Photo-Oxidation of Amine-Terminated Self-Assembled Monolayers on Gold
Date Issued
2010
Date
2010
Author(s)
Lee, Szu-Hsian
Abstract
Alkanethiol anchored self-assembled monolayers (SAMs) on gold are widely used to immobilize and detect molecules including DNA and proteins. Most of these molecules are covalently bonded with the SAM on the Au surface and cannot be released easily. Amine-terminated self-assembled monolayers (SAMs) on Au surfaces are commonly used to immobilize and detect various types of molecules. By using different functional groups, the interfacial charge of SAMs can be selected, and thus, they can be considered as adaptors for immobilizing and releasing materials selectively through electrostatic interaction under given conditions. In previous work, as an additional factor to control the surface charge, SAMs with mixed functional groups are presented, and it is demonstrated that the isoelectric point (IEP) can be tailored by the ratio of functional groups. Using carboxylic acid- and amine-SAM on gold substrates as an example, isoelectric points (IEPs) from 3.5 to 6.5 can be obtained arbitrarily. Furthermore, using different functional groups can make series of suface functional groups and head groups forming dipoles, it can modify work function from 3.3 eV to 3.9eV on metal electrode. However, little is known about the stability of these types of surfaces. In this work, it was observed that the surface potential (as well as the isoelectric point) of amine-bearing SAMs on flat gold substrates changed significantly with time, indicating that the surface functional group is not stable to storage under ambient conditions (standard temperature and pressure). Two methods for retarding the oxidation of the amine functional group are presented in this work. By isolating the SAM from either light or oxygen, the oxidation is suppressed and the surface properties are preserved. In other words, the shelf life of the amine-modified gold substrates is prolonged.
Subjects
SAMs
degradation
photooxidation
isoelectric point
drug delivery
Type
thesis
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