Forces between Binary Self-Assembled Monolayer Modified AFM Probes and Materials in Aqueous Environments
Date Issued
2012
Date
2012
Author(s)
Yen, Guo-Zhi
Abstract
The use of gold substrate in Biochemistry has increasingly been the object of study for its high biologic compatibility in recent years. The continuing improvements in materials processing and surface modification of gold have led to many new and fascinating applications in material science, chemistry, biology, and medicine. A majority of studies have suggested that modified gold substrate provide an efficient way to covalently bond biologic molecules such as plasmid DNA and proteins in the fields of biosensors and biologic transportation. However, the application of covalently-bonded combination is limited by its difficulty in desorption of molecules.
In this work, the gold-coated probes are modified by self-assembled monolayers (SAMs) of mixed carboxylic acid and amine functional groups in a series of ratio, and the iso-electronic points (IEPs) between 3.5~6.3 are obtained. Using the contact mode atomic force microscopy in liquid, the electrostatic interactions between modified probes v.s. APTES or modified probes v.s. SiO2 are measured at different pH values by using the force curve. Because the interacting surfaces can have the same or opposite sign of potential, repulsive or attractive interaction can be observed. Furthermore, since the surface potential is a function of pH, the observed interactions between a given set of surfaces changes with the aqueous environment.
Through analyzing the electrostatic interactions, we examined the repulsive and attractive behaviors on SAMs-modified gold substrates of different IEP in aqueous environment. By controlling the interactions using SAMs of different chemical composition, this result may provide a promising mean for drug delivery systems (DDS).
Subjects
Self Assembled Monolayer
Surface Potential
Isoelectric Point
Force Curve
Type
thesis
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