Response Time Of Sensor Research Articles

Investigating the impact of crystal face on SnO2/GO-A humidity sensor via adsorption kinetics and DFT calculations

Ranging from monitoring indoor air quality to controlling processes in the food, pharmaceutical, and electronics industries, humidity-sensitive sensors play a pivotal role in various industrial and environmental applications. The crystallographic orientation of their surfaces is one of the key factors influencing the performance of metal oxide-based humidity sensors. However, the study of different crystal faces of metal oxides is rarely discussed, such as surface energy, charge distribution and reactivity, which can significantly affect their water absorption behavior and thus affect the sensitivity and response time of the humidity sensor. Hence, the present study introduces a meticulously designed SnO2/GO-A sensor that not only validates the successful fabrication of SnO2/GO-A sensor featuring optimized crystal alignment but also delves into the intricate water absorption mechanisms operative across various SnO2 crystal faces. The First-principles results show that (110) face of SnO2 is more sensitive to the water molecule than others. Consequently, due to the (110) crystal surface growth with annealing process, the SnO2/GO-A sensor demonstrates significant performance enhancements, especially in response speed, recovery time, linearity, and repeatability. In particular, the SnO2/GO-A sensor exhibiting faster response and recovery times of 20s and 18s, respectively, which is higher than SnO2 and SnO2/GO sensor. This advantage makes SnO2/GO-A sensor a potential candidate for humidity sensing applications.

Single walled carbon nanotubes/ZnO nanowires heterostructure array for NO2 gas sensing at low ppm levels

A layer-by-layer ZnO nanowire (NW)-Single Walled Carbon Nanotube (CNT) hybrid gas sensor has been proposed for effective detection of NO2 gas under a low exposure limit of 5 ppm. The fabricated hybrid sensor displayed good sensor response (S %), good selectivity and fast response time towards the target gas. S % value of 36.4 % under 5 ppm NO2 level at 250 °C and good selectivity response towards different interfering gases like SO2, CO and H2 have been observed. Meanwhile, fast response time values of 44.08 s (response) and 62.11 s (recovery) were observed at 300 °C under 5 ppm NO2 level. The sensor baseline resistance of the hybrid heterostructure (HS) was also found to be lower when compared to that of a bare ZnO NW sensor. In addition, the presence of Single Walled CNT in the HS was also shown to reduce the operational temperature of the sensor. Temperature played a significant role by controlling the adsorption and desorption kinetics of gas molecules on the surface. Moreover, the formation of p-n interface between Single Walled CNT (p-type) and ZnO NW (n-type) might have modulated the potential charge barrier on interacting with the adsorbed gases which inturn might have impacted the response of the hybrid sensor. In addition, the large surface areas offered by both NWs and nanotubes might have improved the gas adsorption capability thereby enhancing the overall hybrid sensor’s response.

Surface acoustic wave platform integrated with ultraviolet activated rGO-SnS2 nanocomposites to achieve ppb-level dimethyl methylphosphonate detection at room-temperature

Dimethyl methylphosphonate (DMMP) is commonly used as an alternative for demonstrating to detect sarin, which is one of the most toxic but odorless chemical nerve agents. Among various types of DMMP sensors, those utilizing surface acoustic wave (SAW) technology provide notable advantages such as wireless/passive monitoring, digital output, and a compact, portable design. However, key challenges for SAW-based DMMP sensors operated at room temperature lies in simultaneous enhancement of sensitivities and reduction of detection limits. In this study, we developed a binary material strategy by combining reduced graphene oxide (rGO) and tin disulfide (SnS2) with (100)-facets orientation as sensing layers of SAW device for DMMP detection utilized at room temperature. Ultraviolet (UV) light was applied to activate the sensitive film and reduce the sensor's response time. The developed SAW DMMP sensor demonstrated a superior sensitivity (−1298.82 Hz/ppm), a low detection limit of 50 ppb, and a hysteresis below 1.5%, along with fast response/recovery time (39.2 s/28.4 s), excellent selectivity, long-term stability and repeatability. The formation of shrub-like rGO-SnS2 heterojunctions with abundant surface defects and large specific surface areas, high-energy (100) crystalline surfaces of SnS2, and photogenerated carriers generated by UV irradiation were pinpointed as the crucial sensing mechanisms. These factors collectively enhanced adsorption and reaction dynamics of DMMP molecules.

Parameter-Free Data Reduction for Short-Time Hypersonic Heat Flux Measurements

High-speed flows associated with hypersonics require significant, diverse, and successful ground-test campaigns before engaging in a flight test program. The present investigation focuses on demonstrating a new data reduction pathway for estimating the source heat flux using an elegant, though fragile, thin-film temperature gauge. The rapid response time of such sensors makes them well-suited for shock tunnel experiments. In such experiments, contaminated flow, composed of diaphragm debris, can often damage the sensing element. For the moment, the existence of an ideal coating (or even a hardened sensing element) is presumed that preserves the sensor’s survivability and accuracy over several test runs. A dynamic, physics-based data reduction methodology is proposed that accounts for the protective coating and that is applicable to millisecond testing times. This paper addresses three critical issues for acquiring the best estimate of the source heat flux. These issues include a) the formation of a baseline data reduction view that accounts for thin coatings; b) the development of a dynamic calibration method that removes the need for specifying thermophysical or geometrical properties; and c) the introduction of a time-scaling that allows for calibration to be performed in alternative and convenient time frames. This last point demonstrates the concept of the dimensionless time map and its novel consequences. The procedure is demonstrated on a reduced formulation, illustrating the merit of the concepts.

A Study Based on the First-Principle Study of the Adsorption and Sensing Properties of Mo-Doped WSe2 for N2O, CO2, and CH4

As industry continues to develop rapidly, the greenhouse effect is becoming increasingly severe. CO2, CH4, and N2O are the three primary greenhouse gases, making their effective monitoring a crucial step in reducing emissions. This paper investigates the gas sensing performance of Mo-doped WSe2 for these three gases, through a theoretical study. First, using first-principles calculations, the doping behavior of Mo in WSe2 is examined. Subsequently, the adsorption properties of Mo-WSe2 for CO2, CH4, and N2O are analyzed by calculating adsorption energy, charge transfer, the electron localization function (ELF), Hirshfeld partition (IGMH), and the density of states (DOSs), culminating in an analysis of its sensing properties. The results indicate that when Mo is positioned above the upper Se atom, the structure is most stable. Therefore, this position is selected as the optimal adsorption site for studying the adsorption of the three gases. The adsorption energies for CO2, CH4, and N2O are 1.349 eV, −1.194 eV, and −0.528 eV, respectively, with corresponding charge transfers of 0.418, 0.450, and 0.115. In the N2O and CO2 adsorption systems, significant adsorption energy and charge transfer are observed, leading to relatively better adsorption compared to the CH4 system. Additionally, considering the adsorption performance, Mo-WSe2 demonstrates good sensor response and desorption times for N2O and CO2 at temperatures above 298 K. The findings of this research provide theoretical guidance for the application of Mo-WSe2 as a gas sensing material for detecting greenhouse gases.

The Analysis Of Ultrasonic Sensors In Smart Trash Bin Technology Based On Arduino Nano Microcontroller

Waste is an environmental problem that is increasing along with population growth and public consumption. To solve this problem, an automatic device that controls the opening and closing of the trash can without direct touch is developed using an Arduino Nano microcontroller, HC-SR04 ultrasonic sensor, VL53L0X LIDAR, and MG996R servo motor. This research aims to evaluate the responsiveness of the sensor in detecting objects, the effect of the interaction of distance, angle, and object thickness on the sensor response time and aims to determine the effect of garbage volume on the response time of the indicator LED light. The test was conducted using the experimental method of distance variation of 20 cm, 30 cm, 40 cm, and 50 cm; angle variation of 0°, 10°, and 20°; and thickness variation of 10 mm, 65 mm, and 120 mm. Data analysis using multiple linear regression research methods shows a P-Value of 0.409 for the ultrasonic sensor with ɑ of 0.05, if the P-Value > ɑ, then H0 is accepted and H1 is rejected which mean that there is no significant effect of the interaction between distance, angle, and thickness of the object on the response time of the trash can lid opening sensor.

Influence of surface roughness on the response time of iridium oxide pH sensors

Iridium oxide (IrOx) formed by the carbonate melt oxidation method has been reported to exhibit excellent pH response characteristics. Although slope of the response and long-term response stability have been reported in relation to fabrication conditions and composition, the response kinetics of IrOx pH sensors have not been investigated in detail. The IrOx layers were shown to have a columnar structure with high aspect ratio, which resulted in deep recesses in the IrOx surface. In the present study, the influence of the surface roughness of IrOx on the response time of IrOx pH sensors is investigated. The 90 % response times of the sensors were found to be in the order of several hundreds of milliseconds and became longer as the IrOx layer became thicker and as the surface recesses became deeper. The results indicated that the diffusion of ions in the recessed structures strongly influenced the response time of the IrOx pH sensors. It is therefore important to lower the density of the recessed structures in the surface of the IrOx layers oxidized in lithium carbonate melts to achieve IrOx pH sensors that display rapid and reproducible responses.

Fabrication of Graphene-based Ammonia Sensors: A Review

Abstract: Graphene gas sensors have gained much scientific interest due to their high sensitivity, selectivity, and fast detection of various gases. This article summarizes the research progress of graphene gas sensors for detecting ammonia gas at room temperature. Firstly, the performance and development trends of the graphene/semiconductor Schottky diode sensor are discussed. Secondly, manufacturing methods and the latest developments in graphene field-effect transistor sensors are reviewed. Finally, the basic challenges and latest efforts of functional ammonia gas sensors are studied. The discussion delves into each sensor type's detection principles and performance indicators, including selectivity, stability, measurement range, response time, recovery time, and relative humidity. A comparative analysis is conducted to highlight the progress achieved in research, elucidating the advantages, disadvantages, and potential solutions associated with various sensors. As a result, the paper concludes by exploring the future development prospects of graphene-based ammonia sensors.

A Highly Sensitive NiO Flexible Temperature Sensor Prepared by Low-Temperature Sintering Electrohydrodynamic Direct Writing.

Flexible temperature sensors have diverse applications and a great potential in the field of temperature monitoring, including healthcare, smart homes and the automotive industry. However, the current flexible temperature sensor preparation generally suffers from process complexity, which limits its development and application. In this paper, a nickel oxide (NiO) flexible temperature sensor based on a low-temperature sintering technology is introduced. The prepared NiO flexible temperature sensor has a high-resolution temperature measurement performance and good stability, including temperature detection over a wide temperature range of (25 to 70 °C) and a high sensitivity performance (of a maximum TCR of -5.194%°C-1 and a thermal constant of 3938 K). The rapid response time of this temperature sensor was measured to be 2 s at 27-50 °C, which ensures the accuracy and reliability of the measurement. The NiO flexible temperature sensor prepared by electrohydrodynamic direct writing has a stable performance and good flexibility in complex environments. The temperature sensor can be used to monitor the temperature status of the equipment and prevent failure or damage caused by overheating.

Electropsun non-woven luminescent two-dye pH sensors: Effect of morphology on the sensing performance

Electrospun (ES) non-woven matrices are regarded as promising platforms for the development of miniaturized sensing systems with improved detection capacity. Their high specific surface area and void-to-volume ratio are expected to promote higher and faster interaction of the sensing molecular probes with the target stimuli increasing sensor sensitivity and response time. However, the poor light transparency of ES non-woven mats appears as the main limiting effect regarding their use as optical sensor platforms being important to determine to what extent it affects the sensor prediction accuracy. This work addresses this question providing a comparative analysis of the performance of flat cast and ES non-woven cellulose acetate luminescent platforms loaded with a pH sensitive dye-pair, i.e. fluorescein isothiocyanate (FITC) and rhodamine 6 G (R6G). This study follows a comprehensive approach aiming at clarifying the effect of the platform morphology on the sensitivity of their spectral properties to pH and to understand about the advantages of using dual dye systems for pH detection. The presence of R6G improved remarkably the sensitivity of these ES matrices extending the analytical capacity of the probes to the alkaline range. The emission of ES matrices showed stronger sensitivity to pH. However, pH prediction accuracy was found to depend crucially on a synergistic effect from the platform morphology and the signal analysis methodology. ES non-woven matrices allows for accurate pH prediction, characterized by determination errors < 10 % for pH < 10, by exponential analysis of the dye-pair emission at λExc of 450 nm and λEm of 519 nm. Furthermore, it shows a strong reduction of the determination errors, at extremely acidic conditions, resulting in values comparable to that obtained by analysis of the emission signal from flat cast platforms with more complex Förster Resonance Energy Transfer (FRET) methodologies.

Recycling of reduced graphene oxide from graphite rods in disposable zinc battery applicable to optical sensing

We report a low cost, simple method to fabricate reduced graphene oxide (rGO) optical sensors from recycled batteries. The rGO nanosheets were exfoliated by electrochemical method under the assistant of electric arc using 5 % KOH or NaOH electrolytes. The rGO nanosheets show interlayer distances ranging from 3.98 to 6.22 Å, and thicknesses from 0.62 to 6.00 nm, corresponding from 1 to 10 layers, respectively, determined from X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) measurements. Selected area electron diffraction (SAED) measurement indicates that rGO nanosheets content Miller-Bravais indices of (1–210) and (0–110) planes, and the hexagonal diffraction pattern of (0–110) plane of graphene sheets with d-spacing of 2.13 Å. Low defect densities in exfoliated rGO nanosheets were confirmed by ID/IG ratios ∼0.16 to 0.18 via Raman. The rGO nanosheets exfoliated in NaOH electrolyte have 19.35 % lower oxygen content compared to those exfoliated in KOH electrolyte inspected from XPS spectra. The performance of the rGO optical sensors is controlled by defects created from oxygen functional groups formed during exfoliation process. The responsivity and response (rise) time of NaOH-exfoliated rGO sensor are 0.46 A/W and 2.3 s, respectively. These values are 21 % (for responsivity) larger and 35 % (for rise time) smaller than those of KOH-exfoliated rGO sensor. The best-in-class of high gain were demonstrated in this study for the rGO optical sensors prepared from disposed graphite rods. The results demonstrate how disposed batteries can be recycled to produce photodetectors and other optoelectronic devices using cheap and relatively nontoxic methods.

Low-concentration H2S gas sensors based on MOF-derived Co3O4 nanomaterials

Metal-organic frameworks (MOF)-based gas sensors have garnered significant interest and are highly desirable for monitoring indoor air quality and mitigating various environmental reclamation challenges. Herein, we describe a unique approach for fabricating hydrogen sulfide (H2S) gas sensors based on MOF-derived cobalt oxide nanosheets (Co3O4 Ns) nanostructures. The surface morphology and porosity of the fabricated material were confirmed through comprehensive Brunauer-Emmett-Teller (BET) and electron microscopy analyses. Chemical composition and phase purity were identified using Energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The sensor exhibited remarkable sensitivity towards hydrogen sulfide in the range of 0.5–100 ppm, reaching a maximum response of 1702.61 % at an operating temperature of 250 °C for 100 ppm H2S gas. Furthermore, the sensor demonstrated a detection limit of 500 ppb with a response rate of 78.22 %. A consistent stability over 30 days was observed, validating its suitability for real-world applications. The response and recovery times of the H2S gas sensors were assessed with τres/τrec = 63.56/103.34 s, offering valuable insights into their real-world applicability.

Oxygen-defect rich SnO2-based homogenous composites for fast response and recovery hydrogen sensor

As a kind of green energy, hydrogen (H2) has been widely concerned and applied by people. One of the biggest challenges for sensing applications is the quick detection of hydrogen leaks or their release in various conditions, particularly in large electric vehicle batteries. This study successfully constructed a quick response and recovery hydrogen sensor based on the In2O3-SnO2 heterojunction. The response and recovery time of the In2O3-SnO2 hydrogen sensor is 1.1/1.9 s to 50 ppm H2. This is reduced to 11.0 %/9.5 % compared to the SnO2 hydrogen sensor. This sensor's remarkable gas detecting properties are mainly attributed to the In2O3-SnO2 heterojunction creation, crystal structure modification, and increased specific surface area (92.9 m2/g). Homogenous In2O3-SnO2 nanocomposites contain more oxygen defects, which is the primary factor enhancing the sensor's ability to detect gases. Firstly, indium ions are incorporated in the lattice of SnO2 results in lattice distortion and enhances the presence of oxygen deficiency in the composites, which plays a pivotal role in achieving rapid response and recovery of the sensor. Secondly, In2O3-SnO2 heterostructures promote rapid adsorption of oxygen molecules and target gases by facilitating effective electron mobility on their surface. The quicker response and recovery times of hydrogen sensors based on In2O3-SnO2 heterojunctions are observed. This innovative approach to creating fast-responding gas sensors highlights the promise of heterojunction-based hydrogen sensors for real-time H2 monitoring and opens up new research directions.

Fiber optic relative humidity and temperature sensor with the cascaded Vernier effect based on the C-shaped cavity structure

The water-absorbent sensing film, coated on the surface of traditional optical fiber humidity sensors, often suffers from detachment issues. In this paper, we present what we believe to be a new fiber-optic cascaded Fabry-Perot interferometer sensor for detecting relative humidity (RH) and temperature, without the need for sophisticated instrumentation. The sensing structure comprises two sections of single-mode optical fibers and a C-shaped cavity between them. The C-shaped cavity is created by grinding the side of a hollow-core fiber with fiber optic abrasive paper. The Vernier effect arises from the cascaded interaction between the C-shaped cavity filled with ultraviolet optical glue (NOA61) and the subsequent single-mode fiber pigtail. The sensor exhibits a high RH sensitivity of 0.248 nm/%RH (35-95%RH) and an RH resolution of up to 0.08%RH. It also has high-temperature sensitivities of -1.091 nm/°C (25 - 65°C). Furthermore, simultaneous measurement of RH and temperature is achieved by establishing a dual parameter matrix, and the sensor's response time and recovery time for RH and temperature are within 300s. Therefore, this work provides a simple and cost-effective manufacturing process and the proposed RH and temperature sensor features a compact size, strong environmental adaptability, and significant potential for practical applications.

Direct Ink Writing of SiCN/RuO2/TiB2 Composite Ceramic Ink for High-Temperature Thin-Film Sensors.

Direct ink writing (DIW) of high-temperature thin-film sensors holds significant potential for monitoring extreme environments. However, existing high-temperature inks face a trade-off between cost and performance. This study proposes a SiCN/RuO2/TiB2 composite ceramic ink. The added TiB2, after annealing in a high-temperature atmospheric environment, forms B2O3 glass, which synergizes with the SiO2 glass phase formed from the SiCN precursor to effectively encapsulate RuO2 particles. This enhances the film's density and adhesion to the substrate, preventing RuO2 volatilization at high temperatures. Additionally, the high conductivity of TiB2 improves the film's overall conductivity. Test results indicate that the SiCN/RuO2/TiB2 film exhibits high linearity from room temperature to 900 °C, high stability (resistance drift rate of 0.1%/h at 800 °C), and high conductivity (4410 S/m). As a proof of concept, temperature sensors and a heat flux sensor were successfully fabricated on a metallic hemispherical surface. Performance tests in extreme environments using high-power lasers and flame guns verified that the conformal thin-film sensor can accurately measure spherical temperature and heat flux, with a heat flux sensor response time of 53 ms. In conclusion, the SiCN/RuO2/TiB2 composite ceramic ink developed in this study offers a high-performance and cost-effective solution for high-temperature conformal thin-film sensors in extreme environments.

Room temperature detection of isopropyl alcohol using CTAB-assisted silver-doped ZnO nanorods as chemiresistive gas sensor

In this study, pristine silver-doped zinc oxide (Ag–ZnO) and Plumbago zeylanica leaf extract (PZE) incorporated with Ag–ZnO, along with the additional material of cetyltrimethylammonium bromide (CTAB)-assisted Ag–ZnO nanorods, were synthesized and extensively characterized. The basic properties of the samples were studied and optimized. Gas sensing measurements were conducted, and the obtained results were thoroughly interpreted. The study includes demonstrating and examining pure Ag–ZnO, PZE-added Ag–ZnO, and CTAB-assisted Ag–ZnO. Notably, the presence of CTAB exhibited a favorable effect on the Ag–ZnO, indicating an enhanced isopropyl alcohol gas sensing response time of 20 s at 15 ppm within an ambient temperature. Additionally, improvements in selectivity and reduced sensor resistance in current (nanoampere - nA) were observed in CTAB-assisted Ag–ZnO. The sensing mechanism was investigated, focusing on the depletion layer of Ag–ZnO with the surfactant. The work emphasizes the sensing abilities of PZE-assisted Ag–ZnO and CTAB Ag–ZnO, highlighting the significance of these noble metals in systematic gas sensing applications.

Research Progress of Flexible Piezoresistive Sensors Based on Polymer Porous Materials.

Flexible piezoresistive sensors are in high demand in areas such as wearable devices, electronic skin, and human-machine interfaces due to their advantageous features, including low power consumption, excellent bending stability, broad testing pressure range, and simple manufacturing technology. With the advancement of intelligent technology, higher requirements for the sensitivity, accuracy, response time, measurement range, and weather resistance of piezoresistive sensors are emerging. Due to the designability of polymer porous materials and conductive phases, and with more multivariate combinations, it is possible to achieve higher sensitivity and lower detection limits, which are more promising than traditional flexible sensor materials. Based on this, this work reviews recent advancements in research on flexible pressure sensors utilizing polymer porous materials. Furthermore, this review examines sensor performance optimization and development from the perspectives of three-dimensional porous flexible substrate regulation, sensing material selection and composite technology, and substrate and sensing material structure design.

Real-time cationic sensing using plasmonic fiber optic sensor based phosphoryl-carrageenan

We report Fiber Optic-Localized Surface Plasmon Resonance (FO-LSPR) spectroscopy sensors comprising a coating of spherical silver nanoparticles (AgNPs) embedded in phosphoryl-carrageenan. This is a novel report on modified carrageenan namely phosphoryl-carrageenan as sensing materials for cations specifically ammonium ions (NH4+). The morphology of carrageenan and phosphoryl-carrageenan coatings on the fiber optic probe was uneven and wavelike topography, indicating the successful coating on the fiber optic probe surface. The FO-LSPR showed a distinct dip in reflectivity in the region of 370–400 nm due to the resonance frequency of spherical AgNPs. The response and recovery times of FO-LSPR sensors for 1 ppm NH4+ and deionized water were <20 s and ∼1.2 minutes, respectively, with five times stable repeatability. The sensitivity of the FO-LSPR phosphoryl-carrageenan was 3.441 nm/ppm. Equally, the limits of detection and quantitation of fiber optic FO-LSPR were 0.336 and 1.018 ppm, respectively. Meanwhile, the dynamic range of the FO-LSPR was 0.3 – 2.0 ppm. The proposed sensor demonstrated strong selectivity towards NH4+ over common cationic interferents. Furthermore, the reported FO-LPSR sensor offered a comparable measurement performance to current methods, while being low cost and portable, and allowing in-situ real-time monitoring of cation ammonium. Thus, reported FO-LPSR sensors are highly promising for water monitoring applications.

A room-temperature ammonia gas sensor based on the h-MoO3@Graphene composite film with fast response time

The release of ammonia (NH3) in industry or daily life is harmful to human health. A gas sensor was developed using h-MoO3 nanorods and graphene film to detect and eliminate this. The h-MoO3 nanorods were first synthesized by chemical bath deposition using ammonium molybdate tetrahydrate (NH4)6Mo7O24•4H2O and HNO3 and then deposited on the graphene film transferred to SiO2/Si substrate by electrochemical bubbling method. Subsequently, gas-sensitive h-MoO3@Graphene composite films were prepared and analyzed using Raman, XRD, SEM, and UV–vis. The gas sensor's performance was evaluated to detect NH3 at a room temperature concentration range of 1–60 ppm. Compared with graphene, the conductivity of the composite film with 10 mg/ml h-MoO3 nanorods was increased by 40 % and the sensitivity increased by 10 times. The sensor h-MoO3@G-10 showed the best sensing performance to 1 ppm NH3. Sensor sensitivity, response and recovery time are 1.1 %, 46.8 s and 17.8 s.

Silver nanowires@TiO2 core-shell for room-temperature 1000 ppm NH3 gas sensors

This study employs a simple liquid-phase deposition method to grow TiO2 onto nanoscale silver wires, with a diameter of 90 nm and a length of 15∼20 μm. This core-shell structure possesses a high specific surface area, which enhances the gas reaction surface. Measurements can be conducted at room temperature. The main mechanism relies on the conductive properties of silver to transmit electrons, while Schottky barriers between Ag and TiO2 further accelerate oxygen ionization and surface redox reactions. This structure may contribute to enhancing the response value, response time, and recovery time of gas sensors.