Sensing layer, humidity sensor comprising sensing layer, preparation method and application

Abstract

The invention relates to a sensing layer, a humidity sensor comprising the sensing layer, a preparation method and application. The sensing layer has electric response to humidity change and is composed of a few-layer black phosphorus film layer and gold nanoparticles distributed on the few-layer black phosphorus film layer; and the gold nanoparticles are adsorbed on the black phosphorus film layer through Van der Waals force. According to the sensing layer with the electric response to the humidity change, the black phosphorus and the gold nanoparticles are utilized, the defect that the black phosphorus is prone to oxidation is overcome, the stability of the sensing layer in different environments (such as a use environment and a manufacturing environment) is improved, meanwhile, the humidity sensing performance of the sensor layer is improved, the resistance response is in the range of 1.8-10 kilohms, and the sensing layer has the good application prospect. The sensitivity is correspondingly in a range of 1500-4000%, and the stability reaches more than 7 days under the maximum relative humidity of 65%-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 comprising the same, a preparation method and uses thereof, and in particular to a sensing layer that is electrically responsive to humidity changes, a preparation method thereof, a humidity sensor comprising the same and uses thereof. Background Art

[0002] Nanomaterials refer to materials that have at least one dimension in the 0.1-100nm scale in three-dimensional space or are composed of them as basic units. Nanomaterials have huge specific surface areas and interfaces and are very sensitive to changes in the external environment. Changes in temperature, light, humidity and atmosphere will cause changes in the valence state and electronic 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, mainly 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. Existing humidity sensors cannot be directly used in wearable devices to contact biological surfaces for human health monitoring (such as monitoring respiratory rate through humidity changes) because it is difficult to achieve a small-sized film shape or they are not flexible enough.

[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 purposes of the present application is to provide a sensing layer that is electrically responsive to humidity changes, wherein the sensing layer is 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 higher molecular adsorption capacity, and can adsorb water molecules to the maximum extent. However, when black phosphorus is exposed to oxygen, water and light at the same time, an irreversible oxidation reaction will occur. The present invention uses black phosphorus as the main structure of the sensing layer, and uses gold nanoparticles adsorbed by van der Waals force to prevent black phosphorus oxidation, thereby improving the stability of the sensing layer in different environments (such as use environment, manufacturing environment, etc.), and also improving the humidity sensing performance of the sensor layer. The possible reasons are as follows: ① The lone pair of electrons in the P atoms of the black phosphorus film layer can be partially transferred to the electron acceptor (gold nanoparticles) through electrostatic interaction, thereby reducing the oxidation reactivity of FL-BP (a few-layer black phosphorus film layer); ② The surface of the gold nanoparticles adsorbed by van der Waals force has a high hydrophilicity, which makes it easy for water molecules to adsorb to its surface, thereby improving the sensitivity of the sensing layer 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 to 20 nm, for example, 13 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, etc.

[0008] The thickness of the black phosphorus film layer is 12 to 20 nm, which can further improve the sensitivity of the sensing layer while ensuring that it has good mechanical flexibility. The continuity of the sensing layer below 12 nm is difficult to control and is prone to unstable performance problems. The sensitivity of the sensing layer above 20 nm is reduced.

[0009] Preferably, the particle size of the gold nanoparticles is 10 to 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 to 600 gold nanoparticles dispersed on each square of the black phosphorus film layer, 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 on each square meter 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 meter 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 the present 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 a black phosphorus block as a cathode and a tetrabutylammonium acetate solution dispersed with gold acetate as an electrolyte, electrolytic intercalation, and post-treatment 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 on 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 layer dispersed with gold nanoparticles.

[0016] In the preparation method of 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 through van der Waals forces, and then a black phosphorus thin film is obtained through self-assembly of the black phosphorus thin layer, and the sensing layer is obtained after multiple stacking. The preparation method is simple, and the thickness of the black phosphorus thin film can be controlled by the number of self-assembly, and the control method is simple; the preparation method adds gold acetate to the electrolyte, so that the formation of gold nanoparticles and the stripping of black phosphorus are synchronized, thereby obtaining a black phosphorus thin layer that adsorbs gold nanoparticles, and in the subsequent process of stacking black phosphorus thin layers to form a black phosphorus thin film, the gold nanoparticles can be dispersed in different black phosphorus thin layers, thereby improving the sensitivity of the sensing layer.

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

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

[0019] Preferably, the added amount 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 of them.

[0022] The mica layer may be typically, but not limitedly, fluorphologous mica 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 and yield of black phosphorus. Too high a voltage or too long an ionization time may reduce the adhesion stability of gold nanoparticles on the black phosphorus surface and affect the stabilization effect on 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 being stacked into a black phosphorus film; 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 being stacked into a black phosphorus film.

[0027] Preferably, the amount of the black phosphorus thin layer dispersion containing adsorbed gold nanoparticles is added dropwise to the surface of deionized water in step (2) is 1.0 to 1.5 μL / cm 2 , for example 1.1 μL / cm 2 , 1.2μL / cm 2 , 1.3μL / cm 2 , 1.4μL / 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 spreading 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 peeled off, 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 the present 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 bonded to the few-layer black phosphorus layer by van der Waals forces.

[0033] The fourth object of the present 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] The 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: preparing 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 forms 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 is electrically responsive 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 gas with a flow rate of 280-300 sccm and hydrogen gas 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 the present 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, the production control field, the food storage status detection, the drug production status detection and the 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 that are electrically responsive to humidity changes provided by the present application utilize black phosphorus and gold nanoparticles to overcome the defect that black phosphorus is easily oxidized, thereby improving the stability of the sensing layer in different environments (such as usage environment, manufacturing environment, etc.), and at the same time also improving the humidity sensing performance of the sensor layer, with a resistance response in the range of 1.8 to 10 kΩ and a corresponding sensitivity in the range of 1500-4000%. At a maximum relative humidity of 65% to 90%, the stability reaches more than 7 days; in a preferred embodiment, at a relative humidity of 85% to 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 the humidity sensor from step (4) to step (5);

[0048] Figure 2 Scanning electron microscope 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 protection scope 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 a cathode, and using a DMF solution of tetrabutylaminoacetate dispersed with gold acetate (gold acetate concentration of 1.5 mol / L) as an electrolyte (the concentration of the DMF solution of tetrabutylaminoacetate is 2 mol / L, and the amount added is 10 mL), electrolytic intercalation (voltage of 20 V, time of 30 min), centrifuging once to remove the thick layer of black phosphorus block that has not been stripped, and centrifuging twice to concentrate to obtain a high-concentration black phosphorus nanosheet dispersion, and obtaining a black phosphorus thin layer dispersion dispersed with adsorbed gold nanoparticles (dispersion concentration of 1.0 mg / mL, gold nanoparticles with a particle size of 20 nm, and 550 gold nanoparticles dispersed on each square of the dense black phosphorus film layer);

[0059] (2) A fluorophlogopite substrate was provided and placed in deionized water, and then a black phosphorus thin layer dispersion containing adsorbed gold nanoparticles was dropped onto the surface of the deionized water (the drop amount was 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) 3 times until the thickness of the sensing layer reaches a predetermined thickness (18 nm);

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

[0062] (5) A 1×1 cm interdigital electrode was selected as a mask plate, and the channel width of the interdigital electrode mask plate was 100 μm. The mask plate was placed on the surface of the structure of the substrate material plate-sensing layer (the surface of the sensing layer), and 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 the humidity sensor from step (4) to step (5) is given. The humidity sensor comprises 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 a black phosphorus block as a cathode, and a tetrabutylaminoacetate solution (gold acetate concentration of 1 mol / L) dispersed with gold acetate as an electrolyte (the concentration of the tetrabutylaminoacetate in DMF solution is 2 mol / L, and the amount added is 10 mL), electrolytic intercalation (voltage of 25 V, time of 20 min), centrifuging once to remove the thick layer of black phosphorus blocks that have not been stripped, and centrifuging twice to obtain a high-concentration black phosphorus nanosheet dispersion, and obtaining a black phosphorus thin layer dispersion dispersed with adsorbed gold nanoparticles (dispersion concentration of 1.0 mg / mL, gold nanoparticles with a particle size of 15 nm, and 500 gold nanoparticles dispersed on each square of the dense black phosphorus film layer);

[0067] (2) A fluorophlogopite substrate was provided and placed in deionized water, and then a black phosphorus thin layer dispersion containing adsorbed gold nanoparticles was dropped onto the surface of the deionized water (the drop amount was 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 a predetermined thickness (12 nm);

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

[0070] (5) A 1×1 cm interdigital electrode was selected as a mask plate, and the channel width of the interdigital electrode mask plate was 100 μm. The mask plate was placed on the surface of the structure of the substrate material plate-sensing layer (the surface of the sensing layer), and 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 a black phosphorus block as a cathode, and a tetrabutylaminoacetate solution (gold acetate concentration of 2.0 mol / L) dispersed with gold acetate as an electrolyte (the concentration of the tetrabutylaminoacetate in DMF solution is 2 mol / L, and the amount added is 10 mL), electrolytic intercalation (voltage of 15 V, time of 40 min), centrifuging once to remove the thick layer of black phosphorus block that has not been stripped, and centrifuging twice to concentrate to obtain a high-concentration black phosphorus nanosheet dispersion, and obtaining a black phosphorus thin layer dispersion dispersed with adsorbed gold nanoparticles (dispersion concentration of 1.0 mg / mL, gold nanoparticles with a particle size of 20 nm, and 600 gold nanoparticles dispersed on each square of the dense black phosphorus film layer);

[0074] (2) A fluorophlogopite substrate was provided and placed in deionized water, and then a black phosphorus thin layer dispersion containing adsorbed gold nanoparticles was dropped onto the surface of the deionized water (the drop amount was 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) 3 times until the thickness of the sensing layer reaches a predetermined thickness (20 nm);

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

[0077] (5) A 1×1 cm interdigital electrode was selected as a mask plate, and the channel width of the interdigital electrode mask plate was 100 μm. The mask plate was placed on the surface of the structure of the substrate material plate-sensing layer (the surface of the sensing layer), and 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 fluorophlogopite 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 setting 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 a 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 micro-dense black phosphorus film layer.

[0088] Example 9

[0089] The only difference from Example 1 is that the gold acetate concentration is 4 mol / L, and step (2) cannot self-assemble into a black phosphorus film. This may be because the gold acetate concentration is almost saturated when it is greater than 2 mol / L, and the acetate ion concentration is too high, which reduces the stripping amount of the black phosphorus film. 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 gold nanoparticles are not adsorbed, comprises the following steps:

[0092] (1) using a black phosphorus block as a cathode and a tetrabutylaminoacetate solution as an electrolyte (the concentration of the tetrabutylaminoacetate solution in DMF is 2 mol / L and the amount added is 10 mL), electrolytic intercalation (voltage is 20 V, time is 30 min), centrifuging once to remove the thick layer of black phosphorus blocks that have not been stripped, and centrifuging twice 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 (dropping amount 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 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) 3 times until the thickness of the sensing layer reaches a predetermined thickness (18 nm);

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

[0096] (5) A 1×1 cm interdigital electrode was selected as a mask plate, and the channel width of the interdigital electrode mask plate was 100 μm. The mask plate was placed on the surface of the structure of the substrate material plate-sensing layer (the surface of the sensing layer), and 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 (SEM) of Hitachi High-Tech Corporation, model SU-8020, and the test condition was room temperature. The structure of the substrate material plate-sensing layer in step (4) of Example 1 was characterized by a SEM. 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 is an atomic force microscope (Dimension ICON) of Bruker Corporation, and the test condition is room temperature. 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 were characterized by atomic force microscopy. Figure 3 The atomic force microscopy characterization of the structure of the substrate material plate-sensing layer (thickness 18 nm) in step (4) of Example 1 is given. Figure 3 It can be seen that the thickness of the sensing layer (gold nanoparticle-black phosphorus film layer) in the base material plate-sensing layer is about 18 nm;

[0100] (3) TEM characterization: The test instrument was a field emission transmission electron microscope (TECNAI G2F20) produced by FEI, 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 a field emission transmission electron microscope. Figure 4 The base material plate of step (4) of Example 1 is given

[0101] - Field emission transmission electron microscopy characterization of the structure of the sensing layer Characterization images at different magnifications, from 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.

[0102] Performance Testing:

[0103] (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.

[0104] (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. The sensitivity S (%) = (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 relative humidity of 35%; the current values ​​are all current values ​​at a voltage of 2V;

[0105] (3) Stability of humidity measurement: The humidity sensor provided in Example 1 was placed in a constant temperature (25° C.) constant humidity chamber under different humidity conditions (40%, 50%, 60%, 70%, 80%, 90%) for 14 days, and then an electrical test was 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. The stability test in Table 1 is performed by placing the sensor in a 25°C constant humidity chamber for 14 days at maximum relative humidity, and performing an electrical humidity test every day using a KEITHLEY 2614B until there is no current response. The number of days with current response is recorded as stability (Day).

[0106] Table 1 shows the performance test results of the humidity sensors of the embodiments and comparative examples.

[0107] Table 1

[0108]

[0109]

[0110] 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.

[0111] 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, but it still has obvious advantages compared to the embodiment without adding gold nanoparticles.

[0112] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned 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 is electrically responsive to humidity changes, characterized in that: The sensing layer is 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.

2. The sensing layer according to claim 1, characterized in that The black phosphorus film layer is a few-layer black phosphorus layer, and the thickness of the black phosphorus film layer is 12 to 20 nm; Preferably, the particle size of the gold nanoparticles is 10 to 25 nm.

3. The sensing layer according to claim 1, characterized in that In the sensing layer, the dispersion density of the gold nanoparticles is 500 to 600 gold nanoparticles dispersed on each square of the dense black phosphorus film layer.

4. A method for preparing a sensing layer that is electrically responsive to humidity changes, characterized in that: The preparation method comprises the following steps: (1) using a black phosphorus block as a cathode and a tetrabutylammonium acetate solution dispersed with gold acetate as an electrolyte, electrolytic intercalation, and post-treatment 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 on 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) repeating step (2) n times until the thickness reaches a predetermined thickness, thereby obtaining a sensing layer that is electrically responsive to humidity changes; Preferably, n≥2; Preferably, the predetermined thickness is 12 to 20 nm; Preferably, the added amount of gold acetate is 1-2 mol / L.

5. The preparation method according to claim 4, characterized in that: The base layer is a rigid material layer or a flexible material layer; Preferably, the base layer comprises any one of a silicon dioxide / silicon material layer, a mica layer, and a polyimide layer, or a combination of at least two thereof; Preferably, the voltage of the intercalation ionization in step (1) is 15 to 25 V, and the intercalation ionization time is 20 to 40 min; Preferably, the concentration of the black phosphorus thin layer dispersion containing adsorbed gold nanoparticles in step (1) is 0.5 to 2.0 mg / mL; Preferably, the amount of the black phosphorus thin layer dispersion containing adsorbed gold nanoparticles is added dropwise to the surface of deionized water in step (2) is 1.0 to 1.5 μL / cm 2 ; Preferably, the post-treatment in step (1) is a first centrifugation to remove the thick black phosphorus blocks that have not been peeled off, and a second centrifugation to concentrate to obtain a high-concentration black phosphorus nanosheet dispersion; Preferably, the first centrifugation is performed at 1000-3000 r / min for 5-10 min; Preferably, the secondary centrifugation is performed at 8000-12000 r / min for 5-10 min.

6. A use of a two-dimensional black phosphorus film layer, characterized in that: 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 bonded to the few-layer black phosphorus layer through van der Waals force.

7. A humidity sensor, characterized in that: The humidity sensor comprises: a substrate layer, a sensing layer electrically responsive to humidity changes as claimed in any one of claims 1 to 3 arranged on the substrate layer, and an electrode layer arranged on a side of the sensing layer away from the substrate layer.

8. The humidity sensor according to claim 7, characterized in that: The electrode layer is any one of metal chromium, metal nickel, metal gold, and metal palladium, or a combination of at least two thereof; Preferably, the electrode layer is a chromium layer and a gold layer attached to the chromium layer.

9. A method for preparing a humidity sensor according to claim 7 or 8, characterized in that: The steps include: S1: preparing a sensing layer formed on a substrate according to steps (1) to (3); 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; Preferably, the annealing condition is annealing at 300-350° C. for 80-90 min in an atmosphere of argon gas with a flow rate of 280-300 sccm and hydrogen gas with a flow rate of 90-110 sccm; 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.

10. Use of the humidity sensor according to claim 7 or 8, characterized in that: The humidity sensor is used in the detection field or the monitoring field, preferably in any one of the agricultural monitoring field, the production control field, the food storage status detection, the drug production status detection and the plant health status detection, preferably in human health monitoring.

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