Jalali, Hanifa

This paper describes an innovative and simple technique for analyzing defects in silane-based self-assembled monolayers. The assembly of monolayers is a simple method for chemically modifying surfaces, which can be important for resisting chemical attack or adhesion of biomolecules. Measuring the molecular scale properties of monolayers and the reproducibility of their ability to uniformly modify a surface requires tools that provide limits of detection at the level of at least a few atoms per million with specificity to the top couple nanometers of the surface. To achieve this level of sensitivity a new technique is developed that combines spectroscopy and microscopy techniques (particularly atomic force microscopy) with chemical amplification of exposed silicon in self-assembled monolayers of silane molecules. This development is an important achievement for monitoring the quality of monolayers as a function of modifications to the method(s) used to deposit the silane molecules. Techniques presented here could be easily extended to assessing the molecular scale quality of other surface modifications.

The m-terphenyl 4-mercaptomethyl-2,6-diphenylbenzoic acid (3), was prepared and shown to form ω-carboxyl terminated self-assembled monolayers (SAMs) on gold with high surface pKa (10.1 ± 0.2) and low density favourable for the binding of biological macromolecules.

2,4,6-Triphenylbenzaldehyde 1 undergoes a condensation reaction with 2-aminophenol to give N-(2′,4′,6′-triphenylbenzylidene)-2-iminophenol (TPIP) 2. The imine 2 can be reduced with NaBH4 in ethanol to form N-(2′,4′,6′-triphenylbenzyl)-2-aminophenol (TPAP) 3. Addition of trimethylaluminum to 2 or 3 results in the formation of the complexes TPIP-AlMe2·AlMe3 (4) or TPAP-AlMe2 (5). Compounds 2, 3, and 4 have been crystallographically characterized. [ABSTRACT FROM AUTHOR]

Silane-based self-assembled monolayers (SAMs) are commonly used as protective coatings against chemical etchants and adhesion of biomolecules. The conventional methods of producing SAMs are very time consuming and energy intensive processes. This thesis presents an efficient technique to produce silane-based SAMs approximately 300 times faster while consuming over 750 times less energy than the conventional method. Silane-based SAMs produce monolayers containing various types of defects. New techniques are developed to identify defects in SAMs and to correct for them. Chemical amplification of defects is developed for easily detecting defects in SAMs by traditional microscopy and spectroscopy techniques. Extraction and refilling methods are used to increase the packing density of the molecules in these monolayers and reduce the number of defects present in SAMs. By increasing the efficiency of silane deposition and improving the packing density of molecules, high quality SAMs can be produced within a short period of time.