NH3 Detection Research Articles

Investigation of a flexible, room-temperature fiber-shaped NH3 sensor based on PANI-Au-SnO2.

A sensitive compound was successfully obtained by coating polyaniline (PANI) on the surface of composite nanoparticles consisting of Au-loaded tin dioxide, named as PANI-Au-SnO2, using an in situ polymerization method. NH3 sensors in thin-film and fiber-shaped forms were prepared by inkjet printing and impregnation methods, respectively, based on PANI-Au-SnO2. The response characteristics of these NH3 sensors developed from composite sensitive materials were investigated in detail. Results indicate an effective response of the sensors to NH3 at room temperature. The thin-film sensor demonstrated a good linear relationship between the resistance change and NH3 concentration within the range of 5-40 ppm, indicating its excellent repeatability and long-term stability. In comparison to the thin film sensor, the fiber-shaped sensor showed a consistently stable response to NH3 even after 1000 cycles of repeated bending deformation. To demonstrate the practical application of the flexible fiber-shaped NH3 sensor, a cap designed for NH3 detection was fabricated by integrating the as-prepared sensor with a circuit board and an LED digital display. This assembly was incorporated into a commercially available ducktail cap, resulting in a wearable device capable of dynamically monitoring environmental NH3 levels and displaying real-time values. This innovative application underscores the potential of these sensors in real-world scenarios, particularly in occupational safety, where workers might be exposed to harmful levels of NH3. The cap could serve as a personal safety device, alerting the wearer to hazardous concentrations of NH3, which is particularly relevant in industrial or agricultural settings.

TPU-Supported Ti3C2Tx/TiO2/Ru electrospun mat towards flexible and multi-functional sensors for human motion and NH3 detection

Nowadays, the demand for smart wearable devices has been increasing significantly. Integrating multiple functions into a single sensor has become a continuous challenge for researchers. To address these issues, a novel two-dimensional material, MXene (Ti3C2Tx), is now being utilized to fabricate flexible multifunctional sensors. TPU (thermoplastic polyurethane) fiber mats are prepared through electrospinning. Using TPU fiber mats as the substrate, MXene/TiO2/Ru composites are synthesized through a simple and effective method and loaded onto the fiber mats. Experimental tests have revealed that the TPU/MXene/TiO2/Ru flexible sensor exhibits characteristics such as a large stretching range, good durability, high sensitivity, and excellent breathability. The response of the TPU/MXene/TiO2/Ru flexible sensor can reach up to 80.4 k when it is stretched to 120 % of its original length at a stretching speed of 0.5 mm/s. Moreover, this sensor can be used to detect movements in human wrists, arms, faces, legs, fingers, and even vocal cord vibrations, responding to voice recognition through specific word combinations. Furthermore, this sensor exhibits a maximum response of 15.06 % to 100 ppm NH3 at room temperature, accompanied by high selectivity and stability, indicating its excellent multifunctionality in the fields of human health and environmental protection.

An electrostatically spun cellulose-based self-powered mask with high efficiency air filtration and ammonia sensing

On construction sites impacted by particulate matter and hazardous gases, portable integrated air filtration equipment with high efficiency, minimal pressure drops and ammonia (NH3) alarms is critical. Triboelectric nanogenerators (TENG) present a sustainable solution by generating self-powered electricity to fulfill these requirements. In this study, we synthesized zeolitic imidazolate framework-8 (ZIF-8) in situ on the surface of titanium carbide (Ti3C2Tx) to create Ti3C2Tx/ZIF-8, grafted it onto cellulose diacetate via tetraethyl orthosilicate, and ultimately developed a cellulose-based nanofibrous membrane through electrospinning, combining it with a negative triboelectric material to construct a self-powered TENG-based mask. The device achieved a balance between a low pressure drop (61 Pa) and high filtration efficiency (99.21 %, 99.71 %, and 99.98 % for PM0.3, PM0.5, and PM1, respectively). Furthermore, the device responds swiftly to NH3; at a concentration of 100 ppm NH3, it achieves a rapid response rate of 83 %, with a response/recovery time as low as 12/14 s. Notably, the device retains its rapid sterilization capability within a short duration (20 min) and demonstrates remarkable stability across its various performance metrics, even after multiple washes. This study presents a novel approach to the development of multi-use, self-powered wearable devices featuring excellent air filtration performance and NH3 detection capabilities.

Pt-modified hollow tube-like polyaniline-based NH3 sensor

Polyaniline (PANI) has significant applications in room-temperature NH3 detection due to its unique and reversible doping-dedoping chemical state, stable electrical conductivity and easy and convenient synthesis process. However, pristine PANI still suffers from poor performance in terms of sensitivity, response speed and detection limit. To address issues of low sensitivity and high detection limit, a platinum (Pt)-modified hollow PANI (Pt-PANI) sensor was designed. The Pt-PANI was fabricated by an in-situ sacrificial template method, and Pt-MnO2 nanowires obtained from hydrothermal combined impregnation methods, utilizing the potential generated during the sacrificial reaction with acid to induce the polymerization of aniline on the nanowires' surfaces. This hollow tube-like structure with the unique inlay of Pt particles provides numerous gas diffusion pathways, facilitating the penetration of the target gas into the internal space, enhancing the utilization of the inner surface and accelerating the electron transfer. Meanwhile, the presence of Pt particles not only forms Schottky junctions that cause large changes in the resistance of the composites, but also catalysis and accelerates the gas sensing reaction between the target gas and the sensitive materials. Gas sensitivity tests revealed that the prepared Pt-PANI-3 gas sensor exhibits a low NH3 detection limit of 20.3 ppb, along with reproducibility and long-term stability. Compared to pure PANI-sensor, the sensitivity to 20 ppm NH3 increased by 17 times. This work offers real-time sensing and monitoring of environmental changes, making it highly promising for future applications.

Ni-doped (MoO3/MoS2) heterostructure chemiresistive sensor for dual selective detection of NH3 and NOx at room temperature

The transition metal dichalcogenide heterostructures are emerging as promising candidates for room-temperature gas sensors. This work presents a Ni-doped (MoO3/MoS2) heterostructure, synthesized via hydrothermal methods with varying Ni concentrations, for the dual selective detection of NH3 and NOx gases. The electronic sensitization of Ni improves the sensitivity of heterostructure. The heterostructure was characterized by using X-ray diffractometer, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM), with Ni incorporation confirmed by X-ray photoelectron spectroscopy (XPS). The 10 % Ni-doped MoO3/MoS2 heterostructure showed high sensitivity, achieving responses of 15 % and 18.3 % towards 10 ppm NH3 and NOx, respectively, with detection limits of 0.13 ppm and 0.11 ppm. Furthermore, the sensor demonstrated outstanding cyclic stability, device-to-device reproducibility, and long-term stability, with a retained response of 98.1 % and 98.5 % towards NH3 and NOx, respectively. These findings highlight the potential of Ni-doped (MoO3/MoS2) heterostructures for dual gas sensing applications at room temperature.

Room temperature gas sensors for NH3 detection based on the heterojunction of 2D Ti3C2Tx MXenes and Bi2S3.

Bi2S3/Ti3C2Tx nanomaterials were successfully prepared through a simple hydrothermal method. Various methods were used for their characterization, including XRD, XPS, SEM, EDS, and BET, along with testing their gas-sensing properties. The results showed that the response value to 100ppm ammonia at room temperature reached 107%, which was 14.1 times higher than that of pure few-layer MXene. After undergoing anti-humidity interference testing, we observed that Bi2S3/Ti3C2Tx exhibited a higher response value in real-time monitoring of ammonia as humidity increased. Specifically, under 90% humidity conditions, its response value reached 1.32 times that of normal humidity conditions. This exceptional moisture resistance ensures that the sensor can maintain stability, and even exhibit superior performance, in harsh environments. Therefore, it possesses excellent selectivity, high-moisture-resistance, and long-term stability, making it significant in the field of medical and health monitoring.

High-performance PANI sensor on silicon nanowire arrays for sub-ppb NH3 detection

For industrial production and disease diagnosis, real-time detection of low concentrations of NH3 is crucial, necessitating a gas-sensitive sensor compatible with integrated processes and exhibiting excellent performance. Herein, we employed wet etching and rapid in-situ polymerization on silicon nanowire substrates to grow polyaniline fibers, thereby fabricating NH3 gas sensors with p-p heterojunction and three-dimensional network structures. Characterization and gas sensing performance testing were conducted. The results demonstrate the outstanding NH3 detection capabilities of the sensor, providing stable responses down to concentrations as low as 1 ppb, which indicates its LOD is one to two orders of magnitude lower than current similar products. It also exhibits verified selectivity and long-term reliability. The excellent sensing performance is attributed to the high surface area from the silicon nanowire structure and efficient synergy of p-p heterojunction. Additionally, the influence of doping types of the substrates and annealing process were explored. This work serves as a reference for the design of silicon-based gas sensors with high sensitivity, low detection limits, and extended operational lifetimes, suitable for deployment in commercial integrated monitoring systems.

Investigation of CuO/Co3O4/PSi thin films for ultrafast detection of NH3 at room temperature

In this study, CuO/Co3O4/PSi thin films were fabricated and tested for NH₃ vapor detection at room temperature. The CuO/Co3O4 nanocomposite was successfully synthesized by the simple nitrate method and subsequently deposited on porous silicon (PSi) using the thermal evaporation technique. Spectral, structural, morphological, and optical characterizations were performed employing scanning electron microscopy (SEM), atomic force microscopy (AFM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and spectrophotometry (UV–vis). The electrical parameters of the CuO/Co3O4/PSi system, including current-voltage (I-V), sensitivity-voltage (S-V), sensivity-concentration (S-C), and current-time (I-t), were measured at room temperature in the presence of ammonia vapor. The sensor exihibited remarkable sensitivity towards NH₃ (with a response of 200 % at 170 ppm), along with short response times of 3 s and 4 s at 68 ppm and 340 ppm, respectively, and very fast recovery time of 1 s at both concentrations. Furthermore, the mechanisms for NH3 vapor sensing based on CuO/Co3O4/PSi were described. The obtained results emphasize the critical significance of the CuO/Co3O4 nanocomposite deposited on PSi in improving ammonia detection efficiency at room temperature.

Low temperature ammonia sensor with giant sensitivity and selectivity based on W@WO2.92 internal ohmic contact core-shell nanostructures

Ammonia (NH3) detection is crucial for both harnessing hydrogen energy and safeguarding public health. However, the NH3 sensors based on semiconductors is currently constrained by their necessity to operate at elevated temperatures and their limited ability to distinguish NH3 from other gases. In this study, the high oxygen vacancy W@WO2.92 core-shell nanostructures have been synthesized by pulsed laser ablation in water. The gas sensors based on W@WO2.92 nanoparticles response to NH3 with high sensitivity (|Ra-Rg|/Ra=72.6 %@100 ppm, Ra and Rg represent the resistance of the material when exposed to air and the test gas, respectively.) at room temperature with detection limit of 730 ppb. Additionally, the response to NH3 can achieve 55 % even at 5℃, which plays a great role in timely detection of NH3 during low temperature transportation. Furthermore, the sensors reveal outstanding selectivity toward NH3 in the presence of 11 other potential interfering gases. This research presents a groundbreaking strategy, holding significant potential for the development of high-performance NH3 sensors that operate efficiently at low temperatures.

Two-dimensional p-n heterojunctions of black phosphorus nanosheet-sensitized α-MoO3 nanoflake for low-temperature chemiresistive NH3 recognition

Of diverse NH3 gas-detection strategies applied in the fields of individual healthcare and industrial production, chemiresistive gas sensors gain the most popularity owing to the superior merits of low cost, convenient signal processing and high sensitivity. However, severe challenges still exist such as elevated operation temperature (>200 °C), limited sensitivity and unsatisfactory selectivity especially under low-concentration and high-humidity conditions. To overcome these hindrances, a sensing layer of black phosphorus nanosheets (BP)-modified α-MoO3 nanoflakes was prepared in this work. After subtle optimization of ingredient composition and operation temperature, the composite sensor S2 could recognize NH3 gas with the concentration spanning from 0.4 to 25 ppm at 40 °C. In particular, a larger mean response (27 % vs. ∼ 2.3 %) with a response/recovery speed of 275/388 s toward 10 ppm NH3 and lower detection of limit (LoD, 0.4 ppm vs. 10 ppm) was achieved with respect to pure BP counterpart. In addition, excellent repeatability, selectivity, long-term stability and humidity-tolerant features were demonstrated for Sensor S2. The improved sensing performance after α-MoO3 incorporation was primarily ascribed to abundant p-n heterojunctions, excellent conductivity of BP and hydrophilic MoO3 that mitigated the water corrosion effect on susceptible BP nanosheets. This work offers an alternative strategy for sensitive and low-temperature NH3 detection, and well cater for the demanding requirements of high sensitivity and low-power consumption in the field of novel gas sensors applicable in the future Internet of Things and exhaled breath-oriented medical diagnosis.

Fe(OH)3/Ti3C2Tx nanocomposites for enhanced ammonia gas sensor at room temperature

Two-dimensional material (2D material) MXene has great application potential in gas sensors because of its excellent controllable performance and vast specific surface area. In this study, we used a straightforward in-situ electrostatic self-assembly technique to create Fe(OH)3/Ti3C2Tx nanocomposites, which were then used to fabricate gas sensors for ammonia detection at room temperature (25 ℃). Several characterization methods were performed aimed at determining the surface appearance and construction of the nanocomposites, and the sensing characteristics and mechanism were also systematically examined. The findings demonstrate the effective incorporation of amorphous Fe(OH)3 nanoparticles on the surface of Ti3C2Tx. Additionally the nanocomposites of Fe(OH)3/Ti3C2Tx have considerably higher specific surface area than pure Ti3C2Tx, hence offering more active NH3 adsorption sites. The response of the sensor to 100 ppm NH3 was 48.6% at room temperature, which was 9.3 times more higher than that of pure Ti3C2Tx. The sensors also have the advantages of long-term stability (33 days), low NH3 detection limit (500 ppb), and rapid recovery time (85 s) and response times (78 s). It is anticipated that this work will be helpful for developing the new generation of wearable ammonia sensors at room temperature.

In situ generation of cuprous oxide in metal-organic framework for significantly enhanced room-temperature ammonia sensing: Synergy enabling excellent sensitivity and selectivity

Development of effective strategies to improve the response sensitivity of metal-organic frameworks (MOFs) to target gases is imperative to further enhancing their application potential in gas sensing. In this work, series of CuHHTP/Cu2O (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) composites are successfully constructed by in-situ electrochemical reduction treatment of CuHHTP, and the changing trend of first increasing and then decreasing with increase of CuHHTP electrochemical reduction degree for their sensitivity to NH3 detection is revealed. When the average size of Cu2O nanoparticles generated in CuHHTP is 3.6 nm, the corresponding CuHHTP/Cu2O-A composite exhibits the best NH3 sensing performance compared to pristine CuHHTP, including significantly enhanced response sensitivity, ultralow experimental detection limit of 10 ppb, superior selectivity, good reproducibility, and excellent response stability even after placed for 90 days. More impressively, thanks to integration and synergy of the uniformly-dispersed small-sized Cu2O nanoparticles with significantly enhanced adsorption activity and capacity for NH3, the released large amount of uncoordinated hydroxyl groups that can interact with NH3, as well as the active sites of the CuHHTP substrate itself, the 10 ppb experimental detection limit for the CuHHTP/Cu2O-A-based sensors is not only the lowest one reported in the past 10 years for NH3 sensors based on copper-containing MOF and oxide materials, but also superior to that of 0.1–1 ppm for the existing commercial NH3 sensors. This work opens the avenue for design and development of novel MOF-based sensing materials.

Detection of CO2, H2S, NH3, and gas mixtures using a quartz crystal microbalance sensor array with five sensitive materials

The large-scale development of chicken farms has inevitably led to an increase in the emission of harmful gases, which has prompted rapid research development on the detection of harmful gases, such as quartz crystal microbalance (QCM) sensors. In this research, a QCM sensor array modified with ethyl cellulose (EC), polyethyleneimine (PEI), polypyrrole (PPy), tetramethylammonium fluoride tetrahydrate (TMAF), and Nitrogen-doped tungsten carbide supported on carbon nanosheets (WC@NC) was established to detect gas mixtures. By analyzing the relationship between the fundamental frequency shift and the number of sensitive material layers for the QCM sensor, the optimal number of layers was determined. The QCM sensor array consisted of a blank QCM sensor, an 8-layer EC sensor, a 4-layer PEI sensor, a 3-layer PPy sensor, an 8-layer TMAF sensor, and an 8-layer WC@NC sensor. The results showed that the PEI sensor exhibited maximum frequency shifts when detecting gases, while TMAF and WC@NC films had the highest contribution to NH3 detection. TMAF, PEI, and WC@NC played significant roles in the binary classification of exceeding the standard detection of NH3. Additionally, WC@NC and EC sensors played an important role in detecting H2S and CO2, respectively. The QCM sensor array could accurately classify the excessive state of CO2. Overall, the QCM sensor array demonstrated a correct recognition rate of 87.5 %, indicating its potential for classifying the exceedance of NH3, CO2, and H2S gases in gas mixtures. This work provides basic information for research on QCM sensor arrays in gas detection.

Fabrication of TPU-Supported Au-Bi2S3/Ti3C2Tx electrospun mat: Towards flexible and Multi-functional sensors for human motion and NH3 detection at room temperature

The potential applications of wearable sensors in health monitoring, micro-environment detection, and advanced soft electronic noses have attracted widespread attention. However, due to the inherent limitations of traditional organic flexible substrates, simultaneously achieving excellent flexibility, high sensitivity, robustness, and breathability remains a significant challenge. Herein, using the electrospinning method, a flexible TPU substrate film was prepared, and Bi2S3/Ti3C2Tx nanocomposite materials were synthesized through a simple one-step hydrothermal method. Au nanoparticles were attached to the surface of the composite material using sodium borohydride, and finally, the surface impregnation method was used to successfully prepare the Au-Bi2S3/Ti3C2Tx-TPU flexible electrospun mat. The as-prepared sensor demonstrated an outstanding response of 154 % to 100 ppm NH3 at room temperature, coupled with high selectivity, repeatability, and long-term stability. The strain properties of the sensor were also evaluated, showcasing its potential for human motion and physiological feature detection, such as breathing, swallowing, and limb movements. The study’s findings indicated that the Au-Bi2S3/Ti3C2Tx-TPU electrospun mat sensor has promising applications in flexible electronics, wearable environmental monitoring devices, and human healthy monitoring.

Preparation and Ammonia Sensing of Copper Iodide Nanomaterials Combined with Copper Iodide‐Isopropanolamine Complexes

AbstractWith the increasing awareness of the hazards associated with ammonia (NH3) contamination and the potential application of NH3 detection in physical health monitoring, the exploration of high‐performance NH3 sensors has attracted significant attention in recent years. In this paper, we prepared copper iodide (CuI) nanomaterials combined with CuI‐isopropanolamine (C3H9NO) complexes by dissolving CuI in C3H9NO and subsequent annealing. The resulting product demonstrated exceptional sensing performance to 0.15 (mole fraction) NH3, exhibiting a maximum response of 7.5×105 with a response time of 5 s. The achieved detection limit was 10 ppm. Our findings provide a valuable reference for further research on NH3 sensors utilizing complexes formed by copper compounds and organic amines.

Novel Gas Sensing Approach: ReS2/Ti3C2Tx Heterostructures for NH3 Detection in Humid Environments.

Continuous monitoring of ammonia (NH3) in humid environments poses a notable challenge for gas sensing applications because of its effect on sensor sensitivity. The present work investigates the detection of NH3 in a natural humid environment utilizing ReS2/Ti3C2Tx heterostructures as a sensing platform. ReS2 nanosheets were vertically grown on the surface of Ti3C2Tx sheets through a hydrothermal synthetic approach, resulting in the formation of ReS2/Ti3C2Tx heterostructures. The structural, morphological, and optical properties of ReS2/Ti3C2Tx were investigated using various state-of-the-art techniques, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, zeta potential, Brunauer-Emmett-Teller technique, and Raman spectroscopy. The heterostructures exhibited 1.3- and 8-fold increases in specific surface area compared with ReS2 and Ti3C2Tx, respectively, potentially enhancing the active gas adsorption sites. The electrical investigations of the ReS2/Ti3C2Tx-based sensor demonstrated enhanced selectivity and superior sensing response ranging from 7.8 to 12.4% toward 10 ppm of NH3 within a relative humidity range of 15-85% at room temperature. These findings highlight the synergistic effect of ReS2 and Ti3C2Tx, offering valuable insights for NH3 sensing in environments with high humidity, and are explained in the gas sensing mechanism.

Optical chemical gas sensor based on spectral autocorrelation: A method for online detection of nitric oxide and ammonia in exhaled breath

The detection of nitric oxide (NO) and ammonia (NH3) in exhaled breath (EB) plays a crucial role in non-invasive diagnosis of airway inflammatory and kidney diseases. Here we report an optical chemical gas sensor for NO and NH3 based on spectral autocorrelation. In our sensor system, the target gas is removed through a chemical reaction with a sensing material and the spectrum of the target gas is extracted from the spectra obtained before and after the reaction by autocorrelation. Our method focuses on the ability of the material to eliminate the target gas without the need for detecting signals of the reaction, greatly relaxing the requirements on material properties. Fundamentally different from optical sensors that obtain spectra by spectral decoupling, our sensor relies on autocorrelation operation to acquire the spectrum of the target gas, thereby overcoming spectra overlap. Lab-based results show that the sensor enables detection of NO (2.28–451.82 ppb) and NH3 (11.52–12,725.42 ppb) with mean absolute errors (MAEs) of 0.79 ppb and 6.13 ppb and measurement accuracies of 0.8 % and 1.4 %, respectively. The EB experiment proves that the sensor can detect exhaled NO and NH3 and distinguish EB between healthy subjects and simulated patients.

Captivating 2H-MoS2 nanoflowers for efficient NH3 detection and photocatalytic dye degradation

This research unveils the gas sensing and photocatalytic potential of 2H-MoS2 nanoflowers, offering a promising solution for ammonia sensing and wastewater remediation. The 2H phase of MoS2 nanoflowers is synthesized via a simple one-step hydrothermal method using ammonium heptamolybdate and thiourea. The elemental and morphological study confirms the formation of the 2H phase of MoS2 nanoflowers with an average sheet thickness of 14 nm. The XRD and HR-TEM analysis findings are in good accordance with the interlayer spacing of MoS2, calculated to be 0.64 nm. The 2H-MoS2 nanomaterial based chemiresistive sensor is tested for six different targets (NH3, C2H5OH, C3H6O, C3H7OH, HCHO, and C6H5CH3) and shows good selectivity towards ammonia (NH3) with the highest response of 81 %. The response-recovery time, repeatability, concentration, and humidity-based analysis are conducted for the analysis of the sensor. The fabricated 2H-MoS2 based sensor shows a response time of 8.5 s and a recovery time of 4.3 s. Furthermore, three model water contaminated dyes, MB, MO, and RB, are chosen for the photocatalytic experiment under visible light irradiation. The reusability, relative degradation, and pseudo-first-order analysis are used to evaluate the photocatalytic dye degradation properties of 2H-MoS2 nanoflowers. The reaction rate constant of 2H-MoS2 nanomaterials for MB, MO, and RB dyes is calculated to be (0.05010) min−1, (0.03458) min−1, and (0.02516) min−1, respectively. The maximum degradation efficiency of 2H-MoS2 nanoflowers towards MB, MO, and RB dye is 95 %, 86 %, and 76 %, respectively, under visible light irradiation. These findings suggest that the hydrothermally synthesized 2H-MoS2 nanoflowers have multifunctional applications such as effective NH3 sensors as well as photocatalysts for organic dye degradation, paving the way for more efficient and sustainable gas sensing and wastewater treatment technologies.

An ultrafast optical sensor for simultaneous detection of NH3 temperature and concentration based on ultraviolet absorption spectral redshift combined with spectral reconstruction

As a renewable and carbon-free fuel with high energy density, ammonia (NH3) is a promising alternative to fossil fuels. Real-time detection of its temperature and concentration is significant in improving NH3 combustion efficiency. In this paper, we report an optical sensor, which enables simultaneous measurement of temperature and concentration of NH3. The key idea is to acquire the temperature of NH3 through absorption spectral redshift, and determine its concentration by building three-dimensional field map combined with spectral reconstruction. Firstly, we explain the generation mechanism of temperature-induced redshift in ultraviolet differential absorption spectrum based on energy level distribution theory. The relationship between spectral redshift and temperature is then established using spectral autocorrelation algorithm. Secondly, a spectral reconstruction method based on absorbed intensity mapping wavelength is proposed to ensure real-time detection of NH3. Finally, a three-dimensional field map between temperature, reconstruction slope, and concentration is constructed to achieve the detection. Results indicated that the mean relative error in temperature measurement was 1.04 % and the mean absolute error in concentration detection was 0.26 mg/m3 in air. Additionally, the NH3 sensor enabled long-term detection with a detection limit of 15.50 μg/m2, demonstrating its potential to broaden the application of NH3 as a fuel.

Sensitive detection of NH3 at room temperature at ppb level via facile ZIF calcination

This study introduces an innovative approach for preparing gas sensors involving the formation of metal oxides from metal–organic framework materials via a two-step calcination process. A gas-sensitive material capable of detecting NH3 at a concentration of 11 ppb at room temperature was developed using a simple and facile experimental method. Compared with materials produced in previous studies by one-step calcination, the C-doped ZnO developed in this study had a dispersed cubic porous morphology with a higher specific surface area and smaller pore size. During two-step calcination, urea acts as a structure-directing agent and increases the gas adsorption capacity of the final material. Additionally, the incorporation of urea slightly reduced the material's band gap. Further examinations confirmed the material's exceptional selectivity and long-term stability in detecting NH3, and response tests at 59 %, 75 %, and 85 % relative humidity indicated its tolerance to high-humidity environments. These outstanding characteristics suggest that the proposed fabrication method can produce metal-oxide materials with substantially enhanced gas-sensing performance.