Ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots and preparation method and application thereof

Abstract

The invention discloses an ultra-long-time near-infrared water-soluble afterglow luminescent carbon dot and a preparation method and application thereof, and belongs to the field of fluorescent carbon nanomaterials. The preparation method of the near-infrared water-soluble afterglow luminescent carbon dot comprises: (1) crushing plant stems and leaves, soaking them in an organic solvent for 1-48 hours, and obtaining a plant stem and leaf soaking liquid; (2) filtering the plant stem and leaf soaking liquid, and heat-treating it at 20-200°C for 1-24 hours to obtain a carbon dot solution; (3) using dichloromethane as a drainage agent to chromatograph the carbon dot solution, collecting the first chromatographically obtained green solution, and obtaining a dichloromethane solution of the carbon dots; (4) adding polyether F127 to the dichloromethane solution of the carbon dots, stirring, and then adding water for ultrasonic emulsification, continuing to stir and heating to 20-70°C for reaction for 1-6 hours, and obtaining a carbon dot aqueous solution, and freeze-drying to obtain an ultra-long-time near-infrared water-soluble afterglow luminescent carbon dot, wherein the carbon dot exhibits a near-infrared afterglow luminescence with a life span of more than 4 hours in the aqueous solution.

Description

Technical Field

[0001] The present invention belongs to the field of fluorescent carbon nanomaterials, relates to the technical field of preparation of fluorescent carbon quantum dots, and in particular to an ultra-long time near-infrared water-soluble afterglow luminescent carbon dot and a preparation method and application thereof. Background Art

[0002] Afterglow, also known as persistent luminescence, is a long-lived emission in which the phosphor can slowly convert the stored metastable energy into photons with different energies after the cessation of additional photoexcitation. This unique luminescence ability endows afterglow materials with good application potential in data storage, optoelectronic devices, chemical sensors, and bioimaging. In particular, in bioimaging technology, long-wavelength emission afterglow bioimaging has good signal-to-noise ratio and large tissue penetration depth due to the absence of interference from excitation light and tissue autofluorescence. However, the currently used afterglow luminescent materials, such as inorganic metal-doped nanoparticles, have multiple limitations, such as cumbersome preparation, potential cytotoxicity, low solubility, and high cost, which seriously hinder their practical application prospects in various bioimaging fields, such as image-guided surgery, early diagnosis of inflammation, and ultrasensitive detection of cancer cells. Therefore, it is of great significance to develop new long afterglow materials and gain a deep understanding of their luminescence properties or mechanisms.

[0003] As a carbon-based luminescent nanomaterial with tunable wavelength, high physicochemical inertness, low biological toxicity and easy preparation, carbon dots have attracted extensive research interest in the fields of bioimaging, information encryption, and light-emitting devices. However, to date, most carbon dot-based afterglow emissions are usually confined to the green region, and in a physiological water environment, the afterglow luminescence is easily affected by dissolved oxygen and quenched. So far, although afterglow related to red and near-infrared (NIR) aqueous solutions has been reported, their afterglow lifetimes are mostly less than 1 second. Such a short afterglow time seriously limits its clinical application in the field of bioimaging. In this case, it is still a huge challenge to develop afterglow carbon dots with both near-infrared emission and ultra-long aqueous solution lifetime. Summary of the invention

[0004] To solve the above technical problems, the present invention provides an ultra-long time near-infrared water-soluble afterglow luminescent carbon dots and a preparation method and application thereof. The preparation method is simple and easy, and the raw materials, plant stems and leaves, are abundant in resources, cheap and easy to obtain.

[0005] The present invention is specifically achieved through the following technical solutions:

[0006] A method for preparing ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots comprises the following steps:

[0007] (1) After crushing the plant stems and leaves, soak them in an organic solvent for 1-48 hours to obtain a plant stem and leaf soaking liquid.

[0008] (2) The plant stem and leaf soaking liquid obtained in step (1) is filtered and then heat treated at 20-200° C. for 1-24 h to obtain a carbon dot solution.

[0009] (3) Using dichloromethane as a drainage agent, the carbon dot solution of step (2) is chromatographed by column chromatography, and the green solution first chromatographed out is collected to obtain a dichloromethane solution of carbon dots; dichloromethane is highly volatile and can be quickly evaporated in the next step of water-soluble treatment.

[0010] (4) Adding polyether F127 to the dichloromethane solution of the carbon dots in step (3), stirring to coat the carbon dots in the polyether F127, then adding water for ultrasonic emulsification, continuing to stir and heating to 20-70°C for reaction for 1-6 hours, removing excess dichloromethane, dissolving the carbon dots in water, and obtaining a carbon dot aqueous solution, which is freeze-dried to obtain ultra-long near-infrared water-soluble afterglow luminescent carbon dots.

[0011] In the step (1), the mass volume ratio of plant stems and leaves to the organic solvent is 1:(10-100).

[0012] The plant stems and leaves in step (1) are fresh plant stems or leaves.

[0013] The organic solvent in step (1) is any one of ethanol, methanol, ethyl acetate, acetone, toluene, dichloromethane, petroleum ether or N,N-dimethylformamide.

[0014] In the step (3), the concentration of carbon dots in the dichloromethane solution of carbon dots is 50 mg / L-5000 mg / L.

[0015] In the step (4), the concentration of polyether F127 in the dichloromethane solution of carbon dots is 1 g / L-10 g / L.

[0016] In the step (4), the volume ratio of water to the dichloromethane solution of carbon dots is 5:(1-25).

[0017] The present invention also includes ultra-long time near-infrared water-soluble afterglow luminescent carbon dots prepared by the above method.

[0018] The present invention also includes the application of the ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots in biological imaging.

[0019] The present invention also includes the application of the ultra-long near-infrared water-soluble afterglow luminescent carbon dots in tumor imaging.

[0020] The near-infrared long afterglow luminescence of the carbon dots of the present invention has an oxidative afterglow luminescence mechanism, in which the chemical energy in the reaction process is transferred to the carbon dots themselves to activate their luminescence, and the fluorescence of the carbon dots themselves is near-infrared luminescence. Therefore, the luminescence of the carbon dots stimulated by chemical energy is also near-infrared luminescence, and its luminescence center is consistent with the fluorescence of the carbon dots.

[0021] Beneficial effects of the present invention:

[0022] 1. The preparation method provided by the present invention is simple and easy, and the raw material plant stems and leaves are abundant, cheap and easy to obtain. The ultra-long near-infrared water-soluble afterglow luminescent carbon dots can exhibit near-infrared afterglow luminescence with a lifetime of more than 4 hours in aqueous solution, which can be applied to biological imaging and ultra-long-term clinical surgical imaging guidance, and has a certain reference value for broadening the clinical application of carbon dots in the field of biological imaging.

[0023] 2. The lifetime of the near-infrared water-soluble afterglow luminescence achieved in the present invention exceeds 4 hours, which is due to the new afterglow luminescence mechanism and the characteristics of the carbon nanomaterial itself. In the present invention, the afterglow luminescence of the carbon dots comes from the oxidation afterglow luminescence, and its luminescence is activated by the chemical energy released by the breaking of high-energy chemical bonds produced by the continuous oxidation of the carbon dots. Therefore, its luminescence is affected by the oxidation process of the carbon dots themselves. Compared with the traditional triplet afterglow luminescence, its luminescence mechanism enables it to have a longer afterglow luminescence lifetime. Secondly, compared with small molecule materials, the high degree of polymerization of the carbon dots themselves gives it a higher steric hindrance effect, slowing down the oxidation process of the carbon dots, so that the carbon dots are slowly oxidized, thereby having a longer afterglow luminescence lifetime. Therefore, the present invention achieves an ultra-long near-infrared water-soluble afterglow luminescence with a lifetime of more than 4 hours, which provides a new research idea for exploring new long-term afterglow luminescent materials and applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 This is a transmission electron microscopy image of the carbon dots prepared in Example 1.

[0026] Figure 2 This is the fluorescence excitation-emission spectrum of the carbon dots prepared in Example 1.

[0027] Figure 3 This is the afterglow emission spectrum of the carbon dots prepared in Example 1.

[0028] Figure 4This is a transmission electron microscopy image of the carbon dots in Example 1 after being coated with polyether F127.

[0029] Figure 5 This is the afterglow luminescence lifetime diagram of the carbon dots in Example 1 after being coated with polyether F127.

[0030] Figure 6 This is a photo of the tumor imaging of mice after injection of the carbon dot aqueous solution in Example 1.

[0031] Figure 7 This is a photo of the tumor imaging of mice after injection of the carbon dot aqueous solution in Example 2. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are conventional methods.

[0034] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0035] The concentrations of the reagents used in the embodiments of the present invention are all analytically pure, and the water used is deionized water.

[0036] Example 1

[0037] This embodiment provides a method for preparing ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots, comprising the following steps:

[0038] (1) The stems of the Chinese herbal medicine Solanum nigrum were used as raw materials, crushed, and soaked in ethanol for 1 hour to obtain a Solanum nigrum stem soaking liquid, wherein the mass volume ratio of the Solanum nigrum stem to the ethanol was 1:10.

[0039] (2) The Solanum nigrum stem soaking liquid was filtered and transferred into a polytetrafluoroethylene reactor, and heat-treated at 140 degrees Celsius for 4 hours to obtain a carbon dot solution.

[0040] (3) Using dichloromethane as a drainage agent, the carbon dot solution was chromatographed by column chromatography, and the green solution that was first chromatographed was collected to obtain a dichloromethane solution of carbon dots, wherein the concentration of the carbon dots was 3 mg / mL.

[0041] (4) Take 20 mL of the dichloromethane solution of the above carbon dots, add 20 mg of polyether F127 thereto, and stir to coat the carbon dots in the polyether F127; add 20 mL of water to the solution, perform ultrasonic emulsification, continue stirring and heat to 70 °C for 1 hour, remove excess dichloromethane, dissolve the carbon dots in water, and obtain a carbon dot aqueous solution; freeze-dry the carbon dot aqueous solution to obtain powdered ultra-long near-infrared water-soluble afterglow luminescent carbon dots.

[0042] Figure 1 3 is a transmission electron microscope image of the carbon dots prepared in this example. It can be seen that the synthesized carbon dots are evenly dispersed and have an average size of 5.6 nanometers.

[0043] Figure 2 : is the fluorescence excitation-emission spectrum of the carbon dots prepared in this example. It can be seen that the fluorescence emission center of the carbon dots is at 670 nanometers.

[0044] Figure 3 This is the afterglow emission spectrum of the carbon dots prepared in this example. It can be seen that the carbon dots show obvious afterglow luminescence signals, and the afterglow luminescence wavelength is 670 nanometers, which is in the near-infrared luminescence band.

[0045] Figure 4 3 is a transmission electron microscope image of the carbon dots after being coated with polyether F127 in this embodiment. It can be seen that the carbon dots are well coated with polyether F127 and the overall size is about 87.8 nanometers.

[0046] Figure 5 2 is a graph of the afterglow lifetime of the carbon dots after being coated with polyether F127 in this embodiment. It can be seen that the carbon dots after being coated with polyether F127 exhibit an extremely long afterglow lifetime of about 4.6 hours.

[0047] Example 2

[0048] This embodiment provides a method for preparing ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots, which is basically the same as the steps in Example 1, except that: in step (1), the stems of the Chinese herbal medicine Solanum nigrum are replaced with cabbage leaves, which are soaked in ethanol to obtain a cabbage leaf soaking liquid; in step (2), the cabbage leaf soaking liquid of step (1) is heat-treated at 80° C. for 8 hours to obtain a carbon dot solution. Finally, ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots are obtained.

[0049] Example 3

[0050] This embodiment provides a method for preparing ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots, which is basically the same as the steps in Example 1, except that: in step (1), the stems of the Chinese herbal medicine Solanum nigrum are replaced with cabbage leaves, which are soaked in methanol for 20 hours to obtain a cabbage leaf soaking liquid, wherein the mass volume ratio of cabbage leaves to methanol is 1:20; in step (2), the cabbage leaf soaking liquid of step (1) is heat-treated at 20° C. for 24 hours to obtain a carbon dot solution. Finally, ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots are obtained.

[0051] Example 4

[0052] This embodiment provides a method for preparing ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots, which is basically the same as the steps of embodiment 1, except that: in step (1), the stems of the Chinese herbal medicine Solanum nigrum are replaced with peony leaves, which are soaked in ethyl acetate for 48 hours to obtain a peony leaf soaking solution, wherein the mass volume ratio of peony leaves to ethyl acetate is 1:100; in step (2), the peony leaf soaking solution of step (1) is heat-treated at 200°C for 1 hour to obtain a carbon dot solution. Finally, ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots are obtained.

[0053] Example 5

[0054] This embodiment provides a method for preparing ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots, which is basically the same as the steps in Example 1, except that: in step (1), the stems of the Chinese herbal medicine Solanum nigrum are replaced with chrysanthemum stems, which are soaked in acetone to obtain a chrysanthemum stem soaking liquid; in step (3), the concentration of carbon dots in the dichloromethane solution of carbon dots is 5 mg / mL; in step (4), the amount of polyether F127 added is 100 mg, the amount of water added is 4 mL, and the mixture is continuously stirred and heated to 20° C. for 6 hours. Finally, ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots are obtained.

[0055] Example 6

[0056] This embodiment provides a method for preparing ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots, which is basically the same as the steps of embodiment 1, except that: in step (1), the stems of the Chinese herbal medicine Solanum nigrum are replaced with Nepeta tenuifolia leaves, which are soaked in toluene to obtain Nepeta tenuifolia soaking liquid; in step (3), the concentration of carbon dots in the dichloromethane solution of carbon dots is 0.05 mg / mL; in step (4), the amount of polyether F127 added is 200 mg, the amount of water added is 100 mL, and the mixture is continuously stirred and heated to 40° C. for reaction for 5 hours. Finally, ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots are obtained.

[0057] Example 7

[0058] This embodiment provides a method for preparing ultra-long-lasting near-infrared water-soluble afterglow luminescent carbon dots, which is basically the same as the steps in Example 1, except that: in step (1), the stems of the Chinese herbal medicine Solanum nigrum are replaced with mint leaves, which are soaked in N,N-dimethylformamide to obtain a mint leaf soaking liquid. Finally, ultra-long-lasting near-infrared water-soluble afterglow luminescent carbon dots are obtained.

[0059] Implementation effect example 1

[0060] The ultra-long near-infrared water-soluble afterglow luminescent carbon dots prepared in Example 1 are applied to tumor imaging, comprising the following steps:

[0061] (1) dissolving the ultra-long near-infrared water-soluble afterglow luminescent carbon dots in water to prepare a carbon dot aqueous solution with a concentration of 300 mg / L;

[0062] (2) The carbon dot aqueous solution prepared in step (1) was injected into the tumor site of the mouse by subcutaneous injection. After 5 minutes of light treatment, long afterglow imaging was performed on the tumor site of the mouse.

[0063] Figure 6 This is a tumor imaging photo of mice after injection of the carbon dot aqueous solution in this implementation example. It can be seen that the carbon dots emit obvious afterglow luminescence signals after being injected into the tumor site of the mouse, and long-term afterglow luminescence imaging of the mouse tumor can be performed.

[0064] Embodiment Effect 2

[0065] The ultra-long near-infrared water-soluble afterglow luminescent carbon dots prepared in Example 1 are applied to tumor imaging, comprising the following steps:

[0066] (1) Dissolving the ultra-long near-infrared water-soluble afterglow luminescent carbon dots in water to prepare a carbon dot aqueous solution with a concentration of 300 mg / L;

[0067] (2) The carbon dot aqueous solution prepared in step (1) was injected into the tumor site of the mouse via tail vein injection. After 1 minute of light treatment, long afterglow imaging of the tumor site of the mouse was performed.

[0068] Figure 7 This is a tumor imaging photo of mice after injection of carbon dot aqueous solution in this implementation example. It can be seen that the carbon dots emitted obvious afterglow luminescence signals at the tumor site 24 hours after being injected into the mouse's body by the tail vein, and long-term afterglow luminescence imaging of mouse tumors can be performed.

[0069] 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, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultra-long near-infrared water-soluble afterglow luminescent carbon dot, characterized in that: The afterglow luminescence of the ultra-long near-infrared water-soluble afterglow luminescent carbon dots comes from the oxidation afterglow luminescence, which is activated by the chemical energy released by the breaking of high-energy chemical bonds generated by the continuous oxidation of the carbon dots, and the afterglow luminescence lifetime exceeds 4 hours; The preparation method comprises the following steps: (1) crushing fresh plant stems and leaves, and soaking them in an organic solvent for 1-48 hours to obtain a plant stem and leaf soaking liquid; (2) filtering the plant stem and leaf soaking liquid obtained in step (1) and heat treating the solution at 20-200° C. for 1-24 h to obtain a carbon dot solution; (3) using dichloromethane as a drainage agent, the carbon dot solution of step (2) is chromatographed, and the green solution first chromatographed out is collected to obtain a dichloromethane solution of carbon dots; (4) Adding polyether F127 to the dichloromethane solution of carbon dots in step (3), stirring, adding water for ultrasonic emulsification, and then continuing to stir and heating to 20-70° C. for reaction for 1-6 hours to obtain a carbon dot aqueous solution, and freeze-drying to obtain ultra-long near-infrared water-soluble afterglow luminescent carbon dots; The plant stems and leaves in step (1) are stems of the Chinese herbal medicine Solanum nigrum.

2. The ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots according to claim 1, characterized in that: In the step (1), the mass volume ratio of plant stems and leaves to the organic solvent is 1:(10-100).

3. The ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots according to claim 1, characterized in that: The organic solvent in step (1) is any one of ethanol, methanol, ethyl acetate, acetone, toluene, dichloromethane, petroleum ether or N,N-dimethylformamide.

4. The ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots according to claim 1, characterized in that: In the step (3), the concentration of carbon dots in the dichloromethane solution of carbon dots is 50 mg / L-5000 mg / L.

5. The ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots according to claim 1, characterized in that: In the step (4), the concentration of polyether F127 in the dichloromethane solution of carbon dots is 1 g / L-10 g / L.

6. The ultra-long-time near-infrared water-soluble afterglow luminescent carbon dots according to claim 1, characterized in that: In the step (4), the volume ratio of water to the dichloromethane solution of carbon dots is 5:(1-25).

7. Application of the ultra-long near-infrared water-soluble afterglow luminescent carbon dots described in claim 1 in biological imaging.

8. Use of the ultra-long near-infrared water-soluble afterglow luminescent carbon dots described in claim 1 in the preparation of tumor imaging agents.

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