Permeability of Alkanethiols Self-Assembled Monolayers on Gold Prepared by Neat Thiols and Ethanolic Thiols

摘要

In this article we investigated the permeability of alkanethiols (CnSH, n = 6, 10, 12, 16) self-assembledmonolayers (SAMs) on gold prepared by neat thiols and ethanolic thiols. The electrochemical* parameters (interfacial capacitance Cd, phase angle 1 Hz and ions transfer resistance Rit at 1 Hz,current density difference j and charge transfer resistance Rct) from cyclic voltammetry (CV) andelectrochemical impedance spectroscopy (EIS) were used to explore the permeability of SAMs.Results indicated that alkanethiols SAMs prepared by neat thiols had smaller Cd than by ethanolicthiols. Thus, the neat thiols SAMs were more compacted than ethanolic thiols SAMs. The dielectricconstant of alkane chain in SAMs were calculated to be 1.2 (neat thiols) and 3.0 (ethanolic thiols) respectively based on the linear slopes of Cd ~n plots. A hydrophobic gap possibly existed on neatthiols SAMs-water interface, which might lead to smaller (1.2) than the reported value (2.3) byo literatures. The 1 Hz of neat thiols SAMs were bigger and close to 88 as an ions insulator and theethanolic thiols SAMs were ions permeable SAMs. The permeable constants (p) of neat thiols SAMsand ethanolic thiols SAMs on gold were 0.097/CH2 and 0.111/CH2 respectively based on the linear* slopes of lnRit ~ n plots. However, to our surprise, the tunneling constant of neat thiols SAMs wascalculated to be 0.238/CH2 based on the linear slopes of lnRct ~ n plots (Rct was the charge transfer34.