Monitoring Of Hazardous Gases Research Articles

ZIF-L(Co) derived cobalt doped In2O3 hollow nanofibers with high surface activity for efficient formaldehyde gas sensing

Gas sensors based on semiconductor metal oxides are identified as a highly promising candidate for toxic gas detection, yet they still suffer from high operating temperature due to low surface activity at low temperature. To address this issue, we present an elaborate design for the homogeneous functionalization of ZIF-L(Co) derived cobalt (Co) catalysts into hollow In2O3 frameworks, aiming to highly activate the redox capacity and catalytic efficacy of the In2O3 sensor to HCHO gas. Benefiting from the Co catalysts doping boosts the catalytic activity and generates abundant oxygen vacancies, the optimized 1 wt% Co-doped In2O3 HNFs sensor exhibits a high response of 40.4 toward 100 ppm HCHO at a moderately low temperature of 180 ℃, which is 4 times higher than that of pristine In2O3 HNFs. Moreover, 1 wt% Co-doped In2O3 HNFs sensor has virtues of high selectivity and excellent long-term stability for HCHO sensing. This study highlights the important influence of Co catalyst on the modulation of surface active sites of metal oxides-based sensors, inspiring the development of cost-effective sensors for indoor hazardous gas monitoring.

High-performance specific detection of NO2 based on PCN-222-Mn doped with Bi electron mediator

Continuous real-time monitoring of hazardous gases is essential for safeguarding public health and environmental integrity, necessitating the utilization of highly selective and sensitive gas sensors. Herein, the chemiresistive sensor for NO2 was fabricated based on Bi nanoparticles (NPs) doped Mn-porphyrin MOF PCN-222-Mn (Bi@PCN-222-Mn) through a straightforward in situ reduction process. Bi NPs serve as electron donors, facilitating the migration of electrons towards the PCN-222-Mn through the formation of a Schottky barrier caused by electrostatic interaction. Besides the Mn-porphyrin as detecting site in PCN-222-Mn, the Bi NPs in Bi@PCN-222-Mn act as supportive sites, enabling NO2 adsorption and electron transfer to NO2 simultaneously, thus enhancing the response signal amplification. Consequently, Bi@PCN-222-Mn exhibited the specific sensing for NO2 with 5 times higher sensitivity (238.6 % ppm−1) in the range of 0.05–2 ppm and a lower limit of detection (LOD) (13 ppb) compared to PCN-222-Mn. Moreover, the Bi@PCN-222-Mn-based chemiresistive sensor also exhibited outstanding long-term stability and moisture resistance, applicable for the practical detection of NO2. These results prove the feasibility of improvement of gas detection performance by introducing metal NPs as electron mediator and an idea for the application of MOFs in gas sensing.

An Eco-Friendly and Dual-Functional Ag@BMO-Chitosan-Based Triboelectric Nanogenerator for Self-Powered Gas Sensing Application

Real-time monitoring of hazardous gases is critical to determine the influence of the air environment on the lives of people. Herein, a highly biodegradable chitosan-based triboelectric gas sensor has been successfully fabricated by using Ag@Bi2MoO6-Chitosan (Ag@BMO-CS) bilayer film obtained with the facile drop-casting method, which paired with polydimethylsiloxane (PDMS) film as triboelectric layers. The output voltage of the 5% Ag-modified chitosan bilayer-based triboelectric nanogenerator reaches up to 8.35 V at 2 Hz operating frequency. The integrated self-powered gas sensor based on the triboelectrification and gas adsorption effects shows the ability to distinguish ammonia (NH3) gas sensitively, and the response to 20 ppm NH3 (ΔV/Va = 59.1%) is 1.4 times larger than the separated self-powered sensor. In addition, the sensing mechanism combining the triboelectric effect and gas-sensing reaction was proposed to demonstrate the enhancement of NH3 sensing performance for Ag@BMO-CS-based triboelectric gas sensors. This work presents a sustainable self-supply gas sensor based on TENG for the detection of NH3 gas without any external power supply, which has a broad spectrum of applications in hazardous gas leaks, non-invasive diagnostics and fresh food transportation.

Mechanism of adsorption of hazardous gases by MoTe2 monolayers modified with nanoclusters

For the detection and monitoring of hazardous gases, for which two-dimensional material gas-sensitive elements have excellent gas-sensitive properties, the adsorption behavior and electrical response to hazardous gases (NO2 and SO2) revealed by MoTe2 monolayers modified by Cun, Agn and Aun (n = 1 to 4) are investigated in this article using first principles. To better simulate the situation under realistic doping, the number of nanoclusters doped ranges from 1–4, while the most stable calculated structure is chosen based on the formation energy. Calculations of the energy band structure, work function, density of states, frontier molecular orbitals and other electronic properties of the adsorbed systems show that the introduction of metal atoms effectively improves the electrical conductivity of the MoTe2 monolayer, with significant improvements for the gas-sensitive response, as well as increasing the adsorption capacity of the gas. The adsorption strength for NO2 molecules is higher than that for SO2 molecules in the three atom-doped systems. By analyzing the electronic and adsorption properties, it is found that Cu atoms show excellent properties among the three metal atoms, especially the Cu3 system has good adsorption and desorption properties for gases. These studies provide a theoretical basis for preparing high-performance MoTe2 gas-sensitive elements with selectivity and sensitivity for detecting and removing hazardous gases.

Recent Advances and Trends in Metal Oxide-based Semiconductor Gas Sensors

With rapid industrial development, a large amount of waste gases has been produced, causing severe industrial disasters and human health problems. In order to avoid gas-related accidents and prevent potential health issues, the detection and monitoring of hazardous gases is essential. In order to effectively detect harmful gases, semiconductor gas sensors have gained increasing attention due to their high sensitivity, small size, cost-effectiveness and ease of manufacturing. This article reviews metal oxide-based semiconductor gas sensors. Firstly, features of metal oxide-based semiconductor gas sensors including major advantages and limitations are discussed. Then, the operating mechanism of semiconductor gas sensors are discussed with a list of widely studied metal oxides. Finally, the semiconductor gas sensors made of four different metal oxides – i) tin oxide (SnO<sub>2</sub>), ii) indium oxide (In<sub>2</sub>O<sub>3</sub>), iii) zinc oxide (ZnO), and iv) tungsten trioxide (WO<sub>3</sub>) – are discussed from the aspects of current challenges, recent research strategies and future perspectives.

Design and Build a Hazardous Gas Monitoring Device (CO, CO2, CH4) Upon Cigarette Smoke in an Enclosed Space Based on Arduino Uno and GSM SIM 900 A

Increasing cigarette usage in daily activities contributes to air pollution caused by cigarette smoke, which is a factor in the onset of numerous respiratory ailments. This research intends to develop a technology that will simplify users' monitoring of hazardous gases (CO, CO2, and CH4) levels in a room using Arduino Uno and GSM SIM 900A with MQ-4, MQ-9, and MQ-135 sensors. The method comprises hardware design, software design, and testing. The research was performed twice. The testing gas employed in this research is cigarette smoke gas. The red LED, fan, and buzzer turn on when the CH4 gas level reaches 250, the CO level reaches 300, or the CO2 gas level reaches 2000. A GSM SIM 900A sends a short message through SMS to the user's device. The initial test results were acquired in the 240th second when CH4 gas reached 299.84 299.84 ppm (hazardous), CO reached 310.06 ppm 299.84 ppm (hazardous), and CO2 reached 291.45 ppm (safe). The second test revealed that at 160 seconds, CO2 reached 308.98 ppm (hazardous), CO reached 161 ppm, and CH4 reached 315.6 ppm (hazardous). Three media specialists conducted validation to determine the viability. The average category rating for the validation test findings was 95.5% so that the instrument can monitor the room's gas levels.

Air Quality and Hazardous Gas Detection using IoT for Household and Industrial Areas

The detection and monitoring of hazardous gases is essential for ensuring the safety of individuals in various settings, such as industrial environments and residential areas. gas detectors detect gases like LPG, NH3, alcohol, NOx, Benzene, CO2, Alcohol, Propane, Hydrogen, Methane, Carbon Monoxide, and smoke in the area around them. In this study, we present a system for real-time detection and monitoring of hazardous gases using MQ135 and MQ2 sensors. The system consists of a monitor that is placed in a fixed location and a mobile device that can be carried by the user. The MQ135 sensor is used to detect gases such as ammonia, while the MQ2 sensor is used to detect gases such as carbon monoxide and hydrocarbons. Each of these gases is known through the Parts per Million (PPM) values and can be determined which gas it is. The system utilises a microcontroller to process the sensor data and display the gas concentrations on a user interface. The mobile device also has the capability to alert the user and send notifications through an accompanying App if the gas concentrations exceed a predetermined threshold. The system is reliable, accurate, and easy to use, making it an ideal solution for detecting and mitigating the risks associated with hazardous gases in various settings. The system was tested in various environments and was able to accurately detect and monitor the presence of hazardous gases and it is a reliable and convenient solution for detecting and monitoring hazardous gases in real-time.

AgNWs@SnO2/CuO nanocomposites for ultra-sensitive SO2 sensing based on surface acoustic wave with frequency-resistance dual-signal display

Surface acoustic wave (SAW) and metal-oxide-semiconductor sensor have been extensively studied for real-time monitoring of hazardous gases, such as sulphur dioxide (SO2). However, they often suffer from high operating temperature, long response/recovery time, low sensitivity and selectivity. In this work, a composite SO2 sensor with frequency-resistance dual-signal display has been designed based on SAW device and metal-oxide-semiconductor. Where silver nanowires@ stannic oxide/ cupric oxide (AgNWs@SnO2/CuO) with the heterogeneous SnO2/CuO structure and AgNWs acting as the support skeleton and catalytic material were used as sensitive materials. With a limit of detection (LOD) as low as 0.25 ppm, a short response/recovery time of 40 s/60 s, and a low operating temperature of 80 °C, the novel composite sensor offers good stability, reproducibility, accuracy, and selectivity. The high SO2 gas-sensing performance obtained was due to the n–p heterostructures of SnO2/CuO, the three-dimensional multi-vacancy structure of AgNWs, and the strong catalytic effect of Ag.

Metal Oxide Semiconductor Nanostructure Gas Sensors with Different Morphologies

There is an increasing need for the development of low-cost and highly sensitive gas sensors for environmental, commercial, and industrial applications in various areas, such as hazardous gas monitoring, safety, and emission control in combustion processes. Considering this, resistive-based gas sensors using metal oxide semiconductors (MOSs) have gained special attention owing to their high sensing performance, high stability, and low cost of synthesis and fabrication. The relatively low final costs of these gas sensors allow their commercialization; consequently, they are widely used and available at low prices. This review focuses on the important MOSs with different morphologies, including quantum dots, nanowires, nanofibers, nanotubes, hierarchical nanostructures, and other structures for the fabrication of resistive gas sensors.

Ultra-sensitive narrow-band plasmonic perfect absorber for sensing applications

Plasmonic nanostructure-based sensors have a broad range of applications in food assessment, hazardous gas monitoring, medical diagnosis, and vapor sensing. However, it is still challenging to establish a high performance plasmonic sensing platform that simultaneously provides high refractive index sensitivity and high figure of merit values. Based on simulations using the finite element method, we engineered an ultra-sensitive all-metal plasmonic perfect absorber (a-MPPA) for sensing applications. The proposed a-MPPA structure is based on closely spaced silver (Ag) nanocones over an Ag thin film and it exhibits ultra-sharp spectral absorption with robust hot spots of electric and magnetic fields. The high optical absorption and localized giant field enhancement depend on the structural configuration of the platform. We observed that the absorbance of the optimized structure exceeded 99%, with an ultra-narrow plasmonic peak (4.3 nm), thereby suggesting that the proposed nanostructure is a good candidate for sensing applications. The sensing performance of the a-MPPA platform was outstanding, with bulk sensitivity of 1006 nm/RIU, large figure of merit value of 233.9 RIU−1, and high quality factor of 233.4. Theoretical analyses based on Campbell’s model indicated that the a-MPPA platform is suitable for molecular detection, with a detection range extending to 50 nm. The proposed narrow-band perfect absorption plasmonic nanostructure has great potential for applications in sensing.

Microporous‐Ceria‐Wrapped Gold Nanoparticles for Conductometric and SERS Dual Monitoring of Hazardous Gases at Room Temperature

AbstractThis work proposes a novel and simple synthesis method for microporous‐ceria‐wrapped gold (Au@mp‐CeO2) nanoparticles (NPs) based on linker molecule‐induced stacking of ultrafine CeO2 particles (or beads) on the surface of pre‐prepared gold NPs. The resulting NPs have a uniform size and microporous CeO2 shells with a mean thickness of 28 nm and porosity of 42%. The shell is highly tunable from about 4 to 30 nm thick. This method is universal and suitable for other metal@mp‐oxide nanoarchitectures (such as Au@mp‐CuO NPs, Au@mp‐Cr2O3 NPs, Ag@mp‐CeO2 NPs, and Ag@mp‐CeO2 nanowires) simply via changing the pre‐prepared metal cores or shell precursors. Most significantly, the as‐prepared Au@mp‐CeO2 NPs can be used for accurate monitoring of toluene vapor (10 ppm level) at room temperature based on their conductometric and surface‐enhanced Raman spectroscopy (SERS) dual response. Moreover, these NPs can be also used for other hazardous gases, such as chlorobenzene, hydrogen sulfide, and 1‐dodecanethiol. This excellent performance benefits from the micropore‐enhanced interaction between CeO2 and gas molecules. This work not only provides new and controllable preparation for metal@mp‐oxide nanoarchitectures, but also demonstrates the great potential applications of these materials in real‐time and identifiable monitoring of hazardous gases.

Simple synthesis of porous ZnO nanoplates hyper-doped with low concentration of Pt for efficient acetone sensing

The realization of accurate and real-time monitoring of hazardous gases has received much recent attention. To facilitate the detection of toxic gases, multifarious nanofabrication techniques have been explored to make various gas sensors with excellent sensitivity, good reliability, and fast response/recovery available. In this contribution, two-dimensional (2D) porous ZnO nanoplates (NPs) hyper-dispersed with low concentration of Pt were synthesized via a convenient hydrothermal reaction followed by in-situ calcination when aged sensor film on the alumina tubes. Applying acetone as a probe molecule, gas sensing characteristics of both pristine ZnO and Pt-doped ZnO NPs were systematically investigated. The results have been proved that the as-prepared 0.01 mol% Pt-doped ZnO NPs sensor showed marked sensitivity toward acetone over 11 times higher than that of the pure ZnO sensor. Also, 0.01% Pt-doped ZnO NPs sensor exhibited superior selectivity against other reference gases, and outstanding trace sensing capability (Ra/Rg = 1.64–100 ppb). Probably both the hyper-dispersion of Pt species and the abundant surficial oxygen species jointly responsible for enhanced sensing performance of the obtained hybrid materials.

Development of Web-based Mobile Olfaction System for Confined Space Hazardous as Monitoring

Hazardous gas in the confined space is an issue that often causes danger to the worker while doing the tasks i.e. installation, cleaning and maintenance. The nature of the area may exposure the worker to hazardous gas leakage. It is important to monitor the hazardous gas in the surrounding area before the worker start their task inside the confined space. This paper proposes a study of developing a web-based mobile olfaction system for confined space hazardous gas monitoring. The system is integration between a mobile robot and an electronic nose (e-nose). The system will reduce the danger faced by the worker from the hazardous gas. The e-nose consists of a sensor array, embedded controller, electronic components and wireless GSM communication. The instrument sensors i.e. hydrogen sulphide, oxygen, carbon monoxide and methane are used to acquire the confined space air sample. It will also acquire the environment temperature and humidity. The robot which piggyback the instrument will manoeuvre through the environment while acquires data. The data acquired were transmitted and monitored wirelessly to the web-based information system. The website layout is designed using HTML and JavaScript. Data received from e-nose will be stored into a database, MySQL server before being process by the website. The data will go through the conversion process from digital value to PPM. Then the data will be classified using ANN to obtain the Hazardous Gas Concentration Index (HGCI). The website will display the HGCI mapping of the area in real-time. Results show that the system performance is good and can be used to monitor the hazardous gas in the confined space.

Ultrafast Response/Recovery and High Selectivity of the H2S Gas Sensor Based on α-Fe2O3 Nano-Ellipsoids from One-Step Hydrothermal Synthesis.

Ultrafast response/recovery and high selectivity of gas sensors are critical for real-time and online monitoring of hazardous gases. In this work, α-Fe2O3 nano-ellipsoids were synthesized using a facile one-step hydrothermal method and investigated as highly sensitive H2S-sensing materials. The nano-ellipsoids have an average long-axis diameter of 275 nm and an average short-axis diameter of 125 nm. H2S gas sensors fabricated using the α-Fe2O3 nano-ellipsoids showed excellent H2S-sensing performance at an optimum working temperature of 260 °C. The response and recovery times were 0.8 s/2.2 s for H2S gas with a concentration of 50 ppm, which are much faster than those of H2S gas sensors reported in the literature. The α-Fe2O3 nano-ellipsoid-based sensors also showed high selectivity to H2S compared to other commonly investigated gases including NH3, CO, NO2, H2, CH2Cl2, and ethanol. In addition, the sensors exhibited high-response values to different concentrations of H2S with a detection limit as low as 100 ppb, as well as excellent repeatability and long-term stability.

Selective discrimination of hazardous gases using one single metal oxide resistive sensor

Monitoring of hazardous gases is nowadays very important, since the urbanized environment is more subject to this kind of pollutants. Therefore, a capillary network of small gas sensors capable to check the quality of the environment is necessary. Metal oxide gas nanosensors are small economic devices that can be easily integrated in any context, however they unfortunately lack of selectivity. We present an approach using hydrothermally grown nickel oxide nanowires working at different temperatures and creating a virtual sensors array, thus exploiting the thermal fingerprints (sensor response as a function of temperature) of the gases. Using only one nanostructured material (nickel oxide) and different machine learning techniques, the system can easily discriminate any of 7 harmful gases (C2H5OH, H2, CO, LPG, CO2, NH3 and H2S, all of them reducing gases) with an accuracy of 100%. Furthermore, the nanosensor also evaluates the gas concentration with an average error lower than 15%. Our results show that, exploiting thermal fingerprints from a temperature gradient, single metal oxide resistive nanosensors can efficiently discriminate specific hazardous gases.

Comprehensive Evaluation of Hazardous Chemical Exposure Control System at a Semiconductor Manufacturing Company in South Korea.

The goal of this study was to evaluate the hazardous chemical exposure control system in a semiconductor manufacturing company and recommend an appropriate exposure surveillance system for hazardous agents. We reviewed compliance-based chemical exposure data compiled between 2012 and 2014 by the study company. The chemical management system, characteristics of chemical use and hazardous gas monitoring system were also investigated. We evaluated the airborne isopropyl alcohol (IPA) and acetone generally used as cleaning solvents, volatile organic compounds and metals levels using internationally recommended sampling and analytical methods. Based on the results of past working environment measurement data and of our investigation, the overall current exposure to chemicals by semiconductor workers during routine production work appears to be controlled below occupational exposure limits. About 40% of chemical products used were found to contain at least one unidentifiable trade-secret substance. There are several situations and maintenance tasks that need special attention to reduce exposure to carcinogens as much as possible. In addition, a job-exposure matrix as a tool of surveillance system that can examine the exposure and health status of semiconductor workers according to type of operation and type of job or task is recommended.

Dual-Function Metal-Organic Framework-Based Wearable Fibers for Gas Probing and Energy Storage.

Metal-organic frameworks (MOFs) coupled with multiwalled carbon nanotubes (MWCNTs) have been developed with an ultrahigh sensitivity for hazardous gas monitoring. Both the MOF/MWCNT and as-derived metal oxides (MOs)/MWCNTs hybrid fibers deliver an ultralow detection limit for NO2 down to 0.1 ppm without external heating, and they can be further bent into different angles without loss of sensing performance. Also, a high specific capacitance of 110 F cm-3 can also be obtained for MO/MWCNT hybrid fibers, demonstrating promising application for integrated wearable devices.

Monitoring of Hazardous Gases in Process Industries Through Internet

Monitoring of Hazardous Gases in Process Industries Through Internet

Gravure-printed ammonia sensor based on organic polyaniline colloids

A chemoresistive ammonia sensor with sensitive polyaniline layer has been fabricated by gravure printing on flexible poly(ethylene terephthalate) substrate. Novel colloids of polyaniline hydrochloride, which were synthetized in xylene or chloroform in the presence of surfactant, were used as a printing formulation. The sensor characteristics of the colloid-based sensitive layers were compared with in-situ polymerized layers of polyaniline. The colloid-based sensors showed a good response to ammonia concentrations in the range from hundreds of ppb to tens of ppm. This provides an opportunity to use these sensors for both monitoring of maximum exposure limits for humans in workplaces as well as environmental air-pollution. Therefore, these fully printed, metal-free, low cost and flexible ammonia sensors based on organic materials can be used in detection systems for monitoring of hazardous gases.

Odour and hazardous gas monitoring system for swiftlet farming using wireless sensor network (WSN)

The production of edible swiftlet nest is a growing industry in Malaysia; where farmers recreate the bird’s habitat in buildings referred to as swiftlet houses. The conditions in these swiftlet houses are however, largely unknown as there seems to be lack of research effort in this newly formed industry. This paper presents the odour and hazardous gas monitoring system utilising wireless sensor network. Several gas sensor readings including humidity, temperature, luminance and rainfall were recorded in a swiftlet house in Arau, Perlis. A single sensor element was found to be insufficient to monitor a specific gas as the odour is a synergy, inhibition and masking between different compounds. Indoor and outdoor humidity and temperature variations were also investigated. The studies have shown that the sensor responses were affected by the odour resulting from different combinations of four different groups of compounds. Minimum threshold level is proposed to alert the breeder so that efforts to reduce the gas levels to a safe and comfortable level can be taken.