Tribotronic transistor sensor for enhanced hydrogen detection

Hydrogen detection with a high sensitivity is necessary for preventing potential explosions and fire.In this study,a novel ZnO tribotronic transistor is developed by coupling a ZnO field effect transistor （FET） and triboelectric nanogenerator in free-standing mode and is used as a sensor for hydrogen detection at room temperature.Tribotronic modulated performances of the hydrogen sensor are demonstrated by investigating its output characteristics at different sliding distances and hydrogen concentrations.By applying an external mechanical force to the device for sliding electrification,the detection sensitivity of the ZnO tribotronic transistor sensor is improved,with a significant enhancement achieved in output current by 62 times at 500 ppm hydrogen and 1 V bias voltage.This study demonstrates an extension of the applications of emerging tribotronics for gas detection and a prospective approach to improve the performance of the hydrogen sensor via human-interfacing.

Sensitive absorption measurements of hydrogen sulfide at 1.578 μm using wavelength modulation spectroscopy

Sensitive detection of hydrogen sulfide（H2S） has been performed by means of wavelength modulation spectroscopy（WMS） near 1.578 μm. With the scan amplitude and the stability of the background baseline taken into account, the response time is 4 s for a 0.8 L multi-pass cell with a 56.7 m effective optical path length. Moreover, the linearity has been tested in the 0–50 ppmv range. The detection limit achievable by the Allan variance is 224 ppb within 24 s under room temperature and ambient pressure conditions. This tunable diode laser absorption spectroscopy（TDLAS） system for H2 S detection has the feasibility of real-time online monitoring in many applications.

An optical sensor for hydrogen sulfide detection in open path using WMS-2f/1f technique

An optical hydrogen sulfide(H_2S) sensor based on wavelength modulation spectroscopy with the second harmonic(2f) corrected by the first harmonic(1f) signal(WMS-2f/1f) is developed using a distributed feedback(DFB) laser emitting at 1.578 μm and a homemade gas cell with 1-m-long optical path length. The novel sensor is constructed by an electrical cabinet and an optical reflecting and receiving end. The DFB laser is employed for targeting a strong H_2S line at 6 336.62 cm^(-1) in the fundamental absorption band of H_2S. The sensor performance, including the minimum detection limit and the stability, can be improved by reducing the laser intensity drift and common mode noise by means of the WMS-2f/1f technique. The experimental results indicate that the linearity and response time of the sensor are 0.999 26 and 6 s(in concentration range of 15.2—45.6 mg/m^3), respectively. The maximum relative deviation for continuous detection(60 min) of 30.4 mg/m^3 H_2S is 0.48% and the minimum detection limit obtained by Allan variance is 79 μg/m^3 with optimal integration time of 32 s. The optical H_2S sensor can be applied to environmental monitoring and industrial production, and it has significance for real-time online detection in many fields.

Selective and self-validating breath-level detection of hydrogen sulfide in humid air by gold nanoparticle-functionalized nanotube arrays

We demonstrate the selective detection of hydrogen sulfide at breath concentration levels under humid airflow,using a self-validating 64-channel sensor array based on semiconducting single-walled carbon nanotubes(sc-SWCNTs).The reproducible sensor fabrication process is based on a multiplexed and controlled dielectrophoretic deposition of sc-SWCNTs.The sensing area is functionalized with gold nanoparticles to address the detection at room temperature by exploiting the affinity between gold and sulfur atoms of the gas.Sensing devices functionalized with an optimized distribution of nanoparticles show a sensitivity of 0.122%/part per billion(ppb)and a calculated limit of detection(LOD)of 3 ppb.Beyond the self-validation,our sensors show increased stability and higher response levels compared to some commercially available electrochemical sensors.The cross-sensitivity to breath gases NH3 and NO is addressed demonstrating the high selectivity to H2S.Finally,mathematical models of sensors’electrical characteristics and sensing responses are developed to enhance the differentiation capabilities of the platform to be used in breath analysis applications.

Optical fiber hydrogen sensor using metasurfaces composed of palladium

Palladium-based hydrogen sensors have been typically studied due to the dielectric function that changes with the hydrogen concentration. However, the development of a reliable, integral, and widely applicable hydrogen sensor requires a simple readout mechanism and an optimization of the fast detection of hydrogen. In this work, optical fiber hydrogen sensing platforms are developed using an optimized metasurface, which consists of a layer of palladium nanoantennas array suspended above a gold mirror layer. Since the optical properties of these palladium nanoantennas differ from the traditional palladium films, a high reflectance difference can be achieved when the sensor based on the metasurface is exposed to the hydrogen atmosphere. Finally, the optimized reflectance difference ΔR of ~0.28 can be obtained when the sensor is exposed in the presence of hydrogen. It is demonstrated that this integrated system architecture with an optimized palladium-based metasurface and a simple optical fiber readout system provides a compact and light platform for hydrogen detection in various working environments.

Design and realization of 3D printed fiber-tip microcantilever probes applied to hydrogen sensing

Cantilevers in microelectromechanical systems have the advantages of non-labeling,real-time detection,positioning,and specificity.Rectangular solid,rectangular hollow,and triangular microcantilevers were fabricated on an optical fiber tip via two-photon polymerization.The mechanical properties were characterized using finite element simulations.Coating the microcantilever with a palladium film enabled high sensitivity and rapid hydrogen detection.The shape of the cantilever determines the sensitivity,whereas the thickness of the palladium film determines the response time.Additional microelectromechanical systems can be realized via polymerization combined with optical fibers.

Realization of palladium-based optomechanical cantilever hydrogen sensor

Hydrogen has attracted attention as an alternative fuel source and as an energy storage medium.However,the flammability of hydrogen at low concentrations makes it a safety concern.Thus,gas concentration measurements are a vital safety issue.Here we present the experimental realization of a palladium thin film cantilever optomechanical hydrogen gas sensor.We measured the instantaneous shape of the cantilever to nanometer-level accuracy using diffraction phase microscopy.Thus,we were able to quantify changes in the curvature of the cantilever as a function of hydrogen concentration and observed that the sensor’s minimum detection limit was well below the 250 p.p.m.limit of our test equipment.Using the change in curvature versus the hydrogen curve for calibration,we accurately determined the hydrogen concentrations for a random sequence of exposures.In addition,we calculated the change in film stress as a function of hydrogen concentration and observed a greater sensitivity at lower concentrations.

Design of a novel mitochondria targetable turn-on fluorescence probe for hydrogen peroxide and its two-photon bioimaging applications

Considering that hydrogen peroxide(H2O2)plays significant roles in oxidative stress,the cellular signal transduction and essential biological process regulation,the detection and imaging of H2O2 in living systems undertakes critical responsibility.Herein,we have developed a novel two-photon fluorescence turn on probe,named as Pyp-B for mitochondria H2O2 detection in living systems.Selectivity studies show that probe Pyp-B exhibit highly sensitive response toward H2O2 than other reactive oxygen species(ROS)and reactive nitrogen species(RNS)as well as biologically relevant species.The fluorescence colocalization studies demonstrate that the probe can localize in the mitochondria solely.Furthermore,as a bio-compatibility molecule,the highly selective and sensitive of fluorescence probe Pyp-B have been confirmed by its cell imaging application of H2O2 in living A549 cells and zebrafishes under the physiological conditions.

Porous microtubes of nickel-cobalt double oxides as non-enzymatic hydrogen peroxide sensors

Non-enzymatic electrochemical sensors for the determination of hydrogen peroxide(H_(2)O_(2))have attracted more and more concerns.A series of nickel and cobalt double oxides(Ni_(x)Co_(y)-DO)with the different ratios of Ni/Co have been prepared by a polyol-mediated solvothermal method for H_(2)O_(2)detection.The obtained products exhibit honeycomb-like open porous microtubes constituted with the low-dimensional nanostructured Ni_(x)Co_(y)-DO blocks after the calcination treatment.Compared with nickel oxides,the introduced Co ions in Ni_(x)Co_(y)-DO can induce the production of surficial oxygen vacancies,and further enhance the electrode surface activity.In particular,the NiCo-DO sample(with an atomic ratio of Ni/Co=4:3)shows the richest surficial oxygen vacancies and presents the highest H_(2)O_(2)detection activity among all the as-prepared samples,demonstrating an excellent sensitivity of698.60μAL mmol^(-1)cm^(-2)(0~0.4 mmol/L),low detection limit(0.28μmol/L,S/N=3),as well as long stability,high selectivity and good reproducibility.This work lends a new impetus to the potential application of double metal oxides for the next generation of non-enzymatic sensors.