H2S Sensor Research Articles

Bimetallic AuPt alloy nanoparticles decorated on ZnO nanowires towards efficient and selective H2S gas sensing

The development of high-performance H2S sensor is imperative for monitoring H2S in the living environment. Metal oxide semiconductors (MOSs) have been regarded as the strongest candidates for H2S detection due to their high sensitivity, miniaturization, and good durability. However, a single MOS-based gas sensor is unable to selectively detect gases, which limits its practical application. Functionalization of noble metal nanoparticles (e.g., Pt, Pd, and Au) on the surface of MOS can improve its selectivity. Herein, ZnO nanowires decorated with AuPt bimetallic nanoparticles are designed and fabricated on MEMS for H2S detection. The AuPt@ZnO nanowires-based sensor shows a response of 17.7–20 ppm H2S at 300 °C which is 4.0 times higher than that of pristine ZnO nanowires-based sensor. The sensor also exhibits a rapid response-recovery process, brilliant long-term stability, and excellent selectivity to H2S among various interfering gases. The remarkable improvement of the sensing performance, especially selectivity, could be ascribed to the electronic and chemical sensitization and the synergistic effect of the AuPt bimetal. Thus, the AuPt@ZnO nanowires-based sensor has a great potential application for H2S detection.

Achieving highly-efficient H2S gas sensor by flower-like SnO2–SnO/porous GaN heterojunction

A flower-like SnO2–SnO/porous GaN (FSS/PGaN) heterojunction was fabricated for the first time via a facile spraying process, and the whole process also involved hydrothermal preparation of FSS and electrochemical wet etching of GaN, and SnO2–SnO composites with p–n junctions were loaded onto PGaN surface directly applied to H2S sensor. Meanwhile, the excellent transport capability of heterojunction between FSS and PGaN facilitates electron transfer, that is, a response time as short as 65 s and a release time up to 27 s can be achieved merely at 150 °C under 50 ppm H2S concentration, which has laid a reasonable theoretical and experimental foundation for the subsequent PGaN-based heterojunction gas sensor. The lowering working temperature and high sensitivity (23.5 at 200 ppm H2S) are attributed to the structure of PGaN itself and the heterojunction between SnO2–SnO and PGaN. In addition, the as-obtained sensor showed ultra-high test stability. The simple design strategy of FSS/PGaN-based H2S sensor highlights its potential in various applications.

Thermal shock-stabilized metal catalysts on oxide hemitubes: Toward ultrasensitive chemiresistors

To achieve powerful gas sensors oxide semiconductor chemiresistors, the uniform functionalization of nanocatalysts on the desired metal oxides is considered as a key strategy. However, still, it is challenging to achieve the nanocatalysts decoration on desired oxides without deterioration of target materials. In this study, thermal-shock (rapid joule-heating method) was applied to uniformly decorate Pt nanoparticles (NPs) on the surface of carbon nanofibers (CNFs) to achieve the uniform distribution of Pt NPs on one-dimensional structures. And then, SnO2 was physically deposited on the Pt NPs loaded CNFs and continuous heat-treatment was conducted to transfer the Pt NPs to desired SnO2 porous hemitubes. Thanks to the well-distributed Pt NPs on porous SnO2 hollow structures, the Pt laoded SnO2 hemitubes showed an exceptional sensitivity (Rair/Rgas = 1500 at 5 ppm) in H2S. Also, it showed high selectivity for H2S and high stability even under continuous gas exposure, confirming its potential as an effective H2S sensor.

Concentration recognition of gas sensor with organic field-effect transistor assisted by artificial intelligence

Many gas analytes have been detected with organic field-effect transistor (OFET) sensors. However, most of the analytes are detected with known concentrations and few OFET sensors have been used to quantify analytes. Here, we integrated the multiple independent parameters of OFETs with artificial neural network (ANN) to quantify toxic H2S. The precise concentration recognition was confirmed as the difference between real and predicted values was less than 5%. The H2S sensors also showed high responsivity over 6500% at 150 ppm, and quick response in ten seconds. Moreover, the multiple parameters provided the possibility to differentiate eight different analytes. Thus, the artificial intelligence combined with OFET sensors realized precise quantification and fingerprint recognition of gas analytes for real applications.

CuO-sensitized amorphous ZnSnO3 hollow-rounded cubes for highly sensitive and selective H2S gas sensors

Hydrogen sulfide (H2S), a toxic and flammable gas, poses a substantial threat to human health and the ambient environment. Therefore, producing responsive H2S sensors that have excellent selectivity and work at low temperatures has been a goal for researchers. In this study, hollow-rounded cubes composed of copper oxide (CuO)-sensitized amorphous zinc stannate (zinc tin oxide (ZTO)) were prepared by a coprecipitation method combined with an impregnation treatment. Various characterization methods are employed to analyze the crystal phase, morphology, and composition of the synthetic materials. The results showed that the materials were composed of hollow, rounded, amorphous cubes with a 500–700 nm uniform particle size. The as-prepared materials were applied to gas sensors, and their H2S-sensing performance was systematically tested. Compared with the ZTO- and CuO-based sensors, the CuO/ZTO-based sensor exhibited excellent gas-sensing performance toward H2S, with a maximum response value of 574–10 ppm H2S and a low operating temperature of 160 °C. In addition, the sensor showed higher selectivity and a low detection limit of 200 ppb. The findings indicate that the CuO/ZTO composite is promising as an H2S-sensing material with potential applications in the field of environmental air monitoring.

A new Multi-GAS system for continuous monitoring of CO2/ CH4 ratios at active volcanoes

We have designed, built, and tested a new Multi-GAS instrument which includes a CH4 sensor, along with CO2, H2O, and H2S sensors. We conducted laboratory-based experiments to calibrate the sensors, analyze possible cross-interferences among sensors, and evaluate the quality of the measurements. The results of these experiments demonstrate high-quality measurements with each sensor, with no cross-interferences and accurate and precise CO2/CH4 concentration ratios. These promising results from the laboratory experiments were validated with field measurements. We tested the new Multi-GAS instrument at four different sites on the flanks of Rincón de la Vieja and Miravalles volcanoes in Costa Rica. At each site, direct samples were also collected to compare these results to the Multi-GAS measurements. The results from direct sampling and Multi-GAS showed excellent agreement. These field tests confirmed that this Multi-GAS instrument has the potential to shed new light upon the dynamic interactions of magmatic systems with hydrothermal systems and therefore could help forecast phreatic and other types of volcanic eruptions.

Highly sensitive and selective H2S sensors with ultra-low power consumption based on flexible printed carbon-nanotube-thin-film-transistors

Flexible printed carbon-nanotube-thin-film-transistors (CNT-TFTs) with characteristics of low cost, low operating voltage, low power consumption, and signal amplification have great potential for emerging electronics powered by self-powered systems or low-power density thin-film solar cells. In this work, we have fabricated flexible printed CNT-TFTs using the printing process to selectively deposit semiconducting CNTs in device channels as channel materials, printed silver electrodes as side gates, and printed ion gel as the dielectric layer. The as-prepared TFTs exhibited an extremely high sensitivity to H2S (up to 1565% ppm-1) at room temperature (25 ℃) and the relative humidity (RH) of 5%, excellent signal amplification (response increased from 1% to 4045.5% towards 2 ppm H2S), ultra-low working power consumption (1.03 nW under 2 ppm H2S), excellent selectivity, fast response/recovery time (10 s/26 s) and great mechanical flexibility (stable after 10,000 times bending with 5 mm radius). The outstanding improvement of sensor characteristics was related to the enrichment and absorption of H2S by ionic liquids, and the resistor-mode device's response to 2 ppm H2S increased from ~1% to 80% after the device channel was covered by ion gel. To the best of our knowledge, our H2S sensors demonstrated the recorded low power consumption (1.03 nW) and high response (4045.4%) when exposed to 2 ppm H2S at room temperature, making our sensors a promising candidate for portable applications in gas detection.

Strain-Assisted Single Pt Sites on High-Curvature MoS 2 Surface for Ultrasensitive H 2 S Sensing

Strain-Assisted Single Pt Sites on High-Curvature MoS ₂ Surface for Ultrasensitive H ₂ S Sensing

Synergistic effect of PdO and parallel nanowires assembled CuO microspheres enables high performance room-temperature H2S sensor

High-performance semiconductor gas sensors comprising of metal oxides have offered appealing promise to environment monitor devices but remain challenging due to their high working temperature and sluggish response/recovery speed. Here we report a simple impregnation method that utilizing the high catalytic activity of palladium oxide activates copper oxide parallel nanowires assembled hierarchical microspheres (PdO-CuO NWMs). And then gas-sensing devices with different decorating concentrations were fabricated to investigate their sensing performance on hydrogen sulfide (H2S). It was demonstrated that the CuO microspheres with 2 wt% PdO decorating concentration is the optimum, with high response of 6.8 and extremely short response/recovery time of 1.8/4.1 s towards 50 ppm H2S at 30 °C, effective enhancing the response (4.9–50 ppm H2S) and working temperature (150 °C) of pristine CuO NWMs sensor. The boosting sensing performance of our PdO-CuO NWMs gas sensor was attributed to the synergistic effect of high catalytic noble nanoparticles and hierarchical structures. The coupling strategy offers new insights to explore room temperature and real-time monitoring gas sensors.

Humidity-activated H2S sensor based on SnSe2/WO3 composite for evaluating the spoilage of eggs at room temperature

Hydrogen sulfide (H2S), as a representative food spoilage gas produced by the breakdown of sulfur-containing proteins, is highly irritant and toxic. Designing gas sensors sensitive to H2S for food spoilage evaluation is of great significance for automated quality control in the modern food industry. However, humidity in the environment can generally deteriorate the detection performance of conventional metal oxide semiconductor gas sensors. Therefore, it is critical to develop H2S sensors based on novel materials that can operate effectively in atmospheric humidity conditions. In this work, tin diselenide (SnSe2) nanosheets decorated with tungsten trioxide (WO3) nanoparticles are synthesized by a one-step ultrasound strategy, and used as sensing layers for H2S gas sensors. The water molecule activated charge-transfer of the SnSe2/WO3 composite boosts H2S sensing ability at high relative humidity (RH) levels. At room temperature (25 °C), the SnSe2/WO3 composite sensor with optimal mass ratio exhibits enhanced H2S response value (33.80%@10 ppm) compared with that of the pristine SnSe2 sensor (14.29%@10 ppm) at 82% RH. In addition, the fabricated sensor is proven to be practically effective for evaluating the spoilage of eggs by comparing the sensing response of a fresh egg with that of a spoiled egg. This study offers possibilities for evaluating the spoilage of foods in poultry, aquatic, and food processing industries using a rapid and sensitive humidity-activated H2S gas sensor.

Transformation growth of nanoflower-like GO-ZnO as an active site platform for H2S sensors

The transformation of the dimensional structure of nanoflower-like GO-ZnO (GO-ZnO NFs) has been studied for sensitive detection of H2S. The dimensional structure of materials depends on several factors such as base concentration, surfactants as structure controlling agents, temperature, and reaction time of the hydrothermal process. Our study finds that changing nanostructure to 3-D can improve the surface area and enhance the H2S gas response at room temperature. H2S sensing performance test is carried out by determining resistance (Ro) during exposed gas molecules. The optimum composition of GO-ZnO NFs is found at a weight ratio of 1:1. Moreover, the prepared sensor exhibits excellent performance for monitoring H2S with a limit of detection (LOD) at 0.0051 (3σ) and regression linear at 0.9973. In addition, the prepared material shows selective H2S gas in the presence of other matrix gases. Therefore, the GO-ZnO NFs materials have the potential for analysis and monitoring of H2S in the environment.

A hydrostable CuII coordination network prepared hydrothermally as a "turn-on" fluorescent sensor for S2- and a selective adsorbent for methylene blue.

The effective monitoring of water pollution and further purification are pressing yet challenging issues for guaranteeing the health of human beings and the stabilization of ecological systems. For this purpose, the development of efficient sensing and adsorption materials as a result of supramolecular interactions, including coordination and H-bonding etc., have been attracting increasing attention. With the aid of a coordination-driven self-assembly strategy, a new nonporous 2D CuII coordination network, [Cu2L(H2O)2]n (donated as CuCP), based on H4L, where H4L = 4-(4-(3,5-di-carboxy-pyridin-4-yl)phenyl)pyridine-2,6-dicarboxylic acid, was afforded hydrothermally. Structural analysis indicated that CuCP featured a wrinkled network similar to the ancient Chinese folding screens and constructed by the fully deprotonated ligand L4- with the coordination mode of bis(μ2-η1:η1:η2) and penta-coordinated Cu2+, which could be further upgraded to a supramolecular 3D framework as a result of the synergism of multiple C-H⋯O hydrogen bonds. The hydrostability of CuCP could be maintained within a wide pH range from 2 to 12 as verified by PXRD determination, endowing it with potential environmental applications. Thanks to the combination of the soft Lewis acidity of Cu2+ and its large conjugated structure, CuCP could be used as a turn-on fluorescence sensor for S2- and exhibited a different fluorescence response when Na2S, (NH4)2S or H2S were incorporated, even in actual water samples. The sensing mechanisms were disclosed in detail by the combination of experiments and density functional theory (DFT) calculations. Furthermore, CuCP was shown to be a selective and recoverable adsorbent with a maximum adsorption capacity of 379 mg g-1 in 60 minutes for methylene blue (MB). The adsorption mechanism could be a combination of π⋯π stacking, n⋯π interaction, aggregation effects and Soft and Hard Acid-Base theory (HSAB). The results presented herein open up new perspectives for CuII species in environmental applications.

Synthesis and characterizations of highly responsive H2S sensor using p-type Co3O4 nanoparticles/nanorods mixed nanostructures

High-quality p-type semiconducting Co3O4 with mixed morphology of nanoparticles/nanorods are synthesized using a hydrothermal route for high response and selective hydrogen sulphide (H2S) sensor application. XRD and Raman studies revealed the crystal structure and molecular bonding for obtained Co3O4, respectively. The nanoparticles/nanorods-like structures were confirmed for Co3O4 using FESEM and TEM analysis. The EDS and XPS spectra analysis were carried out for elemental composition and chemical atomic states of Co3O4. The Co3O4 sensor is investigated for gas sensing properties in dynamic conditions. The sensor exhibited the highest selectivity towards H2S among various hydrogen-contained gases at 225 °C. The sensor revealed a high response of 357% and 44% for 100 and 10 ppm H2S gas concentrations, respectively. The Co3O4 sensor exhibited a systematic dynamic resistance response for 100–10 ppm range H2S gas. The excellent dynamic resistance repeatability of the sensor was shown towards 25 ppm H2S gas. The response of Co3O4 sensor was investigated at different operating temperatures and H2S concentrations. The sensor stability and H2S sensing mechanism for the Co3O4 sensor have been reported. Highly uniform and mixed nanostructures of Co3O4 can be the potential sensor material for real-time high-performance H2S sensor application.

Metal organic framework-derived Ni4Mo/MoO2@C composite nanospheres as the sensing materials for hydrogen sulfide detection

Hydrogen sulfide is carcinogenic, corrosive, and flammable, and pathological for most physiological processes. Nevertheless, precise and efficient H2S detection remains challenging. Metal organic framework (MOF) derived metal alloy/oxide nanostructures have been developed recently that show enormous potential and outstanding performance for accurate H2S detection. This paper proposes a new category of MOF derived metal alloy/oxide nanostructures prepared by wet chemical synthesis as plausible H2S gas sensing materials. Compared with pristine sensors, NiMo-MOF sensors exhibit improved H2S gas sensing performance attributed to synergistic effects and large surface areas. NiMo-MOF sensing material achieves the best known gas response for H2S with negligible response to other gas molecules, including HCHO, SO2, C2H5OH, CH3OH, and NH3. Hydrogen sulfide gas response for NiMo-MOF is 3.5 and 2.6 fold higher than bare Ni-MOF and Mo-MOF respectively. The real-time gas response shows that constructed H2S sensor follows an adsorption-oxidation-desorption mechanism and achieved Rg/Ra value is 126 for NiMo-MOF. Thus, the proposed approach provides a mechanism to employ MOF-derived metal alloy/oxide nanostructures as active candidates for improved gas sensing towards effective H2S detection.

Nanocrystalline SnO2 Functionalized with Ag(I) Organometallic Complexes as Materials for Low Temperature H2S Detection.

This paper presents a comparative analysis of H2S sensor properties of nanocrystalline SnO2 modified with Ag nanoparticles (AgNPs) as reference sample or Ag organic complexes (AgL1 and AgL2). New hybrid materials based on SnO2 and Ag(I) organometallic complexes were obtained. The microstructure, compositional characteristics and thermal stability of the composites were thoroughly studied by X-ray diffraction (XRD), X-ray fluorescent spectroscopy (XRF), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and Thermogravimetric analysis (TGA). Gas sensor properties to 2 ppm H2S demonstrated high sensitivity, selectivity toward other reducing gases (H2 (20 ppm), NH3 (20 ppm) and CO (20 ppm)) and good reproducibility of the composites in H2S detection at low operating temperatures. The composite materials also showed a linear detection range in the concentration range of 0.12–2.00 ppm H2S even at room temperature. It was concluded that the predominant factors influencing the sensor properties and selectivity toward H2S in low temperature region are the structure of the modifier and the chemical state of silver. Thus, in the case of SnO2/AgNPs reference sample the chemical sensitization mechanism is more possible, while for SnO2/AgL1 and SnO2/AgL2 composites the electronic sensitization mechanism contributes more in gas sensor properties. The obtained results show that composites based on nanocrystalline SnO2 and Ag(I) organic complexes can enhance the selective detection of H2S.

Mechanism of enhanced H2S sensor ability based on emerging Li0.5La0.5TiO3-SnO2 core-shell structure

The Li0.5La0.5TiO3 (LLTO) is a new sensing material demonstrating ultrafast response to H2S within one second. To further enhance the sensitivity, a LLTO-SnO2 core-shell structure was constructed by the assembly of thin SnO2 nanoflakes on the porous hollow LLTO spheres. The absorption and reaction activity of oxygen on the surface as well as the electron transfer processes were modified and discussed in detail. The formation of oxygen vacancy improves the onset potential of oxygen reduction from 0.61 V to 0.75 V. The effective separation of electrons across the interface helps to take advantage of high response property of SnO2. The response value was improved by 4.5 times than that of pristine LLTO with sub-second response time and excellent stability.

Switching Effect of p-CuO Nanotube/n-In2S3 Nanosheet Heterostructures for High-Performance Room-Temperature H2S Sensing.

High operating temperature and low response restrict the application of H2S sensors. Due to the strong chemical affinity of CuO to H2S and the large band gap and high stability of β-In2S3, CuO nanotube/In2S3 nanosheet p/n heterostructures have been delicately designed for binder-free gas sensors by a facile method consisting of sputtering, chemical etching, and annealing. A switching effect of H2S concentration on the response of CuO/In2S3 gas sensors has been observed. When exposed to low-concentration H2S (1-10 ppm), the response is less than 0.10 and dominated by the surface-type adsorption-desorption process between CuO and H2S. When exposed to high-concentration H2S, the sensor exhibits a superior response of 3511 toward 50 ppm H2S, considerable selectivity, and long-term stability at room temperature. This dramatically enhanced response can be explained by the transformed junction from the CuO/In2S3 heterojunction to the CuS/In2S3 Schottky junction. These results suggest that the binder-free ceramic tube-type CuO/In2S3 gas sensor with considerable performance will have promising potential for H2S gas detection. Moreover, this method provides an effective strategy to fabricate other binder-free gas sensors.

Development of an Electrochemical Dual H2S/Ca2+ Microsensor and Its In Vivo Application to a Rat Seizure Model.

A dual electrochemical microsensor was fabricated for concurrent monitoring of hydrogen sulfide (H2S) and calcium ions (Ca2+), which are closely linked important signaling species involved in various physiological processes. The dual sensor was prepared using a dual recessed electrode consisting of two platinum (Pt) microdisks (50 μm in diameter). Each electrode was individually optimized for the best sensing ability toward a target analyte. One electrode (WE1, amperometric H2S sensor) was modified with electrodeposition of Au and electropolymerized polyaniline coating. The other electrode (WE2, all-solid-state Ca2+-selective electrode) was composed of Ag/AgCl onto the recessed Pt disk formed via electrodeposition/chloridation, followed by silanization and Ca2+-selective membrane loading. The current of WE1 and the potential of WE2 in a dual sensor responded linearly to H2S concentration and logarithm of Ca2+ concentration, respectively, without a crosstalk between the sensing signals. Both WE1 and WE2 presented excellent sensitivity, selectivity (, i = CO, NO, O2, NO2-, AP, AA, DA, and GABA; and , j = Na+, K+, and Mg2+), and fast response time with reasonable stability (during ca. 6 h in vivo experiment). Particularly, WE2 prepared using a mixture of two ionophores (ETH1001 and ETH129) and two plasticizers (2-nitrophenyl octyl ether and bis(2-ethylhexyl) sebacate) showed a very shortened response time (tR to attain the ΔE/Δt slope of 0.6 mV/min = 3.0 ± 0.2 s, n ≥ 10), a critically required factor for real-time analysis. The developed sensor was utilized for simultaneous real-time monitoring of H2S and Ca2+ changes at the brain cortex surface of a living rat during spontaneous epileptic seizures induced by a cortical 4-aminopyridine injection. The dynamic changes of H2S and Ca2+ were clearly observed in an intimate correlation with the electrophysiological recording of seizures, demonstrating the sensor feasibility of in vivo and real-time simultaneous measurements of H2S and Ca2+.

Flexible H2S sensors: Fabricated by growing NO2-UiO-66 on electrospun nanofibers for detecting ultralow concentration H2S

Wearable electronics based on metal–organic frameworks (MOFs) capable of monitoring various environmental pollutants is a promising approach for realizing gas sensing of chemical information. However, their sensing application combined with electronic textile with breathable, washable and flexible features has not been completely established yet. Herein, we describe a facile and effective strategy to fabricate flexible gas sensor for rapidly detecting hydrogen sulfide (H2S) through integrating NO2-UiO-66 on electrospun nanofibers membrane (NO2-UiO-66 NM) firmly and uniformly. Different from the inherent brittleness and poor processability of powder MOFs, the achieved NO2-UiO-66 NM delivers enhanced porosity and surface area, outstanding flexibility, desirable breathability, stable to washing and strong accessibility, more suitable for practical applications. Consequently, the fabricated NO2-UiO-66 NM sensor exhibits a significantly high detection selectivity for H2S among various analytes (H2S, SO2, C6H6, CO and NH3) and remarkable sensitivity for H2S with unprecedentedly ultralow detection limit reaching down to 10 ppb. Moreover, the sensing performance can be greatly remained after around five weeks at concentration down to 1 ppm; also, there are slight impact of deformation on sensing activities, revealing superior H2S sensing stability. This study offers a feasible solution to develop electronic textiles for chemical sensing application.

Near-infrared laser photoacoustic gas sensor for simultaneous detection of CO and H2S.

A ppb-level H2S and CO photoacoustic spectroscopy (PAS) gas sensor was developed by using a two-stage commercial optical fiber amplifier with a full output power of 10 W. Two near-infrared diode lasers with the central wavenumbers of 6320.6 cm-1 and 6377.4 cm-1 were employed as the excitation laser source. A time-division multiplexing method was used to simultaneously detect CO and H2S with an optical switch. A dual-resonator structural photoacoustic cell (PAC) was theoretically simulated and designed with a finite element analysis. A µV level background noise was achieved with the differential and symmetrical PAC. The performance of the multi-component sensor was evaluated after the optimization of frequency, pressure and modulation depth. The minimum detection limits of 31.7 ppb and 342.7 ppb were obtained for H2S and CO at atmospheric pressure.