Making inorganic oxides stimuli responsive via surface modification

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Copyright: Chen, Xin
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Abstract
In this thesis, we presented the preparation, performance and optimization of various surface modification strategies on two different inorganic oxide surfaces (indium tin oxide, ITO and silicon oxide), and further applications of these modified structures. Firstly, the comparison between self-assembled monolayers (SAMs) and electrochemical reductive layers on ITO were performed. The results showed that the structure of SAMs on ITO is much more ordered than the structure of aryl diazonium salt derived surfaces but at the cost of stability. To improve the stability optimization of the preparation condition of SAMs was explored. Four different molecules and a series of organic solvent were used to form the self-assembled monolayers. Higher density, more stable monolayers were formed from solvents with low dielectric constants and weak interactions with the ITO. This modified ITO substrate is expected to plays a significant role in electrochemical sensing. To achieve the desired electrochemical properties, silver nanoparticles (AgNPs) were combined with ITO because of their excellent electro transfer ability. Before that, AgNPs were rendered stimuli-responsive by modifying the particles functional groups that provide selectivity for different stimuli. Subsequently, cyclodextrin (CD) functionalized AgNPs were combined with SAMs modified ITO electrodes as an electrochemical sensor for nitroaromatic compounds even isomers. As one of the most important inorganic oxides, the modification and application of silica formed the second part of the thesis. In this work, we focused on mesoporous silica nanoparticles (MSNs). The preparation and functionalization of MSNs using 3-aminopropyltriethoxysilane by in situ formation of polysiloxane was presented in the thesis. By combining with L-cysteine modified gold nanoparticles or polymers, the MSNs could be used as nanocarrier for two types of drug delivery which is responsive to different biological stimuli. For the first type, these stimuli to trigger drug release are either: low pH (pH < 5); or elevated levels of adenosine triphosphate (ATP) (concentration > 4 mM), which is called "OR gate". For the second type, these stimuli to trigger drug release have to be both: low pH (pH < 5.5); and elevated levels of esterase (concentration > 1 mM), which is called "AND gate"
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Author(s)
Chen, Xin
Supervisor(s)
Justin, Gooding
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Publication Year
2013
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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