Gas Detection Research Articles

An Enhanced YSZ Gas Sensor through Optimizing Electrode Thickness for ppb-level H2S Detection

Nowadays, there is uncertainty regarding the impact of sensing electrode thickness on the gas sensing performance of mixed potential gas sensors due to simultaneous competitive heterogeneous catalytic reaction and electrochemical reaction. In this study, yttrium oxide doped zirconia gas sensors with varying thickness of NiFe2O4 sensing electrode have been fabricated for H2S gas detection. The operating temperature of yttrium oxide doped zirconia gas sensors have been firstly optimized, followed by a systematic study of the effects of NiFe2O4 sensing electrode thickness on H2S sensing performance. The best sensing performance have been achieved for the yttrium oxide doped zirconia gas sensor with a 10 μm-thick sensing electrode (S-10 sensor). Sensitivities of −8.7 and −44.6 mV/decade have been attained for 10–100 ppb and 100–10000 ppb, respectively, with a lower limit of detection as low as 10 ppb at 510 °C for the S-10 sensor. Furthermore, the potential application of the S-10 sensor in halitosis detection was further evaluated using simulated exhaled breath from patient with halitosis and healthy volunteers. The significant change in human exhaled gas response values detect by the S-10 sensor at different times provide additional support for the prospect of diagnosing halitosis.

Concentration calculation model for calibration of non-dispersive infrared gas detection system

Non-dispersive infrared (NDIR) gas detection systems have been extensively used for gas monitoring because they are considered the simplest approach with moderate sensitivity and fast response. Concentration calculation models for calibration are particularly important in NDIR gas detection systems because of the nonlinear relationship between the output voltage ratio and concentration. We propose a concentration calculation model with two fitting parameters for non-dispersive infrared gas detection systems, accounting for the fact that not all IR radiation that impinges upon the detector is absorbed by the gas and for the saturation effects in absorption peaks leading to the nonlinear relationship. Despite the small number of fitting parameters of the proposed concentration calculation model, it presents high quality curve fitting to experimental data. The performance of the proposed model is compared to that of other concentration calculation models.

Pd-Adsorbing CrS2 monolayer as sensing material for detecting CO, C2H2, and C2H4 in dissolved gases: A first-principles study

This study employs density functional theory to initially examine the adsorption characteristics of Pd atom on CrS2 monolayer (termed Pd@CrS2). Subsequently, the adsorption capabilities of Pd@CrS2 monolayer for CO, C2H2, and C2H4 are simulated to assess its prospects for dissolved gas detection. Stable adsorption of Pd atoms onto the CrS2 monolayer atop Cr atoms is observed with a binding energy of −2.69 eV. Pd@CrS2 exhibits chemisorption towards CO, C2H2, and C2H4 with respective adsorption energies of −1.49, −1.13, and −1.22 eV. The band structure and density of states analysis indicate significant alterations in the electronic properties of CrS2 upon Pd adsorption and upon exposure to the gases. The bandgap of Pd@CrS2 is modified by −29.6 %, −24.7 %, and −27.1 % after CO, C2H2, and C2H4 adsorption, corresponding to highly sensitive detection responses of −99.6 %, −98.9 %, and −99.3 %. The research highlights the gas sensing capabilities of Pd@CrS2 monolayers for monitoring the operational status in dissolved gas analysis, showcasing the promising application potential of CrS2.

Assessment of harmful gases emission and its impact using IoT and geospatial technology

Numerous industries in our daily lives use a variety of dangerous chemical gases, and workers are frequently exposed to these gases. The losses due to harmful gases can be reduced by developing an automatic harmful gases detection and alerting system. This study aims to design, develop, and implement an automatic warning system using series of gas sensors to deduct. The designed system is implemented to monitor 3 locations to detect the hazardous pollutions parameters, namely Large-Scale industries, wood burning sites and residential housings and analysed to understand the pollution level. This study observed elevated temperatures (35–45 °C) and heat index (30–50 °C) in large-scale industries, along with higher harmful gases compared to wood-burning sites and homes. Interestingly, wood-burning sites exhibited higher humidity (60–70 %) and peak ozone and methane levels compared to other locations. These variations underscore the unique environmental characteristics of each site, emphasizing the need for tailored monitoring and safety measures.

High-Resolution Continuous-Wave Laser Spectroscopy of Long-Lived Rydberg States in NO.

High-resolution continuous-wave (cw) laser spectroscopy of nitric oxide (NO) molecules has been performed to study and characterize the energy-level structure of and effects of electric fields on the high Rydberg states. The experiments were carried out with molecules flowing through a room temperature gas cell. Rydberg-state photoexcitation was implemented using the resonance enhanced three-color three-photon excitation scheme. Excited molecules were detected by high-sensitivity optogalvanic methods. Detailed measurements were made of Rydberg states with principal quantum numbers n = 22 and 32 in the series converging to the lowest rotational and vibrational state of the NO+ cation. The experimental data were compared with the results of numerical calculations which provided insight into the orbital angular momentum character of the intermediate H 2Σ+ state, improved determinations of the nf and ng quantum defects, a bound on the magnitude of the nh quantum defect, and information on the decay rates of the nf and ng Rydberg states. These measurements represent a step-change in laser spectroscopic studies of high Rydberg states in small atmospheric molecules. They open opportunities for more detailed studies of slow decay processes of Rydberg NO molecules confined in electrostatic traps, the synthesis of ultralong range Rydberg bimolecules, and the development of optical methods for trace gas detection.

Synthesis, analysis and characterization of surfactant-assisted TiO2 nanoparticles for ammonia gas sensor applications

In our study, we focused on gas sensing, particularly ammonia detection. We synthesized and examined three types of nanoparticles: pure and conducting polymer-based TiO2 nanoparticles. The nanoparticles were prepared by an easy sol-gel approach. All of the samples were characterized using XRD, FTIR, UV-vis, FESEM, EDAX and BET. Gas sensing measurements were carried out for each sample. Among them, PEG-TiO2 stood out with remarkable gas sensing abilities, distinguishing it from other gas detection technologies. We thoroughly investigated the sensor performance, focusing close scrutiny to metrics such as response and recovery times. The greatest reduction in response time and recovery time (95 s / 123 s) was achieved at 25 ppm. These metrics provide insights into how quickly the sensor detects and recovers from the presence of the target gas. Our findings offer important insights for optimizing the sensor performance of PEG-TiO2, highlighting its remarkable gas sensing capabilities.

Single feature to achieve gas recognition: Humidity interference suppression strategy based on temperature modulation and principal component linear discriminant analysis

Metal oxide semiconductor (MOS) sensors have been broadly employed for gas detection. However, the distinctive chemical detection principle of MOS sensors renders them susceptible to interference by humidity. This paper proposes a novel method for suppressing humidity interference. This method possesses advantages, including rapid recognition, low power consumption, and the capability to achieve recognition using a single feature. Temperature modulation technology was used to record the sensor's resistance variation, and the response features of the obtained dynamic response signal are affected by both humidity and the measured gas. The suppression of humidity interference is achieved through the investigation of the response features of humidity and the measured gas. The response features of humidity and gas are amplified by column normalization. Principal Component Linear Discriminant Analysis (PC-LDA) is utilized to acquire humidity and gas information within data. Using ethanol as the primary experimental subject, suppression of humidity interference is achieved through a single feature (PC-LD2). Quantitative recognition of relative humidity (RH) can be achieved using PC-LD1. Multiple types of waveform and sensor were used to demonstrate the generalization of this method.

Impact of SiGe pocket on different shape TFET structures for gas sensing application

Gas sensing requires highly sensitive and selective sensor technologies for environmental monitoring, industrial safety, and public health objectives. Although conventional MOSFET-based gas sensors are widely utilized, their detection of low quantities of gases, such as ammonia, is hindered by a number of severe constraints. TFET is emerged as the better device than MOSFET, particularly for the sensing applications. In this work we discussed the source engineered and shape engineered techniques to improve the performance of TFETs, specifically for ammonia gas detection. Comprehensive simulations on SILVACO TCAD and compared the four TFET structures SiGe-pocket DGTFET, SiGe-pocket vertical TFET SiGe-pocket Z-shape TFET, and SiGe-pocket U-shape TFET structure on the basis of various electrical characterization parameters. Significant improvements in efficiency and sensitivity are obtained by adjusting the work function of the molybdenum (4.40–4.60 eV) catalytic gate metal to find the optimal values. The findings reveal that the SiGe-pocket U-shape TFET structure exhibits superior performance, demonstrating an ION of 8.01 × 10−4 A/μm, an ION/IOFF ratio of 1.25×1013, and an OFF current sensitivity (SOFF) of 1.262. These results highlight the enhanced sensitivity and efficacy of the proposed SiGe-pocket U-shape tunnel FET in ammonia gas sensing applications, making it a promising candidate for practical uses in environmental monitoring and industrial safety.

Theoretical analysis of a refractive index sensor based on optical Tamm state of graphene metastructure under arbitrary polarization deflection angle

In this paper, a refractive index sensor based on a metastructure (MS) is proposed, which achieves sensing through the sharp valleys formed in the reflection spectrum by the excitation of optical Tamm states (OTS) by gyroidal graphene. Differences in the refractive index of the filling medium in the pores of gyroidal graphene will cause shifts in the reflection valleys. The graphene layer is followed by a periodic structure consisting of alternating zirconium dioxide (ZrO2) and α-molybdenum trioxide (α-MoO3). The 4 × 4 transfer matrix method (TMM) is used for the calculation of the results, which allows the case of arbitrary polarization deflection angles ϕ to be considered in the discussion. Different values of ϕ can lead to a switch in the dominance of the sensor, specifically, the structure has a larger linear interval but lower sensitivity at ϕ = 0°, which is the opposite of the situation at ϕ = 90°. The sensor can be used in a variety of scenarios such as biochemical sensing, gas detection, etc, and brings the polarization deflection angle of the incident wave into the discussion.

Characterization and Ambient Temperature Hydrogen Sulfide Sensing of Annealed NiO-MnO₂ Thin Films Prepared via Jet Nebulizer Spray Pyrolysis

A jet nebulizer spray pyrolysis technique to synthesize NiO-MnO2 thin films was demonstrated. These nanosheets were annealed at 350, 450 and 550 °C for 2 hours. The thin films surface morphology and structure were characterized using scanning electron microscopy, XRD, and UV spectroscopy. Subsequently, utilized as gas sensors for the detection of hydrogen sulphide gas. The introduction of NiO into MnO2 nanosheets significantly improved the gas-sensing performance. Notably, the gas-sensing response of the NiO-MnO2 nanosheet sensor surpassed that of both NiO and MnO2 alone, reaching a notable value of 165 when detecting 100 ppm hydrogen sulfide gas with the NiO-MnO2 thin film sensor. A remarkable feature of the NiO-MnO2 thin film sensor is its accelerated response time, registering at 10 seconds when exposed to 100 ppm of hydrogen sulfide gas. The mechanism underlying gas sensing and the factors contributing to the enhanced gas response of NiO-MnO2 thin film is thoroughly discussed. From a broader perspective, these developed sensors present a novel platform for the identification and monitoring of hydrogen sulfide gas, showcasing significant advancements in gas-sensing technology.

Study on highly selective NO2 gas sensors based on (Fe, Mo)-doped monolayer WSe2

The two-dimensional (2D) material WSe2 is frequently employed in gas sensors due to its excellent electrical properties. However, the weak interaction between the pristine WSe2 and gas molecules limits its application. Therefore, in this paper, the adsorption behavior of transition metal X (X = Fe, Mo) atom-doped monolayers WSe2 on H and O atoms and molecules of NO2, HCN, and CO gases is investigated to gain insights into the physical mechanisms of adsorbent-substrate interactions. Doping significantly improves the adsorption properties between the substrate and the gas molecules, with the best adsorption showing for NO2 gas molecules and O atoms. The relationship between transition metals and the improvement of adsorption performance is explored by the center position of transition metal d orbitals in different systems, and it is found that the higher the center position of the transition metal d band, the stronger the adsorption between adsorbent and substrate. Compared to pristine WSe2, Mo atom doping in the transition metal doped system has higher adsorption sensitivity to gas molecules and exhibits highly selective adsorption and chemisorption behaviors through high adsorption energies and electron transfer to NO2 molecules. It is demonstrated that X (X = Fe, Mo) doped WSe2 can be used as a gas-sensitive material for efficient gas detection.

Construction of Solution Processable NUS-8/PANI Nanosheets via Template-Directed Polymerization for Ultratrace Gas Sensing.

The advancement of wireless gas sensing signifies a substantial leap forward in gas detection and intelligent monitoring technologies. This necessitates stringent design criteria for gas sensitive materials with good solution processability, conductivity, and porosity, whose design and synthesis remain challenging yet highly sought-after. Herein, the fabrication of NUS-8/polyaniline (PANI) nanosheets is presented with excellent solution processability, high porosity, triboelectric property, and superior electrical conductivity via a template-directed polymerization strategy. Solution processable NUS-8 nanosheets, synthesized directly by a "one-pot" approach, serve as templates to enhance the "on-site" polymerization of aniline, resulting in the formation of PANI layer on NUS-8 nanosheets with a thickness of 7nm. The resultant NUS-8/PANI nanosheets exhibit outstanding solution processability, and a film conductivity of 8.6 Sm-1. The solution processability enables the facile fabrication of homogeneous and compact NUS-8/PANI films and thus their integration onto electronic devices targeted for multifunctional sensing. The NUS-8/PANI coated sensors demonstrate sensitive and selective detection at room temperature toward ultratrace ammonia with a detection limit of 120 ppb. A wireless sensing system based on the NUS-8/PANI-coated sensor is capable to monitor the spoilage process of meat. This study paves novel avenues for designing and synthesizing gas-sensitive materials for practical applications.

Decorated-Induced Oxygen Vacancy Engineering for Ultra-Low Concentration Nonanal Sensing: A Case Study of La-Decorated Bi2O2CO3.

La-decorated Bi2O2CO3 (BCO-La) microspheres are synthesized using a facile wet chemical strategy for sensing low-concentration nonanal (C9H18O) at room temperature. These BCO-La gas sensors are applied to evaluate agricultural product quality, specifically for cooked rice. The sensitivity of the BCO-6La sensor significantly surpassed that of the pure BCO sensor, achieving a response value of 174.6 when detecting 30ppm nonanal gas. Notably, the BCO-6La sensor demonstrated a faster response time (36 s) when exposed to 18ppm of nonanal. Additionally, the selectivity toward nonanal gas detection is higher (approximately 4-24 times) compared to interfering gases (1-octanol, geranyl acetone, linalool, hexanal, 2-pentyfuran, and 1-octen-3-ol) during cooked rice quality detection. The gas sensing mechanism and the factors contributing to the enhanced sensing performance of the BCO-La microspheres are demonstrated through in situ FT-IR spectra and DFT analysis while the realistic detection scenario is carried out. In a broader context, the reported sensors here represent a novel platform for the detection and monitoring of gases released by agricultural products during storage.

Adsorption and gas sensing properties of CH4, C2H2, and C2H4 dissolved gases in transformer oil on Pdn(n = 1–4)-doped WTe2 monolayers: A DFT study

This paper investigates the potential of palladium (Pd) and its clusters-doped tungsten ditelluride (WTe2) monolayer materials for the detection of dissolved gases (such as CH4, C2H2, and C2H4) in transformer oil. Density functional theory (DFT) was used to study the effect of Pdn (n = 1–4) doping on the gas sensing and adsorption properties of WTe2 monolayer materials. The results show that Pdn doping can significantly improve the adsorption capacity and gas sensing performance of WTe2 to these gas molecules, especially showing excellent performance in detecting acetylene and ethylene. Studies have shown that Pdn doping improves the electrical conductivity of WTe2, making it more suitable for the development of gas sensors. Through the calculation of state density, molecular orbital and charge density difference, the adsorption mechanism of Pdn-doped WTe2 monolayer to different gas molecules was revealed. This study provides a theoretical basis and guidance for the development of efficient sensor materials for fault gas detection in transformer oil. In conclusion, the proposed Pd-doped WTe2 monolayer demonstrates promising potential for detecting dissolved gases in transformer oil. Future work will focus on experimental validation and further optimization of the material’s sensitivity and selectivity towards other gas species.

Operation Temperature Effects on a Microwave Gas Sensor with and without Sensitive Material.

Microwave gas sensors have garnered attention for their high sensitivity and selectivity in the detection of volatile organic compounds (VOCs). However, traditional gas sensors generally rely on sensitive materials that degrade over time and are easily affected by the environment, compromising their stability and accuracy. This study proposes a microwave VOC gas sensor based on the condensation effect. The sensor adopts a novel design without sensitive materials, utilizing the condensation effect to detect acetone gas. The sensor system consists of a microwave sensor and a temperature control device. As the sensor temperature is lowered below the boiling point of acetone, the condensation of acetone gas on the sensor surface is achieved, enabling accurate detection of acetone gas. Experimental results indicate that the accumulated amount of acetone on the sensor surface is positively correlated with its response, with the maximum response of 3000 ppm acetone gas reaching 0.34 dB. Additionally, this study investigated the detection mechanism of the sensor after adding the sensitive material MXene and compared the performance of the sensor at different temperatures (-10 °C, 0 °C, and 60 °C). The results show that at -10 °C the sensor mainly captures acetone through physical adsorption, while at 25 and 60 °C, it primarily responds through chemical adsorption, with a maximum response of 0.29 dB. The VOC sensor based on the condensation effect without sensitive materials not only achieves the same sensitivity as traditional microwave sensors but also demonstrates stronger stability and anti-interference capabilities.

Efficient evolution mechanism of electrolytic gas products from laser-assisted electrolyte jet machining

Efficient evolution of electrolytic gas products is one of the mechanisms for increased material removal rate in laser-assisted electrolyte jet machining. However, the evolution mechanism of electrolytic gas products with multiple energy fields in laser-assisted electrolyte jet machining is not clear. In order to quantitatively characterize the laser-assisted facilitation of the evolution of electrolytic gas products, a gas quantification and detection device was designed and built in this paper. Compared to traditional electrolyte jet machining, laser-assisted electrolyte jet machining of 2024-T3 aluminum alloy increased the gas production by 52 % in 180 s. For the anode, the surface modification induced by laser texturing reduces the oxygen evolution potential and surface free energy and promotes gas nucleation and detachment. In addition, laser-induced conductive plasma can enhance transient currents for electrolyte jet machining and cause machining vibrations. The cathodic gas discharge phenomenon was characterized in conjunction with interelectrode gap visualization experiments and cathodic nozzle damage. Experimental results show that cathodic gas discharge depends on strong electric field and high laser pulse fluence. In summary, laser temperature rise, anode surface modification, laser-induced plasma, plasma recoil and cathode gas discharge can all contribute to the evolution of electrolytic gas products.

Laser-Induced Graphene for Advanced Sensing: Comprehensive Review of Applications.

Laser-induced graphene (LIG) and Laser-scribed graphene (LSG) are both advanced materials with significant potential in various applications, particularly in the field of sustainable sensors. The practical uses of LIG (LSG), which include gas detection, biological process monitoring, strain assessment, and environmental variable tracking, are thoroughly examined in this review paper. Its tunable characteristics distinguish LIG (LSG), which is developed from accurate laser beam modulation on polymeric substrates, and they are essential in advancing sensing technologies in many applications. The recent advances in LIG (LSG) applications include energy storage, biosensing, and electronics by steadily advancing efficiency and versatility. The remarkable flexibility of LIG (LSG) and its transformative potential in regard to sensor manufacturing and utilization are highlighted in this manuscript. Moreover, it thoroughly examines the various fabrication methods used in LIG (LSG) production, highlighting precision and adaptability. This review navigates the difficulties that are encountered in regard to implementing LIG sensors and looks ahead to future developments that will propel the industry forward. This paper provides a comprehensive summary of the latest research in LIG (LSG) and elucidates this innovative material's advanced and sustainable elements.

Metal clusters modified hexagonal boron nitride for adsorption and sensing of lithium batteries thermal runaway gases

Developing efficient gas sensing materials for monitoring lithium batteries thermal runaway gases is essential for human safety. In this study, a detailed examination of the CH4, CO2, CO, and H2 adsorption property for the h-BN with metal clusters modification was conducted utilizing density functional theory. The incorporation of metal clusters (Pd4, Rh4, and Ru4) significantly improved the adsorption energy and charge transfer of h-BN towards gases compared to the unmodified h-BN. The Ru4/h-BN system demonstrated the highest adsorption capacity across all four gases, while the Pd4/h-BN system displayed remarkable recovery ability at room temperature (298 K). Furthermore, studying the adsorption mechanism via DOS revealed enhanced gas adsorption due to orbital hybridization. The work offers reliable theoretical foundation for the detection and prevention of thermal runaway gases in lithium batteries through the use of h-BN modified with metal clusters.

Convective assembly of silica colloidal particles inside photonic integrated chip-based microfluidic systems for gas sensing applications.

Optofluidics is a new field of modern science that stands at the interface of microfluidics and photonics and has good prospects for application in gas sensors. Microfluidics offers a promising platform for tuning and assembling monolayer structures that are used as sensitive layers for gas detection. Herein, we evaluate the concept of monolayer formation on a silicon nitride substrate enabling a surface coverage up to 59% through a microfluidic convective assembly and couple it with a photonic integrated chip to probe gas sensing performance.

Facile synthesis of ultrafine WO3 nanoparticles for highly sensitive acetoin biomarker gas detection

Facile synthesis of metal oxide semiconductors (MOSs) nanoparticles with ultrafine size is quite promising to improve gas sensing performance due to the large effect of the particle size on the electron depletion layer (EDL), however, which is currently difficult to realize. In this work, we synthesized ultrafine WO3 nanoparticles of 20 ∼ 30 nm via room-temperature hydrolysis with following annealing and investigated the gas sensing performance of the WO3 nanoparticles towards acetoin biomarker released by Listeria monocytogenes (LMs). The WO3 gas sensor displays high response (Ra/Rg = 32.0@5 ppm), excellent selectivity and low detection limit at 140 °C. The ultrafine size of WO3 comparable to its Debye length can lead to a larger variation of EDL thus a higher sensor response. Our work has provided a facile, low cost and large-scale synthetic route to constructing high-performance acetoin biomarker gas sensors and might contribute to the development for LMs detection.