Generic Methods for Micrometer-
And Nanometer-Scale
Surface Derivatization Based on Photochemical Coupling of Primary
Amines to Monolayers of Aryl Azides on Gold and Aluminum Oxide Surfaces
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Abstract
A series of aryl azide terminated thiols and phosphonic
acids has
been synthesized, and used to prepare self-assembled monolayers on
(respectively) gold and aluminum oxide surfaces. The rates of photoactivation
were determined using contact angle measurement and X-ray photoelectron
spectroscopy (XPS). The behavior of a diazirine functionalized aryl
thiol was also studied. The rates of activation were found to be similar
for all five adsorbates. However, the extent of photochemical coupling
of a primary amine was significantly greater for the aryl azides than
for the diazirine. A range of primary amines was successfully coupled
to all of the azides with high yield. Little difference in reactivity
was observed following perfluorination of the aromatic ring. Micrometer-scale
patterns were fabricated by carrying out exposures of the aryl azide
terminated SAMs through a mask submerged under a film of primary amine.
Contrasting amines could be introduced to unreacted regions in a subsequent
maskless step. A scanning near-field optical microscope was used to
fabricate nanopatterns. Exposure of the azides to irradiation at 325
nm in air enabled selective deactivation of azides. The surrounding
surface was functionalized with a primary amine in a maskless process;
when a protein-resistant oligo(ethylene glycol) functionalized amine
was used it was possible to produce protein nanopatterns, by adsorbing
protein to features defined using near-field exposure