Studies of Self-Assembled Monolayers of 10-Mecaptodecanesulfonic Acid

• Main Authors: Chao-YiPeng, 彭朝驛
• Other Authors: Jui-Che Lin
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/63129291278630081048

碩士 === 國立成功大學 === 化學工程學系碩博士班 === 98 === Self-assembled monolayers (SAMs) have been recognized as the surface being able to form a well-defined structure. In addition to their ease of preparation, the terminal functionality of these SAMs can be tailored in preparing surfaces with different surface properties. In this study, a novel SAM was prepared by the 10-mercaptodecanesulfonic acid on gold substrate. In our group’s previous study, a proper cleaning method has been developed for the gold substrate prior to the SAM formation by the 10-mercaptodecanesulfonic acid ethanolic solution. In addition, the kinetic of the SAM formation with this sulfonic acid-terminated alkanethiol was analyzed with Langmuir model. It was noted the formation of sulfonic acid terminated SAM from 0.01 mM ethanolic solution could be successfully fitted with Langmuir kinetics while that from the 2mM ethaolic solution cannot. In this study, a further evaluation on these sulfonic acid-terminated SAMs was attempted using electrochemical analysis methods. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) with different electrical redox couple were used to further analyze the growth mechanism of these sulfonic acid terminated SAMs that were prepared from different ethanolic solutions. Based on these electrochemical analyses results, the surface of sulfonic acid terminated SAMs were becoming more filled with the alkanethiols as the immersion time increase, irrespective of the alkanethiol concentration. This is contradictory to what was proposed in our group’s previous study that part of the adsorbed alkanethiols might be desorbed as the immersion time increase. Besides, for the SAMs prepared from the 2 mM solution, the surface density of the sulfonic acid terminated alkanethiol was higher than that on the SAMs prepared from the 0.01 mM ethanolic solution in the short immersion time. However, as the immersion time further increased (e.g. 24 hours), the SAMs prepared from 2 mM solution would become less well organized as indicated by the increase of surface contact angle. This is likely attributed to the exposure of the alkyl chain on the surface following the reorientation of the alkanethiol on the SAMs.