Ppm NH3 Research Articles

Hybrid materials based on pyrene-substituted metallo phthalocyanines as sensing layers for ammonia detection: Effect of the number of pyrene substituents

In this work, the effect of the number of pyrene substituents in zinc(II) phthalocyanine molecules on the sensor properties of their hybrid materials with single-walled carbon nanotubes (SWCNT) is studied. For this purpose, hybrid materials of SWCNTs modified with five different trioxyethylenethio substituted zinc(II) phthalocyanines containing 0, 1, 2, and 4 methoxypyrene substituents in the phthalocyanine ring were prepared and characterized by Raman spectroscopy, scanning electron microscopy and inductively coupled plasma atomic emission spectrometry. The chemiresistive sensor response of the prepared hybrids toward low concentrations of ammonia (1–100 ppm) was studied to reveal the effect of the number of pyrene substituents in the phthalocyanine ring on the sensor performance of the hybrid materials. It was demonstrated that the hybrids with zinc(II) phthalocyanine bearing four methoxypyrene substituents exhibited the maximal sensor response to ammonia with the limit of detection of 0.4 ppm. The sensitivity of the hybrid materials to ammonia was shown to be much higher than to CO2, H2, H2S, CH4, ethanol, acetone, and dichloromethane vapors, however, an oxidizing gas such as NO2 was an interfering compound in the determination of ammonia. 1 ppm NO2 show the same absolute value of the response than 10 ppm NH3. The quantum-chemical calculations were performed to explain this effect as well as the dependence of the binding energy of substituted zinc(II) phthalocyanines with carbon nanotubes on the number of pyrene substituents.

A wearable mask sensor based on polyaniline/CNT nanocomposites for monitoring ammonia gas and human breathing

Flexible gas sensors have been widely used in environmental and human health monitoring due to their flexibility and compatibility with electronic device substrates. Herein, we prepared a porous polypropylene/carbon nanotube/polyaniline (p-PP/CNT/PANI) nanocomposite gas sensor using disposable surgical masks as a flexible substrate. The CNT aqueous solution with a surfactant was drop-coated on the porous polypropylene fibers (p-PP) of the mask, followed by in-situ polymerization of aniline on the p-PP/CNT composite. The fabricated flexible p-PP/CNT/PANI gas sensor exhibited fast response (93 s) and recovery times (36 s), low detection limit (500 ppb), high response value (452% towards 70 ppm NH3), and good stability at room temperature. The excellent sensing performance was mainly attributed to the p-PP/CNT/PANI network with a higher specific surface area and their conductive channels. Moreover, the composite sensor in a disposal mask can detect breathing patterns in real-time for potential noninvasive monitoring of respiratory rate.

One-pot synthesis of tin oxide/reduced graphene oxide composite coated fabric for wearable ammonia sensor with fast response/recovery rate

By using polyimide (PI) fabric as a flexible substrate, tin dioxide (SnO2)/reduced graphene oxide (rGO) composite coated fabrics (PI-SnO2/rGO) were prepared via electrostatic layer-by-layer self-assembly and in situ hydrothermal method. The morphology and microstructure of PI-SnO2/rGO were characterized by FT-IR, Raman, XPS and SEM, and its ammonia (NH3) sensing performance at room temperature was tested. The results show that the average size of SnO2 nanoparticles in the composite coating is about 3 nm, and there is a strong interfacial interaction between SnO2 and rGO. Consequently, PI-SnO2/rGO exhibits n-type sensing for NH3 with excellent linear response (R2 =0.995) in the range of 50–400 ppm, high sensitivity (5.16 % for 100 ppm NH3), fast response/recovery rate (94 s/57 s) and excellent selectivity. In addition, the sensor exhibits good mechanical robustness. The sensitivity is decreased by only 3 % after 2000 stretches.

PSS-doped PANI nanoparticle/Ti3C2Tx composites for conductometric flexible ammonia gas sensors operated at room temperature

The detection of ammonia (NH3) is significant because it can seriously damage human health and atmospheric environment. However, the development of high-performance flexible NH3 gas sensors operated at room temperature is still challenging. Thus, a flexible NH3 film sensor based on poly(4-stryenesulfonate)-doped polyaniline nanoparticle (PANI:PSS)/Ti3C2Tx composite was developed by in-situ polymerization. This optimized PANI:PSS/Ti3C2Tx film displayed the high response of 0.57–1 ppm NH3, which was improved by 1.78-fold in comparison with PANI:PSS film. Besides, the response value of this film to NH3 was 1.46 times higher than to NO2, and this value was much higher than to other interfering gases (NO, toluene, ethanol, and acetone). Additionally, this film sensor possessed excellent mechanical stability and low detection limit (20 ppb) at room temperature. The abundant Schottky heterojunctions formed in PANI:PSS/Ti3C2Tx composite, the numerous -SO3H groups introduced by PSS anion chains, and the improved protonation degree of PANI component are responsible for the enhanced sensing properties. The monitoring experiment of shrimp spoilage has demonstrated the application feasibility of this film sensor. This research provides a novel and practical method for constructing high-performance polymer/MXene based gas sensors.

Evaluation of Zirconia Ceramic Processed by Digital Light 3D Printing Applicated as Solid-Electrolyte Sensor

Zirconia slurry aimed to apply in digital light process (DLP) printing technology were made of the 3 mol% yttrium oxide (Y2O3) stabilized micro-nano zirconium dioxide (3YSZ) powders. An overall mechanical strength can be obtained via a precise control of two-step sintering process. The results show that Y2O3 in 3YSZ would diffuses into the ceramic lattice, further stabilizing the metastable tetragonal zirconia (t-ZrO2) toughening phase in sub-micro sized grains with nearly 100% crystal phase transition ratio. The Vickers hardness of sintered ceramic parts reaches 12.94 ± 0.186 GPa. The fracture toughness (KIC) of sintered ceramics is 5.63 ± 0.015 MPa·m1/2. The propagation law of Vickers crack reveals the mechanism of strengthening and toughening of fine grains on matrix fracture toughness. Due to the uniform crystals also can make the corrosion better to construct a three-phase boundary sensitive process, the response of the T-ZrO2-SnO2 to 30 ppm NH3 is 15.7 mV which is 2 times more than the commercial ZrO2. A relative short response and recovery times of 6 s and 33 s can achieve with a good reproducibility of continuous response and recovery transients.

Silver nanoparticles modified two-dimensional polarizative PbTiO3 nanoplates with high active plane and improved NH3 sensitivity at low temperature

Two-dimensional (2D) perovskite PbTiO3 is an important ferroelectric material with spontaneous polarization below Curie temperature and readily adsorbs oxygen molecules in the atmosphere, a preliminary step for NH3 response. However, the surface of 2D PbTiO3 lacks enough active adsorption sites for NH3 gas. Here, 2D PbTiO3 nanoplates (NLs) with highly polarized (001) plane was synthesized by a two-step hydrothermal strategy without templates and surfactants, and Ag+ ions on (001) plane were further in-situ reduced by an impregnation method. Specially, the negatively polarized surface (ζ (zeta potential) = −22.3 mV) for (001) plane promoted the reduction of Ag+ ions in AgNO3 solution to Ag0 nanoparticles (NPs). Where, Ag NPs with high density on (001) plane can produce spillover effect, promoting adsorption of O2 in air and subsequent formation of O2−. The response of PbTiO3-based gas sensor to 100 ppm NH3 is 3.6 at room temperature (25 °C), while the response is improved by 2.6 times on 1.5 at% Ag/PbTiO3 NLs with Schottky junctions. Even at 15 °C, the response reaches to 6. The ammonia sensor based on Ag/PbTiO3 NFs is verified with high sensitivity, fast response-recovery and distinct selectivity at low operating temperature.

Ultrasensitive memristor-based gas sensor (gasistor) with gas-triggered switch and memory function for dilute NH3 detection

Accurately recording the time of toxic gas leakage is beneficial to find out the cause of the accident and evaluate the safety of the equipment. However, conventional gas sensors do not have the memory function without external storage devices. To develop gas sensors with both sensing and memory functions, memristor-based gas sensors have been proposed. The memristor-based gas sensors could be used as gas-triggered switch and gas sensors with a built-in memory, which was named gasistor. In this study, a TiO2-based gasistor was proposed for dilute NH3 detection at room temperature (RT). The gasistor displayed bipolar resistive switching behavior, excellent repeatability and stability. Gas-sensing measurements showed that TiO2-based gasistor could be used for ultrasensitive detection of NH3. The response to 1 ppm NH3 in the high resistance state (HRS) was as high as 164.2, and the response/recovery time was < 1 s, respectively. Especially, as the NH3 concentration decreased, the gasistor switched from the HRS to the low resistance state (LRS) and the NH3 leakage time was recorded. Based on the experimental results, we propose a more realistic gas-triggered switch mechanism model, which can be used to provide a reference for the prediction of gas-triggered voltage and compliance voltage.

A Room Temperature ZnO-NPs/MEMS Ammonia Gas Sensor.

This study uses ultrasonic grinding to grind ZnO powder to 10–20-nanometer nanoparticles (NPs), and these are integrated with a MEMS structure to form a ZnO-NPs/MEMS gas sensor. Measuring 1 ppm NH3 gas and operating at room temperature, the sensor response for the ZnO-NPs/MEMS gas sensor is around 39.7%, but the origin-ZnO powder/MEMS gas sensor is fairly unresponsive. For seven consecutive cycles, the ZnO-NPs/MEMS gas sensor has an average sensor response of about 40% and an inaccuracy of <±2%. In the selectivity of the gas, the ZnO-NPs/MEMS gas sensor has a higher response to NH3 than to CO, CO2, H2, or SO2 gases because ZnO nanoparticles have a greater surface area and more surface defects, so they adsorb more oxygen molecules and water molecules. These react with NH3 gas to increase the sensor response.

A fast-response visual indicator film based on polyvinyl alcohol/methylcellulose/black wolfberry anthocyanin for monitoring chicken and shrimp freshness

Natural anthocyanins are considered favorable indicators for new sensing materials because of their wide pH color range. Here, a smart visual indicator film was developed by introducing black wolfberry (BW) anthocyanins to a solid matrix composed of polyvinyl alcohol (PVOH) and methylcellulose (MC). Fourier transform infrared and X-ray showed that the introduction of BW anthocyanins enhanced hydrogen-bond interactions among the polymers and the anthocyanins were well fixed in the polymer matrix. 5 % BW could improve the stability of the PVOH/MC/BW and increase its tensile strength and breakage elongation by 63.2 % and 53.0 %, respectively. Optical observations and freshness monitoring suggested that the film loaded with 5 % BW could respond to acidic and basic vapors within 10 s and as low as 25 ppm NH3 in chicken and shrimp during storage at 4 °C. Therefore, PVOH/MC/BW-5% may potentially be used as a smart sensor to determine freshness in practical applications.

Impedimetric-type NO2 sensor based on the p-NiO/n-NiNb2O6 heterojunction sensing electrode

Development of high-performance NO2 gas sensors with good sensitivity and long-term stability at high temperatures is expected for exhaust gas monitoring. The sensor performance mainly depends on sensing material. In this work, p-NiO/n-NiNb2O6 heterojunction material is successfully synthesized and an impedimetric NO2 sensor was assembled using the above material as sensing electrode (SE) and gadolinia-doped ceria (CGO) with a dense/porous bilayer structure as a solid electrolyte. Introduction of SE to the CGO porous layer by screen printing followed by cold isostatic pressing treatment before calcination allows SE to successfully enter inside the porous layer and greatly increases the area of the three-phase boundary (TPB) and improves the long-term stability of the sensor. Using NiO/NiNb2O6 heterojunction SE can effectively improve the modulus (|Z|) response value (S|Z| = (|Z|air - |Z|gas)/|Z|air) of the sensor. Among the sensors, 90NiO/10NiNb2O6 (the mass ratio of NiO to Nb2O5 is 9:1) based NO2 sensor exhibits the best response performance and the highest sensitivity (0.34/ppm at 500 °C). The sensor also shows an excellent anti-interference property. Introduction of 300 ppm CO2, CH4, NO, CO, or H2 into 300 ppm NO2 makes response signal change below 3 % and 300 ppm NH3 only leads to signal reduction by 8.9 %, which is relatively low in a similar sensing system. The sensor response toward NO2 is slightly affected by O2 concentration change in 5–21 %. The superior performance of the sensor can be principally attributed to the heterojunction effect, which promotes the charge transfer and the adsorption capacity for NO2.

Mechanism of NH3 gas sensing by SnO2/PANI nanocomposites: charge transport and temperature dependence study

Metal oxide-Polyaniline (PANI) nanocomposites have shown improved gas sensing characteristics that can be attributed to the formation of a p–n junction between the n-type metal oxide and the p-type PANI. The charge transport, grain boundary depletion region, and intragrain resistance are studied to understand the gas sensing mechanism of pristine metal oxide gas sensors. However, gas sensing mechanisms for metal-oxide/PANI nanocomposites have not been studied extensively. In this work, we have studied the gas sensing mechanism of SnO2/PANI nanocomposites using electrochemical impedance spectroscopy, and temperature dependent gas sensing experiments. Well-defined SnO2 nanoclusters were observed in the PANI matrix. The n-type SnO2 was covered by p-type PANI, and a depletion region was formed at the interface. The presence of the p–n junction depletion region was confirmed by impedance spectroscopy. The polarons in PANI were trapped by NH3 leading to a change in the width of the conducting path due to rearrangement of charge carriers along the depletion region. The change in the conduction path, along with the trapped polarons, enhanced the sensor response. For higher loadings of SnO2, the depletion region was deformed, and the sensor response decreased due to non-uniform boundaries. 1 wt% SnO2 with respect to aniline precursor in in situ synthesis showed the best response of 37.8% for 100 ppm NH3 at 35 °C. The response was stable for low humidity levels up to 51%RH. The response increased for higher humidity levels. The sensor response increased from 0.17 to 2.99 upon bending 1000 times at 7.8 mm diameter due to cracks in the surface. The sensor showed only 10% variation in response after 9 months.

Constructing ultrathin defective Co3O4/MoS2 nanosheets based 2D/2D heterojunction toward room temperature NH3 detection

Ultrathin 2D/2D face-to-face heterostructures have shown promising applications in gas sensing devices. Synthesis of ultrathin 2D/2D metal oxide/MoS2 based heterostructures, however, remains challenging probably due to the difficulty in preparing ultrathin 2D metal oxides. Here, ultrathin defective Co3O4/MoS2 nanosheets (NSs) with large heterointerfaces and high specific surface area are prepared via in-situ growth of MoS2 on salt-template-synthetic Co3O4 NSs. The as-obtained Co3O4/MoS2 sensor exhibits a high response value of 2.1 toward 5 ppm NH3 at room temperature, outperforming most sensors based on metal oxide/MoS2 reported hitherto. Moreover, the ultrathin defective Co3O4/MoS2 NSs sensor presents excellent selectivity and long-term stability. The excellent gas sensing performances of the Co3O4/MoS2 based sensor are attributed to the presence of rich defects and intimate interfacial electronic interaction, which ensures abundant active adsorption sites and rapid electrons transfer. Our method demonstrates a versatile integration strategy to construct 2D/2D heterostructures for innovative applications including but not limited to the gas sensing fields.

Mesoporous WS2/MoO3 Hybrids for High-Performance Trace Ammonia Detection.

Mesoporous WS2/MoO3 hybrids were synthesized by a facile two-step and additive-free hydrothermal approach and employed for high-performance trace ammonia gas (NH3) detection. Compared with single WS2 and MoO3 counterparts, WS2/MoO3 sensors exhibited an improvement in NH3-sensing performance at room temperature (22 ± 3 °C). Typically, the optimal WS2/MoO3 sensor showed a higher and quicker response of 31.58% within 57 s toward 3 ppm of NH3, which was 17.7- and 57.4-fold larger than that of pure MoO3 (1.78% within 251 s) and WS2 (0.55% within 153 s) ones. Meanwhile, good reversibility, sensitivity, and selectivity, reliable long-term stability, and the lowest detection limit of 9.0 ppb were achieved. These superior properties were probably ascribed to numerous heterojunctions favorable for additional carrier-concentration modulation via the synergetic effect between WS2 and MoO3 components and the large specific surface area beneficial for richer sorption sites and faster molecular transfer at room temperature. Such achievements also imply that the designed WS2/MoO3 heterostructure nanomaterials have the potential in achieving trace NH3 recognition catering for the requirements of high sensitivity and low power consumption in future gas sensors.

Ti3C2Tx MXene/urchin-like PANI hollow nanosphere composite for high performance flexible ammonia gas sensor

Ammonia (NH3) has been used as a typical indicator to monitor food spoilage, human health, and air quality. However, the development of flexible NH3 sensors with high response, excellent selectivity and low cost remains a huge challenge. Herein, a high performance NH3 sensor based on Ti3C2Tx MXene nanosheet/urchin-like PANI hollow nanosphere composite (MP) was fabricated through template method and in situ polymerization. The NH3 sensor is fabricated with no high cost electrodes through directly depositing this composite on flexible polyethylene terephthalate (PET) during polymerization. This optimized MP film sensor exhibits high response of 3.70 to 10 ppm NH3 at room temperature, which is 4.74-fold in comparison with urchin-like PANI hollow nanosphere (u-PANI). It also shows excellent selectivity, good repeatability, satisfactory flexibility, air stability and low detection limit of 30 ppb. The effective morphology control and heterojunction construction of MP composite are responsible for superior sensing performance. Moreover, the application of this film sensor in the monitoring of the spoilage process of fresh pork is demonstrated. This study offers a new strategy for fabricating high performance flexible room-temperature NH3 sensors, which may be scale fabrication and application in daily life.

Effects of electrolyte variation on ammonia sensing temperature for BiVO4 sensing electrode in mixed potential gas sensor

The aim of the present study is to investigate BiVO4 sensing electrode (SE) based electrochemical gas sensor for ammonia (NH3) sensing. Additionally, this study is also focused to reduce the operating temperature of sensor by applying different electrolytes i.e., yttria stabilized zirconia (YSZ) and gadolinia doped ceria (GDC). The maximum sensor response obtained for YSZ and GDC based cells towards 80 ppm NH3 were − 103.03 and − 78.81 mV at 600 ℃ and 550 ℃, respectively. Corresponding sensitivity of YSZ and GDC based cells for NH3 sensing were − 99.24 and − 42.66 mV/decade, respectively. Both the sensors demonstrate excellent selectivity as well as stability against 80 ppm NH3 (10 cycles) and humidity variation (pH2O = 0–0.12 atm.). Electrochemical impedance spectra (EIS) and dc polarization (I-V) curves confirms the mixed-potential sensing mechanism of the sensors. The systematic dependency of electrode’s resistance at a given frequency on the gas concentration reveals a novel pathway for prediction of sensors’ behavior. Additionally, the presence of GDC electrolyte decreases the response/recovery time (16/125 s) compared to YSZ-based cells (21/159 s) against 320 ppm NH3 at 550 ℃ which demonstrate its low temperature sensing capability. This 50 ℃ reduction in the operating temperature can be useful for extension of lifetime of sensor.

PtO2-decorated MoS2 ultrathin nanostructures for enhanced NH3 gas sensing properties

Recently, transition metal dichalcogenides (TMDs) have attracted much attention due to their high surface-to-volume ratio, various active edge sites, and adjustable bandgaps. However, in general, TMDs still exhibit low gas response and incomplete recovery. Surface modification is an effective way to facilitate the adsorption and desorption processes, thus enhancing the TMD gas sensor's sensing performance. In this study, a PtO2-decorated MoS2 nanostructure gas sensor was fabricated using a chemical reduction process. The result showed that the as-obtained nanostructures consist of accumulated ultrathin MoS2 nanosheets decorated with spherical PtO2 nanoparticles. The gas response of the as-obtained PtO2-decorated MoS2 gas sensor toward NH3 is remarkably high, with 450% upon 500 ppm NH3, which is almost 20 times higher than that of the pristine MoS2 nanostructure gas sensor in their optimal working conditions. The enhancement in gas sensing properties was attributed to the catalytic spillover effect of PtO2 nanoparticles as well as the formation of p-p heterojunction on the MoS2 surface.

Template- and etching-free fabrication of two-dimensional hollow bimetallic metal-organic framework hexagonal nanoplates for ammonia sensing

This work reports the template- and etching-free fabrication of hollow bimetallic nickel-cobalt benzenetricarboxylic acid (Ni-Co BTC) hexagonal nanoplates by a polyvinylpyrrolidone (PVP)-assisted approach. The incorporation of PVP can reduce the stacking of these nanoplates along the vertical direction and generate depletion forces between them to reduce aggregation. When employed for the quartz crystal microbalance (QCM) sensing of ammonia (NH3), the hollow Ni-Co BTC hexagonal nanoplates exhibit 1.6, 3.8, and 7.5 times higher sensitivity to 69.5 ppm of NH3 than non-hollow Ni-Co BTC nanoplates, Ni-BTC nanobelts, and Co-BTC microrods, respectively, and a low limit of detection (LOD) of 1.53 ppm. Additionally, they show good selectivity to NH3 in the presence of other interfering compounds and excellent stability with only a very small decrease of 2.86 % in sensitivity after 6 months. The NH3 adsorption on the hollow Ni-Co BTC hexagonal nanoplates follows a pseudo first-order kinetic model with the adsorption rate being 6.1 and 7.1 times faster than Ni-BTC nanobelts and Co-BTC microrods, respectively. The good sensing performance of the hollow Ni-Co BTC hexagonal nanoplates to NH3 is attributed to the existence of carboxyl and hydroxyl groups which can provide energetic sites for the chemisorption of NH3 molecules and the increased adsorption sites provided by the hollow two-dimensional structure and the bimetallic composition of this MOF.

DFT insights into the selective NH3 sensing mechanism of two dimensional ZnTe monolayer

Exploring novel NH3 sensing materials is crucial in chemical industries, fertilizing plants and medical fields. Herein, for the first time, the NH3 sensing behaviors and sensing mechanisms of two dimensional (2D) ZnTe monolayer are systematically investigated by density functional theory calculations. It is shown that 2D ZnTe monolayer exhibits excellent selective NH3 sensing properties. (220) crystal facet of ZnTe possesses a higher NH3 adsorption energy (−1.59 eV) and a larger charge transfer (0.195e) than (111) and (311) crystal facets. The positive charges could enhance NH3 sensing while the negative charges could reduce NH3 sensing. The NH3 adsorption strengths are significantly improved in O2 atmosphere while it is negligibly affected by N2 atmosphere and H2O atmosphere. Moreover, the presence of Zn vacancy and Fe, Co, Ni doping could improve the NH3 sensing of ZnTe. Additionally, the experimental results confirms that ZnTe possesses a low detection limit of 0.1 ppm NH3. These theoretical predictions and experimental results present a wide range of possibilities for the further development of ZnTe monolayer in NH3 sensing fields.

Computational assisted tuning of Co-doped TiO2 nanoparticles for ammonia detection at room temperatures

Improved gas sensors based on pure anatase TiO2 and Co-doped TiO2 nanoparticles were evaluated. A cobalt-doped TiO2 nanoparticle with a diameter of 40 nm was first synthesized. The morphology of the nanoparticles was analyzed by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The doped Co ion was confirmed to have entered the TiO2 lattice. Subsequently, gas sensors with different Co-doping concentrations were developed to investigate gas sensitivity to NH3. Compared with pure anatase TiO2 operating at 180 °C, Co-doped TiO2 samples were developed as NH3 gas sensors operating at room temperature. The 20% Co-doped sample exhibited the best performance, with a response value of 14 for 50 ppm NH3, which was 7 times higher than that of pure TiO2. The response and recovery times of the sensor were only 25 and 48 s, respectively, and exhibited both good stability and selectivity. Based on density functional theory (DFT), the calculated bandgap of Co-doped TiO2 decreased by 72% compared to pure TiO2. Structural simulation and mechanism analysis elucidated the good gas-sensing performance at room temperature and the property enhancement of the Co-doped TiO2 gas sensor.

Gas Sensitive Characteristics of Polyaniline Decorated with Molybdenum Ditelluride Nanosheets

In this work, hydrochloric acid (HCl)-doped molybdenum ditelluride (MoTe2) nanosheets/polyaniline (PANI) nanofiber composites are prepared by in situ chemical oxidation polymerization, and then the composites are deposited on interdigital electrodes (IDEs) to fabricate a NH3 gas sensor. Morphological analysis of the composites reveals that the PANI fibers are deposited on 2D MoTe2 sheets, showing a porous mesh microstructure structure with a more continuous distribution of PANI layer. FTIR spectrum analysis indicates the interaction between the MoTe2 nanosheets and the PANI in the MoTe2/PANI composites. The results demonstrate that the as-prepared MoTe2/PANI composites exhibit higher response than the pure PANI, in particular, the 8 wt.% MoTe2/PANI composites display about 4.23 times enhancement in response value toward 1000 ppm NH3 gas compared with the pure PANI. The enhanced NH3 gas-sensitive properties may be due to the increasing surface area of MoTe2/PANI composite films and the possible interaction of the P-N heterojunctions formed between PANI and the 2H-MoTe2 nanosheets.