SELF-ASSEMBLED MONOLAYERS ON SI(111): FORMATION, CHARACTERIZATION, MODIFICATION, AND PROTEIN ADSORPTION

The aim of this thesis was to design and develop a stepwise strategy for fabricating protein resistant silicon surfaces. The adsorbate molecule comprises two alkyne groups separated by an 8 carbon alkyl chain and a triethyleneglycol chain. This diyne molecule was able to form 24 Å thick monolayers on hydrogen terminated Si(111) under high vacuum conditions via UV assisted hydrosilylation reaction. The estimated packing density of the monolayers was 60%, indicating a very dense packing of the adsorbates. Thus closely packed monolayers yielded a good stability both in ambient air and the PBS solution. By screening CuAAC (Copper-Catalyzed Azide-Alkyne Cycloaddition) reaction conditions, it was found that with a reagent concentration of 1.25 mM copper, 10 mM OEG7-azide, 25 mM ascorbate, and 1.25 mM histidine as accelerating ligand, and a reaction time of 2 h in an anaerobic chamber, a modified film with minimum protein adsorbance could be formed. The non-basicity and non-toxicity of this commercially available ligand histidine is believed to have important applications in the field of bio-conjugation, and bio-adhesions. An apparatus with the use of a multichannel pipette and multiwell plate, the methodology of optimization and the screening of more CuAAC reaction conditions on the surfaces was designed and built. Preliminary results showed that the fluorescence intensity data resulted from adsorbed fibrinogen-Alexa Flore 488 was reliably comparable with that of the traditional ellipsometry and XPS data, and under higher ligand concentrations, four similar compounds could be used as effective accelerating ligands for CuAAC reactions on the surfaces.