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immersion in boiling methanol to remove organic residue and
metallic dust. The cleaned substrates were stored in an oven at
100 C.
Films were formed on the native oxide surface of the two alloys
and their constituents using solution deposition methods (either
dipping or spraying).
17,32,36,37
The experimental procedures used
to formmonolayers for eachof themetal/alloy-acid combination
are tabulated in Table 1. The final procedures were arrived at by
varying experimental procedures including increasing the deposi-
tion time, organic concentration, deposition temperature, and
solution depositionmethod in an attempt to obtain successful film
formation. Numerous unsuccessful procedures were performed
and not included in the article. The procedures adopted to form
monolayers are as discussed below. All substrates were stored at
100 C prior to deposition.
1. The substrates were sprayed using a 0.35mMsolution of the
acid at room temperature and allowed to dry at room tempera-
ture.
2. The substrates were sprayed using a 0.75mMsolution of the
acid at roomtemperature and allowed to dry at roomtemperature
for 20 min, and then the same spraying procedure was repeated
one more time.
3. A 1.5 mM solution was used to spray the substrates three
times at room temperature and dried in the oven at 120 Cfor
20 min between sprays.
4. Substrates were dipped in 1mMsolution of the acid at room
temperature for 1 min.
5. Substrateswere left in a 1mMsolution of the organic acid for
3-5 min at room temperature.
6. Substrates were dipped in a warm (50 C) 1 mMsolution of
the acid for 2 h and then dried in the oven at 100 C overnight.
7. Substrates were placed on a dishwhich was then placed in
an ice bath for 1 h. The substrates were then dipped in a warm
(50 C) 1mMsolution of the acid for 2 h, taken out of solution
without solvent meniscus, and stored in the oven at 100 C
overnight.
8. Substrateswere placed on a dishwhich was then placed in an
ice bath for 1 h.The substrateswere then dipped in awarm(50 C)
2 mM solution of the acid for 2 h, taken out of solution without
solvent meniscus, and stored in the oven at 100 C overnight.9. Substrates were placed on a dish, and the dish was placed in
an ice bath for 1 h. The substrates were then dipped in a warm
(50 C) 2 mM solution of the acid for 2 h, taken out of solution
with solventmeniscus, and stored in the oven at 100 C overnight.
The monolayers were checked for ordering of the alkyl chains
by IR and contact angle to confirm condensed film formation.
Contact angle data and AFM imaging of dipping and spraying
procedures showed similar organization of the films on the sur-
face.
Characterization of theMonolayers. Infrared Spectros-
copy. After the formation of monolayers, DRIFT was used to
analyze the ordering and orientation of the molecules in the
monolayer formed. Spectra were collected under nitrogen for
1024 scanswith a resolution of 1 cm-1
on each sample and ratioed
with a background reference spectrumof the samemetal or alloy.
After verifying the presence of films after the deposition, the
samples were rinsed in THF for 15 min and analyzed by DRIFT
spectroscopy again to confirm the presence of the films. The
substrates were then sonicated in THF for 15 min to test the
mechanical stability of the films.
ContactAngleMeasurement. Static contact angle ofwater on
the filmswasmeasured to determine thewettability of the surface.
The average contact angle value and standard deviation of six
measurements each on at least three samples (18 measurements
total) have been reported.
Atomic Force Microscopy. An atomic force microscope