QCM (Quartz Crystal Microbalance) sensor for detecting droplets as well as preparation method and application of QCM sensor

Abstract

The invention discloses a QCM sensor for detecting droplets as well as a preparation method and application of the QCM sensor, and belongs to the technical field of sensors. The QCM comprises a QCM substrate, a nanometer titanium dioxide / black phosphorus quantum dot film is arranged on the QCM substrate, nanometer titanium dioxide particles have good chemical stability in air, in addition, phosphorus atoms on the edges of black phosphorus quantum dots and oxygen atoms in the air can easily form covalent bonds, and the oxygen atoms in the air can form a covalent bond. Stronger interaction (such as hydrogen bond connection) can be formed between oxygen atoms and water molecules, so that the black phosphorus quantum dots are very strong in hydrophilicity, and the combination of the oxygen atoms and the water molecules enables the sensor to have higher adsorption capacity on droplets while having high stability. According to the invention, the sensor can adsorb more tiny droplets flying along with the cough airflow, and can generate a signal change which is large enough so as to judge whether the droplets are detected or not; through testing, the QCM sensor can detect droplets generated by cough of a testee at the position of 2.4 m.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors, and in particular relates to a QCM sensor for detecting droplets and a preparation method and application thereof. Background Art

[0002] Detecting respiratory droplets transmitted between people is crucial to reducing the spread of respiratory diseases. It can provide information on droplet infection, enable timely intervention and isolation of the source, reduce the risk of transmission, and protect public health. Currently, the main method for detecting droplets is to use some optical imaging techniques (such as high-speed photography, schlieren method, laser scattering method, etc.). Simha et al. used the schlieren method to study droplet transmission in the document Universal trends in human cough airflows at large distances (Physics of Fluids, 2020, Vol. 32, No. 8). However, these optical devices are expensive and bulky, making them difficult to use in daily protection.

[0003] Therefore, how to provide a sensor that is easy to detect droplets is a difficult problem that needs to be explored in this field. Patent No. CN118348075A discloses a droplet sensor and its preparation method and application, which realizes the detection of droplets. However, its maximum detection distance is 2 meters. Researching sensors that can detect droplet transmission farther is of great significance to improving the effect of daily protection. Summary of the invention

[0004] In order to further improve the detection distance of the droplet sensor, the present invention provides a QCM sensor for detecting droplets and a preparation method and application thereof.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A QCM sensor for detecting droplets comprises a QCM substrate on which a nano titanium dioxide film doped with black phosphorus quantum dots is arranged.

[0007] After adopting this technical solution, the QCM substrate prepared by the present invention has its basic resonance frequency significantly improved through precise regulation of the resonance characteristics, thereby having a greater mass sensitivity and being able to produce obvious signal changes after detecting tiny droplets; the nano-titanium dioxide particles have good chemical stability in the air. In addition, the phosphorus atoms at the edges of the black phosphorus quantum dots easily form covalent bonds with oxygen atoms in the air, and a strong interaction (such as hydrogen bond connection) can be formed between the oxygen atoms and water molecules, making the black phosphorus quantum dots highly hydrophilic. The combination of the two makes the sensor have high stability while also having a strong adsorption capacity for droplets. At the same time, due to the strong adsorption capacity brought by the black phosphorus quantum dots, the sensor also has an extremely fast response speed, which plays a key role in detecting rapidly evaporating droplets.

[0008] Preferably, the nano-titanium dioxide in the nano-titanium dioxide film doped with black phosphorus quantum dots is in granular form, and the particle size is less than or equal to 50 nm.

[0009] Preferably, the diameter of the black phosphorus quantum dots in the nano-titanium dioxide film doped with black phosphorus quantum dots is less than or equal to 10 nm.

[0010] Preferably, the QCM substrate comprises a quartz crystal and a second electrode and a first electrode respectively arranged on the upper surface and the lower surface of the quartz crystal, and the nano titanium dioxide film doped with black phosphorus quantum dots is arranged on the second electrode.

[0011] Preferably, the first electrode and the second electrode are formed by vacuum deposition.

[0012] Preferably, the vacuum coating method is an evaporation coating method or a sputtering coating method.

[0013] Preferably, the first electrode and the second electrode are both made of silver or gold.

[0014] Preferably, the area of ​​the quartz crystal is less than 10 mm 2 .

[0015] Preferably, the fundamental resonant frequency of the QCM substrate is above 14.7 MHz.

[0016] A method for preparing a QCM sensor for detecting droplets, comprising:

[0017] Fabrication of QCM substrate;

[0018] Configuration of nano titanium dioxide solution;

[0019] Configuration of black phosphorus quantum dot solution;

[0020] The nano titanium dioxide solution and the black phosphorus quantum dot solution are configured into a nano titanium dioxide / black phosphorus quantum dot solution;

[0021] A nano titanium dioxide / black phosphorus quantum dot solution is made to form a nano titanium dioxide film doped with black phosphorus quantum dots on a QCM substrate to obtain a QCM sensor for detecting droplets.

[0022] Preferably, the concentration of the nano-titanium dioxide solution is 0.1-10 mg / ml, the concentration of the black phosphorus quantum dot solution is 0.01-1 mg / ml, and the nano-titanium dioxide solution and the black phosphorus quantum dot solution are configured in a volume ratio of 1:0.1-5 to form a nano-titanium dioxide / black phosphorus quantum dot solution.

[0023] Preferably, the nano-titanium dioxide / black phosphorus quantum dot solution is formed on the QCM substrate by atomization natural deposition method to form a nano-titanium dioxide film doped with black phosphorus quantum dots.

[0024] Preferably, the specific process of the atomization natural deposition method is: take 1 to 5 ml of the prepared nano-titanium dioxide / black phosphorus quantum dot solution and put it into the medicine cup of the atomizer to prepare for atomization, place the prepared QCM substrate horizontally with the sensitive surface facing up, use the atomization natural deposition method, so that the atomization airflow does not directly impact the sensitive surface of the substrate, and fill the container after the solution is atomized into mist particles, let it stand for 15 to 60 minutes to allow the particles to naturally deposit on the substrate surface, and then dry the QCM substrate in a room temperature environment not higher than 35 degrees Celsius for 1 to 2 hours to obtain a QCM substrate with a uniform distribution of nano-titanium dioxide / black phosphorus quantum dot film.

[0025] Preferably, the dosage of the nano titanium dioxide solution and the black phosphorus quantum dot solution is 0.01-0.05 ml / cm 2 , and the amount of the nano titanium dioxide solution and the black phosphorus quantum dot solution increases as the bottom area of ​​the container used in the atomization natural deposition method increases.

[0026] After adopting this technical solution, the larger the bottom area of ​​the container used in the atomized natural deposition method, the more dispersed the atomized solution is, the less solution falls on the substrate, and the thinner the formed nano titanium dioxide / black phosphorus quantum dot film is. By controlling the bottom area of ​​the container and the amount of solution used, the thickness of the nano titanium dioxide / black phosphorus quantum dot film can be controlled within an appropriate range, avoiding the nano titanium dioxide / black phosphorus quantum dot film from being too thick, making the adsorption and desorption of water molecules faster, and improving the response speed of the sensor; avoiding the titanium dioxide / black phosphorus quantum dot film from being too thin, and improving the sensitivity of the sensor.

[0027] Preferably, the nebulizer is a compressed air nebulizer or an ultrasonic nebulizer.

[0028] The invention discloses an application of a QCM sensor for detecting droplets in detecting droplets.

[0029] After adopting this technical solution, the sensor can absorb more tiny droplets flying with the cough airflow and can produce a sufficiently large signal change to determine whether droplets are detected; after testing, the QCM sensor of the present invention can detect droplets generated by the tester's cough at a distance of 2.4 meters.

[0030] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0031] The QCM substrate prepared by the present invention has its basic resonance frequency significantly improved through precise regulation of resonance characteristics, thereby having greater mass sensitivity and being able to produce obvious signal changes after detecting tiny droplets; the nano-titanium dioxide particles have good chemical stability in the air, and in addition, the phosphorus atoms at the edge of the black phosphorus quantum dots easily form covalent bonds with oxygen atoms in the air, and a strong interaction (such as hydrogen bond connection) can be formed between the oxygen atoms and water molecules, making the black phosphorus quantum dots highly hydrophilic. The combination of the two makes the sensor have high stability and strong adsorption capacity for droplets; at the same time When the black phosphorus quantum dots and nano-titanium dioxide particles are connected, a heterojunction can be formed. The interface of this structure can form a special built-in electric field, which further enhances the adsorption capacity of droplets. In addition, the Langmuir monolayer adsorption model calculates that after the nano-titanium dioxide particle film is doped with black phosphorus quantum dots, the Gibbs free energy of the adsorption reaction is reduced by about 1.5 kilojoules / mole, proving that the adsorption capacity of the film is enhanced after the addition of black phosphorus quantum dots. In addition, due to the thin thickness of the nano-titanium dioxide / black phosphorus quantum dot film, the sensor has an extremely fast response speed, which plays a key role in detecting droplets that evaporate rapidly. Under the combined effect of these effects, the sensor can adsorb more tiny droplets flying with the cough airflow, and can generate a sufficiently large signal change to determine whether droplets are detected; after testing, the QCM sensor of the present invention can detect droplets generated by the tester's cough at 2.4 meters. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A cross-sectional schematic diagram of a QCM sensor for detecting droplets of the present invention;

[0033] Figure 2 It is a schematic diagram of film making by the atomized natural deposition method of the present invention;

[0034] Figure 3 This is a diagram showing the stability test results of the QCM sensor for detecting droplets of the present invention;

[0035] Figure 4 A waveform diagram of droplets generated at different distances detected by the QCM sensor for detecting droplets of the present invention;

[0036] Wherein: 1-QCM substrate, 11-quartz crystal, 12-first electrode, 13-second electrode, 14-nano titanium dioxide film doped with black phosphorus quantum dots, 141-nano titanium dioxide particles, 142-black phosphorus quantum dots, 2-drug solution cup, 3-container. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0038] Example 1

[0039] A QCM sensor for detecting droplets comprises a QCM substrate 1, on which a nano titanium dioxide film 4 doped with black phosphorus quantum dots is arranged. Figure 1 As shown, the QCM substrate 1 includes a quartz crystal 11 with an area of ​​8 square millimeters, and the upper and lower surfaces of the quartz crystal 11 are respectively provided with a second electrode 13 and a first electrode 12; in this embodiment, the first electrode 12 and the second electrode 13 are both made of silver, and in other embodiments they can also be made of gold.

[0040] The preparation method of the QCM sensor for detecting droplets is as follows:

[0041] Step 1: A first electrode 12 is formed on the surface of a quartz crystal 11 using a vacuum coating method (specifically, an evaporation coating method or a sputtering coating method), and a second electrode 13 is formed on the other surface of the quartz crystal using the same method to obtain a QCM substrate 1. The basic resonant frequency of the QCM substrate 1 is 19.6 MHz.

[0042] Step 2: Add nano-titanium dioxide particles 141 with a particle size of 20 nm to deionized water for dilution, and prepare a nano-titanium dioxide solution with a concentration of 5 mg / ml by ultrasonic treatment for 15 minutes; add black phosphorus quantum dots 142 with a sheet size of 3 nm to deionized water for dilution, and prepare a black phosphorus quantum dot solution with a concentration of 0.1 mg / ml by ultrasonic treatment for 15 minutes; then mix the prepared nano-titanium dioxide solution and black phosphorus quantum dot solution in a volume ratio of 1:3 and ultrasonic treatment for 15 minutes to obtain a nano-titanium dioxide / black phosphorus quantum dot solution;

[0043] Step 3: Take 2 ml of the nano titanium dioxide / black phosphorus quantum dot solution prepared in step 2 and put it into the liquid cup 2 of the compressed air nebulizer to prepare for atomization (such as Figure 2), place the QCM substrate 1 prepared in step 1 with the sensitive surface (second electrode 13) facing upward horizontally, use the atomization natural deposition method to control the atomization gas flow upward, and wait for the solution to be atomized into mist particles and fill the container 3, the bottom area of ​​the container 3 is 10cm*10cm, let it stand for 20 minutes to allow the particles to naturally deposit on the surface of the QCM substrate 1, and then dry the QCM substrate 1 in a room temperature environment not higher than 35 degrees Celsius for 2 hours to obtain a QCM sensor with a uniform distribution of nano-titanium dioxide film 14 doped with black phosphorus quantum dots.

[0044] like Figure 3 As shown, when the QCM sensor in this embodiment is placed in an environment with an ambient temperature of about 25 degrees Celsius and a humidity of 43% RH, after two hours of testing, the maximum frequency deviation is only 0.82 Hz, while the minimum droplet signal measured in the experiment is about 2.4 Hz. Therefore, the sensor has good stability, and its own fluctuations will hardly affect the detection of droplet signals.

[0045] Figure 4 This is a waveform diagram of the QCM sensor detecting droplets at different distances in this embodiment. The horizontal axis is time in seconds, and the vertical axis is frequency deviation in Hertz. During the test, the environment was about 25 degrees Celsius and the ambient humidity was about 45% RH. It can be seen from the waveform diagram that the QCM sensor can detect droplets at a distance of 2.4 meters, and the signal of detecting droplets increases as the distance decreases.

[0046] Example 2

[0047] This embodiment is substantially the same as Embodiment 1, except that the prepared nano-titanium dioxide solution and the black phosphorus quantum dot solution are mixed in a volume ratio of 1:0.1.

[0048] Example 3

[0049] This embodiment is substantially the same as Embodiment 1, except that the prepared nano-titanium dioxide solution and the black phosphorus quantum dot solution are mixed in a volume ratio of 1:5.

[0050] Example 4

[0051] This embodiment is basically the same as Embodiment 1, except that the amount of the nano-titanium dioxide / black phosphorus quantum dot solution used is 1 ml.

[0052] Example 5

[0053] This embodiment is basically the same as Embodiment 1, except that the amount of the nano-titanium dioxide / black phosphorus quantum dot solution used is 5 ml.

[0054] Comparative Example 1

[0055] This comparative example is basically the same as Example 1, except that only the prepared nano titanium dioxide solution is used without mixing the black phosphorus quantum dot solution, and the amount of the nano titanium dioxide solution used is equal to the total amount of the mixed solution in Example 1.

[0056] Comparative Example 2

[0057] This comparative example is substantially the same as Example 1, except that the prepared nano-titanium dioxide solution and the black phosphorus quantum dot solution are mixed in a volume ratio of 1:10.

[0058] Comparative Example 3

[0059] This comparative example is basically the same as Example 1, except that the amount of the nano-titanium dioxide / black phosphorus quantum dot solution used is 0.5 ml.

[0060] Comparative Example 4

[0061] This comparative example is basically the same as Example 1, except that the amount of the nano-titanium dioxide / black phosphorus quantum dot solution used is 10 ml.

[0062] Comparative Example 5

[0063] This comparative example is basically the same as Example 1, except that the titanium dioxide used is titanium dioxide nanowires, and the amount used is equal to that in Example 1.

[0064] The performance of the sensors obtained in the above embodiments and comparative examples was tested, and the obtained data are shown in Table 1:

[0065] Table 1

[0066]

[0067] As can be seen from Table 1, the sensors prepared in Examples 1-5 all have the ability to detect droplets more than 2 meters away. The performance of the sensor in Example 1 is the best, with a response time of only 0.2 seconds, and it can detect droplets as far as 2.4 meters and generate signals. Comparative Example 1 is a sensor without the addition of black phosphorus quantum dots, and its maximum droplet detection distance is 0.6 meters shorter than that of Example 1. In Comparative Example 3, there is very little sensitive material deposited on the substrate. Although the sensor responds quickly, the sensitivity is not enough. The titanium dioxide nanowires added in Comparative Example 5 will change the microstructure of the sensor's sensitive film, affecting the sensor's ability to capture long-distance droplets. In addition, due to the excessive addition of black phosphorus quantum dots in Comparative Example 2, the viscosity of the sensitive film will be too large; in Comparative Example 4, excessive sensitive materials are deposited on the substrate, and the QCM cannot oscillate normally. It can be seen that adding an appropriate amount of black phosphorus quantum dots to the nano-titanium dioxide particles and forming a film of moderate thickness on the substrate are the key to the sensor's ability to detect long-distance droplets.

[0068] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A QCM sensor for detecting droplets, characterized in that: It comprises a QCM substrate (1), on which a nano titanium dioxide film (4) doped with black phosphorus quantum dots is arranged.

2. A QCM sensor for detecting droplets according to claim 1, characterized in that: The nano titanium dioxide in the nano titanium dioxide film (4) doped with black phosphorus quantum dots is in granular form, and the particle size is less than or equal to 50 nm. The diameter of the black phosphorus quantum dots in the nano titanium dioxide film (4) doped with black phosphorus quantum dots is less than or equal to 10 nm.

3. A QCM sensor for detecting droplets according to claim 1, characterized in that: The QCM substrate (1) comprises a quartz crystal (11) and a second electrode (13) and a first electrode (12) respectively arranged on the upper surface and the lower surface of the quartz crystal (11); the nano titanium dioxide film (4) doped with black phosphorus quantum dots is arranged on the second electrode (13).

4. A QCM sensor for detecting droplets according to claim 3, characterized in that: The area of ​​the quartz crystal (11) is less than 10 mm 2 .

5. A QCM sensor for detecting droplets according to any one of claims 1 to 4, characterized in that: The fundamental resonance frequency of the QCM substrate (1) is above 14.7 MHz.

6. A method for preparing a QCM sensor for detecting droplets, characterized in that: include: Preparation of QCM substrate (1); Configuration of nano titanium dioxide solution; Configuration of black phosphorus quantum dot solution; The nano titanium dioxide solution and the black phosphorus quantum dot solution are configured into a nano titanium dioxide / black phosphorus quantum dot solution; A nano titanium dioxide / black phosphorus quantum dot solution is formed on a QCM substrate (1) into a nano titanium dioxide film (4) doped with black phosphorus quantum dots, thereby obtaining a QCM sensor for detecting droplets.

7. The method for preparing a QCM sensor for detecting droplets according to claim 6, characterized in that: The concentration of the nano titanium dioxide solution is 0.1-10 mg / ml, the concentration of the black phosphorus quantum dot solution is 0.01-1 mg / ml, and the nano titanium dioxide solution and the black phosphorus quantum dot solution are configured in a volume ratio of 1:0.1-5 to form a nano titanium dioxide / black phosphorus quantum dot solution.

8. The method for preparing a QCM sensor for detecting droplets according to claim 6 or 7, characterized in that: A nano titanium dioxide / black phosphorus quantum dot solution is formed on a QCM substrate (1) by an atomized natural deposition method to form a nano titanium dioxide film (4) doped with black phosphorus quantum dots.

9. The method for preparing a QCM sensor for detecting droplets according to claim 8, characterized in that: The dosage of the nano titanium dioxide solution and the black phosphorus quantum dot solution is 0.01-0.05 ml / cm 2 , and the amount of the nano titanium dioxide solution and the black phosphorus quantum dot solution increases as the bottom area of ​​the container (3) used in the atomization natural deposition method increases.

10. Use of the QCM sensor for detecting droplets according to any one of claims 1 to 5 in detecting droplets.

Images