Solvent-dependent biomass carbon dots and light conversion film comprising same

Abstract

The invention discloses a solvent-dependent biomass carbon dot and a light conversion film comprising the same. According to the biomass carbon dots, plants containing chlorophyll serve as raw materials, chlorophyll in plant juice is extracted and / or dispersed through a solvent, then after standing is conducted, supernate is absorbed to serve as a carbon source, and the red and blue double-emission carbon dots are prepared through a solvothermal method. The solvent comprises water and / or an organic solvent; the volume ratio of the water to the organic solvent is (0-1): (0-1), and the volume ratio of the water to the organic solvent is not 0 at the same time. During preparation, the chlorophyll extraction amount is adjusted and dispersed through matching of different solvents, and then the double-emission carbon dots with different red and blue light proportions are prepared under different chlorophyll contents. Meanwhile, the biomass carbon dots are used as raw materials to prepare a light conversion film, the light conversion film can convert ultraviolet light in sunlight into blue light and red light which can be efficiently utilized by crops, the matching of a light conversion spectrum ratio and a spectrum ratio required by the crops can be realized through regulation and control, and the growth and development of the plants are promoted.

Description

Technical Field

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

[0002] Sunlight is the main energy source for plant growth and development. The solar spectrum reaching the surface is in the range of 290-3000nm, which can be divided into ultraviolet light (290-400nm), visible light (400-780nm) and infrared light (780-3000nm). Light of different components has different effects on plant growth. As a key influencing factor in the light environment, light quality generally regulates the life cycle of plants through light receptor conduction pathways such as photosensitive pigments, cryptochromes and phototropins, especially in photosynthesis and photomorphogenesis. Visible light with a wavelength of 400-700nm can directly affect plant photosynthesis and be absorbed by plants, among which blue-violet light (400-480nm) and red light (600-700nm) are particularly important for promoting plant growth and development. In addition, high-energy ultraviolet light is harmful to plants, and yellow-green light with a wavelength of 500-600nm will be 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 is conducive to the accumulation of carbohydrates and the accumulation of soluble sugar content, which is particularly critical for the development and formation of photosynthetic tissues and organs, while blue light can promote protein formation and is closely related to the formation of chloroplasts, the synthesis of chlorophyll and the opening of leaf epidermal stomata. Composite red and blue light is conducive to reducing the accumulation of nitrate content. Therefore, the lack of any red and blue light will lead to photosynthetic ineffectiveness and poor plant growth. A large number of studies have found that red and blue combined light is more conducive to plant growth than monochromatic light. Different types of crops and different growth periods of the same crop require specific "light formulas" to be more conducive to the growth and development of crops. 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, and the blue light ratio is between 0-50%. The photosynthetic capacity of cucumber leaves increases with the increase of the blue light ratio; for the accumulation of nutritional quality of cherry tomato fruit, there is a threshold for the optimal red-blue light ratio of the light source. When the blue light ratio is large, it is conducive to the accumulation of nutrients. When the blue light accounts for 60% of the red-blue light combination light source, it is a light source with relatively good cherry tomato fruit quality. 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 hotspot for facility vegetable cultivation.

[0004] Artificial lighting (such as LED) can be used to finely control the light environment for crop growth, but its equipment is complex and costly, and the use of light sources is accompanied by huge energy consumption. Compared with artificial lighting, the light conversion film that realizes spectrum conversion by adding light conversion materials can convert ultraviolet light and green light in sunlight that are harmful or useless to plant growth into blue-violet light and red-orange light required for growth, thereby enhancing plant photosynthesis. Among them, the light conversion agent is the main factor affecting the performance of the light conversion film. At present, commonly used light conversion agents include organic dyes, inorganic salts, and rare earth organic complexes, but the existing light conversion agents still have problems such as the difficulty in matching the excitation spectrum with the spectrum that is harmful and useless to crops, the emission spectrum with the spectrum required by crops, poor stability, poor light transmittance, and high cost, which limit their application and promotion.

[0005] Carbon dots (CDs) are considered to be very promising nano-photoluminescent materials based on their adjustable luminescence properties, low toxicity, good dispersibility and excellent optical properties. By changing the chemical composition, size, shape and surface structure of carbon dots, their emission of blue-violet light and red-orange light required by plants can be effectively regulated. Therefore, using carbon dots as light conversion agents, light conversion films with spectral matching, good light transmittance and good stability can be prepared. In particular, carbon dots synthesized under solvent thermal or microwave conditions by a bottom-up method using biomass raw materials as carbon sources have the advantages of simple operation, low cost, good biocompatibility and adjustable optical properties. They are more suitable for large-scale production and application in the preparation of light conversion 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 are issues that researchers in this field need to solve urgently. Summary of the invention

[0007] Based on the above defects, the first object of the present invention is to provide a solvent-dependent biomass carbon dot. The biomass carbon dot is prepared from plants containing chlorophyll as raw materials, and the chlorophyll in the plant juice is extracted and / or dispersed by a solvent, and the chlorophyll content entering the solvent is changed by different solvent combinations, thereby preparing dual-emission carbon dots with different red and blue light ratios under different chlorophyll contents.

[0008] The second object of the present invention is to provide a method for preparing the solvent-dependent biomass carbon dots as described above. The preparation method is simple to operate, has a wide range of raw materials and low cost, and has mild preparation conditions, and can quickly prepare a series of dual-emission carbon dots with different red and blue light ratios.

[0009] The third object of the present invention is to provide a light conversion film with an adjustable wavelength range and ratio prepared by using the above-mentioned biomass carbon dots. The light conversion film does not add toxic or expensive light conversion agents, and uses the above-mentioned prepared biomass carbon dots, which are low in cost and environmentally friendly. The light conversion film 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 light conversion spectrum with the spectrum required by crops through regulation, thereby improving the utilization rate of sunlight and promoting plant growth and development.

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

[0011] A fifth object of the present invention is to provide an application of the light conversion film as 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 scheme:

[0014] The present invention discloses a solvent-dependent biomass carbon dot, wherein 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;

[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 they are not combined.

[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 contents of chlorophyll from plants. After obtaining different contents of chlorophyll, dual-emission carbon dots with different proportions of red and blue light can be prepared by participating in the subsequent solvent thermal reaction; 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 in 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, chlorophyll cannot be extracted from plants such as carrots and potatoes that do not contain chlorophyll, which also affects the preparation of dual-emission carbon dots later. The second is the combination of different solvents. Since chlorophyll in different solvents has different It shows different solubility, so different content 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 solvent, the solubility of organic solvent to chlorophyll is changed due to the influence of water. Usually, 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 emission light of the biomass carbon dots accounts for 70-100% of the total emission 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 in 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 biomass carbon dot fluorescence spectrum test. For example, when using organic solvents such as ethanol to disperse the biomass carbon dots 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; conversely, when the solvent for preparing biomass carbon dots is only organic solvent, chlorophyll can be extracted and dispersed in the organic phase, and the organic solvent is used to disperse the biomass carbon dots for fluorescence spectrum testing. The emission spectrum of the obtained biomass carbon dots is mainly red light. If water or a mixed system of water and organic solvents 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 is also found that the proportion of red light in the emission spectrum is reduced; that is to say, different dispersing solvents used in fluorescence spectrum testing can also play a secondary adjustment role in the emission spectrum. Based on this discovery, inspiration can be provided for the subsequent preparation of light-converting films with adjustable light-conversion range, namely: when using biomass carbon dots (prepared with organic solvents) with a relatively high 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 beneficial 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 relatively high 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 beneficial 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 plants containing chlorophyll to obtain pulp; add a solvent to the pulp and perform ultrasonic extraction to extract and / or disperse the chlorophyll in the pulp; after extraction, let it stand for 0.5-1h and absorb the supernatant;

[0026] The supernatant is transferred to a reactor for solvent thermal reaction. After the reaction is completed, the product is filtered and the filtrate is 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, radish leaves, rapeseed, kale, fennel, lettuce, water spinach, 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.

[0028] Furthermore, the solvent includes water and / or an organic solvent. Different combinations of solvents will affect the extraction and dispersion of chlorophyll in the slurry 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, thereby 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 from entering the reaction system while effectively extracting chlorophyll.

[0032] The operation coordinated with the ultrasonic extraction method is to let it stand for a period of time after the extraction to allow the molecules to gradually settle freely, especially when water is used as the solvent, so that the chlorophyll dispersed in the aqueous phase will not be completely settled. 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 is 0.1-1h, ultrasonic frequency is 40KHz, and ultrasonic power is 0-180W.

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

[0036] The invention discloses a light-conversion film based on solvent-dependent biomass carbon dots. The raw materials of the light-conversion film include film-forming polymers and the biomass carbon dots as claimed in the claim.

[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 objective, 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 dots solution;

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

[0043] The biomass carbon dot solution is added to the film-forming polymer solution, and after being mixed evenly, the mixed solution is cast into a film, and dried and solidified to obtain a 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 adjusted secondary 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, and other adjustment strategies for solvent combinations can be directly obtained on the basis of the present invention, and all belong to the protection scope of the present invention.

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

[0046] The 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. The biomass carbon dots are prepared from plants containing chlorophyll as raw materials, and the chlorophyll in the plant juice is extracted or dispersed by a solvent, and the chlorophyll content entering the solvent is changed by different solvent combinations, thereby preparing dual-emission carbon dots with different red and blue light ratios under different chlorophyll contents.

[0049] The present invention also provides a light-conversion film based on solvent-dependent biomass carbon dots, in which no toxic or expensive light-conversion agent is added, and the selected biomass carbon dots are low in cost and environmentally friendly. The light-conversion film can convert ultraviolet light in sunlight into blue light and red light that can be efficiently utilized by crops, and can achieve matching of the light-conversion spectrum with the spectrum required by crops through regulation, thereby improving the utilization rate of sunlight and promoting plant growth and development. In addition, the preparation method of the light-conversion film is simple and easy to obtain, and the secondary regulation of the emission spectrum of the light-conversion film can be achieved by adjusting the solvent used in the preparation of the light-conversion film. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0051] Figure 1 This is the UV-Vis absorption spectrum of the ethanol extraction solution 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 obtained excitation spectrum was tested.

[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 obtained excitation spectrum was tested.

[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] Fig. 9 The biomass carbon dots prepared in Example 2 were dispersed in water, and the obtained excitation spectrum was tested.

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

[0061] Fig.11 The biomass carbon dots prepared in Example 2 were dispersed in ethanol, and the obtained excitation spectrum was tested.

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

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

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

[0065] Fig.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] Fig.16 The biomass carbon dots prepared in Example 3 are dispersed in V 水 :V 乙醇 The fluorescence emission spectra of the 3:1 mixture at different excitation wavelengths (320-420nm).

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

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

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

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

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

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

[0073] Fig.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 mixed solution.

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

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

[0076] Fig.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 365nm ultraviolet light.

[0077] Fig. 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 content specifically described below 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 of light conversion films based on the solvent-dependent biomass carbon dots obtained in the experiment and the light conversion performance test.

[0081] Example 1

[0082] This embodiment 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 water with paper, and use a wall-breaking machine to grind them into juice; add 40 mL of ethanol to the juice, and ultrasonically extract them at room temperature to extract and disperse the chlorophyll in the juice, wherein the ultrasonic extraction time is 0.5 h, the ultrasonic power is 100 W, and the supernatant is absorbed after standing for 1 h;

[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 a 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 Test:

[0086] Test 1: Use TU-1901 UV-Vis spectrophotometer to test the UV-Vis absorbance of 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. There are also characteristic peaks belonging 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 is 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 (310-430nm) ( Figure 6 ). Its fluorescence emission spectrum shows that the emission ratio of blue light to red light is about 1:3, and the blue light emission is excitation-dependent.

[0090] Example 2

[0091] This embodiment is a scheme for synthesizing biomass carbon dots using amaranth (containing chlorophyll) as raw material and water as solvent. The specific implementation steps are as follows:

[0092] Weigh 15 g of amaranth leaves, wash them, dry the surface water with paper, and use a wall-breaking machine to grind them into juice; add 40 mL of water to the juice, and perform ultrasonic treatment at room temperature to disperse the chlorophyll in the juice into the water, wherein the ultrasonic extraction time is 0.5 h, the ultrasonic power is 100 W, and the supernatant is absorbed after standing for 1 h;

[0093] The supernatant was transferred to a reactor, reacted at 150° C. for 7 hours using a solvothermal method, and cooled to obtain a crude product after the reaction was completed; 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 (H2O), which was placed in a 4° C. refrigerator for later use.

[0094] Performance Testing:

[0095] Test 1: Use TU-1901 UV-Vis spectrophotometer to test the UV-Vis absorbance of 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, ,which indicated that when water was used as the extraction solvent, a small amount of amaranth slurry 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 result shows that there is almost no characteristic peak attributed to porphyrin, indicating that there are very few porphyrin groups on the surface of CD.

[0097] Test 2: 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 wavelength ( Fig. 9 ), and its fluorescence emission spectra at different excitation wavelengths (320-420nm) ( Fig.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 is tested using an FLS1000 transient / steady-state fluorescence spectrometer to measure its excitation wavelength ( Fig.11), and its fluorescence emission spectra at different excitation wavelengths (320-420nm) ( Fig.12 ). Its fluorescence spectrum shows that the emission ratio of blue light to red light is about 10:1, and the blue light emission is excitation-dependent.

[0099] Example 3

[0100] This embodiment is a scheme for synthesizing biomass carbon dots using amaranth (containing chlorophyll) as raw material and a water / ethanol mixture with a volume ratio of 3:1 as solvent. The specific implementation steps are as follows:

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

[0102] 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 a 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 placed in a 4°C refrigerator for later use.

[0103] Performance Testing:

[0104] Test 1: Use TU-1901 UV-Vis spectrophotometer to test the UV-Vis absorbance of a 3:1 water:ethanol mixed extract of amaranth. Fig.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, part of the chlorophyll would be dissolved in a small amount of ethanol.

[0105] Fig.14 This is the UV-visible absorption spectrum of the CD prepared in Example 3. The result shows that there are a small amount of characteristic peaks attributed to porphyrin, indicating that there are a small amount of porphyrin groups on the surface of the CD.

[0106] Test 2: Weigh 1 mg of the prepared biomass carbon dots and disperse them 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 ( Fig.15 ), and its fluorescence emission spectra at different excitation wavelengths (320-420nm) ( Fig.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 embodiment is a scheme for synthesizing biomass carbon dots using amaranth (containing chlorophyll) as raw material and a water / ethanol mixture with a volume ratio of 1:3 as solvent. The specific implementation steps are as follows:

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

[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 a 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 placed in a 4°C refrigerator for later use.

[0111] Performance Testing:

[0112] Test 1: Use TU-1901 UV-Vis spectrophotometer to test the UV-Vis absorbance of a 1:3 volume ratio water: ethanol mixed extract of amaranth. Fig.17 The results showed that when a small amount of water and a large 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 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] Fig.18 This is the UV-visible absorption spectrum of the CD prepared in Example 4. The results show that there are a large number of characteristic peaks attributed to porphyrin, indicating that there are a large number of porphyrin groups on the surface of the CD.

[0114] Test 2: Weigh 1 mg of the prepared biomass carbon dots and disperse them 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 ( Fig.19 ), and its fluorescence emission spectra at different excitation wavelengths (310-430nm), such as Fig. 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 is a synthesis of carbon dots using amaranth (containing chlorophyll) as a raw material and a water / ethanol mixture with a volume ratio of 1:1 as an extraction solvent. The specific implementation steps are as follows:

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

[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 a 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 placed in a 4°C refrigerator 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. Fig.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, part of the chlorophyll would be dissolved in the ethanol in the mixed solution.

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

[0122] Test 2: Weigh 1 mg of the prepared biomass carbon dots and disperse them 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 ( Fig.23 ), and its fluorescence emission spectra at different excitation wavelengths (310-430nm) ( Fig.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 embodiment is a scheme for synthesizing biomass carbon dots using spinach (containing chlorophyll) as raw material and acetone as solvent. The specific implementation steps are as follows:

[0125] Weigh 15 g of spinach leaves, wash them, dry the surface water with paper, and use a wall-breaking machine to grind them into juice; add 40 mL of acetone to the juice, and perform ultrasonic extraction at room temperature to extract and disperse the chlorophyll in the juice, wherein the ultrasonic extraction time is 0.3 h, the ultrasonic power is 100 W, and after standing for 0.5 h, the supernatant is aspirated and transferred;

[0126] The supernatant was added 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 a 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 placed in a 4°C refrigerator for later use.

[0127] Example 7

[0128] This embodiment 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 water with paper, and use a wall-breaking machine to grind them into juice; add 40 mL of dichloromethane to the juice, and perform ultrasonic extraction at room temperature to extract and disperse the chlorophyll in the juice, wherein the ultrasonic extraction time is 0.2 h, the ultrasonic power is 100 W, and the supernatant is absorbed after standing for 0.5 h;

[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 a 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 placed in a 4°C refrigerator for later use.

[0131] Comparative Example 1

[0132] This comparative example is a scheme for synthesizing biomass carbon dots using carrots (without chlorophyll) as raw materials and ethanol as solvent. The specific implementation steps are as follows:

[0133] Weigh 15 g of carrots, wash them, dry the surface water with paper, and use a wall-breaking machine to grind them into juice; add 40 mL of ethanol to the juice, and ultrasonicate at room temperature, wherein the ultrasonic extraction time is 1 h, the ultrasonic power is 100 W, and the supernatant is aspirated after standing for 1 h;

[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 a 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 placed in a 4°C refrigerator 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). Fig.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 specifically implemented as follows:

[0139] Weigh 5 mg of biomass carbon dots and disperse them in 0.5 mL of ethanol to obtain a 10 mg / mL carbon dot solution; weigh 1.1 g of commercially available DOWSIL SYLGARD 184 PDMS (including 1 g of polydimethylsiloxane and 0.1 g of cross-linking agent), add 1 mL of n-hexane to dilute and stir to obtain a polymer solution; add 100 μL of 10 mg / mL carbon dot solution to the polymer solution and stir to mix; spread the mixture on a 2.5×7.6 cm glass plate and cure at 60°C for 5 hours; finally peel off the cured film to obtain a red light-converting polymer film. The amaranth carbon dots in the light-converting film are 0.1% of the PDMS mass.

[0140] The preparation steps of blank PDMS film are as follows:

[0141] Weigh 1.1 g of commercially available DOWSIL SYLGARD 184 PDMS (including 1 g of polydimethylsiloxane and 0.1 g of a cross-linking agent), add 1 mL of n-hexane to dilute and stir to obtain a polymer solution, spread the solution on a 2.5×7.6 cm glass plate, and cure it 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, such as Fig.26 The insets are photos of the light-converting film under natural light and 365nm ultraviolet light, respectively, indicating that it emits strong red light under ultraviolet excitation. The ultraviolet-red-light-converting film is suitable for promoting the increase of dry and fresh weight of tomatoes and lettuce, and promoting the elongation of the stems of eggplants and cucumbers.

[0143] Example 9

[0144] The preparation of the light-converting film based on the biomass carbon dots prepared in Example 1 is specifically implemented as follows:

[0145] Weigh 5 mg of biomass carbon dots and disperse them in 0.5 mL of ethanol to obtain a 10 mg / mL carbon dot solution; weigh 0.2 g of polyvinyl alcohol and add it to 30 mL of water, stir at 95 ° C for 1 hour to dissolve, and obtain a polyvinyl alcohol solution; add 100 μL of a 10 mg / mL carbon dot solution to the polyvinyl alcohol solution and stir to mix; quickly pour the mixture into a glass petri dish with a diameter of 8 cm and dry at 60 ° C for 2 hours; finally peel off the cured film to obtain a red and blue dual-emission polyvinyl alcohol light-conversion film. The amaranth carbon dots in the light-conversion film are 0.5% of the mass of polyvinyl alcohol.

[0146] The fluorescence emission spectrum of the polyvinyl alcohol light-transferring film obtained by testing shows that it has a 3:1 red light and blue light emission ratio under ultraviolet light 365nm excitation ( Fig. 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 cucumber leaf area, chlorophyll content and N content.

[0147] Example 10

[0148] The preparation of the light-converting film based on the biomass carbon dots prepared in Example 6 is specifically implemented as follows:

[0149] Weigh 5 mg of spinach carbon dots S-CD and disperse them in 0.5 mL of toluene to obtain a 10 mg / mL carbon dot solution; weigh 0.5 g of linear low-density polyethylene, add 30 mL of cyclohexane, stir and reflux at 120 ° C for 8 hours to dissolve, and obtain a polyethylene solution; add 100 μL of a 10 mg / mL carbon dot solution to the polyethylene solution and stir to mix; quickly pour the mixture into a glass petri dish with a diameter of 10 cm and vacuum dry at 60 ° C for 2 hours; finally peel off the cured film to obtain a red-light-converting polyethylene film. The spinach carbon dots in the light-converting film are 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 protection scope of the present invention.

Claims

1. A solvent-dependent biomass carbon dot, characterized in that: 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 juice 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 they are not combined.

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

4. The biomass carbon dots 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 method for preparing biomass carbon dots according to any one of claims 1 to 4, characterized in that: The steps include: Wash and pulp the plants containing chlorophyll to obtain pulp; add a solvent to the pulp and perform ultrasonic extraction to extract and / or disperse the chlorophyll in the pulp; after extraction, let it stand for 0.5-1h and absorb the supernatant; The supernatant is transferred to a reaction kettle for solvent thermal reaction. After the reaction is completed, the product is filtered and the filtrate is freeze-dried to obtain the product.

6. The preparation method according to claim 5, characterized in that: The mass volume ratio of the plant to the solvent is 1 g:(1-4) mL; Preferably, the plants containing chlorophyll include one or more of amaranth, spinach, chrysanthemum, radish leaves, rapeseed, kale, fennel, lettuce, water spinach, 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.

7. A light-converting film based on solvent-dependent biomass carbon dots, characterized in that: The raw materials of the light-converting film include a film-forming polymer and the biomass carbon dots according to any one of claims 1 to 4; Preferably, 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 7, characterized in that: 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. The method for preparing a light-converting film according to any one of claims 7 or 8, characterized in that: The steps include: mixing the biomass carbon dots with a solvent to obtain a biomass carbon dots solution; Mixing the film-forming polymer with the solvent to obtain a film-forming polymer solution; The biomass carbon dot solution is added to the film-forming polymer solution, and after being mixed evenly, the mixed solution is cast into a film, and dried and solidified to obtain a film.

10. Use of the light-converting film according to any one of claims 7 or 8 or the light-converting film prepared by the preparation method according to claim 9 in crop seedling cultivation or crop growth.

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