An easily purified Ca 2+ and Mg 2+ Preparation methods and applications of responsive carbon dots

Abstract

This invention belongs to the field of chemical synthesis and relates to the preparation of carbon-based materials, specifically an easily purified Ca... 2+ and Mg 2+ Preparation method and application of responsive carbon dots. This invention synthesizes easily purified Ca2+ carbon dots via a one-step hydrothermal method using CTAB and Pd particles as precursors. 2+ and Mg 2+ Responsive carbon dots (CDs). The presence of Pd particles in the precursor enhances the fluorescence intensity of these CDs. Since CTAB readily precipitates at low temperatures, carbon dot purification and precursor reuse were achieved through 4°C refrigeration and centrifugation. Furthermore, these carbon dots respond to Ca... 2+ and Mg 2+ Excellent fluorescence responsiveness enables the quantitative detection of these two ions. The present invention synthesizes a detectable Ca... 2+ and Mg 2+ The preparation process of CDs is simple and the purification steps are quick, which not only provides a new method for the purification of CDs, but also broadens the application field of CDs and lays the foundation for their development.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis and relates to the preparation of carbon-based materials, specifically an easily purified Ca... 2+ and Mg 2+ Preparation methods and applications of responsive carbon dots. Background Technology

[0002] The discovery of carbon quantum dots (CQDs) in 2004 attracted widespread attention from researchers. CQDs, also known as carbon dots (CDs), are a class of zero-dimensional carbon-based nanomaterials with significant fluorescence properties, typically smaller than 10 nm in size. CDs possess advantages such as low toxicity, good water solubility, and environmental friendliness, showing promising applications in medical imaging, environmental monitoring, and chemical analysis. However, the optical properties of CDs are usually influenced not only by their composition, size, and morphology, but also by unreacted precursors or byproducts. Therefore, the purification process for CDs is essential.

[0003] Currently, the main purification methods for CDs include dialysis, column chromatography, and electrophoresis. Dialysis involves placing the CD solution in a dialysis bag, then immersing the bag in the desired solution. Utilizing the principle of diffusion pressure, the CDs are retained inside the dialysis bag, while salts and small molecules diffuse out. Column chromatography separates components based on the different adsorption forces of substances on silica gel. Electrophoresis separates particles based on their different charges or charge-to-mass ratios, achieving separation through varying migration distances. However, while dialysis is simple and energy-efficient, it is time-consuming and expensive. Column chromatography, while capable of separating and purifying CDs, has low separation efficiency and cannot be operated continuously. Electrophoresis, while highly efficient, is cumbersome. Therefore, new methods are needed to improve the purification efficiency of CDs.

[0004] In industrial circulating cooling water, the risk of scale formation clogging heat exchanger pipes is constantly increasing. Calcium and magnesium salts deposit on the surface of heat exchangers, leading to scale formation. Therefore, detecting the concentration of calcium and magnesium ions is of great significance for industrial production. Currently, the main techniques for detecting calcium and magnesium ions include complexometric titration, spectrophotometry, ion chromatography, and atomic absorption spectrometry. However, these methods usually require expensive equipment or cumbersome sample preparation, limiting their application in detection. Therefore, there is still a need to develop an economical, efficient, sensitive, and simple technique for detecting calcium and magnesium ions. Some researchers have applied calcium ions (CDs) to human cells to detect calcium and magnesium ions. 2+ or Mg 2+ However, there is very little research on the use of CDs for the detection of calcium and magnesium ions in water.

[0005] Addressing the shortcomings of existing CDs purification methods and the detection of Ca 2+ and Mg 2+Traditional methods for determining the content of Ca2+ involve high instrument costs, long detection times, or complex sample preparation. This article presents a method that is easy to purify and effective against Ca2+. 2+ and Mg 2+ There are corresponding methods for preparing carbon dots and their applications. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes an easily purified Ca... 2+ and Mg 2+ Preparation and application of responsive carbon dots (CDs): The preparation and purification method of these CDs is rapid, efficient, simple, and easy to implement. The prepared CDs respond to Ca... 2+ and Mg 2+ Both exhibit fluorescence enhancement response and can be used for Ca in water. 2+ and Mg 2+ The detection.

[0007] The technical solution of this invention is implemented as follows:

[0008] A method for preparing fluorescent CDs using hexadecyltrimethylammonium bromide (CTAB) and palladium (Pd) as precursors includes the following steps: Powdered CTAB is placed in a sample vial, a small amount of ultrapure water is added, and the solution is dissolved by sonication and a water bath. Then, metallic Pd particles are added, and ultrapure water is added again to bring the total system volume to 15 mL. The solution is placed in a high-pressure reactor for high-temperature heating. After the reaction, the solution is cooled to room temperature, and Pd is removed by centrifugation. The solution is then placed at low temperature to allow CTAB to precipitate, which is recovered by centrifugation to obtain a pure CDs solution. The solution is freeze-dried to obtain CDs powder, which is stored at 4°C.

[0009] Furthermore, the mass ratio of CTAB to Pd nanoparticles is 150~225:0~9.

[0010] Preferably, the reaction concentration of CTAB is 0.01-0.015 g / mL, and the reaction concentration of Pb nanoparticles is 0-0.0006 g / mL.

[0011] Furthermore, the precursor solution is placed in a sample vial, and the container for the high-temperature heating reaction is a high-pressure reactor with a polytetrafluoroethylene liner.

[0012] Furthermore, the high-pressure heating reaction temperature is 160~200℃, and the reaction time is 2~3.5 h.

[0013] Furthermore, after centrifuging the CDs solution cooled to room temperature to remove Pd, it was placed at 4°C to allow CTAB to precipitate, followed by centrifugation. This refrigeration and centrifugation process was repeated 1-3 times.

[0014] The blue light emitting carbon dots prepared by the above method have a particle size distribution of about 3~10 nm, with an average particle size of about 6 nm; the surface functional groups include hydroxyl and amino groups; the optimal excitation wavelength is 330 nm and the optimal emission wavelength is 424 nm.

[0015] The carbon dots mentioned are in the metal ion Ca 2+ and Mg 2+ In the detection application, CDs are used as detection materials, and their fluorescence changes are used to detect Ca in aqueous solutions. 2+ and Mg 2+ Conduct testing.

[0016] Furthermore, a gradient of Ca was added to the CDs solution. 2+ and Mg 2+ The fluorescence intensity of the solution was measured using a fluorescence spectrometer, and the change in fluorescence intensity was plotted against Ca. 2+ and Mg 2+ Concentration-relative curve.

[0017] This application also seeks protection for the aforementioned Ca. 2+ and Mg 2+ Response-type carbon dots detect Ca during preparation 2+ and Mg 2+ Applications in reagents and / or instruments.

[0018] The present invention has the following beneficial effects:

[0019] 1. This invention uses hexadecyltrimethylammonium bromide (CTAB) as both carbon and nitrogen sources, and synthesizes easily purified Ca through a one-step hydrothermal method under the coexistence of palladium (Pd) particles. 2+ and Mg 2+ Responsive carbon dots (CDs). The presence of Pd particles in the precursor enhances the fluorescence intensity of these CDs. Since the precursor CTAB readily precipitates at low temperatures, unreacted CTAB can be removed and recovered by refrigeration at 4°C and centrifugation, with the recovered CTAB potentially reusable. This post-processing method is faster and more efficient than traditional dialysis and chromatography, providing a new approach for CD post-processing. Furthermore, these carbon dots respond to Ca... 2+ and Mg 2+ Both exhibit good responsiveness; the fluorescence intensity gradually increases with increasing concentration of each ion, enabling quantitative detection of these two ions. The present invention synthesizes a detectable Ca... 2+ and Mg 2+ The preparation process of CDs is simple and easy to purify, which not only provides a new method for the purification of CDs, but also broadens the application field of CDs and lays the foundation for their development.

[0020] 2. This invention provides a synthesis of CDs using CTAB as the main precursor and under conditions where metal Pd particles coexist. The coexistence of metal Pd particles effectively enhances the fluorescence intensity of the CDs. This CDs synthesis process and post-processing method are rapid, efficient, and easy to implement. Based on the measurement of fluorescence intensity after mixing different types of metal ion solutions with this CDs solution under the same conditions, it was found that Al... 3+ Ba 2+ Cu 2+ Cr 3+ Plasma has little effect on the fluorescence quenching or enhancement of CDs, but it does not significantly affect Ca. 2+ and Mg 2+ It is responsive. Therefore, the CDs are responsive to Ca. 2+ and Mg 2+ It offers a high degree of selectivity.

[0021] 3. The blue light emitting CDs prepared by this invention not only have a positive effect on Ca 2+ and Mg 2+ There is a response, and the degree of response increases with Ca. 2+ and Mg 2+ The concentration increases and the effect is enhanced, which is beneficial for the detection of Ca in water by fluorescent CDs. 2+ and Mg 2+ This provides a new direction for the development of the field. Attached Figure Description

[0022] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is the fluorescence spectrum of CDs.

[0024] Figure 2 This is a transmission electron microscope image of CDs.

[0025] Figure 3 This is the infrared spectrum of CDs.

[0026] Figure 4 For CDs and CDs 13 A comparison of fluorescence intensity.

[0027] Figure 5 This is a standard curve of CTAB absorbance.

[0028] Figure 6 Detection of different concentrations of Ca in CDs 2+ The graph shows the change in fluorescence intensity after fluorescence.

[0029] Figure 7 CDs fluorescence intensity as a function of Ca 2+ Linear fitting plot of concentration change.

[0030] Figure 8 For the detection of different concentrations of Mg by CDs 2+ The graph shows the change in fluorescence intensity after fluorescence.

[0031] Figure 9 CDs fluorescence intensity with Mg 2+ Linear fitting plot of concentration change.

[0032] Figure 10 For CDs in Ca 2+ and Mg 2+ Fluorescence response diagrams at concentrations of 1 mol / L. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] The easily purified Ca in this embodiment 2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0036] Weigh 0.150 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min and bathe in a 40℃ water bath for 10 min to dissolve it. After the temperature drops to room temperature, add 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 160℃ for 2 h. After cooling to room temperature, place it at 4℃ and remove unreacted CTAB by repeated refrigeration and centrifugation to obtain a pure CDs1 solution.

[0037] The purified CDs1 solution was used to measure its fluorescence intensity under excitation wavelengths of 300–370 nm. The excitation and emission bandwidths were both 5 nm, the scan rate was 1200 nm / min, the scan interval was 1 nm, the optimal excitation wavelength was 330 nm, the optimal emission wavelength was 425 nm, and the fluorescence intensity was 623.

[0038] Example 2

[0039] The easily purified Ca in this embodiment2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0040] Weigh 0.182 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min and bathe in a 40℃ water bath for 10 min to dissolve it. After the temperature drops to room temperature, add 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 160℃ for 2 h. After cooling to room temperature, place it at 4℃ and remove unreacted CTAB by repeated refrigeration and centrifugation to obtain a pure CDs2 solution.

[0041] The purified CDs2 solution was used to measure its fluorescence intensity under excitation wavelengths of 300–370 nm. The excitation and emission bandwidths were both 5 nm, the scan rate was 1200 nm / min, the scan interval was 1 nm, the optimal excitation wavelength was 330 nm, the optimal emission wavelength was 424 nm, and the fluorescence intensity was 708.

[0042] Example 3

[0043] The easily purified Ca in this embodiment 2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0044] Weigh 0.225 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min and bathe in a 40℃ water bath for 10 min to dissolve it. After the temperature drops to room temperature, add 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 160℃ for 2 h. After cooling to room temperature, place it at 4℃ and remove unreacted CTAB by repeated refrigeration and centrifugation to obtain a pure CDs3 solution.

[0045] The purified CDs3 solution was used to measure its fluorescence intensity under excitation wavelengths of 300–370 nm. The excitation and emission bandwidths were both 5 nm, the scan rate was 1200 nm / min, and the scan interval was 1 nm. At the optimal excitation wavelength of 330 nm, the optimal emission wavelength was 422 nm, and the fluorescence intensity was 705.

[0046] Example 4

[0047] The easily purified Ca in this embodiment 2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0048] Weigh 0.182 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min and bathe in a 40℃ water bath for 10 min to dissolve it. After the temperature drops to room temperature, add 3 mg of Pd particles and continue to add 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 160℃ for 2 h. After cooling to room temperature, place it at 4℃ and remove unreacted CTAB by repeated refrigeration and centrifugation to obtain a pure CDs4 solution.

[0049] The purified CDs4 solution was used to measure its fluorescence intensity under excitation wavelengths of 300–370 nm. The excitation and emission bandwidths were both 5 nm, the scan rate was 1200 nm / min, the scan interval was 1 nm, the optimal excitation wavelength was 330 nm, the optimal emission wavelength was 424 nm, and the fluorescence intensity was 721.

[0050] Example 5

[0051] The easily purified Ca in this embodiment 2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0052] Weigh 0.182 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min and bathe in a 40℃ water bath for 10 min to dissolve it. After the temperature drops to room temperature, add 6 mg of Pd particles and continue to add 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 160℃ for 2 h. After cooling to room temperature, place it at 4℃ and remove unreacted CTAB by repeated refrigeration and centrifugation to obtain a pure CDs5 solution.

[0053] The purified CDs5 solution was used to measure its fluorescence intensity under excitation wavelengths of 300–370 nm. The excitation and emission bandwidths were both 5 nm, the scan rate was 1200 nm / min, the scan interval was 1 nm, the optimal excitation wavelength was 330 nm, the optimal emission wavelength was 422 nm, and the fluorescence intensity was 769.

[0054] Example 6

[0055] The easily purified Ca in this embodiment 2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0056] Weigh 0.182 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min and bathe in a 40℃ water bath for 10 min to dissolve it. After the temperature drops to room temperature, add 9 mg of Pd particles and continue to add 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 160℃ for 2 h. After cooling to room temperature, place it at 4℃ and remove unreacted CTAB by repeated refrigeration and centrifugation to obtain a pure CDs6 solution.

[0057] The purified CDs6 solution was used to measure its fluorescence intensity under excitation wavelengths of 300–370 nm. The excitation and emission bandwidths were both 5 nm, the scan rate was 1200 nm / min, the scan interval was 1 nm, the optimal excitation wavelength was 330 nm, the optimal emission wavelength was 425 nm, and the fluorescence intensity was 758.

[0058] Example 7

[0059] The easily purified Ca in this embodiment 2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0060] Weigh 0.182 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min and bathe in a 40℃ water bath for 10 min to dissolve it. After the temperature drops to room temperature, add 6 mg of Pd particles and continue to add 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 170℃ for 2 h. After cooling to room temperature, place it at 4℃ and remove unreacted CTAB by repeated refrigeration and centrifugation to obtain a pure CDs7 solution.

[0061] The purified CDs7 solution was used to measure its fluorescence intensity under excitation wavelengths of 300–370 nm. The excitation and emission bandwidths were both 5 nm, the scan rate was 1200 nm / min, the scan interval was 1 nm, the optimal excitation wavelength was 330 nm, the optimal emission wavelength was 421 nm, and the fluorescence intensity was 858.

[0062] Example 8

[0063] The easily purified Ca in this embodiment 2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0064] Weigh 0.182 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min and bathe in a 40℃ water bath for 10 min to dissolve it. After the temperature drops to room temperature, add 6 mg of Pd particles and continue to add 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 185℃ for 2 h. After cooling to room temperature, place it at 4℃ and remove unreacted CTAB by repeated refrigeration and centrifugation to obtain a pure CDs8 solution.

[0065] The purified CDs8 solution was used to measure its fluorescence intensity under excitation wavelengths of 300–370 nm. The excitation and emission bandwidths were both 5 nm, the scan rate was 1200 nm / min, the scan interval was 1 nm, the optimal excitation wavelength was 330 nm, the optimal emission wavelength was 425 nm, and the fluorescence intensity was 903.

[0066] Example 9

[0067] The easily purified Ca in this embodiment 2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0068] Weigh 0.182 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min and bathe in a 40℃ water bath for 10 min to dissolve it. After the temperature drops to room temperature, add 6 mg of Pd particles and continue to add 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 200℃ for 2 h. After cooling to room temperature, place it at 4℃ and remove unreacted CTAB by repeated refrigeration and centrifugation to obtain a pure CDs9 solution.

[0069] The purified CDs9 solution was used to measure its fluorescence intensity at excitation wavelengths ranging from 300 to 370 nm. Both the excitation and emission bandwidths were 5 nm, the scan rate was 1200 nm / min, and the scan interval was 1 nm. At the optimal excitation wavelength of 330 nm, the optimal emission wavelength was 423 nm, and the fluorescence intensity was 895.

[0070] Example 10

[0071] The easily purified Ca in this embodiment 2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0072] Weigh 0.182 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min, and then dissolve in a 40°C water bath for 10 min. After the temperature drops to room temperature, add 6 mg of Pd granules, followed by 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 185°C for 2.5 h. After cooling to room temperature, place it at 4°C and repeatedly refrigerate and centrifuge to remove unreacted CTAB, obtaining pure CDs. 10 Solution.

[0073] Take the purified CDs as described above 10 The fluorescence intensity of the solution was measured under excitation wavelengths ranging from 300 to 370 nm. The excitation and emission bandwidths were both 5 nm, the scan rate was 1200 nm / min, the scan interval was 1 nm, the optimal excitation wavelength was 330 nm, the optimal emission wavelength was 424 nm, and the fluorescence intensity was 956.

[0074] Example 11

[0075] The easily purified Ca in this embodiment 2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0076] Weigh 0.182 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min and bathe in a 40℃ water bath for 10 min to dissolve it. After the temperature drops to room temperature, add 6 mg of Pd particles and continue to add 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 185℃ for 3 h. After cooling to room temperature, place it at 4℃ and remove unreacted CTAB by repeated refrigeration and centrifugation to obtain a pure CDs solution.

[0077] The purified CDs solution was taken and its fluorescence intensity was measured at excitation wavelengths of 300–370 nm. The results are as follows: Figure 1 As shown. The excitation and emission bandwidths were both 5 nm, the scan rate was 1200 nm / min, the scan interval was 1 nm, the optimal excitation wavelength was 330 nm, the optimal emission wavelength was 424 nm, and the fluorescence intensity was 10¹³. It was characterized by transmission electron microscopy and infrared spectroscopy, as shown below. Figure 2 , Figure 3 As shown in the figure. The results indicate that CDs were successfully synthesized, with an average particle size of approximately 6 nm, and containing amino and hydroxyl groups.

[0078] Example 12

[0079] The easily purified Ca in this embodiment 2+ and Mg2+ The preparation method of responsive carbon dots includes the following steps:

[0080] Weigh 0.182 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min, and then dissolve in a 40°C water bath for 10 min. After the temperature drops to room temperature, add 6 mg of Pd granules, followed by 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 200°C for 3.5 h. After cooling to room temperature, place it at 4°C and repeatedly refrigerate and centrifuge to remove unreacted CTAB, obtaining pure CDs. 12 Solution.

[0081] Take the purified CDs as described above 12 The fluorescence intensity of the solution was measured under excitation wavelengths ranging from 300 to 370 nm. Both the excitation and emission bandwidths were 5 nm, the scan rate was 1200 nm / min, and the scan interval was 1 nm. At the optimal excitation wavelength of 330 nm and the optimal emission wavelength of 425 nm, the fluorescence intensity was 987.

[0082] Comparative Example 1

[0083] The easily purified Ca in this comparative example 2+ and Mg 2+ The preparation method of responsive carbon dots includes the following steps:

[0084] Under the conditions of Example 11, the fluorescence intensity without the addition of Pd particles was measured, specifically as follows:

[0085] Weigh 0.182 g CTAB into a sample vial, add 5 mL of ultrapure water, sonicate for 2 min, and then dissolve in a 40°C water bath for 10 min. After the temperature drops to room temperature, add 10 mL of ultrapure water. Place the prepared precursor solution in a high-pressure reactor with a polytetrafluoroethylene liner and heat at 185°C for 3 h. After cooling to room temperature, place it at 4°C and remove unreacted CTAB by repeated refrigeration and centrifugation to obtain pure CDs. 13 Solution.

[0086] Take the purified CDs as described above 13 The fluorescence intensity of the solutions was measured under excitation wavelengths ranging from 300 to 370 nm. Both the excitation and emission bandwidths were 5 nm, the scan rate was 1200 nm / min, and the scan interval was 1 nm. At the optimal excitation wavelength of 330 nm and the optimal emission wavelength of 421 nm, the fluorescence intensity was 835. CDs and CDs were used. 13 The spectrum at an excitation wavelength of 330 nm was compared to the effect of Pd particles on the fluorescence intensity of CDs. The results are as follows: Figure 4 As shown in the figure. Experiments show that the addition of Pd particles effectively enhances the fluorescence intensity of CDs.

[0087] Comparative Example 2

[0088] The difference between the preparation method of carbon dots in this comparative example and that in Example 11 is as follows: after the reaction solution is cooled to room temperature, it is centrifuged to remove Pd particles. Then, the reaction solution is placed at 4°C for refrigeration to allow CTAB to precipitate. This CTAB is then removed by centrifugation. This process is repeated only once, with each repetition occurring 4 hours apart. The CTAB content in the solution is determined by spectrophotometry.

[0089] Comparative Example 3

[0090] The difference between the preparation method of carbon dots in this comparative example and that in Example 11 is as follows: after the reaction solution is cooled to room temperature, it is centrifuged to remove Pd particles. Then, the reaction solution is placed at 4°C for refrigeration to allow CTAB to precipitate. This CTAB is then removed by centrifugation. This process is repeated only twice, with a 4-hour interval between each precipitation. The CTAB content in the solution is determined by spectrophotometry.

[0091] Comparative Example 4

[0092] The difference between the preparation method of carbon dots in this comparative example and that in Example 11 is as follows: after the reaction solution is cooled to room temperature, it is centrifuged to remove Pd particles. Then, the reaction solution is placed at 4°C for refrigeration to allow CTAB to precipitate. This CTAB is then removed by centrifugation. This process is repeated only three times, with a 4-hour interval between each precipitation. The CTAB content in the solution is determined by spectrophotometry.

[0093] After refrigeration and centrifugation for different periods, the CTAB content was determined spectrophotometrically. The standard curves for comparative examples 1-4 are shown below. Figure 5 As shown, the CTAB removal rate was 51.1% after two treatments, 83.3% after three treatments, and 83.6% after four treatments. The results indicate that the CTAB removal rate essentially reaches its peak after three treatments using this method. While some residual CTAB may remain in the solution, its concentration is extremely low; the remaining CTAB is involved in CDs synthesis.

[0094] Application Example 1

[0095] The easily purified Ca prepared in this application 2+ and Mg 2+ Linear relationship of responsive carbon dots:

[0096] Take CaCl2 or MgCl2 solution and mix it with 1 mL of 0.85 mg / mL CDs solution to make a total volume of 2 mL, in which Ca... 2+ and Mg2+ The concentration range was 0~1.0 mol / L, and the results were as follows: Figure 10 As shown. Based on the results analysis, carbon dots affect Ca... 2+ and Mg 2+ All showed a response, and the fluorescence intensity of CDs increased with Ca. 2+ and Mg 2+ The effect increases with increasing concentration, as shown in the following figure. Figure 6 , Figure 8 As shown; the fluorescence intensity change value and Ca 2+ and Mg 2+ The concentration showed a linear relationship, as shown in the results. Figure 7 , Figure 9 As shown. Where, ΔF Ca 2+ =241.28C Ca 2+ +5.77, R 2 =97.7%; ΔF Mg 2+ =39.28C Mg 2+ +21.01, R 2 =96.1%. Figure 10 For CDs in Ca 2+ and Mg 2+ Fluorescence response diagrams at concentrations of 1 mol / L.

[0097] Application Example 2

[0098] The easily purified Ca prepared in this application 2+ and Mg 2+ Selectivity of responsive carbon dots:

[0099] CDs are subjected to Ca 2+ and Mg 2+ Selective detection. 8.5 mg of CDs were dissolved in 10 mL of PBS buffer (10 mmol / L), divided into 10 groups. 1 mL of the same concentration of Al was added to 1 mL of each CDs solution. 3+ Ba 2+ Ca 2+ Cu 2+ Cr 3+ Fe 2+ Fe 3+ Hg 2+ Mg 2+ Zn 2+ The fluorescence intensity was measured after thorough mixing of the aqueous solution (100 mmol / L). The results showed that, under the same detection conditions, except for CDs, which affected Ca... 2+ and Mg 2+Apart from the response, other ions did not show a significant quenching or enhancement effect on the fluorescence intensity of CDs, indicating that CDs have a negative effect on Ca. 2+ and Mg 2+ It offers a high degree of selectivity.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A readily purified Ca 2+ and Mg 2+ A method for preparing a responsive carbon dot, characterized by, The steps are: taking CTAB and Pd nanoparticles as precursors to synthesize Ca 2+ and Mg 2+ responsive carbon dots by one-step hydrothermal method.

2. The Ca 2+ and Mg 2+ A method for preparing a responsive carbon dot, characterized by: The mass ratio of the CTAB and the Pd nanoparticles is [150, 225]: (0, 9].

3. The Ca of claim 1 2+ and Mg 2+ A method for preparing a responsive carbon dot, characterized by comprising the steps of: The reaction temperature of the one-step hydrothermal method is 160-200 DEG C, and the time is 2-3.5 h.

4. The Ca of any one of claims 1-3 2+ and Mg 2+ A method for preparing a responsive carbon dot, characterized by, The specific steps are: (1) dissolving CTAB into ultrapure water, mixing after ultrasonic and heating, and then adding Pd particles to obtain a mixed solution; (2) after the mixed solution of step (1) is subjected to hydrothermal reaction, cooling to room temperature, and then repeatedly refrigerating and centrifuging, a purified CDs solution is obtained. (3) The CDs solution of step (2) is freeze-dried to obtain Ca 2+ and Mg 2+ responsive carbon dot powder.

5. The Ca of claim 4 2+ and Mg 2+ A method for preparing a responsive carbon dot, characterized by comprising the steps of: In step (1), the concentration of CTAB in the mixed solution is 0.010-0.015 g / mL, and the concentration of Pd nanoparticles in the mixed solution is greater than 0 g / mL and less than 0.0006 g / mL.

6. The Ca of claim 4 2+ and Mg 2+ A method for preparing a responsive carbon dot, characterized by comprising the steps of: The ultrasonic time is 2 min, the heating temperature is 40 DEG C, and the heating time is 10 min.

7. The Ca of claim 4 2+ and Mg 2+ The preparation method of the responsive carbon dots, characterized in that: In step (2), the hydrothermal reaction temperature is 160-200 DEG C, and the reaction time is 2-3.5 h; after the reaction is completed, the mother liquor is refrigerated at 4 DEG C, centrifuged every 4 h, the centrifugal speed is 8000 rpm, the time is 10 min, and the number of repetitions is 1-3 times.

8. The Ca of any one of claims 1-3, 5-7, prepared by the method. 2+ and Mg 2+ responsive carbon dots.

9. The Ca of claim 8 2+ and Mg 2+ Responsive carbon dots characterized in that: The Ca 2+ and Mg 2+ The responsive carbon dots are blue light emitting carbon dots, the particle size distribution is 3-10 nm, the average particle size is 6 nm, the surface functional groups are hydroxyl and amino groups, the optimal excitation wavelength is 330 nm, and the optimal emission wavelength is 424 nm.

10. The Ca of claim 9 2+ and Mg 2+ Responsive carbon dots for use in reagents and / or instruments for simultaneous detection of Ca 2+ and Mg 2+ .

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