title: Electrochemical characterization of self-assembled thiol-porphyrin monolayers on gold electrodes by SECM.
abstract: Herein, the scanning electrochemical microscopy (SECM) approach is applied to study the formation of thiol-porphyrin self-assembled monolayer (SAMs). Using cyclic voltammetry (CV), the formation process is characterized adopting different probe molecules. The observed phenomena indicate that the formation process is affected by solution properties and the molecular structure of the probe molecules. In K(3)Fe(CN)(6) , the SAMs show a strong electron-transfer (ET) blocking effect on a pure porphyrin-modified electrode. However, addition of metal ions to the porphyrin molecules leads to ET. A consistent tendency is observed throughout the modification process using CV and SECM methods. Furthermore, k(eff) values, the apparent heterogeneous rate constants, obtained for different modification periods affirm the validity of these results. SECM images are used to collect surface information in the course of the modification process when the substrate potential is 0.5 V versus Ag/AgCl. The effect of the substrate potential indicates that the oxidation of the porphyrin molecules is supported by more positive potentials because of the similar bimolecular reaction of the porphyrin ring with positive charge and the probe molecules with negative charge.
authors.affiliation: College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, 730070, GanSu, China. luxq@nwnu.edu.cn
authors.forename: Xiaoquan
authors.initials: X
authors.lastname: Lu
authors.forename: Limin
authors.initials: L
authors.lastname: Zhang
authors.forename: Minrui
authors.initials: M
authors.lastname: Li
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Wang
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xiuhui
authors.initials: X
authors.lastname: Liu
authors.forename: Guofang
authors.initials: G
authors.lastname: Zuo
mesh_terms: D004563:Electrochemistry; D004566:Electrodes; D004583:Electrons; D006046:Gold / Q000737:chemistry*; D008567:Membranes, Artificial; D008855:Microscopy, Electron, Scanning / Q000379:methods; D011166:Porphyrins / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D008567:Membranes, Artificial; D011166:Porphyrins; D013438:Sulfhydryl Compounds; D006046:Gold