A carbon nitride light conversion agent, a preparation method thereof, and an application thereof

Abstract

The present invention discloses a carbon nitride light conversion agent, a preparation method and application thereof, and belongs to the technical field of organic materials. The carbon nitride light conversion agent provided by the present invention is a rare earth ion doped carbon nitride light conversion agent, and the preparation method thereof is as follows: urea and chitosan are mixed, fully ground, heated for reaction, and carbon nitride is obtained; carbon nitride, rare earth ion salt and sodium citrate are added into water, stirred for reaction; then antibiotics are added, stirred for reaction, and rare earth ion doped carbon nitride light conversion agent is obtained. The rare earth ion doped carbon nitride light conversion agent of the present invention has good stability, can convert ultraviolet light into blue light and red light at the same time, and the emission spectrum is compatible with the photosynthesis spectrum of plants. When it is incorporated into agricultural film, the agricultural film can have a good light conversion effect, which plays a better role in increasing plant yield and quality.

Description

Technical Field

[0001] The invention belongs to the technical field of organic materials, and specifically relates to a carbon nitride light conversion agent, a preparation method and application thereof. Background Art

[0002] Plants cannot grow without the sun. Sunlight is the energy source for photosynthesis. However, different light qualities have different effects on plant growth and development. For example, blue light is beneficial to the growth of plant stems and leaves, while red light is beneficial to improving the taste and quality of fruits and vegetables. Plant photosynthesis occurs in chloroplasts. The maximum absorption wavelength of the pigments in chloroplasts is 400-480nm blue light and 600-680nm red-orange light. Ultraviolet light below 380nm and green light from 500 to 580nm are basically not absorbed but reflected. Therefore, developing an efficient light conversion material that converts green light and ultraviolet light that are unfavorable or harmful to plants into red light and blue light required for photosynthesis, so as to improve the efficiency of plant utilization of light energy, is of great significance to increasing crop yield, early maturity and improving nutritional content.

[0003] In the 1980s, agricultural films were mainly PE mulch films, and their main function was to keep warm. After continuous research, aging-resistant PVC agricultural films and LDPE dripping agricultural films were born, and multifunctional agricultural films were also developed one after another. In the late 1990s, a variety of special greenhouse films and agricultural film varieties that focused on light quality research attracted attention. As a rising controlled functional agricultural film, light-converting agricultural film not only retains the heat preservation and high light transmittance of traditional agricultural films, but also can convert part of the ultraviolet light and green light in sunlight into blue light and red-orange light required for plant growth, thereby improving the photosynthetic utilization rate of plants by improving light quality. The coverage of light-converting agricultural film not only promotes the growth and development of crops and increases their yield, allowing crops to be harvested earlier, but also improves the quality of crops. Therefore, the development and research of light-converting agricultural film has become one of the hot topics in the field of agricultural films.

[0004] Rare earth ion-based light converters are a commonly used light energy conversion material. They have attracted extensive attention and research due to their stable structure, excellent fluorescence performance, long luminescence lifetime and high compatibility with thin films. However, since the ff electron transition of the rare earth ion itself is a forbidden transition, the absorption intensity is very low, and it is difficult to excite the rare earth ion to emit light. However, some organic substances have a high light absorption coefficient, which allows the organic substances to combine with rare earth ions, and through intramolecular energy transfer, the absorbed energy is effectively transferred to the rare earth ions, allowing the rare earth ions to emit light, and the luminescence range of the spectrum can be adjusted by adjusting the ratio of the rare earth central ion. Summary of the invention

[0005] The present invention provides a method for preparing a rare earth ion-doped carbon nitride light conversion agent, the steps of which are as follows:

[0006] The urea and chitosan are mixed, fully ground, and heated for reaction to obtain carbon nitride; the carbon nitride, rare earth ion salt and sodium citrate are added into water and stirred for reaction; then antibiotics are added and stirred for reaction to obtain a rare earth ion doped carbon nitride light conversion agent.

[0007] In the above preparation method, the rare earth ion is selected from europium ion; the rare earth ion salt is selected from Eu(NO 3 ) 3 , C 6 H 9 EO 6 and EuCl 3 One of them.

[0008] In the above preparation method, the mass ratio of urea to chitosan is selected from 800 to 1500:1, preferably 1000:1.

[0009] In the above preparation method, the heating reaction conditions are selected from: heating at 500-600°C for 1-10 hours; preferably: heating at 550°C for 4 hours.

[0010] In the above preparation method, the mass ratio of carbon nitride, rare earth ion salt and sodium citrate is selected from 80-120:0.5-1.5:0.6-1.2; preferably 100:1:1.

[0011] In the above preparation method, water provides a good liquid reaction environment for carbon nitride, rare earth ion salt and sodium citrate. The amount of water used is based on the reaction conditions. The mass ratio of water to carbon nitride is 2.5-3.5:0.002-0.02, preferably 3:0.01.

[0012] In the above preparation method, the amount of antibiotic is selected from the mass ratio of 0.6-1.2:50-250 to carbon nitride, preferably 1:100. The antibiotic is selected from one of chlortetracycline, oxytetracycline and tetracycline, preferably tetracycline.

[0013] In the above preparation method, the stirring reaction is based on the complete reaction, and the reaction conditions can also be selected from: stirring at room temperature for 6 to 20 hours.

[0014] The present invention provides a rare earth ion doped carbon nitride light conversion agent prepared by the above method, wherein the light conversion agent is preferably a europium doped carbon nitride light conversion agent.

[0015] The present invention provides the use of the rare earth ion-doped carbon nitride light conversion agent in converting ultraviolet light into blue light and / or red light.

[0016] The present invention provides the use of the rare earth ion doped carbon nitride light conversion agent in the preparation of light conversion agricultural film.

[0017] The present invention provides a light-converting agricultural film, which is composed of a rare earth ion-doped carbon nitride light-converting agent and polyethylene; preferably, it is composed of a europium-doped carbon nitride light-converting agent and polyethylene.

[0018] The light-converting agricultural film can be prepared by a conventional agricultural film manufacturing method.

[0019] In a specific embodiment, the present invention provides a method for preparing a light-converting agricultural film, the steps of which are as follows:

[0020] Add europium-doped carbon nitride light conversion agent and polyethylene into an internal mixer, and mix at 130°C for 1 hour to obtain a uniformly mixed block polymer melt; add the block polyethylene melt into a forced feeder, adjust the temperature to 180°C, and use a single-screw extruder to extrude strip polymer; add the strip polymer into a pelletizer, the rotation frequency of the pelletizer is 20.00Hz, and light conversion masterbatch is obtained; mix the light conversion masterbatch and polyethylene, and add them into the hopper of a film blowing machine, the barrel temperatures of the three temperature zones of the film blowing machine are 160°C, 180°C and 220°C respectively, the head temperature is 200°C, the screw rotation frequency is 12.00Hz, and the winding speed is 160rpm, to prepare a light conversion agricultural film.

[0021] In the above-mentioned method for preparing light-converting agricultural film, the mass ratio of the europium-doped carbon nitride light-converting agent to polyethylene is selected from 1:1000; and the mass ratio of the light-converting masterbatch to polyethylene is selected from 2:125.

[0022] The beneficial effects of the present invention are:

[0023] The present invention provides a europium ion-doped carbon nitride light conversion agent, which has a simple synthesis process and good stability, can simultaneously convert ultraviolet light into blue light and red light, and the emission spectrum is compatible with the photosynthesis spectrum of plants. When it is added to agricultural films, the agricultural films can have a good light conversion effect, which plays a better role in increasing plant yield and quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the XRD pattern of europium-doped carbon nitride light conversion agent;

[0025] Figure 2 This is the FTIR image of europium-doped carbon nitride light conversion agent;

[0026] Figure 3 This is the SEM image of the europium-doped carbon nitride light conversion agent;

[0027] Figure 4 This is the TEM image of europium-doped carbon nitride light conversion agent;

[0028] Figure 5 The UV absorption spectrum of the light-converting agricultural film;

[0029] Figure 6 This is the normalized excitation spectrum of the light-converting agricultural film, where the emission wavelength is Em = 620 nm, and the selected parameters are: voltage 700 V, scanning step length 1 nm;

[0030] Figure 7 This is the normalized emission spectrum of the light-converting agricultural film, where the excitation wavelength is Ex = 320 nm, and the selected parameters are: voltage 700 V, scanning step length 1 nm;

[0031] Figure 8 The normalized emission spectrum of the light-converting agricultural film changes with the concentration of tetracycline antibiotics; wherein the excitation wavelength is Ex = 320nm, and the selected parameters are: voltage 700V, scanning step length 1nm;

[0032] Fig. 9 This is a graph showing the change in fluorescence of the light-converting agricultural film with the concentration of tetracycline antibiotics, with the excitation wavelength being Ex=320nm. DETAILED DESCRIPTION

[0033] Other materials used in the present invention, if not otherwise stated, can be obtained through commercial channels. Other terms used in the present invention, unless otherwise specified, generally have the meanings commonly understood by those of ordinary skill in the art. The present invention is further described in detail below in conjunction with specific examples and with reference to data. The following examples are only for illustrating the present invention, and are not intended to limit the scope of the present invention in any way.

[0034] Example 1

[0035] 1. Preparation of Europium-doped Carbon Nitride Light Conversion Agent:

[0036] 3 g urea and 3 mg chitosan were mixed, ground thoroughly, and then transferred to a crucible with a lid and heated at 550 °C for 4 h to obtain chitosan-modified gC 3 N 4 200 mg chitosan-modified gC 3 N 4 、2mg Eu(NO 3 ) 3 and 2 mg of sodium citrate (CitNa) were added to 60 mL of water in sequence, stirred for 2 h, and then 2 mg of tetracycline was added, stirred at room temperature for 12 h to obtain a europium-doped carbon nitride light conversion agent.

[0037] In the above preparation method, only blue light can be emitted without adding antibiotics. After adding antibiotics, the whole system can emit both blue light and red light.

[0038] The XRD, FTIR, SEM and TEM images of the europium-doped carbon nitride light conversion agent are shown in Figure 1. Figure 1 to Figure 4 As shown. Figure 1It can be seen that the prepared europium-doped carbon nitride light conversion agent has an obvious diffraction peak near 27.5°, which belongs to the diffraction peak of the carbon nitride (002) crystal plane. Figure 2 It can be seen that the prepared material is at 3500cm -1 A strong absorption peak appeared near the -OH and -NH 2 The absorption peak at 3000cm -1 and 2700cm -1 There is an absorption peak near each, which belongs to the absorption peak of OH hydrogen bond. Figure 3 and Figure 4 It can be seen that the prepared carbon nitride light conversion agent has a flake structure.

[0039] 2. Preparation of light conversion masterbatch:

[0040] 100 mg of europium-doped carbon nitride light conversion agent and 500 g of polyethylene were added to an internal mixer and mixed at 130°C for 1 hour to obtain a uniformly mixed block polymer melt; the block polyethylene melt was added to a forced feeder, the temperature was adjusted to 180°C, and a single-screw extruder (the extruder speed was 300 rpm and the extruder die head temperature was 300°C) was used to extrude the strip polymer; the strip polymer was added to a pelletizer, the rotation frequency of the pelletizer was 20.00 Hz, and a light conversion masterbatch was obtained.

[0041] 3. Preparation of light-converting agricultural film:

[0042] 8g of light-converting masterbatch and 500g of polyethylene were mixed and added into the hopper of a film blowing machine. The barrel temperatures in the three temperature zones of the film blowing machine were 160°C, 180°C and 220°C, the head temperature was 200°C, the screw rotation frequency was 12.00Hz, and the winding speed was 160rpm to prepare a light-converting agricultural film.

[0043] 1. Light conversion test

[0044] The UV-visible absorption spectrum of light-converting agricultural film is shown in the figure below: Figure 5 As shown in the figure, it can be seen that the agricultural film has a strong absorption peak in the range of 250-350nm.

[0045] The light-converting agricultural film prepared in Example 1 was tested for its excitation range at an emission wavelength of 620 nm using a combined transient / steady-state fluorescence spectrometer (FLS920, Edinburgh Instruments, UK). Figure 6 As shown in the figure: It can be seen from the figure that the light-converting agricultural film has two excitation ranges, 250-350nm and 350-450nm, which is consistent with the UV-visible absorption spectrum of the light-converting agricultural film.

[0046] The emission range of the light-converting agricultural film prepared by the present invention was tested at an excitation wavelength of 320 nm. The results are as follows: Figure 7 As shown in the figure, it can be seen that the light-converting agricultural film can emit strong red light (620-660nm) and blue light (400-500nm) under the excitation of ultraviolet light.

[0047] It can be seen that the light-converting agricultural film prepared by the present invention can absorb ultraviolet light that is not conducive to plant growth and convert it into red light and blue light that are beneficial to plant growth.

[0048] Comparative Example 1

[0049] Preparation of ordinary agricultural film:

[0050] 500 kg of polyethylene was added into the hopper of the film blowing machine. The barrel temperatures in the three temperature zones of the film blowing machine were 160° C., 180° C. and 220° C., the head temperature was 200° C., the screw rotation frequency was 12.00 Hz, and the winding speed was 160 rpm to prepare ordinary agricultural film.

[0051] 2. Application Test

[0052] The trial period started from July 2023 to September 2023, and an experiment was conducted on covering and planting two crops of vegetables (broccoli and lettuce).

[0053] The test results are shown in Table 1:

[0054] Table 1

[0055]

[0056] It can be seen from Table 1 that the use of light-converting agricultural film can effectively promote the early maturity of vegetables and achieve the effect of increasing yield. Moreover, when the light-converting agent in the light-converting agricultural film used is co-doped with trivalent rare earth ions or replaced by cations, the afterglow effect can be improved, making the early maturity and yield-increasing effects of vegetables better.

[0057] The present invention also provides other feasible preparation cases of europium-doped carbon nitride light conversion agents, as shown below:

[0058] Example 2

[0059] Preparation of Europium-doped Carbon Nitride Light Conversion Agent:

[0060] 3 g urea and 3 mg chitosan were mixed, ground thoroughly, and then transferred to a crucible with a lid and heated at 550 °C for 4 h to obtain chitosan-modified gC 3 N 4 200 mg chitosan-modified gC 3 N 4 、2mg Eu(NO 3 ) 3and 2 mg of sodium citrate (CitNa) were added to 60 mL of water in sequence, stirred for 2 h, and then 0 mg of tetracycline was added, stirred at room temperature for 12 h to obtain a europium-doped carbon nitride light conversion agent.

[0061] Example 3

[0062] Preparation of Europium-doped Carbon Nitride Light Conversion Agent:

[0063] 3 g urea and 3 mg chitosan were mixed, ground thoroughly, and then transferred to a crucible with a lid and heated at 550 °C for 4 h to obtain chitosan-modified gC 3 N 4 200 mg chitosan-modified gC 3 N 4 、2mg Eu(NO 3 ) 3 and 2 mg of sodium citrate (CitNa) were added to 60 mL of water in sequence, stirred for 2 h, and then 0.5 mg of tetracycline was added, stirred at room temperature for 12 h to obtain a europium-doped carbon nitride light conversion agent.

[0064] Example 4

[0065] Preparation of Europium-doped Carbon Nitride Light Conversion Agent:

[0066] 3 g urea and 3 mg chitosan were mixed, ground thoroughly, and then transferred to a crucible with a lid and heated at 550 °C for 4 h to obtain chitosan-modified gC 3 N 4 200 mg chitosan-modified gC 3 N 4 、2mg Eu(NO 3 ) 3 and 2 mg of sodium citrate (CitNa) were added to 60 mL of water in sequence, stirred for 2 h, and then 1 mg of tetracycline was added, stirred at room temperature for 12 h to obtain a europium-doped carbon nitride light conversion agent.

[0067] Example 5

[0068] Preparation of Europium-doped Carbon Nitride Light Conversion Agent:

[0069] 3 g urea and 3 mg chitosan were mixed, ground thoroughly, and then transferred to a crucible with a lid and heated at 550 °C for 4 h to obtain chitosan-modified gC 3 N 4 200 mg chitosan-modified gC 3 N 4 、2mg Eu(NO 3 ) 3and 2 mg of sodium citrate (CitNa) were added to 60 mL of water in sequence, stirred for 2 h, and then 1.5 mg of tetracycline was added, stirred at room temperature for 12 h to obtain a europium-doped carbon nitride light conversion agent.

[0070] Example 6

[0071] Preparation of Europium-doped Carbon Nitride Light Conversion Agent:

[0072] 3 g urea and 3 mg chitosan were mixed, ground thoroughly, and then transferred to a crucible with a lid and heated at 550 °C for 4 h to obtain chitosan-modified gC 3 N 4 200 mg chitosan-modified gC 3 N 4 、2mg Eu(NO 3 ) 3 and 2 mg of sodium citrate (CitNa) were added to 60 mL of water in sequence, stirred for 2 h, and then 3 mg of tetracycline was added, stirred at room temperature for 12 h to obtain a europium-doped carbon nitride light conversion agent.

[0073] Figure 8 The fluorescence spectra of the light-converting agricultural films prepared by the light-converting agents described in Examples 2 to 6 are shown in FIG. 4, wherein at 450 nm, the curves from top to bottom are the light-converting agricultural films prepared by the light-converting agents described in Examples 2 to 6. It can be seen from the figure that the generation ratio of red light and blue light can be changed by adjusting the concentration of tetracycline. Fig. 9 The fluorescence color diagram (excitation wavelength is 320 nm) of the light conversion agricultural film prepared by the light conversion agent described in Examples 1 to 6, wherein from left to right are the light conversion agricultural films prepared by the light conversion agents described in Examples 2 to 5, Example 1 and Example 6. It can be seen from the figure that the color of the film can be adjusted by changing the concentration of tetracycline to meet the light quality requirements of different crops.

[0074] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a rare earth ion doped carbon nitride light conversion agent, characterized in that: Here are the steps: The urea and chitosan are mixed, fully ground, and heated for reaction to obtain carbon nitride; the carbon nitride, rare earth ion salt and sodium citrate are added into water and stirred for reaction; then antibiotics are added and stirred for reaction to obtain a rare earth ion doped carbon nitride light conversion agent; The rare earth ion is selected from europium ion; the rare earth ion salt is selected from one of Eu(NO3)3, C6H9EuO6 and EuCl3; The mass ratio of urea to chitosan is selected from 800 to 1500:1; The heating reaction conditions are selected from: heating at 500-600° C. for 1-10 h; The mass ratio of the carbon nitride, the rare earth ion salt and the sodium citrate is selected from 80 to 120: 0.5 to 1.5: 0.6 to 1.2; The dosage of the antibiotic is selected from a mass ratio of 0.6-1.2:50-250 with carbon nitride; the antibiotic is tetracycline.

2. The rare earth ion-doped carbon nitride light conversion agent prepared by the method of claim 1.

3. Use of the rare earth ion-doped carbon nitride light conversion agent according to claim 2 in converting ultraviolet light into blue light and / or red light.

4. Use of the rare earth ion doped carbon nitride light conversion agent according to claim 2 in the preparation of light conversion agricultural film.

5. A light-converting agricultural film, characterized in that: The light-converting agricultural film is composed of the rare earth ion-doped carbon nitride light-converting agent according to claim 2 and polyethylene.

Images