Fluorescent carbon dot material as well as preparation method and application thereof

Abstract

The invention provides a carbon dot material emitting red fluorescence and having quantum efficiency fluorescence exceeding 90%, and a preparation method and application thereof. The preparation method of the fluorescent carbon dot material comprises the following steps: dissolving 8-hydroxyjulolidine-9-formaldehyde and organic carboxylic acid in water in proportion to prepare a mixture solution; and carrying out hydrothermal reaction treatment on the mixture solution in a sealed environment, and then carrying out purification treatment. According to the preparation method of the fluorescent carbon dot material, the fluorescent carbon dot material is prepared by adopting a hydrothermal method, so that the prepared fluorescent carbon dot material not only has very high quantum efficiency, but also is low in cost, low in toxicity and stable in particle size and fluorescence performance.

Description

Technical Field

[0001] This invention belongs to the field of chemical power source technology, and particularly relates to a fluorescent carbon dot material, its preparation method and application. Background Technology

[0002] Nanoscale carbon dots possess advantages such as low cost, low toxicity, simple preparation methods, and tunable and stable fluorescence spectra, making them promising candidates for numerous applications, particularly in optoelectronic devices, sensing, bioimaging, and document security, where they have seen rapid development and attracted widespread attention. For each application, high quantum efficiency is a fundamental characteristic that carbon dots must possess, not only saving costs but also improving performance. Therefore, preparing carbon dots with high quantum efficiency is a basic condition for promoting their industrialization.

[0003] Currently, there are many methods for preparing carbon dots, but only a handful can achieve quantum efficiencies close to 100%. Furthermore, the fluorescence range of these high-quantum-efficiency carbon dots is limited to blue, green, and yellow light; the quantum efficiency of red-light carbon dots is still significantly lower than 100%. Among the reported red-light carbon dot materials, only three have quantum efficiencies exceeding 80%: one obtained by hydrothermal reaction of flowers in nitric acid solution (80% quantum efficiency); one obtained by solvothermal reaction of N,N-dipropyl-p-phenylenediamine in N,N-dimethylacetamide solution (86% quantum efficiency); and one obtained by hydrothermal reaction of tris(4-aminophenyl)amine in hydrochloric acid aqueous solution (84% quantum efficiency). It is evident that the quantum efficiency of these reported red fluorescent carbon dots still has room for improvement, and they utilize potentially hazardous raw materials, such as perylene (a Group 3 carcinogen) and N,N-dipropyl-p-phenylenediamine (which has some toxicity). Therefore, developing a simple, feasible, and environmentally friendly method to prepare red fluorescent carbon dots with higher quantum efficiency has important scientific research and practical value. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for preparing carbon dot materials that emit red fluorescence and have a quantum efficiency of over 90%, thereby solving the technical problem of low quantum efficiency of fluorescent carbon dot materials prepared by existing methods.

[0005] To achieve the objective of this invention, one aspect of this invention provides a method for preparing fluorescent carbon dot materials. The method for preparing the fluorescent carbon dot materials includes the following steps:

[0006] 8-hydroxyjulonidine-9-carboxaldehyde and citric acid were dissolved in water in a certain proportion to prepare a mixture solution; the mixture solution was subjected to hydrothermal reaction treatment in a sealed environment, and then purified.

[0007] In another aspect, the present invention provides a fluorescent carbon dot material. The fluorescent carbon dot material is grown using the preparation method of the fluorescent carbon dot material of the present invention.

[0008] In another aspect, the present invention provides applications of the fluorescent carbon dot materials. These fluorescent carbon dot materials have potential applications in mitochondrial targeting and imaging.

[0009] Compared with existing technologies, the method for preparing room temperature phosphorescent carbon dot materials of the present invention uses 8-hydroxyjulonidine-9-carboxaldehyde and citric acid as raw materials and adopts a hydrothermal method to directly prepare fluorescent carbon dot materials. On the one hand, the preparation method is easy to control, which reduces economic costs and ensures the stability of the properties of the prepared fluorescent carbon dot materials, such as particle size and phosphorescence performance. On the other hand, the prepared fluorescent carbon dot materials have high quantum efficiency, stable optical performance, low toxicity and good biocompatibility. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the preparation method of fluorescent carbon dot material according to Embodiment 1 of the present invention;

[0011] Figure 2 This is a transmission electron microscope image of the fluorescent carbon dot material provided in Embodiment 1 of the present invention;

[0012] Figure 3 This is a high-resolution transmission electron microscope image of the fluorescent carbon dot material provided in Embodiment 1 of the present invention;

[0013] Figure 4 The infrared spectrum of the fluorescent carbon dot material provided in Embodiment 1 of the present invention;

[0014] Figure 5 The full spectrum of X-ray photoelectron energy of the fluorescent carbon dot material provided in Embodiment 1 of the present invention;

[0015] Figure 6 The narrow spectrum of X-ray photoelectron energy of carbon element in the fluorescent carbon dot material provided in Embodiment 1 of the present invention is shown.

[0016] Figure 7 The narrow spectrum of X-ray photoelectron energy of nitrogen in the fluorescent carbon dot material provided in Embodiment 1 of the present invention is shown.

[0017] Figure 8 The narrow spectrum of X-ray photoelectron energy of oxygen in the fluorescent carbon dot material provided in Embodiment 1 of the present invention is shown.

[0018] Figure 9 The UV-Vis absorption spectrum of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Embodiment 1 of the present invention;

[0019] Figure 10 The optimal excitation and emission spectra of the purple color of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Embodiment 1 of the present invention;

[0020] Figure 11 The fluorescence lifetime curve of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Embodiment 1 of the present invention is shown.

[0021] Figure 12 The fluorescence quantum efficiency diagram of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Embodiment 1 of the present invention;

[0022] Figure 13 This is a 3D spectrum of the aqueous solution of the fluorescent carbon dot material provided in Embodiment 1 of the present invention;

[0023] Figure 14 The fluorescence quantum efficiency diagram of the aqueous solution of the fluorescent carbon dot material provided in Embodiment 1 of the present invention;

[0024] Figure 15 The UV-Vis absorption spectrum of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 9 of this invention;

[0025] Figure 16 The optimal excitation and emission spectra of the purple color of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 9 of this invention;

[0026] Figure 17 The fluorescence quantum efficiency diagram of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 9 of the present invention;

[0027] Figure 18 The UV-Vis absorption spectrum of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 10 of this invention;

[0028] Figure 19 The optimal excitation and emission spectra of the purple color of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 10 of this invention;

[0029] Figure 20 The fluorescence quantum efficiency diagram of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 10 of the present invention;

[0030] Figure 21 The graph shows the relationship between the fluorescence intensity of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 3 of the present invention and the irradiation time with a 365nm ultraviolet lamp.

[0031] Figure 22 This is a graph showing the relationship between cell viability and the concentration of fluorescent carbon dot material after co-incubation of HeLa cells with the fluorescent carbon dot material provided in Example 5 of the present invention.

[0032] Figure 23A comparison of the fluorescence intensity distribution of the fluorescent carbon dot material and the commercial mitochondrial probe after co-incubation with HeLa cells, as provided in Embodiment 1 of the present invention.

[0033] Figure 24 The image shows a microscopic image of HeLa cells after co-incubation with the fluorescent carbon dot material provided in Embodiment 1 of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the following description, in conjunction with the accompanying drawings and several specific embodiments, illustrates the implementation of fluorescent carbon dot materials, their preparation methods, and applications, providing a more detailed explanation of the invention. The specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0035] Example 1

[0036] This embodiment provides a fluorescent carbon dot material and its preparation method. The fluorescent carbon dot material is prepared according to a method including the following steps:

[0037] S11: Weigh out 0.1 g of 8-hydroxyjulonidine-9-carboxaldehyde and 0.1 g of citric acid for later use;

[0038] S12: Place the weighed 8-hydroxyjulodin-9-carboxaldehyde and citric acid into a polytetrafluoroethylene reactor, and continue to add 20 ml of hydrochloric acid solution with a pH of 2. Stir until 8-hydroxyjulodin-9-carboxaldehyde and citric acid are completely dissolved.

[0039] S13: After sealing the reactor, place it in an oven and heat it at a constant temperature of 180℃ for 6 hours. After heating, allow the oven temperature to cool naturally to room temperature.

[0040] S14: The solution obtained after the reaction is filtered using a needle filter to remove impurities. The filtered solution is then placed into a 500 Da dialysis bag and dialyzed in a beaker containing 2 liters of ultrapure water to obtain a dark red carbon dot solution.

[0041] S15: The obtained dark red carbon dot solution is placed in a vacuum freeze dryer and dried to finally obtain dark red carbon dot powder.

[0042] Example 2

[0043] This embodiment provides a fluorescent carbon dot material and its preparation method. The fluorescent carbon dot material is prepared according to a method including the following steps:

[0044] S11: Weigh out 0.1 g of 8-hydroxyjulonidine-9-carboxaldehyde and 0.1 g of citric acid for later use;

[0045] S12: Place the weighed 8-hydroxyjulodin-9-carboxaldehyde and citric acid into a polytetrafluoroethylene reactor, and continue to add 20 ml of hydrochloric acid solution with a pH of 2. Stir until 8-hydroxyjulodin-9-carboxaldehyde and citric acid are completely dissolved.

[0046] S13: After sealing the reactor, place it in an oven and heat it at a constant temperature of 180℃ for 12 hours. After heating, allow the oven temperature to cool naturally to room temperature.

[0047] S14: The solution obtained after the reaction is filtered using a needle filter to remove impurities. The filtered solution is then placed into a 500 Da dialysis bag and dialyzed in a beaker containing 2 liters of ultrapure water to obtain a dark red carbon dot solution.

[0048] S15: The obtained dark red carbon dot solution is placed in a vacuum freeze dryer and dried to finally obtain dark red carbon dot powder.

[0049] Example 3

[0050] This embodiment provides a fluorescent carbon dot material and its preparation method. The fluorescent carbon dot material is prepared according to a method including the following steps:

[0051] S11: Weigh out 0.1 g of 8-hydroxyjulonidine-9-carboxaldehyde and 0.1 g of citric acid for later use;

[0052] S12: Place the weighed 8-hydroxyjulodin-9-carboxaldehyde and citric acid into a polytetrafluoroethylene reactor, and continue to add 20 ml of hydrochloric acid solution with a pH of 2. Stir until 8-hydroxyjulodin-9-carboxaldehyde and citric acid are completely dissolved.

[0053] S13: After sealing the reactor, place it in an oven and heat it at a constant temperature of 140℃ for 6 hours. After heating, allow the oven temperature to cool naturally to room temperature.

[0054] S14: The solution obtained after the reaction is filtered using a needle filter to remove impurities. The filtered solution is then placed into a 500 Da dialysis bag and dialyzed in a beaker containing 2 liters of ultrapure water to obtain a dark red carbon dot solution.

[0055] S15: The obtained dark red carbon dot solution is placed in a vacuum freeze dryer and dried to finally obtain dark red carbon dot powder.

[0056] Example 4

[0057] This embodiment provides a fluorescent carbon dot material and its preparation method. The fluorescent carbon dot material is prepared according to a method including the following steps:

[0058] S11: Weigh out 0.1 g of 8-hydroxyjulonidine-9-carboxaldehyde and 0.2 g of citric acid for later use;

[0059] S12: Place the weighed 8-hydroxyjulodin-9-carboxaldehyde and citric acid into a polytetrafluoroethylene reactor, and continue to add 20 ml of hydrochloric acid solution with a pH of 2. Stir until 8-hydroxyjulodin-9-carboxaldehyde and citric acid are completely dissolved.

[0060] S13: After sealing the reactor, place it in an oven and heat it at a constant temperature of 180℃ for 6 hours. After heating, allow the oven temperature to cool naturally to room temperature.

[0061] S14: The solution obtained after the reaction is filtered using a needle filter to remove impurities. The filtered solution is then placed into a 500 Da dialysis bag and dialyzed in a beaker containing 2 liters of ultrapure water to obtain a dark red carbon dot solution.

[0062] S15: The obtained dark red carbon dot solution is placed in a vacuum freeze dryer and dried to finally obtain dark red carbon dot powder.

[0063] Example 5

[0064] This embodiment provides a fluorescent carbon dot material and its preparation method. The fluorescent carbon dot material is prepared according to a method including the following steps:

[0065] S11: Weigh out 0.05 g of 8-hydroxyjulonidine-9-carboxaldehyde and 0.1 g of citric acid for later use;

[0066] S12: Place the weighed 8-hydroxyjulodin-9-carboxaldehyde and citric acid into a polytetrafluoroethylene reactor, and continue to add 20 ml of hydrochloric acid solution with a pH of 2. Stir until 8-hydroxyjulodin-9-carboxaldehyde and citric acid are completely dissolved.

[0067] S13: After sealing the reactor, place it in an oven and heat it at a constant temperature of 180℃ for 6 hours. After heating, allow the oven temperature to cool naturally to room temperature.

[0068] S14: The solution obtained after the reaction is filtered using a needle filter to remove impurities. The filtered solution is then placed into a 500 Da dialysis bag and dialyzed in a beaker containing 2 liters of ultrapure water to obtain a dark red carbon dot solution.

[0069] S15: The obtained dark red carbon dot solution is placed in a vacuum freeze dryer and dried to finally obtain dark red carbon dot powder.

[0070] Example 6

[0071] This embodiment provides a fluorescent carbon dot material and its preparation method. The fluorescent carbon dot material is prepared according to a method including the following steps:

[0072] S11: Weigh out 0.01 g of 8-hydroxyjulonidine-9-carboxaldehyde and 0.01 g of citric acid for later use;

[0073] S12: Place the weighed 8-hydroxyjulodin-9-carboxaldehyde and citric acid into a polytetrafluoroethylene reactor, and continue to add 20 ml of hydrochloric acid solution with a pH of 1.5. Stir until 8-hydroxyjulodin-9-carboxaldehyde and citric acid are completely dissolved.

[0074] S13: After sealing the reactor, place it in an oven and heat it at a constant temperature of 180℃ for 6 hours. After heating, allow the oven temperature to cool naturally to room temperature.

[0075] S14: The solution obtained after the reaction is filtered using a needle filter to remove impurities. The filtered solution is then placed into a 500 Da dialysis bag and dialyzed in a beaker containing 2 liters of ultrapure water to obtain a dark red carbon dot solution.

[0076] S15: The obtained dark red carbon dot solution is placed in a vacuum freeze dryer and dried to finally obtain dark red carbon dot powder.

[0077] Example 7

[0078] This embodiment provides a fluorescent carbon dot material and its preparation method. The fluorescent carbon dot material is prepared according to a method including the following steps:

[0079] S11: Weigh out 0.1 g of 8-hydroxyjulonidine-9-carboxaldehyde and 0.1 g of citric acid for later use;

[0080] S12: Place the weighed 8-hydroxyjulodin-9-carboxaldehyde and citric acid into a polytetrafluoroethylene reactor, and continue to add 20 ml of hydrochloric acid solution with a pH of 1. Stir until 8-hydroxyjulodin-9-carboxaldehyde and citric acid are completely dissolved.

[0081] S13: After sealing the reactor, place it in an oven and heat it at a constant temperature of 180℃ for 6 hours. After heating, allow the oven temperature to cool naturally to room temperature.

[0082] S14: The solution obtained after the reaction is filtered using a needle filter to remove impurities. The filtered solution is then placed into a 500 Da dialysis bag and dialyzed in a beaker containing 2 liters of ultrapure water to obtain a dark red carbon dot solution.

[0083] S15: The obtained dark red carbon dot solution is placed in a vacuum freeze dryer and dried to finally obtain dark red carbon dot powder.

[0084] Example 8

[0085] This embodiment provides a fluorescent carbon dot material and its preparation method. The fluorescent carbon dot material is prepared according to a method including the following steps:

[0086] S11: Weigh out 0.1 g of 8-hydroxyjulonidine-9-carboxaldehyde and 0.1 g of citric acid for later use;

[0087] S12: Place the weighed 8-hydroxyjulodin-9-carboxaldehyde and citric acid into a polytetrafluoroethylene reactor, and continue to add 20 ml of hydrochloric acid solution with a pH of 2. Stir until 8-hydroxyjulodin-9-carboxaldehyde and citric acid are completely dissolved.

[0088] S13: After sealing the reactor, place it in an oven and heat it at a constant temperature of 160℃ for 12 hours. After heating, allow the oven temperature to cool naturally to room temperature.

[0089] S14: The solution obtained after the reaction is filtered using a needle filter to remove impurities. The filtered solution is then placed into a 500 Da dialysis bag and dialyzed in a beaker containing 2 liters of ultrapure water to obtain a dark red carbon dot solution.

[0090] S15: The obtained dark red carbon dot solution is placed in a vacuum freeze dryer and dried to finally obtain dark red carbon dot powder.

[0091] Example 9

[0092] This embodiment provides a fluorescent carbon dot material and its preparation method. The fluorescent carbon dot material is prepared according to a method including the following steps:

[0093] S11: Weigh out 0.1 g of 8-hydroxyjulonidine-9-carboxaldehyde and 0.1 g of terephthalic acid for later use;

[0094] S12: Place the weighed 8-hydroxyjulodin-9-carboxaldehyde and terephthalic acid into a polytetrafluoroethylene reactor, and continue to add 20 ml of hydrochloric acid solution with a pH of 1.5. Stir until 8-hydroxyjulodin-9-carboxaldehyde and terephthalic acid are completely dissolved.

[0095] S13: After sealing the reactor, place it in an oven and heat it at a constant temperature of 180℃ for 6 hours. After heating, allow the oven temperature to cool naturally to room temperature.

[0096] S14: The solution obtained after the reaction is filtered using a needle filter to remove impurities. The filtered solution is then placed into a 500 Da dialysis bag and dialyzed in a beaker containing 2 liters of ultrapure water to obtain a dark red carbon dot solution.

[0097] S15: The obtained dark red carbon dot solution is placed in a vacuum freeze dryer and dried to finally obtain dark red carbon dot powder.

[0098] Example 10

[0099] This embodiment provides a fluorescent carbon dot material and its preparation method. The fluorescent carbon dot material is prepared according to a method including the following steps:

[0100] S11: Weigh out 0.1 g of 8-hydroxyjulonidine-9-carboxaldehyde and 0.1 g of p-aminobenzenesulfonic acid separately for later use;

[0101] S12: Place the weighed 8-hydroxyjulonidine-9-carboxaldehyde and p-aminobenzenesulfonic acid into a polytetrafluoroethylene reactor, and continue to add 20 ml of hydrochloric acid solution with a pH of 1. Stir until 8-hydroxyjulonidine-9-carboxaldehyde and p-aminobenzenesulfonic acid are completely dissolved.

[0102] S13: After sealing the reactor, place it in an oven and heat it at a constant temperature of 160℃ for 6 hours. After heating, allow the oven temperature to cool naturally to room temperature.

[0103] S14: The solution obtained after the reaction is filtered using a needle filter to remove impurities. The filtered solution is then placed into a 500 Da dialysis bag and dialyzed in a beaker containing 2 liters of ultrapure water to obtain a dark red carbon dot solution.

[0104] S15: The obtained dark red carbon dot solution is placed in a vacuum freeze dryer and dried to finally obtain dark red carbon dot powder.

[0105] Related feature tests

[0106] 1. Characterization and analysis of the fluorescent carbon dot materials in the embodiments of the present invention:

[0107] The fluorescent carbon dot materials provided in Examples 1 to 10 were characterized by transmission electron microscopy (TEM). The TEM image of the fluorescent carbon dot material provided in Example 1 is shown below. Figure 2 As shown in the transmission electron microscope (TEM) images, the particle size of the room-temperature phosphorescent carbon dot material is approximately 4–6 nm. Figure 3 The high-resolution transmission lens image of the fluorescent carbon dot material shown shows that the lattice spacing of the fluorescent carbon dot material is 0.22 nm, which corresponds to the (100) crystal plane of graphite carbon.

[0108] The fluorescent carbon dot materials provided in Examples 1 to 8 were subjected to infrared testing. The infrared spectrum of the fluorescent carbon dot material provided in Example 1 is as follows: Figure 4As shown in the infrared spectrum, the fluorescent carbon dot material contains a variety of chemical bonds and groups, namely -OH, C=O, CO, C=C, and CN.

[0109] X-ray photoelectron spectroscopy (XPS) analysis was performed on the fluorescent carbon dot materials and their C, N, and O elements provided in Examples 1 to 8. The XPS spectrum of the fluorescent carbon dot material provided in Example 1 is shown below. Figure 5 As shown, the X-ray photoelectron spectrum of the C element in the fluorescent carbon dot material provided in Example 1 is as follows. Figure 6 As shown, the X-ray photoelectron spectrum of the nitrogen element contained in the fluorescent carbon dot material provided in Example 1 is as follows. Figure 7 As shown, the X-ray photoelectron spectrum of the O element contained in the fluorescent carbon dot material provided in Example 1 is as follows. Figure 8 As shown in the figure, the X-ray photoelectron spectrum of the fluorescent carbon dot material indicates that it contains three elements: C, O, and N, with elemental contents of 65.6%, 31.15%, and 3.25%, respectively. The X-ray photoelectron spectrum of the C element in the fluorescent carbon dot material shows that the chemical bonds in the material are mainly CC / C=C, CO / CN, COC, -C-OH, and C=O.

[0110] 2. Fluorescence property analysis of the fluorescent carbon dot materials in the embodiments of the present invention:

[0111] The dimethyl sulfoxide solutions of the fluorescent carbon dot materials provided in Examples 1 to 8 were subjected to UV-Vis absorption spectroscopy, optimal excitation, and emission spectroscopy analysis, respectively. The UV-Vis absorption spectrum, optimal excitation, and emission spectrum of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 1 are shown below. Figure 9 and 10 As shown in the diagram, the UV-Vis absorption spectrum, optimal excitation and emission spectra of the fluorescent carbon dot material solution indicate that the fluorescent carbon dot material has two absorption peaks at 360 and 585 nm, with optimal excitation and emission wavelengths of 585 nm and 605 nm, respectively. The fluorescence lifetime of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 1 is shown in the diagram. Figure 11 As shown, the fluorescence lifetime of the fluorescent carbon dot material solution is 4.28 nanoseconds. The quantum efficiency of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 1 is as follows: Figure 12 As shown, the quantum efficiency of the fluorescent carbon dot material solution is 95.56%.

[0112] The aqueous solutions of the fluorescent carbon dot materials provided in Examples 1 to 8 were subjected to 3D spectral analysis and fluorescence quantum efficiency analysis, respectively. Specifically, the aqueous solution of the fluorescent carbon dot material provided in Example 1 was subjected to 3D spectral analysis as follows: Figure 13As shown, the 3D spectrum of the fluorescent carbon dot material solution indicates that the coordinates of the emission center of the fluorescent carbon dot material are (571, 589). The quantum efficiency of the aqueous solution of the fluorescent carbon dot material provided in Example 1 is as follows: Figure 14 As shown, the quantum efficiency of the fluorescent carbon dot material solution is 75.89%.

[0113] The dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 9 was subjected to UV-Vis absorption spectroscopy, optimal excitation, and emission spectroscopy analysis. The UV-Vis absorption spectrum of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 9 is as follows: Figure 15 As shown in the UV-Vis absorption spectrum of the fluorescent carbon dot material solution, the fluorescent carbon dot material exhibits two absorption peaks at 360 and 571 nm. The optimal excitation and emission spectra of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 9 are shown below. Figure 16 As shown in the UV-Vis absorption spectrum of the fluorescent carbon dot material solution, the optimal excitation and emission wavelengths of the fluorescent carbon dot material are 584 nm and 603 nm, respectively. The quantum efficiency of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 9 is as follows: Figure 17 As shown, the quantum efficiency of the fluorescent carbon dot material solution is 92.80%.

[0114] The dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 10 was subjected to UV-Vis absorption spectroscopy, optimal excitation, and emission spectroscopy analysis. The UV-Vis absorption spectrum of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 10 is as follows: Figure 18 As shown in the UV-Vis absorption spectrum of the fluorescent carbon dot material solution, the fluorescent carbon dot material exhibits two absorption peaks at 360 and 582 nm. The optimal excitation and emission spectra of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 10 are shown below. Figure 19 As shown in the UV-Vis absorption spectrum of the fluorescent carbon dot material solution, the optimal excitation and emission wavelengths of the fluorescent carbon dot material are 582 nm and 605 nm, respectively. The quantum efficiency of the dimethyl sulfoxide solution of the fluorescent carbon dot material provided in Example 10 is as follows: Figure 20 As shown, the quantum efficiency of the fluorescent carbon dot material solution is 92.17%.

[0115] 3. Photostability and toxicity analysis of the fluorescent carbon dot materials of the embodiments of the present invention:

[0116] The photostability of the fluorescent carbon dot materials provided in Examples 1 to 10 was analyzed. Specifically, the fluorescence intensity change of the fluorescent carbon dot material provided in Example 3 under continuous irradiation with a 365nm ultraviolet lamp is shown below. Figure 21As shown, the fluorescence intensity change of the fluorescent carbon dot material indicates that the fluorescence emitted by the fluorescent carbon dot material did not decay after continuous irradiation with a 365nm ultraviolet lamp for 3600 seconds.

[0117] The fluorescent carbon dot materials provided in Examples 1 to 10 were subjected to biotoxicity analysis. In Example 1, the fluorescent carbon dot material was diluted to different concentrations with ultrapure water and then incubated with HeLa cells for 24 hours. The cell viability was as follows: Figure 22 As shown in the graph, the survival rate of HeLa cells at different concentrations is such that even when the concentration of the fluorescent carbon dot material reaches 400 micrograms per milliliter, the survival rate of HeLa cells is still higher than 90%, indicating that the fluorescent carbon dot material provided by this invention has almost no toxicity.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0119] 4. Application of the fluorescent carbon dot material of the present invention in cell imaging:

[0120] The fluorescent carbon dot materials provided in Examples 1 to 10 were used for cell imaging. In Example 1, the fluorescence intensity distribution of the fluorescent carbon dot material within cells after co-incubation with cells was compared with that of a commercial mitochondrial probe. Figure 23 As shown in the figure, the fluorescence intensity distribution of the fluorescent carbon dot material overlaps with that of a commercial mitochondrial probe by 94%, indicating that the fluorescent carbon dot material of this invention is a nanomaterial that highly targets mitochondria. Cell imaging under a microscope after co-incubation of the fluorescent carbon dot material provided in Example 1 with cells is shown in the figure. Figure 24 As shown, the fluorescent carbon dot materials described herein are enriched on mitochondria within the cell, indicating that the fluorescent carbon dot materials provided by this invention can be used for mitochondrial imaging within cells.

Claims

1. A method for preparing red high quantum efficiency fluorescent carbon dot materials, characterized in that, Includes the following steps: (1) Dissolve a julonidine derivative containing hydroxyl and / or aldehyde groups with an organic acid or its salt containing one or more carboxyl groups in an acidic reaction medium. (2) Place the obtained solution in a sealed container for hydrothermal or solvothermal reaction at a temperature of 120-220℃ for 2-24 hours. (3) The reaction solution was filtered and dialyzed to a molecular weight cutoff of 300-1000 Da to obtain red fluorescent carbon dot materials.

2. The method according to claim 1, wherein the aromatic compound is selected from at least one of 8-hydroxyjulonidine-9-carboxaldehyde, 9-hydroxyjulonidine-8-carboxaldehyde, 8-hydroxyjulonidine-10-carboxaldehyde, or derivatives thereof.

3. The method according to claim 1, wherein the organic acid is selected from citric acid, oxalic acid, tartaric acid, malic acid, succinic acid, glutaric acid, maleic acid, terephthalic acid, p-aminobenzenesulfonic acid, or any combination thereof.

4. The method according to claim 1, wherein the pH of the acidic reaction medium is 0.5-4, and is provided by hydrochloric acid, sulfuric acid, nitric acid or a combination thereof.

5. The method according to claim 1, wherein the solvent is water, ethanol, methanol, or a mixture of water and a polar solvent.

6. The method according to claim 1, wherein the filtration employs a 0.22 μm microporous membrane.

7. A red fluorescent carbon dot material, characterized in that: (1) Particle size is 1-10 nm; (2) Contains C, O and / or N elements; (3) The surface contains at least one functional group selected from hydroxyl, carboxyl, ether, amide or imine bonds; (4) It has an excitation absorption peak in the range of 540-620nm and a fluorescence emission peak in the range of 580-650nm; (5) The fluorescence quantum efficiency in dimethyl sulfoxide is ≥80%, preferably ≥90%; (6) Prepared by the method of any one of claims 1-6.

8. The fluorescent carbon dot material according to claim 7, wherein the particle size is 2-6 nm.

9. The fluorescent carbon dot material according to claim 7, wherein the fluorescence emission peak under 370 nm excitation is located at 590-610 nm.

10. The fluorescent carbon dot material according to claim 7, wherein the zeta potential ranges from +5mV to +45mV.

11. The fluorescent carbon dot material according to claim 7, with a cell viability ≥90% in the concentration range of 0-400 μg / mL.

12. The fluorescent carbon dot material according to claim 7 maintains a stable red fluorescence intensity in the pH range of 3-12.

13. The use of a red fluorescent carbon dot material in the preparation of mitochondrial-targeted fluorescent imaging probes.

14. The use according to claim 13, wherein the fluorescent carbon dot material is used for intracellular imaging, subcellular organelle labeling, biofluorescent probes, or live-cell imaging.

15. The use according to claim 13, wherein the fluorescent carbon dot material is the material according to any one of claims 7-12.

16. The use according to claim 13, wherein the fluorescent carbon dots have high photostability, low photobleaching properties, and good biocompatibility.

17. The use of a red fluorescent carbon dot material in the preparation of red luminescent anti-counterfeiting ink.

18. The use according to claim 17, wherein the fluorescent carbon dots are used in photoluminescent materials.

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