Formaldehyde gas sensor based on quantum dots and preparation method thereof

Abstract

The invention belongs to the field of gas sensors, and particularly discloses a formaldehyde gas sensor based on quantum dots and a preparation method of the formaldehyde gas sensor. The preparation method comprises the following steps: incubating a first electrode of a semiconductor device covered with a quantum dot film for 30-70 minutes by utilizing a formaldehyde dehydrogenase solution with the concentration of 0.1-1.5 mg / mL at the temperature of 25-37 DEG C, so that formaldehyde dehydrogenase is combined with the surface of the quantum dot film, and the formaldehyde gas sensor is obtained; wherein the semiconductor device is a planar electrochemical three-electrode or HEMT (High Electron Mobility Transistor); and the first electrode is a working electrode of the planar electrochemical three-electrode or a grid electrode of the HEMT. The response of the formaldehyde gas sensor to 50 ppm formaldehyde gas reaches 1.71, and meanwhile, the formaldehyde gas sensor can meet the requirement for detection of formaldehyde in multi-component gas.

Description

Technical Field

[0001] The present application belongs to the field of gas sensors, and more specifically, to a quantum dot-based formaldehyde gas sensor and a preparation method thereof. Background Art

[0002] The present application belongs to the technical field of design and application of quantum dot-based formaldehyde gas sensors, and relates to a highly specific formaldehyde gas sensor based on biological protein-modified quantum dots, and specifically to the construction and application of an electrochemical formaldehyde gas sensor based on biological enzyme protein-labeled colloidal quantum dots and a HEMT chip.

[0003] Formaldehyde is a common indoor air pollutant. It mainly comes from the slow release of binders in decoration and renovation materials. It is harmful to human health. Formaldehyde is a primary carcinogen. Long-term exposure to an environment with excessive formaldehyde will increase the risk of cancer and leukemia. At present, electrochemical gas sensors are one of the methods for formaldehyde sensing and detection, but the low detection limit and poor anti-interference ability restrict the development of formaldehyde gas sensors. Therefore, it is urgent to develop a formaldehyde gas sensor with a low detection limit and high anti-interference ability. In order to grasp the pollution status of indoor household formaldehyde in real time and improve the efficient formaldehyde control technology.

[0004] The existing technology uses spectral analysis and semiconductor gas sensor technology to detect formaldehyde in gas components, but the spectral analysis equipment is expensive, requires professional personnel to operate, and the equipment is not portable. Semiconductor gas sensor products are low-cost and suitable for civilian gas detection needs. However, it is limited by the fact that the sensor is cross-sensitive to multiple gases, so its anti-interference ability is poor, and it is easy to produce errors and false alarms when multi-component gases such as acetone, ethanol, benzene, phenol, ammonia, nitrogen oxides, etc. are present. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of the present application is to construct a quantum dot gas sensor that is specific to formaldehyde gas and a preparation method thereof to avoid interference from other gases.

[0006] The present application provides a method for preparing a formaldehyde gas sensor based on quantum dots, wherein a first electrode of a semiconductor device covered with a quantum dot film is incubated for 30 min to 70 min using a 0.1 mg / mL to 1.5 mg / mL formaldehyde dehydrogenase solution at a temperature of 25°C to 37°C, so that the formaldehyde dehydrogenase is bound to the surface of the quantum dot film, thereby obtaining the formaldehyde gas sensor; Wherein, the semiconductor device is a planar electrochemical three-electrode or HEMT; the first electrode is a working electrode of the planar electrochemical three-electrode or a gate of the HEMT.

[0007] Preferably, the formaldehyde dehydrogenase solution further comprises 2.5 mM to 10 mM β-nicotinamide adenine dinucleotide, and the pH value of the formaldehyde dehydrogenase solution is 7.2 to 7.6.

[0008] Preferably, the material of the quantum dot film is PbS, Bi 2 S 3 or WO 3 One or more of the foregoing, wherein the thickness of the quantum dot film is 500 nm to 1000 nm.

[0009] As a further preferred method, the preparation method of the first electrode of the semiconductor device covered with a quantum dot film is: drop-coating a colloidal quantum dot solution with a concentration of 7 mg / mL to 15 mg / mL on the surface of the first electrode of the semiconductor device to form a quantum dot film, and the size of the colloidal quantum dots in the colloidal quantum dot solution is 3.09 nm to 3.71 nm.

[0010] The present application also discloses a formaldehyde gas sensor, which comprises a three-electrode semiconductor device, wherein a quantum dot film is covered on the first electrode of the semiconductor device, and a 0.796 mg / cm 2 ~3.981 mg / cm 2 of formaldehyde dehydrogenase; The semiconductor device is a planar electrochemical three-electrode or HEMT; the first electrode is a working electrode of the planar electrochemical three-electrode or a gate of the HEMT; The electrolyte used in the formaldehyde gas sensor includes glycerol with a volume fraction of 10% to 40%. When the formaldehyde gas sensor is working, the specific catalytic effect of the formaldehyde dehydrogenase on formaldehyde is utilized to cause a redox reaction of formaldehyde to generate a current signal, thereby achieving specific detection of the formaldehyde concentration in the gas to be tested.

[0011] Preferably, the density of formaldehyde dehydrogenase bound to the surface of the quantum dot film is 0.796 mg / cm 2 ~1.194 mg / cm 2 .

[0012] Preferably, the pH value of the electrolyte is 7.2-7.6.

[0013] Preferably, the surface of the quantum dot film is also combined with 1.2 mg / cm 2 ~4.7mg / cm 2 β-nicotinamide adenine dinucleotide, or the neutral electrolyte also includes 2.5 mM ~10 mM β-nicotinamide adenine dinucleotide.

[0014] Preferably, the operating temperature of the formaldehyde gas sensor is 25°C to 37°C.

[0015] The present application also provides a method for detecting formaldehyde concentration using the above-mentioned formaldehyde gas sensor, comprising the following steps: S1. Under the condition that β-nicotinamide adenine dinucleotide is bound to the surface of the quantum dot film of the first electrode of the formaldehyde gas sensor, the first electrode of the formaldehyde gas sensor is covered with a neutral electrolyte, and the formaldehyde gas sensor is calibrated with formaldehyde gas of a standard concentration at a temperature of 25° C. to 37° C.; S2. Using the calibrated formaldehyde gas sensor to detect formaldehyde concentration at a temperature of 25°C to 37°C.

[0016] The present application also provides a method for detecting formaldehyde concentration using a quantum dot sensor, comprising the following steps: S1. Incubate the first electrode of the semiconductor device covered with the quantum dot film with a 0.1 mg / mL to 1.5 mg / mL formaldehyde dehydrogenase solution at a temperature of 25°C to 37°C for 30 min to 70 min to obtain a first electrode bound to formaldehyde dehydrogenase; S2. Under the condition that the surface of the first electrode bound to formaldehyde dehydrogenase is covered with β-nicotinamide adenine dinucleotide, the working area of ​​the semiconductor device is covered with a neutral electrolyte, and the semiconductor device is calibrated using a standard concentration of formaldehyde gas at a temperature of 25° C. to 37° C., wherein the neutral electrolyte includes 10% to 40% by volume of glycerol; S3. Detecting the formaldehyde concentration at a temperature of 25°C to 37°C using the calibrated semiconductor device; when the formaldehyde gas sensor is working, the formaldehyde dehydrogenase is used to specifically catalyze formaldehyde, causing a redox reaction of formaldehyde to generate a current signal, thereby achieving specific detection of the formaldehyde concentration in the gas to be tested; Preferably, the neutral electrolyte or the formaldehyde dehydrogenase solution further comprises 2.5 mM to 10 mM β-nicotinamide adenine dinucleotide.

[0017] Preferably, the semiconductor device is a planar electrochemical three-electrode or a high electron mobility transistor (HEMT); when the semiconductor device is a planar electrochemical three-electrode, the first electrode of the semiconductor device is the working electrode of the planar electrochemical three-electrode; when the semiconductor device is a HEMT, the first electrode of the semiconductor device is the gate of the HEMT.

[0018] Preferably, the material of the quantum dot film in step S1 is PbS, Bi 2 S3 or WO 3 One or more of the foregoing, wherein the thickness of the quantum dot film is 500 nm to 1000 nm.

[0019] Preferably, in step S2, the preparation method of the first electrode of the semiconductor device covered with a quantum dot film is: drop-coating a colloidal quantum dot solution with a concentration of 7 mg / mL to 15 mg / mL on the surface of the first electrode of the semiconductor device to form a quantum dot film, and the size of the colloidal quantum dots in the colloidal quantum dot solution is 3.09 nm to 3.71 nm.

[0020] Preferably, the pH value of the neutral electrolyte and the formaldehyde dehydrogenase solution is 7.2-7.6.

[0021] Preferably, in step S1, the density of the formaldehyde dehydrogenase on the surface of the first electrode combined with the formaldehyde dehydrogenase is 0.796 mg / cm 2 ~3.981mg / cm 2 .

[0022] As a further preferred embodiment, the density of the surface formaldehyde dehydrogenase of the first electrode combined with formaldehyde dehydrogenase is 0.796 mg / cm 2 ~1.194 mg / cm 2 .

[0023] In general, the above technical solutions conceived by this application have the following technical advantages compared with the prior art: 1. This application is based on the specific catalytic oxidation of formaldehyde by formaldehyde dehydrogenase in organisms, and utilizes the electron redox reaction of β-nicotinamide adenine dinucleotide coenzyme to nicotinamide adenine dinucleotide (NAD + ) and the reduced coenzyme (NADH), a formaldehyde dehydrogenase-based quantum dot gas sensor was designed to solve the problem of poor anti-interference ability of traditional formaldehyde gas sensors; 2. Based on the principle of biological bionics, this application uses electrochemical electrodes / HEMT chips as conversion elements and fixed carriers, fixes biological sensitive substances and enzymes as sensitive elements on the electrodes, and converts the target molecules and their reaction signals into electrical signals through the specific recognition between biological molecules, thereby achieving qualitative or quantitative detection of the target analyte; 3. Using an electrolyte containing a certain volume of glycerol can ensure good conductivity while maintaining a slow volatilization rate, thereby ensuring that the activity of formaldehyde dehydrogenase and β-nicotinamide adenine dinucleotide will not decrease during the detection process; 4. The preparation method of the enzyme-based quantum dot gas sensor is simple, with high specificity for formaldehyde gas and a response sensitivity of 50 ppm. It can also meet the detection of formaldehyde in multi-component gases; 5. During the preparation, the quantum dot film is prepared by the drop coating method. Without relying on organic cross-linking agents, the coupling of enzyme and quantum dots is achieved by the solid phase one-step labeling method, and the coupling interface between quantum dots and enzyme is regulated to achieve efficient transfer of electrons at the interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a gas-sensitive cyclic voltammetry test curve diagram of the prepared quantum dot sensor Example 1 in formaldehyde gas with different concentrations; Figure 2 The repeatability test results of the gas sensor prepared in Example 1 for 100 ppm formaldehyde at room temperature for 3 consecutive times; Figure 3 is a dynamic response test curve of the gas sensor prepared in Example 1 to 100 ppm formaldehyde at room temperature; Figure 4 is the response recovery curve of the quantum dot gas sensor of Example 1 to formaldehyde gas of different concentrations; Figure 5 The test results of the quantum dot gas sensor prepared in Example 1 at room temperature for 100 ppm ethanol, 100 ppm formaldehyde, 100 ppm ammonia, 100 ppm benzene, 50 ppm nitric oxide, 100 ppm acetone, 100 ppm p-xylene, and 50 ppm nitrogen dioxide; Figure 6 is the transfer characteristic curve test result of the quantum dot gas sensor of Example 8; Figure 7 This is the test result of the output characteristic curve of the quantum dot gas sensor of Example 8. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the feature. In the description of the present application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0027] In addition, references throughout this specification to "one embodiment"; "one embodiment", "an example" or similar language indicate that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present application. Thus, appearances of the phrase "in one embodiment"; "in one embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0028] Colloidal quantum dots have significant surface and size effects, and exhibit unique sensitivity in gas molecule detection. Formaldehyde dehydrogenase exists in most prokaryotes and all eukaryotic organisms. As an important formaldehyde detoxification system in organisms, formaldehyde dehydrogenases from different sources have high sequence similarity. The conservative existence of formaldehyde dehydrogenase proves its important role in organisms. Based on the specific catalytic effect of formaldehyde dehydrogenase on formaldehyde, the formaldehyde dehydrogenase is fixed on the colloidal quantum dots by using the "electronic glue" of colloidal quantum dots to achieve specific detection of formaldehyde gas in complex atmospheres.

[0029] The purpose of the present application is to provide a novel method for synthesizing a novel nicotinamide adenine dinucleotide (NAD + ) quantum dot formaldehyde gas sensor. Formaldehyde dehydrogenase (FALDH) utilizes the coenzyme nicotinamide adenine dinucleotide (NAD + ) as an electron acceptor to oxidize formaldehyde into formic acid with lower toxicity, and at the same time obtain reduced coenzyme (NADH), thereby realizing specific detection of formaldehyde gas. Therefore, the technical problem to be solved by this application is to construct a quantum dot gas sensor that is specific to formaldehyde gas and can avoid interference from other gases.

[0030] The present application provides a method for detecting formaldehyde concentration using a quantum dot sensor, comprising the following steps: S1. Incubate the first electrode of the semiconductor device covered with a quantum dot film with a formaldehyde dehydrogenase solution at a temperature of 25°C to 37°C for 30 min to 70 min to obtain a first electrode combined with formaldehyde dehydrogenase; specifically, the material of the quantum dot film is PbS, Bi 2 S 3 or WO 3 One or more of the following, wherein the thickness of the quantum dot film is 500 nm to 1000 nm; Correspondingly, the density of the formaldehyde dehydrogenase on the surface of the first electrode is related to the concentration of the formaldehyde dehydrogenase solution and the incubation time. If the solution concentration is too low, the incubation time will be increased, which may cause the enzyme to be inactivated due to long exposure time at room temperature. Therefore, the concentration of the formaldehyde dehydrogenase solution is preferably 0.1 mg / mL to 1.5 mg / mL, and the corresponding density of the formaldehyde dehydrogenase on the surface of the first electrode after incubation is 0.796 mg / cm 2 ~3.981 mg / cm 2 In some embodiments, when the surface density of formaldehyde dehydrogenase of the first electrode is 0.796 mg / cm 2 ~1.194 mg / cm 2 The detection performance is best when The semiconductor device is a planar electrochemical three-electrode or HEMT; when the semiconductor device is a planar electrochemical three-electrode, the first electrode of the semiconductor device is a working electrode of the planar electrochemical three-electrode; when the semiconductor device is a HEMT, the first electrode of the semiconductor device is a gate of the HEMT; S2. Under the condition that the surface of the first electrode bound to formaldehyde dehydrogenase is covered with β-nicotinamide adenine dinucleotide, the first electrode of the semiconductor device is covered with a neutral electrolyte, the semiconductor device is calibrated using a standard concentration of formaldehyde gas at a temperature of 25°C to 37°C, and a test curve corresponding to the electrical signal and the formaldehyde gas concentration is established; the neutral electrolyte includes glycerol with a volume fraction of 10% to 40%; specifically, the formaldehyde gas of the standard concentration can be a formaldehyde gas with different concentration gradients after being diluted with a carrier gas, and the carrier gas and the specific concentration are determined according to the specific conditions of the gas to be detected. For example, when the formaldehyde concentration in the air of the gas to be detected is (at a concentration of about 100 ppm), air can be used as the carrier gas, and the concentration can adopt a concentration gradient between 50 ppb and 200 ppm.

[0031] S3. Using the calibrated semiconductor device to detect formaldehyde concentration at a temperature of 25° C. to 37° C.

[0032] Specifically, there are two methods for achieving the condition that the surface of the first electrode is covered with β-nicotinamide adenine dinucleotide in step S2: the first method is to add 2.5 mM to 10 mM β-nicotinamide adenine dinucleotide to the formaldehyde dehydrogenase solution in step S1, and incubate β-nicotinamide adenine dinucleotide and formaldehyde dehydrogenase on the surface of the first electrode at the same time (the density of β-nicotinamide adenine dinucleotide on the surface of the first electrode is about 1.2 mg / cm 2 ~4.7mg / cm 2). The second method is to add 2.5 mM to 10 mM β-nicotinamide adenine dinucleotide and 10% to 40% by volume of glycerol to the neutral electrolyte in step S2, so that β-nicotinamide adenine dinucleotide exists in the electrolyte environment; When the formaldehyde gas sensor is working, the specific catalytic effect of the formaldehyde dehydrogenase on formaldehyde is utilized to cause a redox reaction of formaldehyde to generate a current signal, thereby realizing the calibration and specific detection of the formaldehyde concentration in the gas to be tested; at the same time, as the neutral electrolyte evaporates under the airflow, the current test baseline will drift, affecting the accuracy of the test; glycerol, as a moisturizing solution, can effectively slow down the volatilization of the neutral electrolyte, and can also absorb moisture in the air to play a role in moisture compensation, maintain the stability of the enzyme-gas reaction interface, and ensure that the activities of formaldehyde dehydrogenase and β-nicotinamide adenine dinucleotide will not decrease during the detection process, avoiding the deviation of the test results from the test curve after the activity decreases, thereby ensuring the accuracy of the test results.

[0033] In some embodiments, the pH values ​​of the neutral electrolyte and the formaldehyde dehydrogenase solution are both 7.2-7.6, so PBS can be used as a dilution solvent.

[0034] Specifically, the method for preparing the first electrode of the semiconductor device covered with the quantum dot film in step S1 is: S1. At a temperature of 95℃~120℃, colloidal quantum dots with a size of 3.09 nm~3.71 nm were synthesized using an organic hot injection method; by regulating the temperature of hot injection, colloidal quantum dots of different sizes can be synthesized, wherein the size of the quantum dots corresponding to the hot injection temperature of 95℃ is 3.09 nm, the size of the quantum dots corresponding to the hot injection temperature of 100℃ is 3.50 nm, the size of the quantum dots corresponding to the hot injection temperature of 110℃ is 3.59 nm, and the size of the quantum dots corresponding to the hot injection temperature of 120℃ is 3.71 nm, and the interface between biomolecules and colloidal quantum dots can be regulated; S2. Dropping a colloidal quantum dot solution having a concentration of 7 mg / mL to 15 mg / mL onto the surface of the first electrode of the semiconductor device to form a quantum dot film, wherein the thickness of the quantum dot film is 500 nm to 1000 nm.

[0035] The following are specific examples, and the sources of the reagents and equipment involved in the examples are as follows: Formaldehyde dehydrogenase: purchased from Shanghai Yuanye Biotechnology Co., Ltd.; β-Nicotinamide adenine dinucleotide: mass fraction 98%: purchased from Beijing Inokai Technology Co., Ltd.; Phosphate buffered saline (PBS): purchased from Beijing Inokai Technology Co., Ltd.; Glycerol solution (100%, sterile): purchased from Beijing Inokai Technology Co., Ltd.; Formaldehyde dehydrogenase solution: Dissolve the lyophilized formaldehyde dehydrogenase powder in PBS solution and shake for 10 min until fully dissolved to obtain a formaldehyde dehydrogenase solution with the corresponding mass fraction; Coenzyme solution: Dissolve the corresponding mass of β-nicotinamide adenine dinucleotide in PBS and shake for 10 min until fully dissolved to obtain a coenzyme solution with the corresponding mass fraction / molar concentration; Glycerol-PBS mixed solution: a solution obtained by mixing PBS and glycerol at a volume ratio of 4:1; Coenzyme glycerol solution: Dissolve the corresponding mass of β-nicotinamide adenine dinucleotide in a glycerol PBS mixed solution and shake for 10 min until fully dissolved to obtain a coenzyme solution with the corresponding mass fraction / molar concentration; Toluene: purchased from Sinopharm Chemical Reagent Co., Ltd.; Electrochemical planar three electrodes: purchased from Botan Technology (Weihai) Co., Ltd. High electron mobility transistor chip (HEMT): homemade in the laboratory; Electrochemical workstation CHI760E: purchased from Shanghai Chenhua Instrument Co., Ltd. Semiconductor parameter analyzer: Keysight B1500A semiconductor parameter analyzer; V-1530T constant temperature heating platform: purchased from Dongguan V-1530T Automation Technology Co., Ltd. High-precision dynamic gas distribution device: homemade in the laboratory; Planar electrochemical gas sensing test chamber: homemade in the laboratory.

[0036] Example 1 S1. Synthesis of colloidal quantum dots: PbS colloidal quantum dots were synthesized by the classic organic hot injection method. 1.8 g of lead oxide was placed in a three-necked flask. 6 mL of oleic acid and 20 mL of octadecene were injected and stirred at high speed. The precursor of lead oleate was prepared by vacuuming and heating to 90 °C. After vacuuming for 8 hours, the temperature of the precursor was raised to 120 °C. In the glove box, 280 μL of TMS was taken with a pipette and dissolved in the vacuumed octadecene (10 mL) to prepare the sulfur precursor. The sulfur precursor was quickly injected into the lead precursor under a nitrogen environment. After the hot injection reaction for 30 s, the heating jacket was turned off and removed, and the three-necked flask was placed in a pre-prepared cold water bath for rapid cooling. The cooled PbS quantum dot source solution was aspirated into a centrifuge tube with a dropper in four batches. A certain amount of acetone was added for centrifugal washing once, and the supernatant was discarded. The remaining product was dispersed and dissolved in toluene, and then acetone was added for centrifugal washing. The speed of each centrifugation is 8000 rpm, and the time is controlled within 10 minutes. After three centrifugations, the black precipitate obtained is PbS quantum dots. The quantum dots are then stored in a toluene solution and prepared into a 10 mg / mL solution for later use.

[0037] S2. Preparation of quantum dot film: The quantum dot solution was drop-coated on the working electrode of the planar electrochemical three-electrode by the drop-coating method. After the solvent evaporated, a quantum dot film was formed. After testing, the size of the quantum dots was about 3.71 nm and the thickness of the quantum dot film was about 550 nm.

[0038] S3. Incubation of formaldehyde dehydrogenase: A 0.1% formaldehyde dehydrogenase solution was drop-coated on the prepared quantum dot film. The volume ratio of the quantum dot solution to the formaldehyde dehydrogenase solution was 1:1. The film was incubated at 37°C for 1 h to form a stable formaldehyde dehydrogenase-quantum dot binding interface. The unit area density of formaldehyde dehydrogenase was about 0.796 mg / cm 2 ; S4. Add 1 mL of 0.295% coenzyme glycerol solution (equivalent to a molar concentration of 5 mM) to completely cover the electrochemical planar three electrodes (the mass of the coenzyme per unit area is 0.796-1.194 mg / cm 2 ), a formaldehyde gas sensor is obtained. A certain concentration of formaldehyde gas is introduced through a high-precision gas distribution system, and the potential of the constant potential current-time test is determined according to the position of the redox peak through the cyclic voltammetry test curve, for subsequent testing.

[0039] Example 2 Example 1 was repeated with the same steps, except that in step S1, the temperature of the precursor was raised to 110°C before hot injection. In step S2, it was detected that the size of the quantum dots was about 3.59 nm.

[0040] Example 3 Example 1 was repeated with the same steps, except that in step S1, the temperature of the precursor was raised to 100°C before hot injection. In step S2, it was detected that the size of the quantum dots was about 3.50 nm.

[0041] Example 4 Example 1 was repeated with the same steps, except that in step S1, the temperature of the precursor was raised to 95°C before hot injection. In step S2, it was detected that the size of the quantum dots was about 3.09 nm.

[0042] Example 5 Example 1 was repeated with the same steps, except that in step S3, the mass fraction of the formaldehyde dehydrogenase solution was 0.15%.

[0043] Example 6 Example 1 was repeated with the same steps, except that in step S4, the mass fraction of the coenzyme glycerol solution was 0.356% (equivalent to a molar concentration of 6 mM).

[0044] Example 7 Repeat steps S1 and S2, S3 and S4 of Example 1 in the same manner as follows: S3. A coenzyme glycerol solution with a mass fraction of 0.295% (equivalent to a molar concentration of 5 mM) was mixed with an equal volume of a formaldehyde dehydrogenase solution with a mass fraction of 0.1%, and the mixture was drop-coated on the prepared quantum dot film and incubated at a constant temperature of 25°C for 1 h. The volume ratio of the quantum dot solution, the formaldehyde dehydrogenase solution, and the coenzyme glycerol solution was 1:1:1, forming a stable formaldehyde dehydrogenase / β-nicotinamide adenine dinucleotide-quantum dot binding interface; S4. Add glycerol PBS mixed solution dropwise until the three electrochemical electrodes are completely covered to obtain a formaldehyde gas sensor.

[0045] Example 8 Design and preparation method of formaldehyde gas sensor based on quantum dots: Repeat steps S1-S3 of Example 1 in the same manner, except that, in step S2, the quantum dot solution is drop-coated on the gate region of the high electron mobility field effect transistor (HEMT) by a drop coating method, and the solvent evaporates to form a quantum dot film; Step S4 is as follows: A coenzyme glycerol solution with a mass fraction of 0.295% (equivalent to a molar concentration of 5 mM) was directly added dropwise to completely cover the gate area of ​​the high electron mobility field effect transistor (HEMT) chip to obtain a formaldehyde gas sensor for subsequent testing.

[0046] Comparative Example This comparative example provides a quantum dot gas sensor, which is different from Example 1 only in that no quantum dot film is formed, and the same concentration of formaldehyde dehydrogenase solution and coenzyme glycerol solution are directly drop-coated on the working electrode area of ​​the electrochemical three-electrode to obtain a gas sensor with only formaldehyde dehydrogenase modified electrode.

[0047] Test Example 1 Cyclic voltammetry test curves in different concentrations of formaldehyde gas The sensor of Example 1 was tested using a CHI760 electrochemical workstation. Figure 1 As shown. The test results show that as the formaldehyde gas concentration (carrier gas is air) increases, the intensity of the reduction peak gradually decreases, proving that the prepared quantum dot gas sensor has a good response to formaldehyde gas.

[0048] Test Example 2 Response to formaldehyde gas The gas-sensing performance of the device of Example 1 was tested at room temperature using a Chenhua electrochemical workstation. First, air was introduced into the test chamber, then formaldehyde diluted with air to different concentrations was introduced, and then air was introduced to obtain a gas-sensitive response curve. The quantum dot gas sensor prepared in Example 1 was tested for 100 ppm formaldehyde at room temperature. It can be seen from the figure that the sensor exhibits good response recovery characteristics, which confirms that the prepared quantum dot sensor can sensitively detect formaldehyde gas at room temperature and has excellent response characteristics.

[0049] Test Example 3: Repeatability of the response to formaldehyde gas The conditions of Test Example 2 were kept consistent. The quantum dot sensor prepared in Example 1 was tested three times in a 100 ppm formaldehyde atmosphere. The results were as follows: Figure 3 As shown, it can be found that the sensor has good repeatability and at least three repeatability tests can be achieved.

[0050] Test Example 4 Response of quantum dot-based formaldehyde gas sensor to formaldehyde gas of different concentrations Consistent with the conditions of Test Example 2, different concentrations of formaldehyde (50 ppb~200 ppm) were tested at room temperature. Figure 4 As shown, it can be seen that the embodiment has a response of 1.71 to 50 ppm formaldehyde gas. Therefore, the quantum dot gas sensor exhibits excellent response recovery characteristics to formaldehyde of different concentrations.

[0051] Test Example 5 Specificity of quantum dot-based formaldehyde gas sensor Consistent with the conditions of Test Example 2, 14 gases including formaldehyde with different concentrations after being diluted with air were tested at room temperature, including 100 ppm acetone, 100 ppm ammonia, 100 ppm carbon monoxide, 100 ppm hydrogen sulfide, 100 ppm ethanol, 100 ppm ethyl acetate, 100 ppm formaldehyde, 10 ppm phenol, 50 ppm sulfur dioxide, 50 ppm nitric oxide, 50 ppm benzene, 50 ppm hydrogen, 50 ppm nitrogen dioxide, and 200 ppm acetic acid; Figure 5 As shown, it can be seen that, except for formaldehyde gas, the gas sensor prepared in Example 1 has only a very weak response to ethyl acetate, and the sensor shows excellent specificity to formaldehyde gas.

[0052] Based on the above performance test results, it is shown that the response of the quantum dot gas sensor prepared in the embodiment of the present application to 50 ppm formaldehyde gas at room temperature is 1.7, and it has excellent selectivity and good repeatability.

[0053] On the basis of Example 1, the incubation temperature of step S3 is adjusted between 25°C and 37°C, the concentration of the formaldehyde dehydrogenase solution is adjusted between 0.01wt% and 0.15wt%, or the incubation time of step S3 is adjusted between 30 and 70min, or the concentration of the coenzyme in step S4 is adjusted between 2.5 mM and 10 mM, or the volume ratio of PBS and glycerol in the glycerol-PBS mixed solution used to dissolve the coenzyme is adjusted between 3:2 and 10:1; after testing, the obtained formaldehyde gas sensors all have a specific response to formaldehyde gas; however, when the glycerol-PBS mixed solution for dissolving the coenzyme is replaced by a pure PBS solution, it is difficult to determine the characteristics of the specific response. This may be because glycerol, as a moisturizing solution, can effectively slow down the volatilization of the neutral electrolyte, and can also absorb moisture in the air, thereby playing a role in moisture compensation, maintaining the stability of the enzyme-gas reaction interface, and ensuring the accuracy of the test results.

[0054] Test Example 6 Transfer characteristic curve test of quantum dot-based formaldehyde gas sensor chip The transfer characteristic curve of the formaldehyde sensor chip in Example 8 in air was tested using a semiconductor parameter tester. Figure 6 As shown in the figure, when the drain voltage is 0.1 V to 0.5 V, it can be seen that the threshold voltage shifts to the left. The control gate voltage has a strong ability to regulate the drain current of the sensor.

[0055] Test Example 7 Output characteristic curve of quantum dot-based formaldehyde gas sensor chip The test conditions are consistent with those of Test Example 6. When the field effect transistor operates in the subthreshold swing region, the leakage current of the sensor in formaldehyde gas changes most significantly. When the control gate bias VCG is fixed at −3V, the output characteristic curve of the sensor in a formaldehyde atmosphere of 0 to 100 ppm is further tested. Figure 7 As shown in Figure 2, as the formaldehyde gas concentration increases, the sensor threshold voltage will shift negatively.

[0056] On the basis of Example 8, the concentration of the coenzyme in step S4 is adjusted between 2.5 mM and 10 mM, or the volume ratio of PBS and glycerol in the glycerol PBS mixed solution used to dissolve the coenzyme is adjusted between 3:2 and 10:1; after testing, both exhibited similar electrical properties to the formaldehyde gas sensor chip of Example 8.

[0057] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing a formaldehyde gas sensor based on quantum dots, characterized in that: At a temperature of 25° C. to 37° C., incubating the first electrode of the semiconductor device covered with the quantum dot film with a 0.1 mg / mL to 1.5 mg / mL formaldehyde dehydrogenase solution for 30 min to 70 min, so that the formaldehyde dehydrogenase binds to the surface of the quantum dot film, thereby obtaining the formaldehyde gas sensor; Wherein, the semiconductor device is a planar electrochemical three-electrode or HEMT; the first electrode is a working electrode of the planar electrochemical three-electrode or a gate of the HEMT.

2. The preparation method according to claim 1, characterized in that The formaldehyde dehydrogenase solution also includes 2.5 mM to 10 mM β-nicotinamide adenine dinucleotide, and the pH value of the formaldehyde dehydrogenase solution is 7.2 to 7.

6.

3. The preparation method according to claim 1, characterized in that The material of the quantum dot film is one or more of PbS, Bi2S3 or WO3, and the thickness of the quantum dot film is 500 nm~1000 nm.

4. The preparation method according to claim 3, characterized in that The method for obtaining the first electrode of the semiconductor device covered with a quantum dot film is: drop-coating a colloidal quantum dot solution with a concentration of 7 mg / mL to 15 mg / mL on the surface of the first electrode of the semiconductor device to form a quantum dot film, wherein the size of the colloidal quantum dots in the colloidal quantum dot solution is 3.09 nm to 3.71 nm.

5. A formaldehyde gas sensor, characterized in that: A semiconductor device comprising three electrodes, wherein a quantum dot film is covered on the first electrode of the semiconductor device, and a 0.796 mg / cm 2 ~3.981mg / cm 2 of formaldehyde dehydrogenase; The semiconductor device is a planar electrochemical three-electrode or HEMT; the first electrode is a working electrode of the planar electrochemical three-electrode or a gate of the HEMT; The electrolyte used in the formaldehyde gas sensor includes glycerol with a volume fraction of 10% to 40%. When the formaldehyde gas sensor is working, the specific catalytic effect of the formaldehyde dehydrogenase on formaldehyde is utilized to cause a redox reaction of formaldehyde to generate a current signal, thereby achieving specific detection of the formaldehyde concentration in the gas to be tested.

6. The formaldehyde gas sensor according to claim 5, characterized in that: The pH value of the electrolyte is 7.2-7.

6.

7. The formaldehyde gas sensor according to claim 5, characterized in that: The surface of the quantum dot film is also combined with 1.2 mg / cm 2 ~4.7mg / cm 2 β-nicotinamide adenine dinucleotide, or the electrolyte further includes 2.5 mM ~10 mM β-nicotinamide adenine dinucleotide.

8. The formaldehyde gas sensor according to claim 5, characterized in that: The operating temperature of the formaldehyde gas sensor is 25°C to 37°C.

9. A method for detecting formaldehyde concentration using the formaldehyde gas sensor according to any one of claims 5 to 8, characterized in that: The following steps are involved: S1. Under the condition that β-nicotinamide adenine dinucleotide is bound to the surface of the quantum dot film of the first electrode of the formaldehyde gas sensor, the first electrode of the formaldehyde gas sensor is covered with a neutral electrolyte, and the formaldehyde gas sensor is calibrated with formaldehyde gas of a standard concentration at a temperature of 25° C. to 37° C.; S2. Using the calibrated formaldehyde gas sensor to detect formaldehyde concentration at a temperature of 25°C to 37°C.

10. The method according to claim 9, wherein the pH value of the neutral electrolyte is 7.2-7.6.

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