Room Temperature Ammonia Gas Sensor Research Articles

Ammonia Sensing Performance at Room Temperature of Ca-Doped CNFs/Al2O3 Gas Sensor.

When NH3 in the environment exceeds a certain concentration, it may have adverse effects on human health. Ammonia gas sensors currently on the market usually work under high temperatures and are not only expensive but also have poor performance in terms of selectivity. Therefore, the preparation of an ammonia gas sensor that works at room temperature, is low cost, and has high sensitivity and selectivity is particularly important. This paper introduces a room temperature ammonia gas sensor based on a Ca-doped CNFs/Al2O3 nanocomposite material, prepared using electrospinning, pre-oxidation, and carbonization processes. The surface morphology, microstructure, and chemical composition of the materials have been characterized by scanning electron microscopy, Raman, and X-ray photoelectron spectroscopy. The Ca-doped CNFs/Al2O3 gas sensor has excellent selectivity for ammonia at room temperature and low sensitivity to other volatile gases such as ethanol, dimethylformamide, HCl, and methanol. At 100 ppm of NH3, the response value of the Ca-doped CNFs/Al2O3 gas sensor can reach 22.73, demonstrating excellent repeatability and long-term stability. Its performance is not affected by environmental temperature and humidity, providing great convenience for practical applications. In addition, we also discuss the sensing mechanism of the Ca-doped CNFs/Al2O3 gas sensor. This paper not only provides effective materials and methods for the development of high-performance room temperature ammonia gas sensors but is also expected to play a role in the field of environmental monitoring.

Nanofiber-coated quartz crystal microbalance with chitosan overlay for highly sensitive room temperature ammonia gas sensor

Ammonia is toxic and can pose health risks. Ensuring the safety of individuals working with or around ammonia sensors is crucial, adding complexity to the design and use of such sensors. An ammonia gas sensor by quartz crystal microbalance coated with chitosan-overlaid polyvinyl acetate (PVAc) nanofiber has been studied to have high performance in both sensitivity and selectivity. The scanning electron microscope (SEM) and Fourier-transform infrared (FTIR) spectroscopy were used to analyze the sensing surface, which was the electrospun PVAc nanofiber with chitosan overlay. The nanofiber showed a morphological change and had a more active layer after being overlaid by chitosan. The estimation of PVAc nanofiber thickness on the QCM sensor is (12.0 ± 2.1) µm, measured using a digital microscope. The QCM sensor deposited with PVAc nanofiber only had a sensitivity of 0.076 Hz·ppm−1. It improved to 3.012 Hz·ppm−1 after overlaid with 0.7 wt% chitosan (denoted as PVAc/Ch7 sensor), an increase of 39.6 times. Moreover, the PVAc/Ch7 sensor had a rapid response and recovery times of 9 and 35 s with a very low detection limit of 0.526 ppm. The sensor also exhibited good selectivity toward other analytes. In addition, the sensor also had outstanding in other performances, such as linearity, repeatability, reversibility, and excellent long-term stability. This proposed QCM-based ammonia sensor could be an alternative to analyzing ammonia in various fields.

Hierarchical 0D/1D/2D Au/PANI/WS2 ternary nanocomposite NH3 sensor with high performance and fast response/recovery for food spoilage detection

Ammonia (NH3) gas is regarded as a biomarker for clinical diagnosis of various diseases and a potential indicator for the spoilage of protein-rich foods. The acuate detection of the ammonia gas concentration depend on reliable gas sensor. In this paper, flexible room temperature ammonia gas sensor based on hierarchical Au/PANI/WS2 ternary composite was successfully prepared by in-situ polymerization, reduction and drop-coating process. The Au/PANI/WS2-based ammonia sensor was tested for its room temperature sensing property including response value, response/recovery time, selectivity, and long-term stability. The effects of flexible state, humidity and operating temperature on the sensor response were also investigated. The 0D/1D/2D Au/PANI/WS2-based sensor showed significantly enhanced ammonia sensing property both in response and response/recovery time as compared to that of pristine WS2. Gas sensing mechanism of the prepared sensor was investigated by complex impedance spectroscopy and in-situ fourier transform infrared spectroscopy analysis. Besides, the sensor was proved for its practical usability in seafood spoilage detection and warning. The construction of multidimensional materials into hierarchical structure may provide an instructive way for the sensibilization of layered two-dimensional nanomaterial of WS2.

A room-temperature ammonia gas sensor based on the h-MoO3@Graphene composite film with fast response time

The release of ammonia (NH3) in industry or daily life is harmful to human health. A gas sensor was developed using h-MoO3 nanorods and graphene film to detect and eliminate this. The h-MoO3 nanorods were first synthesized by chemical bath deposition using ammonium molybdate tetrahydrate (NH4)6Mo7O24•4H2O and HNO3 and then deposited on the graphene film transferred to SiO2/Si substrate by electrochemical bubbling method. Subsequently, gas-sensitive h-MoO3@Graphene composite films were prepared and analyzed using Raman, XRD, SEM, and UV–vis. The gas sensor's performance was evaluated to detect NH3 at a room temperature concentration range of 1–60 ppm. Compared with graphene, the conductivity of the composite film with 10 mg/ml h-MoO3 nanorods was increased by 40 % and the sensitivity increased by 10 times. The sensor h-MoO3@G-10 showed the best sensing performance to 1 ppm NH3. Sensor sensitivity, response and recovery time are 1.1 %, 46.8 s and 17.8 s.

High response chemiresistive room temperature ammonia gas sensor based on La-doped ZnO samples

The current study describes the excellent sensing properties of zinc oxide samples with varying La doping concentrations (1, 3, and 5 %). The X-ray diffraction (XRD) study suggests that the produced ZnO samples exhibit hexagonal structure. Due to varying concentrations of La, a notable difference in the morphological image of the samples was observed using a Field Emission Scanning Electron Microscope (FESEM). The existence of La, Zn, and O elements in the sample was analyzed by Energy Dispersive X-Ray Analysis (EDX). The Fourier Transform Infrared Spectroscopy (FTIR) studies validate the sample's structure and functional group. The UV–Vis results showed that the maximum optical reflectance of 90 % was attained in the visible region and the obtained band gap values for the samples were in the range of 3.27–3.33 eV. At ambient temperature, the La-doped samples demonstrated high sensitivity towards ammonia (NH3) and had the highest response value of 1940 % for the 250 ppm. According to the results, an excellent operating stability, and response/recovery time were obtained for the ZnO:La1% sample which suggests that the sample can serve as the most appropriate metal oxide for the detection of NH3 at room temperature.

Nitrogen-doped carbon nano-onions/polypyrrole nanocomposite based low-cost flexible sensor for room temperature ammonia detection

One of the frontier research areas in the field of gas sensing is high-performance room temperature-based novel sensing materials, and new family of low-cost and eco-friendly carbon nanomaterials with a unique structure has attracted significant attention. In this work, we propose a novel low-cost flexible room temperature ammonia gas sensor based on nitrogen-doped carbon nano-onions/polypyrrole (NCNO-PPy) composite material mounted low-cost membrane substrate was synthesized by combining hydrothermal and in-situ chemical polymerization methods. The proposed flexible sensor revealed high sensing performance when employed as the sensing material for ammonia detection at room temperature. The NCNO-PPy ammonia sensor exhibited 17.32% response for 100 ppm ammonia concentration with a low response time of 26 s. The NCNO-PPy based flexible sensor displays high selectivity, good repeatability, and long-term durability with 1 ppm as the lower detection limit. The proposed flexible sensor also demonstrated remarkable mechanical robustness under extreme bending conditions, i.e., up to 90° bending angle and 500 bending cycles. This enhanced sensing performance can be related to the potential bonding and synergistic interaction between nitrogen-doped CNOs and PPy, the formation of defects from nitrogen doping, and the presence of high reactive sites on the surface of NCNO-PPy composites. Additionally, the computational study was performed on optimized NCNO-PPy nanocomposite for both with and without NH3 interaction. A deeper understanding of the sensing phenomena was proposed by the computation of several electronic characteristics, such as band gap, electron affinity, and ionization potential, for the optimized composite.

Fabrication of a Fully Printed Ammonia Gas Sensor Based on ZnO/rGO Using Ultraviolet-Ozone Treatment.

In this study, a room-temperature ammonia gas sensor using a ZnO and reduced graphene oxide (rGO) composite is developed. The sensor fabrication involved the innovative application of reverse offset and electrostatic spray deposition (ESD) techniques to create a ZnO/rGO sensing platform. The structural and chemical characteristics of the resulting material were comprehensively analyzed using XRD, FT-IR, FESEM, EDS, and XPS, and rGO reduction was achieved via UV-ozone treatment. Electrical properties were assessed through I-V curves, demonstrating enhanced conductivity due to UV-ozone treatment and improved charge mobility from the formation of a ZnO-rGO heterojunction. Exposure to ammonia gas resulted in increased sensor responsiveness, with longer UV-ozone treatment durations yielding superior sensitivity. Furthermore, response and recovery times were measured, with the 10 min UV-ozone-treated sensor displaying optimal responsiveness. Performance evaluation revealed linear responsiveness to ammonia concentration with a high R2 value. The sensor also exhibited exceptional selectivity for ammonia compared to acetone and CO gases, making it a promising candidate for ammonia gas detection. This study shows the outstanding performance and potential applications of the ZnO/rGO-based ammonia gas sensor, promising significant contributions to the field of gas detection.

1D/2D Heterostructured WS2@PANI Composite for Highly Sensitive, Flexible, and Room Temperature Ammonia Gas Sensor.

Flexible and room-temperature (RT) ammonia gas sensors are needed for exhaled breath detection and recognition. Two-dimensional transition metal disulfides are potential materials for RT gas sensing because of their low band gap and a large number of edge-exposed sites that can provide strong binding to gas molecules. In this work, a 1D/2D heterostructured composite material of 2D tungsten disulfide (WS2) modified with 1D polyaniline (PANI) was proposed. The fibrous PANI adsorbed on the edges and inserted in the interlayers of the laminated WS2 provide more diffusion channels for the ammonia gas and act as sensing sites. The WS2@PANI-based sensor shows high selectivity for ammonia with satisfying reproducibility and long-term stability. A response of 216.3% and a short response/recovery time of 25 s/39 s were achieved for 100 ppm ammonia gas. The sensing mechanism was investigated in detail via complex impedance spectra and in situ FT-IR, which was attributed to the synergistic effect of WS2 and PANI. The excellent sensing performance coupled with its resistance to thermal and humidity interference endows the WS2@PANI-based sensor with potential for human exhaled detection and wearable electronics.

Light-assisted room temperature ammonia gas sensor based on porphyrin-coated V2O5 nanosheets

This study explores the gas-sensing capabilities of light-activated porphyrin-coated V2O5 nanosheets for ammonia detection. The nanosheets were synthesized via a hydrothermal method, heat treatment, and solution dispersion. They were then coated with thin layers of Zn-porphyrin and Cu-porphyrin derivatives. The gas-sensing performance of the porphyrin/V2O5 sensor was evaluated under dark and visible light conditions. The combination of materials significantly improves the sensor's performance compared to pure V2O5 nanosheets sensor. The study also investigated selectivity, temporal stability, and proposed a mechanism for ammonia detection based on the interaction between photo-excited charge carriers and adsorbed gas molecules. With such performance, compact size, cost-effectiveness, and low energy consumption, this sensor holds substantial promise for monitoring freshness and spoilage along food supply chains.

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.

Room Temperature Ammonia (NH3) Gas Sensor based on Molybdenum Disulfide and Reduced Graphene Oxide (MoS2/rGO) Heterojunction.

Nanocomposites based on 2D materials exhibit synergistic behavior at their interfaces, making them a promising candidate for gas sensing applications. The MoS2/rGO nanocomposite used in this study was synthesized using a one-step hydrothermal process. By using X-ray diffraction (XRD), the synthesized composite was thoroughly characterized. The spin coater was used to deposit the nanomaterial thin film onto the glass substrate. The nanocomposite sensing was tested at a 40 ppm concentration of ammonia gas. An increase in ammonia concentration was found to correspond with a rise in the resistance of the sensor. The nanocomposite interface of this sensor enabled it to exhibit a synergistic behavior, resulting in several desirable characteristics, including low power consumption, fast response and recovery times, high selectivity, and a low operating temperature.

A chemiresistive room temperature ammonia gas sensor based on self-assembled PPy/Zntpp

There is an increasing demand for monitoring ammonia in livestock farming, which can prevent livestock products from being contaminated by bacteria and viruses. As a prospective material for resistive sensors, polypyrrole (PPy) still suffers from low sensitivity and poor selectivity. Herein, zinc-tetra(p-sulfonylphenyl) porphyrin (Zntpp) particles are anchored on the PPy network by a one-step mild electrodeposition route to form a resistive sensor with the wrinkle-like nanostructure. The optimal PPy/Zntpp (Pzt) sensor demonstrates an outstanding response value of 104.3 % toward ammonia with a response/recovery time of 42/223 s, compared with that of PPy (7.2 % in response and 47/230 s). The durability and stabilities have been explored, and the limit of detection for Pzt is calculated to be ∼8.63 ppm, which enables trace ammonia in livestock farming. Additionally, the sensing mechanism can be attributed to the p-n heterojunction. Furthermore, a wireless sensor device that consists of a Pzt sensory unit, a microcomputer, and a Bluetooth module is assembled, and the concentration information can be read precisely in real-time by a smartphone, indicating the great application prospects in the field of livestock farming.

Ultrasensitive room-temperature flexible ammonia gas sensor based on Au-functionalized polypyrrole wrapped enriched edge sulfur vacancies MoS2 nanosheets

Au/MoS2/polypyrrole (Au/MoS2/PPy) nanocomposite is successfully synthesized by the liquid-phase ultrasonic exfoliation process combined with in-situ polymerization method and then Au particles are decorated on its surface. Abundant sulfur (S) vacancies in the exfoliated layered MoS2 nanosheets act as active adsorption sites, and Au particles also play an efficient catalyst to enhance the NH3 gas sensing properties of Au/MoS2/PPy flexible sensor at room temperature. It results in higher NH3 gas sensing response, faster recovery rate, and more stable sensing performance even under complex environment conditions such as high relative humidity and high bending angle/numbers compared with that of pristine PPy sensor. The enhancement sensing mechanisms of Au/MoS2/PPy sensor are attributed to the p-n heterojunction between layered MoS2 and PPy, the active sites of S vacancies, the catalysis and dehydrogenation effect of Au particles, which have been verified by XPS, current-voltage (I-V), and in-situ FITR, etc. Moreover, the density-functional theory (DFT) calculations are employed to further illustrate the selectivity sensing mechanism, and reveal the S vacancies, the nanocomposite of MoS2/PPy possess high superiority for improving NH3 sensing properties at room temperature.

Room-temperature ammonia gas sensor based on Ni-doped MoO3 thin film prepared by spray pyrolysis method

Room-temperature ammonia gas sensor based on Ni-doped MoO3 thin film prepared by spray pyrolysis method

UV activated single aligned TiO2 nanofiber embedded silver nanoparticles as room temperature ammonia gas sensor

In this work, by using an electro-spinning process and a secondary electrostatic field on rectangular electrodes, a single-aligned nanofiber of silver nanoparticle (SNP)-TiO2 fabricated for NH3 gas sensing with UV irradiation at room temperature. XRD, FE-SEM and UV spectroscopy adopted for characterization of the single nanofiber. The response of SNP-TiO2 single nanofiber sensor evaluated for 70 ppb to 12 ppm ammonia gas at room temperature up to the optimum temperature of 150 °C. The response of this sensor for 5 ppm ammonia gas is 46.1 at the optimum temperature of 150 °C. However, the response is also evaluated at room temperature under 365 nm UV illumination. The response improved up to 4 times from 11 at dark condition to 45.1 under UV illumination for the ammonia gas concentration of 5 ppm. In addition, UV light exposure led to a considerable reduction in both the response and recovery times. Moreover, the results for detecting other gases such as methanol, ethanol, propanol and water vapor compare to ammonia shows that for SNP-TiO2 sensor the best response is for ammonia gas, whereas its sensitivity to humidity is considerably low (about 9%). This shows the sensor can be used in related applications like breath analysis.

A nanostructured Al-doped ZnO as an ultra-sensitive room-temperature ammonia gas sensor.

Novel chemi-resistive gas sensors with strong detection capabilities operating at room temperature are desirable owing to their extended cycle life, high stability, and low power consumption. The current study focuses on detecting NH3 at room temperature using lower gas concentrations. The co-precipitation technique was employed to produce pure and Al-doped ZnO nanoparticles, which were calcined at 300°Cfor three hours. The effect of aluminium (Al) doping on the structural, morphological, optical, and gas-sensing abilities was investigated and reported. The presence of aluminium was confirmed by XRD, EDX, and FTIR spectroscopy. Additionally, to assess the various characteristics of Al-doped ZnO nanoparticles, scanning electron microscopy (SEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), atomic force microscopy (AFM), and Brunauer-Emmett-Teller (BET) techniques were used. The crystallite size increased from 14.82 to 17.49nm in the XRD analysis; the SEM pictures showed a flower-like morphology; and the energy gap decreased from 3.240 to 3.210eV when Al doping was raised from 1 wt% to 4 wt%. AFM studies revealed topographical information with significant roughness in the range of 230-43nm. BET analysis showed a mesoporous nature with surface areas varying from 25.274 to 14.755 m2/g and pore diameters ranging from 8.34 to 7.00nm. The sensing capacities of pure and Al-doped ZnO nanoparticles towards methanol (CH3OH), toluene (C7H8), ethanol (C2H5OH), and ammonia (NH3) were investigated at room temperature. The one-wt% Al-doped ZnO sensor demonstrated an ultrafast response and recovery times at one ppm compared to other AZO-based sensors towards NH3.

Edge sites enriched vanadium doped MoS2/RGO composites as highly selective room temperature ammonia gas sensors with ppb level detection

Ammonia sensing mechanism of vanadium doped MoS2/RGO composite.

A room temperature ammonia gas sensor based on cerium oxide/MXene and self-powered by a freestanding-mode triboelectric nanogenerator and its multifunctional monitoring application

A high-precision CeO2/V2C sensor for NH3 capable of operating at room temperature is constructed via in situ polymerization and exhibits excellent response and stability, low detection limit, and fast response/recovery time.

Room Temperature Ammonia Gas Sensor Based on p-Type-like V2O5 Nanosheets towards Food Spoilage Monitoring

Gas sensors play an important role in many areas of human life, including the monitoring of production processes, occupational safety, food quality assessment, and air pollution monitoring. Therefore, the need for gas sensors to monitor hazardous gases, such as ammonia, at low operating temperatures has become increasingly important in many fields. Sensitivity, selectivity, low cost, and ease of production are crucial characteristics for creating a capillary network of sensors for the protection of the environment and human health. However, developing gas sensors that are not only efficient but also small and inexpensive and therefore integrable into everyday life is a difficult challenge. In this paper, we report on a resistive sensor for ammonia detection based on thin V2O5 nanosheets operating at room temperature. The small thickness and porosity of the V2O5 nanosheets give the sensors good performance for sensing ammonia at room temperature (RT), with a relative change of resistance of 9.4% to 5 ppm ammonia (NH3) and an estimated detection limit of 0.4 ppm. The sensor is selective with respect to the seven interferents tested; it is repeatable and stable over the long term (four months). Although V2O5 is generally an n-type semiconductor, in this case the nanosheets show a p-type semiconductor behavior, and thus a possible sensing mechanism is proposed. The device's performance, along with its size, low cost, and low power consumption, makes it a good candidate for monitoring freshness and spoilage along the food supply chain.

PTB7 Decorated ZnO-Nanorod-Based Room-Temperature Ammonia Gas Sensor

We demonstrate a poly ([4,8-bis[(2-ethylhexyl) oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl][3-fluoro-2-[(2-et- hylhexyl)carbonyl]thieno[3,4-b] thiophenediyl]) (PTB7) decorated zinc oxide (ZnO) nanorod-based interdigitated metal–semiconductor–metal (MSM) device as ammonia (NH3) sensor at room temperature. The gas sensor response is 66.92% at 20 ppm and 2 V of bias at ambient temperature (~25 °C). The average roughness and the root-mean-square roughness of the hydrothermally synthesized ZnO nanorods (ZnO NRs) were measured as 0.140 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.175 ~\mu \text{m}$ </tex-math></inline-formula> , respectively. The device was found sensitive at gas concentration as low as ~2 ppm with a response of 7.12%. At a gas flow rate of 20 ppm and a bias of 2 V, the response and recovery times of the as-fabricated device were measured to be 5 and 30 s, respectively.