Carbon dot loaded composite gel microspheres as well as preparation method and application thereof

Abstract

The invention discloses a carbon dot loaded composite gel microsphere as well as a preparation method and application thereof. The preparation method comprises the following steps: by taking sucrose as a carbon source, preparing a carbon dot nano material through phosphoric acid and ethidene diamine treatment; sodium alginate and carboxymethyl chitosan are mixed to form a gel skeleton, tetraethyl silicate is used as a cross-linking agent, and the composite gel microspheres loaded with the carbon dots are synthesized in situ in a calcium chloride solution. The composite gel microspheres are subjected to specific reaction with tetracycline under ultraviolet irradiation to generate color change, the chromaticity is in direct proportion to the concentration of tetracycline, and visual colorimetric detection of tetracycline can be realized; meanwhile, tetracycline is efficiently removed by the microspheres through the synergistic effect of adsorption and photocatalytic degradation, and the highest removal rate reaches 96%. The method realizes synchronous detection and removal of tetracycline, has the advantages of simple operation, low cost, environmental protection, high efficiency and the like, and is suitable for rapid early warning and purification of tetracycline in a water body.

Description

Technical Field

[0001] This invention pertains to the preparation of nanomaterials and their applications in the environmental field, specifically relating to a carbon dot composite gel microsphere, its preparation method, and its application. Background Technology

[0002] Antibiotics are widely used in human medicine and animal husbandry, but their overuse and residues have led to increasingly serious water pollution problems. Tetracycline antibiotics, due to their structural stability and strong persistence, are frequently detected in the aquatic environment, posing a threat to ecosystems and human health. Currently, the detection of tetracyclines mainly relies on instrumental analytical methods such as spectrophotometry, gas chromatography, and liquid chromatography. While these methods are highly accurate, they require specialized equipment, involve cumbersome pretreatment, and are costly, making rapid on-site detection difficult. Furthermore, while simpler methods such as colorimetry are easy to operate, they often lack removal capabilities, failing to achieve simultaneous treatment of pollutants.

[0003] In tetracycline removal, adsorption is widely used due to its simplicity and low cost; however, adsorption only transfers the pollutant to the solid phase, potentially causing secondary pollution. Photocatalytic oxidation technology can degrade antibiotics into harmless small molecules, but existing materials mostly focus on a single function and cannot simultaneously achieve detection and removal. Therefore, developing a green material that can both rapidly detect tetracycline concentration and efficiently remove tetracycline has become an urgent need in the field of environmental remediation. Summary of the Invention

[0004] The purpose of this invention is to provide a carbon dot-loaded composite gel microsphere, its preparation method, and its application, solving the problem that tetracycline detection and removal cannot be performed simultaneously in existing technologies. This composite gel microsphere achieves both visual colorimetric detection and photocatalytic degradation of tetracycline through the synergistic effect of carbon dot nanomaterials and a gel framework. This composite gel microsphere combines colorimetric detection and photocatalytic degradation functions, and can be used for rapid visual monitoring and efficient purification of tetracycline antibiotics in water.

[0005] To solve the above-mentioned technical problems, the technical solution proposed in this application is as follows:

[0006] This invention provides a method for preparing carbon dot-loaded composite gel microspheres, comprising the following steps: (a) Preparation of carbon dot nanomaterials; (b) Preparation of a mixed solution of sodium alginate and carboxymethyl chitosan; (c) Using tetraethyl silicate as a crosslinking agent, carbon dot nanomaterials are reacted with a mixed solution of sodium alginate and carboxymethyl chitosan, and then dropped into a calcium chloride solution to form composite gel microspheres.

[0007] Further, step (a) includes: dissolving sucrose in phosphoric acid and an aqueous solution, heating and reacting, adding ethylenediamine, and then obtaining carbon dot nanomaterials through ultrafiltration, dialysis, and reduction treatment.

[0008] Furthermore, the sucrose has a mass of 6g, the phosphoric acid has a volume of 6mL, the water has a volume of 18mL, the heating temperature is 80℃, and the heating time is 50min; the ethylenediamine has a volume of 18mL; the reduction treatment uses NaBH4 and is stirred at room temperature for 48h.

[0009] Further, in step (b), the sodium alginate solution has a mass fraction of 1-4% and the carboxymethyl chitosan has a mass fraction of 0-3wt%.

[0010] Furthermore, the sodium alginate solution has a mass fraction of 3%, and the carboxymethyl chitosan has a mass fraction of 1.5%.

[0011] Further, step (c) includes: dissolving tetraethyl silicate in ethanol and aqueous solution, adding carbon dot solution, stirring, adding sodium alginate and carboxymethyl chitosan mixed solution, continuing stirring, cooling, and then adding dropwise to calcium chloride solution.

[0012] Further, the volume of the tetraethyl silicate is 2 mL, the volume of the ethanol is 0.64 mL, the volume of the water is 0.44 mL, the mass fraction of the carbon dot solution is 0-20 wt%, the stirring temperature is 60 °C, and the stirring time is 1-6 h; the mass fraction of the calcium chloride solution is 3%.

[0013] Furthermore, the carbon dot solution has a mass fraction of 10%.

[0014] On the other hand, this application also claims protection for a carbon dot-loaded composite gel microsphere, prepared by any of the above-described preparation methods, comprising a network interpenetrating structure formed by ionic crosslinking of carboxymethyl chitosan and sodium alginate, and carbon dot nanomaterials encapsulated in the network interpenetrating structure; the network interpenetrating structure is a double network structure, which keeps the dried microspheres round and has a loose porous structure; the interior of the microspheres exhibits irregular wrinkles and a porous structure with different pore sizes.

[0015] Furthermore, this application also claims protection for a method for applying the above-mentioned carbon dot composite gel microspheres to the simultaneous detection and removal of tetracycline, comprising the following steps: (d) Add carbon dot composite gel microspheres to a tetracycline solution and react under ultraviolet light irradiation; (e) By acquiring optical images of the gel microspheres, analyze the color changes, and qualitatively or quantitatively detect the tetracycline concentration; (f) Evaluate tetracycline removal efficiency by measuring changes in tetracycline concentration.

[0016] Further, in step (d), the dosage of the loaded carbon dot composite gel microspheres is 0.4-1.5 g / L, the concentration of the tetracycline solution is 10-500 μM, the ultraviolet wavelength is 365 nm, the reaction temperature is 35 °C, and the reaction time is 0-48 h.

[0017] Furthermore, the dosage of the carbon dot composite gel microspheres was 0.8 g / L.

[0018] Further, in step (e), an optical image is acquired using a digital camera or mobile phone, in accordance with CIE 1976 L. a b. The color difference formula is used to calculate the color difference value, ΔE. The calculation formula is:

[0019] in Indicates brightness. Indicates red-green hue. Indicates the shade of yellow-blue.

[0020] Compared with the prior art, the present invention achieves the following beneficial technical effects: This application achieves simultaneous, visualized detection and efficient removal of tetracycline pollutants in water by constructing composite gel microspheres loaded with carbon dots. The material exhibits a significant color reaction upon contact with tetracycline, with the color intensity directly correlated with the pollutant concentration. Rapid qualitative and quantitative analysis can be performed using a regular mobile phone, eliminating the need for complex instruments. Simultaneously, through the synergistic effect of adsorption and photocatalysis, the material can completely degrade tetracycline, avoiding secondary pollution. Furthermore, the microsphere morphology facilitates recycling and reuse, providing an innovative solution for constructing a green environmental remediation technology integrating real-time early warning, deep purification, and material recycling. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The images show the physical specimen, transmission electron microscope (TEM) image, and particle size distribution diagram of the carbon dots synthesized in Example 1 of this invention.

[0023] Figure 2 The images show the physical image and scanning electron microscope (SEM) image (surface and cross-section) of the composite gel microspheres synthesized in Example 1 of this invention.

[0024] Figure 3This invention provides the colorimetric response and detection standard curve of the product in Example 2 for changes in tetracycline concentration, as well as the detection selectivity for different types of antibiotics.

[0025] Figure 4 This is an analysis of the degradation efficiency of the product of Example 3 of the present invention for the target substance tetracycline under different concentration conditions over time.

[0026] Figure 5 This is a time-removal rate / color difference value resolution diagram of the product of Example 4 of the present invention for the target substance tetracycline. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0028] This invention provides a method for preparing carbon dot-loaded composite gel microspheres, comprising the following steps: (a) Preparation of carbon dot nanomaterials; (b) Preparation of a mixed solution of sodium alginate and carboxymethyl chitosan; (c) Using tetraethyl silicate as a crosslinking agent, carbon dot nanomaterials are reacted with a mixed solution of sodium alginate and carboxymethyl chitosan, and then dropped into a calcium chloride solution to form composite gel microspheres.

[0029] In this application, step (a) includes: dissolving sucrose in phosphoric acid and an aqueous solution, heating and reacting, adding ethylenediamine, and then obtaining carbon dot nanomaterials through ultrafiltration, dialysis, and reduction treatment.

[0030] In this application, the sucrose mass is 6g, the phosphoric acid volume is 6mL, the water volume is 18mL, the heating temperature is 80℃, and the heating time is 50min; the ethylenediamine volume is 18mL; the reduction treatment uses NaBH4 and is stirred at room temperature for 48h.

[0031] In this application, in step (b), the sodium alginate solution has a mass fraction of 1-4% and the carboxymethyl chitosan has a mass fraction of 0-3wt%.

[0032] In this application, the sodium alginate solution has a mass fraction of 3%, and the carboxymethyl chitosan has a mass fraction of 1.5%.

[0033] In this application, step (c) includes: dissolving tetraethyl silicate in ethanol and aqueous solution, adding carbon dot solution, stirring, adding sodium alginate and carboxymethyl chitosan mixed solution, continuing to stir, cooling, and then adding dropwise to calcium chloride solution.

[0034] In this application, the volume of tetraethyl silicate is 2 mL, the volume of ethanol is 0.64 mL, the volume of water is 0.44 mL, the mass fraction of carbon dot solution is 0-20 wt%, the stirring temperature is 60 °C, and the stirring time is 1-6 h; the mass fraction of calcium chloride solution is 3%.

[0035] In this application, the carbon dot solution has a mass fraction of 10%.

[0036] This application also claims protection for a carbon dot-loaded composite gel microsphere, prepared by any of the above-described preparation methods, comprising a network interpenetrating structure formed by ionic crosslinking of carboxymethyl chitosan and sodium alginate, and carbon dot nanomaterials encapsulated in the network interpenetrating structure; the network interpenetrating structure is a double network structure, which keeps the dried microspheres round and has a loose porous structure; the interior of the microspheres exhibits irregular wrinkles and a porous structure with different pore sizes.

[0037] The gel microspheres prepared by this invention have, on the one hand, a porous structure formed by cross-linking of carboxymethyl chitosan and sodium alginate, which adsorbs carbon dots and tetracycline degradation products to avoid secondary pollution; on the other hand, the carbon dots loaded in the cross-linked network exhibit excellent photocatalytic performance for tetracycline, so as to achieve efficient removal of tetracycline.

[0038] This application also claims protection for a method for applying the above-mentioned carbon dot composite gel microspheres to the simultaneous detection and removal of tetracycline, comprising the following steps: (d) Add carbon dot composite gel microspheres to a tetracycline solution and react under ultraviolet light irradiation; (e) By acquiring optical images of the gel microspheres, analyzing the color change, the concentration of tetracycline can be qualitatively or quantitatively detected; after the gel microspheres prepared in this invention adsorb tetracycline, they will show obvious purple at low concentrations and obvious purplish-black at high concentrations, and the color is proportional to the concentration of adsorbed tetracycline. Therefore, tetracycline can be qualitatively and quantitatively analyzed based on the changes in color and color intensity. (f) Evaluate tetracycline removal efficiency by measuring changes in tetracycline concentration.

[0039] In this application, in step (d), the dosage of the loaded carbon dot composite gel microspheres is 0.4-1.5 g / L, the concentration of the tetracycline solution is 10-500 μM, the ultraviolet wavelength is 365 nm, the reaction temperature is 35 °C, and the reaction time is 0-48 h.

[0040] In this application, the dosage of the carbon dot composite gel microspheres is 0.8 g / L.

[0041] In this application, in step (e), an optical image is acquired using a digital camera or mobile phone, in accordance with CIE 1976 L. a b. The color difference formula is used to calculate the color difference value, ΔE. The calculation formula is:

[0042] in Indicates brightness. Indicates red-green hue. Indicates the degree of yellow-blue. Specifically, , and L a and b The difference between the measured value and the corresponding standard value.

[0043] Preferably, Photoshop is selected as the color picking software in step (e). Furthermore, compared to the commonly used RGB model, the color model selected in this invention is the Lab model, where the L channel represents the brightness range from black (0) to white (100), and the a channel represents red (+a)... ) to green (-a The color changes between () and (), while the b channel changes from yellow (+b) to yellow (+b). ) to blue (-b In terms of color gamut representation, Lab mode is more comprehensive, independent of lighting and device, and its processing speed is just as fast as RGB mode.

[0044] This application utilizes software to analyze the resulting images, replacing commonly used spectrometers and chromatographs. It is simple to operate, economical, and requires only a mobile phone and a portable laptop to complete the detection and analysis, which is of great significance for achieving efficient, economical, and intuitive portable detection.

[0045] The present application will be further described below with reference to embodiments: Example 1 A method for preparing carbon dot-loaded composite gel microspheres: (1) Preparation of carbon dot nanomaterials: 6 g of sucrose was dissolved in 6 mL of phosphoric acid and 18 mL of aqueous solution, and heated in a water bath at 80 °C for 50 min to obtain a yellow liquid; while hot, 18 mL of ethylenediamine was added dropwise, and after thorough stirring, the dark brown viscous substance was ultrafiltered through a membrane (0.22 μm) and dialyzed for 72 h (500-1000 Da) to obtain a pale yellow liquid. Then, excess NaBH4 was added and gently stirred at room temperature for 48 h to obtain reduced carbon dot nanomaterials. Excess reducing agent was removed by heating at 80 °C and dialyzing. Finally, the final substance was obtained by vacuum freeze-drying for 72 h and frozen at 4 °C for subsequent use. (2) Preparation of sodium alginate / carboxymethyl chitosan mixed solution: Select 1-4% sodium alginate solution and add carboxymethyl chitosan standard sample (0-3 wt%) to prepare mixed solution.

[0046] (3) Preparation of composite hydrogel microspheres: Tetraethyl silicate was selected as the crosslinking agent. 2 mL of tetraethyl silicate was mixed with 0.64 mL of ethanol and 0.44 mL of aqueous solution, and 2 mL of carbon dot solution (3 wt%) was added. The mixture was magnetically stirred at 60 °C for 1 h. Then, 5 mL of sodium alginate / carboxymethyl chitosan mixed solution was added, and the mixture was magnetically stirred at 60 °C for 6 h. After the product cooled to room temperature, it was ultrasonically treated to remove air bubbles, and then added dropwise to 3% CaCl2 solution to obtain composite hydrogel microspheres with a nearly spherical shape, smooth surface, and uniform size. The microspheres were washed multiple times with distilled water and then freeze-dried under vacuum for subsequent use.

[0047] like Figure 1 As shown, the final product of carbon dots obtained after vacuum freeze-drying is a white solid powder (e.g. Figure 1 (As shown in a). Transmission electron microscopy images show that the carbon dots are round or elliptical and have good dispersibility, mainly due to the abundance of hydrophilic functional groups on their surface (such as...). Figure 1 (As shown in b) The particle size of over 600 reduced carbon dots was statistically analyzed using Nano Measurer software. The particle size ranged from 0.75 to 4.25 nm, and the particle size distribution conformed to a Gaussian distribution, with an average size of 2.09 ± 0.7 nm (as shown in b). Figure 1 (As shown in c in the image). Meanwhile... Figure 1 The built-in illustration in b is a high-resolution lattice diagram of carbon dots. It can be clearly seen that carbon dots have obvious lattice structures. The distance between two adjacent lattice fringes is 0.208 nm, which corresponds to the (100) crystal plane of carbon dots.

[0048] like Figure 2As shown, the microsphere samples exhibit a well-defined spherical shape with an average particle size of approximately 3 mm. After drying, the microspheres do not collapse and remain rounded. This is due to the high degree of cross-linking, which forms a double-network structure, allowing the microspheres to maintain good mechanical properties and a loose, porous structure (e.g., Figure 2 As shown in a and b in the figure). The interior of the microspheres exhibits irregular folds and a porous structure with different pore sizes (e.g., ...). Figure 2 (as shown in c) This is beneficial for providing a wide range of internal active sites and abundant electron transport pathways.

[0049] Example 2 Applications of tetracycline detection: Carbon dot nanomaterial-loaded composite gel microspheres (0.8 g / L) were added to 100 mL of tetracycline standard solutions of different concentrations (10-500 μM), and the reaction was carried out at a constant temperature of 35 °C (180 rpm, 6 h) under ultraviolet light (365 nm) irradiation. Optical images of the chromogenic gel microspheres were acquired using a digital camera or mobile phone at a fixed distance and transferred to a computer as JPEG files. The images were then analyzed according to CIE 1976 L. a b. A color difference formula is used to measure the color difference between the sample and the standard to determine the content of the analyte. Furthermore, the target substance tetracycline in the detection system was replaced with different types of antibiotics (chloramphenicol CPL, chlortetracycline hydrochloride CTC, oxytetracycline OTC, cephalexin CL, and bleomycin sulfate BLM) to investigate the detection selectivity of the composite microspheres for tetracycline.

[0050] like Figure 3 As shown, when the composite gel microspheres were added to the TC solution, the microspheres changed from their original milky white color to purple, and the purple chromaticity value of the microspheres gradually increased with the increase of the TC concentration in the system. Figure 3 (a) The Lab values ​​of the optical images of the gel microspheres were read using Photoshop image software, and the ΔE color difference value of the sample microspheres was calculated using a formula. The results are as follows: Figure 3 As shown in b: when the TC concentration is between 10 μM and 500 μM, the logarithm of the TC concentration shows a good linear relationship with the change in the purple color difference value of the image (R0). 2 = 0.991), which yielded a low detection limit of 1.84 μM (S / N = 3). For CTC and OTC, the composite gel microspheres only adsorbed and removed them; the colorimetric effect of the antibiotic solution was transferred to the microspheres, but no significant colorimetric effect occurred. However, for CPL, CL, and BLM, the composite gel microspheres did not participate in the significant removal and colorimetric processes. Figure 3 (c) This indicates that the composite gel spheres have good selectivity for TC detection.

[0051] Example 3 Tetracycline removal efficiency analysis: Carbon dot nanomaterial composite gel microspheres (0.8 g / L) were added to 100 mL tetracycline standard solutions of different concentrations (10-500 μM). The reaction was carried out at 35 °C (180 rpm) under UV light (365 nm) irradiation. The supernatant was collected at different time intervals (0-48 h) and filtered through a 0.22 µm filter membrane. The change in tetracycline concentration over time was measured by HPLC. The specific test steps are as follows: The chromatographic column is a reverse-flow C18 column, the mobile phase composition is acetonitrile:sodium dihydrogen phosphate = 35:65 (v / v), where the sodium dihydrogen phosphate solution concentration is 0.01 M, the pH is adjusted to 2.5 with 30% (v / v) nitric acid solution, the column temperature is 25 ± 0.8℃, the mobile phase flow rate is 1.0 mL / min, the retention time is set to 5-6 min, the corresponding tetracycline peak time is 2.4 min, and the tetracycline injection volume and detection wavelength are set to 50 μL and 355 nm, respectively.

[0052] like Figure 4 As shown, Figure 4 Figure a shows the UV-Vis absorption spectrum changes from 210 to 450 nm during the TC degradation process over 24 hours. The results indicate that the characteristic peak of TC at 355 nm, the characteristic wavelength of tetracycline, gradually decreases to near zero over 24 hours, suggesting that most of the TC is degraded during the reaction. Simultaneously, the absorption peak at 270 nm shows a slight shift and gradually decreases over time, while the absorption peaks in the UV region (163-230 nm) gradually increase. This phenomenon suggests that the conjugated structure of TC is disrupted, decomposing into some intermediate products and smaller molecular structures. Figure 4 Figure b shows the time-dependent photocatalytic degradation rate of tetracycline by the composite gel microspheres at different concentrations (25-200 μM). At different TC concentrations, the composite gel microspheres maintained a high removal efficiency of over 95% within 36 h, and the reaction rate constants under each concentration condition were [evaluated / discussed]. Figure 4 The c and d in the text are shown.

[0053] Example 4 Synchronous detection and removal kinetics: Carbon dot nanomaterial composite gel microspheres (0.8 g / L) were added to 100 mL tetracycline standard solutions of different concentrations (10-500 μM). The reactions were carried out at 35 °C under darkness (180 rpm, 1 h) and under ultraviolet light irradiation (180 rpm, 46 h). The supernatant was collected after fixed time intervals and filtered through a 0.22 µm filter membrane. The changes in tetracycline concentration and color over time were measured by colorimetric analysis and HPLC, respectively.

[0054] like Figure 5 As shown, the time-removal rate / color difference value resolution diagram of the composite gel microspheres for the target substance tetracycline is presented. Adsorption contributes approximately 45% of the removal rate in the dark, while light exposure accelerates the degradation efficiency to >90%. The reaction rate initially shows a significant increasing trend, but as the reaction time increases, the curves under various concentration conditions gradually stabilize, reaching a steady state in the later stages. Color changes exhibit a similar trend: the color difference value initially increases gradually over time, then decreases, and subsequently stabilizes. The decrease is attributed to the further photodegradation of the purple intermediate product generated by the photocatalytic reaction under UV excitation, leading to a reduction in color development.

[0055] Example 5 Practical applications: To evaluate the practicality of this invention under real-world environmental conditions, the research scope was expanded from laboratory simulation systems to natural surface water collected from major rivers and lakes in China. The steps and methods were basically the same as in Example 4, except that the sampling frequency was adjusted to a single sampling, the detection sampling time was 24 hours, and the removal sampling time was 48 hours. Representative stations covering different hydrogeographic regions, including the Yangtze River, Yellow River, Pearl River, and major inland lakes, were selected for sampling to evaluate the monitoring and remediation performance of the composite gel microspheres against tetracycline in complex natural water systems. As shown in Table 1, the practical environmental applicability analysis was consistent with the laboratory observation results; the composite gel microspheres exhibited a good colorimetric response to the target substance tetracycline in natural water bodies, ΔE The readings were highly correlated with the TC concentration determined by high performance liquid chromatography-mass spectrometry. Its detection limit and linear response range remain comparable to those under controlled conditions, demonstrating the system's robustness against interference from coexisting natural organic matter, ions, and particulate matter matrices. Notably, smartphone imaging reliably captures and quantifies colorimetric output, proving the feasibility of rapid on-site analysis. Parallel removal experiments further confirm that the composite gel microspheres can efficiently degrade tetracycline in natural water samples. Although the adsorption capacity is slightly reduced due to competitive interactions with background species, the overall removal efficiency still exceeds 85% under visible light irradiation, validating the robustness of the synergistic adsorption-photocatalysis process in real aquatic environments. The integrated platform for simultaneous pollutant detection and degradation constructed based on composite gel microspheres is not only effective in simulated experimental environments but also adaptable to complex natural aquatic ecosystems. Nationwide sampling operations have validated its broad environmental applicability, reinforcing the potential of this self-assessment remediation system as a scalable solution for monitoring and controlling antibiotics in various water bodies.

[0056] Table 1. Summary of different sampling points for the analysis of tetracycline application in practical scenarios using composite gel microspheres

[0057] This application's composite gel microspheres achieve simultaneous detection and removal of tetracycline, demonstrating significant integrated remediation advantages. By integrating colorimetric sensing and high-efficiency adsorption functions into a single platform, it enables real-time visual monitoring and in-situ fixation and enrichment of pollutants, greatly simplifying the remediation process. This "detect-and-remove" mode relies on a three-dimensional network constructed through internal hydrogen bonds and other interactions within the material. This not only improves purification efficiency and reduces the risk of secondary pollution, but the microsphere morphology also facilitates recycling and reuse, providing an innovative solution for constructing a sustainable environmental remediation technology that integrates real-time early warning, deep purification, and material recycling.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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; and these 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 carbon dot-loaded composite gel microspheres, characterized in that, Includes the following steps: (a) Preparation of carbon dot nanomaterials; (b) Preparation of a mixed solution of sodium alginate and carboxymethyl chitosan; (c) Using tetraethyl silicate as a crosslinking agent, carbon dot nanomaterials are reacted with a mixed solution of sodium alginate and carboxymethyl chitosan, and then dropped into a calcium chloride solution to form composite gel microspheres.

2. The preparation method according to claim 1, characterized in that, Step (a) includes: dissolving sucrose in phosphoric acid and an aqueous solution, heating the reaction and then adding ethylenediamine, followed by ultrafiltration, dialysis and reduction treatment to obtain carbon dot nanomaterials.

3. The preparation method according to claim 2, characterized in that, The sucrose weighs 6g, the phosphoric acid volume is 6mL, the water volume is 18mL, the heating temperature is 80℃, and the heating time is 50min; the ethylenediamine volume is 18mL; the reduction treatment uses NaBH4 and is stirred at room temperature for 48h.

4. The preparation method according to claim 1, characterized in that, In step (b), the sodium alginate solution has a mass fraction of 1-4% and the carboxymethyl chitosan has a mass fraction of 0-3 wt%.

5. The preparation method according to claim 4, characterized in that, The sodium alginate solution has a mass fraction of 3%, and the carboxymethyl chitosan has a mass fraction of 1.5%.

6. The preparation method according to claim 1, characterized in that, Step (c) includes: dissolving tetraethyl silicate in ethanol and aqueous solution, adding carbon dot solution, stirring, adding sodium alginate and carboxymethyl chitosan mixed solution, continuing to stir, cooling, and then adding dropwise to calcium chloride solution.

7. The preparation method according to claim 6, characterized in that, The volume of the tetraethyl silicate is 2 mL, the volume of the ethanol is 0.64 mL, the volume of the water is 0.44 mL, the mass fraction of the carbon dot solution is 0-20 wt%, the stirring temperature is 60℃, and the stirring time is 1-6 h; the mass fraction of the calcium chloride solution is 3%.

8. The preparation method according to claim 7, characterized in that, The carbon dot solution has a mass fraction of 10%.

9. A carbon dot-loaded composite gel microsphere, characterized in that, Prepared by the preparation method according to any one of claims 1-8, the microspheres include a network interpenetrating structure formed by ionic crosslinking of carboxymethyl chitosan and sodium alginate, and carbon dot nanomaterials encapsulated in the network interpenetrating structure; the network interpenetrating structure is a double network structure, which keeps the dried microspheres in a rounded state and has a loose porous structure; the interior of the microspheres exhibits irregular wrinkles and a porous structure with different pore sizes.

10. A method for applying the carbon dot composite gel microspheres of claim 9 to the simultaneous detection and removal of tetracycline, characterized in that, Includes the following steps: (d) Add carbon dot composite gel microspheres to a tetracycline solution and react under ultraviolet light irradiation; (e) By acquiring optical images of the gel microspheres, analyze the color changes, and qualitatively or quantitatively detect the tetracycline concentration; (f) Evaluate tetracycline removal efficiency by measuring changes in tetracycline concentration.

11. The method according to claim 10, characterized in that, In step (d), the dosage of the loaded carbon dot composite gel microspheres is 0.4-1.5 g / L, the concentration of the tetracycline solution is 10-500 μM, the ultraviolet wavelength is 365 nm, the reaction temperature is 35 °C, and the reaction time is 0-48 h.

12. The method according to claim 11, characterized in that, The dosage of the carbon dot composite gel microspheres was 0.8 g / L.

13. The method according to claim 10, characterized in that, In step (e), an optical image is acquired using a digital camera or mobile phone, and the color difference value is calculated using the CIE 1976 L*a*b color difference formula. The formula for calculating the color difference value ΔE* is as follows: in Indicates brightness. Indicates red-green hue. Indicates the shade of yellow-blue.

Images