Detection Of Nitrogen Dioxide Research Articles

WO3-Based Thin Films Grown by Pulsed Laser Deposition as Gas Sensors for NO2 Detection.

Thin films based on tungsten oxide (WO3) were grown by nanosecond pulsed laser deposition on alumina printed-circuit boards to fabricate electrochemical sensors for nitrogen dioxide (NO2) detection. Samples exposed to thermal annealing (400 °C for 3 h) were also produced to compare the main properties and the sensor performance. Before gas testing, the morphology and structural properties were investigated. Scanning electron microscopy and atomic force microscopy showed the formation of granular films with a more compact structure before the thermal treatment. Features of the main WO3 phases were identified for both as-deposited and annealed samples by Raman spectroscopy, whereas X-ray diffraction evidenced the amorphous nature of the as-deposited samples and the formation of crystalline phases after thermal annealing. The as-deposited samples showed a higher W/O ratio, as displayed by energy-dispersive X-ray spectroscopy. An Arrhenius plot revealed a lower activation energy (0.11 eV) for the as-deposited thin films, which are the most electrically conductive samples, presenting a better gas response (30% higher than the response of the annealed ones) in the investigated NO2 concentration range of 5-20 ppm at the moderate device operating temperature of 75 °C. This behavior is explained by a larger quantity of oxygen vacancies, which enhances the sensing mechanism.

(ZnO)1-x(SnO2)x/c-nSi gas sensors prepared by pulsed laser deposition technique for selective detection of nitrogen dioxide

(ZnO)1-x(SnO2)x/c-nSi gas sensors prepared by pulsed laser deposition technique for selective detection of nitrogen dioxide

Wearable electro-optical sensor for monitoring of nitrogen dioxide gas in environment

Environmental monitoring for detection of harmful pollutants is a challenge in today’s world. Development of wearable sensors with cost-effectiveness and practicality, while using accessible electronic components can be a solution to this challenge. In the present work ultraviolet light emitting diodes (UV-LEDs) and a Light Dependent Resistor (LDR) pair with carefully designed programmable circuitry is used to detect Nitrogen Dioxide (NO2) in the environment. The sensor is battery operated and rechargeable, making it convenient and eco-friendly. The sensor developed is miniaturized and wearable in nature for the detection of analyte gas in the environment. The sensor is stable and inexpensive as compared to the existing NO2 sensors available, which are electro-chemical, or oxide based. The sensor system is sensitive and selective to its exposure to NO2 gas and has no interference with typical environmental attributes such as humidity and temperature, which is a common challenge in gas detection technologies. The principle of gas detection is absorption based, light falling on the detector absorbed by the test gas present in the environment, thus changing the detector resistance. Absorption-based gas detection is indigenously simple but highly effective technique. This method not only ensures good sensitivity but enhances the selectivity of the electro-optical sensor towards the test gas preventing false triggering in the presence of other interfering gases.

Quantum Confinement and End-Sealing Effects for Highly Sensitive and Stable Nitrogen Dioxide Detection: Homogeneous Integration of Ti3C2Tx-Based Flexible Gas Sensors.

The real-time and room-temperature detection of nitrogen dioxide (NO2) holds significant importance for environmental monitoring. However, the performance of NO2 sensors has been hampered by the trade-off between the high sensitivity and stability of conventional sensitive materials. Here, we present a novel fully flexible paper-based gas sensing structure by combining a homogeneous screen-printed titanium carbide (Ti3C2Tx) MXene-based nonmetallic electrode with a MoS2 quantum dots/Ti3C2Tx (MoS2 QDs/Ti3C2Tx) gas-sensing film. These precisely designed gas sensors demonstrate an improved response value (16.3% at 5 ppm) and a low theoretical detection limit of 12.1 ppb toward NO2, which exhibit a remarkable 3.5-fold increase in sensitivity compared to conventional Au interdigital electrodes. The outstanding performance can be attributed to the integration of the quantum confinement effect of MoS2 QDs and the conductivity of Ti3C2Tx, establishing the main active adsorption sites and enhanced charge transport pathways. Furthermore, an end-sealing effect strategy was applied to decorate the defect sites with naturally oxygen-rich tannic acid and conductive polymer, and the formed hydrogen bonding network at the interface effectively mitigated the oxidative degradation of the Ti3C2Tx-based gas sensors. The exceptional stability has been achieved with only a 1.8% decrease in response over 4 weeks. This work highlights the innovative design of high-performance gas sensing materials and homogeneous gas sensor techniques.

Optimizing NO2 gas sensor performance: Investigating the influence of cobalt doping on WO3 recovery kinetics for enhanced gas sensing application

Gas sensors utilizing a chemiresistive metal oxide semiconductor (MOS) are extensively employed, particularly for detecting nitrogen dioxide (NO2) at moderate temperatures. However, the gas response and the recovery time are hindering the performance of the MOS. In this research, to enhance the gas response and the recovery time a systematic investigation was performed to explore the impact of cobalt (Co) doping in tungsten trioxide (WO3) and its gas sensing properties. Fascinatingly, the 3 mM% Co-doped WO3 sensor exhibits a remarkable gas sensing response of 20776 % at 10 ppm NO2, showcasing a seven-fold enhancement compared to the pristine WO3 sample at 200 ℃. The findings demonstrated that the sensor exhibited an outstanding repeatability, selectivity and long-term stability of 95 % over 8 weeks. Moreover, the sensor possessed a fast response and recovery time 15 s/23 s as compared to the pristine sensor 26 s/154 s. The exceptional gas-sensing capabilities can be ascribed to the existence of defects (oxygen vacancy) within the structure. These defects effectively boost the surface reactivity of WO3 nanoplates, thereby augmenting their sensitivity and enabling a broad-range sensing performance. As a result, this research demonstrates considerable promise for utilizing environmental NO2 monitoring applications.

Room temperature ppb level-NO2 sensor based on WS2 with Fe -ni co-catalyst modification

Rapid and highly sensitive detection of toxic gases at room temperature is crucial for ensuring health protection. However, the sensing materials reported thus far face the challenge of exhibiting relatively low response values at room temperature. In this study, we propose a facile synthesis method to prepare a Fe and Ni co-doped WS2 gas sensor capable of detecting nitrogen dioxide (NO2) at parts-per-billion (ppb) levels even at room temperature. The Fe-Ni@WS2 gas sensor exhibits excellent response performance (The response value is 81 at 1 ppm NO2). The incorporation of Fe and Ni into WS2 forms a Schottky junction that effectively regulates charge transfer behavior within the sensor material through conduction tunneling. Furthermore, the catalytic properties of Fe and Ni promote gas-sensitive reactions on the surface of WS2. This investigation elucidates the sensing mechanism of WS2 towards NO2 under bimetallic modification and provides an effective approach for constructing high-performance gas sensors through rational design of active sites.

ZnO nanowires decorated with Pt nanoclusters for selective detection of ppb-level nitrogen dioxide

Noble metal loading is an efficient way to improve the sensing performance of metal oxide semiconductor (MOS) gas sensors. In this work, platinum (Pt) nanoclusters loaded ZnO nanowires (Ptc-ZnO) were used to fabricate a NO2 sensor. Pure ZnO nanowires were prepared by a solvothermal method and Pt nanoclusters were loaded via a sacrificial templating route. The Ptc-ZnO based sensor with a trace of Pt loading (0.17 wt%) shows a high response to ppb-level NO2 (26.1–100 ppb), 4.4 times higher than that of pure ZnO. Additionally, it also exhibits excellent selectivity, low theoretical limit of detection (1.19 ppb) and good stability to humidity. The enhancing mechanism on gas sensing performance by Pt loading was discussed and investigated via HAADF-STEM, XPS, NO2-TPD and other methods. This work provides a way to develop gas sensor for ultralow NO2 concentration real-time detection.

Improved nitrogen dioxide detection utilizing electronic interactions of POT/SnO2 nanocomposite

In this study, we present a unique technique utilizing POT/SnO2 nanocomposites to create an ultrafast and extremely sensitive nitrogen dioxide gas sensor. Various characterization approaches, including XRD, FE-SEM, UV–Vis spectroscopy, Raman spectroscopy, and FTIR, were systematically applied to verify the successful synthesis of the POT/SnO2 nanocomposite. We tested the conductivity and sensing efficiency with an emphasis on the chemosensitivity component. The sensor based on POT/SnO2 has remarkable sensitivity over a broad range of NO2 concentrations from 5 to 650 ppm. Our results indicate that the incorporation of SnO2 into POT significantly enhanced the sensor sensitivity, increasing from 26 % for pure POT to 87 % for the composite. This improvement produced rapid response and recovery times of 47 s and 44 s, respectively, along with remarkable long-term stability at room temperature. With its remarkable sensitivity and performance characteristics, our sensor emerges as a strong contender for real-time nitrogen dioxide detection, representing a noteworthy advancement in gas sensing technology.

Dynamic Response and Swift Recovery of Filament Heater‐Integrated Low‐Power Transparent CNT Gas Sensor

AbstractDesigning a transparent carbon nanotube (CNT) gas sensor for nitrogen dioxide (NO2) detection at room temperature (RT), which is unaffected by humidity, is a critical challenge in various technologies. To solve this issue, a filament‐based memristor heater (MH) embedded low‐power CNT gas sensor is proposed to address humidity‐related issues, and dynamic response with a low power consumption of 6.15 µW and swift recovery of <1 ms/30.8 µW is successfully demonstrated, without any serious effects on humidity. This study reveals that the MH can effectively heat the surface of the active region due to the joule heating effect, which improves the absorption and desorption of the target gases and mitigates the influence on the humidity, which is in a response that is below 7.5%. As a result, it is believed that the proposed MH‐embedded transparent CNT gas sensors can address the humidity issues and slow response/recovery with ultralow‐power consumption and high‐accuracy gas sensing characteristics.

Construction of a CoNiHHTP MOF/PHI Z-Scheme Heterojunction for ppb Level NO2 Photoelectric Sensing with 405 nm Irradiation at RT.

Ultrasensitive photoelectric detection of nitrogen dioxide (NO2) with PHI under visible light irradiation at room temperature (RT) remains an ongoing challenge due to the low charge separation and scarce adsorption sites. In this work, a dimensionally matched ultrathin CoNiHHTP MOF/PHI Z-scheme heterojunction is successfully constructed by taking advantage of the π-π interactions existing between the CoNiHHTP MOF and PHI. The amount-optimized heterojunction possesses a record detection limit of 1 ppb (response = 15.6%) for NO2 under 405 nm irradiation at RT, with reduced responsive (3.6 min) and recovery (2.7 min) times, good selectivity and reversibility, and long-time stability (150 days) compared with PHI, even superior to others reported at RT. Based on the time-resolved photoluminescence spectra, in situ X-ray photoelectron spectra, and diffuse reflectance infrared Fourier transform spectroscopy results, the resulting sensing performance is attributed to the favorable Z-scheme charge transfer and separation. Moreover, the Ni nodes favorably present in adjacent metal sites between the lamellae contribute to charge transfer and redistribution, whereas Co nodes could act as selective centers for promoted adsorption of NO2. Interestingly, it is confirmed that the CoNiHHTP MOF/PHI heterojunction could effectively reduce the influence of O2 in the gas-sensitive reaction due to their unique bimetallic (Co and Ni) nodes, which is also favorable for the improved sensing performances for NO2. This work provides a feasible strategy to develop promising PHI-based optoelectronic gas sensors at RT.

Perancangan Sistem Pendeteksi Polusi Udara Di Dalam Kamar Mesin Secara Wireless Menggunakan Sensor MQ135 Dan TGS2106 Berbasis Lora Ra-02

Air pollution is a problem that needs attention because it can threaten human life. Many human activities cause air pollution. Especially in closed rooms such as ship engine rooms. Therefore, an air pollution detection tool is needed to determine the air pollution index in that place in order to maintain pollution levels below the threshold value. Therefore, it is necessary to have a tool to detect air pollution using the MQ-135 gas sensor to detect carbon dioxide (CO2) gas and TGS2106 to detect nitrogen dioxide (NO2) gas. The type of research method used is the experimental research method. After designing the tool, testing the tool, the air pollution detection system in the engine room wirelessly using the MQ135 and TGS2106 sensors based on LoRa Ra-02 had an average error rate of 1.3% for the MQ135 sensor reading while the TGS2106 sensor reading had an average level. -average error of 6%. Therefore, the Air Pollution Detection System in the Engine Room Wirelessly Using the MQ135 and TGS2106 Sensors Based on LoRa Ra-02 can work well.

Aerosol-Synthesized Surfactant-Free Single-Walled Carbon Nanotube-Based NO2 Sensors: Unprecedentedly High Sensitivity and Fast Recovery.

This study pioneers a chemical sensor based on surfactant-free aerosol-synthesized single-walled carbon nanotube (SWCNT) films for detecting nitrogen dioxide (NO2). Unlike conventional CNTs, the SWCNTs used in this study exhibit one of the highest surface-to-volume ratios. They show minimal bundling without the need for surfactants and have the lowest number of defects among reported CNTs. Furthermore, the dry-transferrable and facile one-step lamination resultsin promising industrial viability. When applied to devices, the sensor shows excellent sensitivity (41.6% at 500ppb), rapid response/recovery time (14.2/120.8s), a remarkably low limit of detection (below ≈0.161ppb), minimal noise, repeatability for more than 50 cycles without fluctuation, and long-term stability for longer than 6months. This is the best performance reported for a pure CNT-based sensor. In addition, the aerosol SWCNTs demonstrate consistent gas-sensing performance even after 5000 bending cycles, indicating their suitability for wearable applications. Based on experimental and theoretical analyses, the proposed aerosol CNTs are expected to overcome the limitations associated with conventional CNT-based sensors, thereby offering a promising avenue for various sensor applications.

Machine learning‐assisted wearable sensor array for comprehensive ammonia and nitrogen dioxide detection in wide relative humidity range

AbstractThe fast booming of wearable electronics provides great opportunities for intelligent gas detection with improved healthcare of mining workers, and a variety of gas sensors have been simultaneously developed. However, these sensing systems are always limited to single gas detection and are highly susceptible to the inference of ubiquitous moisture, resulting in less accuracy in the analysis of gas compositions in real mining conditions. To address these challenges, we propose a synergistic strategy based on sensor integration and machine learning algorithms to realize precise NH3 and NO2 gas detections under real mining conditions. A wearable sensing array based on the graphene and polyaniline composite is developed to largely enhance the sensitivity and selectivity under mixed gas conditions. Further introduction of backpropagation neural network (BP‐NN) and partial least squares (PLS) algorithms could improve the accuracy of gas identification and concentration prediction and settle the inference of moisture, realizing over 99% theoretical prediction level on NH3 and NO2 concentrations within a wide relative humidity range, showing great promise in real mining detection. As proof of concept, a wireless wearable bracelet, integrated with sensing arrays and machine‐learning algorithms, is developed for wireless real‐time warning of hazardous gases in mines under different humidity conditions.image

Enhanced Gas Sensing Performance of CuO-ZnO Composite Nanostructures for Low-Concentration NO2 Detection

The detection of nitrogen dioxide (NO2) is essential for safeguarding human health and addressing environmental sustainability. That is why, in the last decades, gas sensors have been developed to detect NO2 to overcome these hazards. This study explores the use of a novel CuO-ZnO composite synthesized through a polyol and sol–gel technique to enhance gas sensing performance. The CuO-ZnO composite offers the advantage of a synergic combination of its properties, leading to improved sensitivity, selectivity, and low detection limit. The innovative polyol technique employed in this research enables the controlled synthesis of hierarchical CuO and porous ZnO structures. The composite formation is achieved using the sol–gel method, resulting in CuO-ZnO composites with different ratios. The structural, morphological, and optical properties of the materials have been characterized using FESEM, X-ray diffraction, and UV-vis spectroscopy. Gas sensing experiments demonstrate enhanced performance, particularly in sensitivity and selectivity for NO2, even at low concentrations. The composites also exhibit improved baseline stability compared to pristine CuO and ZnO. This study explains the influence of humidity on gas sensing properties by examining interactions between water molecules and sensor surfaces. Notably, the developed CuO-ZnO composite displays excellent selectivity towards NO2, attributed to favorable bonding characteristics and acid-base properties. Overall, this research contributes to advancing gas sensor technology, providing a promising potential for sensitive and selective NO2 detection, thereby addressing critical needs for human health and environmental protection.

Leveraging electronic interactions in poly (O-toluidine)/ cadmium sulfide nanocomposite for improved nitrogen dioxide sensing

Detecting nitrogen dioxide (NO2) at room temperature remains challenging for current gas sensor technologies. This study aims to address these limitations by developing chemiresistive sensors based on poly (O-toluidine) (POT)/Cadmium sulfide (CdS) nanocomposites. The combination of POT and CdS nanoparticles creates a specialized architecture to enable swift and sensitive NO2 detection at room temperature. Gas sensing evaluations demonstrated significant performance enhancements including 104/73 s response/recovery times and 73% sensitivity at 60 ppm NO2. The sensors also showed repeatability over cycles and stability over 60 days. Comparative analysis confirmed that integrating POT with CdS amplifies sensitivity and reduces response times compared to using POT alone. This establishes a materials-by-design strategy to surpass existing gas sensing limitations.

Mesoporous and Encapsulated In2O3/Ti3C2Tx Schottky Heterojunctions for Rapid and ppb-Level NO2 Detection at Room Temperature.

Rapid and ultrasensitive detection of toxic gases at room temperature is highly desired in health protection but presents grand challenges in the sensing materials reported so far. Here, we present a gas sensor based on novel zero dimensional (0D)/two dimensional (2D) indium oxide (In2O3)/titanium carbide (Ti3C2Tx) Schottky heterostructures with a high surface area and rich oxygen vacancies for parts per billion (ppb) level nitrogen dioxide (NO2) detection at room temperature. The In2O3/Ti3C2Tx gas sensor exhibits a fast response time (4 s), good response (193.45% to 250 ppb NO2), high selectivity, and excellent cycling stability. The rich surface oxygen vacancies play the role of active sites for the adsorption of NO2 molecules, and the Schottky junctions effectively adjust the charge-transfer behavior through the conduction tunnel in the sensing material. Furthermore, In2O3 nanoparticles almost fully cover the Ti3C2Tx nanosheets which can avoid the oxidation of Ti3C2Tx, thus contributing to the good cycling stability of the sensing materials. This work sheds light on the sensing mechanism of heterojunction nanostructures and provides an efficient pathway to construct high-performance gas sensors through the rational design of active sites.

Fast response 2D semiconductor gas sensor for memory-type NO2 detection: Test system construction, performance evaluation, and mechanism study

Two-dimensional (2D) materials, such as those in the graphene family, tin-selenide, and transition metal sulfides (TMDs), hold great promise for various applications, including gas-sensitive devices, photodetectors, and lithium batteries. In this study, we propose a fast response gas sensor for ppb-level nitrogen dioxide (NO2) detection using two-dimensional (2D) semiconductor molybdenum disulfide (MoS2). Firstly, we have constructed a gas-sensitive test system to evaluate the performance of the device. The test results demonstrate that the constructed device responds significantly to gas concentrations as low as 40 ppb and as high as 10 ppm, with a fast response time of around 8 s. We have also analyzed and explained the relevant mechanism of the response to NO2. By providing detailed insights into the construction and performance analysis of the test system, as well as the related mechanism study, our research offers valuable information for the development of fast response memory-type gas sensors for ppb-level NO2 detection.

Synthesis of Bitter gourd-shaped Cu-doped ZnO nanostructures and their investigation for the detection of NO2 gas at low concentrations

Nitrogen dioxide (NO2) exposure can have several adverse health impacts on people, especially the respiratory system. Low selectivity, a lack of long-term stability, and structural and morphological optimization are some challenges associated with using ZnO for NO2 gas sensing. Therefore, we intended copper (Cu) doping in ZnO to alter its shape and gas-sensing characteristics. This study explores the synthesis, properties, and gas-sensing capabilities of bitter gourd-shaped Cu-doped zinc oxide (ZnO) nanostructures for the detection of nitrogen dioxide (NO2). A facile hydrothermal synthesis method was employed to synthesize bitter gourd-shaped Cu-doped ZnO nanostructures and comprehensively characterized by several techniques. Comprehensive characterizations of our produced Cu-doped ZnO nanomaterial demonstrated by X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDS), and different energy spectrum. The material was annealed at 400 °C in a controlled dry air environment to improve its suitability for gas sensor applications. A series of temperature-ranging experiments were conducted to get gas-sensing readings from 25 °C to 300 °C. The resulting sensor, founded upon the distinctive morphology of Cu-doped ZnO structures reminiscent of the intricate shape of bitter gourd, unveiled good selectivity with a pronounced affinity for detecting NO2 gas. Notably, the zenith of its performance was attained at an operating temperature of 200 °C, where its selectivity and sensitivity were most pronounced. Even at a low concentration of 1 ppm, the sensors displayed a maximum response of 3.7, highlighting their high sensitivity. The sensors demonstrated excellent reproducibility, selectivity, and a low detection limit. These findings position bitter gourd-shaped Cu-doped ZnO nanostructures as promising candidates for NO2 sensing applications across diverse environments.

Overall perspective of electrospun semiconductor metal oxides as high-performance gas sensor materials for NOx detection.

Gas sensors based on nanostructured semiconductor metal oxide (SMO) materials have been extensively investigated as key components due to their advantages over other materials, namely, high sensitivity, stability, affordability, rapid response and simplicity. However, the difficulty of working at high temperatures, response in lower concentration and their selectivity are huge challenges of SMO materials for detecting gases. Therefore, researchers have not stopped their quest to develop new gas sensors based on SMOs with higher performance. This paper begins by highlighting the importance of nitrogen monoxide (NO) and nitrogen dioxide (NO2) detection for human health and addresses the challenges associated with existing methods in effectively detecting them. Subsequently, the mechanism of SMO gas sensors, analysis of their structure and fabrication techniques focusing on electrospinning technique, as well as their advantages, difficulties, and structural design challenges are discussed. Research on enhancing the sensing performance through tuning the fabrication parameters are summarized as well. Finally, the problems and potential of SMO based gas sensors to detect NOx are revealed, and the future possibilities are stated.

WO3/WS2 nanoflowers fabricated by low-temperature in-situ oxidation for rapid detection of nitrogen dioxide

Long response time and serious baseline drift have always hampered the practical applications of two-dimensional transition metal sulfides (TMD) in the field of gas sensors. Here, we constructed flower-like WO3/WS2 heterojunction materials via a low-temperature in-situ oxidation method to detect NO2 gas. The WO3/WS2 sensors exhibit satisfactory improvements in the response speed, sensitivity, selectivity, and baseline drift in comparison with the original WS2 sensor. The WO3/WS2 materials with different WO3 ratios were obtained by in-situ oxidizing WS2 under different calcination temperatures. The gas-sensing results show that the W-200 sensor has a gas response of Ra/Rg = 2.3–32 ppm NO2, a rapid response time of 27 s, and a low detection limit of 100 ppb, accompanied by good selectivity and reproducibility to NO2 at the optimal working temperature of 79 °C, making it a promising candidate for the optimization of WS2-based gas sensors in practical use.