CN104502420A - Humidity-sensitive composite membrane, preparation method of humidity-sensitive composite membrane and humidity sensor - Google Patents

Abstract

The moisture-sensitive composite membrane disclosed by the invention is composed of a polyelectrolyte membrane and a conductive metal nanoparticle membrane. The polyelectrolyte membrane is obtained by cross-linking and quaternizing a polymer containing a pyridine ring with a dihalogenated alkane. The metal nanoparticles The film is obtained by in-situ reduction and cross-linking after forming a film from a mixed solution of metal salt and polymer. The moisture-sensitive composite film of the present invention has low impedance (≤10 megohm, even ≤1 megohm, which is very convenient for equipment detection) under low humidity (≤30%RH), and high response sensitivity (under optimal conditions, 1 -30%RH impedance change rate can reach 2000%), good stability and water resistance, etc., can be widely used in industrial and agricultural production, storage, meteorology, electricity safety and protection, and detection and control of environmental humidity in daily life. It is especially suitable for sensitive detection of humidity in low-humidity environments such as insulating gas SF6 in the transformer box.

Description

A kind of humidity sensitive composite film, its preparation method and humidity sensor

technical field

The invention relates to the field of sensitive materials, in particular to a moisture-sensitive composite film, a preparation method thereof and a humidity sensor.

Background technique

The research and application of chemically sensitive materials is an important field in the development of science and technology in today's society. It plays a very important role in modern industrial and agricultural production and the detection and regulation of people's living environment.

Humidity is a physical quantity indicating the water vapor content in the air, and relative humidity is the percentage of the partial pressure of water vapor actually contained in the air (P _W ) and the partial pressure of saturated water vapor (P _N ) at the same temperature, namely

Usually, the symbol %RH is used to represent relative humidity (Relative Humidity). When the temperature and pressure change, the relative humidity of the water vapor in the gas will change even if the pressure of the water vapor in the gas is the same due to the change of saturated water vapor. Generally speaking, the relative humidity index is often used for air humidity (see pages 129-130 of "Sensitive Materials and Sensors" edited by Chen Ai, Chemical Industry Press).

Humidity sensor, as an important class of chemical sensor, is mostly made of humidity-sensitive film, and has received increasing attention and attention, and its development is very rapid at present. Among many humidity materials, research on polymer sensitive materials is very active, and a variety of polymer humidity sensors have been commercialized. However, it also has shortcomings such as low response sensitivity, slow response time, large hysteresis, poor response reproducibility, and high impedance under low humidity, which makes it impossible to measure (that is, beyond the test range of conventional instruments), which hinders its development. research and wide application.

Nanostructured materials have a much larger specific surface area than conventional bulk materials. On the one hand, they can provide more reactive sites, help to improve the sensitivity of the response, and also facilitate the detection of the diffusion of water molecules, thereby speeding up the response. and improve reversibility.

The sensitivity of the sensor refers to the ratio of the output change when it reaches a stable working state to the input change that causes this change (see page 7 of "Sensor Principles and Applications" edited by Wang Huaxiang and Zhang Shuying, Tianjin University Press). The impedance type humidity sensor is a sensor that uses the principle that the impedance value of the humidity sensor changes with the change of humidity to measure the humidity. The impedance type humidity sensor often has a very high impedance under low humidity (≤30%RH) conditions, especially When it is lower than 10%RH, its impedance (usually hundreds to several gigaohms, or even higher) is often far beyond the range of conventional detection circuits (equipment) (usually tens of megohms), conventional detection The circuit (device) cannot measure the output (impedance) of an impedance type humidity sensor. In the case of a certain input variation range (≤30%RH), the impedance change rate can be used to characterize the sensitivity of the impedance humidity sensor. For the impedance humidity sensor, the output variation is the variation R ₁ -R of the impedance value ₀ (wherein, R ₁ is the impedance value after the change, R ₀ is the initial impedance value), and its sensitivity S is the ratio of the impedance change rate to the output initial value, that is , In the case where the impedance of the impedance type humidity sensor cannot be measured, the impedance change rate and sensitivity cannot be measured.

The response time of the humidity sensor refers to the time required for the humidity sensor to complete the process of moisture absorption or dehumidification and dynamic balance (the characteristic quantity of moisture sensing reaches the equilibrium value, for the impedance type humidity sensor, the characteristic quantity of humidity sensing is the impedance value) when the ambient humidity changes time. The change of the humidity-sensing characteristic quantity lags behind the change of the ambient humidity, and this phenomenon is called hysteresis. In practice, 63.2% or 90% of the response time is used, that is, the time required for the change of the characteristic quantity of humidity to reach 63.2% or 90% of the total change (see pages 166-167 of "Sensitive Materials and Sensors" edited by Chen Ai, Chemical Industry Press). The response time standards adopted in the present invention are all 90% response time.

For the existing impedance type humidity sensor, as the humidity decreases, its impedance increases. Under low humidity (≤30%RH) conditions, the impedance type humidity sensor often has very high impedance, and its impedance (usually several Megohms or even higher) are often far beyond the range of conventional detection circuits (equipment) (usually tens of megohms), and conventional detection circuits (equipment) cannot measure the output (impedance) of impedance-type humidity sensors, let alone measure Its change rate and sensitivity make it difficult for the existing impedance type humidity sensor to be applied to the sensitive detection of low humidity environment (≤30%RH). Especially in the environment below 10%RH, the impedance type humidity sensor is often unable to detect the humidity response due to its high impedance. For daily production, it is often necessary to accurately detect the humidity in a low-humidity environment, especially for the safe use and protection of electrical equipment. For example, the insulation medium of substation facilities (such as transformer boxes) in power systems is often insulating gas (such as sulfur hexafluoride), and the moisture content in the insulating gas plays a key role in its insulation performance under high voltage. Control its moisture content at a very low level, because when the moisture content increases, its insulation decreases and it is easy to be broken down, resulting in dangerous electricity use. At present, sulfur hexafluoride is mostly used as insulating gas in power substation facilities, which itself can react with water to produce harmful gases such as hydrofluoric acid. It is even more necessary to strictly control the humidity of sulfur hexafluoride in the substation box. However, it is difficult and cumbersome to accurately detect low-humidity environments (≤30%RH), and the required equipment such as dew point meters has a long measurement cycle (generally more than one week), and the equipment is expensive (generally more than 100,000 yuan). Therefore, there is an urgent need for a low-impedance (less than tens of megohms) in a low-humidity environment (1%-30%RH), which is convenient for conventional detection circuits (equipment) detection, and has high response sensitivity (high impedance change rate). ), which can accurately detect low-humidity environments, has the advantages of good stability and water resistance, and can realize real-time detection of humidity sensors, and the core of the sensor is a sensitive material.

Contents of the invention

Aiming at the deficiencies of the existing technology, the technical problem to be solved by the present invention is to provide a low impedance (≤10 megohm, very easy to realize equipment detection) in a low humidity environment (≤30%RH) at the same time, Moreover, it has high response sensitivity (high impedance change rate, high sensitivity), can accurately detect low humidity environment, has good stability and water resistance, and can realize real-time detection of humidity, and is a humidity sensitive device with the advantages of simple preparation and low cost. A composite film and a humidity sensor comprising the humidity-sensitive composite film.

Preferably, the impedance of the moisture-sensitive composite film provided by the present invention is ≤1 megohm, and the impedance change rate is ≥1000% in the low humidity range of 1%RH-30%RH.

The present invention adopts following technical scheme:

A moisture-sensitive composite film, the moisture-sensitive composite film is composed of a polyelectrolyte film with a crosslinked structure and a conductive metal nanoparticle film deposited thereon, and the conductive metal nanoparticle film is a polymer crosslinked network The structure is composed of conductive metal nanoparticles uniformly dispersed in the polymer cross-linked network structure, and the conductive metal nanoparticle film can reduce impedance and improve the conductivity of the material. The polymer cross-linked network in the conductive metal nanoparticle film and the metal nanoparticles uniformly dispersed therein work together to provide a good conductive channel for the electronic conduction of the conductive metal nanoparticle film; the polyelectrolyte film and The conductive metal nanoparticle films deposited thereon produce a synergistic effect to jointly form a conductive network; the conductive network acts simultaneously with the ion conduction of the polyelectrolyte film and the electronic conduction of the conductive metal nanoparticle film, and Accompanied by the tunneling effect, the polyelectrolyte film and the conductive metal nanoparticle film respectively form a conductive channel, which makes the humidity sensitive film have a lower impedance (≤10 megohm, It can even reach ≤1 megohm), and high response sensitivity (high impedance change rate). The cross-linked structure of the polyelectrolyte film and the cross-linked structure of the conductive metal nanoparticle film work together to provide good stability and water resistance for the humidity-sensitive film.

Preferably, the conductive metal nanoparticle film is prepared by an in-situ reduction cross-linking method, and the in-situ reduction cross-linking method reduces the metal salt solution to generate conductive metal nanoparticles and at the same time cross-links the polymer reaction to prepare a conductive metal nanoparticle film, and the conductive metal nanoparticle film is composed of a polymer crosslinked network structure and conductive metal nanoparticles uniformly dispersed in the polymer crosslinked network structure. The cross-linking agent for the cross-linking reaction should not only have the ability to reduce the metal salt solution to conductive metal nanoparticles, but also have the ability to cross-link the polymer to form a polymer cross-linked network structure.

Preferably, the in-situ reduction cross-linking method comprises the following steps: preparing a mixed solution of a metal salt and a polymer; Conductive metal nanoparticle films. The film forming method can be dip coating, spin coating, drop coating and other methods. the

Preferably, the polymer is a polymer containing hydroxyl groups in repeating units, which may be selected from polyvinyl alcohol (PVA), polyethylene glycol (PEG), polylactic acid, polylactic acid and its copolymers, polypropylene glycol and the like. The cross-linking agent for the in-situ reduction cross-linking reaction can be selected from dialdehydes, and the dialdehydes can be selected from glutaraldehyde, adipaldehyde, glyoxal, malondialdehyde and the like.

Preferably, the electrical conductivity of the conductive metal needs to meet certain conditions in order to generate a tunneling effect with the polyelectrolyte membrane with a cross-linked structure, preferably the electrical conductivity of the conductive metal is ≥5×10 ⁶ S·m ^-1 , More preferably, the conductivity of the conductive metal is ≥40×10 ⁶ S·m ^-1 .

Preferably, the impedance change rate of the moisture-sensitive composite film in the low humidity range of 1%RH-30%RH is ≥1000%, and its impedance is ≤10 megohm; more preferably, the impedance is ≤1 megohm.

Preferably, the conductive metal is selected from Au, Ag, Cu. In the present invention, Ag is preferred, that is, the metal salt solution used is preferably silver nitrate solution. At this time, the impedance change rate of the humidity-sensitive composite film in the low humidity range of 1%RH-30%RH can reach 2000%, and its impedance≤ 10 megohm; more preferred impedance ≤ 1 megohm.

Preferably, the polyelectrolyte membrane is a polymer membrane containing a pyridine ring with a cross-linked quaternized structure, which may be poly(4-vinylpyridine), poly(2-vinylpyridine), etc., and the cross-linked quaternary The ammonizing agent is preferably a dihaloalkane, and can be 1,4-dibromobutane, 1,5-dibromopentane, 1,6-dibromohexane, 1,4-dichlorobutane, etc., preferably For 1,4-dibromobutane, the preferred polyelectrolyte membrane is a cross-linked quaternized poly(4-vinylpyridine) membrane.

The second object of the present invention is to provide a method for preparing the moisture-sensitive composite film, comprising the steps of:

1) preparing a polyelectrolyte precursor solution, and then adding a cross-linking quaternization reagent to obtain a mixed solution, which is then heat-treated after forming a film to obtain a polyelectrolyte membrane with a cross-linking quaternization structure; The polyelectrolyte membrane with a cross-linked structure has a sensitive response to humidity, which can improve the sensitivity of the composite membrane to humidity;

2) Prepare a mixed solution of metal salt and polymer, form a film on the polyelectrolyte membrane prepared in step 1), and then reduce and cross-link in situ to obtain a conductive metal nanoparticle film, which has the same cross-linking properties as described in step 1). The polyelectrolyte membranes with biquaternized structure together constitute a moisture-sensitive composite membrane. The conductive metal nanoparticle film is composed of a polymer crosslinked network structure and conductive metal nanoparticles uniformly dispersed in the polymer crosslinked network structure, and the conductive metal nanoparticle film plays a role in reducing impedance , can improve the conductivity of the material. The polymer cross-linked network in the conductive metal nanoparticle film and the metal nanoparticles uniformly dispersed therein work together to provide a good conductive channel for the electronic conduction of the conductive metal nanoparticle film; the polyelectrolyte film and The conductive metal nanoparticle films deposited thereon produce a synergistic effect to jointly form a conductive network; the conductive network acts simultaneously with the ion conduction of the polyelectrolyte film and the electronic conduction of the conductive metal nanoparticle film, and Accompanied by the tunneling effect, the polyelectrolyte film and the conductive metal nanoparticle film respectively form a conductive channel, which makes the humidity sensitive film have a lower impedance (≤10 megohm, even ≤1 megohm) under low humidity . The cross-linked structure of the polyelectrolyte film and the cross-linked structure of the conductive metal nanoparticle film work together to provide good stability and water resistance for the humidity-sensitive film.

Preferably, the in-situ reduction cross-linking method comprises the following steps: preparing a mixed solution of a metal salt and a polymer; Conductive metal nanoparticle films. The film forming method can be dip coating, spin coating, drop coating and other methods.

Preferably, the polyelectrolyte membrane in step 1) is a polymer membrane containing a pyridine ring with a cross-linked quaternized structure, which can be poly(4-vinylpyridine), poly(2-vinylpyridine), etc. ; The concentration of the polyelectrolyte precursor is preferably 5 to 400 mg/mL.

As a preference, the cross-linking quaternization reagent in step 1) is preferably a dihaloalkane, which can be 1,4-dibromobutane, 1,5-dibromopentane, 1,6-dibromohexane, 1,4-dichlorobutane, etc., more preferably 1,4-dibromobutane; the amount of the crosslinking quaternizing agent is preferably 0.2 to 15 times the molar ratio of the polyelectrolyte precursor.

As a preference, the heat treatment temperature in step 1) is preferably 40-200°C, and the time is preferably 0.2-48 h.

As a preference, a film-forming agent can be added in the step 1) to assist the mixed solution to form a film, and the film-forming agent is selected from polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, etc., More preferably polyvinyl butyral; the concentration of the film-forming agent is preferably 0.5-100 mg/mL.

Preferably, the concentration of the polymer in the step 2) is preferably 3-300 mg/mL.

Preferably, the polymer in step 2) is a polymer containing hydroxyl groups in repeating units, which can be selected from polyvinyl alcohol (PVA), polyethylene glycol (PEG), polylactic acid, polylactic acid and its copolymers, Polypropylene glycol etc.; The cross-linking agent of described in-situ reduction cross-linking reaction can be optional dialdehydes, dialdehydes can be glutaraldehyde, adipaldehyde, glyoxal, malondialdehyde etc.; preferred original The reduction crosslinking temperature is 10-200°C, and the time is 0.1-48 h.

Preferably, the impedance change rate of the moisture-sensitive composite film in the low humidity range of 1%RH-30%RH is ≥1000%, and its impedance is ≤10 megohm; more preferably, the impedance is ≤1 megohm.

Preferably, the metal salt in step 2) is selected from soluble salts containing Au ⁺ , Au ³⁺ , Ag ⁺ , Cu ²⁺ ; H[AuCl ₄ ], AgNO ₃ , CuSO ₄ , etc. are preferred; the metal The concentration of the salt is preferably 0.005 to 1 mol/L.

A more preferred metal salt is AgNO ₃ . At this time, the impedance change rate of the humidity-sensitive composite film in the low humidity range of 1%RH-30%RH can reach 2000%, and its impedance is ≤10 megohm; more preferably Impedance ≤ 1 megohm.

As preferably, the preparation method of the moisture-sensitive composite film specifically includes the following steps:

① Prepare a mixed solution of polyelectrolyte precursor and film-forming agent, the concentration of the polyelectrolyte precursor is preferably 5-400 mg/mL, and the concentration of film-forming agent is preferably 0.5-100 mg/mL;

② Add dihaloalkane with a molar ratio of 0.2 to 15 times that of the polyelectrolyte precursor, and age for 0.5 to 48 hours to form a mixed solution;

③The mixed solution in step ② is formed into a film, dried and heated at 40-200°C for 0.2-48 h to obtain a polyelectrolyte membrane;

④ Prepare a mixed solution of metal salt and polymer, the concentration of the metal salt is preferably 0.005-1 mol/L, and the concentration of the polymer is preferably 3-300 mg/mL;

5. the mixed solution described in step 4. is formed into a film on the polyelectrolyte membrane;

⑥ Under the environment of cross-linking agent, carry out in-situ reductive cross-linking reaction at a temperature of 10-200 °C for 0.1-48 h to prepare a moisture-sensitive composite film.

As a preference, the polyelectrolyte precursor in the step ① is a polymer containing a pyridine ring, such as poly(4-vinylpyridine), poly(2-vinylpyridine), etc.;

As preferably, a film-forming agent can be added in the step ① to assist the mixed solution to form a film, and the film-forming agent is selected from polyvinyl alcohol, polyvinyl butyral, polyvinyl and pyrrolidone, etc., more Polyvinyl butyral is preferred;

As preferably, the cross-linking quaternization reagent in the step 2. is preferably a dihaloalkane, optional 1,4-dibromobutane, 1,5-dibromopentane, 1,6-dibromohexane, 1 , 4-dichlorobutane, etc., more preferably 1,4-dibromobutane;

As a preference, the temperature of the heat treatment in the step ③ is preferably 40-200°C, and the time is preferably 0.2-48 h;

Preferably, the polymer in step ④ is a polymer containing hydroxyl groups in the repeating unit, which can be selected from polyvinyl alcohol (PVA), polyethylene glycol (PEG), polylactic acid and its copolymers, polypropylene glycol, etc. ;

Preferably, the metal salt in step ④ is selected from soluble salt solutions containing Au ⁺ , Au ³⁺ , Ag ⁺ , Cu ²⁺ ; optional H[AuCl ₄ ], AgNO ₃ , CuSO ₄ , etc., more preferably AgNO ₃ solutions;

Preferably, the cross-linking agent in the step ⑥ can be selected from dialdehydes, and the dialdehydes can be glutaraldehyde, adipaldehyde, glyoxal, malondialdehyde, etc.;

A third object of the present invention is to provide a humidity sensor utilizing the humidity-sensitive composite film as a sensitive material, the humidity sensor has a substrate, and the substrate can be a ceramic substrate, a glass substrate, an ITO substrate, a silicon chip substrate There are many pairs of interdigitated gold electrodes on the surface of the substrate by photolithography and evaporation, and lead wires are connected on the interdigitated gold electrodes, and film-forming means such as dip coating, spin coating, and drop coating are applied on the substrate and the interdigitated gold electrodes. A polyelectrolyte film with a cross-linked structure and a conductive metal nanoparticle film deposited on the surface are deposited on the surface. The polyelectrolyte film with a cross-linked structure is a polymer containing a pyridine ring. The ammonium reaction is obtained, and the conductive metal nano particle film is prepared by an in-situ reduction cross-linking method, which is obtained through an in-situ reduction cross-linking reaction between a mixed solution of a metal salt and a polymer and a cross-linking agent. The humidity sensor of the present invention can be widely used in industrial and agricultural production, warehousing, meteorology, electricity safety and protection, and the detection and control of environmental humidity in daily life, especially for the detection and control of humidity in low-humidity environments such as insulating gas SF6 in transformer boxes. Sensitive detection.

The beneficial effects of the present invention are:

1. The present invention constructs a novel double-layer moisture-sensitive composite film, wherein the polyelectrolyte film has a sensitive response to humidity, which can improve the sensitivity of the composite film to humidity; the conductive metal nanoparticle film plays a role in reducing impedance, It can improve the conductivity of the material, especially the conductivity in low humidity environment; the moisture sensitive composite film obtained after the combination of the two layers of film can reduce the impedance (<1 megohm) in low humidity environment, avoiding the high impedance This leads to problems that cannot be measured, and at the same time has good sensitivity (under the environment of 1-30%RH, the impedance change rate can reach 2000%). This is currently one of the most sensitive devices under low humidity conditions in the world, and can successfully realize sensitive detection of humidity in low humidity environments.

2. In the double-layer structure, the reduction of the conductive metal nanoparticle layer and the introduction of a cross-linked structure can effectively avoid the agglomeration of the metal nanoparticles and ensure that a good conductive path can be formed in the conductive metal nanoparticle layer without making the conductive metal nanoparticle layer Metal nanoparticles agglomerate, resulting in a short circuit that cannot reflect the humidity response. The polyelectrolyte membrane and the conductive metal nanoparticle film interact synergistically to form a conductive network, and the conductive network acts simultaneously with the ion conduction of the polyelectrolyte membrane and the electronic conduction of the conductive metal nanoparticle film, accompanied by There is a tunneling effect, and the polyelectrolyte film and the conductive metal nanoparticle film respectively form a conductive channel.

3. The double-layer structure moisture-sensitive composite membrane, the polyelectrolyte membrane uses a cross-linked quaternization reagent as a cross-linking agent to realize the cross-linked quaternization of polymers containing pyridine rings, which can provide the necessary quaternary ammonium salt for the conductive process Ions, the conductive metal nanoparticle film adopts the crosslinking agent to crosslink the polymer to form a crosslinked network structure, which can effectively improve the distribution uniformity of the conductive metal nanoparticle in the conductive metal nanoparticle film. The two layers of films both have a cross-linked structure, which can effectively improve the stability of the moisture-sensitive composite film.

4. Electrostatic spraying of conductive metal nanoparticles or direct compounding with polyelectrolyte will cause the conductivity of the material to decrease instead, while the conductive metal nanoparticles formed by the in-situ reduction method of the present invention are evenly distributed and are sensitive films in a discontinuous state. The applicant unexpectedly discovered that the flat but non-dense structure conductive network thus formed can greatly improve the conductivity of the moisture-sensitive composite film, thereby ensuring that the material has sufficient conductivity under low humidity, and is suitable for humidity detection in low humidity environments. Foundation. And because the preparation method is in-situ reduction, the method has many advantages such as good controllability, mild reaction conditions, uniform reduction degree, less cross-linking agent consumption, and reduced environmental pollution.

5. The moisture absorption response time of the moisture sensor comprising the moisture sensitive composite film of the present invention can be significantly shortened, and the moisture absorption time only needs 20-30 seconds.

6. The ultraviolet surface plasmon resonance spectra of conductive metal nanoparticles film and polyelectrolyte film show that there is a strong interaction between conductive metal nanoparticles and polyelectrolyte, and this synergistic effect can be used to improve the conductivity and promote different Charge migration under humidity, there is a very close synergy between the two, accompanied by tunneling effect, which is not found in the previous work of the present invention.

Description of drawings

Fig. 1 is the cross-sectional scanning electron micrograph of the sensor with the humidity-sensitive composite film that is made by the method of the present invention;

Fig. 2 is the scanning electron micrograph of the surface morphology of the conductive metal nanoparticle film made by the method of the present invention;

Fig. 3 is the moisture-sensitive response curve of the moisture-sensitive composite film prepared by the inventive method;

Fig. 4 is the response cycle test result diagram of the moisture-sensitive composite film of the present invention for different humidity;

Fig. 5 is a graph showing the response test results of the moisture-sensitive composite film of the present invention to a low-humidity environment.

Detailed ways

the

Further illustrate the present invention below in conjunction with accompanying drawing and embodiment.

Example 1

The preparation method of moisture-sensitive composite film of the present invention comprises the following steps:

① Prepare a mixed solution of poly(4-vinylpyridine) and polyvinyl butyral, the concentration of poly(4-vinylpyridine) is 36 mg/mL, and the concentration of polyvinyl butyral is 5 mg/mL;

②Add poly(4-vinylpyridine) 1,4-dibromobutane with a molar ratio of 2 times, and age for 10 h to form a mixed solution;

③After drying the mixed solution in step ② to form a film, heat at 110°C for 10 h to prepare the first layer of polyelectrolyte membrane;

④ Prepare a mixed solution of silver nitrate and polyvinyl alcohol, the concentration of silver nitrate is 0.05mol/L, and the concentration of polyvinyl alcohol is 30mg/mL;

5. the mixed solution in step 4. is formed into a film on the polyelectrolyte membrane and dried;

⑥ Under the environment of glutaraldehyde, the in situ reductive cross-linking reaction was carried out at 100 °C for 6 h to prepare the moisture-sensitive composite film.

The steps of ①～⑥ can be used to form a film on a ceramic substrate to make a sensor with the moisture-sensitive composite film as a functional layer; the cross-sectional view of the sensor is shown in Figure 1, and the moisture-sensitive composite film of the present invention is made A polyelectrolyte membrane with a cross-linked quaternized structure and a conductive metal nanoparticle film are composed together. The polyelectrolyte membrane with a cross-linked quaternized structure is synthesized by poly(4-vinylpyridine) and 1,4-dibromo The butane cross-linking quaternization reaction is obtained, and the conductive metal nano-particle film is prepared by in-situ reducing cross-linking reaction with glutaraldehyde after forming a film from a mixed solution of silver nitrate and polyvinyl alcohol.

The surface morphology of the prepared humidity-sensitive composite film is shown in Figure 2. The metal nanoparticles are evenly distributed and uniform in size. The prepared humidity-sensitive composite film has excellent humidity-sensitive characteristics, and its response to humidity is shown in Figure 3. As shown, the response figure to low humidity (1%-30%RH) conditions is as shown in Figure 5, and it can be seen that the humidity information under the low-humidity environment can be sensitively detected by the described humidity-sensitive composite film, and the humidity information in the range of 1%-30%RH Inside, use the formula The sensitivity S=2000% can be calculated. In addition, the response cycle diagram of the moisture-sensitive composite film is shown in FIG. 4 . It can be seen that it has good stability and recovery, and its moisture absorption response time only needs 20-30 s through calculation.

Comparative Example 1

① Prepare a mixed solution of poly(4-vinylpyridine) and polyvinyl butyral, the concentration of poly(4-vinylpyridine) is 36 mg/mL, and the concentration of polyvinyl butyral is 5 mg/mL;

②Add poly(4-vinylpyridine) 1,4-dibromobutane with a molar ratio of 2 times, and age for 10 h to form a mixed solution;

③After drying the mixed solution in step ② to form a film, heat at 110°C for 10 h to prepare the first layer of polyelectrolyte membrane;

4. prepare silver nitrate solution, the concentration of silver nitrate is 0.05mol/L;

5. the solution in step 4. is formed into a film on the polyelectrolyte membrane and dried;

⑥ Under the environment of glutaraldehyde, the in situ reductive cross-linking reaction was carried out at 100 °C for 6 h to prepare the moisture-sensitive composite film.

Detect the impedance and the sensitivity of the moisture-sensitive composite film that Comparative Example 1 makes: the impedance of the moisture-sensitive composite film obtained under low humidity (≤30%RH) conditions is very low, only less than 1 thousand ohms, but the humidity-sensitive The composite film has almost no response to humidity, and its sensitivity is only 10% in the range of 1%-90%RH; the difference between this comparative example and Example 1 is that no polyvinyl alcohol is added in step ④, and no conductive The polymer cross-linking network in the metal nanoparticle film results in extremely low sensitivity of the moisture-sensitive composite film, indicating that the polymer cross-linking network has a great contribution to the sensitivity of the moisture-sensitive composite film.

Comparative Example 2

① Prepare a mixed solution of poly(4-vinylpyridine) and polyvinyl butyral, the concentration of poly(4-vinylpyridine) is 36 mg/mL, and the concentration of polyvinyl butyral is 5 mg/mL;

②Add poly(4-vinylpyridine) 1,4-dibromobutane with a molar ratio of 2 times, and age for 10 h to form a mixed solution;

③After drying the mixed solution in step ② to form a film, heat at 110°C for 10 h to prepare the first layer of polyelectrolyte membrane;

4. prepare the mixed solution of graphene and polyvinyl alcohol, the concentration of graphene is 3mg/mL, the concentration of polyvinyl alcohol is 30mg/mL;

5. the mixed solution in step 4. is formed into a film on the polyelectrolyte membrane and dried;

⑥ Under the environment of glutaraldehyde, the in situ reductive cross-linking reaction was carried out at 100 °C for 6 h to prepare the moisture-sensitive composite film.

Detect the impedance and the sensitivity of the moisture-sensitive composite film that Comparative Example 2 makes: the impedance of the moisture-sensitive composite film obtained is low under low humidity (≤30%RH) conditions, only less than 10 megohms, but the moisture-sensitive The composite membrane has almost no response to humidity, and its sensitivity is only 175% in the range of 1%-30%RH. The difference between this comparative example and Example 1 is that in step ④, no soluble salt of conductive metal is added, but graphene with the best conductivity among carbon materials is added, and no conductive metal nanoparticles are formed, resulting in wet The sensitivity of the sensitive composite film is very low, indicating that the conductive metal nanoparticles have a great contribution to the sensitivity of the moisture-sensitive composite film.

Comparative Example 3

① Prepare a mixed solution of poly(4-vinylpyridine) and polyvinyl butyral, the concentration of poly(4-vinylpyridine) is 36 mg/mL, and the concentration of polyvinyl butyral is 5 mg/mL;

②Add poly(4-vinylpyridine) 1,4-dibromobutane with a molar ratio of 2 times, and age for 10 h to form a mixed solution;

③After drying the mixed solution in step ② to form a film, heat at 110°C for 10 h to prepare the first layer of polyelectrolyte membrane;

④ Prepare a mixed solution of carbon nanotubes and polyvinyl alcohol, the concentration of carbon nanotubes is 5 mg/mL, and the concentration of polyvinyl alcohol is 30 mg/mL;

5. the mixed solution in step 4. is formed into a film on the polyelectrolyte membrane and dried;

⑥ In the glutaraldehyde environment, the in situ reduction exchange reaction was carried out at a temperature of 100 ° C for 6 h to prepare a moisture-sensitive composite film.

Detect the impedance and the sensitivity of the moisture-sensitive composite film obtained in Comparative Example 3: the impedance of the obtained moisture-sensitive composite film under low humidity (≤30%RH) conditions is low, less than 10 megohms, but the humidity-sensitive composite film The membrane barely responded to humidity, with a sensitivity of only 130% in the 1%-30%RH range. The difference between this comparative example and Example 1 is that in step ④, no soluble salt of conductive metal is added, but carbon nanotubes with better conductivity in carbon materials are added, and no conductive metal nanoparticles are formed, resulting in The sensitivity of the moisture-sensitive composite film is very low, indicating that the conductive metal nanoparticles have a great contribution to the sensitivity of the moisture-sensitive composite film.

Comparative Example 4

① Prepare a mixed solution of poly(4-vinylpyridine) and polyvinyl butyral, the concentration of poly(4-vinylpyridine) is 36 mg/mL, and the concentration of polyvinyl butyral is 5 mg/mL;

②Add poly(4-vinylpyridine) 1,4-dibromobutane with a molar ratio of 2 times, and age for 10 h to form a mixed solution;

③After drying the mixed solution in step ② to form a film, heat at 110°C for 10 h to prepare the first layer of polyelectrolyte membrane;

④ Prepare a mixed solution of silver nitrate and polyvinyl alcohol, the concentration of silver nitrate is 0.05mol/L, and the concentration of polyvinyl alcohol is 350mg/mL;

5. the mixed solution in step 4. is formed into a film on the polyelectrolyte membrane and dried;

⑥ Under the environment of glutaraldehyde, the in situ reductive cross-linking reaction was carried out at 100 °C for 6 h to prepare the moisture-sensitive composite film.

Detect the impedance and the sensitivity of the moisture-sensitive composite membrane that comparative example 4 makes: the impedance of the moisture-sensitive composite membrane obtained under low humidity (≤30%RH) condition is very high, reaches tens of megohms, at 1%-30% In the RH range, its sensitivity is only 470%. The difference between this comparative example and Example 1 is that an excessive amount (350 mg/mL) of polyvinyl alcohol was added in step ④ to form an excessive polymer cross-linked network, resulting in high impedance but low sensitivity, indicating that The amount of polymer cross-linked network has a great influence on the resistance and sensitivity of the moisture-sensitive composite membrane.

Comparative Example 5

① Prepare a mixed solution of poly(4-vinylpyridine) and polyvinyl butyral, the concentration of poly(4-vinylpyridine) is 36 mg/mL, and the concentration of polyvinyl butyral is 5 mg/mL;

② Add poly(4-vinylpyridine) 1,4-dibromobutane with a molar ratio of 2 times to obtain mixed solution A;

3. prepare the mixed solution of silver nitrate and polyvinyl alcohol, the concentration of silver nitrate is 0.05mol/L, the concentration of polyvinyl alcohol is 350mg/mL, obtains mixed solution B;

④ mixing the mixed solution A and the mixed solution B to obtain the mixed solution C, aging for 5h;

⑤The mixed solution C in step ④ is formed into a film and dried;

⑥ Under the environment of glutaraldehyde, the in situ reductive cross-linking reaction was carried out at 100 °C for 6 h to prepare the moisture-sensitive composite film.

Detect the impedance and the sensitivity of the moisture-sensitive composite membrane that comparative example 5 makes: the impedance of the moisture-sensitive composite membrane obtained is very high under low humidity (≤30%RH) conditions, reaching tens of megohms, at 1%-30% In the RH range, its sensitivity is only 340%. The difference between this comparative example and Example 1 is that the polyelectrolyte membrane and the conductive metal nanoparticle membrane are made into a one-layer membrane structure instead of a double-layer structure. The synergistic effect of has a great influence on the impedance and sensitivity of the moisture-sensitive composite film.

Example 2

① Prepare a mixed solution of poly(2-vinylpyridine) and polyvinyl alcohol, the concentration of poly(2-vinylpyridine) is 5 mg/mL, and the concentration of polyvinyl alcohol is 100 mg/mL;

② Add 1,5-dibromopentane with a molar ratio of 0.2 times poly(2-vinylpyridine), and age for 48 h to form a mixed solution;

③ After drying the mixed solution in step ② to form a film, heat at 40°C for 48 h to prepare the first layer of polyelectrolyte membrane;

④ prepare a mixed solution of copper sulfate and polyethylene glycol, the concentration of copper sulfate is 0.005mol/L, and the concentration of polyethylene glycol is 300mg/mL;

5. the mixed solution in step 4. is formed into a film on the polyelectrolyte membrane and dried;

⑥ Under the environment of adipaldehyde, carry out in situ reductive cross-linking reaction for 48 hours at a temperature of 10°C to prepare a moisture-sensitive composite film.

The resulting moisture-sensitive composite film has a low impedance of less than 10 megohms under low humidity (≤30%RH) conditions, and has a good response to humidity. In the range of 1%-30%RH, its sensitivity reaches 1160 %.

Example 3

① Prepare a mixed solution of poly(4-vinylpyridine) and polyvinylpyrrolidone, the concentration of poly(4-vinylpyridine) is 400 mg/mL, and the concentration of polyvinylpyrrolidone is 0.5 mg/mL;

② Add 1,6-dibromohexane with a molar ratio of 15 times poly(4-vinylpyridine), and age for 0.5 h to form a mixed solution;

③After drying the mixed solution in step ② to form a film, heat at 200°C for 0.2 h to prepare the first layer of polyelectrolyte membrane;

④ Prepare a mixed solution of chloroauric acid (H[AuCl ₄ ]) and polypropylene glycol, the concentration of chloroauric acid is 1mol/L, and the concentration of polypropylene glycol is 3mg/mL;

5. the mixed solution in step 4. is formed into a film on the polyelectrolyte membrane and dried;

⑥ Under the environment of malondialdehyde, in situ reductive cross-linking reaction was carried out at 200 °C for 0.1 h to prepare the moisture-sensitive composite film.

The obtained moisture-sensitive composite film has a low impedance under low humidity (≤30%RH) conditions, no more than 10 megohms, and has a good response to humidity. In the range of 1%-30%RH, its sensitivity reaches 1350 %.

Example 4

① Prepare a mixed solution of poly(2-vinylpyridine) and polyvinyl butyral, the concentration of poly(2-vinylpyridine) is 72 mg/mL, and the concentration of polyvinyl butyral is 75 mg/mL;

② Add poly(2-vinylpyridine) 1,4-dichlorobutane with a molar ratio of 4 times, and age for 5 h to form a mixed solution;

③ After drying the mixed solution in step ② to form a film, heat at 50°C for 20 h to prepare the first layer of polyelectrolyte membrane;

④ Prepare a mixed solution of silver nitrate, polylactic acid and its copolymer, the concentration of silver nitrate is 0.1mol/L, and the concentration of polylactic acid and its copolymer is 100mg/mL;

5. the mixed solution in step 4. is formed into a film on the polyelectrolyte membrane and dried;

⑥ Under the environment of glyoxal, carry out the in-situ reductive cross-linking reaction at 120°C for 8 hours to prepare the moisture-sensitive composite film.

The obtained moisture-sensitive composite film has a low impedance under low humidity (≤30%RH) conditions, no more than 10 megohms, and has a good response to humidity. In the range of 1%-30%RH, its sensitivity reaches 1660 %.

Example 5

① Prepare a mixed solution of poly(4-vinylpyridine) and polyvinyl butyral, the concentration of poly(4-vinylpyridine) is 144 mg/mL, and the concentration of polyvinyl butyral is 200 mg/mL;

②Add poly(4-vinylpyridine) 1,4-dibromobutane with a molar ratio of 3 times, and age for 3 h to form a mixed solution;

③ After drying the mixed solution in step ② to form a film, heat at 180°C for 5 h to prepare the first layer of polyelectrolyte membrane;

④ Prepare a mixed solution of silver nitrate and polyvinyl alcohol, the concentration of silver nitrate is 0.01mol/L, and the concentration of polyvinyl alcohol is 150mg/mL;

5. the mixed solution in step 4. is formed into a film on the polyelectrolyte membrane and dried;

⑥ Under the environment of glutaraldehyde, the in situ reductive cross-linking reaction was carried out at 150 °C for 4 h to prepare the moisture-sensitive composite film.

The obtained moisture-sensitive composite film has a low impedance under low humidity (≤30%RH) conditions, no more than 10 megohms, and has a good response to humidity. In the range of 1%-30%RH, its sensitivity reaches 1100 %.

Example 6

① Prepare a mixed solution of poly(4-vinylpyridine) and polyvinyl butyral, the concentration of poly(4-vinylpyridine) is 288 mg/mL, and the concentration of polyvinyl butyral is 50 mg/mL;

② Add poly(4-vinylpyridine) 1,4-dibromobutane with a molar ratio of 12 times, and age for 1 h to form a mixed solution;

③After drying the mixed solution in step ② to form a film, heat at 180°C for 24 hours to prepare the first layer of polyelectrolyte membrane;

④ Prepare a mixed solution of copper sulfate and polylactic acid, the concentration of silver nitrate is 0.8mol/L, and the concentration of polylactic acid is 200mg/mL;

5. the mixed solution in step 4. is formed into a film on the polyelectrolyte membrane and dried;

⑥ Under the environment of glutaraldehyde, the in situ reduction cross-linking reaction was carried out at 130 °C for 8 h to prepare the moisture-sensitive composite film.

The obtained moisture-sensitive composite film has a low impedance under low humidity (≤30%RH) conditions, no more than 10 megohms, and has a good response to humidity. In the range of 1%-30%RH, its sensitivity reaches 1850 %.

The above embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims (10)

1. a wet sensitive composite membrane, it is characterized in that: described wet sensitive composite membrane is made up of the polyelectrolyte film with cross-linked structure and the conducting metal film of nanoparticles be deposited thereon, described conducting metal film of nanoparticles is that cross-linked network structure polymkeric substance and the conducting metal nano particle be dispersed in described cross-linked network structure polymkeric substance are formed jointly.

2. wet sensitive composite membrane according to claim 1, is characterized in that: described conducting metal film of nanoparticles is obtained by in-situ reducing cross-linking method.

3. wet sensitive composite membrane according to claim 2, it is characterized in that: described in-situ reducing cross-linking method comprises the steps: the mixed solution of preparing metal salt and polymkeric substance, after film forming, reducing metal ions is become conducting metal nano particle, and make polymkeric substance generation cross-linking reaction, obtain conducting metal film of nanoparticles.

4. wet sensitive composite membrane according to claim 1, is characterized in that: impedance rate of change >=1000% of described wet sensitive composite membrane in the low humidity interval of 1%RH-30%RH.

5. wet sensitive composite membrane according to claim 1, is characterized in that conductivity>=5 × 10 of described conducting metal ⁶sm ^-1.

6. wet sensitive composite membrane according to claim 1, is characterized in that: described conducting metal is selected from Au, Ag, Cu.

7. wet sensitive composite membrane according to claim 1, is characterized in that: described polymkeric substance is the polymkeric substance of hydroxyl in repetitive.

8. the wet sensitive composite membrane according to any one of claim 1-7, is characterized in that: described polyelectrolyte film is the polymer film containing pyridine ring with crosslinked quaternized structure.

9. the preparation method of wet sensitive composite membrane described in claim 2, is characterized in that comprising the steps:

1) prepare polyelectrolyte precursor solution, then add crosslinked quaternizing agent and obtain mixed solution, heat-treated after described mixed solution film forming, the obtained polyelectrolyte film with crosslinked quaternary ammoniated structure;

2) mixed solution of preparing metal salt and polymkeric substance, in step 1) obtained by polyelectrolyte film on film forming, then in-situ reducing be cross-linked, obtain wet sensitive composite membrane.

10. a humidity sensor, is characterized in that: described sensor comprises the wet sensitive composite membrane described in any one of claim 1-8.