Fluorescent probe based on dual-emission carbon quantum dots and application of fluorescent probe in methanol detection

Abstract

The invention discloses a fluorescent probe based on dual-emission carbon quantum dots and application of the fluorescent probe in methanol detection, and belongs to the technical field of fluorescent probes. According to the preparation method, p-phenylenediamine (p-PD) is only used as a single precursor, the carbon quantum dots (p-PD CDs) with blue light and red light dual-emission characteristics are successfully prepared by regulating and controlling a solvent environment and adopting a two-step synthesis strategy, and the carbon quantum dots can be stably stored for a long time. The carbon quantum dot can quickly, simply, conveniently and efficiently identify and detect the methanol concentration in a methanol-ethanol system, by increasing the methanol content, the blue emission peak of the carbon quantum dot is subjected to red shift, the fluorescence intensity is gradually reduced, and the fluorescence intensity of the red emission peak is slightly reduced. The result shows that when the concentration of methanol is 0-60% and 70%-100%, the fluorescence intensity ratio of the carbon quantum dots and the concentration of methanol have a good linear relationship. Meanwhile, the carbon quantum dots can also be used for detecting low-concentration methanol in ethanol, and the detection limit is 0.38%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fluorescent probe, and particularly relates to a fluorescent probe based on double-emission carbon quantum dots and application thereof in methanol detection. BACKGROUND

[0002] Methanol is widely used in industrial alcohol, fuel, cleaning agent and various chemical synthesis processes as a basic chemical raw material and cheap solvent. However, methanol has significant toxicity, its vapor can enter the human body through inhalation, liquid can enter the human body through skin contact or accidental ingestion, and it is metabolized into toxic formic acid in the body, causing irreversible damage to the optic nerve and central nervous system, and even fatal. Therefore, the regulations of various countries have strict limit values for methanol residues in the air of the workplace and consumer products (such as industrial alcohol). In practical applications, methanol becomes a major source of safety hazards in two situations: one is that unscrupulous manufacturers add methanol into solvents such as ethanol to make cheap "industrial alcohol" or cleaning agents for profit, which can easily lead to mass poisoning if accidentally ingested; two is that methanol is left in the recovered solvent or product as a byproduct or impurity in chemical production, which continuously threatens process safety and personnel health. Methanol and common organic solvents such as ethanol and isopropanol are highly similar in physical properties such as odor and boiling point, making it difficult to distinguish them by sensory or conventional methods, which provides concealment for their illegal addition or accidental mixing. Among various organic solvents, ethanol is particularly important in the clinical, biochemical and beverage industries, and the lower price of methanol and its similar properties to ethanol further encourage adulteration. Therefore, developing a rapid, sensitive and reliable methanol detection method to accurately identify and quantify methanol in organic solvents has become an urgent need to ensure production safety, product quality and public health. In this context, developing a high-sensitivity fluorescent probe that can distinguish between methanol and ethanol not only has important scientific value, but also has broad application prospects.

[0003] At present, gas chromatography, discoloration acid colorimetry, electrochemical method, enzyme catalysis technology, gas sensor and Raman spectroscopy have been applied to methanol detection in different scenarios. Among them, gas chromatography has been established as the standard method for determining the content of methanol in alcoholic beverages and fruits due to its high accuracy and low detection limit. However, these methods generally have limitations such as expensive equipment, complex process, long detection period, and the instruments used are usually large in size and high in price, which need to be operated by professional personnel in a laboratory environment, making it difficult to apply to on-site rapid analysis. Therefore, developing efficient, accurate, simple and rapid methanol detection technology has become the focus of current research. Fluorescence spectroscopy has high practical application potential due to its simple operation, high sensitivity and fast response speed. In recent years, researchers have synthesized a series of fluorescent compounds with solvent-induced discoloration effect, which can be used for methanol recognition, but due to the similar properties of alcohols, it is still extremely challenging to selectively detect a specific alcohol (especially methanol) from a complex polyhydric alcohol coexistence system.

[0004] Carbon quantum dots (CDs), as a novel zero-dimensional carbon-based nanomaterial, have shown broad application prospects in fields such as recognition sensing, bioimaging, drug delivery, and solar cells due to their unique optical properties, excellent water solubility, good biocompatibility, low toxicity, and ease of functionalization. [1-5] Compared to many cumbersome detection methods, carbon quantum dots offer significant advantages in target analysis and detection. As a result, chemical sensors based on carbon quantum dots are increasingly common. In recent years, researchers have developed various methanol fluorescence detection methods based on carbon quantum dots. For example, Latha et al. prepared nitrogen-doped carbon oxide quantum dots (NOCDs) as on / off fluorescent nanoprobes for detecting trace amounts of methanol in water and alcoholic beverages. [6] Wang's team synthesized amoxicillin carbon quantum dots (AMO-CDs) using a one-step microwave method, achieving rapid identification and quantification of methanol in edible alcohol. [7] While these methods exhibit high detection sensitivity, they are susceptible to interference from other substances and have weak anti-interference capabilities. Furthermore, most existing methods rely on changes in single-emission fluorescence signals for detection, and their measurement accuracy is easily affected by factors such as probe concentration, instrument efficiency, and photobleaching, leading to result deviations. In contrast, dual-emission ratio fluorescent carbon quantum dots, by simultaneously recording fluorescence signals at two different wavelengths, effectively reduce interference from instrument and environmental factors, significantly improve the signal-to-noise ratio, and achieve more reliable quantitative analysis even in complex environments. Summary of the Invention

[0005] The purpose of this invention is to provide a fluorescent probe based on dual-emission carbon quantum dots and its application in methanol concentration detection. This invention uses p-phenylenediamine (…). p Carbon quantum dots exhibiting dual blue-red fluorescence were synthesized via a two-step synthesis method using PD as a single precursor. Their structure and morphology were characterized using Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). These carbon quantum dots with dual blue-red fluorescence can serve as fluorescent probes for rapid and sensitive recognition of methanol in methanol-ethanol solutions, and can be used for highly sensitive quantitative detection of methanol in industrial ethanol.

[0006] like Figure 1As shown, the fluorescent probe based on dual-emission carbon quantum dots of the present invention is prepared by the following method: 6-10 mg of p-phenylenediamine is dissolved in 5-10 mL of water. After complete dissolution, the solution is transferred to a high-pressure reactor with a polytetrafluoroethylene liner. The solution is subjected to hydrothermal reaction at 160-200 °C for 6-10 h. After natural cooling to room temperature, a carbon quantum dot (W-CDs) solution synthesized by a one-step hydrothermal method is obtained. The water in the carbon quantum dot (W-CDs) solution is then removed by rotation to obtain a solid product. Next, 6-10 mg of p-phenylenediamine is dissolved in 5-10 mL of anhydrous ethanol. This solution is mixed with the above solid product and, after complete dissolution, transferred to a high-pressure reactor with a polytetrafluoroethylene liner. The solution is subjected to hydrothermal reaction at 160-200 °C for 4-6 hours. After the reactor is naturally cooled to room temperature, the fluorescent probe based on dual-emission carbon quantum dots of the present invention is obtained. p Fluorescent probe solution of PD CDs.

[0007] like Figure 2 As shown, under excitation at a wavelength of 365 nm, carbon quantum dots (W-CDs) synthesized by a one-step hydrothermal method exhibit a shoulder peak at 490 nm in ethanol and a high-resolution fluorescence emission band at 598 nm; while carbon quantum dots prepared by a two-step synthesis method ( p -PD CDs showed dual fluorescence emission peaks at 445 nm and 598 nm. Compared to W-CDs, p -PD CDs exhibit a larger bipeak spacing and significantly enhanced fluorescence intensity. Integrating sphere combined with pulsed laser photoacoustic spectroscopy results indicate that... p -PD CDs achieved a fluorescence quantum yield (QY) of 11.86% at the red emission peak, significantly higher than the 6.17% of W-CDs (Table 1), confirming that the two-step synthesis strategy effectively improved the fluorescence efficiency of red light emission from carbon quantum dots.

[0008] Unlike previous preparation methods that relied on multiple carbon sources, passivating agents, or post-synthesis separation techniques, this invention uses p-phenylenediamine (PPE) p Using α-PD as a single precursor, carbon quantum dots exhibiting dual emission characteristics of blue light (445 nm) and red light (598 nm) were successfully prepared by controlling the solvent environment and employing a two-step synthesis strategy. p -PD CDs). This carbon quantum dot emits dual-color fluorescence when excited at a wavelength of 365 nm, exhibiting purple fluorescence under ultraviolet light irradiation. Based on this, the present invention provides a dual-emission carbon quantum dot fluorescent probe that can rapidly, easily, and efficiently identify methanol, and can be used for fluorescence spectral analysis and visualization detection of methanol concentration.

[0009] This invention also relates to the application of the aforementioned blue and red dual-emission carbon quantum dots in methanol detection.

[0010] Furthermore, the present invention also relates to the application of the methanol detection fluorescent probe based on blue and red dual-emission carbon quantum dots in the fluorescence detection of methanol concentration in a methanol-ethanol system; Furthermore, the present invention also relates to the application of the methanol detection fluorescent probe based on blue and red dual-emission carbon quantum dots in the visual detection of methanol concentration in a methanol-ethanol system; The fluorescent probe was applied to detect methanol concentration in a methanol-ethanol system. By increasing the methanol concentration, the blue emission peak of the probe shifted to red and the fluorescence intensity gradually decreased, while the red emission peak slightly decreased. Results showed that when the methanol volume concentration was in the ranges of 0–60% and 70%–100%, there was a good linear relationship between the ratio of the emission intensity of the fluorescent probe at 445 and 598 nm and the methanol volume concentration. The linear equations are as follows: I 445 / I 598 = 1.990 - 0.2173[Methanol](R 2 = 0.998) and I 445 / I 598 = 1.005 - 0.00604 [Methanol](R 2 = 0.992). In particular, this probe can also detect methanol in a lower volume concentration range; when the methanol volume concentration is 0–10%, its linear response equation is: I 445 / I 598 = 1.997 - 0.02237[Methanol](R 2 =0.999); its detection limit for methanol is 0.38%. Based on the above p - The linear response equation of PD CDs to methanol volume concentration in the methanol-ethanol system. p -PD CDs can be used for the quantitative detection of methanol in industrial ethanol (recovery rate 99.5~101.7%). [Methanol] is the volume concentration of methanol.

[0011] Furthermore, the present invention also relates to the application of the methanol detection fluorescent probe based on blue and red dual-emission carbon quantum dots in the fluorescence detection of methanol concentration in industrial ethanol; Attached Figure Description

[0012] Figure 1 Example 1: A schematic diagram of the synthetic route for preparing dual-emission fluorescent carbon quantum dots using p-phenylenediamine as a raw material; Figure 2Under excitation by a 365 nm light source, the fluorescent probe solution (W-CDs and) prepared in Example 1 p Fluorescence emission spectrum of -PD CDs in ethanol; Figure 3 The fluorescent probe solution prepared in Example 1 ( p Fourier transform infrared (FT-IR) absorption spectra of -PD CDs; Figure 4 (a): Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images of carbon quantum dots in the fluorescent probe solution prepared in Example 1 (inset). Figure 4 (b): Particle size distribution of carbon quantum dots in the fluorescent probe solution prepared in Example 1; Figure 5 (a): Fluorescence spectra of the fluorescent probe solution prepared in Example 1 in methanol-ethanol solutions of different concentrations (volume concentration 0~100%) under 365 nm light source excitation; Figure 5 (b): The fluorescence intensity ratio of the fluorescent probe solution prepared in Example 1 ( I 445 / I 598 Linear relationship between methanol concentration (volume concentration 0~100%) and methanol concentration; Figure 5 (c): Photographs of the fluorescence emission of the fluorescent probe solution prepared in Example 1 in different methanol-ethanol solutions under ultraviolet light (365 nm) irradiation; Figure 5 (d): CIE images of the fluorescent probe solution prepared in Example 1 in methanol-ethanol solution (volume concentration 0~100%); Figure 6 (a): Fluorescence spectra of the fluorescent probe solution prepared in Example 1 in methanol-ethanol solutions of different concentrations (volume concentration 0~10%) under 365 nm light source excitation; Figure 6 (b): The fluorescence intensity ratio of the fluorescent probe solution prepared in Example 1 ( I 445 / I 598 Linear relationship between methanol concentration (volume concentration 0~10%) and methanol concentration; Figure 7 Fluorescence spectra of the fluorescent probe solution prepared in Example 1 under 365 nm light source excitation in methanol-industrial ethanol solutions of different concentrations (methanol volume concentration 0~4%). Table 1: Fluorescence quantum efficiency data of carbon quantum dots; Table 2: Data on methanol content in 99.5% industrial ethanol after dehydration, detected using fluorescent probe solution; Table 1: Fluorescence quantum efficiency data of carbon quantum dots Sample name Fluorescence quantum yield (QY) W-CDs 6.17% -PD CDs 11.86% Table 2: Data on methanol content in 99.5% industrial ethanol after dehydration, detected using fluorescent probe solution. Detailed Implementation

[0013] The following examples further illustrate the content of the present invention, but the present invention is not limited to these examples. The p-phenylenediamine, anhydrous ethanol, methanol, and industrial ethanol used in the present invention were purchased from Shanghai Aladdin Reagent Co., Ltd., and deionized ultrapure water was used throughout the entire experimental process.

[0014] Example 1 Synthesis and characterization of fluorescent probe solutions: such as Figure 1 As shown, 8.65 mg of p-phenylenediamine was dissolved in 8 mL of water. After complete dissolution, the solution was transferred to a high-pressure reactor with a polytetrafluoroethylene (PTFE) liner. The reaction was carried out hydrothermally at 180 °C for 8 h. After natural cooling to room temperature, a carbon quantum dot (W-CDs) solution synthesized by a one-step hydrothermal method was obtained. Then, 8 mL of the carbon quantum dot (W-CDs) solution was transferred to a round-bottom flask, and the water was removed by rotation to obtain a solid product. Next, 8.65 mg of p-phenylenediamine was dissolved in 8 mL of anhydrous ethanol, and this solution was mixed with the solid product obtained in the previous step. After complete dissolution, the solution was transferred to a high-pressure reactor with a PTFE liner. The reaction was then carried out hydrothermally at 180 °C for another 5 hours. After the reactor naturally cooled to room temperature, the carbon quantum dot (W-CDs) solution synthesized by the present invention was obtained. p The fluorescent probe solution of -PD CDs has a concentration of 2 mg / mL for dual-emission carbon quantum dots.

[0015] like Figure 2 As shown, the fluorescence probe solution obtained in Example 1 emitted wavelengths of 445 and 598 nm. Compared with carbon quantum dots (W-CDs) synthesized via a one-step hydrothermal method, the fluorescence probe obtained in Example 1 resulted in a larger spacing between the two emission peaks and a significantly enhanced fluorescence intensity. Further measurements of the W-CDs and... p The fluorescence quantum yields (QY) of -PD CDs at the red emission peak were 6.17% and 11.86%, respectively, indicating that the two-step synthesis strategy effectively improved the quantum efficiency of red emission (Table 1). Unlike previous methods that relied on multiple carbon sources, passivators, or post-synthesis separation techniques to prepare dual-emission carbon quantum dots, this invention uses only p-phenylenediamine (PDCDs) as the source. p Using PD as a single precursor, carbon quantum dots with dual emission characteristics of blue and red light were successfully prepared by controlling the solvent environment and adopting a two-step synthesis strategy.

[0016] The structure and surface functional groups of red-light carbon quantum dots were characterized using Fourier transform infrared spectroscopy. Figure 3 As shown, at 3443 cm -1 3327 cm -1 and 3203 cm -1 Three characteristic peaks were observed in the high wavenumber region. These three characteristic peaks are caused by the stretching vibration of OH and the antisymmetric and symmetric stretching vibrations of -NH2. [8] At 2921 cm -1 and 2852 cm -1 The absorption peak at 1674 cm⁻¹ corresponds to the stretching vibrations of the methyl and methylene groups of ethanol. -1 1625 cm -1 1603 cm -1 and 1516cm -1 1398 cm -1 The absorption peaks at these locations are attributed to the stretching vibration peaks of C=O, C=N, and C=C, and the bending vibration peaks of NH4, respectively. [9] 1360 cm -1 The absorption peak at 1000-1200 cm⁻¹ corresponds to the stretching vibration peak of CN, and is located in the range of 1000-1200 cm⁻¹. -1 The broad peaks within the range are attributed to the stretching vibrations of CN or CO.

[10] Therefore, the surface of this dual-emission carbon quantum dot contains free hydroxyl and amino groups. The morphology of the carbon quantum dots was further characterized using transmission electron microscopy. Figure 4 It can be seen that the prepared carbon quantum dots are well dispersed in ethanol and are spherical particles. Statistical results of about 200 particles show that the average particle size is about 3.21 nm. High-resolution images show that the lattice spacing is 0.21 nm, which is consistent with the (100) crystal plane of graphitic carbon.

[0017] Example 2 Fluorescence response of the fluorescent probe solution to methanol in a methanol-ethanol solution: Methanol-ethanol mixed solutions with different methanol volume concentrations (0%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% respectively) were prepared. Then, 980 µL of each methanol-ethanol mixed solution and 20 µL of the dual-emission carbon quantum dot-based fluorescent probe solution prepared in Example 1 (the dual-emission carbon quantum dot fluorescent probe solution prepared in Example 1 was diluted 4 times with ethanol) were added to a cuvette. After thorough mixing, the fluorescence spectra of the solutions were measured. Figure 5The experimental results in (a) show that as the methanol volume concentration increases, the fluorescence signal at 445 nm of the carbon quantum dots in the fluorescent probe solution gradually weakens, the emission wavelength gradually redshifts to 465 nm, and the fluorescence signal intensity at 598 nm slightly decreases. 445 nm was used as the response signal, and 598 nm as the reference signal. The fluorescence intensity ratio at 445 nm and 598 nm of the fluorescent probe solution was plotted. I 445 / I 598 Relationship between ) and methanol volume concentration () Figure 5 (b) It can be clearly seen that when the volume concentration of methanol is in the range of 0~60% and 70~100%, the fluorescent probe solution... I 445 / I 598 The relationship between the volume concentration of methanol and the concentration of methanol exhibits a good linear response, and the linear response equations are as follows: I 445 / I 598 = 1.990 - 0.2173[Methanol](R 2 = 0.998) and I 445 / I 598 = 1.005 -0.00604 [Methanol](R 2 = 0.992), where, I 445 / I 598 The fluorescence intensity ratio of the fluorescent probe at 445 nm and 598 nm is represented by [Methanol], which represents the volume concentration of methanol.

[0018] Example 3 Visual response of the fluorescent probe solution to high concentrations of methanol: When methanol-ethanol mixed solutions with different volume concentrations of methanol containing the fluorescent probe solution prepared in Example 2 were irradiated with a UV lamp (365 nm), the mixed solutions exhibited distinctly different color changes, thus providing a visual response of the fluorescent probe solution to methanol solutions of different concentrations under UV irradiation. Figure 5 As shown in (c): the fluorescent probe solution is purple under ultraviolet light, and gradually changes from purple to orange with increasing methanol volume concentration. This color transition corresponds to a linear change in the CIE chromaticity diagram. Figure 5 (d)). These results indicate that p -PD CDs can directly quantify the methanol concentration in a methanol-ethanol mixture by detecting changes in fluorescence emission color.

[0019] Example 4 Fluorescence response of the fluorescent probe solution to low concentrations of methanol in a methanol-ethanol solution: Methanol-ethanol mixed solutions with different methanol volume concentrations (0%, 0.1%, 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%) were prepared respectively. Then, 980 µL of each methanol-ethanol mixed solution and 20 µL of fluorescent probe solution (the dual-emission carbon quantum dot fluorescent probe solution prepared in Example 1 was diluted 4 times with ethanol) were added to a cuvette. After thorough mixing, the fluorescence spectra of the solutions were measured. Figure 6 The experimental results in (a) show that the fluorescence intensity of the fluorescent probe solution gradually decreases with increasing methanol concentration. Meanwhile, a graph showing the relationship between the fluorescence intensity of the fluorescent probe solution and the volume concentration of methanol was plotted. Figure 6 (b) Demonstration: When the methanol volume concentration is in the range of 0-10%, the fluorescent probe solution I 445 / I 598 There is a good linear response relationship between the volume concentration of methanol and the concentration of methanol (R0). 2 =0.994), the linear equation is: I 445 / I 598 =1.997 - 0.02237 [Methanol], and the calculated limit of detection for methanol is 0.38%. I 445 / I 598 The fluorescence intensity ratio of the fluorescent probe at 445 nm and 598 nm is represented by [Methanol], which represents the volume concentration of methanol.

[0020] Example 5 Detection of methanol concentration in industrial ethanol using fluorescent probe solution: First, the industrial ethanol (purity 99.5%, CAS number: 64-17-5) was dehydrated using a 3A molecular sieve to eliminate interference from water in the detection results. 980 µL of the dehydrated industrial ethanol and 20 µL of a dual-emission carbon quantum dot fluorescent probe solution (the dual-emission carbon quantum dot fluorescent probe solution prepared in Example 1 was diluted 4 times with ethanol) were added to a cuvette, and after thorough mixing, the fluorescence emission spectrum of the above solutions was measured. Figure 7 The black line). The recorded fluorescence intensity ratios were applied to the relationship curve between the fluorescence intensity of the fluorescent probe solution and the volume concentration of methanol established in Example 4 (…). Figure 6(b) indicates that 99.5% industrial ethanol contains almost no methanol. Recovery was then determined by adding known amounts of methanol (volume concentrations of 1%, 2%, 3%, and 4%) to dehydrated industrial ethanol. As shown in Table 2, the methanol recovery rate in high-quality industrial ethanol ranged from 99.5% to 101.7%, validating the accuracy of the established method for methanol determination in real samples.

[0021] Furthermore, it should be noted that the specific embodiments listed in this specification are merely illustrative of the content of the present invention and do not limit the scope of protection of the present invention in any way; those skilled in the art can make improvements or changes based on the above descriptions, but all such improvements and changes should fall within the scope of protection of the claims of the present invention.

[0022] References [1] Y. Lin, D. Knopp, Anal. Chem. 89 (2017), 5637–5645 [2] J. Shangguan, J. Tang, Anal. Chem. 89 (2017), 7477–7484 [3] Q. Zheng, L. Wang, Nanotechnology 31 (2020) 175102 [4] W. Sun, L. Fan, J. Phys. Chem. Lett. 11(4) (2020) 1357−1363 [5] H. Wang, G. Zou, Nanoscale Research Letters 11(27) (2016) 3−6 [6] H. Wang, X. Zhao, Microchem. J. 201 (2024) 110509 [7] M. Latha, N.K.R. Bogireddy, RSC Adv. 10 (2020) 22522–22532 [8] R Gao, X Yi, React. Funct. Polym. 197 (2024) 105877 [9] XH Duan, Y. Li, Food Chem. 428 (2023) 136733

[10] XL Tian, X He, New J. Chem. 48(3) (2024) 1081-1085.

Claims

1. A methanol detection fluorescent probe based on blue and red dual-emission carbon quantum dots, which is prepared by the following method: 6-10 mg of p-phenylenediamine is dissolved in 5-10 mL of water. After complete dissolution, the solution is transferred to a high-pressure reactor with a polytetrafluoroethylene liner. The reactor is subjected to hydrothermal reaction at 160-200 °C for 6-10 h. After natural cooling to room temperature, a carbon quantum dot solution synthesized by a one-step hydrothermal method is obtained. The carbon quantum dot solution is then rotated to remove water to obtain a solid product. 6-10 mg of p-phenylenediamine is then dissolved in 5-10 mL of anhydrous ethanol. This solution is mixed with the solid product and, after complete dissolution, transferred to a high-pressure reactor with a polytetrafluoroethylene liner. The reactor is subjected to hydrothermal reaction at 160-200 °C for 4-6 hours. After the reactor is naturally cooled to room temperature, the fluorescent probe solution based on dual-emission carbon quantum dots is obtained.

2. The application of blue and red dual-emission carbon quantum dots in methanol detection as described in claim 1.

3. The application of blue and red dual-emission carbon quantum dots in methanol detection as described in claim 2, characterized in that: This refers to the application of fluorescence detection of methanol concentration in a methanol-ethanol system.

4. The application of blue and red dual-emission carbon quantum dots in methanol detection as described in claim 2, characterized in that: It is an application of visual detection of methanol concentration in the methanol-ethanol system.

5. The application of blue and red dual-emission carbon quantum dots in methanol detection as described in claim 2, characterized in that: This is an application of fluorescence detection of methanol concentration in industrial ethanol.

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