S
1
Supporting Information
S
train
-
based chemiresistive
polymer
-
coated graphene vapor
sensor
s
Annelise C. Thompson
†
,
Kyra S. Lee
†
, and Nathan S. Lewis*
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena,
CA,
91125, United States
†
These authors contributed equally
*Corresponding author:
nslewis@caltech.edu
Table of Contents
•
Exposure concentrations
•
4% PEVA solution spin curve
•
∆
R
max
/
R
b
response
s from all control
sensors
•
Raw response curves of control sensors to single pulses of pyridine at
P
/
P
o
•
Sensor optimization
o
Thickness dependence of sensors
o
Area dependence of sensors
o
Pitch dependence of sensors
•
2D
PCA
plots
S
2
Supporting Data
The c
oncentrations of the analytes
in ppm
derived from analyte partial pressures relative to the
analyte vapor pressure
(
P
/
P
o
) used in this work were calculated using the following equation
:
푃
/
푃
표
=
푐푃
푣푎푝표푟
101
.
325
∗
10
6
where
c
is the concentration of the analyte in percent and
P
vapor
is the vapor pressure of the
analyte at 25°C in kPa. Calculations are tabulated in Table
S
1.
Table
S
1. Concentration of analytes given percent exposure
Analyte
P
vapor
at 20°C
‡
kPa
P
/
P
o
ppm
Isopropanol
4.4
0.001
43
0.002
87
0.003
130
0.005
217
Ethanol
5.9
0.001
58
0.002
116
0.003
175
0.005
291
Ethyl acetate
12.8
0.001
96
0.002
191
0.003
287
0.005
479
Acetone
24.0
0.001
237
0.002
474
0.003
711
0.005
1184
THF
20.0
0.001
197
0.002
395
0.003
592
0.005
987
Toluene
2.9
0.001
29
0.002
57
0.003
86
0.005
143
Pyridine
2.0
0.001
20
0.002
39
0.003
59
0.005
99
‡
Vapor pressures complied from Ref.
1
S
3
Figure S
1
. Spin curve fo
r 4% PEVA in toluene. The change in thickness of the PEVA follow
ed
the expected square root dependence with respect to spin speed with an R
2
value of 0.93. The
large error bars for the thickness at 7000 and 8000 rpm influenced the final choice of samples
spun at 6000 rpm for the optimized sensors.
Table
S
2. Thickness of 4% PEVA in toluene spun at different speeds
Speed (rpm)
Thickness (nm)
St
andard Deviation (nm)
1000
317
33
2000
218
15
3000
158
22
4000
129
17
5000
111
13
6000
104
8
7000
101
28
8000
102
19
S
4
4% PEVA/CB (col)
4% PEVA/CB (Flat)
Graphene Alone (flat)
Graphene Alone (Col)
4% PEVA/Gr (Flat)
4% PEVA/Gr (col)
0
2
4
6
8
10
12
D
R/R
b
(%)
0.1% Ethanol
0.1% Ethyl Acetate
0.1% THF
0.2% Ethanol
0.2% Ethyl Acetate
0.2% THF
0.3% Ethanol
0.3% Ethyl Acetate
0.3% THF
0.5% Ethanol
0.5% Ethyl Acetate
0.5% THF
0.1% Toluene
0.1% Acetone
0.1% Pyridine
0.2% Toluene
0.2% Acetone
0.2% Pyridine
0.3% Toluene
0.3% Acetone
0.3% Pyridine
0.5% Toluene
0.5% Acetone
0.5% Pyridine
Figure
S
2
.
Various c
ontrol sensors versus
4%
PEVA/Gr on columns (far right)
exposed to
various VOC
partial pressures as a fraction of the analyte vapor pressure
(
P
/
P
o
) at a flow rate of
3000
ml
min
-
1
under
N
2
as the carrier gas.
The
largest
∆
R
max
/
R
b
response
was observed
from
the PEVA
-
graphene film on a glass substrate
having
150 nm high columns with a 3 μm diameter
and a
7 μm pitch
.
S
5
200
300
400
305
306
307
308
309
310
Resistance (R)
Time(s)
0.001
0.002
0.003
0.005
200
300
400
1564000
1568000
1572000
1576000
Resistance (R)
Time(s)
0.001
0.002
0.003
0.005
Figure
S
3
.
Overlay of
(A)
bare
Gr
(col)
, (B)
4% PEVA/CB
(flat), and (C)
4% PEVA/CB
(flat)
response curves to single pulses of pyridine at
P
/
P
o
of either
0.001, 0.002, 0.003,
or
0.005. Bare
Gr exhibited
a
sharper downturn curve after exposure to VOC
s,
suggesting faster recovery
relative to the
PEVA/Gr (col)
sensor
shown in Figure 2 of the main t
ext. PEVA/CB (flat)
exhibited
a more rapid
recovery compared to Gr sensors in A and
in
Figure
3
of the
main text.
PEVA/CB (col),
like
PEVA/CB (flat) exhibited
a substantial, rapid
recovery compared to Gr
sensors in A and
in
Figure
3
of the
main text
.
A
B
C
200
300
400
58800
59200
59600
60000
60400
Resistance (R)
Time(s)
0.001
0.002
0.003
0.005
S
6
50nm
100nm
150nm
200nm
300nm
0
5
10
15
20
0.1 Isopropanol
0.1 Acetone
0.1 Toluene
0.2 Isopropanol
0.2 Acetone
0.2 Toluene
0.3 Isopropanol
0.3 Acetone
0.3 Toluene
0.5 Isopropanol
0.5 Acetone
0.5 Toluene
0.1 Ethyl Acetate
0.1 THF
0.1 Pyridine
0.2 Ethyl Acetate
0.2 THF
0.2 Pyridne
0.3 Ethyl Acetate
0.3 THF
0.3 Pyridine
0.5 Ethyl Acetate
0.5 THF
0.5 Pyridine
D
R/Rb (%)
Column Height
Figure
S
4
.
Response of PEVA/Gr (col) vs.
column height
,
with the
sensors
exposed to
various
VOC
partial pressures as a fraction of the analyte vapor pressure
(
P
/
P
o
) at a flow rate of 3000
ml
min
-
1
under
N
2
as the carrier gas
.
S
7
320nm
220nm
160nm
130nm
80nm
~75nm
~73nm
~71nm
0
2
4
6
8
10
12
14
16
18
20
D
R/R
b
(%)
Polymer Spin Speed
0.1% Isopropanol
0.1% Ethyl Acetate
0.1% Acetone
0.2% Isopropanol
0.2% Ethyl Acetate
0.2% Acetone
0.3% Isopropanol
0.3% Ethyl Acetate
0.3% Acetone
0.5% Isopropanol
0.5% Ethyl Acetate
0.5% Acetone
0.1% THF
0.1% Toluene
0.1% Pyridine
0.2% THF
0.2% Toluene
0.2% Pyridne
0.3% THF
0.3%Toluene
0.3% Pyridine
0.5% THF
0.5% Toluene
0.5% Pyridine
Figure
S
5
.
Response of PEVA/Gr (col) vs.
polymer overlayer thickness
,
with
the
sensors
exposed to various VOC
partial pressures as a fraction of the analyte vapor
pressure
(
P
/
P
o
) at a
flow rate of
3000
ml min
-
1
under N
2
as the carrier gas. The spin speed (rpm) of the polymer
thickness was correlated as 1
k (320nm), 2
k (220nm), 3
k (160nm), 4
k (130nm), 5
k (80nm), 6
k (~75nm), 7
k (73nm), and 8
k (71nm), respectively.
S
8
3.5μm
7.5μm
15μm
30μm
60μm
120μm
0
2
4
6
8
10
12
14
D
R/R
b
(%)
Pitch
0.1% Isopropanol
0.1% Ethyl Acetate
0.1% THF
0.2% Isopropanol
0.2% Ethyl Acetate
0.2% THF
0.3% Isopropanol
0.3% Ethyl Acetate
0.3% THF
0.5% Isopropanol
0.5% Ethyl Acetate
0.5% THF
0.1% Toluene
0.1% Acetone
0.1% Pyridine
0.2% Toluene
0.2% Acetone
0.2% Pyridne
0.3% Toluene
0.3% Acetone
0.3% Pyridine
0.5% Toluene
0.5% Acetone
0.5% Pyridine
Figure
S
6
.
Controls for
the
number of columns/pitch of the substrate at various VOC
partial
pressures as a fraction of the analyte vapor
pressure
(
P
/
P
o
) at a flow rate of 3000 ml min
-
1
under
N
2
as the carrier gas. The l
ine displays
the
trend of the VOC response
as a function of
the
pitch
of the columns.
S
9
Figure S
7
. Raman spectrum for monolayer graphene after transfer to a glass sensor body.
While the overall signal for the response is
greatly attenuated on the glass as compared to the
typical 300nm SiO2 on Si substrate, the distinctive D and 2D peaks are still visible at 1585 cm
-
1
and 2678 cm
-
1
respectively with the ratio of 1:4 expected for a monolayer.
S
10
Figure S
8
. Scatter plots
of the first three principal components for sensors tested in this work.
The plots of PC1 vs. PC2 or PC3 show that the first principal component separates toluene and
chloroform from the others while plots of PC2 vs. PC3 demonstrate that the remaining VOC
s
are well separated from each other.
References
1.
Reichardt, C. Solvents and solvent effects in organic chemistry. (2004).