Dual-emission fluorescent carbon dots synthesized by alcohol-thermal method and application of dual-emission fluorescent carbon dots

Abstract

According to the dual-emission fluorescent carbon dots synthesized through the alcohol-thermal method and the application of the dual-emission fluorescent carbon dots, 2, 4-diaminobenzene sulfonic acid and a cross-linking auxiliary agent serve as carbon sources, ethyl alcohol serves as a solvent, a carbon dot solution is prepared through a synthesis reaction, the carbon dot solution is purified to obtain powdery carbon dots, and the cross-linking auxiliary agent is polyethyleneimine, citric acid, o-phenylenediamine or acetic acid; the carbon dots have double fluorescence emission peaks. The synthesized carbon dots have the properties of good optical stability, independent excitation and the like. The dual-fluorescence emission peak of the solution system is sensitive to the pH value of the solution and a water solvent, and has the luminescent properties of up-conversion fluorescence, long afterglow in a solid-phase matrix and the like. The whole preparation process has the advantages of simplicity in operation, low cost and easiness in repetition. The fluorescence signal of the carbon dot has linear quenching response to the acetylpromazine maleate drug, and can be used for establishing a novel drug content analysis method.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorescent carbon nanomaterials, and particularly relates to an alcohol-thermal method for synthesizing dual-emission fluorescent carbon dots and applications thereof. Background Art

[0002] Carbon dots (CDs) are a new type of dispersed spherical fluorescent carbon nanomaterial with a size of less than 10 nm. Compared with traditional organic fluorescent dyes and semiconductor quantum dots, they have the characteristics of high water solubility, adjustable luminescence range, chemical inertness, good photostability, low toxicity, resistance to photobleaching, easy functionalization and good biocompatibility. They have potential application prospects in sensing, anti-counterfeiting, photocatalysis, biomedicine (bioimaging, biosensing, drug delivery, etc.).

[0003] The fluorescence emission band of carbon dots can cover the blue to red range. Blue-emitting carbon dots often exhibit strong fluorescence emission and high quantum yield (HQY), but they also exhibit small Stokes shifts and relatively poor photobleaching resistance. In recent years, research on carbon dots with longer emission bands has become increasingly prevalent. Although their luminescence efficiency is generally lower than that of blue-emitting CDs, their low-energy long-wavelength excitation light source minimizes damage to biological samples and reduces background interference, making them beneficial for biological research and garnering increasing attention.

[0004] Currently, most methods for synthesizing carbon dots are "bottom-up" methods, and the one-step solvent thermal method has become the most commonly used synthesis scheme due to its simplicity and rapidity. However, no matter which method is used to prepare carbon dots, their structure and performance are closely related to the type of carbon source selected. Studies have shown that the introduction of heteroatoms directly leads to significant differences in the luminescence properties of carbon dots. The chemical composition of the carbon source and passivating agent directly affects the surface group structure of the carbon dots. Introducing a carbon source with amino and thiol groups in its molecular structure during the reaction can quickly and easily produce nitrogen-sulfur doped carbon dots, significantly improving the fluorescence quantum yield of the carbon dots.

[0005] Previous studies have shown that introducing benzenesulfonic acid containing a benzene ring and a sulfur-containing group as a carbon source can significantly improve the luminescence properties of synthesized carbon dots; however, the carbon dot systems demonstrated in previous studies all have single fluorescence emission characteristics, and the influence of the molecular structure of aminobenzenesulfonic acid on the luminescence properties of synthesized carbon dots has not been explored in detail.

[0006] In view of this, the inventor of this case conducted in-depth research, which led to the creation of this case. Summary of the Invention

[0007] The purpose of the present invention is to provide an alcohol thermal method for synthesizing dual-emission fluorescent carbon dots using aminobenzenesulfonic acid as a carbon source.

[0008] Another object of the present invention is to provide an application of an alcohol thermal method for synthesizing dual-emission fluorescent carbon dots using aminobenzenesulfonic acid as a carbon source.

[0009] In order to achieve the above object, the technical solution of the present invention is: The invention discloses an alcohol thermal method for synthesizing dual-emission fluorescent carbon dots. The method uses 2,4-diaminobenzenesulfonic acid as a carbon source and a cross-linking auxiliary agent as a carbon source, and uses ethanol as a solvent. The carbon dot solution is prepared through an alcohol thermal synthesis reaction. The fluorescence quantum yield of the carbon dot solution reaches 50.07%. The cross-linking auxiliary agent is polyethyleneimine, citric acid, o-phenylenediamine or acetic acid. The carbon dots have a fluorescence dual emission peak.

[0010] Furthermore, the carbon dots are sensitive to the pH value of the solution and the water solvent. The fluorescence emitted by the carbon dots in a solution environment with a pH value less than 6 is double-emission fluorescence, the fluorescence emitted by the carbon dots in a solution environment with a pH value greater than 6 is single-emission fluorescence, and the fluorescence emitted by the carbon dots in a solution environment with water as the solvent is single-emission fluorescence.

[0011] Furthermore, the cross-linking auxiliary agent is citric acid, and the molar ratio of the 2,4-diaminobenzenesulfonic acid to the citric acid is 1:2; The carbon dot solution forms fluorescence double emission peaks at 348 nm and 500 nm when excited by a light source with a wavelength of 274 nm.

[0012] Furthermore, the temperature of the alcohol thermal synthesis reaction is 160-190° C., and the time of the alcohol thermal synthesis reaction is 4-10 hours.

[0013] Furthermore, the ethanol solution of the carbon dots has upconversion properties.

[0014] Furthermore, the carbon dots have a lattice structure.

[0015] An application of dual-emission fluorescent carbon dots synthesized by an alcohol-thermal method, wherein the carbon dots are used as green fluorescent probes for component detection of acepromazine maleate, rutin, or quercetin.

[0016] Furthermore, the carbon dots are used for content detection of acepromazine maleate drug.

[0017] After adopting the above technical solution, the alcohol-thermal method for synthesizing dual-emission fluorescent carbon dots of the present invention has the following beneficial effects: The synthesized carbon dots exhibit excellent optical stability and excitation independence. The dual fluorescence emission peaks in the solution system are sensitive to solution pH and the aqueous solvent, and exhibit luminescence properties such as upconversion fluorescence and long afterglow in the solid-phase matrix. The entire preparation process is simple to operate, low-cost, and easily reproducible.

[0018] The application of the dual-emission fluorescent carbon dots synthesized by an alcohol-thermal method of the present invention has the following beneficial effects: the fluorescence signal of the carbon dots has dual-emission fluorescence peaks for the detection of the components of acepromazine maleate, rutin or quercetin, the solution exhibits green fluorescence under ultraviolet light, and the fluorescence emission peak intensity of the carbon dot solution at 497 nm has obvious signal responses to acepromazine maleate, rutin and quercetin, and can be used to detect the presence or absence of the corresponding components.

[0019] Furthermore, the fluorescence signal of the carbon dots has a linear quenching response to the drug acepromazine maleate, which can be used to establish a new method for drug content analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a comparison of the fluorescence spectra of carbon dots synthesized with different types of cross-linking auxiliary agents and 2,4-DABS of the present invention; Figure 2 Comparison of photos of carbon dots synthesized with different types of cross-linking auxiliary agents and 2,4-DABS under sunlight (a) and ultraviolet light (b); Figure 3 Comparison of fluorescence spectra of carbon dots synthesized with different main carbon sources and CA in the present invention; Figure 4 Comparison of photos of carbon dots synthesized with different main carbon sources and CA under sunlight (a) and ultraviolet light (b); Figure 5 for Figure 5 (a) Fluorescence spectra of carbon dots synthesized in different solvents. Figure 5 (b) Photos of carbon dots under sunlight and UV light; Figure 6 for Figure 6 (a) Fluorescence spectra of carbon dots synthesized with different carbon source ratios, Figure 6 (b) Photos of carbon dots under sunlight and UV light; Figure 7 Carbon dots synthesized at different reaction temperatures; Figure 7 (a) Fluorescence spectrum, Figure 7 (b) Emission peak position, Figure 7 (c) Fluorescence intensity, Figure 7 (d) UV spectrum; Figure 8 Fluorescence spectra of carbon dots synthesized at different reaction times; Figure 9 for Figure 9 (a) Fluorescence and UV spectra of DABS-CA CDs (the inset is a photo of the solution under sunlight and UV light). Figure 9 (b) Upconversion fluorescence spectra of DABS-CA CDs; Figure 10 DABS-CA CDs under the condition of magnification to 100 nm Figure 10 (a) Transmission electron microscopy image, Figure 10 (b) Particle size distribution histogram, Figure 10 (c) Transmission electron microscopy image of DABS-CA CDs at a magnification of 10 nm. Figure 11 DABS-CA CDs under different excitation wavelengths Figure 11 (a) Fluorescence emission spectrum, Figure 11 (b) Changes in emission peak position, Figure 11 (c) Fluorescence intensity changes; Figure 12 The DABS-CA CDs were observed with the increase of 365 nm UV light irradiation time. Figure 12 (a) Changes in emission peak position, Figure 12 (b) Fluorescence intensity changes; Figure 13 The DABS-CA CDs with the increase of NaCl solution volume Figure 13 (a) Changes in emission peak position, Figure 13 (b) Fluorescence intensity changes; Figure 14 DABS-CA CDs in BR buffer solutions with different pH values Figure 14 (a) Fluorescence emission spectrum, Figure 14 (b) Changes in the position of the emission peak, Figure 14 (c) Fluorescence intensity changes, Figure 14 (d) Photographs taken under UV light, Figure 14 (e) Zeta potential change value; Figure 15 The fluorescence spectra of carbon dots after adding different volumes of buffer to DABS-CA CDs; Figure 16 This is a diagram showing the response of DABS-CA CDs to different drugs; Figure 17 The two emission peaks of DABS-CA CDs respond to acepromazine maleate. Figure 17 (a) Fluorescence spectrum, Figure 17 (b) Linear fitting diagram at the 355 nm emission peak. Figure 17 (c) Linear fitting plot at the 497 nm emission peak. DETAILED DESCRIPTION

[0021] Example 1 The present invention discloses an alcohol-thermal method for synthesizing dual-emission fluorescent carbon dots. The specific preparation process is as follows: an appropriate amount of 2,4-diaminobenzenesulfonic acid (DABS) is weighed, dissolved in a dilute HCl solution, and adjusted to a pH of 1 to prepare a solution A with a concentration of 0.1 mol / L. A certain amount of a cross-linking auxiliary agent (a molar ratio of DABS to cross-linking auxiliary agent of 1:2) is added to 2 mL of solution A, and the volume is adjusted to 12 mL with anhydrous ethanol. The solution is then ultrasonically dissolved and mixed. The solution is then transferred to a 15 mL polytetrafluoroethylene-lined autoclave and placed in a 160°C oven for reaction for 4 hours. After the reaction is completed and cooled, it is filtered through a 0.45 μm microporous membrane to obtain a first carbon dot solution.

[0022] The first carbon dot solution was further purified. After dialyzing the solution for 24 hours using a dialysis bag, the solution was concentrated using a rotary evaporator and dried in a vacuum freeze dryer for 36 hours to obtain carbon dot powder. Specifically, the dialysis bag was pretreated by cutting a 500 MW dialysis bag to an appropriate length, boiling it for 10 minutes, and finally rinsing it twice with distilled water. The first carbon dot solution was placed into the pretreated dialysis bag, clamped at both ends with clips, placed in a large beaker filled with distilled water, and stirred with a magnetic stirrer for 4 hours. The dialyzed first carbon dot solution was then concentrated to 5-10 mL using a rotary evaporator. The concentrated solution was placed in an ultra-low temperature freezer for 24 hours and then dried in a vacuum freeze dryer for 36 hours to obtain carbon dot powder.

[0023] In the present invention, crosslinking agents such as polyethyleneimine (PEI), citric acid (CA), o-phenylenediamine (oPD), and acetic acid (AC) all react with 2,4-diaminobenzenesulfonic acid, resulting in a first carbon dot solution exhibiting dual fluorescence peaks and green fluorescence under ultraviolet light. Citric acid, when used as a crosslinking agent, exhibits the highest fluorescence intensity and is stable at room temperature, making it the optimal crosslinking agent.

[0024] In this embodiment, the cross-linking auxiliary agent is specifically citric acid.

[0025] Using the above technical solution, the present invention synthesizes dual-emission fluorescent carbon dots via an alcohol-thermal method. Using 2,4-diaminobenzenesulfonic acid and organic citric acid as the main carbon sources and ethanol as the solvent, the carbon dots are heated at 160°C for 4 hours. The alcohol-thermal reaction yields a carbon dot solution with a fluorescence quantum yield as high as 50.07% (measured using an integrating sphere method). The solution exhibits a uniform, transparent yellow color and, under excitation with a 274 nm wavelength, exhibits distinct dual-emission peaks at 348 nm and 500 nm. Under ultraviolet illumination, it exhibits a bright green fluorescence. The dual-emission fluorescence of the carbon dots is sensitive to solution pH and the aqueous solvent. At pH values below 6, the carbon dots exhibit dual-emission fluorescence, while at pH values above 6 or when using water as the solvent, they exhibit single-emission fluorescence. The dual-emission fluorescence signal of the carbon dot ethanol solution exhibits a linear response to acepromazine maleate. Furthermore, the carbon dot ethanol solution exhibits upconversion luminescence, with a fluorescence peak at 496 nm under excitation with an 850 nm wavelength. The solid powder CDs@B2O3 prepared with boron oxide as the matrix exhibits yellow fluorescence under 356nm ultraviolet light, and has a room temperature afterglow emission at 531 nm for up to 3s after the light source is turned off.

[0026] Compared to similar carbon quantum dots, the carbon dots of this invention feature a simple synthesis process, excitation wavelength independence, excellent photobleaching resistance, and biocompatibility. Their high luminescence quantum yield makes them suitable for cell imaging. They are sensitive to pH and aqueous solvents, making them suitable for use as fluorescent probes for pH response in solutions and for water molecules in organic solvents. The fluorescence signal of the carbon dots exhibits a linear quenching response to the drug acepromazine maleate, enabling the development of new methods for drug content analysis.

[0027] Comparative Example 1 (Optimization of Carbon Source Cross-linking Auxiliary Agent Type) An appropriate amount of 2,4-diaminobenzenesulfonic acid was weighed and dissolved in dilute HCl solution and adjusted to pH 1 to prepare a 0.1 mol / L solution A. A certain amount of cross-linking auxiliary agent (DABS:cross-linking auxiliary agent molar ratio of 1:2) was added to 2 mL of solution A, and the volume was adjusted to 12 mL with anhydrous ethanol. After ultrasonic dissolution and mixing, the solution was transferred to a 15 mL polytetrafluoroethylene-lined autoclave and placed in a 160°C oven for 4 h. After the reaction was completed and cooled, it was filtered through a 0.45 μm microporous membrane to obtain the first carbon dot solution.

[0028] The fluorescence spectrum of the first carbon dot solution was measured after diluting it 100 times with anhydrous ethanol. The experimental results are as follows: Figure 1 and Figure 2As shown, when ethylenediamine (EDA) was used as a crosslinking auxiliary, the resulting carbon dots exhibited only a single emission peak at approximately 341 nm, and the solution exhibited blue fluorescence. This indicates that the molecular structure of ethylenediamine is not conducive to crosslinking with DABS, preventing the formation of a unique nucleated luminescent structure. When polyethyleneimine (PEI), citric acid (CA), o-phenylenediamine (oPD), and acetic acid (AC) were used as crosslinking auxiliary agents, all of which reacted with 2,4-diaminobenzenesulfonic acid. The resulting first carbon dot solutions exhibited dual fluorescence peaks, exhibiting green fluorescence under UV light. Citric acid exhibited the highest fluorescence intensity and was stable at room temperature, making it the optimal crosslinking auxiliary agent.

[0029] Comparative Example 2 (Optimization of the main carbon source type) Citric acid was used as the optimal cross-linking auxiliary agent to optimize the main carbon source type: appropriate amounts of benzenesulfonic acids of different structural types (monoamino structure benzenesulfonic acid, para-aminobenzenesulfonic acid structure and 2,4-diaminobenzenesulfonic acid) were weighed, dissolved in dilute HCl solution and adjusted to pH = 1 to prepare a solution with a concentration of 0.1 mol / L. 0.076 g of citric acid was added to 2 mL of the solution (the molar ratio of DABS: cross-linking auxiliary agent was 1:2), and the volume was adjusted to 12 mL with anhydrous ethanol. After ultrasonic dissolution and mixing, it was transferred to a high-pressure reactor containing 15 mL polytetrafluoroethylene lining and placed in an oven at 160°C for 4 hours. After the reaction was completed and cooled, it was filtered with a 0.45 μm microporous membrane to obtain the first carbon dot solution. The first carbon dot solution was diluted 100 times with anhydrous ethanol and the fluorescence spectrum was measured. The fluorescence spectrum of the carbon dots was obtained after the reaction. The measurement results are shown as follows. Figure 3 and Figure 4 As shown in Figure 2 . Carbon dots synthesized by reacting monoaminobenzenesulfonic acid and para-aminobenzenesulfonic acid with citric acid also have a single emission peak at approximately 413 nm, resulting in a blue-violet fluorescence in solution. However, only the unique structure of 2,4-diaminobenzenesulfonic acid can react with citric acid via an alcohol-thermal method to synthesize carbon dots with dual fluorescence emission peaks, one at 354 nm and one at 498 nm. The solution exhibits green fluorescence with the highest fluorescence intensity and is stable at room temperature. This suggests that the molecular structure of 2,4-diaminobenzenesulfonic acid is a key factor in generating the characteristic dual fluorescence emission signal.

[0030] Comparative Example 3 (Optimization of reaction solvent) The reaction solvent was optimized according to the experimental method described in Comparative Example 1. The fluorescence spectrum of the carbon dots obtained after the reaction was measured as follows: Figure 5As shown. The first carbon dot solution synthesized by the hydrothermal reaction of 2,4-DABS and citric acid has only one emission peak around 348 nm. The solution exhibits light blue fluorescence under ultraviolet light, and the luminescence effect is weak. However, using ethanol as the solvent, the carbon dots synthesized by the reaction have dual emission peaks at 354 nm and 498 nm, and the solution exhibits bright green fluorescence, indicating that the highly polar water solvent has an effect on the core structure of the dual fluorescence emission peak carbon dots formed, resulting in the disappearance of the long-wavelength emission peak. Therefore, ethanol was selected as the reaction solvent to synthesize the carbon dot system of the present invention.

[0031] Comparative Example 4 (Optimization of Carbon Source Ratio) The carbon source ratio was optimized according to the experimental method described in Comparative Example 1. The fluorescence spectrum of the carbon dots obtained after the reaction was measured as follows: Figure 6 As shown in Figure 2, 2,4-Diaminobenzenesulfonic acid (2,4-DABS) and citric acid increase in molar ratio, the emission peak around 497 nm gradually red-shifts and decreases in intensity. At a higher DABS ratio of 3:1, the resulting first carbon dot solution exhibits stratification and instability at room temperature. A molar ratio of 1:2 yields both higher fluorescence intensity and stability. Therefore, a 1:2 molar ratio was selected as the optimal carbon source ratio for synthesis.

[0032] Comparative Example 5 (reaction temperature optimization) The reaction temperature was optimized according to the experimental method described in Comparative Example 1. The fluorescence spectrum and ultraviolet spectrum of the carbon dots were measured as follows: Figure 7 As shown. The emission peak intensity of the carbon dots synthesized at a low temperature of 140 °C at around 355 nm is not high, and the corresponding absorption peak intensities at the three bands of 270 nm, 415 nm, and 465 nm are relatively low. As the reaction temperature increases, the dual emission fluorescence peak intensity of the first synthesized carbon dot solution first increases and then decreases, and tends to be stable at 160 °C-190 °C. The corresponding short-wavelength absorption peak blue-shifts to 260 nm and is enhanced with 465 nm to form two strong absorption peaks. At the same time, the absorption peak at 415 nm disappears. When the reaction temperature is higher than 200 °C, the fluorescence and ultraviolet spectra of the synthesized carbon dots also show a single emission peak at low temperature. In summary, the surface group state of the carbon dots formed at a specific reaction temperature determines its spectral characteristics, so 160 °C is selected as the optimal reaction temperature.

[0033] Comparative Example 6 (reaction time optimization) The reaction time was optimized according to the experimental method described in Comparative Example 1. The fluorescence spectrum of the carbon dots was measured as follows: Figure 8 As the reaction time increases, the fluorescence intensity of carbon dots generally decreases. When the reaction time is 4 h, the fluorescence intensity is the highest. Therefore, 4 h is selected as the optimal reaction time for synthesizing carbon dots.

[0034] Example 2 The DABS-CA carbon dot powder obtained after the reaction in Example 1 (i.e., the optimal conditions) was prepared into a second carbon dot solution (referred to as DABS-CA CDs solution) with a final concentration of 27 mg / mL using anhydrous ethanol for structural characterization and property experiments.

[0035] (1) Characterization of carbon dots (1) Spectral characterization of the second carbon dot solution The second carbon dot solution was taken for structural characterization and property experiments.

[0036] The second carbon dot solution was diluted 100 times with anhydrous ethanol and the fluorescence spectrum and UV spectrum were measured. The results are as follows: Figure 9 As shown. DABS-CA CDs exhibit dual fluorescence emission peaks at 348 nm and 497 nm under the optimal excitation wavelength of 274 nm. The fluorescence quantum yield can reach 50.07% when directly measured using an integrating sphere at the 497 nm emission peak. They exhibit yellow fluorescence under natural light at room temperature and green fluorescence under 365 nm UV light. Under excitation with a long-wavelength excitation light source of 855 nm, DABS-CA CDs exhibit a short-wavelength emission peak at 496 nm, demonstrating upconversion properties. DABS-CA CDs have strong UV absorption peaks at 260 nm and 465 nm.

[0037] (2) Morphological characterization The second carbon dot solution was diluted 100 times with anhydrous ethanol and the Zeta potential was measured using a Malvern laser particle size analyzer. The results showed that its Zeta = +4.23 mV, indicating that the surface of DABS-CA CDs was positively charged. Then, an appropriate amount of solution was added dropwise to the porous carbon film of the copper mesh. After drying under an infrared lamp, the carbon dots were characterized using a Talos field emission transmission electron microscope. The acceleration voltage of the field emission transmission electron microscope was set to 10 kV and the magnification was 100,000 to 600,000 times. The obtained image was analyzed and processed using Nano measure software. The experimental results are shown in Figure 2. Figure 10 As shown, it can be seen that the average particle size of DABS-CA CDs is 16.83 nm, and they are irregularly shaped and relatively dispersed. It can be found that they have an obvious lattice structure, indicating that the core of the carbon dots may have graphite structural characteristics.

[0038] (2) Experimental study on the properties of carbon dots (1) Excitation wavelength dependence The second carbon dot solution was diluted 100 times with anhydrous ethanol and the fluorescence spectrum was measured. The excitation wavelength was set in the range of 220-320 nm and the emission spectrum curve was measured at intervals of 10 nm to explore the excitation wavelength dependence of DABS-CA CDs. The experimental results are shown in Figure 2. Figure 11 As shown in the figure, the two emission peak positions of the DABS-CA CDs solution did not change significantly with the change of the excitation wavelength, indicating that DABS-CA CDs are independent of the excitation wavelength and the optimal excitation wavelength is 270 nm.

[0039] (2) Anti-photobleaching The second carbon dot solution was diluted 100 times with anhydrous ethanol to investigate the photobleaching resistance of DABS-CA CDs. The experimental results are shown in Figure 2. Figure 12 As shown in the figure, with the increase of 365 nm UV lamp irradiation time, the fluorescence intensities of the two emission peaks of DABS-CA CDs showed a downward trend and tended to be stable after 20 min. The positions of the double emission peaks did not change, indicating that DABS-CA CDs have a certain resistance to photobleaching.

[0040] (3) Salt resistance The second carbon dot solution was diluted 100 times with anhydrous ethanol to investigate its salt resistance. The experimental results are as follows: Figure 13 As shown in the figure, with the increase of the volume of NaCl solution added, the fluorescence intensity and emission peak position of the two emission peaks of DABS-CA CDs did not change significantly, indicating that DABS-CA CDs have good salt resistance.

[0041] (4) Response to pH solution environment Take 11 10 mL colorimetric tubes, add 100 μL of the second carbon dot solution (27 mg / mL) to each, then add 5 mL of BR buffer solution with different pH values, dilute to 10 mL with anhydrous ethanol and shake well. The pH values of the added BR buffer are: 1.81, 2.87, 3.78, 4.78, 5.72, 6.8, 7.96, 8.95, 9.91, 10.88, 11.82. Take another colorimetric tube, add 100 μL of 27 mg / mL carbon dot solution, then add 5 mL of distilled water, dilute to 10 mL with anhydrous ethanol and shake well as a blank control. Investigate the effect of BR buffer with different pH values on the fluorescence intensity and Zeta potential value of DABS-CA CDs. The experimental results are shown in Figure 2. Figure 14As shown, the fluorescence emission peak intensity of DABS-CA CDs at 350 nm does not change significantly with pH. The green fluorescence emission peak at 497 nm is stable and strong under acidic conditions with a pH value below 6. When the pH value is greater than 7 under alkaline conditions, it shows a cliff-like downward trend, with the fluorescence intensity dropping by more than half, and the corresponding photo under UV light becomes significantly darker (see Figure 14 d). When the pH value is above 7 in alkaline BR buffer, the emission peak of carbon dots at around 350 nm disappears and a single emission is presented. The corresponding Zeta potential values of carbon dot solutions at different pH values are as follows: Figure 14 As shown in Figure e, under acidic conditions, the carbon dots exhibit a positive surface charge distribution, with a maximum zeta potential of +24 mV. At pH values greater than or equal to 6, the zeta potential of the carbon dots begins to become negative, indicating that the carbon dots are sensitive to solution pH and act as acid-base indicators.

[0042] Example 3 The first carbon dot solution obtained after the reaction in Example 1 (i.e., the optimal conditions) was subjected to drug response studies.

[0043] (1) Volume of different buffer solutions The effect of different volumes of pH 4.78 BR buffer on the fluorescence intensity of DABS-CA CDs was investigated. Figure 15 As shown in the figure, with the increase of the volume of BR buffer added, the emission peak fluorescence intensity of DABS-CA CDs at around 355 nm gradually increased, and the emission peak fluorescence intensity at around 497 nm tended to be stable above 3 mL. Therefore, 4 mL of BR buffer was selected for drug response experiments.

[0044] 2. Response by drug type Use anhydrous ethanol as solvent to prepare 1×10 -3 mol / L acepromazine maleate solution, quercetin solution, rutin solution, progesterone solution, chlorpromazine hydrochloride solution, and atropine sulfate solution. Take 6 colorimetric tubes, add 100 μL of DABS-CACDs solution (the first carbon dot solution), then add 4 mL of BR buffer with pH = 4.78, and then add 1 mL of the different drug solutions prepared above, dilute to 10 mL with anhydrous ethanol and shake thoroughly. After mixing evenly, let it stand for 3 minutes to measure the fluorescence spectrum. The change in fluorescence signal is used to determine whether the carbon dots respond to the drug. The experimental results are as follows. Figure 16 As shown, the fluorescence emission peak intensity at 497 nm of DABS-CA CDs showed obvious signal responses to acepromazine maleate, rutin and quercetin, and the quenching response to acepromazine maleate was the most obvious.

[0045] (III) Working curve of acepromazine maleate Take 0.5 mL of DBS-CA CDs solution (first carbon dot solution) and add 0.4 mL of BR buffer solution with pH = 4.78. Add anhydrous ethanol to 1 mL, mix well and place in a fluorescence cuvette. Measure the fluorescence spectra of 10 sets of blank solutions, and then gradually add 1×10 -4 mol / L maleic acid acepromazine solution was mixed and allowed to stand for 3 minutes to measure the fluorescence spectrum. Data analysis was performed based on the degree of change in the solution's fluorescence intensity to explore the linear response relationship of DABS-CA CDs to maleic acid acepromazine. The experimental results are shown in Figure 2. Figure 17 As shown in Figure 2, the fluorescence intensity of the two emission peaks of the carbon dots gradually decreased with the increase of the concentration of acepromazine maleate, showing a good linear change, and anhydrous ethanol as a solvent had no effect on the quenching results. -6 ~1.5×10 -5 The correlation working curve equation at the 355 nm fluorescence emission peak is I0 / I=0.07244×105Cace+1.0641, the correlation coefficient r=0.99539, S is the slope of the working curve, the RSD value of 10 blank experiments is 0.86%, and the corresponding detection limit LOD is 3 RSD / S=3.56×10 -7 mol / L. The relevant working curve equation at the 497 nm fluorescence emission peak is: I0 / I=0.03485×10 5 Cace + 0.99203, correlation coefficient r = 0.99981, S is the slope of the working curve, the RSD value of 10 blank experiments = 0.32%, corresponding to the detection limit LOD = 3 RSD / S = 9.2 × 10 -7 The results showed that DABS-CA CDs could be used as a green fluorescent probe, and a new method for the detection of acepromazine maleate was established based on the linear quenching response of the fluorescence signal.

[0046] In the present invention, the experimental reagents used are shown in Table 1 below. Table 1 Experimental reagents

[0047] The above embodiments and drawings do not limit the methods and applications of the present invention. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the patent scope of the present invention.

Claims

1. An alcohol thermal method for synthesizing dual-emission fluorescent carbon dots, characterized by: A carbon dot solution was prepared by alcohol thermal synthesis reaction using 2,4-diaminobenzenesulfonic acid and a cross-linking auxiliary agent as carbon sources and ethanol as solvent. The fluorescence quantum yield of the carbon dot solution reached 50.07%. The cross-linking auxiliary agent was polyethyleneimine, citric acid, o-phenylenediamine or acetic acid. The carbon dots had a double fluorescence emission peak.

2. The alcohol-thermal method for synthesizing dual-emission fluorescent carbon dots according to claim 1, wherein: The carbon dots are sensitive to the pH value of the solution and the water solvent. The fluorescence emitted by the carbon dots in a solution environment with a pH value less than 6 is double-emission fluorescence, and the fluorescence emitted in a solution environment with a pH value greater than 6 is single-emission fluorescence. The fluorescence emitted by the carbon dots in a solution environment with water as the solvent is single-emission fluorescence.

3. The alcohol-thermal method for synthesizing dual-emission fluorescent carbon dots according to claim 1, wherein: The cross-linking auxiliary agent is citric acid, and the molar ratio of the 2,4-diaminobenzenesulfonic acid to the citric acid is 1:2; The carbon dot solution forms fluorescence double emission peaks at 348 nm and 500 nm when excited by a light source with a wavelength of 274 nm.

4. The alcohol-thermal method for synthesizing dual-emission fluorescent carbon dots according to claim 1, wherein: The temperature of the alcohol thermal synthesis reaction is 160~190℃, and the time of the alcohol thermal synthesis reaction is 4~10h.

5. The alcohol-thermal method for synthesizing dual-emission fluorescent carbon dots according to claim 1, wherein: The ethanol solution of the carbon dots has upconversion characteristics.

6. The alcohol-thermal method for synthesizing dual-emission fluorescent carbon dots according to claim 1, wherein: The carbon dots have a lattice structure.

7. An application of an alcohol thermal method to synthesize dual-emission fluorescent carbon dots, characterized by: The carbon dots according to any one of claims 1 to 6 are used as green fluorescent probes for the detection of acepromazine maleate, rutin or quercetin.

8. The use of the alcohol thermal method for synthesizing dual-emission fluorescent carbon dots as claimed in claim 7, characterized in that: The carbon dots are used for content detection of acepromazine maleate drug.

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