A fluorescent enhanced aluminum ion probe based on carbon dots and a preparation method and application thereof

Abstract

The application provides a carbon dot-based fluorescence-enhanced aluminum ion probe and a preparation method and application thereof. The preparation method is as follows: sucrose and anhydrous ethanol are added into a reaction kettle, stirred uniformly, reacted through a solvothermal method, and cooled to room temperature; the obtained solution is filtered, purified by anhydrous ethanol dialysis, and a fluorescent carbon dot solution is obtained, which is stored in the dark. The application first uses anhydrous ethanol and sucrose as raw materials to prepare fluorescent carbon dots through a solvothermal reaction. The fluorescent carbon dots can be used as a novel aluminum ion fluorescence probe to realize aluminum ion detection in water. The probe is rich in oxygen-containing functional groups such as hydroxyl groups and carboxyl groups, can realize coordination with aluminum ions, induce carbon dot aggregation, and cause fluorescence enhancement. The fluorescence probe has the advantages of easy preparation, easy purification, high sensitivity, high selectivity and the like.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent probe technology, specifically relating to a fluorescence-enhanced aluminum ion probe based on carbon dots, its preparation method, and its application. Background Technology

[0002] Aluminum, a widely distributed element in nature, is extensively used in daily life, including in cookware manufacturing, cosmetic containers, and pharmaceutical packaging. However, long-term exposure to high doses of aluminum ions can lead to their accumulation in the human body, potentially causing adverse effects on bone metabolism cells, kidney function, and the nervous system. Commonly used methods for aluminum ion detection include atomic absorption spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), and fluorescence spectrophotometry. While atomic absorption spectrometry and ICP-MS typically require complex sample pretreatment processes such as digestion and calcination, fluorescence analysis offers advantages such as high sensitivity, ease of operation, and relative environmental friendliness for aluminum ion detection.

[0003] Carbon dots are carbon nanomaterials with fluorescent emission properties. They are easily synthesized, low in cost, low in toxicity, and have tunable optical properties, leading to their increasing application in the development of novel aluminum ion fluorescent probes. Carbon dot-based fluorescent probes typically utilize the recognition and binding of aluminum ions to functional groups on the carbon dot surface. This quenching of fluorescence is induced by photoinduced electron transfer and internal filtering effects, thereby enabling the determination of aluminum ions. However, this type of quantitative detection method based on fluorescence quenching is susceptible to interference from other metal ions, and its selectivity needs improvement. Conversely, developing carbon dot-based fluorescence-enhanced aluminum ion probes can improve the selectivity and specificity of the method for the target analyte, which has significant practical application value.

[0004] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0005] To address the shortcomings of existing aluminum ion determination technologies, such as complex procedures, high costs, and the generation of toxic and hazardous waste that pollutes the environment, and the fact that existing detection methods using fluorescent carbon dots are mostly based on the principle of fluorescence quenching induced by the target analyte, which requires improved selectivity, this invention aims to provide a carbon dot-based fluorescence-enhanced aluminum ion probe, its preparation method, and its applications. This probe achieves aluminum ion detection based on the principle of fluorescence enhancement induced by aluminum ions using carbon dots, exhibiting high specificity and sensitivity.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a fluorescence-enhanced aluminum ion probe based on carbon dots. The preparation method is as follows: sucrose and anhydrous ethanol are added to a reaction vessel, stirred evenly, reacted by a solvothermal method and cooled to room temperature; the resulting solution is filtered and purified by dialyzing with anhydrous ethanol to obtain a fluorescent carbon dot solution, which is then stored in the dark.

[0008] Preferably, the molar ratio of sucrose to anhydrous ethanol is 0.1-1.0 mmol: 20 mL;

[0009] The reaction temperature of the solvothermal method is 180℃-220℃, and the reaction time is 4h-8h.

[0010] Preferably, the molar ratio of sucrose to the volume ratio of anhydrous ethanol is 0.5 mmol: 20 mL;

[0011] The reaction temperature for the solvothermal method is 200℃, and the reaction time is 6h.

[0012] Preferably, the reaction is carried out by heating to the reaction temperature at a heating rate of 10℃ / min;

[0013] Filtration was performed using a 0.22μm organic filter membrane; during dialysis, the molecular weight cutoff of the dialysis bag was 100-500 Da; the dialysis purification time was 48 h; and the product was stored at 4℃ protected from light.

[0014] This invention provides a fluorescence-enhanced aluminum ion probe based on carbon dots, wherein the fluorescence-enhanced aluminum ion probe is prepared by the aforementioned preparation method.

[0015] This invention provides an application of the aforementioned carbon dot-based fluorescence-enhanced aluminum ion probe in aluminum ion detection.

[0016] Preferably, the aluminum ion detection is performed using a fluorescence method.

[0017] Preferably, the step of detecting aluminum ions by fluorescence method is as follows:

[0018] (1) Dilute the fluorescent carbon dot solution with anhydrous ethanol to prepare a fluorescent probe solution with a final concentration of 0.16-8.2 mg / mL;

[0019] (2) Preparation of standard solutions:

[0020] Solutions containing aluminum ions at different concentration gradients were prepared using deionized water. Equal volumes of these solutions were then added to the same volume of fluorescent probe solution, resulting in a final aluminum ion concentration of 1.00 × 10⁻⁶. -6 mol / L - 80.0 × 10 -6Several mol / L standard solutions were mixed thoroughly and reacted at 15℃ for 5 min; the concentration of the fluorescent probe was the same in each standard solution.

[0021] Using a fluorescence spectrophotometer, the fluorescence intensity of the standard solution at 453 nm was measured under an excitation wavelength of 360 nm, and denoted as Fn, where n is the number of standard solutions and n is an integer.

[0022] (3) Preparation of blank solution: Add only deionized water to the fluorescent probe solution to obtain blank solution. After mixing evenly, react at 15℃ for 5 min. Under the condition of excitation wavelength of 360nm, measure its fluorescence intensity at 453nm and record it as F0.

[0023] (4) Calculate the relative fluorescence intensity of the standard solution: (Fn-F0) / F0, and obtain the linear relationship between the final concentration of aluminum ions in the standard solution and the relative fluorescence intensity of the standard solution;

[0024] (5) Determination of the test solution: Add the test solution to the fluorescent probe solution to obtain the test mixture. After mixing evenly, react at 15℃ for 5 min. Under the condition of excitation wavelength of 360nm, measure its fluorescence intensity at 453nm. According to the linear relationship obtained in step (4), the aluminum ion concentration in the test solution is obtained.

[0025] Preferably, in step (1), the volume ratio of the aluminum ion-containing solution to the fluorescent probe solution added to each standard solution is 1:9, and the volume of the fluorescent probe solution added to each standard solution is the same.

[0026] The final concentration of the fluorescent probe in the standard solution in step (2) is 0.14-7.38 mg / mL.

[0027] Preferably, the final concentration of the fluorescent probe solution prepared in step (1) is 0.82 mg / mL; and the final concentration of the fluorescent probe in the standard solution in step (2) is 0.74 mg / mL.

[0028] Step (3) The concentration of the fluorescent probe in the blank solution is the same as the concentration of the fluorescent probe in the standard solution; Step (5) The concentration of the fluorescent probe in the test mixture is the same as the concentration of the fluorescent probe in the standard solution; The standard solution, blank solution and test solution have the same volume.

[0029] Beneficial effects:

[0030] This invention, for the first time, uses anhydrous ethanol and sucrose as raw materials to prepare fluorescent carbon dots via a solvothermal reaction. These fluorescent carbon dots can serve as a novel fluorescent probe for aluminum ion detection in aqueous solutions. The abundant hydroxyl and carboxyl groups on the probe facilitate coordination with aluminum ions and induce carbon dot aggregation, leading to enhanced fluorescence. The fluorescent probe of this invention offers advantages such as ease of preparation, easy purification, high sensitivity, and high selectivity.

[0031] Compared to traditional detection methods that require complex pretreatment processes, the fluorescent probe of this invention for aluminum ion detection is more environmentally friendly, convenient, and rapid. Furthermore, compared to aluminum ion fluorescent probes prepared based on organic small molecules and other fluorescent nanomaterials, the carbon dot-based fluorescent probe preparation method of this invention has advantages such as low cost, low toxicity, and ease of preparation. Simultaneously, this probe utilizes the principle of fluorescence enhancement to achieve aluminum ion detection, exhibiting high specificity, sensitivity, and practicality. Attached Figure Description

[0032] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0033] Figure 1 This is a transmission electron microscope (TEM) image of the fluorescent carbon dots obtained in Example 1.

[0034] Figure 2 The fluorescence emission spectra of the fluorescent carbon dots obtained in Example 1 at different wavelengths are shown.

[0035] Figure 3 This is a comparison of the fluorescence intensity of aluminum ions by fluorescent carbon dots of different concentrations according to the present invention.

[0036] Figure 4 The fluorescence response spectra of the fluorescent carbon dots obtained in Example 1 to different concentrations of aluminum ions are shown.

[0037] In the figure, the curves from bottom to top correspond to aluminum ion concentrations that increase sequentially from low to high (0 μM to 80 μM).

[0038] Figure 5 This is a graph showing the linear relationship between aluminum ion concentration and relative fluorescence intensity in Example 4.

[0039] Figure 6 This is a comparison of the fluorescence enhancement results of different metal ions on fluorescent carbon dots in Comparative Example 1.

[0040] Figure 7 This is a comparison of the fluorescence enhancement results of different metal ions on fluorescent carbon dots in Comparative Example 2.

[0041] Figure 8The image shows a comparison of the fluorescence intensity of the fluorescent carbon dots obtained in Example 1, Comparative Example 3, and Comparative Example 4. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0043] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0044] To address the problems of complex and costly aluminum ion determination procedures, the generation of toxic and hazardous waste that pollutes the environment, and the fact that existing detection methods using fluorescent carbon dots are mostly based on the principle of fluorescence quenching induced by the target analyte, which requires improved selectivity, this invention provides a method for preparing a fluorescence-enhanced aluminum ion probe based on carbon dots.

[0045] The fluorescent probe prepared in this invention is used for the detection of aluminum ions. On the one hand, it avoids the cumbersome pretreatment steps in traditional detection methods and avoids the emission of toxic and harmful waste. On the other hand, this method is based on the principle of aluminum ion-induced carbon dot fluorescence enhancement. The carbon dot preparation and purification process is simple, there are fewer interference factors in fluorescence enhancement, and it has high specificity. For example, traditional detection methods for aluminum ions usually require sample pretreatment using methods such as microwave digestion, acidification, or evaporation, and the emissions from these processes are environmentally unfriendly. The preparation process of aluminum ion fluorescent probes based on organic small molecules and other fluorescent nanomaterials is more complex and costly than this method. This method uses fluorescence analysis, requiring only direct mixing of the test solution with carbon dots. By detecting the enhancement of the fluorescence emission intensity of the carbon dots, the specificity and sensitivity of trace aluminum ions can be achieved.

[0046] The preparation method of the carbon dot-based fluorescence-enhanced aluminum ion probe of the present invention is as follows: sucrose and anhydrous ethanol are added to a reaction vessel, stirred evenly, reacted by a solvothermal method and cooled to room temperature; the resulting solution is filtered and purified by dialyzing with anhydrous ethanol to obtain a clear yellow fluorescent carbon dot solution, which is stored at 4°C in the dark.

[0047] In a preferred embodiment of the present invention, the molar ratio of sucrose to the volume ratio of anhydrous ethanol is 0.1-1 mmol:20 mL (e.g., 0.1 mmol:20 mL, 0.25 mmol:20 mL, 0.5 mmol:20 mL, 0.75 mmol:20 mL or 1 mmol:20 mL).

[0048] In a preferred embodiment of the present invention, the molar ratio of sucrose to the volume ratio of anhydrous ethanol is 0.5 mmol: 20 mL.

[0049] In a preferred embodiment of the present invention, the reaction temperature of the solvothermal method is 180℃-220℃ (e.g., 180℃, 200℃ or 220℃), and the reaction time is 4h-8h (e.g., 4h, 6h or 8h).

[0050] In a preferred embodiment of the present invention, the reaction temperature of the solvothermal method is 200°C and the reaction time is 6 hours.

[0051] In a preferred embodiment of the present invention, the temperature is increased to the reaction temperature at a heating rate of 10°C / min, and then a solvothermal reaction is carried out.

[0052] In a preferred embodiment of the present invention, a 0.22 μm organic filter membrane is used for filtration; the molecular weight cutoff of the dialysis bag is 100-500 Da during dialysis; and the dialysis purification time is 48 hours. The purification steps of the method of the present invention are simple and easy to operate.

[0053] This invention provides a fluorescence-enhanced aluminum ion probe based on carbon dots, wherein the fluorescence-enhanced aluminum ion probe is prepared by the aforementioned preparation method.

[0054] This invention provides an application of a carbon dot-based fluorescence-enhanced aluminum ion probe in aluminum ion detection.

[0055] In a preferred embodiment of the present invention, the aluminum ion detection is performed using a fluorescence method.

[0056] In a preferred embodiment of the present invention, the step of detecting aluminum ions by fluorescence method is as follows:

[0057] (1) Dilute the fluorescent carbon dot solution with anhydrous ethanol to prepare a fluorescent probe solution with a final concentration of 0.16-8.2 mg / mL;

[0058] (2) Preparation of standard solutions:

[0059] Solutions containing aluminum ions at different concentration gradients were prepared using deionized water. Equal volumes of these solutions were then added to the same volume of fluorescent probe solution, resulting in a final aluminum ion concentration of 1.00 × 10⁻⁶. -6 mol / L - 80.0 × 10 -6 Several mol / L standard solutions (e.g., 1.00 × 10⁻⁶ mol / L) -6 mol / L, 2.50×10 -6 mol / L, 5.00×10 - 6 mol / L, 10.0×10 -6 mol / L, 20.0×10-6 mol / L, 30.0×10 -6 mol / L, 40.0×10 -6 mol / L, 50.0×10 - 6 mol / L, 60.0×10 -6 mol / L and 80.0×10 -6 The solutions were mixed thoroughly and reacted at 15°C for 5 minutes (mol / L); the concentration of the fluorescent probe was the same in each standard solution.

[0060] Using a fluorescence spectrophotometer, the fluorescence intensity of the standard solution at 453 nm is measured under an excitation wavelength of 360 nm and denoted as Fn, where n is the number of standard solutions and is an integer (e.g., n is 1, 2, 3, 4, 5, 6, 7 or 8).

[0061] (3) Preparation of blank solution: Add only deionized water to the fluorescent probe solution to obtain blank solution. After mixing evenly, react at 15℃ for 5 min. Under the condition of excitation wavelength of 360nm, measure its fluorescence intensity at 453nm and record it as F0.

[0062] (4) Calculate the relative fluorescence intensity of the standard solution: (Fn-F0) / F0, and obtain the linear relationship between the final concentration of aluminum ions in the standard solution and the relative fluorescence intensity of the standard solution;

[0063] (5) Determination of the test solution: Add the test solution to the fluorescent probe solution to obtain the test mixture. After mixing evenly, react at 15℃ for 5 min. Under the condition of excitation wavelength of 360nm, measure its fluorescence intensity at 453nm. According to the linear relationship obtained in step (4), the aluminum ion concentration in the test solution is obtained.

[0064] In a preferred embodiment of the present invention, the final concentration of the fluorescent probe solution prepared in step (1) is 0.82 mg / mL.

[0065] In a preferred embodiment of the present invention, the concentration of the fluorescent probe in the blank solution in step (3) is the same as the concentration of the fluorescent probe in the standard solution; the concentration of the fluorescent probe in the test mixture in step (5) is the same as the concentration of the fluorescent probe in the standard solution; and the standard solution, the blank solution and the test solution have the same volume.

[0066] In a preferred embodiment of the present invention, the final concentration of the fluorescent probe in the standard solution in step (2) is 0.14-7.38 mg / mL.

[0067] In a preferred embodiment of the present invention, the final concentration of the fluorescent probe in the standard solution in step (2) is 0.74 mg / mL.

[0068] In a preferred embodiment of the present invention, the final concentration of the fluorescent probe solution in step (1) is 0.82 mg / mL; in step (2), the mixing volume ratio of the aluminum ion-containing solution to the fluorescent probe solution in each standard solution is 1:9, and the volume of fluorescent probe solution added to each standard solution is the same.

[0069] 1) To obtain the optimal fluorescence enhancement effect based on carbon dots, the fluorescence enhancement factor (F / F0) of fluorescent carbon dots under aluminum ion induction is affected by the concentration of substrate carbon dots. Under the same concentration of aluminum ions, fluorescent probes with different carbon dot concentrations exhibit different fluorescence enhancement factors. Therefore, to ensure detection sensitivity, the volume of aluminum ion solution added needs to be optimized to reduce its impact on the concentration of fluorescent carbon dots.

[0070] 2) To obtain a linear range that is easy to operate and measure in practical applications. The content of aluminum ions in actual test samples is usually in the trace or micro-level. If the volume ratio of the test solution to the probe is too small, it will lead to an excessively large sample dilution factor. In actual measurements, sample enrichment and concentration may be required for pretreatment. Therefore, to ensure the practicality of the detection method, the volume of the aluminum ion solution added needs to be optimized.

[0071] 3) In optimizing the preparation of carbon dots, a higher concentration of metal ion solution is selected to mix with the carbon dots, so as to better evaluate the fluorescence enhancement effect induced by aluminum ions when high concentration of interference ions are present.

[0072] The present invention specifically optimizes the mixing volume ratio of fluorescent probe solution to aluminum ion solution to 9:1, which can ensure sensitivity and also have a wider linear range, making it more practical.

[0073] The following detailed description of the carbon dot-based fluorescence-enhanced aluminum ion probe, its preparation method, and its application is illustrated through specific embodiments.

[0074] Example 1: Preparation of a fluorescence-enhanced aluminum ion probe

[0075] This embodiment provides a method for preparing a fluorescence-enhanced aluminum ion probe based on carbon dots, the specific steps of which are as follows:

[0076] Add 0.5 mmol of sucrose and 20 mL of anhydrous ethanol (sucrose powder dissolved in anhydrous ethanol) to a polytetrafluoroethylene reactor. Stir well and raise the temperature to 200 °C at a rate of 10 °C / min. Maintain this temperature for 6 hours, then allow the reaction to cool naturally to room temperature. Filter the resulting solution through a 0.22 μm organic filter membrane and dialysis with anhydrous ethanol for 48 hours (dialysis bag molecular weight cutoff: 100-500 Da). Obtain a clear yellow fluorescent carbon dot solution, which should be stored at 4 °C protected from light.

[0077] (1) Transmission electron microscopy (TEM) analysis:

[0078] The fluorescent carbon dot solution obtained in Example 1 was diluted to a suitable concentration with anhydrous ethanol, dropped onto an ultrathin carbon film, and dried. After drying, analysis was performed using a high-resolution transmission electron microscope (TEM), and the results are as follows. Figure 1 As shown. By Figure 1 It can be seen that the fluorescent carbon dots are monodisperse uniform particles with a particle size of 5.6-8.7 nm.

[0079] (2) Fluorescence emission spectroscopy analysis:

[0080] The fluorescent carbon dot solution obtained in Example 1 was subjected to fluorescence emission spectroscopy analysis, and the results are as follows: Figure 2 As shown. By Figure 2 It can be seen that the maximum excitation wavelength of the fluorescent carbon dots is 360 nm, and the maximum emission wavelength is 453 nm.

[0081] (3) Analysis of aluminum ion-induced fluorescence enhancement effect:

[0082] Using deionized water as a control, the fluorescence enhancement effect in the presence of 500 μM aluminum ions was calculated. The specific method and steps are as follows:

[0083] 1) Take the fluorescent carbon dot solution obtained in this example, dilute it with anhydrous ethanol, and prepare a fluorescent probe solution with a final concentration of 0.82 mg / mL;

[0084] 2) Take 180 μL of fluorescent probe solution, add 20 μL of deionized water solution, mix well, and react at 15℃ for 5 min.

[0085] 3) Take 180 μL of fluorescent probe solution and add 20 μL of solution with a concentration of 500.0 × 10⁻⁶. -5 A mol / L aluminum ion solution was mixed thoroughly and reacted at 15℃ for 5 min, then set aside for later use.

[0086] 4) Using a fluorescence spectrophotometer, under an excitation wavelength of 360 nm, measure the fluorescence intensity of the solutions in steps 2) and 3) at 453 nm, and record them as F0 and F, respectively, and calculate the fluorescence enhancement factor (F / F0).

[0087] The fluorescence enhancement factor (F / F0) of the fluorescent carbon dots obtained in this embodiment is 3.72 times.

[0088] The quantum yield of the fluorescent carbon dots obtained in this embodiment was 2.10% ± 0.16%.

[0089] Example 2: Preparation of a fluorescence-enhanced aluminum ion probe

[0090] The method for preparing the fluorescence-enhanced probe for detecting aluminum ions in this embodiment differs from that in Example 1 only in that the amount of sucrose added is 0.25 mmol.

[0091] This embodiment provides a method for preparing a fluorescence-enhanced aluminum ion probe based on carbon dots, the specific steps of which are as follows:

[0092] Add 0.25 mmol of sucrose and 20 mL of anhydrous ethanol to a polytetrafluoroethylene reactor, stir well, and raise the temperature to 200 °C at a rate of 10 °C / min. Maintain this temperature for 6 hours, and then allow the mixture to cool naturally to room temperature. Filter the resulting solution through a 0.22 μm organic filter membrane and dialysis with anhydrous ethanol for 48 hours (dialysis bag molecular weight cutoff: 100-500 Da) to obtain a clear yellow fluorescent carbon dot solution, which is stored at 4 °C protected from light.

[0093] Referring to the aluminum ion-induced fluorescence enhancement effect analysis method in Example 1, the fluorescence enhancement factor (F / F0) of the fluorescent carbon dots obtained in this example is 3.53 times.

[0094] Example 3: Preparation of a fluorescence-enhanced aluminum ion probe

[0095] The method for preparing the fluorescence-enhanced probe for detecting aluminum ions in this embodiment differs from that in Example 1 only in that the reaction temperature of the solvothermal method is 180°C.

[0096] This embodiment provides a method for preparing a fluorescence-enhanced aluminum ion probe based on carbon dots, the specific steps of which are as follows:

[0097] Add 0.5 mmol of sucrose and 20 mL of anhydrous ethanol to a polytetrafluoroethylene reactor, stir well, and raise the temperature to 180 °C at a rate of 10 °C / min. Maintain this temperature for 6 hours, and then allow the mixture to cool naturally to room temperature. Filter the resulting solution through a 0.22 μm organic filter membrane and dialysis with anhydrous ethanol for 48 hours (dialysis bag molecular weight cutoff: 100-500 Da) to obtain a clear yellow fluorescent carbon dot solution, which is stored at 4 °C protected from light.

[0098] Referring to the aluminum ion-induced fluorescence enhancement effect analysis method in Example 1, the fluorescence enhancement factor (F / F0) of the fluorescent carbon dots obtained in this example is 2.01 times.

[0099] Example 4: Preparation of a fluorescence-enhanced aluminum ion probe

[0100] To further determine the sucrose dosage, reaction temperature, and reaction time in the preparation method of the fluorescence-enhanced aluminum ion probe, this embodiment relates to a method for preparing a fluorescence-enhanced probe for detecting aluminum ions. The only difference from Example 1 is the amount of sucrose added, the reaction temperature, or the reaction time. The fluorescence enhancement response of fluorescent carbon dots prepared under different conditions to aluminum ions was investigated, with the fluorescence enhancement factor used as the optimization criterion (referring to the aluminum ion-induced fluorescence enhancement effect analysis method in Example 1), as shown in Table 1 below.

[0101] This embodiment provides a method for preparing a fluorescence-enhanced aluminum ion probe based on carbon dots, the specific steps of which are as follows:

[0102] Add 0.1-1 mmol of sucrose and 20 mL of anhydrous ethanol to a polytetrafluoroethylene (PTFE) reactor, stir well, and raise the temperature to 180-220°C at a rate of 10°C / min. Maintain this temperature for 4-8 hours, then allow the reaction to cool naturally to room temperature. Filter the resulting solution through a 0.22 μm organic filter membrane and dialysis with anhydrous ethanol for 48 hours (dialysis bag molecular weight cutoff: 100-500 Da) to obtain a clear yellow fluorescent carbon dot solution, which should be stored at 4°C protected from light.

[0103] Table 1. Fluorescence enhancement response of fluorescent carbon dots prepared under different conditions to aluminum ions.

[0104] 0.1 200 6 2.543 0.25 200 6 3.527 0.5 200 6 3.721 0.75 200 6 2.675 1 200 6 2.406 0.5 180 6 2.009 0.5 220 6 2.697 0.5 200 4 2.450 0.5 200 8 2.889

[0105] Note: F and F0 represent Al respectively. 3+ Fluorescence emission intensity of carbon dots in the presence and absence of (500 μM).

[0106] As shown in Table 1, the fluorescent carbon dots exhibited the best fluorescence enhancement response to aluminum ions under the conditions of 0.5 mmol of sucrose, a reaction temperature of 200℃, and a reaction time of 6 h.

[0107] Example 5: Fluorescence-enhanced aluminum ion probe for detecting aluminum ions

[0108] (1) The fluorescent carbon dot solution (8.2 mg / mL) obtained in Example 1 was diluted with anhydrous ethanol. In order to obtain the best fluorescence enhancement effect based on carbon dots, the fluorescence enhancement factor of different concentrations of carbon dots in the presence of aluminum ions at the maximum emission wavelength was investigated. The specific method steps are as follows:

[0109] 1) Take the fluorescent carbon dot solution obtained in this example, dilute it with anhydrous ethanol, and prepare a fluorescent probe solution with a final concentration of 0.16-8.2 mg / mL;

[0110] 2) Take 180 μL of fluorescent probe solution, add 20 μL of deionized water solution, mix well, and react at 15℃ for 5 min.

[0111] 3) Take 180 μL of fluorescent probe solution and add 20 μL of solution with a concentration of 500.0 × 10⁻⁶. -5 A mol / L aluminum ion solution was mixed thoroughly and reacted at 15℃ for 5 min, then set aside for later use.

[0112] 4) Using a fluorescence spectrophotometer, at an excitation wavelength of 360 nm, measure the fluorescence intensity of the solutions from steps 2) and 3) at 453 nm, respectively, and record them as F0 and F, and calculate the fluorescence enhancement factor (F / F0). The results are as follows: Figure 3 As shown.

[0113] Depend on Figure 3 It can be seen that when fluorescent carbon dot solutions are mixed with aluminum ion solutions in the concentration range of 0.16-8.2 mg / mL, the fluorescence enhancement factor (F / F0) shows a trend of first increasing and then decreasing, and the fluorescence enhancement factor is the largest when the concentration of fluorescent carbon dots is 0.82 mg / mL.

[0114] Therefore, in this experiment, the concentration of fluorescent carbon dots corresponding to the maximum fluorescence enhancement factor was selected, and the fluorescent carbon dot solution obtained in Example 1 was diluted with anhydrous ethanol to prepare a fluorescent probe solution with a final concentration of 0.82 mg / mL.

[0115] (2) Preparation of standard solutions: Take 180 μL of the fluorescent probe solution obtained in step (1) in 10 portions, and add 20 μL of aluminum ion concentration of 1.00 × 10⁻⁶ to each portion. -5 mol / L, 2.50×10 -5 mol / L, 5.00×10 -5 mol / L, 10.0×10 -5 mol / L, 20.0×10 -5 mol / L, 30.0×10 -5 mol / L, 40.0×10 -5 mol / L, 50.0×10 -5 mol / L, 60.0×10 -5 mol / L, 80.0×10 -5 A mol / L aluminum ion-deionized aqueous solution yielded final aluminum ion concentrations ranging from 1.00 to 80.0 × 10⁻⁶ mol / L. -6 A standard solution of mol / L (with the same concentration of fluorescent carbon dots and gradually increasing aluminum ion concentration) was mixed thoroughly and reacted at 15℃ for 5 min.

[0116] Using a fluorescence spectrophotometer, the fluorescence intensity of 10 standard solutions at 453 nm was measured under an excitation wavelength of 360 nm, denoted as Fn (n = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10). The results are as follows: Figure 4 As shown.

[0117] (3) Preparation of blank solution: Take 180 μL of the fluorescent probe solution obtained in step (1), add 20 μL of deionized water solution, mix well and react at 15℃ for 5 min. Under the condition of excitation wavelength of 360 nm, measure its fluorescence intensity at 453 nm and record it as F0.

[0118] (4) Calculate the relative fluorescence intensity (Fn-F0) / F0 to obtain the linear relationship between the final concentration of aluminum ions in the standard solution and the relative fluorescence intensity of the standard solution. The results are as follows: Figure 5 As shown.

[0119] Depend on Figure 4 It can be seen that the fluorescence intensity of the emission peak at 453 nm of the standard solution increases with the increase of aluminum ions.

[0120] Depend on Figure 5 It can be seen that the relative fluorescence intensity (Fn-F0) / F0 increases with increasing aluminum ion concentration, and the final aluminum ion concentration is between 1.00 and 80.0 × 10⁻⁶. -6 It exhibits a good linear relationship within the concentration range of mol / L, R 2 =0.9909, the calculated detection limit is 0.28×10 -6 mol / L.

[0121] Comparative Example 1: Selective recognition of aluminum ions at the upper limit of the linear range by a fluorescence-enhanced aluminum ion probe.

[0122] The selectivity of the fluorescent probe for aluminum ions was detected using the method described in Example 5. The specific steps are as follows:

[0123] (1) The fluorescent carbon dot solution obtained in Example 1 was diluted with anhydrous ethanol to prepare a fluorescent probe solution with a final concentration of 0.82 mg / mL.

[0124] (2) Preparation of metal ion solution: Take 180 μL of the fluorescent probe solution obtained in step (1) in 10 portions, and add 20 μL of 80.0 × 10⁻⁶ solution to each portion. -5 Different metal ion-deionized aqueous solutions with concentrations of mol / L yielded a final concentration of 80.0 × 10⁻⁶. -6 The mol / L metal ion-fluorescent probe solution was mixed thoroughly and reacted at 15℃ for 5 min.

[0125] The aluminum ion selective identification and detection test of this method was carried out by selecting common metal ion impurities. The different metal ion-deionized aqueous solutions were potassium ion solution, sodium ion solution, silver ion solution, calcium ion solution, magnesium ion solution, zinc ion solution, copper ion solution, mercury ion solution, lead ion solution, aluminum ion solution and iron ion solution.

[0126] (3) Preparation of blank solution: Take 180 μL of the fluorescent probe solution obtained in step (1), add 20 μL of deionized water solution, mix well and react at 15℃ for 5 min.

[0127] (4) Using a fluorescence spectrophotometer, under the condition of an excitation wavelength of 360 nm, the fluorescence intensity of the above metal ion-fluorescent probe solution and blank solution at 453 nm is measured and recorded as F and F0, respectively, and the fluorescence enhancement factor (F / F0) is calculated.

[0128] The results are as follows Figure 6 It can be seen that at 80.0×10 -6 In mixed solutions of different metal ions and fluorescent probes at mol / L, only aluminum ions significantly enhanced the fluorescence of carbon dots under the experimental conditions of this method, while other metal ions had no significant effect, indicating that this method has strong specific recognition performance for aluminum ions. Comparative Example 2: Selective recognition of aluminum ions at concentrations above the linear range by a fluorescence-enhanced aluminum ion probe.

[0129] The selectivity of the fluorescent probe for aluminum ions was detected using the method described in Example 5. The specific steps are as follows:

[0130] (1) The fluorescent carbon dot solution obtained in Example 1 was diluted with anhydrous ethanol to prepare a fluorescent probe solution with a final concentration of 0.82 mg / mL.

[0131] (2) Preparation of metal ion solution: Take 180 μL of the fluorescent probe solution obtained in step (1) in 10 portions, and add 20 μL of 500.0 × 10⁻⁶ solution to each portion. -5 Different metal ion-deionized aqueous solutions with concentrations of mol / L yielded a final concentration of 500.0 × 10⁻⁶. - 6 The mol / L metal ion-fluorescent probe solution was mixed thoroughly and reacted at 15℃ for 5 min.

[0132] The aluminum ion selective identification and detection test of this method was carried out by selecting common metal ion impurities. The different metal ion-deionized aqueous solutions were potassium ion solution, sodium ion solution, silver ion solution, calcium ion solution, magnesium ion solution, zinc ion solution, copper ion solution, mercury ion solution, lead ion solution, aluminum ion solution and iron ion solution.

[0133] (3) Preparation of blank solution: Take 180 μL of the fluorescent probe solution obtained in step (1), add 20 μL of deionized water solution, mix well and react at 15℃ for 5 min.

[0134] (4) Using a fluorescence spectrophotometer, under the condition of an excitation wavelength of 360 nm, the fluorescence intensity of the above metal ion-fluorescent probe solution and blank solution at 453 nm is measured and recorded as F and F0, respectively, and the fluorescence enhancement factor (F / F0) is calculated.

[0135] The results are as follows Figure 7 It can be seen that the upper limit of the linear range is 6.25 times (500.0 × 10⁻⁶). -6 In a mixed solution of different metal ions and fluorescent probes (mol / L), only aluminum ions significantly enhanced the fluorescence of carbon dots under the experimental conditions of this method, while other metal ions had no obvious effect, indicating that this method has strong specific recognition performance for aluminum ions.

[0136] Comparative Example 3: Effect of deionized water as reaction solvent on fluorescence enhancement of aluminum ion fluorescent probe

[0137] The effect of deionized water as a reaction solvent on the fluorescence enhancement of aluminum ion fluorescent probes was investigated. The only difference between the method of preparing the fluorescent probe in this comparative example and that in Example 1 is that anhydrous ethanol is replaced with deionized water.

[0138] This comparative example provides a method for preparing a fluorescence-enhanced aluminum ion probe based on carbon dots, the specific steps of which are as follows:

[0139] Add 0.5 mmol of sucrose and 20 mL of deionized water to a polytetrafluoroethylene reactor, stir well, and raise the temperature to 200 °C at a rate of 10 °C / min. Maintain this temperature for 6 hours, and then allow the mixture to cool naturally to room temperature. Filter the resulting solution through a 0.22 μm organic filter membrane and dialysis with anhydrous ethanol for 48 hours (dialysis bag molecular weight cutoff: 100-500 Da) to obtain a clear yellow fluorescent carbon dot solution, which is stored at 4 °C protected from light.

[0140] The analytical method for the fluorescence enhancement effect induced by aluminum ions obtained in this comparative example:

[0141] 1) Dissolve the fluorescent carbon dot solution obtained in this comparative example in deionized water to prepare a fluorescent probe solution with a final concentration of 0.82 mg / mL.

[0142] 2) Preparation of aluminum ion solution: Take 180 μL of fluorescent probe solution and add 20 μL of a solution with a concentration of 500.0 × 10⁻⁶. -5 A final concentration of 500.0 × 10⁻⁶ mol / L aluminum ion-deionized water solution was obtained. -6The aluminum ion-fluorescent probe solution was mixed thoroughly and reacted at 15°C for 5 min.

[0143] 3) Preparation of blank solution: Take 180 μL of fluorescent probe solution, add 20 μL of deionized water solution, mix well and react at 15℃ for 5 min.

[0144] 4) Using a fluorescence spectrophotometer, under an excitation wavelength of 360 nm, the fluorescence intensity of the blank solution and the aluminum ion-fluorescent probe solution was measured at 453 nm. The results are as follows: Figure 8 The results shown are from the "sucrose + water" heat-treated group, and compared with the fluorescent probe obtained in Example 1 (prepared with a final concentration of 500.0 × 10⁻⁶). -6 Aluminum ion-fluorescent probe solution (mol / L) Figure 8 A comparison was made between the "sucrose + ethanol" heat treatment group and the group in question.

[0145] Depend on Figure 8 It was found that the fluorescence emission intensity of fluorescent carbon dots prepared using deionized water as the reaction solvent was quenched by aluminum ions, with a quenching rate of 22.7%. This result indicates that fluorescent carbon dots prepared using deionized water as the reaction solvent cannot achieve the aluminum ion-induced fluorescence enhancement effect.

[0146] Comparative Example 4: Effect of sucrose as a reaction precursor on the fluorescence enhancement of aluminum ion fluorescent probes

[0147] The effect of sucrose as a reaction raw material on the fluorescence enhancement of aluminum ion fluorescent probe was investigated. The only difference between the method of preparing the fluorescent probe in this comparative example and that in Example 1 is that no sucrose was added.

[0148] This comparative example provides a method for preparing a fluorescence-enhanced aluminum ion probe based on carbon dots, the specific steps of which are as follows:

[0149] 20 mL of anhydrous ethanol was added to a polytetrafluoroethylene (PTFE) reactor. The temperature was increased to 200 °C at a rate of 10 °C / min and maintained at this temperature for 6 hours. The mixture was then allowed to cool naturally to room temperature. The resulting solution was filtered through a 0.22 μm organic filter membrane and purified by dialyzing with anhydrous ethanol for 48 hours (dialysis bag molecular weight cutoff: 100-500 Da). A clear yellow fluorescent carbon dot solution was obtained and stored at 4 °C protected from light.

[0150] The comparative example provides an analytical method for analyzing the fluorescence enhancement effect induced by aluminum ions using the fluorescent probe.

[0151] 1) Dissolve the fluorescent carbon dot solution obtained in this comparative example in anhydrous ethanol to prepare a fluorescent probe solution with a final concentration of 0.82 mg / mL.

[0152] 2) Preparation of aluminum ion solution: Take 180 μL of fluorescent probe solution and add 20 μL of a solution with a concentration of 500.0 × 10⁻⁶. -5 A final concentration of 500.0 × 10⁻⁶ mol / L aluminum ion-deionized water solution was obtained. -6 The aluminum ion-fluorescent probe solution was mixed thoroughly and reacted at 15°C for 5 min.

[0153] 3) Preparation of blank solution: Take 180 μL of fluorescent probe solution, add 20 μL of deionized water solution, mix well and react at 15℃ for 5 min.

[0154] 4) Using a fluorescence spectrophotometer, under an excitation wavelength of 360 nm, the fluorescence intensity of the blank solution and the aluminum ion-fluorescent probe solution was measured at 453 nm. The results are as follows: Figure 8 As shown (“Ethanol” heat treatment group).

[0155] Depend on Figure 8 It is known that the fluorescence emission intensity of fluorescent carbon dots prepared using only ethanol as a reaction precursor is relatively weak and is basically unaffected by the presence of aluminum ions. Therefore, only when sucrose is used as a reaction precursor and anhydrous ethanol is used as a reaction solvent can the prepared fluorescent carbon dots exhibit the aluminum ion-induced fluorescence enhancement effect.

[0156] Comparison of Comparative Example 5 with the results measured by inductively coupled plasma atomic emission spectrometry (ICP-MS)

[0157] The aluminum hydroxide content in compound aluminum hydroxide tablets was determined using the method described in Example 5, and the results were compared with those obtained by inductively coupled plasma atomic emission spectrometry (ICP-MS).

[0158] Accurately weigh 20 compound aluminum hydroxide tablets, grind them into a fine powder, accurately weigh an appropriate amount and place it in a beaker. Add 2 mL of hydrochloric acid and 50 mL of water, boil, cool, filter, and wash the residue three times with 10 mL of water. Combine the filtrate and washings. Dilute the obtained sample solution to 100 mL for later use. Dilute the prepared sample solution to an appropriate factor for later use.

[0159] Take 3 portions of the fluorescent probe solution obtained in step (1) of Example 5 (180 μL), add 20 μL of the diluted sample solution to be tested, mix well, and react at 15°C for 5 min. Under the condition of excitation wavelength of 360 nm, measure its fluorescence intensity at 453 nm. Calculate the aluminum hydroxide content in the solution according to the linear relationship obtained in step (4) of Example 5, and calculate the relative standard deviation (RSD).

[0160] The aluminum hydroxide content in the above solution was determined and calculated using ICP-MS. The relative standard deviation was calculated and compared with the detection results of this method. The results are shown in Table 2 below.

[0161] Table 2 Comparison of results obtained by this method and ICP-MS method.

[0162]

[0163] As shown in Table 2 above, although the precision of this method is weaker than that of the ICP-MS method, according to the precision requirements of the "9101 Analytical Method Validation Guidelines" in the 2020 edition of the Chinese Pharmacopoeia, and considering the content of the analyte in this sample, the precision of this method is within an acceptable range after pretreatment of the analyte content. Compared with existing technologies, this invention has considerable sensitivity and accuracy, and also offers high convenience and practicality.

[0164] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon dot-based fluorescence-enhanced aluminum ion probe, characterized in that, The preparation method is as follows: sucrose and anhydrous ethanol are added to a reaction vessel, with the molar ratio of sucrose to anhydrous ethanol being 0.1-1.0 mmol: 20 mL; the mixture is stirred evenly, and the reaction is carried out by a solvothermal method and cooled to room temperature. The reaction temperature of the solvothermal method is increased to 180℃-220℃ at a heating rate of 10℃ / min, and the reaction time is 4h-8h; the solution obtained from the reaction is filtered and purified by dialysis with anhydrous ethanol. The resulting fluorescent carbon dot solution was stored away from light.

2. The preparation method according to claim 1, characterized in that, The molar ratio of sucrose to anhydrous ethanol is 0.5 mmol: 20 mL; the reaction temperature of the solvothermal method is 200 °C, and the reaction time is 6 h.

3. The preparation method according to claim 1, characterized in that, Filtration was performed using a 0.22μm organic filter membrane. During dialysis, the molecular weight cutoff of the dialysis bag was 100-500 Da. The dialysis purification time was 48 hours. The product was stored at 4℃ protected from light.

4. A fluorescence-enhanced aluminum ion probe based on carbon dots, characterized in that, The fluorescence-enhanced aluminum ion probe is prepared by the preparation method according to any one of claims 1-3.

5. The application of the carbon dot-based fluorescence-enhanced aluminum ion probe as described in claim 4 in aluminum ion detection.

6. The application as described in claim 5, characterized in that, The aluminum ion detection method is used to detect aluminum ions using fluorescence.

7. The application as described in claim 6, characterized in that, The steps for detecting aluminum ions using the fluorescence method are as follows: (1) Dilute the fluorescent carbon dot solution with anhydrous ethanol to prepare a fluorescent probe solution with a final concentration of 0.16-8.2 mg / mL; (2) Preparation of standard solutions: The solutions containing aluminum ions with different concentration gradients were prepared with deionized water, the same volume of the solutions containing aluminum ions with different concentration gradients was taken, the same volume of the fluorescent probe solution was added respectively, and several standard solutions with the final concentration of aluminum ions of 1.00x10 -6 mol / L-80.0x10 -6 mol / L were obtained, which were mixed uniformly and reacted at 15°C for 5 min; wherein the concentration of the fluorescent probe in each standard solution was the same; Using a fluorescence spectrophotometer, the fluorescence intensity of the standard solution at 453 nm was measured under an excitation wavelength of 360 nm, and denoted as Fn, where n is the number of standard solutions and n is an integer. (3) Preparation of blank solution: Add only deionized water to the fluorescent probe solution to obtain blank solution. After mixing evenly, react at 15℃ for 5 min. Under the condition of excitation wavelength of 360nm, measure its fluorescence intensity at 453nm and record it as F0. (4) Calculate the relative fluorescence intensity of the standard solution: (Fn-F0) / F0, and obtain the linear relationship between the final concentration of aluminum ions in the standard solution and the relative fluorescence intensity of the standard solution; (5) Determination of the test solution: Add the test solution to the fluorescent probe solution to obtain the test mixture. After mixing evenly, react at 15℃ for 5 min. Under the condition of excitation wavelength of 360nm, measure its fluorescence intensity at 453nm. According to the linear relationship obtained in step (4), the aluminum ion concentration in the test solution is obtained.

8. The application as described in claim 7, characterized in that, In step (2), the volume ratio of the aluminum ion-containing solution to the fluorescent probe solution added to each standard solution is 1:9, and the volume of the fluorescent probe solution added to each standard solution is the same. The final concentration of the fluorescent probe in the standard solution in step (2) is 0.14-7.38 mg / mL.

9. The application as described in claim 7, characterized in that, The final concentration of the fluorescent probe solution prepared in step (1) is 0.82 mg / mL; the final concentration of the fluorescent probe in the standard solution in step (2) is 0.74 mg / mL. Step (3) The concentration of the fluorescent probe in the blank solution is the same as the concentration of the fluorescent probe in the standard solution; Step (5) The concentration of the fluorescent probe in the test mixture is the same as the concentration of the fluorescent probe in the standard solution; The standard solution, blank solution and test solution have the same volume.

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