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基对单分子导电性的作用:对醇,氨基和碳酸终结分子的比较研究
Fang Chen1, Xiulan Li, Joshua Hihath
1Department of Electrical Engineering & Center for Solid State Electronics Research, Arizona State University, Tempe, Arizona 85287, USA.
Journal of the American Chemical Society
|December 7, 2006
概括
定组通过影响电子合和能量水平,显著影响单分子导电性. 导电性还显示了某些群体的pH敏感度,揭示了分子电子和电极相互作用的洞察力.
科学领域:
- 分子电子学分子电子学
- 凝聚物质物理学 凝聚物质物理学
- 纳米技术纳米技术
背景情况:
- 了解单分子导电性对于分子电子学至关重要.
- 固定组的选择会影响分子-电极相互作用.
- 带有滴醇,二胺和二氧酸组的基作为模型系统.
研究的目的:
- 研究不同固群对单个分子导电性的影响.
- 阐明负责运输机制的定小组的作用.
- 分析固组对接触电阻和结合强度的影响.
主要方法:
- 制造和表征众多分子连接点.
- 对导电量值和电流-电压 (I-V) 特性进行统计分析.
- 用分子长度和拉伸长度测量导电性衰变.
主要成果:
- 对于每个定组,观察到多个导电量值.
- 道被确定为主要导电机制.
- 导电性衰变的前因子对定群敏感,而衰变常数则不那么依赖.
- 导电表现出对二胺和二糖酸组的pH敏感性.
结论:
- 定组调节分子-电极接口的电子合和能量水平对齐.
- 接触阻力受到固定组的强烈影响.
- 基组的质子化/解质子化会影响导电量,从而提供pH值依赖的控制.
- 拉伸长度的分析提供了对固组与金电极的结合强度的洞察.
相关概念视频
01:31Substituent Effects on Acidity of Carboxylic Acids
The acidity of carboxylic acids is influenced by the nature of the substituents bounded to the functional group. The acid strength is determined by the stability of the carboxylate anion—the conjugate base formed by dissociating the corresponding carboxylic acid.
01:19Amines to Amides: Acylation of Amines
Various carboxylic acid derivatives (such as acid chlorides, esters, and anhydrides) can be used for the acylation of amines to yield amides. The reaction requires two equivalents of amines. The first amine molecule functions as a nucleophile and attacks the carbonyl carbon to produce a tetrahedral intermediate. This is followed by the loss of the leaving group and restoration of the C=O bond.
Next, the second equivalent of amine serves as a Brønsted base and deprotonates the quaternary amide...
Next, the second equivalent of amine serves as a Brønsted base and deprotonates the quaternary amide...
01:13Relative Reactivity of Carboxylic Acid Derivatives
Carboxylic acid derivatives such as acid halides, anhydrides, esters, and amides undergo nucleophilic acyl substitution reactions with varying degrees of reactivity.
A key factor in assessing the reactivity of the acid derivatives is the basicity of the substituent or the leaving group. The lower the basicity of the leaving group, the higher the reactivity of the derivative. The basicity of the leaving group follows this order:
Halide ions < Acyloxy ions < Alkoxy ions < Amine ions
A key factor in assessing the reactivity of the acid derivatives is the basicity of the substituent or the leaving group. The lower the basicity of the leaving group, the higher the reactivity of the derivative. The basicity of the leaving group follows this order:
Halide ions < Acyloxy ions < Alkoxy ions < Amine ions
02:17Structure and Nomenclature of Thiols and Sulfides
Thiols and sulfides are sulfur analogs of alcohols and ethers, respectively, where the sulfur atom takes the place of the oxygen atom. Thus, thiols are generally represented as RSH, where R is an alkyl substituent and —SH is the functional group. On the other hand, in sulfides, the central sulfur atom is bonded to two hydrocarbon groups on either side. Depending upon the type of group, sulfides can be either symmetrical or asymmetrical. Both thiols and sulfides display a bent geometry, similar...
01:32Lipids as Anchors
In the plasma membrane, the lipids forming the bilayer can also act as an anchor to tether proteins to the membrane. The three main types of lipid anchors found in eukaryotes are – prenyl groups, fatty acyl groups, and glycosylphosphatidylinositol or GPI groups. Prenyl and fatty acyl groups act as anchors on the cytosolic surface of the membrane, whereas GPI anchors proteins on the extracellular side.
The carboxy-terminal of most of the prenylated proteins, such as Ras proteins, contains the...
The carboxy-terminal of most of the prenylated proteins, such as Ras proteins, contains the...
02:34Molecular Structure and Acidity
An acid can be deprotonated to form a conjugate base or an anion. If the produced anion is more stable, then the acid is stronger. On the contrary, if the anion is unstable, then the acid is weaker. Hence, to determine the acidity of the compound, the stability of its conjugate base is studied using various factors.
The size effect explains the change in atomic size on acidity. When comparing the acids formed from elements that belong to the same column in the periodic table, their atomic sizes...
The size effect explains the change in atomic size on acidity. When comparing the acids formed from elements that belong to the same column in the periodic table, their atomic sizes...