Electrochemical impedance spectroscopy study of carbohydrate-terminated alkanethiol monolayers on nanoporous gold: Implications for pore wetting.
Electrochemical impedance spectroscopy study of carbohydrate-terminated alkanethiol monolayers on nanoporous gold: Implications for pore wetting.
复制标题
DOI：
10.1016/j.jelechem.2016.10.013
复制
发表时间：
2016-12-01
期刊：
影响因子：
--
通讯作者：
Stine KJ
中科院分区：
文献类型：
--
作者：
Sharma A;Bhattarai JK;Nigudkar SS;Pistorio SG;Demchenko AV;Stine KJ
电化学阻抗谱（EIS）是用来比较的表观电子转移速率常数（kapp）为一系列的烷乙氧基化物和碳水化合物封端的烷乙氧基化物的自组装单分子膜（SAMs）的平面金和纳米多孔金（np-Au）。使用通过氧化物剥离测定的np-Au的表面积，烷醇改性的np-Au的kapp值最初比在平坦的Au上发现的值小两个数量级以上。这一结果提供了证据表明，扩散氧化还原探针Fe（CN）63−/4−在烷基硫醇改性后仅能接触到一小部分np-Au表面，这表明由于这些表面的疏水性，内部孔隙的润湿非常有限。相比之下，对于由碳水化合物封端的（甘露糖或半乳糖）烷硫醇修饰的np-Au，kapp的值比平坦的金小约10-40倍，这表明扩散氧化还原探针在孔内的更广泛的进入和更好但仍然不完全的润湿，也发现了用巯基十二烷酸修饰np-Au的结果。发现短链PEG硫醇衍生物导致kapp值的比较，这表明该高度亲水性衍生物的内部孔几乎完全润湿。这些结果对于SAM修饰的np-Au在电化学传感器中的潜在应用具有重要意义，特别是对于那些基于碳水化合物-蛋白质识别的电化学传感器，或者那些由具有极性末端基团的SAM修饰的np-Au。
Electrochemical impedance spectroscopy (EIS) is used to compare the apparent electron transfer rate constant (kapp) for a series of alkanethiol and of carbohydrate-terminated alkanethiol self-assembled monolayers (SAMs) on both flat gold and on nanoporous gold (np-Au). Using the surface area for np-Au determined by oxide stripping, the values of kapp for the alkanethiol modified np-Au are initially over two orders of magnitude smaller than the values found on flat Au. This result provides evidence that the diffusing redox probe Fe(CN)63−/4− only accesses a fraction of the np-Au surface after alkanethiol modification suggesting very limited wetting of the internal pores due to the hydrophobic nature of these surfaces. In contrast, for np-Au modified by carbohydrate-terminated (mannose or galactose) alkanethiols the values of kapp are about 10–40 fold smaller than on flat gold, suggesting more extensive access of the diffusing redox probe within the pores and better but still incomplete wetting, a result also found for modification of np-Au with mercaptododecanoic acid. A short chain PEG thiol derivative is found to result in a comparison of kapp values that suggests nearly complete wetting of the internal pores for this highly hydrophilic derivative. These results are of significance for the potential applications of SAM modified np-Au in electrochemical sensors, especially for those based on carbohydrate–protein recognition, or those of np-Au modified by SAMs with polar terminal groups.