Search Results (353)

Hydrogen (H₂) gas sensors are essential for detecting leaks and ensuring safety, thereby supporting the broader adoption of hydrogen energy. The performance of H₂ sensors has been shown to be improved by the incorporation of TiO₂ nanostructures. The key findings are summarized as follows: (1) Resistive random-access memory (ReRAM) technology was used to fabricate extremely compact H₂ sensors via various forming techniques, and substantial sensor performance enhancement was investigated. (2) A nanocontact composed of titanium oxide (TiO_x)/platinum (Pt) was subjected to various forming operations to establish a Schottky junction with a nanogap structure on a tantalum oxide (Ta₂O₅) layer, and its properties were assessed. (3) When the Pt electrode was on the positive side during the forming operation used for ReRAM technology, a Pt nanopillar structure was produced. By contrast, when the forming operation was conducted with a positive bias on the TiO_x side, a mixed oxide film of Ta and Ti was produced, which indicates local Ta doping into the TiO_x. A sensor response of over 1000 times was achieved at a minimal voltage of 1 mV at room temperature. (4) This sensor fabrication technology based on the forming operation is promising for the development of low-power consumption sensors. Full article

Hydrogen sulfide (H₂S), once regarded solely as a highly toxic gas, is now recognized as a crucial signaling molecule in plants, bacteria, and mammals. In humans, H₂S signaling plays a role in numerous physiological and pathological processes, including vasodilation, neuromodulation, and cytoprotection. To exploit its biological functions and therapeutic potential, a wide range of H₂S-releasing compounds, known as H₂S donors, have been developed. These donors are designed to release H₂S under physiological conditions in a controlled manner. Among them, self-reporting H₂S donors are seen as a particularly innovative class, combining therapeutic delivery with real-time fluorescence-based detection. This dual functionality enables spatiotemporal monitoring of H₂S release in biological environments, eliminating the need for additional sensors or probes that could disrupt cellular homeostasis. This review summarizes recent advancements in self-reporting H₂S donor systems, organizing them based on their activation triggers, such as specific bioanalytes, enzymes, or external stimuli like light. The discussion covers their design strategies, performance in biological applications, and therapeutic potential. Key challenges are also highlighted, including the need for precise control of H₂S release kinetics, accurate signal quantification, and improved biocompatibility. With continued refinement, self-reporting H₂S donors offer great promise for creating multifunctional platforms that seamlessly integrate diagnostic imaging with therapeutic H₂S delivery. Full article

There is a lack of an effective approach to measure vacuum conditions inside sealed vacuum electronic devices (VEDs) and other small-space vacuum instruments. In this study, the application performance of an innovative low-pressure gas sensor based on the emission enhancements of multi-walled carbon nanotube (MWCNT) field emitters was investigated, and the in situ vacuum performance of X-ray tubes was studied for the advantages of miniature dimension and having low power consumption, extremely low outgassing, and low thermal disturbance compared to conventional ionization gauges. The MWCNT emitters with high crystallinity presented good pressure sensing performance for nitrogen, hydrogen, and an air mixture in the range of 10⁻⁷ to 10⁻³ Pa. The miniature MWCNT sensor is able to work and remain stable with high-temperature baking, important for VED applications. The sensor monitored the in situ pressures of the sealed X-ray tubes successfully with high-power operations and a long-term storage of over two years. The investigation showed that the vacuum of the sealed X-ray tube is typical at a low 10⁻⁴ Pa level, and pre-sealing degassing treatments are able to make the X-ray tube work under high vacuum levels with less outgassing and keep a stable high vacuum for a long period of time. Full article

Highly sensitive real-time detection of hydrogen sulfide (H₂S) is important for human health and environmental protection due to its highly toxic properties. The development of high-performance H₂S sensors remains challenging for poor selectivity, high limit detection and slow recovery from irreversible sulfidation. To solve these problems, we strategically prepared a layered structure of CuO-sensitized WO₃ flower-like hollow spheres with CuO as the sensitizing component. A 15 wt% CuO/WO₃ exhibits an ultra-high response (R_a/R_g = 571) to 10 ppm H₂S (131-times of pure WO₃), excellent selectivity (97-times higher than 100 ppm interference gas), and a low detection limit (100 ppb). Notably, its fast response (4 s) is accompanied by full recovery within 236 s. After 30 days of continuous testing, the response of 15 wt% CuO/WO₃ decreased slightly but maintained the initial response of 90.5%. The improved performance is attributed to (1) the p-n heterojunction formed between CuO and WO₃ optimizes the energy band structure and enriches the chemisorption sites for H₂S; (2) the reaction of H₂S with CuO generates highly conductive CuS, which significantly reduces the interfacial resistance; and (3) the hierarchical flowery hollow microsphere structure, heterojunction, and oxygen vacancy synergistically promote the desorption. This work provides a high-performance H₂S gas sensor that balances response, selectivity, and response/recovery kinetics. Full article

Hydrogen sulfide (H₂S) is a highly toxic and corrosive gas generated in numerous industrial and environmental processes; rapid, sensitive detection at low ppm levels is therefore crucial for ensuring occupational safety and protecting public health. This work explores the effect of grafting various loadings of pendant aniline tetramer pendants (PEDA) onto electroactive poly(amic acid) (EPAA) films and evaluates their performance as H₂S gas sensors. Comprehensive characterization including ion trap mass spectrometry (Ion trap MS), Fourier-transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), and four-probe conductivity measurements, confirmed successful PEDA incorporation and revealed enhanced electrical conductivity with increasing PEDA content. Gas sensing tests revealed that EPAA3 (3 wt% PEDA) achieved the best overall performance toward 10 ppm H₂S, producing a 591% response with a rapid 108 s response time. Selectivity studies showed that the response of EPAA3 to H₂S exceeded those for SO₂, NO₂, NH₃, and CO by factors of five to twelve, underscoring its excellent discrimination against common interferents. Repeatability tests over five successive cycles gave a relative standard deviation of just 7.4% for EPAA3, and long-term stability measurements over 16 days in ambient air demonstrated that EPAA3 retained over 80%. These findings establish that PEDA-grafted PAA films combine the processability of poly(amic acid) with the sharp, reversible redox behavior of pendant aniline tetramers, delivering reproducible, selective, and stable H₂S sensing. EPAA3, in particular, represents a balanced composition that maximizes sensitivity and durability, offering a promising platform for practical environmental monitoring and industrial safety applications. Full article

The current solicitude in hydrogen production and its utilization as a greenhouse-neutral energy vector pushed deep interest in developing new and reliable systems intended for its detection. Most sensors available on the market offer reliable performance; however, their limitations, such as restricted dynamic range, hysteresis, reliance on consumables, transducer–sample interaction, and sample dispersion into the environment, are not easily overcome. In this paper, a non-dispersive Raman effect-based system is presented and compared with its dispersive alternative. This approach intrinsically guarantees no sample dispersion or preparation, as no direct contact is required between the sample and the transducer. Moreover, the technique does not suffer from hysteresis and recovering time issues. The results, evaluated in terms of sample pressures and camera integration time, demonstrate promising signal-to-noise ratio (SNR) and limit of detection (LOD) values, indicating strong potential for direct field application. Full article

Ammonia is emerging as a promising zero-carbon marine fuel due to its high hydrogen density, low storage pressure, and long-term stability, making it well-suited for supporting sustainable maritime energy systems. However, its adoption introduces serious safety challenges, as its toxic, flammable, and corrosive properties pose greater risks than many other alternative fuels, necessitating rigorous risk assessment and safety management. This study presents a comprehensive investigation of potential ammonia leakage scenarios that may arise during the fuel gas supply process within confined compartments of marine vessels, such as the fuel preparation room and engine room. The simulations were conducted using FLACS-CFD V22.2, a validated computational fluid dynamics tool specialized for flammable gas dispersion and explosion risk analysis in complex geometries. The model enables detailed assessment of gas concentration evolution, toxic exposure zones, and overpressure development under various leakage conditions, providing valuable insights for emergency planning, ventilation design, and structural safety reinforcement in ammonia-fueled ship systems. Prolonged ammonia exposure is driven by three key factors: leakage occurring opposite the main ventilation flow, equipment layout obstructing airflow and causing gas accumulation, and delayed sensor response due to recirculating flow patterns. Simulation results revealed that within 1.675 s of ammonia leakage and ignition, critical impact zones capable of causing fatal injuries or severe structural damage were largely contained within a 10 m radius of the explosion source. However, lower overpressure zones extended much further, with slight damage reaching up to 14.51 m and minor injury risks encompassing the entire fuel preparation room, highlighting a wider threat to crew safety beyond the immediate blast zone. Overall, the study highlights the importance of targeted emergency planning and structural reinforcement to mitigate explosion risks in ammonia-fueled environments. Full article

Hydrogen is gaining prominence as a clean energy vector, yet its extreme flammability demands robust detection solutions for industrial safety. In this study, we present the development and experimental validation of a microwave hydrogen gas sensor based on a patch-type microstrip antenna with a silver sensing element. The device operates at 5.99 GHz and was tested under controlled environmental conditions (humidity: 20 ± 0.4%, temperature: 27 ± 0.2 °C). Hydrogen exposure induces measurable shifts in the antenna’s resonant frequency due to dielectric modulation of the silver layer. The sensor exhibited a linear sensitivity of 3 kHz/ppm in the 310–600 ppm concentration range, with a residual standard deviation of 31.1 kHz and a calculated limit of detection (LOD) of approximately 31 ppm. The reflection coefficient remained below −10 dB throughout, confirming that the antenna maintains functional RF performance during sensing. These results demonstrate the sensor’s dual functionality for gas detection and communication, offering a compact and scalable platform for hydrogen safety monitoring. Full article

Hydrogen gas sensing is critical for energy storage, industrial safety, and environmental monitoring. However, traditional sensors still face challenges in selectivity, sensitivity, and stability. This work introduces an innovative N-polar GaN/AlGaN high-electron-mobility transistor (HEMT) with a 10 nm Pd catalytic layer as a hydrogen sensor. The device achieves ppm-level H₂ detection with rapid recovery and reusability, which is comparable to or even exceeds the performance of conventional Ga-polar HEMTs. The N-polar structure enhances sensitivity through its unique polarization-induced 2DEG and intrinsic back barrier, while the Pd layer catalyzes H₂ dissociation, forming a dipole layer that can modulate the Schottky barrier height. Experimental results demonstrate superior performance at both room temperature and elevated temperatures. Specifically, at 200 °C, the sensor exhibits a response of 102% toward 200 ppm H₂, with response/recovery times of 150 s/17 s. This represents a 96% enhancement in sensitivity and a reduction of 180 s/14 s in response/recovery times compared to room-temperature conditions (23 °C). These findings highlight the potential of N-polar HEMTs for high-performance hydrogen sensing applications. Full article

A technique has been proposed and experimentally tested for measuring the hydrogen concentration in an inert atmosphere within a closed system. This method utilizes a metal-oxide-semiconductor field-effect capacity-type (MOSFEC) sensor under harsh conditions such as exposure to inert gases, pressure fluctuations, and varying temperatures. The measurement is performed during the thermal decomposition of metal hydrides in a liquid sodium environment. The developed measurement technique for determining hydrogen concentration released from metal hydride samples in a system with a closed gas path is cost-effective compared to standardized, resource-intensive open-volume flow measurement methods. The use of the developed MOSFEC sensor technique allows for rapid and efficient investigation of the in situ real-time dynamics of gas release from various metal hydride materials differing in their hydrogen content within a small closed volume. Additionally, this approach enables precise determination of the specific gas release temperatures. Full article

Hydrogen (H₂) monitoring demonstrates significant practical importance for safety assurance in industrial production and daily life, driving the demand for gas-sensing devices with enhanced performance and reduced power consumption. This study developed a room-temperature (RT) hydrogen-sensing platform utilizing two-dimensional (2D) Ag-doped SnS₂ nanomaterials activated by light illumination. The Ag-SnS₂ nanosheets, synthesized through hydrothermal methods, exhibited exceptional H₂ detection capabilities under blue LED light activation. The synergistic interaction between silver dopants and photo-activation enabled remarkable gas sensitivity across a broad concentration range (5.0–2500 ppm), achieving rapid response/recovery times (4 s/18 s) at 2500 ppm under RT. Material characterization revealed that Ag doping induced S vacancies, enhancing oxygen adsorption, while simultaneously facilitating photo-induced hole transfer for surface hydrogen activation. The optimized sensor maintained good response stability after five-week ambient storage, demonstrating excellent operational durability. Experimental results further demonstrated that Ag dopants enhanced hydrogen adsorption–activation, while S vacancies improved the surface oxygen affinity. This work provides fundamental insights into defect engineering strategies for the development of optically modulated gas sensors, proposing a viable pathway for the construction of energy-efficient environmental monitoring systems. Full article

This study investigates the X-ray emissions from Hydrogen Rydberg Matter (HRM) using a state of-the-art Timepix3 detector with a Cadmium Telluride (CdTe) sensor, which offers imaging operation. The experimental setup featured an ultra-high vacuum (UHV) chamber containing potassium-doped iron oxide catalytic source, exposed to hydrogen or deuterium gas flowing through the source. A 1064 nm pulsed YAG laser was used to stimulate the HRM. The Timepix detector was calibrated with Cs-137 662 keV and 21 keV source. Results show a prominent emission peak in the 25–50 keV range, with significant contributions at 406 keV identified through aluminum foil attenuation experiments. These findings advance our understanding of radiation phenomena in hydrogen-loaded systems and suggest new avenues for exploring the unique emissions from HRM, potentially impacting material science and catalysis. Full article

Knudsen force phenomenon caused by non-uniform temperature fields in rarefied gas has been a topic of interest among researchers of gas sensing and structure actuating for micro-electromechanical systems (MEMS). The effects of gas–surface interaction conditions (accommodation coefficients, temperature differences, and carrier gases) on gas flows and hydrogen detection performance (Knudsen force) in MEMS gas sensors, consisting of a series of triangular cold beams and rectangular hot beams, are studied by using direct simulation Monte Carlo (DSMC) method combined with the Cercignani–Lampis–Lord (CLL) model in this work. The research results reveal that Knudsen force strongly depends on accommodation coefficients, temperature difference, and carrier gases. Specifically, the dependence of Knudsen force on accommodation coefficients is stronger at high pressure than at low pressure. In particular, Knudsen force increases slightly as accommodation coefficients are reduced from 1 to 0.1 but dramatically rises when accommodation coefficients verge on 0. In addition, Knudsen force is almost a linear function of temperature difference. The peak value of Knudsen force can be increased by roughly 28 times when the temperature difference rises from 10 K to 300 K. Last but not least, the linear correlation of hydrogen concentration in binary gas mixtures with Knudsen force is proposed for gas concentration detection in practice. Full article

Combustible gas leakage remains a critical safety concern in industrial and indoor environments, necessitating the development of detection systems that are both accurate and practically deployable. This study presents a wireless gas detection system that integrates a gas sensor array, a low-power microcontroller with Zigbee-based communication, and a Back Propagation (BP) neural network optimized via a sequential hybrid strategy. Specifically, Particle Swarm Optimization (PSO) is employed for global parameter initialization, followed by Dung Beetle Optimization (DBO) for local refinement, jointly enhancing the network’s convergence speed and predictive precision. Experimental results confirm that the proposed PSO-DBO-BP model achieves high correlation coefficients (above 0.997) and low mean relative errors (below 0.25%) for all monitored gases, including hydrogen, carbon monoxide, alkanes, and smog. The model exhibits strong robustness in handling nonlinear responses and cross-sensitivity effects across multiple sensors, demonstrating its effectiveness in complex detection scenarios under laboratory conditions within embedded wireless sensor networks. Full article

The study of the gas-phase behavior of proteins has recently gained momentum due to numerous prospective applications in, e.g., the construction of molecular sensors or nano-machines. The study of proteins outside their standard water environment, necessary to arrive at their successful applied use, is, however, limited by the loss of the structure and function of the macromolecules in the gas phase. We selected two enzymatic proteins with great potential for applied use, the digestive enzyme trypsin and the cytochrome sterol demethylase, for which to develop gas-phase structural models. The employed levels of theory were semiempirical, density functional tight binding, and polarizable force-field techniques. The convergence of the self-consistent field equations was very slow and in most cases led to oscillatory behavior, encouraging careful tuning of the convergence parameters. The structural optimization and molecular dynamics simulations indicated the parts of the proteins most prone to structural distortion under gas-phase conditions with unscreened electrostatics. This problem was more pronounced for cationic trypsin, for which the stability of the simulation was lower. The fate of the hydrogen bonding network of the catalytic triad in the gas phase was also investigated. Full article