Detection Of Harmful Gases Research Articles

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.

Detection of harmful gases (NO, NO2) by GaN@MoSSe heterostructures embedded with transition metal (Cu, Fe and Mn) atoms: A DFT study

Monitoring and identifying air pollutants, such as NO and NO2, is crucial due to their detrimental impact on both the environment and human health. This work employs density functional theory (DFT) with the PBE + U functional to investigate the adsorption and sensing performance of NO and NO2 on transition metal (TM)-doped GaN@MoSSe heterostructures. The adsorption energy, charge transfer, electron localization functions, charge density difference, spin density, band gaps and density of states are analyzed. The findings reveal that a transition from physisorption to chemisorption occurs after TM atoms doping. Also, when the surface is embedded with Cu, Fe and Mn atoms, there is a significant improvement in the behavior related to gas adsorption. The bandgap and its variations lead to the change in surface electrical conductivity, thereby affecting the gas sensitivity of the adsorption system. Particularly, the CuGa-GaN@MoSSe and FeGa-GaN@MoSSe systems exhibit improved gas sensitivity toward NO due to their significant band gap reduction. Meanwhile, the CuSe−MoSSe@GaN, CuGa-GaN@MoSSe, FeGa-GaN@MoSSe and MnGa-GaN@MoSSe systems also demonstrate enhanced sensing capabilities for NO2. This work offers valuable theoretical insights for exploring the potential applications of TM-GaN@MoSSe heterostructures in gas sensing.

Design of Intelligent Window Automatic Monitoring System Based on Microcontroller Control

To ensure the safety of residents’ lives and property by using automatic opening and closing of ordinary windows, this article designs an intelligent window automatic monitoring system. The article proposes a software and hardware design scheme for the system, which comprises a microcontroller control module, temperature and humidity detection module, harmful gas detection module, rainfall detection module, human thermal radiation induction module, Organic Light-Emitting Diode (OLED) display module, stepper motor drive module, Wi-Fi communication module, etc. Users use this system to monitor environmental data such as temperature, humidity, rainfall, harmful gas concentrations, and human health. Users can control the opening and closing of windows through manual, microcontroller, and mobile application (app) remote methods, providing users with a more convenient, comfortable, and safe living environment.

Constructing Adsorption Site-Enhanced Vo-BiOCl/rGO Heterostructures for Efficient Response to NO2/NH3 Gases at Room Temperature.

Real-time detection of harmful gases at room temperature has become a serious problem in public health and environmental monitoring. Two-dimensional materials with semiconductor properties BiOCl is a promising gas-sensitive material due to its large specific surface area and adjustable band gap as well as outstanding safety characteristics. However, limited by the weak gas adsorption sites and sluggish charge-transfer ability, the performance of BiOCl could not be fully exploited. Oxygen vacancy (Vo) engineering can introduce lattice defects, thereby significantly increasing the local charge density and enhancing the adsorption of gases, which is an effective strategy to enhance the gas-sensing performance. In this work, we composite BiOCl with a vacancy (Vo-BiOCl) and reduced graphene oxide (rGO) to construct a Vo-BiOCl/rGO heterostructure with enhanced gas adsorption sites. Experimental and theoretical calculations show that Vo can enhance the adsorption of gases and the introduction of rGO forms a high-quality heterostructure with BiOCl, which can effectively reduce the band gap of BiOCl and promote electron transfer, thereby improving the sensitivity of the sensor. Benefiting from above, Vo-BiOCl/rGO achieves the ability to detect low concentrations of NO2/NH3 at room temperature, with high sensitivity (55% at 1 ppm of NO2 and -28% at 1 ppm of NH3), fast response time (40 s at 1 ppm of NO2 and 2 s at 1 ppm of NH3), good stability (over 150 days), and fully recoverable gas sensitivity.

Copper oxide/reduced graphene oxide/graphene composite structure for the chemiresistive detection of acetaldehyde at room temperature

In this work, the acetaldehyde (CH3CHO) sensing performance of Copper(II) oxide nanoparticles/reduced Graphite oxide/Graphene composite structure (CuO NPs/rGO/G) was systematically studied. Firstly, CuO NPs/rGO composite nanostructures were prepared by hydrothermal synthesis, Then, CuO NPs/rGO was uniformly deposited on graphene film to prepare CuO NPs/rGO/G composite structure. CH3CHO sensing tests have shown that the CuO NPs/rGO/G composite structure exhibits a fast and highly sensitive response to CH3CHO at room temperature. At the test concentration of 100 ppm CH3CHO, the response of CuO NPs/rGO/G composite structure is 39.94 times that of graphene, 11.37 times that of CuO NPs/rGO, and 5.90 times that of CuO NPs, up to 82.67 %. The response time is only 22 seconds, the recovery time is 159 seconds, and its theoretical limit of detection is 95.10 ppb. In addition, the CuO NPs/rGO/G composite structure has excellent selectivity, repeatability, and long-term stability for the sensing of CH3CHO. The CuO NPs/rGO/G composite structure studied in this paper solves the problems of poor response, slow response, slow desorption and even inability to desorption of graphene in CH3CHO sensing, and has great application potential in respiratory VOCs detection, environmental harmful gas detection, etc.

Boron-nitride nanostructures for the detection of harmful gases (CO, CO2, H2S, N2O, and SO2)

Boron-nitride (BN) structures are considered materials with several applications, including sensing platforms. Through density functional theory calculations based on the PBE-D3/6-311G(d,p) level of theory, we propose the boron-nitride nanosheet, armchair nanotube (5,5), and fullerene as possible sensors for the harmful gases CO, CO2, H2S, N2O, and SO2. According to our results, the systems exhibit adsorption energies of −0.10 eV to −1.26 eV, and remarkable electronic parameters such as chemical potential, energy gap, and HOMO and LUMO energies, ideal for serving as chemical sensors of such pollutant gases. The nanostructures can be selective to sense a particular gas, mainly CO, N2O, and SO2. Additionally, we note a dramatic change in the electrical conductivity up to 2.14 eV, and low recovery time from 15 μs to 6.2 s. Finally, the BNNS-SO2, BNNT-N2O, BNNT-SO2, and BNF-CO are the more promissory systems to be used as chemical sensors of SO2, N2O, and CO.

Photoluminescent Transparent Wood with Excellent UV-Shielding Function.

At present, light transmission, energy saving, environmental protection, and UV-shielding materials are very important for optimizing indoor living environment. Here, a fluorescent transparent wood (FTW) with UV-shielding function was prepared by encapsulating a carbon quantum dot and epoxy resin into a delignification wood template. FTW exhibits excellent optical transmittance (about 91%), water absorption stability (weight gain rate less than 9%), longitudinal tensile strength (139 MPa), and UV-shielding properties. Due to the photoluminescence characteristics of the carbon quantum dot and the natural cellulose skeleton of wood, FTW can show uniform luminescence under ultraviolet lamps. At the same time, it has remarkable UV-shielding performance. This kind of photoluminescent transparent wood with a UV-shielding function also has the potential to be applied to fields such as electromagnetic shielding and harmful gas detection.

Gallium phosphide nanoribbon-based carbon monoxide sensors: insights from first principles study

The priority of research efforts over the past two decades has been focused on the effective detection of harmful gases and the development of small, efficient, and reliable nanodimensional sensors. The adsorption of carbon monoxide (CO) gas molecules on zigzag gallium phosphide nanoribbons (zGaPNRs) has been studied using first-principle calculations within the context of Density Functional Theory (DFT). Here, we have evaluated the potential of single-atom thick zGaPNRs in different configurations of nanoribbons for the detection of CO. Many possible configurations of studying the CO molecule adsorption on zGaPNRs have been explored. It is established that the interaction of CO molecules has an impact on the electrical and transport properties of zGaPNRs. The H-GaP-H is the most stable structure with the binding energy ([Formula: see text]) of −5.70[Formula: see text]eV. The stability is compromised with CO adsorption with CO-GaP-CO being the least stable structure. Pristine structure is semiconducting with the energy band gap ([Formula: see text]) of −3.95[Formula: see text]eV. The computed sensitivity (S) values are found to be highest for Co-GaPNRs with the S value of [Formula: see text] and the least sensitive structure is H-GaP-CO with the computed S as [Formula: see text]. Additionally, it is noted that CO molecules always establish a stable chemical bond with the nanoribbon edges through the C-side. The unique behavior is revealed by the transport characteristics, which demonstrates that when CO adsorption occurs near the Ga edge, the current magnitude is noticeably greater. Our research demonstrates the potential of specific CO adsorption and detection for the development of nanosensors.

DFT study of sensing properties of defected and transition-metal doped V2CF2 towards CH4

As a new type of gas sensor, MXenes material is of great significance in indoor harmful gas detection. The geometric, electronic, and magnetic properties of CH4 adsorbed on intact, F-vacancy defected, and transition-metal (TMs: Mn, Co, Ni, Zn, Nb, Mo) doped V2CF2 have been investigated based on density functional theory. Perfect V2CF2 and F-vacancy defected substrates exhibited low charge transfer, long adsorption distance, and small adsorption energy for CH4. The adsorption mechanism was physical adsorption. After introducing Co and Ni dopants, the adsorption mechanism of CH4 changed to be chemisorption. Additionally, the asymmetric electron spin distribution between the dopant and V atom caused the substrate to change from being non-magnetic to magnetic, as shown by the electronic density of states diagrams. The hybridization between TM-3d orbitals and the p orbitals of the CH4 molecule significantly improved the adsorption stability. It is hoped that the results could provide ideas for creating new CH4 gas sensors based on MXenes.

Design and Implementation of Arduino-Based Sterilization Robot

In this paper, the primary objective is to design implement a low-cost mobile robot used for the sterilization and control of toxic and flammable gas leaks in the polluted areas. To implement the proposed robot, we employ a tank robot structure equipped with sensors/modules for detection, sterilization, and environmental analysis. The robot is outfitted with a camera to enhance its surveillance capabilities. For sterilization, we utilize ultraviolet rays emitted by a UV Lamp (220V Sterilizer 8W-T5 Tube) in infested areas. Special sensors are strategically placed to identify gases and viruses in the target locations. The sensors include MQ-2 for detecting gases like methane, butane, and smoke, MQ-9 for identifying carbon monoxide and flammable gases, and MQ-135 for continuous measurement of air purity. The UV rays can be remotely activated and deactivated through an infrared control system. Simultaneously, the sensor values (MQ-2, MQ-9, MQ-135) are consistently monitored and transmitted to a central authority responsible for remote surveillance. If any hazardous or toxic gases are detected, the system triggers an alarm, notifying relevant authorities to take prompt action. This integrated approach ensures the efficient sterilization of contaminated areas while actively monitoring and responding to potential gas leaks. The combination of sterilization technology, gas detection sensors, and remote monitoring enhances the safety and effectiveness of the entire system. In the future developments, many approaches can be used such as increasing the controlling area by using Wi-Fi or LoRa and using additional sensors for harmful gas detection.

MXene-activated graphene oxide enhancing NO2 capture and detection of surface acoustic wave sensors

Surface acoustic wave (SAW) technology has been widely used in the field of harmful gas detection, but there remain a lot of challenges, such as long response/recovery time as well as poor selectivity and repeatability. Herein, we activate graphene oxide (GO) using MXene with excellent adsorption capacity (MXene/GO) to realize efficient NO2 gas detection. The SAW sensor assembled with the multilayered MXene/GO composite showcases an enhanced gas sensing performance to the NO2 gas (1–200 ppm) enabling high sensitivity (Δf=260 Hz/ppm), fast response/recovery time, excellent selectivity, and good repeatability at room temperature. The enhanced high sensitivity and selectivity detection of NO2 gas is attributed to the large pore size, hydrophilicity, and abundant surface functional groups of the multilayered MXene/GO composite. This elaborate design is expected to propel the development of next-generation acoustic gas phase sensors.

Sensing of H2S, NO2, SO2, and O3 through pristine and Ni-doped Zn12O12 nanocage

Harmful gases pose a serious threat to life on Earth therefore, their detection is quite vital for sustainable life. For this purpose the adsorption properties of harmful gases (H2S, NO2, SO2, and O3) were investigated to gain insights into the influence of adsorbed gas molecules on the electronic properties of pristine and Ni-doped Zn12O12 nanocages, and how these effects could be applied to design more sensitive gas sensing materials. Adsorption energies for these gases on pristine Zn12O12 nanocages ranged from −9.89 to −43.23 kcal/mol. The adsorption energies were further enhanced in Ni-doped Zn12O12 nanocages. The highest interaction energy was observed for the NO2@Ni-Zn12O12 complex (−85.23 kcal/mol), followed by O3@Ni-Zn12O12 (−57.42 kcal/mol). Non-covalent interaction (NCI), quantum theory of atoms in molecules (QTAIM), and electron density difference (EDD) analyses were performed for both pristine and doped complexes. The electronic properties of the complexes were studied using natural bond orbital (NBO), frontier molecular orbital (FMO), and density of states (DOS) analyses. When H2S adsorbed on pristine and doped nanocages, charge transfer occurred towards the nanocages. On the other hand, NO2, SO2, and O3 extracted charges from both types of nanocages. The highest charge transfer was observed in O3@Ni-Zn12O12 (−0.699 e−) and the lowest in H2S@Ni-Zn12O12 (0.045 e−). The largest decrease in the EH-L gap was observed for O3@Zn12O12 (2.06 eV) compared to pristine Zn12O12 nanocages (4.13 eV). In Ni-doped Zn12O12, the HOMO-LUMO gap decreased to 2.49 eV (O3@Ni-Zn12O12) and 2.32 eV (H2S@Ni-Zn12O12) from 2.79 eV (Ni-Zn12O12), indicating the sensitivity of Ni-doped Zn12O12 nanocages to O3 and H2S. Therefore, Ni-doped Zn12O12 nanocages exhibit high sensitivity to harmful gases and can be employed as highly sensitive electrochemical sensors. This study may provide valuable guidance for the design and development of new sensors for the detection of harmful gases.

Unveiling the gas sensing potential of CxNy monolayer through ab initio screening

The development of superior performance and safety metal free sensors for harmful gas detection is of great significance, but it is still challenging. In this study, we developed a new strategy denoted as ‘5S’ (stability, sensitivity, selectivity, speed recovery time and safety) to screen CxNy (x:2∼5, y:1∼8) monolayer as outstanding performance gas sensors (NO, NO2, NH3, CO and CO2) via density functional theory (DFT). The results indicate that all gas molecules are adsorbed on the CxNy surface due to the negative adsorption energy; interestingly, the electron transfer changes slightly during the interaction between CxNy and the adsorbed gas molecules. The adsorption energy of C2N, C3N4, C3N5, C5N8 for NO2 hazardous gas is particularly pronounced and difficult to desorb from CxNy compared to the other candidate CxNy, which suggests that it hinders to be a promising gas sensor. Conversely, the adsorption energies of C2N and C5N8 for small gas molecules are too small, resulting in insufficient sensibility. It is worth noting that C3N4, C3N5 is a potential candidate substrate for NO due to its optimized adsorption/desorption properties and fast recovery time. Furthermore, C3N4 can be used as a gas sensor for NH3 due to its suitable adsorption/desorption properties and fast recovery time compared to other substrates. This work not only theoretically screens C3N5 and C3N4 substrates for excellent performance as gas sensors, but also provides a new ‘5S’ screening strategy for other 2D materials as candidates for gas sensors.

The effect of Pt and IrO2 interlayers on enhancing the adhesion of Ti/SnO2 interface: A first principles density functional theory study

With potential applications from gas sensors to anode electrodes, Ti/SnO2 interfacial systems play a crucial role in the detection of harmful gases and the destruction of refractory organic pollutants via electrochemical advanced oxidation processes. However, there is an issue with the stability of the Ti/SnO2 interface, in which having an interlayer of another metal or ceramic may work to improve it. First principles density functional theory calculations were performed to study how the addition of Pt and/or IrO2 interlayers affect the stability and adhesion of Ti/SnO2. The calculations showed that Ti/SnO2 interfaces are destabilized by the movement of oxygens from the surface of SnO2 into the Ti phase, causing the adhesion between the newly oxidized Ti phase to be weak with the surface Sn atoms. In contrast, both Pt and IrO2 were found to form stable interfaces with both Ti and SnO2. Further investigation found that Ti/Pt/SnO2 and Ti/IrO2/SnO2 formed stable systems that promoted adhesion between all phases. However, having both Pt and IrO2 combined as interlayers did not form a stable system. Overall, the results show that both Pt and IrO2 may serve as potential interlayer for Ti/SnO2 that promotes adhesion, but combined together they do not.

Experimental and theoretical comparative analysis of modified graphene (G-O, Pd-G, Pd-G-O) sensing performance toward SO2 in agricultural greenhouse

Sulfur dioxide (SO2) is one of the main harmful gas in agricultural greenhouse. Its concentration can effectively reflect the health status of plants in agricultural greenhouse. In this paper, the adsorption characteristics of SO2 on modified graphene-based were studied in comparison. The adsorption models of epoxy grouped graphene (G-O), palladium doped graphene (Pd-G) and epoxy and palladium co-doped graphene (Pd-G-O) to SO2 were established based on the first-principles, analyzing in terms of adsorption energy, density of states, orbitals, charge density and desorption time of the adsorption models. The results showed that Pd-G-O exhibited strong chemisorption with adsorption energy of -1.237 eV. Furthermore, three modified graphene-based sensing materials were prepared via the redox method in this paper, and their crystal morphology and chemical elemental composition were investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), respectively. The response performance of the graphene-based sensor to SO2 was tested by a gas-sensitive testbed. The test results confirmed that the response of the Pd-G-O sample to 50 ppm SO2 at room temperature was 10.5 (1.567 and 1.235 times than that of G-O, Pd-G). Pd-G-O provides theoretical basis and experimental support for the development of a highly sensitive and fast response sensor for the detection of harmful gases in agricultural greenhouse.

Enhancing Hydrogen Sulfide Detection at Room Temperature Using ZIF-67-Chitosan Membrane.

Developing new materials for energy and environment-related applications is a critical research field. In this context, organic and metal-organic framework (MOF) materials are a promising solution for sensing hazardous gases and saving energy. Herein, a flexible membrane of the zeolitic imidazole framework (ZIF-67) mixed with a conductivity-controlled chitosan polymer was fabricated for detecting hydrogen sulfide (H2S) gas at room temperature (RT). The developed sensing device remarkably enhances the detection signal of 15 ppm of H2S gas at RT (23 °C). The response recorded is significantly higher than previously reported values. The optimization of the membrane doping percentage achieved exemplary results with respect to long-term stability, repeatability, and selectivity of the target gas among an array of several gases. The fabricated gas sensor has a fast response and a recovery time of 39 s and 142 s, respectively, for 15 ppm of H2S gas at RT. While the developed sensing device operates at RT and uses low bias voltage (0.5 V), the requirement for an additional heating element has been eliminated and the necessity for external energy is minimized. These novel features of the developed sensing device could be utilized for the real-time detection of harmful gases for a healthy and clean environment.

Voting Ensemble Learning Model (VELM) for Harmful Gas Detection Systems: A Proposed Model

An increase in industrialization has caused the release of harmful gases into the atmosphere and this has resulted in environmental pollution that greatly affects the health of both plants and animals alike. Over time, sensor-based technology has been used to develop gas detection systems, but they were faced with some major challenges, such as sensor failure and poor performance that have greatly affected their performance. Also, the use of machine learning techniques has been developed for this purpose by leveraging the powers of sensor-based technology. However, they were faced with issues, such as poor feature selection criteria and missing data, which resulted in delays and inaccurate prediction performance of the models. This study, therefore, seeks to survey existing ensemble learning models and to design a Voting Ensemble Learning Model (VELM) for harmful gas detection systems. The methodology adopted for this study is a comparative analysis of the classification models used for the study. The study concludes that there is a need to develop advanced machine learning models to be used for detecting harmful gas and other detection systems such as earthquake, volcano, and landslide detection systems, in real-time that can inform future research. Also, a recommendation was made for the implementation of the developed model based on its low variance and low bias when dealing with widely dispersed data points in a dataset in addition to its ability to deal with local minima and overfitting that affect classic machine learning. Keywords: Detection System, Ensemble Learning, Machine Learning, Sensor

Mechanisms of NO2 Detection in Hybrid Structures Containing Reduced Graphene Oxide: A Review.

The sensitive detection of harmful gases, in particular nitrogen dioxide, is very important for our health and environment protection. Therefore, many papers on sensor materials used for NO2 detection have been published in recent years. Materials based on graphene and reduced graphene oxide deserve special attention, as they exhibit excellent sensor properties compared to the other materials. In this paper, we present the most recent advances in rGO hybrid materials developed for NO2 detection. We discuss their properties and, in particular, the mechanism of their interaction with NO2. We also present current problems occuring in this field.

Humidity-Tolerant Chemiresistive Gas Sensors Based on Hydrophobic CeO2/SnO2 Heterostructure Films

The accelerated evolution of the Internet of Things has brought new challenges to the gas sensors, which are required to work persistently under harsh conditions, like high humidity. However, currently, it is quite challenging to solve the hindrance of the trade-off between gas-sensing performance and anti-humidity ability of the chemiresistive gas sensors. Herein, hydrophobic inorganic CeO2/SnO2 heterostructure films were prepared by depositing the CeO2 layers with a thickness of a few nanometers onto the SnO2 film via a magnetron sputtering method. The sensors based on the CeO2/SnO2 heterostructure films demonstrated excellent gas-sensing performance toward trimethylamine (TEA) with high response, wide detection range (0.04-500 ppm), low record detection limit (0.04 ppm), ideal reproducibility, and long-term stability, while concurrently possessing promising anti-humidity ability. A portable, wireless TEA-sensing system containing the CeO2/SnO2 sensor was constructed to realize the real-time monitoring of trace concentration of the volatiles released from a fish. This work provides a novel strategy to prepare advanced chemiresistive gas sensors for humidity-independent detection of harmful gases and vapors and will accelerate their commercialization process in the field of food safety and public health.

Highly sensitive and selective nitric oxide sensor based on biomorphic ZnO microtubes with dual-defects assistance at low temperature

Fabrication of diverse surface defects-assisted metal oxide materials is an effective avenue to achieve rapid and accurate detection of harmful gases. Herein, through the confinement effect of tracheids and vesicles in cajuput bark template, biomorphic ZnO hierarchical materials (ZnO-6) constructed from spherical nanoparticles were simply synthesized by zinc salt immersion and calcination at 600 °C in air. Porous ZnO-6 microtubes can greatly improve the rapid transmission and desorption behavior of target gas. Especially, the presence of electron donor dual-defects oxygen vacancy (VO) and zinc interstitial (Zni) can provide more active sites for surface gas adsorption and chemical reactions, thus effectively enhancing the detection ability of ZnO sensing material to toxic NO gas. At a low operating temperature of 92 °C, the high response value of 118 to 10 ppm NO for ZnO-6 sensor is 5.4 times higher than that of as-synthesized template-free ZnO-0 nanoparticles, and also represents the highest response among reported metal oxide-based gas sensors at low energy consumption. Meanwhile, this sensor has rapid recovery characteristic, good selectivity, long-term stability and moisture resistance. Moreover, the surface defects and their induced sensing mechanism are also characterized and explored.