Preparation method and application of fluorescent filter membrane sensor for visual Cu < 2 + > detection

Abstract

The invention discloses a preparation method and application of a fluorescent filter membrane sensor for visual Cu < 2 + > detection, and the preparation method comprises the following steps: respectively weighing phthalic acid and o-phenylenediamine, mixing, adding deionized water, carrying out ultrasonic pretreatment, and synchronously adding phosphoric acid; transferring the mixed system into a lining of a reaction kettle, and carrying out heating reaction; and after the reaction, cooling, collecting the centrifuged supernatant, and filtering to obtain the crude mother liquor of the carbon dots. And dialyzing the crude mother liquor to obtain carbon dot mother liquor (marked as N-P-CDs). And diluting the N-P-CDs solution, dripping the diluted N-P-CDs solution onto a filter membrane, standing, dripping a copper ion solution, placing under a 365 nm ultraviolet lamp, and observing the change of the fluorescence color on the filter membrane. The operation is simple.

Description

Technical Field

[0001] This invention relates to the technical field of heavy metal detection, and in particular to a visual Cu... 2+ Preparation method and application of fluorescence filter membrane sensor for detection. Background Technology

[0002] Copper is a common heavy metal pollutant. Industrial wastewater discharge and mining activities can introduce large amounts of copper ions into water bodies. Excessive copper ions can be toxic to aquatic organisms and disrupt the balance of aquatic ecosystems. For example, high concentrations of copper ions can inhibit algal photosynthesis, reduce oxygen production in the water, and affect the survival of fish and other aquatic animals. Detecting the concentration of copper ions in water bodies allows for the timely detection of water pollution, providing a basis for environmental governance and protection.

[0003] Methods for detecting copper ions include chemical analysis, colorimetry, instrumental analysis, electrochemical analysis, and fluorescence analysis. Fluorescence analysis offers several advantages: high sensitivity and selectivity (by designing and synthesizing fluorescent probes with specific structures and functions, selective recognition of copper ions can be achieved, reducing interference from other coexisting ions); simple and rapid operation (generally, only mixing the fluorescent probe with the sample and then measuring the fluorescence is required, eliminating the need for complex separation and pretreatment steps, and providing results in a short time); and real-time, in-situ detection (through the design of suitable fluorescent probes and detection devices, real-time, in-situ detection of copper ions is a significant advantage).

[0004] Carbon dots possess excellent fluorescence properties, allowing them to function as fluorescent probes that respond to specific chemical substances, thus enabling their use in the fabrication of chemical sensors. For instance, by leveraging the selective recognition of metal ions and biomolecules by carbon dots, rapid and sensitive detection of environmental pollutants and biomarkers can be achieved.

[0005] Compared to traditional organic fluorescent dyes, carbon dots exhibit better photostability and chemical stability. They maintain strong fluorescence intensity even under prolonged light exposure or harsh chemical environments, and are not prone to photobleaching or chemical degradation, thus ensuring their long-term stability in practical applications.

[0006] In view of this, the inventor of this case conducted in-depth research, which led to the creation of this case. Summary of the Invention

[0007] The purpose of this invention is to provide a method for quickly, sensitively, and stably visualizing Cu. 2+ Preparation method and application of fluorescence filter membrane sensor for detection.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: A visual Cu 2+ The method for preparing the fluorescence filter membrane sensor includes the following steps: Step 1: Weigh out phthalic acid and o-phenylenediamine, mix them, add deionized water for ultrasonic pretreatment, and simultaneously add phosphoric acid to obtain a mixed system. The molar ratio of phthalic acid to o-phenylenediamine is 1:3~3.1. The mixture was transferred to a polytetrafluoroethylene high-pressure reactor liner and then heated at 170-190℃ for 5-7 hours to carry out the reaction. After the reaction was terminated, the reactor was cooled and the reactants were centrifuged at 8000 r / min using a high-speed centrifuge. The supernatant after centrifugation was collected and filtered through a 0.22 μm pore size filter membrane to obtain the carbon dot crude mother liquor. The crude carbon dot mother liquor was placed in an activated dialysis bag and dialyzed for 12 hours, with deionized water replaced every 4 hours. The solution obtained after dialysis was the carbon dot mother liquor, labeled as NP-CDs. Step 2: Dilute the NP-CDs solution 25 times and then drop 100 μL onto the filter membrane. After drying naturally at room temperature, the fluorescent filter membrane sensor is obtained.

[0009] Furthermore, in step 1, the amount of phosphoric acid is between 0.8 and 1.2 mL.

[0010] Furthermore, in step 2, the natural drying time at room temperature is 30 minutes or more.

[0011] Furthermore, in step 1, the amount of deionized water added to the mixing system is 15 mL, and the ultrasonic pretreatment time is 10 minutes.

[0012] A visual Cu 2+ Applications of fluorescence filter membrane sensors for detection, Cu 2+ The detection procedure is as follows: 80-150 μL of copper ion solution with a concentration of less than 400 μM is dropped onto the fluorescent filter membrane sensor. After standing until there are no water droplets on the filter membrane, it is placed under a 365 nm ultraviolet lamp to observe the fluorescence color on the filter membrane.

[0013] Furthermore, the copper ion solution is a copper sulfate solution. First, prepare five fluorescent filter membrane sensors, and add 100 μL of copper sulfate solution with concentrations of 25, 50, 100, 200, and 400 μM respectively to each sensor. Let them stand until there are no water droplets on the filter membrane, and place them under a 365 nm ultraviolet lamp to observe the changes in fluorescence color on the filter membrane corresponding to different copper sulfate solutions, so as to obtain color reference standards corresponding to different concentrations of copper ions. Then, the sample to be tested is dropped onto the fluorescent filter membrane sensor, left to stand until there are no water droplets on the filter membrane, and placed under a 365 nm ultraviolet lamp. The copper ion concentration of the sample to be tested is obtained according to the fluorescence color reference standard.

[0014] After adopting the above technical solution, the present invention provides a visualization of Cu 2+ The method for preparing the fluorescent filter membrane sensor has the following advantages: it has the significant advantages of widely available raw materials and simple operation; it does not require instruments, and the concentration of copper ions can be directly determined by observing the color change of the filter membrane; and it can achieve rapid, sensitive, and stable detection. Attached Figure Description

[0015] Figure 1 XRD powder diffraction pattern of NP-CDs; Figure 2 Fourier transform infrared images of NP-CDs; Figure 3 The image shows the UV-Vis spectrum of NP-CDs. Figure 4 Fluorescence spectra of NP-CDs at different excitation wavelengths; Figure 5 The effect of different metal ions on the fluorescence intensity of NP-CDs; Figure 6 The effect of different concentrations of copper sulfate on the fluorescence intensity of NP-CDs and its relationship with F0 / F; Figure 7 NP-CDs-Cu 2+ Anti-interference analysis diagram; Figure 8 This is a graph showing the fluorescence color change of the NP-CDs filter membrane sensor in the concentration range of 0-400 μM. Detailed Implementation

[0016] To further explain the technical solution of the present invention, the present invention will be described in detail below through specific embodiments.

[0017] I. Preparation Example 1 A visual Cu 2+ The method for preparing the fluorescence filter membrane sensor includes the following steps: Step 1: Weigh 0.25g of phthalic acid and 0.5g of o-phenylenediamine and mix them (the molar ratio of phthalic acid to o-phenylenediamine is 1:3.07). Add 15mL of deionized water and place the mixture in an ultrasonic cleaner for ultrasonic pretreatment for 10min. Simultaneously add 1mL of phosphoric acid. The resulting mixture is transferred to a 20mL polytetrafluoroethylene high-pressure reactor liner. The reactor is then heated at 180℃ for 6h in a temperature-controlled drying oven. After the reaction is terminated, the reactor is allowed to stand at room temperature and allowed to cool naturally. Then, it is centrifuged at 8000 r / min for 20min. The supernatant is collected and filtered through a 0.22μm filter membrane to obtain the crude carbon dot mother liquor.

[0018] The crude mother liquor was placed in an activated dialysis bag and dialyzed for 12 hours, with the deionized water changed every 4 hours. The solution obtained after dialysis is the carbon dot mother liquor (labeled as NP-CDs).

[0019] Step 2: Dilute the NP-CDs solution 25 times and drop 100 μL onto the filter membrane. Allow it to air dry at room temperature for 30 minutes to obtain the fluorescent filter membrane sensor.

[0020] The application of a fluorescence filter membrane sensor further includes the following steps: Step 3: Take five fluorescent filter membrane sensors. Add 100 μL of copper sulfate solution with concentrations of 25, 50, 100, 200, and 400 μM respectively to each sensor. Specifically, add 100 μL of 25 μM copper sulfate solution to the first sensor, 100 μL of 50 μM copper sulfate solution to the second, 100 μL of 100 μM copper sulfate solution to the third, 100 μL of 200 μM copper sulfate solution to the fourth, and 100 μL of 400 μM copper sulfate solution to the fifth. Let stand for 30 minutes until no water droplets remain on the filter membrane. Place under a 365 nm UV lamp and observe the fluorescence color on the filter membrane (see...). Figure 8 ), to obtain color reference standards corresponding to different concentrations of copper ions.

[0021] Then, the sample to be tested is dropped onto the fluorescent filter membrane sensor, left to stand until there are no water droplets on the filter membrane, and placed under a 365 nm ultraviolet lamp. The copper ion concentration of the sample to be tested is obtained according to the fluorescence color reference standard.

[0022] Example 2 A visual Cu 2+ The method for preparing the fluorescence filter membrane sensor includes the following steps: Step 1: Weigh 0.25g of phthalic acid and 0.5g of o-phenylenediamine, mix them, add 15mL of deionized water, and place the mixture in an ultrasonic cleaner for ultrasonic pretreatment for 10min. Simultaneously add 1.1mL of phosphoric acid to obtain a mixed system. Transfer the mixed system to a 20mL polytetrafluoroethylene high-pressure reactor liner, and then heat it at 180℃ for 6h in a programmable temperature-controlled drying oven to carry out the reaction. After the reaction is terminated, allow the reactor to cool naturally at room temperature, and then centrifuge it at 8000r / min for 20min. Collect the supernatant after centrifugation, and filter the supernatant through a 0.22μm filter membrane to obtain the crude carbon dot mother liquor.

[0023] The crude mother liquor was placed in an activated dialysis bag and dialyzed for 12 hours, with the deionized water changed every 4 hours. The solution obtained after dialysis is the carbon dot mother liquor (labeled as NP-CDs).

[0024] Step 2: Dilute the NP-CDs solution 25 times and drop 100 μL onto the filter membrane. Allow it to air dry at room temperature for 30 minutes to obtain the fluorescent filter membrane sensor.

[0025] An application of a fluorescent filter membrane sensor includes the following steps: Step 3: Add 100 μL of 100 μM copper sulfate solution to the fluorescent filter membrane sensor and let it stand for 30 minutes until no water droplets remain on the filter membrane. Place it under a 365 nm UV lamp and observe the fluorescence color on the filter membrane. (See...) Figure 8 Obtain color reference standards corresponding to different concentrations of copper ions.

[0026] Then, the sample to be tested is dropped onto the fluorescent filter membrane sensor, left to stand until there are no water droplets on the filter membrane, and placed under a 365 nm ultraviolet lamp. The copper ion concentration of the sample to be tested is obtained according to the fluorescence color reference standard.

[0027] II. Structural Characterization and Analysis of NP-CDs 1. Powder diffraction of the NP-CDs prepared in Example 1 is as follows: Figure 1 As shown in the figure, a diffraction peak appears between 20-30°, corresponding to the (002) crystal plane of the disordered graphite-like structure in the carbon material. Within this peak range, especially around 2θ=20°, a relatively sharp diffraction peak appears. This may be because when the carbon particles are relatively uniform in size, i.e., the particles are similar in size, the scattering behavior of similarly sized particles towards X-rays is highly consistent during X-ray diffraction, allowing the diffraction signal to be more concentrated at specific angles, thus resulting in a sharp diffraction peak.

[0028] 2. The Fourier transform infrared image of the NP-CDs prepared in Example 1 is shown below. Figure 2 As shown in the figure, at 2929cm-1 1700cm -1 1640cm -1 1050cm -1 There is wavenumber absorption, with the absorption peak at 2929 cm⁻¹ belonging to the CH stretching vibration peak of the carbon point. At 1640 cm⁻¹... -1 The peak value in the region is attributed to the -C=C- stretching vibration zone, at 1700cm. -1 The peak value in the region is attributed to the C=O stretching vibration zone, at 1400 cm. -1 The absorption peak that appears nearby is COO - The vibrational peaks of the CN group confirm that nitrogen is incorporated into the carbon lattice in the form of graphitic nitrogen, at 1050 cm⁻¹. -1 The vicinity shows CO stretching vibration peaks, and infrared spectroscopy indicates that the surface of NP-CDs may contain CH, -C=C-, C=O, CN, and -COO. - Functional groups.

[0029] 3. The UV-Vis spectrum of the NP-CDs prepared in Example 1 is shown below. Figure 3 As shown in the figure, the NP-CDs solution appears pale yellow in white light transmission mode. Under 365 nm UV excitation, the NP-CDs solution exhibits pale blue fluorescence. Strong absorption peaks are observed in the 200-350 nm wavelength range of NP-CDs, which is due to the π→π* transitions in NP-CDs. The absorption peak near 230 nm may be due to the C=C π→π* transition, and the absorption peak near 280 nm may be due to the C=O π→π* transition. 4. The fluorescence spectrum of the NP-CDs prepared in Example 1 is shown below. Figure 4 As shown in the figure, increasing the excitation wavelength of NP-CDs from 280 nm to 400 nm did not result in a significant wavelength shift in the fluorescence emission peak, indicating low dependence on the excitation wavelength. This suggests that NP-CDs fluorescence exhibits low wavelength dependence, and its emission spectrum is relatively stable, remaining largely unchanged with variations in the excitation wavelength. This means that regardless of the excitation wavelength used, it can stably emit fluorescence at a specific wavelength, demonstrating good fluorescence stability and repeatability. Therefore, it is suitable for fabricating filter membrane sensors.

[0030] 5. Figure 5 The effect of different metal ions on the fluorescence intensity of NP-CDs prepared in Example 1 is shown in Figure 5. This clearly demonstrates the influence of Cu on the fluorescence intensity. 2+ It exhibits a specific fluorescence quenching effect on NP-CDs. At the same concentration, Cu... 2+ Theoretically, the fluorescence quenching rate of CDs can reach 96%.

[0031] 6. Figure 6 The effect of different concentrations of copper sulfate on the fluorescence intensity of NP-CDs and its relationship with F0 / F.

[0032] a can be seen that when Cu 2+ When the concentration increases in the range of 0 to 192.46 μmol / L, the fluorescence intensity of NP-CQDs decreases.

[0033] b indicates that within the concentration range of 0-200 μmol / L, there is a non-linear relationship between copper sulfate concentration and the fluorescence intensity ratio F0 / F of NP-CDQs. Only within the concentration range of 50-200 μmol / L does the fluorescence intensity ratio F0 / F show a highly linear positive correlation with its concentration (R0). 2 =0.9953).

[0034] 7. Figure 7 NP-CDs-Cu 2+ Anti-interference analysis diagram, this diagram mainly examines various metal ions (including Mg). 2 + Mn 2+ Na + Ni 2+ Fe 3+ Zn 2+ Fe 2+ ) and anions (such as PO4) 3- S2O3 2- Cl - CO3 2- SO3 2- NO2 - CH3COO - ) and Cu 2+ The effect of coexistence on the fluorescence intensity of the N-P-CDs quenching system. The results clearly show that when Cu... 2+ When Cu coexists with these competing ions, 2+ The -N-P-CDs quenching system can meet the requirements of heavy metal detection in terms of anti-interference.

[0035] 8. Figure 8 The fluorescence color changes of the N-P-CDs filter membrane sensor within the concentration range of 0-400 μM are shown. It is clearly observed that this filter membrane sensor exhibits concentration-dependent colorimetric characteristics. With Cu... 2+ As the concentration gradually increases, the filter membrane sensor produces a color gradation change that can be directly discerned by the naked eye. This significant characteristic strongly demonstrates the sensor's potential for visual detection without the need for sophisticated instruments.

[0036] The above embodiments and accompanying drawings are not intended to limit the product form and style of the present invention. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of the present invention.

Claims

1. A visualization of Cu 2+ The method for preparing the fluorescence filter membrane sensor includes the following steps: Step 1: Weigh out phthalic acid and o-phenylenediamine, mix them, add deionized water for ultrasonic pretreatment, and simultaneously add phosphoric acid to obtain a mixed system. The molar ratio of phthalic acid to o-phenylenediamine is 1:3~3.

1. The mixture was transferred to a polytetrafluoroethylene high-pressure reactor liner and then heated at 170-190℃ for 5-7 hours to carry out the reaction. After the reaction was terminated, the reactor was cooled and the reactants were centrifuged at 8000 r / min using a high-speed centrifuge. The supernatant after centrifugation was collected and filtered through a filter membrane with a pore size of 0.22 μm to obtain the carbon dot crude mother liquor. The crude carbon dot mother liquor was placed in an activated dialysis bag and dialyzed for 12 hours, with deionized water replaced every 4 hours. The solution obtained after dialysis was the carbon dot mother liquor, labeled as NP-CDs. Step 2: Dilute the NP-CDs solution 25 times and then drop 100 μL onto the filter membrane. After drying naturally at room temperature, the fluorescent filter membrane sensor is obtained.

2. A visualization Cu according to claim 1 2+ The method for preparing a fluorescence filter membrane sensor for detection is characterized by: In step 1, the amount of phosphoric acid is between 0.8 and 1.2 mL.

3. A visualization of Cu according to claim 1 2+ The method for preparing a fluorescence filter membrane sensor for detection is characterized by: In step 2, the air-drying time at room temperature is 30 minutes or more.

4. A visualization Cu as described in claim 1 2+ The method for preparing a fluorescence filter membrane sensor for detection is characterized by: In step 1, the amount of deionized water added to the mixing system is 15 mL, and the ultrasonic pretreatment time is 10 minutes.

5. A visualization Cu according to claims 1-4 2+ The application of the fluorescence filter membrane sensor for detection is characterized by, Cu 2+ The detection procedure is as follows: 80-150 μL of copper ion solution with a concentration of less than 400 μM is dropped onto the fluorescent filter membrane sensor. After standing until there are no water droplets on the filter membrane, it is placed under a 365 nm ultraviolet lamp to observe the fluorescence color on the filter membrane.

6. A visualization of Cu according to claim 5 2+ The application of the fluorescence filter membrane sensor for detection is characterized by: The copper ion solution is a copper sulfate solution. First, prepare five fluorescent filter membrane sensors and add 100 μL of copper sulfate solution with concentrations of 25, 50, 100, 200, and 400 μM respectively. Let them stand until there are no water droplets on the filter membrane, place them under a 365 nm ultraviolet lamp, and observe the changes in fluorescence color on the filter membrane corresponding to different copper sulfate solutions to obtain color reference standards corresponding to different concentrations of copper ions. Then, the sample to be tested is dropped onto the fluorescent filter membrane sensor, left to stand until there are no water droplets on the filter membrane, and placed under a 365 nm ultraviolet lamp. The copper ion concentration of the sample to be tested is obtained according to the fluorescence color reference standard.

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