Dual-emission CDs / QDs@ZIF-8 ratio fluorescent sensor, preparation method thereof and application of the sensor in detection of hydrogen peroxide

Abstract

The application discloses a double-emission CDs / QDs@ZIF-8 ratio fluorescent sensor, a preparation method thereof and application of the double-emission CDs / QDs@ZIF-8 ratio fluorescent sensor in detection of hydrogen peroxide; through an in-situ growth method, carbon dots (CDs) and mercaptoacetic acid-terminated CdTe quantum dots (CdTe QDs) are encapsulated in ZIF-8 to obtain the double-emission CDs / QDs@ZIF-8 ratio fluorescent sensor which is used for detecting hydrogen peroxide (HP) in the environment; the CDs / QDs@ZIF-8 has high selectivity and sensitivity in detection of HP, and a good linear relationship (R2=0.9946) is presented in a concentration range of 0-120 muM, and the detection limit is 162 nM.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a dual-emission CDs / QDs@ZIF-8 ratiometric fluorescence sensor and its preparation method, as well as its application in hydrogen peroxide detection. Background Technology

[0002] Hydrogen peroxide (HP), an important inorganic compound, contains an unstable peroxide bond (-OO-) in its molecular structure. It is a colorless, transparent liquid at room temperature, exhibiting strong oxidizing and weak acidic properties. Chemically, HP can act as a strong oxidizing agent (e.g., bleaching organic matter, killing microorganisms) and also participate in reactions as a reducing agent in strongly oxidizing environments (e.g., redox reactions with potassium permanganate). This dual nature of chemical properties makes it widely applicable in biological, medical, military, industrial, and everyday fields. For example, low-concentration HP solutions of 3%-6% are widely used for medical wound disinfection and contact lens cleaning, while high-concentration solutions of 30% and above are used in industrial processes such as pulp bleaching and semiconductor wafer cleaning. In organisms, appropriate amounts of HP can protect cells, while excessive HP can generate highly reactive hydroxyl radicals through the Fenton reaction, initiating oxidative damage such as lipid peroxidation, protein cross-linking, and DNA strand breaks, ultimately leading to oxidative stress, cell damage, and a series of serious diseases. Therefore, establishing rapid, sensitive, and highly specific HP detection methods is of great significance.

[0003] Currently, reported methods for detecting Helicobacter pylori (HP) include UV-Vis absorption spectrometry, high-performance liquid chromatography (HPLC), titration, colorimetry, electrochemical methods, and chemiluminescence. However, these methods still have some drawbacks, such as cumbersome operation, high detection costs, and low sensitivity. Therefore, there is an urgent need to develop rapid, sensitive, and efficient methods for detecting HP residues. In recent years, fluorescence sensing technology based on nanomaterials has become an important method in the field of HP analysis due to its fast response speed, high sensitivity, ease of visualization, and portable analysis capabilities.

[0004] Metal-organic frameworks (MOFs) are organic-inorganic hybrid materials that combine the rigidity of inorganic materials with the flexibility of organic materials, making them a hot topic in modern materials chemistry research. The ultra-high porosity, large specific surface area, and tunable pore size of MOFs facilitate the containment of various luminescent substances. A large number of luminescent MOFs (LMOFs) have been synthesized and are widely used in fluorescence sensing, bioimaging, light-emitting diodes, and photocatalysis. ZIF-8 is a well-known MOF, composed of Zn... 2+As a metal center, 2-methylimidazole (2-MIM) serves as an organic bridging ligand. Due to its high porosity, high specific surface area, tunable pore structure, and good biocompatibility, it shows broad application potential in the field of fluorescence sensing.

[0005] Carbon dots (CDs), as a novel type of fluorescent nanoparticle, have attracted widespread attention in recent years due to their excellent optical properties, including broad absorption, narrow emission, large Stokes shift, stable luminescence, high quantum yield, and long fluorescence lifetime. However, CDs are easily quenched by various ions and some chemical substances, and they also exhibit self-aggregation, which limits their practical applications.

[0006] Quantum dots (QDs) are a class of semiconductor nanocrystals with quantum confinement effects, possessing unique optical properties such as size dependence, tunable photoluminescence, long-term photostability, high quantum yield, and long excited-state decay lifetimes. These properties make them ideal optical probes, demonstrating significant application value in fluorescence sensing, bioimaging, and single-molecule tracking. Among them, CdTeQDs, due to their tunable bandgap and ease of surface functionalization, have become the most extensively researched and representative in this field. However, current fluorescence sensing based on CdTeQDs for HP detection mainly relies on single-wavelength fluorescence signal measurement. While simple and easy to implement, it is susceptible to interference from factors such as excitation source fluctuations, probe concentration variations, complex sample matrix effects, and background fluorescence, resulting in low accuracy and poor reproducibility of the detection results. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a dual-emission CDs / QDs@ZIF-8 ratiometric fluorescence sensor, its fabrication method, and its applications.

[0008] This invention uses an "in-situ growth method" to co-encapsulate two different luminescent guests, carbon dots (CDs) and thioglycolic acid-terminated CdTe quantum dots (CdTeQDs), in a ZIF-8 to obtain a dual-emission CDs / QDs@ZIF-8 ratiometric fluorescence sensor, which can be used for rapid and sensitive detection of hydrogen peroxide (HP) in the environment.

[0009] The technical solution of the present invention is as follows: A dual-emission CDs / QDs@ZIF-8 ratiometric fluorescence sensor was prepared by the following method: (1) Blue light nitrogen-sulfur co-doped carbon dots (CDs) were synthesized by hydrothermal method using citric acid (CA) as carbon source and thiourea (TU) as nitrogen-sulfur source. Specific procedure: Dissolve citric acid and thiourea in deionized water, mix by ultrasonication, transfer to a hydrothermal reactor, react at 100~200 ℃ for 3~8 h, then filter and dry to obtain carbon dots; The preferred molar ratio of citric acid to thiourea is 1~10:10~20; (2) Using cadmium acetate dihydrate (Cd(CH3COO)2·2H2O) and potassium tellurite (K2TeO3) as raw materials, CdTe quantum dots (CdTe QDs) capped with mercaptoacetic acid were synthesized in the presence of mercaptoacetic acid (TGA) and sodium borohydride. Specific operation: Dissolve cadmium acetate dihydrate and mercaptoacetic acid in deionized water, adjust the pH to 8.0~13.0, add potassium tellurite and sodium borohydride, stir evenly, and place the reaction solution in a polytetrafluoroethylene-lined reactor. React at 100~140℃ for 4~8 h. After washing and drying, TGA-terminated CdTeQDs are obtained. The preferred mass ratio of cadmium acetate dihydrate to potassium tellurite is 0.1~0.5:0.02~0.05; The preferred ratio of cadmium acetate dihydrate, mercaptoacetic acid, and sodium borohydride is 0.1–0.5 g: 140–750 μL: 0.01–0.08 g; (3) By using the “in-situ growth method”, the blue light nitrogen-sulfur co-doped carbon dots obtained in step (1) and the mercaptoacetic acid-capped CdTe quantum dots obtained in step (2) are encapsulated together in ZIF-8 to construct a dual-emission CDs / QDs@ZIF-8 ratio fluorescence sensor. Specific operation: Dissolve 2-methylimidazole (2-MIM) in anhydrous methanol, add the blue light nitrogen-sulfur co-doped carbon dots obtained in step (1), the CdTe quantum dots capped with mercaptoacetic acid obtained in step (2), and add anhydrous methanol solution of Zn(NO3)2·6H2O. Mix well and react at room temperature (25 ℃) for 1~3 h. After centrifugation, washing and drying, a dual-emission CDs / QDs@ZIF-8 ratio fluorescence sensor is obtained. The preferred molar ratio of Zn(NO3)2·6H2O to 2-methylimidazole is 1:10; The preferred ratio of Zn(NO3)2·6H2O, blue light nitrogen-sulfur co-doped carbon dots, and mercaptoacetic acid-capped CdTe quantum dots is 1 mmol: 1~4 mg: 4~8 mg.

[0010] The dual-emission CDs / QDs@ZIF-8 ratio fluorescence sensor of this invention can be used to detect hydrogen peroxide (HP).

[0011] The principle of ratiometric fluorescence detection of hydrogen peroxide (HP): HP can quench the fluorescence of CDs / QDs@ZIF-8 through IFE. The intensity of the red emission peak of CdTe QDs at 675 nm gradually decreases with increasing HP concentration, while the intensity of the blue fluorescence peak of CDs at 440 nm remains basically unchanged; the fluorescence intensity ratio (Ig) is used to quench the fluorescence of CDs / QDs@ZIF-8. 675 / I440 This allows for the obtaining of the ratio fluorescence monitoring working curve, thus enabling the quantitative detection of HP.

[0012] The specific detection method is as follows: At room temperature (25 ℃), CDs / QDs@ZIF-8 were uniformly dispersed in a buffer solution, and hydrogen peroxide solutions of different concentrations were added. After the mixture stabilized for 1~10 min, the fluorescence emission spectrum of the mixture was detected using a fluorescence spectrophotometer at an excitation wavelength of 370 nm. The excitation and emission slit widths were set to 5~10 nm, and the fluorescence emission intensities at 675 nm and 440 nm under 370 nm excitation were recorded. Finally, the fluorescence intensity ratio (I0.05) was used to determine the fluorescence emission intensity. 675 / I 440 The working curve for ratio fluorescence monitoring can then be obtained; The preferred buffer solution is PBS buffer (50 mM, pH=7.4), and the concentration of CDs / QDs@ZIF-8 in the buffer solution is 0.1~0.25 mg / mL. The preferred concentration range of hydrogen peroxide in the mixed system is 0–120 μM; Ic of CDs / QDs@ZIF-8 675 / I 440 The fluorescence intensity ratio showed a good linear correlation with the HP concentration in the range of 0–120 μM, and the limit of detection (LOD) for hydrogen peroxide was 162 nM.

[0013] Based on the obvious color change from blue to yellow-green that occurs after adding hydrogen peroxide (HP), this invention further develops a smartphone-based POCT platform for the visual monitoring of HP; specifically: After CDs / QDs@ZIF-8 were reacted with different concentrations of HP, the color of the solution was captured by a smartphone under 365 nm ultraviolet light excitation, and the RGB values ​​were extracted from the photos using color scanning software. The ratio of G value to B value (G / B) was used as the HP detection signal. There was a good linear relationship between G / B and HP concentration, and the detection limit was 295 nM.

[0014] The technical principles of this invention include: This invention, based on the structural designability of MOFs and the luminescent properties of CDs and QDs, focuses on the synergistic mechanism of host-guest materials and interface modulation strategies. By introducing a dual-emission probe system, combining analyte-dependent fluorescence signals with internal standard fluorescence signals, a novel luminescent MOF material was designed and synthesized. The main method involves self-assembling CDs and CdTeQDs within a ZIF-8 framework to construct a dual-emission ratiometric fluorescence sensor, which is then used to determine HP (e.g., ...). Figure 1 (As shown).

[0015] This dual-emission fluorescent probe system involves a combination of blue-emitting CDs and red-emitting CdTeQDs. The CDs serve as internal standard fluorophores, while TGA-terminated CdTeQDs act as responsive fluorophores. Furthermore, by controlling the pore size of the ZIF-8 shell to allow only HP to pass through, the selectivity of the sensor is significantly improved. The pore confinement effect of ZIF-8 also prevents the aggregation or precipitation of CDs and CdTeQDs. Adding HP to the mixed probe solution induces depassivation of CdTeQDs, thereby reducing the red emission intensity, while the fluorescence intensity of the blue-emitting CDs remains unchanged. This dual-emission ratiometric fluorescent probe construction strategy provides a new approach for high-sensitivity detection of HP.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention constructs a dual-emission, single-signal response ratiometric fluorescence sensor and applies it to high-sensitivity detection in HP sensors. The main innovation lies in the fact that this ratiometric fluorescence sensor has a dual-channel "signal-reference" function. Compared to traditional single-emission or physically hybrid sensors, this invention achieves precise spatial isolation of the two fluorophores through the confinement effect of ZIF-8, avoiding energy crosstalk and providing a multi-component co-encapsulation paradigm for HP sensing.

[0017] Meanwhile, by precisely controlling the crystal structure of MOFs, selective permeation of HP molecules can be achieved, while shielding irrelevant interfering substances, thus improving the selectivity coefficient of the sensor by 2 to 3 orders of magnitude. The nanoconfinement effect of MOFs can fix QDs within rigid channels, effectively suppressing their surface oxidation and photoinduced electron-hole recombination, thereby maintaining the photostability of the probe.

[0018] The CDs / QDs@ZIF-8 of this invention exhibit excellent selectivity and sensitivity for the detection of HP, showing good linearity (R2=0.9946) in the concentration range of 0~120 μM, with a detection limit of 162 nM. Attached Figure Description

[0019] Figure 1 Schematic diagram of the preparation of CDs / QDs@ZIF-8 and their use in detecting HP.

[0020] Figure 2 Examples 1-15 show the fluorescence response time of the CDs / QDs@ZIF-8 sensor for detecting HP (A); and the effect of different pH values ​​on the fluorescence intensity of the CDs / QDs@ZIF-8 sensor (B).

[0021] Figure 3 In Example 16, the fluorescence emission spectra (A) of the CDs / QDs@ZIF-8 ratiometric fluorescence sensing platform in the presence of different concentrations of HP (0~120 μM); I675 / I 440 Relationship with corresponding HP concentration (B).

[0022] Figure 4 Example 17: A graph showing the variation of the fluorescence intensity ratio of the CDs / QDs@ZIF-8 sensor in the presence of different substances.

[0023] Figure 5 Example 17: The graph showing the change in fluorescence intensity ratio of the CDs / QDs@ZIF-8 sensor under the coexistence of HP and different substances. Detailed Implementation

[0024] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0025] In the following embodiments, Synthesis of carbon dots (CDs): Citric acid (0.7685 g, 4 mmol) and thiourea (1.522 g, 20 mmol) were dissolved in 20 mL of deionized water, sonicated, and then transferred to a hydrothermal reactor and heated at 160 °C for 6 h. Carbon dot powder was obtained after filtration and drying.

[0026] Synthesis of quantum dot (QDs): 0.1333 g of cadmium acetate dihydrate and 140 μL of mercaptoacetic acid were dissolved in 40 mL of deionized water, stirred, and the pH was adjusted to 11. Then, 0.0254 g of potassium tellurite and 0.0378 g of sodium borohydride were added to the solution, stirred until homogeneous, and then placed in a polytetrafluoroethylene-lined reactor. The reaction was continued at 120 °C for 6 h. After washing and drying, TGA-terminated CdTeQDs were obtained.

[0027] Preparation of dual-emission CDs / QDs@ZIF-8 ratiometric fluorescence sensor: 2-methylimidazole (0.821 g, 10.0 mmol) was completely dissolved in 30 mL of anhydrous methanol, 2 mg CDs and 8 mg TGA-terminated CdTe QDs were added, and 10 mL of 0.1 mol / L Zn(NO3)2·6H2O methanol solution was added. After thorough mixing, the mixture was reacted at room temperature (25 °C) for 2 h. The resulting suspension was centrifuged, washed with anhydrous methanol to remove unreacted residues, and finally dried to obtain the CDs / QDs@ZIF-8 ratiometric fluorescence sensor.

[0028] The CDs / QDs@ZIF-8 ratiometric fluorescence sensor was tested at 25℃. The excitation wavelength of the fluorescence spectrophotometer was set to 370 nm for fluorescence emission spectroscopy detection. The excitation and emission slit widths were set to 5–10 nm. The fluorescence intensities at 675 nm and 440 nm were recorded, and Ig was calculated.675 / I 440 Fluorescence intensity ratio is used as a detection parameter.

[0029] Examples 1-8: The prepared CDs / QDs@ZIF-8 material was dispersed in PBS buffer (50 mM, pH 7.4). 200 μL of 0.2 mg / mL CDs / QDs@ZIF-8 probe solution was added to hydrogen peroxide solution (final HP concentration 60 μM). The reaction was carried out at 25 °C for 0, 2, 4, 6, 8, 10, 12, and 14 min, respectively. The fluorescence emission intensity at 675 nm and 440 nm under 370 nm excitation was recorded using a fluorescence spectrophotometer. Finally, the Ig at different reaction times was obtained. 675 / I 440 The value of can be used to obtain the monitored reaction time, and the result is as follows: Figure 2 As shown in Figure A.

[0030] Examples 9-15: The prepared CDs / QDs@ZIF-8 material was dispersed in PBS buffer (50 mM, pH 7.4). 200 μL of 0.2 mg / mL CDs / QDs@ZIF-8 probe solution was added to hydrogen peroxide solution (final HP concentration 60 μM). The reaction was carried out at 25 ℃ for 8 min, and the pH values ​​of the solution were adjusted to 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, and 9.0. The fluorescence emission intensity at 675 nm and 440 nm under 370 nm excitation was recorded using a fluorescence spectrophotometer. Finally, the I emission intensity at different pH values ​​was obtained. 675 / I 440 The value of the pH value is used to determine the optimal pH for detection, such as... Figure 2 As shown in B.

[0031] Example 16: At 25 °C, CDs / QDs@ZIF-8 were added to PBS buffer (50 mM, pH 7.4). Then, 100 μL of HP solution was added to 200 μL of 2 mg / mL CDs / QDs@ZIF-8 probe solution to prepare a series of mixed solutions (final HP concentrations of 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, and 120 μM). After incubation at room temperature (25 °C) for 8 min, the samples were placed in quartz cuvettes with a 10 mm optical path length, and fluorescence was measured using a fluorescence spectrophotometer. The excitation wavelength was 370 nm, and the excitation and emission slit widths were both 10 nm. The ratio of fluorescence intensity at 675 nm to that at 440 nm (I0) was recorded.675 / I 440 ) to perform quantitative analysis.

[0032] The results are as follows Figure 3 As shown, the intensity of the red emission peak of CdTe QDs at 675 nm gradually decreases with increasing HP concentration, while the intensity of the blue fluorescence peak of CDs at 440 nm remains essentially unchanged, achieving a good linear range of 0–120 μM. The detection limit of HP is 162 nM. Compared with other HP detection technologies, the CDs / QDs@ZIF-8 ratiometric fluorescence sensing platform provides a lower detection limit and a wider linear concentration range.

[0033] Example 17: To evaluate whether the dual emission ratio fluorescence sensor of the present invention can achieve specific detection of HP, and the influence of external interference on fluorescence sensing, specificity and interference experiments were conducted.

[0034] Interfering substances include common reactive oxygen species (O2). - NO, ·OH, ·OtBu, ClO - ), metal ions and anions (K) + Ca 2+ Na + Mg 2+ Al 3+ Mn 2+ Cl - NO3 - CO3 2- SO4 2- The concentrations of the interfering substances were 400 μM and the concentration of HP was 100 μM. The amino acids (L-Lys, L-Cys, L-Asp, GSH, Glu, Urea) were also present.

[0035] The aforementioned interfering substance was added to the detection system instead of heparin (HP), and the fluorescence intensity of the system was measured. Three parallel replicates were performed. The solution without the interfering substance and HP was used as a blank control group for the specificity experiment. The results are as follows: Figure 4 and Figure 5 As shown in the figure. It can be seen that after the above interfering substances are added to the CDs / QDs@ZIF-8 solution, their dual emission fluorescence ratio (IL) is significantly reduced. 675 / I 440 The ratio remained almost unchanged, but after the addition of HP, the ratio changed more significantly, indicating that CDs / QDs@ZIF-8 has good selectivity and anti-interference ability for the detection of HP.

[0036] Example 18: Leveraging the excellent resolution and high stability of the ratiometric fluorescence sensor CDs / QDs@ZIF-8, a visualization detection platform for hydrogen peroxide (HP) detection was developed. It was observed that after CDs / QDs@ZIF-8 reacts with 0-500 μM hydrogen peroxide, a clear color change from blue and yellow-green to green can be observed under 365 nm UV excitation. Photos were taken with an iPhone 16 smartphone, and RGB values ​​were extracted from the photos using color scanning software. The G / B ratio can be used as the readout signal for HP detection, and a good linear relationship exists between G / B and HP concentration, with a detection limit of 295 nM. This indicates that the CDs / QDs@ZIF-8 ratiometric fluorescence sensor developed in this invention can be used for the visual detection of hydrogen peroxide.

Claims

1. A dual-emission CDs / QDs@ZIF-8 ratiometric fluorescence sensor, characterized in that, It is prepared according to the following method: (1) Blue light nitrogen-sulfur co-doped carbon dots were synthesized by hydrothermal method using citric acid as carbon source and thiourea as nitrogen-sulfur source; (2) Using cadmium acetate dihydrate and potassium tellurite as raw materials, CdTe quantum dots capped with mercaptoacetic acid were synthesized in the presence of mercaptoacetic acid and sodium borohydride; (3) By using the "in-situ growth method", the blue light nitrogen-sulfur co-doped carbon dots obtained in step (1) and the CdTe quantum dots capped with mercaptoacetic acid obtained in step (2) are encapsulated together in ZIF-8 to construct a dual-emission CDs / QDs@ZIF-8 ratio fluorescence sensor.

2. The dual-emission CDs / QDs@ZIF-8 ratiometric fluorescence sensor as described in claim 1, characterized in that, Step (1) is as follows: Dissolve citric acid and thiourea in deionized water, mix them by ultrasonication, transfer them to a hydrothermal reactor, react them at 100~200 ℃ for 3~8 h, then filter and dry to obtain carbon dots; The molar ratio of citric acid to thiourea is 1~10:10~20.

3. The dual-emission CDs / QDs@ZIF-8 ratiometric fluorescence sensor as described in claim 1, characterized in that, Step (2) is as follows: Dissolve cadmium acetate dihydrate and mercaptoacetic acid in deionized water, adjust pH to 8.0~13.0, add potassium tellurite and sodium borohydride, stir evenly, and place the reaction solution in a polytetrafluoroethylene-lined reactor. React at 100~140 ℃ for 4~8 h. After washing and drying, TGA-terminated CdTeQDs are obtained. The mass ratio of cadmium acetate dihydrate to potassium tellurite is 0.1~0.5:0.02~0.05; The ratio of cadmium acetate dihydrate, mercaptoacetic acid, and sodium borohydride is 0.1~0.5 g: 140~750 μL: 0.01~0.08 g.

4. The dual-emission CDs / QDs@ZIF-8 ratiometric fluorescence sensor as described in claim 1, characterized in that, Step (3) is as follows: 2-methylimidazole is dissolved in anhydrous methanol, and the blue light nitrogen-sulfur co-doped carbon dots obtained in step (1) and the CdTe quantum dots capped with mercaptoacetic acid obtained in step (2) are added. Anhydrous methanol solution of Zn(NO3)2·6H2O is added, mixed evenly, and reacted at room temperature for 1~3 h. After centrifugation, washing and drying, a dual-emission CDs / QDs@ZIF-8 ratio fluorescence sensor is obtained. The molar ratio of Zn(NO3)2·6H2O to 2-methylimidazole is 1:10; The ratio of Zn(NO3)2·6H2O, blue light nitrogen-sulfur co-doped carbon dots, and mercaptoacetic acid-capped CdTe quantum dots was 1 mmol: 1~4 mg: 4~8 mg.

5. The application of the dual-emission CDs / QDs@ZIF-8 ratio fluorescence sensor as described in claim 1 in the detection of hydrogen peroxide.

6. The application as described in claim 5, characterized in that, Application methods include: At room temperature, CDs / QDs@ZIF-8 were uniformly dispersed in 50 mM PBS buffer (pH 7.4). Different concentrations of hydrogen peroxide solution were added, and after the mixture stabilized for 1–10 min, fluorescence emission spectra were detected using a fluorescence spectrophotometer at an excitation wavelength of 370 nm. The excitation and emission slit widths were set to 5–10 nm, and the fluorescence emission intensities at 675 nm and 440 nm under 370 nm excitation were recorded. The fluorescence intensity ratio I was used to analyze the fluorescence emission intensity. 675 / I 440 A working curve was constructed to demonstrate the linear correlation between hydrogen peroxide concentration and the concentration. The concentration range of hydrogen peroxide in the mixed system is 0~120 μM.

7. A POCT platform for visual monitoring of hydrogen peroxide, characterized in that, Build it as follows: After reacting the dual-emission CDs / QDs@ZIF-8 ratiometric fluorescence sensor of claim 1 with hydrogen peroxide of different concentrations, the solution color was captured by a smartphone under 365 nm ultraviolet light excitation, showing the gradual change from blue and yellow-green to green. The RGB values ​​were extracted from the photos using color scanning software, and the ratio of the G value to the B value was used as the hydrogen peroxide detection signal.

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