pubs.acs.org/acssensors

ArticleMechanistic Approach for Long-Term Stability of a Polyethylene
Glycol−Carbon Black Nanocomposite Sensor
Wenjun Li, Kazuki Nagashima,* Takuro Hosomi, Chen Wang, Yosuke Hanai, Atsuo Nakao,
Atsushi Shunori, Jiangyang Liu, Guozhu Zhang, Tsunaki Takahashi, Wataru Tanaka, Masaki Kanai,
and Takeshi Yanagida*

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sı Supporting Information*

ABSTRACT: Polymer−carbon nanocomposite sensor is a promising molecular sensing device for electronic nose (e-nose) due toits printability, variety of polymer materials, and low operation
temperature; however, the lack of stability in an air environmenthas been an inevitable issue. Here, we demonstrate a designconcept for realizing long-term stability in a polyethylene glycol(PEG)−carbon black (CB) nanocomposite sensor by understanding the underlying phenomena that cause sensor degradation.
Comparison of the sensing properties and infrared spectroscopy on
the same device revealed that the oxidation-induced consumption of PEG is a crucial factor for the sensor degradation. According to
the mechanism, we introduced an antioxidizing agent (i.e., ascorbic acid) into the PEG−CB nanocomposite sensor to suppress the
PEG oxidation and successfully demonstrated the long-term stability of sensing properties under an air environment for 30 days,
which had been diﬃcult in conventional polymer−carbon nanocomposite sensors.
KEYWORDS: chemiresistive sensor, carbon black, polyethylene glycol, nanocomposite, long-term stability

C

response to 46% of its initial value after 100 cycles of acetone
sensing at 45 °C.26 Wu et al. reported the degradation of thesensing response in a similar sensor device to ca. 50% of its initialvalue within 4 days at 25 °C in air.27 These degradations ofsensing responses strongly aﬀect the pattern recognition
performance in e-nose and plausibly cause fatal errors in data
analysis. As such, a rational design concept to realize the longterm stable polymer−carbon composite sensor is strongly
desired.
Here, we demonstrate a design concept for realizing long-term
stability in a polyethylene glycol (PEG)−carbon black (CB)nanocomposite sensor under an air environment. Comparisonof the sensing properties and infrared (IR) spectroscopy on thesame device revealed that the oxidation-induced consumption of
PEG is a crucial factor for sensor degradation. According to themechanism, we introduced an antioxidizing agent (i.e., ascorbicacid) into the PEG−CB nanocomposite sensor to suppress the
PEG oxidation and successfully demonstrate the long-term
stability of sensing properties for 30 days, which had been

hemiresistive sensors, which transduce volatile moleculesin surrounding environments into digital information,
have recently gained increasing attention due to their ability tocollect and monitor chemical information for various usages
such as environmental monitoring, healthcare, food safety, andqualiﬁcation of industrial ﬁne products in upcoming Internet ofThings (IoT) era.1−8 Chemiresistive sensors are utilized ascomponents of artiﬁcial olfaction system’s so-called electronicnose (e-nose), and the molecular sensing data collected throughthe multisensor array in e-nose are analyzed based on a patternrecognition technique by mimicking the biological olfaction
system.9,10 The goal in this ﬁeld is to collect time-seriesmolecular sensing data by using IoT devices and exploit them as
chemical big data.11,12 Therefore, development of a long-term
stable and low-energy consumption chemiresistive sensor is amajor challenge. Among various chemiresistive sensors, apolymer−carbon nanocomposite-based sensor is a promising
candidate for e-nose due to its printability, variety of applicable
polymer materials, and low operation temperature (usually atroom temperature),13,14 which are hardly attainable in conventional metal-oxide semiconductor sensors.15−21 Previous studies
have been mainly devoted to polymer design for detecting
various analyte molecules.22−25 However, the polymer−carbon
nanocomposite sensors often suﬀer from degradation of sensing
performance in an air environment. For example, Chiou et al.
reported that a polyethylene glycol/multiwalled carbon nanotube nanocomposite sensor exhibited degradation of sensing© 2021 American Chemical Society

Received: September 2, 2021
Accepted: November 5, 2021
Published: November 17, 2021

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ArticleFigure 1. (a,b) Schematic illustrations of (a) chemiresistive sensor array and (b) the working principle of a polymer−carbon nanocomposite sensor.
(c) Optical microscopy images of the chemiresistive sensor array (left) and a sensor device of PEG (PEG, PEG4000)−CB nanocomposite (right). (d)Successive sensing responses to 2.7 ppm nonanal at Day 1 (left) and Day 30 (right). (e) Duration of the sensing response to 2.7 ppm nonanal whenstoring the sensor sample at room temperature in air with RH 67%. All sensing measurements were performed at room temperature in air with N2
carrier gas.

tendency of the sensing response is more clearly seen in Figure
1e. During the test, the device experienced 150 cycles ofmolecular sensing. Since the stable sensing response was stillobserved even after the successive 150 cycles of molecularsensing at Day 1 (Figure S2), the degradation of the sensing
response must originate from storing the device rather than fromthe molecular sensing operation. Thus, the degradation of thesensing response under an air environment is proven to be an
inevitable issue in a PEG−CB nanocomposite sensor.
In order to specify what caused the degradation of the sensing
response, we designed a PEG−CB nanocomposite sensor device
capable of performing both molecular sensing and IR spectroscopy on the same device by precisely controlling the gap size of
Pt electrodes and the thickness of the nanocomposite (seedetails in the Experimental Section). Such a “2-way device”
allows us to directly link the variations of molecular sensing
properties and chemical states of the nanocomposite sensor.
Figure 2a,b shows the schematic illustration and the photo of the
2-way device, respectively. By using the 2-way device, we ﬁrst
conducted molecular sensing with aging tests under various
environments. Figure 2c shows the sensing responses of the 2way device to 2.7 ppm nonanal at Day 1 and Day 6 for the aging
tests in air with RH 0%, N2 with RH 95%, and N2 with RH 0%.
The aging tests were conducted at 120 °C. Signiﬁcantdegradations of the sensing response were observed at Day 6
in air with RH 0% and N2 with RH 95%, while the sensing
response in N2 with RH 0% was almost unchanged. Under theformer two conditions, the degradation started from Day 2 andprogressed with increasing time as shown in Figure 2d. The
aging test in O2 with RH 0% revealed that the observed
degradation in air with RH 0% was crucially governed by oxygen(Figure S3). These results suggest that both oxygen and water
are the major factors for the degradation of the sensing response

diﬃcult in conventional polymer−carbon nanocomposite
sensors.

■

RESULTS AND DISCUSSION
Figure 1(a,b) shows the schematic images of the polymer−
carbon nanocomposite-based chemiresistive sensor array and its
working principle. The sensor consists of electrically conductive
carbon nanoparticles and an electrically insulative polymer. In
previous studies, 16 types of gas chromatography stationary
phases, which exhibit a wide range of adsorption properties forvolatile molecules, were selected as polymer materials for enose.28,29 The adsorption of analyte molecules in the polymer
matrix induces a volumetric change of the nanocomposite,leading to the increase of electrical resistance by extending the
distance between the carbon nanoparticles. Figure 1c shows the
optical microscopy images of the polymer−carbon nanocomposite-based chemiresistive sensor array and a sensor device
composed of a PEG−CB nanocomposite (PEG 4000, m.w.
3600−4400). PEG is a typical polymer material for thepolymer−carbon nanocomposite sensor,30,31 which enables
the detection of a variety of polar molecules. The PEG−CB
nanocomposite has a granular shape as shown in the Supporting
Information Figure S1. Figure 1d shows the successive sensing
responses of a PEG−CB nanocomposite sensor to 2.7 ppm
nonanal at Day 1 and Day 30. Nonanal is a component of
perfume,32 an attractant for Culex mosquitoes,33 an indicator for
lipid peroxidation in muscle foods,34 and a lung cancer
biomarker in exhaled breath.35 The sensing measurements
were conducted once a day at room temperature in air withﬂowing N2 carrier gas, and at other times, the device was stored
at room temperature in air with 67% relative humidity (RH)
under dark conditions. The sensing response signiﬁcantly
decreased to ca. 30% of its initial value within 30 days, whichis consistent with the previous studies.36,37 Such a decreasing152

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ArticleFigure 2. (a) Schematic illustration and (b) photo of the 2-way device capable of performing molecular sensing and IR spectroscopy on the samedevice. (c) Successive sensing responses to 2.7 ppm nonanal at Day 1 (upper) and Day 6 (lower) when aging the devices in air with RH 0% (leftcolumn), N2 with RH 95% (middle column), and N2 with RH 0% (right column), respectively. (d) Duration of the sensing response (i.e., responsechange ratio) to 2.7 ppm nonanal when aging the devices in air with RH 0%, N2 with RH 95%, and N2 with RH 0%. The aging tests were conducted at
120 °C. All sensing measurements were performed at room temperature in air with a N2 carrier gas.

Figure 3. Time-dependent IR spectra of 2-way devices that were aged in (a,d) air with RH 0%, (b,e) N2 with RH 95%, and (c,f) N2 with RH 0%,
respectively. Panels (a−c) show the regions for alkyl group (2800−3200 cm−1) and hydroxyl group (3100−3500 cm−1) and panels (d−f) show the
carbonyl region (CO and COO, 1400−1800 cm−1). The aging tests were conducted at 120 °C.

in the PEG−CB nanocomposite sensor under an air environment (Figure 1e).

To obtain an in-depth understanding of the degradation
mechanism of the PEG−CB nanocomposite sensor in terms of153

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the chemical states, we next performed Fourier transform
infrared (FTIR) spectroscopy measurements during the aging
tests and compared the results with their molecular sensing data
by using the 2-way device. Figure 3 shows the time-dependent
FTIR spectra of the 2-way device during the aging tests in (a,d)
air with RH 0%, (b,e) N2 with RH 95%, and (c,f) N2 with RH
0%, respectively. The aging tests were conducted at 120 °C.
Figure 3a−c shows the regions for alkyl group (2800−3200cm−1) and hydroxyl group (3100−3500 cm−1) and Figure 3d−fshows the carbonyl region (CO and COO, 1400−1800
cm−1). Similar to the sensing responses shown in Figure 2d,
signiﬁcant variations of IR spectra were observed after Day 2 inair with RH 0% (Figure 3d) and in N2 with RH 95% (Figure3b,e), while no obvious variation was seen in N2 with RH 0%(Figure 3c,f). These trends well correspond to the degradationof the sensing responses shown in Figure 2d and also remind usof the crucial role of oxygen and water. Here, we ﬁrst discuss thevariation of the chemical state of the nanocomposite sensor
induced by oxygen. For the aging test in air with RH 0%, threepeaks tended to appear at around 1448, 1548, and 1727 cm−1 inthe carbonyl region (Figure 3d), which are associated with thevibrations of carboxyl groups νs(COO) and νas(COO) andcarbonyl group ν(CO), respectively.38 They correlate withthe formation of aldehyde, formic acid, and acetic acid asoxidation products of PEG.39−41 The peaks of νs(COO) andνas(COO) became smaller after Day 4, implying the removal ofoxidation products. Such formation/removal of carboxyl groups
might be irreversible phenomena because they involve thevariation of alkyl group as shown in Figure 3a. A similar tendency
was observed in the IR spectra of PEG (without CB) but not CB(Figure S5). These results clearly indicate that the oxidation of
PEG triggered the degradation of the sensing response.
Next, we discuss how the chemical state of the PEG−CB
nanocomposite sensor varies due to water. For the aging test in
N2 with RH 95%, several peaks tend to appear at around 1460−
1540 cm−1, 1580−1760 cm−1, and 3100−3500 cm−1. Two
broad peaks at around 1650−1700 cm−1 and 3100−3500 cm−1
are assigned to δ(OH) and ν(OH), which plausibly originate
from the adsorption of water molecules.42 Consistent results
were observed in the sensor resistance, that is, the sensor
resistance decreased due to the ionic conduction of adsorbed
water (Figure S4). The peak at 1727 cm−1 assigned to ν(CO)
tended to be larger during the aging test, which was plausibly due
to the formation of an aldehyde group via the gradual oxidationof PEG in aqueous solution.43 The other peaks at 1614 and 1499
cm−1 were almost unchanged after Day 2. These peaks weresometimes observed in a previous study of PEG while their
origins are unclear.44 Unlike the aging test in air with RH 0%, nosigniﬁcant variation in alkyl group was observed. These results
imply that the basic structure of PEG was maintained during theaging test in N2 with RH 95%. In order to investigate the eﬀect ofadsorbed water on the aging of PEG, we performed a thermal
treatment to remove the adsorbed water molecules. Figure 4ashows the sensing responses of the 2-way device to 2.7 ppm
nonanal at the initial state, after 5 days of aging in N2 with RH
95% and after 48 h of annealing in N2 with RH 0%, and Figure
4b,c shows the corresponding IR spectra. Remarkably, thedegraded sensing response was recovered to 90% of its initialstate after annealing. Consistent results were also observed in the
IR spectra, that is, all peaks emerged during the aging test
disappeared after the annealing and the shape of the IR spectrum
changed back to the initial one. The results indicate that theadsorbed water does not cause fatal degradation in PEG and the

ArticleFigure 4. (a) Successive sensing responses of the 2-way device to 2.7
ppm nonanal at the initial state after 5 days of aging in N2 with RH 95%
and after 48 h of annealing in N2 with RH 0% for dehydration,
respectively. The aging test and thermal annealing were conducted at
120 °C. All sensing measurements were performed at room
temperature in air with N2 carrier gas. (b,c) IR spectra of the 2-way
device at the initial state after 5 days of aging in N2 with RH 95% andafter 48 h of annealing in N2 with RH 0% for dehydration, respectively.
Panel (b) shows the regions for alkyl group (2800−3200 cm−1) andhydroxyl group (3100−3500 cm−1) and panel (c) show the carbonyl
region (CO and COO, 1400−1800 cm−1).

sensing response. Also, they clearly highlight that the fatal
degradation of the nanocomposite sensor is solely induced by
the oxidation of PEG.
Here, we consider why the oxidation of PEG led to thedegradation of the sensing response in the PEG−CB nanocomposite sensor. The comparison of molecular sensing data
and IR spectra (Figures 2d and 3d) on the same device showsthat the degradation of the sensing response was triggered by theoxidation of PEG and further progressed even when theoxidation products were removed. First, we consider that thechemical state of oxidized PEG caused the degradation of thesensing response. This is because the adsorption of analytemolecules and the resultant volumetric change in the polymer−
carbon nanocomposite sensor are strongly determined by theaﬃnity between analyte molecules and the polymer material.
However, the observed sensor degradation might not be
governed by the chemical state of oxidized PEG since a similar
degradation trend in sensing response was seen when examining
the molecular sensing using the higher polarity molecule ofmethanol (Figure S6). Next, we assume that the consumption of
PEG seriously caused the degradation of the sensing response.
This is because the total volumetric change of the nanocomposite sensor during molecular sensing must be suppressed
when the amount of PEG is reduced. In fact, the sensing
response tended to decrease with decreasing amount ratio of
PEG in the PEG−CB nanocomposite (Figure S7). In principle,
the oxidation of PEG involves cleavage of the C−C bond.39−41
Therefore, PEG is supposed to be shorter and consumed via
oxidation and the following removal of COO bonds as CO2 gas(Figure 5a) as implicated by the IR spectra in Figure 3a,d. To
directly validate the consumption of PEG, we evaluated theweight of PEG during the aging test in air. As we expected, theweight of PEG drastically decreased during the aging test in air
with RH 0% (Figure 5b). Thus, we conclude that the154

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Articleexamined the addition of an antioxidizing agent (i.e., ascorbic
acid (AA))43 to the nanocomposite sensor. We expect that theoxidation of PEG is prevented by alternatively oxidizing AA as
schematically shown in Figure 5a. In fact, the consumption of
PEG was drastically suppressed by the AA addition (Figure S8).
Figure 5c shows the successive sensing response of the 2-way
device to 2.7 ppm nonanal at Day 1 and Day 6 for the aging testin air with RH 0% when AA of 5 mg/mL was added to thenanocomposite. The aging test was conducted at 120 °C.
Contrary to the result shown in Figure 2c, no signiﬁcantdegradation of the sensing response was seen in the AA-added
nanocomposite sensor. The eﬀect of the antioxidizing agent ismore clearly seen in Figure 5d. The degradation of the sensing
response can be prevented by increasing the AA concentration.
Note that excess AA addition over 10 mg/mL resulted in thelowering of the sensing response (Figures 5e and S8). Thisimplies that the excess AA interferes with the interaction
between PEG and analyte molecules. The eﬀect of AA additionon the suppression of degradation in the sensing response wasalso conﬁrmed by acetone sensing, showing the diverse
applicability of the present approach to various analytes (FigureS9). Figure 5f,g shows the IR spectra of the 2-way device during
the aging test in air with RH 0% when AA of 5 mg/mL was added
to the nanocomposite. The peaks associated with AA cannot beseen at the examined concentration condition (Figure S10). The
appearance of νs (COO) and νas (COO) peaks and the variationof alkyl group were not seen in the spectra, indicating that theoxidation of PEG is substantially prevented by adding AA. Sucha trend was well consistent with the results of the X-ray
diﬀraction (XRD) measurement (Figure S11). Thus, theseresults indicate that the oxidation of PEG, which is responsible
for the degradation of the PEG−CB nanocomposite sensor, wassuccessfully prevented while maintaining the sensing responseby adding an antioxidizing agent (i.e., AA) with a precisely
controlled concentration.
Finally, we examined the long-term stability of a PEG−CB
nanocomposite sensor. Figure 6a,b shows the optical microscopy images of an AA-added (5 mg/mL) PEG−CB nanocomposite sensor and its successive sensing response to 2.7 ppm
nonanal at Day 1 and Day 30. For this experiment, the molecularsensing was performed once a day and the device was kept atroom temperature in air with RH 67%. There are no signiﬁcantvariations in the morphology and the sensing response of thenanocomposite sensor. The eﬀect of AA addition on the longterm stability of the nanocomposite sensor can be more clearlyseen in Figure 6c. The degradation of the sensing response wassigniﬁcantly improved by adding AA while maintaining theamplitude of the sensing response. Also, the humidity-induced
degradation of the sensing response was not seen. This isplausibly due to the fact that the adsorbed water in the
nanocomposite sensor is removed by the self-Joule heating
occurring during the molecular sensing measurement. Thus, thelong-term stability of the PEG−CB nanocomposite sensor for
30 days was successfully achieved by rationally preventing theoxidation of PEG.

Figure 5. (a) Degradation mechanism of PEG and the proposed
approach for suppressing degradation using AA. (b) Duration of weight(i.e., weight change ratio) of PEG and 5 mg/mL AA-added PEG during
the aging test. (c) Successive sensing responses of the 5 mg/mL AAadded 2-way device to 2.7 ppm nonanal at Day 1 and Day 6 during theaging test. (d) Durations of the sensing response (i.e., response change
ratio) to 2.7 ppm nonanal and (e) sensor resistance of the 2-way device
with various AA concentrations. All sensing measurements andcharacterization of sensor resistance were performed at room
temperature in air with N2 carrier gas. (f,g) Time-dependent IR spectraof the 5 mg/mL AA-added 2-way device during the aging test. Panel (f)shows the regions for alkyl group (2800−3200 cm−1) and hydroxyl
group (3100−3500 cm−1) and panel (g) shows the carbonyl region(CO and COO, 1400−1800 cm−1). The aging test was conducted at
120 °C in air at with RH 0%.

■

CONCLUSIONSIn conclusion, we conducted a mechanistic study for understanding the degradation of the sensing response and realizing
long-term stability in a PEG−CB nanocomposite sensor underan air environment, which had been a bottleneck issue inpolymer-based chemiresistive sensors. A device capable ofperforming both electrical molecular sensing and IR spectros-

consumption of PEG, triggered by the oxidation, is responsible
for the degradation of the sensing response.
The above results suggest that preventing the oxidation of
PEG is of crucial importance to achieve the long-term stability of
the PEG−CB nanocomposite sensor. In this regard, we
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photolithography. The PEG−CB mixed solution was dropped on thepatterned substrate by means of ink-jet printing (custom-made, SIJ
Technology Inc.). For the latter device (i.e., electrical sensing/IR
spectroscopy 2-way sensor device), Pt electrodes with a Ti adhesive
layer were patterned on a 30 × 5 mm2-sized substrate by means of metal
mask. The gap distance and thickness of Pt electrodes for the 2-way
device were 2 mm and 300 nm, respectively. The nanocomposite wasthen spin-coated on the electrode-patterned substrate with thecondition of 2000 rpm for 200 s. Both sensor devices were thenvacuum-annealed at 120 °C for 24 h to fully remove the solvent. The
morphologies of the nanocomposite and the sensor device werecharacterized by ﬁeld emission scanning electron microscopy (FESEM,JEOL JSM-7610F) at an accelerating voltage of 15 kV and optical
microscopy (OLYMPUS DP21). XRD measurement was performed toevaluate the crystal structure of the nanocomposite. FTIR spectroscopy(Thermo Fisher Scientiﬁc Nicolet iS50) was performed for monitoring
the degradation of the nanocomposite. The electrical properties and themolecular sensing response of the fabricated sensor devices werecharacterized by a probe station equipped with a gas supply system, asemiconductor parameter analyzer (Keithley 4200-SCS, for a 2-way
device), and a homemade sensing module (for a component of the 16channel sensor array). The molecular sensing measurements wereconducted using 2.7 ppm nonanal, 5.6 ppm methanol, and 3.9 ppm
acetone at room temperature in air. Nitrogen (N2) was utilized as thecarrier gas. The readout voltage was 1 V. The sensing response wasdeﬁned as (Rg − RN2)/RN2 × 100%, where Rg and RN2 are theresistances of sensor devices exposed to nonanal and N2, respectively.
For the aging tests, the fabricated sensor devices were kept at 120 °C in
air with RH 0%, N2 with RH 95%, and N2 with RH 0%. Five or six
devices were fabricated and characterized for each aging condition inorder to obtain reliable data.

Figure 6. (a) Optical microscopy images of a PEG−CB nanocomposite
sensor device with the addition of 5 mg/mL AA at Day 1 (left) and Day
30 (right). (b) Successive sensing responses to 2.7 ppm nonanal at Day
1 (left) and Day 30 (right). (c) Duration of the sensing response to 2.7
ppm nonanal with and without the addition of AA when storing thesensor sample at room temperature in air with RH 67%. All sensing
measurements were performed at room temperature in air with N2
carrier gas.

■

ASSOCIATED CONTENT

sı Supporting Information*

The Supporting Information is available free of charge athttps://pubs.acs.org/doi/10.1021/acssensors.1c01875.

copy was designed to link the degradation of sensing response
and the chemical state in a PEG−CB nanocomposite sensor.
Comparison of the sensing properties and IR spectroscopy on
the same device revealed that the oxidation-induced consumption of PEG is a crucial factor for the sensor degradation.
According to the mechanism, we introduced an antioxidizing
agent (i.e., AA) into the PEG−CB nanocomposite sensor tosuppress the PEG oxidation and successfully demonstrated thelong-term stability of sensing properties under an air environment for 30 days. Since oxidation is a common issue in polymer
materials, the proposed approach is applicable to diverse
polymer−carbon nanocomposite sensors for improving theirlong-term stability in an air environment.

■

Article■EXPERIMENTAL SECTION

The polymer−CB nanocomposite used in this study was prepared bymixing CB (CB2350, Mitsubishi Chemical) and PEG (PEG4000,
Aldrich Chemical Co.) in deionized water with the same quantity of 10
mg/mL. AA (Fujiﬁlm Wako Pure Chemical Co.) was then added to thenanocomposite for suppressing the oxidation of PEG with aconcentration of 0−10 mg/mL. The as-prepared nanocomposite wasdeposited on a Si substrate (n-type, capped with a 100 nm-thick SiO2
layer) to fabricate two types of sensor devices including a component of
16-channel sensor array and an electrical sensing/IR spectroscopy 2way sensor device. For the former sensor device, comb-shaped Pt
electrodes with a Ti adhesive layer were ﬁrst patterned on a 7 × 7 mm2sized substrate by combining photolithography and radio frequency
sputtering. The gap distance and the thickness of Pt electrodes were 40
μm and 400 nm, respectively. A SU-8 photoresist layer with 45 μm
thickness was then coated on the electrode-patterned substrate by spincoating, and circular holes were patterned on the SU-8 layer by

Surface morphology of the PEG−CB nanocomposite
sensor; cycle dependence of successive nonanal sensing
responses; nonanal sensing response with aging test in anoxygen atmosphere; variation of base resistance during
aging tests; FTIR spectra for PEG4000 and CB with aging
test; methanol sensing response with aging test; nonanal
sensing response with varying CB/PEG ratios; nonanal
sensing response with varying AA concentrations; acetone
sensing response with aging test and AA addition; FTIR
spectra of AA; XRD patters of the PEG−CB nanocomposite, PEG4000 and CB with aging test and AA
addition; and morphological variation of the PEG−CB
nanocomposite sensor with aging test and AA addition(PDF)

AUTHOR INFORMATION

Corresponding Authors

Kazuki Nagashima − Department of Applied Chemistry,
Graduate School of Engineering, The University of Tokyo,
Tokyo 113-8656, Japan; PRESTO, Japan Science andTechnology Agency, Kawaguchi-shi, Saitama 332-0012,
Japan; orcid.org/0000-0003-0180-816X; Email: kazun@g.ecc.u-tokyo.ac.jp
Takeshi Yanagida − Department of Applied Chemistry,
Graduate School of Engineering, The University of Tokyo,
Tokyo 113-8656, Japan; Interdisciplinary Graduate School ofEngineering Sciences, Kyushu University, Kasuga, Fukuoka
816-8580, Japan; Institute for Materials Chemistry andEngineering, Kyushu University, Fukuoka 816-8580, Japan;

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ArticleACKNOWLEDGMENTS
This work was supported by the Cooperative Research Programof “Network Joint Research Center for Materials and Devices,”
KAKENHI (Grant Numbers JP18H01831, JP18KK0112,
JP18H05243, and JP20H02208) and CAS-JSPS Joint Research
Projects (Grant No. JPJSBP120187207). K.N. and T.H. were
supported by the MEXT Project of “Integrated ResearchConsortium on Chemical Sciences.” T.Y. was supported by
CREST (Grant No. JPMJCR19I2) and Mirai R&D of Japan
Science and Technology Corporation (J.S.T.). K.N. was
supported by JST PRESTO (Grant No. JPMJPR19J7). K.N.
acknowledges the JACI Prize for Encouraging Young
Researcher. This work was partly performed under the
Cooperative Research Program of “Dynamic Alliance forOpen Innovation Bridging Human, Environment, and Materials” and “CORE Lab of Network Joint Research Center for
Materials and Devices.”orcid.org/0000-0003-4837-5701; Email: yanagida@g.ecc.u-tokyo.ac.jp
Authors

Wenjun Li − Department of Applied Chemistry, Graduate
School of Engineering, The University of Tokyo, Tokyo 1138656, Japan; Interdisciplinary Graduate School of Engineering
Sciences, Kyushu University, Kasuga, Fukuoka 816-8580,
Japan
Takuro Hosomi − Department of Applied Chemistry, Graduate
School of Engineering, The University of Tokyo, Tokyo 1138656, Japan; PRESTO, Japan Science and Technology Agency,
Kawaguchi-shi, Saitama 332-0012, Japan; orcid.org/
0000-0002-5649-6696
Chen Wang − Interdisciplinary Graduate School of Engineering
Sciences, Kyushu University, Kasuga, Fukuoka 816-8580,
Japan
Yosuke Hanai − Panasonic Corporation, Industrial Solutions
Company, Sensing Solutions Development Center, Kadoma,
Osaka 571-8506, Japan
Atsuo Nakao − Panasonic Corporation, Industrial Solutions
Company, Sensing Solutions Development Center, Kadoma,
Osaka 571-8506, Japan
Atsushi Shunori − Panasonic Corporation, Industrial Solutions
Company, Sensing Solutions Development Center, Kadoma,
Osaka 571-8506, Japan
Jiangyang Liu − Department of Applied Chemistry, Graduate
School of Engineering, The University of Tokyo, Tokyo 1138656, Japan
Guozhu Zhang − Department of Applied Chemistry, Graduate
School of Engineering, The University of Tokyo, Tokyo 1138656, Japan
Tsunaki Takahashi − Department of Applied Chemistry,
Graduate School of Engineering, The University of Tokyo,
Tokyo 113-8656, Japan; PRESTO, Japan Science andTechnology Agency, Kawaguchi-shi, Saitama 332-0012,
Japan; orcid.org/0000-0002-2840-8038
Wataru Tanaka − Department of Applied Chemistry, Graduate
School of Engineering, The University of Tokyo, Tokyo 1138656, Japan
Masaki Kanai − Institute for Materials Chemistry andEngineering, Kyushu University, Fukuoka 816-8580, Japan■

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Author Contributions

Sample preparation and characterization were performed by
W.L., C.W., Y.H., A.N., and A.S. Fabrication and sensing
measurements of chemiresistive sensor devices were conductedby W.L., C.W., Y.H., A.N., A.S., and J.L. FTIR measurements
were performed by W.L. and C.W. The degradation mechanismof the polymer−CB nanocomposite chemiresistive sensor was
discussed by W.L., K.N., T.H., Y.H., G.Z., T.T., W.T., M.K. and
T.Y. K.N., Y.H., and T.Y. designed the experiments. K.N. wrote
this manuscript and W.L., T.H., T.T., T.W., M.K., and T.Y.
contributed to improve the manuscript. All authors contributed
to the manuscript preparation and approved the ﬁnal version of
the manuscript.
Notes

The authors declare no competing ﬁnancial interest.
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