Preparation method of carbon dot-based panchromatic afterglow material capable of being excited by sunlight

Abstract

The invention belongs to the technical field of luminescent materials, and discloses a preparation method of a carbon dot-based panchromatic afterglow material capable of being excited by sunlight. The preparation method comprises the following steps: (1) dispersing rhodamine B and ammonium halide in a solvent, carrying out solvothermal reaction at 140-240 DEG C for 6-10 hours, and then naturally cooling to room temperature to obtain a carbon dot solution; and (2) dispersing the carbon dot solution obtained in the step (1) and boric acid in water, heating at 140-240 DEG C for 3-10 hours, naturally cooling to room temperature, and grinding the obtained solid to obtain the carbon dot-based afterglow material. According to the invention, low-cost rhodamine B is used as a raw material, halogen elements are doped, the carbon dots are synthesized by a solvothermal method, the energy level and electronic structure of the carbon dots are changed, transition of triplet state restriction becomes possible, and after the prepared carbon dots are compounded with boric acid, a solid afterglow material is prepared, so that the afterglow material has a good application prospect. Moreover, the afterglow of the afterglow material is thermally activated delayed fluorescence, shows blue, green, yellow and red full-color afterglow, and can be excited by sunlight, so that the preparation and application cost of the afterglow material is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of luminescent material preparation, and in particular relates to a method for preparing a carbon dot-based full-color afterglow material that can be excited by sunlight. Background Art

[0002] Due to their outstanding Stokes shift and long luminescence lifetime, afterglow materials have a wide range of applications in information storage and encryption, advanced anti-counterfeiting, sensing, optoelectronics, bioimaging and diagnosis. However, most traditional room temperature afterglow materials are inorganic or metal-organic complexes containing precious metal elements, which are expensive and toxic, hindering the development of room temperature afterglow materials. In addition, most room temperature afterglow materials can only be excited by high-energy ultraviolet light, which brings potential safety hazards and increases the development cost of applications, hindering the practical application of room temperature afterglow materials. Therefore, there is an urgent need to develop low-cost, non-toxic and sunlight-excited afterglow material alternatives to solve the current difficulties encountered in this field.

[0003] Carbon dots (CDs) are a new type of zero-dimensional carbon nanomaterials, which have attracted widespread attention due to their abundant raw materials, simple preparation methods, low toxicity, good biocompatibility, excellent optical properties and tunable photophysical properties. A large number of studies have reported room temperature afterglow based on CDs. Shi et al. used a one-step hydrothermal method to heat (3-aminopropyl) trimethoxysilane (APTMS) and phosphoric acid to synthesize a CDs with blue phosphorescence emission, with an absolute photoluminescence quantum yield (PLQY) and phosphorescence quantum yield (PQY) of 37.8% and 12.4%, respectively. Yang et al. used triethanolamine as a carbon source and phosphoric acid as a dopant to synthesize nitrogen and phosphorus co-doped carbon dots (P-CDs) by microwave method. P-CDs exhibited blue fluorescence emission and green phosphorescence emission, and the quantum efficiency of its solid powder was 26.69%. However, the emission wavelengths of these materials are mostly concentrated in the blue-green region, and the quantum yield is low. In addition, due to limited absorption bands, these room temperature afterglow materials can only be excited by high-energy ultraviolet (UV) light with a wavelength below 380nm, and high-energy UV sources pose a significant threat to human health, which limits their widespread application in civilian environments. In contrast, visible light, especially sunlight, is less harmful to human health and has the potential to penetrate deep into biological specimens for analysis and imaging, as well as the convenience of practical applications. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing a carbon dot-based full-color afterglow material that can be excited by sunlight.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for preparing a carbon dot-based full-color afterglow material that can be excited by sunlight, the preparation steps are as follows: (1) Disperse rhodamine B and ammonium halide in a solvent, perform a solvothermal reaction at 140-240°C for 6-10 hours, and then naturally cool to room temperature to obtain a carbon dot solution; (2) taking the carbon dot solution obtained in step (1), dispersing it in water together with boric acid, then heating it at 140-240° C. for 3-10 hours, and then naturally cooling it to room temperature, and grinding the obtained solid to obtain a carbon dot-based afterglow material; The raw material dosage ratio is Rhodamine B: ammonium halide: solvent: carbon dot solution: boric acid: water = (0.01~1) g: (0.01~0.5) g: (10~20) mL: (1~1000) μL: (1~5) g: (20~100) mL.

[0006] Preferably, in step (1), the solvent is sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution or ethanol.

[0007] Furthermore, the concentrations of the sodium hydroxide solution and the potassium hydroxide solution are 0.5-1.5 mol / L; the concentrations of the sodium carbonate solution and the potassium carbonate solution are 0.1-1 mol / L; and the volume purity of the ethanol is 20-80%.

[0008] Furthermore, when the solvent in step (1) is a sodium hydroxide solution or a potassium hydroxide solution and rhodamine B: ammonium halide: solvent: carbon dot solution: boric acid: water = (0.01-1) g: (0.01-0.5) g: (10-20) mL: (1-20) μL: (1-5) g: (20-100) mL, the carbon dot-based afterglow material is a blue light carbon dot@boron trioxide composite afterglow material; When the solvent in step (1) is a sodium carbonate solution or a potassium carbonate solution and rhodamine B: ammonium halide: solvent: carbon dot solution: boric acid: water = (0.01-1) g: (0.01-0.5) g: (10-20) mL: (1-20) μL: (1-5) g: (20-100) mL, the carbon dot-based afterglow material is a green carbon dot@boron trioxide composite afterglow material; When the solvent in step (1) is a sodium carbonate solution or a potassium carbonate solution and rhodamine B: ammonium halide: solvent: carbon dot solution: boric acid: water = (0.01-1) g: (0.01-0.5) g: (10-20) mL: (100-300) μL: (1-5) g: (20-100) mL, the carbon dot-based afterglow material is a yellow carbon dot@boron trioxide composite afterglow material; When the solvent in step (1) is ethanol and rhodamine B: ammonium halide: solvent: carbon dot solution: boric acid: water = (0.01~1) g: (0.01~0.5) g: (10~20) mL: (50~150) μL: (1~5) g: (20~100) mL, the carbon dot-based afterglow material is a red light carbon dot@boron trioxide composite afterglow material.

[0009] Preferably, in step (1), after the solvothermal reaction is completed and the solution is naturally cooled to room temperature, the resulting reaction solution is subjected to a post-treatment purification step to finally obtain a carbon dot solution.

[0010] Furthermore, the post-processing purification step is first microporous membrane filtration, and then elution or dialysis.

[0011] Beneficial effects: The present invention uses low-cost Rhodamine B as a raw material, and synthesizes carbon dots by doping with halogen elements (F, Cl, Br, I) through a solvent thermal method, thereby changing the energy level and electronic structure of the carbon dots, making triplet forbidden transitions possible. After the prepared carbon dots are compounded with boric acid, a solid afterglow material is prepared. Moreover, the afterglow of the afterglow material of the present invention is thermally activated delayed fluorescence (TADF), showing a full-color afterglow of blue, green, yellow and red, which can be excited by sunlight, greatly reducing the preparation and application costs of the afterglow material. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 : Transmission electron microscope photograph of the carbon dot solution CD1 prepared in Example 1.

[0013] Figure 2 : Transmission electron microscope photograph of the carbon dot solution CD2 prepared in Example 2.

[0014] Figure 3 : Transmission electron microscope photograph of the carbon dot solution CD3 prepared in Example 4.

[0015] Figure 4 : B-CD@B prepared in Example 1 2 O 3 Transmission electron microscope photograph of .

[0016] Figure 5 : G-CD@B prepared in Example 2 2 O 3 Transmission electron microscope photograph of .

[0017] Figure 6 : Y-CD@B prepared in Example 3 2 O 3 Transmission electron microscope photograph of .

[0018] Figure 7 : R-CD@B prepared in Example 4 2 O3 Transmission electron microscope photograph of .

[0019] Figure 8 : XRD pattern of the carbon dot solution CD1 prepared in Example 1.

[0020] Figure 9 : XRD pattern of the carbon dot solution CD2 prepared in Example 2.

[0021] Figure 10 : XRD pattern of the carbon dot solution CD3 prepared in Example 4.

[0022] Figure 11 : B-CD@B prepared in Example 1 2 O 3 XRD pattern of .

[0023] Figure 12 : G-CD@B prepared in Example 2 2 O 3 XRD pattern of .

[0024] Figure 13 : Y-CD@B prepared in Example 3 2 O 3 XRD pattern of .

[0025] Figure 14 : R-CD@B prepared in Example 4 2 O 3 XRD pattern of .

[0026] Figure 15 : B-CD@B prepared in Example 1 2 O 3 Afterglow emission spectrum.

[0027] Figure 16 : G-CD@B prepared in Example 2 2 O 3 Afterglow emission spectrum.

[0028] Figure 17 : Y-CD@B prepared in Example 3 2 O 3 Afterglow emission spectrum.

[0029] Figure 18 : R-CD@B prepared in Example 4 2 O 3 Afterglow emission spectrum.

[0030] Figure 19 : B-CD@B prepared in Example 1 2 O 3 The quantum yield of .

[0031] Figure 20 : G-CD@B prepared in Example 2 2 O 3 The quantum yield of .

[0032] Figure 21 : Y-CD@B prepared in Example 3 2 O 3 The quantum yield of .

[0033] Figure 22 : R-CD@B prepared in Example 4 2 O 3 The quantum yield of .

[0034] Figure 23 : B-CD@B prepared in Example 1 2 O 3 life span.

[0035] Figure 24 : G-CD@B prepared in Example 2 2 O 3 life span.

[0036] Figure 25 : Y-CD@B prepared in Example 3 2 O 3 life span.

[0037] Figure 26 : R-CD@B prepared in Example 4 2 O 3 life span.

[0038] Figure 27 : B-CD@B prepared in Example 1 2 O 3 The temperature spectrum of .

[0039] Figure 28 : G-CD@B prepared in Example 2 2 O 3 The temperature spectrum of .

[0040] Figure 29 : Y-CD@B prepared in Example 3 2 O 3 The temperature spectrum of .

[0041] Figure 30 : R-CD@B prepared in Example 4 2 O 3 The temperature spectrum.

[0042] Figure 31 : B-CD@B prepared in Example 1 2 O 3Afterglow photos under 365nm UV light, white light and sunlight.

[0043] Figure 32 : G-CD@B prepared in Example 2 2 O 3 Afterglow photos under 365nm UV light, white light and sunlight.

[0044] Figure 33 : Y-CD@B prepared in Example 3 2 O 3 Afterglow photos under 365nm UV light, white light and sunlight.

[0045] Figure 34 : R-CD@B prepared in Example 4 2 O 3 Afterglow photos under 365nm UV light, white light and sunlight.

[0046] Figure 35 : Afterglow emission spectrum of reference product 1 prepared in reference example 1.

[0047] Figure 36 : Afterglow emission spectrum of reference product 2 prepared in reference example 2.

[0048] Figure 37 : Afterglow emission spectrum of reference product 3 prepared in reference example 3.

[0049] Figure 38 : Afterglow emission spectrum of reference product 4 prepared in reference example 4.

[0050] Figure 39 : Afterglow photograph of control product 1 prepared in control example 1 under sunlight.

[0051] Figure 40 : Afterglow photograph of control product 2 prepared in control example 2 under sunlight.

[0052] Figure 41 : Afterglow photograph of control product 3 prepared in control example 3 under sunlight.

[0053] Figure 42 : Afterglow photograph of control product 4 prepared in control example 4 under sunlight. DETAILED DESCRIPTION

[0054] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the described embodiments, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present invention.

[0055] In the following examples, the preparation method of 1 mol / L NaOH solution is as follows: 4 g NaOH is dissolved in 10 mL distilled water, and after cooling to room temperature, the solution is transferred to a 100 mL volumetric flask, and distilled water is added to make up the volume, and the solution is shaken to obtain a 1 mol / L NaOH solution; 0.36 mol / L K 2 CO 3 The solution is prepared as follows: 5g K 2 CO 3 Dissolve in 10 mL of distilled water, and after cooling to room temperature, transfer the solution to a 100 mL volumetric flask, add distilled water to make up the volume, and shake well to obtain 0.36 mol / L K 2 CO 3 Solution.

[0056] Example 1

[0057] 0.5 g of rhodamine B and 0.05 g of ammonium iodide were ultrasonically dispersed in 20 mL of 1 mol / L NaOH solution, and then transferred to an autoclave lined with polytetrafluoroethylene, heated at 220 ° C for 8 h, and then naturally cooled to room temperature to obtain a carbon dot solution CD1; 5 μL of the carbon dot solution CD1 was ultrasonically dispersed in 50 mL of water together with 3 g of boric acid, and then transferred to a beaker, heated at 180 ° C for 5 h, and then naturally cooled to room temperature. The obtained solid was ground to obtain a blue light carbon dot@boron trioxide composite afterglow material powder, marked as B-CD@B 2 O 3 .

[0058] Figure 1 The transmission electron microscope photograph of the carbon dot solution CD1 prepared in Example 1 shows that the carbon dots are spherical or quasi-spherical in structure, the average particle size of the carbon dots CD1 is 2.35 nm, and the high-resolution transmission electron microscope photograph shows that the carbon dots have a 0.21 nm interplanar spacing, corresponding to the graphite (100) crystal plane, which means that the carbon dots have a graphitized structure.

[0059] Figure 4 B-CD@B prepared in Example 1 2 O 3 From the transmission electron microscope photo, we can see that the carbon dots are coated with boron trioxide.

[0060] Figure 8: This is the XRD pattern of the carbon dot solution CD1 prepared in Example 1, wherein the diffraction peak at 22.43° corresponds to the interlayer spacing of the (002) plane of graphite.

[0061] Figure 11 B-CD@B prepared in Example 1 2 O 3 The XRD pattern of the carbon dots shows that the diffraction peaks at 25.27° and 42.23° are coated with boron trioxide.

[0062] Figure 15 B-CD@B prepared in Example 1 2 O 3 From the afterglow emission spectrum, we can see that the emission peak is at 470nm, proving that the afterglow color is blue.

[0063] Figure 19 B-CD@B prepared in Example 1 2 O 3 The fluorescence quantum yield is 80%.

[0064] Figure 23 B-CD@B prepared in Example 1 2 O 3 The lifetime is 637.5 ms.

[0065] Figure 27 B-CD@B prepared in Example 1 2 O 3 From the temperature-dependent spectrum, we can see that the emission intensity at 77-117K decreases with increasing temperature, which belongs to phosphorescence, while the emission intensity at 137-337K increases with increasing temperature, which belongs to thermally activated delayed fluorescence.

[0066] Figure 31 B-CD@B prepared in Example 1 2 O 3 Afterglow photos under UV light, white light and sunlight. 2 O 3 Under ultraviolet light, white light and sunlight, the afterglow time that can be observed by the naked eye is 8s, 10s and 4s respectively. The reason for this is that the boric acid molecules dehydrate under high temperature conditions to form a rigid network structure of boron trioxide-coated carbon dots, which causes S 1 With T 1 The energy level difference between the two is reduced, ensuring effective reverse intersystem crossing, thereby realizing TADF; at the same time, boric acid can also be used as a cross-linking agent. Continuous heating induces covalent cross-linking between carbon dots and boron trioxide generated by boric acid, further enhancing the structural rigidity and coupling the carbon dot luminescence center, causing energy level splitting and reducing S 1energy level, making the composite material easily excited by low-energy light or even sunlight.

[0067] Example 2

[0068] 0.04g rhodamine B and 0.2g ammonium fluoride were ultrasonically dispersed in 20mL 0.36mol / L K 2 CO 3 The solution was then transferred to an autoclave lined with polytetrafluoroethylene, heated at 180°C for 6 hours, and then naturally cooled to room temperature to obtain a carbon dot solution CD2; 10 μL of the carbon dot solution CD2 was ultrasonically dispersed in 50 mL of water together with 3 g of boric acid, and then transferred to a beaker, heated at 180°C for 5 hours, and then naturally cooled to room temperature. The obtained solid was ground to obtain a green light carbon dot@boron trioxide composite afterglow material powder, marked as G-CD@B 2 O 3 .

[0069] Figure 2 The transmission electron microscope photograph of the carbon dot solution CD2 prepared in Example 2 shows that the carbon dots are spherical or quasi-spherical in structure, the average particle size of the carbon dots CD2 is 3.34 nm, and the high-resolution transmission electron microscope photograph shows that the carbon dots have a 0.21 nm interplanar spacing, corresponding to the graphite (100) crystal plane, which means that the carbon dots have a graphitized structure.

[0070] Figure 5 G-CD@B prepared in Example 2 2 O 3 From the transmission electron microscope photo, we can see that the carbon dots are coated with boron trioxide.

[0071] Figure 9 This is the XRD pattern of the carbon dot solution CD2 prepared in Example 2, wherein the diffraction peak at 22.91° corresponds to the interlayer spacing of the (002) plane of graphite.

[0072] Figure 12 G-CD@B prepared in Example 2 2 O 3 The XRD pattern of the carbon dots shows that the diffraction peaks at 25.27° and 42.23° are coated with boron trioxide.

[0073] Figure 16 G-CD@B prepared in Example 2 2 O 3 From the afterglow emission spectrum, we can see that the emission peak is at 524nm, proving that the afterglow color is green.

[0074] Figure 20 G-CD@B prepared in Example 2 2 O 3The fluorescence quantum yield is 79.80%.

[0075] Figure 24 G-CD@B prepared in Example 2 2 O 3 The lifetime is 169.62 ms.

[0076] Figure 28 G-CD@B prepared in Example 2 2 O 3 From the temperature-dependent spectrum, we can see that the emission intensity at 77-137K decreases with increasing temperature, which belongs to phosphorescence, while the emission intensity at 157-357K increases with increasing temperature, which belongs to thermally activated delayed fluorescence.

[0077] Figure 32 G-CD@B prepared in Example 2 2 O 3 Afterglow photos under UV light, white light and sunlight. G-CD@B prepared in Example 2 2 O 3 Under ultraviolet light, white light and sunlight, the naked eye can observe that the afterglow time is 4s, 6s and 2s respectively.

[0078] Example 3

[0079] 0.04 g rhodamine B and 0.2 g ammonium fluoride were ultrasonically dispersed in 20 mL 0.36 mol / L K 2 CO 3 The solution was then transferred to an autoclave lined with polytetrafluoroethylene, heated at 180 °C for 6 h, and then naturally cooled to room temperature to obtain a carbon dot solution CD2; 120 μL of the carbon dot solution CD2 was ultrasonically dispersed in 50 mL of water together with 3 g of boric acid, and then transferred to a beaker, heated at 180 °C for 5 h, and then naturally cooled to room temperature. The obtained solid was ground to obtain a yellow carbon dot@boron trioxide composite afterglow material powder, marked as Y-CD@B 2 O 3 .

[0080] The transmission electron microscope photo of the carbon dot solution CD2 prepared in Example 3 is the same as Figure 2 .

[0081] Figure 6 Y-CD@B prepared in Example 3 2 O 3 From the transmission electron microscope photo, we can see that the carbon dots are coated with boron trioxide.

[0082] The XRD pattern of the carbon dot solution CD2 prepared in Example 3 is the same as Figure 9 .

[0083] Figure 13 Y-CD@B prepared in Example 3 2 O 3 The XRD pattern of the carbon dots shows that the diffraction peaks at 25.27° and 42.23° are coated with boron trioxide.

[0084] Figure 17 Y-CD@B prepared in Example 3 2 O 3 From the afterglow emission spectrum, we can see that the emission peak is at 571nm, proving that the afterglow color is yellow.

[0085] Figure 21 Y-CD@B prepared in Example 3 2 O 3 The fluorescence quantum yield is 53.83%.

[0086] Figure 25 Y-CD@B prepared in Example 3 2 O 3 The lifetime is 334.46 ms.

[0087] Figure 29 Y-CD@B prepared in Example 3 2 O 3 From the temperature-dependent spectrum, we can see that the emission intensity at 77-117K decreases with increasing temperature, which belongs to phosphorescence, while the emission intensity at 137-317K increases with increasing temperature, which belongs to thermally activated delayed fluorescence.

[0088] Figure 33 Y-CD@B prepared in Example 3 2 O 3 Afterglow photos under UV light, white light and sunlight. 2 O 3 Under ultraviolet light, white light and sunlight, the naked eye can observe the afterglow time as 5s, 8s and 2s respectively.

[0089] Example 4

[0090] 0.5 g of rhodamine B and 0.2 g of ammonium fluoride were ultrasonically dispersed in 20 mL of 50 v% ethanol, and then transferred to an autoclave lined with polytetrafluoroethylene, heated at 220 ° C for 8 h, and then naturally cooled to room temperature to obtain a carbon dot solution CD3; 90 μL of the carbon dot solution CD3 was ultrasonically dispersed in 50 mL of water together with 3 g of boric acid, and then transferred to a beaker, heated at 180 ° C for 5 h, and then naturally cooled to room temperature. The obtained solid was ground to obtain a red light carbon dot @ boron trioxide composite afterglow material powder, marked as R-CD@B 2 O3 .

[0091] Figure 3 The transmission electron microscope photograph of the carbon dot solution CD3 prepared in Example 4 shows that the carbon dots are spherical or quasi-spherical in structure, the average particle size of the carbon dots CD3 is 2.71 nm, and the high-resolution transmission electron microscope photograph shows that the carbon dots have a crystal plane spacing of 0.21 nm, corresponding to the graphite (100) crystal plane, which means that the carbon dots have a graphitized structure.

[0092] Figure 7 R-CD@B prepared in Example 4 2 O 3 From the transmission electron microscope photo, we can see that the carbon dots are coated with boron trioxide.

[0093] Figure 10 This is the XRD pattern of the carbon dot solution CD3 prepared in Example 4, wherein the diffraction peak at 22.62° corresponds to the interlayer spacing of the (002) plane of graphite.

[0094] Figure 14 R-CD@B prepared in Example 4 2 O 3 The XRD pattern of the carbon dots shows that the diffraction peaks at 25.27° and 42.23° are coated with boron trioxide.

[0095] Figure 18 R-CD@B prepared in Example 4 2 O 3 From the afterglow emission spectrum, we can see that the emission peak is at 617nm, proving that the afterglow color is red.

[0096] Figure 22 R-CD@B prepared in Example 4 2 O 3 The fluorescence quantum yield is 19.99%.

[0097] Figure 26 R-CD@B prepared in Example 4 2 O 3 The lifespan is 114.7ms.

[0098] Figure 30 R-CD@B prepared in Example 4 2 O 3 From the temperature-dependent spectrum, we can see that the emission intensity at 97-197K decreases with increasing temperature, which belongs to phosphorescence, while the emission intensity at 217-357K increases with increasing temperature, which belongs to thermally activated delayed fluorescence.

[0099] Figure 34 R-CD@B prepared in Example 42 O 3 Afterglow photos under UV light, white light and sunlight. 2 O 3 Under ultraviolet light, white light and sunlight, the naked eye can observe the afterglow time as 1s, 1s and 0.05s respectively.

[0100] Comparative Example 1 The difference from Example 1 is that ammonium iodide is not added when preparing the carbon dot solution CD1; specifically, the preparation steps are as follows: 0.5 g of rhodamine B was ultrasonically dispersed in 20 mL of 1 mol / L NaOH solution, and then transferred to an autoclave lined with polytetrafluoroethylene, heated at 220 ° C for 8 h, and then naturally cooled to room temperature to obtain a carbon dot solution; 5 μL of the carbon dot solution was ultrasonically dispersed in 50 mL of water together with 3 g of boric acid, and then transferred to a beaker, heated at 180 ° C for 5 h, and then naturally cooled to room temperature, and the obtained solid was ground to obtain a control product 1.

[0101] The afterglow emission spectrum of the control product 1 is as follows Figure 35 As shown, the emission peak is 477nm, which is a blue afterglow; its afterglow photo under sunlight excitation is shown in Figure 39 As shown, the afterglow time that can be observed by the naked eye is 3s, which is shorter than that of the product B-CD@B in Example 1. 2 O 3 .

[0102] Comparative Example 2 The difference from Example 2 is that ammonium fluoride is not added when preparing the carbon dot solution CD2; specifically, the preparation steps are as follows: 0.04g rhodamine B was ultrasonically dispersed in 20mL 0.36mol / L K 2 CO 3 The mixture was then transferred to a polytetrafluoroethylene-lined autoclave, heated at 180°C for 6 h, and then naturally cooled to room temperature to obtain a carbon dot solution; 10 μL of the carbon dot solution was ultrasonically dispersed in 50 mL of water together with 3 g of boric acid, and then transferred to a beaker, heated at 180°C for 5 h, and then naturally cooled to room temperature, and the obtained solid was ground to obtain a control product 2.

[0103] The afterglow emission spectrum of reference sample 2 is as follows Figure 36 As shown, the main emission peak is 480nm, which is blue afterglow; its afterglow photo under sunlight excitation is shown in Figure 40 As shown, the afterglow time observable by the naked eye is 4s, but relative to the product of Example 2, the afterglow color has changed from green light to blue light.

[0104] Comparative Example 3 The difference from Example 3 is that ammonium fluoride is not added when preparing the carbon dot solution CD2; specifically, the preparation steps are as follows: 0.04g rhodamine B was ultrasonically dispersed in 20mL 0.36mol / L K 2 CO 3 The mixture was then transferred to a polytetrafluoroethylene-lined autoclave, heated at 180 °C for 6 h, and then naturally cooled to room temperature to obtain a carbon dot solution; 120 μL of the carbon dot solution was ultrasonically dispersed in 50 mL of water together with 3 g of boric acid, and then transferred to a beaker, heated at 180 °C for 5 h, and then naturally cooled to room temperature, and the obtained solid was ground to obtain a control product 3.

[0105] The afterglow emission spectrum of reference sample 3 is as follows Figure 37 As shown in Figure 1, the main emission peak is 477nm, which is a blue afterglow. Figure 41 As shown, the afterglow time observable by the naked eye is 4s, but relative to the product of Example 3, the afterglow color has changed from yellow light to blue light.

[0106] Comparative Example 4 The difference from Example 4 is that ammonium fluoride is not added when preparing the carbon dot solution CD3; specifically, the preparation steps are as follows: 0.5 g of rhodamine B was ultrasonically dispersed in 20 mL of 50 v% ethanol, then transferred to an autoclave lined with polytetrafluoroethylene, heated at 220 ° C for 8 h, and then naturally cooled to room temperature to obtain a carbon dot solution; 90 μL of the carbon dot solution was ultrasonically dispersed in 50 mL of water together with 3 g of boric acid, then transferred to a beaker, heated at 180 ° C for 5 h, and then naturally cooled to room temperature, and the obtained solid was ground to obtain a control product 4.

[0107] The afterglow emission spectrum of the control product 4 is as follows Figure 38 As shown, the emission peak is 622nm, which is red afterglow. Its afterglow photo under sunlight excitation is shown in Figure 42 As shown, no afterglow is observed by the naked eye, indicating that the product of Control Example 4 requires higher excitation energy and cannot be excited by sunlight.

[0108] By comparing the afterglow photos of Examples 1 to 4 and Control Examples 1 to 4, it can be seen that: under the same reaction conditions, after adding ammonium halide, multi-color afterglow can be obtained (the afterglow color can be green, blue, yellow and red), while without adding ammonium halide, only monochrome afterglow (the color is only blue) can be obtained.

Claims

1. A method for preparing a carbon dot-based full-color afterglow material that can be excited by sunlight, characterized in that: The preparation steps are as follows: (1) Disperse rhodamine B and ammonium halide in a solvent, perform a solvothermal reaction at 140-240°C for 6-10 hours, and then naturally cool to room temperature to obtain a carbon dot solution; (2) taking the carbon dot solution obtained in step (1), dispersing it in water together with boric acid, then heating it at 140-240° C. for 3-10 hours, and then naturally cooling it to room temperature, and grinding the obtained solid to obtain a carbon dot-based afterglow material; The raw material dosage ratio is Rhodamine B: ammonium halide: solvent: carbon dot solution: boric acid: water = (0.01~1) g: (0.01~0.5) g: (10~20) mL: (1~1000) μL: (1~5) g: (20~100) mL.

2. The method for preparing the sunlight-excitable carbon dot-based full-color afterglow material according to claim 1, characterized in that: In step (1), the solvent is sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution or ethanol.

3. The method for preparing the carbon dot-based full-color afterglow material that can be excited by sunlight as claimed in claim 2, characterized in that: The concentrations of sodium hydroxide solution and potassium hydroxide solution are 0.5~1.5 mol / L; the concentrations of sodium carbonate solution and potassium carbonate solution are 0.1~1 mol / L; and the volume purity of ethanol is 20~80%.

4. The method for preparing the carbon dot-based full-color afterglow material that can be excited by sunlight as claimed in claim 3, characterized in that: When the solvent in step (1) is sodium hydroxide solution or potassium hydroxide solution and rhodamine B: ammonium halide: solvent: carbon dot solution: boric acid: water = (0.01-1) g: (0.01-0.5) g: (10-20) mL: (1-20) μL: (1-5) g: (20-100) mL, the carbon dot-based afterglow material is a blue light carbon dot@boron trioxide composite afterglow material; When the solvent in step (1) is a sodium carbonate solution or a potassium carbonate solution and rhodamine B: ammonium halide: solvent: carbon dot solution: boric acid: water = (0.01-1) g: (0.01-0.5) g: (10-20) mL: (1-20) μL: (1-5) g: (20-100) mL, the carbon dot-based afterglow material is a green carbon dot@boron trioxide composite afterglow material; When the solvent in step (1) is a sodium carbonate solution or a potassium carbonate solution and rhodamine B: ammonium halide: solvent: carbon dot solution: boric acid: water = (0.01-1) g: (0.01-0.5) g: (10-20) mL: (100-300) μL: (1-5) g: (20-100) mL, the carbon dot-based afterglow material is a yellow carbon dot@boron trioxide composite afterglow material; When the solvent in step (1) is ethanol and rhodamine B: ammonium halide: solvent: carbon dot solution: boric acid: water = (0.01~1) g: (0.01~0.5) g: (10~20) mL: (50~150) μL: (1~5) g: (20~100) mL, the carbon dot-based afterglow material is a red light carbon dot@boron trioxide composite afterglow material.

5. The method for preparing a carbon dot-based full-color afterglow material that can be excited by sunlight as claimed in any one of claims 1 to 4, characterized in that: In step (1), after the solvent thermal reaction is completed and the mixture is naturally cooled to room temperature, the resulting reaction solution is subjected to a post-treatment purification step to finally obtain a carbon dot solution.

6. The method for preparing a carbon dot-based full-color afterglow material that can be excited by sunlight as claimed in claim 5, characterized in that: The post-processing purification step is first microporous membrane filtration, and then elution or dialysis.

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