Preparation method, product and application of cetylamine functionalized sulfadiazine carbon quantum dots

Abstract

The invention relates to the technical field of green chemical synthesis, in particular to a preparation method, a product and application of cetylamine functionalized sulfadiazine carbon quantum dots. The preparation method of the cetylamine functionalized sulfadiazine carbon quantum dots comprises the following steps: adding carbon quantum dots containing carboxyl groups on the surfaces, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide into a solvent, adjusting the pH value to be acidic, and then stirring and activating to obtain an activated solution; adding a cetylamine solution into the activated solution for reaction, and then filtering to obtain the cetylamine functionalized sulfadiazine carbon quantum dots. The cetylamine functionalized sulfadiazine carbon quantum dots are synthesized by adopting a surface functionalization method, and the cetylamine functionalized sulfadiazine carbon quantum dots have good light stability and adjustable photoluminescence characteristics, and have good selectivity and high sensitivity when being used for detecting p-nitrophenol; and trace detection of p-nitrophenol can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of green chemical synthesis, and in particular to a preparation method, product and application of hexadecylamine-functionalized sulfadiazine carbon quantum dots. Background Art

[0002] p-Nitrophenol is one of the common pollutants in water and soil pollution. Its stability and resistance to degradation enable it to exist in the environment for a long time, posing a potential threat to the ecosystem. In addition, p-nitrophenol is a typical oxidative phosphorylation uncoupler. It can be absorbed through the skin, respiratory tract and gastrointestinal tract, and can disrupt the cell energy metabolism process. Even at low concentrations, it can cause adverse reactions such as headache, dizziness, nausea, and vomiting in humans, and in severe cases, it may even lead to death. p-Nitrophenol has significant hazards to the environment and human health. Therefore, the detection of p-nitrophenol in the environment is of great significance for both the environment and human health. Currently, the commonly used methods for detecting p-nitrophenol include liquid chromatography, electrochemistry, chemiluminescence, capillary electrophoresis, etc. These methods are widely used and have their own advantages. However, due to disadvantages such as high cost, cumbersome sample pretreatment procedures, and poor method stability, it is necessary to develop a simple, effective, high-precision and low-cost method for detecting p-nitrophenol. Summary of the Invention

[0003] Based on the above, the present invention provides a preparation method of hexadecylamine-functionalized sulfadiazine carbon quantum dots. The hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared by the method of the present invention can achieve trace detection of p-nitrophenol.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention, a preparation method of hexadecylamine-functionalized sulfadiazine carbon quantum dots, includes the following steps:

[0006] Adding carbon quantum dots with carboxyl groups on the surface, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide into a solvent to adjust the pH to acidic, and then stirring and activating to obtain an activated solution;

[0007] Adding a hexadecylamine solution to the activated solution for reaction, and then filtering to obtain the hexadecylamine-functionalized sulfadiazine carbon quantum dots.

[0008] Another technical solution of the present invention, a hexadecylamine-functionalized sulfadiazine carbon quantum dot prepared according to the above preparation method.

[0009] Another technical solution of the present invention, the application of the above hexadecylamine-functionalized sulfadiazine carbon quantum dots in the detection of p-nitrophenol.

[0010] Fourth technical solution of the present invention: A method for detecting p-nitrophenol in a water sample. After mixing the water sample with the above-mentioned hexadecylamine-functionalized sulfadiazine carbon quantum dots and oscillating, the fluorescence intensity F0 - F is measured. According to the equation F0 - F = 1.084[4-NP] + 3227.4, the concentration of p-nitrophenol in the water sample is calculated; 4-NP in the equation represents p-nitrophenol.

[0011] The present invention discloses the following technical effects:

[0012] The present invention synthesizes hexadecylamine-functionalized sulfadiazine carbon quantum dots by a surface functionalization method. The hexadecylamine-functionalized sulfadiazine carbon quantum dots have good photostability and adjustable photoluminescence properties, and have good selectivity and high sensitivity for detecting p-nitrophenol, and can realize trace detection of p-nitrophenol. Description of the Drawings

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0014] Figure 1 X-ray diffraction pattern of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 of the present invention;

[0015] Figure 2 Particle size distribution diagram of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 of the present invention;

[0016] Figure 3 Infrared spectrum of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 of the present invention;

[0017] Figure 4 XPS spectrum of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 of the present invention;

[0018] Figure 5 Ultraviolet-visible absorption spectrum (blue), fluorescence excitation spectrum (red), and emission spectrum (brown) of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 of the present invention;

[0019] Figure 6 Normalized fluorescence emission spectrum of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 of the present invention;

[0020] Figure 7 Fluorescence emission spectra of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 of the present invention at different excitation wavelengths;

[0021] Figure 8 Fluorescence intensity of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 of the present invention at different ionic strengths;

[0022] Figure 9 Fluorescence intensity of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 of the present invention under different ultraviolet lamp irradiation durations;

[0023] Figure 10 Detection selectivity of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 of the present invention;

[0024] Figure 11 Linear relationship diagram between the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 of the present invention and the concentration of p-nitrophenol; among them, the left figure is the fluorescence emission spectrum diagram, and the right figure is the linear fitting curve;

[0025] Figure 12 Fluorescence spectrum of the carbon quantum dots prepared in Comparative Example 1 of the present invention; among them, the left figure is the fluorescence emission spectrum of the carbon quantum dots prepared in Comparative Example 1 under different excitation wavelengths, and the right figure is the fluorescence excitation spectrum (cyan) and emission spectrum (blue);

[0026] Figure 13 Detection selectivity of the carbon quantum dots prepared in Comparative Example 1 of the present invention;

[0027] Figure 14 Fluorescence emission spectrum diagram between the carbon quantum dots prepared in Comparative Example 1 of the present invention and the concentration of Fe 3+ ;

[0028] Figure 15 Fluorescence emission spectrum diagram between the carbon quantum dots prepared in Comparative Example 1 of the present invention and the concentration of Fe 3+ ; Detailed implementation manners

[0029] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0030] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded within the range.

[0031] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although only preferred methods and materials are described in this invention, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to those documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0032] Without departing from the scope or spirit of this invention, various modifications and variations can be made to the specific embodiments of the specification of this invention, which will be apparent to those skilled in the art. Other embodiments obtained from the specification of this invention will be apparent to those skilled in the art. The specification and examples of this invention are merely exemplary.

[0033] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0034] The first aspect of this invention provides a method for preparing hexadecylamine-functionalized sulfadiazine carbon quantum dots, comprising the following steps:

[0035] Carbon quantum dots with carboxyl groups on the surface, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide are added to a solvent, and the pH is adjusted to acidic, and then stirred and activated to obtain an activated solution;

[0036] A hexadecylamine solution is added to the activated solution for reaction, and then filtered to obtain the hexadecylamine-functionalized sulfadiazine carbon quantum dots.

[0037] In a preferred embodiment of this invention, the mass ratio of the carbon quantum dots with carboxyl groups on the surface, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide is 1:(3-5):(3-5); the mass-volume ratio of the carbon quantum dots with carboxyl groups on the surface to the solvent is 1 mg:2.5 mL; the solvent is dimethylformamide.

[0038] In a preferred embodiment of this invention, adjusting the pH to acidic specifically means adjusting the pH to 6.0; the stirring and activation time is 2-4 hours.

[0039] In a preferred embodiment of this invention, the concentration of the hexadecylamine solution is 2 mg / mL; the solvent of the hexadecylamine solution is dimethylformamide; the mass ratio of hexadecylamine in the hexadecylamine solution to the carbon quantum dots with carboxyl groups on the surface is 1:1.

[0040] In a preferred embodiment of the present invention, the temperature of the reaction is room temperature and the time is 24 hours; the filtration is carried out using a 0.22 μm microporous membrane.

[0041] In a preferred embodiment of the present invention, the method for preparing the carbon quantum dots with carboxyl groups on the surface comprises the following steps:

[0042] Mix sulfadiazine with water and carry out a hydrothermal reaction, and then filter, dialyze, and freeze-dry in sequence to obtain the carbon quantum dots with carboxyl groups on the surface.

[0043] In a preferred embodiment of the present invention, the temperature of the hydrothermal reaction is 170 °C and the time is 4 hours.

[0044] Stirring is carried out during the hydrothermal reaction; the purpose of stirring is to make the hydrothermal reaction more uniform and sufficient. The present invention does not make special limitations on the stirring speed during the hydrothermal reaction, and a stirring speed well-known to those skilled in the art can be adopted.

[0045] After the hydrothermal reaction, there is also a step of adjusting the pH of the reaction system to 6.0 with KOH.

[0046] The filtration is specifically carried out by first filtering once with qualitative filter paper and then filtering twice with a 0.22 μm microporous membrane.

[0047] The dialysis is specifically carried out by dialyzing with a 1000 Da dialysis bag for 24 hours.

[0048] The present invention does not make special limitations on the parameters of freeze-drying (such as pressure, temperature, time), and the freeze-drying parameter settings well-known to those skilled in the art can be adopted.

[0049] The second aspect of the present invention provides hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared by the above preparation method.

[0050] The third aspect of the present invention provides the application of the above hexadecylamine-functionalized sulfadiazine carbon quantum dots in detecting p-nitrophenol.

[0051] The fourth aspect of the present invention provides a method for detecting p-nitrophenol in a water sample. Mix the water sample with the above hexadecylamine-functionalized sulfadiazine carbon quantum dots and oscillate, and then measure the fluorescence intensity F0 - F. Calculate the concentration of p-nitrophenol in the water sample according to the equation F0 - F = 1.084[4-NP] + 3227.4; 4-NP in the equation represents p-nitrophenol.

[0052] The method for detecting p-nitrophenol in a water sample provided by the present invention has the advantages of being simple, effective, highly accurate, and low-cost.

[0053] The technical solutions of the present invention are all conventional solutions in the art unless otherwise specified. The reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0054] In the examples of the present invention, the pore size of the qualitative filter paper used is 0.22 μm.

[0055] The technical solutions provided by the present invention will be described in detail below in conjunction with the examples, but they should not be construed as limiting the protection scope of the present invention.

[0056] In the examples of the present invention, sulfadiazine was used as a precursor (carbon source), and sulfadiazine carbon quantum dots were prepared by a simple hydrothermal synthesis method. Then, hexadecylamine was covalently bonded to the surface of the sulfadiazine carbon quantum dots through an amide coupling reaction to obtain hexadecylamine-functionalized sulfadiazine carbon quantum dots. The reaction route is as follows:

[0057]

[0058] Example 1

[0059] Step 1: Preparation of sulfadiazine carbon quantum dots:

[0060] (1) Take sulfadiazine and add it to the inner liner of the reaction kettle. Add an appropriate amount of deionized water (the amount of deionized water is up to two-thirds of the height of the reaction kettle), seal the reaction kettle, and stir and react at 170 °C for 4 h to obtain a yellow transparent solution;

[0061] (2) After the reaction kettle is cooled to room temperature, adjust the pH of the solution to 6.0 with KOH, filter it once with qualitative filter paper, and then filter it twice with a 0.22-μm microporous membrane. The obtained solution is further dialyzed with a 1000-Da dialysis bag for 24 hours. The filtrate in the dialysis bag after dialysis is the sulfadiazine carbon quantum dot solution.

[0062] (3) Perform freeze-drying treatment on the sulfadiazine carbon quantum dot solution for 24 hours to obtain solid sulfadiazine carbon quantum dots (i.e., carbon quantum dots containing carboxyl groups on the surface).

[0063] Step 2: Preparation of hexadecylamine-functionalized sulfadiazine carbon quantum dots:

[0064] (1) Add solid sulfadiazine carbon quantum dots (10 mg), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC, 30 mg), and N-hydroxysuccinimide (NHS, 30 mg) to 25 mL of dimethylformamide (DMF) according to a mass ratio of 1:3:3. Adjust the pH value of the solution to 6.0 with acetic acid, and then activate it by magnetic stirring for 4 hours;

[0065] (2) Dissolve 10 mg of hexadecylamine in 5 mL of DMF, mix it with the above-activated solution under continuous stirring, and continue stirring for 24 hours for the reaction;

[0066] (3) After the reaction is completed, filter the obtained clear solution with a 0.22 μm microporous filter membrane to obtain a solution containing hexadecylamine-functionalized sulfadiazine carbon quantum dots (abbreviation: carbon quantum dot solution).

[0067] Step 3: Stability test of hexadecylamine-functionalized sulfadiazine carbon quantum dots

[0068] (1) Ion stability: To explore the change in fluorescence intensity of the carbon quantum dots at different ion concentrations, prepare KCl solutions with concentrations of 0.5 M, 1.0 M, 1.5 M, 2.0 M, 2.5 M, 3.0 M, 3.5 M, and 4.0 M. After mixing and shaking for 5 min according to the volume ratio of hexadecylamine-functionalized sulfadiazine carbon quantum dot solution: ion concentration KCl solution = 1:3, record the fluorescence intensity at an excitation wavelength of 380 nm. All fluorescence intensities are measured at an excitation wavelength of 380 nm.

[0069] (2) Light stability: To evaluate the change in fluorescence intensity of the hexadecylamine-functionalized sulfadiazine carbon quantum dots under ultraviolet irradiation, take 3 mL of the carbon quantum dot solution and irradiate it under radiation with an excitation wavelength of 365 nm for 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min respectively, and record the fluorescence intensity at an excitation wavelength of 380 nm. All fluorescence intensities are measured at an excitation wavelength of 380 nm.

[0070] Step 4: Detection of p-nitrophenol by hexadecylamine-functionalized sulfadiazine carbon quantum dots

[0071] (1) Selectivity test: Using deionized water as the solvent, prepare solutions of Co 2+ , Fe 2+ , Ni 3+ , Zn 2+ , Fe 3 + , Ca 2+ , Na + , K + , tetracycline, and p-nitrophenol (i.e., different ion solutions). Prepare the test solutions according to the volume ratio of carbon quantum dot solution: ion solution = 1:3, and measure the fluorescence intensity after shaking well for 20 min.

[0072] (2) Sensitivity determination: Using deionized water as the solvent, p-nitrophenol solutions with concentrations of 0, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1600, 1800, and 2000 μM were prepared. According to the ratio of carbon quantum dot solution:p-nitrophenol solution volume = 1:1, they were added to 2 mL of deionized water. After shaking vigorously for 20 min, the fluorescence intensity was measured.

[0073] The structural characterization of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 was carried out, and the obtained X-ray diffraction pattern; particle size distribution diagram; infrared spectrum; XPS spectrum; ultraviolet-visible absorption spectrum (blue), fluorescence excitation spectrum (red), and emission spectrum (brown); normalized fluorescence emission spectrum; fluorescence emission spectra of carbon quantum dots at different excitation wavelengths; fluorescence intensity at different ionic strengths; fluorescence intensity under different ultraviolet lamp irradiation durations; detection selectivity; and linear relationship diagram with p-nitrophenol concentration are respectively shown by Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 as shown.

[0074] It can be seen from Figure 1 that a broad and gentle diffraction peak appears at about 24° for the sample, corresponding to the (002) crystal plane of the carbon material, indicating that the material is mainly composed of short-range ordered graphite microdomains and amorphous carbon structures. The significant broadening and low-intensity characteristics of the peak shape suggest a high degree of interlayer stacking disorder, which may be caused by the structural distortion or surface functional group interference induced by the functionalization modification of hexadecylamine and sulfadiazine. In addition, no obvious sharp peaks were observed in the high-angle region (40 - 80°), further excluding the existence of a highly crystalline phase, which is consistent with the typical amorphous characteristics of carbon quantum dots.

[0075] From Figure 2 it can be seen that the material shows a relatively concentrated single-peak distribution, and the average hydrodynamic particle size is 26.01 nm. Compared with typical carbon quantum dots (usually <10 nm), the particle size of the current sample is slightly larger, which may be due to the following reasons: First, during the functionalization modification process (such as the introduction of hexadecylamine and sulfadiazine), the surface functional groups increase, and the intermolecular forces enhance, resulting in slight aggregation; Second, incomplete dispersion after synthesis or the solvent environment (such as ionic strength, pH value) affects the particle stability.

[0076] The surface functional groups of the carbon quantum dots prepared in Example 1 were analyzed by Fourier transform infrared spectroscopy. AsFigure 3 As shown, a broad absorption peak was observed at 3290 cm -1 , which is attributed to the stretching vibration of amino groups (N-H) or hydroxyl groups (O-H) on the material surface, and may be related to the primary amine group in sulfadiazine or the water molecules adsorbed on the surface of carbon quantum dots. The absorption peaks near 2854 cm -1 and 1465 cm -1 correspond to the symmetric and antisymmetric stretching vibrations of C-H in the alkyl chain (-CH2-, -CH3) respectively, indicating that the long chain of hexadecylamine was successfully modified on the surface of carbon quantum dots.

[0077] In the range of 1200 - 1650 cm -1 , the strong absorption peak at 1232 cm -1 may originate from the symmetric stretching vibration of S=O or the bending vibration of C-N bond in the sulfonamide group (-SO2-NH-) of sulfadiazine molecules, while the peak near 1575 cm -1 is related to the C=C skeletal vibration or the stretching vibration of C=N bond of the aromatic ring, indicating the existence of π-π stacking or chemical bonding between carbon quantum dots and sulfadiazine. The characteristic peak appearing at 1735 cm -1 may correspond to the stretching vibration of C=O in carboxylic acids or ester groups, suggesting that oxygen-containing functional groups (such as -COOH) were formed on the surface of carbon quantum dots during the synthesis or functionalization process. This phenomenon needs to be further verified by combining XPS characterization. The weak absorption peak at 1629 cm -1 may be the bending vibration of N-H. The results of FT-IR spectroscopy show that hexadecylamine and sulfadiazine were effectively modified on the surface of carbon quantum dots by chemical bonding, and the functional group characteristics are consistent with the expected structure.

[0078] At such as Figure 4In the XPS full spectrum shown, the C1s peak is located near 284 eV, accounting for more than 80% of the intensity, indicating that carbon is the main component of C-CDs. The high-resolution peak deconvolution results of the C1s spectrum show that 284.8 eV corresponds to C-C bonds, 286.04 eV corresponds to C-O / C-N bonds, and 287.85 eV belongs to C=O bonds, indicating that the surface of C-CDs contains oxygen-containing and nitrogen-containing functional groups. The peak of the N1s spectrum is located at 399.55 eV, belonging to C-N bonds, further indicating that the surface of C-CDs contains nitrogen elements. The O1s spectrum is decomposed into two sub-peaks, located at 531.05 eV and 532.68 eV respectively, corresponding to S-O / O-H bonds and C=O bonds respectively, indicating the presence of oxygen-containing functional groups such as sulfonyl, carboxyl, and hydroxyl groups on the surface of C-CDs. In addition, the S2p spectrum shows two peaks, located near 168 eV, which also verifies the existence of sulfur-containing groups such as S-O. Through comprehensive analysis, the surface of C-CDs contains various oxygen-containing, nitrogen-containing, and sulfur-containing functional groups. The existence of these functional groups helps to regulate the optical, electrical, and other properties of C-CDs, and has potential application value in the fields of catalysis or sensors.

[0079] As Figure 5 shown, CQDs have a strong and sharp absorption peak at 268 nm, which may be due to the π-π * transition between carbon-carbon double bonds. It can be Figure 6 mutually verified that the optimal excitation wavelength of CQDs is 380 nm, and the optimal emission wavelength is 480 nm. It can be seen from Figure 6 that the fluorescence intensity of CQDs changes significantly from 360 nm to 410 nm. As the excitation wavelength increases, the intensity of the emission peak first increases and then decreases, and reaches the highest value when the excitation light wavelength is 380 nm. It can be seen from Figure 7 that the position of the emission peak also gradually shifts to the right with the change of the excitation wavelength, indicating that CQDs have excitation wavelength dependence.

[0080] To study the photostability of carbon quantum dots, their fluorescence intensities were measured under different ionic strengths and different ultraviolet irradiation durations respectively. Figure 8 shows the effect of ionic strength on the fluorescence intensity of GDQs. Even at a relatively high ionic strength, carbon quantum dots can maintain good luminescence performance, demonstrating their excellent salt tolerance. As shown in Figure 9 , during the continuous irradiation of the ultraviolet lamp for 10 min - 60 min, the fluorescence intensity of CQDs only shows a weak change, indicating that CQDs have a certain fluorescence stability. The above photostability results show that carbon quantum dots have a strong adaptability to the external environment and are more suitable for application in actual situations.

[0081] When exploring the selectivity of carbon quantum dots for the detection of p-nitrophenol, this experiment recorded the changes in the fluorescence intensity of carbon quantum dots at 380 nm after mixing different compound solutions with the same concentration (100 μM) with the carbon quantum dot solution, and plotted a bar chart of fluorescence quenching efficiency - ion species based on this change. The quenching efficiency of carbon quantum dots is expressed as F0 / F, where F0 is the fluorescence intensity when the analyte is present in the carbon quantum dot solution, and F is the fluorescence intensity when the analyte is absent in the carbon quantum dot solution. Among the fluorescence quenching of different compounds on carbon quantum dots at the same concentration, as Figure 10 shown, only very strong fluorescence quenching occurred after adding p-nitrophenol (4-NP), and the fluorescence quenching of other substances on carbon quantum dots was similar. This indicates that carbon quantum dots have high selectivity for the detection of p-nitrophenol and are suitable for the specific detection of p-nitrophenol.

[0082] When exploring the sensitivity of carbon quantum dots for the detection of p-nitrophenol, this experiment recorded the changes in the fluorescence intensity of carbon quantum dots at 380 nm after mixing p-nitrophenol solutions with different concentrations (0 μM - 2000 μM) with the carbon quantum dot solution, and plotted a fluorescence emission spectrum ( Figure 11 the left figure in). Subsequently, a fitting analysis was performed on the relationship between the fluorescence intensity of carbon quantum dots (expressed as F0 - F) and the concentration of p-nitrophenol, and a linear fitting curve was plotted ( Figure 11 the right figure in).

[0083] It can be seen from Figure 11 that as the concentration of p-nitrophenol gradually increases, the fluorescence intensity of carbon quantum dots shows a regular downward trend; a concentration range of 1200 μM - 2000 μM was selected as the linear relationship between the detection of p-nitrophenol and the fluorescence intensity. The results show that when the concentration of p-nitrophenol changes within the range of 1200 μM - 2000 μM, F0 - F has a significant linear relationship with the concentration of p-nitrophenol, and the linear fitting equation is F0 - F = 1.084[4-NP] + 3227.4, and the correlation coefficient R 2 = 0.998. In summary, hexadecylamine-functionalized sulfadiazine carbon quantum dots have good detection sensitivity and high linear fitting for p-nitrophenol.

[0084] Example 2

[0085] The difference from Example 1 is only that the mass ratio of solid sulfadiazine carbon quantum dots, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC), and N-hydroxysuccinimide (NHS) is 1∶5∶5.

[0086] Example 3

[0087] The difference from Example 1 is only that in (1) of Step 2, the activation time by magnetic stirring is 2 h.

[0088] The stability of the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Examples 2 and 3 and Example 1 and the detection effect on p-nitrophenol were compared. The results showed that the hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared in Example 1 had the best stability and detection effect on p-nitrophenol.

[0089] Comparative Example 1

[0090] The difference from Example 1 is only that the addition of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS) and the step of activating by magnetic stirring for 4 hours are omitted.

[0091] Result: The optimal excitation wavelength of the carbon quantum dots prepared in this comparative example is 285 nm, and the optimal emission wavelength is 345 nm. It can be seen that the fluorescence intensity of the carbon quantum dots prepared under this condition changes significantly from 260 nm to 300 nm. As the excitation wavelength increases, the emission peak intensity first increases and then decreases, and reaches the highest value when the excitation light wavelength is 285 nm. Figure 12 Subsequently, the specific detection of the carbon quantum dots was explored. The carbon quantum dot solution and 100 μmol / L Co

[0092] 、Fe 2+ 、Cu 2+ 、Ni 2+ 、Zn 3+ 、Fe 2+ 、Ca 3+ 、Ba 2+ 、Na 2+ 、K + 、K + solutions were mixed (volume ratio 1:2) for 20 min, and then the fluorescence intensity at an excitation wavelength of 285 nm was measured, and a bar chart of the relationship between ion species - fluorescence intensity was plotted. As shown in Figure 13 shown, the carbon quantum dots were selectively quenched by Fe 3+ ,and the quenching rate reached 74%, indicating that the quantum dots have specificity and high efficiency for the detection of Fe 3+ 。

[0093] Then, the detection sensitivity of the carbon quantum dots to Fe 3+ was tested. The carbon quantum dot solution and different concentrations of Fe 3+Solutions (concentrations: 0.0 mM, 0.1 mM, 0.2 mM, 0.3 mM, 0.4 mM, 0.5 mM, 0.6 mM, 0.7 mM, 0.8 mM, 0.9 mM, 1.0 mM) (volume ratio 1:2) were thoroughly mixed, and the fluorescence intensity was measured at an excitation wavelength of 285 nm. A relationship curve of Fe 3+ concentration - fluorescence intensity was plotted, and the linear fitting equation and correlation coefficient were calculated. As Figure 14 shown, as the Fe 3+ concentration increased, the fluorescence intensity showed a monotonically decreasing trend; the fluorescence intensity of the carbon quantum dots and Fe 3+ could fit a linear equation with a correlation coefficient of 0.9934 in the concentration range of 0.4 mmol / L - 0.8 mmol / L: F = -42790[Fe 3+ +44905.4 (F represents fluorescence intensity; [Fe 3+ represents concentration). In summary, the carbon quantum dots prepared under these conditions have good detection sensitivity for Fe 3+ .

[0094] Adding p-nitrophenol to the carbon quantum dot solution prepared in Comparative Example 1 did not result in obvious fluorescence quenching, indicating that the carbon quantum dots do not have the advantage of selectively detecting p-nitrophenol.

[0095] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of hexadecylamine-functionalized sulfadiazine carbon quantum dots, characterized in that, It includes the following steps: Add carbon quantum dots with carboxyl groups on the surface, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide into a solvent, adjust the pH to acidic, and then stir and activate to obtain an activated solution; Add a hexadecylamine solution to the activated solution for reaction, and then filter to obtain the hexadecylamine-functionalized sulfadiazine carbon quantum dots.

2. The preparation method of hexadecylamine-functionalized sulfadiazine carbon quantum dots according to claim 1, wherein, The mass ratio of the carbon quantum dots with carboxyl groups on the surface, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide is 1∶(3-5)∶(3-5); the mass-volume ratio of the carbon quantum dots with carboxyl groups on the surface to the solvent is 1mg∶2.5mL; the solvent is dimethylformamide.

3. The preparation method of hexadecylamine-functionalized sulfadiazine carbon quantum dots according to claim 1, characterized in that, Adjusting the pH to acidic specifically means adjusting the pH to 6.0; the stirring and activation time is 2-4 hours.

4. The preparation method of hexadecylamine-functionalized sulfadiazine carbon quantum dots according to claim 1, wherein, The concentration of the hexadecylamine solution is 2mg / mL; the solvent of the hexadecylamine solution is dimethylformamide; the mass ratio of hexadecylamine in the hexadecylamine solution to the carbon quantum dots with carboxyl groups on the surface is 1∶1.

5. The preparation method of hexadecylamine-functionalized sulfadiazine carbon quantum dots according to claim 1, wherein, The reaction temperature is room temperature and the time is 24 hours; the filtration uses a 0.22μm microporous membrane.

6. The preparation method of hexadecylamine-functionalized sulfadiazine carbon quantum dots according to claim 1, characterized in that The preparation method of the carbon quantum dots with carboxyl groups on the surface includes the following steps: Mix sulfadiazine with water and perform a hydrothermal reaction, and then filter, dialyze, and freeze-dry in sequence to obtain the carbon quantum dots with carboxyl groups on the surface.

7. The preparation method of hexadecylamine-functionalized sulfadiazine carbon quantum dots according to claim 6, characterized in that, The temperature of the hydrothermal reaction is 170°C and the time is 4 hours.

10. The hexadecylamine-functionalized sulfadiazine carbon quantum dots prepared by the preparation method according to any one of claims 1-7.

11. The application of the hexadecylamine-functionalized sulfadiazine carbon quantum dots as claimed in claim 8 in the detection of p-nitrophenol.

10. A method for detecting p-nitrophenol in a water sample, characterized in that, Mix the water sample with the hexadecylamine-functionalized sulfadiazine carbon quantum dots as claimed in claim 8, oscillate, and then measure the fluorescence intensity F0 - F. Calculate the concentration of p-nitrophenol in the water sample according to the equation F0 - F = 1.084[4-NP] + 3227.4; 4-NP in the equation represents p-nitrophenol.

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