Ppb-level H2S Research Articles

Synthesis and Enhanced H2S Sensing Properties of V2O3-NiO Nanoflower Assembled by Porous Nanosheets

Constructing porous structure has proved to be an effective strategy to improve the gas sensing properties of metal oxide semiconducting materials. In this work, high-performance hydrogen sulfide (H2S) gas sensing material with porous structure were synthesized by growing nickel oxide (NiO) on vanadium trioxide (V2O3) seeds. Morphology and structure characterizations reveal that the novel three-dimensional (3D) nanoflowers are formed by self-assembling two-dimensional (2D) porous nanosheets with high surface area and abundant active sites. Compared with pristine NiO, the sensing performance of V2O3-NiO (VN8, VN7, VN6) with different ratios of V3+: Ni2+ is enhanced due to their porous structure. Among them, VN7 sensor shows excellent sensing properties at 200 °C. The response to 500 ppb H2S can reach 65, which increases as high as 2.2 times compared with the pristine NiO sensor. The response time to 500 ppb H2S is further decreased from 13 s of the pristine NiO sensors to 8 s of VN7 sensor. The VN7 sensor also shows a wide linear range from 20 ppb to 500 ppb, high selectivity, good repeatability, long-term stability, moisture resistance and low detection limit (20 ppb), indicating its potential candidate for ppb-level H2S detection in complex environment of industrial mine.

Room-temperature gas sensors based on titanium dioxide quantum dots for highly sensitive and selective H2S detection

Room-temperature gas sensors with high performance are crucial in practical application. This work prepared a series of controllable-size titanium dioxide quantum dots (TiO2 QDs) via a rapid microwave-assisted solvothermal method for detecting ppb-level H2S at room temperature. The effect of reaction temperature on the nanostructure and gas sensing properties was investigated systematically. The characterization results showed the samples presented ultra-small size (around 5–6 nm) nanostructure and modified surface state (including Ti3+ and oxygen defects). The S120-TiO2 QDs gas sensor showed the best sensing properties towards ppb-level H2S at room temperature, including high response (25.12 @ 500 ppb H2S), rapid response/recovery, low detecting limit level, good selectivity, and operating stability. The gas sensing mechanism was explained through the synergetic effect of ultra-small size nanostructure, large specific surface area, and surface defects, which are in favor of improving the surface activity and charge transfer efficiency. Moreover, the practical application of TiO2 QDs gas sensor in detecting the volatiles of fish (Pangasius) was also verified. This work developed a room temperature TiO2 quantum dots-based gas sensor, which is promised for practical application because of the rapid synthesis and high performance.

Bi2S3/ZnS heterostructures for H2S sensing in the dark: the synergy of increased surface-adsorbed oxygen and charge transfer

Bi2S3/ZnS heterostructures with increased surface-adsorbed oxygen and charge transfer in the dark were designed and used to achieve ppb level H2S detection at room temperature.

Optimized Triple-Phase Boundary in Ysz-Based Electrochemical Gas Sensor Enables to Lower the Operation Temperature for Sensing Ppb Level H2s

Optimized Triple-Phase Boundary in Ysz-Based Electrochemical Gas Sensor Enables to Lower the Operation Temperature for Sensing Ppb Level H2s

Room temperature WO3-Bi2WO6 sensors based on hierarchical microflowers for ppb-level H2S detection

Pristine Bi2WO6 nanosheets and hierarchical WO3-Bi2WO6 microflowers were prepared via a facile hydrothermal technique. WO3-Bi2WO6 microflowers were assembled with thin nanosheets, where WO3 nanoparticles were uniformly loaded. The H2S sensing properties of pristine Bi2WO6 nanosheets and hierarchical WO3-Bi2WO6 microflowers were systematically investigated at room temperature. 20 WO3-Bi2WO6 microflowers sensor displayed the best sensing property towards ppb-level H2S compared with all other samples. The enhancement was ascribed to the catalytic effect of WO3 nanoparticles and the modified microstructure with large specific surface areas. Moreover, the n–n heterojunction structures also increase the thickness of electron depletion layer and potential barrier height, which could efficiently improve the sensing properties. The practical application of 20 WO3-Bi2WO6 microflowers sensor in detecting the volatiles of Pangasius was also studied in this work. Therefore, the hierarchical WO3-Bi2WO6 microflower is a promising ppb-level H2S sensing material for environment monitoring and fish freshness detection.

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.

A trace ppb-level electrochemical H2S sensor based on ultrathin Pt nanotubes

An amperometric sensor has been developed with high sensitivity for real-time measurement of H2S gas at room temperature (25 °C ± 2 °C). In order to enhance the utilization of platinum and improve its catalytic performance, an ultrathin and one-dimensional (1D) Pt nanotubes (Pt NTs, ~3.5 nm in wall thickness) were designed and used as sensing electrode materials. Different concentrations of H2S gas were tested to evaluate the sensitivity of the sensor and to obtain the relationship between the electricity response signal and H2S gas concentration. At room temperature, the sensor based on Pt NTs shows better sensing performance than that based on Pt nanoparticles, which is mainly attributed to two factors, namely, the inherent characteristic of the hollow 1D Pt NTs. The Pt NTs-based sensor shows a detection limit as low as 0.025 ppb, which are the lowest among H2S gas sensors reported in the literatures. The response and recovery times are 0.75 s and 0.86 s for 0.8 ppb H2S, respectively. In addition, the sensor shows a wide range (100 ppm-0.025 ppb), high selectivity compared to other gases (including CO, NH3, CH2O, NO and NO2), good reproducibility, and satisfactory long-term stability. Thus, the ultrathin Pt NTs-based gas sensor would be a great potential to the real-time and online monitoring of the trace ppb-level H2S gas at room temperature.

Selective detection of parts-per-billion H2S with Pt-decorated ZnO nanorods

This work presents a simple and effective strategy for synthesis of robust Pt-functionalized ordered ZnO nanorod array targeting ppb-level H2S detection. ZnO nanorod array was directly grown in-situ on a seeded alumina tube sensor platform, and subsequently functionalized with Pt nanoparticles via a facile immersion-calcination method. Sensors based on Pt-modified ZnO nanorods were highly sensitive to presence of H2S gas at ppb level (20−300 ppb). For the sensor of optimal Pt loading, a high response of 23.1–100 ppb H2S was achieved at 260 °C, 5.8 times higher than that of the pristine ZnO sensor. Moreover, a limit of detection (LOD) as low as 1.1 ppb as well as excellent selectivity to H2S against common interfering gases was obtained. The greatly enhanced H2S-sensing performance may be ascribed to the synergistic effects of the catalytic and electronic promotion of Pt and the unique morphology of nanorods.

Microtubular α-Fe2O3/Fe2(MoO4)3 heterostructure derived from absorbent cotton for enhanced ppb-level H2S gas-sensing performance

Microtubular α-Fe2O3/Fe2(MoO4)3 heterostructure (FFMO) was massively prepared by facile immersion-calcination method with absorbent cotton being employed as template, which is formed by a great number of cross-linking nanoparticles. In comparison with the pure iron molybdate (FMO) microtubules, the small-sized α-Fe2O3 nanocrystals evenly attached to the surface of FMO particles, increasing the specific surface area of FFMO composites and forming broad hierarchical pores. Gas-sensing measurement indicates that the sensor fabricated from FFMO heterostructure presents response of 12.69 toward 10 ppm H2S, being about 2.2 times larger than that of pure FMO-based sensor. And the working temperature also reduces from 170 °C to 133 °C. In particular, the FFMO composite exhibits the fastest response (Tres = 3 s) and the lowest detection limit (50 ppb) to H2S gas among all reported FMO-based sensors. Such rapid response and highly sensitive to trace H2S are dominantly assigned to the synergism of the inherent properties of multistage-pores microtubule, n-n heterojunction, surface adsorbed oxygen, as well as the generation of metastable iron sulfide induced by lattice oxygen. In addition, the gas-sensing mechanism of the sensor is also studied in detail.

In-situ fabrication of ZnO nanoparticles sensors based on gas-sensing electrode for ppb-level H2S detection at room temperature* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11904209 and 61904098), the Natural Science Foundation of Shandong Province, China (Grant No. ZR2019QF018), and Higher Education Research and Development Program of Shandong Province, China (Grant No. J18KA242).

The zinc oxide (ZnO) nanoparticles (NPs) sensors were prepared in-situ on the gas-sensing electrodes by a one-step simple sol-gel method for the detection of hydrogen sulfide (H2S) gas. The sphere-like ZnO NPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), energy dispersive x-ray analysis (EDX), and their H2S sensing performance were measured at room temperature. Testing results indicate that the ZnO NPs exhibit excellent response to H2S gas at room temperature. The response value of the optimal sample to 750 ppb H2S is 73.3%, the detection limit reaches to 30 ppb, and the response value is 7.5%. Furthermore, the effects of the calcining time and thickness of the film on the gas-sensing performance were investigated. Both calcining time and film thickness show a negative correlation with the H2S sensing performance. The corresponding reaction mechanism of H2S detection was also discussed.

Facile synthesis and ppb-level H2S sensing performance of hierarchical CuO microflowers assembled with nano-spindles

CuO microflowers were successfully synthesized via a hydrothermal route followed with a high-temperature treatment. The characterized results showed that CuO microflowers assembled with nano-spindles (length: ~ 800 nm) were obtained and the diameter of microflowers were 2.0–2.5 μm. The gas sensor based CuO microflowers showed a fine response to H2S at 25 °C and a fast recovery after a 10-s voltage pulse. The response (S = Rg/Ra) of CuO sensor was 9.92 to 1 ppm H2S at room temperature, and it even could detect 50 ppb H2S (S = 1.42). Furthermore, the gas sensor demonstrated excellent selectivity and repeatability. The sensing mechanism of CuO microspheres to H2S was also proposed and discussed. This work indicates that the prepared CuO microflowers have potential application in detecting extreme low-concentration H2S.

Ultrasensitive ppb-level H2S gas sensor at room temperature based on WO3/rGO hybrids

Gas sensors with high performance and low energy consumption are necessary for system integration in the environment monitoring of explosives. High-performance room-temperature hydrogen sulfide (H2S) gas sensors were fabricated based on the hybrids of tungsten oxide (WO3)/reduced graphene oxide (rGO). WO3 nanocubes modified with different contents of rGO were synthesized by acid-based hydrothermal method. The optimal amount of rGO in the composite is 5 wt%, at which the room-temperature operating sensor presents the highest sensitivity of approximately 32.7 to 500 ppb H2S, a fast recovery time of ~ 180 s, as well as an excellent sensing selectivity. The overall improvement in sensing performances demonstrated an important progress made in H2S sensor fabrication for portable and real-time gas detection. The improved gas-sensing performance is attributed to the large specific surface area of the WO3 nanocubes, the formation of WO3/rGO heterojunctions, and the enhanced electron transfer efficiency.

Highly selective ppb-level H2S sensor for spendable detection of exhaled biomarker and pork freshness at low temperature: Mesoporous SnO2 hierarchical architectures derived from waste scallion root

Herein, we firstly reported a waste scallion root biotemplate strategy to massively fabricate mesoporous SnO2 hierarchical architectures, which can realize precise detection of ppb-level H2S gas in highly humid atmosphere (RH = 85%). The hierarchical skeleton is made up of the crosslinked nanoparticles of about 13 nm with a layer of nanospheres uniformly loaded on the surface of small-sized particles. Such specially structural characteristic can ensure that SnO2 sensing materials possess large specific surface area and good mesoporous connectivity, enhancing the response and selectivity towards trace H2S in a wide range of 0.5–1000 ppb at low working temperature of 92 °C. Especially, detection limit of 0.5 ppb is the lowest among all reported SnO2-based H2S sensors. Meanwhile, we also monitored the change of trace H2S gas concentration in exhaled breath of healthy human, the decay process of fresh pork in 72 h and the simulated environment of halitosis under high humidity, and the sensor exhibited satisfactory results. Therefore, the mesoporous SnO2 hierarchical structure could be used as a spendable sensing material of detecting ppb-level H2S for the applications in meat freshness monitoring and halitosis diagnosis.

A spendable gas sensor with higher sensitivity and lowest detection limit towards H2S: Porous α-Fe2O3 hierarchical tubule derived from poplar branch

Abstract Development of ppb-level H2S sensors based on semiconductor metal oxides has been highly desirable due to its harmful to the human health even at a concentration as low as 20 ppb. In this work, we reported a spendable and high-performance ppb-level H2S gas sensor based on porous α-Fe2O3 quasi-single crystal hierarchical tubule simply derived from poplar branch. The multi-ordered hollow tubules calcined at 600 °C (Fe-600) are constructed from nano-lamellas assembled by cross-linked chains of ~35 nm nanoparticles with amounts of meso- and macro-pores. The Fe-600 sensor with short response time has higher sensitivity of 24.3 to 10 ppm H2S at low working temperature of 133 °C, which is more twice than those of reported α-Fe2O3 sensing materials. Particularly, the detection limit of 1 ppb is the lowest in all reported α-Fe2O3-based sensors. Furthermore, the result of the Fe-600 sensor in monitoring the freshness of pork is satisfied. The sensing mechanism indicates that such good response towards H2S gas is mainly ascribed to the inherent characteristics of porous α-Fe2O3 hierarchical tubules, surface adsorbed oxygen species and formation of metastable iron sulfide caused by lattice oxygen. The Fe-600 sensing material with outstanding combination performances could be used as a good candidate for application in detecting trace ppb-level H2S.

In situ deposited hierarchical CuO/NiO nanowall arrays film sensor with enhanced gas sensing performance to H2S

Hierarchical and heterogeneous CuO/NiO nanowall arrays were in situ grown on ceramic tubes via a facile template-free hydrothermal route, and then were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption–desorption techniques. The resultant composites exhibit network-like CuO/NiO array structures constructed by interconnected porous nanosheets, in which the decoration of CuO nanoparticles in NiO nanowall arrays was confirmed by XRD, XPS and TEM analyses. The 2.84 at % CuO decorated NiO sensor exhibits excellent sensing properties at 133 °C. The response to 5 ppm H2S attains 36.9, which increases as high as 5.6 times compared to the NiO one. The detection limit to H2S is further decreased from 1 ppb for the pure NiO sensor to 0.5 ppb. The CuO/NiO sensor shows a wide linear range from 50 to 1000 ppb, good repeatability, selectivity and long-term stability, which is expected to be a candidate for ppb-level H2S detection in real and complex environment of industrial production. Furthermore, the dominant H2S sensing mechanism is discussed from the view of the homo- and hierarchical architecture of the CuO/NiO arrays as well as the chemical and electronic sensitization effects of CuO decoration.

YSZ-based solid electrolyte type sensor utilizing ZnMoO4 sensing electrode for fast detection of ppb-level H2S

The planar and compact type all-solid state electrochemical gas sensing device based on yttria-stabilized zirconia (YSZ) and Zinc molybdate (ZnMoO4) composite sensing electrode (SE) was proposed and fabricated to effectively detect ppb-level H2S at high temperature. The gas sensing property of different SEs (ZnMoO4, CoMoO4 and NiMoO4) is compared and explored. The sensor attached with ZnMoO4-SE processes the highest response value of −62.5 mV to 1 ppm H2S and lower detection limit of 5 ppb H2S at 500 °C. The response and recovery times of the sensor to 500 ppb H2S are 20 s and 58 s, respectively. The sensor also displays high sensitivity, good continuous reproducibility, selectivity and stability of humidity and high temperature at 500 °C. In addition, the sensing principle involving mixed potential model was proposed and verified using polarization curves.

A fast response/recovery ppb-level H2S gas sensor based on porous CuO/ZnO heterostructural tubule via confined effect of absorbent cotton

The development of ZnO-based sensors towards the detection of trace H2S has recently aroused extensive attentions due to its very harmful to human health even at a concentration as low as 83 ppb. However, the fast response/recovery ZnO-based sensors for detecting ppb-level H2S were also challenging. In this study, porous CuO/ZnO heterostructural tubule was facilely and massively prepared by metal salt impregnation and subsequently calcination via confined effect of absorbent cotton. The influence of Cu2+ doping amounts and calcination temperature on the corresponding microstructure and gas sensing properties of the composites is investigated. The precursor with 3.67 at% Cu2+ doping was calcined at 600 °C to form heterostructural tubules (3.67 at% CuO/ZnO-600) with the specific surface area of 35.2 m2 g−1, which consist of monoclinic CuO (˜21.8 nm) and hexagonal ZnO (˜33.7 nm). The sensor based on 3.67 at% CuO/ZnO-600 shows better gas sensitivity to 50 ppb H2S at 170 °C with response and recovery times of 35 and 29 s, which represents the fastest response/recovery properties in reported ZnO-based ppb-level H2S sensors to date. Furthermore, the sensor has a low detection limit of 10 ppb and shows a wide linear range from 10 to 1000 ppb, good repeatability and long-term stability. Such excellent ppb-level H2S gas sensing performance is mainly ascribed to the inherent characteristics of hierarchically porous tubular structure, p-n heterojunction and surface adsorbed oxygen species. Moreover, the gas-sensing mechanism is also investigated in detail.

Large-Scale Synthesis of Hierarchically Porous ZnO Hollow Tubule for Fast Response to ppb-Level H2S Gas.

Response and recovery time to toxic and inflammable hydrogen sulfide (H2S) gas are important indexes for metal oxide sensors in real-time environmental monitoring. However, large-scale production of ZnO-based sensing materials for fast response to ppb-level H2S has been rarely reported. In this work, hierarchically porous hexagonal ZnO hollow tubule was simply fabricated by zinc salt impregnation and subsequently calcination using absorbent cotton as the template. The influence of calcination temperature on the corresponding morphology and sensing properties is also explored. The hollow tubules calcined at 600 °C are constructed from abundant cross-linked nanoparticles (∼20 nm). Its Brunauer-Emmett-Teller surface area is 31 m2·g-1 and the meso- and macroporous sizes are centered at 35 and 115 nm, respectively. The sensor with a lower detection limit of 10 ppb exhibits a fast response speed of 29 s toward the 50 ppb H2S rather than those of the reported intrinsic and doped ZnO-based sensing materials. Furthermore, the sensor shows a wide linear range (10-1000 ppb), good reproducibility, and stability. Such excellent trace ppb-level H2S performances are mainly related to the inherent characteristics of hierarchically porous hollow tubular structure and the surface-adsorbed oxygen control type mechanism.

Highly selective ppb-level H2S sensor based on the walnut-like Bi2MoO6 at low temperature

The walnut-like Bi2MoO6 (BMO) hollow microspheres, assembled by nanosheets, were synthesized by a facile solvothermal method based on MoO3 hollow spheres. The Bi2MoO6 compound was calcined at the temperature of 200 °C, 400 °C and 450 °C (denoted as BMO-200, BMO-400 and BMO-450) to measure the gas-sensing properties. The sensor based on BMO-400 exhibits a significant selectivity, a high stability and response, a good repeatability and humidity-resistivity and a better linear relationship to H2S gas at the concentration range of 1–100 ppm level and 0.1–100 ppb level at a low operating temperature of 133 °C. In addition, the detection limit of the sensor towards H2S gas is as low as 0.1 ppb (S = 1.98). According to the sensing mechanism discussed based on X-ray photoelectron spectroscopy (XPS) and gas chromatography-mass spectrometry (GC–MS) analyses, the improvement of response may be attributed to the high oxygen content adsorbed on the surface of the Bi2MoO6 material and the unique hollow structure.

Enhanced H2S gas-sensing performance of Zn2SnO4 hierarchical quasi-microspheres constructed from nanosheets and octahedra.

Most of the reported ternary oxides based sensors have not been realized to detect ppb-level H2S till now. In this work, Zn2SnO4 hierarchical quasi-microspheres were prepared through a facile surfactant-free hydrothermal method followed by calcination in air atmosphere. The quasi-microspheres are composed of nanosheets with the thickness of 100 nm and octahedra with the average size of 0.63 μm, respectively. The sensor fabricated from such Zn2SnO4 hierarchical quasi-microspheres shows excellent selective response to H2S at 133 °C with the lowest detection limit of 1 ppb. The gas response exhibits good linear relationship in the concentration range of 1-1000 ppb. Such outstanding H2S sensing property might be attributed to its porous structure, the synergistic effect of the two typical building blocks and the surface adsorbed oxygen, and the possible sensing mechanism is also discussed.