1
Supporting Information
Tailoring of Interfacial Mechanical Shear
Strength by Surface Chemical Modification of
Silicon Microwires Embedded in Nafion
Membranes
Betar M. Gallant,
1,3
X. Wendy Gu,
2
David
Z.
Chen,
2
Julia R. Greer,
2,3
and Nathan S.
Lewis
1,3,4
1
Division of Chemistry and Chemical Engineering,
2
Division of Engineering and Applied
Sciences,
3
The Kavli Nanoscience Institute at Caltech, and
4
The Beckman Institute at
Caltech, California Institute of Technology, Pasadena, California 91125, United Stat
es
2
Figure S1.
XPS data
in the Si 2p region
for
a Si
-
undecanoic acid surface after a 5
h
reaction.
Figure S2.
XPS data
in the Si 2p region
for
a Si
-
undecanoic acid surface
functionalized
by a 3 h reaction and then exposed
to air for 1 week.
3
F
igure S3.
FTIR spectra of the sample
shown
in Figure 3
of the main text
,
expanded
to
show features in the 2000
–
1000 cm
-
1
region.
Figure S4.
Si 2p high
-
resolution XPS
data
of a
5
h
functionalized
Si(111)
-
BOC
-
amino
butane
surface (a)
as synthesized
,
and (b)
following removal of the BOC protecting
group in TFA
(1
h)
.
4
Figure S5
.
SEM image
s prior to mechanical measurements of
the different
functionalized
wire
samples
used in thi
s study.
Although grips are in contact with the wires at the
initiation of
the mechanical tests, images were taken before any load was applied.
Figure S6
.
SEM image of a debonded wire (Si
-
aminobutane, 5
h) after completion of
the
mechanical test, revealing a clean Si microwire surface.
5
Figure S7
.
(a) Water
contact an
gle measurements of a Si
-
H surface immediately upon
functionalization and following 90 h in air, a Si
-
undecanoic acid surface, and deprotected
Si
-
aminobutane surfaces with 1, 3, and 5 h reaction times. C
orresponding images of Si
-
H
(b) and Si
-
aminobutane su
rfaces (c
-
e).
Figure
S
8
.
True shear stress (normalized to the decreasing contact area of the wire with
Nafion during the pull
-
out phase) as a function of embedded length, obtained from the
data in Figure 5
of the main text
.
6
Figure S9
.
Transmission
FTIR spectra of deprotected Si
-
aminobutane surfaces vs. Si
-
H
backgrounds for 1, 3, and 5
h reaction times.