Micro-vortex quantum dot gas sensor as well as preparation method and application thereof

Abstract

The invention discloses a micro-vortex quantum dot gas-sensitive sensor and a preparation method and application thereof, and belongs to the technical field of sensors, the micro-vortex quantum dot gas-sensitive sensor is developed by designing a spherical coating structure at the top of a silicon nano-column array and combining a quantum dot sensitive layer, and the micro-vortex quantum dot gas-sensitive sensor has the advantages that the micro-vortex quantum dot gas-sensitive sensor is developed; the gas sensitive sensor is a novel gas sensitive device based on a micro eddy current effect. In the gas flowing process, the column-ball combined microstructure in the gas sensor can form a micro vortex field, so that the residence time of gas molecules on the surface of the quantum dot sensitive layer is prolonged, and the molecule capturing capability is enhanced. The selective response characteristic of the quantum dot layer to target gas is optimized through size regulation and surface modification, and NO2, H2S, VOCs and other gases can be efficiently detected at room temperature. The micro-vortex quantum dot gas sensor provided by the invention has remarkable advantages in the aspects of sensitivity, response time, power consumption, environmental adaptability and the like, provides a brand new design idea for breaking through the performance bottleneck of a traditional gas sensor, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and particularly relates to a micro-vortex flow quantum dot gas sensor, a preparation method thereof, and an application thereof. Background Art

[0002] Gas sensors have important application values in the fields of industrial gas monitoring, environmental pollution detection, medical diagnosis, and safety monitoring. In recent years, with the improvement of the requirements for gas detection accuracy and sensitivity, traditional gas sensing technologies have been difficult to meet the needs of small-concentration gas detection, complex environment adaptation, and rapid response. Developing new high-sensitivity and high-selectivity gas sensors has become a research hotspot.

[0003] Currently, common gas sensors include types such as metal oxide semiconductors (MOS), electrochemical sensors, and optical gas detectors. Among them, metal oxide sensors have a simple structure and low cost, but have problems of high working temperature and poor selectivity; electrochemical sensors have high sensitivity and low power consumption, but the detection types are limited and the response speed is slow; optical sensors have high accuracy, but the equipment is complex and the cost is high. The limitations of the above technologies indicate that there is an urgent need in this field for a new type of gas sensing device with low power consumption, a wide detection range, high sensitivity, and adaptability to complex environments.

[0004] The combination of micro-nano structures and quantum dot materials provides a breakthrough direction for the research and development of new gas sensors. Micro-nano structures such as nanocolumns, nanowires, and nanoparticles, due to their high specific surface area, unique surface effects, and optical properties, help to enhance the gas sensing performance, provide more active sites, and strengthen the ability of gas adsorption and charge transfer. In addition, the design of micro-structures can also improve the capture efficiency of gas molecules by changing the gas flow behavior (such as introducing the micro-vortex effect). Quantum dot materials, due to their size tunability, rich surface defect states, and excellent optoelectronic properties, are particularly suitable for use as gas sensing layers. PbSe and PbS quantum dots, due to their narrow bandgap characteristics, high-efficiency light absorption ability, and sensitivity to oxidizing or reducing gases, show excellent performance in the detection of gases such as NO 2 、H 2 S and formaldehyde, etc., and have the characteristics of high sensitivity, fast response, and low power consumption.

[0005] As a hydrodynamic characteristic, the micro-vortex effect can form a stable micro-vortex field during the gas flow process through the design of a column-sphere combined micro-structure, effectively prolonging the residence time of gas molecules on the surface of the sensitive material, thereby significantly improving the molecular capture rate and reaction efficiency of the gas. Compared with traditional gas sensors, this structural design can significantly improve the sensitivity and response speed of the sensor. However, at present, the application of the micro-vortex effect in gas sensing is still in the exploration stage, and there are problems such as insufficient gas selectivity, long response time, and poor environmental stability, which urgently need further research and optimization. Summary of the Invention

[0006] The object of the present invention is to provide a micro-vortex flow quantum dot gas sensor, its preparation method and application to solve the problems existing in the above-mentioned prior art.

[0007] One of the technical solutions provided by the present invention:

[0008] A micro-vortex flow quantum dot gas sensor includes a metal nanowire upper electrode layer, a column-sphere microfluidic structure, a substrate layer and a lower electrode layer stacked from top to bottom. The column-sphere microfluidic structure includes a gas-sensitive quantum dot layer and a gas-sensitive metasurface layer. The gas-sensitive metasurface layer is a frustum-shaped micro-nano structure. The gas-sensitive quantum dot layer uniformly coats the surface of the frustum-shaped micro-nano structure and forms a spherical coating structure on the top of the frustum-shaped micro-nano structure.

[0009] Preferably, the top diameter of the frustum-shaped micro-nano structure is 0 - 800 nm, the bottom diameter is 100 nm - 1000 nm, the height is 100 - 1000 nm, and the bottom diameter is greater than the top diameter, and the top diameter is not 0.

[0010] Preferably, the gas-sensitive quantum dot layer is composed of PbSe quantum dots, PbS quantum dots or MoS 2 quantum dots.

[0011] Preferably, the metal nanowire is selected from gold nanowire, silver nanowire, copper nanowire or aluminum nanowire.

[0012] The micro-vortex flow quantum dot gas sensor provided by the present invention includes a silicon nanowire array. The surface of each nanowire is uniformly coated with PbSe, PbS or MoS 2 quantum dots as the gas-sensitive layer, and a spherical coating structure is formed on the top of the nanowire. The column-sphere microfluidic structure generates a micro-vortex effect during the gas flow process, significantly prolonging the residence time of gas molecules on the sensitive surface and improving the molecular capture rate and reaction efficiency. The quantum dot sensitive layer interacts with target gas molecules through physical adsorption or chemical reaction, resulting in changes in its electrical properties. By integrating the electrode array to collect sensing signals in real time, the device can efficiently detect the concentration of gases such as NO 2 、H 2 S, VOCs, etc., with high sensitivity and fast response speed, and is suitable for industrial gas monitoring, environmental pollution detection and other precision gas sensing scenarios.

[0013] The second technical solution provided by the present invention:

[0014] A preparation method of the above-mentioned micro-vortex flow quantum dot gas sensor includes the following steps: preparing a frustum-shaped micro-nano structure on a substrate by photolithography and etching, conformally coating a quantum dot material on the surface of the frustum-shaped micro-nano structure by ultrasonic inversion spin coating, then performing ligand exchange to obtain a quantum dot conformally coated micro-nano structure, and then preparing quantum dot spheres on the upper surface of the quantum dot conformally coated micro-nano structure by shunt-controlled spin coating and ligand exchange in sequence to prepare a column-sphere microfluidic structure, depositing a lower electrode layer at the bottom of the substrate, and preparing a metal nanowire upper electrode layer on the surface of the column-sphere microfluidic structure.

[0015] The column-sphere microfluidic structure prepared by the present invention can generate micro-vortices. When a gas flows through the column-sphere structure array, the geometric discontinuity formed at the top of the small ball and the surface of the nano-column triggers micro-vortices, increasing the residence time of gas molecules on the surface of the sensitive material.

[0016] Preferably, the ultrasonic inversion spin coating method includes the following steps: immersing the substrate with the frustum-shaped micro-nano structure in a quantum dot solution, keeping one side of the frustum-shaped micro-nano structure facing upward, performing ultrasonic treatment, and immediately spin coating with the side of the frustum-shaped micro-nano structure facing downward after stopping the ultrasonic treatment.

[0017] More preferably, the conditions of the ultrasonic treatment are: power is 50W, frequency is 20KHZ, and time is 5min.

[0018] More preferably, the conditions of the spin coating are: rotation speed is 2000rmp, and time is 6s.

[0019] Preferably, the shunt-controlled spin coating method is: when performing quantum dot spin coating, keeping the side of the frustum-shaped micro-nano structure facing upward and blowing a downward airflow directly above the frustum-shaped micro-nano structure.

[0020] More preferably, the conditions of the spin coating are: rotation speed is 300rmp, and time is 15s.

[0021] More preferably, the flow rate of the airflow is 20mL / min.

[0022] Technical solution three provided by the present invention:

[0023] An application of the above-mentioned micro-vortex flow quantum dot gas sensor in detecting NO 2 、H 2 S and VOCs.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] The present invention develops a micro-vortex quantum dot gas sensor by designing a spherical coating structure on the top of a silicon nanowire array and combining it with a quantum dot sensitive layer. This gas sensor is a novel gas sensing device based on the micro-vortex effect. During the gas flow process, the column-sphere combined microstructure in the gas sensor can form a micro-vortex field, prolong the residence time of gas molecules on the surface of the quantum dot sensitive layer, and enhance the molecular capture ability. The quantum dot layer optimizes the selective response characteristics to target gases through size regulation and surface modification, and can efficiently detect NO 2 、H 2 S, VOCs and other gases. The micro-vortex quantum dot gas sensor provided by the present invention shows significant advantages in terms of sensitivity, response time, power consumption, and environmental adaptability, providing a new design idea for breaking through the performance bottleneck of traditional gas sensors and having broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is a preparation flow chart of the frustum-shaped micro-nano structure in Example 1;

[0028] Figure 2 It is a SEM structure diagram of the silicon nanowire array in Example 1;

[0029] Figure 3 It is a TEM diagram of PbSe quantum dots in Example 1;

[0030] Figure 4 It is an XRD diagram of PbSe quantum dots in Example 1;

[0031] Figure 5 It is a preparation flow chart of the column-sphere microfluidic structure in Example 1;

[0032] Figure 6 It is a SEM diagram of the column-sphere microfluidic structure in Example 1;

[0033] Figure 7 It is a schematic structural diagram of the micro-vortex quantum dot gas sensor prepared in this example, where 1 is the silver nanowire upper electrode layer, 2 is the column-sphere microfluidic structure, 4 is the base layer, and 5 is the lower electrode layer;

[0034] Figure 8 It is the test result of the sensor sensitivity prepared in Example 1 and Comparative Example 1;

[0035] Figure 9 Sensitivity test results of the sensors prepared in Example 2 (left figure) and Comparative Example 2 (right figure) for H 2 S;

[0036] Figure 10 Response time test results of the sensors prepared in Example 1 (left figure) and Comparative Example 1 (right figure);

[0037] Figure 11 Comparison chart of the decay rates of the sensitivities of the sensors prepared in Example 1 (left figure) and Comparative Example 1 (right figure) over time. Detailed implementation manners

[0038] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation embodiments of the present invention.

[0039] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0041] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and embodiments are only exemplary.

[0042] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0043] The room temperature in the present invention refers to 25 ± 2°C.

[0044] An embodiment of the present invention provides a micro-vortex flow quantum dot gas sensor, which includes a metal nanowire upper electrode layer, a column-sphere microfluidic structure, a substrate layer, and a lower electrode layer stacked from top to bottom. The column-sphere microfluidic structure includes a gas-sensitive quantum dot layer and a gas-sensitive metasurface layer. The gas-sensitive metasurface layer is a frustum-shaped micro-nano structure. The gas-sensitive quantum dot layer uniformly coats the surface of the frustum-shaped micro-nano structure and forms a spherical coating structure on the top of the frustum-shaped micro-nano structure. Among them, the metal nanowire upper electrode layer has a micro-mesh, allowing gas molecules to pass through the upper electrode layer to reach the gas-sensitive quantum dot layer. The column-sphere microfluidic structure generates a micro-vortex effect during the gas flow process, significantly prolonging the residence time of gas molecules on the sensitive surface and improving the molecular capture rate and reaction efficiency. The gas-sensitive metasurface layer is composed of a frustum-shaped silicon micro-structure. The gradient change inclination angle of the frustum-shaped micro-nano structure makes it easier for gas molecules to react with the gas-sensitive quantum dot layer coated on its surface. In order to facilitate the preparation of the gas metasurface layer, the substrate layer is selected from silicon materials, and the lower electrode layer is copper.

[0045] In some embodiments of the present invention, the top diameter of the frustum-shaped micro-nano structure is 0 - 800 nm, the bottom diameter is 100 nm - 1000 nm, the height is 100 - 1000 nm, and the bottom diameter is greater than the top diameter, and the top diameter is not 0.

[0046] In the following preferred embodiments of the present invention, the top diameter is 300 nm, 400 nm, or any value between the aforementioned range values, the bottom diameter is 500 nm, 600 nm, or any value between the aforementioned range values, and the height is 800 nm.

[0047] In some embodiments of the present invention, the gas-sensitive quantum dot layer is composed of PbSe quantum dots, PbS quantum dots, or MoS 2 quantum dots. In the following preferred embodiments of the present invention, the gas-sensitive quantum dot layer is composed of PbSe quantum dots or PbS quantum dots.

[0048] In some embodiments of the present invention, the metal nanowires are selected from gold nanowires, silver nanowires, copper nanowires, or aluminum nanowires. In the following preferred embodiments of the present invention, the metal nanowires are gold nanowires or silver nanowires.

[0049] The embodiment of the present invention also provides a method for preparing the above-mentioned micro-vortex flow quantum dot gas sensor:

[0050] The frustum-shaped micro-nano structure is prepared by photolithography and etching. First, photoresist is spin-coated on a silicon substrate (rotation speed: 3000 rmp, time: 30 s), then ultraviolet exposure is carried out for 30 s using a mask plate. After development, a circular photoresist with a diameter of 500 nm remains on the surface of the silicon substrate. A columnar silicon micro-nano structure is obtained by deep silicon etching. The columnar silicon micro-nano structure is further micro-etched using a method combining rotational etching technology and a plasma light source to form a frustum-shaped micro-nano structure.

[0051] To conformally coat the gas-sensitive quantum dot layer on the surface of the frustum-shaped micro-nano structure and form quantum dot spheres on its top, first, the quantum dot material is conformally coated on the surface of the frustum-shaped micro-nano structure by ultrasonic inverted spin-coating, that is, the silicon wafer with the frustum-shaped micro-nano structure is immersed in the quantum dot solution, with the side having the micro-nano structure facing up, and ultrasonic treatment is carried out (power: 50 W, frequency: 20 KHZ, time: 5 min). After stopping the ultrasonic treatment, immediately spin-coat with the side having the micro-nano structure facing down (rotation speed: 2000 rmp, time: 6 s). After spin-coating, it is immersed in a 0.01 wt% ethanedithiol solution for ligand exchange.

[0052] Taking the above ultrasonic inverted spin-coating method as one cycle, 8 cycles of coating are completed to achieve conformal coating and deposition of quantum dots on the surface of the micro-nano structure, and a micro-nano structure with conformal quantum dot coating is prepared.

[0053] After completing the conformal coating and deposition of quantum dots on the surface of the micro-nano structure, a quantum dot sphere is prepared by split-flow controlled spin-coating. Split-flow control means that when spin-coating quantum dots (with the side having the micro-structure facing up), a downward airflow is blown directly above the substrate with the micro-nano structure using a nitrogen gun with a flow rate of 20 mL / min. The spin-coating conditions are rotation speed: 300 rmp, time: 15 s. After completion, it is immersed in a 0.01% ethanedithiol solution for ligand exchange.

[0054] Taking the above split-flow controlled spin-coating method as one cycle, 6 - 10 cycles are completed to prepare quantum dot spheres on the upper surface of the micro-nano structure with conformal quantum dot coating. Thus, a column-sphere microfluidic structure capable of generating micro-vortices is prepared. When gas flows through the column-sphere structure array, the geometric discontinuity formed at the top of the small balls and the surface of the nano-columns triggers micro-vortices, increasing the residence time of gas molecules on the surface of the sensitive material. Finally, an upper electrode layer of metal nanowires is prepared on the surface of the column-sphere microfluidic structure, and metal is evaporated on the other side of the substrate as the lower electrode layer to complete the preparation of the micro-vortex quantum dot gas sensor.

[0055] The embodiment of the present invention also provides the application of the above micro-vortex quantum dot gas sensor in detecting NO 2 、H 2 S and VOCs.

[0056] Example 1

[0057] S1. Fabricate silicon nanocolumn arrays

[0058] Substrate preparation: Use a silicon wafer as the substrate material. First, ultrasonically clean it with deionized water and acetone, then rinse it with absolute ethanol and dry it to remove impurities and oxides on the surface of the substrate material, ensuring the substrate surface is smooth and clean.

[0059] Fabrication of silicon nanocolumns: Use photolithography and etching to fabricate frustum-shaped silicon micro-nano structures. First, spin-coat photoresist on the silicon substrate (rotation speed is 3000 rmp, time is 30 s), then perform 30 s of ultraviolet exposure using a mask plate. After development, a circular photoresist with a diameter of 500 nm remains on the surface of the silicon substrate. Use deep silicon etching to obtain columnar silicon micro-nano structures. Through the deep reactive ion etching (DRIE) technology, an array of nanocolumns with a height of 800 nm and a diameter of 500 nm is etched on the silicon wafer surface, and the spacing between columns is about 500 nm. Use a method combining rotational etching technology and a plasma light source to continue micro-etching the nanocolumn array to form a frustum-shaped micro-nano structure. The top diameter of the obtained frustum-shaped micro-nano structure is 300 nm, the bottom diameter is 500 nm, and the height is 800 nm, thus fabricating the silicon nanocolumn array. Figure 1 is the process flow chart for fabricating the frustum-shaped micro-nano structure; Figure 2 is the SEM structure diagram of the silicon nanocolumn array.

[0060] Surface cleaning and treatment: After etching, clean the silicon wafer to remove residual photoresist and oxide layer, ensuring the surface is free of contaminants, which is beneficial for subsequent coating of quantum dots.

[0061] S2. Prepare PbSe quantum dot solution

[0062] Put 0.64 g of Se powder, 6.4 mL of TOP solution and a magnetic stir bar into a screw-cap bottle, tighten the bottle cap, place it on a magnetic stirrer, and fully dissolve it (time is 2 h). Wait until there are no obvious particles in the bottle, that is, Se is completely dissolved in the TOP solution, and then put it into an ultrasonic cleaner for later use; take 0.892 g of PbO powder, measure 3.15 mL of oleic acid (OA) with a syringe, measure 16.28 mL of octadecene (ODE) with a graduated cylinder, pour them into a three-necked flask, put a magnetic stir bar in it, place the three-necked flask on an electric heating mantle, set the temperature of the electric heating mantle to 30 °C, stir and slowly open the vacuum knob, evacuate for 25 min, then pass nitrogen for about 15 min, and then heat up to 180 °C and keep this temperature for 1 h to ensure a liquid with uniform temperature is obtained. Quickly inject the Se-TOP solution, react for 5 min, and immediately perform an ice-water bath after the reaction is completed to prepare the PbSe quantum dot solution. Figure 3 is the TEM image of PbSe quantum dots, Figure 4 is the XRD pattern of PbSe quantum dots. FromFigure 3 and Figure 4 it can be seen that the size of the prepared PbSe quantum dots is about 10 nm, and the main crystal plane is the (100) plane.

[0063] S3. Preparation of column-sphere microfluidic structure

[0064] First, the PbSe quantum dots prepared in S2 were conformally coated on the surface of the frustum-shaped micro-nano structure by ultrasonic inversion spin coating, that is, the silicon wafer with the frustum-shaped micro-nano structure was immersed in the PbSe quantum dot solution, keeping the side with the micro-nano structure facing up, and ultrasonic treatment was carried out (power: 50 W, frequency: 20 KHZ, time: 5 min). After stopping the ultrasonic treatment, immediately spin coat with the side with the micro-nano structure facing down (rotation speed: 2000 rmp, time: 6 s). After the spin coating is completed, soak it (20 °C, 30 s) in a 0.01% ethanedithiol solution for ligand exchange.

[0065] Taking the above ultrasonic inversion spin coating method as one cycle, complete 8 cycles of coating to achieve conformal coating deposition of quantum dots on the surface of the micro-nano structure, and prepare a quantum dot conformal coating micro-nano structure;

[0066] The quantum dot sphere was prepared by the split-flow controlled spin coating method. Split-flow control means that when spin coating quantum dots (with the side with the micro-nano structure facing up), a downward airflow is blown directly above the substrate with the micro-nano structure by a nitrogen gun with a flow rate of 20 mL / min. The spin coating conditions are a rotation speed of 300 rmp and a time of 15 s. After the spin coating is completed, soak it in a 0.01% ethanedithiol solution for ligand exchange.

[0067] Taking the above split-flow controlled spin coating method as one cycle, complete 8 cycles to complete the preparation of the quantum dot sphere on the upper surface of the quantum dot conformal coating micro-nano structure, and prepare a column-sphere microfluidic structure (i.e., quantum dot conformal coating micro-nano structure + quantum dot sphere). Figure 5 is the preparation flow chart of the column-sphere microfluidic structure. Figure 6 is the SEM image of the column-sphere microfluidic structure. From Figure 6 it can be seen that the column-sphere microfluidic structure is a granular structure, which is beneficial to gas contact, and the coated quantum dots form a loose mushroom shape, which is more conducive to gas sensing detection.

[0068] S4. Preparation of electrodes

[0069] Preparation of the lower electrode: A metal electrode (such as gold) was deposited on the bottom of the silicon wafer by photolithography technology and evaporation process. The thickness of the lower electrode is 200 nm, and the size is the same as the bottom of the substrate, both being 10 mm * 10 mm.

[0070] Preparation of the upper electrode: To enable gas molecules to reach the surface of the sensitive material smoothly and make full contact with the sensitive material, a mesh of gold nanowires was spin-coated (2000 rmp, 60 s) on the surface of the column-sphere microfluidic structure to prepare the upper electrode layer. The diameter of the gold nanowires was 15 nm and the length was 2 μm. The mesh metal structure neither affects the passage of gas nor the transmission of electrons, thus improving the sensitivity of the gas sensor.

[0071] Comparative Example 1

[0072] S1. Same as Example 1;

[0073] S2. Same as Example 1;

[0074] S3. Preparation of quantum dot conformal coating micro-nano structure

[0075] First, the PbSe quantum dots prepared in S2 were conformally coated on the surface of the frustum-shaped micro-nano structure by ultrasonic inversion spin coating, that is, the silicon wafer with the frustum-shaped micro-nano structure was immersed in the PbSe quantum dot solution, keeping the side with the micro-nano structure facing up, and ultrasonic treatment was carried out (power 50 W, frequency 20 KHZ, time 5 min). After stopping the ultrasonic treatment, immediately spin coat with the side with the micro-nano structure facing down (rotation speed 2000 rmp, time 6 s). After spin coating, it was immersed in a 0.01% ethanedithiol solution for ligand exchange.

[0076] Taking the above ultrasonic inversion spin coating method as one cycle, 8 cycles of coating were completed to achieve conformal coating deposition of quantum dots on the surface of the micro-nano structure, and a quantum dot conformal coating micro-nano structure was prepared;

[0077] S4. Preparation of electrodes

[0078] Preparation of the lower electrode: A metal electrode (such as gold) was deposited on the bottom of the silicon wafer by photolithography technology and evaporation process. The thickness of the lower electrode was 200 nm, and the size was the same as the bottom of the substrate, both being 10 mm * 10 mm.

[0079] Preparation of the upper electrode: To enable gas molecules to reach the surface of the sensitive material smoothly and make full contact with the sensitive material, a mesh of gold nanowires was spin-coated (2000 rmp, 60 s) on the surface of the quantum dot conformal coating micro-nano structure to prepare the upper electrode. The diameter of the gold nanowires was 15 nm and the length was 2 μm.

[0080] Example 2:

[0081] Compared with Example 1, PbS quantum dots were used as the sensitive material and silver nanowires were used as the upper electrode in Example 2.

[0082] S1. Preparation of silicon nanowire arrays:

[0083] Substrate preparation: Use a silicon wafer as the substrate material. First, ultrasonically clean it with deionized water and acetone, then rinse and dry it with anhydrous ethanol to remove impurities and oxides on the surface of the substrate material, ensuring the substrate surface is smooth.

[0084] Preparation of silicon nanocolumns: Use photolithography and etching to prepare frustum-shaped silicon micro-nano structures. First, spin-coat photoresist on the silicon substrate (rotation speed is 3000 rmp, time is 30 s), then perform 30 s of ultraviolet exposure using a mask plate. After development, a circular photoresist with a diameter of 500 nm remains on the surface of the silicon substrate. Use deep silicon etching to obtain columnar silicon micro-nano structures. Through reactive ion etching technology (DRIE), etch a nano-column array with a height of 800 nm and a diameter of 500 nm on the silicon wafer surface. The spacing between columns is about 500 nm.

[0085] Use a method combining rotational etching technology and a plasma light source to continue micro-etching the nano-column array to form a frustum-shaped micro-nano structure. The upper surface diameter of the frustum-shaped micro-nano structure is 400 nm, the lower surface diameter is 600 nm, and the height is 800 nm.

[0086] S2. Prepare a PbS quantum dot solution

[0087] Add 0.45 g of PbO, 3 mL of octadecene (ODE), and 1.5 mL of oleic acid (OA) to a three-necked flask, add a magnetic stir bar, and charge high-purity nitrogen for 5 min to remove the original air in the three-necked flask. After removing the air, continue to pass nitrogen and turn on the constant-temperature magnetic stirrer to heat and stir the liquid. Turn on the intelligent temperature controller. After 10 min, the temperature will stabilize at 140 °C. After continuous heating for 1 h, close the nitrogen valve, stop charging nitrogen, open the vacuum valve, and start pumping vacuum. During this process, the temperature continues to be maintained at 140 °C. After pumping vacuum for 1 h, the reaction ends, and the Pb precursor has been prepared.

[0088] Turn off the constant-temperature magnetic stirrer and stop heating. Let the three-necked flask cool down to an appropriate value. Keep the vacuum valve open during this process so that the Pb precursor is in a vacuum state. Lower the three-necked flask and place it in a heating mantle, turn on the constant-temperature magnetic stirrer to start heating, set the temperature of the temperature controller to 100 °C, and wait for 30 min to make the temperature stabilize at 100 °C. The preparation work for the reaction is completed. Then mix and stir 10 mL of octadecene (ODE) and 210 μL of hexamethyldisilathiane (TMS) 2 S evenly, use a syringe to take the mixed solution of ODE and (TMS) 2 S, and quickly inject it into the three-necked flask (since (TMS) 2 S is a colorless liquid with a pungent odor, this process should be carried out under ventilation conditions, and promptly put the container of (TMS) 2Seal the medicine bottle of S and handle the pipette and syringe used when taking (TMS). 2 After 5 minutes, synthesize PbS quantum dots while handling the pipette and syringe used for S).

[0089] S3. Prepare the column-sphere microfluidic structure as in Example 1, except that the silicon wafer with frustum-shaped micro-nano structures is immersed in the PbS quantum dot solution, and the quantum dot material on the surface of the prepared column-sphere microfluidic structure is the gas-sensitive quantum dot layer, and the frustum-shaped micro-nano structure inside is the gas-sensitive metasurface layer.

[0090] S4. Prepare the electrodes

[0091] Preparation of the lower electrode: Deposit a metal electrode (such as gold) on the bottom of the silicon wafer using photolithography technology and evaporation process. The thickness of the lower electrode layer is 200 nm, and the size is the same as the bottom of the substrate, both being 10 mm * 10 mm.

[0092] Preparation of the upper electrode: Disperse silver nanowires in a mixed solution of ethanol, deionized water, and polyethylene glycol (PEG) (ethanol: water: PEG = 3:1:0.5) to obtain a silver nanowire suspension of 10 mg / mL. Using the stepwise speed-up spin-coating method, with an initial speed of 400 rpm / s, a middle stage of 1200 rpm / s, and a final stage of 2000 rpm / s, spin-coat a breathable and conductive silver nanowire upper electrode layer on the surface of the column-sphere microfluidic structure prepared in S3. Figure 7 Schematic diagram of the micro-vortex flow quantum dot gas sensor structure prepared in this example, where 1 is the silver nanowire upper electrode layer, 2 is the column-sphere microfluidic structure, 4 is the substrate layer, and 5 is the lower electrode layer.

[0093] Comparative Example 2

[0094] S1. Prepare the silicon nanocolumn array: same as Example 2;

[0095] S2. Prepare the PbS quantum dot solution: same as Example 2;

[0096] S3. Prepare the quantum dot conformal coating micro-nano structure: same as Example 2, except that the quantum dot spheres are not prepared by the split-flow controlled spin-coating method;

[0097] S4. Prepare the electrodes

[0098] Preparation of the lower electrode: Deposit a metal electrode (such as gold) on the bottom of the silicon wafer using photolithography technology and evaporation process. The thickness of the lower electrode is 200 nm, and the size is the same as the bottom of the substrate, both being 10 mm * 10 mm.

[0099] Preparation of the upper electrode: Silver nanowires were dispersed in a mixed solution of ethanol, deionized water, and polyethylene glycol (PEG) (ethanol: water: PEG = 3:1:0.5) to obtain a silver nanowire suspension with a concentration of 10 mg / mL. Using the stepwise speed-up spin-coating method, with an initial rotation speed of 400 rpm / s, a middle stage of 1200 rpm / s, and a final stage of 2000 rpm / s, an air-permeable and conductive upper electrode was spin-coated on the surface of the quantum dot conformal coating micro-nano structure prepared in S3.

[0100] Performance test experiment:

[0101] 1. Gas sensing detection experiment

[0102] Under room temperature conditions, the sensors prepared in Examples 1-2 and Comparative Examples 1-2 were placed in a sealed space, and 50 ppm of NO 2 gas Figure 8 is the sensitivity test result of the sensors prepared in Example 1 and Comparative Example 1. The sensitivity is defined as Rg / Ra, where Ra is the resistance value of the sensor in air, and Rg is the resistance value of the sensor in the target gas. It can be seen from Figure 8 that the column-sphere micro-vortex structure of the quantum dot conformal coating micro-nano structure + quantum dot sphere (Example 1) has higher sensitivity, which is 2 times that of the single quantum dot conformal coating micro-nano structure (Comparative Example 1).

[0103] Figure 9 is the sensitivity test result of the sensors prepared in Example 2 (left figure) and Comparative Example 2 (right figure) for H 2 S.

[0104] 2. Response time test experiment

[0105] Figure 10 is the response time test result of the sensors prepared in Example 1 (left figure) and Comparative Example 1 (right figure). It can be seen from Figure 10 that for the sensor prepared in Example 1, the response time is: the rise time is 142 s, and the fall time is 716 s. For the sensor prepared in Comparative Example 1, the response time is: the rise time is 364 s, and the fall time is 960 s.

[0106] 3. Environmental adaptability experiment

[0107] Figure 11 is the comparison chart of the sensitivity decay rate of the sensors prepared in Example 1 (left figure) and Comparative Example 1 (right figure) over time.

[0108] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A micro-eddy flow quantum point gas sensor, characterized in that: It includes a metal nanowire upper electrode layer, a pillar-sphere microfluidic structure, a base layer and a lower electrode layer stacked from top to bottom. The pillar-sphere microfluidic structure includes a gas-sensitive quantum dot layer and a gas-sensitive super surface layer. The gas-sensitive super surface layer is a truncated cone-shaped micro-nano structure. The gas-sensitive quantum dot layer uniformly covers the surface of the truncated cone-shaped micro-nano structure and forms a spherical coating structure on the top of the truncated cone-shaped micro-nano structure.

2. The micro-eddy current quantum point gas sensor according to claim 1, characterized in that: The top diameter of the truncated cone-shaped micro-nano structure is 0-800nm, the bottom diameter is 100nm-1000nm, the height is 100-1000nm, the bottom diameter is larger than the top diameter, and the top diameter is not 0.

3. A method for preparing a micro-eddy current quantum dot gas sensor according to claim 1 or 2, characterized in that: The following steps are involved: A truncated cone-shaped micro-nano structure is prepared on a substrate by photolithography and etching, and a quantum dot material is conformally coated on the surface of the truncated cone-shaped micro-nano structure by ultrasonic inverted spin coating. Then, ligand exchange is performed to obtain a quantum dot conformally coated micro-nano structure. Then, quantum dot balls are prepared on the upper surface of the quantum dot conformally coated micro-nano structure by split-fluidic spin coating and ligand exchange in sequence to obtain a column-sphere microfluidic structure. A lower electrode layer is deposited at the bottom of the substrate, and a metal nanowire electrode layer is prepared on the surface of the column-sphere microfluidic structure.

4. The method for preparing the micro-eddy current quantum dot gas sensor according to claim 3, characterized in that: The ultrasonic inverted spin coating method comprises the following steps: immersing a substrate with a truncated cone-shaped micro-nano structure into a quantum dot solution, keeping one side of the truncated cone-shaped micro-nano structure facing upward, performing ultrasound, and after stopping ultrasound, immediately performing spin coating with the side of the truncated cone-shaped micro-nano structure facing downward.

5. The method for preparing the micro-eddy current quantum dot gas sensor according to claim 4, characterized in that: The ultrasonic conditions are as follows: power of 50W, frequency of 20KHZ, and time of 5min.

6. The method for preparing the micro-eddy current quantum dot gas sensor according to claim 4, characterized in that: The spin coating conditions are: rotation speed of 2000 rpm and time of 6 s.

7. The method for preparing the micro-eddy current quantum dot gas sensor according to claim 3, characterized in that: The split-flow controlled spin coating method is as follows: when performing quantum dot spin coating, the side with the truncated cone-shaped micro-nano structure is facing upward, and a downward airflow is blown directly above the truncated cone-shaped micro-nano structure.

8. The method for preparing the micro-eddy current quantum dot gas sensor according to claim 7, characterized in that: The spin coating conditions are: rotation speed of 300 rpm and time of 15 s.

9. The method for preparing the micro-eddy current quantum dot gas sensor according to claim 7, characterized in that: The flow rate of the gas flow is 20 mL / min.

10. Use of the micro-eddy current quantum dot gas sensor according to claim 1 or 2 in detecting NO2, H2S and VOCs.

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