Room-temperature hydrogen sensor as well as preparation method and application thereof

Abstract

The invention provides a room-temperature hydrogen sensor as well as a preparation method and application thereof, and belongs to the technical field of hydrogen sensors. According to the invention, sulfur-metal chemical bond combination between a thiol end group of a dithiol organic molecule and metal is utilized, a layer of porous thiol self-assembled monomolecular layer film is constructed between a palladium hydrogen sensitive layer and a first electrode of a substrate, and the palladium sensitive layer is suspended on the self-assembled monomolecular layer, so that the palladium sensitive layer is fully exposed in a hydrogen atmosphere; the adsorption / desorption dynamic performance of the palladium membrane in the hydrogen response process is greatly improved, so that the response speed of the sensitivity of the sensor is remarkably improved. Besides, the carbon chain structure of the self-assembled monomolecular layer has excellent mechanical toughness and lubricity, interface stress generated in the hydrogen absorption expansion process of the palladium sensitive layer can be effectively relieved, the stability of the sensor is greatly improved, and the service life of the sensor is greatly prolonged. The sensor prepared by the invention can detect low-concentration (1ppm) hydrogen at room temperature, and can stably work for more than 10 years.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen sensors, and in particular relates to a room temperature hydrogen sensor and a preparation method and application thereof. Background Art

[0002] As an efficient and renewable clean energy, hydrogen is widely used in the fields of automobiles, aviation, power generation, etc., which can effectively alleviate the problems of traditional fuels in terms of reserves, unsustainability and pollution. However, hydrogen is a dangerous chemical with great destructive power. Its molecular size is small, it is very easy to leak, and it will ignite and cause serious explosion accidents when exposed to open flames. Therefore, how to achieve rapid and safe detection of hydrogen leakage in the early stage is crucial to the development and utilization of hydrogen energy.

[0003] Conductivity hydrogen sensors play an important role in the field of hydrogen detection due to their simple structure, low power consumption, miniaturization and easy integration. Conductivity hydrogen sensors mainly capture and collect hydrogen information by detecting the changes in electrical signals of the sensitive film after the interaction with hydrogen molecules. Due to the strong chemical reducibility of hydrogen, the surface reaction activity of the sensitive film will be gradually weakened after a long period of work, causing the chemical structure of the sensitive film to change. The accompanying lattice expansion / contraction leads to stress concentration at the interface between the sensitive film and the substrate, which in turn causes crack initiation or diffusion, causing the sensitive film to fall off the substrate surface, resulting in sensor failure. Existing conductivity hydrogen sensors mainly use palladium sensitive films, but they usually rely on micro-hotplate heating to detect hydrogen, and require precise temperature control mechanisms to adapt to different external temperature environments, making the sensor design complex, and high-temperature operation also increases safety risks. At the same time, the detection concentration of existing palladium-based sensors is generally above 1%, and it is difficult to achieve low-concentration detection at room temperature. Therefore, how to improve the detection sensitivity of hydrogen sensors at room temperature while improving the bonding strength between the sensitive film and the substrate to increase the life of the sensor has become a difficult problem in the prior art. Summary of the invention

[0004] The purpose of the present invention is to provide a room temperature hydrogen sensor and a preparation method and application thereof. The hydrogen sensor prepared by the present invention has excellent detection sensitivity at room temperature, and at the same time, the palladium film has better bonding strength with the substrate.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a room temperature hydrogen sensor, comprising the following steps:

[0007] (1) depositing a first contact electrode and a first electrode in sequence on a surface of a substrate to obtain a substrate containing a first electrode;

[0008] (2) depositing a second contact electrode and an insulating layer in sequence on the surface of the substrate containing the first electrode obtained in step (1), wherein the insulating layer contains a hollow structure, to obtain a substrate containing an insulating layer;

[0009] (3) performing molecular self-assembly in the hollow structure of the insulating layer of the substrate containing the insulating layer obtained in step (2) to obtain a substrate containing a self-assembled monolayer; the material of the self-assembled monolayer includes 1,10-decanedithiol or 1,8-octanedithiol;

[0010] (4) depositing a palladium film, a third contact electrode and a second electrode in sequence on the surface of the substrate containing the self-assembled monolayer obtained in step (3) to obtain a room temperature hydrogen sensor.

[0011] Preferably, in step (1), the material of the first contact electrode includes chromium; and the thickness of the first contact electrode is 15-30 nm.

[0012] Preferably, in step (1), the material of the first electrode is a metal that can form a sulfur-metal bond with a thiol molecule; and the thickness of the first electrode is 190-210 nm.

[0013] Preferably, the material of the insulating layer in step (2) includes silicon dioxide, silicon nitride or zirconium oxide; and the thickness of the insulating layer is 300-400 nm.

[0014] Preferably, the material of the self-assembled monolayer in step (3) is 1,10-decanedithiol.

[0015] Preferably, the thickness of the palladium film in step (4) is 70 to 90 nm.

[0016] Preferably, in step (4), the material of the third contact electrode includes titanium; and the thickness of the third contact electrode is 15-30 nm.

[0017] Preferably, in step (4), the material of the second electrode includes platinum, gold or silver; and the thickness of the second electrode is 190-210 nm.

[0018] The present invention also provides a room temperature hydrogen sensor prepared by the preparation method described in the above technical solution.

[0019] The present invention also provides the application of the room temperature hydrogen sensor described in the above technical solution in hydrogen detection.

[0020] The present invention provides a method for preparing a room temperature hydrogen sensor, comprising the following steps: (1) depositing a first contact electrode and a first electrode on the surface of a substrate in sequence to obtain a substrate containing the first electrode; (2) depositing a second contact electrode and an insulating layer in sequence on the surface of the substrate containing the first electrode obtained in step (1), wherein the insulating layer contains a hollow structure to obtain a substrate containing an insulating layer; (3) performing molecular self-assembly in the hollow structure of the insulating layer of the substrate containing the insulating layer obtained in step (2) to obtain a substrate containing a self-assembled monolayer; the material of the self-assembled monolayer includes 1,10-decanedithiol or 1,8-octanedithiol; (4) depositing a palladium film, a third contact electrode and a second electrode on the surface of the substrate containing the self-assembled monolayer obtained in step (3) in sequence to obtain a room temperature hydrogen sensor. The hydrogen sensor prepared by the present invention is a suspended structure design: utilizing the sulfur-metal chemical bond between the thiol end group of the dithiol organic molecule thiol and the metal to construct a porous thiol self-assembled monolayer film between the palladium hydrogen sensitive layer and the first electrode of the substrate, and suspending the palladium sensitive layer on the self-assembled monolayer. This design enables the palladium sensitive layer to be fully exposed to the hydrogen atmosphere, greatly improving the adsorption / desorption kinetics of the palladium film during the hydrogen response process, thereby significantly improving the response speed of the sensor sensitivity. In addition, the carbon chain structure of the self-assembled monolayer has excellent mechanical toughness and lubricity, which can effectively alleviate the interfacial stress generated by the palladium sensitive layer during the hydrogen absorption and expansion process, greatly improving the stability and life of the sensor. The results of the embodiment show that the sensor prepared by the present invention can effectively detect hydrogen as low as 1ppm at room temperature and can work stably for more than 10 years. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A top view of the structural schematic diagram of the room temperature hydrogen sensor prepared in Example 1;

[0022] Figure 2 A side view of the structural schematic diagram of the room temperature hydrogen sensor prepared in Example 1;

[0023] Figure 3 The sensing performance of the hydrogen sensor of Examples 1, 3 to 6 and Comparative Example 1;

[0024] Figure 4 The sensing performance of the hydrogen sensors of Examples 1 to 2 and Comparative Examples 1 to 4;

[0025] Figure 5 This is a gas-sensing performance diagram of the room-temperature hydrogen sensor prepared in Example 1 at room temperature of 1 to 1000 ppm hydrogen;

[0026] Figure 6 This is a performance comparison diagram of the hydrogen sensors of Example 1, Comparative Example 1 and Comparative Example 2 at room temperature;

[0027] Figure 7 This is a fast repeatability experimental diagram of the hydrogen sensor prepared in Example 1 and Comparative Example 1;

[0028] Figure 8 This is a long-term stability experimental diagram of the room temperature hydrogen sensor prepared in Example 1. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing a room temperature hydrogen sensor, comprising the following steps:

[0030] (1) depositing a first contact electrode and a first electrode in sequence on a surface of a substrate to obtain a substrate containing a first electrode;

[0031] (2) depositing a second contact electrode and an insulating layer in sequence on the surface of the substrate containing the first electrode obtained in step (1), wherein the insulating layer contains a hollow structure, to obtain a substrate containing an insulating layer;

[0032] (3) performing molecular self-assembly in the hollow structure of the insulating layer of the substrate containing the insulating layer obtained in step (2) to obtain a substrate containing a self-assembled monolayer; the material of the self-assembled monolayer includes 1,10-decanedithiol or 1,8-octanedithiol;

[0033] (4) depositing a palladium film, a third contact electrode and a second electrode in sequence on the surface of the substrate containing the self-assembled monolayer obtained in step (3) to obtain a room temperature hydrogen sensor.

[0034] The invention deposits a first contact electrode and a first electrode in sequence on the surface of a substrate to obtain a substrate containing the first electrode.

[0035] In the present invention, the substrate is preferably a silicon wafer. In the present invention, the surface of the silicon wafer preferably contains a 280-320 nm thick silicon dioxide oxide layer, more preferably a 300 nm thick silicon dioxide oxide layer. In the present invention, the silicon dioxide oxide layer can further improve the insulation of the substrate.

[0036] The present invention has no special limitation on the size of the substrate, which can be selected according to actual needs. In an embodiment of the present invention, the size of the substrate can be specifically 10 mm*10 mm.

[0037] In the present invention, the substrate is preferably washed and dried in sequence before use.

[0038] In the present invention, the washing is preferably carried out by ultrasonic washing with acetone and anhydrous ethanol in sequence.

[0039] The present invention has no particular limitation on the amount of acetone and anhydrous ethanol used, as long as the amount can cover the substrate.

[0040] The present invention has no special limitation on the power and time of the ultrasound, as long as it can remove impurities on the surface of the substrate.

[0041] In the present invention, the drying is preferably nitrogen drying. The present invention has no special limitation on the operation of nitrogen drying, and the technical solutions well known to those skilled in the art can be used.

[0042] In the present invention, the material of the first contact electrode preferably includes chromium; the thickness of the first contact electrode is preferably 15-30 nm, more preferably 20 nm. In the present invention, the first contact electrode is used to enhance the adhesion between the first electrode and the substrate.

[0043] In the present invention, the deposition of the first contact electrode is preferably performed by magnetron sputtering.

[0044] In the present invention, the power of the magnetron sputtering is preferably 90-110 W, more preferably 100 W; the time of the magnetron sputtering is preferably 2-4 min, more preferably 3 min.

[0045] In the present invention, the material of the first electrode is preferably a metal that can form a sulfur-metal bond with a thiol molecule, more preferably gold or platinum; the thickness of the first electrode is preferably 190 to 210 nm, more preferably 200 nm.

[0046] In the present invention, the deposition of the first electrode is preferably performed by magnetron sputtering.

[0047] In the present invention, the power of the magnetron sputtering is preferably 40-60 W, more preferably 50 W; the time of the magnetron sputtering is preferably 15-25 min, more preferably 20 min; the distance between the target and the substrate during the magnetron sputtering is preferably 14-16 cm, more preferably 15 cm.

[0048] In the present invention, the first contact electrode and the first electrode are preferably patterned by a photolithography process.

[0049] The present invention has no special limitation on the operation of the photolithography process, and a photolithography process familiar to those skilled in the art can be used. In an embodiment of the present invention, the photolithography process can be specifically as follows: spin coating NR77-6000PY photoresist on a substrate at a spin coating rate of 3000 rpm for 60 seconds, drying at 110°C for 2 minutes, then exposing for 6 seconds, then drying at 110°C for 1 minute, and then developing in NMD-3 developer for 25 seconds.

[0050] After the deposition is completed, the present invention preferably places the deposited substrate in N-methyl-2-pyrrolidone for 1 hour to remove the photoresist to obtain a substrate containing the first electrode.

[0051] The present invention has no special limitation on the specific shapes and sizes of the first contact electrode and the first electrode, which can be selected according to actual needs.

[0052] After obtaining a substrate containing a first electrode, the present invention sequentially deposits a second contact electrode and an insulating layer on the surface of the substrate containing the first electrode, wherein the insulating layer contains a hollow structure, to obtain a substrate containing an insulating layer.

[0053] In the present invention, the material of the second contact electrode preferably includes chromium; the thickness of the second contact electrode is preferably 20-30 nm. In the present invention, the second contact electrode is used to enhance the bonding strength between the first electrode and the insulating layer.

[0054] In the present invention, the deposition of the second contact electrode is preferably performed by magnetron sputtering.

[0055] In the present invention, the power of the magnetron sputtering is preferably 90-110 W, more preferably 100 W; the time of the magnetron sputtering is preferably 2-4 min, more preferably 3 min.

[0056] In the present invention, the material of the insulating layer preferably includes silicon dioxide, silicon nitride or zirconium oxide; the thickness of the insulating layer is preferably 300-400 nm.

[0057] In the present invention, the insulating layer contains a hollow structure. In the present invention, the hollow structure penetrates the insulating layer in a direction perpendicular to the horizontal plane.

[0058] In the present invention, the hollow structure is preferably circular. In the present invention, the center of the circular hollow structure is preferably located at the center of the insulating layer. The present invention adopts a circular hollow structure to ensure that the spin-coated photoresist is completely stripped, and the self-assembled monolayer can be stably grown on the first electrode through the hollow structure.

[0059] The present invention has no special limitation on the size of the hollow structure, as long as it is smaller than the size of the insulating layer. In an embodiment of the present invention, the diameter of the circular hollow structure may be specifically 200 μm.

[0060] In the present invention, the insulating layer is preferably deposited by magnetron sputtering.

[0061] In the present invention, the power of the magnetron sputtering is preferably 140-160 W, more preferably 150 W; the time of the magnetron sputtering is preferably 40-50 min, more preferably 45 min; the distance between the target and the substrate during the magnetron sputtering is preferably 12-14 cm, more preferably 13 cm.

[0062] In the present invention, the second contact electrode and the insulating layer are preferably patterned by photolithography.

[0063] The present invention has no special limitation on the operation of the photolithography process, and a photolithography process well known to those skilled in the art can be used. In an embodiment of the present invention, the photolithography process can be specifically as follows: spin coating NR77-6000PY type photoresist on a substrate containing a first electrode, the spin coating rate is 3000 rpm, the spin coating time is 60s, drying at 110°C for 2min, then exposing, the exposure time is 6s, then drying at 110°C for 1min, and then developing in NMD-3 type developer for 25s.

[0064] After the deposition is completed, the present invention preferably places the deposited substrate in N-methyl-2-pyrrolidone for 1 hour to remove the photoresist to obtain a substrate containing an insulating layer.

[0065] The present invention has no special limitation on the specific shape and size of the second contact electrode and the insulating layer, which can be selected according to actual needs. In an embodiment of the present invention, the size of the insulating layer can be specifically 5 mm*5 mm.

[0066] After obtaining the substrate containing the insulating layer, the present invention performs molecular self-assembly in the hollow structure of the insulating layer of the substrate containing the insulating layer to obtain a substrate containing a self-assembled monomolecular layer.

[0067] In the present invention, the material of the self-assembled monolayer includes 1,10-decanedithiol or 1,8-octanedithiol, preferably 1,10-decanedithiol. The present invention uses 1,10-decanedithiol as the self-assembled monolayer, which has better detection performance than other materials.

[0068] The present invention preferably mixes the raw materials of the self-assembled monolayer with anhydrous ethanol to obtain a mixed solution, and then immerses the substrate containing the insulating layer in the mixed solution to grow the self-assembled monolayer to obtain a substrate containing the self-assembled monolayer.

[0069] In the present invention, the raw material of the self-assembled monolayer includes 1,10-decanedithiol or 1,8-octanedithiol, preferably 1,10-decanedithiol.

[0070] In the present invention, the mixing of the raw materials of the self-assembled monolayer and anhydrous ethanol is preferably performed by ultrasound; the ultrasound time is preferably 2 to 6 minutes. The present invention has no particular limitation on the power of the ultrasound, and any ultrasound power known to those skilled in the art can be used.

[0071] In the present invention, the concentration of the raw material of the self-assembled monolayer in the mixed solution is preferably 1 to 20 mmol / L, more preferably 5 to 15 mmol / L, and further preferably 7.5 mmol / L.

[0072] In the present invention, when the size of the substrate is 10 mm*10 mm, the volume of the mixed solution is preferably 8-12 mL, more preferably 10 mL.

[0073] In the present invention, the growth time is preferably 20 to 30 hours, more preferably 24 hours.

[0074] In the present invention, the raw material molecules of the self-assembled monolayer have a hydrophilic terminal group and a hydrophobic alkyl chain, so a self-assembled monolayer structure can be formed on the surface of the first electrode.

[0075] After obtaining a substrate containing a self-assembled monomolecular layer, the present invention sequentially deposits a palladium film, a third contact electrode and a second electrode on the surface of the substrate containing the self-assembled monomolecular layer to obtain a room temperature hydrogen sensor.

[0076] In the present invention, the thickness of the palladium film is preferably 70 to 90 nm, more preferably 80 nm.

[0077] In the present invention, the palladium film is preferably deposited by magnetron sputtering.

[0078] In the present invention, the power of the magnetron sputtering is preferably 40-60 W, more preferably 50 W; the time of the magnetron sputtering is preferably 8-12 min, more preferably 10 min; the distance between the target and the substrate during the magnetron sputtering is preferably 14-16 cm, more preferably 15 cm.

[0079] In the present invention, the material of the third contact electrode preferably includes titanium; the thickness of the third contact electrode is preferably 15 to 30 nm, more preferably 20 to 30 nm. In the present invention, the third contact electrode is used to enhance the bonding strength between the palladium film and the second electrode.

[0080] In the present invention, the deposition of the third contact electrode is preferably performed by magnetron sputtering.

[0081] In the present invention, the power of the magnetron sputtering is preferably 90-110 W, more preferably 100 W; the time of the magnetron sputtering is preferably 2-4 min, more preferably 3 min.

[0082] In the present invention, the material of the second electrode preferably includes platinum, gold or silver; the thickness of the second electrode is preferably 190-210 nm, more preferably 200 nm.

[0083] In the present invention, the deposition of the second electrode is preferably performed by magnetron sputtering.

[0084] In the present invention, the power of the magnetron sputtering is preferably 40 to 60 W, more preferably 50 W; the time of the magnetron sputtering is preferably 15 to 25 min, more preferably 20 min.

[0085] The present invention preferably implements patterning of the palladium film, the third contact electrode and the second electrode through a photolithography process.

[0086] The present invention has no special limitation on the operation of the photolithography process, and a photolithography process well known to those skilled in the art can be used. In the embodiment of the present invention, the photolithography process is the same as the aforementioned photolithography process, and will not be described in detail here.

[0087] The present invention implants a self-assembled monolayer between the palladium sensitive layer and the substrate, which can solve the problems of slow precipitation of dissolved hydrogen in palladium and interface aggregation of hydrogen molecules in the hydrogen sensing process, thereby improving the sensitivity and speed of hydrogen detection; on the other hand, the mechanical lubrication properties of the self-assembled monolayer can help release the interface stress generated by the expansion of the Pd lattice when absorbing hydrogen, thereby improving the bonding strength between the sensitive layer and the substrate and significantly improving the working life of the sensor.

[0088] The present invention solves the problem that it is difficult for palladium-based sensitive materials to detect low-concentration hydrogen at room temperature, and the palladium film absorbs hydrogen and expands, resulting in failure and short life of the palladium sensitive film. The sensitivity of the pure palladium film is greatly improved by the specific combination of the self-assembled monolayer with the palladium film and the first electrode. Since the carbon chain structure of the self-assembled monolayer has unique high elasticity and lubricity, the stress concentration caused by the hydrogen absorption and expansion of the palladium film is released through the carbon chain structure, which greatly improves the life and stability of the palladium film sensor. In addition, the multilayer suspension structure of the sensor fully exposes the palladium film to the hydrogen atmosphere, so that the efficiency of hydrogen adsorption is further improved, thereby improving the response speed of the sensor. Moreover, under the action of the multilayer suspension structure, the sensor can effectively detect hydrogen as low as 1ppm at room temperature, and the device power consumption is as low as 5μW; in addition, the multilayer palladium-based hydrogen sensor is prepared by MEMS process, with simple preparation process and low preparation cost, which is conducive to industrial production. This excellent performance can be combined with the Internet of Things in the fields of aerospace, hydrogen fuel vehicles, new array gas sensors and other fields, and has broad application prospects.

[0089] The present invention also provides a room temperature hydrogen sensor prepared by the preparation method described in the above technical solution.

[0090] In the present invention, the hydrogen sensor is preferably a MEMS hydrogen sensor.

[0091] The hydrogen sensor prepared by the invention has excellent detection sensitivity and speed for hydrogen at room temperature.

[0092] The present invention also provides the application of the room temperature hydrogen sensor described in the above technical solution in hydrogen detection.

[0093] The present invention has no special limitation on the operation of the application, and the technical solutions of the application well known to those skilled in the art may be adopted.

[0094] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0095] Example 1

[0096] A method for preparing a room temperature hydrogen sensor: (1) A silicon wafer (10 mm*10 mm) having a 300 nm thick silicon dioxide oxide layer on its surface is used as a substrate, which is successively immersed in acetone and anhydrous ethanol for ultrasonic cleaning and then blown dry with nitrogen, and the chromium layer and the gold electrode are patterned by a photolithography process, specifically: NR77-6000PY type photoresist is spin-coated on the surface of the cleaned silicon wafer at a spin coating rate of 3000 rpm for 60 s, dried at 110°C for 2 min, then exposed for 6 s, then dried at 110°C for 1 min, and then developed in NMD-3 type developer for 25 s. A chromium layer and a gold electrode are sequentially deposited on a silicon wafer by magnetron sputtering, wherein the magnetron sputtering power of the chromium layer is 100 W, the time is 3 min, the thickness of the chromium layer is 20 nm, the magnetron sputtering power of the gold electrode is 50 W, the time is 20 min, the distance between the target and the substrate is 15 cm, and the thickness of the gold electrode is 200 nm. After the gold electrode is deposited, the substrate is placed in N-methyl-2-pyrrolidone for 1 h to remove the photoresist, thereby obtaining a substrate containing a gold electrode;

[0097] (2) A chromium layer and a silicon dioxide insulating layer (5 mm*5 mm) are sequentially deposited on the surface of the substrate containing the gold electrode obtained in step (1), wherein the silicon dioxide insulating layer contains a circular hollow structure with a diameter of 200 μm, and the center of the circular hollow structure is located at the center of the insulating layer, to obtain a substrate containing an insulating layer; and the chromium layer and the insulating layer are patterned by a photolithography process, specifically: spin coating NR77-6000PY type photoresist on the surface of the substrate containing the gold electrode, the spin coating rate is 3000 rpm, the spin coating time is 60 s, and the substrate is dried at 110° C. for 2 min, and then exposed for 6 s, followed by drying at 110° C. for 1 min, and then developing in NMD-3 type developer for 25 s. A chromium layer and a silicon dioxide insulating layer are sequentially deposited on a substrate containing a gold electrode by magnetron sputtering, wherein the magnetron sputtering power of the chromium layer is 100 W, the time is 3 min, the thickness of the chromium layer is 20 nm, the magnetron sputtering power of the insulating layer is 150 W, the time is 45 min, the distance between the target and the substrate is 13 cm, the thickness of the insulating layer is 300 nm, and after the insulating layer is deposited, the substrate is placed in N-methyl-2-pyrrolidone for 1 h to remove the photoresist, thereby obtaining a substrate containing an insulating layer;

[0098] (3) The reaction bottle was cleaned with anhydrous ethanol for 3 minutes and dried with nitrogen, 10 mL of anhydrous ethanol was transferred into the reaction bottle using a pipette, 1,10-decanedithiol was added and ultrasonicated for 2 minutes to obtain a mixed solution with a concentration of 7.5 mmol / L, and then the substrate containing the insulating layer obtained in step (2) was immersed in the mixed solution for 24 hours to obtain a substrate containing a self-assembled monolayer (SAMs);

[0099] (4) Depositing a palladium film on the surface of the substrate containing the self-assembled monolayer obtained in step (3), and patterning the palladium film by photolithography, specifically: spin coating NR77-6000PY type photoresist on the surface of the substrate containing the self-assembled monolayer, the spin coating rate is 3000 rpm, the spin coating time is 60s, and the surface is dried at 110°C for 2min, and then exposed for 6s, followed by drying at 110°C for 1min, and then developing in NMD-3 type developer for 25s. Depositing a palladium film on the substrate containing the self-assembled monolayer by magnetron sputtering, the magnetron sputtering power is 50W, the time is 10min, the distance between the target and the substrate is 15cm, the palladium film thickness is 80nm, after the palladium film is deposited, the substrate is placed in N-methyl-2-pyrrolidone for 1h to remove the photoresist, and a substrate containing a palladium film is obtained;

[0100] (5) A titanium layer and a platinum electrode are sequentially deposited on the surface of the substrate containing the palladium film obtained in step (4), and the titanium layer and the platinum electrode are patterned by photolithography, specifically: NR77-6000PY type photoresist is spin-coated on the surface of the substrate containing the palladium film, the spin-coating rate is 3000 rpm, the spin-coating time is 60s, and the substrate is dried at 110°C for 2min, then exposed for 6s, then dried at 110°C for 1min, and then developed in NMD-3 type developer for 25s. A titanium layer and a platinum electrode are sequentially deposited on the substrate containing the palladium film by magnetron sputtering, the magnetron sputtering power of the titanium layer is 100W, the time is 3min, and the thickness of the titanium layer is 20nm, the magnetron sputtering power of the platinum electrode is 50W, the time is 20min, and the thickness of the platinum electrode is 200nm. After the platinum electrode is deposited, the substrate is placed in N-methyl-2-pyrrolidone for 1h to remove the photoresist, and a room temperature hydrogen sensor is obtained.

[0101] The top view of the structural schematic diagram of the room temperature hydrogen sensor prepared in Example 1 is as follows Figure 1 As shown, the side view is Figure 2 shown. Figure 1 and Figure 2 In the figure, 1 is a substrate, 2 is a gold electrode, 3 is a silicon dioxide insulating layer, 4 is a self-assembled monolayer, 5 is a palladium film, and 6 is a platinum electrode.

[0102] Example 2

[0103] The 1,10-decanedithiol in step (3) of Example 1 was replaced by 1,8-octanedithiol, and the other parameters were the same as those in Example 1.

[0104] Example 3

[0105] The concentration of the mixed solution in step (3) of Example 1 was replaced with 2.5 mmol / L, and the other parameters were the same as those in Example 1.

[0106] Example 4

[0107] The concentration of the mixed solution in step (3) of Example 1 was replaced with 5 mmol / L, and the other parameters were the same as those in Example 1.

[0108] Example 5

[0109] The concentration of the mixed solution in step (3) of Example 1 was replaced with 10 mmol / L, and the other parameters were the same as those in Example 1.

[0110] Example 6

[0111] The concentration of the mixed solution in step (3) of Example 1 was replaced with 20 mmol / L, and the other parameters were the same as those in Example 1.

[0112] Comparative Example 1

[0113] The self-assembled monolayer in step (3) of Example 1 was omitted, and other parameters were the same as those in Example 1.

[0114] Comparative Example 2

[0115] A palladium film with a thickness of 80 nm is deposited on the surface of the interdigital electrode to obtain a single-layer palladium-based planar structure hydrogen sensor. The material of the interdigital electrode is platinum with a thickness of 200 nm.

[0116] Comparative Example 3

[0117] The 1,10-decanedithiol in step (3) of Example 1 was replaced by 1,4-phenyldithiol, and the other parameters were the same as those in Example 1.

[0118] Comparative Example 4

[0119] The 1,10-decanedithiol in step (3) of Example 1 was replaced by biphenyl-4,4'-dithiol, and the other parameters were the same as those in Example 1.

[0120] The gas testing platform was used to test the sensing performance of the hydrogen sensors of Examples 1, 3 to 6 and Comparative Example 1. The results are as follows: Figure 3 During the test, the two probes of the probe station were connected to the gold electrode and platinum electrode of the sensor respectively. A semiconductor analyzer was used as the data acquisition platform of the sensor. The test voltage of the semiconductor analyzer was 0.1V, the sampling time interval was 1s, and hydrogen and nitrogen were input as gases through the flow controller for testing. The flow rates of hydrogen and nitrogen were both 1000sccm. Figure 3 It can be seen that the sensing performance is best when the concentration of 1,10-decanedithiol is 7.5mmol / L.

[0121] The sensing performance of the hydrogen sensors of Examples 1 to 2 and Comparative Examples 1 to 4 is as follows: Figure 4 As shown, from Figure 4 It can be seen that the multilayer suspension structure containing 1,10-decanedithiol and 1,8-octanedithiol as self-assembled monolayers greatly improves the sensitivity and stability of the sensor, among which 1,10-decanedithiol has the best sensing performance in the dithiol monolayer, and makes the hydrogen sensor with pure palladium film as the sensitive membrane have excellent sensing performance at room temperature.

[0122] The hydrogen sensitivity of the room temperature hydrogen sensor prepared in Example 1 under a hydrogen concentration of 1 to 1000 ppm is as follows: Figure 5 As shown, from Figure 5 It can be seen that the sensor can detect hydrogen as low as 1 ppm at room temperature.

[0123] The results of the hydrogen sensors of Example 1, Comparative Examples 1 and Comparative Examples 2 repeated 4 tests on 1000 ppm hydrogen are as follows: Figure 6 As shown, the response time is 9 minutes and the recovery time is 15 minutes. Figure 6 It can be seen that 1,10-decanedithiol as a self-assembled monolayer and a multilayer suspension structure can greatly improve the sensitivity and stability of the sensor.

[0124] The room temperature hydrogen sensor prepared in Example 1 and the hydrogen sensor in Comparative Example 1 were tested 50 times for 1000 ppm hydrogen. Figure 7 As shown, each response time is 3 minutes and the recovery time is 2 minutes. Figure 7 It can be seen that 1,10-decanedithiol as a self-assembled monolayer can significantly improve the stability and repeatability of the sensor.

[0125] The results of the long-term stability test of the room temperature hydrogen sensor prepared in Example 1 to 1000ppm hydrogen are as follows: Figure 8 As shown, each response time is 9 minutes and the recovery time is 15 minutes. Figure 8 It can be seen that 1,10-decanedithiol as a self-assembled monolayer can make the sensor have excellent long-term stability and reliability.

[0126] In summary, the room temperature hydrogen sensor prepared by the present invention has excellent detection sensitivity and speed for hydrogen at room temperature.

[0127] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a room temperature hydrogen sensor, comprising the following steps: (1) depositing a first contact electrode and a first electrode in sequence on a surface of a substrate to obtain a substrate containing a first electrode; (2) depositing a second contact electrode and an insulating layer in sequence on the surface of the substrate containing the first electrode obtained in step (1), wherein the insulating layer contains a hollow structure, to obtain a substrate containing an insulating layer; (3) performing molecular self-assembly in the hollow structure of the insulating layer of the substrate containing the insulating layer obtained in step (2) to obtain a substrate containing a self-assembled monolayer; the material of the self-assembled monolayer includes 1,10-decanedithiol or 1,8-octanedithiol; (4) depositing a palladium film, a third contact electrode and a second electrode in sequence on the surface of the substrate containing the self-assembled monolayer obtained in step (3) to obtain a room temperature hydrogen sensor.

2. The preparation method according to claim 1, characterized in that: In the step (1), the material of the first contact electrode includes chromium; the thickness of the first contact electrode is 15-30 nm.

3. The preparation method according to claim 1, characterized in that: In the step (1), the material of the first electrode is a metal that can form a sulfur-metal bond with a thiol molecule; the thickness of the first electrode is 190 to 210 nm.

4. The preparation method according to claim 1, characterized in that: The material of the insulating layer in step (2) includes silicon dioxide, silicon nitride or zirconium oxide; the thickness of the insulating layer is 300-400 nm.

5. The preparation method according to claim 1, characterized in that: The material of the self-assembled monolayer in step (3) is 1,10-decanedithiol.

6. The preparation method according to claim 1, characterized in that: The thickness of the palladium film in the step (4) is 70 to 90 nm.

7. The preparation method according to claim 1, characterized in that: In the step (4), the material of the third contact electrode includes titanium; and the thickness of the third contact electrode is 15-30 nm.

8. The preparation method according to claim 1, characterized in that: The material of the second electrode in step (4) includes platinum, gold or silver; the thickness of the second electrode is 190-210 nm.

9. A room temperature hydrogen sensor prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the room temperature hydrogen sensor according to claim 9 in hydrogen detection.

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