A pH-responsive multicolor room-temperature phosphorescent carbon dot nanoparticle and preparation and application thereof

Abstract

The application discloses a kind of pH response multicolor room temperature phosphorescence carbon dot nanoparticles and preparation, application, the nanoparticles are by acid degradable crystalline calcium carbonate matrix and in situ embedding light-emitting component therein, and light-emitting component is carbon dot or its combination with rhodamine dye.In neutral aqueous phase, the rigidity of matrix limits makes it keep spherical and stable long-life phosphorescence emission;In acidic aqueous phase, matrix dissolution leads to limit removal, light-emitting component is exposed to aqueous quenched, realizes high sensitivity phosphorescence " switch " response.Cascaded fluorescence resonance energy transfer system is constructed by co-embedding dye, and the precise red shift of phosphorescence emission peak between 505 nm and 575 nm is realized.The particle has good morphology and size adjustability, and is suitable for visual detection of tumor and other acidic microenvironment.

Description

Technical Field

[0001] This invention belongs to the field of nanoluminescent functional materials technology, specifically relating to a pH-responsive multicolor room-temperature phosphorescent carbon dot nanoparticle and its controllable preparation and application. Background Technology

[0002] Room-temperature phosphorescent carbon dots (RTP-CDs) have shown significant application value in biomedical imaging, information encryption, and sensing due to their advantages such as long lifetime luminescence, excellent biocompatibility, and low cost. However, the triplet excitons of carbon dots are extremely sensitive to the environment. In aqueous systems, the nonradiative relaxation of water molecules and the quenching effect of dissolved oxygen usually lead to the rapid extinguishing of the room-temperature phosphorescent signal of carbon dots.

[0003] To address the problem of phosphorescence quenching in aqueous phases, various strategies have emerged in existing technologies, mainly including:

[0004] 1. Inert Inorganic Matrix Encapsulation Scheme: Existing technologies often use silica, alumina, zeolite, etc., as confinement media. This scheme isolates external quenching factors through a dense inorganic framework, which significantly improves the stability of carbon dots in an aqueous environment. However, these matrices have extremely high chemical inertness and cannot produce physical or chemical responses to external microenvironmental stimuli such as changes in pH, keeping the phosphorescence signal in a "normally on" state and preventing active sensing.

[0005] 2. Polymer / Organic Small Molecule Confinement Scheme: Some studies utilize polyvinyl alcohol (PVA), polyacrylamide, or cyanuric acid, urea, etc., to stabilize the triplet state of carbon dots through hydrogen bonding networks. However, such organic matrices exhibit poor structural stability in aqueous phases, readily undergoing swelling or dissolution. Furthermore, in complex biofluid environments, it is difficult to precisely control the particle size distribution of composite particles, leading to uncontrollable metabolic behavior of nanoparticles within organisms.

[0006] 3. FRET-based multicolor modulation schemes: To broaden the phosphorescence spectrum, existing techniques attempt to construct fluorescence resonance energy transfer (FRET) systems by simultaneously introducing carbon dots and fluorescent dyes (such as rhodamine and fluorescein) into the matrix. However, such schemes often rely on static embedding environments and are mostly simple two-component transfers, lacking means to achieve multicolor, large-amplitude redshift modulation through cascade effects within a single mineralization system. Furthermore, it is difficult to achieve both multicolor output and environmental responsiveness.

[0007] In summary, while existing technical solutions have made progress in addressing the fundamental issue of "aqueous phase stability," significant technical bottlenecks remain in the integrated design of active environmental response, precise particle size control, and multi-color cascade dynamic regulation.

[0008] Therefore, developing a novel carbon dot composite nanomaterial that combines stable phosphorescence in water phase, specific acidic stimulus response, precise controllable particle size, and cascaded FRET multicolor luminescence modulation is a technical challenge that urgently needs to be solved in the field of nanoluminescent materials. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides pH-responsive multicolor room-temperature phosphorescent carbon dot nanoparticles and a controllable preparation method thereof, constructing nanoparticles capable of achieving high-contrast and sensitive responses to acidic microenvironments. These particles utilize the spatial confinement stabilization of phosphorescence by the CaCO3 matrix at neutral pH, and release this confinement through matrix dissolution in acidic environments, thereby obtaining significant changes in phosphorescent signal, which can be used for the visual detection of acidic targets.

[0010] A pH-responsive multicolor room-temperature phosphorescent carbon dot nanoparticle, the nanoparticle comprising an acid-degradable crystalline calcium carbonate matrix and an in-situ co-mineralized luminescent component embedded in the matrix;

[0011] The luminescent component is a bare carbon dot prepared by pyrolysis of levofloxacin as a carbon source and boric acid as an auxiliary agent, or a combination of the bare carbon dot and a rhodamine-based fluorescent dye.

[0012] The nanoparticles maintain a spherical structure and exhibit room-temperature phosphorescence emission in a pH-neutral aqueous phase. In an acidic aqueous phase, the crystalline calcium carbonate matrix dissolves and degrades, releasing the spatial confinement of the luminescent component and exposing it to the aqueous environment.

[0013] Preferably, when the luminescent component is only bare carbon dots, the average particle size of the nanoparticles formed by the calcium carbonate matrix and the bare carbon dots is 867 nm to 1.56 μm; when the luminescent component is a combination of bare carbon dots and rhodamine-based fluorescent dyes, the average particle size of the nanoparticles formed by the calcium carbonate matrix and the combination is 300 nm to 450 nm.

[0014] Preferably, when the luminescent component is a combination of the bare carbon dots and a rhodamine-based fluorescent dye, the rhodamine-based fluorescent dye is rhodamine 6G, or a combination of rhodamine 6G and rhodamine B.

[0015] The bare carbon dots and the rhodamine-based fluorescent dyes form a fluorescence resonance energy transfer system or a cascaded fluorescence resonance energy transfer system within the crystalline calcium carbonate matrix.

[0016] Preferably, when the luminescent component is only bare carbon dots, the room temperature phosphorescence emission peak of the nanoparticles is located at 505 nm; when the luminescent component is bare carbon dots and rhodamine 6G, the room temperature phosphorescence emission peak of the nanoparticles is located at 560 nm; when the luminescent component is bare carbon dots, rhodamine 6G and rhodamine B, the room temperature phosphorescence emission peak of the nanoparticles is located at 575 nm.

[0017] Preferably, when the pH of the neutral aqueous phase is 7.4, the room temperature phosphorescence lifetime of the nanoparticles under this condition is 383.9 ms; when the pH of the acidic aqueous phase is 5.0, the morphology of the nanoparticles disintegrates under this condition.

[0018] This invention also provides a method for preparing multicolor room-temperature phosphorescent carbon dot nanoparticles as described above, characterized in that it employs a gas-phase diffusion in-situ mineralization method, comprising the following steps:

[0019] S01 Levofloxacin was mixed with boric acid and pyrolyzed at 200°C for 3 hours. The resulting product was dispersed, impurities were removed and dried to obtain bare carbon dot powder.

[0020] S02: The bare carbon dots obtained in step S01 and calcium chloride as a precursor are dispersed together in anhydrous ethanol to form a dispersion; or the bare carbon dots, calcium chloride and rhodamine-based fluorescent dyes are dispersed together in anhydrous ethanol to form a dispersion.

[0021] S03 The container containing the dispersion from step S02 is sealed with porous tin foil and placed together with the container containing solid ammonium bicarbonate in a sealed environment; under the set constant temperature conditions, the gas generated by the volatilization of ammonium bicarbonate enters the dispersion to induce calcium carbonate mineralization growth and in-situ embedding of the luminescent component.

[0022] After the S04 reaction is complete, the precipitate is collected, washed, and dried to obtain the nanoparticles with adjustable particle size.

[0023] Preferably, the particle size of the nanoparticles is controlled within the range of 867 nm to 1.56 μm by adjusting the volume of anhydrous ethanol, the temperature and time of the in-situ mineralization reaction in steps S02 and S03.

[0024] Specifically, the control range is as follows: the volume of anhydrous ethanol is 50-80 mL, the reaction temperature is 45-60℃, and the reaction time is 24-72 h.

[0025] The present invention also provides an application of multicolor room-temperature phosphorescent carbon dot nanoparticles according to any of the above descriptions, characterized in that the nanoparticles are used in the preparation of nanoparticles for detecting...

[0026] Or its application in probes for visualizing acidic microenvironments.

[0027] Preferably, the acidic microenvironment is a tumor acidic microenvironment or a lysosome.

[0028] The above technical solution has the following advantages or beneficial effects:

[0029] 1. This invention uses crystalline CaCO3 as a responsive matrix to provide rigid confinement for stable phosphorescence in a neutral environment; in an acidic environment, the spatial confinement is released by the dissolution of the CaCO3 lattice, allowing the luminescent component to be directly exposed to the aqueous phase for quenching. This "matrix degradation-confinement release" mechanism achieves a highly sensitive acidic phosphorescence "switching" response, suitable for the visual detection of acidic targets such as tumors.

[0030] 2. This invention utilizes a gas-phase diffusion in-situ mineralization process to simultaneously embed carbon dots and dyes into a CaCO3 inorganic framework. Based on the spectral overlap of the two, a micro-region cascaded fluorescence resonance energy transfer (FRET) pathway is constructed, achieving a precise redshift of room-temperature phosphorescence from green to yellow and orange light, providing multidimensional luminescence signals for multi-channel imaging and high-order information encryption.

[0031] 3. This invention effectively intervenes in the nucleation and crystal growth kinetics of CaCO3 by systematically controlling the volume, temperature, and time of ethanol in the gas-phase mineralization system. This method achieves continuous and precise control over nanoparticles composed of a calcium carbonate matrix and bare carbon dots within the range of 867 nm to 1.56 μm, resulting in well-defined and uniform particles that significantly improve the size adaptability of the material in different in vivo delivery scenarios.

[0032] 4. This invention utilizes in-situ mineralization to create a dense interfacial bond between carbon dots and CaCO3, effectively blocking non-radiative quenching of water molecules and dissolved oxygen, thus endowing the material with a long aqueous phosphorescence lifetime of 383.9 ms. Simultaneously, the vapor-phase diffusion preparation process is mild and simple, requiring no complex equipment or post-processing, and possesses good reproducibility and potential for large-scale production. Attached Figure Description

[0033] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention, wherein:

[0034] Figure 1 This is a SEM image of the CDs@CaCO3 prepared in Example 1 of this invention.

[0035] Figure 2 SEM images of CDs@CaCO3 of different sizes prepared in Example 2 of this invention.

[0036] Figure 3This is a SEM image of CDs-R6G@CaCO3 prepared in Example 3 of the present invention.

[0037] Figure 4 This is a SEM image of CDs-R6G-RB@CaCO3 prepared in Example 3 of the present invention.

[0038] Figure 5 This is a SEM image of CDs@CaCO3 particles after degradation under pH 5.0 and pH 7.4 conditions in this invention.

[0039] Figure 6 A comparison of the changes in the room temperature phosphorescence signal of CDs@CaCO3 under different pH conditions in this invention. Detailed Implementation

[0040] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0041] Unless otherwise specified, the chemical reagents used in the embodiments and comparative examples of this invention, such as levofloxacin, boric acid, calcium chloride, anhydrous ethanol, ammonium bicarbonate, rhodamine 6G (R6G), and rhodamine B (RB), are all commercially available analytical grade reagents and can be used directly without further purification; the experimental water is deionized water (or ultrapure water). Morphological characterization was performed using scanning electron microscopy (SEM); spectral and phosphorescence lifetime measurements were performed using a fluorescence spectrophotometer (equipped with a delay test module).

[0042] Example 1

[0043] Step 1: Preparation method of bare room temperature phosphorescent carbon dots (CDs)

[0044] 1. Weigh 0.145 g of levofloxacin and 2.48 g of boric acid, and grind them together in an agate mortar for about 15 minutes until a finely mixed solid powder is obtained.

[0045] 2. Transfer the above mixed powder into a beaker, and then place it in an oven for further pyrolysis and carbonization reaction at 200℃ for 3 h.

[0046] 3. After the reaction product has cooled to room temperature, add an appropriate amount of ultrapure water to fully dissolve and disperse the unreacted substrate and water-soluble product. Then centrifuge at 10,000 rpm for 10 min to remove insoluble impurities at the bottom.

[0047] 4. Collect the supernatant and freeze-dry it to obtain pure carbon dot (CDs) powder.

[0048] Characterization results: The average particle size of the obtained carbon dots is about 3.49 nm. The pure carbon dots exhibit bright blue fluorescence under ultraviolet light excitation and have typical green room temperature phosphorescence characteristics in the solid state. However, when they are dispersed in an aqueous system, their room temperature phosphorescence is completely quenched due to the nonradiative relaxation of water molecules and dissolved oxygen.

[0049] Step 2: Preparation of CDs@CaCO3 green phosphorescent nanoparticles with reference particle size

[0050] 1. Weigh 10 mg of the CDs powder prepared in step one and 150 mg of anhydrous CaCl2, and add them together to a beaker containing 80 mL of anhydrous ethanol. Sonicate for 20 min to ensure complete and uniform dispersion. Seal the mouth of the beaker with aluminum foil containing several tiny pores.

[0051] 2. Take another beaker and place 5 g of ammonium bicarbonate solid. Place both beakers together in a sealed container. Place the sealed container in a constant temperature environment of 45℃. Utilize the ammonia and carbon dioxide generated by the thermal decomposition of ammonium bicarbonate to slowly diffuse in the gas phase, inducing an in-situ mineralization reaction in the system. Maintain the temperature for 72 h.

[0052] 3. After the reaction was completed, the precipitate was collected by centrifugation and washed several times with anhydrous ethanol to remove unencapsulated free carbon dots and unreacted impurities on the surface. After vacuum drying, CDs@CaCO3 nanoparticles were obtained.

[0053] Characterization results: SEM showed that the obtained particles were uniform and regular spherical with an average particle size of about 1.06 μm. In the aqueous system, the composite particles emitted 440 nm fluorescence and 505 nm stable green room temperature phosphorescence. The aqueous phosphorescence lifetime was as high as 383.9 ms, and the dispersibility was excellent.

[0054] Example 2

[0055] The purpose of this Example 2 is to provide a method for preparing CDs@CaCO3 nanoparticles of different particle sizes.

[0056] (1) Preparation of small-diameter CDs@CaCO3 nanoparticles

[0057] The basic steps were the same as in Example 1, except that the kinetics of the in-situ mineralization via gas-phase diffusion were controlled: the solvent was maintained at 80 mL of anhydrous ethanol, but the reaction temperature was increased to 60 °C and the reaction time was shortened to 24 h. Small-diameter CDs@CaCO3 nanoparticles were obtained. Characterization results: The rapid nucleation rate reduced the average particle size to approximately 867 nm, with regular morphology and no agglomeration. The particles also retained stable green room-temperature phosphorescence of 505 nm in the aqueous phase.

[0058] (2) Preparation of medium-sized CDs@CaCO3 nanoparticles

[0059] The basic steps were the same as in Example 1, except that the solvent was adjusted to 50 mL anhydrous ethanol, the reaction temperature was 60℃, and the reaction time was 72 h. Medium-sized CDs@CaCO3 nanoparticles were obtained. Characterization results: The obtained product had an average particle size of approximately 1.2 μm, exhibited a regular spherical shape, and showed stable phosphorescence properties in aqueous phase at room temperature.

[0060] (3) Preparation of large-size CDs@CaCO3 nanoparticles

[0061] The basic steps were the same as in Example 1, except that the solvent was adjusted to 50 mL anhydrous ethanol, the reaction temperature was 45℃, and the reaction time was 48 h. Large-sized CDs@CaCO3 nanoparticles were obtained. Characterization results: The obtained product had an average particle size of approximately 1.56 μm, a complete structure, more complete crystal face growth, and no significant attenuation in room temperature phosphorescence performance in aqueous phase.

[0062] Example 3

[0063] The purpose of this Example 3 is to provide a method for preparing multicolor room-temperature phosphorescent nanoparticles.

[0064] (1) Preparation of yellow room temperature phosphorescent CDs-R6G@CaCO3 nanoparticles

[0065] 1. Weigh 10 mg of CDs prepared in Example 1, 50 mg of Rhodamine 6G (R6G) and 150 mg of CaCl2, add them to 80 mL of anhydrous ethanol, and sonicate to disperse evenly to form a precursor solution containing mixed luminescent components.

[0066] 2. The in-situ mineralization, closed reaction, and post-processing steps are exactly the same as step two of Example 1, with a reaction temperature of 45℃ and a reaction time of 72 h. During this process, CDs and R6G are simultaneously co-crystallized and embedded inside the CaCO3 lattice. After centrifugation, washing, and drying, yellow phosphorescent nanoparticles are obtained.

[0067] Characterization results: SEM showed that the product had an average particle size of approximately 387 nm and a uniform morphology. Spectroscopic analysis revealed that the room-temperature phosphorescence emission peak of the composite particles was red-shifted to 560 nm, exhibiting bright yellow phosphorescence. This phenomenon confirms the successful construction of a highly efficient fluorescence resonance energy transfer (FRET) pathway from CDs (donors) to R6G (acceptors) within the crystal lattice, while preserving complete acid pH responsiveness.

[0068] (2) Preparation of orange room temperature phosphorescent CDs-R6G-RB@CaCO3 nanoparticles

[0069] 1. Weigh 10 mg of CDs prepared in Example 1, 50 mg of Rhodamine 6G (R6G), 100 mg of Rhodamine B (RB) and 150 mg of CaCl2, add them to 80 mL of anhydrous ethanol and ultrasonically disperse them evenly.

[0070] 2. The in-situ mineralization, closed reaction, and post-treatment steps are exactly the same as step two of Example 1, with a reaction temperature of 45℃ and a reaction time of 72 h. After centrifugation, washing, and drying, orange phosphorescent nanoparticles are obtained.

[0071] Characterization results: The average particle size is approximately 332 nm. Elemental mapping shows a uniform distribution of nitrogen, proving that CDs and dyes are perfectly and synchronously embedded in multiple components. The room-temperature phosphorescence emission peak further red-shifts to 575 nm, exhibiting orange phosphorescence, demonstrating the successful realization of the complex stepwise cascade FRET process of CDs-R6G-RB in a highly crystalline CaCO3 matrix, with stable acid-responsive degradation performance.

[0072] Example 4

[0073] The purpose of this Example 4 is to provide verification of the pH response performance and signal "switching" of CDs@CaCO3 nanoparticles.

[0074] 1. The CDs@CaCO3 nanoparticles prepared in Example 1 were dispersed in neutral buffer solution (pH 7.4, simulating a normal physiological environment) and acidic buffer solution (pH 5.0, simulating the acidic microenvironment of tumor tissue or lysosomes), respectively. After incubation in a constant temperature shaker at 37°C for 2 hours, samples were taken for SEM morphology characterization and room temperature phosphorescence signal detection.

[0075] The results showed that under pH 7.4 conditions, all composite particles maintained their complete spherical structure without obvious signs of degradation. The sample from Example 1 stably emitted strong room-temperature phosphorescence.

[0076] Under acidic conditions of pH 5.0, the CaCO3 matrix of the composite particles undergoes rapid and complete degradation, and the original regular spherical particle structure in the SEM field of view completely disappears. At this point, the embedded bare carbon dots (and dye) are directly released into the aqueous system. Since the bare carbon dots are easily quenched by water molecules and dissolved oxygen in the aqueous phase through non-radiative quenching, the detection results show that the room temperature phosphorescence signal intensity of each sample exhibits a precipitous drop, almost completely quenched.

[0077] Conclusion: This invention is a "highly sensitive and fast acid-responsive phosphorescent OFF switch" with extremely high signal contrast. This characteristic effectively overcomes the shortcomings of traditional fluorescent / phosphorescent probes that are easily interfered with by background signals in vivo, providing an excellent material basis for the visual and precise diagnosis of targeted specific acidic microenvironments (such as tumors).

[0078] Comparative Example 1

[0079] Comparative Example 1 uses silica (SiO2), a conventional inert matrix in the art, for encapsulation.

[0080] 10 mg of CDs and 50 mg of R6G were dispersed in a mixture of ethanol and deionized water. A suitable amount of ammonia was added as a catalyst, and tetraethyl orthosilicate (TEOS) was slowly added dropwise. The mixture was hydrolyzed and polycondensed at room temperature for 12 h. After centrifugation and washing, CDs-R6G@SiO2 particles were obtained.

[0081] Characterization results comparison: Although the product of Comparative Example 1 can also achieve multicolor luminescence based on FRET, when it is incubated in an acidic buffer solution with pH 5.0, the particle morphology does not change and the phosphorescence signal is not quenched. It completely loses the "acidic microenvironment stimulus-responsive signal switch" function described in this invention, which proves that the present invention has achieved an unexpected intelligent response effect by selecting an acidic and degradable crystalline CaCO3 matrix.

[0082] Comparative Example 2

[0083] Comparative Example 2 was prepared using a simple physical mixing method.

[0084] Purchase commercially available micron-sized calcium carbonate powder, mix it with CDs solution and R6G solution, soak it, and then remove the solvent by rotary evaporation to obtain solid powder.

[0085] Characterization results comparison: When this physical mixture was dispersed in water, tests revealed a very low phosphorescence signal at room temperature, and no FRET phenomenon with a redshift to 560 nm was observed. This indicates that physical adsorption alone cannot allow the luminescent component to enter the matrix for spatial confinement protection, nor can it shorten the spatial distance between the dye and the carbon dots to achieve FRET.

[0086] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A pH-responsive multicolor room-temperature phosphorescent carbon dot nanoparticle, characterized in that, The nanoparticles comprise an acidic, biodegradable crystalline calcium carbonate matrix, and a luminescent component in situ co-mineralized and embedded within the matrix. The luminescent component is a bare carbon dot prepared by pyrolysis of levofloxacin as a carbon source and boric acid as an auxiliary agent, or a combination of the bare carbon dot and a rhodamine-based fluorescent dye. The nanoparticles maintain a spherical structure and exhibit room-temperature phosphorescence emission in a pH-neutral aqueous phase. In an acidic aqueous phase, the crystalline calcium carbonate matrix dissolves and degrades, releasing the spatial confinement of the luminescent component and exposing it to the aqueous environment.

2. The multicolor room-temperature phosphorescent carbon dot nanoparticles according to claim 1, characterized in that, When the luminescent component is a combination of the bare carbon dots and a rhodamine-based fluorescent dye, the rhodamine-based fluorescent dye is rhodamine 6G, or a combination of rhodamine 6G and rhodamine B. The bare carbon dots and the rhodamine-based fluorescent dyes form a fluorescence resonance energy transfer system or a cascaded fluorescence resonance energy transfer system within the crystalline calcium carbonate matrix.

3. The multicolor room-temperature phosphorescent carbon dot nanoparticles according to claim 1, characterized in that, When the luminescent component is only bare carbon dots, the average particle size of the nanoparticles formed by the calcium carbonate matrix and the bare carbon dots is 867 nm to 1.56 μm; when the luminescent component is a combination of bare carbon dots and rhodamine-based fluorescent dyes, the average particle size of the nanoparticles formed by the calcium carbonate matrix and the combination is 300 nm to 450 nm.

4. The multicolor room-temperature phosphorescent carbon dot nanoparticles according to claim 1 or 2, characterized in that, When the luminescent component is only bare carbon dots, the room temperature phosphorescence emission peak of the nanoparticles is located at 505 nm; when the luminescent component is bare carbon dots and rhodamine 6G, the room temperature phosphorescence emission peak of the nanoparticles is located at 560 nm; when the luminescent component is bare carbon dots, rhodamine 6G and rhodamine B, the room temperature phosphorescence emission peak of the nanoparticles is located at 575 nm.

5. The multicolor room-temperature phosphorescent carbon dot nanoparticles according to claim 1, characterized in that, When the pH of the neutral aqueous phase is 7.4, the room temperature phosphorescence lifetime of the nanoparticles under this condition is 383.9 ms; when the pH of the acidic aqueous phase is 5.0, the morphology of the nanoparticles disintegrates under this condition.

6. A method for preparing multicolor room-temperature phosphorescent carbon dot nanoparticles according to any one of claims 1-4, characterized in that, The gas-phase diffusion in-situ mineralization method includes the following steps: S01 Levofloxacin was mixed with boric acid and pyrolyzed at 200°C for 3 hours. The resulting product was dispersed, impurities were removed and dried to obtain bare carbon dot powder. S02: The bare carbon dots obtained in step S01 and calcium chloride as a precursor are dispersed together in anhydrous ethanol to form a dispersion; or the bare carbon dots, calcium chloride and rhodamine-based fluorescent dyes are dispersed together in anhydrous ethanol to form a dispersion. S03 The container containing the dispersion from step S02 is sealed with porous tin foil and placed together with the container containing solid ammonium bicarbonate in a sealed environment; under the set constant temperature conditions, the gas generated by the volatilization of ammonium bicarbonate enters the dispersion to induce calcium carbonate mineralization growth and in-situ embedding of the luminescent component. After the S04 reaction is complete, the precipitate is collected, washed, and dried to obtain the nanoparticles with adjustable particle size.

7. The preparation method according to claim 6, characterized in that, By adjusting the volume of anhydrous ethanol, the temperature and time of the in-situ mineralization reaction in steps S02 and S03, the particle size of nanoparticles can be controlled within the range of 867 nm to 1.56 μm. Specifically, the control range is as follows: the volume of anhydrous ethanol is 50-80 mL, the reaction temperature is 45-60℃, and the reaction time is 24-72 h.

8. The application of the multicolor room-temperature phosphorescent carbon dot nanoparticles according to any one of claims 1-5, characterized in that, Application of the nanoparticles in the preparation of probes for detecting or visualizing acidic microenvironments.

9. The application according to claim 8, characterized in that, The acidic microenvironment is either the tumor acidic microenvironment or the lysosomal acidic environment.

Images