Phosphine-containing poison gas sensor with ultrahigh sensitivity

Abstract

The invention discloses a phosphine-containing poison gas sensor with ultrahigh sensitivity. The phosphine-containing poison gas sensor comprises a piezoelectric substrate; the first interdigital transducer is arranged on the piezoelectric substrate; the second interdigital transducer is arranged on the piezoelectric substrate and is symmetrical to the first interdigital transducer in position; the layered bimetal hydroxide sensitive film is arranged on a surface acoustic wave propagation path between the first interdigital transducer and the second interdigital transducer; the layered bimetal hydroxide sensitive film is used for adsorbing the phosphine-containing poison gas so as to change the resistance value and the mass of the layered bimetal hydroxide sensitive film, change the distribution of an electric field and a force field which are propagated on the surface of the acoustic wave, change the propagation wave velocity of the acoustic surface wave, and decouple from the wave velocity change to obtain the concentration information of the phosphine-containing poison gas. Therefore, the sensitivity of the sensor is greatly improved by utilizing the principle that a large number of alkaline sites of layered double hydroxides (LDHs) have relatively strong adsorption force on phosphine-containing poison gas molecules. The sensor can realize rapid and high-sensitivity detection of phosphine-containing poison gas.

Description

Technical Field

[0001] The invention relates to the technical field of surface acoustic wave gas sensors, and in particular to a phosphine-containing poison gas sensor with ultra-high sensitivity. Background Art

[0002] Chemical gases are highly toxic chemicals that can cause fatal damage to organisms even at extremely low concentrations. Phosphine-containing chemical gases (such as sarin, VX, etc.) are one of the most deadly chemical gases, which can cause irreversible damage to the nervous system within seconds, and exposure for a few minutes can lead to muscle paralysis, respiratory failure, and even death. This requires highly sensitive and rapid detection of phosphine-containing chemical gases. The main detection methods currently available can be divided into optical, semiconductor, and electrochemical methods based on different principles. Although each has its own advantages, they still have deficiencies in sensitivity and other aspects, and cannot reach ppb-level detection indicators at room temperature.

[0003] At present, the rapid monitoring of trace toxic gases is of great significance in the fields of national defense, public safety prevention and control, environmental protection, industrial process monitoring, etc. There are many types of related gas detection technologies, among which surface acoustic wave (SAW) technology has attracted widespread attention with its high sensitivity, fast response, wide detection range, low power consumption, small size and high reliability. The working principle of the surface acoustic wave gas sensor is that the sensitive film on the channel between the input interdigital transducer and the output interdigital transducer adsorbs the gas to be measured, causing the change of the speed of the surface acoustic wave sensor, thereby causing the change of the output and input frequency, causing the drift of the surface acoustic wave oscillation frequency, so as to realize the detection of the gas to be measured.

[0004] Similarly, the surface acoustic wave sensor for phosphine-containing gas mainly takes the form of a combination of a surface acoustic wave device and a sensitive film. The reversible physical adsorption of the sensitive film on the phosphine-containing gas molecules causes its density and conductivity to change, and the propagation speed of the surface acoustic wave is changed through mass load and acoustic-electric coupling effect, thereby changing the observable electrical signal. The target gas can be detected and identified by collecting and processing the electrical signal. Although the surface acoustic wave sensor for phosphine-containing gas has a large and relatively stable response to phosphine-containing gas, its response sensitivity still needs to be further improved. Summary of the invention

[0005] To this end, an embodiment of the present application provides a phosphine-containing toxic gas sensor with ultra-high sensitivity, which can achieve rapid and highly sensitive detection of phosphine-containing toxic gases.

[0006] To this end, the following technical solutions are adopted in the embodiments of the present application:

[0007] A phosphine-containing poisonous gas sensor with ultra-high sensitivity comprises: a piezoelectric substrate; a first interdigital transducer arranged on the piezoelectric substrate; a second interdigital transducer arranged on the piezoelectric substrate and symmetrically arranged with the first interdigital transducer; a layered double hydroxide sensitive film arranged on the surface acoustic wave propagation path between the first interdigital transducer and the second interdigital transducer; the layered double hydroxide sensitive film is used to adsorb the phosphine-containing poisonous gas to change its own resistance value and mass, induce changes in the electric field and force field distribution of the surface acoustic wave propagation, change the propagation velocity of the surface acoustic wave, and decouple the concentration information of the phosphine-containing poisonous gas from the velocity change. In this way, the sensitivity of the sensor is greatly improved by utilizing the principle that a large number of alkaline sites of layered double hydroxide (LDH) have a strong adsorption force on phosphine-containing poisonous gas molecules.

[0008] As a feasible implementation, the layered double hydroxide sensitive film is prepared by uniformly mixing a metal salt solution and an alkaline solution and then drying them.

[0009] As an achievable implementation, the metal salt solution includes a divalent metal salt and a trivalent metal salt; wherein the divalent metal salt includes any one of magnesium nitrate, magnesium sulfate and magnesium chloride; wherein the trivalent metal salt includes any one of aluminum nitrate, aluminum sulfate and aluminum chloride.

[0010] As an achievable implementation method, the molar ratio of the divalent metal salt to the trivalent metal salt is 1: 1-4: 1. In this way, by adjusting the molar ratio of the divalent metal salt to the trivalent metal salt in LDH, the number of basic sites on the surface of the LDH material is increased, and its adsorption capacity for phosphine-containing poisonous gas molecules is further improved, greatly improving the sensitivity of the sensor.

[0011] As an achievable implementation manner, the alkaline solution is a mixed solution of NaOH and Na2CO3, and the molar ratio of NaOH to Na2CO3 is 10:1.

[0012] As an achievable implementation method, the layered double metal hydroxide sensitive film is prepared by the following method:

[0013] Dissolve a divalent metal salt and a trivalent metal salt in a molar ratio of 1:1-4:1 in 120 ml of H2O to obtain a metal salt solution;

[0014] The alkaline solution was prepared by dissolving NaOH and Na2CO3 in a molar ratio of 10:1 in 120 ml of H2O;

[0015] Using the nucleation crystallization isolation method, firstly, the salt solution and the alkaline solution are added dropwise to the colloid mill at 2000-5000 rpm by a flow pump, and the obtained slurry is transferred to a beaker after being evenly mixed, and is continuously stirred and heated to 50-100°C and kept warm for 2-10 hours. After cooling to room temperature 25°C, the obtained precipitate is centrifuged and washed with H2O and ethanol for multiple times until the pH value is 7, and dried at 60°C to obtain MgAl-LDH nanosheets;

[0016] The prepared MgAl-LDH nanosheets are dissolved in distilled water and ultrasonically treated for more than 30 seconds; the MgAl-LDH solution is plated on the sound propagation path of the surface acoustic wave sensor by drop coating or spin coating, and after the distilled water evaporates, a MgAl-LDH film is prepared, which is a layered double hydroxide sensitive film.

[0017] In this embodiment, the layered double hydroxide sensitive film (LDH) is synthesized by colloidal grinding and dispersed in distilled water; ultrasonic oscillation is performed for more than 10 seconds to eliminate the agglomeration of LDH; and the LDH is plated on the surface acoustic wave propagation path between the first interdigital transducer and the second interdigital transducer of the delay line of a surface acoustic wave detection delay line sensor device by drop coating or spin coating, and the large specific surface area and abundant alkaline active sites of the layered double hydroxide are used to achieve ultra-high sensitive phosphine-containing toxic gas sensing response.

[0018] As a feasible implementation, the surface acoustic wave sensor is a delay line structure, and the operating frequency is 200 MHz.

[0019] As an achievable implementation, the piezoelectric substrate is a piezoelectric substrate made of quartz material that is rotated 35° around the Y direction and propagates along the X direction. The temperature coefficient of the piezoelectric substrate at 20-50°C is 0 ppm / °C, and the temperature stability is good.

[0020] As a feasible implementation manner, both the first IDT and the second IDT use aluminum electrodes, and the electrode film thickness is 45 to 200 nanometers.

[0021] As an achievable implementation method, the surfaces of the first interdigital transducer and the second interdigital transducer are respectively covered with a SiO2 film for protection, and the SiO2 film is arranged on the piezoelectric substrate by low-temperature ion beam sputtering or high-temperature plasma enhanced chemical vapor deposition (PECVD), and the thickness of the SiO2 film is 35 to 55 nanometers.

[0022] As an achievable implementation, the first interdigital transducer and the second interdigital transducer both adopt a unidirectional single-phase transducer structure, the number of interpolation pairs is 19 pairs, the electrode width is λ / 2-λ / 4, the aperture size is 55λ, and λ is designed to be the wavelength of the surface acoustic wave. The use of a unidirectional single-phase transducer structure effectively achieves low loss of the sensor device, thereby helping to improve the stability of the sensor system and the detection limit.

[0023] In summary, the present application uses LDH film as a sensitive film and is plated on the surface acoustic propagation path of the surface acoustic wave sensor by drop coating or spin coating; LDH with high specific surface area and abundant alkaline sites enhances its adsorption capacity for phosphine-containing chemical gas molecules and combines with the acoustic-electric coupling effect of the surface acoustic wave sensor to achieve ultra-high sensitivity detection of phosphine-containing chemical gas at room temperature (temperature: 25°C, humidity: 18% RH). The test results show that at room temperature, the sensitivity of the sensor of the present invention can reach 2ppb. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the three-dimensional structure of a phosphine-containing poison gas sensor with ultra-high sensitivity provided in an embodiment of the present application;

[0025] Figure 2 The structure and transmission electron microscope morphology of the layered double hydroxide sensitive film in Example 1 of the present invention;

[0026] Figure 3 This is the response speed test result of the sensor in Example 1 of the present invention.

[0027] In the figure, 1, piezoelectric substrate; 2, first interdigital transducer; 3, second interdigital transducer; 4, layered double hydroxide sensitive film. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0029] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0031] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0033] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0034] Figure 1 FIG. 1 shows a schematic diagram of the three-dimensional structure of a phosphine-containing poison gas sensor with ultra-high sensitivity provided in an embodiment of the present application. Figure 1As shown, the sensor is a surface acoustic wave sensor, the device structure is a delay line structure, the operating frequency is 200MHz, and specifically includes a piezoelectric substrate 1 and a first interdigital transducer 2, a second interdigital transducer 3 and a layered double metal hydroxide sensitive film 4 arranged on the piezoelectric substrate 1.

[0035] Among them, the piezoelectric substrate 1 serves as the base of the entire sensor, and all components use it as a platform for installation. Exemplarily, the piezoelectric substrate 1 is a rectangular parallelepiped structure, and the first interdigital transducer 2 and the second interdigital transducer 3 are symmetrically arranged on the piezoelectric substrate 1, and can be electrically connected to the peripheral circuit respectively. It should be noted that the interdigital transducer is a metal pattern shaped like the crossed fingers of two hands formed on the surface of the piezoelectric substrate 1, and its function is to realize acoustic-electric transduction. The working principle of the surface acoustic wave sensor is: when an alternating electric signal is applied to the input end of a group of interdigital transducers on the piezoelectric substrate 1, a periodically distributed electric field will be generated. Due to the inverse piezoelectric effect, corresponding elastic deformation will be excited near the surface of the piezoelectric medium, thereby causing the vibration of the solid particles and forming a surface acoustic wave propagating along the surface of the substrate. When the surface acoustic wave is transmitted to the other end of the piezoelectric medium, due to the positive piezoelectric effect, charges will be generated at both ends of the metal electrode, so that another group of interdigital transducers can be used to output an alternating electric signal.

[0036] For example, the layered double hydroxide sensitive film 4 can be coated on the surface acoustic wave propagation path between the first interdigital transducer 2 and the second interdigital transducer 3 by drop coating or spin coating. The layered double hydroxide sensitive film 4 has the characteristics of high specific surface area and abundant alkaline sites, which improves its adsorption capacity for phosphine-containing chemical gas molecules. Combined with the acoustic-electric coupling effect of the surface acoustic wave sensor, ultra-high sensitivity detection of phosphine-containing chemical gas is achieved at room temperature (25°C).

[0037] In one embodiment, the piezoelectric substrate 1 is a piezoelectric quartz crystal, lithium niobate, lithium tantalate or lanthanum gallium silicate with a Y-cut of 35°, and the specific material used for the piezoelectric substrate 1 is not limited to piezoelectric quartz, lithium niobate, lithium tantalate or lanthanum gallium silicate. Exemplarily, a piezoelectric crystal made of quartz material rotated 35° around the Y direction and propagated along the X direction is used as the material of the piezoelectric substrate 1; the temperature coefficient of the piezoelectric crystal at 20-50°C is 0ppm / °C, and the temperature stability is good.

[0038] In a specific embodiment, the length, width and height of the piezoelectric substrate are approximately 9 mm*4 mm*0.8 mm, and the first interdigital transducer 2 and the second interdigital transducer 3 are prepared by a peeling process on the surface of the 35-degree Y-cut piezoelectric substrate 1 .

[0039] Optionally, the IDT adopts a common bidirectional interdigital structure or a unidirectional single-phase transducer structure (SPUDTs). Exemplarily, in one embodiment, the first IDT 2 and the second IDT 3 have 80 pairs of fingers and 40 pairs of fingers respectively, the electrode material is aluminum, the electrode thickness is 150nm, and the IDT structure is a common bidirectional interdigital structure.

[0040] In another embodiment, the interdigital transducer structure is a SPUDTs structure, the interpolation pair number is 19 pairs, the electrode material is aluminum, the electrode thickness is 30nm, the electrode width is λ / 2-λ / 4, the aperture size is 55λ, and λ is designed to be the wavelength of the surface acoustic wave. For example, the operating frequency of the surface acoustic wave sensor of the present application is 200MHz, and the corresponding acoustic wave wavelength λ can be 17.2μm. Then the electrode width is 8.6-4.3μm, and the acoustic aperture size is 951.5μm.

[0041] Optionally, the first IDT 2 and the second IDT 3 are covered with a SiO2 film (not shown) to protect the IDT, and the thickness of the SiO2 film is 35 to 55 nanometers. Optionally, the SiO2 film can be covered on the upper surface of the piezoelectric substrate by low-temperature ion beam sputtering or high-temperature plasma enhanced chemical vapor deposition (PECVD) to wrap the first IDT 2 and the second IDT 3 to protect the first IDT 2 and the second IDT 3. It can be understood that when the surface of the first interdigital transducer 2 and the second interdigital transducer 3 is covered with a SiO2 film, the layered double hydroxide sensitive film 4 is located on the upper side of the SiO2 film, wrapping the first interdigital transducer 2 and the second interdigital transducer 3 again, and is used to adsorb target gas molecules (such as phosphine-containing poisonous gases) and produce mass load or acoustic-electric coupling effects on the SAW excited by the interdigital transducer, thereby causing a change in the SAW propagation speed.

[0042] Preferably, in this embodiment, the thickness of the SiO2 film is 40 nanometers.

[0043] In one embodiment, a layered double hydroxide sensitive film 4 (LDH) is synthesized by a colloidal milling method and dispersed in distilled water; ultrasonic oscillation is performed for more than 10 seconds to eliminate the agglomeration of LDH; and the film is plated on the surface acoustic wave propagation path between the first interdigital transducer 2 and the second interdigital transducer 3 of a delay line sensor device for detecting a surface acoustic wave by drop coating or spin coating.

[0044] Further preferably, the synthesis steps of the layered double hydroxide sensitive film 4 include: using the nucleation crystallization isolation method, first, through a flow pump, at 2000-5000rpm, the metal salt solution and the alkali solution are added dropwise to the colloid mill, and after mixing evenly, the resulting slurry is transferred to a beaker, and continuously stirred and heated to 50-100°C and kept warm for 2-10h. After cooling to room temperature, the obtained precipitate is centrifuged and washed with H2O and ethanol for multiple times until the pH value is about 7, and dried at 60°C to obtain LDH nanosheets.

[0045] Further preferably, the metal salt solution includes a divalent metal salt and a trivalent metal salt, wherein the divalent metal salt is any one of magnesium nitrate, magnesium sulfate, and magnesium chloride; the trivalent metal salt is any one of aluminum nitrate, aluminum sulfate, and aluminum chloride; the molar ratio of the divalent metal salt to the trivalent metal salt is 1:1-4:1. The alkaline solution is a mixed solution of NaOH and Na2CO3, and the molar ratio is 10:1.

[0046] Optionally, the molar ratio of the divalent metal salt to the trivalent metal salt may also be 1:1, 2:1, 3:1 or 4:1.

[0047] The technical solution of the present invention is described in detail below through preferred embodiments. It should be noted that the specific embodiments below are only used for illustration and are not used to limit the present invention.

[0048] Example 1

[0049] Embodiment 1 provides a phosphine-containing poison gas sensor with ultra-high sensitivity, with an operating frequency of 200MHz, a piezoelectric substrate using a Y-cut 35°X-propagation quartz piezoelectric crystal substrate, and the length, width and height of the piezoelectric substrate are about 9mm*4mm*0.8mm; a first interdigital transducer 2 and a second interdigital transducer 3 are prepared on the surface of a Y-cut 35-degree piezoelectric substrate 1 by a stripping process, the interdigital transducer structure is a SPUDTs structure, the interpolation pair number is 19 pairs, the electrode material used is aluminum, the electrode thickness is 30nm; the electrode width is 8.6-4.3μm, and the acoustic aperture size is 951.5μm. The film thickness of the SiO2 film is 40nm; a layered double metal hydroxide sensitive film 4 is deposited on the surface of the SiO2 film by spin coating or drop coating.

[0050] Specifically, the preparation method of the layered double metal hydroxide sensitive film 4 is as follows:

[0051] First, prepare the metal salt solution by dissolving 3.846 g Mg(NO3)2·6H2O (0.015 mol) and 1.407 g Al(NO3)3·9H2O (0.0037 mol) in 120 mL H2O. The molar ratio of 3.846 g Mg(NO3)2·6H2O (0.015 mol) and 1.407 g Al(NO3)3·9H2O (0.0037 mol) is 4:1.

[0052] Then, an alkaline solution was prepared by dissolving 1.5 g NaOH (0.0375 mol) and 0.398 g Na2CO3 (0.00376 mol) in 120 mL H2O, wherein the molar ratio of 1.5 g NaOH (0.0375 mol) and 0.398 g Na2CO3 (0.00376 mol) was 10:1.

[0053] Using the nucleation crystallization isolation method, first, the salt solution and the alkaline solution were added dropwise to the colloid mill at 3000 rpm through a flow pump. After mixing evenly, the resulting slurry was transferred to a beaker, stirred continuously and heated to 70°C and kept warm for 8 h. After cooling to room temperature (25°C), the obtained precipitate was centrifuged and washed with H2O and ethanol several times until the pH value was about 7, and dried at 60°C to obtain MgAl-LDH nanosheets.

[0054] Furthermore, the specific steps of coating are as follows: dissolving the prepared MgAl-LDH nanosheets in distilled water. To eliminate the agglomeration of the LDH material, the solution needs to be oscillated in an ultrasonic cleaner for more than 30 seconds. Using a micro-injector to drop-coat or a spin coater to spin-coat, the MgAl-LDH solution is plated on the sound propagation path of the acoustic surface device. After the distilled water evaporates, a MgAl-LDH film (double metal hydroxide sensitive film) is prepared.

[0055] Figure 2 The structure and transmission electron microscope morphology of the layered double hydroxide sensitive film 4 in Example 1 of the present invention. Figure 2 It can be seen that the MgAl-LDH film (magnesium aluminum layered double hydroxide film) has a typical layered structure, which is characterized by alternating layers of hydrated metal hydroxide and exchangeable anion layers. The basic unit of each layer of metal hydroxide is Mg 2+ and Al 3+ The ions are coordinated with the hydroxide ions (OH-) to form a layered structure. The layers are connected by water molecules (H2O) and exchangeable anions (such as Cl - 、NO3 -The MgAl-LDH film has a large specific surface area due to its layered structure, which is conducive to ion exchange and adsorption. This has great advantages for the adsorption of phosphine-containing poisonous gases. Figure 2 From the transmission electron microscope morphology image in the figure, we can see that the MgAl-LDH film prepared in Example 1 of the present application has a uniform film morphology. The transmission electron microscope (TEM) image shows the uniform distribution of the MgAl-LDH film and the obvious layered structure. Moreover, the layered stacking structure on the surface and cross section of the film can be observed from the figure, showing a clear interlayer gap. This layered structure gives the MgAl-LDH film excellent performance in sensors, especially in the monitoring of phosphine-containing toxic gases, so that the sensor in the present application has the characteristics of high sensitivity and fast response speed to phosphine-containing toxic gases at room temperature.

[0056] For example, Figure 3 The response speed test results of the sensor in Example 1 of the present invention are shown in Figure 1. Using dimethyl methyl phosphate (DMMP), a simulant of the phosphine-containing gas sarin, as the detection object at room temperature, under a nitrogen background, different concentrations of DMMP gas were introduced, namely 2ppb, 5ppb, 8ppb, 10ppb, and 15ppb, and the sensor obtained responses of 4.16mV, 10.37mV, 16.26mV, 20.2mV, and 25.04mV, respectively. It can be seen from the response curve that the sensor has a good response when the DMMP concentration is 2-15ppb. The response curve is enlarged to evaluate the response speed. It can be seen that the sensor responds to DMMP at a concentration of 2ppb in about 52 seconds.

[0057] Example 2

[0058] Example 2 also provides a phosphine-containing poison gas sensor with ultra-high sensitivity. The difference from Example 1 is that in the metal salt solution for preparing the layered double metal hydroxide sensitive film 4, the molar ratio of Mg(NO3)2·6H2O to Al(NO3)3·9H2O is 1:1, that is, Mg(NO3)2·6H2O is 0.9615g.

[0059] Example 3

[0060] Example 3 also provides a phosphine-containing poison gas sensor with ultra-high sensitivity. The difference from Example 1 is that in the metal salt solution for preparing the layered double metal hydroxide sensitive film 4, the molar ratio of Mg(NO3)2·6H2O to Al(NO3)3·9H2O is 2:1, that is, Mg(NO3)2·6H2O is 1.923g.

[0061] Example 4

[0062] Example 4 also provides a phosphine-containing poison gas sensor with ultra-high sensitivity. The difference from Example 1 is that in the metal salt solution for preparing the layered double metal hydroxide sensitive film 4, the molar ratio of Mg(NO3)2·6H2O to Al(NO3)3·9H2O is 3:1, that is, Mg(NO3)2·6H2O is 2.8845g.

[0063] Similarly, using dimethyl methyl phosphate (DMMP), a simulant of phosphine-containing gas sarin, as the detection object at room temperature, different DMMP gases with a concentration of 2ppb were introduced under a nitrogen background. The sensors of Examples 2-4 obtained responses of 6.38, 5.22, and 4.25mV, respectively. However, when evaluating the response speed, it can be seen that the response speed of the sensor in Examples 2-4 to DMMP with a concentration of 2ppb is approximately 88, 71, and 58 seconds. It can be seen that the molar ratio of the divalent metal salt and the trivalent metal salt in the metal salt solution can affect the sensitivity and response speed of the layered double metal hydroxide sensitive film 4 to phosphine-containing gas. This may be because by adjusting the molar ratio of the divalent metal salt and the trivalent metal salt, the number of alkaline sites on the surface of the LDH material can be increased, thereby improving its adsorption capacity for phosphine-containing gas molecules, thereby greatly improving the sensitivity of the sensor.

[0064] In summary, the present invention provides a phosphine-containing gas sensor with ultra-high sensitivity. A layered bimetallic compound is used as a gas-sensitive film, a low temperature coefficient Y35°X quartz is used as a piezoelectric crystal, and the film is plated on the surface of a surface acoustic wave device by drop coating or spin coating. The test results show that at room temperature, the sensor of the present invention has a detection sensitivity of 2ppb for dimethyl methyl phosphate (DMMP), a simulant of the phosphine-containing gas sarin.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application. Those skilled in the art should understand that, although the present application is described in detail with reference to the aforementioned embodiments, the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions in the embodiments of the present application.

Claims

1. A phosphine-containing poison gas sensor with ultra-high sensitivity, characterized in that: include: Piezoelectric substrate; A first interdigital transducer is disposed on the piezoelectric substrate; A second interdigital transducer is disposed on the piezoelectric substrate and is symmetrical with respect to the first interdigital transducer; A layered double hydroxide sensitive film is arranged on the surface acoustic wave propagation path between the first interdigital transducer and the second interdigital transducer; the layered double hydroxide sensitive film is used to adsorb phosphine-containing poisonous gases to change its own resistance value and mass, causing changes in the electric field and force field distribution of the surface propagation of acoustic waves, changing the propagation wave velocity of the surface acoustic wave, and decoupling the concentration information of the phosphine-containing poisonous gases from the wave velocity change.

2. The sensor according to claim 1, characterized in that The layered double metal hydroxide sensitive film is prepared by uniformly mixing a metal salt solution and an alkali solution and then drying the mixture.

3. The sensor according to claim 2, characterized in that The metal salt solution includes a divalent metal salt and a trivalent metal salt; wherein the divalent metal salt includes any one of magnesium nitrate, magnesium sulfate and magnesium chloride; and the trivalent metal salt includes any one of aluminum nitrate, aluminum sulfate and aluminum chloride.

4. The sensor according to claim 3, characterized in that The molar ratio of the divalent metal salt to the trivalent metal salt is 1:1-4:

1.

5. The sensor according to claim 2, characterized in that The alkaline solution is a mixed solution of NaOH and Na2CO3, and the molar ratio of NaOH to Na2CO3 is 10:

1.

6. The sensor according to any one of claims 1 to 5, characterized in that: The layered double metal hydroxide sensitive film is prepared by the following method: Dissolve a divalent metal salt and a trivalent metal salt in a molar ratio of 1:1-4:1 in 120 ml of H2O to obtain a metal salt solution; The alkaline solution was prepared by dissolving NaOH and Na2CO3 in a molar ratio of 10:1 in 120 ml of H2O; Using the nucleation crystallization isolation method, firstly, the salt solution and the alkaline solution are added dropwise to the colloid mill at 2000-5000 rpm by a flow pump, and the obtained slurry is transferred to a beaker after being evenly mixed, and is continuously stirred and heated to 50-100°C and kept warm for 2-10 hours. After cooling to room temperature 25°C, the obtained precipitate is centrifuged and washed with H2O and ethanol for multiple times until the pH value is 7, and dried at 60°C to obtain MgAl-LDH nanosheets; The prepared MgAl-LDH nanosheets are dissolved in distilled water and ultrasonically treated for more than 30 seconds; the MgAl-LDH solution is plated on the sound propagation path of the surface acoustic wave sensor by drop coating or spin coating, and after the distilled water evaporates, a MgAl-LDH film is prepared, which is a layered double hydroxide sensitive film.

7. The sensor according to any one of claims 1 to 5, characterized in that: The piezoelectric substrate is a piezoelectric substrate made of quartz material that is rotated 35° around the Y direction and propagates along the X direction.

8. The sensor according to any one of claims 1 to 5, characterized in that: The first interdigital transducer and the second interdigital transducer both use aluminum electrodes, and the electrode film thickness is 45 to 200 nanometers.

9. The sensor according to claim 8, characterized in that The surfaces of the first interdigital transducer and the second interdigital transducer are respectively covered with a SiO2 film for protection. The SiO2 film is arranged on the piezoelectric substrate by low-temperature ion beam sputtering or high-temperature plasma enhanced chemical vapor deposition (PECVD), and the thickness of the SiO2 film is 35 to 55 nanometers.

10. The sensor according to claim 8, characterized in that The first interdigital transducer and the second interdigital transducer both adopt a unidirectional single-phase transducer structure, with 19 interpolation pairs, an electrode width of λ / 2-λ / 4, an aperture size of 55λ, and λ is designed to be the wavelength of the surface acoustic wave.

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