V下的整流比。当R-1 = H时，分子是有序的，并且主要以转展构象存在。然而，当R-1是烷基时（例如，R-1不等于H），它们的构象不能再全反展，分子采用更多的间扭二面角。这种构象类型的改变降低了构象顺序并影响了隧穿速率。当r 1 = r2, CT的利率降低(6.3 x),相对于利率CT观察到通过地空导弹拥有相同的总链的长度,厚度,当r 1 = H r 1不等于H不等于r2的时候,有一个较弱的相关性(相对于,当r 1 = H或r 1 = r2)电流密度与链长度或单层厚度、和在某些情况下,利率的CT通过地空导弹由分子与不同的r2组织是不同的,即使SAMs的厚度（由XPS确定）相同。这些结果表明，由绝缘的、含酰胺的烷硫醇组成的单层膜的厚度并不是决定CT速率的唯一因素，电荷隧穿速率受组成结的分子构象的影响。
This paper demonstrates that the molecular conformation (in addition to the composition and structure) of molecules making up self-assembled monolayers (SAMs) influences the rates of charge tunneling (CT) through them, in molecular junctions of the form AuTS/S(CH2)(2)(CONRR2)-R-1//Ga2O3/EGaIn, where R-1 and R-2 are alkyl chains of different length. The lengths of chains R-1 and R-2 were selected to influence the conformations and conformational homogeneity of the molecules in the monolayer. The conformations of the molecules influence the thickness of the monolayer (i.e. tunneling barrier width) and their rectification ratios at +/- 1.0 V. When R-1 = H, the molecules are well ordered and exist predominantly in transextended conformations. When R-1 is an alkyl group (e.g., R-1 not equal H), however, their conformations can no longer be all-trans-extended, and the molecules adopt more gauche dihedral angles. This change in the type of conformation decreases the conformational order and influences the rates of tunneling. When R-1 = R-2, the rates of CT decrease (up to 6.3x), relative to rates of CT observed through SAMs having the same total chain lengths, or thicknesses, when R-1 = H. When R-1 not equal H not equal R-2, there is a weaker correlation (relative to that when R-1 = H or R-1 = R-2) between current density and chain length or monolayer thickness, and in some cases the rates of CT through SAMs made from molecules with different R-2 groups are different, even when the thicknesses of the SAMs (as determined by XPS) are the same. These results indicate that the thickness of a monolayer composed of insulating, amide-containing alkanethiols does not solely determine the rate of CT, and rates of charge tunneling are influenced by the conformation of the molecules making up the junction.