Effective Gas Sensor Research Articles

Hydrogen sensors of Ce-doped MoS2 with anti- humidity for early warning thermal runaway in lithium-ion batteries

Early warning of thermal runaway in lithium-ion batteries is critical to improving their safety and reliability in energy storage systems, electric vehicles, and other applications. Analyzing gas release, especially H2, is a suitable indicator for early warning of thermal runaway, but the sensitivity and service life of gas sensors are highly susceptible to humidity. Herein, we develop a H2-based sensor to monitor the thermal runaway of lithium-ion batteries using Ce-doped MoS2 modulated by amphiphiles. The unique amphiphiles provide a hydrophobic protective layer, ensuring stability in high-humidity environments for H2 detection. Applying this gas sensor for monitoring thermal runaway in lithium-ion batteries offers a 76-s advance warning compared to traditional temperature signals, effective in both overcharge and overheating induced thermal runaways. While this study presents an effective gas sensor for early thermal runaway warnings in lithium-ion batteries, further optimization is required for future applications due to its high sensitivity to temperature fluctuations (100 ppm H2/°C).

Carborazine doped nanographene (CBNG) sheet as a promising NO2 gas sensor: A theoretician’s approach

Nanographenes (NGs) are a distinct section of graphene in which the dangling bonds are saturated with hydrogen atoms (C42H18). This confinement in size results in unique properties and potential applications. The density functional theory (DFT) is used to investigate the reactivity and electronic sensitivity of a model carborazine (B2C2N2) ring doped nanographene (CBNG) for detecting NO2 gas. In CBNG/NO2 complex, one oxygen atom of the NO2 molecule is positioned at a distance of 2.93Ả from the center of the B2C2N2 ring, with an adsorption energy −6.2 kcal/mol. The adsorption energy of NO2 on CBNG is apparently larger than those of other gas molecules, which fall between the suitable range of strong physical adsorption and weak chemical adsorption. Upon NO2 adsorption, the band gap of CBNG sheet reaches 62.4 %. The outcome of the present study may be exploited in the industry, particularly in the synthesis of effective NO2 gas sensors.

Discharge fault detection of dry air switchgear based on ZnO-MoS2 gas sensor

Abstract When discharge faults occur in dry air switchgear, the air decomposes to produce diverse gases, with NO2 reaching the highest levels. Detecting the NO2 level can reflect the operation status of the equipment. This paper proposes to combine ZnO cluster with MoS2 to improve the gas-sensitive properties of the monolayer. Based on the Density Functional Theory (DFT), the effect of (ZnO)n size on the behavior of MoS2 is considered. Key parameters such as adsorption energy and band gap of (ZnO)n-MoS2/NO2 system were calculated. The ZnO-MoS2 heterojunction was successfully synthesized by a hydrothermal method. The gas sensor exhibits a remarkable response and a fast response-recovery time to 100 ppm NO2. In addition, it demonstrates excellent selectivity, long-term stability and a low detection limit. This work confirms the potential of the ZnO-MoS2 composite structure as a highly effective gas sensor for NO2 detection, which provides valuable theoretical and experimental insights for fault detection in dry air switchgear.

Sub-ppb H2S Sensing with Screen-Printed Porous ZnO/SnO2 Nanocomposite.

Hydrogen sulfide (H2S) is a highly toxic and corrosive gas commonly found in industrial emissions and natural gas processing, posing serious risks to human health and environmental safety even at low concentrations. The early detection of H2S is therefore critical for preventing accidents and ensuring compliance with safety regulations. This study presents the development of porous ZnO/SnO2-nanocomposite gas sensors tailored for the ultrasensitive detection of H2S at sub-ppb levels. Utilizing a screen-printing method, we fabricated five different sensor compositions-ranging from pure SnO2 to pure ZnO-and characterized their structural and morphological properties through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Among these, the SnO2/ZnO sensor with a composition-weight ratio of 3:4 demonstrated the highest response at 325 °C, achieving a low detection limit of 0.14 ppb. The sensor was evaluated for detecting H2S concentrations ranging from 5 ppb to 500 ppb under dry, humid air and N2 conditions. The relative concentration error was carefully calculated based on analytical sensitivity, confirming the sensor's precision in measuring gas concentrations. Our findings underscore the significant advantages of mixture nanocomposites in enhancing gas sensitivity, offering promising applications in environmental monitoring and industrial safety. This research paves the way for the advancement of highly effective gas sensors capable of operating under diverse conditions with high accuracy.

Chemical spray pyrolysis deposited ZnO/ZIF-8 and cobalt doped ZnO/ZIF-8 composite thin films for highly sensitive and selective ammonia sensing at room temperature

ZnO is a widely studied metal oxide for gas sensor applications concerning its biocompatibility and physio-chemical properties. However, the high operating temperature and low response are drawbacks. ZIF-8, the metal-organic framework of Zinc and imidazolate, is renowned for its gas adsorption property. The poor stability of ZIF-8 also limits its application as an effective gas sensor. Thus, a composite thin film of ZnO and ZIF-8 is deposited on a glass substrate using the chemical spray pyrolysis technique to detect ammonia at room temperature (300 K). The composite thin film is stable, has a good response, and is repeatable. Further, to enhance the sensor response at room temperature, Co is doped to the ZnO/ZIF-8 composite thin films. The sensor response for 1 ppm of ammonia for the Co doped ZnO/ZIF-8 is 301 at room temperature. Along with the gas adsorption capability of ZIF-8 providing more active sites, the change in morphology from flakes to spherical grains on doping with Co provided higher active surface area and free electrons and all together instigated fast redox reaction and conduction mechanism in ZnO. Hence, the Co doped ZnO/ZIF-8 composite thin films have an enhanced response of 117,285 to 50 ppm of ammonia.

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.

Fabrication and detection characteristics evaluation of SnO2@WO3 film as an effective NO2 gas sensor

In this article, tin oxide (SnO2) doped tungsten oxide (WO3) was deposited on Si substrate as an effective NO2 gas sensor via pulsed laser deposition (PLD) considering different content of SnO2 to WO3. Further, the correlation between the investigated microstructural and sensing characteristics was thoroughly elaborated. Specifically, an increment in the SnO2 content from 10:90 to 30:70 % resulted in smaller nanoparticle diameter (53.9–45.9 nm); the attained energy bandgap exhibited an inverse profile along considerably high electrical resistance alteration. In detail, the gas response increased from 30.7 to 39.5 for the addressed SnO2 to WO3 contents, respectively. The examined operating temperature indicated a negative correlation along the evaluated sensing profile with R2 value of −0.98. The time-resolved characteristics of the optimum gas sensor (@30:70) revealed rise/fall time of 6 and 13 sec. at 150 °C, respectively; this was found to be pronouncedly higher at higher operating temperatures.

Integrated Mixed Potential Gas Sensor with Efficient Structure for Discriminative Volatile Organic Compounds Detection.

Amid growing interest in the precise detection of volatile organic compounds (VOCs) in industrial field, the demand for highly effective gas sensors is at an all-time high. However, traditional sensors with their classic single-output signal, bulky and complex integrated structure when forming array often involve complicated technology and high cost, limiting their widespread adoption. Here, this study introduces a novel approach, employing an integrated YSZ-based (YSZ: yttria-stabilized zirconia) mixed potential sensor equipped with a triple-sensing electrode array, to efficiently detect and differentiate six types of VOCs gases. This innovative sensor integrates NiSb2O6, CuSb2O6, and MgSb2O6 sensing electrodes (SEs), which are sensitive to pentane, isoprene, n-propanol, acetone, acetic acid, and formaldehyde gases. Through feature engineering based on intuitive spike-based response values, it accentuates the distinct characteristics of every gas. Eventually, an average classification accuracy of 98.8% and an overall R-squared error (R2) of 99.3% for concentration regression toward six target gases can be achieved, showcasing the potential to quantitatively distinguish between industrial hazardous VOCs gases.

Promising CO2 gas sensor application of zinc oxide nanomaterials fabricated via HVPG technique

Highly effective gas sensors for detecting a range of hazardous and toxic gases were successfully applied in the present study using Zinc oxide (ZnO) nanomaterials. In this work, the horizontal vapor phase growth (HVPG) technique was perfectly capable of the synthesis of zinc oxide (ZnO) nanomaterials. The effect of the growth time with different dwell times was discussed by comparing the SEM-EDX analysis and photoluminescence characterization of the samples. Magnetic field (AMF) was also incorporated to determine the effect of AMF on the synthesis of ZnO nanomaterials. The results showed that the ZnO nanorods and root-like shapes are formed with more than 5 μm length and a few nm diameters. The optimum parameter showed the sensors are shiner than the less effective sensor when applied. The introduction of an external magnetic field led to a reduced energy band gap by a maximum of 15 %. The non-AMF band gap energy value is observed to be between 3.51 and 3.58 eV, while the value obtained using AMF is found to be between 2.94 and 3.22 eV. During the CO2 gas sensor test, AMF ZnO nanomaterial samples exhibited higher voltage and gradient compared to non-AMF samples.

Characterization of o-B2N2 monolayer surface for effective sensing and detection of toxic nitrogen oxides

Using density functional theory (DFT), researchers examined how the o-B2N2 monolayer interacts with toxic gases such as NO2 and NO. They investigated various aspects of the adsorption system, including its state density, differential charge density, optimal structure, and other features. The analysis revealed that the o-B2N2 monolayer remained stable throughout the adsorption process. The researchers also examined additional properties of the adsorption process, including work function, sensitivity, response time, recovery time, and energy gap to gain a deeper comprehension of adsorption features of NO2 and NO gases. The findings indicate that the o-B2N2 monolayer exhibits a shorter recovery time at higher temperatures, suggesting improved performance. Furthermore, the monolayer demonstrates higher sensitivity and a greater variation in the work function, indicating its superior adsorption capabilities. The findings suggest that the o-B2N2 monolayer has potential with great promise as an adsorbent for toxic gases like NO2 and NO. This has practical implications for applications such as air purification and environmental protection. Our findings demonstrate that the o-B2N2 monolayer serves as an effective gas sensor at room temperature, exhibiting both high sensitivity and selectivity in detecting NO2 and NO gases. Moreover, it can be reused multiple times for gas detection purposes.

A novel capacitive sensor interface based on a simple capacitance-to-phase converter

Abstract A novel room temperature capacitive sensor interface circuit is proposed and successfully tested, which uses a modified All-Pass filter architecture combined with a simple series resonant tank circuit with a moderate Q-factor. It is fashioned from a discrete inductor with small dissipation resonating with a grounded capacitor acting as the sensing element to obtain a resolution of ∆C ~ 2 zF in a capacitance range of 10 – 30 pF. The circuit converts the change in capacitance to the change in the phase of a carrier signal in a frequency range with a central frequency set up by the tank circuit’s resonant frequency and is configured to act as a close approximation of the ideal All-Pass filter. This cancels out the effects of amplitude modulation when the carrier signal is imperfectly tuned to the resonance. The proposed capacitive sensor interface has been specifically developed for use as a front-end constituent in ultra-precision mechanical displacement measurement systems, such as accelerometers, seismometers, gravimeters and gravity gradiometers, where moving plate grounded air gap capacitors are frequently used. Some other applications of the proposed circuit are possible including the measurement of the electric field, where the sensing capacitor depends on the applied electric field, and cost effective capacitive gas sensors. In addition, the circuit can be easily adapted to function with very small capacitance values (1 - 2 pF) as is typical in MEMS-based transducers.

Preparation of Pt and bamboo charcoal co-modified TiO2 for formaldehyde sensing at room temperature.

Anatase TiO2 has evolved into one of the most attractive materials for gas sensing owing to its strong oxidation activity and excellent sensing properties. In this study, we prepared Pt and bamboo charcoal co-modified nano-TiO2 using a one-pot hydrothermal process and applied it to detect formaldehyde. The successful incorporation of the precious metal Pt and bamboo charcoal onto TiO2 was confirmed by scanning electron microscope, transmission electron microscopy, energy dispersive spectrometer, X-ray diffraction and X-ray photoelectron spectroscopy. Detailed analysis revealed a homogeneous distribution of Pt nanoparticles and bamboo charcoal on the TiO2 surface, which significantly improved the surface area and facilitated gas adsorption. These modifiers significantly enhanced the response of TiO2 to formaldehyde, for instance, the response signal increased fourfold, while the response time decreased from 91 to 68 s. The sample with 0.5@Pt and 0.5@C bamboo charcoal performed the best, showcasing the synergistic effect of metal nanoparticles and carbonaceous materials on gas-sensing properties. Our work highlighted the potential of using biomass-derived carbon to enhance the detection of formaldehyde and demonstrated the importance of material characteristics in designing effective gas sensors.

Extrusion Printing of Surface-Functionalized Metal-Organic Framework Inks for a High-Performance Wearable Volatile Organic Compound Sensor.

Wearable sensors hold immense potential for real-time andnon-destructive sensing ofvolatile organic compounds (VOCs), requiring both efficient sensing performance and robust mechanical properties. However, conventional colorimetric sensor arrays, acting as artificial olfactory systems for highly selective VOC profiling, often fail to meet these requirements simultaneously. Here, a high-performance wearable sensor array for VOC visual detection is proposed by extrusion printing of hybrid inks containing surface-functionalized sensing materials. Surface-modified hydrophobic polydimethylsiloxane (PDMS) improves the humidity resistance and VOC sensitivity of PDMS-coated dye/metal-organic frameworks (MOFs) composites. It also enhances their dispersion within liquid PDMS matrix, thereby promoting the hybrid liquid as high-quality extrusion-printing inks. The inks enable direct and precise printing on diverse substrates, forming a uniform and high particle-loading (70 wt%) film. The printed film on a flexible PDMS substrate demonstrates satisfactory flexibility and stretchability while retaining excellent sensing performance from dye/MOFs@PDMS particles. Further, the printed sensor array exhibits enhanced sensitivity to sub-ppm VOClevels, remarkable resistance to high relative humidity (RH) of 90%, and the differentiation ability for eight distinct VOCs. Finally, the wearable sensor proves practical by in situ monitoring of wheat scab-related VOC biomarkers. This study presents a versatile strategy for designing effective wearable gas sensors with widespread applications.

Building Feedback-Regulation System Through Atomic Design for Highly Active SO2 Sensing.

Reasonably constructing an atomic interface is pronouncedly essential for surface-related gas-sensing reaction. Herein, we present an ingenious feedback-regulation system by changing the interactional mode between single Pt atoms and adjacent S species for high-efficiency SO2 sensing. We found that the single Pt sites on the MoS2 surface can induce easier volatilization of adjacent S species to activate the whole inert S plane. Reversely, the activated S species can provide a feedback role in tailoring the antibonding-orbital electronic occupancy state of Pt atoms, thus creating a combined system involving S vacancy-assisted single Pt sites (Pt-Vs) to synergistically improve the adsorption ability of SO2 gas molecules. Furthermore, in situ Raman, ex situ X-ray photoelectron spectroscopy testing and density functional theory analysis demonstrate the intact feedback-regulation system can expand the electron transfer path from single Pt sites to whole Pt-MoS2 supports in SO2 gas atmosphere. Equipped with wireless-sensing modules, the final Pt1-MoS2-def sensors array can further realize real-time monitoring of SO2 levels and cloud-data storage for plant growth. Such a fundamental understanding of the intrinsic link between atomic interface and sensing mechanism is thus expected to broaden the rational design of highly effective gas sensors.

Nanoscale morphology, optical dynamics and gas sensor of porous silicon

We investigated the multifaceted gas sensing properties of porous silicon thin films electrodeposited onto (100) oriented P-type silicon wafers substrates. Our investigation delves into morphological, optical properties, and sensing capabilities, aiming to optimize their use as efficient gas sensors. Morphological analysis revealed the development of unique surfaces with distinct characteristics compared to untreated sample, yielding substantially rougher yet flat surfaces, corroborated by Minkowski Functionals analysis. Fractal mathematics exploration emphasized that despite increased roughness, HF/ethanol-treated surfaces exhibit flatter attributes compared to untreated Si sample. Optical approaches established a correlation between increased porosity and elevated localized states and defects, influencing the Urbach energy value. This contributed to a reduction in steepness values, attributed to heightened dislocations and structural disturbances, while the transconductance parameter decreases. Simultaneously, porosity enhances the strength of electron‒phonon interaction. The porous silicon thin films were further tested as effective gas sensors for CO2 and O2 vapors at room temperature, displaying notable changes in electrical resistance with varying concentrations. These findings bring a comprehensive exploration of some important characteristics of porous silicon surfaces and established their potential for advanced industrial applications.

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.

Investigation of sensing properties of Sn-doped NiO thin films for the detection of ammonia gas

In this study, we detail the fabrication of Sn-doped nickel oxide thin films using the spin-coating technique, elucidating the impact of Sn doping on structural, optical, and gas sensing properties. Systematic analysis via XRD, SEM, AFM, and UV–Visible spectroscopy delves into the structural and optical characteristics of the films. Notably, gas sensing capabilities, specifically towards NH3, are investigated. XRD analysis reveals the polycrystalline nature of NiO thin films, with crystallinity diminishing as Sn concentration increases. SEM and AFM analyses highlight a uniform film surface with spherical-shaped particles, and increased surface roughness with higher Sn content, a crucial factor for gas sensing applications. Raman analysis showcases first-order phonon modes of vibrations of Ni-O, while optical studies affirm the films' transparency in the visible wavelength. Notably, in ammonia gas sensing tests at room temperature, the 8 mol% Sn-doped NiO thin film exhibits an exceptional response of 3200 %, with a rapid 40-second response time and a 25-second recovery time at a 150 ppm concentration of ammonia gas. These findings suggest that Sn-doped NiO thin films hold promise as effective gas sensors for NH3 detection.

Porous materials as effective chemiresistive gas sensors.

Chemiresistive gas sensors (CGSs) have revolutionized the field of gas sensing by providing a low-power, low-cost, and highly sensitive means of detecting harmful gases. This technology works by measuring changes in the conductivity of materials when they interact with a testing gas. While semiconducting metal oxides and two-dimensional (2D) materials have been used for CGSs, they suffer from poor selectivity to specific analytes in the presence of interfering gases and require high operating temperatures, resulting in high signal-to-noise ratios. However, nanoporous materials have emerged as a promising alternative for CGSs due to their high specific surface area, unsaturated metal actives, and density of three-dimensional inter-connected conductive and pendant functional groups. Porous materials have demonstrated excellent response and recovery times, remarkable selectivity, and the ability to detect gases at extremely low concentrations. Herein, our central emphasis is on all aspects of CGSs, with a primary focus on the use of porous materials. Further, we discuss the basic sensing mechanisms and parameters, different types of popular sensing materials, and the critical explanations of various mechanisms involved throughout the sensing process. We have provided examples of remarkable performance demonstrated by sensors using these materials. In addition to this, we compare the performance of porous materials with traditional metal-oxide semiconductors (MOSs) and 2D materials. Finally, we discussed future aspects, shortcomings, and scope for improvement in sensing performance, including the use of metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and porous organic polymers (POPs), as well as their hybrid counterparts. Overall, CGSs using porous materials have the potential to address a wide range of applications, including monitoring water quality, detecting harmful chemicals, improving surveillance, preventing natural disasters, and improving healthcare.

Enhanced CO sensing with highly sensitive and selective rGO-Ru OEP chemiresistive sensor

The escalating discharge of noxious gases resulting from unmitigated anthropogenic activities has emerged as a pivotal concern, presenting imminent threats to global ecosystems. In response to this pressing challenge, the development of cutting-edge materials within gas sensor systems emerges as a promising avenue for the precise detection of hazardous gaseous pollutants. This investigation delves into the synthesis and characterization of a novel composite material: reduced graphene oxide (rGO) modified with ruthenium Octaethyl porphyrin (Ru OEP), with a primary focus on its chemiresistive sensing properties. The meticulously deposited rGO-modified Ru OEP material onto gold microelectrodes, featuring a 3 µm gap on a silicon Si/SiO2 substrate, resulted in an intricate two-terminal chemiresistive sensor device. Comprehensive structural, spectroscopic, and morphological analyses were conducted to elucidate the intricacies of the composite material. The electrical characterization, evaluated through I-V measurements, provided nuanced insights into the device's resistance properties. Notably, the chemiresistive sensor demonstrated exceptional responsiveness to Carbon monoxide (CO) gas, exhibiting an impressively low limit of detection (LOD) at 2.5 ppm. The fabricated sensor showcased rapid response and recovery times, registering at 43 s and 65 s, respectively, underscoring its efficiency in real-time applications. Furthermore, the sensor maintained linearity and stability across a broad spectrum of conditions, ensuring prolonged reliability and consistent performance. This research underscores the potential of advanced materials, specifically the rGO-modified Ru OEP composite, in crafting highly effective gas sensors to address urgent environmental and safety concerns. The presented findings contribute invaluable insights to the burgeoning field of gas sensor technology, paving the way for innovative solutions to mitigate the adverse impacts of anthropogenic activities on our delicate ecosystems.

Humidity activated ultra-selective room temperature gas sensor based on W doped MoS2/RGO composites for trace level ammonia detection

The lack of highly efficient, cost effective and stable ammonia gas sensors functionable at room temperature even in extreme humid environments poses significant challenge for the future generation gas sensors. The prime factors that impede the development of such next generation gas sensors are the strong interference of humidity and sluggish selectivity. Herein, we fabricated tungsten doped molybdenum disulphide/reduced graphene oxide composite by an in-situ hydrothermal method to exploit the adsorption, dissolution (solubility), ionization and transmission process of ammonia and thereby to effectuate its trace level detection even in indispensable humid environments. The protype based on 5 at.% Tungsten doped MoS2/RGO (W5) gas sensor exhibited 3.8-fold increment in its response to 50 ppm of ammonia when the relative humidity varied from 20 % to 70 % with ultra-high selectivity at room temperature. The as prepared gas sensor revealed a practical detection limit down to 1 ppm with a substantial response and rapid recovery time. Furthermore, W5 gas sensor exhibited a 42-fold increment in response to 50 ppm of ammonia relative to its pristine (MoS2/RGO) MG composite with a RH of 70 %. The proton hopping mechanism accountable for such an enormous enhancement in ammonia sensing and its potential for breath sensor are briefly annotated.