Supporting Online Materials for
Nanocomposite based flexible ultrasensitive resistive gas
sensor for chemical reactions studies
Sadanand Pandey, Gopal K. Goswami and Karuna K. Nanda*
*To
whom
correspondence
should
be
addressed.
E-mail:
nanda@mrc.iisc.ernet.in
Preparation of stock solution of ammonia
A stock solution of different aqueous ammonia concentrations was prepared from 25%
ammonia solution of density 0.91g ml-1 which is equivalent to 2,27,500 ppm with respect to
water.
Calculated at given below:
100ml------------------------25ml x 0.91g ml-1
1000ml-------------------------25x 0.91x 10g
=25 x 0.91 x 104 mg/ L
=25 x 0.91 x 104 ppm
=2,27,500 ppm
Basically the most common dilution method was followed for varying the different ammonia
concentration. As we know that the dilution means the addition of more solvent to a solution
so that the concentration of the solute becomes lower. The total number of mole of solutes in
the solution remains the same after dilution, but the volume of the solution becomes greater,
resulting in change in molarity, ppm or % of solution.
Dilution Calculation
Dilution calculations are performed by using the following equation:
M1V1 = M2V2
where M1 = concentration of the initial solution, V1 = volume of the initial solution,
M2 = concentration of the final solution, V2 = volume of the final solution.
Concentration and volume in the equation above can have any units as long as the units are
the same for the two solutions. As long as we know three of the four parameters from the
above equation, you can calculate the fourth. By using the above equation, ammonia
solutions with varying concentrations (1300ppm, 800ppm, 10ppm, 1ppm, 50ppb etc in DI
water) were easily prepared right before the experiments.
Baseline
75
800 ppm
Current (A)
OFF
50
25
ON
0
0
400
800
1200
time (s)
Figure S1. Temporal response for 800 ppm ammonia for 3 cycles.
% Relative sensitivity
101
100
99
98
97
96
0
20
40
60
Time (Days)
80
100
Figure S2. Stability of sensing film with a ammonia concentration of 800 ppm.
a
c
b
Counts
180
120
60
0
d
5 nm
4
6
8
10 12
Diameter (nm)
e
f
Figure S3. Characterization of GG/Ag nanocomposite. a, TEM image of the GG stabilized
Ag nanoparticles with size distributions and a high magnification image. b & c, HRTEM
image of Ag nanoparticles. d & e, SEM images of GG/Ag films (film I & II) with different
Ag loading. f, SEM images of film II after several measurements.
15
NH3 ON
NH3 OFF
5
NH3 ON
10
N2 OFF, ambient ON
15min O2 exposure NH3 OFF
N2 ON
b
Current (A)
NH3 OFF
NH3 ON
NH3 OFF
0
0
1000
time (s)
1500
15
800
1600
time (s)
NH3 OFF
N2 OFF, ambient ON
30min O2 exposure NH3 OFF
10
5
0
2000
NH3 ON
c
N2 ON
500
Current (A)
0
NH3 ON
5
NH3 ON
10
N2 OFF, ambient ON
5min O2 exposure
N2 ON
Current (A)
a
15
0
0
500
1000
time (s)
1500
2000
Figure S4. Sensing study of sensing film at different oxygen plasma exposure (a) 5, (b) 15
and (c) 30 min. at 30W power under identical condition.
In order to investigate the effect of oxygen plasma, we have carried out the sensing study of
sensing film at different oxygen plasma exposure (5, 15 and 30 min. at 30 W) under identical
condition by Gatan plasma system (Gatan Model 950 advanced plasma system).
2400
8
Id (mA)
6
Vd= 4.9 V
2.5 V
4
2
0
-10
-5
Vg0(V)
5
10
Figure S5. Transfer characteristics (FET) of sensing film at different drain voltages (Vd) of
4.9 and 2.5V.
a1
b1
Ag 3d
Intensity (a.u.)
Intensity (a.u.)
Ag 3d
360
365
370
Binding energy (eV)
a2
360
375
365
370
375
Binding energy (eV)
b2
N1s
Intensity (a.u.)
Intensity (a.u.)
N1s
395
397
399
Binding energy (eV)
a3
401
397
399
401
Binding energy (eV)
b3
O1s
O1s
Intensity (a.u.)
Intensity (a.u.)
395
526
530
Binding energy (eV)
Figure S6.
experiment.
534
526
530
Binding energy (eV)
XPS analysis of sensing film (a) before and (b) after ammonia sensing
534
Sensitivity (s)
65
60
55
20
30
40
50
%RH
60
70
Figure S7. Sensitivity of ammonia under different natural humidity (%RH). The ammonia
concentration is 500 ppm. The sensitivity variation is within 6% if the sensor is calibrated at
50% RH. The humidity is measured using FLUKE 971.
0.25
100
200
400
0.00
-0.25
-20
=00
100
200
-10
0
10
V (V )
18
0
0.00
-0.25
-20
20
Baseline
=0
0
0
0
10
20
40
400
d
-10
0
10
V (V )
20
65
60
12
S
Current (A)
c
0.25
b
=00
Current (A)
Current (A)
a
55
6
50
0
0
700
1400
time (s)
2100
2800
45
0
10
20
30
 (degree)
Figure S8. I-V characteristics of the flexible film at different bending angles in ; (a) nitrogen
and (b) ambient environment. Inset shows the schematic of bend and flat condition of the film
at different bending angle of (c) Temporal response for 500 ppm ammonia and (d)
sensitivity as a function of bending angles.
The operation of the flexible film for ammonia sensing for 500 ppm concentration
under different bending angles has been studied by keeping the other entire parameters
constant (%RH, temperature, etc)
40
100
(a)
(b)
90
2924
1647
%T
814
80
3457
1024
2926
1398
70
1651
1426
847
3426
60
1046
1000
2000
3000
Wavenumber (cm-1)
4000
Figure.S9 FTIR spectra of (a) GG and (b) GG/Ag nanocomposite
9.5
Current ()
(III)
(II)
9.0
8.5
8.0
7.5
7.0
6.5
(I)
6.0
15
20
25
30
35
40
45
Loading of Ag (mM)
Figure S10. Current/conductivity as a function of Ag loading.
Table S1: FTIR results of GG and GG/Ag nanocomposite.
GG
GG/Ag
(cm-1)
(cm-1)
3426
3457
Hydroxyl group (-OH)
Stretching vibration of O-H
2926
2924
Alkyl group (-CH2)
Stretching vibration of C-H
1651
1647
Carbonyl group (-C=O or –CHO)
Stretching vibrations of C=O
1426
1398
Carboxyl group (-COOH)
Stretching vibration of C-O
1046
1024
Hydroxyl group (-OH)
Bending vibration of O-H
847
814
Glycosidic linkage
Bending vibration of C-H
Functional group
Structural characteristics