Red fluorescent carbon quantum dots and preparation method and application thereof

Abstract

The application provides a red fluorescent carbon quantum dot and a preparation method and application thereof. The preparation method comprises the following steps: providing an IR dye solution or an IR dye mixed solution formed by mixing the IR dye and an alkali; heating the IR dye solution or the IR dye mixed solution to obtain a product solution; and separating and purifying the product solution to obtain the red fluorescent carbon quantum dot. The preparation method is simple, economical and easy to operate, and the prepared red fluorescent carbon quantum dot has super-high fluorescent light emitting efficiency, and has good application prospects in the fields of biomedical fields such as biological cells and living body imaging, and high-performance optoelectronic device fields such as LED light emitting devices and solar cells.

Description

Technical Field

[0001] This invention relates to the field of fluorescent materials technology, specifically to a red fluorescent carbon quantum dot, its preparation method, and its applications. Background Technology

[0002] Fluorescent nanoparticles have promising applications in important fields such as biomedicine, LED luminescence, and metal ion detection. However, traditional organic fluorescent dyes suffer from poor stability and are prone to photocatalytic degradation. Semiconductor quantum dot materials offer good photostability and high fluorescence yield, but they have poor solubility in aqueous solutions and contain heavy metals such as Se, Te, and Cd, which can seriously harm human health and cause environmental pollution. This severely limits the application scope of semiconductor quantum dot materials.

[0003] Carbon quantum dots, as a novel type of fluorescent nanoparticle, possess a series of excellent properties, including tunable photoluminescence, high water solubility, good stability, and low biotoxicity. These superior properties make them more promising for applications in LED luminescence, biofluorescent labeling, and metal ion detection compared to dyes and semiconductor quantum dots. Carbon quantum dots with red fluorescence (>600nm) exhibit advantages such as low scattering, weak absorption, high penetration depth, and low fluorescence background due to long-wavelength excitation and emission, effectively overcoming the disadvantages of short-wavelength emission, such as low penetration in biological tissues / aqueous solutions, and photodamage and photobleaching caused by ultraviolet excitation. However, most currently prepared red fluorescent carbon quantum dots have low luminescence efficiency (<50%), limiting their use in practical applications.

[0004] A search revealed that Chinese patent application number 202010837830.5 discloses a red fluorescent carbon dot, its preparation method, and its application. However, the fluorescence efficiency of this carbon quantum dot is only 13%–22.5%, resulting in a low signal-to-noise ratio (SNR) of only 1.2–1.8 for tetracycline, oxytetracycline, and chlortetracycline, limiting its detection effectiveness. Chinese patent application number 202211187183.3 discloses a method for detecting metabisulfite (S₂O₅). 2- The red fluorescent carbon dots and their preparation method were discovered. However, the relative fluorescence efficiency of these carbon quantum dots was only 40.8% to 46.9%, which resulted in a linear detection range of only 2 μM to 48 μM, affecting their practical application in detection scenarios.

[0005] Therefore, there is a need to develop a series of high fluorescence luminescence efficiency (>50%) red fluorescent carbon quantum dots that can be fabricated in a serial manner. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the purpose of this invention is to provide a red fluorescent carbon quantum dot, its preparation method, and its application.

[0007] According to a first aspect of the present invention, a method for preparing red fluorescent carbon quantum dots is provided, comprising:

[0008] Provide IR dye solutions, or provide IR dye mixed solutions formed by IR dyes and alkali;

[0009] Heating the IR dye solution or the IR dye mixture solution yields a product solution;

[0010] The product solution was separated and purified to obtain red fluorescent carbon quantum dots.

[0011] Optionally, the provision of the IR dye solution includes:

[0012] Weigh out 10–20 mg of IR dye;

[0013] The IR dye is added to 10-20 mL of reaction solvent and dissolved to obtain an IR dye solution.

[0014] Optionally, the provision of the IR dye mixed solution formed by the IR dye and the base includes:

[0015] Weigh out the IR dye and the alkaline substance separately;

[0016] The IR dye and the alkaline substance are added to the reaction solvent, mixed and dissolved to obtain an IR dye mixed solution.

[0017] Optionally, the IR dye is any one of IR780, IR806, and IR820; the reaction solvent is methanol or ethanol.

[0018] Optionally, the alkaline substance is any one of sodium hydroxide, ammonia, and polyethyleneimine; the concentration of the alkaline substance in the IR dye mixed solution does not exceed 1 mmol·mL. -1 .

[0019] Optionally, the IR dye solution or the IR dye mixture solution is heated, wherein the heating temperature is 140–220°C and the heating time is 2–6 hours.

[0020] Optionally, separating and purifying the product solution includes:

[0021] Centrifuge to separate the product solution;

[0022] Take the supernatant after centrifugation and filter it using an organic filter membrane to obtain the filtrate;

[0023] The filtrate is placed in a dialysis bag and dialyzed in a methanol or ethanol solution;

[0024] The dialyzed solution was dried by rotary evaporation to obtain red fluorescent carbon quantum dots.

[0025] According to a second aspect of the present invention, a red fluorescent carbon quantum dot is provided, which is prepared using the above-described method for preparing red fluorescent carbon quantum dots.

[0026] According to a third aspect of the present invention, an application of the above-described red fluorescent carbon quantum dots is provided, wherein the red fluorescent carbon quantum dots are used for fluorescence imaging.

[0027] According to a fourth aspect of the present invention, an application of the above-described red fluorescent carbon quantum dots is provided, wherein the red fluorescent carbon quantum dots are encapsulated for use in red LED light emission.

[0028] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0029] 1. The method for preparing red fluorescent carbon quantum dots provided by this invention is simple, economical, easy to operate, and has good reproducibility.

[0030] 2. The red fluorescent carbon quantum dots prepared by this invention have a long fluorescence wavelength, which can effectively avoid the disadvantages of short-wavelength fluorescence, such as low tissue penetration depth, easy light damage to biological tissues, and strong fluorescence background. They are suitable for cell or in vivo biological imaging.

[0031] 3. The red fluorescent carbon quantum dots prepared by this invention have high fluorescence luminescence efficiency and can be applied to high-efficiency LED lamp bead packaging. Attached Figure Description

[0032] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0033] Figure 1 The morphology and optical characteristics of the red fluorescent carbon quantum dots in Example 1 of the present invention are shown in the following figures: (a)-(b) are transmission electron microscopy images, (c) is a particle size distribution map, and (d) is a fluorescence emission spectrum.

[0034] Figure 2 The image shows the cell imaging application of red fluorescent carbon quantum dots in Application Example 1 of the present invention, where: (a) is a fluorescence image, (b) is a bright field image, and (c) is a superimposed image of fluorescence and bright field.

[0035] Figure 3 This is a diagram illustrating the in vivo fluorescence imaging application of red fluorescent carbon quantum dots in Application Example 2 of the present invention;

[0036] Figure 4The following are LED light emission application diagrams of red fluorescent carbon quantum dots in Application Example 3 of the present invention, wherein: (a) is an LED sample diagram, (b) is an LED electroluminescence diagram, and (c) is an LED emission spectrum diagram. Detailed Implementation

[0037] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0038] An embodiment of the present invention provides a method for preparing red fluorescent carbon quantum dots, comprising:

[0039] S1. Provide an IR dye solution, or a mixed solution of IR dye and alkali;

[0040] S2. Heat the IR dye solution or the IR dye mixture to obtain the product solution;

[0041] S3. Separate and purify the product solution to obtain red fluorescent carbon quantum dots.

[0042] In some embodiments, step S1 involves providing an IR dye solution, which includes: weighing 10 mg to 20 mg of IR dye substance; adding the IR dye substance to 10 to 20 mL of reaction solvent, dissolving it, and obtaining an IR dye solution, which is a green solution.

[0043] Specifically, the IR dye is any one of IR780, IR806, and IR820; the reaction solvent is methanol or ethanol, thereby achieving good dye solubility.

[0044] In some embodiments, step S1 involves providing an IR dye mixed solution formed by the IR dye and an alkali, which includes: weighing the IR dye substance and the alkali substance separately; adding the IR dye substance and the alkali substance to the reaction solvent, mixing and dissolving them to obtain the IR dye mixed solution, which is a yellow-green solution.

[0045] Specifically, the IR dye is any one of IR780, IR806, and IR820, and the concentration of the IR dye in the IR dye mixture solution is the same as the concentration of the aforementioned IR dye solutions; the alkaline substance is any one of sodium hydroxide, ammonia, and polyethyleneimine. The reaction solvent is methanol or ethanol, or other solvents that achieve good dispersibility and solubility of the IR dye. The concentration of the alkaline substance in the IR dye mixture solution does not exceed 1 mmol·mL. -1In other embodiments, other types of alkaline substances and reaction solvents can certainly be used, and the method is not limited to these. By providing an alkaline environment, higher luminescence efficiency can be achieved.

[0046] In some embodiments, in step S2, the heating temperature is 140–220°C and the heating time is 2–6 hours to achieve carbon nucleation and growth.

[0047] In some embodiments, step S3, separating and purifying the product solution, includes:

[0048] S31, Centrifugation product solution;

[0049] S32. Take the supernatant after centrifugation and filter it using an organic filter membrane with a pore size of 0.22μm to remove large particulate matter in the reaction product and obtain the filtrate.

[0050] S33. Place the filtrate in a 500-1000D dialysis bag and dialyze it in methanol or ethanol solution to remove small molecule products generated by carbon dots.

[0051] S34. The dialyzed solution was dried by rotary evaporation to obtain red fluorescent carbon quantum dots.

[0052] This invention also provides a red fluorescent carbon quantum dot, which is prepared using the method described above. This carbon quantum dot exhibits red fluorescence with a wavelength greater than 600 nm, reaching up to 640 nm, and possesses high fluorescence efficiency, exceeding 50%, reaching 85%–95.5%.

[0053] The following description includes specific embodiments and application examples. Where specific techniques or conditions are not specified in the embodiments and application examples, they should be performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained through commercial channels.

[0054] Example 1

[0055] This embodiment provides a method for preparing ultra-high luminescence efficiency red fluorescent carbon quantum dots based on IR dyes, as detailed below:

[0056] Take two 50mL centrifuge tubes, rinse them with anhydrous methanol, and dry them for later use.

[0057] Weigh 200 mg of NaOH using weighing paper and add it to one of the 50 mL centrifuge tubes. Add 5 mL of methanol using a 5 mL pipette, and dissolve by sonication to obtain a concentration of 1 mmol / mL. -1 Prepare a NaOH methanol solution for later use.

[0058] Take a 5 mL centrifuge tube and weigh 10 mg of IR806 dye. Dissolve the dye in 10 mL of methanol solution and add the solution to another 50 mL centrifuge tube to obtain a dark green solution.

[0059] Using a 1 mL pipette, take 0.5 mL of the 1 mmol / mL solution prepared above. -1 Add the NaOH methanol solution to the prepared IR806 methanol solution and mix by inverting.

[0060] The resulting yellow-green solution was added to a 25 mL polytetrafluoroethylene (PTFE) liner using a 5 mL pipette. The PTFE liner was then placed in a reaction vessel and heated in an oven at 180 °C for 6 hours.

[0061] After pyrolysis, the reaction products were obtained. The solution was then removed and subjected to a reaction at 8000 r·min. -1 Centrifuge for 10 min. Collect the supernatant and filter it using an organic filter membrane with a pore size of 0.22 μm. Add the filtered solution to a 1000D dialysis bag and dialyze it in 2 L of anhydrous methanol solution for 6 hours. Afterward, remove the solution and dry it using a rotary evaporator for later use.

[0062] Reference Figure 1 Electron microscopy imaging analysis showed that the interplanar spacing of the red fluorescent carbon quantum dots prepared in Example 1 was 0.21 nm, the average particle size was approximately 2.0 nm, and the particle size distribution ranged from 0.6 to 4.2 nm. Ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy measurements showed that the carbon quantum dots had absorption peaks at 540 nm and 570 nm, a fluorescence peak at 640 nm, and a fluorescence quantum yield of 85.6%.

[0063] Example 2

[0064] This embodiment provides a method for preparing ultra-high luminescence efficiency red fluorescent carbon quantum dots based on IR dyes, as detailed below:

[0065] Take two 50mL centrifuge tubes, rinse them with anhydrous methanol, and dry them for later use.

[0066] Weigh 200 mg of polyethyleneimine using weighing paper and add it to one of the 50 mL centrifuge tubes. Add 5 mL of ethanol using a 5 mL pipette, and dissolve by sonication to obtain a concentration of 1 mmol / mL. -1 A polyethyleneimine ethanol solution, for later use.

[0067] Take a 5mL centrifuge tube and weigh 10mg of IR780 dye. Dissolve the weighed dye in 10mL of ethanol solution and add it to another 50mL centrifuge tube to obtain a dark green solution.

[0068] Using a 1 mL pipette, take 0.5 mL of the 1 mmol / mL solution prepared above. -1 Add the polyethyleneimine ethanol solution to the prepared IR780 ethanol solution and mix by inverting.

[0069] The resulting yellow-green solution was added to a 25 mL polytetrafluoroethylene (PTFE) liner using a 5 mL pipette. The PTFE liner was then placed in a reaction vessel and heated in an oven at 220 °C for 6 hours.

[0070] After pyrolysis, the reaction products were obtained. The solution was then removed and subjected to a reaction at 6000 r·min. -1 Centrifuge for 30 min. Collect the supernatant and filter it using an organic filter membrane with a pore size of 0.22 μm. Add the filtered solution to a 1000 D dialysis bag and dialyze it in 2 L of anhydrous ethanol for 6 hours. Afterward, remove the solution and dry it using a rotary evaporator for later use.

[0071] Electron microscopy imaging analysis showed that the red fluorescent carbon quantum dots prepared in Example 3 all had a size of approximately 1.9 nm and an interplanar spacing of 0.21 nm. Ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy measurements showed that the carbon quantum dots had absorption peaks at 540 nm and 570 nm, a fluorescence peak at 640 nm, and a fluorescence quantum yield of 88.9%.

[0072] Example 3

[0073] This embodiment provides a method for preparing ultra-high luminescence efficiency red fluorescent carbon quantum dots based on IR dyes, as detailed below:

[0074] Take two 50mL centrifuge tubes, rinse them with anhydrous methanol, and dry them for later use.

[0075] Weigh 200 mg of NaOH using weighing paper and add it to one of the 50 mL centrifuge tubes. Add 5 mL of ethanol using a 5 mL pipette, and dissolve by sonication to obtain a concentration of 1 mmol / mL. -1 Prepare a NaOH ethanol solution for later use.

[0076] Take a 5mL centrifuge tube and weigh 10mg of IR820 dye. Dissolve the dye in 10mL of ethanol solution and add the solution to another 50mL centrifuge tube to obtain a dark green solution.

[0077] Using a 1 mL pipette, take 0.5 mL of the 1 mmol / mL solution prepared above. -1 Add the NaOH ethanol solution to the prepared IR820 ethanol solution and mix by inverting.

[0078] The resulting yellow-green solution was added to a 25 mL polytetrafluoroethylene (PTFE) liner using a 5 mL pipette. The PTFE liner was then placed in a reaction vessel and heated in an oven at 220 °C for 6 hours.

[0079] After pyrolysis, the reaction products were obtained. The solution was then removed and subjected to a reaction at 7000 r·min. -1 Centrifuge for 20 min. Collect the supernatant and filter it using an organic filter membrane with a pore size of 0.22 μm. Add the filtered solution to a 500D dialysis bag and dialyze it in 1 L of anhydrous ethanol for 6 hours. Afterward, remove the solution and dry it using a rotary evaporator for later use.

[0080] Carbon quantum dots prepared by deionization were placed under oxygen plasma and treated with a discharge current of 10 mA for 2 minutes, followed by rotary evaporation drying for later use.

[0081] Electron microscopy imaging analysis showed that the prepared red fluorescent carbon quantum dots all had a size of approximately 1.9 nm and an interplanar spacing of 0.21 nm. Ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy measurements revealed absorption peaks at 540 nm and 570 nm, a fluorescence peak at 640 nm, and a fluorescence quantum yield of 94%.

[0082] Example 4

[0083] This embodiment provides a method for preparing ultra-high luminescence efficiency red fluorescent carbon quantum dots based on IR dyes, as detailed below:

[0084] Take two 50mL centrifuge tubes, rinse them with anhydrous methanol, and dry them for later use.

[0085] Take a 5 mL centrifuge tube and weigh 10 mg of indocyanine green dye. Dissolve the dye in 10 mL of ethanol solution and add the solution to another 50 mL centrifuge tube to obtain the final solution.

[0086] Add 5 mL of liquid to 25 mL of polytetrafluoroethylene (PTFE) liner using a pipette, place the PTFE liner in the reaction vessel, and heat in an oven at 170°C for 6 hours.

[0087] After pyrolysis, the reaction products were obtained. The solution was then removed and subjected to a reaction at 7000 r·min. -1 Centrifuge for 20 min. Collect the supernatant and filter it using an organic filter membrane with a pore size of 0.22 μm. Add the filtered solution to a 500D dialysis bag and dialyze it in 2 L of anhydrous ethanol for 6 hours. Afterward, remove the solution and dry it using a rotary evaporator for later use.

[0088] Carbon quantum dots prepared by deionization were placed under oxygen plasma and treated with a discharge current of 10 mA for 2 minutes, followed by rotary evaporation drying for later use.

[0089] Electron microscopy imaging analysis showed that the prepared red fluorescent carbon quantum dots all had a size of approximately 1.9 nm and an interplanar spacing of 0.21 nm. Ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy measurements revealed absorption peaks at 540 nm and 570 nm, a fluorescence peak at 640 nm, and a fluorescence quantum yield of 84%.

[0090] Application Example 1

[0091] This application example demonstrates the use of the red fluorescent carbon quantum dots prepared in Example 1 for cell imaging.

[0092] In cell imaging experiments, refer to Figure 2 Images (a)-(c) show, in order, the fluorescence image, bright-field image, and fluorescence-bright-field overlap image of HCT116 colon cancer cells labeled with red fluorescent carbon quantum dots. The experimental results demonstrate that carbon quantum dots exhibit excellent fluorescence properties in the cellular environment, making them suitable for high-efficiency cellular bioluminescence imaging.

[0093] Application Example 2

[0094] This application example demonstrates the use of the red fluorescent carbon quantum dots prepared in Example 2 for in vivo fluorescence imaging.

[0095] In vivo fluorescence imaging experiment reference Figure 3 As shown, nude mice were fasted for 24 hours and then injected subcutaneously with a concentration of 200 μg / mL. -1 Carbon quantum dots, excited at a wavelength of 570 nm, achieve a signal-to-noise ratio of up to 20 in in vivo fluorescence imaging. Experiments demonstrate that carbon quantum dots possess excellent fluorescence properties in a living environment, enabling highly efficient in vivo biological fluorescence imaging.

[0096] Application Example 3

[0097] This application example uses the red fluorescent carbon quantum dots prepared in Example 3 to emit light in an LED.

[0098] Based on LED light emission experiments, refer to Figure 4 The image and emission spectrum of the red fluorescent carbon quantum dots shown in the figure demonstrate that the quantum dots, after encapsulation, achieve red (640nm) LED emission.

[0099] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention. The above preferred features can be used in any combination without conflict.

Claims

1. A method for preparing red fluorescent carbon quantum dots, characterized in that, The application relates to a preparation method of red fluorescent carbon quantum dots. The method comprises the following steps: providing an IR dye mixed solution formed by an IR dye and a base; heating the IR dye mixed solution to obtain a product solution; separating and purifying the product solution to obtain red fluorescent carbon quantum dots; the step of providing the IR dye mixed solution formed by the IR dye and the base comprises: respectively weighing the IR dye and the base; adding the IR dye and the base into a reaction solvent, mixing and dissolving to obtain the IR dye mixed solution; the IR dye is any one of IR780, IR806 and IR820; and the reaction solvent is methanol or ethanol; 2. The method for preparing red fluorescent carbon quantum dots according to claim 1, characterized in that, The basic substance is any one of sodium hydroxide, ammonia water and polyethyleneimine; the concentration of the basic substance in the mixed solution of the IR dyes is not more than 1 mmol·mL -1 .

3. The method for preparing red fluorescent carbon quantum dots according to claim 1, characterized in that, by providing the alkaline environment, the light-emitting efficiency of the red fluorescent carbon quantum dots is improved.

4. The method for preparing red fluorescent carbon quantum dots according to claim 1, characterized in that, The step of heating the IR dye mixed solution comprises the following steps: heating at a temperature of 140-220 DEG C for 2-6 hours. The step of separating and purifying the product solution comprises the following steps: centrifuging the product solution; taking supernatant after centrifugation, filtering by using an organic filter membrane to obtain a filtrate; 5. A red fluorescent carbon quantum dot, characterized by, placing the filtrate in a dialysis bag and dialyzing in a methanol or ethanol solution; 6. Use of the red fluorescent carbon quantum dots according to claim 5, characterized in that, rotary evaporating and drying the dialyzed solution to obtain the red fluorescent carbon quantum dots.

7. Use of the red fluorescent carbon quantum dots according to claim 5, characterized in that, The red fluorescent carbon quantum dots are prepared by using the preparation method of any one of claims 1-4. The red fluorescent carbon quantum dots are used for fluorescence imaging. The red fluorescent carbon quantum dots are used for red LED light emission after encapsulation.

Images