Synthesis of nitrogen-doped carbon quantum dots responding to near-infrared region II under magnetic field and preparation method and application thereof

Abstract

The present invention discloses a nitrogen-doped carbon quantum dot that responds to near-infrared zone II under a magnetic field, and a preparation method and application thereof, and belongs to the technical field of carbon nanomaterials. The preparation method comprises the following steps: using glucose as a carbon source, ammonia water as a nitrogen source, and water as a solvent, and performing a hydrothermal reaction under a magnetic field to obtain the obtained carbon quantum dots. Beneficial effect: In the present invention, specifically using glucose as a carbon source, ammonia water as a nitrogen source, and water as a solvent, and obtaining the nitrogen-doped carbon quantum dots that respond to near-infrared zone II under a magnetic field, the obtained carbon quantum dots are small in size, and have good hydrophilicity, good fluorescence and near-infrared imaging performance, and the adjustable nitrogen doping type and content are beneficial to the photothermal conversion performance.

Description

Technical Field

[0001] The invention relates to the technical field of carbon nanomaterials, and in particular to nitrogen-doped carbon quantum dots that are synthesized under a magnetic field and respond to near-infrared second-zone reactions, and a preparation method and application thereof. Background Art

[0002] In recent years, due to its good biocompatibility, adjustable optical properties, rich surface functional groups and other advantages, carbon dots (<20nm) have shown great application potential in the fields of nanomedicine, electronic devices, photoelectrocatalysis, etc., and have attracted extensive attention from scientific researchers. Since carbon quantum dots with different properties have complex surface and interface properties and rich heterogeneous atom doping types, the synthesis steps of carbon quantum dots are very complicated. For example, due to the difficulty in accurately controlling the type / concentration of nitrogen doping, the photothermal therapy of nitrogen-doped carbon dots (a cancer treatment method that uses near-infrared light to irradiate the tumor area to form local excessive heat to ablate tumor tissue) is inefficient; due to the unclear relationship between structural characteristics and electron transfer and optical properties, the efficiency of phototherapy of carbon nitride dots is difficult to significantly improve. At present, the main methods for synthesizing functional carbon quantum dots include ultrasonic method, hydrothermal / solvothermal method, microwave-assisted method, graphite laser ablation and stripping method, and electrochemical oxidation method. Due to the complexity of the synthesis steps and the uncontrollable functional groups, it is particularly meaningful to develop new methods that can control the functional groups.

[0003] At present, magnetic field has developed into a means to regulate chemical reactions and prepare new materials, similar to temperature and pressure. The process of preparing carbon dots using organic molecules as precursors includes three stages: first, organic molecules form larger molecular intermediates through π-π conjugation or chemical bonds; second, under high temperature / high pressure conditions, the internal chemical bonds of the molecular intermediates are destroyed to form carbon-based fragments and free radicals; third, the carbon-based fragments continue to be carbonized by high temperature / high pressure to obtain carbon dots. A large number of experiments have shown that strong magnetic fields can affect the above three stages: first, they regulate the polymerization of organic molecules with conjugated groups, induce changes in the stacking and orientation of molecular intermediates, and affect the morphology and structure of carbon dots formed after carbonization; second, according to quantum chemical theory, the introduction of magnetic fields will reduce the energy of carbon-based fragments, increase the reactivity of free radicals with carbon-based fragments, and enhance the controllability of heterogeneous doping positions and concentrations; third, they enhance the adsorption / activation ability of free radicals during the crystallization of carbon-based fragments, generate new active sites, improve the conversion efficiency of functional groups of carbon dots, and affect the surface and interface properties of carbon dots.

[0004] However, the current means of regulating the properties of carbon dots are mainly focused on improving parameters under conventional reaction conditions, and it is impossible to develop efficient diagnostic and therapeutic agents that break through the performance limits of existing materials. Therefore, a strong magnetic field is used to regulate the thermal decomposition of organic molecular solvents, regulate the structural characteristics of carbon nitride quantum dots, and then improve the optical properties of carbon nitride quantum dots, and develop efficient diagnostic and therapeutic agents that break through the performance of existing materials.

[0005] A Chinese patent application document with publication number CN109437155A discloses a method for simultaneously preparing carbon quantum dots and carbon nanospheres, wherein the carbon quantum dots are prepared using glucose as a carbon source. The diameter of the carbon quantum dots is 8±2nm and they have good water dispersibility, but they are not doped with heterogeneous atoms and do not have the performance of near-infrared second zone response. Summary of the invention

[0006] The technical problem to be solved by the present invention is how to obtain nitrogen-doped carbon quantum dots that respond to the second near-infrared region under a magnetic field.

[0007] The present invention solves the above technical problems through the following technical means:

[0008] The first aspect of the present invention proposes a method for preparing nitrogen-doped carbon quantum dots that respond to near-infrared second zone under a magnetic field, comprising the following steps: using glucose as a carbon source, ammonia water as a nitrogen source, and water as a solvent, and performing a hydrothermal reaction under a magnetic field to obtain them.

[0009] Beneficial effects: In the present invention, glucose is used as the carbon source, ammonia water is used as the nitrogen source, and water is used as the solvent, and the nitrogen-doped carbon quantum dots that respond to the second near-infrared region are obtained under a magnetic field. The obtained carbon quantum dots are small in size and have good hydrophilicity, good fluorescence and near-infrared imaging performance, and the adjustable nitrogen doping type and content are beneficial to the photothermal conversion performance.

[0010] Preferably, the mass volume ratio of glucose to aqueous ammonia is ≤100 mg:1 mL.

[0011] Preferably, the mass volume ratio of glucose to water is ≤10 mg:1 mL.

[0012] Preferably, the dosage ratio of the glucose, ammonia water and aqueous solution is 100 mg: 1 mL: 14 mL.

[0013] Preferably, the temperature of the hydrothermal reaction is 150-200°C.

[0014] Preferably, the hydrothermal reaction time is ≥5 h.

[0015] Preferably, the intensity of the magnetic field is ≤9T.

[0016] Preferably, the method further comprises dialyzing and drying the product after the hydrothermal reaction.

[0017] Preferably, the method comprises the following steps: mixing glucose, ammonia water and aqueous solution in a dosage ratio of 100 mg: 1 mL: 14 mL to obtain a reaction solution; placing the obtained reaction solution in a hydrothermal reactor, reacting it at 200°C in a magnet with a magnetic field strength of 9 T for 20 hours, cooling it to room temperature after the reaction is completed, sucking the product out into a dialysis bag with a molecular weight cutoff of 100 kD, placing it in distilled water for dialysis, collecting the dialyzed aqueous solution, and freeze-drying it until the aqueous solution completely disappears, thereby obtaining the nitrogen-doped carbon quantum dots that respond to the second near-infrared region.

[0018] The second aspect of the present invention proposes nitrogen-doped carbon quantum dots with near-infrared second-region response prepared by the above-mentioned preparation method.

[0019] Preferably, the nitrogen-doped carbon quantum dots that respond to the second near-infrared region have good photothermal capabilities in the second near-infrared region.

[0020] The third aspect of the present invention proposes the use of nitrogen-doped carbon quantum dots with near-infrared second-region response prepared by the above-mentioned preparation method in electronic devices, fluorescent dyes and nanomedicine.

[0021] The advantages of the present invention are:

[0022] (1) In the present invention, glucose is used as the carbon source, ammonia water is used as the nitrogen source, and water is used as the solvent, and the nitrogen-doped carbon quantum dots that respond to the second near-infrared region are obtained under a magnetic field. The obtained carbon quantum dots are small in size and have good hydrophilicity, good fluorescence and near-infrared imaging performance, and the adjustable nitrogen doping type and content are beneficial to the photothermal conversion performance.

[0023] (2) The present invention generates nitrogen-doped carbon quantum dots, which can be applied to electronic devices, fluorescent dyes, nanomedicine, etc.;

[0024] (3) Compared with other inventions, the raw materials used in the present invention are low in cost and readily available, the synthesis time is short, the steps are simple, and there is great prospect for application in industrial large-scale manufacturing in the future;

[0025] (4) The present invention constructs nitrogen-doped carbon quantum dots with strong fluorescent properties through simple chemical reactions, effectively realizing the high-value utilization of biomass resources. The obtained carbon quantum dots have near-infrared imaging function and good photothermal capacity in the near-infrared region II. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the synthesis steps of preparing carbon quantum dots under a magnetic field in Example 1 of the present invention;

[0027] Figure 2 Transmission electron microscopy characterization of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention, wherein the inset is the size distribution of the synthesized carbon quantum dots obtained by measurement;

[0028] Figure 3 This is a high-resolution image of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention;

[0029] Figure 4 Atomic force microscopy characterization of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention;

[0030] Figure 5 Raman characterization of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention;

[0031] Figure 6 Infrared characterization of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention;

[0032] Figure 7 The X-ray photoelectron spectrum of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention;

[0033] Figure 8 The X-ray photoelectron spectrum C1s spectrum of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention;

[0034] Fig. 9 The X-ray photoelectron spectrum O1s spectrum of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention;

[0035] Fig.10 The X-ray photoelectron spectrum N1s spectrum of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention;

[0036] Fig.11 The ultraviolet-visible absorption spectrum and emission spectrum of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention;

[0037] Fig.12 The photoluminescence of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention is excited in a wide range of 280-500nm;

[0038] Fig.13 The up-conversion photoluminescence spectrum of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention when excited in the range of 650-850nm;

[0039] Fig.14 The photothermal conversion capacity of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention under light irradiation with a wavelength of 1064 nm at different concentrations (50, 100, 200 μg / mL);

[0040] Fig.15This is the heating-cooling process of preparing carbon quantum dots under a magnetic field under irradiation with a wavelength of 1064 nm in Example 1 of the present invention;

[0041] Fig.16 The relationship between t and ln(θ) during the cooling process of preparing carbon quantum dots under a magnetic field in Example 1 of the present invention;

[0042] Fig.17 The tumor cell killing effect of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention at different concentrations (0, 12.5, 25, 50 and 100 μg / mL) with or without near-infrared light irradiation in the second region;

[0043] Fig.18 Live and dead cell staining photos of tumor cells with or without near-infrared light irradiation in the second region at different concentrations (0, 12.5, 25, 50 and 100 μg / mL) of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention;

[0044] Fig.19 Optical images of the dispersion of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention (left picture) and after dilution without (middle picture) / irradiation at a wavelength of 365 nm (right picture);

[0045] Fig. 20 Optical images of dispersion of carbon quantum dots irradiated with aqueous solution (left) / 365nm wavelength (right);

[0046] Fig.21 IVIS imaging photos of different organs collected at an excitation wavelength of 540 to 700 nm after the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention were intravenously injected into mice;

[0047] Fig. 22 Optical images of the dispersion of carbon quantum dots prepared from the original solution of carbon quantum dots under a magnetic field (left picture) and irradiated with a wavelength of 365 nm (right picture) in Example 2 of the present invention;

[0048] Fig.23 Optical images of the dispersion of the carbon quantum dots prepared under a magnetic field in Example 3 of the present invention (left picture) and the carbon quantum dots after dilution without (middle picture) / irradiation at a wavelength of 365 nm (right picture);

[0049] Fig.24 Optical images of the dispersion of the carbon quantum dots prepared under a magnetic field in Example 4 of the present invention (left picture) and after dilution without (middle picture) / irradiation at a wavelength of 365 nm (right picture);

[0050] Fig.25Optical images of the dispersion of the carbon quantum dots prepared under a magnetic field in Example 5 of the present invention (left picture) and after dilution without (middle picture) / irradiation at a wavelength of 365 nm (right picture);

[0051] Fig.26 Optical images of the dispersion of the carbon quantum dots prepared under a magnetic field in Example 6 of the present invention (left picture) and after dilution without (middle picture) / irradiation at a wavelength of 365 nm (right picture);

[0052] Fig. 27 Optical images of the dispersion of carbon quantum dots prepared under magnetic field in Comparative Example 1 of the present invention (left picture) and diluted carbon quantum dots without (middle picture) / irradiated at 365nm wavelength (right picture);

[0053] Fig.28 Optical images of the dispersion of carbon quantum dots prepared under magnetic field in comparative example 2 of the present invention (left picture) and diluted carbon quantum dots without (middle picture) / irradiated at 365nm wavelength (right picture);

[0054] Fig.29 This is the X-ray photoelectron spectrum N1s spectrum of carbon quantum dots prepared in the absence of a magnetic field in Comparative Example 2 of the present invention.

[0055] Fig.30 This is the heating-cooling process of preparing carbon quantum dots under magnetic field under irradiation with light having a wavelength of 1064 nm in Comparative Example 2 of the present invention;

[0056] Fig.31 These are optical images of the dispersion of the carbon quantum dots prepared under a magnetic field in Comparative Example 3 of the present invention (left picture) and the carbon quantum dots after dilution without (middle picture) / irradiation at a wavelength of 365 nm (right picture). DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are 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.

[0058] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0059] Embodiment 1:

[0060] The invention discloses a method for preparing nitrogen-doped carbon quantum dots that respond to near-infrared zone II under a magnetic field, comprising the following steps: weighing 100 mg of glucose, adding it to 14 mL of distilled water to dissolve it evenly, then adding 1 mL of ammonia solution, putting it into a 20 mL hydrothermal reactor, placing it in a magnet with a magnetic field strength of 9 T, heating it to 200° C. and keeping it for 20 hours, cooling it to room temperature after the reaction is completed, sucking the solution inside into a dialysis bag with a molecular weight cutoff of 100 kD, and putting it into 500 mL of distilled water for dialysis; during the dialysis process, collecting the aqueous solution outside the dialysis bag every 24 hours, and adding 500 mL of new distilled water to continue dialysis; finally, freeze-drying all the collected aqueous solutions until the aqueous solution completely disappears, so as to obtain the prepared nitrogen-doped carbon quantum dots that respond to near-infrared zone II.

[0061] Figure 1 This is a schematic diagram of the synthesis of this embodiment. Distilled water is used as the solvent, glucose is used as the C source, and ammonia water is used as the N source. In a 20 mL reactor, the optimal reaction condition is to react at 200°C for 20 h in a magnet with a magnetic field strength of 9 T. The mixed solution is then placed in a dialysis bag to remove large particles, and finally freeze-dried to obtain nitrogen-doped carbon quantum dots under a magnetic field.

[0062] Figure 2 This is a transmission microscope image representation of the nitrogen-doped carbon quantum dots prepared under a magnetic field in Example 1 of the present invention. The size distribution of the synthesized carbon quantum dots measured in the image clearly shows many nitrogen-doped carbon quantum dot particles with a particle size of about 8 nm.

[0063] Figure 3 This is a high-resolution image of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention, wherein the lattice fringes of 0.275 nm belong to the graphite (100) plane.

[0064] Figure 4 This is the atomic force microscope characterization of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention and the height profile distribution diagram corresponding to the white line in the figure, which can prove that the height of the carbon quantum dots is about 8nm.

[0065] Figure 5 This is the Raman characterization of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention, and the D peak and G peak belonging to the carbon material can be clearly seen.

[0066] Figure 6 This is the infrared characterization of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention, which can reveal the various bond positions contained in the carbon quantum dots, 3422cm -1 The characteristic peak at 3260cm corresponds to the stretching vibration of OH. -1 The characteristic absorption band corresponding to NH indicates that the raw glucose has been successfully doped with nitrogen; 2900-3000cm -1The absorption peak at 1630 cm is attributed to CH stretching vibration; -1 The peak appears corresponding to C=O stretching vibration. -1 and 1390cm -1 The two peaks at are referred to as the CH in-plane bending vibration and the NH bending vibration, respectively.

[0067] Figure 7 This is the X-ray photoelectron spectrum of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention. The C content, O content, and N content of the carbon quantum dots are 80.1%, 8.2%, and 11.7%.

[0068] Figure 8 This is the X-ray photoelectron spectrum C1s spectrum of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention. The C1s spectrum shows three peaks of C=C / CC, CO / CN and C=O / CN at 284.8 eV, 286.0 eV and 287.2 eV respectively.

[0069] Fig. 9 This is the X-ray photoelectron spectrum O1s spectrum of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention. The O1s spectrum includes three peaks at 531.1 eV, 532.5 eV and 533.1 eV, which are respectively attributed to C=O, OC and COC.

[0070] Fig.10 This is the N1s spectrum of the X-ray photoelectron spectrum of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention. The N1s spectrum includes three peaks at 398.6 eV, 399.6 eV and 400.2 eV, corresponding to pyridinic nitrogen, pyrrolic nitrogen and graphitic nitrogen, respectively.

[0071] Fig.11 The UV-visible absorption and emission spectra of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention are characterized, wherein the absorption peaks at 269 nm and 301 nm are attributed to π-π and n-π, respectively, and the corresponding photoluminescence (PL) spectrum shows emission (647 nm) under UV excitation (392 nm).

[0072] Fig.12 This is the dispersed photoluminescence of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention and excited in a wide range of 280-500nm. When the excitation wavelength increases from 280nm to 500nm, the emission peak gradually shifts to a longer wavelength, and the PL intensity gradually increases and then decreases.

[0073] More importantly, the spectrum of carbon quantum dots excited by long-wavelength light from 850nm to 650nm ( Fig.13 ) clearly shows the up-converted emission from 488 nm to 396 nm.

[0074] Fig.14 The photothermal conversion capacity of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention under irradiation with light of a wavelength of 1064 nm at different concentrations (50, 100, 200 μg / mL) shows a positive correlation between the increased temperature and the material concentration.

[0075] Fig.15 This is the heating-cooling process of preparing carbon quantum dots under a magnetic field under irradiation with a wavelength of 1064 nm in Example 1 of the present invention, showing that the temperature difference between the equilibrium temperature and the room temperature reaches 21.5°C.

[0076] Fig.16 This is the relationship between t and -ln(θ) during the cooling process of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention, wherein the slope of the fitting straight line is 535.82. According to the photothermal conversion efficiency formula, it can be calculated that the photothermal conversion efficiency of the material is 41.57%.

[0077] Fig.17 The tumor cell killing effect of the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention at different concentrations (0, 12.5, 25, 50 and 100 μg / mL) with / without NIR-II light irradiation is shown. The cell killing efficiency with NIR-II light irradiation is significantly higher than that of the same concentration without illumination, and the cell killing efficiency is positively correlated with the concentration.

[0078] Fig.18 The live and dead cell staining photos of tumor cells with or without near-infrared II light irradiation at different concentrations (0, 12.5, 25, 50 and 100 μg / mL) of carbon quantum dots prepared under a magnetic field in Example 1 of the present invention are shown in red for dead cells and green for live cells. The results show that the cell killing efficiency with NIR-II light irradiation is significantly higher than that without light at the same concentration, and the cell killing efficiency is positively correlated with the concentration.

[0079] Fig.19 Optical photographs of the original carbon quantum dot solution prepared under a magnetic field in Example 1 of the present invention (left picture) and after dilution under sunlight (middle picture), as well as a photograph of the strong blue fluorescence emitted under irradiation with ultraviolet light of a wavelength of 365nm (right picture), indicating that the original solution contains a large amount of carbon quantum dots.

[0080] Fig. 20 These are optical photographs of aqueous solutions irradiated by sunlight (left) and ultraviolet light with a wavelength of 365 nm (right), indicating that the aqueous solution cannot emit fluorescence.

[0081] Fig.21IVIS imaging photos of different organs at an excitation wavelength of 540 to 700 nm were collected after the carbon quantum dots prepared under a magnetic field in Example 1 of the present invention were intravenously injected into mice, indicating that the prepared carbon quantum dots have the function of fluorescent dyes for near-infrared imaging.

[0082] Embodiment 2:

[0083] The invention discloses a method for preparing nitrogen-doped carbon quantum dots that respond to near-infrared zone II under a magnetic field, comprising the following steps: weighing 10 mg of glucose, adding it to 14 mL of distilled water to dissolve it evenly, then adding 1 mL of ammonia solution, putting it into a 20 mL hydrothermal reactor, placing it in a magnet with a magnetic field strength of 9 T, heating it to 195° C. and keeping it for 20 hours, cooling it to room temperature after the reaction is completed, sucking the solution inside into a dialysis bag with a molecular weight cutoff of 100 kD, and putting it into 500 mL of distilled water for dialysis; during the dialysis process, collecting the aqueous solution outside the dialysis bag every 24 hours, and adding 500 mL of new distilled water to continue dialysis; finally, freeze-drying all the collected aqueous solutions until the aqueous solution completely disappears, so as to obtain the prepared nitrogen-doped carbon quantum dots that respond to near-infrared zone II.

[0084] Fig. 22 These are photos of the original solution of carbon quantum dots prepared under a magnetic field in Example 2 of the present invention under sunlight (left picture) and exposed to ultraviolet light with a wavelength of 365nm (right picture). It can be observed that the prepared carbon quantum dots emit obvious fluorescence. Fig. 22 It is proved that the carbon quantum dots prepared in Example 2 are similar to the carbon quantum dots prepared in Example 1. Because the amount of raw materials used is small, the yield of carbon quantum dots produced is also small.

[0085] Embodiment 3:

[0086] The preparation method of nitrogen-doped carbon quantum dots responsive to near-infrared zone II under a magnetic field comprises the following steps: weighing 100 mg of glucose, adding 10 mL of distilled water to dissolve evenly, then adding 5 mL of ammonia solution, putting the mixture into a 20 mL hydrothermal reactor, placing the mixture in a magnet with a magnetic field strength of 9 T, heating the mixture to 200° C. and maintaining the temperature for 20 hours, cooling the mixture to room temperature after the reaction is completed, sucking the solution into a dialysis bag with a molecular weight cutoff of 100 kD, and dialyzing the solution in 500 mL of distilled water; during the dialysis process, collecting the aqueous solution outside the dialysis bag every 24 hours, and adding 500 mL of new distilled water to continue the dialysis; finally freeze-drying all the collected aqueous solutions until the aqueous solution completely disappears, so as to obtain the prepared nitrogen-doped carbon quantum dots responsive to near-infrared zone II.

[0087] Fig.23Optical photographs of the original carbon quantum dot solution prepared under a magnetic field in Example 3 of the present invention (left picture) and after dilution under sunlight (middle picture), as well as a photograph of the strong blue fluorescence emitted under irradiation with ultraviolet light of a wavelength of 365nm (right picture), indicating that the original solution contains a large amount of carbon quantum dots. Fig.23 It is demonstrated that the carbon quantum dots prepared in Example 3 are similar to the carbon quantum dots prepared in Example 1.

[0088] Embodiment 4:

[0089] The preparation method of nitrogen-doped carbon quantum dots responsive to near-infrared zone II under a magnetic field comprises the following steps: weighing 100 mg of glucose, adding 14 mL of distilled water to dissolve evenly, then adding 1 mL of ammonia solution, putting the mixture into a 20 mL hydrothermal reactor, placing the mixture in a magnet with a magnetic field strength of 9 T, heating the mixture to 200° C. and maintaining the temperature for 5 hours, cooling the mixture to room temperature after the reaction is completed, sucking the solution into a dialysis bag with a molecular weight cutoff of 100 kD, and dialyzing the solution in 500 mL of distilled water; during the dialysis process, collecting the aqueous solution outside the dialysis bag every 24 hours, and adding 500 mL of new distilled water to continue the dialysis; finally, freeze-drying all the collected aqueous solutions until the aqueous solution completely disappears, so as to obtain the prepared nitrogen-doped carbon quantum dots responsive to near-infrared zone II.

[0090] Fig.24 Optical photographs of the original carbon quantum dot solution prepared under a magnetic field in Example 4 of the present invention (left picture) and after dilution under sunlight (middle picture), as well as a photograph of the strong blue fluorescence emitted under irradiation with ultraviolet light of a wavelength of 365nm (right picture), indicating that the original solution contains a large amount of carbon quantum dots. Fig.24 It is demonstrated that the carbon quantum dots prepared in Example 4 are similar to the carbon quantum dots prepared in Example 1.

[0091] Embodiment 5:

[0092] The preparation method of nitrogen-doped carbon quantum dots responsive to near-infrared zone II under a magnetic field comprises the following steps: weighing 100 mg of glucose, adding 14 mL of distilled water to dissolve evenly, then adding 1 mL of ammonia solution, putting the mixture into a 20 mL hydrothermal reactor, placing the mixture in a magnet with a magnetic field strength of 1 T, heating the mixture to 200° C. and maintaining the temperature for 20 hours, cooling the mixture to room temperature after the reaction is completed, sucking the solution into a dialysis bag with a molecular weight cutoff of 100 kD, and dialyzing the solution in 500 mL of distilled water; during the dialysis process, collecting the aqueous solution outside the dialysis bag every 24 hours, and adding 500 mL of new distilled water to continue the dialysis; finally, freeze-drying all the collected aqueous solutions until the aqueous solution completely disappears, so as to obtain the prepared nitrogen-doped carbon quantum dots responsive to near-infrared zone II.

[0093] Fig.25Optical photographs of the original carbon quantum dot solution prepared under a magnetic field in Example 5 of the present invention (left picture) and after dilution under sunlight (middle picture), as well as a photograph of the strong blue fluorescence emitted under irradiation with ultraviolet light of a wavelength of 365nm (right picture), indicating that the original solution contains a large amount of carbon quantum dots. Fig.25 It is demonstrated that the carbon quantum dots prepared in Example 5 are similar to the carbon quantum dots prepared in Example 1.

[0094] Embodiment 6:

[0095] The invention discloses a method for preparing nitrogen-doped carbon quantum dots that respond to near-infrared zone II under a magnetic field, comprising the following steps: weighing 100 mg of glucose, adding it to 14 mL of distilled water to dissolve it evenly, then adding 1 mL of ammonia solution, putting it into a 20 mL hydrothermal reactor, placing it in a magnet with a magnetic field strength of 9 T, heating it to 150° C. and keeping it for 20 hours, cooling it to room temperature after the reaction is completed, sucking the solution inside into a dialysis bag with a molecular weight cutoff of 100 kD, and putting it into 500 mL of distilled water for dialysis; during the dialysis process, collecting the aqueous solution outside the dialysis bag every 24 hours, and adding 500 mL of new distilled water to continue dialysis; finally, freeze-drying all the collected aqueous solutions until the aqueous solution completely disappears, so as to obtain the prepared nitrogen-doped carbon quantum dots that respond to near-infrared zone II.

[0096] Fig.26 Optical photographs of the original carbon quantum dot solution prepared under a magnetic field in Example 6 of the present invention (left picture) and after dilution under sunlight (middle picture), as well as a photograph of the strong blue fluorescence emitted under irradiation with ultraviolet light of a wavelength of 365nm (right picture), indicating that the original solution contains a large amount of carbon quantum dots. Fig.26 It is demonstrated that the carbon quantum dots prepared in Example 6 are similar to the carbon quantum dots prepared in Example 1.

[0097] Comparative Example 1:

[0098] The preparation method of nitrogen-doped carbon quantum dots responsive to near-infrared zone II under a magnetic field comprises the following steps: weighing 100 mg of glucose, adding 15 mL of ammonia water to dissolve evenly, putting the glucose into a 20 mL hydrothermal reactor, placing the reactor in a magnet with a magnetic field strength of 9 T, heating the reactor to 200° C. and maintaining the temperature for 20 hours, cooling the reactor to room temperature after the reaction is completed, sucking the solution into a dialysis bag with a molecular weight cutoff of 100 kD, and dialyzing the solution into 500 mL of distilled water; during the dialysis process, collecting the aqueous solution outside the dialysis bag every 24 hours, and adding 500 mL of new distilled water to continue the dialysis; finally, freeze-drying all the collected aqueous solutions until the aqueous solution completely disappears, so as to obtain the prepared nitrogen-doped carbon quantum dots responsive to near-infrared zone II.

[0099] Fig. 27The optical photos of the original solution of carbon quantum dots prepared under magnetic field in Comparative Example 1 of the present invention (left picture) and after dilution under sunlight (middle picture), and the photo of strong blue fluorescence emitted under irradiation with ultraviolet light of wavelength 365nm (right picture), indicating that the original solution contains a large amount of carbon quantum dots. Although carbon quantum dots were prepared in Comparative Example 1, the product has a strong smell and is not applicable.

[0100] Comparative Example 2:

[0101] The preparation method of nitrogen-doped carbon quantum dots responsive to near-infrared zone II under a magnetic field comprises the following steps: weighing 100 mg of glucose, adding 14 mL of distilled water to dissolve evenly, then adding 1 mL of ammonia solution, putting into a 20 mL hydrothermal reactor, placing in a vacuum drying oven with a magnetic field strength of 0 T, heating to 200° C. and maintaining for 20 hours, cooling to room temperature after the reaction is completed, sucking the solution inside into a dialysis bag with a molecular weight cutoff of 100 kD, and putting into 500 mL of distilled water for dialysis; during the dialysis process, collecting the aqueous solution outside the dialysis bag every 24 hours, and adding new 500 mL of distilled water to continue dialysis; finally, freeze-drying all the collected aqueous solutions until the aqueous solution completely disappears, so as to obtain the prepared nitrogen-doped carbon quantum dots responsive to near-infrared zone II.

[0102] Fig.28 The optical photos of the original solution of carbon quantum dots prepared in Comparative Example 2 of the present invention (left picture) and after dilution under sunlight (middle picture), and the photo of strong blue fluorescence emitted under irradiation with ultraviolet light of wavelength 365nm (right picture), indicating that the original solution contains a large number of carbon quantum dots. Although carbon quantum dots were prepared in Comparative Example 2, the type of nitrogen element therein is very different from that of the product prepared under a magnetic field, such as Fig.29 The figure shows the N1s spectrum of the X-ray photoelectron spectrum of carbon quantum dots prepared without a magnetic field. The N1s spectrum includes three peaks at 398.6eV, 399.6eV and 400.2eV, corresponding to pyridinic nitrogen, pyrrolic nitrogen and graphitic nitrogen, respectively. The graphitic nitrogen content is relatively low, which is not conducive to photothermal applications. Fig.30 This is the heating-cooling process of preparing carbon quantum dots under magnetic field under irradiation with light of wavelength 1064 nm in Comparative Example 2 of the present invention, showing that the temperature difference between the equilibrium temperature and the room temperature reaches 14.0°C.

[0103] Comparative Example 3:

[0104] The preparation method of nitrogen-doped carbon quantum dots responsive to near-infrared zone II under a magnetic field comprises the following steps: weighing 100 mg of glucose, adding 15 mL of distilled water to dissolve evenly, putting the glucose into a 20 mL hydrothermal reactor, placing the reactor in a magnet with a magnetic field strength of 9 T, heating the reactor to 200° C. and maintaining the temperature for 20 hours, cooling the reactor to room temperature after the reaction is completed, sucking the solution into a dialysis bag with a molecular weight cutoff of 100 kD, and dialyzing the solution into 500 mL of distilled water; during the dialysis process, collecting the aqueous solution outside the dialysis bag every 24 hours, and adding 500 mL of new distilled water to continue the dialysis; finally, freeze-drying all the collected aqueous solutions until the aqueous solution completely disappears, so as to obtain the prepared nitrogen-doped carbon quantum dots responsive to near-infrared zone II.

[0105] Fig.31 Optical photographs of the original carbon quantum dot solution prepared in Comparative Example 3 of the present invention (left picture) and after dilution under sunlight (middle picture), as well as a photograph of a strong blue fluorescence emitted under irradiation with ultraviolet light of a wavelength of 365nm (right picture), indicating that carbon quantum dots exist in the original solution, but there are also a large number of impurities in the original solution, which is not conducive to application.

[0106] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing nitrogen-doped carbon quantum dots that respond to near-infrared region II under a magnetic field, characterized in that: The following steps are involved: It is obtained by hydrothermal reaction under magnetic field with glucose as carbon source, ammonia as nitrogen source and water as solvent; The dosage ratio of glucose, ammonia water and water is 100 mg: 1 mL: 14 mL; the intensity of the magnetic field is ≤ 9 T; The temperature of the hydrothermal reaction is 150-200°C and the time is ≥5 h.

2. The preparation method according to claim 1, characterized in that: The water is distilled water.

3. The preparation method according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 200°C.

4. The preparation method according to claim 1, characterized in that: The hydrothermal reaction time is 20 h.

5. The preparation method according to claim 1, characterized in that: The strength of the magnetic field is 9 T.

6. The preparation method according to claim 1, characterized in that: The method also includes dialyzing and drying the product after the hydrothermal reaction.

7. The preparation method according to claim 6, characterized in that: The water dialysis specifically uses a dialysis bag with a molecular weight cut-off of 100 kD.

8. The preparation method according to claim 1, characterized in that: The method comprises the following steps: mixing glucose, ammonia water and aqueous solution in a dosage ratio of 100 mg: 1 mL: 14 mL to obtain a reaction solution; placing the obtained reaction solution in a hydrothermal reactor, reacting at 200°C in a magnet with a magnetic field strength of 9 T for 20 h, cooling to room temperature after the reaction, sucking the product into a dialysis bag with a molecular weight cutoff of 100 kD, placing the product in distilled water for dialysis, collecting the dialyzed aqueous solution, and freeze-drying the solution until the aqueous solution completely disappears, thereby obtaining the nitrogen-doped carbon quantum dots that respond to the second near-infrared region.

9. Nitrogen-doped carbon quantum dots with near-infrared second-region response obtained by the preparation method according to any one of claims 1 to 8.

10. Application of the nitrogen-doped carbon quantum dots with near-infrared second-region response as claimed in claim 9 in electronic devices, fluorescent dyes and nanomedicine.

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