A fluorescent carbon dot for detecting hypochlorite and a preparation method and application thereof
Fluorescent carbon dots synthesized by hydrothermal method are used for hypochlorite detection, which solves the problems of cumbersome operation and insufficient sensitivity in existing detection methods. It realizes high sensitivity and specificity of hypochlorite detection and is suitable for rapid detection of environmental and biological samples.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING TECH & BUSINESS UNIV
- Filing Date
- 2026-04-08
- Publication Date
- 2026-06-23
AI Technical Summary
Existing hypochlorite detection methods are cumbersome to operate and lack sufficient sensitivity and specificity, making it difficult to achieve rapid and accurate detection.
Fluorescent carbon dots with uniform particle size and rich hydrophilic groups on the surface were synthesized by a one-step hydrothermal method. Hypochlorite was detected by fluorescence quenching reaction. The emission peak of the fluorescent carbon dots was located at 445 nm under 370 nm excitation. The reaction time was 10 minutes and the pH value was 7.4.
It achieves highly sensitive and specific hypochlorite detection with a detection limit as low as 65 nM, making it suitable for rapid detection in complex environments and biological samples, and exhibiting good environmental adaptability and stability.
Smart Images
Figure CN122254484A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of nanomaterial synthesis and chemical sensing technology. Specifically, it relates to a fluorescent carbon dot for detecting hypochlorite, its preparation method and application, and more specifically, to a novel hydrothermal preparation method for fluorescent carbon dots, and the application of the carbon dot as a fluorescent probe in the specific detection of hypochlorite. Background Technology
[0002] hypochlorite (ClO) - Hypochlorite, as a common strong oxidant, is widely used in drinking water disinfection, food processing, medical environment sterilization, and industrial bleaching. However, excessive hypochlorite residues may induce oxidative stress, damage cell structure, and pose potential hazards to human health and the ecological environment.
[0003] Currently, the main methods for detecting hypochlorite include titration, electrochemical methods, and spectroscopic analysis, as well as qualitative methods such as thin-layer chromatography. However, these methods have many limitations: titration is cumbersome to operate, has low detection accuracy, and is only suitable for detecting high concentrations of hypochlorite; electrochemical methods require sophisticated instruments, the electrodes are easily affected by interference, and the stability is poor; spectroscopic analysis requires large, precision instruments, resulting in high detection costs and poor on-site applicability; while thin-layer chromatography is simple to operate, it has low detection sensitivity, making quantitative detection difficult, and the color development process requires heating steps, limiting detection efficiency.
[0004] In recent years, fluorescent probes, especially fluorescent carbon dots (CDs), have become a research hotspot in novel chemical sensing materials due to their high stability, good biocompatibility, ease of modification, and strong fluorescence properties. Developing a hypochlorite fluorescent probe system that is simple to prepare, has a fast response speed, and high selectivity is of great significance for public health safety and environmental monitoring. Summary of the Invention
[0005] To overcome the problems of cumbersome operation and insufficient sensitivity and specificity of existing hypochlorite detection methods, this invention provides a fluorescent carbon dot for detecting hypochlorite, its preparation method and application. Specifically, it provides a method for preparing carbon dots with uniform particle size, good water solubility and high fluorescence yield, and constructs a highly sensitive fluorescent detection method for hypochlorite based on the carbon dots.
[0006] To achieve the above objectives, the present invention proposes a fluorescent carbon dot for detecting hypochlorite, comprising: The fluorescent carbon dots have a quasi-spherical particle structure, and the surface of the particle structure has functional groups of hydroxyl, carboxyl, amino and carbonyl groups; when excited by a wavelength of 370 nm, its optimal fluorescence emission peak is located at 445 nm.
[0007] Optionally, the optimal working concentration of the fluorescent carbon dots is 10 μg / mL; the pH of the reaction system with hypochlorite is 7.4, and the reaction time is 10 min.
[0008] On the other hand, the present invention provides a method for preparing the above-mentioned fluorescent carbon dots, comprising: Citric acid and o-phenylenediamine are added to deionized water and dissolved to obtain a mixed solution. The mixed solution is subjected to hydrothermal reaction in a high-pressure reactor. The product after cooling of the hydrothermal reaction is centrifuged, filtered, dialyzed and dried to obtain fluorescent carbon dot powder. The mass ratio of citric acid to o-phenylenediamine is 1:1.
[0009] Optionally, the hydrothermal reaction is performed under the following conditions: heating at 180°C for 6 hours.
[0010] Optionally, the centrifugation conditions are 8000 rpm for 10 min.
[0011] Optionally, the filtration is performed using a 0.22 μm filter membrane.
[0012] Optionally, the dialysis is performed using a dialysis bag with a molecular weight cutoff of 1000 Da for 24 hours.
[0013] Optionally, the drying process may be freeze drying.
[0014] On the other hand, the present invention provides an application of the above-mentioned fluorescent carbon dots, which are used as fluorescent probes for detecting hypochlorite in water, environmental or biological samples.
[0015] Optionally, the fluorescent carbon dots are prepared into an aqueous solution, mixed with the sample to be tested, and the concentration of hypochlorite is quantitatively measured by determining the degree of quenching of fluorescence intensity during the reaction.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The preparation process is green and simple: it adopts a one-step hydrothermal method for synthesis, the raw materials are readily available, and the reaction conditions are mild.
[0017] 2. Excellent structure and optical properties: The fluorescent carbon dots are uniform quasi-spherical (2-4nm), with rich hydrophilic groups on the surface, exhibiting obvious excitation dependence and a fluorescence lifetime of 9.3ns.
[0018] 3. Ultra-high sensitivity and specificity: Specifically recognizes ClO - It exhibits fluorescence quenching and is unaffected by 11 other common ions; the limit of detection (LOD) is extremely low, reaching 65 nM, and the linear range is wide (0-1.25 μM).
[0019] 4. Strong environmental adaptability: It can maintain good detection stability in a wide pH range (3-11) and high-salt environment (0-7 mM NaCl), and the reaction time is only 10 minutes, making it very suitable for rapid on-site detection of complex environments and biological samples. Attached Figure Description
[0020] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. In the drawings: Figure 1 Transmission electron microscopy (TEM) images and particle size distribution histograms of fluorescent carbon dots (CDs) prepared for embodiments of the present invention.
[0021] Figure 2 An atomic force microscope (AFM) image and height profile of fluorescent carbon dots prepared for an embodiment of the present invention.
[0022] Figure 3 XPS full spectrum and high-resolution C1s, O1s, and N1s spectra of fluorescent carbon dots prepared in the embodiments of the present invention.
[0023] Figure 4 The XRD pattern of fluorescent carbon dots prepared in an embodiment of the present invention.
[0024] Figure 5 The Fourier transform infrared (FT-IR) spectrum of the fluorescent carbon dots prepared in an embodiment of the present invention is shown.
[0025] Figure 6 The fluorescence lifetime decay curve of the fluorescent carbon dots prepared in the embodiments of the present invention is shown.
[0026] Figure 7 The UV-Vis absorption spectrum of the fluorescent carbon dots prepared in the embodiments of the present invention is shown.
[0027] Figure 8 The fluorescence emission spectra of the fluorescent carbon dots prepared in the embodiments of the present invention at different excitation wavelengths are shown.
[0028] Figure 9 The graph shows the effect of different pH values on the fluorescence quenching efficiency (F0 / F) of the fluorescent carbon dot detection system.
[0029] Figure 10 The graph shows the effect of different reaction times on the fluorescence quenching efficiency (F0 / F) of the fluorescent carbon dot detection system.
[0030] Figure 11 The graph shows the effect of different sodium chloride (NaCl) ionic strengths on the fluorescence quenching efficiency (F0 / F) of the fluorescent carbon dot detection system.
[0031] Figure 12 The graph shows the effect of different fluorescent carbon dot concentrations on the fluorescence quenching efficiency (F0 / F) of the detection system.
[0032] Figure 13 The fluorescent carbon dots of this invention are for hypochlorite (ClO) - Histograms of specific detection responses for ions and other common interfering ions.
[0033] Figure 14 This is a standard working curve showing the fluorescence emission spectra of the fluorescent carbon dots of the present invention under the action of different concentrations of hypochlorite, and the relationship between hypochlorite concentration and fluorescence intensity quenching. Detailed Implementation
[0034] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0035] This invention discloses a fluorescent carbon dot for detecting hypochlorite, its preparation method, and its application, belonging to the field of nanomaterials and chemical sensing. The method uses citric acid and o-phenylenediamine as carbon and nitrogen sources, respectively, and performs a hydrothermal reaction at 180℃ for 6 hours in an aqueous system. Nitrogen-doped fluorescent carbon dots are then obtained by centrifugation, filtration, dialysis, and lyophilization. The obtained carbon dots have a particle size distribution of 2–4 nm, and their surface is rich in water-soluble groups such as hydroxyl and amino groups. They emit strong fluorescence at 445 nm under 370 nm excitation. These carbon dots are effective for detecting hypochlorite (ClO₂). - It exhibits a specific fluorescence quenching response, excellent resistance to salt interference, and extremely high sensitivity, with a detection limit (LOD) as low as 65 nM. The preparation process of this invention is simple, low-cost, and has a fast response speed (10 min), providing an ideal fluorescent probe material for rapid and highly sensitive detection of hypochlorite in fields such as environmental monitoring, food safety, and public health.
[0036] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing fluorescent carbon dots for detecting hypochlorite, comprising the following steps: using citric acid and o-phenylenediamine as precursors, adding them to deionized water for full dispersion and dissolution; transferring the resulting mixed solution to a high-pressure reactor for hydrothermal reaction; after the reaction is completed, naturally cooling to room temperature, and then centrifuging, filtering, dialysis and drying to obtain fluorescent carbon dot powder.
[0037] Specifically, the ratio of citric acid, o-phenylenediamine, and deionized water is as follows: 0.40-0.60g of citric acid and 0.40-0.60g of o-phenylenediamine are added to 15-25mL of deionized water. Citric acid can be replaced with trisodium citrate.
[0038] Specifically, the hydrothermal reaction conditions are as follows: heating at 180℃ for 6 hours; centrifugation conditions are 6000-10000 rpm for 8-15 minutes; filtration is performed using a 0.22 μm filter membrane; dialysis is performed using a dialysis bag with a molecular weight cutoff of 1000 Da for 24 hours, with the dialysis water being replaced every 8 hours; and drying is performed by freeze drying.
[0039] The fluorescent carbon dots prepared by the above method have a quasi-spherical nanoparticle structure with a particle size mainly distributed in the range of 2–4 nm. The surface is rich in hydroxyl, carboxyl, amino and carbonyl functional groups. Under excitation at a wavelength of 370 nm, the optimal fluorescence emission peak is located at 445 nm.
[0040] For applications of fluorescent carbon dots, they are used as fluorescent probes in water, environmental, or biological samples to detect hypochlorite (ClO₂). - Application of ).
[0041] Specifically, the method for detecting hypochlorite is as follows: the fluorescent carbon dots are prepared into an aqueous solution, mixed with the sample to be tested, and the concentration of hypochlorite is quantitatively analyzed by measuring the quenching degree (F0 / F) of the fluorescence intensity of the system.
[0042] Specifically, the detection conditions include: the optimal working concentration of the fluorescent carbon dots is 10 μg / mL; the pH of the reaction system is 7.4; and the reaction time is 10 min.
[0043] The above technical solution is described in detail below: This invention provides a method for detecting hypochlorite based on fluorescent carbon dots, comprising two main steps: preparation of fluorescent carbon dots and detection of hypochlorite. It also protects the application of this method and the dedicated detection reagents. The specific technical solution is as follows: 1. Preparation of fluorescent carbon dots: Citric acid and o-phenylenediamine were added to deionized water at a mass ratio of 1:1, and stirred thoroughly to disperse and completely dissolve. The total amount of citric acid and o-phenylenediamine added was 0.1 g / mL of deionized water. The resulting mixture was transferred to a polytetrafluoroethylene-lined high-pressure reactor, sealed, and subjected to hydrothermal reaction at 180°C for 6 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The reaction solution was centrifuged at 8000 rpm for 10 minutes, and the supernatant was filtered through a 0.22 μm filter membrane to remove larger aggregated particles. The filtrate was placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed in deionized water for 24 hours, with the dialyzing water changed every 8 hours to remove unreacted precursors and small molecule impurities. After dialysis, the sample was freeze-dried to obtain pale yellow fluorescent carbon dots (CDs) powder, which was then sealed for later use.
[0044] The fluorescent carbon dots prepared in this invention are quasi-spherical nanoparticles with particle sizes mainly distributed in the range of 2–4 nm and an average size of about 3 nm. They are uniform in size and have good dispersibility. Their surfaces are rich in oxygen- and nitrogen-containing functional groups such as hydroxyl, carboxyl, amino, and carbonyl groups, and they have good water solubility and optical stability. The fluorescent carbon dots produce the strongest 445 nm fluorescence emission under 370 nm excitation, exhibiting typical excitation-dependent fluorescence characteristics, and the average fluorescence lifetime is about 9.3 ns.
[0045] 2. Detection of hypochlorite: (1) Preparation of fluorescent carbon dot detection solution: Dissolve the fluorescent carbon dot powder prepared above in deionized water to prepare a fluorescent carbon dot aqueous solution with a mass concentration of 10 μg / mL, and adjust the pH value of the solution to 7.4 as a hypochlorite detection solution; (2) Sample pretreatment: The sample to be tested is appropriately diluted or filtered to remove insoluble impurities and avoid interference with fluorescence detection; (3) Mixing reaction: Take an equal volume of fluorescent carbon dot detection solution and mix it with the treated sample to be tested. Shake well and react at room temperature for 10 min. (4) Fluorescence detection: A fluorescence spectrophotometer was used to detect the fluorescence intensity F of the mixed system under the conditions of excitation wavelength 370 nm and emission wavelength 445 nm. At the same time, the original fluorescence intensity F0 of the fluorescent carbon dot detection solution without the sample to be tested was detected. (5) Qualitative and quantitative judgment: Qualitative detection: If the fluorescence intensity of the mixed system is significantly quenched, it indicates that the sample contains hypochlorite; if the fluorescence intensity does not change significantly, it indicates that the sample does not contain hypochlorite. Quantitative detection: The fluorescence quenching efficiency F0 / F was calculated. Based on the linear relationship between F0 / F and hypochlorite concentration (within the range of 0-1.25 μM), and combined with the Stern-Volmer equation F0 / F = 0.99 + Ksv[ClO], -] Calculate the hypochlorite concentration in the sample to be tested.
[0046] In this invention, the detection of hypochlorite by the fluorescent carbon dot detection solution is not affected by ionic strength (within the range of 0-7 mM NaCl), and it can effectively respond to hypochlorite within the pH range of 3 to 11. The detection condition of pH 7.4 is more suitable for actual biological and environmental applications. The detection method has a detection limit of as low as 65 nM for hypochlorite, and it only produces specific fluorescence quenching for hypochlorite ions, with no obvious fluorescence response to other common ions, thus exhibiting excellent selectivity.
[0047] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0048] Example 1 0.50 g of citric acid and 0.50 g of o-phenylenediamine were completely dissolved in 20 mL of deionized water and transferred to a polytetrafluoroethylene high-pressure reactor. The mixture was reacted at 180 °C for 6 h. After cooling, the supernatant was collected by centrifugation at 8000 rpm for 10 min, filtered through a 0.22 μm filter membrane, dialyzed through a 1000 Da dialysis bag for 24 h, and then freeze-dried to obtain carbon dot powder.
[0049] Characterized by TEM and AFM, such as Figure 1 and Figure 2 As shown, the carbon dots are uniformly dispersed quasi-spherical with an average size of approximately 3 nm. The FT-IR and XPS spectra are as follows: Figure 3 Figure 4 as well as Figure 5 As shown, it is confirmed that it contains carbon, oxygen, and nitrogen elements, and its surface is enriched with functional groups such as hydroxyl, carboxyl, and amino groups. Figure 6 As shown, the fluorescence lifetime decay curves of the fluorescent carbon dots are illustrated. Optical characterization is as follows: Figure 7 Figure 8 It shows a significant absorption peak at 370nm, and the optimal excitation / emission wavelengths are 370nm / 445nm.
[0050] Example 2 Experimental optimization was carried out by preparing carbon dot solutions of a certain concentration: 1. pH optimization: Test within the pH range of 3–11, such as… Figure 9 The results showed that the quenching efficiency (F0 / F) was similar and optimal at pH 7 and pH 11. Based on practical applications, the optimal test environment was determined to be pH 7.4.
[0051] 2. Time optimization: Comparison of ClO within 5-30 min - The quenching effect, such as Figure 10 The results showed that the reaction reached stability after 10 minutes with no significant difference, thus determining the optimal reaction time to be 10 minutes.
[0052] 3. Probe concentration optimization: Three concentrations of 10, 20, and 30 μg / mL were selected, such as... Figure 12 The results showed that a carbon dot concentration of 10 μg / mL was effective against 1 μM ClO. - It has the largest F0 / F value and the best quenching effect.
[0053] Example 3 Anti-interference ability, specificity and detection limit: 1. Ionic strength test: Under a 0-7 mM NaCl concentration gradient, such as... Figure 11 The fluorescence intensity of the CDs shown remained essentially unchanged, indicating excellent salt resistance.
[0054] 2. Specificity test: Add 10mM H2O2 and Cl... - NO3 - 11 common ions, such as Figure 13 None of the above caused a significant change in fluorescence, except for ClO. - It produces significant fluorescence quenching (F / F0 approaches 0).
[0055] 3. Detection limit test: Under optimal conditions, different concentrations of ClO were added dropwise. - .like Figure 14 The results showed that F0 / F and ClO - The concentration showed a good linear relationship in the range of 0-1.25 μM (R0). 2 =0.99005). Based on 3σ / S, the limit of detection (LOD) of this fluorescent probe is 65 nM.
[0056] This invention presents a hypochlorite detection method based on fluorescent carbon dots. The preparation process of fluorescent carbon dots is simple, environmentally friendly, and can be mass-produced. The detection method is easy to operate, has a fast response speed, requires no large precision instruments, and can achieve rapid on-site detection. Furthermore, this method exhibits high selectivity, excellent sensitivity, and strong environmental adaptability, and can be applied to qualitative and quantitative detection of hypochlorite in multiple fields such as environmental monitoring, food safety, public health, and industrial production. The hypochlorite detection reagent of this invention has good stability, is easy to use, and can be directly commercialized. Therefore, this invention has significant industrial applicability and broad market application prospects.
[0057] Comparative Example 1 Change the precursor raw materials (do not add nitrogen source).
[0058] (1) Preparation of fluorescent carbon dots: 1.00 g of citric acid (without o-phenylenediamine) was added to 20 mL of deionized water, and the mixture was fully dispersed and dissolved; the remaining hydrothermal reaction, centrifugation, dialysis and drying steps were exactly the same as in Example 1.
[0059] (2) Hypochlorite detection: Hypochlorite was detected using carbon dots without nitrogen source as described above.
[0060] The results show that, due to the lack of o-phenylenediamine as a nitrogen source, the prepared carbon dots lack amino groups and nitrogen-containing heterocyclic structures (such as pyridine N and pyrrole N) on their surface. Their original fluorescence intensity under 370 nm excitation is extremely weak, and no significant fluorescence quenching reaction occurs after the addition of hypochlorite, making it impossible to achieve highly sensitive and specific detection of hypochlorite. This indicates that the co-doping of citric acid and o-phenylenediamine in this invention is the basis for achieving a highly efficient response.
[0061] Comparative Example 2 The working concentration of fluorescent carbon dots in the detection system was changed. Fluorescent carbon dots were prepared according to the method in Example 1, but the working concentration of fluorescent carbon dots was increased from the optimal 10 μg / mL to 30 μg / mL during hypochlorite detection.
[0062] The results showed that when the background concentration of fluorescent carbon dots was too high, adding 1 μMClO - The fluorescence quenching efficiency (F0 / F) dropped significantly to around 1.15. Compared to the optimal quenching effect at 10 μg / mL (F0 / F approximately 1.4), the high-concentration carbon dot system weakened the quenching effect of the target analyte on the monomer luminescence center, resulting in a significant decrease in detection sensitivity.
[0063] Comparative Example 3 The pH environment of the detection system was altered. Fluorescent carbon dots were prepared according to the method in Example 1, and the fluorescent carbon dots were prepared as an aqueous solution of 10 μg / mL, but the initial pH of the detection system was adjusted to a strongly acidic environment of 3.0 using a buffer solution.
[0064] The results showed that under strongly acidic conditions (pH=3), the fluorescence quenching efficiency (F0 / F) of the system in response to hypochlorite decreased to its lowest value (approximately 1.15). In contrast, in a slightly alkaline environment (pH=7.4), the fluorescence quenching efficiency reached approximately 1.5. This indicates that excessively low or high pH values are unfavorable for the electron transfer reaction between the functional groups on the carbon dot surface and hypochlorite ions, thus affecting the sensitivity of actual detection.
[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.
Claims
1. A fluorescent carbon dot for detecting hypochlorite, characterized in that: The fluorescent carbon dots have a quasi-spherical particle structure, and the surface of the particle structure has functional groups of hydroxyl, carboxyl, amino and carbonyl groups; when excited by a wavelength of 370 nm, its optimal fluorescence emission peak is located at 445 nm.
2. The fluorescent carbon dot according to claim 1, characterized in that, The optimal working concentration of the fluorescent carbon dots is 10 μg / mL; the pH of the reaction system with hypochlorite is 7.4, and the reaction time is 10 min.
3. A method for preparing fluorescent carbon dots according to any one of claims 1-2, characterized in that, include: Citric acid and o-phenylenediamine are added to deionized water and dissolved to obtain a mixed solution. The mixed solution is subjected to hydrothermal reaction in a high-pressure reactor. The product after cooling of the hydrothermal reaction is centrifuged, filtered, dialyzed and dried to obtain fluorescent carbon dot powder. The mass ratio of citric acid to o-phenylenediamine is 1:
1.
4. The preparation method according to claim 3, characterized in that, The hydrothermal reaction conditions are: heating at 180°C for 6 hours.
5. The preparation method according to claim 3, characterized in that, The centrifugation conditions were 8000 rpm for 10 minutes.
6. The preparation method according to claim 3, characterized in that, The filtration was performed using a 0.22 μm filter membrane.
7. The preparation method according to claim 3, characterized in that, The dialysis was performed using a dialysis bag with a molecular weight cutoff of 1000 Da for 24 hours.
8. The preparation method according to claim 3, characterized in that, The drying process employs freeze drying.
9. An application of the fluorescent carbon dot according to any one of claims 1-2, characterized in that, Fluorescent carbon dots are used as fluorescent probes to detect hypochlorite in water, environmental, or biological samples.
10. The application according to claim 9, characterized in that, The fluorescent carbon dots are prepared into an aqueous solution and mixed with the sample to be tested. The concentration of hypochlorite is quantitatively measured by determining the degree of quenching of fluorescence intensity during the reaction.