Web Release Date: January 23,
Synthesis of Carboxylic Acid Monolayers by Ozonolysis of 10-Undecenyltrichlorosilane SAMs
and
Chemistry Department, Duke University, and Physics Department, North Carolina State University, Raleigh, North Carolina 27695-8202
Received: October 3, 2007
In Final Form: November 23, 2007
Abstract:
A high-yield method has been developed for the production of carboxyl-terminated alkylsiloxane monolayers
on silicon using the ozonolysis and hydrolysis of 10-undecenyltrichlorosilane self-assembled monolayers
(SAMs). Contact angles with water, a common measure of hydrophilicity and thus an effective measure of
carboxyl termination, were brought to 0
on receding and approximately 16 on advancing, compared to 98
and 105 respectively before ozonation. Ellipsometry showed the presence of a full monolayer, 1 nm thick
before ozonation, that decreases by about 0.2 nm during ozone treatment, largely due to the removal of a
carbon atom in the process. This removed material coalesces as nanoparticles, observed with atomic force
microscopy (AFM) imaging. The process has a surprisingly narrow ozone dose window, with excess ozonation
resulting in complete layer removal. The carboxylate moieties allow further chemical modification of the
surface in addition to the hydrophilic surface that can be produced by exposing the silicon dioxide substrate.
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