A carbon quantum dot, a preparation method, an application, a method for identifying components of a to-be-measured liquid, and a method for detecting concentration

Abstract

The present application relates to a kind of carbon quantum dots, preparation method, application, the component identification method and concentration detection method of to be measured liquid, comprising: urea and ammonium citrate are dissolved in solvent, then transfer to reaction kettle and carry out heating reaction.The carbon quantum dots provided by the present application not only have lower preparation cost itself, but also the detection method of chlorogenic acid and tinidazole is relatively simple, conducive to the low-cost detection of chlorogenic acid and tinidazole.

Description

Technical Field

[0001] This invention relates to the field of chlorogenic acid and tinidazole detection, and in particular to a carbon quantum dot, its preparation method, application, method for identifying the components of the test solution, and method for detecting its concentration. Background Technology

[0002] Chlorogenic acid, a typical phenylpropanoid compound, is widely found in many common vegetables, fruits, and beverages, and possesses significant antioxidant, anti-inflammatory, and anti-cancer properties. However, excessive intake of chlorogenic acid can lead to inflammatory responses, oxidative stress, gastrointestinal symptoms, and dermatitis.

[0003] Tinidazole, a representative synthetic antibacterial agent, is widely used to treat anaerobic bacterial infections in dairy cows. However, improper use of tinidazole may lead to its transfer to humans through dairy products, causing adverse effects such as carcinogenicity.

[0004] For the reasons mentioned above, the detection of chlorogenic acid and tinidazole residues plays a crucial role in food safety. Currently, the detection of chlorogenic acid and tinidazole is mainly achieved through high-performance liquid chromatography (HPLC), atomic absorption spectrometry (AAS), inductively coupled plasma mass spectrometry (ICP-MS), and inductively coupled plasma atomic emission spectrometry (ICP-AES). These methods are typically time-consuming, require expensive equipment, and are difficult to widely implement, thus limiting the detection of chlorogenic acid and tinidazole concentrations. Summary of the Invention

[0005] Therefore, it is necessary to address the high cost of detecting the concentrations of chlorogenic acid and tinidazole by providing a method for the preparation of carbon quantum dots, their application, identification of the components in the test solution, and concentration detection.

[0006] The technical solution provided by this invention is as follows:

[0007] A method for preparing carbon quantum dots includes: dissolving urea and ammonium citrate in a solvent, and then transferring the solution to a reaction vessel for heating and reaction.

[0008] In some embodiments of this application, the mass ratio of urea to ammonium citrate is 3:1 to 1:1.

[0009] In some embodiments of this application, the solvent is deionized water.

[0010] In some embodiments of this application, the reaction temperature in the reactor is 160°C-200°C.

[0011] A carbon quantum dot is prepared using the aforementioned method for preparing carbon quantum dots.

[0012] An application of the aforementioned carbon quantum dots in the detection of chlorogenic acid.

[0013] An application of the aforementioned carbon quantum dots in the detection of tinidazole.

[0014] An application of the aforementioned carbon quantum dots in distinguishing chlorogenic acid and tinidazole.

[0015] A method for identifying the components of a test liquid, comprising:

[0016] The solution of the carbon quantum dots was irradiated with 318 nm excitation light to obtain the fluorescence intensity i of the carbon quantum dots at 438 nm. 318 ;

[0017] The solution of the carbon quantum dots was irradiated with 367nm excitation light to obtain the fluorescence intensity i of the carbon quantum dots at 438nm. 367 ;

[0018] The test solution is added to the solution of the carbon quantum dots to obtain a first solution;

[0019] The first solution was irradiated with 318 nm excitation light to obtain the 438 nm fluorescence intensity I emitted by the carbon quantum dots in the first solution. 318 ;

[0020] The first solution was irradiated with 367nm excitation light to obtain the 438nm fluorescence intensity I emitted by the carbon quantum dots in the first solution. 367 ;

[0021] If i 367 / i 318 >I 367 / I 318 If the test solution contains at least chlorogenic acid;

[0022] If i 367 / i 318 <I 367 / I 318 If the test solution contains at least tinidazole.

[0023] A method for detecting the concentration of chlorogenic acid or tinidazole, comprising:

[0024] The solution of the carbon quantum dots was irradiated with 318 nm excitation light to obtain the fluorescence intensity i of the carbon quantum dots at 438 nm. 318 ;

[0025] The solution of the carbon quantum dots was irradiated with 367nm excitation light to obtain the fluorescence intensity i of the carbon quantum dots at 438nm. 367 ;

[0026] The test solution is added to the solution of the carbon quantum dots to obtain a first solution;

[0027] The first solution was irradiated with 318 nm excitation light to obtain the 438 nm fluorescence intensity I emitted by the carbon quantum dots in the first solution. 318 ;

[0028] The first solution was irradiated with 367nm excitation light to obtain the 438nm fluorescence intensity I emitted by the carbon quantum dots in the first solution. 367 ;

[0029] Based on i 367 / i 318 and I 367 / I 318 Determine the concentration of chlorogenic acid or tinidazole in the test solution.

[0030] The beneficial effects of this invention are as follows:

[0031] The carbon quantum dots provided by this invention have a simple preparation method and use inexpensive raw materials, thus allowing them to be prepared at a relatively low cost.

[0032] The carbon quantum dots described in this invention possess two excitation wavelengths (318 nm and 367 nm) and one emission wavelength of 438 nm. The intensity of the 438 nm fluorescence emitted by the carbon quantum dots under 318 nm excitation light illumination is I. 318 The fluorescence intensity of carbon quantum dots emitting 438nm light under 367nm excitation light is I. 367 .

[0033] Among them, chlorogenic acid can make I 318 and I 367 All showed a significant decrease, while tinidazole could reduce I... 318 A significant decrease occurred, without causing I 367 Significant changes occur. Based on the above characteristics, the bimodal ratio method can be used, specifically through I... 367 / I 318 This method enables the quantitative detection of chlorogenic acid and tinidazole. Furthermore, it allows for the measurement of chlorogenic acid concentration and I... 367 / I 318 There is a negative correlation between tinidazole concentration and I 367 / I 318 There is a positive correlation between them, therefore based on I 367 / I 318 This allows for further differentiation between chlorogenic acid and tinidazole.

[0034] Based on this, the carbon quantum dots provided by the present invention not only have low preparation costs, but also have relatively simple detection methods for chlorogenic acid and tinidazole, which is conducive to achieving low-cost detection of chlorogenic acid and tinidazole. Attached Figure Description

[0035] Figure 1This is a TEM image of carbon quantum dots in an embodiment of the present invention;

[0036] Figure 2 This is a particle size distribution diagram of carbon quantum dots in an embodiment of the present invention;

[0037] Figure 3 The image shows the AFM diagram of carbon quantum dots in an embodiment of the present invention.

[0038] Figure 4 The image shows the XRD pattern of carbon quantum dots in an embodiment of the present invention.

[0039] Figure 5 The FT-IR spectrum of carbon quantum dots in this embodiment of the invention;

[0040] Figure 6 This is the full XPS spectrum of the carbon quantum dots in an embodiment of the present invention;

[0041] Figure 7 This is a high-resolution XPS spectrum of carbon quantum dots in an embodiment of the present invention;

[0042] Figure 8 The UV-vis absorption spectrum, PL spectrum, and PLE spectrum of carbon quantum dots in the embodiments of the present invention are shown below.

[0043] Figure 9 The PL spectra of carbon quantum dots under different wavelengths of light in the embodiments of the present invention are shown.

[0044] Figure 10 The EEM spectrum of carbon quantum dots in this embodiment of the invention;

[0045] Figure 11 This is a fluorescence stability test diagram of carbon quantum dots in an embodiment of the present invention;

[0046] Figure 12 This is a bar chart showing the relative fluorescence intensity of carbon quantum dots mixed with different substances in an embodiment of the present invention;

[0047] Figure 13 The PLE spectra and I of carbon quantum dots and CGA mixtures at different concentrations in embodiments of the present invention are shown. 367 / I 318 The relationship between CGA concentration and other concentrations;

[0048] Figure 14 The PLE spectra and I of carbon quantum dots and different concentrations of TNZ in the embodiments of the present invention are shown. 367 / I 318 The relationship between TNZ concentration and TNZ concentration;

[0049] Figure 15The UV-vis absorption spectrum of CGA and the PL and PLE spectra of carbon quantum dots in the embodiments of the present invention are shown.

[0050] Figure 16 This is the fluorescence decay curve of carbon quantum dots before and after mixing with CGA in an embodiment of the present invention;

[0051] Figure 17 The UV-vis absorption spectra of carbon quantum dots, CGA, the actual UV-vis absorption spectra of the mixture of carbon quantum dots and CGA, and the theoretical UV-vis absorption spectra of the mixture of carbon quantum dots and CGA are shown in the embodiments of the present invention.

[0052] Figure 18 The UV-vis absorption spectra of carbon quantum dots, TNZ, the actual UV-vis absorption spectra of the mixture of carbon quantum dots and TNZ, and the theoretical UV-vis absorption spectra of the mixture of carbon quantum dots and TNZ in the embodiments of the present invention are shown.

[0053] Figure 19 The UV-vis absorption spectrum of TNZ and the PL and PLE spectra of carbon quantum dots in the embodiments of the present invention are shown. Detailed Implementation

[0054] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0055] Example:

[0056] This embodiment provides a carbon quantum dot preparation method comprising the following steps: 2g of urea and 1g of ammonium citrate are ultrasonically dissolved in 20mL of deionized water, then transferred to a reaction vessel and reacted at 180℃ for 8h. After the reaction, the mixture is filtered using a 0.22μm pore diameter membrane, and the filtrate is dialyzed through a 500Da dialysis membrane with deionized water for 48h. Finally, the mixture is freeze-dried to obtain the carbon quantum dots.

[0057] like Figure 1 As shown, the carbon quantum dots exhibit good dispersion and have high-resolution lattice fringes with a lattice spacing of 0.21 nm, matching the (100) crystal plane of graphitic carbon. Figure 2 As shown, the average particle size of the carbon quantum dots is approximately 4 nm. Figure 3 As shown, the height of the carbon quantum dots is between 2.12 nm and 2.89 nm, indicating the presence of several layers of graphite structure within their carbon core. Figure 4 As shown, the carbon quantum dots have a distinct diffraction peak at 24.7°, which matches the (002) crystal plane of graphitic carbon.

[0058] like Figure 5 As shown, at 3000cm -1 -3400cm -1 The absorption peak at 1006 cm⁻¹ indicates the presence of NH₄⁺ and OH⁻ in the carbon quantum dots. -1 -1252cm -1 The absorption peak at 1387 cm⁻¹ corresponds to CO. -1 The absorption peak at 1625 cm⁻¹ corresponds to CN. -1 The absorption peak at that point corresponds to C=O. (Through...) Figure 6 Calculations show that the carbon quantum dots contain 54.4% C, 16.6% N, and 29% O. For example... Figure 7 As shown, in the C 1s spectrum, the peak at 284.5 eV corresponds to CC / C=C, the peak at 285.6 eV corresponds to CO / CN, and the peak at 287.5 eV corresponds to C=O; in the N 1s spectrum, the peak at 398.35 eV corresponds to pyrrole N, the peak at 399.29 eV corresponds to amino N, and the peak at 400.08 eV corresponds to graphitic nitrogen; in the O 1s spectrum, the peak at 530.8 eV corresponds to C=O, the peak at 531.5 eV corresponds to CO, and the peak at 532.6 eV corresponds to OH. Based on Figures 5-7 It can be seen that oxygen-containing groups and nitrogen-containing groups have been successfully incorporated into the carbon quantum dots.

[0059] like Figure 8 As shown, the UV-vis absorption spectrum exhibits three peaks, with the peaks at 208 nm and 235 nm corresponding to the C=C bonds in the aromatic ring. The transition, the peak at 336 nm corresponds to the transition in C=O / C=N. Leap. For example... Figures 8-10 As shown, the emission wavelength of the carbon quantum dots is 438 nm, while the excitation wavelengths are 318 nm and 367 nm. Specifically, the intensity of the 438 nm fluorescence emitted by the carbon quantum dots under 318 nm excitation light is I. 318 The intensity of the 438nm fluorescence emitted by the carbon quantum dots under 367nm excitation light is I. 367 .

[0060] Further as Figure 11As shown, the fluorescence emission intensity of the carbon quantum dots did not decrease significantly after 24 hours of ultraviolet light irradiation; similarly, the fluorescence emission intensity of the carbon quantum dots did not decrease significantly after 30 days of natural light irradiation. Furthermore, even in a 2M NaCl solution, the fluorescence emission intensity of the carbon quantum dots did not decrease significantly, which confirms that the carbon quantum dots have very good physicochemical stability.

[0061] like Figure 12 As shown, the carbon quantum dots, after being mixed with CGA (chlorogenic acid), I 318 and I 367 All showed a significant decrease; the addition of interfering substances to the mixed solution of carbon quantum dots and CGA did not cause I 318 and I 367 Further significant changes occurred; the carbon quantum dots, after being mixed with TNZ (tinidazole), I 318 A significant decrease occurred, while I 367 No significant changes occurred; adding interfering substances to the mixed solution of carbon quantum dots and TNZ also did not cause I. 318 and I 367 Further significant changes occur. This confirms that the carbon quantum dots possess the ability and specificity to detect CGA and TNZ. Based on this, and using I... 367 The degree of change can further enable the differentiation and detection of CGA and TNZ. The interfering substance is specifically Na. + Mg 2+ Al 3+ Cu 2 Zn 2+ K + Fe 3+ Ca 2+ Mn 2+ Ba 2+ Ni 2+ Cd 2+ ,Br - F - I - Cl - CO3 2- SO4 2- L-Asparagine (L-asp), L-serine (L-ser), L-tryptophan (L-try), L-alanine (L-ala), L-cysteine ​​(L-cys), or D-alanine (D-ala).

[0062] Further as Figure 13 As shown, with the increase of CGA concentration in the carbon quantum dot mixture, I 318 and I 367Both are declining, and I 318 The rate of descent is slower than I 367 Among them, as the CGA concentration increases, I 367 / I 318 The concentration of CGA continuously decreases, and when the concentration is in the range of 0.036 μM-40 μM, it can interact with I... 367 / I 318 They maintain a good linear relationship (R) 2 =0.9876), corresponding to a detection limit of 36 nM for CGA concentration.

[0063] Further as Figure 14 As shown, with the increase of TNZ concentration in the carbon quantum dot mixture, I 318 It is constantly declining, while I 367 There was almost no change, which led to I increasing with TNZ concentration. 367 / I 318 On the contrary, it will continue to improve. When TNZ is in the range of 0.068μM-25μM, it can be compared with I. 367 / I 318 They maintain a good linear relationship (R) 2 =0.9973), corresponding to a detection limit of 68 nM for TNZ concentration.

[0064] Therefore, it can be concluded that CGA concentration and I 367 / I 318 There is a negative correlation between TNZ concentration and I 367 / I 318 There is a positive correlation between them, therefore based on I 367 / I 318 It can further distinguish between CGA and TNZ.

[0065] exist Figures 12-14 In this study, the carbon quantum dots used for the detection of CGA and TNZ were both in phosphate-buffered saline (PBS).

[0066] This embodiment provides a method for detecting the concentration of CGA or TNZ, including the following steps:

[0067] Step 101: Irradiate the solution of the carbon quantum dots with 318nm excitation light and obtain the 438nm fluorescence intensity i emitted by the carbon quantum dots. 318 ;

[0068] Step 102: Irradiate the solution of the carbon quantum dots with 367nm excitation light and obtain the 438nm fluorescence intensity i emitted by the carbon quantum dots. 367 ;

[0069] Step 103: Add the test solution to the solution of the carbon quantum dots to obtain the first solution;

[0070] Step 104: Irradiate the first solution with 318nm excitation light to obtain the 438nm fluorescence intensity I emitted by the carbon quantum dots in the first solution. 318 ;

[0071] Step 105: Irradiate the first solution with 367nm excitation light to obtain the 438nm fluorescence intensity I emitted by the carbon quantum dots in the first solution. 367 ;

[0072] Step 106: Based on i 367 / i 318 and I 367 / I 318 Determine the concentration of CGA or TNZ in the test solution.

[0073] Regarding the detection mechanism of carbon quantum dots for CGA and TNZ, the following analysis was conducted in this embodiment.

[0074] See Figure 15 There is significant overlap between the UV-vis absorption spectrum of CGA and the PLE spectrum of carbon quantum dots. (See also...) Figure 16 Under 318 nm excitation light, the fluorescence lifetime slightly decreased from 7.17 ns to 7.13 ns after mixing carbon quantum dots with CGA; under 367 nm excitation light, the fluorescence lifetime slightly decreased from 7.75 ns to 7.68 ns after mixing carbon quantum dots with CGA. Figure 15 and Figure 16 It can be confirmed that the fluorescence quenching mechanism of CGA on carbon quantum dots is the internal filtering effect (IFE).

[0075] See further Figure 17 The carbon quantum dots, after being mixed with CGA, exhibit an additional peak at 348 nm in their actual UV-vis absorption spectrum compared to the theoretical UV-vis absorption spectrum. This indicates that the fluorescence quenching mechanism of CGA on the carbon quantum dots also includes a static quenching mechanism (SQE).

[0076] In summary, the fluorescence quenching mechanism of CGA for the carbon quantum dots includes both IFE and SQE.

[0077] like Figure 18 As shown, the theoretical UV-vis absorption spectrum and the actual UV-vis absorption spectrum of the carbon quantum dots and TNZ mixture have a high degree of overlap. Furthermore, based on the fluorescence decay curves before and after mixing the carbon quantum dots and TNZ, the fluorescence lifetime shows almost no change under both 318 nm and 367 nm excitation light. Figure 19 As shown, the UV-vis absorption spectrum of TNZ and the PLE spectrum of the carbon quantum dots overlap at 318 nm. Based on the above characterization, it can be concluded that the local internal filtering effect (L-IFE) is the main fluorescence quenching mechanism of TNZ on the carbon quantum dots.

[0078] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing carbon quantum dots, characterized in that, include: Urea and ammonium citrate are dissolved in a solvent and then transferred to a reaction vessel for heating and reaction.

2. The method for preparing carbon quantum dots according to claim 1, characterized in that, The mass ratio of urea to ammonium citrate is 3:1 to 1:

1.

3. The method for preparing carbon quantum dots according to claim 1, characterized in that, The solvent is deionized water.

4. The method for preparing carbon quantum dots according to claim 1, characterized in that, The reaction temperature in the reactor is 160℃-200℃.

5. A carbon quantum dot, characterized in that, The carbon quantum dots were prepared using the method described in claim 1, 2, 3, or 4.

6. An application of carbon quantum dots as described in claim 5 in the detection of chlorogenic acid.

7. An application of carbon quantum dots as described in claim 5 in the detection of tinidazole.

8. The use of carbon quantum dots as described in claim 5 in distinguishing between chlorogenic acid and tinidazole.

9. A method for identifying the components of a test liquid, characterized in that, include: The solution of carbon quantum dots as described in claim 5 was irradiated with 318 nm excitation light to obtain the 438 nm fluorescence intensity i emitted by the carbon quantum dots. 318 ; The solution of carbon quantum dots as described in claim 5 was irradiated with 367nm excitation light to obtain the 438nm fluorescence intensity i emitted by the carbon quantum dots. 367 ; The test solution is added to the solution of the carbon quantum dots to obtain a first solution; The first solution was irradiated with 318 nm excitation light to obtain the 438 nm fluorescence intensity I emitted by the carbon quantum dots in the first solution. 318 ; The first solution was irradiated with 367nm excitation light to obtain the 438nm fluorescence intensity I emitted by the carbon quantum dots in the first solution. 367 ; If i 367 / i 318 >I 367 / I 318 If the test solution contains at least chlorogenic acid; If i 367 / i 318 <I 367 / I 318 If the test solution contains at least tinidazole.

10. A method for detecting the concentration of chlorogenic acid or tinidazole, characterized in that, include: The solution of carbon quantum dots as described in claim 5 was irradiated with 318 nm excitation light to obtain the 438 nm fluorescence intensity i emitted by the carbon quantum dots. 318 ; The solution of carbon quantum dots as described in claim 5 was irradiated with 367nm excitation light to obtain the 438nm fluorescence intensity i emitted by the carbon quantum dots. 367 ; The test solution is added to the solution of the carbon quantum dots to obtain a first solution; The first solution was irradiated with 318 nm excitation light to obtain the 438 nm fluorescence intensity I emitted by the carbon quantum dots in the first solution. 318 ; The first solution was irradiated with 367nm excitation light to obtain the 438nm fluorescence intensity I emitted by the carbon quantum dots in the first solution. 367 ; Based on i 367 / i 318 and I 367 / I 318 Determine the concentration of chlorogenic acid or tinidazole in the test solution.

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