Heterostructural (Sr0.6Bi0.305)2Bi2O7/ZnO for novel high-performance H2S sensor operating at low temperature

Delafossite CuGaO2-Based Chemiresistive Sensor for Sensitive and Selective Detection of Dimethyl Disulfide

Dimethyl disulfide (DMDS) is a common odor pollutant with an extremely low olfactory threshold. Highly sensitive and selective detection of DMDS in ambient humid air background, by metal oxide semiconductor (MOS) sensors, is highly desirable to address the increased public concern for health risk. However, it has still been a critical challenge up to now. Herein, p-type delafossite CuGaO2 has been proposed as a promising DMDS sensing material owing to its striking hydrophobicity (revealed by water contact angle measurement) and excellent partial catalytic oxidation properties (indicated by mass spectroscopy). The present CuGaO2 sensor shows a selective DMDS response, with satisfied humidity resistance performance and long-term stability at a relatively low operation temperature of 140 °C. An ultrahigh response of 100 to 10 ppm DMDS and a low limit of detection of 3.3 ppb could be achieved via a pulsed temperature modulation strategy. A smart sensing system based on a CuGaO2 sensor has been developed, which could precisely monitor DMDS vapor in ambient humid air, even with the presence of multiple interfering gases, demonstrating the practical application capability of MOS sensors for environmental odor monitoring.

ZnSnO3 based gas sensors for pyridine volatile marker detection in rice aging during storage

This study reports the development of ZnSnO₃ based gas sensors for pyridine detection in rice aging. Pyridine is one of heterocyclic markers formed via Maillard reaction and lipid oxidation. Herein, graphitic carbon nitride (g-C₃N₄) decorated ZnSnO₃ microstructures were obtained through a template-free approach. And the sensing results reveal that 5 wt%g-C₃N₄ decorated ZnSnO₃ exhibited a high sensitivity (47.9), a short response/recovery time (14/120 s) and a low detection limit (0.45 ppm), which is due to the catalysis of g-C₃N₄ nanosheets, the decorated microstructure and the formation of heterojunctions. Meanwhile, the practical experiment demonstrates that the sensitivity towards volatiles generated from Japonica rice aging is 48.7, which is around 4 and 2.5 times higher than those of Indica rice and Polished Glutinous rice, indicating that the sensor has anticipated application in the development of a high-performance E-nose for the quality inspection of rice and other products.

Bifunctional role of PDMS membrane in designing humidity-tolerant H2S chemiresistors with high selectivity

A thermally evaporated hydrophobic PDMS membrane could significantly mitigate humidity interference/poisoning (without a decline in response at 50% RH for nearly 3 months) and enhance the selectivity of a CuCrO₂ chemiresistor toward erosive H₂S, offering an avenue for the practical applications of (H₂S) chemiresistors in an ambient humid air atmosphere.

Dual-Signaling Photoelectrochemical Biosensor Based on Biocatalysis-Induced Vulcanization of Bi2MoO6 Nanosheets

A magnetic-assisted photoelectrochemical (PEC) and colorimetric (CL) dual-modal biosensing platform with high precision was established to monitor prostate-specific antigen (PSA) based on Bi₂MoO₆ nanosheets (BMO) by coupling the aptamer-guided hybridization chain reaction (HCR) with the hydrolysate-induced vulcanization reaction of Bi₂MoO₆ nanosheets. Upon addition of PSA, trigger DNA (tDNA) was released by the interaction between the target analyte and the aptamer and then further hybridized with anchor DNA (aDNA) conjugated on magnetic beads (MBs). The as-released tDNA initiated the target-assisted HCR in the presence of two alternating hairpin sequences (Bio-H1 and Bio-H2) to produce nicked long double-stranded DNA on the surface of MBs, where numerous alkaline phosphatase (ALP) enzymes could assemble with MBs through the biotin-avidin reaction, resulting in the hydrolysis of sodium thiophosphate (TP) to H₂S. The as-produced H₂S reacted with BMO to form vulcanized BMO (BMO-S), thus leading to obvious enhanced PEC performance under visible light with the color change from light yellow to brown. Having optimized the test conditions, the magnetic-assisted biosensing system holds a good quantitative diagnosis sensitivity area in a range of 5.0 pg mL^-1-100 ng mL^-1 with a calculated detection limit down to 3.5 pg mL^-1. Meanwhile, a visual colorimetric assay on basis of the change in the color of the materials was also realized. Given the exceptional performance of the constructed biosensor, it may possess great promise as an advanced bioanalytical tool for practical applications.

Pt-Anchored CuCrO2 for Low-Temperature-Operating High-Performance H2S Chemiresistors

Recent advances in heterogeneous catalysts indicate that single atoms (SAs), anchored/stabilized on metal oxide nanostructures, exhibit not only high catalyst atom efficiency but also intriguing reactivity and selectivity. Herein, isolated Pt SA-anchored CuCrO₂ (CCO) has been designed by a glycine-nitrate solution combustion synthesis (SCS) route. The density of isolated Pt SAs achieves the highest value of ∼100 μm^-2 for the 1.39 wt % Pt-anchored CCO sample, which results in the drastically boosted H₂S response characteristics, including a high response of 1250 (35 times higher than that of pure CCO) at 10 ppm H₂S and a low operating temperature of 100 °C. Except for CH₄S, the responses of a 1.39 wt % Pt-anchored CCO chemiresistor to diverse vapors with concentrations of 50-100 ppm are less than 2, exhibiting excellent selectivity. Various ex situ characterizations indicate that the spillover catalytic effect of Pt SA sites, other than the conventional sulfuration-desulfuration mechanism, plays a dominant role in the outstanding H₂S response characteristics.

Rapid detection of H2S gas driven by the catalysis of flower-like α-Bi2Mo3O12 and its visual performance: A combined experimental and theoretical study

Metal oxide semiconductor (MOSs) are attractive materials for the development of H₂S gas sensors. However, detecting H₂S with short response and recovery times while also lowering the limit of detection to sub-ppb levels remains a significant challenge. We therefore developed flower-like α-Bi₂Mo₃O₁₂ microspheres for H₂S gas detection that provide fast response and recovery times (3 and 22 s, respectively, for 100 ppm H₂S), while also reducing the limit of detection to 1 ppb. The sensor performs well in terms of sensitivity, reproducibility, long-term stability, including humidity stability. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations revealed that H₂S dissociates readily on the reduced α-Bi₂Mo₃O₁₂ surface and that Mo plays a catalytic role, accelerating the rate of H₂S decomposition and enabling a fast response. Moreover, test strips containing α-Bi₂Mo₃O₁₂ were also prepared, which enabled the naked eye detection of ppm-level H₂S gas at room temperature; a light-yellow to orange to brown color change occurs when exposed to H₂S, due to its conversion into stable sulfides. This work expands the application of α-Bi₂Mo₃O₁₂ to H₂S gas sensing, and provides a strategy for the use of MOSs as sensor materials for the detection of other gases.

Co3O4@TiO2@Y2O3 nanocomposites for a highly sensitive CO gas sensor and quantitative analysis

In order to predict the early failure of organic insulator, Co₃O₄@TiO₂@Y₂O₃ nanocomposites was prepared and characterized (XRD, SEM, EDS, FTIR, UV-vis-NIR, XPS) to detect decomposition CO gas. A simple experimental platform was built to verify the excellent adsorption, stability, selectivity and repeatability of the composite. Then, the mechanism of adsorption enhancement was analyzed by heterojunction. Aiming at 170 sets of gas sensing data sets, Successive Projections Algorithm (SPA) was used to extract data features, and grey wolf optimization vector machine regression (GWO-SVR) model was established to predict carbon monoxide concentration. The correlation coefficient (R_P), root mean square error (RMSEP) and calculation time of prediction set were 99.3025%, 0.0418 and 1.47 s, respectively. Therefore, the combination of the superior properties of a composite sensitive material and the small sample quantitative prediction model is a promising method for gas sensors in the future.

Ultra-sensitive H2S sensor based on sunflower-like In-doped ZnO with enriched oxygen vacancies

In–ZnO with oxygen vacancies exhibits a higher sensing response and a shorter recovery time for H2S compared to ZnO.

Preparation and Application of 2D MXene-Based Gas Sensors: A Review

Since MXene (a two-dimensional material) was discovered in 2011, it has been favored in all aspects due to its rich surface functional groups, large specific surface area, high conductivity, large porosity, rich organic bonds, and high hydrophilicity. In this paper, the preparation of MXene is introduced first. HF etching was the first etching method for MXene; however, HF is corrosive, resulting in the development of the in situ HF method (fluoride + HCl). Due to the harmful effects of fluorine terminal on the performance of MXene, a fluorine-free preparation method was developed. The increase in interlayer spacing brought about by adding an intercalator can affect MXene’s performance. The usual preparation methods render MXene inevitably agglomerate and the resulting yields are insufficient. Many new preparation methods were researched in order to solve the problems of agglomeration and yield. Secondly, the application of MXene-based materials in gas sensors was discussed. MXene is often regarded as a flexible gas sensor, and the detection of ppb-level acetone at room temperature was observed for the first time. After the formation of composite materials, the increasing interlayer spacing and the specific surface area increased the number of active sites of gas adsorption and the gas sensitivity performance improved. Moreover, this paper discusses the gas-sensing mechanism of MXene. The gas-sensing mechanism of metallic MXene is affected by the expansion of the lamellae and will be doped with H2O and oxygen during the etching process in order to become a p-type semiconductor. A p-n heterojunction and a Schottky barrier forms due to combinations with other semiconductors; thus, the gas sensitivities of composite materials are regulated and controlled by them. Although there are only several reports on the application of MXene materials to gas sensors, MXene and its composite materials are expected to become materials that can effectively detect gases at room temperature, especially for the detection of NH3 and VOC gas. Finally, the challenges and opportunities of MXene as a gas sensor are discussed.

Selective Determination of Hydrogen Sulfide Using SnO2–Ag Sensor Working in Non-Stationary Temperature Regime

The application of a non-stationary regime of temperature modulation in metal oxide semiconductor sensor based on SnO2–Ag leads not only to a strongly increased sensor response, but also to a considerably improved sensor selectivity toward hydrogen sulfide. Selectivity with respect to other reducing gases (CO, NH3, H2) is about five orders of magnitude, enabling a correct selective determination of H2S in the presence of interfering gas components.