Sensing layer, humidity sensor containing the same, preparation method and use

Abstract

The present invention relates to a sensing layer, a humidity sensor comprising the same, a preparation method and uses. The sensing layer electrically responsive to humidity changes comprises a few-layer black phosphorus film layer and gold nanoparticles distributed on the few-layer black phosphorus film layer; the gold nanoparticles are adsorbed on the black phosphorus film layer through van der Waals forces. The sensing layer electrically responsive to humidity changes provided in the present application utilizes black phosphorus and gold nanoparticles to overcome the defect of easy oxidation of black phosphorus, improve the stability of the sensing layer in different environments (such as use environment, manufacturing environment, etc.), and also improve the humidity sensing performance of the sensor layer. The resistance response is in the range of 1.8 to 10 kΩ, the sensitivity is correspondingly in the range of 1500-4000%, and the stability reaches more than 7 days at a maximum relative humidity of 65% to 90%.

Description

Technical Field

[0001] The present invention belongs to the field of humidity detection, and specifically relates to a sensing layer, a humidity sensor containing the same, a preparation method and uses, and more particularly to a sensing layer that electrically responds to humidity changes, a preparation method, a humidity sensor containing the same and uses. Background Art

[0002] Nanomaterials are materials with at least one dimension in the 0.1-100 nm scale in three-dimensional space, or materials composed of nanomaterials as basic units. Nanomaterials have enormous surface areas and interfaces, making them highly sensitive to changes in the external environment. Changes in temperature, light, humidity, and atmosphere can cause changes in the valence state and electron output of surface or interface particles, resulting in electrical responses. However, traditional nanomaterials such as polymers and carbon materials often perform poorly in providing high sensitivity, primarily due to their limited specific surface area. Humidity detection, as an indispensable sensing technology, has been widely used in industrial production, food, biology, medicine, and other fields. However, existing humidity sensors cannot be directly used in wearable devices that come into contact with biological surfaces for human health monitoring (such as monitoring respiratory rate through humidity changes) due to the difficulty of achieving small thin film shapes or insufficient flexibility.

[0003] Therefore, there is an urgent need in the art to develop a sensing layer that is electrically responsive to humidity changes, which is expected to have a large surface area and minimal electronic noise. Summary of the Invention

[0004] In view of the shortcomings of the prior art, one of the objectives of this application is to provide a sensing layer that is electrically responsive to humidity changes, wherein the sensing layer comprises a few-layer black phosphorus film layer and gold nanoparticles distributed on the few-layer black phosphorus film layer;

[0005] The gold nanoparticles are adsorbed on the black phosphorus film layer through van der Waals forces.

[0006] Black phosphorus (BP) has excellent electrical properties, a high specific surface area, and a high molecular adsorption capacity, allowing it to maximize the adsorption of water molecules. However, when BP is simultaneously exposed to oxygen, water, and light, it undergoes irreversible oxidation. The present invention uses BP as the primary structure of the sensing layer and utilizes gold nanoparticles adsorbed by van der Waals forces to prevent BP oxidation, thereby improving the stability of the sensing layer in various environments (such as usage and manufacturing). This also enhances the humidity sensing performance of the sensor layer. Possible reasons for this are as follows: ① The lone pairs of electrons in the P atoms of the BP film can be partially transferred to the electron acceptors (gold nanoparticles) through electrostatic interactions, thereby reducing the oxidative reactivity of the FL-BP (few-layer BP film); and ② The van der Waals-adsorbed gold nanoparticles have a highly hydrophilic surface, which facilitates the adsorption of water molecules, thereby enhancing the sensing layer's sensitivity to humidity. Specifically, when the ambient humidity changes, water molecules form an adsorption layer on the surface of gold nanoparticles. Due to the dipole properties of water molecules, the water molecule adsorption layer formed on the surface of gold nanoparticles accumulates charge, thereby improving the conductivity of the sensing layer.

[0007] Preferably, the black phosphorus film layer is a few-layer black phosphorus layer, and the thickness of the black phosphorus film layer is 12-20 nm, for example, 13 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, etc.

[0008] The black phosphorus film has a thickness of 12 to 20 nm, which can further improve the sensitivity of the sensing layer while ensuring good mechanical flexibility. Below 12 nm, the continuity of the sensing layer is difficult to control, and unstable performance is prone to occur. Above 20 nm, the sensitivity of the sensing layer decreases.

[0009] Preferably, the particle size of the gold nanoparticles is 10-25 nm, for example, 11 nm, 13 nm, 15 nm, 17 nm, 18 nm, 20 nm, 22 nm, 24 nm, etc.

[0010] Preferably, in the sensing layer, the dispersion density of the gold nanoparticles is 500-600 gold nanoparticles dispersed on the black phosphorus film layer per square micrometer, for example, 510 gold nanoparticles, 530 gold nanoparticles, 550 gold nanoparticles, 570 gold nanoparticles, 590 gold nanoparticles, etc.

[0011] The dispersion density of gold nanoparticles is 500 to 600 gold nanoparticles dispersed per square micron of black phosphorus film layer, which can more effectively protect the stability of black phosphorus and improve the sensitivity of the sensing layer. The number of gold nanoparticles per square micron of black phosphorus film layer is less than 500, which will reduce the stability of black phosphorus to a certain extent. However, compared with the black phosphorus layer without adsorbed gold nanoparticles, no matter how many gold nanoparticles are adsorbed, the black phosphorus layer can be protected.

[0012] The second object of this application is to provide a method for preparing a sensing layer that is electrically responsive to humidity changes, comprising the following steps:

[0013] (1) Using black phosphorus block as cathode and tetrabutylamine acetate solution dispersed with gold acetate as electrolyte, electrolytic intercalation and post-treatment were performed to obtain a black phosphorus thin layer dispersion dispersed with adsorbed gold nanoparticles;

[0014] (2) providing a substrate, placing it in deionized water, and then dropping a dispersion of a black phosphorus thin layer with adsorbed gold nanoparticles onto the surface of the deionized water to self-assemble into a black phosphorus thin film; then taking the substrate out horizontally and upwardly, so that the black phosphorus thin layer with adsorbed gold nanoparticles adheres to the upper surface of the substrate, removing water, and obtaining a few-layer black phosphorus film layer with dispersed gold nanoparticles formed on the substrate;

[0015] (3) Repeat step (2) n times until the thickness reaches a predetermined thickness of a few-layer black phosphorus film with dispersed gold nanoparticles.

[0016] In the method for preparing the sensing layer described in the present invention, a black phosphorus block is used as a cathode, and electrolysis is performed in a dispersion containing gold acetate to obtain a black phosphorus thin layer that adsorbs gold nanoparticles via van der Waals forces. The black phosphorus thin layers then self-assemble to form a black phosphorus thin film, which is then stacked multiple times to form the sensing layer. The preparation method is simple, and the thickness of the black phosphorus thin film can be controlled by the number of self-assembly cycles, resulting in a simple control method. The preparation method adds gold acetate to the electrolyte, synchronizing the formation of gold nanoparticles with the exfoliation of black phosphorus, thereby obtaining a black phosphorus thin layer that adsorbs gold nanoparticles. During the subsequent stacking of black phosphorus thin layers to form a black phosphorus thin film, the gold nanoparticles can be dispersed across different black phosphorus thin layers, thereby improving the sensitivity of the sensing layer.

[0017] Preferably, n is ≥ 2, such as 3, 4, 5, 7, 9, etc., preferably 3 times.

[0018] Preferably, the predetermined thickness is 12-20 nm.

[0019] Preferably, the concentration of gold acetate is 1-2 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, etc.

[0020] Preferably, the base layer is a rigid material layer or a flexible material layer.

[0021] Preferably, the base layer includes any one of a silicon dioxide / silicon material layer, a mica layer, and a polyimide layer, or a combination of at least two thereof.

[0022] The mica layer may be typically, but not limited to, fluorphlogopite or natural mica.

[0023] Preferably, the voltage of the intercalation ionization in step (1) is 15-25 V (for example, 16 V, 18 V, 20 V, 22 V, 24 V, etc.), and the intercalation ionization time is 20-40 min (for example, 21 min, 24 min, 27 min, 29 min, 31 min, 35 min, 38 min, etc.).

[0024] Appropriate intercalation conditions will improve the stability of black phosphorus and increase its yield. Too high a voltage or too long an ionization time may reduce the adhesion stability of gold nanoparticles on the black phosphorus surface, affecting the stabilization effect of the black phosphorus layer. Too low a voltage or too short an ionization time will reduce the yield of black phosphorus nanosheets.

[0025] Preferably, the concentration of the black phosphorus thin layer dispersion containing adsorbed gold nanoparticles in step (1) is 0.5-2.0 mg / mL, for example, 0.6 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1.1 mg / mL, 1.3 mg / mL, 1.5 mg / mL, 1.7 mg / mL, 1.9 mg / mL, etc.

[0026] If the concentration of the black phosphorus thin layer is too low, defects may easily appear in the black phosphorus thin layer after the black phosphorus thin layer is stacked; if the concentration of the black phosphorus thin layer is too high, the thickness of the black phosphorus thin layer may easily appear uneven after the black phosphorus thin layer is stacked.

[0027] Preferably, the amount of the black phosphorus thin layer dispersion containing adsorbed gold nanoparticles added dropwise to the surface of deionized water in step (2) is 1.0-1.5 μL / cm 2 , for example 1.1 μL / cm 2 , 1.2 μL / cm 2 , 1.3 μL / cm 2 , 1.4 μL / cm 2 wait.

[0028] The amount of black phosphorus thin layer dispersion added was controlled at 1.0~1.5 μL / cm 2 It is more conducive to the dispersion and flattening of the black phosphorus thin layer in deionized water, making it easier to obtain a black phosphorus film with uniform thickness and improving the stability of the hygrometer.

[0029] Preferably, the post-treatment in step (1) is a first centrifugation to remove the thick black phosphorus blocks that have not been stripped, and a second centrifugation to concentrate to obtain a high-concentration black phosphorus nanosheet dispersion.

[0030] Preferably, the first centrifugation is performed at 1000-3000 r / min for 5-10 min;

[0031] Preferably, the secondary centrifugation is performed at 8000-12000 r / min for 5-10 min.

[0032] The third purpose of this application is to provide a use of a two-dimensional black phosphorus film layer, wherein the two-dimensional black phosphorus film layer is used as a sensing layer of a hygrometer, and the two-dimensional black phosphorus film layer includes a few-layer black phosphorus layer and gold nanoparticles bound to the few-layer black phosphorus layer by van der Waals forces.

[0033] The fourth object of this application is to provide a humidity sensor, comprising: a base layer, a sensing layer arranged on the base layer and electrically responsive to humidity changes as described in one of the objects, and an electrode layer arranged on a side of the sensing layer away from the base layer.

[0034] Preferably, the electrode layer is any one of metal chromium, metal nickel, metal gold, and metal palladium, or a combination of at least two thereof;

[0035] Preferably, the electrode layer is a chromium layer and a gold layer attached to the chromium layer.

[0036] A fifth object of the present application is to provide a method for preparing a humidity sensor as described in the fourth object, comprising the following steps:

[0037] S1. Prepare a sensing layer formed on a substrate according to steps (1) to (3);

[0038] S2 annealing the layered structure of step S1 to form a base material plate-sensing layer structure;

[0039] S3 forming an electrode layer on the surface of the sensing layer of the base material plate-sensing layer structure.

[0040] After obtaining the sensing layer that electrically responds to humidity changes, the present application anneals it to eliminate defects and impurities generated during the preparation process, and then forms an electrolytic layer thereon to derive the electrical signal of the electrical response to humidity changes to obtain a humidity sensor.

[0041] Preferably, the annealing condition is annealing at 300-350° C. for 80-90 min in an atmosphere of argon with a flow rate of 280-300 sccm and hydrogen with a flow rate of 90-110 sccm.

[0042] The purpose of annealing is to improve device performance and eliminate defects and impurities generated during the preparation process.

[0043] Preferably, the electrode layer is formed by thermal evaporation or magnetron sputtering; and the electrode layer is patterned by electron beam lithography or physical masking.

[0044] The sixth purpose of this application is to provide a use of a humidity sensor as described in the fourth purpose, wherein the humidity sensor is used in a detection field or a monitoring field, preferably in any one of the agricultural monitoring field, production control field, food storage status detection, drug production status detection and plant health status detection, and preferably in any one of the human health monitoring fields.

[0045] Compared with the prior art, this application has the following beneficial effects:

[0046] The sensing layer and humidity sensor provided in the present application that are electrically responsive to humidity changes utilize black phosphorus and gold nanoparticles to overcome the defect of black phosphorus being easily oxidized, thereby improving the stability of the sensing layer in different environments (such as usage environment, manufacturing environment, etc.), while also improving the humidity sensing performance of the sensor layer. The resistance response is in the range of 1.8~10 kΩ, and the sensitivity is correspondingly in the range of 1500-4000%. At a maximum relative humidity of 65%~90%, the stability reaches more than 7 days; in a preferred embodiment, at a relative humidity of 85%~90%, the sensitivity response shows only a slight decrease within 14 days, and a flexible sensor can be prepared based on a flexible substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic diagram of steps (4) to (5) of the humidity sensor;

[0048] Figure 2 Scanning electron microscopy characterization of the structure of the substrate material plate-sensing layer in step (4) of Example 1;

[0049] Figure 3 Atomic force microscopy characterization of the structure of the substrate material plate-sensing layer (thickness 18 nm) in step (4) of Example 1;

[0050] Figure 4 Field emission transmission electron microscopy characterization of the structure of the substrate material plate-sensing layer in step (4) of Example 1 at different magnification ratios;

[0051] Figure 5 is the resistance value of the humidity sensor of Example 1 at different humidity levels;

[0052] Figure 6 The sensitivity of the humidity sensor of Example 1 at different humidity levels;

[0053] Figure 7 The stability of the humidity sensor of Example 1 under different humidity conditions. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further explained below in conjunction with specific implementation methods. However, it should be noted that the specific implementation methods are only a specific implementation and explanation of the essence of the technical solution of the present invention and should not be understood as a limitation on the scope of protection of the present invention.

[0055] The reagents and instruments used in the examples can all be purchased from commercial products, and the detection methods are conventional methods well known in the art.

[0056] Example 1

[0057] A method for preparing a humidity sensor comprises the following steps:

[0058] (1) Using a black phosphorus block as the cathode and a DMF solution of tetrabutylamine acetate dispersed with gold acetate (gold acetate concentration of 1.5 mol / L) as the electrolyte (the concentration of the DMF solution of tetrabutylamine acetate is 2 mol / L, and the amount added is 10 mL), electrolytic intercalation (voltage of 20 V, time of 30 min), one centrifugation to remove the thick layer of black phosphorus block that has not been stripped, and a second centrifugation to concentrate to obtain a high-concentration black phosphorus nanosheet dispersion, and obtain a black phosphorus thin layer dispersion dispersed with adsorbed gold nanoparticles (dispersion concentration of 1.0 mg / mL, gold nanoparticle size of 20 nm, 550 gold nanoparticles dispersed per square micrometer of black phosphorus film layer);

[0059] (2) Provide a fluorophlogopite substrate and place it in deionized water. Then drop the black phosphorus thin layer dispersion containing adsorbed gold nanoparticles onto the deionized water surface (drop volume is 1.2 μL / cm 2 ), self-assembled into a black phosphorus film; then the substrate is taken out horizontally upward, so that the black phosphorus thin layer adsorbed with gold nanoparticles adheres to the upper surface of the substrate, and dried to remove moisture, thereby obtaining a sensing layer formed on the substrate;

[0060] (3) Repeat step (2) three times until the thickness of the sensing layer reaches the predetermined thickness (18 nm);

[0061] (4) Annealing the layered structure of step S1 in a reducing atmosphere (argon at a flow rate of 290 sccm and hydrogen at a flow rate of 100 sccm) (annealing temperature 320°C, annealing time 85 min) to form a substrate material plate-sensing layer structure;

[0062] (5) A 1×1 cm interdigital electrode was selected as a mask plate with a channel width of 100 μm. The mask plate was placed on the surface of the substrate material plate-sensing layer structure (the surface of the sensing layer). Then, a vacuum thermal evaporation coating machine (micro-nano vacuum VNANO, model: VZZ300) was used to first evaporate a layer of chromium (Cr, 10 nm) on the substrate, and then evaporate a layer of gold (Au, 70 nm). Finally, the mask plate was removed to obtain a humidity sensor.

[0063] Figure 1 A schematic diagram of steps (4) to (5) of the humidity sensor is provided. The humidity sensor includes a substrate layer 20, a sensing layer 10 disposed on the substrate layer 20 and electrically responsive to humidity changes, and an electrode layer 30 disposed on a side of the sensing layer 10 away from the substrate layer 20.

[0064] Example 2

[0065] A method for preparing a humidity sensor comprises the following steps:

[0066] (1) Using black phosphorus as the cathode and tetrabutylamine acetate solution (gold acetate concentration of 1 mol / L) dispersed with gold acetate as the electrolyte (the concentration of the tetrabutylamine acetate in DMF solution is 2 mol / L, and the amount added is 10 mL), electrolytic intercalation (voltage is 25 V, time is 20 min), centrifugation is performed once to remove the thick layer of black phosphorus block that has not been stripped, and secondary centrifugation is performed to concentrate to obtain a high-concentration black phosphorus nanosheet dispersion, thereby obtaining a black phosphorus thin layer dispersion dispersed with adsorbed gold nanoparticles (dispersion concentration is 1.0 mg / mL, the particle size of the gold nanoparticles is 15 nm, and 500 gold nanoparticles are dispersed per square micrometer of the black phosphorus film layer);

[0067] (2) Provide a fluorophlogopite substrate and place it in deionized water. Then drop the black phosphorus thin layer dispersion containing adsorbed gold nanoparticles onto the deionized water surface (drop volume is 1.5 μL / cm 2 ), self-assembled into a black phosphorus film; then the substrate is taken out horizontally upward, so that the black phosphorus thin layer adsorbed with gold nanoparticles adheres to the upper surface of the substrate, and dried to remove moisture, thereby obtaining a sensing layer formed on the substrate;

[0068] (3) Repeat step (2) twice until the thickness of the sensing layer reaches the predetermined thickness (12 nm);

[0069] (4) Annealing the layered structure of step S1 in a reducing atmosphere (argon at a flow rate of 280 sccm and hydrogen at a flow rate of 110 sccm) (annealing temperature 300°C, annealing time 90 min) to form a substrate material plate-sensing layer structure;

[0070] (5) A 1×1 cm interdigital electrode was selected as a mask plate with a channel width of 100 μm. The mask plate was placed on the surface of the substrate material plate-sensing layer structure (the surface of the sensing layer). Then, a vacuum thermal evaporation coating machine (micro-nano vacuum VNANO, model: VZZ300) was used to first evaporate a layer of chromium (Cr, 10 nm) on the substrate, and then evaporate a layer of gold (Au, 70 nm). Finally, the mask plate was removed to obtain a humidity sensor.

[0071] Example 3

[0072] A method for preparing a humidity sensor comprises the following steps:

[0073] (1) Using black phosphorus as the cathode and tetrabutylamine acetate solution (gold acetate concentration of 2.0 mol / L) dispersed with gold acetate as the electrolyte (the concentration of the tetrabutylamine acetate in DMF solution is 2 mol / L, and the amount added is 10 mL), electrolytic intercalation (voltage 15 V, time 40 min), one centrifugation to remove the thick layer of black phosphorus block that has not been stripped, and a second centrifugation to concentrate to obtain a high-concentration black phosphorus nanosheet dispersion, and obtain a black phosphorus thin layer dispersion dispersed with adsorbed gold nanoparticles (dispersion concentration is 1.0 mg / mL, the particle size of the gold nanoparticles is 20 nm, and 600 gold nanoparticles are dispersed per square micrometer of the black phosphorus film layer);

[0074] (2) Provide a fluorophlogopite substrate and place it in deionized water. Then drop the black phosphorus thin layer dispersion containing adsorbed gold nanoparticles onto the deionized water surface (drop volume is 1.0 μL / cm 2 ), self-assembled into a black phosphorus film; then the substrate is taken out horizontally upward, so that the black phosphorus thin layer adsorbed with gold nanoparticles adheres to the upper surface of the substrate, and dried to remove moisture, thereby obtaining a sensing layer formed on the substrate;

[0075] (3) Repeat step (2) three times until the thickness of the sensing layer reaches the predetermined thickness (20 nm);

[0076] (4) Annealing the layered structure of step S1 in a reducing atmosphere (300 sccm argon and 90 sccm hydrogen) (annealing temperature 350°C, annealing time 80 min) to form a substrate material plate-sensing layer structure;

[0077] (5) A 1×1 cm interdigital electrode was selected as a mask plate with a channel width of 100 μm. The mask plate was placed on the surface of the substrate material plate-sensing layer structure (the surface of the sensing layer). Then, a vacuum thermal evaporation coating machine (micro-nano vacuum VNANO, model: VZZ300) was used to first evaporate a layer of chromium (Cr, 10 nm) on the substrate, and then evaporate a layer of gold (Au, 70 nm). Finally, the mask plate was removed to obtain a humidity sensor.

[0078] Example 4

[0079] The only difference from Example 1 is that the fluorphlogopite substrate in step (2) is replaced by a silica / silicon substrate (rigid substrate).

[0080] Example 5

[0081] The only difference from Example 1 is that the fluorinated mica substrate in step (2) is replaced by a polyimide substrate (flexible substrate).

[0082] Example 6

[0083] The only difference from Example 1 is that (3) step (2) of the predetermined thickness of the sensing layer (8 nm) is not repeated.

[0084] Example 7

[0085] The only difference from Example 1 is that (3) step (2) is repeated 5 times until the thickness of the sensing layer reaches the predetermined thickness (30 nm).

[0086] Example 8

[0087] The only difference from Example 1 is that the concentration of gold acetate is 0.5 mol / L; the dispersion density of the gold nanoparticles in the black phosphorus thin layer dispersion for adsorbing gold nanoparticles in step (1) is 300 gold nanoparticles dispersed per square micron of the black phosphorus film layer.

[0088] Example 9

[0089] The only difference from Example 1 is that the gold acetate concentration is 4 mol / L. Step (2) fails to self-assemble into a black phosphorus film. This is probably because the gold acetate concentration is almost saturated when it is greater than 2 mol / L. The acetate ion concentration is too high, which reduces the amount of black phosphorus film stripped. The thickness of the sensing layer obtained in step (3) reaches the predetermined thickness (10 nm).

[0090] Comparative Example 1

[0091] A method for preparing a humidity sensor, which differs from Example 1 in that only a black phosphorus film layer is used as a sensing layer and no gold nanoparticles are adsorbed, comprises the following steps:

[0092] (1) Using black phosphorus as the cathode and tetrabutylamine acetate solution as the electrolyte (the concentration of the tetrabutylamine acetate in DMF solution is 2 mol / L, and the amount added is 10 mL), electrolytic intercalation (voltage is 20 V, time is 30 min), centrifugation is performed once to remove the thick layer of black phosphorus blocks that have not been stripped, and secondary centrifugation is performed to obtain a black phosphorus thin layer dispersion with uniform layer thickness (dispersion concentration is 1.0 mg / mL);

[0093] (2) Provide a fluorophlogopite substrate, place it in deionized water, and then drop the black phosphorus thin layer dispersion onto the deionized water surface (drop volume 1.2 μL / cm 2 ), self-assembled into a black phosphorus thin film; then the substrate is taken out horizontally upward, so that the black phosphorus thin layer adheres to the upper surface of the substrate, and dried to remove moisture, thereby obtaining a sensing layer formed on the substrate;

[0094] (3) Repeat step (2) three times until the thickness of the sensing layer reaches the predetermined thickness (18 nm);

[0095] (4) Annealing the layered structure of step S1 in a reducing atmosphere (argon at a flow rate of 290 sccm and hydrogen at a flow rate of 100 sccm) (annealing temperature 320°C, annealing time 85°C) to form a substrate material plate-sensing layer structure;

[0096] (5) A 1×1 cm interdigital electrode was selected as a mask plate with a channel width of 100 μm. The mask plate was placed on the surface of the substrate material plate-sensing layer structure (the surface of the sensing layer). Then, a vacuum thermal evaporation coating machine (micro-nano vacuum VNANO, model: VZZ300) was used to first evaporate a layer of chromium (Cr, 10 nm) on the substrate, and then evaporate a layer of gold (Au, 70 nm). Finally, the mask plate was removed to obtain a humidity sensor.

[0097] Material characterization:

[0098] (1) SEM characterization: The test instrument was a scanning electron microscope (SU-8020) manufactured by Hitachi High-Tech Corporation, and the test conditions were room temperature. The structure of the substrate material plate-sensing layer in step (4) of Example 1 was characterized by a scanning electron microscope. Figure 2 The scanning electron microscope characterization of the structure of the substrate material plate-sensing layer in step (4) of Example 1 is given. Figure 2 It can be seen that a uniform and dense AuNPs-BP film was obtained in Example 1;

[0099] (2) AFM characterization: The test instrument was an atomic force microscope (Dimension ICON) from Bruker Corporation, and the test conditions were room temperature. AFM characterization was performed on the structure of the base material plate-sensing layer (thickness 18 nm) in step (4) of Example 1, the structure of the base material plate-sensing layer (thickness 8 nm) in step (4) of Example 6, the structure of the base material plate-sensing layer (thickness 30 nm) in step (4) of Example 7, and the structure of the base material plate-sensing layer (thickness 18 nm, without gold nanoparticles) in step (4) of Comparative Example 1. Figure 3 The atomic force microscope characterization of the structure of the substrate material plate-sensing layer (thickness 18nm) in step (4) of Example 1 is given. Figure 3 It can be seen that the thickness of the sensing layer (gold nanoparticles-black phosphorus film layer) in the base material plate-sensing layer is about 18 nm;

[0100] (3) TEM characterization: The test instrument was a FEI field emission transmission electron microscope, model Tecnai G2 F20, and the test conditions were high vacuum and high energy electron beam. The structure of the substrate material plate-sensing layer in step (4) of Example 1 was characterized by field emission transmission electron microscopy. Figure 4 The field emission transmission electron microscope characterization of the structure of the substrate material plate-sensing layer in step (4) of Example 1 at different magnification ratios is given. Figure 4 It can be seen that the gold nanoparticles are uniformly distributed on the black phosphorus nanosheets, and the orientation of the gold nanoparticles is induced by the surface crystal structure of the BP crystals.

[0101] Performance testing:

[0102] (1) Resistance response of humidity measurement: The measurement method is to place the humidity sensor provided in the embodiment in a constant temperature and humidity chamber under different humidity conditions (35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%), and then use KEITHLEY 2614B to perform electrical tests under different humidity conditions. Figure 5 is the resistance value of the humidity sensor of Example 1 at different humidity levels.

[0103] (2) Sensitivity response of humidity measurement: The measurement method is to place the humidity sensor provided in the embodiment in a constant temperature and humidity chamber under different humidity conditions (35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%), and then use KEITHLEY 2614B to perform electrical tests under different humidity conditions. Figure 6The sensitivity of the humidity sensor of Example 1 at different humidity levels is shown in Figure 1. The sensitivity S (%) is calculated as follows: (current value at maximum relative humidity - current value at minimum relative humidity) / current value at minimum relative humidity × 100%. The current value at minimum relative humidity is the current value at 35% relative humidity; all current values ​​are at a voltage of 2V.

[0104] (3) Humidity measurement stability: The humidity sensor provided in Example 1 was placed in a constant temperature (25°C) humidity chamber under different humidity conditions (40%, 50%, 60%, 70%, 80%, 90%) for 14 days, and then electrical tests were performed every day under different humidity conditions using a KEITHLEY 2614B. Figure 7 The stability of the humidity sensor of Example 1 at different humidity levels is shown in Table 1. The stability test was performed daily in a 25°C constant humidity chamber at maximum relative humidity for 14 days using a Keithley 2614B sensor until no current response was detected. The number of days with a current response was recorded as the stability (Day).

[0105] Table 1 shows the performance test results of the humidity sensors of the embodiment and the comparative example.

[0106] Table 1

[0107] ;

[0108] Note: The maximum relative humidity in Table 1 is the maximum relative humidity that can be measured. The larger the maximum relative humidity, the larger the measurement range of the humidity sensor.

[0109] As can be seen from Table 1, the sensing layer provided by the present application can have an electrical response in an environment with a relative humidity of 65% to 90%, and the sensitivity is above 1550%, and it is stable for at least 7 days under the maximum relative humidity. Under the condition that the thickness of the black phosphorus film layer is preferably 12 to 20 nm, the maximum relative humidity can reach 90%, the sensitivity is above 3200%, and the stability is more than 12 days. If the thickness of the black phosphorus film layer is too small or too large, it will still respond to humidity, but it may affect the maximum relative humidity, sensitivity or stability. However, compared with the embodiment without adding gold nanoparticles, it still has obvious advantages.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sensing layer that electrically responds to humidity changes, characterized in that: The sensing layer comprises a few-layer black phosphorus film layer and gold nanoparticles distributed on the few-layer black phosphorus film layer; The gold nanoparticles are adsorbed on the black phosphorus film layer through van der Waals forces; The black phosphorus film layer is a few-layer black phosphorus layer, and the thickness of the black phosphorus film layer is 12-19 nm; The particle size of the gold nanoparticles is 10-25 nm; The dispersion density of gold nanoparticles is 500 to 600 gold nanoparticles dispersed per square micrometer of black phosphorus film.

2. A method for preparing a sensing layer that is electrically responsive to humidity changes as claimed in claim 1, characterized in that: The preparation method comprises the following steps: (1) Using black phosphorus block as cathode and tetrabutylamine acetate solution dispersed with gold acetate as electrolyte, electrolytic intercalation and post-treatment were performed to obtain a black phosphorus thin layer dispersion dispersed with adsorbed gold nanoparticles; (2) providing a substrate, placing it in deionized water, and then dropping a dispersion of a black phosphorus thin layer with adsorbed gold nanoparticles onto the surface of the deionized water to self-assemble into a black phosphorus thin film; then taking the substrate out horizontally and upwardly, so that the black phosphorus thin layer with adsorbed gold nanoparticles adheres to the upper surface of the substrate, removing water, and obtaining a few-layer black phosphorus film layer with dispersed gold nanoparticles formed on the substrate; (3) Repeat step (2) n times until the thickness reaches a predetermined thickness, thereby obtaining a sensing layer that is electrically responsive to humidity changes; The n≥2; the predetermined thickness is 12-19 nm; the concentration of gold acetate is 1-2 mol / L; The concentration of the black phosphorus thin layer dispersion containing adsorbed gold nanoparticles in step (1) is 0.5-2.0 mg / mL; In step (2), the black phosphorus thin layer dispersion containing adsorbed gold nanoparticles is added dropwise to the surface of deionized water at a rate of 1.0 to 1.5 μL / cm 2 .

3. The preparation method according to claim 2, wherein The base layer is a rigid material layer or a flexible material layer.

4. The preparation method according to claim 2, wherein The base layer includes any one of a silicon dioxide-silicon material layer, a mica layer, and a polyimide layer, or a combination of at least two of them.

5. The preparation method according to claim 2, wherein The voltage of the electrolytic intercalation in step (1) is 15-25 V, and the electrolytic intercalation time is 20-40 min.

6. The preparation method according to claim 2, wherein The post-treatment in step (1) is to remove the thick black phosphorus blocks that have not been stripped by centrifugation once, and to concentrate the black phosphorus nanosheets by centrifugation twice to obtain a high-concentration dispersion.

7. The preparation method according to claim 6, wherein The first centrifugation is performed at 1000-3000 r / min for 5-10 min.

8. The preparation method according to claim 6, wherein The secondary centrifugation is performed at 8000-12000 r / min for 5-10 min.

9. A humidity sensor, characterized in that: The humidity sensor comprises a base layer, a sensing layer electrically responsive to humidity changes as claimed in claim 1 and disposed on the base layer, and an electrode layer disposed on a side of the sensing layer away from the base layer.

10. The humidity sensor according to claim 9, wherein The electrode layer is any one of metal chromium, metal nickel, metal gold, and metal palladium, or a combination of at least two of them.

11. The humidity sensor according to claim 9, wherein The electrode layer is a chromium layer and a gold layer attached to the chromium layer.

12. A method for preparing a humidity sensor according to any one of claims 9 to 11, characterized in that: The steps include: S1 forming a sensing layer on a substrate according to the method of any one of claims 2 to 8; S2 annealing the layered structure of step S1 to form a base material plate-sensing layer structure; S3 forming an electrode layer on the surface of the sensing layer of the base material plate-sensing layer structure.

13. The preparation method according to claim 12, wherein The annealing conditions are: annealing at 300-350° C. for 80-90 min in an atmosphere of argon with a flow rate of 280-300 sccm and hydrogen with a flow rate of 90-110 sccm.

14. The preparation method according to claim 12, wherein The electrode layer is formed by a thermal evaporation method or magnetron sputtering; and the electrode layer is patterned by an electron beam lithography method or a physical mask method.

15. Use of the humidity sensor according to any one of claims 9 to 11, characterized in that: The humidity sensor is used in the detection field or the monitoring field.

16. The use according to claim 15, characterized in that The humidity sensor is used in any one of the fields of agricultural monitoring, production control, food storage status detection, drug production status detection, and plant health status detection.

17. A humidity sensor for human health monitoring, characterized in that: The humidity sensor is the humidity sensor according to any one of claims 9 to 11.

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