Room Temperature NH3 Gas Sensors Research Articles

Preparation and NH3 gas-sensing properties of Ag/β-AgVO3 nanorods.

NH3 gas sensors operating at room temperature, consisting of Ag nanoparticles decorated β-AgVO3 nanorods (Ag/β-AgVO3 NRs), were fabricated via a facile hydrothermal method without the need for a template. The surface characteristics and compositions of Ag/β-AgVO3 NRs were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Ag nanoparticles, ranging in diameter from approximately 20 to 40 nm, were dispersed on the surface of monoclinic β-AgVO3 NRs with diameters ranging from 50 to 105 nm and lengths from 0.3 to 1.3 μm. The NH3 gas sensing properties of Ag/β-AgVO3 NRs were studied under both dry air and humid conditions at room temperature. Comparative analysis demonstrated that the Ag/β-AgVO3 NRs exhibited a strong response to NH3 gas under 70% relative humidity (RH) at room temperature compared to α-AgVO3 NRs. Specifically, the response of the Ag/β-AgVO3 NRs to 5 ppm NH3 increased by 2.25 times as the RH varied from 20% to 80% at room temperature. This enhanced response was attributed to the effects of formation of nanoheterojunctions, nano-metallic Ag activity and the conductivity of NH4+ and OH- ions induced by the presence of humidity. The room temperature NH3 gas sensors based on Ag/β-AgVO3 NRs demonstrated strong responses to low NH3 concentrations, high selectivity, good reproducibility, and long-term stability, and show promise for the development of low-power and cost-effective NH3 gas sensors for practical applications even under high humidity.

A high-performance room-temperature NH3 gas sensor based on WO3/TiO2 nanocrystals decorated with Pt NPs.

In this work, a high-performance room-temperature ammonia (NH3) gas sensor based on Pt-modified WO3-TiO2 nanocrystals was synthesized via a two-step hydrothermal method. The structural properties were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The 10 at% Pt@WO3-TiO2 nanocrystals present the highest NH3 sensing performance at room temperature. Compared with the nanocrystals without Pt modification, the sensitivity of the Pt@WO3-TiO2 sensor is tenfold higher, with the lowest concentration threshold reaching the 75 ppb level. The response is approximately 92.28 to 50 ppm, and response and recovery times are 23 s and 8 s, respectively. The improved sensing was attributed to a synergetic mechanism involving the space charge layer effect and Pt metal sensitization, enhancing the electron transfer efficiency, oxygen vacancy and specific surface area. This study is expected to guide the development of high-performance room-temperature ammonia sensors for clinical breath testing.

Trace level sensitivity and selectivity of room temperature NH3 gas sensors based on RGO/ZnO@SiNWs heterostructure

Ammonia (NH3) is one of the most common gaseous pollutants in various environmental and industrial processes which is accountable for various health issues, even for life-threatening situations. Due to this, high-precision detection of NH3 has become a top priority for various sectors so that healthy and safe environment could be ensured. Therefore, this work aims to develop a simple, reliable, and effective sensor with spatially distributed monitoring of NH3 gas wherein reduced graphene oxide (RGO) and Zinc oxide (ZnO) nanocomposite structure prepared using refluxing method were chosen to interact with NH3 gas. The vertically aligned silicon nanowires (SiNWs) were developed by using metal-assisted chemical etching (MACE) method. The RGO/ZnO nanostructure was then deposited on SiNWs to develop a selective and stable sensor for the trace level detection of NH3 gas with varying concentration from 0.01 ppm to 5 ppm at Room temperature (∼30 °C). The prepared materials were characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD), Raman spectrometer, X-Ray Photoelectron Spectrometer (XPS) and Ultraviolet–visible spectrophotometer which provide a thorough explanation about the developed nanostructures. The sensitivity of the sensor was observed to lie between 21 % at 0.01 ppm and 176 % at 5 ppm concentration of NH3 wherein the response/recovery time was measured to be 3 s/6 s and 5 s/12 s respectively. The fast response of the sensor for NH3 gas at low limit of detection (LOD) could be attributed due to the precise interaction of the analyte at the interface of RGO/ZnO@SiNWs Schottky heterostructure. Hence, the reported sensor can continuously be utilized to monitor the target analyte that is NH3 gas at low concentrations and reduces the chance of an unfortunate incident.

Ti3C2Tx MXene-SnO2 nanocomposite for superior room temperature ammonia gas sensor

Recently MXenes become the focus of emerging 2D layered materials family owing to their unique properties and promising potential in gas detection. However, the sensitivity and the stability of the pristine MXenes are poor due to their high carrier concentration and abundant active sites on the surface. Herein, superior NH3 sensors with high response and stability were successfully obtained by wrapping the SnO2 nanoparticles on Ti3C2Tx MXene nanosheets via a facile hydrothermal method. The nanostructures, morphologies, and compositions of the Ti3C2Tx MXene-SnO2 composite were systematically characterized by XRD, FTIR, SEM, TEM and XPS techniques. Results show that SnO2 nanoparticles with high specific surface area are uniformly dispersed on the Ti3C2Tx MXene surface, constructing loose heterostructure, which plays a crucial role in gas adsorption/desorption. In the Ti3C2Tx MXene-SnO2 heterostructure, the Ti3C2Tx MXene acts as a signal amplification channel for electron transfer in gas sensing reaction. The sensors exhibit excellent NH3 gas detection at room temperature. Response as high as 75% is observed for 500 ppm NH3 gas. Fast response and recovery times are also obtained, 109 and 342 s, respectively. Moreover, the sensing performances of the Ti3C2Tx MXene-SnO2 composite with various MXene ratios were systematically studied. It is found out that the 16.8%Ti3C2Tx-SnO2 based sensor shows the highest sensitivity in 10∼100 ppm range, and the 9.1%Ti3C2Tx-SnO2 based sensor exhibits the widest detection range. In addition, the selectivity and repeatability were also studied, revealing high selectivity and stability of the Ti3C2Tx MXene-SnO2 composite. Thus, Ti3C2Tx-SnO2 composite provides a new material to design and develop superior room temperature NH3 gas sensors.

Room temperature NH3 gas sensor based on PMMA/RGO/ZnO nanocomposite films fabricated by in-situ solution polymerization

Effective detection of ammonia gas is of great importance due to its detrimental effects on human health, environment, and ecosystem. High-performance composite gas sensors are vital in accomplishing this goal. Herein, we investigate the performance of an ammonia (NH3) gas sensor fabricated via dip-coating the silver interdigitated electrode for PMMA/RGO/ZnO (PRZ) nanocomposite solution with acetone as a solvent. The PRZ ternary nanocomposite was synthesized using the in-situ solution polymerization method and the resistive properties of the films assembled on the interdigitated electrode were analyzed, with respect to the fixed and varying ammonia gas concentrations, using LCR meter. When the sensor is operated in the controlled chamber containing ammonia gas at room temperature, the sensor responds rapidly to ammonia with a fast recovery of 13.02 s at a gas concentration of 350 ppm. The PRZ sensor exhibits high sensing percentage response (527%), excellent repeatability (four times), high sensitivity at low concentrations (less than 10 ppm), swift response and recovery times (1.94 s/13.02 s), and long-term stability (up to 90 days) with fluctuation of 3.2%, which signifies PRZ composite as a potential material for ammonia gas sensor. Aspects such as simplicity of the synthesis process and fabrication, excellent sensing performance, as well as fast response-recovery time at a particular gas concentration are noteworthy in this study. These features can be utilized for the detection of ammonia gas in chemical and biological fields.

Effect of {010} crystal facets of Bi2MoO6 and 1D/2D heterostructures for conductometric room temperature NH3 gas sensors

High working temperature and the insufficient limits of detection limit the broad applications of semiconductor chemiresistive gas sensors. Herein, pure Bi2MoO6 nanosheets and a series of one-dimensional/two-dimensional (1D/2D) multi-walled CNTs/Bi2MoO6 nanocomposites were developed via a facile hydrothermal route for room-temperature ammonia monitoring. The as-synthesized samples were characterized by various analytical techniques. 0.5 wt% MWCNTs/Bi2MoO6 nanocomposites showed the best sensing properties to 10–50 ppm NH3, including low limit of detection (157 ppb), high response (Ra/Rg = 44.2 @ 50 ppm), good selectivity, reproductivity, and anti-humidity sensing ability. The enhanced gas sensing mechanism was proposed based on the synergetic effect of high-energy crystal facets, modified surface characteristics and p-n heterojunction. Density functional theory (DFT) studies were also carried out to further clarify the gas sensing mechanisms. This work provides a practical approach to design and fabricate high-precision gas sensors working at room temperature.

High performance ammonia gas sensor based on electrospinned Co3O4 nanofibers decorated with hydrothermally synthesized MoTe2 nanoparticles

This paper introduces a room temperature NH3 gas sensor with excellent performance based on cobalt trioxide and molybdenum telluride (Co3O4-MoTe2) nanocomposite. Co3O4 nanofiber was synthesized by electrospinning, and MoTe2 nano particle was synthesized by simple hydrothermal method. MoTe2, Co3O4 and Co3O4-MoTe2 film sensors were prepared on interdigital electrode substrate by drop coating method. X-ray photoelectron spectroscopy (XPS), dispersive spectrometer (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to observe the morphology, microstructure, and composition of the prepared nano-materials. The gas sensing performance of the pristine Co3O4, MoTe2 and Co3O4-MoTe2 composite film sensors were tested at room temperature. The results of experimental research show that the Co3O4-MoTe2 gas sensor has better sensing performance for ammonia than the pure sensor, such as high response (56.20%@1ppm), excellent selectivity, good stability, short response/recovery time (7s/7s@1ppm) and low detection limit (26 ppb). The performance enhancement of the Co3O4-MoTe2 film sensor was mainly attributed to the p-n heterojunction formed between MoTe2 and Co3O4.

Highly sensitive and rapidly responding room-temperature NH3 gas sensor that is based on exfoliated black phosphorus

Black phosphorus (BP) has recently attracted significant interest in gas sensing because of its outstanding electronic and optical properties. In this paper, we demonstrated a series of gas sensors for detecting NH3 at room temperature that were based on BP nanosheets that were exfoliated for various durations. The BP nanosheet gas sensors showed excellent sensitivity for the detection of NH3 down to 100 ppb (~32%) under ambient conditions compared to previous reports. The BP nanosheets that were exfoliated for 60 min showed the highest response to 100 ppm NH3, namely, 121%, which was 2.5 times greater than the response of ground BP. The corresponding sensor also exhibited a relatively stable response in humidity between 22% RH and 35% RH. Moreover, the prepared NH3 gas sensor showed high selectivity, fast response and recovery, and excellent repeatability. According to various experimental and theoretical studies, the response and binding energy of BP towards NOx were higher than those towards NH3. However, very interestingly, the response of the exfoliated BP nanosheets to NH3 was higher than that to NOx in our work. The selectivity transformation from NOx to NH3 was mainly caused by the different layer spacing of the ground BP and the change in spacing between the BP nanosheet layers with different exfoliation times, increased oxygen incorporation, phosphate ions and defects that is induced by the liquid-phase exfoliation process, which led to the variations in its band gap and surface states.

Fabrication of noble metal (Au, Ag, Pt)/polythiophene/reduced graphene oxide ternary nanocomposites for NH3 gas sensing at room temperature.

Room temperature NH3 gas sensors composed of noble metal (Au, Ag or Pt)/polythiophene/reduced graphene oxide (Au, Ag or Pt/PTh/rGO) ternary nanocomposite films were fabricated using a simple one-pot redox reaction. The surface morphology and composition of Au, Ag or Pt/PTh/rGO ternary nanocomposite films were analyzed using Fourier transform infrared spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Compared with Ag/PTh/rGO and Pt/PTh/rGO ternary nanocomposite films, obviously bright Au nanoparticles were observed on the surface of the massive lamination PTh film which wrapped the rGO, and encapsulated Au nanoparticles were observed in the Au/PTh/rGO film. Comparative gas sensing results showed that the Au/PTh/rGO ternary nanocomposite film had the highest response compared with Ag/PTh/rGO and Pt/PTh/rGO ternary nanocomposite films at room temperature, especially when the testing concentration of NH3 gas was below 5 ppm. The Au/PTh/rGO ternary nanocomposite film also had a fast response time and good reproducibility. The combination of the high catalytic activity of naked Au nanoparticles and the formation of effective carrier transfer channels by encapsulated Au nanoparticles was responsible for the improved response of the Au/PTh/rGO ternary nanocomposite film.

Highly Sensitive and Rapidly Responding Room-Temperature Nh3 Gas Sensor that is Based on Exfoliated Black Phosphorus

Highly Sensitive and Rapidly Responding Room-Temperature Nh3 Gas Sensor that is Based on Exfoliated Black Phosphorus

Highly Sensitive and Rapidly Responding Room-Temperature Nh3 Gas Sensor that is Based on Exfoliated Black Phosphorus

Highly Sensitive and Rapidly Responding Room-Temperature Nh3 Gas Sensor that is Based on Exfoliated Black Phosphorus

Facile fabrication of spinel structured n-type CuAl2O4 thin film with nano-grass like morphology by sputtering technique

This article describes a facile fabrication of spinel structured n-type CuAl2O4 thin film with nano-grass like morphological feature by radio frequency (RF) magnetron sputtering technique and the direct realization of this structure as room temperature NH3 gas sensor. X-ray diffraction (XRD) study confirmed the predominant presence of cubic phase CuAl2O4 in the homemade sputtering target and also in the fabricated films. X-ray photoelectron spectroscopic (XPS) investigation confirms the formation of Al3+ and Cu2+ chemical states in the films. Purity and stoichiometry of the deposited films were further confirmed by energy dispersive X-ray spectroscopy (EDX). A randomly aligned nano-grass like morphology with diameters of 25–100 nm and lengths in the range of 0.5 to 2 μm was observed for the film deposited with 300 W sputtering power on quartz substrate by FESEM study, which provides more reaction sites for gas molecules due to their high aspect ratios (length/diameter). The gas sensing measurements revealed that the prepared n-type CuAl2O4 thin films exhibited superior sensing performance towards ammonia gas in terms of high sensor response, quick response time and recovery time, high sensitivity, long stability, and good reproducibility even at room temperature operation condition. Therefore, we believe that the prepared n-type CuAl2O4 thin films have potential for the detection of ammonia gas leaks in chemical industries.

High-performance room temperature NH3 gas sensors based on polyaniline-reduced graphene oxide nanocomposite sensitive membrane

In this study, polyaniline-reduced graphene oxide (PANI-rGO) nanocomposite films were used as sensitive membranes in NH3 gas sensors operated at room temperature (300 K). The responsivity and response speed of the PANI-rGO NH3 gas sensors were improved by homogeneously distributing PANI nanospheres on both surfaces of rGO nanosheets. The optimal weight ratio was 125 which was obtained by changing the weight ratio of PANI/rGO in the NH3 gas sensors. The NH3 gas sensors based on rGO and PANI sensitivity membranes had responsivities of 0.5% and 8.3%, whereas the recovery times were 8.0 and 48.0 min, respectively. The optimal responsivity and recovery time of these PANI-rGO NH3 gas sensors operated at room temperature under a 15-ppm NH3 gas environment were 13.0% and 22.1 min, respectively. However, because the responsivity of a rGO sensing membrane was considerably less than that of a PANI sensing membrane, the responsivity of the PANI-rGO NH3 gas sensors was reduced by incorporating more rGO content. The lowest detectable NH3 gas concentration of the PANI-rGO NH3 gas sensors was 0.3 ppm.

Reduced graphene oxide-CuFe2O4 nanocomposite: A highly sensitive room temperature NH3 gas sensor

Sensitive and selective detection of NH3 at room temperature is required for proper environmental monitoring and also to avoid any health hazards in the industrial areas. Towards this objective, a low-cost, one-step and combustion route mediated reduced graphene oxide (rGO)-CuFe2O4 nanocomposite was exploited as a high–performance NH3 gas sensor by combining the excellent electrical properties of rGO and sensing capabilities of CuFe2O4. This nanocomposite was characterized using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM) and N2 adsorption-desorption analysis. The TEM images demonstrate the uniform distribution of the nanoparticles on the rGO surface and high-resolution transmission electron microscopy (HRTEM) confirms an average particle size of 15–20 nm. The designed sensor can detect NH3 at low concentrations up to 5 ppm at room temperature. Besides high sensing ability, the designed nanocomposite showed good recyclability suggesting its potential applications for the detection of environmentally toxic gases. The enhanced sensing behavior can be attributed to the synergistic behavior between individual rGO and CuFe2O4 component.

Elaboration of Pd-nanoparticle decorated polyaniline films for room temperature NH3 gas sensors

This study introduces an effective method of decorating noble metal palladium (Pd) nanoparticles on the surface of polyaniline (PANi) to enhance NH3 gas-sensing performance. The surface structure analysis conducted through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the diameters of the synthesized PANi nanowires were 50–100nm. The chemical composition structure of the PANi composites was studied by Raman spectroscopy. Energy-dispersive X-ray spectroscopy (EDS) was applied to identify the composition of modified Pd on the PANi composite surface. The obtained results demonstrate the applicability of the PANi composites to improve the sensitivity, response time, and recovery time of NH3 gas sensors.

SnO2/SnS2 nanotubes for flexible room-temperature NH3 gas sensors

Composite SnO2/SnS2 nanotubes were synthesized via an in situ hydrothermal sulfuration process and were used as sensing elements for flexible room-temperature NH3 gas sensors.

Highly sensitive room temperature ammonia gas sensor based on Ir-doped Pt porous ceramic electrodes

Room temperature NH3 gas sensors based on Pt and Pt-Ir (Ir doping Pt) porous ceramic electrodes have been fabricated by both electroplating and sputtering methods. The properties of the gaseous ammonia sensors have been examined by polarization and chronoamperometry techniques. The influence of humidity on the features of the resulting sensors in the system has also been discussed, and the working potential was optimized. Water vapors seem to hugely improve the electrochemical activity of the electrode. With increasing the relative humidity, the response of the Pt-Ir(E)/Pt(S)/PCP sensor to NH3 gas could be enhanced remarkably, and the sensitivity increases from 1.14 to 12.06μAppm−1cm−2 .Then we have also discussed the sensing mechanism of the Pt-Ir sensor and the result has been confirmed by X-ray photoelectron spectroscopy of the electrode surface before and after reaction in the end.

NH3 gas sensor based on Pd/SnO2/RGO ternary composite operated at room-temperature

Novel room-temperature NH3 gas sensors based on Pd, tin oxide (SnO2) and reduced graphene oxide (RGO) ternary nanocomposite (Pd/SnO2/RGO) film were fabricated by the one-pot route. The Pd/SnO2/RGO ternary nanocomposite films were characterized by Fourier transform infrared spectroscopy (FTIR), Raman, X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Microstructural observations revealed that the Pd and SnO2 nanoparticles easily and homogeneously attached to the surface of RGO. The sensor that was based on a Pd/SnO2/RGO ternary nanocomposite film responded strongly to low concentrations of NH3 gas at room-temperature. Its better sensor sensitivity than that of the pristine of SnO2 and SnO2/RGO nanocomposite film was related to the higher conductivity and catalytic activity of the Pd/SnO2/RGO ternary nanocomposite film.

Room-temperature NH3 gas sensors based on Ag-doped γ-Fe2O3/SiO2 composite films with sub-ppm detection ability

In this report, NH3 gas sensors based on Ag-doped γ-Fe2O3/SiO2 composite films are investigated. The composite films were prepared with a sol–gel process, and the films’ electrical resistance responded to the change of NH3 concentration in the environment. The SEM and AFM investigations showed that the films had a porous structure, and the XRD investigation indicated that the size of Ag particles changed with the modification of Ag loading content. Through a comparative gas sensing study among the Ag-doped composite films, undoped composite film, γ-Fe2O3 film, and SiO2 film, the Ag-doped composite films were found to be much more sensitive than the sensors based on the undoped composite film and γ-Fe2O3 film at room temperature, indicating the significant influences of the SiO2 and Ag on the sensing property. Moreover, the sensor based on Ag-doped (4%) γ-Fe2O3/SiO2 composite film was able to detect the NH3 gas at ppb level. Conversely, the responses of the sensor to other test gases (C2H5OH, CO, H2, CH4 and H2S) were all markedly low, suggesting excellent selectivity.

Single-layer MoSe2 based NH3 gas sensor

High performance chemical sensor is highly desirable to detect traces of toxic gas molecules. Two dimensional (2D) transition metal dichalcogenides (TMDC) semiconducting materials has attracted as high performance gas sensor device applications due to unique properties such as high surface to volume ratio. Here, we describe the utilization of single-layer MoSe2 as high-performance room temperature NH3 gas sensors. Our single-layer MoSe2 based gas sensor device shows comprehensible detection of NH3 gas down to 50 ppm. We also confirmed gas sensing measurement by recording the Raman spectra before and after exposing the device to NH3 gas, which subsequently shows the shift due to charger transfer and analyte gas molecule adsorption on surface of single-layer MoSe2 nanosheet. Our investigations show the potential use of single-layer and few layer thick MoSe2 and other TMDC as high-performance gas sensors.