A hydrogen sensor based on nanoparticles, its preparation method and application

Abstract

This invention provides a hydrogen sensor based on nanoparticles, its preparation method, and its application, belonging to the field of hydrogen sensor technology. The nanoparticle-based hydrogen sensor provided by this invention includes a substrate and at least one pair of electrodes spaced apart on the surface of the substrate. The substrate surface between the electrodes is covered with nanoparticles, and the electrode surfaces and nanoparticle surfaces are covered with a thin film layer. The nanoparticles include one or more of palladium nanoparticles, platinum nanoparticles, and alloy nanoparticles, wherein the alloy nanoparticles contain palladium and / or platinum. The material of the thin film layer includes one or more of polymethyl methacrylate, naphthol, silica, alumina, polytetrafluoroethylene, diamond-like carbon film, silicon nitride, and silicon carbide. The nanoparticle-based hydrogen sensor provided by this invention has high sensitivity and excellent stability, enabling rapid and accurate determination of hydrogen in an air environment.

Description

Technical Field

[0001] This invention relates to the field of hydrogen sensor technology, and in particular to a hydrogen sensor based on nanoparticles, its preparation method, and its application. Background Technology

[0002] Hydrogen sensors have significant application value in fields such as industrial safety, energy monitoring, and environmental detection. With the rapid development of hydrogen energy technology, the demand for hydrogen sensors with high sensitivity, high stability, and wide applicability is becoming increasingly urgent. Hydrogen sensors based on palladium or platinum nanoparticles have become a research and application hotspot due to their excellent hydrogen absorption expansion effect and rapid response characteristics.

[0003] Traditional hydrogen sensors typically rely on the hydrogen absorption and expansion effect of palladium or platinum nanoparticles to detect hydrogen by sensing changes in conductivity. In experimental research, performance testing and practical applications of hydrogen sensors are often limited to nitrogen atmospheres or other inert gas environments to prevent palladium or platinum nanoparticles from catalyzing the catalytic combustion reaction between hydrogen and oxygen. In a nitrogen atmosphere, hydrogen sensors generally exhibit good sensitivity and response time, meeting the needs of laboratory research. However, in real-world applications, hydrogen sensors often need to operate in air, especially in scenarios such as industrial safety monitoring and environmental detection. In these environments, palladium or platinum nanoparticles readily catalyze the catalytic combustion reaction between hydrogen and oxygen, leading to a significant decrease in the sensitivity and stability of the hydrogen sensor. This phenomenon not only limits the application of palladium or platinum nanoparticle-based hydrogen sensors in complex real-world environments but also poses a serious challenge to the long-term stability and reliability of hydrogen sensors.

[0004] Although researchers have tried various methods (such as surface modification and nanostructure regulation) to improve the antioxidant properties of palladium or platinum nanoparticles, how to effectively suppress catalytic combustion reactions to maintain high sensitivity and excellent stability remains a key problem that needs to be solved in the field of hydrogen sensors. Summary of the Invention

[0005] The purpose of this invention is to provide a hydrogen sensor based on nanoparticles, its preparation method, and its application. The hydrogen sensor based on nanoparticles provided by this invention has high sensitivity and excellent stability, and can achieve rapid and accurate determination of hydrogen in an air environment.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: The present invention provides a hydrogen sensor based on nanoparticles, including a substrate and at least a pair of electrodes disposed at intervals on the surface of the substrate, wherein the substrate surface between the electrodes is covered with nanoparticles, and the electrode surface and the nanoparticle surface are covered with a thin film layer. The nanoparticles include one or more of palladium nanoparticles, platinum nanoparticles, and alloy nanoparticles, wherein the alloy nanoparticles contain palladium and / or platinum. The material of the thin film layer includes one or more of polymethyl methacrylate, naphthol, silicon dioxide, alumina, polytetrafluoroethylene, diamond-like carbon film, silicon nitride, and silicon carbide.

[0007] Preferably, the thickness of the thin film layer is 10 nm to 20 μm.

[0008] Preferably, the average particle size of the nanoparticles is 2~100nm, the coverage of the nanoparticles is 5~90%, and the initial conductivity is 10nS~100μS.

[0009] Preferably, the electrode comprises a parallel plate electrode or an interdigitated electrode; the electrode material comprises gold, silver, platinum, aluminum, indium tin oxide, fluorine-doped tin oxide, or graphene.

[0010] Preferably, the substrate material includes ordinary glass, quartz glass, silicon, alumina, mica, polyethylene terephthalate, polydimethylsiloxane, or polyimide.

[0011] This invention provides a method for preparing the nanoparticle-based hydrogen sensor described above, comprising the following steps: At least one pair of electrodes spaced apart are prepared on a substrate surface, nanoparticles are prepared on the substrate surface between the electrodes, and thin film layers are prepared on the electrode surface and the nanoparticle surface to obtain the nanoparticle-based hydrogen sensor.

[0012] Preferably, the preparation method of the nanoparticles includes electrochemical deposition, chemical vapor deposition, or physical vapor deposition; the physical vapor deposition method includes cluster beam deposition, magnetron sputtering, or thermal evaporation.

[0013] Preferably, the method for preparing the thin film layer includes physical vapor deposition, chemical vapor deposition, or wet coating; the physical vapor deposition method includes electron beam evaporation or magnetron sputtering; the chemical vapor deposition method includes atomic layer deposition or plasma-enhanced chemical vapor deposition; and the wet coating method includes spin coating.

[0014] This invention provides the application of the nanoparticle-based hydrogen sensor described in the above technical solution or the nanoparticle-based hydrogen sensor prepared by the preparation method described in the above technical solution in hydrogen detection.

[0015] Preferably, the applicable environment for hydrogen detection includes an air environment, a rare gas environment, or a pure hydrogen environment; the hydrogen concentration in the applicable environment is 20~10000ppm.

[0016] Beneficial Effects: The nanoparticle-based hydrogen sensor provided by this invention includes a substrate and at least one pair of electrodes spaced apart on the surface of the substrate. The substrate surface between the electrodes is covered with nanoparticles, and the electrode surfaces and the nanoparticle surfaces are covered with a thin film layer. The nanoparticles include one or more of palladium nanoparticles, platinum nanoparticles, and alloy nanoparticles, wherein the alloy nanoparticles contain palladium and / or platinum. The material of the thin film layer includes one or more of polymethyl methacrylate, naphthol, silicon dioxide, alumina, polytetrafluoroethylene, diamond-like carbon film, silicon nitride, and silicon carbide. The nanoparticle-based hydrogen sensor provided by this invention is a hydrogen sensor with oxygen isolation function. By covering the nanoparticle surface with a thin film layer, it can effectively solve the problem of decreased sensitivity and insufficient stability of traditional hydrogen sensors in air environments caused by the catalytic combustion of hydrogen and oxygen by nanoparticles. Specifically, by covering the nanoparticles with a thin film layer, this invention effectively isolates the nanoparticles from contact with oxygen and ensures the transport of hydrogen, thereby significantly inhibiting the occurrence of catalytic combustion reactions. Based on this, not only is the good response of nanoparticles to hydrogen gas retained, but the detection limit, sensitivity and stability of hydrogen sensors are also significantly improved, providing important technical support for the practical application of hydrogen sensors. Attached Figure Description

[0017] Figure 1 This is a cross-sectional schematic diagram of a hydrogen sensor based on nanoparticles in an embodiment of the present invention; Figure 2 A photograph of the gold forked finger electrode in an embodiment of the invention; Figure 3 This is a cross-sectional view of the hydrogen sensor covered with a polymethyl methacrylate film in Example 1, obtained by SEM. Figure 4 The images show the TEM morphology and size distribution of the palladium nanoparticles in Example 1. Figure 5 The graph shows the response of the hydrogen sensor in Example 1 to different concentrations of hydrogen before it was covered with a polymethyl methacrylate film. Figure 6 The graph shows the response of the hydrogen sensor covered with a polymethyl methacrylate film in Example 1 to different concentrations of hydrogen. Figure 7 The graph shows the stability cycle test results of the hydrogen sensor covered with a polymethyl methacrylate film in Example 1. Figure 8 The image shows the TEM morphology and coverage of the palladium nanoparticles in Example 2. Figure 9 The graph shows the response of the hydrogen sensor to different concentrations of hydrogen before it was covered with the naphthol film in Example 2. Figure 10 The graph shows the response of the hydrogen sensor covered with a naphthol film in Example 2 to different concentrations of hydrogen. Figure 11 The graph shows the response of the hydrogen sensor in Example 3 to different concentrations of hydrogen before it was covered with a silicon dioxide film. Figure 12 The graph shows the response results of the hydrogen sensor covered with a silicon dioxide film in Example 3 to different concentrations of hydrogen. Figure 13 The graph shows the response of the hydrogen sensor before it was covered with the PTFE film in Example 4 to different concentrations of hydrogen. Figure 14 The graph shows the response results of the hydrogen sensor covered with a PTFE film in Example 4 to different concentrations of hydrogen. Figure 15 This is a comparison chart of the sensor response on the first day and the sixtieth day under different hydrogen concentrations after covering with a PTFE membrane in Example 4. Detailed Implementation

[0018] The present invention provides a hydrogen sensor based on nanoparticles, including a substrate and at least a pair of electrodes disposed at intervals on the surface of the substrate, wherein the substrate surface between the electrodes is covered with nanoparticles, and the electrode surface and the nanoparticle surface are covered with a thin film layer. The nanoparticles include one or more of palladium nanoparticles, platinum nanoparticles, and alloy nanoparticles, wherein the alloy nanoparticles contain palladium and / or platinum. The material of the thin film layer includes one or more of polymethyl methacrylate, naphthol, silicon dioxide, alumina, polytetrafluoroethylene, diamond-like carbon film, silicon nitride, and silicon carbide.

[0019] This invention solves the problem of catalytic combustion in hydrogen sensors in air environments by coating the surface of nanoparticles with a thin film, which effectively isolates the nanoparticles from oxygen while ensuring hydrogen transport. This maintains the high sensitivity of the nanoparticles to hydrogen. Test results show that the hydrogen sensor provided by this invention improves the detection sensitivity of hydrogen by approximately 30%, shortens the response time to less than 120 seconds, and maintains excellent stability even after continuous long-term testing. Furthermore, the hydrogen sensor provided by this invention covers a wide concentration range of hydrogen from 10,000 ppm to 20 ppm, making it suitable for various applications such as industrial safety, energy monitoring, and environmental detection. Therefore, this invention not only significantly improves the performance of hydrogen sensors but also provides reliable technical support for the practical application of hydrogen detection technology in complex environments. The following is a detailed description of the nanoparticle-based hydrogen sensor described in this invention.

[0020] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0021] The hydrogen sensor based on nanoparticles described in this invention includes a substrate. In one embodiment of this invention, the substrate material includes ordinary glass, quartz glass, silicon, alumina, mica, polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), or polyimide (PI); specifically, a quartz glass sheet or a silicon wafer is used as the substrate in this embodiment; the thickness of the substrate can be 0.5~2mm, specifically 1mm.

[0022] The nanoparticle-based hydrogen sensor of this invention includes at least one pair of electrodes spaced apart on the surface of the substrate. In one embodiment, the electrodes can be parallel plate electrodes or interdigitated electrodes, with the interdigitation distance between the interdigitated electrodes ranging from 5 to 50 μm, specifically 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm. In another embodiment, the electrode material includes gold, silver, platinum, aluminum, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), or graphene, specifically gold or silver. This invention uses highly conductive materials to fabricate the electrodes, providing a stable conductive path for the hydrogen sensor. In yet another embodiment, the electrode thickness can be 100 to 200 nm.

[0023] In the nanoparticle-based hydrogen sensor of the present invention, the substrate surface between the electrodes is covered with nanoparticles; the nanoparticles include one or more of palladium nanoparticles, platinum nanoparticles, and alloy nanoparticles, wherein the alloy nanoparticles contain palladium and / or platinum. As one embodiment of the present invention, the average particle size of the nanoparticles is 2~100 nm, specifically 2 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 50 nm, 80 nm, or 100 nm, and in the embodiments 9.07 nm, 10.14 nm, 10.63 nm, or 15.36 nm; the coverage rate of the nanoparticles is 5~90%, specifically 5%, 20%, 30%, 40%, 45%, 50%, 5%, 90 ... The coverage of the nanoparticles described in this invention is calculated using ImageJ software, with values ​​of 5%, 60%, 70%, 80%, or 90%, and specifically 38.76%, 42.68%, 43.65%, or 55.36% in the examples. The initial conductivity is 10 nS to 100 μS, specifically 10 nS, 50 nS, 100 nS, 500 nS, 1 μS, 5 μS, 10 μS, 50 μS, or 100 μS, and 7.5225 × 10⁻⁶ in the examples. -7 S, 6.1826×10 -7S, 5.3643×10 -6 S or 8.5723×10 -7 S. In this invention, the average particle size, coverage, and initial conductivity of the nanoparticles are limited to the above-mentioned ranges, which helps to ensure their efficient adsorption and expansion effect on hydrogen.

[0024] In the nanoparticle-based hydrogen sensor of this invention, the electrode surface and the nanoparticle surface are covered with a thin film layer. The material of the thin film layer includes one or more of polymethyl methacrylate (PMMA), naphthol, silica, alumina, polytetrafluoroethylene (PTFE), diamond-like carbon (DLC), silicon nitride, and silicon carbide, specifically polymethyl methacrylate, naphthol, silica, or PTFE. As one embodiment of this invention, the thickness of the thin film layer is 10 nm to 20 μm, further 10 nm to 1 μm, and even further 10 to 100 nm, specifically 10 nm, 20 nm, 30 nm, 45 nm, 50 nm, 60 nm, 80 nm, or 100 nm; the thin film layer is a dense thin film. This invention limits the material and thickness of the thin film layer to the above ranges, effectively isolating oxygen from contact with the nanoparticles without affecting the diffusion and adsorption of hydrogen molecules, especially polymethyl methacrylate, naphthol, silica, and PTFE, which are particularly effective.

[0025] This invention provides a method for preparing the nanoparticle-based hydrogen sensor described above, comprising the following steps: At least one pair of electrodes spaced apart are prepared on a substrate surface, nanoparticles are prepared on the substrate surface between the electrodes, and thin film layers are prepared on the electrode surface and the nanoparticle surface to obtain the nanoparticle-based hydrogen sensor.

[0026] This invention first prepares at least one pair of electrodes spaced apart on a substrate surface. Preferably, a clean and smooth substrate is used. In one embodiment, the electrodes are prepared using photolithography or thermal evaporation. This invention does not impose special limitations on the operating conditions of these methods, as long as the electrodes meet the aforementioned shape and thickness requirements are obtained.

[0027] After obtaining the electrodes, the present invention prepares nanoparticles on the substrate surface between the electrodes. As one embodiment of the present invention, the preparation method of the nanoparticles includes electrochemical deposition, chemical vapor deposition, or physical vapor deposition; the physical vapor deposition method includes cluster beam deposition, magnetron sputtering, or thermal evaporation. The present invention does not impose special limitations on the operating conditions of the above methods, as long as the preparation of uniformly distributed nanoparticles that meet the above requirements for particle size, coverage, and initial conductivity is achieved. In this embodiment of the present invention, the nanoparticles are specifically prepared using cluster beam deposition, the conditions of which include: a bulk vacuum of 3.5 × 10⁻⁶. -4 ~4×10 -4 Pa, sputtering gas flow rate of 50~55 sccm, buffer gas flow rate of 60~65 sccm, both buffer gas and sputtering gas are argon, condensation chamber pressure of 78~82 Pa, sputtering power of 30~35 W, deposition rate of 0.28~0.3 Å / S.

[0028] After obtaining the nanoparticles, the present invention prepares a thin film layer on the electrode surface and the nanoparticle surface to obtain the nanoparticle-based hydrogen sensor. As one embodiment of the present invention, the preparation method of the thin film layer includes physical vapor deposition, chemical vapor deposition, or wet coating; the physical vapor deposition method includes electron beam evaporation or magnetron sputtering; the chemical vapor deposition method includes atomic layer deposition or plasma-enhanced chemical vapor deposition; and the wet coating method includes spin coating. The present invention does not impose special limitations on the operating conditions of the above methods, as long as a thin film layer meeting the above thickness requirements is obtained. In the embodiments of the present invention, spin coating, plasma-enhanced chemical vapor deposition, or magnetron sputtering are specifically used to prepare the thin film layer. In this embodiment of the invention, a spin-coating method is specifically used to prepare a polymethyl methacrylate (PMMA) film or a naphthol film. The conditions for preparing the PMMA film include: the mass fraction of the PMMA solution used can be 1.8-2%, the solvent can be toluene, the spin-coating speed can be 2800-3000 rpm, the spin-coating time can be 0.5-1 min, and the drying temperature after spin-coating can be 55-60°C. The conditions for preparing the naphthol film include: the mass fraction of the naphthol solution used can be 0.8-1%, the solvent can be ethanol, the spin-coating speed can be 4800-5000 rpm, the spin-coating time can be 0.5-1 min, and the drying method after spin-coating is natural air drying. In another embodiment of the present invention, a silicon dioxide thin film is prepared by plasma-enhanced chemical vapor deposition. The steps and conditions for preparing the silicon dioxide thin film include: evacuating the chamber and heating it to 290-300°C; introducing a silane (SiH4) / nitrous oxide (N2O) system as the reaction gas, wherein the SiH4 flow rate is 55-60 sccm and the N2O flow rate is 480-500 sccm, and controlling the N2O / SiH4 molar ratio to be 33-35; under a chamber pressure of 0.8-0.9 Torr, setting the radio frequency to 13-13.56 MHz and the radio frequency power to 110-120 W, exciting the plasma and performing deposition at a deposition rate of 23-25 ​​nm·min. -1 In another embodiment of the present invention, a polytetrafluoroethylene (PTFE) film is specifically prepared by magnetron sputtering. The conditions for preparing the PTFE film include: a bulk vacuum of 3.8 × 10⁻⁶. -4 ~4×10 -4 The sputtering gas was argon, the condensation chamber pressure was 1.2~1.5Pa, the sputtering power was 38~40W, and the deposition rate was 0.07~0.08Å / s.

[0029] After obtaining the nanoparticle-based hydrogen sensor, the present invention preferably connects the electrodes of the nanoparticle-based hydrogen sensor to an external circuit for measuring conductance via leads, and calibrates the nanoparticle-based hydrogen sensor in environments with different hydrogen concentrations (20~10000ppm). The applicable calibration environments include air environments, rare gas environments, or pure hydrogen environments. The present invention does not specifically limit the specific calibration method; methods well known to those skilled in the art can be used.

[0030] This invention provides the application of the nanoparticle-based hydrogen sensor described in the above technical solution or the nanoparticle-based hydrogen sensor prepared by the preparation method described in the above technical solution in hydrogen detection.

[0031] As one embodiment of the present invention, the applicable environment for hydrogen detection includes an air environment, a rare gas environment, or a pure hydrogen environment; the hydrogen concentration in the applicable environment is 20~10000ppm, further can be 50~10000ppm, and even further can be 100~10000ppm.

[0032] The core principle of this invention is based on the hydrogen absorption and expansion effect of nanoparticles, such as palladium nanoparticles, platinum nanoparticles, or alloy nanoparticles containing palladium and / or platinum, combined with the physical barrier effect of the thin film layer, to achieve highly sensitive detection of hydrogen while effectively inhibiting the catalytic combustion reaction of hydrogen and oxygen catalyzed by the nanoparticles. Nanoparticles, such as palladium nanoparticles, platinum nanoparticles, or alloy nanoparticles containing palladium and / or platinum, are materials with excellent hydrogen adsorption properties. When hydrogen molecules diffuse to the surface of the nanoparticles, they are adsorbed by the nanoparticles through dissociative or non-dissociative adsorption and further diffuse into the interior of the nanoparticles, causing the nanoparticles to expand in volume. This volume expansion reduces the spacing between the nanoparticles, thus reducing the tunneling junction size. This allows electrons under a specific bias voltage to tunnel through the close-range nanoparticles, increasing the conductivity of the nanoparticle array and generating a detectable electrical signal. However, in an air environment, nanoparticles not only react with hydrogen but also readily catalyze the catalytic combustion reaction of hydrogen and oxygen. This catalytic combustion reaction also generates additional heat and the chemical byproduct water, affecting the stability and long-term reliability of the sensor. Furthermore, this reaction leads to the formation of an oxide layer on the surface of the nanoparticles, significantly reducing their adsorption capacity and sensitivity for hydrogen. Therefore, how to inhibit the catalytic combustion reaction of hydrogen and oxygen catalyzed by nanoparticles is a key issue in improving the performance of hydrogen sensors.

[0033] This invention effectively isolates nanoparticles from direct contact with oxygen by coating the surface of nanoparticles with a thin film layer, utilizing the film's physical barrier effect. Therefore, the film layer needs to possess good chemical stability and mechanical strength, capable of preventing the reaction between oxygen molecules and the nanoparticle surface without affecting hydrogen molecule diffusion. Specifically, the film layer forms a dense protective layer, significantly reducing the probability of contact between oxygen molecules and the nanoparticle surface, thereby inhibiting the catalytic combustion reaction. Simultaneously, due to the small size and high diffusion capacity of hydrogen molecules, the film layer does not hinder the diffusion and adsorption of hydrogen molecules, thus maintaining the nanoparticles' high sensitivity to hydrogen.

[0034] In summary, by introducing a thin film layer on the surface of nanoparticles, this invention successfully solves the catalytic combustion problem inherent in traditional hydrogen sensors operating in air environments, while retaining the high sensitivity response of nanoparticles to hydrogen. Experimental results show that the hydrogen sensor provided by this invention exhibits significantly improved sensitivity and stability in air environments, and a faster hydrogen detection response time. This provides a reliable technical guarantee for the practical application of hydrogen detection technology in complex environments, demonstrating good practicality and promotional value.

[0035] Figure 1 This is a cross-sectional schematic diagram of a hydrogen sensor based on nanoparticles in an embodiment of the present invention, including a substrate and electrodes disposed on the substrate. The substrate surface between the electrodes is covered with nanoparticles, and the electrode surface and the nanoparticle surface are covered with a thin film layer. Figure 2 This is a photograph of the gold forked finger electrode in an embodiment of the invention.

[0036] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0037] Example 1 This embodiment of the hydrogen sensor based on palladium nanoparticles includes a substrate, electrodes, nanoparticles, and a thin film layer: the substrate is a quartz glass sheet with a thickness of 1 mm; the electrodes are gold interdigitated electrodes with a thickness of 100 nm and a finger spacing of 5 μm; the nanoparticles are palladium nanoparticles with an average particle size of 10.14 nm, a coverage of 42.68%, and an initial conductivity of 7.5225 × 10⁻⁶. -7 S; The thin film layer is a polymethyl methacrylate film with a thickness of 30 nm.

[0038] The method for preparing the palladium nanoparticle-based hydrogen sensor includes the following steps: (1) Select a clean and smooth quartz glass plate as the substrate; (2) A gold interdigitated electrode is fabricated on the surface of the substrate using photolithography; (3) Using a cluster beam spectrometer, palladium nanoparticles are uniformly distributed on the substrate surface between the finger electrodes of the gold interdigitated electrode (the resulting hydrogen sensor is denoted as sensor a); the deposition conditions include: a bulk vacuum of 4 × 10⁻⁶. - 4 Pa, sputtering gas flow rate of 50 sccm, buffer gas flow rate of 60 sccm, both buffer gas and sputtering gas are argon, condensation chamber pressure of 78 Pa, sputtering power of 35 W, deposition rate of 0.3 Å / S; (4) A polymethyl methacrylate film is coated on the surface of the gold interdigitated electrode and the surface of the palladium nanoparticles. Specifically, polymethyl methacrylate is dissolved in toluene to obtain a polymethyl methacrylate solution with a mass fraction of 2%. The polymethyl methacrylate solution is spin-coated, and the spin-coating speed is controlled at 3000 rpm for 1 min. Then, it is dried on a heating stage at 60°C to form a polymethyl methacrylate film, thus obtaining a hydrogen sensor based on palladium nanoparticles (denoted as sensor b).

[0039] Figure 3 This is a cross-sectional view of the hydrogen sensor covered with a polymethyl methacrylate film in Example 1, showing that the top of the hydrogen sensor is covered with a polymethyl methacrylate film.

[0040] Figure 4 The images shown are TEM images of the palladium nanoparticles in Example 1 and their size distribution. It can be seen that the average particle size of the palladium nanoparticles is 10.14 nm and the particle size distribution is relatively uniform.

[0041] The electrodes of the prepared hydrogen sensor are connected to the external circuit for measuring conductivity via leads. The hydrogen sensor is then placed in an air environment with different hydrogen concentrations (100~10000ppm) for calibration.

[0042] The hydrogen sensor was tested: First, sensor a was tested by mixing air and hydrogen in a specific ratio to obtain test gases with different hydrogen concentrations. Then, sensor a was tested, and the real-time response curve of the relative conductivity of the nanoparticles in sensor a to the change in hydrogen concentration was measured. Figure 5 As shown; Then, sensor a is further assembled in step (4) to obtain sensor b. The real-time response curve of the relative conductivity of the nanoparticles in sensor b to the change in hydrogen concentration is measured, as shown in the figure. Figure 6 As shown.

[0043] Depend on Figure 5 and Figure 6 It can be seen that before covering with a polymethyl methacrylate (PMMA) film (i.e., before coating), a stable step can be formed in the high concentration range of 10,000 ppm to 4,000 ppm, and the step shows a monotonically decreasing trend as the hydrogen concentration decreases. However, when the concentration decreases to 2,500 ppm and below, the step amplitude is significantly compressed, and the latter half of the curve is more prone to plateau fluctuations and slow drift. This indicates that in the low concentration range, the hydrogen sensor output is more susceptible to the influence of adsorbed state reconstruction and slow side reaction processes such as O2 / H2O in the air, resulting in a decrease in the effective signal-to-noise ratio and an imperfect steady-state plateau, thereby weakening the calibrability and repeatability in the low concentration range. After covering with a PMMA film (i.e., after coating), the response curve exhibits a more standard step-like morphology: the rising edge is clearer, the steady-state plateau is flatter, and the concentration coverage range extends to lower ends (down to 100 ppm). In terms of quantitative amplitude, the steady-state responses after coating at 10000ppm, 8000ppm, 6000ppm, and 4000ppm are approximately 31.8%, 23.3%, 15.6%, and 11.2%, respectively, which are significantly higher than before coating. Taking 10000ppm as an example, the response increases from approximately 13.7% to approximately 31.8%, a gain of approximately 2.32 times. At the same time, a clearly discernible step-like output is maintained in the low concentration range: approximately 2-3% response is obtained at 200ppm, and approximately 1% response signal is still visible at 100ppm, indicating that the low-concentration detectability of the hydrogen sensor is significantly improved after coating.

[0044] The above comparative results demonstrate that introducing a thin film layer onto the surface of nanoparticles in this invention not only enhances the response amplitude of the hydrogen sensor but also improves the stability of the low-concentration plateau and baseline consistency. This can be understood as follows: the thin film layer reduces the flux of O2 / H2O from the air to the Pd surface, weakening competitive adsorption and side reaction diversion, thus facilitating the dissociation, injection, and formation of PdH by hydrogen molecules. x The effective channel ratio is increased; simultaneously, after the interfacial adsorption state fluctuations are suppressed, the interparticle gap modulation caused by hydrogenation expansion in the discrete nanoparticle array "tunneling-percolation network" can be more fully and stably converted into a macroscopic ΔG / G0 plateau output. In summary, the coating strategy in this invention can effectively alleviate the interference of air background on the hydrogen sensing output of the Pd nanoparticle array, making the response curve closer to a calibrable signal with a steady-state plateau.

[0045] The stability of sensor b was tested, and the specific steps were as follows: sensor b was placed in a mixture of hydrogen and air with a hydrogen concentration of 10000 ppm for multiple cycle tests, and its real-time response curve of relative conductivity was measured. The results are as follows. Figure 7 As shown, by Figure 7It can be seen that sensor b can consistently generate a regular "rise-plateau-fall" periodic waveform throughout the entire test process, indicating that the hydrogen response of sensor b has clear reversibility and repeated triggering characteristics.

[0046] Example 2 This embodiment of the hydrogen sensor based on palladium nanoparticles includes a substrate, electrodes, nanoparticles, and a thin film layer: the substrate is a silicon wafer with a thickness of 1 mm; the electrodes are silver interdigitated electrodes with a thickness of 100 nm and a finger spacing of 50 μm; the nanoparticles are palladium nanoparticles with an average particle size of 9.07 nm, a coverage of 43.65%, and an initial conductivity of 6.1826 × 10⁻⁶. -7 S; The thin film layer is a naphthol film with a thickness of 35 nm.

[0047] The method for preparing the palladium nanoparticle-based hydrogen sensor includes the following steps: (1) Select a clean and smooth silicon wafer as the substrate; (2) Silver interdigitated electrodes are prepared on the surface of the substrate using a thermal evaporation method; (3) Using a cluster beam spectrometer, uniformly distributed palladium nanoparticles are deposited on the substrate surface between the finger electrodes in the silver forked electrode (the resulting hydrogen sensor is denoted as sensor c); the deposition conditions include: a bulk vacuum of 3.5 × 10⁻⁶. - 4 Pa, sputtering gas flow rate of 55 sccm, buffer gas flow rate of 65 sccm, both buffer gas and sputtering gas are argon, condensation chamber pressure of 82 Pa, sputtering power of 30 W, deposition rate of 0.28 Å / s; (4) A naphthol film is coated on the surface of the silver interdigitated electrode and the surface of the palladium nanoparticles. Specifically, naphthol is dissolved in ethanol to obtain a naphthol solution with a mass fraction of 1%. The naphthol solution is spin-coated, and the spin-coating speed is controlled at 5000 rpm for 1 min. Then it is allowed to dry naturally to form a naphthol film, and a hydrogen sensor based on palladium nanoparticles (denoted as sensor d) is obtained.

[0048] Figure 8 The image shows the TEM electron microscope morphology and coverage of the palladium nanoparticles in Example 2. It can be seen that the coverage of the palladium nanoparticles is 43.65%, and the distribution is relatively uniform.

[0049] The electrodes of the prepared hydrogen sensor are connected to the external circuit for measuring conductance via leads. The hydrogen sensor is then placed in an air environment with different hydrogen concentrations (200~10000ppm) for calibration.

[0050] The hydrogen sensor was tested: First, sensor c was tested by mixing air and hydrogen in a specific ratio to obtain test gases with different hydrogen concentrations. Then, sensor c was tested, and the real-time response curve of the relative conductivity of the nanoparticles in sensor c to the change in hydrogen concentration was measured. Figure 9 As shown; Then, the sensor c is further assembled in step (4) to obtain sensor d. The real-time response curve of the relative conductivity of the nanoparticles in sensor d to the hydrogen concentration is measured, as shown in the figure. Figure 10 As shown.

[0051] Depend on Figure 9 and Figure 10 It can be seen that before the naphthol film is applied (i.e., before coating), the hydrogen sensor can form a relatively clear stepped response in the high concentration range (10000ppm to 4000ppm). The response amplitude generally decreases monotonically as the hydrogen concentration decreases, indicating that at high hydrogen concentrations, the Pd nanoparticle array can stably establish a PdH2O structure. x The formation of a conductivity modulation channel is dominated by enhanced interparticle tunneling coupling. However, when the concentration drops to 1500 ppm and below, the step amplitude is significantly compressed, and the latter half of the curve is more prone to plateau fluctuations and slow drift, exhibiting typical "low-concentration instability" characteristics. This usually means that in the weak signal region, slow processes such as adsorption-desorption and oxygen-containing adsorption state reconstruction introduced by O2 / H2O in the air begin to significantly perturb the tunneling barrier and critical permeation channel, resulting in poor baseline consistency and an imperfect steady-state plateau, thereby weakening the calibrability and repeatability in the low-concentration range.

[0052] After coating with a naphthol film (i.e., after coating), the response curve of the hydrogen sensor exhibits a more standard stepped morphology: the rising edge is clearer, the steady-state plateau is flatter, and the concentration coverage range expands significantly towards the lower end, resolving down to 200 ppm. Simultaneously, the steady-state response amplitude in the mid-to-high concentration range is significantly increased. For example, at 10000 ppm, the response increases from approximately 19.4% before coating to approximately 22.7% after coating, corresponding to a gain of approximately 1.17 times. Furthermore, a discernible stepped output is maintained at the low concentration end, indicating that the introduction of the naphthol film effectively extends the low-concentration detectability capability of the hydrogen sensor.

[0053] The aforementioned improvements can be understood as the dual regulatory effect of the naphthol film on both "air interference flux" and "surface adsorption state". As a small molecule capping layer, the naphthol film forms a thin organic regulatory interface on the surface of Pd nanoparticles: on the one hand, it reduces the effective flux of O2 / H2O to Pd active sites, weakens oxygen competitive adsorption and side reaction diversion, and allows more hydrogen to participate in the surface dissociation-implantation process, thereby improving PdH xThe formation efficiency is enhanced and the interparticle compression effect caused by hydrogenation expansion is amplified. On the other hand, when the random barrier fluctuations caused by oxygen-containing adsorption states are suppressed, the "tunneling-permeation network" of the discrete nanoparticle array can more stably transform the nanoparticle interparticle modulation into a macroscopic ΔG / G0 plateau output, which is characterized by a flatter plateau, weaker drift, and more discernible low-concentration steps. In summary, the naphthol film coating transforms the hydrogen sensor output from a "composite response with significant air slow-process perturbations" to a "calibrable step response dominated by hydrogenation modulation," providing a more reliable signal basis for subsequent low-concentration quantitative calibration and long-term stability assessment.

[0054] Example 3 This embodiment of the hydrogen sensor based on palladium nanoparticles includes a substrate, electrodes, nanoparticles, and a thin film layer: the substrate is a quartz glass sheet with a thickness of 1 mm; the electrodes are gold interdigitated electrodes with a thickness of 100 nm and a finger spacing of 5 μm; the nanoparticles are palladium nanoparticles with an average particle size of 10.63 nm, a coverage of 38.76%, and an initial conductivity of 5.3643 × 10⁻⁶. -6 S; The thin film layer is a silicon dioxide thin film with a thickness of 50 nm.

[0055] The method for preparing the palladium nanoparticle-based hydrogen sensor includes the following steps: (1) Select a clean and smooth quartz glass plate as the substrate; (2) A gold interdigitated electrode is fabricated on the surface of the substrate using photolithography; (3) Using a cluster beam spectrometer, uniformly distributed palladium nanoparticles are deposited on the substrate surface between the finger electrodes of the gold interdigitated electrode (the resulting hydrogen sensor is denoted as sensor e); the deposition conditions include: a bulk vacuum of 4 × 10⁻⁶. - 4 Pa, sputtering gas flow rate of 55 sccm, buffer gas flow rate of 60 sccm, both buffer gas and sputtering gas are argon, condensation chamber pressure of 80 Pa, sputtering power of 33 W, deposition rate of 0.3 Å / s; (4) A silica film is coated on the surface of the gold interdigitated electrode and the surface of the palladium nanoparticles. Specifically, silica is deposited on the surface of the gold interdigitated electrode and the surface of the palladium nanoparticles by plasma-enhanced chemical vapor deposition (PECVD) to form a silica film, thereby obtaining a hydrogen sensor based on palladium nanoparticles (denoted as sensor f). The plasma-enhanced chemical vapor deposition includes: placing the sample into the PECVD reaction chamber, evacuating and heating to 300°C, and introducing a silane (SiH4) / nitrous oxide (N2O) system as the reaction gas, wherein the SiH4 flow rate is 60 sccm and the N2O flow rate is 500 sccm, and the N2O / SiH4 molar ratio is controlled to be 35; under the condition of a chamber pressure of 0.9 Torr, the radio frequency frequency is set to 13.56 MHz and the radio frequency power is 120 W, the plasma is excited and deposition is performed, and the deposition rate is 25 nm·min. -1 .

[0056] The electrodes of the prepared hydrogen sensor are connected to the external circuit for measuring conductivity via leads. The hydrogen sensor is then placed in an air environment with different hydrogen concentrations (50~10000ppm) for calibration.

[0057] The hydrogen sensor was tested: First, sensor e was tested by mixing air and hydrogen in a specific ratio to obtain test gases with different hydrogen concentrations. Then, sensor e was tested, and the real-time response curve of the relative conductivity of the nanoparticles in sensor e to the change in hydrogen concentration was measured. Figure 11 As shown; Then, the sensor e is further assembled in step (4) to obtain sensor f. The real-time response curve of the relative conductivity of the nanoparticles in sensor f to the change in hydrogen concentration is measured, as shown in the figure. Figure 12 As shown.

[0058] Depend on Figure 11 and Figure 12It can be seen that both sets of curves exhibit a typical step-like morphology of "hydrogen flow rise - purge fall," with the response gradually decreasing as the concentration decreases. This indicates that the hydrogen sensor maintains its reversible response to hydrogen both before and after the introduction of the SiO2 film. Specifically, before covering with the SiO2 film (i.e., before coating), the steps in the high-concentration range are clear, but the response at the low-concentration end decreases and is accompanied by drift. After covering with the SiO2 film (i.e., after coating), the response steps are more regular, and the low-concentration coverage range significantly extends downwards. Furthermore, after covering with the SiO2 film, the dynamic curve exhibits a more standard step-like morphology: the rising / falling edges of each step are clearer, the steady-state plateau is flatter, and the concentration coverage range expands to a lower end (down to 50 ppm). In terms of amplitude, the coating maintains a considerable response at high concentrations, for example, a responsivity of approximately 26.1% at 10,000 ppm, an improvement of about 1.79 times compared to before coating (approximately 14.6%). In the 800–200 ppm range, continuous steps (on the order of 2–6%) can still be distinguished after coating, whereas before coating, noise / drift dominated in this range, indicating that the SiO2 film substantially improves the detection limit for low concentrations. In summary, covering with a SiO2 film does not weaken the basic response capability of the hydrogen sensor to high concentrations of hydrogen, while significantly improving the distinguishability of steps and plateau stability at low concentrations, demonstrating strong air isolation and anti-interference effects.

[0059] Example 4 This embodiment of the hydrogen sensor based on palladium nanoparticles includes a substrate, electrodes, nanoparticles, and a thin film layer: the substrate is a quartz glass sheet with a thickness of 1 mm; the electrodes are gold interdigitated electrodes with a thickness of 100 nm and a finger spacing of 5 μm; the nanoparticles are palladium nanoparticles with an average particle size of 15.36 nm, a coverage of 55.36%, and an initial conductivity of 8.5723 × 10⁻⁶. -7 S; The thin film layer is a polytetrafluoroethylene film with a thickness of 45 nm.

[0060] The method for preparing the palladium nanoparticle-based hydrogen sensor includes the following steps: (1) Select a clean and smooth quartz glass plate as the substrate; (2) A gold interdigitated electrode is fabricated on the surface of the substrate using photolithography; (3) Using a cluster beam spectrometer, palladium nanoparticles are uniformly distributed on the substrate surface between the finger electrodes of the gold interdigitated electrode (the resulting hydrogen sensor is denoted as sensor g); the deposition conditions include: a bulk vacuum of 4 × 10⁻⁶. - 4 Pa, sputtering gas flow rate of 50 sccm, buffer gas flow rate of 60 sccm, both buffer gas and sputtering gas are argon, condensation chamber pressure of 78 Pa, sputtering power of 35 W, deposition rate of 0.3 Å / S; (4) A polytetrafluoroethylene (PTFE) film is coated on the surface of the gold interdigitated electrode and the surface of the palladium nanoparticles. Specifically, PTFE is deposited on the surface of the gold interdigitated electrode and the surface of the palladium nanoparticles by magnetron sputtering to form a PTFE film, thereby obtaining a hydrogen sensor based on palladium nanoparticles (denoted as sensor h). The deposition conditions include: a bulk vacuum of 4 × 10⁻⁶. -4 The sputtering gas was argon, the condensation chamber pressure was 1.5 Pa, the sputtering power was 40 W, and the deposition rate was 0.08 Å / s.

[0061] The electrodes of the prepared hydrogen sensor are connected to the external circuit for measuring conductivity via leads. The hydrogen sensor is then placed in an air environment with different hydrogen concentrations (20~10000ppm) for calibration.

[0062] The hydrogen sensor was tested: First, sensor g was tested by mixing air and hydrogen in a specific ratio to obtain test gases with different hydrogen concentrations. Then, sensor g was tested, and the real-time response curve of the relative conductivity of the nanoparticles in sensor g to the change in hydrogen concentration was measured. Figure 13 As shown; Then, the sensor g is further assembled in step (4) to obtain sensor h. The real-time response curve of the relative conductivity of the nanoparticles in sensor h to the hydrogen concentration is measured, as shown in the figure. Figure 14 As shown.

[0063] Figure 13 and Figure 14 The hydrogen step-cycle response curves of the same Pd nanoparticle array hydrogen sensor were compared before and after coating with a PTFE film against an air background, with the concentration switching gradually from high to low. The output was characterized by ΔG / G0. The results showed that both sets of curves exhibited a typical step-like morphology of "hydrogen rise - purge fall," and the response amplitude gradually decreased with decreasing concentration, indicating that the hydrogen sensor maintained reversible response capability to H2 before and after coating. However, the PTFE film significantly changed the step discernibility, low-concentration output, and baseline stability. Specifically, before coating, high concentrations could form a response step, but the low-concentration end decayed rapidly and was accompanied by a baseline rise, and a negative response appeared. After coating with the PTFE film: the response became more plateaued, and the concentration coverage range significantly decreased to 20 ppm. After coating, the regularity of the step response was significantly improved, the rising edges of each step were more consistent, the steady-state plateau was flatter, and the baseline was closer to zero and remained stable during long-term testing. Especially in terms of concentration coverage, the post-coating curve can consistently resolve concentrations down to 20 ppm. In contrast, before coating, the step at the end of the low-concentration range is almost dominated by drift / noise. This demonstrates that the PTFE film significantly improves the detection of low concentrations.

[0064] The long-term stability of the sensor h was tested, and the specific steps were as follows: The sensor h (i.e., the hydrogen sensor covered with a polytetrafluoroethylene film) was stored statically in an air environment, and hydrogen gradient concentration tests were performed under the same conditions on day 1 and day 60. The results are as follows. Figure 15 As shown, the responsivity of sensor h only decreased slightly after 60 days, with the overall trend consistent with that of day 1. Taking 10000ppm as an example, the responsivity was approximately 56% on day 1 and approximately 50% on day 60, with a retention rate of approximately 89%. The long-term stability of the PTFE film can be attributed to its inherent resistance to damp heat, oxidation, and low water absorption. Furthermore, the PTFE film formed by magnetron sputtering exhibits relatively stable morphology in air, resulting in minimal changes in the interface state over time. This effectively inhibits the long-term penetration of oxygen and water from the air and the occurrence of side reactions at the interface, thus contributing to better long-term stability.

[0065] From the above results, it can be seen that the present invention has at least the following beneficial effects: (1) The introduction of the thin film layer in this invention effectively suppresses the catalytic combustion reaction of hydrogen and oxygen catalyzed by nanoparticles, reduces the conductivity fluctuation caused by the combustion reaction, and thus significantly improves the sensitivity of the hydrogen sensor. Experimental results show that the detection limit of the hydrogen sensor in this invention can reach 20 ppm. In addition, the thin film layer can ensure that hydrogen molecules can diffuse rapidly to the surface of nanoparticles, further enhancing the sensitivity of the hydrogen sensor.

[0066] (2) The introduction of the thin film layer not only improves the sensitivity but also significantly optimizes the response time of the hydrogen sensor. Experimental results show that the response time of the hydrogen sensor in this invention can be shortened to less than 120s when the hydrogen concentration is 10,000 ppm. At the same time, the thin film layer also improves the recovery performance of the hydrogen sensor. When the hydrogen concentration is reduced to the background level, the recovery time can be controlled to less than 100s, which significantly improves the dynamic response capability of the hydrogen sensor.

[0067] (3) The thin film layer significantly improves the long-term stability of the hydrogen sensor. Experimental results show that the hydrogen sensor in this invention still has good hydrogen responsiveness after being placed in an air environment for 60 days, demonstrating a significant stability advantage. In addition, the mechanical strength and chemical stability of the thin film layer are also conducive to further improving the stability of the hydrogen sensor in complex environments such as high temperature and high humidity.

[0068] (4) Because the thin film layer effectively inhibits the catalytic combustion reaction and reduces structural damage and performance degradation of nanoparticles, the service life of the hydrogen sensor in this invention is significantly extended. This extended service life not only reduces the maintenance cost of the hydrogen sensor but also enhances its application value in industrial and environmental monitoring fields.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A hydrogen sensor based on nanoparticles, comprising a substrate and at least a pair of electrodes disposed at intervals on the surface of the substrate, wherein the substrate surface between the electrodes is covered with nanoparticles, and the electrode surfaces and the nanoparticle surfaces are covered with a thin film layer. The nanoparticles include one or more of palladium nanoparticles, platinum nanoparticles, and alloy nanoparticles, wherein the alloy nanoparticles contain palladium and / or platinum. The material of the thin film layer includes one or more of polymethyl methacrylate, naphthol, silicon dioxide, alumina, polytetrafluoroethylene, diamond-like carbon film, silicon nitride, and silicon carbide.

2. The hydrogen sensor based on nanoparticles according to claim 1, characterized in that, The thickness of the thin film layer is 10 nm to 20 μm.

3. The nanoparticle-based hydrogen sensor according to claim 1 or 2, characterized in that, The nanoparticles have an average particle size of 2-100 nm, a coverage of 5-90%, and an initial conductivity of 10 nS-100 μS.

4. The nanoparticle-based hydrogen sensor according to claim 1 or 2, characterized in that, The electrodes include parallel plate electrodes or interdigitated electrodes; the materials of the electrodes include gold, silver, platinum, aluminum, indium tin oxide, fluorine-doped tin oxide, or graphene.

5. The hydrogen sensor based on nanoparticles according to claim 1, characterized in that, The substrate material includes ordinary glass, quartz glass, silicon, alumina, mica, polyethylene terephthalate, polydimethylsiloxane, or polyimide.

6. A method for preparing the nanoparticle-based hydrogen sensor according to any one of claims 1 to 5, comprising the following steps: At least one pair of electrodes spaced apart are prepared on a substrate surface, nanoparticles are prepared on the substrate surface between the electrodes, and thin film layers are prepared on the electrode surface and the nanoparticle surface to obtain the nanoparticle-based hydrogen sensor.

7. The preparation method according to claim 6, characterized in that, The nanoparticles are prepared by electrochemical deposition, chemical vapor deposition, or physical vapor deposition; the physical vapor deposition method includes cluster beam deposition, magnetron sputtering, or thermal evaporation.

8. The preparation method according to claim 6, characterized in that, The methods for preparing the thin film include physical vapor deposition, chemical vapor deposition, or wet coating; the physical vapor deposition method includes electron beam evaporation or magnetron sputtering; the chemical vapor deposition method includes atomic layer deposition or plasma-enhanced chemical vapor deposition; and the wet coating method includes spin coating.

9. The application of the nanoparticle-based hydrogen sensor according to any one of claims 1 to 5 or the nanoparticle-based hydrogen sensor prepared by the preparation method according to any one of claims 6 to 8 in hydrogen detection.

10. The application according to claim 9, characterized in that, The applicable environment for hydrogen detection includes air environment, rare gas environment or pure hydrogen environment; the hydrogen concentration in the applicable environment is 20~10000ppm.

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