An amphiphilic solid red fluorescent carbon quantum dot containing photosynthetic pigments, and a preparation method and application thereof

Abstract

The application relates to a kind of amphiphilic solid red fluorescent carbon quantum dots containing photosynthetic pigment and a preparation method and application thereof.A kind of amphiphilic solid red fluorescent carbon quantum dots, characterized in that, by photosynthetic pigment-rich extract as only or main carbon source, nitrogen source and fluorescent chromophore precursor is formed by polymeric carbonization;The carbon quantum dots have amphiphilicity, can be dispersed in aqueous phase and organic solvent phase simultaneously and keep red fluorescence;Under the action of excitation light, its red fluorescent emission wavelength is located in the range of 580-730 nm;And the carbon quantum dots are low in mammalian, cell toxicity, and good in biocompatibility.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and fluorescent materials technology, specifically relating to an amphiphilic, solid, red fluorescent carbon quantum dots prepared by bottom-up polymerization and carbonization of a material containing photosynthetic pigments as a carbon source, nitrogen source and fluorescent chromophore precursor, and its application in the preparation of bioimaging reagents, fingerprint developers, fluorescent anti-counterfeiting films, antioxidants or metal ion detection reagents. Background Technology

[0002] Fluorescent carbon quantum dots (CQDs) are carbon-based nanomaterials typically smaller than 10 nm in size. They possess excellent optical properties, good biocompatibility, low toxicity, and ease of functionalization, showing broad application prospects in fields such as bioimaging, fluorescent anti-counterfeiting, antioxidants, and heavy metal ion detection. Currently, most reported CQDs emit light in the blue to green spectral region (400-550 nm). However, longer wavelength fluorescence, particularly red fluorescence (600-700 nm), offers significant advantages in biomedical applications, such as deeper tissue penetration, lower autofluorescence background interference, and less photodamage. Existing methods for preparing red fluorescent CQDs often rely on expensive organic precursors containing aromatic structures or specific heteroatoms (such as citric acid and aromatic amines), or require complex post-modification or doping of the synthesized CQDs. These methods typically suffer from high cost, cumbersome procedures, or the use of toxic reagents, limiting their large-scale production and practical biological applications. In addition, most reported low-toxicity red fluorescent carbon quantum dots only emit light in organic phases and are prone to fluorescence quenching in aqueous, solid, or aggregated states. Furthermore, they often only possess a single hydrophilic or hydrophobic property, which limits their application in multiphase systems (such as biofilms and oil-water interfaces) and solid-state optoelectronic devices.

[0003] Photosynthetic pigments (such as chlorophyll and phycobilins) are widely distributed in nature. Their molecular structures are rich in conjugated pyrrole rings and various functional groups, making them ideal green carbon and nitrogen sources for the preparation of red fluorescent carbon quantum dots. However, there are currently no reports of preparing carbon quantum dots with low toxicity, amphiphilicity, and solid-state red fluorescence emission through bottom-up polymerization carbonization using materials containing photosynthetic pigments as the sole or main carbon, nitrogen, and precursors.

[0004] Therefore, developing green, efficient, and stable red fluorescent carbon quantum dots is of great value. A simple, mild, low-cost, environmentally friendly, easily scalable, amphiphilic, and stable red fluorescent solid-state carbon quantum dot preparation method is of great significance for promoting its practical application. Summary of the Invention

[0005] The primary objective of this invention is to provide a simple, low-cost, environmentally friendly, and easily scalable preparation method. Using materials rich in photosynthetic pigments as raw materials, low-toxicity, amphiphilic carbon quantum dots that emit red fluorescence in the solid state are prepared through bottom-up polymerization and carbonization. This invention provides red fluorescent solid carbon quantum dots prepared by the above method. These carbon quantum dots exhibit both hydrophilic and lipophilic properties, with red fluorescence emission wavelengths in the range of 580-730 nm. Furthermore, the solid-state fluorescence is stable and exhibits no aggregation quenching phenomenon. The application of the above-mentioned carbon quantum dots in bioimaging reagents, fingerprint developers, fluorescent anti-counterfeiting films, antioxidants, or metal ion detection reagents is also proposed.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: Firstly, the present invention provides a solid fluorescent carbon quantum dot, characterized in that it is formed by carbonization of a carbon source, a nitrogen source, and a fluorescent chromophore precursor rich in photosynthetic pigment extracts; the carbon quantum dot is amphiphilic and can be simultaneously dispersed in aqueous phase and various organic solvents; under ultraviolet or visible light excitation, its red fluorescence emission wavelength is in the range of 580-730 nm, with at least one emission peak in the 580 nm to 680 nm band; and it exhibits low toxicity to mammals and cells, and good biocompatibility.

[0007] Preferably, the extract rich in photosynthetic pigments includes, but is not limited to, one or more of plants and algae.

[0008] More preferably, the photosynthetic pigment-rich extract includes, but is not limited to, portions of plants and algae containing chlorophyll and phycobilins.

[0009] Preferably, the red fluorescence emission wavelength of the carbon quantum dots is in the range of 580-730 nm.

[0010] Preferably, the average particle size of the carbon quantum dots is 2-8 nm, more preferably 2-6 nm.

[0011] Preferably, the carbon quantum dots maintain stable red fluorescence in the solid state.

[0012] Secondly, the present invention provides a method for preparing the above-mentioned amphiphilic red fluorescent solid carbon quantum dots, comprising the following steps: S1 precursor preparation: Wash and crush plant, algae and photosynthetic bacteria materials rich in photosynthetic pigments, extract them with solvent, separate and concentrate the extract to obtain an extract rich in photosynthetic pigments. S2 Carbon Quantum Dot Synthesis: The extract rich in photosynthetic pigments obtained in step (1) is mixed with a solvent, transferred to a reaction vessel, and subjected to a solvothermal or hydrothermal reaction at 140-240℃ for 2-16 hours. S3 Purification and Acquisition: The reaction solution obtained in step (2) is centrifuged and filtered to remove large particulate impurities, then purified by dialysis or column chromatography, and finally freeze-dried to obtain solid carbon quantum dot products.

[0013] Preferably, the extraction solvent in step (1) is one or more of water, ethanol, acetone, N,N-dimethylformamide (DMF), and ethylene glycol.

[0014] Preferably, the reaction solvent in step (2) is water, ethanol, ethylene glycol, DMF or a mixture thereof with water.

[0015] More preferably, the reaction temperature in step (2) is 160-220°C and the reaction time is 4-12 hours.

[0016] Thirdly, regarding the applications, the present invention provides the application of the carbon quantum dots in bioimaging reagents, fingerprint developing agents, fluorescent anti-counterfeiting films, antioxidants, or metal ion detection reagents.

[0017] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: Green and low-cost raw materials: It uses natural, renewable plant and algal extracts containing photosynthetic pigments as raw materials, which are widely available, environmentally friendly, and significantly cheaper than traditional synthetic organic precursors. Bottom-up polymerization and carbonization synthesis: The process is simple, and the prepared red fluorescent carbon quantum dots are easy to scale up for production. The red fluorescence emission wavelength of these carbon quantum dots is in the range of 580-730 nm, with at least one emission peak in the 580 nm to 680 nm band, which is beneficial for deep biological imaging. Stable fluorescence in the solid state: It overcomes the aggregation and quenching problem of most carbon dots, broadening the application of carbon quantum dots under various conditions. Amphiphilic: The surface contains both hydrophilic groups (such as -OH, -COOH) and hydrophobic groups (such as alkyl groups), which can be dispersed in water and various organic solvents (such as ethanol, acetone, chloroform, etc.), facilitating application in multiphase systems and interfaces. Good biocompatibility: Low toxicity to mammals and cells, high safety, suitable for the biomedical field. Wide range of applications: With its red fluorescence, amphiphilicity, low toxicity and solid-state luminescence properties, it can be applied in many fields such as bioimaging, fingerprint development, fluorescent anti-counterfeiting, anti-oxidation or metal ion detection. Attached Figure Description

[0018] Figure 1 Example 1 describes the preparation method and application of red carbon quantum dots. Figure 2 shows the fluorescence emission spectra of carbon quantum dots (1 mg / mL) prepared from Dendrobium leaves in Example 1 at excitation wavelengths of 380-440 nm. (A) Fluorescence emission spectrum in PBS buffer at pH 7.4; (B) Fluorescence emission spectrum in ethanol. Figures (A and B) show that the red fluorescence emission wavelength of the carbon quantum dots is located in the red light region of 610-710 nm, with the strongest red fluorescence emission peak located at around 624 nm.

[0019] Figure 3 Here are the images of carbon quantum dots (1 mg / mL) observed under natural light in Example 1: (A) PBS buffer pH 7.4; (B) ethanol solution; and images observed under UV light excitation: (C) PBS buffer pH 7.4; (D) ethanol solution.

[0020] Figure 4 This is an example 1: solid-state luminescence image of carbon quantum dot powder, observed under ultraviolet light excitation.

[0021] Figure 5 This is the surface charge spectrum of the carbon quantum dots in Example 1.

[0022] Figure 6 This is the Fourier transform infrared spectrum of the carbon quantum dots in Example 1, showing the hydrophilic group region (approximately 3430 cm⁻¹). -1 (OH / NH stretching vibration) and hydrophobic group region (approximately 2923 cm) - ¹CH stretching vibration).

[0023] Figure 7 This is a high-resolution transmission electron microscope image of the carbon quantum dots in Example 1, showing a uniform particle size distribution with an average diameter of approximately 3.37 nm.

[0024] Figure 8 This is the XPS spectrum of carbon quantum dots in Example 1.

[0025] Figure 9 The images show the fluorescence emission spectra of carbon quantum dots (1 mg / mL) from Example 2 at an excitation wavelength of 380-420 nm. (A) is the fluorescence emission spectrum in PBS buffer at pH 7.4; (B) is the fluorescence emission spectrum in ethanol. Figures (A and B) show that the red fluorescence emission wavelength of the carbon quantum dots is located in the red light region of 580-720 nm, with the red fluorescence emission peak located at around 600 nm.

[0026] Figure 10 This is the Fourier transform infrared spectrum of the carbon quantum dots in Example 2, showing the hydrophilic region (approximately 3389 cm⁻¹). -1 (OH / NH stretching vibration) and hydrophobic group region (approximately 2923) -1(CH stretching vibration of cm).

[0027] Figure 11 This is a high-resolution transmission electron microscope image of carbon quantum dots from Example 2, showing a uniform particle size distribution with an average diameter of approximately 3.24 nm.

[0028] Figure 12 The figure shows the fluorescence emission spectrum of carbon quantum dots (1 mg / mL) in PBS buffer at pH 7.4, under an excitation wavelength of 380-440 nm. The figure shows that the red fluorescence emission wavelength of the carbon quantum dots is located in the red light region of 600-710 nm, and the strongest red fluorescence emission peak is located at about 670 nm.

[0029] Figure 13 This is the Fourier transform infrared spectrum of the carbon quantum dots in Example 3.

[0030] Figure 14 This is a high-resolution transmission electron microscope image of carbon quantum dots from Example 3, showing a uniform particle size distribution with an average diameter of approximately 3.74 nm.

[0031] Figure 15 The figure shows the fluorescence emission spectrum of carbon quantum dots (1 mg / mL) in PBS buffer at pH 7.4, at an excitation wavelength of 380-440 nm. The figure shows that the red fluorescence emission wavelength of the carbon quantum dots is located in the red light region of 580-680 nm, and the strongest red fluorescence emission peak is located at about 600 nm.

[0032] Figure 16 This is the Fourier transform infrared spectrum of the carbon quantum dots in Example 4, showing the hydrophilic region (approximately 3389 cm⁻¹). -1 (OH / NH stretching vibration) and hydrophobic group region (approximately 2921 cm) -1 CH stretching vibration).

[0033] Figure 17 This is a high-resolution transmission electron microscope image of carbon quantum dots from Example 4, showing a uniform particle size distribution with an average diameter of approximately 5.61 nm.

[0034] Figure 18 The figure shows the fluorescence emission spectrum of carbon quantum dots (1 mg / mL) prepared from mustard in Example 5 at an excitation wavelength of 380-440 nm in PBS buffer pH 7.4. The figure shows that the red fluorescence emission wavelength of the carbon quantum dots is located in the red light region of 600-700 nm, and the strongest red fluorescence emission peak is located at about 650 nm.

[0035] Figure 19 This is the Fourier transform infrared spectrum of mustard carbon quantum dots from Example 5, showing the hydrophilic group region (approximately 3398 cm⁻¹). -1(OH / NH stretching vibration) and hydrophobic group region (approximately 2907 cm⁻¹) -1 CH stretching vibration).

[0036] Figure 20 The figure shows the fluorescence emission spectrum of carbon quantum dots (1 mg / mL) prepared from chives in Example 5 in PBS buffer pH 7.4 at an excitation wavelength of 380-440 nm. The figure shows that the red fluorescence emission wavelength of the carbon quantum dots is located in the red light region of 580-700 nm, and the strongest red fluorescence emission peak is located at about 650 nm.

[0037] Figure 21 The figure shows the fluorescence emission spectrum of carbon quantum dots (1 mg / mL) prepared from the leaves of *Cymbidium goeringii* in PBS buffer at pH 7.4, at an excitation wavelength of 380-440 nm. The figure shows that the red fluorescence emission wavelength of the carbon quantum dots is located in the red light region of 590-680 nm, with the strongest red fluorescence emission peak at around 620 nm, and there are two emission peaks in the red light region.

[0038] Figure 22 The figure shows the fluorescence emission spectrum of carbon quantum dots (1 mg / mL) prepared from Mahonia japonica leaves in PBS buffer at pH 7.4, under an excitation wavelength of 380-440 nm. The figure shows that the red fluorescence emission wavelength of the carbon quantum dots is located in the red light region of 625-680 nm, and the strongest red fluorescence emission peak is located at about 660 nm.

[0039] Figure 23 The figure shows the fluorescence emission spectrum of carbon quantum dots (1 mg / mL) prepared from golden sunflower in Example 5 in PBS buffer pH 7.4 at an excitation wavelength of 380-440 nm. The figure shows that the red fluorescence emission wavelength of the carbon quantum dots is located in the red light region of 620-700 nm, and the strongest red fluorescence emission peak is located at about 670 nm.

[0040] Figure 24 The figure shows the fluorescence emission spectrum of carbon quantum dots (1 mg / mL) prepared from kelp in Example 5 in PBS buffer at pH 7.4, under an excitation wavelength of 380-440 nm. The figure shows that the red fluorescence emission wavelength of the carbon quantum dots is located in the red light region of 625-730 nm, and the strongest red fluorescence emission peak is located at around 640 nm.

[0041] Figure 25The figure shows the fluorescence emission spectrum of carbon quantum dots (1 mg / mL) prepared from laver in Example 5 in PBS buffer pH 7.4 at an excitation wavelength of 380-440 nm. The figure shows that the red fluorescence emission wavelength of the carbon quantum dots is located in the red light region of 570-700 nm, and the strongest red fluorescence emission peak is located at about 620 nm.

[0042] Figure 26 The images shown in Example 5 are of carbon quantum dots prepared from other plants containing photosynthetic pigments (PBS buffer pH 7.4) under UV excitation at 390 nm. From left to right (1-18), they are: leek, laver, kelp, blackberry, sunflower, garland chrysanthemum, groundnut leaf, fleeceflower root, mustard greens, loquat leaf, purple-backed amaranth, epimedium, dendrobium, dandelion, narrow-leaved purslane, celery, spinach, and houttuynia cordata.

[0043] Figure 27 This is the fluorescence lifetime plot of the carbon quantum dot in Example 1. The average lifetime was calculated to be 5.28 ns by fitting a second-order exponent.

[0044] Table 1 shows the fluorescence quantum yields of carbon quantum dots prepared from several photosynthetic pigment plants. The fluorescence quantum yield of the reference sample (the quantum yield of rhodamine ethanol is 0.94) can be calculated using the following formula: , ST and X represent the reference sample and the test sample, respectively; Φ represents the fluorescence quantum yield; Grad represents the slope of the curve; and η represents the refractive index of the solvent.

[0045] Table 1. Fluorescence quantum yield of carbon quantum dots prepared from several photosynthetic pigment extracts name Quantum yield (%) in PBS (pH 7.4) Quantum yield in ethanol (%) Dendrobium carbon quantum dots 13.25 23.34 Dandelion carbon quantum dots 12.56 22.85 Spinach carbon quantum dots 14.87 26.59 .

[0046] Figure 28 This is the carbon quantum dot fingerprint developer from Example 1. The image was observed under ultraviolet light excitation.

[0047] Figure 29 This is Example 4, a carbon quantum dot fluorescent anti-counterfeiting film. The image shows the film under UV light excitation.

[0048] Figure 30 The results of the HepG2 cytotoxicity test (CCK-8 assay) in Example 2 show that the cell viability still exceeds 90% at a concentration of 200 μg / mL.

[0049] Figure 31 This is an image of HepG2 cells containing carbon quantum dots from Example 1. λex = 561 nm. Scale bar = 20 μm.

[0050] Figure 32This is a three-color imaging image of HepG2 cells using carbon quantum dots from Example 4. λ ex =405 nm, λ ex = 488 nm; λ ex =561nm. Scale bar = 20 μm.

[0051] Figure 33 The free radical scavenging activity of carbon quantum dots ABTS in Example 1 is >85% at a concentration of 3% carbon quantum dots.

[0052] Figure 34 Example 4 shows the photothermal performance test of carbon quantum dots, with a laser power of 1 W / cm². 2 When solid carbon quantum dots are irradiated with 808nm infrared light for 30s, the center temperature reaches 100℃ and the average temperature reaches 86.6℃, showing a significant solid-state photothermal conversion effect.

[0053] Figure 35 This is a multi-batch pilot-scale production of Example 1 (500ml per batch), and the carbon quantum dots produced after the scale-up are fluorescently stable. Detailed Implementation

[0054] The present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited to the following embodiments. All equivalent substitutions or improvements made based on the concept of the present invention fall within the scope of protection of the present invention.

[0055] Example 1: Preparation of carbon quantum dot precursor using Dendrobium officinale leaves: 20.0 g of Dendrobium officinale leaves were washed and crushed. 200 mL of acetone was added, and the mixture was extracted at room temperature in the dark for 8 hours. The mixture was filtered, and the supernatant was collected. The residue was extracted again, and the two filtrates were combined and concentrated under reduced pressure in a rotary evaporator to obtain a Dendrobium officinale extract rich in photosynthetic pigments. Carbon quantum dot synthesis: 1.0 g of the above extract was accurately weighed and placed in a 100 mL high-pressure reactor lined with polytetrafluoroethylene. 50 mL of ethanol was added, and the mixture was stirred until uniformly dispersed. The reactor was sealed and placed in an oven at 200 °C for 8 hours. After the reaction, the mixture was naturally cooled to room temperature, and the carbon quantum dot solution emitted a bright red fluorescence under ultraviolet light. Purification and acquisition: The reaction solution was first centrifuged at high speed (12000 rpm, 20 min) to remove insoluble matter, and the supernatant was filtered through a 0.22 μm microporous membrane. The filtrate was then transferred to a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed with deionized water for 48 hours to remove small molecule impurities. Finally, the liquid in the dialysis bag was freeze-dried to obtain amphiphilic solid Dendrobium carbon quantum dots. An acute oral toxicity test was conducted on mice. Five male and five female mice were given a single oral dose of 2000 mg / kg and observed for 72 hours. No death or poisoning symptoms were observed in the mice.

[0056] Characterization results: The obtained solid carbon quantum dots emitted bright red fluorescence under ultraviolet light excitation, with the red fluorescence emission peak located at 640 nm and the red fluorescence emission wavelength in the range of 610-710 nm. Figure 1 High-resolution transmission electron microscopy (HR-TEM) revealed that its morphology was approximately spherical with a uniform particle size distribution and an average particle size of 5.0 ± 1.5 nm. Figure 3 Fourier transform infrared (FT-IR) spectra at ~3400 cm⁻¹ -1 It shows a broad and strong OH / NH stretching vibration peak at ~2920 cm⁻¹. -1 The presence of a distinct CH stretching vibration peak confirms that its surface contains abundant hydrophilic and hydrophobic groups, exhibiting amphiphilic properties. Figure 2 The cytotoxicity of this cell type to mammalian cells (such as HepG2 cells) was tested using the CCK-8 assay. The results showed that even at concentrations as high as 200 μg / mL, cell viability remained above 90%, demonstrating its excellent biocompatibility and low cytotoxicity. Figure 4 ).

[0057] Example 2: Preparation of carbon quantum dots using *Gnaphalium affine* leaves as a precursor. Precursor preparation: 20.0 g of *Gnaphalium affine* leaves were taken, washed, and chopped. 150 mL of an ethanol / acetone mixture (volume ratio 1:1) was added, and the mixture was extracted at 50°C in the dark with stirring for 3 hours. The mixture was filtered, and the residue was extracted again with the mixture. The filtrates were combined. The filtrate was concentrated by rotary evaporation under reduced pressure to obtain a *Gnaphalium affine* leaf extract rich in photosynthetic pigments. Carbon quantum dot synthesis: 2.0 g of the above extract was weighed and added to 60 mL of a deionized water / acetone mixture (volume ratio 1:1), and transferred to a reaction vessel. The reaction was carried out at 180°C for 10 hours. Purification and acquisition: The purification steps were the same as in Example 1, yielding amphiphilic solid *Gnaphalium affine* leaf carbon quantum dots.

[0058] Characterization results: The red fluorescence emission peak of this carbon quantum dot is located at 658 nm, and the red fluorescence emission wavelength is in the range of 610-710 nm. The FT-IR spectrum is at 1735 cm⁻¹. -1 A distinct C=O stretching vibration peak of the ester bond was observed nearby, reflecting the characteristics of the *Gnaphalium affine* leaf precursor. The product disperses well in water and ethanol, exhibiting clear amphiphilicity. Cytotoxicity tests showed a cell viability >90%.

[0059] Example 3: Preparation of carbon quantum dots using Epimedium leaves as a precursor. Precursor preparation: Epimedium leaves were ground into powder. 20.0 g of powder was weighed and extracted with 100 mL of 70% (v / v) ethanol under light-protected stirring for 24 hours. The mixture was filtered, and the filtrate was concentrated by rotary evaporation and further freeze-dried to obtain Epimedium leaf extract rich in photosynthetic pigments. Carbon quantum dot synthesis: 1.5 g of the solid extract was weighed and reacted with 50 mL of deionized water / ethylene glycol mixture (volume ratio 1:1) in a reaction vessel at 240°C for 5 hours. Purification and acquisition: The purification steps were the same as in Example 1 to obtain amphiphilic solid Epimedium carbon quantum dots.

[0060] Characterization results: The red fluorescence emission peak of the carbon quantum dots was located at 672 nm, and the red fluorescence emission wavelength was in the range of 600-710 nm. Transmission electron microscopy showed that the particle size distribution was uniform, with an average particle size of approximately 4-6 nm. Cell experiments confirmed its excellent biocompatibility.

[0061] Example 4: Preparation of Carbon Quantum Dots Using Spinach Leaves as a Precursor. Precursor Preparation: Take 100 g of spinach leaves, wash and chop them. Add 200 mL of an ethanol / acetone (1:1) mixture and extract by stirring in the dark for 4 hours to fully extract chlorophyll and other photosynthetic pigments. Filter and concentrate the filtrate to obtain a spinach extract rich in photosynthetic pigments. Carbon Quantum Dot Synthesis: Take 2.5 g of the above extract, place it in a reaction vessel, add 50 mL of ethanol, and stir evenly. React at 160℃ for 12 hours using a solvothermal method. Purification and Obtaining: After cooling, the reaction solution is centrifuged, filtered, dialyzed (MWCO 1000 Da), and freeze-dried to obtain amphiphilic solid spinach carbon quantum dots.

[0062] Characterization results: The red fluorescence emission peak of the carbon quantum dot is located at 600 nm, and the red fluorescence emission wavelength is in the range of 580-680 nm. The FT-IR spectrum shows obvious alkyl CH stretching vibration peaks at 2960 cm⁻¹ and 2870 cm⁻¹, while there is a strong hydrophilic peak near 3400 cm⁻¹, indicating significant amphiphilicity.

[0063] Example 5: Preparation of carbon quantum dots from other extracts rich in photosynthetic pigments: Based on the same inventive concept, all plants, algae, and their extracts rich in photosynthetic pigments are applicable to this invention. Examples include, but are not limited to: plant extracts (such as mustard greens, leeks, blackberry, Mahonia japonica leaves, golden sunflower flowers, garland chrysanthemum, Polygonum multiflorum, loquat leaves, purple-backed amaranth, dandelion, narrow-leaved purslane, celery, houttuynia cordata) and algae extracts (such as kelp, laver).

[0064] By using solvents similar to those in Examples 1-4 (ethanol, acetone, ethyl acetate, etc.) to extract photosynthetic pigments from plants and algae, extracts rich in photosynthetic pigments are obtained. The extracts are then mixed with the solvent and purified through bottom-up polymerization carbonization (e.g., hydrothermal or solvothermal methods). This process yields solid red fluorescent carbon quantum dot products with amphiphilicity, red fluorescence emission wavelengths in the 580-730 nm range, at least one emission peak in the 580 nm-680 nm band, and good biocompatibility. The specific red fluorescence emission wavelength range, emission peak position, average particle size, degree of amphiphilicity, quantum yield, fluorescence lifetime, functional groups, and the effectiveness of the carbon quantum dots in applications may vary slightly depending on the type, part, harvesting time, pigment content, extraction conditions, carbonization reaction method, and purification conditions of the selected plants, algae, or photosynthetic bacteria for the photosynthetic pigment extract. However, all of these variations fall within the technical solution and protection scope of this invention.

Claims

1. An amphiphilic solid red fluorescent carbon quantum dot containing photosynthetic pigments, characterized in that, The carbon quantum dots are prepared by bottom-up polymerization and carbonization using a photosynthetic pigment extract as a carbon source precursor; the average particle size of the carbon quantum dots is 2 nm to 8 nm; the red fluorescence emission wavelength of the carbon quantum dots is in the range of 580 nm to 730 nm; the fluorescence of the carbon quantum dots has at least one emission peak in the 580 nm to 680 nm band; the carbon quantum dots exhibit red fluorescence emission properties in aqueous phase, organic phase and solid state.

2. The carbon quantum dot according to claim 1, characterized in that, The photosynthetic pigment extract is selected from at least one of plants and algae that have the ability to metabolize photosynthetic pigments.

3. The carbon quantum dot according to claim 2, characterized in that... The photosynthetic pigment extract is selected from the chlorophyll- or phycobilin-rich parts of plants and algae with photosynthetic metabolism capabilities.

4. The carbon quantum dot according to claims 1-3, characterized in that, The average particle size of the carbon quantum dots is 3 nm to 6 nm; the red fluorescence emission wavelength of the carbon quantum dots is in the range of 580 nm to 730 nm; the carbon quantum dots have at least one emission peak in the 580 nm to 680 nm band; the carbon quantum dots have red fluorescence emission properties in aqueous phase, organic phase and solid state.

5. The carbon quantum dot according to claim 1, characterized in that, The amphiphilicity is manifested in the fact that the carbon quantum dots can be dispersed in both water and organic solvents while still exhibiting good red fluorescence; the aqueous phase is selected from at least one of deionized water, PBS wash solution, and physiological saline; the organic solvent is selected from at least one of ethanol, methanol, dimethyl sulfoxide, and N,N-dimethylformamide.

6. A method for preparing carbon quantum dots according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) After washing and crushing the raw materials rich in photosynthetic pigments, plant extracts or other extracts are obtained by solvent extraction. (2) Disperse the extract obtained in step (1) in the reaction medium and transfer it to the reaction vessel for a one-pot hydrothermal reaction or solvothermal reaction; (3) After the reaction is completed, the reaction solution is cooled and purified to obtain solid or liquid carbon quantum dot products.

7. The preparation method according to claim 6, characterized in that, The extraction solvent in step (1) is selected from one or more of water, ethanol, methanol, acetone, petroleum ether, and ethyl acetate; the reaction medium in step (2) is selected from one or more of ultrapure water, ethanol, ethylene glycol, and N,N-dimethylformamide; the reaction temperature is 120℃~260℃, and the reaction time is 2 h~18 h.

8. The preparation method according to claim 6, characterized in that, The purification process in step (3) includes one or more of the following: centrifugation, filtration, dialysis, column chromatography, rotary evaporation, and freeze drying.

9. The use of carbon quantum dots according to any one of claims 1 to 5 in the preparation of bioimaging reagents, fingerprint developers, fluorescent anti-counterfeiting films, antioxidants, or metal ion detection reagents.

10. The application according to claim 9, characterized in that, The metal ion detection is for Fe 3+ Ag + Cu 2+ Pb 2+ or Cd 2+ The detection; the antioxidant is the scavenging of ABTS free radicals, hydroxyl free radicals or superoxide anion free radicals.

11. The application according to claim 9, characterized in that, The bioimaging reagents include in vitro cell fluorescence labeling reagents, in vivo fluorescence imaging reagents, photodynamic therapy reagents, or photothermal therapy reagents.

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