Synthesis of sulfur-selenium co-doped carbon quantum dots with near-infrared II ultraviolet absorption under magnetic or non-magnetic field conditions, its preparation method and application

Abstract

This invention discloses a method for synthesizing near-infrared II ultraviolet-absorbing sulfur-selenium co-doped carbon quantum dots under magnetic or non-magnetic field conditions, along with its preparation and applications, belonging to the field of carbon nanomaterials technology. The preparation method includes the following steps: using benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole, and benzoic acid compounds as precursors, a mixed solution of ethylene glycol and water as solvent, and H2O2 as oxidant, a hydrothermal reaction is carried out under magnetic or non-magnetic field conditions to obtain the quantum dots. Beneficial effects: The carbon quantum dots prepared by this invention possess excellent hydrophilicity, good fluorescence, and near-infrared and ultraviolet absorption properties. The raw materials used are low-cost, the synthesis time is short, and the operation is easy, enabling efficient mass production and providing feasibility for industrial-scale applications. Furthermore, the controllable sulfur-selenium co-doping type and content are beneficial to photodynamic properties, exhibiting photosensitizer characteristics.

Description

Technical Field

[0001] This invention relates to the field of carbon nanomaterials technology, and more particularly to a method for synthesizing near-infrared II ultraviolet-absorbing sulfur-selenium co-doped carbon quantum dots under magnetic or non-magnetic field conditions, as well as their preparation and application. Background Technology

[0002] The near-infrared II (NIR-II, 1000-1700 nm) region serves as an "optical transparency window" for biological tissues. Due to the weak light absorption and scattering by tissues and the large penetration depth (up to several centimeters), it exhibits significant advantages in biomedical imaging, photothermal therapy, photodynamic therapy, and photocatalysis. Achieving strong absorption in the NIR-II band is a core prerequisite for related applications, and the development of nanomaterials with efficient NIR-II absorption has become a current research hotspot. Currently, NIR-II absorbing materials mainly include inorganic semiconductor nanocrystals (such as PbS, Ag2S, CuInSe2), organic small molecule dyes (such as IR-26, IR-1061), and some carbon-based materials. Among these, while inorganic semiconductors offer excellent absorption performance, they suffer from high biotoxicity, poor environmental stability, and complex preparation processes; organic dyes face bottlenecks such as rapid photobleaching, low quantum yield, and difficulty in large-scale preparation. Carbon quantum dots (CQDs), as a novel zero-dimensional carbon-based nanomaterial, are considered ideal NIR absorption candidates due to their wide availability of raw materials, good biocompatibility, and high photochemical stability. However, the optical absorption of traditional CQDs is mainly concentrated in the ultraviolet-visible region (<800 nm), and the absorption in the NIR-II band is extremely weak or even non-responsive, making it difficult to directly meet the needs of deep tissue applications.

[0003] To extend the absorption range of CQDs, researchers have modulated their band structure through heteroatom doping (such as N, S, P, B, etc.) or surface functional group modification, attempting to redshift the absorption edge to the NIR region. For example, nitrogen-doped CQDs can narrow the band gap by introducing intermediate energy levels, extending the absorption edge to the near-infrared I region (NIR-I, 800-1000 nm); sulfur-doped CQDs, due to the hybridization of the 2p orbitals of S and C, can further reduce the conduction band bottom energy, with some materials reaching an absorption edge of 1200 nm. Furthermore, single-element doped CQDs generally exhibit low absorption intensities in the NIR-II region (molar extinction coefficients are mostly below 10⁴ L·mol⁻¹). - ¹·cm - ¹), and the absorption peak is relatively wide and the half-peak width is large, which limits the optical efficiency.

[0004] To address the above problems, co-doping strategies have been proposed to optimize the electronic structure through the synergistic effect of two or more heteroatoms. For example, sulfur-phosphorus co-doped CQDs can simultaneously utilize the 2p orbitals of S and the 3p orbitals of P to form richer defect states; sulfur-nitrogen co-doped CQDs further reduce the band gap by coupling the lone pair electrons of N with the empty d orbitals of S. However, these co-doped systems still face the following key challenges: (1) Insufficient NIR-II absorption intensity, making it difficult to achieve efficient photothermal / photocatalytic conversion; (2) The absorption range only reaches the low wavelength region of NIR-II, especially lacking absorption in the 1200 nm long-wavelength region; (3) CQDs prepared by traditional hydrothermal / solvothermal methods often require high temperature (>200℃) or strong acid / strong base conditions, which easily leads to uneven heteroatom distribution and excessively large particle size (>10nm), affecting dispersibility and biocompatibility; (4) Lack of systematic theoretical guidance, making it difficult to accurately control the correspondence between doping ratio and absorption performance.

[0005] In particular, selenium (Se), as a Group VI element in the same group as sulfur, can form a lower conduction band depth than sulfur after its 4p orbital hybridizes with the 2p orbital of carbon, theoretically enabling a more effective red-shift of the absorption edge. However, selenium's high reactivity (easily oxidized to SeO3) limits its absorption. 2- Its low solubility (easily precipitates in aqueous phase) limits its effective doping in CQDs. Currently, there are very few studies on sulfur-selenium co-doped CQDs, with only a few reports mentioning its enhanced absorption in the visible light region, but none covering the absorption characteristics in the NIR-II region, and even less exploration of its controllable synthesis under a magnetic field.

[0006] Currently, magnetic fields have been developed into a means, similar to temperature and pressure, to regulate chemical reactions and prepare new materials. The process of preparing carbon dots using organic molecules as precursors involves 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 broken, forming carbon-based fragments and free radicals; third, the carbon-based fragments are further subjected to high temperature / high pressure to carbonize, yielding carbon dots. Numerous experiments have shown that strong magnetic fields can influence these three stages: first, they regulate the polymerization of organic molecules with conjugated groups, inducing changes in the stacking and orientation of molecular intermediates, affecting the morphology and structure of the carbon dots after carbonization; second, according to quantum chemical theory, the introduction of a magnetic field lowers the energy of the carbon-based fragments, increases the reactivity of free radicals with the carbon-based fragments, and enhances the controllability of heterodoping positions and concentrations; third, they enhance the adsorption / activation capacity of free radicals during the crystallization process of carbon-based fragments, generating new active sites, improving the conversion efficiency of functional groups in carbon dots, and affecting the surface and interfacial properties of carbon dots.

[0007] In summary, existing near-infrared II (NIR-II) absorbing materials generally suffer from high toxicity, poor stability, or insufficient absorption performance. While traditional CQDs exhibit good biocompatibility, their NIR-II absorption capacity is limited. Although co-doping strategies can extend the absorption range, the NIR-II absorption mechanism of sulfur-selenium co-doped systems remains unclear, and efficient and green preparation methods are lacking. Therefore, developing a sulfur-selenium co-doped carbon quantum dot synthesized under zero magnetic field conditions, possessing strong NIR-II absorption (1200 nm), high stability, and good biocompatibility, has significant scientific and application value. Summary of the Invention

[0008] The technical problem to be solved by this invention is how to obtain a near-infrared II ultraviolet absorber synthesized under magnetic or non-magnetic field conditions. Sulfur-selenium co-doped carbon quantum dots (1200 nm).

[0009] The present invention solves the above-mentioned technical problems through the following technical means:

[0010] The first aspect of this invention proposes a method for synthesizing near-infrared II ultraviolet absorption under magnetic or non-magnetic field conditions. A method for preparing sulfur-selenium co-doped carbon quantum dots (1200 nm) includes the following steps: using benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole and benzoic acid compounds as precursors, a mixed solution of ethylene glycol and water as solvent, and H2O2 as oxidant, a hydrothermal reaction is carried out under a magnetic field or a non-magnetic field.

[0011] Preferably, the mass ratio of benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole, and benzoic acid compounds is (30~80):(30~68):(60~138); more preferably (35~70):(40~65):(65~120).

[0012] Preferably, the volume ratio of ethylene glycol to water is (6~9):(7~10); more preferably (6.5~7.5):(8.5~9.5).

[0013] Preferably, the ratio of benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole, benzoic acid compounds, ethylene glycol, water, and H2O2 is 30-80 mg: 30-68 mg: 60-138 mg: 6-9 mL: 7-10 mL: 1.8-3 mL. More preferably, the ratio is 35-70 mg: 40-65 mg: 65-120 mg: 6.5-7.5 mL: 8.5-9.5 mL: 2.3-2.8 mL. Even more preferably, the ratio is 45 mg: 52 mg: 83 mg: 7 mL: 9 mL: 2.5 mL.

[0014] Preferably, the concentration of H2O2 is 25-35% (w / w); more preferably 30% (w / w).

[0015] Preferably, the hydrothermal reaction conditions are 180~210℃ for 18~24 h; more preferably 190~200℃ for 21~23 h.

[0016] Preferably, the strength of the magnetic field is greater than zero and less than or equal to 9 T.

[0017] Preferably, the process further includes water dialysis and drying of the product after the hydrothermal reaction.

[0018] Preferably, the dialysis uses a dialysis bag with a molecular weight cutoff of 2000-4000 Da; more preferably, it is 3000 Da.

[0019] Preferably, the dialysis time is 20-28 hours; more preferably 24 hours.

[0020] Preferably, the method includes the following steps: dissolving benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole and benzoic acid compounds in a mixed solution of ethylene glycol and water, mixing thoroughly, adding H2O2 solution, heating to react, cooling to room temperature after the reaction is complete, dialyzing the product, collecting the dialyzed aqueous solution, and freeze-drying to obtain sulfur-selenium co-doped carbon dots (SeS-CDs) powder.

[0021] Preferably, the benzoic acid compounds include, but are not limited to, any one or more of p-hydroxybenzoic acid and terephthalic acid.

[0022] Preferably, the process includes the following steps: dissolving benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole, and p-hydroxybenzoic acid in a ratio of 40 mg:34 mg:69 mg in a mixture of ethylene glycol and water at a ratio of 8 mL:8 mL, and stirring and sonicating for 10 minutes to ensure uniform mixing; adding 2 mL of 30% H2O2 solution and continuing sonication for 10 minutes; transferring the resulting reaction solution to a 25 mL polytetrafluoroethylene-lined stainless steel high-pressure reactor and reacting it in a 200°C oven for 20 h; cooling to room temperature after the reaction, centrifuging the mixture at 8000 rpm for 3 minutes, collecting the supernatant, and dialyzing it in deionized water for 48 hours using a dialysis bag with a molecular weight cutoff of 3000 Da; collecting the dialysis aqueous solution, freeze-drying it until the aqueous solution completely disappears to obtain sulfur-selenium co-doped carbon dots (SeS-CDs) powder.

[0023] A second aspect of the present invention proposes a near-infrared II region ultraviolet absorber prepared by the above-described preparation method. Sulfur-selenium co-doped carbon quantum dots (1200 nm)

[0024] Preferably, the near-infrared II region ultraviolet absorption ( Sulfur-selenium co-doped carbon quantum dots (1200 nm) exhibit good photodynamic effects in the near-infrared II region. 1 mL of a SeS-CDs aqueous solution (0.2 mg / mL) was transferred to a 1.5 mL transparent centrifuge tube, which was placed 2 cm from the output port of a 1208 nm laser. The laser was turned on, and its power was adjusted to 0.5 W before irradiation began. Irradiation was then paused at different times, and tetramethylbenzidine (TMB) reagent was added. The UV absorbance was then measured.

[0025] A third aspect of the present invention proposes a near-infrared II region ultraviolet absorber prepared by the above-described preparation method. Application of sulfur-selenium co-doped carbon quantum dots (1200 nm) as fluorescent dyes.

[0026] This invention also proposes the application of the above-mentioned sulfur-selenium co-doped carbon quantum dots in electronic devices, photosensitizers, and nanomedicine.

[0027] The beneficial effects of this invention are as follows: 1. In this invention, benzeneselenic acid is used as the selenium source, 2-mercapto-5-methyl-1,3,4-thiadiazole is used as the sulfur source, a mixed solution of ethylene glycol and water is used as the solvent, and H2O2 is used as the oxidant. The near-infrared II region ultraviolet absorption is obtained under magnetic or non-magnetic field conditions. The carbon quantum dots co-doped with sulfur and selenium (1200 nm) have good hydrophilicity, good fluorescence and near-infrared II ultraviolet absorption properties, and have good photodynamic therapy capabilities when excited by a 1208 nm light source.

[0028] 2. The near-infrared II region ultraviolet absorption of the present invention ( Sulfur-selenium co-doped carbon quantum dots (i.e., non-metallic carbon dots) with a wavelength of 1200 nm exhibit good hydrophilicity, good fluorescence, and near-infrared II ultraviolet absorption properties.

[0029] 3. This invention generates near-infrared II region ultraviolet absorption (… The sulfur-selenium co-doped carbon quantum dots (1200 nm) utilize low-cost raw materials, have short synthesis time, and are easy to operate, enabling efficient mass production and providing feasibility for industrial-scale applications.

[0030] 4. This invention constructs a near-infrared II region ultraviolet absorption structure through a simple chemical reaction. The sulfur-selenium co-doped carbon quantum dots (1200 nm) have tunable sulfur-selenium co-doping type and content, and generate reactive oxygen species under near-infrared II light source excitation, exhibiting photosensitizer properties.

[0031] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the process for preparing sulfur-selenium co-doped carbon quantum dots in Example 1 of the present invention; Figure 2 This is the X-ray diffraction pattern of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention; Figure 3 This is the Raman spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention; Figure 4 This is the ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention; Figure 5 These are photographs of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention under sunlight (left) and ultraviolet light (right); Figure 6 This is the fluorescence spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention, showing photoluminescence in a wide range of 400-580 nm. Figure 7 This is the X-ray photoelectron spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention; Figure 8 This is the C1s X-ray photoelectron spectroscopy spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention; Figure 9 This is the O1s X-ray photoelectron spectroscopy spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention; Figure 10 This is the N1s X-ray photoelectron spectroscopy spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention; Figure 11 This is the S2p X-ray photoelectron spectroscopy spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention; Figure 12 This is the Se3d X-ray photoelectron spectroscopy spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention; Figure 13 The photothermal properties of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention; Figure 14These are photos of the photodynamic properties of sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention after irradiation with a 1208 nm laser for different times; Figure 15 These are the ultraviolet absorption spectra of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention after irradiation with a 1208 nm laser for different times; Figure 16 This is the electron spin spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention after irradiation with a 1208 nm laser; Figure 17 This is a comparison of the ultraviolet absorption spectra of sulfur-selenium co-doped carbon quantum dots prepared in Examples 1 and 2 of this invention; Figure 18 These are comparative images of the photodynamic properties of sulfur-selenium co-doped carbon quantum dots prepared in Example 1 (left) and Example 2 (right) of this invention after irradiation with a 1208 nm laser. Figure 19 This is the ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 2 of this invention after irradiation with a 1208 nm laser; Figure 20 This is the ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 3 of this invention; Figure 21 These are comparative images of the photodynamic properties of sulfur-selenium co-doped carbon quantum dots prepared in Example 3 (left) and Example 1 (right) after irradiation with a 1208 nm laser. Figure 22 This is the ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 3 of this invention after irradiation with a 1208 nm laser; Figure 23 These are the ultraviolet absorption spectra of the sulfur-selenium co-doped carbon quantum dots prepared in Example 3 of this invention after irradiation with a 1208 nm laser for different times; Figure 24 These are photographs of reactive oxygen generation in sulfur-selenium co-doped carbon quantum dots prepared in Example 3 of the present invention after different times of irradiation with or without 1208 nm laser. Figure 25 These are the electron spin spectra of the sulfur-selenium co-doped carbon quantum dots prepared in Example 3 of this invention after irradiation with a 1208 nm laser for different times; Figure 26 The image shows the ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Comparative Example 2 of this invention. Figure 27 The image shows the ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Comparative Example 3 of this invention. Figure 28 This is the ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Comparative Example 4 of this invention; Figure 29 This is the ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Comparative Example 5 of this invention; Figure 30 This is the ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Comparative Example 6 of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art.

[0034] Unless otherwise specified, the test materials and reagents used in the following examples are commercially available or prepared by known methods.

[0035] Unless otherwise specified, all techniques or conditions described in the embodiments can be performed in accordance with the techniques or conditions described in the literature in this field or in the product manual. Unless otherwise specified, the quantitative experiments in the following embodiments are all repeated three times or more, and the results are averaged.

[0036] Example 1: A method for synthesizing near-infrared II ultraviolet absorption under non-magnetic field ( A method for preparing sulfur-selenium co-doped carbon quantum dots (1200 nm) includes the following steps: 40 mg of benzeneselenic acid, 34 mg of 2-mercapto-5-methyl-1,3,4-thiadiazole and 69 mg of hydroxybenzoic acid are weighed and dissolved evenly in 8 mL of distilled water and 8 mL of ethylene glycol. Then, 2 mL of 30% (w / w) H2O2 solution is added. The mixed solution is transferred to a 25 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and placed in a heating oven at 200 °C for 20 h. After the reaction, the mixture is cooled to room temperature. The supernatant is centrifuged and transferred to a dialysis bag with a molecular weight cutoff of 3000 Da. The bag is then dialyzed in 500 mL of distilled water. During dialysis, the aqueous solution outside the dialysis bag is collected every 24 h, and 500 mL of fresh distilled water is added to continue dialysis. Finally, all collected aqueous solutions are freeze-dried until the aqueous solution completely disappears to obtain sulfur-selenium co-doped carbon dots (SeS-CDs) powder.

[0037] The preparation process diagram of Example 1 is shown below. Figure 1As shown, distilled water and ethylene glycol were used as solvents, benzeneselenic acid and 2-mercapto-5-methyl-1,3,4-thiadiazole were used as Se source and S source, respectively, hydroxybenzoic acid was used as hydroxyl substituent source, and H2O2 was used as oxidant. The reaction was carried out in a 25 mL reactor at 200 °C for 20 h. Then the mixed solution was placed in a dialysis bag to remove impurities, and finally freeze-dried to obtain sulfur-selenium co-doped carbon quantum dots.

[0038] The X-ray diffraction pattern of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 is shown below. Figure 2 As shown, the spectrum shows a distinct diffraction peak signal at ~26.4°, which is attributed to the π-π interlayer stacking motif of the (002) crystal plane of graphite.

[0039] The Raman spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 is as follows: Figure 3 As shown, at ~1350 and ~1600 cm -1 The signals exhibited by the D and G bands, typical of graphene structures, were observed at ~258 and ~292 cm⁻¹, respectively. -1 Characteristic peaks for Se / S and S were also captured at that location.

[0040] The ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 is shown below. Figure 4 As shown, compared with the blank control, it has a significant absorption peak at 1208 nm.

[0041] The sulfur-selenium co-doped carbon quantum dots prepared in Example 1 are photographed under sunlight (left) and ultraviolet light (right). Figure 5 As shown, it appears as a pale yellow solution under sunlight, but exhibits significant fluorescence under ultraviolet light with a wavelength of 365 nm. Therefore, this sulfur-selenium co-doped carbon quantum dot can be used as a fluorescent dye.

[0042] The fluorescence spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1, exhibiting photoluminescence over a wide range of 400-580 nm, is shown below. Figure 6 As shown, when the excitation wavelength increases from 400 nm to 580 nm, the emission peak gradually shifts to a longer wavelength, and the PL intensity gradually increases and then decreases.

[0043] The X-ray photoelectron spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention is as follows: Figure 7 As shown, the carbon quantum dots contain 70.05% C, 3.47% N, 22.65% O, 3.22% S, and 0.61% Se.

[0044] The X-ray photoelectron spectroscopy (C1s) spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention is as follows: Figure 8As shown, the C1s spectra show four peaks for CC, C-Se / CN, CO, and C=O at 284.8 eV, 285.5 eV, 286.2 eV, and 288.0 eV, respectively.

[0045] The X-ray photoelectron spectroscopy (O1s) spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention is as follows: Figure 9 As shown, the O1s spectrum includes three peaks at 531.6 eV, 532.0 eV, and 532.8 eV, which are attributed to SO / Se-O, C=O, and CO, respectively.

[0046] The N1s X-ray photoelectron spectroscopy spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention is as follows: Figure 10 As shown, the N1s spectrum includes three peaks at 399.5 eV, 400.6 eV, and 401.4 eV, corresponding to pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen, respectively.

[0047] The X-ray photoelectron spectroscopy (S2p) spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention is as follows: Figure 11 As shown, the S2p spectrum includes three peaks at 162.0 eV, 166.4 eV, and 169.3 eV, corresponding to CS, S, and S, respectively. 4+ -O and S 6+ -O.

[0048] The X-ray photoelectron spectroscopy (Se3d) spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention is as follows: Figure 12 As shown, the Se3d spectrum includes two peaks at 54.2 eV and 56.2 eV, corresponding to Se... 2- and Se-O.

[0049] The photothermal properties of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention are as follows: Figure 13 As shown, the photothermal capacity tested at a concentration of 0.2 mg / mL for 5 minutes was only 2.3°C higher than that of pure water, indicating that under excitation light of 1208 nm, its photothermal conversion capacity could not be significantly improved.

[0050] Photodynamic performance images of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention after irradiation with a 1208 nm laser for different times are shown below. Figure 14 As shown, the blue color of the solution gradually deepens with prolonged irradiation time, indicating the generation of more reactive oxygen species.

[0051] The ultraviolet absorption spectra of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention after irradiation with a 1208 nm laser for different times are as follows: Figure 15As shown, the characteristic peak of the solution at 651 nm gradually increases with the extension of irradiation time, indicating that more reactive oxygen species are generated.

[0052] The electron spin spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 1 of this invention after irradiation with a 1208 nm laser is as follows: Figure 16 As shown, using the reactive oxygen species scavenger 5,5-dimethyl-1-pyrrolline-N-oxide (DMPO) in conjunction with electron spin spectroscopy, the type of reactive oxygen species generated was determined to be hydroxyl radicals.

[0053] Example 2: The difference between this embodiment and Embodiment 1 is that a 9T magnetic field environment was applied during the reaction process, specifically: A method for synthesizing near-infrared II ultraviolet absorption under a magnetic field ( A method for preparing sulfur-selenium co-doped carbon quantum dots (1200 nm) includes the following steps: Weigh 40 mg of benzeneselenic acid, 34 mg of 2-mercapto-5-methyl-1,3,4-thiadiazole and 69 mg of hydroxybenzoic acid, add 8 mL of distilled water and 8 mL of ethylene glycol to dissolve evenly, then add 2 mL of 30% (w / w) H2O2 solution, transfer the mixed solution to a 25 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, place it in a magnet with a magnetic field strength of 9 T, and heat to 200 °C for 20 h. After the reaction is completed, cool to room temperature, centrifuge the mixed solution, and collect the supernatant into a dialysis bag with a molecular weight cutoff of 3000 Da, and dialyze it in 500 mL of distilled water; during the dialysis process, collect the aqueous solution outside the dialysis bag every 24 h, and add fresh 500 mL of distilled water. The solution was dialyzed with mL of distilled water; finally, all the collected aqueous solution was freeze-dried until the aqueous solution disappeared completely, and sulfur-selenium co-doped carbon dots (SeS-CDs) powder was obtained.

[0054] The UV absorption spectra of the sulfur-selenium co-doped carbon quantum dots prepared in Examples 1 and 2 of this invention are compared as follows: Figure 17 As shown, the absorption peak of the sulfur-selenium co-doped carbon quantum dots prepared under the magnetic field in Example 2 is at the same position as the absorption peak in Example 1, and the sample under the magnetic field has a wider peak position span. This indicates that the overall absorbance of Example 2 is significantly higher than that of Example 1, and it may be more efficient in terms of light absorption and conversion, and the heating effect is more significant.

[0055] Photodynamic performance images of sulfur-selenium co-doped carbon quantum dots prepared in Example 2 of this invention after 1208 nm laser irradiation for 5 minutes (e.g.) Figure 18 As shown in the middle right image), its color intensity after 1208 nm irradiation for 5 minutes is compared to that of Example 1 (as shown in the middle right image). Figure 18 (As shown in the middle left image) Shallow.

[0056] The ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 2 of this invention after irradiation with a 1208 nm laser is as follows: Figure 19 As shown. With Figure 18 The results shown are consistent, with its absorption peak at 651 nm being lower than that of Example 1.

[0057] Example 3: The difference between this embodiment and Embodiment 1 is that: Replace “p-hydroxybenzoic acid” with “terephthalic acid”, and the rest is the same as in Example 1.

[0058] The ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 3 of this invention is shown below. Figure 20 As shown, the absorption peak of the sulfur-selenium co-doped carbon quantum dots with terephthalic acid as a precursor is at the same position as the absorption peak in Example 1.

[0059] Photodynamic performance images of sulfur-selenium co-doped carbon quantum dots prepared in Example 3 of this invention after 1208 nm laser irradiation for 5 minutes (e.g.) Figure 21 As shown in the left image of the middle figure), its color intensity after being irradiated at 1208 nm for 5 minutes is compared to that of Example 1 (as shown in the left image of the middle figure). Figure 21 (As shown in the middle right image) Shallow.

[0060] The ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Example 3 of this invention after irradiation with a 1208 nm laser is as follows: Figure 22 As shown. With Figure 21 The results shown are consistent, with its absorption peak at 651 nm being lower than that of Example 1.

[0061] The ultraviolet absorption spectra of the sulfur-selenium co-doped carbon quantum dots prepared in Example 3 of this invention after irradiation with a 1208 nm laser for different times are as follows: Figure 23 As shown, the characteristic peak of the solution at 651 nm gradually increases with the extension of irradiation time, but a long irradiation time is required to produce a significant photodynamic effect.

[0062] Images of reactive oxygen species generated by sulfur-selenium co-doped carbon quantum dots prepared in Example 3 of this invention after different times of irradiation with and without 1208 nm laser are shown below. Figure 24 As shown, the darker the color, the more reactive oxygen species are produced. The results show that the longer the irradiation time, the more reactive oxygen species are produced.

[0063] The electron spin spectra of the sulfur-selenium co-doped carbon quantum dots prepared in Example 3 of this invention after irradiation with a 1208 nm laser for different times are as follows: Figure 25 As shown, using DMPO and an electron spin spectrometer, the type of reactive oxygen species generated was determined to be hydroxyl radicals, and the production of hydroxyl radicals increased with the extension of irradiation time.

[0064] Example 4: The difference between this embodiment and Embodiment 1 is that: The amounts of benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole, benzoic acid compounds, ethylene glycol, water, and H2O2 were 30 mg, 30 mg, 60 mg, 6 mL, 7 mL, and 1.8 mL, respectively. The concentration of the H2O2 solution is 35% (w / w); The reaction conditions were: 180℃, 24 h; Dialysis bags with a molecular weight cutoff of 2000 Da.

[0065] The rest is the same as in Example 1.

[0066] Example 5: The difference between this embodiment and Embodiment 1 is that: The amounts of benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole, benzoic acid compounds, ethylene glycol, water, and H2O2 were 80 mg, 68 mg, 138 mg, 9 mL, 10 mL, and 3 mL, respectively. The concentration of the H2O2 solution is 25% (w / w); The reaction conditions were: 210℃, 18 h; Dialysis bags with a molecular weight cutoff of 4000 Da.

[0067] The rest is the same as in Example 1.

[0068] Example 6: The difference between this embodiment and Embodiment 1 is that: The amounts of benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole, benzoic acid compounds, ethylene glycol, water, and H2O2 were 35 mg, 40 mg, 65 mg, 6.5 mL, 8.5 mL, and 2.3 mL, respectively. The reaction conditions were: 190℃, 23 h; The rest is the same as in Example 1.

[0069] Example 7: The difference between this embodiment and Embodiment 1 is that: The amounts of benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole, benzoic acid compounds, ethylene glycol, water, and H2O2 were 70 mg, 65 mg, 120 mg, 7.5 mL, 9.5 mL, and 2.8 mL, respectively. The reaction conditions were: 200℃, 23 h; The rest is the same as in Example 1.

[0070] The sulfur-selenium co-doped carbon quantum dots prepared in Examples 4-7 have similar properties to those in Example 1.

[0071] Example 8: The difference between this embodiment and Embodiment 2 is as follows: Replace the magnetic field strength "9T" with "4T"; The rest is the same as in Example 2.

[0072] The performance of the sulfur-selenium co-doped carbon quantum dots prepared in Example 8 is similar to that in Example 2.

[0073] Comparative Example 1: The difference between this comparative example and Example 1 is that the amount of H2O2 solution used is changed from "2 mL" to "4 mL", otherwise it is the same as Example 1.

[0074] Result: After the reaction was completed and cooled to room temperature, the polytetrafluoroethylene liner was directly destroyed by the excessive hydrogen peroxide, and no sample could be obtained.

[0075] Comparative Example 2: The difference between this comparative example and Example 1 is that the amount of benzeneselenic acid used is changed from "40 mg" to "20 mg", otherwise it is the same as Example 1.

[0076] The ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Comparative Example 2 of this invention is shown below. Figure 26 As shown, the absorption peak (1196 nm) of sulfur-selenium co-doped carbon quantum dots with low dose of benzene-selenic acid as precursor is lower than the absorption peak (1208 nm) in Example 1.

[0077] Comparative Example 3: The difference between this comparative example and Example 1 is that "ethylene glycol" is replaced with "acetone", otherwise it is the same as Example 1.

[0078] The ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Comparative Example 3 of this invention is shown below. Figure 27 As shown, the absorption peak (1190 nm) of sulfur-selenium co-doped carbon quantum dots prepared by replacing ethylene glycol with acetone is lower than 1200 nm.

[0079] Comparative Example 4: The difference between this comparative example and Example 1 is that it lacks "2-mercapto-5-methyl-1,3,4-thiadiazole", otherwise it is the same as Example 1.

[0080] The ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Comparative Example 4 of this invention is shown below. Figure 28 As shown, sulfur-selenium co-doped carbon quantum dots prepared without 2-mercapto-5-methyl-1,3,4-thiadiazole do not have an absorption peak after 1200 nm.

[0081] Comparative Example 5: The difference between this comparative example and Example 1 is that it lacks "H2O2 solution", otherwise it is the same as Example 1.

[0082] The ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Comparative Example 5 of this invention is shown below. Figure 29 As shown, sulfur-selenium co-doped carbon quantum dots prepared without hydrogen peroxide do not exhibit an absorption peak after 1200 nm.

[0083] Comparative Example 6: The difference between this comparative example and Example 1 is that "ethylene glycol" is replaced with "ethanol", otherwise it is the same as Example 1.

[0084] The ultraviolet absorption spectrum of the sulfur-selenium co-doped carbon quantum dots prepared in Comparative Example 6 of this invention is shown below. Figure 30 As shown, sulfur-selenium co-doped carbon quantum dots prepared in ethanol solvent do not have an absorption peak after 1200 nm.

[0085] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing sulfur-selenium co-doped carbon quantum dots with near-infrared II ultraviolet absorption under magnetic or non-magnetic field conditions, characterized in that, Includes the following steps: The product is obtained by hydrothermal reaction under magnetic or non-magnetic field conditions, using benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole and benzoic acid compounds as precursors, a mixed solution of ethylene glycol and water as solvent, and H2O2 as oxidant.

2. The preparation method according to claim 1, characterized in that, The mass ratio of benzene selenite, 2-mercapto-5-methyl-1,3,4-thiadiazole, and benzoic acid compounds is (30~80):(30~68):(60~138).

3. The preparation method according to claim 1, characterized in that, The volume ratio of ethylene glycol to water is (6~9):(7~10).

4. The preparation method according to claim 1, characterized in that, The ratio of benzeneselenic acid, 2-mercapto-5-methyl-1,3,4-thiadiazole, benzoic acid compounds, ethylene glycol, water, and H2O2 is 30~80 mg: 30~68 mg: 60~138 mg: 6~9 mL: 7~10 mL: 1.8~3 mL.

5. The preparation method according to claim 1, characterized in that, The concentration of H2O2 is 25-35%.

6. The preparation method according to claim 1, characterized in that, The hydrothermal reaction conditions are 180~210℃ for 18~24 h.

7. The preparation method according to claim 1, characterized in that, The strength of the magnetic field is greater than zero and less than or equal to 9 T.

8. The preparation method according to claim 1, characterized in that, It also includes water dialysis and drying of the products after hydrothermal reaction; the dialysis specifically uses a dialysis bag with a molecular weight cutoff of 2000~4000 Da.

9. Sulfur-selenium co-doped carbon quantum dots with near-infrared II ultraviolet absorption prepared by the preparation method according to any one of claims 1-8.

10. The application of the sulfur-selenium co-doped carbon quantum dots according to claim 9 in electronic devices, fluorescent dyes, photosensitizers, and nanomedicine.

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