A three-dimensional nano gas sensor

Abstract

The application relates to a three-dimensional nano gas sensor, which comprises a sensing layer capable of changing its electrical property based on the contact and sensing reaction of a gas to be detected; a catalytic layer for accelerating the process of changing the electrical property of the sensing layer when the sensing reaction occurs; a double-pass AAO nanotube for providing a carrier required for the deposition of the sensing layer and the catalytic layer and transferring the electrical parameter of the sensing layer; before the sensing layer and the catalytic layer are sequentially deposited on the inner wall of the double-pass AAO nanotube, the double-pass AAO nanotube is subjected to roughening treatment to encourage the sensing layer and the catalytic layer to be deposited and integrated on the inner wall surface of the double-pass AAO nanotube in a mismatched manner. The inner wall of the roughened AAO nanotube can block the close stacking tendency of the sensing particles during the deposition of the sensing particles, so that the sensing particles are irregularly arranged with gaps between the sensing particles, the pores between the sensing particles are increased, the gas to be detected can enter the sensing layer from the surface of the sensing layer through the pores to be detected, and the sensing efficiency of the sensing layer is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sensor devices, in particular to a three-dimensional nanometer gas sensor. BACKGROUND

[0002] In recent years, the media frequently report sudden toxic gas leakage events, and people are increasingly concerned about detecting toxic gas leaks. Toxic gases such as carbon monoxide, hydrogen sulfide, carbon dioxide, sulfur dioxide, etc. pose a significant threat to human health. However, due to the long testing time of traditional toxic gas detection methods, the testing instrument requires professional operation, the operation is complicated, and it is not easy to use on site, so it cannot be effectively promoted. In general, non-professionals need to use toxic gas detection devices, in order to be able to quickly detect toxic gases in a large area, it is required that the toxic gas detection device must have the characteristics of fast response speed, simple operation, miniaturization and portability.

[0003] Toxic gas detection involves gas sensor technology. Currently, there are many types of gas sensors, among which semiconductor gas sensors are widely used due to their advantages of easy miniaturization of integrated circuit design, low cost, large batch size, etc. However, most semiconductor gas sensors have a complex manufacturing process, high cost, low sensitivity at low gas concentration, poor stability, and can only detect a single toxic gas. This series of problems makes it difficult to apply to toxic gas detection devices.

[0004] In addition, today's society is developing faster and faster, wireless connection technology, network technology, and electronic technology are increasingly combined, and the requirements for intelligence and humanization are increasingly high. Combining gas sensors with wireless connection technology and network technology allows for simultaneous detection and real-time monitoring of toxic gases, greatly facilitating people's timely detection of toxic gases. Therefore, how to manufacture a miniature, reliable, portable, high-sensitivity, real-time monitoring of different toxic gas detection system has great significance.

[0005] Prior art such as patent document CN105900236B discloses a semiconductor sensor device comprising: a substrate; a non-conformal seed layer located above the substrate; at least one electrode located above the non-conformal seed layer; and a porous sensing layer directly supported by the non-conformal seed layer and in electrical communication with the at least one electrode, the porous sensing layer defining a plurality of grain boundaries formed using atomic layer deposition by spaced nucleation on the non-conformal seed layer.

[0006] CN106706728B discloses a high-sensitivity nitrogen dioxide sensor, comprising a cylindrical ceramic tube, ceramic end caps are inserted into the center of both ends of the ceramic tube, a spiral heating wire is arranged in the ceramic tube, both ends of the spiral heating wire are led out from the center hole of the ceramic end cap through wires, an Au reference electrode is arranged on the end face of one end of the ceramic tube, an Au working electrode is arranged on the end face of the other end of the ceramic tube, the Au working electrode is covered with a TiO sensitive electrode, Pt lead wires are respectively led out from the reference electrode and the sensitive electrode, a nano-indium tin oxide spray sintering layer is arranged on the outer periphery of the ceramic tube, a plurality of gold wires are arranged outside the spray sintering layer, and the gold wires are connected between the working electrode and the reference electrode. The sensor is not sensitive to water vapor, gasoline, carbon monoxide and other gases, is easy to manufacture, has high detection sensitivity, and can be used for detecting the concentration of NO2 in a gas environment.

[0007] The above application file provides a method for detecting gas by using a porous sensing layer to adsorb the to-be-detected gas and then generating a sensing reaction, and especially judging the type of the to-be-detected gas based on the change of the electrical property of the sensing layer. However, the specific surface area of the sensing layer that can contact and adsorb the to-be-detected gas molecules is small, and the change of the electrical property cannot accurately respond to the sensing reaction of the to-be-detected gas and the sensing layer. When the concentration of the to-be-detected gas molecules is low, the detection sensitivity is poor, the type of the to-be-detected gas molecules cannot be accurately measured, and only the sensing particles on the surface can contact the to-be-detected gas. The sensing particles inside cannot accommodate the to-be-detected gas for sensing due to the small intermolecular distance, and the sensing efficiency is low.

[0008] In addition, on the one hand, there are differences in the understanding of those skilled in the art; on the other hand, the inventor has studied a large number of literatures and patents when making the present application, but due to the limited space, all the details and contents are not listed in detail. However, this does not mean that the present application does not have these characteristics of the prior art. On the contrary, the present application has all the characteristics of the prior art, and the applicant reserves the right to add relevant prior art in the background art. SUMMARY

[0009] To solve at least one of the above problems in the prior art, the application provides a three-dimensional nano gas sensor, which comprises: a sensing layer, which can change its electrical properties based on the contact and sensing reaction of the gas to be detected; a catalytic layer, which is used to accelerate the process of changing the electrical properties of the sensing layer when the sensing layer undergoes a sensing reaction; a double-pass AAO nanotube, which is used to provide a carrier for the deposition of the sensing layer and the catalytic layer and transmit the electrical parameters of the sensing layer; and a roughening treatment is performed on the double-pass AAO nanotube before the sensing layer and the catalytic layer are deposited on the inner wall of the double-pass AAO nanotube in sequence to encourage the sensing layer and the catalytic layer to be deposited and integrated on the inner wall of the double-pass AAO nanotube in a mismatched manner. The application uses etching or impact grinding to groove or embed holes in the inner wall of the double-pass AAO nanotube, so that the sensing layer and the catalytic layer are not tightly stacked on the inner wall. The grooves or embedded holes provide an integration basis for the smooth deposition and integration of the sensing layer and the catalytic layer on the inner wall of the nanotube, so that the sensing layer and the catalytic layer can be easily integrated. Further, the roughened inner wall of the AAO nanotube can block the close stacking of the sensing particles during deposition, and the irregular gaps between the sensing particles can increase the porosity between the sensing particles. The gas to be detected can enter the sensing layer from the surface of the sensing layer through the pores for detection, thereby improving the utilization rate of the sensing layer and further improving the sensing efficiency of the sensing layer.

[0010] Preferably, the sensing particles constituting the sensing layer have at least one contact point with another particle on the defined particle boundary of the sensing particle in a mismatched deposition manner, and the contact points form a frame capable of accommodating molecules of the gas to be detected. In the case where the sensing particles are not tightly stacked, the molecules of the gas to be detected can enter the frame formed by the sensing particles through the pores between the sensing particles and react with the sensing particles. The gas molecules entering the frame can maintain contact with the sensing particles under the influence of the frame, and are not prone to sensing interruption and detection failure.

[0011] Preferably, the nanotubes of the double-pass AAO nanotube are connected at both ends, and the nanotubes are arranged in a uniform array without gaps. When the double-pass AAO nanotube with both ends connected is used to detect the gas molecules to be detected, the poor gas flow caused by the closed end and the problem that the sensing layer located in the deep part of the AAO nanotube cannot work can be reduced, and the detection sensitivity of the gas sensor can be greatly improved.

[0012] Preferably, the double-pass AAO nanotube is provided with a first electrode plate and a second electrode plate at the two ends in the third direction, respectively, and the first electrode plate and the second electrode plate are oppositely arranged.

[0013] Preferably, the second electrode plate is provided with an oxide layer in the third direction negative direction, and the oxide layer is provided with a heating layer in the third direction negative direction, and the oxide layer can transfer the heat generated by the heating layer to the double-channel AAO nanotube in a uniform conduction manner. By setting the oxide layer between the double-channel AAO nanotube and the heating layer, the rate of the heat generated by the heating layer entering the double-channel AAO nanotube can be controlled, and the case that the double-channel AAO nanotube fails to detect due to the temperature changing too fast can be prevented.

[0014] Preferably, the heating layer is provided with a reinforcing layer in the third direction negative direction for enhancing the physical strength of the three-dimensional nanometer gas sensor. Adding the reinforcing layer (also called substrate) in the nanometer sensor can enhance the mechanical strength of the sensor, so as to prevent the three-dimensional nanometer sensor from being damaged during packaging, transportation and installation.

[0015] Preferably, the double-channel AAO nanotube is not completely closed at the tube opening and is deposited with a polymer layer, and the thickness h of the polymer layer matches the tube diameter R of the double-channel AAO nanotube, and preferably, the thickness of the polymer layer is set as: R / 10<h<R / 2; more preferably, the thickness of the polymer layer is set as: R / 4<h<R / 3. By depositing the polymer layer in at least one end of the double-channel AAO nanotube, the number of undetected to-be-detected gas molecules directly escaping from one end of the nanotube to the other end of the nanotube is reduced, and the detection sensitivity of the device is improved.

[0016] Preferably, when the gas sensor detects the to-be-detected gas molecules, part of the to-be-detected gas molecules can circulate in the tube of the double-channel AAO nanotube in a manner of forming a vortex near the tube opening. The to-be-detected gas molecules near the nanotube wall form a vortex near the polymer layer in the tube under the action of the molecular thermal motion and the gas flow from the nanotube axis position, and can approach the nanotube wall multiple times under the action of the vortex until the sensing reaction occurs, thereby increasing the probability of the to-be-detected gas molecules contacting the sensing layer, reducing the problem that only the to-be-detected gas molecules close to the nanotube wall can be detected, and improving the detection capability of the device.

[0017] Preferably, the material components of the polymer layer can be the same as those of the sensing layer, so that the double-channel AAO nanotube can detect the to-be-detected gas molecules near the nanotube opening that fail to enter the double-channel AAO nanotube. The polymer layer uses the same material as the sensing layer, so that the polymer layer can detect the gas molecules that cannot enter the nanotube for detection due to the blocking of the polymer layer, thereby overcoming the problem of only being able to detect through the in-tube sensing. The polymer layer also increases the sensing area of the sensing particles that can contact the to-be-detected gas molecules to some extent, thereby further improving the sensing sensitivity.

[0018] Preferably, the gas sensor further comprises an impedance connected in series with the first electrode plate, the second electrode plate and the double-pass AAO nanotube, and a sensor voltage source providing a voltage for the series circuit, so that a voltage drop based on the impedance can determine the type of the gas molecules to be detected.

[0019] The present application has at least the following advantages:

[0020] 1. High heating efficiency per unit area: the longitudinal heat conduction of the double-pass AAO nanotube is better than the transverse heat conduction, so that most of the heat is transmitted longitudinally along the nanotube to reduce the transverse heat loss;

[0021] 2. Higher sensitivity at lower power consumption: the deposition of the gas-sensitive material on the nanotube wall can obtain a very high specific surface area, thereby realizing more sufficient contact with the gas molecules and higher sensitivity, and reducing the required working temperature of the sensor. In combination with the high heating efficiency of the micro-heater, higher sensitivity at lower power consumption can be realized;

[0022] 3. The sensing ability of the sensor in the case of low concentration of the gas to be detected can be improved, and the probability of the sensing reaction of the gas molecules to be detected on the sensing layer is increased, thereby amplifying the sensing effect;

[0023] 4. The ability of the double-pass AAO nanotube to detect the gas molecules outside the tube is increased, and the detection efficiency is improved;

[0024] 5. The heat loss inside the double-pass AAO nanotube is reduced, the energy utilization rate is improved, and the energy in the detection process is saved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a structural schematic diagram of the present application;

[0026] Figure 2 is a circuit connection schematic diagram of the present application;

[0027] Figure 3 is a deposition schematic diagram of the inner wall of the double-pass AAO nanotube of the present application;

[0028] Figure 4 is a longitudinal sectional view of a single nanotube of the present application;

[0029] Figure 5 is a top view of a single nanotube of the present application;

[0030] Figure 6 is a streamline diagram of the gas to be detected near the polymerization layer position of the present application.

[0031] LIST OF REFERENCE NUMBERS

[0032] 100: three-dimensional nano-gas sensor; 101: gas sensor device; 102: sensor voltage source; 103: heating voltage source; 104: impedance; 105: reinforcement layer; 106: oxide layer; 107: heating layer; 109: first electrode plate; 110: second electrode plate; 111: sensing layer; 112: catalytic layer; 113: sensing particle; 114: frame; 115: double-pass AAO nanotube; 116: polymer layer; 117: eddy current. DETAILED DESCRIPTION

[0033] The application will be described in greater detail with reference to the accompanying drawings.

[0034] In order to make the above objectives, features and advantages of the present application more apparent, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0035] In the description of the present application, it should be understood that, if the orientations or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like are based on the orientations or positional relationships shown in the drawings, they are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0036] In the description of the present application, it should be understood that "the first direction" refers to the direction parallel to the axis X, "the second direction" refers to the direction parallel to the axis Y, and "the third direction" refers to the direction parallel to the axis Z.

[0037] As Figure 2 The exemplary embodiment of the three-dimensional nano-gas sensor 100 shown includes a gas sensor device 101 (shown as electrically connected to a sensor voltage source 102), a heating voltage source 103, and an impedance 104. The sensor voltage source 102 and the heating voltage source 103 are direct current voltage sources for maintaining the pressure value of the gas sensor device 101 and the heating power of the heater, respectively. The impedance 104 is any resistance device of a known resistance amount. As Figure 1The gas sensor device 101 shown includes a reinforcing layer 105, an oxide layer 106, a heating layer 107, a double-pass AAO nanotube 115, a first electrode plate 109, a second electrode plate 110, and a sensing layer 111. The reinforcing layer 105 is usually formed by a silicon layer in a silicon crystal. The reinforcing layer 105 is used to improve the physical strength of the three-dimensional nanometer gas sensor 100, i.e., the substrate in the art. The oxide layer 106 is located between the heating layer 107 and the second electrode plate 110, and is configured to isolate the heat of the heating layer 107 from directly conducting onto the AAO nanotube, and maintain the heat conduction rate. Preferably, the oxide layer 106 can be formed by silicon dioxide (SiO2) or other insulating materials. The heating layer 107 is located between the reinforcing layer 105 and the oxide layer 106 and is electrically connected to the heating voltage source 103. The heating layer 107 is a material that can convert electrical energy into heat energy when an electric current passes through it. The thermal power of the heating layer 107 is configured to be at a temperature environment suitable for the sensing layer 111 to contact the gas and cause a resistance change when the heat generated by the heating layer 107 is uniformly conducted to the sensing layer 111 through the oxide layer 106. Preferably, other suitable materials for forming the heating layer 107 can be silicon dioxide, platinum, and composite materials, etc.

[0038] As Figure 1 The gas sensor device shown, the double-pass AAO nanotube 115 is an anodic aluminum oxide nanotube, the thickness is preferably 100 nm-100 um, and the pore size is preferably 100 nm-1 um; the double-pass AAO nanotube 115 is a porous honeycomb structure. The nanopore of the double-pass AAO nanotube 115 is a test tube-like structure with a closed lower end and a connected upper end to the outside. The sensing layer 111 and the catalytic layer 112 are sequentially deposited on the pore wall of the double-pass AAO nanotube 115. The sensing layer 111 is preferably SnO2, and of course, in other embodiments, the sensing layer 111 can also be TiO2, ZnO, and other metal oxides. The first electrode plate 109 and the second electrode plate 110 electrically connected to the sensor voltage source 102 are respectively arranged on the upper surface and the lower surface of the double-pass AAO nanotube 115, wherein the first electrode plate 109 and the second electrode plate 110 are respectively arranged on the upper and lower ends of the AAO nanotube in a manner of not completely covering the surface of the double-pass AAO nanotube 115. The first electrode plate 109 and the second electrode plate 110 are respectively attached to the surface of the double-pass AAO nanotube 115 and are in contact with the AAO nanotube in series. The sensing layer 111 is located on the inner wall of the double-pass AAO nanotube 115, wherein the sensing layer 111 and the double-pass AAO nanotube 115 are integrated in a mismatched manner, and the integration manner is suitable for the sensing layer 111 to be deposited on the wall of the double-pass AAO nanotube 115 in a spaced-apart and not tightly adsorbed manner.

[0039] According to a preferred embodiment, the inner wall of the double- walled AAO nanotube 115 is "roughened" by etching or impact grinding to encourage the deposition of the sensing layer 111 on the inner wall of the double- walled AAO nanotube 115. Preferably, the "roughening" includes crystallization or formation of certain partitions on the inner wall of the double-walled AAO nanotube 115 to space the oxides of the sensing layer 111 apart, etc.

[0040] According to a preferred embodiment, the first electrode plate 109 and the second electrode plate 110 at the upper and lower ends of the double-walled AAO nanotube 115 can be composed of any conductive material as can be imagined by those skilled in the art. Preferably, the first electrode plate 109 and the second electrode plate 110 are formed of titanium and are electrically isolated from each other by the double-walled AAO nanotube 115. The arrangement spacing between the first electrode plate 109 and the second electrode plate 110 is defined by the longitudinal length of the double-walled AAO nanotube 115. The first electrode plate 109 and the second electrode plate 110 have vertically opposite upper and lower portions, and the vertically opposite upper and lower portions of the first electrode plate 109 and the second electrode plate 110 are marked as overlapping portions. The oxide layer 106 is disposed on the lower surface of the second electrode plate 110. The heating layer 107 is grown on the lower surface of the oxide layer 106, and the heating layer 107 is vertically opposite to the overlapping portions. The reinforcing layer 105 is disposed on the lower surface of the heating layer 107 for increasing the physical strength of the device. Preferably, the area of the reinforcing layer 105 is greater than the area of the oxide layer 106, which is greater than the lateral area of the double-walled AAO nanotube 115.

[0041] According to a preferred embodiment, the sensing layer 111 is deposited on the inner wall of the double-walled AAO nanotube 115, and based on the extremely high specific surface area of the AAO nanotube, gas molecules can be sufficiently contacted to the sensing layer 111 and fully reflected to obtain higher sensitivity. The overlapping portions of the heating layer 107 and the first electrode plate 109 and the second electrode plate 110 are oppositely disposed in the longitudinal direction of the double-walled AAO nanotube 115, and since the heat conduction efficiency of the double-walled AAO nanotube 115 in the axial direction is higher than that in the radial direction, the arrangement of the heating layer 107 and the electrodes can achieve better gas sensing sensitivity at lower heat loss. The oxide layer 106 as an insulating layer not only separates the heating layer 107 from the double-walled AAO nanotube 115, but also uniformly transmits the heat of the heating layer 107 to the sensing mechanism and maintains a constant temperature environment at the position of the double-walled AAO nanotube 115. Preferably, the oxide layer 106 can be a hierarchical structure composed of SiO2, so as to ensure that the heat transmitted by the heating layer 107 to the double-walled AAO nanotube 115 is conducted through the barrier of the oxide layer 106. The area of the oxide layer 106 is set to be greater than the area of the heating layer 107. Preferably, although the number of electrodes in the present embodiment is two, the number of electrode plates can also be any number arranged longitudinally opposite.

[0042] According to a preferred embodiment, the sensing layer 111 is deposited on the "roughened" inner wall of the dual access AAO nanotube 115 between the first electrode plate 109 and the second electrode plate 110. The sensing layer 111 is in electrical communication with the first electrode plate 109 and the second electrode plate 110 such that an electrical current can flow through the sensing layer 111 between the first electrode plate 109 and the second electrode plate 110. The thickness of the sensing layer 111 is less than the nanotube radius of the dual access AAO nanotube 115. The deposition thickness of the sensing layer 111 depends on the desired thickness of the gas sensor device 101 such that as many constituent particles of the sensing layer 111 are deposited as possible without affecting the passage of the gas through the dual access AAO nanotube 115. Preferably, the deposition material used to form the sensing layer 111 can be metal oxides such as tin dioxide (Sn02), zinc oxide (ZnO), and tungsten trioxide (W03). The sensing layer 111 and the first electrode plate 109, the second electrode plate 110, and the impedance 104 are connected in series to the sensor voltage source 102.

[0043] According to a preferred embodiment, as shown in FIG. 1, the sensing layer 111 is deposited on the inner wall of the dual access AAO nanotube 115. The sensing layer 111 is deposited on the inner wall of the dual access AAO nanotube 115 prior to the deposition of the catalytic layer 112 on the inner wall of the dual access AAO nanotube 115. The sensing layer 111 is integrated on the inner surface of the dual access AAO nanotube 115 in a mismatched manner. The catalytic layer 112 is further integrated on the surface of the sensing layer 111 in a mismatched manner on the basis of the mismatched integration of the sensing layer 111 on the inner wall of the dual access AAO nanotube 115. The catalytic layer 112 is used to accelerate the reaction rate when the sensing layer 111 adsorbs and reacts with the gas to be detected to improve the detection sensitivity of the gas sensor device 101. According to the accompanying drawings and detailed description, the catalytic layer 112 is further integrated on the sensing layer 111 in a mismatched manner. Figure 3 According to a preferred embodiment, as shown in FIG. 1, the sensing layer 111 is deposited on the inner wall of the dual access AAO nanotube 115. The sensing layer 111 is deposited on the inner wall of the dual access AAO nanotube 115 prior to the deposition of the catalytic layer 112 on the inner wall of the dual access AAO nanotube 115. The sensing layer 111 is integrated on the inner surface of the dual access AAO nanotube 115 in a mismatched manner. The catalytic layer 112 is further integrated on the surface of the sensing layer 111 in a mismatched manner on the basis of the mismatched integration of the sensing layer 111 on the inner wall of the dual access AAO nanotube 115. The catalytic layer 112 is used to accelerate the reaction rate when the sensing layer 111 adsorbs and reacts with the gas to be detected to improve the detection sensitivity of the gas sensor device 101. According to the accompanying drawings and detailed description, the catalytic layer 112 is further integrated on the sensing layer 111 in a mismatched manner. Figure 3 According to a preferred embodiment, as shown in FIG. 1, the sensing layer 111 is deposited on the inner wall of the dual access AAO nanotube 115. The sensing layer 111 is deposited on the inner wall of the dual access AAO nanotube 115 prior to the deposition of the catalytic layer 112 on the inner wall of the dual access AAO nanotube 115. The sensing layer 111 is integrated on the inner surface of the dual access AAO nanotube 115 in a mismatched manner. The catalytic layer 112 is further integrated on the surface of the sensing layer 111 in a mismatched manner on the basis of the mismatched integration of the sensing layer 111 on the inner wall of the dual access AAO nanotube 115. The catalytic layer 112 is used to accelerate the reaction rate when the sensing layer 111 adsorbs and reacts with the gas to be detected to improve the detection sensitivity of the gas sensor device 101. According to the accompanying drawings and detailed description, the catalytic layer 112 is further integrated on the sensing layer 111 in a mismatched manner.

[0044] According to a preferred embodiment, the specific structure of the "mismatched" integrated sensing particles 113 is that any sensing particle 113 is surrounded by a plurality of other sensing particles, the sensing particle 113 has at least one contact point with the other sensing particles, and the other sensing particles also have one contact point between any two adjacent sensing particles. The contact points between the sensing particles 113 and the other particles cooperate with the contact points of the adjacent sensing particles to form an incomplete closed frame 114 surrounded by a plurality of contact points. Any two adjacent frames 114 are only separated by an incomplete closed frame 114 through the contact points, and all the frames 114 are interconnected, so that the gas molecules to be detected can enter the deep frames 114 of the sensing layer 111 from the frames 114 on the surface and then pass through a plurality of frames to reach the sensing particles 113 and react with them. By forming frames 114 between the sensing particles 113 that can allow the gas molecules to be detected to enter, the part of the sensing layer 111 that can contact the gas molecules to be detected is not limited to the surface of the sensing layer 111, and the sensing particles located near the inner wall of the double-channel AAO nanotube 115 can also contact the gas molecules to be detected and react, thereby improving the utilization rate of the sensing particles 113 in the sensing layer 111.

[0045] According to a preferred embodiment, the gas sensor device 101 is configured to detect the presence of one or more gases to be detected in the space, wherein the gas to be detected can be ammonia, methane, carbon monoxide, carbon dioxide, volatile organic compounds, etc. Due to the microstructure of the three-dimensional nanometer gas sensor 100, the device can be used in various fields according to the shape of the carrier to detect gases: household kitchen, smart device, automobile exhaust emission system, electronic device manufacturing workshop, gas station, gas storage room, etc. Any application site that needs to detect gas can be imagined by those skilled in the art.

[0046] According to a preferred embodiment, in combination with Figure 1 and Figure 2The heating voltage source 103 applies a voltage to the heating layer 107. In response to the voltage, the heating layer 107 is heated to a temperature that at least matches the value of the resistance of the heating voltage source 103 and the heating layer 107. The temperature generated by the heating layer 107 is uniformly conducted via the oxide layer 106 and is transmitted to the sensing layer 111 on the double- walled AAO nanotube 115. The sensing layer 111 is heated to a sensing temperature by the heating layer 107 within a heating time period. The sensing temperature is at least based on the properties of the gas to be detected and the sensing temperature of the sensing layer 111 and the temperature of the location where the three-dimensional nanometer gas sensor 100 is located. For example, the sensing temperature ranges from 200 to 300 degrees Celsius. Since the thickness of the sensing layer 111 is in the nanometer level, the distance between the sensing layer 111 and the heating layer 107 can be ignored even if the oxide layer 106 is present, so the heating layer 107 can substantially instantly heat the sensing layer 111 to the sensing temperature. Preferably, in order to achieve the effect of small-area heating, a folded heating resistance wire is provided in the embodiment. The heating electrode is preferably rectangular in structure. Since the length of the folded heating resistance wire is greater than that of the heating electrode and the width is much smaller than that of the heating electrode, the heating part of the heating layer is mainly concentrated on the folded heating resistance wire. Therefore, the effect of small-area heating can be achieved. Since the double-walled AAO nanotube 115 has a porous structure, the longitudinal thermal conductivity coefficient is greater than the transverse thermal conductivity coefficient, so the transverse heat loss is small, and higher heating efficiency can be obtained in the longitudinal direction.

[0047] After the sensing layer 111 is heated to the sensing temperature, the voltage from the sensor voltage source 102 establishes a current through the first electrode plate 109, the sensing layer 111, the second electrode plate 110, and the impedance 104. The value of the current is at least based on the combined resistance of the first electrode plate 109, the sensing layer 111, the second electrode plate 110, and the impedance 104, and since the first electrode plate 109, the sensing layer 111, the second electrode plate 110, and the impedance 104 are connected in series with each other, the current passing through them is equal. When the three-dimensional nanometer gas sensor 100 is placed in a space containing the gas to be detected or not containing the gas to be detected, the gas sensor device 101 and the impedance 104 form a voltage division circuit, and the presence or absence of the gas to be detected in the space is determined by detecting the voltage drop of the impedance 104. In particular, if the gas to be detected is a reducing gas, as the gas to be detected enters and is adsorbed and combined on the sensing layer 111, the resistance of the sensing layer decreases and the current passing through increases; if the gas to be detected is an oxidizing gas, as the gas to be detected enters and is adsorbed and combined on the sensing layer 111, the resistance of the sensing layer increases and the current passing through decreases. The change in the voltage across the impedance 104 is detected by the external circuit to monitor the change in the current.

[0048] According to a preferred embodiment, the double-channel AAO nanotube 115 is a honeycomb structure with both ends connected. The preparation method of the double-channel AAO nanotube is as follows (for details, see CN201710321598.8):

[0049] S1: select aluminum sheet with purity of 5N, cut into a rectangle, then sequentially clean with deionized water and electrochemical polishing;

[0050] S2: perform secondary anodic oxidation on the aluminum sheet completed in step S1;

[0051] S3: cut the aluminum sheet after secondary anodic oxidation, then spray a layer of gold on the A surface of the aluminum sheet, open a circular hole on the plastic sealing film, then adhere the A surface of the aluminum sheet to the aluminum foil and use a plastic sealing machine to perform double-sided plastic sealing on it, wherein the aluminum sheet is completely plastic sealed and the aluminum foil is not completely plastic sealed; the B surface of the aluminum sheet faces the hole opened on the plastic sealing film, so that the B surface is not completely covered by the plastic sealing film, that is, there is a circular hole on the B surface after plastic sealing;

[0052] S4: remove the aluminum oxide layer in the unsealed area of the B surface of the plastic sealed aluminum sheet with sodium hydroxide solution, then remove the aluminum substrate with saturated copper chloride solution, then perform barrier layer removal and hole expansion treatment on the surface of the template after removing the aluminum substrate, and finally clean with deionized water and dry to obtain a double-channel AAO nanotube template;

[0053] S5: prepare HAuCl solution, use a platinum sheet electrode as an auxiliary electrode, a mercury electrode as a reference electrode, and the double-channel AAO nanotube template prepared in S4 as a working electrode to perform Au nanowire electrodeposition in a three-electrode system.

[0054] According to a preferred embodiment, the preparation method of the three-dimensional nanometer gas sensor 100 is as follows:

[0055] Step one: deposit nanoscale sensing particles 113 on the inner wall of the double-channel AAO nanotube 115 to form a sensing layer 111; when the sensing particles 113 are selected as SnO2, the specific deposition method is as follows: use tetrabutyltin as a tin source, open the ALD tin source valve for 300 ms, close the tin source pump valve, and the tin source stays in the cavity for 30 s; open the ALD gaseous water source valve for 30 ms, close the gaseous water source pump valve, and the gaseous water stays in the cavity for 30 s; open the ammonia gas pump valve to clean the cavity for 5 s. The thickness of SnO2 deposited on the inner wall of the double-channel AAO nanotube 115 in one cycle is 0.1 nm, and after multiple cycles of deposition, a sensing layer film suitable for the diameter of the double-channel AAO nanotube 115 is obtained, and then high-temperature calcination and solidification are performed in air.

[0056] Step two: distribute catalyst nanoparticles on the surface of the sensing layer 111; preferably, the catalyst nanoparticle material forming the catalytic layer 112 can be platinum nanoparticles, and the distribution can be achieved by immersing the double-barreled AAO nanotube 115 with the deposited sensing layer 111 in a solution with catalyst particles. The double-barreled AAO nanotube 115 is rotated or moved in other ways to facilitate the penetration of catalyst particles into the inner wall of the double-barreled AAO nanotube 115.

[0057] Step three: evaporate the first electrode plate 109 on the upper surface of the double-barreled AAO nanotube 115 and the second electrode plate 110 on the lower surface of the double-barreled AAO nanotube 115; the first electrode plate 109 and the second electrode plate 110 have vertically opposite parts, which are marked as overlapping parts.

[0058] Step four: deposit the oxide layer 106 on the lower surface of the second electrode plate 110, and ensure that the area of the oxide layer 106 matches the area of the heating layer 107. Preferably, the material of the oxide layer 106 can be SiO2.

[0059] Step five: evaporate the heating layer 107 on the lower surface of the oxide layer 106, which includes a heating electrode and a resistance wire electrically connected to the heating electrode, and the resistance wire is vertically opposite to the overlapping parts. Specifically: on the lower surface of the oxide layer 106, a metal layer or metal accumulation is evaporated as the heating layer 107 by thermal evaporation and electron beam evaporation techniques in a high vacuum environment.

[0060] Step six: deposit the reinforcing layer 105 on the lower surface of the heating layer 107. The reinforcing layer 105 is used to increase the physical strength of the three-dimensional nanometer gas sensor 100. Preferably, the material of the reinforcing layer 105 can be SiO2.

[0061] Step seven: package the three-dimensional nanometer gas sensor 100. Preferably, after cutting the AAO device to any size suitable for its use purpose, the AAO device is packaged in a ceramic tube using conductive glue.

[0062] According to a preferred embodiment, the double-pass AAO nanotube 115 is distinguished from the traditional single-pass AAO nanotube in that the double-pass AAO nanotube can accommodate the to-be-detected gas to enter for detection at both ends. The traditional single-pass AAO nanotube has some of the ambient gas stored in the nanotube itself when the to-be-detected gas enters for detection. When the to-be-detected gas is detected, only the random motion of the to-be-detected gas molecules can push the original gas molecules in the nanotube out to enter the inner wall of the nanotube to contact the sensing layer. This makes the rate of the to-be-detected gas molecules entering the nanotube lower, and the sensing layer 111 needs a longer time to contact and react with the to-be-detected gas molecules. At the same time, most of the to-be-detected gas molecules are adsorbed near the mouth of the nanotube, causing the to-be-detected gas molecules to accumulate at the mouth of the nanotube, and the sensing layer deposited in the deep part of the nanotube can only adsorb a small amount or cannot adsorb the to-be-detected gas for sensing reaction. This phenomenon greatly reduces the detection sensitivity of the three-dimensional nanometer gas sensor. The double-pass AAO nanotube 115 can accommodate the to-be-detected gas to enter at both ends, and the gas flowability in the nanotube is strong, so that the to-be-detected gas molecules can more easily enter the nanotube to be adsorbed by the sensing layer 111 and react. The double-pass AAO nanotube 115 is connected at both ends, and there is no dead angle for gas molecule flow. The to-be-detected gas molecules can fully contact the sensing layer 111 on the nanotube and react.

[0063] According to a preferred embodiment, as Figure 4A polymer layer 116 is deposited at both ends of the dual-channel AAO nanotube 115 in a partially sealed manner. The polymer layer 116 can be made of SnO2 particles, the same material as the sensing layer 111. Preferably, SnO2 particles can be deposited on the nanotube wall near the opening of the dual-channel AAO nanotube 115 using any method conceivable in the art, with the opening of the dual-channel AAO nanotube 115 partially sealed. For example, the dual-channel AAO nanotube with the sensing layer 111 already deposited is brought close to and in contact with the tetramethylaminotin solution with its axis perpendicular to the horizontal plane of tetramethylaminotin. The reaction part is rinsed using an ammonia pump valve. The ALD gaseous water source valve is opened for 30 ms, the gaseous water source pump valve is closed, and the gaseous water remains at the deposition site at the opening for 30 s. The opening is then cleaned with an ammonia pump valve for 5 s. Such a cycle can deposit a SnO2 layer with a thickness of 0.1 nm at the opening of the dual-channel AAO nanotube 115. Through repeated cycles, a polymer layer 116 of any desired thickness can be deposited at both ends of the dual-channel AAO nanotube 115. When the two ends of the dual-channel AAO nanotube 115 are connected, only the gas molecules near the tube wall can contact the sensing layer 111 and react. The remaining molecules pass through the nanotube due to their own thermal molecular motion. When the concentration of the gas molecules to be detected is low, the number of gas molecules that can be adsorbed onto the nanotube wall is small, the degree to which the sensing layer 111 adsorbs and reacts with the gas molecules to be detected is low, the change in current through the sensing layer 111 is small, and the accuracy of judging whether the gas molecules to be detected are low based on the voltage drop range of the impedance 104. That is, when a low concentration of gas molecules enters the dual-channel AAO nanotube, only a small number of gas molecules near the nanotube wall can be adsorbed and react with the sensing layer 111, while most of the remaining gas molecules pass through the dual-channel AAO nanotube without reacting with the sensing layer 111. The polymer layer 116 deposited at the opening of the dual-channel AAO nanotube 115 can, to a certain extent, partially block some gas molecules from exiting the nanotube opening, trapping them between the polymer layer 116 and the inner wall of the nanotube. Figure 6 The diagram shows the streamline of the gas to be detected flowing out of the small hole at the center of the polymer layer 116 from left to right. Under the influence of the airflow, the gas molecules form a vortex 117 near the polymer layer 116 within the nanotube. The gas molecules in the vortex 117 can circulate and reciprocate near the polymer layer 116, thereby increasing the probability of contact between the gas molecules and the sensing layer 111. The gas molecules in the vortex 117 are more likely to contact the sensing layer 111 and trigger a sensing response. When the sensing layer 111 contacts and adsorbs as many gas molecules as possible, its resistance value can be changed based on the number of molecules, further altering the voltage drop across the impedance 104 connected in series with the sensing layer 111.

[0064] According to a preferred embodiment, as Figure 5 , the thickness of the incompletely closed aggregation layer 116 is limited by the ratio of the number of gas molecules to be detected that can enter and circulate under the influence of the eddy current 117 generated under its influence to the number of gas molecules to be detected that cannot enter the nanotube for detection under the influence of the incompletely closed aggregation layer. That is, when the thickness h of the aggregation layer 116 reaches the radial radius R of the double-pass AAO nanotube 115, the gas to be detected in the external environment cannot enter the double-pass AAO nanotube for detection. When the thickness of the aggregation layer 116 is negligible, it cannot generate an eddy current 117 with sufficient ability to block as many gas molecules to be detected as possible to react with the nanotube. The number of gas molecules to be detected that can enter and circulate under the influence of the eddy current 117 is positively correlated with the thickness of the aggregation layer 116. The higher the thickness of the aggregation layer 116, the larger the volume of the eddy current 117 it can generate, and the more gas molecules it can accommodate. Preferably, the thickness of the aggregation layer 116 can be set as: R / 10 < h < R / 2; more preferably: the thickness of the aggregation layer 116 can be set as: R / 4 < h < R / 3.

[0065] According to a preferred embodiment, particles of the same material as the sensing layer 111 are deposited as the aggregation layer 116, increasing the number and area of the sensing particles 113 that can detect the gas molecules to be detected in the lateral range, so that the gas to be detected that cannot enter the double-pass AAO nanotube for detection due to the blockage of the aggregation layer 116 can react with the sensing particles 113 on the aggregation layer 116 during the process of contacting and being blocked by the aggregation layer 116. The sensing current of the sensing layer 111 also changes when the aggregation layer 116 undergoes a sensing reaction, solving the problem that the sensing reaction and detection can only occur inside the double-pass AAO nanotube, and further improving the detection sensitivity of the three-dimensional nano gas sensor 100.

[0066] According to a preferred embodiment, the aggregation layer 116 is located at both ends of the double-pass AAO nanotube 115 and plays a certain role in closing the nanotube. When the heat of the heating layer 107 is conducted to the double-pass AAO nanotube 115 through the oxide layer 106, the heat in the longitudinal direction of the double-pass AAO nanotube 115 will not immediately flow out and dissipate from the tube opening, and the temperature environment inside the double-pass AAO nanotube 115 can reach the temperature conditions required for the sensing reaction faster. The aggregation layer 116 can reduce the heat loss inside the tube during the sensing reaction, thereby reducing the heat loss during the sensing detection process.

[0067] It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that those skilled in the art will be able to devise modifications which, though perhaps not explicitly described or shown herein, nonetheless fall within the scope of the application. Accordingly, the patentable scope of the application is defined by the appended claims and their equivalents.

Claims

1. A three-dimensional nanogas sensor, comprising: The sensing layer (111) can change its own electrical properties based on the contact and sensing response of the gas to be detected; Dual-channel AAO nanotubes (115) are used to provide a carrier for the deposition of the sensing layer (111) and to transmit the electrical parameters of the sensing layer (111); The feature is that, before sequentially depositing the sensing layer (111) and the catalyst layer (112) on the inner wall of the dual-channel AAO nanotube (115), the inner wall of the dual-channel AAO nanotube (115) is roughened by crystallization or by forming partitions that separate the oxides of the sensing layer (111) to encourage the sensing layer (111) and the catalyst layer (112), which are incompletely closed structures formed by multiple sensing particles (113), to be deposited and integrated in a mismatched manner on the inner wall surface of the dual-channel AAO nanotube. The roughness causes the sensing particles (113) to be deposited in a spaced-out, loosely stacked manner on the inner wall of the double-pass AAO nanotube (115); there is at least one contact point between the sensing particles (113), and multiple contact points form a partially closed enclosure (114). Any two adjacent enclosures (114) are only partially closed and separated by the contact point. The gas molecules to be detected can pass through multiple enclosures (114) from the enclosure (114) on the surface and enter the enclosure (114) deep in the sensing layer (111) and react with the sensing particles (113).

2. The gas sensor according to claim 1, characterized in that, In the mismatched deposition of the sensing particles (113) constituting the sensing layer (111), the sensing particles (113) have at least one contact point with a sensing particle (113) on their defined particle boundaries, and the contact points form a frame (114) capable of accommodating the gas molecules to be detected.

3. The gas sensor according to claim 1 or 2, characterized in that, The two ends of the dual-channel AAO nanotube (115) are connected, and the dual-channel AAO nanotubes (115) are arranged in a uniform array without gaps between them.

4. The gas sensor according to claim 3, characterized in that, The dual-channel AAO nanotube (115) has a first electrode plate (109) and a second electrode plate (110) respectively at its three directional ends, with the first electrode plate (109) and the second electrode plate (110) arranged opposite to each other.

5. The gas sensor according to claim 4, characterized in that, The second electrode plate (110) is provided with an oxide layer (106) in the third negative direction, and a heating layer (107) is provided in the third negative direction of the oxide layer (106). The oxide layer (106) can transfer the heat generated by the heating layer (107) to the double-pass AAO nanotube (115) in a uniform conduction manner.

6. The gas sensor according to claim 5, characterized in that, The heating layer (107) is provided with a reinforcing layer (105) in the third negative direction to enhance the physical strength of the three-dimensional nano gas sensor (100).

7. The gas sensor according to claim 3, characterized in that, The opening of the dual-channel AAO nanotube (115) is not completely sealed and a polymer layer (116) is deposited thereon. The thickness h of the polymer layer (116) is matched with the diameter R of the dual-channel AAO nanotube (115), and the thickness of the polymer layer (116) is set to: R / 10. <h<R / 2。 8. The gas sensor according to claim 7, characterized in that, When the gas sensor detects the gas molecules to be detected, some of the gas molecules to be detected can circulate in a manner that forms a vortex (117) near the opening of the dual-channel AAO nanotube (115).

9. The gas sensor according to claim 7, characterized in that, The material composition of the polymer layer (116) can be the same as that of the sensing layer (111), so that the dual-channel AAO nanotube (115) can detect the gas molecules to be detected that have not passed through the polymer layer (116) and entered the dual-channel AAO nanotube (115) near the opening of the nanotube.

10. The gas sensor according to claim 4, characterized in that, The gas sensor also includes an impedance (104) connected in series with the first electrode plate (109), the second electrode plate (110) and the dual-channel AAO nanotube (115) and a sensor voltage source (102) that provides voltage to the series circuit, such that the type of gas molecule to be detected can be determined based on the voltage drop of the impedance (104).

11. The gas sensor according to claim 7, characterized in that, The thickness of the polymer layer (116) is set to: R / 4 <h<R / 3。

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