Carbon dot for absorbing ultraviolet light and green light, light conversion film and preparation method and application thereof

Abstract

The invention belongs to the technical field of light conversion materials, and provides a carbon dot capable of absorbing ultraviolet light and green light, a light conversion film and a preparation method and application of the light conversion film. The preparation method of the carbon dots capable of absorbing the ultraviolet light and the green light comprises the following steps: mixing o-phenylenediamine, acrylic acid and water, then carrying out hydrothermal reaction, and sequentially carrying out centrifugation, filtration, dialysis and freeze drying on a reaction product, so as to obtain the carbon dots capable of absorbing the ultraviolet light and the green light. A light conversion film prepared by using the carbon dots capable of absorbing the ultraviolet light and the green light as a light conversion agent can be used for plant growth. The light conversion film not only can block and absorb ultraviolet light and convert the ultraviolet light into spectrums absorbed by plants in a blue light area and a red light area, but also can block and absorb green light and convert the green light into spectrums absorbed by the plants in the red light area, so that the photosynthesis of the plants is improved, the germination, growth and development of plant seeds are promoted, and the crop yield is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of light conversion materials, and in particular to a carbon dot capable of absorbing ultraviolet light and green light, a light conversion film, and a preparation method and application thereof. Background Art

[0003] If the efficiency of plant photosynthesis can be increased by 10%, it will greatly enhance its carbon fixation capacity and is expected to absorb an additional quarter of the world's carbon emissions. This means that by optimizing the photosynthesis process, plants can significantly mitigate the threat of climate change and bring good news to the earth's ecosystem. Improving the efficiency of photosynthesis will not only help slow global warming, but also promote plant growth and enhance the stability and biodiversity of ecosystems. Sunlight is one of the key factors in the growth, development and metabolism of organisms on Earth. Plants use photosynthesis to convert it into oxygen, food and other substances needed for life. Blue light helps crops grow, while red light helps flowering, fruiting and coloring. Therefore, photosynthesis is the main driving force for plant growth and production, and is also the source of the carbon skeleton needed to maintain plant growth.

[0004] In order to improve crop yield and quality, making full use of photosynthesis has become the focus of research. Although the research on agricultural light conversion films at home and abroad has achieved certain results, and some have been put into practical application, it has not yet achieved large-scale and efficient popularization. The biggest problem at present is that there are relatively few light conversion film materials with suitable prices and excellent performance. Although organic light conversion agents have the advantages of good compatibility with resins and easy film formation, they still have problems such as easy oxidation and decomposition, short life, low sunlight utilization, affecting the light transmittance of light conversion films, and high cost. As a new type of carbon nanomaterial, carbon dots have excellent optical properties, low preparation cost, strong resistance to photobleaching, good biocompatibility, good water solubility, rich surface functional groups, and non-toxicity. They are widely used in various fields. At present, most light conversion films only have blue light or red light single light conversion performance, and have the defect of single light conversion. Therefore, how to provide a light conversion film material with a wide light conversion range, low cost and excellent performance has become a problem that technicians in this field need to solve urgently. Summary of the invention

[0005] In view of this, the present invention provides a carbon dot that absorbs ultraviolet light and green light, a light conversion film, and a preparation method and application thereof, the purpose of which is to solve the technical problems of existing light conversion film materials such as narrow light conversion range and poor light conversion performance.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] The present invention provides a method for preparing carbon dots that absorb ultraviolet light and green light, comprising the following steps:

[0008] After mixing o-phenylenediamine, acrylic acid and water, a hydrothermal reaction occurs, and the reaction product is centrifuged, filtered, dialyzed and freeze-dried in sequence to obtain carbon dots that absorb ultraviolet light and green light;

[0009] The dosage ratio of the o-phenylenediamine, acrylic acid and water is 0.1-0.2 g: 2-4 mL: 5-15 mL.

[0010] Furthermore, the temperature of the hydrothermal reaction is 170-190° C., and the time of the hydrothermal reaction is 7-9 hours.

[0011] Furthermore, the centrifugal speed is 8000-12000 rpm, and the centrifugal time is 15-20 min;

[0012] The pore size of the filter membrane used in the filtration is 0.2-0.3 μm;

[0013] The molecular weight cut-off of the dialysis is 300-800Da, and the dialysis time is 36-72h;

[0014] The freeze drying temperature is -65 to -75°C, and the freeze drying time is 24 to 36 hours.

[0015] The present invention provides carbon dots that absorb ultraviolet light and green light and are prepared by the above preparation method.

[0016] The present invention provides a light-converting film, which comprises a film substrate and the above-mentioned carbon dots that absorb ultraviolet light and green light;

[0017] The mass ratio of the film substrate to the carbon dots absorbing ultraviolet light and green light is 1000:5-50.

[0018] Furthermore, the film substrate comprises polyvinyl alcohol.

[0019] The present invention provides a method for preparing the light-converting film, comprising the following steps:

[0020] The film substrate, carbon dots absorbing ultraviolet light and green light and water are mixed to obtain a mixed solution, and the mixed solution is successively subjected to ultrasonic degassing and vacuum drying to obtain a light conversion film;

[0021] The usage ratio of the membrane substrate, the carbon dots for absorbing ultraviolet light and green light, and water is 1 g: 0.005-0.05 g: 20-40 mL.

[0022] Furthermore, the mixing time is 30 to 40 minutes, the power of the ultrasonic degassing is 250 to 400 W, and the ultrasonic degassing time is 20 to 30 minutes.

[0023] Furthermore, the vacuum degree of the vacuum drying is 8000-9000 Pa, the temperature of the vacuum drying is 40-50° C., and the time of the vacuum drying is 12-16 hours.

[0024] The invention also provides application of the light conversion film in plant growth.

[0025] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. The carbon dots provided by the present invention use o-phenylenediamine and acrylic acid as raw materials. These raw materials are cheap and easily available. The preparation method is simple and convenient, green and sustainable, and the yield is as high as 18%, which is suitable for mass production.

[0027] 2. The carbon dots prepared in the present invention are used as light conversion agents, polyvinyl alcohol (PVA) is used as a light conversion film substrate, and the carbon dots are evenly dispersed in the film substrate, so that it has excellent light conversion performance.

[0028] 3. The light conversion film provided by the present invention has a wide emission spectrum range and can meet the needs of different plants for light qualities of different wavelengths in the blue light region and the red light region.

[0029] 4. The light conversion film provided by the present invention can improve the utilization rate of sunlight by plants, enhance photosynthesis, block and absorb ultraviolet light and green light that are not conducive to plant growth, convert them into red light and blue light that can be absorbed by plants, promote photosynthesis rate, and increase agricultural output.

[0030] 5. The light-converting film provided by the present invention can be excited by high-energy, short-wavelength ultraviolet light and medium-wavelength green light and emit long-wavelength, low-energy blue light and red light. At the same time, the energy difference generated is released in the form of heat energy, which increases the temperature inside the film and promotes the germination and growth and development of crops.

[0031] 6. Due to the increase in the internal temperature of the light-converting film and the improvement in the photosynthetic capacity of the plants, the growth rate of crops covered with the light-converting film is higher than that of ordinary films, which significantly promotes the growth and development of crops and increases yields. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The XRD pattern of the carbon dots absorbing ultraviolet light and green light prepared in Example 1;

[0033] Figure 2 TEM images and particle size distribution diagrams of carbon dots absorbing ultraviolet light and green light prepared in Example 1, wherein (a) is a TEM image of the carbon dots, and (b) is a particle size distribution diagram of the carbon dots;

[0034] Figure 3The emission fluorescence spectra of the carbon dots absorbing ultraviolet light and green light prepared in Example 1, wherein (a) shows the best excitation and best emission spectra of the carbon dots, (b) shows the fluorescence spectrum of the carbon dots under ultraviolet light excitation (320-380 nm, interval 10 nm), (c) shows the fluorescence spectrum of the carbon dots under green light excitation (500-560 nm, interval 10 nm), (d) shows the normalized fluorescence spectrum of the carbon dots under ultraviolet light excitation (320-380 nm, interval 10 nm), and (e) shows the normalized fluorescence spectrum of the carbon dots under green light excitation (500-560 nm, interval 10 nm);

[0035] Figure 4 The infrared spectrum of the carbon dots absorbing ultraviolet light and green light prepared in Example 1;

[0036] Figure 5 The XPS spectra of the carbon dots prepared in Example 1 that absorb ultraviolet light and green light, wherein (a) is the full XPS spectrum of the carbon dots, (b) is the C1s spectrum of the carbon dots, (c) is the N1s spectrum of the carbon dots, and (d) is the O1s spectrum of the carbon dots;

[0037] Figure 6 The fluorescence spectrum of the light conversion film prepared in Example 4, wherein (a) is the fluorescence spectrum excited by ultraviolet light, and (b) is the fluorescence spectrum excited by green light;

[0038] Figure 7 The fluorescence spectrum of the light conversion film prepared in Example 5, wherein (a) is the fluorescence spectrum excited by ultraviolet light, and (b) is the fluorescence spectrum excited by green light;

[0039] Figure 8 The fluorescence spectrum of the light conversion film prepared in Example 6, wherein (a) is the fluorescence spectrum excited by ultraviolet light, and (b) is the fluorescence spectrum excited by green light;

[0040] Fig. 9 The fluorescence spectrum of the light conversion film prepared in Example 7, wherein (a) is the fluorescence spectrum excited by ultraviolet light, and (b) is the fluorescence spectrum excited by green light;

[0041] Fig.10 The best excitation and best emission spectra of the light conversion film prepared in Example 4;

[0042] Fig.11 The transmittance comparison diagram of the light conversion films containing different mass ratios of carbon dots to PVA (2%, 3%, 4%, 5%, 6%) prepared in Examples 4 to 7;

[0043] Fig.12 This is a diagram of the growth process of the experimental vegetables, where the left side is Chinese cabbage, the middle is lettuce, and the right side is Chinese cabbage;

[0044] Fig.13 The actual pictures of Chinese cabbage planted under different treatments;

[0045] Fig.14 The following are the actual pictures of lettuce planted under different treatments;

[0046] Fig.15 Actual pictures of Chinese cabbage grown under different treatments. DETAILED DESCRIPTION

[0047] The present invention provides a method for preparing carbon dots that absorb ultraviolet light and green light, comprising the following steps:

[0048] After mixing o-phenylenediamine, acrylic acid and water, a hydrothermal reaction occurs, and the reaction product is centrifuged, filtered, dialyzed and freeze-dried in sequence to obtain carbon dots that absorb ultraviolet light and green light.

[0049] In the present invention, the usage ratio of o-phenylenediamine, acrylic acid and water is 0.1-0.2 g: 2-4 mL: 5-15 mL, preferably 0.12-0.18 g: 2.5-3.5 mL: 6-12 mL, and more preferably 0.14-0.16 g: 3.0 mL: 8-10 mL.

[0050] In the present invention, the temperature of the hydrothermal reaction is 170-190° C., preferably 175-185° C., and more preferably 180° C.; the time of the hydrothermal reaction is 7-9 h, and preferably 8 h.

[0051] In the present invention, the centrifugal speed is 8000-12000 rpm, preferably 9000-11000 r / min, more preferably 10000 r / min; the centrifugal time is 15-20 min, preferably 16-19 min, more preferably 17-18 min;

[0052] The pore size of the filter membrane used in the filtration is 0.2-0.3 μm, preferably 0.22-0.28 μm, and more preferably 0.24-0.26 μm;

[0053] The molecular weight cut-off of the dialysis is 100 to 1000 Da, preferably 200 to 800 Da, and more preferably 400 to 600 Da; the dialysis time is 36 to 72 h, preferably 40 to 60 h, and more preferably 48 to 55 h;

[0054] The freeze-drying temperature is -65 to -75°C, preferably -70°C; the freeze-drying time is 24 to 36 hours, preferably 26 to 34 hours, and more preferably 28 to 32 hours.

[0055] The present invention provides carbon dots that absorb ultraviolet light and green light and are prepared by the above preparation method.

[0056] The present invention provides a light-converting film, which comprises a film substrate and the above-mentioned carbon dots that absorb ultraviolet light and green light;

[0057] The mass ratio of the film substrate to the carbon dots absorbing ultraviolet light and green light is 1000:5-50, preferably 1000:10-40, and more preferably 1000:20-30.

[0058] In the present invention, the film substrate includes polyvinyl alcohol.

[0059] The present invention provides a method for preparing the light-converting film, comprising the following steps:

[0060] The film substrate, carbon dots absorbing ultraviolet light and green light and water are mixed to obtain a mixed solution, and the mixed solution is successively subjected to ultrasonic degassing and vacuum drying to obtain a light conversion film;

[0061] The usage ratio of the membrane substrate, the carbon dots absorbing ultraviolet light and green light, and water is 1g: 0.005-0.05g: 20-40mL, preferably 1g: 0.01-0.04g: 25-35mL, and further preferably 1g: 0.02-0.03g: 30mL.

[0062] In the present invention, the mixing time is 30 to 40 minutes, preferably 32 to 38 minutes, and more preferably 34 to 36 minutes; the power of the ultrasonic degassing is 250 to 400 W, preferably 280 to 350 W, and more preferably 300 to 320 W; the ultrasonic degassing time is 20 to 30 minutes, preferably 22 to 28 minutes, and more preferably 24 to 26 minutes.

[0063] In the present invention, the vacuum degree of the vacuum drying is 8000-9000Pa, preferably 8200-8800Pa, and more preferably 8400-8600Pa; the temperature of the vacuum drying is 40-50°C, preferably 42-48°C, and more preferably 44-46°C; the time of the vacuum drying is 12-16h, preferably 13-15h, and more preferably 14h.

[0064] The invention also provides application of the light conversion film in plant growth.

[0065] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0066] Preparation of carbon dots absorbing ultraviolet and green light

[0067] Example 1

[0068] Weigh 0.2g of o-phenylenediamine, add 3mL of acrylic acid and 10mL of deionized water to a 50mL reactor, react at 180℃ for 8h, take out, put the liquid product after the reaction into a centrifuge tube, and centrifuge it at a speed of 10000r / min for 20min using a high-speed centrifuge. After taking it out, filter the supernatant through a disposable filter membrane (0.22μm) to obtain a purified red carbon dot solution. Use a 500Da dialysis bag to dialyze at room temperature for 48h for purification, and change the water every 2h during the period. Pour it into a petri dish and put it in a freezer for freezing (-20℃, 24h), put the frozen solid into a freeze dryer (-70℃) for freeze drying for 36h, and finally obtain a pink carbon dot solid powder.

[0069] Figure 1 The XRD pattern of the carbon dots absorbing ultraviolet light and green light prepared in this example is Figure 1 It can be seen that the XRD diffraction peak of the carbon dots is 21.66°.

[0070] Figure 2 TEM images and particle size distribution diagrams of carbon dots absorbing ultraviolet light and green light prepared in this example, wherein (a) is a TEM image of carbon dots, and (b) is a particle size distribution diagram of carbon dots. Figure 2 It can be seen that the carbon dots prepared in this example are quasi-spherical, with an average particle size of 2.03±0.73 nm and a lattice spacing of 0.21 nm, which is close to the (002) crystal plane of graphite carbon.

[0071] Figure 3 The emission fluorescence spectra of carbon dots that absorb ultraviolet light and green light prepared in Example 1, wherein (a) shows the optimal excitation and optimal emission spectra of carbon dots, (b) shows the fluorescence spectrum of carbon dots under ultraviolet light excitation (320-380nm, interval 10nm), (c) shows the fluorescence spectrum of carbon dots under green light excitation (500-560nm, interval 10nm), (d) shows the normalized fluorescence spectrum of carbon dots under ultraviolet light excitation (320-380nm, interval 10nm), and (e) shows the normalized fluorescence spectrum of carbon dots under green light excitation (500-560nm, interval 10nm). Figure 3 It can be seen that the optimal excitation wavelengths of the carbon dots prepared in this embodiment are 350nm and 530nm respectively. Under the excitation of 350nm ultraviolet light, its optimal emission wavelength is in the 445nm blue light region and the 600nm red light region. Under the excitation of 530nm green light, its optimal emission wavelength is in the 610nm red light region.

[0072] Figure 4 The infrared spectrum of the carbon dots prepared in this example that absorb ultraviolet light and green light is shown in FIG. Figure 4 It can be seen that 3443cm -1 The absorption peak at 2952 cm is attributed to the overlapping stretching vibrations of OH and NH. -1 、1724cm -1 、1456cm -1 、1415cm -1 、1172cm -1 They are respectively attributed to the stretching vibrations of CH, C=O, C=C, CN, and CO bonds.

[0073] Figure 5 This is the XPS spectrum of the carbon dots absorbing ultraviolet light and green light prepared in this example. Figure 5 (a) XPS spectrum shows that the carbon dots are mainly composed of 68.07% C, 1.87% N and 29.43% O; Figure 5 (b) It can be seen that the C1s spectrum has three peaks at 284.78 eV, 285.18 eV and 288.88 eV, which can be attributed to CC / C=C, CN / CO and C=O respectively; Figure 5 (c) The N1s spectrum of the carbon dots is composed of two peaks, CN and NH, at 399.48 eV and 401.18 eV respectively; the O1s spectrum of the carbon dots Figure 5 (d) shows that O1s contains two components: C=O at 531.98 eV and CO at 533.38 eV.

[0074] Example 2

[0075] Weigh 0.1g o-phenylenediamine, add 2mL acrylic acid and 5mL deionized water to a 50mL reactor, react at 170℃ for 7h, take out, put the liquid product after the reaction into a centrifuge tube, and centrifuge it at 10000r / min for 20min using a high-speed centrifuge. After taking it out, filter the supernatant through a disposable filter membrane (0.22μm) to obtain a purified red carbon dot solution. Use a 500Da dialysis bag to dialyze at room temperature for 48h for purification, and change the water every 2h during the period. Pour it into a culture dish and put it in a freezer for freezing (-20℃, 24h), put the frozen solid into a freeze dryer (-65℃) for freeze drying for 24h, and finally obtain a pink carbon dot solid powder.

[0076] Example 3

[0077] Weigh 0.15g of o-phenylenediamine, add 4mL of acrylic acid and 15mL of deionized water to a 50mL reactor, react at 190℃ for 7h, take out, put the liquid product after the reaction into a centrifuge tube, and centrifuge it at a speed of 10000r / min for 20min using a high-speed centrifuge. After taking it out, filter the supernatant through a disposable filter membrane (0.22μm) to obtain a purified red carbon dot solution. Use a 500Da dialysis bag to dialyze at room temperature for 48h for purification, and change the water every 2h during the period. Pour it into a petri dish and put it in a freezer for freezing (-20℃, 24h), put the frozen solid into a freeze dryer (-75℃) for freeze drying for 24h, and finally obtain a pink carbon dot solid powder.

[0078] Preparation of light-transfer film

[0079] Example 4

[0080] 1g of polyvinyl alcohol (PVA) and 40mg of carbon dots in Example 1 were mixed, and then 20mL of deionized water was added and stirred for 20min to obtain a viscous liquid mixture, and then the mixture was placed in an ultrasonic cleaning machine for ultrasonic degassing at a power of 300W for 30min, and finally the mixed solution was quickly poured into a culture dish, and dried at 50°C under vacuum (vacuum degree = 8000Pa) for 12h to obtain a light-converting film. The carbon dots in the light-converting film accounted for 4% of the mass of PVA.

[0081] Example 5

[0082] The same as Example 4, except that 20 mg of carbon dots were added in this example, and the carbon dots in the obtained light conversion film accounted for 2% of the mass of PVA.

[0083] Example 6

[0084] The same as Example 4, except that 30 mg of carbon dots were added in this example, and the carbon dots in the obtained light conversion film accounted for 3% of the mass of PVA.

[0085] Example 7

[0086] The same as Example 4, except that 30 mg of carbon dots were added in this example, and the carbon dots in the obtained light conversion film accounted for 5% of the mass of PVA.

[0087] Figures 6 to 9 The fluorescence spectra of the light-conversion films prepared in Examples 4 to 7 containing different mass ratios of carbon dots and PVA (2%, 3%, 4%, and 5%) are shown in FIG. Figures 6 to 9 It can be seen that the light conversion films containing different mass ratios of carbon dots and PVA (2%, 3%, 4%, 5%) have fluorescence spectra in the blue and red regions under ultraviolet light excitation, and in the red region under green light excitation.

[0088] Fig.10 The optimal excitation and emission spectra of the light-converting film prepared in Example 4 are given by Fig.10 It can be obtained that the optimal excitation wavelengths of the carbon dot light conversion film prepared in Example 4 are 330nm and 530nm respectively. Under the excitation of ultraviolet light 330nm, its optimal emission wavelength is in the 420nm blue light region and the 610nm green light region. Under the excitation of green light 530nm, its optimal emission wavelength is in the 610nm red light region.

[0089] Fig.11 The transmittance comparison diagram of the light conversion films prepared in Examples 4 to 7 containing different mass ratios of carbon dots to PVA (2%, 3%, 4%, 5%, 6%) is shown in FIG. Fig.11 It can be seen that with the increase of carbon dot content, the transmittance of ultraviolet light of the light conversion film decreases, ultraviolet light can be converted into blue light and the harm of ultraviolet light to crops can be blocked, which is beneficial to the growth of crops.

[0090] Performance Testing

[0091] A greenhouse was built outdoors for the experiment. The dimensions of the greenhouse were 200 cm long, 100 cm wide, 80 cm high, and 1.6 m in volume. 3 The test crops were Chinese cabbage, lettuce, and Chinese cabbage. The test crop seeds were purchased online. They were planted on seedling trays, with 4 healthy vegetable seeds planted in each seedling tray. Water and fertilizer management methods were carried out in the usual way. In order to obtain more accurate experimental data, a light-converting film with a carbon dot content of 4% was used as the test covering film, and 3 groups of tests were set up.

[0092] Experiment: Three kinds of vegetables, Chinese cabbage, lettuce and Chinese cabbage, were planted from left to right on the seedling tray, with four rows for each vegetable. The greenhouse was divided into three groups from inside to outside, with five rows in each group. The blue-red dual-light conversion film, PVA film and no film were covered 30 cm above them. The growth of the three vegetables, Chinese cabbage, lettuce and Chinese cabbage, was continuously monitored and photographed from the day the seeds were planted. The cultivation lasted for 45 days. The growth process of the three vegetables is shown in Figure 2. Fig.12 .

[0093] 1. Select 30 sprouted Chinese cabbages (such as Fig.13 The plant height, root length, leaf length and leaf width were measured (as shown), and the average values ​​were taken. Thirty Chinese cabbage plants were selected for fresh weight and dry weight weighing. The average values ​​were taken after multiple weighings. The records are shown in Table 1.

[0094] Table 1 Effect of light-conversion film with 4% carbon dot content on the growth and development of Chinese cabbage

[0095]

[0096]

[0097] Weigh 0.2 g of freshly removed leaf veins of Chinese cabbage, and measure its photosynthetic pigments using an acetone-ethanol equal volume mixed solution method. The average value is taken after multiple tests, and the measurement results are shown in Table 2.

[0098] Table 2 Effect of light-conversion film with a carbon dot content of 4% on the content of photosynthetic pigments in Chinese cabbage

[0099]

[0100] Weigh 0.2g of freshly removed leaf veins of pakchoi leaves and measure their nutrient content. The soluble protein content was measured by the Coomassie brilliant blue method; the vitamin C content was measured by the 2,6-dichlorophenol indophenol titration method; the soluble sugar content was measured by the anthrone colorimetric method; the polyphenol content was measured by the Folin phenol method; and the flavonoid content was measured by the sodium nitrite method. The average value of multiple tests was taken, and the measurement results are shown in Table 3 below.

[0101] Table 3 Effect of light-conversion film with a carbon dot content of 4% on the nutrient content of pakchoi

[0102]

[0103] As shown in Tables 1 to 3, compared with the other two groups, the germination rate of Chinese cabbage in the double-light conversion film group was 16.18% and 6.76% higher than that in the non-film group and PVA film group, respectively; the plant height increased by 40.76% and 22.56%, the fresh weight increased by 152.73% and 35.28%, the dry weight increased by 83.87% and 26.67%, the root length increased by 49.20% and 15.46%, the leaf length increased by 79.02% and 24.27%, and the leaf width increased by 56.58% and 2 The contents of chlorophyll a and chlorophyll b increased by 13.89% and 5.13%, chlorophyll a+b increased by 64.70% and 50.00%, carotenoids increased by 96.00% and 33.64%, soluble protein increased by 21.59% and 12.95%, vitamin C increased by 24.87% and 11.84%, soluble sugar increased by 13.89% and 5.13%, polyphenol content increased by 48.95% and 16.39%, flavonoid content increased by 133.91% and 56.48%.

[0104] Second, select 30 sprouted lettuces (such as Fig.14The plant height, root length, leaf length and leaf width were measured (as shown), and the average values ​​were taken. Thirty lettuce plants were selected for fresh weight and dry weight weighing. The average values ​​were taken after multiple weighings. The records are shown in Table 4.

[0105] Table 4 Effect of light-conversion film with 4% carbon dot content on the growth and development of lettuce

[0106]

[0107] Weigh 0.2 g of fresh lettuce leaves with veins removed, and measure the photosynthetic pigments using an acetone-ethanol equal volume mixed solution method. The average value is taken after multiple tests, and the measurement results are shown in Table 5 below.

[0108] Table 5 Effect of light-conversion film with a carbon dot content of 4% on the content of photosynthetic pigments in lettuce

[0109]

[0110] Weigh 0.2g of fresh lettuce leaves with veins removed, and measure their nutrient content. The soluble protein content was measured by the Coomassie brilliant blue method; the vitamin C content was measured by the 2,6-dichlorophenol indophenol titration method; the soluble sugar content was measured by the anthrone colorimetric method; the polyphenol content was measured by the Folin phenol method; and the flavonoid content was measured by the sodium nitrite method. The average value of multiple tests was taken, and the measurement results are shown in Table 6 below.

[0111] Table 6 Effect of light-conversion film with a carbon dot content of 4% on the nutrient content of lettuce

[0112]

[0113] As shown in Tables 4 to 6, compared with the other two groups, the germination rate of lettuce in the double-light conversion film group was 36.36% and 13.64% higher than that in the non-film group and PVA film group, respectively; the plant height increased by 41.24% and 15.44%, the fresh weight increased by 143.92% and 49.89%, the dry weight increased by 100% and 16.67%, the root length increased by 122.72% and 19.51%, the leaf length increased by 100% and 15.38%, the leaf width increased by 113.33% and 18.52%, and the chlorophyll a content increased by 106.25% and 15.70%, respectively. 22.22%, chlorophyll b content increased by 13.89% and 5.13% respectively, chlorophyll a+b content increased by 64.70% and 50.00% respectively, carotenoid content increased by 96.00% and 33.64% respectively, soluble protein content increased by 29.43% and 29.20% respectively, vitamin C content increased by 17.31% and 11.93% respectively, soluble sugar content increased by 86.67% and 7.69% respectively, polyphenol content increased by 12.21% and 0.68% respectively, and flavonoid content of lettuce increased by 53.09% and 33.02% respectively.

[0114] 3. Select 30 sprouted cabbage hearts (such as Fig.15 The plant height, root length, leaf length and leaf width were measured (as shown), and the average values ​​were taken. Thirty Chinese cabbage plants were selected for fresh weight and dry weight weighing. The average values ​​were taken after multiple weighings. The records are shown in Table 7.

[0115] Table 7 Effect of light-converting film with a carbon dot content of 4% on the growth and development of Chinese cabbage

[0116]

[0117] Weigh 0.2 g of freshly deveined Chinese cabbage leaves and measure their photosynthetic pigments using an acetone-ethanol equal volume mixed solution method. The average value of multiple tests is obtained, and the measurement results are shown in Table 8 below.

[0118] Table 8 Effect of light-conversion film with a carbon dot content of 4% on the content of photosynthetic pigments in Chinese cabbage

[0119]

[0120] Weigh 0.2g of freshly deveined Chinese cabbage leaves and measure their nutrient content. The Coomassie brilliant blue method was used to measure the soluble protein content; the 2,6-dichlorophenol indophenol titration method was used to measure the vitamin C content; the anthrone colorimetric method was used to measure the soluble sugar content; the Folin phenol method was used to measure the polyphenol content; and the sodium nitrite method was used to measure the flavonoid content. The average value of multiple tests was taken, and the measurement results are shown in Table 9 below.

[0121] Table 9 Effect of light-converting film with a carbon dot content of 4% on the nutritional elements content of Chinese cabbage

[0122]

[0123] As shown in Tables 7 to 9, compared with the other two groups, the germination rate of Chinese cabbage in the double-light conversion film group was 26.23% and 8.45% higher than that of the non-film group and the PVA film group, respectively; the plant height increased by 60.22% and 36.73%, the fresh weight increased by 160.74% and 53.90%, the dry weight increased by 111.11% and 29.82%, the root length increased by 37.97% and 21.96%, the leaf length increased by 31.95% and 8.31%, the leaf width increased by 41.15% and 23.89%, and the chlorophyll a content increased by 72.1%. 4% and 26.18% respectively, the chlorophyll b content increased by 73.33% and 53.33% respectively, the chlorophyll a+b content increased by 41.88% and 14.83% respectively, the carotenoid content increased by 1.42% and 0.71% respectively, the soluble protein content increased by 9.40% and 3.50% respectively, the vitamin C content increased by 3.37% and 2.01% respectively, the soluble sugar content increased by 73.33% and 13.04% respectively, the polyphenol content increased by 22.73% and 3.85% respectively, the flavonoid content of Chinese cabbage increased by 37.35% and 2.03% respectively.

[0124] From the data of the above different vegetables, it can be seen that the conversion of light by the light conversion film affects the germination of the seeds of the three vegetables, the absorption of nutrients in the soil by the roots, the content of chlorophyll in the leaves, the content of various nutrients, and the photosynthesis process such as water metabolism in many aspects. It shows that the light conversion film of the present invention can significantly improve the utilization rate of sunlight by crops and enhance their photosynthetic capacity. The light conversion film can convert ultraviolet light and green light that are not conducive to plant growth into blue light and red light that can be absorbed by chlorophyll a, b and carotenoids, thereby improving the light quality of the transmitted light, promoting the photosynthesis of crops, increasing the germination rate of seeds, and ultimately increasing the yield of agricultural crops.

[0125] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing carbon dots that absorb ultraviolet light and green light, characterized in that: The following steps are involved: After mixing o-phenylenediamine, acrylic acid and water, a hydrothermal reaction occurs, and the reaction product is centrifuged, filtered, dialyzed and freeze-dried in sequence to obtain carbon dots that absorb ultraviolet light and green light; The dosage ratio of the o-phenylenediamine, acrylic acid and water is 0.1-0.2 g: 2-4 mL: 5-15 mL.

2. The preparation method according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 170-190° C., and the time of the hydrothermal reaction is 7-9 hours.

3. The preparation method according to claim 2, characterized in that: The centrifugal speed is 8000-12000 rpm, and the centrifugal time is 15-20 min; The pore size of the filter membrane used in the filtration is 0.2-0.3 μm; The molecular weight cut-off of the dialysis is 300-800Da, and the dialysis time is 36-72h; The freeze drying temperature is -65 to -75°C, and the freeze drying time is 24 to 36 hours.

4. Carbon dots absorbing ultraviolet light and green light prepared by the preparation method according to any one of claims 1 to 3.

5. A light conversion film, characterized in that: The light-converting film comprises a film substrate and the carbon dots for absorbing ultraviolet light and green light as described in claim 4; The mass ratio of the film substrate to the carbon dots absorbing ultraviolet light and green light is 1000:5-50.

6. The light-converting film according to claim 5, characterized in that: The film substrate includes polyvinyl alcohol.

7. A method for preparing the light-converting film according to claim 5 or 6, characterized in that: The following steps are involved: The film substrate, carbon dots absorbing ultraviolet light and green light and water are mixed to obtain a mixed solution, and the mixed solution is successively subjected to ultrasonic degassing and vacuum drying to obtain a light conversion film; The usage ratio of the membrane substrate, the carbon dots for absorbing ultraviolet light and green light, and water is 1 g: 0.005-0.05 g: 20-40 mL.

8. The method for preparing the light-converting film according to claim 7, characterized in that: The mixing time is 30 to 40 minutes, the power of the ultrasonic degassing is 250 to 400 W, and the ultrasonic degassing time is 20 to 30 minutes.

9. The method for preparing a light-converting film according to claim 7 or 8, characterized in that: The vacuum degree of the vacuum drying is 8000-9000 Pa, the temperature of the vacuum drying is 40-50° C., and the time of the vacuum drying is 12-16 hours.

10. Use of the light conversion film according to claim 5 or 6 in plant growth.

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