A solvent-dependent biomass carbon dot and a light-converting film containing the same

Abstract

The present invention discloses a solvent-dependent biomass carbon dot and a light-conversion film containing the same. The biomass carbon dot uses plants containing chlorophyll as raw materials, uses a solvent to extract and / or disperse the chlorophyll in the plant juice, and then absorbs the supernatant as a carbon source after standing, and adopts a solvent thermal method to prepare the red and blue dual-emission carbon dots; the solvent includes water and / or an organic solvent; the volume ratio of the water to the organic solvent is 0-1:0-1, and the water and the organic solvent are not 0 at the same time. During preparation, the chlorophyll extraction amount is adjusted and dispersed by combining different solvents, and then dual-emission carbon dots with different proportions of red and blue light are prepared under different chlorophyll contents. At the same time, the present invention also uses the biomass carbon dot as raw material to prepare a light-conversion film, which can convert ultraviolet light in sunlight into blue light and red light that can be efficiently used by crops, and can achieve matching of the conversion spectrum ratio with the spectrum ratio required by crops through regulation, thereby promoting plant growth and development.

Description

Technical Field

[0001] The present invention relates to the technical field of nano fluorescent materials and functional films, and more specifically to solvent-dependent biomass carbon dots and a light-converting film containing the same. Background Art

[0002] Sunlight is the primary energy source for plant growth and development. The solar spectrum reaching the Earth's surface is in the 290-3000 nm range and can be divided into ultraviolet (290-400 nm), visible light (400-780 nm), and infrared (780-3000 nm). Different light components have different effects on plant growth. Light quality, a key factor influencing the light environment, generally regulates the plant life cycle through light receptor pathways such as phytochromes, cryptochromes, and phototropins, playing a particularly important role in photosynthesis and photomorphogenesis. Visible light with a wavelength of 400-700 nm directly influences plant photosynthesis and is absorbed by plants. Blue-violet light (400-480 nm) and red light (600-700 nm) are particularly important for promoting plant growth and development. High-energy ultraviolet light is harmful to plants, while yellow-green light with a wavelength of 500-600 nm is reflected by plant leaves. Therefore, how to improve lighting conditions, enhance plant photosynthesis, promote plant growth and improve plant quality is a major research topic in modern agriculture.

[0003] In the spectrum of photosynthetically active radiation, red light promotes the accumulation of carbohydrates and increases the accumulation of soluble sugar content, which is particularly critical for the development and formation of photosynthetic tissues and organs. Blue light promotes protein formation and is closely related to the formation of chloroplasts, the synthesis of chlorophyll, and the opening of stomata in the leaf epidermis. Composite red and blue light helps reduce the accumulation of nitrate content. Therefore, the lack of either red or blue light will lead to photosynthetic inefficiency and poor plant growth. Numerous studies have found that a combination of red and blue light is more beneficial to plant growth than monochromatic light. Different crop species and different growth stages of the same crop require specific "light recipes" to be more conducive to crop growth and development. For example, when the red-blue light ratio is 93:7, the photosynthetic capacity of cucumber leaves is twice that of 100% red light treatment. When the blue light ratio is between 0-50%, the photosynthetic capacity of cucumber leaves increases with the increase of blue light ratio. For the accumulation of nutritional quality of cherry tomato fruit, there is a threshold for the optimal red-blue light ratio. A larger blue light ratio is conducive to the accumulation of nutrients. When blue light accounts for 60% of the red-blue light combination, the cherry tomato fruit quality is relatively good. Therefore, how to develop safe, energy-saving, environmentally friendly, economical and efficient strategies to achieve precise control of light quality is an important issue facing the development of modern facility agriculture, and is also a research direction and hot spot in facility vegetable cultivation.

[0004] Artificial lighting (such as LEDs) allows for precise control of the light environment for crop growth, but the equipment required is complex and costly, and the use of light sources is accompanied by significant energy consumption. Compared to artificial lighting, light conversion films, which achieve spectral conversion by adding light-converting materials, can convert harmful or undesirable ultraviolet and green light in sunlight into the blue-violet and red-orange light required for plant growth, thereby enhancing plant photosynthesis. The light conversion agent is a major factor influencing the performance of light conversion films. Currently, commonly used light conversion agents include organic dyes, inorganic salts, and rare earth organic complexes. However, existing light conversion agents still suffer from difficulties matching their excitation spectra with those harmful or undesirable to crops, their emission spectra with those required by crops, poor stability, low light transmittance, and high cost, limiting their application and widespread adoption.

[0005] Carbon dots (CDs) are considered highly promising nanophotoluminescent materials due to their tunable luminescence properties, low toxicity, excellent dispersibility, and outstanding optical properties. By varying their chemical composition, size, shape, and surface structure, CDs can effectively control their emission of the blue-violet and red-orange light required by plants. Therefore, using CDs as light-converting agents, light-converting films with spectral matching, excellent light transmittance, and excellent stability can be prepared. In particular, CDs synthesized from biomass feedstocks via a bottom-up approach under solvothermal or microwave conditions offer advantages such as ease of operation, low cost, excellent biocompatibility, and tunable optical properties, making them particularly suitable for large-scale production and application in the preparation of light-converting agricultural films.

[0006] Therefore, how to prepare biomass-based carbon dots with spectral matching and adjustable light-quality ratio, as well as light-conversion films based on biomass carbon dots, is an urgent problem that researchers in this field need to solve. Summary of the Invention

[0007] To address these shortcomings, the first objective of the present invention is to provide a solvent-dependent biomass carbon dot. These biomass carbon dots are prepared from chlorophyll-containing plants. The chlorophyll in the plant sap is extracted and / or dispersed using a solvent. By varying the solvent mix, the chlorophyll content in the solvent is varied, resulting in dual-emission carbon dots with varying red and blue light ratios at varying chlorophyll contents.

[0008] A second objective of the present invention is to provide a method for preparing the solvent-dependent biomass carbon dots described above. This method is simple to operate, utilizes a wide range of low-cost raw materials, and operates under mild conditions. It can rapidly produce a series of dual-emission carbon dots with varying proportions of red and blue light.

[0009] A third objective of the present invention is to provide a light-conversion film prepared using the aforementioned biomass carbon dots, with an adjustable wavelength range and ratio. This film, which utilizes the aforementioned biomass carbon dots without the addition of toxic or expensive light-conversion agents, is low-cost and environmentally friendly. It converts ultraviolet light from sunlight into blue and red light that crops can efficiently utilize. The converted light spectrum can be adjusted to match the spectrum required by crops, thereby improving sunlight utilization and promoting plant growth.

[0010] A fourth object of the present invention is to provide a method for preparing the light-converting film as described above.

[0011] A fifth object of the present invention is to provide an application of the light-converting film described above in crop seedling cultivation or crop growth.

[0012] In the technical solution of the present invention, since the light conversion condition (ratio of red and blue light) of biomass carbon dots is affected by the solvent formula added during the preparation process, the biomass carbon dots prepared by the present invention are defined as solvent-dependent biomass carbon dots.

[0013] In order to achieve the above first object, the present invention adopts the following technical solutions:

[0014] The present invention discloses a solvent-dependent biomass carbon dot, which is prepared by a solvothermal method using plants containing chlorophyll as raw materials, extracting and / or dispersing the chlorophyll in the plant slurry with a solvent, and then absorbing the supernatant as a carbon source after standing.

[0015] Wherein, the solvent includes water and / or an organic solvent;

[0016] The volume ratio of water to organic solvent is 0-1:0-1, and the volume ratio of water to organic solvent is 0 when the water and the organic solvent are not present.

[0017] In the present invention, plants containing chlorophyll are selected as raw materials to prepare red and blue dual-emission carbon dots. Combined with a large number of experiments, it is found that different solvent combinations can be used to extract and / or disperse different amounts of chlorophyll from plants. After obtaining different amounts of chlorophyll, dual-emission carbon dots with different proportions of red and blue light can be prepared by participating in subsequent solvent thermal reactions; the blue light emission of the dual-emission carbon dots mainly comes from the carbon core in the carbon dots, and the red light emission mainly comes from the porphyrin group in the surface structure of the carbon dots, and the porphyrin ring is the main structure constituting chlorophyll.

[0018] The chlorophyll content extracted and / or dispersed into the solvent during the preparation stage is affected by two factors. The first is the chlorophyll content of the plant itself. The chlorophyll content here mainly refers to the total content of chlorophyll a and chlorophyll b in higher plants. The chlorophyll content in the leaves of green vegetables such as amaranth, spinach, and rapeseed is relatively high, and the solvent can extract or disperse chlorophyll with a high content. However, plants such as carrots and potatoes that do not contain chlorophyll cannot extract chlorophyll, which also affects the subsequent preparation of dual-emission carbon dots. The second is the different solvent combinations. Since chlorophyll in different solvents has different It shows different solubility, so different amounts of chlorophyll can be extracted when different solvent systems are used; since chlorophyll is insoluble in water, when water is used as the solvent, although water cannot directly extract chlorophyll from plants, during extraction, a small amount of molecules in the plant juice will be transferred to the aqueous phase through the free movement between molecules. This is because water plays the purpose of dispersing the plant juice. When the solvent is a mixed system of water and organic solvents, the solubility of the organic solvent in chlorophyll is changed due to the influence of water. Under normal circumstances, the obtained biomass carbon dots have a higher proportion of blue light during testing.

[0019] Furthermore, when the volume ratio of water to organic solvent is 1:0-0.2, blue light in the emitted light of the biomass carbon dots accounts for 90-100% of the total emitted light, and the rest is red light.

[0020] Furthermore, when the volume ratio of water to organic solvent is 0-0.5:1, red light in the emitted light of the biomass carbon dots accounts for 70-100% of the total emitted light, and the rest is blue light.

[0021] When the solvent for preparing biomass carbon dots is only water, only a small amount of chlorophyll is dispersed into the water system, which will affect the proportion of red light in the emission spectrum of the biomass carbon dots. If the biomass carbon dots are dispersed with water for light conversion testing, the emission spectrum of the biomass carbon dots obtained is mainly blue light. However, later experiments found that based on the hydrophobicity of the porphyrin groups in the surface structure of biomass carbon dots, the emission spectrum of the biomass carbon dots can be further adjusted by adjusting the dispersing solvent used in the fluorescence spectrum test of the biomass carbon dots. For example, when the biomass carbon dots are dispersed with organic solvents such as ethanol for testing, the porphyrin groups on the surface of the carbon dots are in a dispersed state, which will emit blue light. The proportion of red light in the emission spectrum is now increased; on the contrary, when the solvent for preparing biomass carbon dots is only organic solvent, chlorophyll can be extracted and dispersed in the organic phase. When the fluorescence spectrum test is performed, the organic solvent is used to disperse the biomass carbon dots for testing, and the emission spectrum of the obtained biomass carbon dots is mainly red light. If water or a mixed system of water and organic solvent is used to disperse the biomass carbon dots for testing, the porphyrin groups on the surface of the carbon dots are in a clustered state, and it will be found that the proportion of red light in the emission spectrum is reduced. In other words, the different dispersion solvents used in the fluorescence spectrum test can also play a secondary adjustment role in the emission spectrum. Based on this discovery, it can provide inspiration for the subsequent preparation of light-converting films with adjustable light-conversion range, that is: when using biomass carbon dots (prepared with organic solvents) with a higher proportion of red light in the emission spectrum as raw materials, in order to increase the proportion of blue light in the emission spectrum of the light-converting film, water can be introduced during the preparation of the light-converting film, which is conducive to the increase of the proportion of blue light. Conversely, when using biomass carbon dots (prepared with water or a mixed solvent with a water proportion of more than 50%) with a higher proportion of blue light in the emission spectrum as raw materials, in order to increase the proportion of red light in the emission spectrum of the light-converting film, only organic solvents can be introduced during the preparation process, which is conducive to the increase of the proportion of red light.

[0022] Furthermore, when the volume ratio of water to organic solvent is 1:0.2-0.5:1, and does not include 1:0.2 and 0.5:1, the emission light of the biomass carbon dots is between the above two situations, with red light accounting for 20-70% of the total emission light and the rest being blue light.

[0023] In order to achieve the above second purpose, the present invention adopts the following technical solutions:

[0024] The present invention discloses a method for preparing the biomass carbon dots as described above, comprising the following steps:

[0025] Wash and pulp the chlorophyll-containing plants to obtain pulp; add a solvent to the pulp and perform ultrasonic extraction to extract and / or disperse the chlorophyll in the pulp; let it stand for 0.5-1 hour after extraction, and absorb the supernatant;

[0026] The supernatant was transferred to a reactor for solvent thermal reaction. After the reaction was completed, the product was filtered and the filtrate was freeze-dried to obtain the product.

[0027] Furthermore, the plants containing chlorophyll include but are not limited to one or more of amaranth, spinach, chrysanthemum, bitter chrysanthemum, radish leaves, rapeseed, kale, fennel, lettuce, wood ear vegetable, water spinach, shepherd's purse, cabbage, broccoli, celery, green pepper, poplar leaves, willow leaves, ginkgo leaves, cypress leaves, tall fescue, clover, purslane, foxtail grass, morning glory leaves and Stephania tetrandra.

[0028] Furthermore, the solvent includes water and / or an organic solvent. Different solvent combinations will affect the extraction and dispersion of chlorophyll in the pulp during the preparation process, thereby affecting the emission spectrum of the biomass carbon dots.

[0029] Furthermore, the organic solvent includes, but is not limited to, one or more of ethanol, methanol, acetone, N,N-dimethylformamide, tetrahydrofuran, formamide, ethyl acetate, n-hexane and chloroform.

[0030] Furthermore, the mass volume ratio of the plant to the solvent is 1 g:(1-4) mL.

[0031] Furthermore, ultrasonic extraction can transfer the molecules in the juice to the solvent in a relatively stable state, achieving the purpose of extraction or dispersion. Compared with strong mixing methods such as stirring and oscillation, it can avoid a large amount of plant tissue entering the reaction system while effectively extracting chlorophyll.

[0032] The operation used in conjunction with the ultrasonic extraction method is to let the solution stand for a period of time after extraction to allow the molecules to gradually and freely settle down. In particular, when water is used as the solvent, the chlorophyll dispersed in the aqueous phase will not completely settle down. Compared with other solid-liquid separation methods, the separation method of the present invention is relatively gentle. Unlike strong separation methods such as centrifugation and filtration, in the absence of external force, more chlorophyll can be retained in the supernatant, which is the key to finally obtaining dual-emission carbon dots.

[0033] Furthermore, the solvent thermal reaction time is 2-24 hours, and the reaction temperature is 120-200°C.

[0034] Furthermore, the ultrasonic conditions are as follows: ultrasonic time of 0.1-1 h, ultrasonic frequency of 40 KHz, and ultrasonic power of 0-180 W.

[0035] In order to achieve the third object, the present invention adopts the following technical solutions:

[0036] The present invention discloses a light-converting film based on solvent-dependent biomass carbon dots. The raw materials of the light-converting film include film-forming polymers and the biomass carbon dots described above.

[0037] Furthermore, the mass ratio of the biomass carbon dots to the film-forming polymer is 0.0001-0.01:1.

[0038] Furthermore, the film-forming polymer includes but is not limited to one or more of polyethylene, polyvinyl alcohol, polyetheretherketone, polyetherimide, polyimide, polyvinyl chloride, polydimethylsiloxane, fluororesin, polyamide, polyolefin and ethylene-vinyl acetate copolymer.

[0039] In order to achieve the fourth purpose above, the present invention adopts the following technical solutions:

[0040] The present invention discloses a method for preparing the light-converting film as described above, comprising the following steps:

[0041] mixing the biomass carbon dots with a solvent to obtain a biomass carbon dot solution;

[0042] mixing a film-forming polymer with a solvent to obtain a film-forming polymer solution;

[0043] The biomass carbon dot solution is added to the film-forming polymer solution, mixed evenly, and then the mixed solution is cast into a film, dried and solidified to obtain the film.

[0044] Furthermore, the solvent includes but is not limited to one or more of water, ethanol, methanol, acetone, N,N-dimethylformamide, tetrahydrofuran, formamide, ethyl acetate, n-hexane and chloroform. When preparing the light-converting film, the emission spectrum can be secondary adjusted by adding different solvents. The adjustment strategy can be: when the solvent used in preparing the biomass carbon dots is a mixed solvent with a water content of more than 50%, only organic solvents are used as solvents when preparing the light-converting film, which can increase the proportion of red light in the emission spectrum of the light-converting film; when the solvent used in preparing the biomass carbon dots is an organic solvent, water can be used to dissolve the film-forming polymer when preparing the light-converting film, thereby increasing the proportion of blue light in the emission spectrum of the light-converting film. The present invention only provides the above two adjustment strategies. Other adjustment strategies for solvent combinations can be directly obtained on the basis of the present invention, and all fall within the scope of protection of the present invention.

[0045] In order to achieve the fifth purpose, the present invention adopts the following technical solutions:

[0046] The present invention discloses an application of the light-conversion film described above in crop seedling cultivation or crop growth.

[0047] The beneficial effects of the present invention are as follows:

[0048] The present invention discloses solvent-dependent biomass carbon dots. These biomass carbon dots are prepared using chlorophyll-containing plants as raw materials. The chlorophyll in the plant sap is extracted or dispersed using a solvent. Different solvent combinations are used to vary the chlorophyll content in the solvent, thereby producing dual-emission carbon dots with varying red and blue light ratios at varying chlorophyll contents.

[0049] The present invention also provides a light-conversion film based on solvent-dependent biomass carbon dots. This film does not contain toxic or expensive light-conversion agents. The selected biomass carbon dots are low-cost and environmentally friendly. This film can convert ultraviolet light from sunlight into blue and red light that can be efficiently utilized by crops. The converted light spectrum can be regulated to match the spectrum required by crops, improving sunlight utilization and promoting plant growth and development. Furthermore, the film's preparation method is simple and easy, and the film's emission spectrum can be adjusted secondary by adjusting the solvent used in its preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0051] Figure 1 This is the UV-Vis absorption spectrum of the ethanol extract of amaranth leaves in Example 1.

[0052] Figure 2 This is the UV-Vis absorption spectrum of the biomass carbon dots prepared in Example 1.

[0053] Figure 3 The biomass carbon dots prepared in Example 1 were dispersed in ethanol, and the resulting excitation spectrum was measured.

[0054] Figure 4 Fluorescence emission spectra of the biomass carbon dots prepared in Example 1 dispersed in ethanol at different excitation wavelengths (340-430 nm).

[0055] Figure 5 The biomass carbon dots prepared in Example 1 were dispersed in water, and the resulting excitation spectrum was measured.

[0056] Figure 6 Fluorescence spectra of the biomass carbon dots prepared in Example 1 dispersed in water at different excitation wavelengths (310-430 nm).

[0057] Figure 7 This is the UV-Vis absorption spectrum of the water extract solution of Amaranth leaves in Example 2.

[0058] Figure 8 This is the UV-Vis absorption spectrum of the biomass carbon dots prepared in Example 2.

[0059] Figure 9 The biomass carbon dots prepared in Example 2 were dispersed in water, and the resulting excitation spectrum was measured.

[0060] Figure 10 Fluorescence emission spectra of the biomass carbon dots prepared in Example 2 dispersed in water at different excitation wavelengths (320-420 nm).

[0061] Figure 11 The biomass carbon dots prepared in Example 2 were dispersed in ethanol, and the resulting excitation spectrum was measured.

[0062] Figure 12 Fluorescence emission spectra of the biomass carbon dots prepared in Example 2 dispersed in ethanol at different excitation wavelengths (320-420 nm).

[0063] Figure 13 is the V of the amaranth leaves in Example 3 水 :V 乙醇 The UV-Vis absorption spectrum of the 3:1 mixed extraction solution.

[0064] Figure 14 This is the UV-Vis absorption spectrum of the biomass carbon dots prepared in Example 3.

[0065] Figure 15 The biomass carbon dots prepared in Example 3 are dispersed in V 水 :V 乙醇 The excitation spectrum was obtained by testing the mixture in a 3:1 ratio.

[0066] Figure 16 The biomass carbon dots prepared in Example 3 are dispersed in V 水 :V 乙醇 Figure 2 shows the fluorescence emission spectra of a 3:1 mixture at different excitation wavelengths (320-420 nm).

[0067] Figure 17 is the V of the amaranth leaves in Example 4 水 :V 乙醇 The UV-Vis absorption spectrum of the 1:3 mixed extraction solution.

[0068] Figure 18 This is the UV-Vis absorption spectrum of the biomass carbon dots prepared in Example 4.

[0069] Figure 19 The biomass carbon dots prepared in Example 4 are dispersed in V 水 :V 乙醇 The excitation spectrum obtained by testing the mixture was 1:3.

[0070] Figure 20 The biomass carbon dots prepared in Example 4 are dispersed in V水 :V 乙醇 Figure 2 shows the fluorescence emission spectra of a 1:3 mixture at different excitation wavelengths (310-430 nm).

[0071] Figure 21 is the V of the amaranth leaves in Example 5 水 :V 乙醇 The UV-Vis absorption spectrum of the 1:1 mixed extraction solution.

[0072] Figure 22 This is the UV-Vis absorption spectrum of the biomass carbon dots prepared in Example 5.

[0073] Figure 23 The biomass carbon dots prepared in Example 5 are dispersed in V 水 :V 乙醇 The excitation spectrum was measured in a 1:1 mixture.

[0074] Figure 24 The biomass carbon dots prepared in Example 5 are dispersed in V 水 :V 乙醇 Figure 2 shows the fluorescence emission spectra of the 1:1 mixture at different excitation wavelengths (310-430 nm).

[0075] Figure 25 Fluorescence emission spectra of the biomass carbon dots prepared in Comparative Example 1 dispersed in ethanol at different excitation wavelengths (340-420 nm).

[0076] Figure 26 The photosynthetically active radiation of the light-conversion film prepared in Example 8 and the homemade blank PDMS film; the insets are photos of the light-conversion film prepared in Example 8 under natural light and 365 nm ultraviolet light.

[0077] Figure 27 This is the fluorescence emission spectrum of the polyvinyl alcohol light-transmitting film prepared in Example 9. DETAILED DESCRIPTION

[0078] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the following detailed description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0079] In addition, unless otherwise specified, the raw materials used in the present invention can be obtained commercially, and any range recorded in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0080] Examples 1-7 are the synthesis method of solvent-dependent biomass carbon dots and the photoluminescence performance test, and Examples 8-10 are the preparation and light conversion performance test of the light conversion film based on the solvent-dependent biomass carbon dots obtained in the experiment.

[0081] Example 1

[0082] This example is a scheme for synthesizing biomass carbon dots using amaranth (containing chlorophyll) as raw material and ethanol as solvent. The specific implementation steps are as follows:

[0083] Weigh 15 g of amaranth leaves, wash them, dry the surface with paper, and then use a wall-breaking machine to grind them into a pulp. Add 40 mL of ethanol to the pulp and ultrasonically extract the chlorophyll in the pulp at room temperature for 0.5 h at an ultrasonic power of 100 W. After standing for 1 h, aspirate the supernatant.

[0084] The supernatant was transferred to a reactor and reacted at 150°C for 7 hours using a solvothermal method. After the reaction was completed, the crude product was cooled to obtain the crude product. The crude product was filtered using a 0.22 μm filter head, and the filtrate was collected and freeze-dried to obtain the biomass carbon dot A-CD (EtOH), which was placed in a 4°C refrigerator for later use.

[0085] Performance testing:

[0086] Test 1: Use TU-1901 UV-visible spectrophotometer to test the UV-visible absorbance of the amaranth ethanol extract. Figure 1 The results showed that the characteristic peaks (Q band and Soret band) of porphyrin in chlorophyll existed in the ethanol extract and the peak intensity was high, indicating that when ethanol was used as the extraction solvent, the extracted chlorophyll content was high.

[0087] Figure 2 This is the UV-visible absorption spectrum of the CD prepared in Example 1, which also shows the characteristic peaks attributed to porphyrin, indicating that the CD surface has porphyrin groups.

[0088] Test 2: Weigh 1 mg of the prepared biomass carbon dots and dissolve it in 10 mL of ethanol. The resulting solution was tested using an FLS1000 transient / steady-state fluorescence spectrometer to measure its excitation spectrum ( Figure 3 ), and its fluorescence emission spectra at different excitation wavelengths (340-430nm) ( Figure 4 ). Its fluorescence emission spectrum shows that red light emission accounts for about 98% of the total red and blue light emission, and the blue light emission spectrum shifts with the change of excitation wavelength, that is, it has excitation dependence.

[0089] Test 3: Weigh 1 mg of the prepared biomass carbon dots and dissolve them in 10 mL of water. The resulting solution is tested using an FLS1000 transient / steady-state fluorescence spectrometer to measure its excitation spectrum ( Figure 5 ), and its fluorescence spectra at different excitation wavelengths (310-430 nm) ( Figure 6 ). Its fluorescence emission spectrum shows that the emission ratio of blue light to red light is approximately 1:3, and the blue light emission is excitation-dependent.

[0090] Example 2

[0091] This example uses amaranth (containing chlorophyll) as raw material and water as solvent to synthesize biomass carbon dots. The specific implementation steps are as follows:

[0092] Weigh 15 g of amaranth leaves, wash them, dry the surface with paper, and then use a wall-breaking machine to grind them into a pulp. Add 40 mL of water to the pulp and sonicate at room temperature to disperse the chlorophyll in the pulp into the water. The ultrasonic extraction time is 0.5 h at an ultrasonic power of 100 W. After standing for 1 h, the supernatant is aspirated.

[0093] The supernatant was transferred to a reactor and reacted at 150°C for 7 hours using a solvothermal method. After the reaction was completed, the crude product was cooled to obtain the crude product. The crude product was filtered using a 0.22 μm filter head, and the filtrate was collected and freeze-dried to obtain the biomass carbon dots A-CD (H2O), which was placed in a refrigerator at 4°C for later use.

[0094] Performance testing:

[0095] Test 1: Use TU-1901 UV-visible spectrophotometer to test the UV-visible absorbance of the amaranth ethanol extract. Figure 7 ,The results showed that the characteristic peaks (Q band and Soret band) of porphyrin in chlorophyll also existed in the ,water extract, but the peak intensity was very low, indicating that when water was used as the ,extraction solvent, a small amount of amaranth pulp was dispersed into the water, ,and trace amounts of chlorophyll were present.

[0096] Figure 8 This is the UV-visible absorption spectrum of the CD prepared in Example 2. The results show that there is almost no characteristic peak attributed to porphyrin, indicating that there are very few porphyrin groups on the surface of the CD.

[0097] Test 2: Weigh 1 mg of the prepared biomass carbon dots and dissolve them in 10 mL of water. The resulting solution was tested using an FLS1000 transient / steady-state fluorescence spectrometer to measure its excitation wavelength ( Figure 9 ), and its fluorescence emission spectra at different excitation wavelengths (320-420 nm) ( Figure 10 ). More than 99% of its fluorescence emission spectrum is blue light emission, and the blue light emission is excitation-dependent.

[0098] Test 3: Weigh 1 mg of the prepared biomass carbon dots and disperse them in 10 mL of ethanol. The resulting solution was tested using an FLS1000 transient / steady-state fluorescence spectrometer to measure its excitation wavelength ( Figure 11 ), and its fluorescence emission spectra at different excitation wavelengths (320-420 nm) ( Figure 12 ). Its fluorescence spectrum shows that the emission ratio of blue light to red light is approximately 10:1, and the blue light emission is excitation-dependent.

[0099] Example 3

[0100] This example uses amaranth (containing chlorophyll) as raw material and a water / ethanol mixture with a volume ratio of 3:1 as solvent to synthesize biomass carbon dots. The specific implementation steps are as follows:

[0101] Weigh 15 g of amaranth leaves, wash them, dry the surface with paper, and then use a wall-breaking machine to grind them into a pulp. Add a mixture of 30 mL of water and 10 mL of ethanol to the pulp and perform ultrasonic extraction at room temperature to extract and disperse the chlorophyll in the pulp. The ultrasonic extraction time is 0.5 h and the ultrasonic power is 100 W. After standing for 1 h, the supernatant is aspirated.

[0102] The supernatant was transferred to a reactor and reacted at 150°C for 7 hours using a solvothermal method. After the reaction was completed, the crude product was cooled to obtain the crude product. The crude product was filtered using a 0.22 μm filter head, and the filtrate was collected and freeze-dried to obtain the biomass carbon dots, which were then placed in a refrigerator at 4°C for later use.

[0103] Performance testing:

[0104] Test 1: The UV-visible absorbance of a 3:1 water:ethanol mixed extract of amaranth was tested using a TU-1901 UV-visible spectrophotometer. Figure 13 The results showed that when water and a small amount of ethanol were used as a mixed extract, characteristic peaks of porphyrin in chlorophyll (Q band and Soret band) existed and the peak intensity was higher than that of pure water, indicating that when the mixed solution was used as the extraction solvent, some chlorophyll would be dissolved in a small amount of ethanol.

[0105] Figure 14 This is the UV-visible absorption spectrum of the CD prepared in Example 3. The results show the presence of a small amount of characteristic peaks attributable to porphyrin, indicating that there are a small amount of porphyrin groups on the surface of the CD.

[0106] Test 2: 1 mg of the prepared biomass carbon dots was weighed and dispersed in 10 mL of a water / ethanol mixture with a volume ratio of 3:1. The resulting solution was tested using an FLS1000 transient / steady-state fluorescence spectrometer to measure its excitation wavelength ( Figure 15 ), and its fluorescence emission spectra at different excitation wavelengths (320-420 nm) ( Figure 16 ), the results showed that its blue light emission accounted for about 98% of the total red and blue light emission, and the blue light emission was excitation-dependent.

[0107] Example 4

[0108] This example uses amaranth (containing chlorophyll) as raw material and a water / ethanol mixture with a volume ratio of 1:3 as solvent to synthesize biomass carbon dots. The specific implementation steps are as follows:

[0109] Weigh 15 g of amaranth leaves, wash them, dry the surface with paper, and then use a wall-breaking machine to grind them into a pulp. Add a mixture of 10 mL of water and 30 mL of ethanol to the pulp and perform ultrasonic extraction at room temperature to extract and disperse the chlorophyll in the pulp. The ultrasonic extraction time is 0.5 h and the ultrasonic power is 100 W. After standing for 1 h, the supernatant is aspirated.

[0110] The supernatant was transferred to a reactor and reacted at 150°C for 7 hours using a solvent thermal method. After the reaction was completed, the crude product was cooled to obtain the crude product. The crude product was filtered using a 0.22 μm filter head, and the filtrate was collected and freeze-dried to obtain the biomass carbon dots, which were then placed in a refrigerator at 4°C for later use.

[0111] Performance testing:

[0112] Test 1: The UV-visible absorbance of a 1:3 water:ethanol mixed extract of amaranth was tested using a TU-1901 UV-visible spectrophotometer. Figure 17 The results showed that when a small amount of water and a large amount of ethanol were used as a mixed extract, the characteristic peaks of porphyrin in chlorophyll (Q band and Soret band) existed and the peak intensity was relatively high (slightly lower than that of pure ethanol extract), indicating that when the mixed solution was used as the extraction solvent, a large amount of chlorophyll would still be dissolved in ethanol.

[0113] Figure 18 This is the UV-visible absorption spectrum of the CD prepared in Example 4. The results show the presence of a large number of characteristic peaks attributed to porphyrin, indicating that the CD surface has a large number of porphyrin groups.

[0114] Test 2: 1 mg of the prepared biomass carbon dots was weighed and dispersed in 10 mL of a water / ethanol mixture with a volume ratio of 1:3. The resulting solution was tested using an FLS1000 transient / steady-state fluorescence spectrometer to measure its excitation wavelength ( Figure 19 ), and its fluorescence emission spectra at different excitation wavelengths (310-430 nm), such as Figure 20 The results showed that its red light emission accounted for about 98% of the total red and blue light emission, and the blue light emission was excitation-dependent.

[0115] Example 5

[0116] This example uses amaranth (containing chlorophyll) as raw material and a water / ethanol mixture with a volume ratio of 1:1 as the extraction solvent to synthesize carbon dots. The specific implementation steps are as follows:

[0117] Weigh 15 g of amaranth leaves, wash them, dry the surface with paper, and then use a wall-breaking machine to grind them into a pulp. Add a mixture of 20 mL of water and 20 mL of ethanol to the pulp and perform ultrasonic extraction at room temperature to extract and disperse the chlorophyll in the pulp. The ultrasonic extraction time is 0.5 h and the ultrasonic power is 100 W. After standing for 1 h, the supernatant is aspirated.

[0118] The supernatant was transferred to a reactor and reacted at 150°C for 7 hours using a solvent thermal method. After the reaction was completed, the crude product was cooled to obtain the crude product. The crude product was filtered using a 0.22 μm filter head, and the filtrate was collected and freeze-dried to obtain the biomass carbon dots, which were then placed in a refrigerator at 4°C for later use.

[0119] Light conversion performance test:

[0120] Test 1: The UV-visible absorbance of a 1:1 water:ethanol mixed extract of amaranth was tested using a TU-1901 UV-visible spectrophotometer. Figure 21 The results showed that when the same volume of water and ethanol was used as a mixed extract, the characteristic peaks of porphyrin in chlorophyll (Q band and Soret band) were also present, but the peak intensity was significantly lower than that of a 1:3 water:ethanol mixed extract, and higher than that of a 3:1 water:ethanol mixed extract, indicating that the content of organic solvent in the mixed solution would affect the amount of chlorophyll extracted. When the mixed solution was not extracted, some chlorophyll would be dissolved in the ethanol in the mixed solution.

[0121] Figure 22 This is the UV-visible absorption spectrum of the CD prepared in Example 5. The results show that there are many characteristic peaks attributable to porphyrin, indicating that there are many porphyrin groups on the surface of the CD.

[0122] Test 2: 1 mg of the prepared biomass carbon dots was weighed and dispersed in 10 mL of a water / ethanol mixture with a volume ratio of 1:1. The resulting solution was tested using an FLS1000 transient / steady-state fluorescence spectrometer to measure its excitation wavelength ( Figure 23 ), and its fluorescence emission spectra at different excitation wavelengths (310-430 nm) ( Figure 24 ), the results showed that the emission ratio of blue light to red light was about 8:1, and the blue light emission was excitation-dependent.

[0123] Example 6

[0124] This example uses spinach (containing chlorophyll) as raw material and acetone as solvent to synthesize biomass carbon dots. The specific implementation steps are as follows:

[0125] Weigh 15 g of spinach leaves, wash them, dry them with paper, and then use a wall-breaking machine to grind them into a pulp. Add 40 mL of acetone to the pulp and ultrasonically extract the chlorophyll in the pulp at room temperature for 0.3 h at a power of 100 W. After standing for 0.5 h, aspirate and transfer the supernatant.

[0126] The supernatant was transferred to a reactor and reacted at 130°C for 12 hours using a solvent thermal method. After the reaction was completed, the crude product was cooled to obtain the crude product. The crude product was filtered using a 0.22 μm filter head, and the filtrate was collected and freeze-dried to obtain the biomass carbon dot S-CD, which was then placed in a refrigerator at 4°C for later use.

[0127] Example 7

[0128] This example is a scheme for synthesizing biomass carbon dots using rapeseed (containing chlorophyll) as raw material and dichloromethane as solvent. The specific implementation steps are as follows:

[0129] Weigh 15 g of rapeseed leaves, wash them, dry the surface with paper, and then use a wall-breaking machine to grind them into a pulp. Add 40 mL of dichloromethane to the pulp and perform ultrasonic extraction at room temperature to extract and disperse the chlorophyll in the pulp. The ultrasonic extraction time is 0.2 h at an ultrasonic power of 100 W. After standing for 0.5 h, the supernatant is aspirated.

[0130] The supernatant was transferred to a reactor and reacted at 130°C for 10 hours using a solvent thermal method. After the reaction was completed, the crude product was cooled to obtain the crude product. The crude product was filtered using a 0.22 μm filter head, and the filtrate was collected and freeze-dried to obtain the biomass carbon dots, which were then placed in a 4°C refrigerator for later use.

[0131] Comparative Example 1

[0132] This comparative example uses carrots (without chlorophyll) as raw materials and ethanol as solvent to synthesize biomass carbon dots. The specific implementation steps are as follows:

[0133] Weigh 15 g of carrots, wash them, dry the surface with paper, and then use a wall-breaking machine to grind them into a pulp. Add 40 mL of ethanol to the pulp and sonicate at room temperature for 1 h at a power of 100 W. After standing for 1 h, aspirate the supernatant.

[0134] The supernatant was transferred to a reactor and reacted at 150°C for 7 hours using a solvent thermal method. After the reaction was completed, the crude product was cooled to obtain the crude product. The crude product was filtered using a 0.22 μm filter head, and the filtrate was collected and freeze-dried to obtain the biomass carbon dots, which were then placed in a refrigerator at 4°C for later use.

[0135] Light conversion performance test:

[0136] 1 mg of the prepared biomass carbon dots was weighed and dispersed in 10 mL of ethanol. The resulting solution was tested using an FLS1000 transient / steady-state fluorescence spectrometer to obtain its fluorescence spectra at different excitation wavelengths (340-420 nm). Figure 25 ,The results showed that its fluorescence emission spectrum showed blue light emission,and was excitation-dependent.

[0137] Example 8

[0138] The preparation of the light-converting film based on the biomass carbon dots prepared in Example 1 is carried out in the following specific steps:

[0139] 5 mg of biomass carbon dots were weighed and dispersed in 0.5 mL of ethanol to obtain a 10 mg / mL carbon dot solution. 1.1 g of commercially available DOWSIL SYLGARD 184 PDMS (containing 1 g of polydimethylsiloxane and 0.1 g of a crosslinker) was weighed and diluted with 1 mL of n-hexane and stirred to obtain a polymer solution. 100 μL of the 10 mg / mL carbon dot solution was added to the polymer solution and stirred to mix. The mixture was spread evenly on a 2.5 × 7.6 cm glass plate and cured at 60°C for 5 h. Finally, the cured film was peeled off to obtain a red-light-converting polymer film. The amaranth carbon dots in the film constituted 0.1% of the PDMS mass.

[0140] Preparation of blank PDMS film, steps are as follows:

[0141] Weigh 1.1 g of commercially available DOWSIL SYLGARD 184 PDMS (containing 1 g of polydimethylsiloxane and 0.1 g of a cross-linker), dilute with 1 mL of n-hexane, and stir to obtain a polymer solution. Spread the solution onto a 2.5 × 7.6 cm glass plate and cure at 60°C for 5 h. Finally, peel off the cured film to obtain a blank PDMS membrane.

[0142] The photosynthetically active radiation of the light-converting film of Example 8 and the homemade blank PDMS film was tested under sunlight using a handheld plant lighting spectrum detector UPRtek PG-200N. The results showed that the prepared light-converting film had significant ultraviolet absorption and red light emission properties, as shown in FIG. Figure 26 The inset photos show the film under natural light and 365 nm UV light, respectively, demonstrating its strong red emission under UV excitation. This UV-to-red film is suitable for increasing the dry and fresh weight of tomatoes and lettuce, and promoting stem elongation in eggplant and cucumber.

[0143] Example 9

[0144] The preparation of the light-converting film based on the biomass carbon dots prepared in Example 1 is carried out in the following specific steps:

[0145] 5 mg of biomass carbon dots were weighed and dispersed in 0.5 mL of ethanol to obtain a 10 mg / mL carbon dot solution. 0.2 g of polyvinyl alcohol (PVA) was added to 30 mL of water and stirred at 95°C for 1 hour to dissolve the solution. To this PVA solution, 100 μL of the 10 mg / mL PVD solution was added and stirred to mix. The mixture was quickly poured into an 8 cm diameter glass Petri dish and dried at 60°C for 2 hours. Finally, the cured film was peeled off to obtain a red and blue dual-emission PVA light-conversion film. The amaranth PVD content in the film was 0.5% of the PVA mass.

[0146] The fluorescence emission spectrum of the obtained polyvinyl alcohol light-transferring film was tested, showing that under the excitation of ultraviolet light at 365 nm, it has a red light and blue light emission ratio of 3:1 ( Figure 27 ), which can increase the leaf area and dry matter yield of leaf lettuce, promote the growth of spinach and radish, and promote the increase of leaf area, chlorophyll content and N content of cucumber.

[0147] Example 10

[0148] The preparation of the light-converting film based on the biomass carbon dots prepared in Example 6 is carried out in the following specific steps:

[0149] 5 mg of spinach carbon dots (S-CD) were weighed and dispersed in 0.5 mL of toluene to obtain a 10 mg / mL carbon dot solution. 0.5 g of linear low-density polyethylene (LLDPE) was added to 30 mL of cyclohexane and dissolved at 120°C with stirring and reflux for 8 hours to obtain a polyethylene solution. 100 μL of the 10 mg / mL carbon dot solution was added to the polyethylene solution and stirred to mix. The mixture was quickly poured into a 10 cm diameter glass Petri dish and vacuum-dried at 60°C for 2 hours. Finally, the cured film was peeled off to obtain a red-light-converting polyethylene film. The spinach carbon dots in the film constituted 0.2% of the polyethylene mass.

[0150] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a light-converting film based on solvent-dependent biomass carbon dots, characterized in that: The steps include: mixing the biomass carbon dots with a solvent to obtain a biomass carbon dot solution; mixing a film-forming polymer with a solvent to obtain a film-forming polymer solution; Adding the biomass carbon dot solution to the film-forming polymer solution, mixing evenly, casting the mixture into a film, and drying and solidifying it to obtain a film; The biomass carbon dots are prepared by a solvothermal method using plants containing chlorophyll as raw materials, extracting and / or dispersing the chlorophyll in the plant slurry with a solvent, and then absorbing the supernatant as a carbon source after standing. Wherein, the solvent includes water and / or an organic solvent; The volume ratio of water to organic solvent is 0-1:0-1, and the volume ratio of water to organic solvent is 0 when water and organic solvent are not present; The mass volume ratio of the plant to the solvent is 1 g: (1-4) mL; The chlorophyll-containing plants include one or more of amaranth, spinach, chrysanthemum, bitter chrysanthemum, radish leaves, rape, kale, fennel, lettuce, wood ear vegetable, water spinach, shepherd's purse, cabbage, broccoli, celery, green pepper, poplar leaves, willow leaves, ginkgo leaves, cypress leaves, tall fescue, clover, purslane, foxtail grass, morning glory leaves and Stephanotis chinensis; When the solvent used in preparing biomass carbon dots is a mixed solvent with a water content of more than 50%, only organic solvents are used in preparing the light-converting film, thereby increasing the proportion of red light in the emission spectrum of the light-converting film; when the solvent used in preparing biomass carbon dots is an organic solvent, water is used to dissolve the film-forming polymer in the preparation of the light-converting film, thereby increasing the proportion of blue light in the emission spectrum of the light-converting film.

2. The preparation method according to claim 1, characterized in that When the volume ratio of water to organic solvent is 1:0-0.2, blue light in the emitted light of the biomass carbon dots accounts for 90-100% of the total emitted light, and the rest is red light.

3. The preparation method according to claim 1, characterized in that When the volume ratio of water to organic solvent is 0-0.5:1, red light in the emitted light of the biomass carbon dots accounts for 70-100% of the total emitted light, and the rest is blue light.

4. The preparation method according to claim 1, characterized in that When the volume ratio of water to organic solvent is 1:0.2-0.5:1, and does not include 1:0.2 and 0.5:1, red light in the emitted light of the biomass carbon dots accounts for 20-70% of the total emitted light, and the rest is blue light.

5. The preparation method according to claim 1, characterized in that The preparation of the biomass carbon dots comprises the following steps: Wash and pulp the chlorophyll-containing plants to obtain pulp; add a solvent to the pulp and perform ultrasonic extraction to extract and / or disperse the chlorophyll in the pulp; let it stand for 0.5-1 hour after extraction, and absorb the supernatant; The supernatant was transferred to a reactor for solvent thermal reaction. After the reaction was completed, the product was filtered and the filtrate was freeze-dried to obtain the product.

6. A light-converting film based on solvent-dependent biomass carbon dots, characterized in that: The light-converting film is prepared by the preparation method according to any one of claims 1 to 5; the raw materials of the light-converting film include film-forming polymers and biomass carbon dots.

7. The light-converting film according to claim 6, characterized in that: The mass ratio of the biomass carbon dots to the film-forming polymer is 0.0001-0.01:

1.

8. The light-converting film according to claim 6, wherein: The film-forming polymer includes one or more of polyethylene, polyvinyl alcohol, polyetheretherketone, polyetherimide, polyimide, polyvinyl chloride, polydimethylsiloxane, fluororesin, polyamide, polyolefin and ethylene-vinyl acetate copolymer.

9. Use of the light-converting film according to any one of claims 6 to 8 or the light-converting film prepared by the preparation method according to any one of claims 1 to 5 in crop seedling cultivation or crop growth.

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