The long-range effect induced by untying hydrogen bonds for single cell test using SECM

Abstract

The enhanced positive feedback current of scanning electrochemical microscopy (SECM) is observed at a large separation between the tip and the substrate surface in the case of a 3-mercaptopropionic acid (3-MPA) self-assembled monolayer (SAM). The effect that induces the large separation (named the long-range effect) is confirmed by SECM and quantitatively studied by electrochemical quartz crystal microbalance (EQCM). A key finding is that the long-range effect results from untying hydrogen bonds beforehand formed between the hydroxyl group of tip redox species and the carboxyl group of 3-MPA SAM. It is found that the long-range effect is increased with the packing density of the 3-MPA SAM. On the basis of these findings,

Electrochemical investigation of the intermolecular hydrogen bond on the surface of self-assembled monolayer

“…前面介绍了探针电极上MPA与二茂铁甲醇之间 图 1 在MPA SAM电极上的分子间氢键可逆组装与解组装 过程示意图 [22] (网络版彩图) [22] (网络版彩图) 图 3 存在分子间氢键情况下二茂铁甲醇的电化学氧化过程示意图(红色峰: 氢键键合二茂铁甲醇的峰; 蓝色峰: 非氢键键合 二茂铁甲醇的峰) [23] (网络版彩图) [29] (网络版彩图) [29] (网络版彩图) 图 8 分子间氢键诱导"长程效应"的机理示意图 [34] Figure 8 Schematic representation of the mechanism of the longrange effect which induced by the intermolecular hydrogen bond [34]. 图 9 探针向不同基底的渐近曲线图.…”

“…图 9 探针向不同基底的渐近曲线图. 黑线: 金基底, 含二茂 铁甲醇的电解液; 红线: 绝缘基底, 含二茂铁甲醇的电解液; 蓝线: MPA SAM修饰的金基底, 含二茂铁甲醇的电解液; 绿 线: MPA SAM修饰的金基底, 含亚铁氰化钾的电解液; 电解 液pH均为6.4 [34] (网络版彩图) [34] (网络版彩图) 图 11 SECM的SG/TC模式中MPA SAM表面氢键向静电转 变过程的示意图 [37] (网络版彩图) 图 13 SECM反馈模式探究SAM表面阳离子开关示意图 [38] (网络版彩图) [39] (网络版彩图) 图 15 基于电荷翻转的天冬氨酸和精氨酸分子识别原理示意图 [39] (网络版彩图) [39] (网络版彩图)…”

“…Figure 10Approach curves of FcCH 2 OH toward MPA modified gold substrate in different pH electrolyte[34] (color online).…”

Electrochemical Quantification of Intermolecular Hydrogen Bonding between Ferrocenemethanol and 3-Mercaptopropanoic Acid on Gold

“…19−22 We previously demonstrated that the intermolecular hydrogen bonding exists between the redox species ferrocenylmethanol (FcCH 2 OH) and 3-mercaptopropionic acid (MPA). 23 More recently, we reported on the use of cyclic voltammetry as platforms for regulating the intermolecular hydrogen bonding between FcCH 2 OH and MPA in which we found the features of the cyclic voltammetry were complicated by intermolecular hydrogen bonding. 24 As the amount of transferred electrons devoted to the anodic peak or cathodic peak of cyclic voltammogram is related to amount of the redox species involved in the electrochemical process, 25,26 we intend to quantify the amount of intermolecular hydrogen bonding in the above-mentioned molecular recognition model by interpreting the slight changes of cyclic voltammogram.…”

“…More details about EQCM measurement can be found in our previous work. 23 The increased mass (m) of MPA SAM on gold was measured by Sauerbrey's equation, seen below, where A is the surface area of the gold electrode (A = 0.2 cm 2 ), ρ is the density of quartz, μ is the shear modulus of quartz, and F is the inherent frequency (9 MHz) of the quartz crystal. The absolute value of the frequency change (ΔF) has been used as an indicator of surface coverage of the MPA monolayer; thus, ΔF is increasing along with the addition of mass.…”