A photocatalytic filter layer structure based on carbon quantum dots

Abstract

This application relates to the field of air purification, and specifically provides a photocatalytic filter layer structure based on carbon quantum dots. The photocatalytic filter layer structure of the present invention application includes carbon quantum dot particles, photocatalyst particles, flexible fibers, and an activated carbon layer. One end of the flexible fiber is fixedly arranged on one side of the activated carbon layer, and the other end of the flexible fiber is a free end. The carbon quantum dot particles and the photocatalyst particles are fixedly arranged on the surface of the flexible fiber, and the activated carbon layer is a porous activated carbon cotton. In the present invention, by fixedly arranging carbon quantum dot particles on the surface of the flexible fiber, the carbon quantum dots absorb visible light and generate photogenerated electrons and photogenerated holes therein. The photogenerated electrons and photogenerated holes are captured by the surface functional groups on the surface of the carbon quantum dot particles and react with organic pollutants in the air, playing a role in purifying the air. The present invention makes full use of the visible light in the light source and effectively improves the intensity of the photocatalytic reaction. Therefore, the air purification efficiency of the photocatalytic filter layer structure of the present invention is relatively high.

Description

Technical Field

[0001] This application relates to the field of air purification, and specifically provides a photocatalytic filter layer structure based on carbon quantum dots. Background Art

[0002] As a new type of zero-dimensional nanomaterial in the carbon nanomaterial family, the main component of carbon quantum dots is the C element. The raw material source is rich, the preparation is simple, and the cost is low. Carbon quantum dots are spherical and composed of a carbon core and abundant surface functional groups. The carbon core is composed of amorphous carbon or sp 2 or sp 3 hybridized nanocrystalline carbon, located at the center of the carbon quantum dots. The surface functional groups are hydroxyl, carboxyl, carbonyl, epoxy group, etc. Carbon quantum dots have obvious absorption in the ultraviolet-visible light band.

[0003] A photocatalytic air purification device is a common air purification device. The core component is the filter layer structure, in which photocatalyst particles and other substances for photocatalytic reactions are arranged. The filter layer structure is arranged at the necessary path of air. During operation, under the action of light, the photocatalyst particles generate photogenerated electrons and photogenerated holes; the photogenerated electrons and photogenerated holes react with oxygen and water molecules in the air to generate strongly oxidative and reductive oxygen anions and hydroxyl radical groups; the oxygen anions and hydroxyl radical groups react with organic pollutants such as formaldehyde in the air to be purified, and finally generate non-toxic carbon dioxide and water, that is, toxic pollutants such as formaldehyde are converted into non-toxic carbon dioxide and water through photocatalytic reactions to achieve the purpose of purifying air.

[0004] The commonly used photocatalyst material is titanium dioxide, and the band gap of titanium dioxide is 3.1 eV. Since the photocatalytic process requires the generation of photogenerated electrons and photogenerated holes, that is, the photon energy needs to be greater than the band gap of titanium dioxide, so as to excite the electrons in titanium dioxide from the valence band to the conduction band to generate photogenerated electrons and photogenerated holes; therefore, titanium dioxide can only absorb ultraviolet light, and the large part of the visible light with a large energy proportion does not participate in the photocatalytic reaction, and the utilization rate of the light source is low; this makes it difficult to further improve the purification efficiency of the photocatalytic filter layer structure.

[0005] In summary, due to the insufficient utilization of visible light for photocatalytic reactions, the photocatalytic reaction intensity in the existing photocatalytic filter layer structure is weak, so it is difficult to further improve the air purification efficiency of the photocatalytic filter layer structure. Summary of the Invention

[0006] The object of the present invention is to provide a photocatalytic filter layer structure based on carbon quantum dots in view of the deficiencies in the above-mentioned prior art. The technical concept of the present invention is as follows: By arranging carbon quantum dot particles capable of absorbing visible light in the photocatalytic filter layer structure, visible light can participate in the photocatalytic reaction, improving the utilization rate of the light source, thereby enhancing the intensity of the photocatalytic reaction and improving the air purification efficiency. In addition, in the present invention, the photocatalyst particles and the carbon quantum dot particles are fixed and arranged on the surface of the flexible fiber, so that the movement amplitude of the photocatalyst particles and the carbon quantum dot particles at the end far from the activated carbon layer is greater than that of the photocatalyst particles and the carbon quantum dot particles at the end close to the activated carbon layer, enabling the photocatalyst particles and the carbon quantum dot particles at the end close to the activated carbon layer to be fully irradiated, thereby enhancing the intensity of the photocatalytic reaction and further improving the air purification efficiency.

[0007] The technical solution adopted by the present invention is as follows:

[0008] The present application provides a photocatalytic filter layer structure based on carbon quantum dots. The structure includes carbon quantum dot particles, photocatalyst particles, flexible fibers, and an activated carbon layer. The activated carbon layer is a porous activated carbon cotton, which is used to remove particulate pollutants and some gaseous pollutants in the air, and can also provide support for the flexible fibers. The specific shape of the activated carbon layer matches the shape and size of the filter layer designed in the photocatalytic air purifier used, that is, it matches the size and shape of the fixing components such as the card slots and snap rings used, and can be in the shape of a cylinder, a cuboid, etc. One end of the flexible fiber is fixedly arranged on one side of the activated carbon layer, and the other end of the flexible fiber is a free end. In this way, when in use, the flexible fiber sways under the drive of the air flow, and the swaying amplitude of the free end is greater than that of the fixed end. Specifically, the diameter of the flexible fiber is 20-100 μm. The carbon quantum dot particles and the photocatalyst particles are fixedly arranged on the surface of the flexible fiber. Specifically, it can be fixedly connected by adhesion, or fixed by the interaction force between the carbon quantum dot particles and the photocatalyst particles and the surface of the flexible fiber. Preferably, carbon quantum dot particles are also arranged on the surface of the photocatalyst particles. The material of the photocatalyst particles is titanium dioxide, that is, the photocatalyst particles are titanium dioxide particles; the particle size of the photocatalyst particles is 15-100 nm, and the particle size of the carbon quantum dot particles is less than 10 nm.

[0009] The length of the flexible fiber is greater than 0.5 cm. This length greater than 0.5 cm gives the flexible fiber a larger surface area, enabling more carbon quantum dot particles and photocatalyst particles to be disposed thereon, thereby enhancing the intensity of the photocatalytic reaction and improving the purification efficiency. The flexible fiber is one of glass fiber, plastic fiber, artificial fiber, and plant fiber. Preferably, the flexible fiber is glass fiber or plastic fiber because glass fiber or plastic fiber is a transparent material with a refractive index greater than 1 and has a localizing effect on the light field. During use, the light emitted by the light source can be localized within the flexible fiber, so that the distance between the light field and the photocatalyst particles and carbon quantum dots is closer, and the interaction is stronger. The photocatalyst particles and carbon quantum dots can absorb more light fields, generating more photo-generated electrons and photo-generated holes to participate in the photocatalytic reaction, thereby enhancing the photocatalytic intensity and further improving the purification efficiency.

[0010] The filter layer structure can be used in a photocatalytic air purification device. When the filter layer structure is used in a photocatalytic air purification device, an ultraviolet-visible light source is used.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0012] In the present invention, carbon quantum dot particles are fixedly disposed on the surface of the flexible fiber. The carbon quantum dots absorb the visible light band in the light source, generating photo-generated electrons and photo-generated holes therein. The photo-generated electrons and photo-generated holes are captured by the surface functional groups on the surface of the carbon quantum dot particles and aggregated on the surface of the carbon quantum dots. The surface functional groups that have captured electrons and holes have strong oxidation and reduction capabilities, and can thus react with organic pollutants in the air, playing a role in purifying the air. The present invention makes full use of the visible light in the light source, effectively enhancing the intensity of the photocatalytic reaction. Therefore, the air purification efficiency of the photocatalytic filter layer structure of the present invention is relatively high.

[0013] Meanwhile, during operation, the flexible fiber can swing. The swing amplitude of the photocatalyst particles and carbon quantum dot particles at the end far from the activated carbon layer is greater than that of the photocatalyst particles and carbon quantum dot particles at the end close to the activated carbon layer, enabling the photocatalyst particles and carbon quantum dot particles at the end close to the activated carbon layer to also be fully irradiated, thereby enhancing the intensity of the photocatalytic reaction and further improving the air purification efficiency. Therefore, the air purification efficiency of the photocatalytic filter layer structure of the present invention is relatively high. Description of the Drawings

[0014] Figure 1 It is a schematic diagram of a photocatalytic filter layer structure based on carbon quantum dots provided by the present invention.

[0015] Reference numerals: 1 - carbon quantum dot particles; 2 - photocatalyst particles; 3 - flexible fiber; 4 - activated carbon layer. Detailed Embodiments

[0016] To make the implementation process of the present invention clearer, the following will be described in detail with reference to the accompanying drawings.

[0017] The present invention provides a photocatalytic filter layer structure based on carbon quantum dots. This structure includes carbon quantum dot particles 1, photocatalyst particles 2, flexible fibers 3, and an activated carbon layer 4. The activated carbon layer 4 is a porous activated carbon cotton, which is used to remove particulate pollutants and some gaseous pollutants in the air. The thickness of the activated carbon layer is greater than 2 cm, so that it can effectively remove particulate pollutants in the air and at the same time provide support for the flexible fibers 3. The specific shape of the activated carbon layer 4 matches the shape and size of the filter layer designed in the photocatalytic air purifier used, that is, it matches the size and shape of the fixing components such as the card slots and snap rings used, and can be in the shape of a cylinder, a cuboid, etc.

[0018] One end of the flexible fiber 3 is fixedly arranged on one side of the activated carbon layer 4, and the other end of the flexible fiber is a free end. In this way, when in use, the flexible fiber 3 sways under the drive of the air flow, and the swaying amplitude of the free end is greater than that of the fixed end. Specifically, the flexible fiber 3 is adhesively fixedly connected to the surface of the activated carbon layer 4. The activated carbon layer 4 is a porous structure. The flexible fiber 3 can be adhesively fixed on the plane of the surface of the activated carbon layer 4, or fixed on the inner wall edge of the pore structure on the surface of the activated carbon layer 4. More specifically, the diameter of the flexible fiber 3 is 20 - 100 μm, and the number of flexible fibers 3 fixedly arranged per square centimeter on the surface of the activated carbon layer 4 with the flexible fibers 3 fixed is 8000 - 12000 to ensure that there are enough flexible fibers 3.

[0019] The carbon quantum dot particles 1 and the photocatalyst particles 2 are fixedly arranged on the surface of the flexible fiber. The flexible fiber 3 has a large surface area, which increases the number of the carbon quantum dot particles 1 and the photocatalyst particles 2, enabling the photocatalytic reaction to proceed fully and improving the purification efficiency. Specifically, it can be fixedly connected by adhesion, or fixed by using the interaction force between the carbon quantum dot particles 1 and the photocatalyst particles 2 and the surface of the flexible fiber 3. The material of the photocatalyst particles 2 is titanium dioxide, that is, the photocatalyst particles 2 are titanium dioxide particles. Specifically, during preparation, the flexible fiber 3 and the activated carbon layer 4 are first treated with plasma in an argon atmosphere for a treatment time greater than 10 s, which improves the adhesion of the surface of the flexible fiber 3 and makes it easy to adsorb the carbon quantum dot particles 1 and the photocatalyst particles 2. Generally speaking, when the carbon quantum dot particles are in powder form or transformed from solution state to solid state, due to direct π-π interaction and fluorescence resonance energy transfer, the carbon quantum dot particles will agglomerate together, resulting in fluorescence quenching. That is, to make the carbon quantum dot particles produce fluorescence in a solid environment, the carbon quantum dot particles need to be dispersed. Due to the strong surface interaction, the surface of the flexible fiber 3 after plasma treatment makes the carbon quantum dot particles not easily agglomerate together, so that the carbon quantum dot particles can produce a better fluorescence effect. The flexible fiber 3 can also be subjected to plasma treatment before being fixed on the activated carbon layer 4. The treated flexible fiber 3 is partially immersed in a carbon quantum dot solution or an aqueous solution of photocatalyst particles or a mixed solution of carbon quantum dot particles and photocatalyst particles for more than 5 s. Specifically, it can be first immersed in the carbon quantum dot solution and then in the aqueous solution of photocatalyst particles, or first immersed in the aqueous solution of photocatalyst particles and then in the carbon quantum dot solution, or directly immersed in the mixed solution of carbon quantum dot particles and photocatalyst particles. Finally, annealing is carried out in an inert protective atmosphere to make the contact between the flexible fiber 3 and the carbon quantum dot particles 1 and the photocatalyst particles 2 closer and the interaction force stronger. The annealing temperature is 40 - 50 °C, and the annealing time is 1.5 - 2.0 h, and it is obtained after natural cooling. It should be noted that when soaking twice, after the first time, annealing needs to be completed before the second time, and annealing is also required after the second soaking. Preferably, it is completed by one soaking. In this way, on the one hand, the preparation time is shortened, and on the other hand, it is not necessary to strictly control the concentration of the carbon quantum dot solution. When soaking twice, if the concentration of the carbon quantum dot solution is too small, the amount of the carbon quantum dot particles 1 will be less. If the concentration of the carbon quantum dot solution is too large, the smaller carbon quantum dot particles 1 will first adhere to the surface of the flexible fiber 3, and when entering the aqueous solution of photocatalyst particles again later, the photocatalyst particles 2 are not easily attached to the surface of the flexible fiber 3.

[0020] Under ultraviolet-visible light irradiation, the photocatalyst particles 2 absorb ultraviolet light to generate photogenerated electrons and holes. The photogenerated electrons and holes react with oxygen and water molecules in the air to generate oxygen anions and hydroxyl radical groups with strong oxidation and reduction properties. The oxygen anions and hydroxyl radical groups react with organic pollutants such as formaldehyde in the air to be purified, and finally generate non-toxic carbon dioxide and water, that is, toxic pollutants such as formaldehyde are converted into non-toxic carbon dioxide and water through photocatalytic reactions to achieve the purpose of purifying the air. The generated photogenerated electrons and holes will recombine within the time scale of nanoseconds. Only the non-recombined electron-hole pairs contribute to the photocatalytic reaction. Therefore, generating more photogenerated electrons and preventing the recombination of the generated photogenerated electrons and holes are the keys to enhancing the photocatalytic reaction of the photocatalyst particles 2.

[0021] The π-π of the C=C bond in the carbon quantum dot particles * Migration and the n-π of C=O * Migration enables the carbon quantum dots to have strong absorption in the ultraviolet band, and the absorption peaks are located at 230-280 nm and 320-360 nm. The surface states of the surface functional groups can capture photons in the visible light range, that is, the carbon quantum dot particles 1 also have strong absorption in the visible light range. Therefore, the carbon quantum dot particles can absorb ultraviolet light and visible light. Under the irradiation of an ultraviolet-visible light source, photogenerated electrons and holes are generated inside the carbon quantum dot particles 1, and the electrons change from the ground state to the excited state. The energy of the excited state electrons is mainly divided into three parts. The first part is transferred to lattice vibrations and converted into heat energy, which is inevitable and has nothing to do with the air purification process. The second part is captured by the surface functional groups of the carbon quantum dot particles 1 and used to react with organic pollutants in the air. This part is mainly used for air purification. The third part returns from the excited state to the ground state and recombines with the electron-hole pairs, emitting fluorescence in a radiative manner. Most of the fluorescence emitted by the carbon quantum dot particles 1 is in the visible light band, which has no promoting effect on the photocatalytic reaction of the carbon quantum dot particles 1 themselves. However, the emitted fluorescence irradiates on the adjacent carbon quantum dot particles 1, which can cause the adjacent carbon quantum particles 1 to generate more photogenerated electrons and holes, thereby promoting the photocatalytic reaction of the adjacent carbon quantum particles, that is, improving the utilization rate of visible light and the air purification efficiency. In addition, non-radiative electron transitions between the carbon core and the surface functional groups will also cause fluorescence emission, thereby enhancing the effect in the third aspect.

[0022] The particle size of the photocatalyst particles 2 is 15 - 100 nm, and the particle size of the carbon quantum dot particles 1 is less than 10 nm. The sizes of the carbon quantum dot particles 1 can be the same or different; the sizes of the photocatalyst particles 2 can be the same or different. The carbon quantum dot particles 1 and the photocatalyst particles 2 may or may not be in contact with each other. Specifically, when the carbon quantum dot particles 1 and the photocatalyst particles 2 are not in contact, it is easy to prepare, and during the preparation, it is not necessary to precisely control the concentrations of the carbon quantum dot particles 1 and the photocatalyst particles 2, etc. When the carbon quantum dot particles 1 and the photocatalyst particles 2 are in contact, in addition to having the respective beneficial effects of the carbon quantum dot particles 1 and the photocatalyst particles 2, the following beneficial effects are also achieved: after contact, there is electron migration between the carbon quantum dot particles 1 and the photocatalyst particles 2, that is, the electrons in the photocatalyst particles 2 migrate into the carbon quantum dot particles 1, avoiding the recombination between the electron holes in the photocatalyst particles 2. The migrated electrons are captured by the surface functional groups on the surface of the carbon quantum dot particles 1 near the contact point and are used for the photocatalytic reaction, improving the photocatalytic reaction efficiency; the electrons captured by the surface functional groups gather, including not only the electrons from within the photocatalyst particles 2, forming an electric field with a fixed direction near them. This electric field drives the electrons and holes in the photocatalyst particles 2 to move in opposite directions and are not easily recombined together, thereby enhancing the photocatalytic reaction intensity of the photocatalyst particles 2 and further improving the photocatalytic efficiency.

[0023] The photocatalyst particles 2 are not in contact with each other, and the distance between them is 20 - 60 nm, so that more carbon quantum dot particles 1 can be arranged around them in contact with them. The distance between the carbon quantum dot particles 1 is less than 20 nm, so that the carbon quantum dot particles 1 can be irradiated by the fluorescence emitted by the adjacent carbon quantum dot particles 1. When the distance is too large, the fluorescence intensity irradiating on the adjacent carbon quantum dot particles will be weak, resulting in a poor purification effect.

[0024] The length of the flexible fiber 3 is greater than 0.5 cm. Only when the length is greater than 0.5 cm can the swinging amplitude of the flexible fiber 3 be large enough, resulting in a relatively large air resistance. This will make the interaction time between the photocatalyst particles 2 and the carbon quantum dot particles 1 and the air longer, thus increasing the time of the photocatalytic reaction. At the same time, the length greater than 0.5 cm makes the surface area of the flexible fiber 3 larger, so that more carbon quantum dot particles 1 and photocatalyst particles 2 can be set on it, thereby enhancing the intensity of the photocatalytic reaction and improving the purification efficiency. When the flexible fiber 3 swings, the swinging amplitude of the carbon quantum dot particles 1 and the photocatalyst particles 2 near the free end is greater than that of the carbon quantum dot particles 1 and the photocatalyst particles 2 near the fixed end. This enables the carbon quantum dot particles 1 and the photocatalyst particles 2 near the fixed end to be fully exposed to the light field, allowing the light field to fully interact with the carbon quantum dot particles 1 and the photocatalyst particles 2 near the fixed end, enhancing the utilization of visible light, generating a photocatalytic reaction, and thus enhancing the overall intensity of the photocatalytic reaction and improving the purification efficiency. When the flexible fiber 3 swings, it will make the air flow more strongly. During the photocatalytic reaction, the oxygen and water molecules in the air are continuously consumed. The decrease in the concentration of oxygen and water molecules will slow down or even stop the photocatalytic reaction process. The stronger air flow enables more fresh air to exist around the carbon quantum dot particles 1 and the photocatalyst particles 2, providing sufficient concentrations of oxygen and water molecules for the photocatalytic reaction to proceed. Therefore, the setting of the flexible fiber 3 improves the air purification efficiency.

[0025] The flexible fiber 3 is one of glass fiber, plastic fiber, artificial fiber, and plant fiber. Preferably, the flexible fiber 3 is glass fiber or plastic fiber because glass fiber or plastic fiber is a transparent material with a refractive index greater than 1 and has a localizing effect on the light field. When in use, it can localize the light emitted by the light source within the flexible fiber 3. In this way, the distance between the light field and the photocatalyst particles 2 and the carbon quantum dot particles 1 is closer, and the interaction with the light field is stronger. The photocatalyst particles 2 and the carbon quantum dot particles 1 can absorb more light field energy, generate more photogenerated electrons and photogenerated holes to participate in the photocatalytic reaction, thereby enhancing the photocatalytic intensity and further improving the purification efficiency.

[0026] Specifically, the aqueous solution of photocatalyst particles and the carbon quantum dot solution can be directly purchased as reagents of corresponding sizes or can be prepared. In this embodiment, photocatalyst particles, namely titanium dioxide nanoparticles, were purchased and dissolved in deionized water. After sufficient stirring, an aqueous solution of photocatalyst particles was obtained, with a configured concentration of 1.5%. The carbon quantum dot solution was prepared. The carbon quantum dots can be prepared by hydrothermal method, microwave method, direct pyrolysis method, or template method. When the obtained product is in powder form, it is dissolved in deionized water, ultrasonicated, and centrifuged, and the supernatant is taken to obtain the carbon quantum dot solution. Specifically, in this embodiment, the microwave method was used for preparation, and doped with sp was directly generated by microwave-assisted pyrolysis in a formaldehyde solvent. 3Carbon quantum dot particles of C. It should be noted that the doping here is not a limitation on the carbon quantum dot particles, but only one implementation. Specifically, the general process is as follows: Potassium hydrogen phthalate, sodium azide, boric acid, and formaldehyde are mixed in a beaker in a corresponding ratio of 1 g:1 g:2 g:10 mL. After ultrasonic treatment for 10 minutes, a transparent solution is formed. It is heated in a microwave oven at a power of 800 W for 10 minutes, and then taken out after natural cooling to obtain powdery carbon quantum dot particles; 5 g of the obtained carbon quantum dot particles are added to 500 mL of deionized water, ultrasonicated, and after centrifugation at a rotation speed of 8000 rpm for 8 minutes, the supernatant is taken to obtain a carbon quantum dot solution. The surface functional groups prepared by the method of this embodiment include -OH groups, -HN groups, C=O groups, C=C groups, C=N groups, C=O groups, C-N groups, B-N groups, C-H groups, B-O groups, C-B groups, C-O groups. After these abundant surface functional groups capture photo-generated electrons and holes, they have strong redox ability and can react with organic pollutants in the air to achieve the purpose of purifying the air. At the same time, the carbon quantum dot particles prepared by the method of this embodiment have good fluorescence generation in the solid state due to the inhibition of the fluorescence resonance energy transfer process.

[0027] Furthermore, carbon quantum dot particles 1 are also provided on the surface of the photocatalyst particles 2. The carbon quantum dot particles 1 are distributed on the surface of the photocatalyst particles 2. Preferably, the spacing is less than 10 nm, so that more carbon quantum dot particles 1 can be provided on the surface of the limited photocatalyst particles 2. On the one hand, more carbon quantum dot particles 1 can be provided on the surface of the larger photocatalyst particles 2, thereby improving the air purification efficiency. On the second hand, the number of active sites formed at the contact between the carbon quantum dot particles 1 and the photocatalyst particles 2 is relatively large, that is, the presence of the carbon quantum dot particles 1 reduces the recombination of electrons and holes in the photocatalyst particles 2, thereby improving the air purification efficiency of the photocatalyst particles 2. On the third hand, a doping structure is formed between the photocatalyst particles 2 and the carbon quantum dot particles 1 with a smaller band gap, which causes new metastable energy levels to be formed between the conduction band and the valence band of the photocatalyst particles 2. Photons irradiated on the photocatalyst particles 2 can first transition from the valence band to the metastable energy level, and then from the metastable energy level to the conduction band. In this way, photons with photon energy lower than the band gap of the photocatalyst material can also excite photo-generated electrons and holes on the photocatalyst particles 2, enabling the photocatalyst particles 2 to make full use of visible light and generate more photo-generated electrons and holes, so that the photocatalytic reaction is stronger and the photocatalytic efficiency is further improved. During preparation, the photocatalyst particles 2 are first prepared on the surface of the flexible fiber 3, and then the carbon quantum dot particles 1 are prepared. Otherwise, if the carbon quantum dot particles 1 with a smaller particle size adhere to the surface of the flexible fiber 3, the photocatalyst particles 2 with a larger particle size will not be able to adhere to the surface of the flexible fiber 3.

[0028] The filter layer structure of the present invention can be used in a photocatalytic air purification device. When the filter layer structure is used in a photocatalytic air purification device, an ultraviolet-visible light source is used, and the ultraviolet-visible light source includes at least the wavelength band of 150 - 600 nm.

[0029] During application, the ultraviolet-visible light irradiates from the side of the activated carbon layer 4 where the flexible fiber 3 is arranged, that is, the light directly irradiates on one side of the flexible fiber 3, and air flows in from the side of the activated carbon layer 4 away from the flexible fiber 3. During operation, the air to be purified flows in from the side of the activated carbon layer 4 away from the flexible fiber 3, and solid particle pollutants and some gas pollutants are filtered out by the activated carbon layer 4, and then pass through the flexible fiber 3. When passing through, the flexible fiber 3 sways, so that the carbon quantum dot particles 1 and photocatalyst particles 2 on its surface fully interact with the air and the light field, generating a photocatalytic reaction. The purified air flows out from the side of the flexible fiber 3 away from the activated carbon layer 4, and the purification is completed. During operation, the free end of the flexible fiber 3 is far from the fixed end, so that the flexible fiber 3 is perpendicular to the plane where the activated carbon layer 4 is located. In this way, the interaction distance between the air and the carbon quantum dot particles 1 and photocatalyst particles 2 on it is longer and the interaction is more sufficient. At the same time, during the swinging process, the relative distance between the flexible fibers 3 changes, making it easier for the light field to irradiate on the surface of the flexible fiber 3, so that the interaction between the light field and the carbon quantum dot particles 1 and photocatalyst particles 2 is more sufficient. The present invention enhances the utilization of visible light by setting the carbon quantum dot particles 1, thereby improving the photocatalytic efficiency. Specifically, on the one hand, carbon quantum dot particles 1 capable of absorbing visible light are set; on the other hand, the photocatalyst particles 2 can also absorb visible light by forming metastable energy levels; on the other hand, through the electron transfer and the formation of a local electric field between the carbon quantum dot particles 1 and the photocatalyst particles 2, the photo-generated electrons and photo-generated holes generated by the photocatalyst particles 3 are not easily recombined, and thus participate in the photocatalytic reaction. Therefore, the purification efficiency of the photocatalytic filter layer structure of the present invention is relatively high.

[0030] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A photocatalytic filter layer structure based on carbon quantum dots, characterized in that, The filter layer structure includes carbon quantum dot particles, photocatalyst particles, flexible fibers, and an activated carbon layer. One end of the flexible fiber is fixedly arranged on one side of the activated carbon layer, and the other end of the flexible fiber is a free end. The length of the flexible fiber is greater than 0.5 cm. The flexible fiber is a glass fiber. The carbon quantum dot particles and the photocatalyst particles are fixedly arranged on the surface of the flexible fiber. The particle size of the photocatalyst particles is greater than that of the carbon quantum dot particles. The carbon quantum dot particles are also arranged on the surface of the photocatalyst particles; the activated carbon layer is a porous activated carbon cotton.

2. The structure of the photocatalytic filtration layer based on carbon quantum dots according to claim 1, characterized in that, The particle size of the carbon quantum dot particles is less than 10 nm.

3. The structure of the photocatalytic filtration layer based on carbon quantum dots according to claim 2, wherein, The diameter of the flexible fiber is 20 - 100 μm.

4. The structure of the photocatalytic filtration layer based on carbon quantum dots according to claim 3, characterized in that, The particle size of the photocatalyst particles is 15 - 100 nm.

5. The structure of the photocatalytic filter layer based on carbon quantum dots according to claim 4, wherein, The thickness of the activated carbon layer is greater than 2 cm.

6. The structure of the photocatalytic filter layer based on carbon quantum dots according to claim 5, characterized in that, The material of the photocatalyst particles is titanium dioxide.

7. Use of a photocatalytic filter layer structure based on carbon quantum dots according to any one of claims 1-6, characterized in that, The filter layer structure is used in a photocatalytic air purification device, and an ultraviolet-visible light source is used when the filter layer structure is used in the photocatalytic air purification device.

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