Effect of surface chemical composition on the surface potential and iso-electric point of silicon substrates modified with self-assembled monolayers

Self-assembled monolayer (SAM)-modified nano-materials are a new technology to deliver drug molecules. While the majority of these depend on covalently immobilizing molecules on the surface, it is proposed that electrostatic interactions may be used to deliver drugs. By tuning the surface potential...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2011-03, Vol.13 (9), p.3649-3653
Main Authors: Kuo, Che-Hung, Chang, Hsun-Yun, Liu, Chi-Ping, Lee, Szu-Hsian, You, Yun-Wen, Shyue, Jing-Jong
Format: Article
Language:English
Subjects:
Amines
Chemistry
Concentration (composition)
Deposition
Drugs
Electrolytes - chemistry
Electrostatics
Exact sciences and technology
General and physical chemistry
Isoelectric Point
Nanostructure
Photoelectron Spectroscopy
Propylamines - chemistry
Self-assembled monolayers
Silanes - chemistry
Silicon - chemistry
Silicon substrates
Static Electricity
Substrate Specificity
Surface Properties
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Summary:Self-assembled monolayer (SAM)-modified nano-materials are a new technology to deliver drug molecules. While the majority of these depend on covalently immobilizing molecules on the surface, it is proposed that electrostatic interactions may be used to deliver drugs. By tuning the surface potential of solid substrates with SAMs, drug molecules could be either absorbed on or desorbed from substrates through the difference in electrostatic interactions around the selected iso-electric point (IEP). In this work, the surface of silicon substrates was tailored with various ratios of 3-aminopropyltrimethoxysilane (APTMS) and 3-mercaptopropyltrimethoxysilane (MPTMS), which form amine- and thiol-bearing SAMs, respectively. The ratio of the functional groups on the silicon surface was quantified by X-ray photoelectron spectrometry (XPS); in general, the deposition kinetics of APTMS were found to be faster than those of MPTMS. Furthermore, for solutions with high MPTMS concentrations, the relative deposition rate of APTMS increased dramatically due to the acid-base reaction in the solution and subsequent electrostatic interactions between the molecules and the substrate. The zeta potential in aqueous electrolytes was determined with an electro-kinetic analyzer. By depositing SAMs of binary functional groups in varied ratios, the surface potential and IEP of silicon substrates could be fine-tuned. For
ISSN:1463-9076
1463-9084
DOI:10.1039/c0cp02615h