From a Relatively Hydrophobic and Triethylamine (TEA) Adsorption-Selective Core-Shell Heterostructure to a Humidity-Resistant and TEA Highly Selective Sensing Prototype: An Alternative Approach to Improve the Sensing Characteristics of TEA Sensors

Reverse Hydrogen Spillover on Metal Oxides for Water-Promoted Catalytic Oxidation Reactions

Understanding the water-involved mechanism on metal oxide surface and the dynamic interaction of water with active sites is crucial in solving water poisoning in catalytic reactions. Herein, this work solves this problem by designing the water-promoted function of metal oxides in the ethanol oxidation reaction. In situ multimodal spectroscopies unveil that the competitive adsorption of water-dissociated *OH species with O2 at Sn active sites results in water poisoning and the sluggish proton transfer in CoO-SnO2 imparts water-resistant effect. Carbon material as electron donor and proton transport channel optimizes the Co active sites and expedites the reverse hydrogen spillover from CoO to SnO2. The water-promoted function arises from spillover protons facilitating O2 activation on the SnO2 surface, leading to crucial *OOH intermediate formation for catalyzing C-H and C-C cleavage. Consequently, the tailored CoO-C-SnO2 showcases a remarkable 60-fold enhancement in ethanol oxidation reaction compared to bare SnO2 under high-humidity conditions.

Bioinspired multi-scale interface design for wet gas sensing based on rational water management

Natural organisms have evolved multi-scale wet gas sensing interfaces with optimized mass transport pathways in biological fluid environments, which sheds light on developing artificial counterparts with improved wet gas sensing abilities and practical applications. Herein, we highlighted current advances in wet gas sensing taking advantage of optimized mass transport pathways endowed by multi-scale interface design. Common moisture resistance (e.g., employing moisture resistant sensing materials, post-modifying moisture resistant coatings, physical heating for moisture resistance, and self-removing hydroxyl groups) and moisture absorption (e.g., employing moisture absorption sensing materials and post-modifying moisture absorption coatings) strategies for wet gas sensing were discussed. Then, the design principles of bioinspired multi-scale wet gas sensing interfaces were provided, including macro-level condensation mediation, micro/nano-level transport pathway adjustment and molecular level moisture-proof design. Finally, perspectives on constructing bioinspired multi-scale wet gas sensing interfaces were presented, which will not only deepen our understanding of the underlying principles, but also promote practical applications.

Ultrasensitive triethylamine gas sensors with ZnSe nanospheres/nest-like Cr-doped MoO3

Developing high-sensitivity TEA sensors has extremely important significance for human health. Design of three-dimensional (3D) nanostructures assembled from one-dimensional nanomaterials can effectively improve sensing performance. In this work, a nest-like structure assembled by Cr-doped MoO3 (Cr-MoO3) nanorods with relatively higher specific surface area was prepared. In order to improve the sensing performance, Cr-MoO3 skeleton was combined with ZnSe nanospheres of different mass ratios as sensing materials (ZnSe/Cr-MoO3), and the successful construction of the heterojunction structure was supported by various spectroscopies and charge density calculation. The prepared composite with an optimal moiety ratio showed very high response values of 371 and 1301 for 10 ppm and 50 ppm for TEA at 200 °C, respectively. Simultaneously, the composite sensor also exhibited a low detection limit (1.7 ppb). The improvement of the sensing performance of ZnSe/Cr-MoO3 was attributed to the formation of oxygen vacancies induced by Cr doping, the 3D nest-like structure provided an efficient network for charge transport/collection and the n-n heterojunctions between Cr-MoO3 nanorods and ZnSe nanospheres. The simulation analysis based on density functional theory (DFT) calculations indicated that the heterojunctions could effectively enhance the adsorption energy of TEA and the more charges transferring from TEA to the Cr-MoO3 nanorods.

Oxygen vacancies induced by lanthanum-doped indium oxide nanofibers for promoted temperature-dependent triethylamine and formaldehyde sensing

A novel TEA and HCHO dual-function temperature-dependent sensing material (3La-In2O3) with ultra-high sensitivity was developed via a facile electrospinning process. Though rare earth doped in In2O3-based sensors have been widely reported, the low sensitivity, poor selectivity and high operating temperature remain restrict their application. Herein, the In2O3 nanofibers with different contents of La3+ ions are firstly obtained by a facile electrospinning process. The sensing performance investigation confirms that the 3% La/In molar ratio of La3+ doped in In2O3 nanofibers are more appropriate as the sensing material for TEA and HCHO detection. The 3La-In2O3 exhibits greatest response value of 3721.60-10 ppm TEA and 1469.65-10 ppm HCHO at their best working temperature (100 ℃ and 160 ℃), approximately 23.85-fold and 10.85-fold higher than that of pristine In2O3 nanofibers. In addition, the excellent selectivity, repeatability, and long-term stability ensure the further application of the 3La-In2O3-based sensor in actual environment. The promoted sensing performance is mainly ascribed to the more oxygen vacancies, the increasing specific surface area, the smaller grain size of In2O3 nanofibers induced by La3+ doping. The DFT results demonstrate the beneficial effect of La and oxygen vacancies on the improved target gas adsorption energy.

Utilizing Data Mining for the Synthesis of Functionalized Tungsten Oxide with Enhanced Oxygen Vacancies for Highly Sensitive Detection of Triethylamine

The optimal combination of metal ions and ligands for sensing materials was estimated by using a data-driven model developed in this research. This model utilized advanced computational algorithms and a data set of 100,000 literature pieces. The semiconductor metal oxide (SMO) that is most suitable for detecting triethylamine (TEA) with the highest probability was identified by using the Word2vec model, which employed the maximum likelihood method. The loss function of the probability distribution was minimized in this process. Based on the analysis, a novel hierarchical nanostructured tungsten-based coordination with 2,5-dihydroxyterephthalic acid (W-DHTA) was synthesized. This synthesis involved a postsynthetic hydrothermal treatment (psHT) and the self-assembly of tungsten oxide nanorods. The tungsten oxide nanorods had a significant number of oxygen vacancies. Various techniques were used to characterize the synthesized material, and its sensing performance toward volatile organic compound (VOC) gases was evaluated. The results showed that the functionalized tungsten oxide exhibited an exceptionally high sensitivity and selectivity toward TEA gas. Even in a highly disturbed environment, the detection limit for TEA gas was as low as 40 parts per billion (ppb). Furthermore, our findings suggest that the control of oxygen vacancies in sensing materials plays a crucial role in enhancing the sensitivity and selectivity of gas sensors. This approach was supported by the utilization of density functional theory (DFT) computation and machine learning algorithms to assess and analyze the performance of sensor devices, providing a highly efficient and universally applicable research methodology for the development and design of next-generation functional materials.

Three-Dimensional van der Waals Heterostructure-Based Nanocages as Supersensitive 3-Hydroxy-2-butanone Gas Sensors at Room Temperature

3-Hydroxy-2-butanone is one of the biomarkers of Listeria monocytogenes, which is quite important for the intelligent detection of 3H-2B. However, it is still a challenge to fabricate sensing materials obtaining excellent sensitivity and selectivity under the ppb-level detection limit. Herein, a plasma-assisted synthetic approach was proposed for the construction of hierarchical nanostructures and the simultaneous loading of TAPP-COFs, which could reduce interlayer interaction and convert the metallized sites on the surface of predesigned porphyrin rings into quantum nanoparticles. These multichannel pathways of Co-TAPP-COFs@SnO₂@MWCNTs nanocages contributed to the gas adsorption and diffusion, thus enhancing the sensing behavior. The nanocages exhibited a highly specific sensing performance toward 3H-2B with the highest sensitivity (R_a/R_g = 100.9 to 0.5 ppm) in all reported sensing materials. The 3H-2B sensor presented outstanding long-term stability, and the detection limit was 100 ppb at room temperature. Furthermore, the synthesized materials were integrated into the sensing module connecting to an Internet of Things platform, providing rapid and real-time detection of 3H-2B. We also applied machine learning methods to analyze the nanocage-based sensors and found that the combined effects of modified sites on the heterointerfaces contributed to the improvement of the sensing performance.

A room-temperature formaldehyde sensor based on hematite for breast cancer diagnosis

Formaldehyde (HCHO) is regarded as one kind of indoor pollutant. Additionally, HCHO serves as a biomarker in the exhaled breath of breast cancer patients. Early warning and management are crucial for the environment and human health. Thus, we have elaborately synthesized hematite (α-Fe₂O₃) employing a facet-engineering hydrothermal strategy using the fine-tuned solvent composition, with special attention to the effect of different exposed surfaces on HCHO detection. The spindle-like α-Fe₂O₃ nanocrystals with the (012) facet exposed exhibited impressively higher response towards HCHO at room temperature than that of the disk-like α-Fe₂O₃ with mainly the (001) facet exposed, partly due to the abundant vacancy oxygen and adsorbed oxygen of high-index facets of α-Fe₂O₃. More importantly, our experimental results coincide with theoretical calculations. Overall, the surface engineering strategy could be extended to a versatile approach for HCHO detection.

Humidity-Tolerant Chemiresistive Gas Sensors Based on Hydrophobic CeO2/SnO2 Heterostructure Films

The accelerated evolution of the Internet of Things has brought new challenges to the gas sensors, which are required to work persistently under harsh conditions, like high humidity. However, currently, it is quite challenging to solve the hindrance of the trade-off between gas-sensing performance and anti-humidity ability of the chemiresistive gas sensors. Herein, hydrophobic inorganic CeO₂/SnO₂ heterostructure films were prepared by depositing the CeO₂ layers with a thickness of a few nanometers onto the SnO₂ film via a magnetron sputtering method. The sensors based on the CeO₂/SnO₂ heterostructure films demonstrated excellent gas-sensing performance toward trimethylamine (TEA) with high response, wide detection range (0.04-500 ppm), low record detection limit (0.04 ppm), ideal reproducibility, and long-term stability, while concurrently possessing promising anti-humidity ability. A portable, wireless TEA-sensing system containing the CeO₂/SnO₂ sensor was constructed to realize the real-time monitoring of trace concentration of the volatiles released from a fish. This work provides a novel strategy to prepare advanced chemiresistive gas sensors for humidity-independent detection of harmful gases and vapors and will accelerate their commercialization process in the field of food safety and public health.

Electrospinning Derived NiO/NiFe2O4 Fiber-in-Tube Composite for Fast Triethylamine Detection under Different Humidity

Designing high-performance triethylamine gas sensors with the stable gas response and low resistance variation in air under a wide relative humidity range is expected for human health and environmental surveillance. Here, a novel porous NiO/NiFe₂O₄ fiber-in-tube nanostructure is prepared by the electrospinning process. The characterizations related to microstructure and surface morphology are carried out. Meanwhile, the gas sensing performance of the porous fiber-in-tube NiO/NiFe₂O₄ materials is evaluated and compared systematically. The results indicate that the introduction of NiO as the second component can not only reduce the baseline resistance of NiFe₂O₄ gas sensors dramatically but also optimize the gas sensing performance to a significant extent. Especially, the fabricated sensor based on the NiO/NiFe₂O₄ fiber-in-tube with a Ni/Fe molar ratio of 1.5 exhibits the best performance. The gas response while detecting 50 ppm triethylamine at 300 °C is about 3.6 times higher than that with Ni/Fe molar ratio of 0.5. Moreover, the response values become more stable, and the baseline resistance has a lower variation under a wide relative humidity range, demonstrating the excellent humidity resistance. These phenomena might be ascribed to the distinctive fiber-in-tube nanostructure as well as the heterojunction between NiFe₂O₄ and NiO.

Semiconductor Gas Sensor for Triethylamine Detection

With the demanding detection of unique toxic gas, semiconductor gas sensors have attracted tremendous attention due to their intriguing features, such as, high sensitivity, online detection, portability, ease of use, and low cost. Triethylamine, a typical gas of volatile organic compounds, is an important raw material for industrial development, but it is also a hazard to human health. This review presents a concise compilation of the advances in triethylamine detection based on chemiresistive sensors. Specifically, the testing system and sensing parameters are described in detail. Besides, the sensing mechanism with characterizing tactics is analyzed. The research status based on various chemiresistive sensors is also surveyed. Finally, the conclusion and challenges, as well as some perspectives toward this area, are presented.

Vacuum Based Gas Sensing Material Characterization System for Precise and Simultaneous Measurement of Optical and Electrical Responses

Gas sensing performance characterization systems are essential for the research and development of gas sensing materials and devices. Although existing systems are almost completely automatically operated, the accuracies of gas concentration control and of pressure control and the ability to simultaneously detect different sensor signals still require improvement. In this study, a high-precision gas sensing material characterization system is developed based on vacuum technology, with the objective of enabling the precise and simultaneous measurement of electrical responses. Because of the implementation of vacuum technology, the gas concentration control accuracy is improved more than 1600 times, whereas the pressure of the test ambient condition can be precisely adjusted between vacuum and 1.2 bar. The vacuum-assisted gas-exchanging mechanism also enables the sensor response time to be determined more accurately. The system is capable of performing sensitivity, selectivity, and stability tests and can control the ambient relative humidity in a precise manner. More importantly, the levels of performance of three different optical signal measurement set-ups were investigated and compared in terms of detection range, linearity, noise, and response time, based on which of their scopes of application were proposed. Finally, single-period and cyclical tests were performed to examine the ability of the system to detect optical and electrical responses simultaneously, both at a single wavelength and in a spectral region.

Boosting selective H2 sensing of ZnO derived from ZIF-8 by rGO functionalization

H2 sensors have attracted considerable attention for safety warning of traditional industries and energy storing systems. This ZnO/rGO composite demonstrated excellent H2 sensing performances, good baseline stability and excellent selectivity.

Plasma-induced oxygen vacancies enabled ultrathin ZnO films for highly sensitive detection of triethylamine

Metal oxide semiconductor (MOS) thin films hold great promise for electronic devices such as gas sensors. However, the low surface activity of pristine MOS often leads to inferior sensitivity and the sensitization mechanism of ultrathin MOS films has received rare attention. Herein, we report a high performance gas sensor based on plasma-etched ZnO thin films. The ultrathin ZnO films (20 nm) were deposited on SiO₂ wafers by atomic layer deposition (ALD), which enables high-throughput production of sensor devices. The ZnO sensor shows typical n-type conductivity, which is highly variable to the exposure of triethylamine (TEA). Annealing temperature of the films is found to impact the sensor response, revealing calcination at a moderate temperature, i.e. 700 °C, leads to the best response. Further treatment by Ar plasma results in a remarkable decrease of sensor working temperature from 300 °C of untreated films to 250 °C and nearly 4-fold enhancement in the sensor response to 10 ppm TEA. Notably, the plasma-treated ZnO sensor also shows decent response even at room temperature (RT), which has been seldom reported for ZnO-based sensors. Structure and mechanism investigations reveal that the superior sensor properties are derived from the abundant oxygen vacancies generated by Ar plasma etching.