Ppm NH3 Gas Research Articles

Sensing by Surface Work Function Modulation: High Performance Gas Sensing using van der Waals Stacked Bipolar Junction Transistor

We propose and demonstrate a new principle for sensing. Impact of light, radiation, charge particle and gas molecular etc. can induce the change of the surface work function of a solid. This will result in a profound effect to a device’s output, such as current and voltage. Such an effect is in particular outstanding in a nanodevice using van der Waals stacked two-dimensional (2D) atomic crystals. In this paper, a study of a gas sensing device relying on such a principle is presented. Van der Waals bipolar junction transistors (V2D-BJT) based on vertically stacked MoS2/WSe2/MoS2 and WSe2/MoS2/WSe2 heterostructures are separately fabricated to detect NH3 and NO2 gas. Kelvin probe force microscope measurement shows that the work function change at the overlapped region of MoS2/WSe2/MoS2 heterostructure upon exposure to 50 ppm NH3 gas is 80 meV. In addition, the MoS2/WSe2/MoS2 V2D-BJT manifest superior sensing performances in detecting NH3, while the WSe2/MoS2/WSe2 V2D-BJT exhibited superior NO2 sensing properties in terms of high sensitivity (18), low power dissipation (12 nW), fast response (26 s) and recovery (14 s) time. We demonstrate that the NH3 and NO2 gas can be selectively detected by the V2D-BJT through changing the van der Waals heterostructure stacking sequences.

Preparation and Characterization of Mixed In2O3 –AgxO Nanostructure Thin Films on porous silicon as NH3 High Gas Sensor

Mixed nanostructured thin films composed of In2O3 – AgxO, were synthesized on glass and porous silicon to produce NH3-gas sensor. The films’ structure of the sensor was analyzed by XRD and AFM. The results obtained that polycrystalline nanostructure thin films were prepared. The optical properties indicate that the transmission and the energy gap were decreased with the increase in AgxO ratio. The sensor conductivity changed from n-type for In2O3 up to 10 Vol% AgxO to p-type with mixed oxides. The synthesis gas sensor gives sensitivity toward 40 ppm NH3 gas at different temperatures (50, 100, 150 and 200) ˚C. The maximum sensitivity of mixed films on porous silicon for 15% AgxO ratio is 94.13% with a response time of 11.85 s and a recovery time of 20 s. Porous silicon improves the sensitivity of the prepared sensor by a factor of two with respect to the sensor over the glass. The good sensor properties of In2O3 – AgxO nanostructure mixed oxide at a low temperature indicated as highly efficient NH3 gas sensor.

A flexible polypyrrole/silk-fiber ammonia sensor assisted by silica nanosphere template

Flexible polypyrrole (PPy)@silk-fiber and PPy@sponge sensors were fabricated using the silica nanosphere (SiO2 NS) template via a facile in situ chemical oxidation polymerization method. Exposed to 100 ppm NH3 gas at room temperature in 68 ± 5 % relative humidity (RH), the response of the PPy/NS@silk-fiber sensor (73.25 %) was five-fold higher than that of the PPy/NS@sponge sensor (14.51 %). Meanwhile, the recovery time (69 s) of the PPy/NS@silk-fiber sensor was reduced to two-thirds of that (98 s) of the PPy/NS@sponge sensor for 100 ppm NH3. Additionally, the PPy/NS@silk-fiber sensor exhibited excellent reproducibility, flexibility, selectivity, and long-term stability to NH3 at room temperature. The improved gas-sensing properties can be attributed to the high surface area of the flexible PPy/NS@silk-fiber with relative rough hill-like shapes. This investigation indicated that the PPy/NS@silk-fiber is promising sensing material for developing flexible and wearable NH3 sensors.

Electrodeposition of Polyaniline/Three- Dimensional Reduced Graphene Oxide Hybrid Films for Detection of Ammonia Gas at Room Temperature

Reliable, sensitive and selective ammonia gas sensing at room temperature is very important for monitoring the environment for hazardous pollutants. In this study, ammonia (NH3) gas sensor is proposed based on polyaniline/three-dimensional reduced graphene oxide (PANI/3D-RGO) hybrid samples, which are loaded on glass substrates by electrochemical polymerization method. The PANI/3D-RGO hybrid samples with different weight percentages of 3D-RGO (weight% =0.05, 0.2, 0.5 and 1) are characterized by field emission-scanning electron microscopy, Fourier transform infrared and X-ray diffraction. The specific surface area is analyzed by the Brunauer-Emmett-Teller (BET) equation. The gas-sensing performances of the fabricated sensors indicate that PANI/3D-RGO (0.2wt. %) exhibits the best response for 50 ppm NH3 gas at room temperature, this sensor response to lower concentrations of NH3 (5ppm, 10 ppm and 25 ppm) too. The PANI/3D-RGO (0.2wt. %) hybrid sensor shows represent response values of about 3.72 and acceptable response and recovery times (98 s and 288 s) to 50 ppm NH3 which is about 4.27 fold higher than that of pure PANI in 50 ppm NH3 gas. The excellent sensing performance of the developed gas sensor can be attributed to the synergetic effects of PANI and 3D-RGO, $\pi -\pi $ interaction between the two components, efficient increase in hole-like carriers and substantial increase in active sites.

Structural and optical properties of pure SnO2 and V2O5/SnO2 nanocomposite thin films for gas sensing application

In this study, pure SnO2 and V2O5/SnO2 nanocomposite thin film NH3 sensors with varying V2O5 contents were successfully prepared by spray pyrolysis method. The prepared thin films were characterized by X-ray diffraction, Field emission scanning electron microscopy, Energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, stylus profilometry and Ultra violet–Visible and transmittance spectroscopies. NH3 gas sensing property was also studied. XRD results suggested that all the thin films exhibited a tetragonal rutile crystal structure, while the average crystallite size increases with V2O5 content. FESEM images of the thin films showed the presence of both nano and micro-sized grains in the range ~ 53–194 nm. EDX spectra confirmed the inclusion of V2O5 into the SnO2 matrix. The vibrational bands associated with the thin films were verified from the FTIR spectra. Thickness measurements revealed that the thickness increases with V2O5 content. Change in transparency and bandgap narrowing were also noticed from the transmittance and UV–Vis spectra. NH3 gas sensing measurements suggested that the transient resistance of V2O5/SnO2 thin film was lower than pure SnO2. Further, in the operating temperature 300 °C and 100 ppm NH3 gas, the sensor response of V2O5/ SnO2 thin film (99.13) is found to be higher than pure SnO2 thin film (92.34). Also, the response and recovery times of pure SnO2 thin film (30 and 44 s) are lower than V2O5/SnO2 thin film (39 and 180 s). These results indicate that V2O5/SnO2 thin film could serve as a suitable material for NH3 gas sensing application.

Enhancement and Optimization in Sensing Characteristics of Ammonia Gas Sensor Based on Light Assisted Nanostructured WO3 Thin Film

In this study, hydrothermally synthesized nanostructured WO3 thin film with interdigitated chromium electrode based ammonia gas sensor have been fabricated. The influence of different pH values for WO3 synthesis on structural, morphological, optical, and electrical were examined and reported. Sensor shows excellent response characteristics towards ammonia detection, even at lower gas concentration. The best sensing response have been obtained for WO3 nanostructure thin film at pH 2.25 with 250 °C operating temperature. For 5 PPM and 50 PPM NH3 gas concentration, sensor shows response 5.11 and 12.54 with 23/25 and 13/34 sec response/recovery time. It was also found that, enhancement in sensor response (7.32) with 21/25 sec response/recovery time (5 ppm) has been observed for blue light emission. The sensor has been tested for different period/interval of time and found that the proposed device is sensitive, reliable, inexpensive and eco-friendly for semiconductor applications.

High performance ammonia gas sensor based on GaN honeycomb nanonetwork

In this work, we have demonstrated a FET-like ammonia (NH3) gas sensor fabricated on a unique structure namely GaN honeycomb nanonetwork (GaN-HN) which is in-plane electrically conductive together with large surface-to-volume ratio. Utilizing ohmic contact Ti/Al/Ti/Au multilayers as the source and the drain terminals and Pt nanonetwork layer as the gate terminal, the FET-like NH3 gas sensors were fabricated by a two-mask photolithography process. The fabricated NH3 gas sensors have high selectivity, fast response/recovery, and a wide detection range up to 5000 ppm. The response and recovery time for 5 ppm NH3 gas are 23 s and 101 s at a moderate operating temperature of 120 °C. Interestingly, this sensor is capable to detect trace NH3 gas and the low limit of detection (LOD) is as small as 0.31 ppm. Its absorption activation energy Ea is also investigated by the transient-state study.

The role of rare-earth metal (Y, Ru and Cs)-doped ZnO thin films in NH3 gas sensing performances at room temperature

Pure and rare-earth metal [Yttrium (Y), Ruthenium (Ru) and Caesium (Cs)]-doped ZnO thin films were deposited onto In-doped SnO2 substrates by chemical bath deposition. The present study detailed investigated the effect of rare-earth metal-doped ZnO on NH3 gas sensing. X-ray diffraction analysis indicated that the incorporated rare-earth metal ions substitute Zn sites in the ZnO lattice. Dimension of ZnO films decreased with rare-earth metal doping which detected from surface morphology images. The response of 100 ppb NH3 gas was calculated to be 0.80 (200 °C), 14.00 (90 °C), 17.00 (50 °C), and 10.00 (120 °C) for the pure, Y-, Ru-, and Cs-doped ZnO films, respectively. In addition, the response of 15 ppm NH3 gas at room temperature was calculated to be 0.20, 27.00, 57.00, and 18.00 for undoped Y-, Ru-, and Cs-doped ZnO films, respectively.

Enhancement in NH3 sensing performance of ZnO thin-film via gamma-irradiation

In this work, chemically synthesized Zinc Oxide (ZnO) thin films were exposed to Cobalt-60 (Co-60), 1.25 MeV average energy of gamma source at different doses for possible augmentation in NH3 sensing. The hexagonal crystalline structure was confirmed by XRD spectra and an enhancement in crystallite size was observed with an increase in radiation followed by decrease at 50 kGy dose. The FTIR spectra showed there were no significant changes in the peak position after gamma-irradiation. The morphological investigation showed the maturation of 1D ZnO hexagonal nanorods over the surface of the film. However, after gamma-irradiation, the ZnO nanorods were found connected, forming bunches. The band-gap increased for 50 kGy doses as compared to pristine ZnO thin film. However, characterization result analysis showed that gamma-irradiation produced conspicuous improvements in chemically prepared ZnO microstructure. It was found that post-irradiated (at 30 kGy) ZnO thin film sensor achieved 7.29 as response factor for 400 ppm NH3 gas sensing compared to 1.01 for the pristine sample. The outcome of this study showed that gamma-irradiation is an effective technique for improvement in the sensing performance of ZnO thin films which has great potential to use gamma irradiated ZnO sensor in chemical industries and laboratories.

Sensitivity Enhancement of Ammonia Gas Sensor Based on Hydrothermally Synthesized rGO/WO3 Nanocomposites

An ultrasensitive ammonia gas sensor based on hydrothermally synthesized rGO/WO3 nanocomposite with interdigitated chromium electrode has been fabricated. Device properties such as structural, morphological, optical, and electrical were analyzed and reported. A correlation between stability and performance of the device with electrical properties has been established. Sensor shows excellent selectivity and sensitivity towards ammonia detection, even at lower gas concentration and low operating temperature. At room temperature, the sensor depicts the sensing response 4.35 with 13/20 sec response/recovery time for 10 PPM NH3 gas concentration. Although the best sensing performance has been obtained for 150 °C operating temperature. For 10 PPM and 100 PPM NH3 gas concentration, we found sensor response 10.89 and 27.7 with 11/17 and 7/19 sec response/recovery time. The sensor has been tested for different period/interval of time and found that the proposed nanocomposite has excellent stability and reproducibility thus can be utilized for various gas sensing applications.

Dynamic liquid phase deposition of doped nanostructured PANI tube sensor for trace-level NH3 gas detection

We proposed a polyaniline-camphorsulfonic acid/titanium dioxide (PANI-CSA/TiO2) coated glass capillary tube sensor structure in this work. The PANI-CSA/TiO2 sensitive material was grown on the inner wall of silica glass capillary tube. A dynamic liquid phase deposition (DLPD) process was developed to fabricate the tube sensor samples. The optimum processing parameters, microstructures, morphology and gas detective performances of the PANI-CSA/TiO2 tube sensors were investigated. PANI-CSA/TiO2 capillary tube sensor samples (core size 1 mm, length 7 cm) with better properties were obtained at an optimum liquid flow rate of 0.62 mL min−1. The tube sensor shows response time of 84 s, response of 877 % and recovery time of 55 s for detecting 3 ppm NH3 gas while the plane sensor sample has response time of 152 s, response of 17.8 % and recovery time of 367 s. The capillary tube sensor exhibits convenience for detecting a small volume of gas sample. For a 1 mL, 0.1 ppm NH3 gas sample, the PANI-CSA/TiO2 capillary tube sensor exhibits 54 s response time, 454 % response while the plane-shaped sensor fails to detect.

3D Hollow Quasi-Graphite Capsules/Polyaniline Hybrid with a High Performance for Room-Temperature Ammonia Gas Sensors.

Designing sensing materials with novel morphologies and compositions is eminently challenging to achieve high-performance gas sensor devices. Herein, an in situ oxidative polymerization approach is developed to construct three-dimensional (3D) hollow quasi-graphite capsules/polyaniline (GCs/PANI) hierarchical hybrids by decorating protonated PANI on the surface of GCs; as a result, an immensely active and sensitive material was developed for sensing ammonia gas at room temperature. Moreover, the GCs possessed a capsule-like hollow/open structure with partially graphitized walls, and PANI nanospheres were uniformly decorated on the GC surfaces. Furthermore, the inflexible and rigid 3D ordered chemistry of these materials provides the resulting hybrids with a large interfacial surface area, which not only allows for rapid adsorption and charge transfer but also provides the necessary structural stability. The 3D hollow GCs/PANI hybrids exhibit excellent performance; the GCs/PANI-3 hybrid is highly sensitive (with a response value of 1.30) toward 10 ppm NH3 gas and has short response and recovery times of 34 and 42 s, respectively. The GCs/PANI-3 hybrid also demonstrates a good selectivity, repeatability, and long-term stability, which are attributed to the substantial synergistic effect of the GCs and PANI. The design of such a unique 3D ordered framework provides a promising pathway to achieve room-temperature gas sensors for commercial applications.

Room-temperature high-performance ammonia gas sensor based on hydroxyapatite film

A room-temperature high-performance ammonia (NH3) gas sensor based on hydroxyapatite (HAp) film with three-dimensional network structure was reported in this paper. The gas sensor was fabricated on the indium tin oxide glass (ITO) interdigital electrode via simple electrochemical deposition technique. The HAp film gas sensor shows good sensitivity, high reproducibility and excellent selectivity to NH3 gas under dry and relative humidity (RH) conditions at room temperature. The response and recovery time of the HAp film gas sensor to 1000 ppm NH3 gas are 23 s and 14 s under N2 (dry) condition, and are 4 s and 11 s under air (RH ≈ 30) condition, respectively. The HAp film gas sensor has no considerable deviation in the 1000 ppm NH3 gas for 3 cycles under N2 (dry), and so is air (RH ≈ 30) conditions. The HAp film gas sensor shows excellent selectivity to methanol, acetone and ethanol under N2 (dry) and air (RH ≈ 30) conditions. Above all, two sensing mechanisms of the HAp film gas sensor to NH3 gas have been also researched in this work.

High sensitivity NH3 gas sensor with electrical readout made on paper with perovskite halide as sensor material

In this paper we report a cheap, paper electronics based solid state gas sensor to detect NH3 gas selectively with a detection capability of better than 1 ppm. The sensor uses perovskite halide CH3NH3PbI3 (MAPI) as the active sensor material grown on a paper. This paper based sensor works at room temperature. The current through the paper sensor increases by one order on exposure to only 10 ppm NH3 gas. The calibrated sensitivity is ~55% for 1 ppm of NH3 gas in Nitrogen or Air. The current noise limited resolution estimated to be ~10 ppb. This work establishes perovskite halide as a new solid state gas sensing material that can reach sub ppm sensitivity using simple paper electronics. Use of paper and also solution method used to grow the active material makes the sensor cost effective and easy to manufacture. This type of disposable high sensitive paper sensor can be used for detection of NH3 as a marker in exhaled breathes for non-invasive diagnosis. The sensor formed on the paper, since it supports unheated operation, needs less than few nanowatt power for its operation.

Improvement in Sensitivity of InN Resitive Gas Sensor By Thickness Modulation for Liver Malfunction Application

The detection of Volatile Organic Compounds (VOCs) biomarkers from the exhaled breath has opened the new techniques for medical diagnostics because of its noninvasive and inexpensive way of disease detection. Exhaled breath contains more than 1840 VOCs 1 which concentration may vary in ppb or in ppt range. The signature of some VOCs present in breath abruptly change with the specific disease, called biomarkers. Ammonia is an important biomarker for liver disease 2. There are many conventional techniques to detect ammonia in sub-ppm range including, proton transfer reaction mass spectrometry (PTR-MS), selected ion flow tube coupled mass spectrometry (SIFT-MS) 3, but these instruments are bulky and very costly. Metal Oxide (MOS) based gas sensors are very promising sensors for detection of breath biomarkers, but it also has a disadvantage of high operation temperature (more than 300ºC). Extensive attention has been paid recently to the indium nitride (InN) epitaxial layers and devices for gas sensing application because of its exceptional electronic properties, including excellent electron mobility, high electron density and comparatively low operation temperature ~200ºC. Moreover, an unusual phenomenon of strong electron accumulation at the surface of InN makes it highly sensitive gas sensor for VOCs detection 4. In this work, two InN based gas sensors of different thickness of the sensing film T1 (40nm) and T2 (60nm) are used respectively, for gas sensing. When the various concentration (0.3ppm, 0.5ppm, 1 ppm and 2ppm) of NH3 gas are exposed on the sensors, the current response is obtained at different thickness shown in (Figure 1a and 1b) respectively. The current variation response of 2 ppm NH3 gas on T1 is approx. 10 fold higher than T2 as shown in (Figure 1c). The current variation response for 0.5ppm on T1 is 0.04% while T2 showed negligible response as shown in (Figure 1d). The change at the surface of InN epilayer will be more significance on the total conductivity of thin layer as compare to thick layer 5. Hence, the lower thickness of the InN epilayer has higher response as compare to higher thickness. Therefore, lower thickness (40 nm) is suitable for diagnosis of liver malfunction. References B. de Lacy Costello, A. Amann, H. Al-Kateb, C. Flynn, W. Filipiak, T. Khalid, D. Osborne, and N. M. Ratcliffe, Journal of breath research, 8 (1), 014001 (2014).A. Kundra, A. Jain, A. Banga, G. Bajaj, and P. Kar, Clinical biochemistry, 38 (8), 696-699 (2005).S. T. Krishnan, J. P. Devadhasan, and S. Kim, Analytical and bioanalytical chemistry, 409 (1), 21-31 (2017).S. Rai, K.-W. Kao, S. Gwo, A. Agarwal, W. Lin, and J. Yeh, Sensors, 18 (11), 3887 (2018).H. Lu, W. J. Schaff, and L. F. Eastman, Journal of applied physics, 96 (6), 3577-3579 (2004). Figure 1: (a) current response at T1 (40 nm thickness), (b) current response at T2 (60 nm thickness), (c) current variation response at 2 ppm NH3 gas at T1 and T2, (d) current variation response at 0.5 ppm NH3 gas at T1 and T2. Figure 1

Improvement in Sensitivity of InN Resitive Gas Sensor by Thickness Modulation for Liver Malfunction Application

The traces of sub-ppm ammonia in the human breath is useful for the detection of the liver condition in humans. In this work, we have fabricated two InN based gas sensors of different thickness of the sensing film T1 (40 nm) and T2 (60 nm) respectively by RF-MOMBE. The current variation response of 2 ppm NH3 gas on T1 is approximately 10 fold higher than T2. The current variation response for 0.5 ppm on T1 is 0.04% while T2 showed a negligible response. The change at the surface of InN epilayer will be more significant on the total conductivity of the thin layer as compared to the thick layer. Hence, the lower thickness of the InN epilayer has a higher response as compared to higher thickness. Therefore, lower thickness (40 nm) is suitable for the diagnosis of liver malfunction.

A room temperature operated ammonia gas sensor based on Ag-decorated TiO2 quantum dot clusters.

In this research, nanometer size aggregates (clusters) of titanium dioxide (TiO2) quantum dot clusters (QDs) have been successfully prepared via a convenient hydrolysis method at a low temperature (80 °C). Then different amounts (0–5%) of Ag were further decorated on the TiO2 QDs via dipping and annealing under a nitrogen atmosphere. After Ag decoration, the TiO2 QD sensing materials were synthesized, and characterization and NH3 gas sensing performance studies were carried out. Analysis via XRD and EDS was conducted, and the results showed that Ag+ ions were successfully reduced to Ag and decorated on the surface of the anatase TiO2 QDs. Noble metal Ag acted as the sites for adsorbates, catalysts, or promoters during the surface reactions, and as the element improving the thermal stability of the nanostructure. Therefore, the Ag-decorated gas sensor possessed better gas sensing performance than an undecorated gas sensor, and 3% Ag dopant proved to be the optimal amount of addition. The fabricated 3% Ag-decorated TiO2 QDs gas sensor, compared with the undecorated TiO2 QDs sensor, displayed a 6-times-higher sensing response at room temperature and demonstrated excellent gas sensing properties toward 10–100 ppm NH3 gas, good selectivity, gas sensitivity and stability, rapid response/recovery time, and a linear relationship between the response and the target gas concentration. In particular, the excellent performance of the Ag decorated-TiO2 QDs gas sensor was achieved at room temperature, which suggests the great possibility of a prompt gas sensing response, with the use of paper as a substrate, that requires a low operation temperature.

Study on NH<sub>3</sub> Gas Sensors using a WO<sub>3</sub>-based Multiple-layered Thin Film with Pt Catalyst

NH3 gas is a poisonous substance that adversely affects the environment and humans. A low level NH3 is created by human bodies and emitted as a component of urine and exhaled breath. Therefore, the detection of NH3 gas is important to monitor human health conditions. A novel WO3 multiple-layered thin film NH3 sensor using Pt catalyst has been developed in this study. WO3 thin film coated with Pt nanoparticles successfully improves the sensitivity to NH3 gas. Furthermore, WO3 multiple-layered thin film with an interspace has the effect of enhancing the sensitivity and lowering the optimum operating temperature. The developed sensor can detect as low as 1 ppm NH3 gas.

A Highly Stable Two-Dimensional Copper(II) Organic Framework for Proton Conduction and Ammonia Impedance Sensing.

This work reports the design and fabrication of a proton conductive 2D metal-organic framework (MOF), [Cu(p-IPhHIDC)]n (1) (p-IPhH3 IDC=2-(p-N-imidazol-1-yl)-phenyl-1 H-imidazole-4,5-dicarboxylic acid) as an advanced ammonia impedance sensor at room temperature and 68-98 % relative humidity (RH). MOF 1 shows the optimized proton conductivity value of 1.51×10-3 S cm-1 at 100 °C and 98 % RH. Its temperature-dependent and humidity-dependent proton conduction properties have been explored. The large amount of uncoordinated carboxylate groups between the layers plays a vital role in the resultant conductivity. Distinctly, the fabricated MOF-based sensor displays the required stability toward NH3 , enhanced sensitivity, and notable selectivity for NH3 gas. At room temperature and 68 % RH, it gives a remarkable gas response of 8620 % to 130 ppm NH3 gas and lower detection limit of 2 ppm towards NH3 gas. It is also found that the gas response of the ammonia sensor increases linearly with the increase of NH3 gas concentration under 68-98 % RH and room temperature. Moreover, the sensor indicates excellent reversibility and selectivity toward NH3 versus N2 , H2 , O2 , CO, CO2 , benzene, and MeOH. Based on structural analyses, activation energy calculations, water and NH3 vapor absorptions, and PXRD determinations, proton conduction and NH3 sensing mechanisms are suggested.

Highly sensitive and wearable gas sensors consisting of chemically functionalized graphene oxide assembled on cotton yarn.

Highly sensitive and wearable chemical sensors for the detection of toxic gas molecules are given significant attention for a variety of applications in human health care and environmental safety. Herein, we demonstrated fiber-type gas sensors based on graphene oxide functionalized with organic molecules such as heptafluorobutylamine (HFBA), 1-(2-methoxyphenyl)piperazine (MPP), and 4-(2-keto-1-benzimidazolinyl)piperidine (KBIP) by assembling functionalized graphene oxide (FGO) on a single yarn fabric. These gas sensors of FGO on yarn exhibited extraordinarily higher sensitivity upon exposure to gas molecules than chemically reduced graphene oxide due to many active functional groups on the GO surface. Furthermore, the mechanical stability and chemical durability of the resulting gas sensors are well-maintained. Based on these results, we expected that our sensors with high sensitive and wearability will provide a good premise for wearable chemical sensors-based multidisciplinary applications.