Ppb-level H2S Research Articles

Ultra-fine ppb-level H2S detection based on designed (Cu0.2Co0.8)Co2O4 frameworks

Ultra-fine ppb-level H2S detection based on designed (Cu0.2Co0.8)Co2O4 frameworks

High Performance H2S Sensor Based on Ordered Fe2O3/Ti3C2 Nanostructure at Room Temperature.

The utilization of a heterogeneous nanojunction design has shown significant enhancements in the gas sensing capabilities of traditional metal oxide gas sensors. In this study, a novel room temperature H2S gas sensor employing Fe2O3 functionalized Ti3C2 MXene as the sensing material has been developed. This sensor exhibits a broad detection range (0.01-500 ppm), low detection limit (10 ppb), and rapid response/recovery times (10 s/15 s), making it ideal for ppb-level H2S detection. The exceptional gas sensitivity of Fe2O3/Ti3C2 composite to H2S can be attributed to several key factors. First, the unique layered frame structure of Fe2O3/Ti3C2 significantly amplifies the surface area of the hybrid material, enhancing the absorption and diffusion capabilities of H2S molecules. Second, the abundance of functional groups (-O, -OH, and -F) on the surface of Ti3C2 MXene nanosheets provides additional active sites for H2S adsorption, The density functional theory calculation confirms that the adsorption energy of the Fe2O3/Ti3C2 composite for H2S (-2.93 eV) is significantly lower than that of pure Fe2O3 (-2.37 eV) and Ti3C2 (-0.2 eV). Lastly, the remarkable metal conductivity of Ti3C2 MXene ensures efficient electron transfer, thereby enhancing overall sensing performance.

Ultrasensitive detection of hazardous gas at room temperature enabled by MOF@MXene 0D-2D heterostructure

Achieving high sensitivity in detecting trace concentrations of toxic gases, particularly under room temperature (RT) conditions, remains a significant challenge. Herein, a 0D-2D heterostructure that can detect ppb-level H2S at RT is proposed by self-assembling cobalt-based metal–organic framework (Co-MOF) on Ti3C2Tx MXene. Co-MOFs with high specific surface areas can capture and concentrate target gas molecules, enhancing host-guest interactions and thereby boosting the selectivity and sensitivity. MXene nanosheets with high conductivity enable rapid electron transport at heterointerface, hence efficiently accelerating the reaction kinetics. Thereby, the as-prepared chemiresistive gas sensor based on Co-MOF@MXene 0D–2D heterostructure possessed excellent sensitivity against interfering gases and delivered an excellent response value of 11.1 to 400 ppb H2S at RT. The judicious design of MOF@MXene heterostructure may spur advanced hybrid material systems for superior sensing applications.

In Situ Generatable and Recyclable Oxygen Vacancy-Modified Fe2O3-Decorated WO3 Nanowires with Super Stability for ppb-Level H2S Sensing.

Detecting hydrogen sulfide (H2S) odor gas in the environment at parts-per-billion-level concentrations is crucial. However, a significant challenge is the rapid deactivation caused by SO42- deposition. To address this issue, we developed a sensing material comprising Fe2O3-decorated WO3 nanowires (FWO) with strong interfacial interaction. During the H2S sensing process, important oxygen vacancies (OVs) are generated in situ and are recyclable on the surface of the Fe2O3 cluster. This sensor achieves a response of 140 (Ra/Rg) toward 50 ppm of H2S at 250 °C, with an experimentally measured detection limit of 1 ppb. It also exhibits remarkable stability, with no significant change observed over a long period of 150 days. Based on a combination of in situ DRIFT and DFT calculations, we have identified that the overactivation of O2 is the key step in the formation of SO42-. This overactivation can be partially modulated by the synergistic effect of Fe2O3 decoration and the in situ generated OVs, regulating the oxidation product to SO2 rather than the toxic SO42-. Furthermore, the continuous generation of OVs compensates for the loss of active sites pertaining to SO42- deposition, thereby contributing to the excellent stability of the sensor. This study underscores the beneficial impact of in situ OV generation in FWO for H2S sensing, offering a dynamic strategy to enhance sensor performance, particularly in terms of stability.

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.

Flexible room temperature gas sensor based on α-Fe2O3/Ti3C2Tx MXene composites for ppb-level H2S detection

Ti3C2Tx MXene have attracted enormous attention in portable, wearable electronics areas due to its excellent flexible, electrical conductivity and outstanding physical and chemical properties. Here, 2D α-Fe2O3/Ti3C2Tx MXene composites were synthesized by in-suit growth of α-Fe2O3 on the surface of Ti3C2Tx MXene and between the layers of Ti3C2Tx MXene by solvothermal and annealing methods. Compared with pure α-Fe2O3, the optimal α-Fe2O3/Ti3C2Tx MXene composites exhibited excellent gas sensitive performance (100 ppm can reach 20.27) and a theoretical ultra-low limit-of-detection of 10.19 ppb to H2S gas at room temperature (25 ○C). The combination of α-Fe2O3 and Ti3C2Tx lead to the layer spacing of Ti3C2Tx MXene are further enlarged which is more favorable for H2S gas adsorption. And the excellent performance is maintained even under bending conditions. This work provides a new idea for MOS/Ti3C2Tx MXene in the field of flexible room temperature sensors.

Chemiresistive room temperature H2S gas sensor based on MoO3 nanobelts decorated with MnO2 nanoparticles

In this work, we develop ultrafast detection and reversible H2S gas sensor at room temperature (RT, 23 ℃). The optimized MoO3/MnO2 (MM-10) sensor exhibits remarkable sensitivity to H2S with a response of 32.51–100 ppm H2S at RT, which is approximately 21.82 times higher than that of the MoO3 sensor. Further, the MM-10 sensor demonstrates a fast response of 5.71–1000 ppb H2S with response/recovery times of 40/42 s at RT. More surprisingly, the theoretical limit of the MM-10 sensor for detecting H2S gas is as low as 4.58 ppb at RT, which addresses the limitation of binary heterojunction-based sensors in detecting ppb-level H2S gas at RT. After 49 days, the MM-10 sensor still demonstrates reliable stability, ensuring the long-term detection to ppb-level H2S at RT in practical applications. Notably, as the relative humidity increases from 30 % to 90 %, the response only decreases by about 17 %, indicating an excellent shielding ability against water molecules. Additionally, it is found that 1 % relative humidity change has a comparable effect on MM-10 sensor as approximately 5.58 ppb H2S gas. The significant enhancement mechanism on the sensing surface in the context of H2S/MoO3/MnO2 interaction is also thoroughly discussed.

Construction of Ag2O/WO3-based hollow microsphere p-n heterojunction for continuous detection of ppb-level H2S gas sensor

Three-dimensional (3D) hierarchical hollow microsphere WO3 and Ag2O/WO3 heterojunction materials were prepared by a simple hydrothermal method for a highly sensitive continuous response H2S gas sensor. The results show that compared with the original WO3 (Ra/Rg=12.5, 10 ppm, 70℃), the sensor based on Ag2O/WO3 has excellent H2S sensing performance at 60℃. Including ultra-high sensitivity (Ra/Rg=207.12, 10 ppm), continuous detection of different concentrations of H2S gas (0.05–50 ppm), fast response capability (15 s), low detection limit (50 ppb), high selectivity and reliable stability. The study of gas sensing mechanism shows that the synthesized 3D hierarchical hollow microsphere structure provides more channels for gas diffusion and transmission. The dispersion of Ag2O nanoparticles (NPs) on the surface of WO3 provides more reactive sites for gas adsorption. At the same time, the charge transfer is promoted by constructing Ag2O/WO3 p-n heterojunction. Sulfurization of Ag2O improved the response value and selectivity to H2S gas. These factors together determine the superior performance of the prepared Ag2O/WO3 H2S-based sensor.

A novel Cu-doped ZnO confined structure: Precisely preparation, and sensitization mechanism for ppb-level H2S gas detection

It is still highly desired and challengeable to design H2S sensor with high selectivity and sensitivity due to its toxicity and new application in biomarkers like monitoring halitosis. Here, we reported a novel confined structure as highly sensitive and selective H2S gas sensor. The sensing material was prepared with a HKUST-1 templated method by atomic layer deposition (ALD) ZnO decorated on HKUST-1 and calcination. The gas sensor exhibits a high gas sensitivity (Ra/Rg = 2.67 @ 2 ppm) with excellent selectivity to H2S. Furthermore, the obtained sensor shows ppb-level detection ability (Ra/Rg = 1.13 @ 0.1 ppm). Apart from releasing electrons by the oxidization of H2S on oxygen vacancies with adsorbed oxygen species O2− on ZnO surface (Langmuir-Hinshelwood mechanism), the Cu was proved to be the active sites, and would react with surficial S species. The suggestion was confirmed by operando XAS (X-ray adsorption spectrum) measurements combined with DFT calculations (Mars-van Krevelen mechanism). This work provides valuable insights for developing efficient sensing materials and understanding the sensing mechanism.

SnO2-inserted 2D Layered Ti3C2Tx MXene: From heterostructure construction to ultra-high sensitivity for Ppb-level H2S detection

Two-dimensional (2D) materials emerge as a focus in chemiresistive gas sensors in recent years due to their flexibly modifiable surfaces and low energy consumption. Here, SnO2-inserted 2D layered Ti3C2Tx MXene composite was synthesized by solvothermal and subsequent annealing processes. It inherits the advantages of SnO2 and Ti3C2Tx MXene gas sensitive materials, including fast response/recovery and low operating temperature. Unexpectedly, the SnO2/Ti3C2Tx composite exhibits a theoretical ultra-low limit-of-detection of 5.76 ppb and an ultra-high sensitivity toward H2S gas. The optimal sensing response to 30 ppm H2S can reach 150 (11 times than pure SnO2), which is one of the highest sensitivities of all reported 2D materials and MXene-based H2S sensors. The excellent performances can be attributed to the formation of p-n heterojunction between Ti3C2Tx MXene and SnO2, and the more active sites for gas absorption provided by layer structure of Ti3C2Tx MXene. Moreover, DFT calculations were performed to explore H2S adsorption behaviors. SnO2/Ti3C2Tx composite shows a higher adsorption energy to H2S gas than both pure SnO2 and Ti3C2Tx MXene. This work provides a new idea for designing and constructing high performance MOS/MXene H2S gas sensors.

Cu-Pt/CrN Fuel Cell Gas Sensor Achieves ppb-Level H2S Detection at Room Temperature.

Fuel cell gas sensors have emerged as promising advanced sensing devices owing to their advantageous features of low power consumption and cost-effectiveness. However, commercially available Pt/C electrodes pose significant challenges in terms of stability and accurate detection of low concentrations of target gases. Here, we introduce an efficient Cu-Pt/CrN-based fuel cell gas sensor, designed specifically for the ultrasensitive detection of hydrogen sulfide (H2S) at room temperature. Compared to the commercial Pt/C sensor, the Cu-Pt/CrN sensor exhibits excellent sensitivity (0.26 μA/ppm), with an increase in the selectivity by a factor of 2.5, and demonstrates good stability over a 2 month period. The enhanced sensing performance can be attributed to the modulation of the electronic arrangement of Pt by Cu, resulting in an augmentation of H2S adsorption. The Cu-Pt/CrN fuel cell gas sensor provides an opportunity for detecting parts per billion-level H2S in various applications.

Ppb-level H2S sensor with super selectivity based on Fe-NiOx nanotube assembled by AAO template

Hydrogen sulfide is a kind of widely distributed toxic gas, therefore, it is strongly necessary to conduct highly selective detection at lower concentrations. However, due to the high affinity of sulfur elements to transition metals, hydrogen sulfide sensors based on metal oxide semiconductors often have slower recovery and poor selectivity. In this work, Fe-NiOx nanotubes with unique structure and high specific surface area (175 m2/g) were synthesized by using anodized aluminum oxide templates for detecting sub-ppm H2S. The gas sensor based on 2 wt% Fe-doped NiOx nanotube performed exceptional gas sensing properties to 800 ppb H2S, featured with the high sensitivity (|ΔR/Ra| = 5.24), excellent selectivity (SH2S/SNO2 = 8.3) and fast response/recovery speed (3.2/8.1 s) at 270 °C. Density function theory calculation proved the critical function of Fe3+ to lower the adsorption enthalpy of H2S and changing the selectivity. This work not only provided a superior ppb-level H2S gas sensor, but also induced a synthesis strategy to enhance the gas sensing properties.

One-pot facile synthesis of rod-like Bi2S3 particles in deep eutectic solvent and their ppb-level selective H2S gas detection.

Bismuth sulfide, Bi2S3, was prepared by a one-pot reaction using various choline chloride-based deep eutectic solvents (DESs) as the reaction field. Rod-like particles obtained with acetamide-thioacetamide-based DESs were found to exhibit specifically dominant detection properties for H2S gas, and the gas detection mechanism was discussed by adsorption reaction.

Light-induced thermoelastic sensor for ppb-level H2S detection in a SF6 gas matrices exploiting a mini-multi-pass cell and quartz tuning fork photodetector

We present an optical sensor based on light-induced thermoelastic spectroscopy for the detection of hydrogen sulfide (H2S) in sulfur hexafluoride (SF6). The sensor incorporates a compact multi-pass cell measuring 6 cm × 4 cm × 4 cm and utilizes a quartz tuning fork (QTF) photodetector. A 1.58 µm near-infrared distributed feedback (DFB) laser with an optical power of 30 mW serves as the excitation source. The sensor achieved a minimum detection limit (MDL) of ∼300 ppb at an integration time of 300 ms, corresponding to a normalized noise equivalent absorption coefficient (NNEA) of 3.96 × 10−9 W·cm−1·Hz−1/2. By extending the integration time to 100 s, the MDL can be reduced to ∼25 ppb. The sensor exhibits a response time of ∼1 min for a gas flow rate of 70 sccm.

Cu-doped SnO2/rGO nanocomposites for ultrasensitive H2S detection at low temperature

Hydrogen sulfide (H2S) detection remains a significant concern and the sensitivity, selectivity, and detection limit must be balanced at low temperatures. Herein, we utilized a facile solvothermal method to prepare Cu-doped SnO2/rGO nanocomposites that have emerged as promising candidate materials for H2S sensors. Characterization of the Cu-SnO2/rGO was carried out to determine its surface morphology, chemical composition, and crystal defects. The optimal sensor response for 10 ppm H2S was ~1415.7 at 120 °C, which was over 320 times higher than that seen for pristine SnO2 CQDs (Ra/Rg = 4.4) at 280 °C. Moreover, the sensor material exhibited excellent selectivity, a superior linear working range (R2 = 0.991, 1–150 ppm), a fast response time (31 s to 2 ppm), and ppb-level H2S detection (Ra/Rg = 1.26 to 50 ppb) at 120 °C. In addition, the sensor maintained a high performance even at extremely high humidity (90%) and showed outstanding long-term stability. These superb H2S sensing properties were attributed to catalytic sensitization by the Cu dopant and a synergistic effect of the Cu-SnO2 and rGO, which offered abundant active sites for O2 and H2S absorption and accelerated the transfer of electrons/holes.

A room-temperature ppb-level H2S sensor based on MoO3/CuO/g-C3N4 via a simple synthesis

The detection of H2S for biomarkers or special occasions often requires a lower detection limit. In this work, the ppb-level H2S sensor based on MoO3/CuO/g-C3N4 (MCC) was presented by a simple method. The characterized results show that MCC-2 possesses a larger specific surface area, and has more adsorbed oxygen and oxygen vacancy compared to MoO3 and MoO3/CuO. The gas-sensitive test results show that the response of the MCC-2 sensor to 1000 ppb H2S is up to 8.24 at room temperature, which is 1.31 times of MoO3/CuO (6.28). More importantly, the theoretical detection limit of the MCC-2 sensor is as low as 1.1 ppb, which is the lowest in the recent H2S sensor. In addition, the MCC-2 sensor has reliable repeatability, excellent selectivity to H2S, and still maintains a high response after continuous test for 5 weeks. Simultaneously, the MCC-2 sensor also keeps an outstanding response at high relative humidity. The excellent gas sensing properties are due to the larger specific surface area that can enable more gases to be adsorbed on the material surface. In addition, the oxygen vacancy reduces the energy required to adsorb the target gas and the formed heterojunctions by MoO3/CuO/g-C3N4 expedite carrier migration.

Highly sensitive detection of H2S gas at low temperature based on ZnCo2O4 microtube sensors

It is extremely necessary to detect Hydrogen sulfide (H2S) due to the hazardous nature. Thus, it is required to design a material which can detect H2S gas at low temperature. In this work, ZnCo2O4 microtubes are prepared by using absorbent cotton as template, combining immersion method in metal salt solution (Zn:Co=1:2) with calcination treatment in air. The influence of calcination temperature on the particle size and sensing property was also discussed. The diameter of particles on the ZnCo2O4 microtubes increases with increasing calcination temperature. The hollow microtubes of ZnCo2O4 materials calcined at 600 °C (ZCO-600) exhibit superb sensing performance to H2S at 90 °C with the lowest detection limit of 50 ppb. The optimum operating temperature (90 °C) was lower than the other reported ZnCo2O4 sensors. ZCO-600 sensor also shows excellent selectivity, repeatability, stability, humidity resistance and the good linear relationship in ppb and ppm level H2S. In addition, the feasible sensing mechanism of ZCO-600 to H2S is explored on the basis of XPS analysis. Thus, ZnCo2O4 as a sensing material possesses widespread application prospects for the detection of trace H2S gas.

Room-Temperature ppb-Level H2S Gas Sensors Based on Ag Nanowire/Hollow PPy Nanotube Nanocomposites

H2S gas sensors were fabricated using Ag nanowire/hollow polypyrrole nanotube nanocomposite (Ag NW/hollow PPy NT) film for sensing ppb-level H2S gas at room temperature. The morphology, phase composition and crystalline structure of Ag NW/hollow PPy NT nanocomposites were analyzed via scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Fourier-transform infrared spectroscopy (FTIR). TEM and SEM images revealed that Ag NWs were well dispersed in the hollow PPy NT matrix. IR results showed no interaction between Ag NWs and hollow PPy NTs in the Ag NW/hollow PPy NT nanocomposites. The effect of the amount of added Ag NWs on the response of the Ag NW/hollow PPy NT nanocomposites to the ppb-level H2S gas was investigated. Comparative gas-sensing results revealed that the introduction of Ag NWs onto hollow PPy NTs was effective in promoting the sensor response to H2S gas. More importantly, the Ag NW/hollow PPy NT nanocomposite had a strong response to ppb-level H2S gas at room temperature.

Cadmium sulfide in-situ derived heterostructure hybrids with tunable component ratio for highly sensitive and selective detection of ppb-level H2S

Herein, we reported cadmium sulfide derivatives pine needles-like CdS/CdO heterostructure hybrids synthesized by hydrothermal treatment and subsequent self-template oxidation approach. The component ratio of the CdS/CdO hybrids can be controlled specifically via tuning the annealing treatment protocol, and thereby giving rise to the optimization of morphology, electrical characteristics, and gas sensing properties of derived hybrids. As proof of concept, the pine needles-like CdS/CdO, which obtained after different annealing temperatures and durations, as sensitive material was employed to manufacture H2S gas sensors. The sensor based on CdS/CdO hybrids (400 °C & 1 h) exhibited high sensitivity (73.5 to 5 ppm), ppb-level limit of detection (10 ppb), and excellent selectivity regardless of the interference of other gases at optimal working temperature of 200 °C. Due to the abnormal resistance variation of n-type cadmium sulfide derived hybrids while contacting with H2S, the sensing mechanism mainly depends on the surface chemical conversion from oxide to sulfide. The pine needles-like hierarchical morphology provided an excellent scaffold for the carriers transportation and the growth of the CdO, which played a key role in resistance modulation both in air and target gas, resulting in the enhanced H2S sensing performance ultimately.

Ppb-level H2S gas sensor based on CuNi-MOFs derivatives for meat freshness detection at low temperature environment

H2S is usually used as one of the landmark gases for meat freshness detection under low temperature storage conditions. In this paper, the NiO-doped CuO composite derived from MOFs was synthesized by a low temperature (−25 ℃) precursor hydrothermal and sintering procedure for H2S detection. The influence of precursor solution temperature and sintering temperature on the structure of MOFs derivatives were discussed by SEM, TEM, and XRD characterization. The hydrothermal method of low-temperature precursor has guiding significance in improving the gas response performance of MOFs/MOFs derivatives. The sensor based on NiO-doped CuO composites derived from MOFs exhibited a ppb-level response to H2S gas. The sensor response is 106 % to 50 ppb H2S. Meanwhile, the sensor has good selectivity, and the response and recovery time are 115 s and 251 s, respectively. The low temperature precursor hydrothermal method directly affected the morphology and structure of MOFs derivatives by regulating the kinetics for MOFs nucleation and crystal growth, obtains more active adsorption sites. In addition, the composite has good sensing performance for H2S at the ambient temperature of 4 ℃ and −18 ℃, which verified the effectiveness for the detection of meat spoilage under a low temperature storage. Furthermore, the sensor based on NiO-doped CuO composites is a good candidate for H2S gas detection in meat freshness evaluation. Finally, an integrated circuit detection system was designed to detect H2S gas at different ambient temperatures. This work provides a new idea for meat freshness detection in a cold storage environment.