Preparation And Application Of Functional Gold Surface And Gold Nanoparticles

There has been considerable interest in studying functional gold surface and gold nanoparticles (AuNPs), as they have great potential applications in many fields, such as electron devices, sensors, chemical engineering, meditech, biotechnologies, catalysis and so on. This thesis based on the recent progress on the preparation and application of functional gold surface and AuNPs, combining with the long-term research accumulation of our group. The research area is proposed, which is preparation of functional gold surface and AuNPs, and its application research. In this work, several novel functional gold surfaces and AuNPs were prepared, using thiol self-assembled monolayer (SAM) technology, and combining with some chemical conjugation techniques (eg. click coupling, EDC/NHS coupling). The surface properties, morphologies, structures and compositions of the prepared materials were well characterized were examined by means of various techniques. This dissertation focuses on using functional gold surfaces and AuNPs to investigate phenomena at surfaces and interfaces, such as permeability, wetting, adsorption, surface charge distribution, electron transfer theory and molecular recognition.This dissertation consists of six chapters, including overview of history, actuality and applications of functional gold surfaces and AuNPs; study of permselectivity and interface electron transfer of fluorine-containing amphipathic SAMs on gold electrode; protein adsorption and cell adhesion controlled by the surface chemistry of binary perfluoroalkyl (PFA)/oligo(ethylene glycol)(OEG) SAMs on gold; fabrication of amphipathic SAMs on gold by "click" graft for antifouling surfaces; synthesis and characterization of water-soluble AuNPs with control over size and surface functionalities; surface molecularly imprinted sensor based on electrodeposited AuNPs self-assembled by/7-aminothiophenol for organophosphates recognition.In chapter one, highlights on new findings with significance in preparation and application of functional gold surfaces and AuNPs were viewed. The developing history, properties, character studies and various applications of functional gold surfaces and AuNPs were given. And a brief introduction of this dissertation research content and innovation.In chapter two, the effect of monolayer structure and solution composition on electrochemical response at fluorine-containing amphipathic SAM (FEG-SAM) on gold has been investigated. Mixed self-assembled monolayer presenting propargyl groups to allow conjugation of azide-bearing molecules were prepared through co-assembly of co-hydroxyltetra(ethylene glycol) and co-propargyltetra(ethylene glycol) terminated hexanethiol. And the amphipathic FEG-SAM, which with hydrophilic interior and hydrophobic exterior, was obtained by coupling the propargyl-terminated SAMs with N3-AJ-O-C9F17. Various techniques, such as X-ray photoelectron spectrometry (XPS), grazing incidence reflectance infrared spectroscopy (GIR) and contact angle measurement (CA) were used to characterize the prepared surfaces. Cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the permselectivity of the prepared SAMs-F to a variety of probes, which with different hydrophilic/hydrophobic and charge, and the interface electron transfer mechanisms of different electrochemical probes were discussed.In chapter three, we have studied the effect of surface chemistry on protein adsorption and cell adhesion using a model system of binary alkanethiol SAMs presenting termini of PFA and OEG, two segments of distinctly difference in wettability, in varying ratios on gold substrates. The addressed issues include the difference in the compositions between the assembly solution and the subsequently formed SAM, the relation between the surface composition and surface energy, the effect of surface composition to protein adsorption and cell adhesion. Results reveal that, compared to OEG, PFA tended to be a higher fraction of the composition in SAM than in the assembly solution. More interestingly, the nearly38%PFA SAM had a strong antifouling property whereas the74%PFA SAM showed a high adsorption capacity to protein and cell. The binary PFA/OEG SAMs were favorable for maintaining the fibrinogen conformation, hence its high activity. This study provides useful information for the fabrication of fluorine-containing materials with the distinct property that is highly resistant or highly favorable toward protein adsorption and cell adhesion.In chapter four, amphipathic SAMs on gold were fabrication for antifouling application, which were obtained via "click" modification of mixed oo-propargyl/(o-hydroxyltetra(ethylene glycol) hexanethiol SAMs with N3-PFA in the presence of Cu(I) catalyst. The coverage of PFA on the amphipathic SAM changes with varying co-propargyltetra(ethylene glycol) hexanethiol percentage in the assembly solution. The prepared SAMs were characterized by XPS, GIR and CA, and the surface chemistry effects on the antifouling performance of the SAMs were evaluated by fibronectin absorption and obteoblasts adhesion, using surface plasmon resonance (SPR) and fluorescence microscopy. It shows that the amphiphilic SAMs undergo water-induced surface reorganization, and the heterogeneity of the surface microphase separation structure is the key to achieving surfaces that can prevent biofouling.In chapter five, mixed poly(ethylene glycol)(PEG) thiol capped AuNPs (AuNPs-PEG) in aqueous phase were synthesised, with narrow size distribution nanocrystals over the size range between1and13nm. The NP size was simply controlled by varying the molar ratio of Au-to-PEG ligand. These water-soluble AuNPs carry carboxyl groups at the solvent-exposed interface, which can be used for further conjugation of biologically active molecules. Furthermore, we present a UV-based assay for the characterization of the functionalized AuNPs. An UV-active molecule,3-aminophenylboronic acid, was used to conjugate with the AuNPs via EDN/NHS coupling. We quantitatively determined the average number of3-aminophenylboronic acid per NP, thus the number of surface ligands on each AuNP can be evaluated. The developed assay provides essential information for the successive derivatization of the AuNPs.In chapter six, a surface molecularly imprinted poly (p-aminothiophenol)(PATP)/AuNPs composite film with high dense imprinted sites for paraoxon (PO) is developed. We designed a surface molecular self-assembly directing strategy for high densely imprinting PO in the electropolymerized PATP film at the surface of ATP-capped AuNPs on screen printed carbon electrode (SPCE). The AuNPs were formed by in situ electrodeposition and modified with ATP. Then PO molecules were assembled onto the ATP monolayer, forming a basis of surface molecular imprinting. While an additional amount of PO was further replenished into a precursor mixture, an electropolymerization was performed toward the controllable preparation of PO imprinted PATP/AuNPs composite film at the electrode surface. The combination of surface molecular assembly with nanomaterial in the imprinting technique can create a great number of effective recognition sites. The resulting imprinted PATP/AuNPs composite film reveals high sensitivity, affinity and selectivity toward PO.