Date of Award

2000

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Robin L. McCarley

Abstract

The successful formation and characterization of 1,6-diisocyanohexane (DICH) molecules self assembled onto Au and Pt is realized in this dissertation. Exposure of Au substrates to methanolic solutions of DICH can result in the formation of either a monolayer or polymeric multilayer of DICH. Cyclic voltammograms of solution-phase redox probes at poly(DICH)-coated electrode surfaces (both Au and Pt) exhibit behavior that demonstrates that the poly(DICH) layers are effective transport barriers. Cross-linking of the poly(DICH) films can be increased by treating the poly(DICH) films with aqueous Ni2+ solutions; in addition, the free isocyanide functionalities in the poly(DICH) films can be electrochemically converted to isocyanates. Both treatments considerably increase the blocking capabilities of the poly(DICH) films. Stability experiments on poly(DICH) films performed in air demonstrate that the poly(DICH) multilayers are physically bound to Au. Monoisocyanides with various alkyl chain lengths (n-alkylisocyanides) are capable of chemically binding to Au surfaces to form isocyanide monolayers. The surface coverage, stability in organic environments, and the electrochemical blocking capability decrease in the order: C18-NC > C12-NC > C6-NC. It was found that pristine isocyanide monolayers formed on Au surfaces can be polymerized to generate polymeric isocyanides, poly(imines), upon being exposed to air or pure oxygen environments for times greater than 24 h. These polymeric isocyanides are found to be physically bound to the Au surface. Scanning tunneling microscopy images of DICH monolayer/Au(111) surfaces and monoisocyanide monolayer/Au(111) surfaces are obtained in air. It is found that monoisocyanide monolayer/Au surfaces are similar to those of alkanethiol monolayers on Au, as noted by the observation of a large number of pits on such modified Au(111) surfaces. It is confirmed by infrared spectroscopy and scanning tunneling microscopy that DICH monolayers can be formed on Au(111) by using either high dosing concentrations and short dosing times or low dosing concentrations and long dosing times. In addition, the pits on DICH/Au(111) surfaces were found to diffuse to step edges during STM imaging due to strong STM tip/sample interactions. The adsorption of DICH films onto Au(111) as a function of dosing time was monitored by STM.

ISBN

9780599906051

Pages

133

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