Toxic Gas Sensors Research Articles

Monolayer Penta-BeAs2: A Promising 2D Materials for Toxic Gas Sensor with High Selectivity.

The discovery of novel materials with high gas sensing selectivity is a key driver of gas sensor technology. Based on the recently reported two-dimensional (2D) pentagonal BeP2, we introduce penta-BeAs2 as a new member of the pentagonal family of materials for toxic gas sensors based on density functional theory (DFT). For electronic applications, a band structure calculation showed that penta-BeAs2 has indirect band gaps of 0.38 and 0.79 eV, using GGA-PBE or HSE functionals. Stability analysis confirmed that penta-BeAs2 is dynamically, mechanically, and thermally stable. The adsorption of toxic gases (CO, NO, and NO2) and nontoxic gases (H2, N2, H2O, and CO2) on the penta-BeAs2 monolayer was studied. The contrasting adsorption behavior observed between toxic and nontoxic gases on penta-BeAs2 (physisorption vs chemisorption) underscores its high selectivity for toxic gas-sensing applications. Adsorption energies for toxic gases fall within a moderate range (0.4-0.8 eV), indicating good reversibility and short recovery times at room temperature. Additionally, the quantum transport properties of penta-BeAs2 were studied using the nonequilibrium Green's function (NEGF) approach, confirming strong sensitivity and selectivity toward toxic gases.

A DFT investigation of monolayer InP: Effective toxic gas sensor with adsorption and optical response

An examination was conducted on the electronic and optical characteristics of gas (H2S, CO2, CO, SO2, and SO) adsorption on a monolayer of InP using first-principles calculations based on DFT. To identify the optimal and most sensitive adsorption site for the adsorbed gases, four initial adsorption sites were selected. Various aspects such as adsorption distance, charge densities, and adsorption energy were analyzed across different types of adsorption to determine the most favorable adsorption configurations. Our research indicates that InP monolayers can chemically adsorb CO2, CO, SO2, and SO, forming new bonds with these gas molecules. Furthermore, H2S can be physically absorbed onto InP with a high level of adsorption energy. The optical findings reveal that the presence of gas molecules alters the conductivity and optical properties of the InP monolayer, especially noticeable in the UV range. InP emerges as a suitable material for detecting CO2, CO, SO2, and SO due to its distinct characteristics.

C-doped [formula omitted] monolayer as toxic gas scavenger or sensor based on first-principles study

The selective adsorption mechanism of C-CdS2 monolayer was revealed using density functional theory. The results show that C-CdS2 has good adsorption properties for SO2, NO, NH3, NO2 and Cl2, and all of them are chemisorbed. Under the adsorption of different gas molecules, the electronic structure of C-CdS2 changed to varying degrees, which provided a theoretical basis for the use of C-CdS2 as a gas sensor or scavenger for these gases.

(Invited) Past, Present and Future for Electrochemical Gas Sensors in Energy Applications

The markets for modern low-cost electrochemical gas sensors have been growing for longer than sensors have been around. Energy markets for gas sensors include the oil, gas and electricity industries as well as the new developing and fast growing green energy sectors. The primary gases to detect include combustible hydrocarbons, oxygen, and toxic gases. Specifically, we are interested in methane (blue and green), ammonia, and H2 for the renewable energy sectors but include hydrocarbon fuels and CO2 as a greenhouse gas emission. The reasons for monitoring crosscut all areas of the energy business and include applications in production, transport, storage and use. Primary sensor uses include: 1) health and safety (people and assets), 2) leak detection and isolation to help mitigate product losses, 3) monitoring to protect the environment and 4) measurements for process control and efficacy. Each of these areas of sensing have special requirements and demand cost-effective and time efficient sensor performance in many and varied real world scenarios.Electrochemical gas sensors have a long and rich history starting with the commercialization of the first practical potentiometric CO2 gas sensor by Severinghaus in 1954 and the O2 amperometric sensor by Clark in 1956 that launched the modern blood gas analysis industry. Additional milestones include the introduction of the “diffusion electrode” in 1968 creating the modern amperometric sensor which has produced a large array of sensors for toxic and hazardous gases including H2, ammonia, and other energy gases. Progress has been made in the field of electrochemical gas sensors, not only in improving performance, sensitivity, selectivity, response time, and stability, but also in logistical properties including miniaturization, lower power consumption, low cost as well as communication and computation to make automated-operational systems. New high-volume production has contributed to lower costs commensurate with a chip-based sensor mentality. The evolution of one of the gas sensor technologies is given below (the room temperature AGS or amperometric gas sensor) and similar progress has been seen in mixed potential and solid state gas sensors.The growing understanding of the sensor’s fundamental electrocatalytic reactions has led to tailored designs of electrode-electrolyte combinations and packages for the various applications. Often ignored in sensor publications of performance, the fundamental electrocatalytic studies are poised to make significant advances in energy gas sensor selectivity and sensitivity. The additional implementation of intelligent algorithms (AI/ML) to make “smart” sensors and sensor arrays complements advanced nano-materials and designs for improving sensor performance. One major improvement is our understanding of the sensor response mechanisms at the electrocatalytic level. This new research will enable new electrochemical sensor advances that are poised to impact the health and wellbeing of both people and the planet. Ideas and concepts that significantly contribute to the safe and efficient rollout of the newest green energy platforms are presented. Figure 1

Ab Initio Study of the Graphyne-like γ-SiC Nanoflake for Toxic Gas-Sensing Applications.

This study focuses on the geometrical, electronic, and optical properties of the γ-graphyne-like novel γ-SiC nanoflake of the γ-silicon carbide (SiC) monolayer using density functional theory calculations. γ-SiC was revealed to be a stable semiconducting nanoflake confirmed by a negative cohesive energy, real vibrational frequencies, and a 1.749 eV energy gap. The adsorption of COCl2, HCN, PH3, AsH3, CNCl, and C2N2 toxic gases on the γ-SiC nanoflake is also studied, which revealed an attractive gas-nanoflake interaction with the adsorption energy ranging from -0.21 to -0.38 eV. The adsorption results in a significant charge transfer between gas-adsorbent complexes. A significant variation in the energy gap and electrical conductivity was observed due to gas adsorption. γ-SiC showed maximum sensitivity at room temperature for CNCl gas. The entire process of adsorption is exothermic and thermodynamically stable. γ-SiC showed a high absorption coefficient over 104 orders with a significant variation in the absorption peak intensity and blue peak shifting. According to the quantum theory and reduced density gradient analysis, all of the gases are physisorbed on the γ-SiC nanoflake due to van der Waals interactions. The obtained results signify the usability of γ-SiC as a potential toxic gas sensor.

Defective Diamane: A Superior Sensor for Toxic Gases Capture and Detection with Excellent Selectivity, Sensitivity, and Reversibility at Room Temperature.

The toxic gases emitted from industrial production have caused significant damage to the environment and human health, necessitating efficient gas sensors for their detection and removal. In this work, first-principles calculations are employed to investigate the potential application of diamanes for high-performance toxic gas sensors. The results show that nine gas molecules (CO, CO2, NO, NO2, NH3, SO2, N2, O2, and H2O) are physisorbed on pristine diamane by weak van der Waals interactions. After introducing H/F defects, diamane can effectively capture specific toxic gases (CO, NO, NO2, and SO2) in the presence of interfering gases (N2, O2, and H2O), suggesting excellent selectivity and anti-interference ability. Orbital hybridization and significant charge redistribution between gas molecules and defective diamane dominate the enhanced adsorbate-substrate interactions. More importantly, the high sensitivity and good reversibility of defective diamane for detecting CO, NO, and SO2 molecules enable its reuse as a superior resistance-type gas sensor. Our calculations provide valuable insights into the potential of defective diamane for detecting toxic gases and shed light on the practical application of novel carbon-based materials in the gas-sensing field.

Pure and doped graphene as a suitable material for the detection of hazardous gases

The need for highly sensitive toxic gas sensors is significant, and achieving this sensitivity is possible. Researchers have utilized density functional theory (DFT) computations to examine adsorption of different gas molecules (COX2, where X is F, Cl, or Br) over Au-doped and pristine graphene. This investigation aims to determine possibility of employing Au-doped graphene as a basis for gas sensors. Multiple adsorption positions and orientations were examined for each gas molecule. The configuration that exhibited the highest stability was identified, and adsorption energy (Eads) values, considering van der Waals (vdW) interactions, have been computed using NCI analyses. In addition, the electronic properties, including LUMOHOMO orbital density and charge transfer, were analyzed to acquire a deeper understanding of process by which adsorption occurs. Findings indicated that gas molecules under investigation exhibited weak adsorption on pristine graphene, with low Eads values. In contrast, Eads values of every gas molecule on Au-doped graphene displayed varying degrees of increase. Notably, COX2 exhibited a high sensitivity to Au-doped graphene. Furthermore, in the effect of doping Au into graphene, the Eads absorption of COCl2 gas has increased from 0.155 to 1.028 eV. This indicates the strong tendency of Au-doped graphene to interact with gas COCl2 compared to two other COX2 gas species. This strong adsorption can be ascribed to significant substantial charge transfer (CT) between COCl2 and Au-doped graphene and orbital hybridization. The charge transfer amount of the doped states has increased by more than double compared to the pure state. The band gap of Au-doped graphene has decreased from 2.14 to 1.83 eV due to the absorption of gas COCl2, indicating the highest amount of reduction compared to other gases. Moreover, the enhanced electrical conductivity of Au-doped graphene renders it more valuable and sensitive in the context of sensing COX2 gases.

Adsorption of toxic gases by Janus MoSeTe monolayers doped with transition metals and surface defects: A first-principles study

In recent years, two-dimensional TMDs materials have been proved to be high-performance gas sensor materials. Janus material is a member of the TMD family, and its gas sensing performance research is particularly important. Gas sensing mechanism of toxic gases on transition metal dichalcogenides based Janus MoSeTe monolayers is investigated using the density functional theory. Six transition metals are considered to modify the MoSeTe surface, by comparing the adsorption energies of the transition metal on both sides of the MoSeTe monolayer, it is found that the transition metal doping is more stable on the Se side. The MoSeTe surface is activated by transition metal modification, and the gas behavior is improved by transition metal modification, it is found that Ir-MoSeTe had the best sensing performance for NO2, Os-MoSeTe had the best sensing performance for CO, and Ru-MoSeTe had the best sensing performance for H2S, NO, and SO2. After that, we explain the adsorption mechanism of gas molecules by calculating the band structure, state density, differential charge density and work function of the adsorption structure, and the recovery time explain the reuse performance of the sensor. The results show that transition metal doped MoSeTe is a promising toxic gas sensor, which provides a theoretical basis for the development of new gas sensors.

Development of toxic gas sensor from anthocyanin-embedded polycaprolactone-co-polylactic acid nanofibrous mat

The colorless ammonia gas has been a significant intermediate in the industrial sector. However, prolonged exposure to ammonia causes harmful effects to organs or even death. Herein, an environmentally friendly solid-state ammonia sensor was developed utilizing colorimetric polycaprolactone-co-polylactic acid nanofibrous membrane. Pomegranate (Punica granatum L.) peel contains anthocyanin (ACN) as a naturally occurring spectroscopic probe. A mordant (potassium aluminum sulfate) is used to immobilize the anthocyanin direct dyestuff inside nanofibers, generating mordant/anthocyanin (M/ACN) coordinated complex nanoparticles. When exposed to ammonia, the color change of anthocyanin-encapsulated polycaprolactone-co-polylactic acid nanofibrous membrane from purple to transparent was examined by absorbance spectra and CIE Lab color parameters. With a quick colorimetric shift, the polycaprolactone-co-polylactic acid fabric exhibits a detection limit of 5–150 mg/L. The absorbance spectra showed a hypsochromic shift when exposed to ammonia, displaying an absorption shift from 559 nm to 391 nm with an isosbestic point of 448 nm. Scanning electron microscopy (SEM) images revealed that the polycaprolactone-co-polylactic acid nanofibers had a diameter of 75–125 nm, whereas transmission electron microscopy (TEM) images revealed that M/ACN nanoparticles exhibited diameters of 10–20 nm.

A DFT study of Mg9O9 nanoring for gas sensing and removal applications

The toxic gas molecules are extremely harmful to both the environment and human health. To address this issue, we need to develop materials that can detect these gases and assist in their removal from the surrounding. Here, we analyzed the structure and electronic properties along with stability of newly predicted Mg9O9 nanoring i.e. allotrope of cyclo[18]carbon (C18 nanoring) employing density functional theory (DFT). In addition, present work also investigated the sensing properties of Mg9O9 nanoring towards toxic gases such as CO, NO and NH3. The substantial interaction of NO and NH3 gases with Mg9O9 nanoring is confirmed by the high adsorption energy and short adsorption distance. In contrast, weak interaction of CO gas molecule with Mg9O9 nanoring is verified by the comparatively long adsorption distance and small adsorption energy. The modulation in the dipole moment of the nanoring after adsorption of toxic gas molecules further confirms interaction between them. Our results indicate that the Mg9O9 nanoring is suitable for work-function-based sensor for NO and NH3 gases, as well as an electronic sensor only for NO gas molecule. The Mg9O9 nanoring shows an optimal recovery time (τ) for NO gas, indicating its applications as a sensor. Conversely, a longer τ observed for NH3 gas with Mg9O9 nanoring depicts its potential for gas adsorption or removal from the environment. Our findings unequivocally demonstrate that the Mg9O9 nanoring can function as a highly effective toxic gas sensor.

Interaction study of CO and NO pollutant gases with pristine, defected and doped α-CX (X=N, P) monolayers using density functional theory

CO and NO are two of the most pollutant gases that exist in the environment, which makes their tracing highly crucial. In this problem, we have investigated the adsorption performances of highly toxic CO and NO gases over pristine, defect-tuned, and Aluminium (Al)-doped α-CX (X=N, P) monolayers. In addition to the adsorption properties, we have calculated electronic properties such as band structure, projected density of states (PDOS) and charge transfer, sensing properties such as work function and recovery time for pristine, defect-tuned, and Al-doped α-CX before and after the gas adsorption process. Given the poor adsorption energies and large adsorption distances, pristine α-CX monolayers are not suitable candidates for the toxic gas sensors. In case of functionalized α-CX, the adsorption energy is highest in case of C-defected α-CN for CO gas adsorption. For interaction of NO gas molecule with functionalized α-CX, Al-doped α-CN is deemed to be best candidate for adsorption. The computed recovery times are extremely long (exceeding several hours) in the best-case scenarios, this implies that C-defected α-CN and Al-doped α-CN are most suitable for CO and NO gas removal applications.

Understanding sensing mechanism of N-doped graphene-based toxic gas sensors using electronic, thermal, mechanical, electrical, and sensing properties:A DFT study

A facile and feasible protocol for the evolution of sensing characteristics of three dissimilar nitrogen-doped graphene (N-G)-based ethanol, methanol, and nitrogen-oxide gas sensors using first-principle calculations. Simulated X-ray diffraction (XRD) investigation demonstrates the sharp peak located at 7.9, 11, 13.8, and 15.4° represents (100), (111), (026), and (012) facets. Electronic properties calculations predict that toxic gas adsorption reduces the charge carrier concentration and induces internal resistance. Thermal properties analyses suggest that the nature of adsorption depends on changes in Gibbs free energy. Charge density and distribution analysis disclose that the adsorption of toxic gases leads to charge transfer between toxic gases and N-G. Mechanical properties analyses predict the mechanical superiority. The N-G's electrical conductivity and resistivity of are 49.95 × 103 Ω/m, and 2 × 10−5 Ω-m respectively. The electrical properties demonstrate that the adsorption of toxic gases would be a reason for the change in electrical conductivity and resistivity. The sensing response of N-G-M in terms of resistivity is 96.04 %. The sensing response of ethanol, NO are 17.12 %, and 5.95 %. Responses of N-G-E, N-G-M, N-G-N″-Z are 0.01, 0.06, 0.14 respectively.

Fiber colorimetric sensors with ambient humidity tolerance for NH3 sensing

Colorimetric sensors with visual color changes toward toxic gas have been investigated to prevent potential hazardous accidents caused by leakage. The sensitivity of most colorimetric sensors in practical applications is interfered with ambient humidity. This work introduced a hygroscopic substance lithium chloride (LiCl) to be used as humidity compensation to alleviate humidity interference to colorimetric sensor. Cellulose-based colorimetric fibers were prepared from waste cotton using chlorophenol red as an indicator dye in a LiCl/DMAc solvation system. The obtained colorimetric fibers responded quickly to NH3 within 30 s at 50% RH. At the same time, this colorimetric fiber has excellent selectivity and excellent reusability, which could maintain 82% of the original colorimetric response over several cycles. Because of the flexibility, this NH3 sensing colorimetric fiber can be sewn into patterned textiles for manufacturing wearable toxic gas sensors with visual output.

Potential application of a defective NiCl2 monolayer as a toxic gas sensor: a computational study

An experimentally feasible defective NiCl2 monolayer is used as a substrate in this paper, and its feasibility as a gas sensor for detecting O2 and CO gases under different conditions is demonstrated by density functional theory calculations.

An ultra-sensitive and recyclable FET-type toxic gas sensor based on WTe2 monolayers

Field-effect-transistor (FET)-type gas sensors have attracted a surge of research interest due to their low power dissipation and exceptional sensitivity.

Two-dimension Cd-N co-doped α-AsP as high sensitivity and selectivity NO and NO2 sensor: A first-principles study

This study aims to develop a newfangled toxic gas (NO and NO2) sensor. The adsorption and gas-sensing performance of toxic gas absorbed on the two-dimension arsenic-phosphorus (α-AsP) monolayer was theoretically researched using the DFT calculations. It is found that α-AsP monolayer has weak adsorption performance, and the single non-metal/metal atom doped AsP systems have weak-physical/strong-chemical adsorption behaviors. However, metallic (Cd, Ag, Au, Pt and Fe) and N co-doped AsP systems exhibit excellent gas sensing performance to NO and NO2 gases. These adsorption systems exhibit enhanced gas-sensing performance by regulating the adsorption energy between weak physical adsorption and strong chemical adsorption. It is worth mentioning that the sensitivity of NO and NO2 adsorption on Cd-N co-doped AsP reaches a surprising 94.908% and 78.291%, respectively. Moreover, we predicted that the CdN-AsP system is suitable for NO and NO2 gas-sensing under multiple gas environment by comparing the selectivity, electronic and adsorption properties. Our work has provided a critical reference to develop the potential gas sensor for NO and NO2 detections.

Theoretical screening into urea-based receptor as a promising toxic gas sensor upon SO2, NH3 and H2S

The adsorption of toxic gases such as NH3, SO2, H2S, on 1,3 bis (4-nitrophenyl) urea (BNPU) was investigated via the M062X/6–311++ g (d, p) level of theory to evaluate the utility of BNPU-based gas sensors. For each gas molecule, the most stable configuration was determined and the adsorption energies were calculated. The trend of adsorption stability of complexes is observed as, SO2@BNPU≈NH3@BNPU>H2S@BNPU. Further, electronic properties such as orbital analysis, natural bond orbital analysis, and density of states were investigated to understand the mechanism of sensing. The HOMO-LUMO gap was lowered upon adsorption with these gases. The QTAIM analysis was carried out to sketch the nature of the hydrogen bond. An external electric field (EF) of intensity -0.15 V/Å up to +0.15 V/Å was used to further improve the toxic gas-sensing properties of the BNPU. Furthermore, the presence of the EF has a significant effect on the dipole moment and the HOMO-LUMO energy gap.

Blue phosphorus phase GeSe monolayer for nitrogenous toxic gas sensing: A DFT study

Continuing industrialization, a variety of toxic gases are emitted into the air, yet gas concentrations at low levels are extremely hard to detect. So the development of high-performance toxic gas sensors is imminent. Two-dimensional materials with advantages such as large specific surface area and unique electronic properties open new paths for gas sensors. In this study, a monolayer of blue phosphorus phase germanium selenide (GeSe) was used as the substrate material. The absorption performance of ambient nitrogenous toxic gases (NO, NO2, NH3, N2O) on the surface of GeSe monolayers was explored by the density-functional theory (DFT) calculations. The results show that the interaction between GeSe and the four gases exhibits physisorption. Based on four optimal adsorption structures, Bader charge, work function, band structure, density of states, and recovery time were calculated. Charge transfer is promoted due to the presence of GeSe intrinsic dipoles and only NH3 was found to be the charge donor. The significant changes in work function and electronic properties of GeSe monolayer adsorption of NO indicate significant changes in electrical signals during gas detection. This work reveals that GeSe monolayer has higher sensitivity and selectivity for NO hazardous gas.

Modeling of the lyotropic cholesteric liquid crystal based toxic gas sensor using adaptive neuro-fuzzy inference systems

Detection of toxic gases is important in a variety of settings, including industrial facilities, laboratories, and even in homes. In these settings, toxic gas detection can help prevent accidents and protect the health and safety of workers, researchers, and others who may be exposed to these gases. This study evaluates an Adaptive Neuro-Fuzzy Inference System (ANFIS) models in predicting the machining responses in the detection of toxic gases vapor, such as toluene (T), phenol (P) and 1,2 dichloropropane (D) using lyotropic cholesteric crystal (CLC) have been shown to have potential as gas sensors due to their unique optical and liquid crystal (LC) properties, and the ANFIS model may be used to better understand and optimize these properties for toxic gas detection. Experiments were carefully carried out to gather data on the response of a lyotropic CLC toxic gas vapor sensor. The effectiveness of using ANFIS combined with Grid Partitioning (GP) was then carefully studied and evaluated in terms of modeling and predicting the responses of the sensor. The best ANFIS-GP model is chosen from these criteria; RSS, PCC, R2, RMSE, MSE, MAE, and MAPE. In addition, validation was performed between the model and experimental data using the LOOCV method. The results show that the ANFIS-GP5 model with 96 fuzzy inference systems (FIS) rules with high R2 values. According to the ANFIS-GP5 model, R2varied ranges from 0.77 to 1 for train, test, and total data of lyotropic CLC sensor exposed to toluene, phenol and 1,2 dichloropropane toxic gases vapors.

Capacitive Toxic Gas Sensors Based on Oxide Composites: A Review

Capacitive Toxic Gas Sensors Based on Oxide Composites: A Review