A one-step method for preparing oil-soluble carbon dot-based afterglow luminescent materials

Abstract

This invention relates to the field of luminescent carbon nanomaterials, and more particularly to the technical field of fluorescent carbon dots (CDs) preparation, specifically to a one-step method for preparing oil-soluble carbon dot-based afterglow luminescent materials. In this method, carbon dots generated in situ are embedded into a rare-earth fluoride NaReF4 matrix under high-temperature conditions. The resulting CDs@NaReF4 nanocomposite material can be uniformly and stably dispersed in an organic solvent and emits a long-lifetime green room-temperature afterglow under ultraviolet light excitation.

Description

Technical Field

[0001] This invention relates to the field of luminescent carbon nanomaterials, and more particularly to the technical field of fluorescent carbon dots (CDs) preparation, specifically to a one-step method for preparing oil-soluble carbon dot-based afterglow luminescent materials. Background Technology

[0002] Carbon dots are novel, near-spherical, zero-dimensional carbon nanomaterials that emit multicolor fluorescence in the ultraviolet-visible absorption region. They have attracted widespread attention due to their simple synthesis methods, good photostability, excellent biocompatibility, and low toxicity. In recent years, it has been discovered that embedding carbon dots into various matrices can effectively induce room-temperature afterglow by suppressing nonradiative transitions in molecules and protecting the triplet states of the carbon dots. Carbon dot-based room-temperature afterglow materials can eliminate interference from background fluorescence and light scattering, and possess the advantages of tunable band gaps and simple structural design, showing broad application prospects in information encryption, sensing, fingerprint recognition, and bioimaging.

[0003] To date, carbon dot-based room-temperature afterglow has expanded from primarily solid-state afterglow to water-soluble afterglow. After years of research, carbon dot-based room-temperature afterglow materials with different lifetimes and emission wavelengths have been obtained. However, due to the inherent defects of composite materials, liquid-phase CDs-based room-temperature afterglow materials still face several challenges. For example, composite materials obtained through inorganic salt melting and rigid hydrogen bond network immobilization methods often suffer from excessively large particle sizes, severely hindering their further development in the biological field. Composite materials prepared through SiO2 coating methods exhibit severe agglomeration due to the reaction between numerous Si-OH hydrophilic groups on the SiO2 gel layer, resulting in slow development in biomedical analysis and imaging. Furthermore, the controllable preparation of composite materials and the cumbersome surface modification processes also contribute to the fact that research on liquid-phase CDs-based room-temperature afterglow materials is still in its early stages. Therefore, developing new matrices that can stabilize the excited triplet state of CDs, possess uniform size and morphology, and are easily modifiable is of great significance.

[0004] In response, current research has gradually shifted its focus from single materials to composite materials, leading to the development of rare earth fluoride / CDs composite luminescent nanomaterials (CDs@rare earth fluorides). However, existing CDs@rare earth fluorides are primarily liquid-phase carbon dot-based materials. Liquid-phase carbon dot-based materials can only dissolve and react well in water-soluble solutions, not in oil-soluble solutions, which limits the application of CDs@rare earth fluorides in oil-soluble reactions. Furthermore, current CDs@rare earth fluorides are limited to micrometer-scale sizes. Larger micrometer-scale CDs@rare earth fluorides are prone to precipitation during reactions, resulting in unstable dispersion on the corresponding materials and affecting the afterglow emission effect. In addition, existing methods for preparing CDs@rare earth fluorides typically employ multi-step synthesis methods involving in-situ growth, self-assembly, and intermediate medium bridging to obtain multifunctional nanocomposites, making the preparation process complex. Therefore, obtaining hydrophobic afterglow with excellent stability in carbon dot-based materials remains a significant challenge. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art by providing a one-step method for preparing oil-soluble carbon dot-based afterglow luminescent materials. This method can produce small-sized hydrophobic carbon dot-based afterglow luminescent materials with the advantage of stable afterglow luminescence, and the method is easy to operate.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A one-step method for preparing oil-soluble carbon dot-based afterglow luminescent materials is provided, comprising the following steps:

[0008] S1. Add Re(CH3CO2)3 aqueous solution, oleic acid and 1-octadecene to the container, mix well to obtain the first mixed solution;

[0009] S2. Heat the first mixed solution to 120℃~180℃, react for 0.3h~1h, then add citrate and stop heating;

[0010] S3. After cooling the first mixed solution to room temperature, add NaOH methanol solution and NH4F methanol solution, mix well, and obtain the second mixed solution.

[0011] S4. Add the second mixed solution to 40℃~60℃ and keep it at that temperature for 0.4h~0.6h, then continue to raise the temperature to 100℃~110℃ and perform vacuum treatment;

[0012] S5. Raise the temperature of the second mixed solution to 280℃~320℃, and then continue the reaction for 1h~3h under a nitrogen atmosphere;

[0013] S6. Stop heating and allow the second mixed solution to cool naturally to room temperature. Add ethanol solution and cyclohexane solution and mix evenly. Then let it stand to obtain precipitated NH4F methanol solution CDs@NaReF4 nanoparticles. Collect the CDs@NaReF4 nanoparticles and wash them to obtain hydrophobic carbon dot-based afterglow luminescent material.

[0014] In some embodiments, in S1, 7 ml to 12 ml of oleic acid and 10 ml to 18 ml of 1-octadecene are added per mole of Re(CH3CO2)3 aqueous solution.

[0015] In some embodiments, in S2, 2 to 5 mg of citrate is added to each milliliter of the first mixed solution.

[0016] In some embodiments, in S3, 0.1 mmol to 0.3 mmol of NaOH methanol solution and 0.12 mmol to 0.18 mmol of NH4F methanol solution are added to each milliliter of the first mixed solution.

[0017] In some embodiments, in step S4, the vacuum treatment step includes connecting a vacuum pump to a double-row tube, which degasses the second mixed solution for 15-20 minutes.

[0018] In some embodiments, in S6, the method of settling includes: centrifuging the second mixed solution in a centrifuge at a speed of 8000 rpm to 12000 rpm for a time of 3 min to 10 min.

[0019] In some embodiments, in step S6, the washing step includes: washing the CDs@NaReF4 nanoparticles sequentially with an ethanol solution and a cyclohexane solution, repeating the process three times, and then dispersing the resulting hydrophobic carbon dot-based afterglow luminescent material in a cyclohexane solution for storage.

[0020] The beneficial effects of the one-step method for preparing oil-soluble carbon dot-based afterglow luminescent materials of the present invention are as follows:

[0021] (1) A one-step method for preparing oil-soluble carbon dot-based afterglow luminescent materials according to the present invention. This method can react with carbon dots in Re(CH3CO2)3 aqueous solution, so that NaReF4 matrix and carbon dots are generated simultaneously and carbon dots are embedded in NaReF4 matrix at the same time, to obtain new materials CDs@NaReF4 nanoparticles with small nanoscale size. This method is easy to operate, has the advantages of low cost, and is suitable for large-scale production and application.

[0022] (2) The method of preparing oil-soluble carbon dot-based afterglow luminescent material in one step of the present invention overcomes the problem that the obtained CDs@NaReF4 particles are nanoscale in size, which is due to the large size of traditional micron-sized CDs@rare earth fluorides that cannot be stably dispersed in the material, resulting in unstable afterglow emission.

[0023] (3) The present invention provides a one-step method for preparing oil-soluble carbon dot-based afterglow luminescent materials. The resulting CDs@NaReF4 particles have a large amount of oleic acid ligands on their surface, which are hydrophobic. This makes the CDs@NaReF4 particles hydrophobic and able to be stably dispersed in organic solutions, thus expanding the application range of CDs@NaReF4 particles and making them no longer limited to aqueous solutions.

[0024] An oil-soluble carbon dot-based afterglow luminescent material is also provided, which is prepared by the one-step method described above. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below:

[0026] Figure 1 This is a scanning electron microscope image of the CDs@NaYF4 composite material synthesized in Experimental Example 1.

[0027] Figure 2 This is a transmission electron microscope (TEM) image of the CDs@NaYF4 composite material synthesized in Experimental Example 1.

[0028] Figure 3 The fluorescence emission spectrum, afterglow excitation / emission spectrum, and afterglow lifetime decay curve of the CDs@NaYF4 composite material synthesized in Example 1 were measured after being dispersed in a cyclohexane solution.

[0029] Figure 4 The images show the CDs@NaYF4 composite material synthesized in Example 1, dispersed in the organic solvents cyclohexane, dichloromethane, and acetic acid, and ultrasonically treated for 30 min, after being exposed to fluorescent light and a 365nm ultraviolet light with the light source and then turned off. Detailed Implementation

[0030] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention have been shown, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0031] The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0032] Example 1

[0033] This embodiment discloses a one-step method for preparing oil-soluble carbon dot-based afterglow luminescent materials, comprising the following steps:

[0034] S1. Add Re(CH3CO2)3 aqueous solution, oleic acid, and 1-octadecene to the container, mix well, and obtain the first mixed solution.

[0035] In the above steps, Re(CH3CO2)3 exhibits good size morphology and monodispersity. Currently, NaReF4 crystals with a size smaller than 50 nm can be obtained through a simple co-precipitation method, and Re(CH3CO2)3 is widely available. This Re(CH3CO2)3 is used to introduce Re... 3+ Ions. Oleic acid and 1-octadecene form a solution that acts as both a reaction solvent and a surfactant. During the reaction, they influence the crystal growth size of the NaReF4 matrix and provide hydrophobic groups.

[0036] S2. Heat the first mixed solution to 120~180℃, preferably 160℃, and react for 0.3~1h, preferably 0.5h, then add citrate and stop heating. 2~5mg of citrate, preferably 4mg, is added per milliliter of the first mixed solution.

[0037] In the above steps, citrate mainly serves as a precursor for carbon dots (CDs).

[0038] S3. After the first mixed solution cools to room temperature, add NaOH methanol solution and NH4F methanol solution, mix well to obtain a second mixed solution, wherein 0.1~0.3 mmol of NaOH methanol solution, preferably 0.2 mmol and 0.12~0.18 mmol of NH4F methanol solution, preferably 0.15 mmol, is added to each milliliter of the first mixed solution;

[0039] In the above steps, the addition of NaOH methanol solution is mainly to introduce Na ions, while the addition of NH4F methanol solution is to introduce F ions.

[0040] S4. Add the second mixed solution to 40~60℃, preferably 50℃, and keep it at this temperature for 0.4~0.6h, preferably 0.5h. Then continue to raise the temperature to 100~110℃, preferably 105℃, and perform vacuum treatment.

[0041] The above steps ensure that all substances can react fully.

[0042] S5. Raise the temperature of the second mixed solution to 280~320°C, preferably 300°C, and then continue the reaction for 1~3 hours, preferably 2 hours, by introducing a nitrogen atmosphere;

[0043] S6. Stop heating and allow the second mixed solution to cool naturally to room temperature. Add ethanol solution and cyclohexane solution for washing. After mixing, let it stand to obtain precipitated NH4F methanol solution CDs@NaReF4 nanoparticles. Collect the CDs@NaReF4 nanoparticles and wash them to obtain oil-soluble carbon dot-based afterglow luminescent material.

[0044] In the above steps, after the reaction is complete, the addition of ethanol solution is mainly to precipitate the CDs@NaReF4 nanoparticles so that they can be separated from the solvent by centrifugation. The addition of cyclohexane solution is mainly to remove unreacted oleic acid and 1-octadecene.

[0045] In this embodiment, in step S4, the vacuum treatment step includes connecting a vacuum pump to a double-row tube, wherein the double-row tube degasses the second mixed solution for 15-20 minutes, preferably 16 minutes.

[0046] In this embodiment, in S6, the method of allowing the mixture to stand after mixing includes: centrifuging the second mixed solution in a centrifuge at a speed of 8000~12000rpm, preferably 10000rpm; and a centrifugation time of 3~10min, preferably 5min.

[0047] In this embodiment, the washing step in S6 includes: washing with ethanol solution and cyclohexane solution in sequence, repeating three times, and dispersing the obtained oil-soluble carbon dot-based afterglow luminescent material in cyclohexane solution for storage.

[0048] The above method is a one-step high-temperature co-precipitation strategy for preparing hydrophobic carbon dot-based afterglow luminescent materials. Under high-temperature conditions, in-situ generated carbon dots are embedded in a rare-earth fluoride (NaReF4) matrix. The resulting CDs@NaReF4 nanocomposite material can be uniformly and stably dispersed in some organic solvents and can emit a long-lifetime green room-temperature afterglow under ultraviolet light excitation.

[0049] The one-step method described above for preparing oil-soluble carbon dot-based afterglow luminescent materials CDs@NaReF4 nanocomposites can be uniformly and stably dispersed in some organic solvents. Under ultraviolet light excitation, they can emit green room-temperature afterglow with a long lifetime. Through the spatial confinement effect of the NaReF4 matrix on the carbon dots, the afterglow emission of carbon dot-based room-temperature afterglow materials under ultraviolet light excitation is realized.

[0050] Test Example 1

[0051] To further illustrate the properties of the material obtained by the method of the present invention, the following experimental example 1 was conducted, specifically including the following steps:

[0052] (1) First, prepare a 50 mL double-necked round-bottom flask, then add 0.4 mmol of Y(CH3CO2)3 solution, 4 mL of oleic acid and 7 mL of 1-octadecene.

[0053] (2) Place the flask in the heating device and heat the mixed solution to 150°C while stirring. After reacting at 150°C for 0.5 h, add 30 mg of magnesium citrate and stop heating.

[0054] (3) After the mixed solution has cooled to room temperature, add 1 mmol of NaOH methanol solution and 1.32 mmol of NH4F methanol solution.

[0055] (4) Raise the temperature of the above mixed solution to 50°C and maintain it at this temperature for 0.5 h.

[0056] (5) Continue to raise the temperature to 110°C and degas under vacuum conditions for 20 minutes using a vacuum pump and double-row tubes.

[0057] (6) Finally, the mixed solution is heated to 310°C and reacted under a nitrogen atmosphere for 1.5 h.

[0058] (7) Stop heating and allow the mixed solution to cool naturally to room temperature before adding ethanol and cyclohexane solutions. Centrifuge (10,000 rpm, 5 min) to obtain precipitated CDs@NaYF4 nanoparticles.

[0059] (8) Wash three more times with ethanol solution and cyclohexane solution, and redisperse the hydrophobic CDs@NaYF4 composite material obtained in the reaction in cyclohexane solution.

[0060] Performance testing:

[0061] The performance of the CDs@NaYF4 composite material obtained in Experimental Example 1 was tested, and the following results were obtained:

[0062] Figure 1 This is a scanning electron microscope (SEM) image of the CDs@NaYF4 composite material synthesized in Example 1. The image shows the morphology and size of the material, exhibiting a spherical shape with raised surfaces, uniform particle size distribution, and an average particle size of approximately 200 nm. It is evident that the CDs@NaYF4 composite material prepared in this invention can achieve nanoscale particle size, enabling better and more stable dispersion in water, thus improving the dispersion stability of the CDs@NaYF4 composite material in applied materials.

[0063] Figure 2The image shown is a transmission electron microscope (TEM) image of the CDs@NaYF4 composite material synthesized in Example 1. The sample morphology and size correspond to the scanning electron microscope (SEM) image, further demonstrating that the size of the CDs@NaYF4 composite material prepared in this invention can reach the nanometer level.

[0064] Figure 3 The images show the fluorescence and afterglow excitation / emission spectra of the CDs@NaYF4 composite material synthesized in Example 1, dispersed in a cyclohexane solution, measured under different excitation wavelengths, as well as the afterglow lifetime decay curves measured at 365 nm excitation and 520 nm emission. The fluorescence emission spectrum shows that the maximum fluorescence emission peak of CDs@NaYF4 is located around 470 nm. The afterglow emission spectra under different excitation wavelengths show that the composite material exhibits bimodal emission, approximately located around 470 nm and 520 nm. A three-exponential fitting of the afterglow lifetime decay curve at 360 nm excitation yields an afterglow lifetime of 530 ms. Therefore, the CDs@NaYF4 composite material prepared in this invention can stably emit afterglow.

[0065] Figure 4 The images show the CDs@NaYF4 composite material synthesized in Example 1 dispersed in the organic solvents cyclohexane, dichloromethane, and acetic acid, and then sonicated for 30 min. The images are then photographed under fluorescent light and a 365nm UV lamp with and without the UV lamp on. A noticeable afterglow phenomenon is observed after the UV lamp is turned off, indicating that the composite material has good stability in organic solvents and can be used in some special environments. Therefore, the CDs@NaYF4 composite material prepared in this invention is hydrophobic.

[0066] The present invention has been illustrated with the above embodiments to explain the detailed method of the present invention. However, the present invention is not limited to the detailed method described above, that is, it does not mean that the present invention must rely on the detailed method described above to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials in the method of the present invention, the addition of auxiliary components, the selection of specific methods, etc., without departing from the principle of the present invention, all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A one-step method for preparing oil-soluble carbon dot-based afterglow luminescent materials, characterized in that, Includes the following steps, S1. Add Re(CH3CO2)3 aqueous solution, oleic acid and 1-octadecene to the container, mix well to obtain the first mixed solution; S2. Heat the first mixed solution to 120℃~180℃, react for 0.3h~1h, then add citrate and stop heating; S3. After cooling the first mixed solution to room temperature, add NaOH methanol solution and NH4F methanol solution, mix well, and obtain the second mixed solution. S4. Add the second mixed solution to 40℃~60℃ and keep it at that temperature for 0.4h~0.6h, then continue to raise the temperature to 100℃~110℃ and perform vacuum treatment; S5. Raise the temperature of the second mixed solution to 280℃~320℃, and then continue the reaction for 1h~3h under a nitrogen atmosphere; S6. Stop heating and allow the second mixed solution to cool naturally to room temperature. Add ethanol solution and cyclohexane solution and mix evenly. Centrifuge the second mixed solution to obtain precipitated CDs@NaReF4 nanoparticles. Collect the CDs@NaReF4 nanoparticles and wash them to obtain hydrophobic carbon dot-based afterglow luminescent material. The Re is Y, and the citrate is magnesium citrate.

2. The method for preparing oil-soluble carbon dot-based afterglow luminescent materials in one step according to claim 1, characterized in that, In S1, 7 ml to 12 ml of oleic acid and 10 ml to 18 ml of 1-octadecene are added to each mole of Re(CH3CO2)3 aqueous solution.

3. The method for preparing oil-soluble carbon dot-based afterglow luminescent materials in one step according to claim 1, characterized in that, In S2, 2-5 mg of citrate is added to each milliliter of the first mixed solution.

4. The method for preparing oil-soluble carbon dot-based afterglow luminescent materials in one step according to claim 1, characterized in that, In S3, 0.1 mmol to 0.3 mmol of NaOH methanol solution and 0.12 mmol to 0.18 mmol of NH4F methanol solution are added to each milliliter of the first mixed solution.

5. The method for preparing oil-soluble carbon dot-based afterglow luminescent materials in one step according to claim 1, characterized in that, In S4, the vacuuming process includes connecting a vacuum pump to a double-row tube, which degasses the second mixed solution for 15-20 minutes.

6. The method for preparing oil-soluble carbon dot-based afterglow luminescent materials in one step according to claim 1, characterized in that, In S6, the centrifugation speed is 8000 rpm to 12000 rpm; the centrifugation time is 3 min to 10 min.

7. The method for preparing oil-soluble carbon dot-based afterglow luminescent materials in one step according to claim 1, characterized in that, In S6, the washing step includes: washing the CDs@NaReF4 nanoparticles sequentially with ethanol solution and cyclohexane solution, repeating the process three times, and then dispersing the resulting hydrophobic carbon dot-based afterglow luminescent material in cyclohexane solution for storage.

8. An oil-soluble carbon dot-based afterglow luminescent material, characterized in that, It is prepared by the one-step method for preparing oil-soluble carbon dot-based afterglow luminescent materials as described in any one of claims 1 to 7.

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