Physical a High-Sensitivity Graphene Ammonia Sensor Via

Home , Graphene

Sensors and Actuators A 318 (2021) 112434

Contents lists available at ScienceDirect

Sensors and Actuators A: Physical

journal homepage: www.elsevier.com/locate/sna

A high-sensitivity graphene ammonia sensor via aerosol jet printing

a,b a,b a,b,∗ c a,b

Yuchao Zhu , Lingke Yu , Dezhi Wu , Wenlong Lv , Lingyun Wang

School of Aerospace Engineering, Xiamen University, Xiamen, 361005, China

Shenzhen Research Institute of Xiamen University, Shenzhen, 518057, China

Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen, 361005, China

a r t i c l e i n f o a b s t r a c t

Article history: High-sensitivity ammonia gas sensors are paramount to many ﬁelds in our industries and lives. Due

Received 2 February 2020

to its complicated fabrication processes, large size and long recovery time of most existing ammonia

Received in revised form

gas sensors, we present a micron-scale graphene-based ammonia gas sensor using aerosol-jet printing

19 September 2020

technology. The graphene sensor exhibited high response sensitivity (∼4.64 % for 4.35 ppm NH3 and

Accepted 8 November 2020

∼52.01 % for 97.19 ppm NH3, respectively), short adsorption / desorption time ranging from 50 s to 150

Available online 4 December 2020

s, good reversibility and repeatability. Further employment of micro-heater close to the sensing line

reduced desorption time more than ∼14.3 % when 10 V being applied onto the heater. Such design of the

Keywords:

Graphene ammonia gas sensor by aerosol-jet printing can give an insight for graphene-based ammonia gas sensors,

which may pave a way for the convenient integration with other sensors in portable instruments for coal

Ammonia gas sensors

Aerosol jet printing miners and pathﬁnders etc.

1. Introduction hybrid composite materials (graphene/PANI, pf-MWCNT/PANI,

PANI/TiO2, RGO/PANI, graphene-PEDOT/PSS, PEDOT/PSS-SWCNTs)

Ammonia gas, a strong irritant, colorless and ﬂammable gas, can [18–23], and conducting polymers (polyaniline (PANI), poly

be found in various applications, including mines, caves, chemical (3,4-ethylenedioxythiophene)/ poly (styrenesulfonate) (PEDOT-

manufacturing and nitrogenous fertilizers [1,2]. However, it could PSS), poly (maminoben-zene sulfonic acid) (PABS), poly(3-

not only easily corrode the upper respiratory tract of human beings hexylthiophene)) [24–30] in many literatures. Among them, carbon

or animals but also set off chemical reaction react with other air materials have been proved to be one of the most promising candi-

pollutants (NOx or SOx) to form particulate matter less than 2.5 ␮m dates to sense ammonia gas due to its high speciﬁc surface area and

to cause severe diseases [3]. Therefore, the permitted maximum the sensitivity of electrons inside transferring inside are very sen-

concentration of ammonia ca. 20 ppm in the workplace [4] and a sitive to the ammonia molecules adsorbed on the surface [31–33].

short-term (15 min) exposure limit of 35 ppm NH3 vapor in ambient Zhang et al. demonstrated a ﬂexible wireless sensor using RGO dec-

conditions has been recommended by the US Occupational Safety orated with Ag-NPs as the gas-sensitive material that can monitor

and Health Administration (OSHA) [5]. So it is of great signiﬁcance NH3 gas at a low concentration about 5 ppm and had a fast response

to design and fabricate a high-sensitivity ammonia sensor. and recovery time (7.5 s and 20 s, respectively) [34]. Graphene-

In the past few decades, electrically based ammonia sen- based device functionalized with Au-NPs could reach the maximum

sor is a preferred selection in which the signal could be sensitivity (∼8 %) for 58 ppm of NH3 [35]. The reduced graphene

conveniently detected with less transferring processes, com- oxide (RGO)–polyaniline (PANI) hybrids ammonia (NH3) gas sensor

paring with optical and mass sensitive ammonia sensors [6,7]. presented by Huang et al. exhibited much better response (25.1 %

Nowadays, numerous materials have been used in NH3 sen- and 59.2 % of resistance change with the concentration of NH3 gas

sors, including carbon nanomaterials (carbon nanotubes (CNT), at 5 and 50 ppm, respectively) [36]. The prepared composite com-

graphene, reduced graphene oxide (RGO)) [8–13], metal oxide bined effect of rGO/CNTs/ZnO showed good response to ammonia

(In2O3, SnO2, ZnO, CuO, Fe2O3, V2O5, WO3, CeO2) [14–17], vapor at room temperature with fast response and recovery time

(55 s and 116 s towards 10 ppm concentration, respectively) [37].

Graphene owns two-dimensional honeycomb structure to allow

a full exposure of its atoms for the better adsorption of gas

∗

Corresponding author at: School of Aerospace Engineering, Xiamen University, molecules, thus maximizing the sensor’s surface area to volume and

Xiamen, 361005, China. increasing its sensitivity to gas molecules. Moreover, it has intrinsi-

E-mail address: [email protected] (D. Wu).

https://doi.org/10.1016/j.sna.2020.112434

Y. Zhu, L. Yu, D. Wu et al. Sensors and Actuators A 318 (2021) 112434

Fig. 1. Schematic diagram of aerosol-jet printing system.

Fig. 2. Schematic illustration of the test system of ammonia gas sensor.

Table 1

cally low electrical noise owing to its crystal lattice, which tends to

Recommended printing parameters of the aerosol-jet system on Si/ SiO2 wafers for

screen charge ﬂuctuations more effectively than one-dimensional

ammonia gas test.

carbon nanomaterials such as carbon nanotubes [38,39]. Besides

Material Graphene

the combination of various materials, many methods including

Sheath Gas Flow Rate (ccm) 65 CVD, laser direct writing, electrospinning, printing, coating etc.

Atomizer Flow Rate (ccm) 11 have been proposed to fabricate sensors. In the future, laser 3D

Ultrasonic Atomizer Power (V) 45

printing could be another way to fabricate the high sensitivity sen-

Nozzle diameter (␮m) 250

sor [40]. A scaffold of porous nickel foam as a template was used to

Deposition velocity (mm/s) 0.5

◦

fabricate graphene foam network to enhance its gas detection per-

Substrate temperature ( C) 80

formance (∼30 % resistance change for 1000 ppm NH3 and ∼5% for

20 ppm NH3) compared to that of CVD monolayer graphene [45].

Seekaew et al. presented a simple inkjet-printing of PEDOT:PSS

Y. Zhu, L. Yu, D. Wu et al. Sensors and Actuators A 318 (2021) 112434

Fig. 3. Optical microscopes of the printed graphene lines and its relationship between line width and various printing processing parameters (a)-(b) sheath gas ﬂow, (c)-(d)

stage moving speed, (e)-(f) number of the printing passes.

composite ﬁlm to fabricate a gas sensor with sensitivity of 0.06 performance including sensitivity, response/recovery time and

−1

% ppm in a wide scope of NH3 concentrations from 5 to 1000 repeatability were evaluated with/without heating under differ-

ppm [22]. Additive manufacturing technologies such as u-contact ent concentrations, and experiments results showed that high

printing, electrohydrodynamic direct writing etc. are regarded as response magnitude (∼4.64 % for 4.35 ppm and ∼52.01 % for 97.19

simple and promising tools for large-scale roll-to-roll fabrication. ppm NH3 gas, respectively), fast response (response and recovery

Here we introduce a rapid printing technology, aerosol-jet print- time were both 50−150 seconds), good reversibility and repeatabil-

ing, to manufacture a micron-scale sized ammonia gas sensor on ity were ﬁnally obtained. Also heating process with applied voltage

a silicon substrate to exhibit its superb sensing properties. Further of 10 V facilitated reduction of desorption time at least 14.3 %.

employment of additional micro-heater around the periphery of

the sensing unit via aerosol-jet printing gains faster and repro-

2. Experimental

ducible sensing performance.

In this work, the printing process parameters were dis-

A commercial aerosol-jet printing system (Aerosol Jet 300, M3D,

cussed ﬁrstly to fabricate uniform and stable sensors. Then their

Optomec, USA) shown in Fig. 1, including three major parts such as

Y. Zhu, L. Yu, D. Wu et al. Sensors and Actuators A 318 (2021) 112434

an aerosol actuator, a deposition nozzle and a moving stage, was

used to fabricate sensor samples, which has been also reported

in details in other literatures [46–48]. Compared to the ink jet

systems, aerosol jet printers have clog resistant nozzle, a contin-

uous stream of high-density microdroplets, the ability to deposit a

wide range of viscosity of inks (1–1000 cP for pneumatic atomizer,

1–10 cP for ultrasonic atomizer), and more tightly focused patterns.

Graphene aqueous solution (conc: 1 mg/mL, MW: 12.01 g/mol,

Sigma-Aldrich) in the atomizing tank was atomized to become

aerosol, and then delivered to the deposition nozzle through a plas-

tic tube and ﬁnally transferred onto the sensor substrates on a

heating plate attached to the moving stage with the help of sheath

gas. During the study of the effects of the processing parameters on

width and resistance, ﬁve samples were fabricated under the same

condition. The recommended printing parameters have been listed

in Table 1.

Fig. 2 illustrates the ammonia gas-sensing measurement setup,

which includes two bottles, two injectors (one was ﬁlled with air,

the other was ﬁlled with ammonia water), an air pump, a switch

valve, a computer, a digital multimeter and a power source. Bottle

I was used for the volatilization of ammonia and Bottle II was for

gas detection.

Fig. 2 also shows a sensor with micro-heater and a sensor with-

out a heater for comparison was also built as illustrated in Fig.

S1. They were both deposited by aerosol-jet printing system on

the Si/SiO2 substrates, involving nano-silver wires. When 20 mL

ammonia water was injected into the Bottle I, ammonia gas quickly

evaporated to ﬁll the bottle. Then the valve was switched on and

different volumes (∼2−60 mL) of the air were injected into the

Bottle II for test and the valve was switched off immediately. After

ammonia gas molecules and sensing unit were in full contact for

a moment, the vent was opened and the air pump was simultane-

ously operated at full load to quickly pump the ammonia gas out

of the bottle. The same method was used to evaluate the selectiv-

ity of the sensor through the comparison to other gas species such

as ethanol gas and H2 gas. All the gas sensing experiments were

performed at room temperature. In order to explore the inﬂuence

of humidity, graphene interconnects were put into a constant tem-

perature and humidity chamber (ITH-150-70-CP-AR, Giant Force,

China) for test.

2.1. Experiment of sensor with heater

To test the performance of the sensor with a micro-heater, its

resistance was maintained stable for a few seconds (15 s or 45 s)

at ﬁrst and different volumes (∼2 mL, ∼25 mL and ∼35 mL) of

Fig. 4. The resistance of graphene lines verse different parameters: (a) number of ammonia gas were injected to Bottle II. The valve was then imme-

printing passes, (b) atomizer gas ﬂux, (c) ﬂux of the sheath gas.

diately switched off. After the resistance value steadily increased

in one minute, the vent was unblocked and the air pump was syn-

chronously operated at half load in order to demonstrate an obvious

comparison of desorption process. At the same time, a series of

voltages ranging from 0 to 10 V were applied to the heater. As the

Fig. 5. Schematic diagram of the ammonia gas sensor.

Y. Zhu, L. Yu, D. Wu et al. Sensors and Actuators A 318 (2021) 112434

Table 2

The intensity ratios and FWHM determined from the spectra.

Parameters coating printing

IG /IG 0.2611 0.2220

ID/IG 0.1949 0.0902

FWHM, IG 25 27

FWHM, IG 82 89

3. Results and discussion

3.1. The effect of main printing parameters on line width and its

conductivity

Fig. 3(a) shows that the graphene lines deposited with 65 ccm

sheath gas ﬂux are more uniform than that with 50–60 ccm. When

the ﬂux of sheath gas gradually increased from 55 ccm to 65 ccm

with increment of 5 ccm, the average line width of the graphene

lines dropped off from 66.4 ␮m to 48.0 ␮m as shown in Fig. 3(b).

As the moving speed of the stage increased to more than 1 mm/s,

the tracks of the graphene lines became more blurred (Fig. 3(c))

and the line width decreased from 52.4 ␮m to 39.6 ␮m (Fig. 3(d)).

On the contrary, with the growth of printing passes (Fig. 3(e) and

(f)), the lines became apparently wider and the maximum line-

width was ca. 48 ␮m at eight printing passes. Thus, the parameters

of 65 ccm sheath gas and 0.5 mm/s stage moving speed were

selected to obtain a reliable and repeatable graphene sensing unit

and the graphene lines need to be further explored by appropriately

increasing the number of printing passes.

The effects of the printing parameters on the resistance were

also discussed. As depicted in Fig. 4(a), when the printing passes

was increased to more than 40, the graphene composite line began

to be conductive. Its average resistance decreased from 2.38 M to

Fig. 6. Raman and SEM images of graphene after (a) coating and (b) printing on Si/

1.02 M as the printing passes increased from 40 to 80 due to the

SiO2 wafers.

accumulated graphene pieces. It could be seen that the resistance

gradually became stable by increasing printing passes to more than

60. So it could be concluded that the resistance decreased with

increasing the passes. Fig. 4(b) illustrated that when the atomizer

gas ﬂux increased from 11 ccm to 13 ccm, its average resistance

reduced from 1.72 M to 0.24 M .

During the experiment, the heating of the substrate could pro-

mote the evaporation speed of solvent, thereby the graphene sheets

were more closely stacked after printing, leading to more conduc-

tive channels for electrons to transport. From Fig. S2, we could see

that when the atomizer gas ﬂux was set to be 11 ccm, heating pro-

cess helped to reduce the resistance of the graphene lines by at

least 40 %. As the atomizer gas ﬂux was gradually increased to 13

ccm, the resistances were reduced by about 60 %. When the number

of printing passes reached 80, the resistance could reach 45.2 k .

The function of sheath gas was to constrain the atomizer gas. So as

the sheath gas ﬂux grew up, the ﬂux of the atomizer gas indirectly

decreased, and the average resistance rose from 0.36 M to 0.77

Fig. 7. Response characteristics of graphene sensors with different printing passes

M as depicted in Fig. 4(c).

(40, 60 and 80, respectively) for ammonia gas sensing.

3.2. The sensing principles and morphologies of the sensing

resistance went back to its initial state, the air pump was ceased element

and vent was plugged promptly.

The samples were characterized by Scanning Electron

The principles of gas molecular adsorption on the graphene sur-

Microscopy (Su-70 thermal ﬁeld emission scanning electron

face have been discussed in previous studies and NH3 molecules act

microscope, Hitachi, Japan) and Raman spectroscopy (IDSpec

as donors which are physically adsorbed on the pristine graphene

ARCTIC, Zolix, China). The concentrations of gas in Bottle II were

[49,50]. As illustrated in Fig. 5, the printed graphene sensing ele-

checked by a commercial gas sensor (MQ137, Winsen Electronic

ment spanned the two silver electrodes. The graphene micron-scale

Technology CO., LTD, China). The resistance values were measured

pieces were stacked irregularly, increasing surface area for molec-

by a digital multimeter (Agilent 34410A) and transmitted to a

ular adsorption of the ammonia gas.

computer for recording. An adjustable DC power (PS-1502DD,

The Raman and morphologies of the graphene on Si/SiO2 wafers

YIHUA) supply was used to offer power to micro-heater.

after coating and printing were exhibited in Fig. 6(a) and (b). Both

Y. Zhu, L. Yu, D. Wu et al. Sensors and Actuators A 318 (2021) 112434

Fig. 8. (a) Dynamic and quantitative responses of our sensor to NH3 with different concentrations. (b) Repeatable responses of our sensor to 23.98-97.19 ppm NH3. (c)

Response and recovery time of the ammonica gas sensor under different concentrations. (d) Selectivity of the sensor to several possible interfering gases such as ethanol, H2

and humidity.

spectra were the average values of ﬁve sample points, including adsorption process. As the variation of resistance declined from

−1

Raman peaks corresponding to the D band (1358 cm ), G band the peak to the initial value, desorption of ammonia gas molecules

−1 −1

(1585 cm ), and G band (2703 cm ). The appearance of a single absorbed on the surface of graphene was ﬁnished. It can be seen that

band, the G band, was the evidence of the presence of graphene both the adsorption and desorption process of the sensor printed in

[51–55]. Table 2 listed the intensity ratios and FWHM determined 80 passes were reliable and showed splendid response and recov-

from the spectra in Fig. 6. The intensity ratio of D band relative to G ery, which could be further explored.

band and G band relative to G band both decreased for the printed In a certain concentration range (4.35−97.19 ppm), the

graphene. The presence of the strong G band and thin G band con- graphene sensor has better response characteristics to ammonia

ﬁrmed that it was graphene with multilayer. The amplitude of D gas. With the increasing of gas concentration, the response ampli-

band and G band both declined after the graphene pieces were tude of the sensor rose from ∼4.64 % to ∼52.01 %. The graphene

deposited on the Si/ SiO2 substrates. This shifting trend indicated sensor performs three cycles of adsorption and desorption at the

the number increasement of graphene’s layer [56–60]. same concentration (Figs. 8(b) and S3). As the concentration was

promoted gradually (from 23.98 ppm to 97.19 ppm), the sen-

3.3. Performance of the graphene-based gas sensor sor exhibited a good repeatability in adsorption, desorption and

response amplitude. After the response and recovery time of dif-

The relative variation of the sensor resistance, deﬁned as sensor ferent concentrations were measured, the experimental data were

response (S), is given by plotted (Figs. 8(c) and S4). The time taken by the sensor to reach 90

% of the total resistance change is deﬁned as the response time in

Rg − Rref R

S = × 100% = × 100% (1) the case of adsorption and the recovery time is in the case of des-

� Rref � R

orption. It can be seen that the response and recovery time, with the

Here, Rref and Rg are the resistances without and with the target concentration growing up, both gradually increased (from 51.2 s to

gas, respectively. Through the above analysis of the relationship 141.6 s, 54.85 s to 147.25 s, respectively). Selectivity experiments

between the processing parameters and the line-width and resis- were also performed and the observed results conﬁrmed that the

tance, the graphene lines for ammonia gas sensing were ﬁnally sensor was highly selective towards NH3 compared to ethanol and

obtained. As described in Fig. 7, when the printing passes varied H2 as shown in Figs. 8(d) and S5. The data also indicated that, as the

from 40, 60 to 80, the response amplitude of the sensor under 23.98 humidity was controlled at 43 RH%-53 RH%, the response to these

ppm increased sharply from ∼2.69 %, 10 % to ∼15.42 %, respec- possible interfering gases was relatively small and negligible.

tively. Meanwhile, sensing elements displayed basically the same A preliminary experiment was performed to verify that the

duration of adsorption and desorption process when approaching graphene line could be used as a micro-heater giving a 3D heat-

to NH3 gas. The ascending curve of the resistance change, which ing. The line was connected to the silver electrodes at both ends

∼

increases rapidly and then reaches the maximum value, is called (Fig. 9(a) and (b)) with gap distance 40 ␮m. A voltage of 10 V

Y. Zhu, L. Yu, D. Wu et al. Sensors and Actuators A 318 (2021) 112434

Fig. 9. (a, b) Optical image of the graphene line sample (a, b) and its thermal response behavior under 10 V applied voltage (c) 0 s, (d) 10 s, (e) 20 s and (f) 30 s.

was applied to the graphene line with resistance of 33.0 k . After tude (∼4.64 % for 4.35 ppm and ∼52.01 % for 97.19 ppm NH3)

◦

heating for 10 s, the temperature was raised by 57.4 C and ﬁnally than that of previously reported. Furthermore, if we introduced a

◦

maintained at about 67 C (Fig. 9(c–f)). It proved that the graphene 3D micro-heater, desorption time of our graphene sensor could be

line had good heating performance to accelerate desorption of NH3. reduced at least ∼14.3 % when the NH3 gas concentration is more

As shown in Fig. 10(a) and (b), as the heating voltage applied onto than 4.35 ppm and the supply voltage of micro-heater is 10 V.

the graphene micro-heater with 34.2 k increased to 5 V and 10

∼ ∼

V, desorption time reduced by 6.8 % and 14.3 %, respectively. 4. Conclusions

As illustrated in Fig. 10(c) and (d), desorption time was reduced

∼ ∼

by 18.6 % and 39.6 %, respectively, when ammonia gas con- An ammonia gas sensor fabricated by aerosol-jet printing of

centrations were further increased to 35.55 ppm and 64.66 ppm. graphene has been successfully proposed to improve its perfor-

Therefore, the micro-heater could improve the desorption speed, mance via the combination of both 3D structure formation and

especially for NH3 with higher concentrations. the micro-heater, where aerosol-jet printing facilitated increas-

The detection range of NH3 for graphene gas sensors based on ing surface area of the sensing element to boost its sensing ability

aerosol-jet printing was 4.35 ppm and 97.19 ppm. Table 3 shows of graphene networks. It can achieve high response magnitude

the recent achievements of the nanoscale materials sensors with (∼4.64 % for 4.35 ppm and ∼52 % for 97.19 ppm, respectively), fast

or without other hybrids towards NH3. The advantages of our 3D response (both 50−150 seconds for response and recovery time),

deposition graphene sensor not only involve using rapid aerosol-jet good reversibility and repeatability. The adoption of the micro-

printing technology to fabricate micron-scale size but also contain heater has been proved to decrease the desorption time. Thus, the

relatively higher NH3-sensing performances in response magni- ammonia gas sensor fabricated by aerosol-jet printing might be

Y. Zhu, L. Yu, D. Wu et al. Sensors and Actuators A 318 (2021) 112434

Fig. 10. (a) An optical image of the ammonia gas sensor with a micro-heater and normalized responses to concentration of (b) ∼4.35 ppm, (c) 35.55 ppm and (d) 64.66 ppm.

Table 3

Response (S), response time (T1), recovery time (T2), studied detection range (DR), materials (M) and measured temperature (Tm) of the various NH3 gas sensors.

◦

Authors S (%) T1 (s) T2 (s) DR (ppm) M Tm ( C)

Zhu et al. (our 4.64 (4.35 ppm), 50−150 50−150 4.35−97.19 3D Deposition 30 ± 1

work) 16.53 (25.19 ppm), Graphene

27.61 (49.24 ppm),

52.01 (97.19 ppm)

Hu et al. [12] 2.4 (1 ppb), 23 (50 60 76 0.001−50 RGO 25

ppm)

Wu et al. [18] 3.65 (20 ppm), 50 23 1−6400 Graphene/PANI 25

11.33 (100 ppm)

Yoo et al. [19] 0.015 (20 ppm), 100 700 0−100 pf-MWCNT/PANI 25

0.075 (100 ppm)

Seekaew et al. [22] 0.9 (5 ppm), 7 180 – 5−1000 Graphene/PEDOT- 25

(1000 ppm) PSS

Gautam et al. [35] 3 (15 ppm), 8 (58 <6.89 (min) <28.61 (min) 15−58 AuNPs /graphene 25

ppm)

Huang et al. [36] 25.1 (5 ppm), 59.2 192 >240 20−50 RGO–PANI hybrids 25

(50 ppm)

Wang et al. [41] 4.2 (5 ppb), 22 (100 <750 <310 0.005−100 Py-rGO 25

ppm)

Cui et al. [42] 7.7 (10 ppm), 17.4 6 402 2500−10000 Silver 25

(10,000 ppm) nanoparticle-

decorated RGO

hybrids

Jian et al. [43] 0.1 (2 ppm), 33 12 18 2−300 SWCNTs/PEDOT- 25

(300 ppm) PSS

Lin et al. [44] 5.9 (10 ppm), 15.9 < 60 < 60 10−50 SnO2/graphene 15

(50 ppm) (GN)

Yavari et al. [45]5(20 ppm), 30 800 800 20−1000 Graphene foam 25

(1000 ppm) network

Y. Zhu, L. Yu, D. Wu et al. Sensors and Actuators A 318 (2021) 112434

a preferred candidate which could be miniaturized and used in [17] Y. Shimizu, T. Okamoto, Y. Takao, et al., Desorption behavior of ammonia from

TiO2-based specimens—ammonia sensing mechanism of double-layer

portable instruments for coal miners and pathﬁnders in future.

sensors with TiO2-based catalyst layers, J. Mol. Catal. A Chem. 155 (1–2)

(2000) 183–191.

CRediT authorship contribution statement [18] Zuquan Wu, et al., Enhanced sensitivity of ammonia sensor using

graphene/polyaniline nanocomposite, Sens. Actuators B Chem. 178 (2013)

485–493.

Yuchao Zhu: Methodology, Visualization, Formal analysis,

[19] K.P. Yoo, K.H. Kwon, N.K. Min, M.J. Lee, C.J. Lee, Effects of O2 plasma treatment

Investigation, Writing - original draft. Lingke Yu: Validation, on NH3 sensing characteristics of multiwall carbon nanotube/polyaniline

composite ﬁlms, Sens. Actuators B Chem. 143 (2009) 333–340.

Formal analysis, Investigation. Dezhi Wu: Conceptualization,

[20] H. Tai, Y. Jiang, G. Xie, J. Yu, X. Chen, Fabrication and gas sensitivity of

Methodology, Writing - review & editing, Project administration,

polyaniline–titanium dioxide nanocomposite thin ﬁlm, Sens. Actuators B

Supervision. Wenlong Lv: Data curation, Investigation. Lingyun Chem. 125 (2007) 644–650.

[21] Xiaolu Huang, et al., Reduced graphene oxide–polyaniline hybrid:

Wang: Methodology, Writing - review & editing.

preparation, characterization and its applications for ammonia gas sensing, J.

Mater. Chem. 22.42 (2012) 22488–22495.

Declaration of Competing Interest [22] Y. Seekaew, S. Lokavee, D. Phokharatkul, A. Wisitsoraat, T. Kerdcharoen, C.

Wongchoosuk, Low-cost and ﬂexible printed graphene–PEDOT: PSS gas

sensor for ammonia detection, Org. Electron. 15 (2014) 2971–2981.

The authors declare that they have no known competing ﬁnan-

[23] S. Abdulla, T.L. Mathew, B. Pullithadathil, Highly sensitive, room temperature

cial interests or personal relationships that could have appeared to gas sensor based on polyaniline-multiwalled carbon nanotubes

(PANI/MWCNTs) nanocomposite for trace-level Ammonia detection, Sens.

inﬂuence the work reported in this paper.

Actuators B Chem. 221 (2015) 1523–1534.

[24] H. Kebiche, D. Debarnot, A. Merzouki, F. Poncin-Epaillard, N. Haddaoui,

Acknowledgements Relationship between ammonia sensing properties of polyaniline

nanostructures and their deposition and synthesis methods, Anal. Chim. Acta

737 (2012) 64–71.

This work was in part supported by National Natural Science

[25] E. Dickey, O. Varghese, K. Ong, D. Gong, M. Paulose, C. Grimes, Room

Foundation of China (52075464), Science and Technology Pro- temperature ammonia and humidity sensing using highly ordered

nanoporous alumina ﬁlms, Sensors 2 (2002) 91–110.

gram of Shenzhen City (JCYJ20180306172700388) and Domain

th [26] J. Huang, J. Wang, C. Gu, K. Yu, F. Meng, J. Liu, A novel highly sensitive gas

Foundation of Equipment Advance Research of 13 Five-year Plan

ionization sensor for ammonia detection, Sens. Actuators A Phys. 150 (2009)

(JZX7Y20190243000801). 218–223.

[27] S. Koul, R. Chandra, S. Dhawan, Conducting polyaniline composite: a reusable

sensor material for aqueous ammonia, Sens. Actuators B Chem. 75 (2001)

Appendix A. Supplementary data 151–159.

[28] G. Zhu, Q. Zhang, G. Xie, Y. Su, K. Zhao, H. Du, Y. Jiang, Gas sensors based on

polyaniline/zinc oxide hybrid ﬁlm for ammonia detection at room

Supplementary material related to this article can be found,

temperature, Chem. Phys. Lett. 665 (2016) 147–152.

in the online version, at doi:https://doi.org/10.1016/j.sna.2020.

[29] L. Huang, P. Jiang, D. Wang, Y. Luo, M. Li, H. Lee, R.A. Gerhardt, A novel

112434. paper-based ﬂexible ammonia gas sensor via silver and SWNT-PABS inkjet

printing, Sens. Actuators B Chem. 197 (2014) 308–313.

[30] G.D. Khuspe, S.T. Navale, M.A. Chougule, V.B. Patil, Ammonia gas sensing

References properties of CSA doped PANi-SnO2 nanohybrid thin ﬁlms, Synth. Met.

185–186 (2013) 1–8.

[1] M. Pushkarsky, M. Webber, C.K.N. Patel, Ultra-sensitive ambient ammonia [31] G. Lu, L.E. Ocola, J. Chen, Reduced graphene oxide for room temperature gas

detection using CO2-laser-based photoacoustic spectroscopy, Appl. Phys. B 77 sensors, Nanotechnol. 20 (2009), 445502.

(2003) 381–385. [32] F. Schedin, A.K. GEIM, S.V. Morozov, E.W. Hill, P. Blake, M.I. Katsnelson, K.S.

[2] K. Xu, L. Zhu, A. Zhang, G. Jiang, H. Tang, A peculiar cyclic voltammetric Novoselov, Detection of individual gas mol-ecules adsorbed on graphene, Nat.

behavior of polyaniline in acetonitrile and its application in ammonia vapor Mater. 6 (2007) 652–655.

sensor, J. Electroanal. Chem. 608 (2007) 141–147. [33] J.T. Robinson, F.K. Perkins, E.S. Snow, Z.Q. Wei, P.E. Sheehan, Reduced

[3] E. Stokstad, Air pollution. Ammonia pollution from farming may exact hefty graphene oxide molecular sensors, Nano Lett. 8 (2008) 3137–3140.

health costs, Science (80-) 343 (6168) (2014) 238. [34] L. Zhang, Q. Tan, H. Kou, et al., Highly sensitive NH3 wireless sensor based on

[4] Björn Timmer, Wouter Olthuis, Albert Van Den Berg, Ammonia sensors and Ag-RGO composite operated at room-temperature, Sci. Rep. 9 (1) (2019) 1–10.

their applications—a review, Sens. Actuators B Chem. 107.2 (2005) 666–677. [35] M. Gautam, A.H. Jayatissa, Ammonia gas sensing behavior of graphene surface

[5] N.A. Travlou, M. Seredych, E. Rodriguez-Castellon, T.J. Bandosz, Activated decorated with gold nanoparticles, Solid State Electronics 78 (6) (2012)

carbon-based gas sensors: effects of surface features on the sensing 159–165.

mechanism, J. Mater. Chem. A Mater. Energy Sustain. 3 (2015) 3821–3831. [36] X. Huang, N. Hu, R. Gao, et al., Reduced graphene oxide–polyaniline hybrid:

[6] Z. Jin, Y. Su, Y. Duan, Development of a polyaniline-based optical ammonia Preparation, characterization and its applications for ammonia gas sensing, J.

sensor, Sens. Actuators B Chem. 72 (1) (2001) 75–79. Mater. Chem. 22 (42) (2012) 22488–22495.

[7] S. Korposh, R. Selyanchyn, S.W. Lee, Nano-assembled thin ﬁlm gas sensors. IV. [37] M. Morsy, et al., Portable and battery operated ammonia gas sensor based on

Mass-sensitive monitoring of humidity using quartz crystal microbalance CNTs/rGO/ZnO nanocomposite, J. Electron. Mater. 48.11 (2019) 7328–7335.

(QCM) electrodes, Sens. Actuators B Chem. 147 (2) (2010) 599–606. [38] H.Y. Jeong, D.-S. Lee, H.K. Choi, D.-S. Lee, J.-E. Kim, J.Y. Lee, et al., Flexible

[8] Douglas R. Kauffman, Alexander Star, Carbon nanotube gas and vapor sensors, room-temperature NO [sub 2] gas sensors based on carbon

Angew. Chemie Int. Ed. 47.35 (2008) 6550–6570. nanotubes/reduced graphene hybrid ﬁlms, Appl. Phys. Lett. 96 (2010), 213105.

[9] T. Zhang, S. Mubeen, N.V. Myung, M.A. Deshusses, Recent progress in carbon [39] X. Huang, N. Hu, L. Zhang, L. Wei, H. Wei, Y. Zhang, The NH 3 sensing

nanotube-based gas sensors, Nanotechnology 19 (2008), 332001-1–14. properties of gas sensors based on aniline reduced graphene oxide, Synth.

[10] P. Bondavalli, P. Legagneux, D. Pribat, Carbon nanotubes based transistors as Met. 185–186 (2013) 25–30.

gas sensors: state of the art and critical review, Sens. Actuat. B Chem. 140 [40] B.H. Lu, H.B. Lan, H.Z. Liu, Additive manufacturing frontier: 3D printing

(2009) 304–318. electronics, Opto-electronic Adv. 1 (2018), 170004.

[11] Dezhi Wu, et al., A simple graphene NH3 gas sensor via laser direct writing, [41] Y. Wang, L. Zhang, N. Hu, et al., Ammonia gas sensors based on chemically

Sensors 18.12 (2018) 4405. reduced graphene oxide sheets self-assembled on Au electrodes, Nanoscale

[12] Nantao Hu, et al., Ultrafast and sensitive room temperature NH3 gas sensors Res. Lett. 9 (1) (2014) 1–12.

based on chemically reduced graphene oxide, Nanotechnology 25.2 (2013), [42] S. Cui, S. Mao, Z. Wen, et al., Controllable synthesis of silver

025502. nanoparticle-decorated reduced graphene oxide hybrids for ammonia

[13] G.Y. Cao, X.S. Gan, H. Lin, B.H. Jia, An accurate design of graphene oxide detection, Analyst 138 (10) (2013) 2877–2882.

ultrathin ﬂat lens based on Rayleigh-Sommerfeld theory, Opto-Electron. Adv. [43] J. Jian, X. Guo, L. Lin, Q. Cai, J. Cheng, J. Li, Gas-sensing characteristics of

1 (2018), 180012. dielectrophoretically assembled composite ﬁlm of oxygen plasma-treated

[14] P. Guo, H. Pan, Selectivity of Ti-doped In2O3 ceramics as an ammonia sensor, SWCNTs and PEDOT/PSS polymer, Sens. Actuators B Chem. 178 (2013)

Sens. Actuators B Chem. 114 (2006) 762–767. 279–288.

[15] N.V. Hieu, D.T.T. Le, N.D. Khoang, N.V. Quy, N.D. Hoa, P.D. Tam, A.T. Le, T. [44] Q. Lin, Y. Li, M. Yang, Tin oxide/graphene composite fabricated via a

Trung, A comparative study on the NH3 gas-sensing properties of ZnO, SnO2, hydrothermal method for gas sensors working at room temperature, Sens.

and WO3 nanowires, Int. J. Nanotechnol. 8 (2011) 174–187. Actuators B Chem. 173 (10) (2012) 139–147.

[16] P. Ivanov, J. Hubalek, K. Malysz, J. Prásek,ˇ X. Vilanova, E. Llobet, X. Correig, A [45] F. Yavari, Z. Chen, A.V. Thomas, et al., High sensitivity gas detection using a

route toward more selective and less humidity sensitive screen-printed SnO macroscopic three-dimensional, graphene foam network, Sci. Rep. 1 (7374)

and WO gas sensitive layers, Sens. Actuators B Chem. 100 (2004) 221–227. (2011) 166.

Y. Zhu, L. Yu, D. Wu et al. Sensors and Actuators A 318 (2021) 112434

[46] Bruce E. Kahn, The M3D aerosol jet system, an alternative to inkjet printing

Lingke Yu received his B.S. from Zhengzhou Univer-

for printed electronics, Org. Print. Electr. 1.1 (2007) 14–17.

sity and now is a Ph.D. student at Xiamen University.

[47] E. Jabari, S. Tong, A. Azhari, Non-planar interconnects in double-sided ﬂexible

His research interests include near-ﬁeld direct writing,

Cu-PET substrates using a laser-assisted maskless microdeposition process:

electrospun nanoﬁber membrane, MEMS, piezo-electric

3D ﬁnite element modeling and experimental analysis, Opt. Lasers Eng.

properties of materials.

(2014) 117–127, 54pp.

[48] E. Jabari, E. Toyserkani, Micro-scale aerosol-jet printing of graphene

interconnects, Carbon 91 (2015) 321–329.

[49] O. Leenaerts, B. Partoens, F.M. Peeters, Adsorption of H2O, NH3, CO, NO2, and

NO on graphene: A ﬁrst-principles study, Phys. Rev. B 77 (12) (2008), 125416.

[50] B. Huang, Z. Li, Z. Liu, et al., Adsorption of gas molecules on graphene

nanoribbons and its implication for nanoscale molecule sensor, J. Phys. Chem.

C 112 (35) (2008) 13442–13446.

[51] Andre K. Geim, Philip Kim, Carbon wonderland, Sci. Am. 298.4 (2008) 90–97.

Dezhi Wu is a professor of Xiamen University, China.

[52] A.C. Ferrari, J.C. Meyer, V. Scardaci, C. Casiraghi, M. Lazzeri, F. Mauri, et al.,

His research interests include soft robots, electronic skin,

Raman spectrum of graphene and graphene layers, Phys. Rev. Lett. 97 (2006),

187401. micro-nano fabrication technology and equipment, etc.

He has presided over the National Natural Science Foun-

[53] A.N. Sidorov, S. Pabba, K.P. Hewaparakrama, R.W. Cohn, G.U. Sumanasekera,

dation of China, Shenzhen Science and Technology R&D

Side-by-side comparison of Raman spectra of anchored and suspended

Fund Project and so on. Up to now, he has published more

carbon nanomaterials, Nanotechnology 19 (2008), 195708.

than 60 papers in internationally renowned journals such

[54] A. Gupta, G. Chen, P. Joshi, S. Tadigadapa, P.C. Eklund, Raman scattering from

as Nanoscale, Organic Electronics, etc. and has about 20

high-frequency phonons in supported n-graphene layer ﬁlms, Nano Lett. 6

authorized patents.

(2006) 2667–2673.

[55] A.M. Rao, E. Richter, S. Bandow, B. Chase, P.C. Eklund, K.A. Williams, et al.,

Diameter-selective Raman scattering from vibrational modes in carbon

nanotubes, Science 275 (5297) (1997) 187–191.

[56] L.M. Malard, et al., Raman spectroscopy in graphene, Phys. Rep. 473.5-6

(2009) 51–87.

[57] Anton N. Sidorov, et al., A surface-enhanced Raman spectroscopy study of

thin graphene sheets functionalized with gold and silver nanostructures by

seed-mediated growth, Carbon 50.2 (2012) 699–705.

[58] Madhav Gautam, Ahalapitiya H. Jayatissa, Adsorption kinetics of ammonia Wenlong Lv received his B.S. and M.S. from Xiamen Uni-

sensing by graphene ﬁlms decorated with platinum nanoparticles, J. Appl. versity in 2003 and 2006 respectively. He is a senior

Phys. 111.9 (2012), 094317. engineer at Pen-Tung Sah Institute of Micro-Nano Science

[59] Robin John, et al., Single-and few-layer graphene growth on stainless steel and Technology, Xiamen University. His research interests

substrates by direct thermal chemical vapor deposition, Nanotechnology include PECVD, MEMS/NEMS, Raman spectrum.

22.16 (2011), 165701.

[60] Andrea C. Ferrari, et al., Raman spectrum of graphene and graphene layers,

Phys. Rev. Lett. 97.18 (2006), 187401.

Biographies

Lingyun Wang is an associate professor of Xiamen Univer-

Yuchao Zhu received his B.S. from Qingdao University of

sity, China. His research interests include MEMS design,

Technology in 2015 and M.S. from Xiamen University in

packaging integration, polymer nanostructure molding

2019 respectively. Now he is an engineer at Graphene

and its application, piezoelectric injection and its applica-

Industry and Engineering Research Institute, Xiamen

tion in the ﬁeld of ﬂexible electronics, etc. He has presided

University. His research interests include graphene gas

over the National Natural Science Foundation of China,

Sensor, electrospun nanoﬁber membrane, e-skins.

Aeronautical Science Foundation program and so on. Up to

now, he has published more than 80 papers in renowned

journals such as AIP Advances, Sensors, etc. and has about

20 authorized patents.