Synthesis and micropatterning of photocatalytically reactive self-assembled monolayers covalently linked to Si(100) surfaces via a Si-C bond.
Selective generation of an amine-terminated self-assembled monolayer bound to silicon wafers via a silicon-carbon linkage was realized by photocatalytically reducing the corresponding azide-terminated, self-assembled monolayers (Az-SAMs). The Az-SAM was obtained by thermal deposition of 11-chloroundecene onto a hydrogen-terminated silicon wafer followed by nucleophilic substitution of the chloride with the azide ion in warm N,N'-dimethylformamide (DMF). The presence of the terminal azide group on the SAM was confirmed by reflection absorption infrared spectroscopy (RAIRS), by X-ray photoelectron spectroscopy (XPS), and by detecting the formation of a triazole upon reaction of the azide with an activated alkyne. The desired terminal amine groups were generated by photocatalytic reduction of the Az-SAM with cadmium selenide quantum dots (CdSe Qdots) using λ > 400 nm. Analysis of the reduced SAM by XPS gave results that were consistent with those obtained with an amine-terminated surface obtained by reducing the Az-SAM with triphenylphosphine. To demonstrate the feasibility of using the Az-SAM for surface patterning, a sample was coated with adsorbed CdSe Qdots and exposed to the output of a diode laser at λ = 407 nm through a micropatterned mask. Using a SEM, the pattern formed in this manner was revealed after removing the CdSe Qdots and subsequently adsorbing 10 nm gold nanoparticles (AuNPs) to the positively charged terminal-amine groups. The formation of the pattern by CdSe-photocatalyzed reduction of the azide demonstrates a novel route to create features by selective modification of organic monolayers on silicon wafers.
Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, California 90095, United States.
Michael K F
MK
Lo
Matthew N
MN
Gard
Bryan R
BR
Goldsmith
Miguel A
MA
Garcia-Garibay
Harold G
HG
Monbouquette