A fiber membrane capable of repeatedly and sensitively detecting hypochlorite and a preparation method thereof

Abstract

The application provides a preparation method of a fiber membrane capable of repeatedly and highly sensitively detecting hypochlorite, comprising the following steps: (1) taking anemone and rape straw, heating at 180-200 DEG C, then centrifuging to obtain supernatant; mixing the supernatant with a polyvinylpyrrolidone aqueous solution, stirring, then performing membrane dialysis and drying; (2) placing the obtained material in step (1), nano-silicon dioxide, nano-titanium dioxide and polymethyl methacrylate in dimethylformamide; then using an electrospinning method to prepare an electrospun fiber membrane. The fiber membrane has high sensitivity when detecting hypochlorite, and the minimum detection limit is as low as 0.15 nM; the fiber membrane uses plants as raw materials, is low in cost, green and environment-friendly, can be repeatedly used after being cleaned and dried, and still has excellent detection performance after being used for at least 10 cycles.

Description

Technical Field

[0001] This invention pertains to the detection of hypochlorite in the field of environmental monitoring, specifically relating to a fiber membrane capable of repeatable and highly sensitive detection of hypochlorite and its preparation method. Background Technology

[0002] Detection of HClO / ClO － Traditional methods for spectroscopy include iodine reduction titration, electrochemical methods, chemiluminescence, and ion chromatography. Compared to traditional methods, spectroscopic methods do not require large instruments or complex operating procedures, and are increasingly favored by industry professionals.

[0003] Fluorescent carbon quantum dots are an important material in spectroscopic detection technology and have been successfully applied in fields such as environmental monitoring, cell and in vivo imaging. In environmental monitoring, fluorescent carbon quantum dots, as fluorescent probes, have been used to detect Hg. 2+ Cu 2+ Ag + ,ClO － Detection of biothiols and proteins.

[0004] However, the current application of fluorescent carbon quantum dots in environmental detection still has the following shortcomings: (1) Carbon quantum dots are prone to agglomeration, making the obtained fluorescent probes unstable; (2) Whether they have fluorescence depends highly on the choice of carbon source and preparation method. Methods such as acid oxidation, microwave method, arc discharge or laser etching usually have high equipment requirements and complex preparation methods; although the hydrothermal method is relatively simple, except for using ascorbic acid, citric acid or other carbon sources as carbon sources to obtain fluorescent carbon quantum dots relatively stably, it is usually difficult to obtain carbon quantum dots with corresponding fluorescence when using plants or their processing waste as raw materials; (3) Poor repeatability, usually only one or a few times; (4) Insufficient sensitivity.

[0005] Invention patent CN 109991200 B utilizes polyethyleneimine-modified ascorbic acid to prepare carbon quantum dots, achieving the detection of hypochlorous acid with a detection limit of 14 nM. Following the same approach, Yin Jianxing et al., in their paper "Preparation of Polymer-Coated Cadmium Sulfide Quantum Dots and Their Application in Hypochlorite Detection" (DOI: 10.16039 / j.cnki.cn22-1249.2020.05.003), prepared cadmium sulfide quantum dots for hypochlorite detection, lowering the detection limit to 0.5 nM. However, ascorbic acid, as a chemical substance, is not a green method for preparing carbon quantum dots. Regarding green preparation technologies for carbon quantum dots, Lu et al. synthesized carbon quantum dots using grapefruit peel and achieved the detection of Hg. 2+For the detection of hypochlorite, Sahu et al. prepared high-intensity fluorescent carbon quantum dots using orange juice (DOI: 10.1039 / c2cc33796g). However, carbon quantum dots prepared by green methods (i.e., based on plants or their processed products) typically have a detection limit below 10 nM when detecting hypochlorite, which limits the application of this type of method in the preparation of hypochlorite detection probes.

[0006] Another important issue is that existing carbon quantum dot probes lack repeatability during detection, making them difficult to reuse and hindering cost reduction.

[0007] Therefore, selecting suitable plants or their processed products as carbon sources to prepare fluorescent carbon quantum dots, and preparing products based on these carbon quantum dots that have low detection limits and reusability when detecting hypochlorite, is a problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To address the shortcomings of existing technologies, one objective of this invention is to provide a method for preparing a repeatable and highly sensitive fiber membrane for detecting hypochlorite. The fiber membrane obtained by this method solves the problem of excessively high detection limits for hypochlorite when using plants as a carbon source to prepare carbon quantum dots in existing technologies; it also addresses the difficulty in achieving reusability in existing technologies.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing a fiber membrane for repeatable and highly sensitive detection of hypochlorite ions, the method comprising the following steps:

[0011] (1) Take Reed and rapeseed straw at a weight ratio of 5:1, crush them, heat them at 180-200℃ for 6-8 hours, then centrifuge to obtain the supernatant; mix the supernatant with a 1.0-1.5wt% polyvinylpyrrolidone aqueous solution, stir and react for 4-5 hours, then perform membrane dialysis, and freeze-dry the dialysate;

[0012] (2) The product obtained in step (1), nano silica, nano titanium dioxide and polymethyl methacrylate are placed in dimethylformamide, and the weight fraction of the solute is 5-6%; then an electrospun fiber membrane is prepared by electrospinning, and then the residual solvent dimethylformamide in the electrospun fiber membrane is dried to obtain the product; wherein, the weight ratio of the product obtained in step (1), nano silica, nano titanium dioxide and polymethyl methacrylate is 8:2:1:25-30.

[0013] *Achnatherum gracile*, a plant belonging to the genus *Achnatherum* of the Poaceae family, is distributed in the northwest and northeast provinces of China, as well as Inner Mongolia, Shanxi, and Hebei. *Achnatherum gracile* has a strong reproductive capacity and is commonly used as livestock feed or for weaving. To the best of our knowledge, prior to this application, no one had used *Achnatherum gracile* as a carbon source to prepare carbon quantum dots. The inventors have verified that carbon quantum dots prepared using *Achnatherum gracile* as a carbon source exhibit fluorescence and can be used for the detection of related substances.

[0014] As shown in the embodiments of the present invention, when using *Achnatherum gracile* as a carbon source to prepare carbon quantum dots, the lowest detection limit for hypochlorite remains very high at 70.02 nM, which is similar to the performance of existing technologies using plants as carbon sources to prepare fluorescent carbon quantum dots. However, when *Achnatherum gracile* and rapeseed straw are used together as carbon sources in a certain proportion, the lowest detection limit for hypochlorite in the resulting carbon quantum dots is significantly reduced.

[0015] The preparation of carbon quantum dots using straw has been reported extensively prior to this application. For example, Liu Caiyun et al. successfully prepared fluorescent carbon quantum dots in their paper "Preparation of Carbon Quantum Dots by Hydrothermal Carbonization of Corn Straw Powder and Study on Their Photocatalytic Performance." Specifically, regarding rapeseed straw, Bai Yaxing et al. also successfully prepared carbon quantum dots using rapeseed straw in their paper "Study on the Photocatalytic Performance of Rapeseed Straw-Based Carbon Quantum Dots Sensitized to P25." However, according to the tests of this invention, the carbon quantum dots prepared using only rapeseed straw as a carbon source had a detection limit of only 53.06 nM when detecting hypochlorite.

[0016] Currently, there are relatively few reports on utilizing plant mixtures as a common carbon source. To the inventors' knowledge, this invention is the first to utilize plant mixtures as a common carbon source to prepare carbon quantum dots for the detection of hypochlorite. Based on the findings of this invention, the inventors previously attempted to use reeds and grapefruit peel as a common carbon source, but the resulting carbon quantum dots did not show a significant impact on the limit of detection (LOD) for hypochlorite. Currently, the inventors do not yet understand why using reeds and rapeseed straw as a common carbon source can significantly lower the LOD for hypochlorite detection; the relevant mechanism requires further investigation.

[0017] In conducting the above research, for ease of detection, the inventors also coated carbon nanodots onto electrospun fiber membranes for detection. During the research process, through continuous experimentation, the inventors ultimately discovered that adding polyvinylpyrrolidone, nano-silica, and nano-titanium dioxide as components of the spinning solution could effectively maintain the lowest detection limit. Surprisingly, the fiber membrane prepared by this invention also possesses reusable properties.

[0018] As one possible embodiment of the present invention, the heat treatment is performed at a temperature of 180°C for 8 hours.

[0019] As one possible embodiment of the present invention, the concentration of the polyvinylpyrrolidone aqueous solution is 1.2 wt%.

[0020] As one possible embodiment of the present invention, when performing membrane dialysis, a 0.2 μm membrane is used for dialysis for 24 hours.

[0021] As a preferred technical solution of the present invention, the weight ratio of the product obtained in step (1), nano silica, nano titanium dioxide and polymethyl methacrylate is 8:2:1:30.

[0022] As one possible embodiment of the present invention, the weight fraction of the solute is 5.5% when preparing the electrospinning solution.

[0023] As one possible embodiment of the present invention, the spinning parameters for preparing the electrospun fiber membrane are as follows: feed speed of 0.2 mL / h, voltage of 10 kV, ambient temperature of 30°C, aluminum foil as receiving plate, and receiving plate distance of 15 cm from needle tip.

[0024] As one possible embodiment of the present invention, when drying the electrospun fiber membrane, the electrospun fiber membrane is placed in a container that has been vacuum-treated for drying.

[0025] Another object of the present invention is to provide a fiber membrane for repeatable and highly sensitive detection of hypochlorite ions prepared according to the above preparation method.

[0026] Another object of the present invention is to provide the application of the above-mentioned fiber membrane in the detection of hypochlorite, wherein the hypochlorite includes hypochlorite; and the hypochlorite includes sodium hypochlorite.

[0027] The beneficial effects of this invention are:

[0028] The fiber membrane of the present invention exhibits high sensitivity in detecting hypochlorite, with a detection limit as low as 0.15 nM; the fiber membrane of the present invention is reusable and retains excellent detection performance after at least 10 cycles. Attached Figure Description

[0029] Figure 1 This is a scanning electron microscope image of the electrospun fiber membrane prepared in Example 1 of the present invention. Detailed Implementation

[0030] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are still within the scope of protection of the present invention.

[0031] Example 1

[0032] 1. Raw materials and instruments

[0033] 1.1 Raw materials: Reed grass was donated; rapeseed straw was collected; polyvinylpyrrolidone (PVP-K30) was purchased from Jinan Hongwang Chemical Co., Ltd.; nano silica (particle size distribution 20-60nm) and nano titanium dioxide (particle size distribution 20-60nm) were purchased from Nanjing Baoket New Materials Co., Ltd.; dimethylformamide and polymethyl methacrylate were available in the laboratory; PBS solution was prepared in the laboratory; sodium hypochlorite standard solution was purchased from Tanmo Quality Inspection Technology Co., Ltd.

[0034] 1.2 Instruments

[0035] Electrospinning machine, centrifuge, fluorescence spectrometer, PTFE-lined autoclave.

[0036] 2. Preparation method

[0037] (1) Take Reed and rapeseed straw at a weight ratio of 5:1, crush them, add them to a polytetrafluoroethylene-lined autoclave, heat them at 180°C for 8 hours, cool them to room temperature (25-30°C), centrifuge them at 13000rpm for 10 minutes, and take the supernatant; mix an equal volume of the supernatant with a 1.2wt% polyvinylpyrrolidone aqueous solution, stir and react at room temperature for 4 hours, then filter and dialyze them through a 0.2μm filter membrane for 24 hours, freeze-dry the dialysate to obtain carbon quantum dot powder;

[0038] (2) Carbon quantum dot powder, nano-silica, nano-titanium dioxide and polymethyl methacrylate were placed in dimethylformamide at a weight ratio of 8:2:1:30 to prepare a solution with a solute weight fraction of 5.5%. The solute was fully dispersed by magnetic stirring until no precipitation occurred after standing for 1 hour. The solution was placed in a microsyringe equipped with a 30G needle tip, and the injection speed was set to 0.2mL / h, the voltage to 10kV, the ambient temperature to 30℃, and aluminum foil was used as the receiving plate. The receiving plate was 15cm away from the needle tip. Electrospinning was performed. After the film was formed at the receiving plate, the electrospun fiber film was collected. The electrospun fiber film was placed in a container that had been vacuum-treated and the residual solvent dimethylformamide was dried.

[0039] 3. Detection of hypochlorite ions

[0040] (1) Detection of hypochlorite ions with carbon quantum dot solution

[0041] Carbon quantum dots (to a final concentration of 0.10 mg / mL) and hypochlorite solutions of different concentrations were added to 150 mL of PBS solution, mixed thoroughly, and then subjected to fluorescence detection at an excitation wavelength of 800 nm. The results showed that at a carbon quantum dot concentration of 0.10 mg / mL, the linear range of the fluorescence response was 0.40 nM to 50.0 nM, with a detection limit of 0.1 nM.

[0042] (2) Take a dried electrospun fiber membrane (3 cm long and 1 cm wide), and drop hypochlorite solutions of different concentrations onto the electrospun fiber membrane. Then perform fluorescence detection with an excitation wavelength of 800 nm. The test showed that the linear range of the fluorescence response was 0.50 nM to 45.0 nM, and the limit of detection was 0.15 nM.

[0043] After use, the electrospun fiber membrane was washed with PBS buffer, dried (at 20–25°C under vacuum), and then subjected to the above tests to verify its reusability. The tests showed that after 10 reuses, the detection limit remained at 0.25 nM, and the fluorescence response linear range was 0.8 nM–40.0 nM.

[0044] Example 2

[0045] Except for the heating treatment, which was performed at 200°C for 6 hours, the process was identical to that in Example 1. The resulting fiber membrane exhibited a linear fluorescence response range of 0.60 nM to 45.0 nM, with a detection limit of 0.22 nM.

[0046] Example 3

[0047] Except for the heating treatment, which was performed at 190°C for 7 hours, the process was identical to that in Example 1. The resulting fiber membrane exhibited a linear fluorescence response range of 0.60 nM to 43.0 nM, with a detection limit of 0.20 nM.

[0048] Example 4

[0049] Except for the weight ratio of carbon quantum dot powder, nano-silica, nano-titanium dioxide, and polymethyl methacrylate being 8:2:1:25, the rest was consistent with Example 1. The resulting fiber membrane exhibited a linear fluorescence response range of 0.70 nM to 40.0 nM, with a detection limit of 0.23 nM.

[0050] Example 5

[0051] Except for the weight ratio of carbon quantum dot powder, nano-silica, nano-titanium dioxide, and polymethyl methacrylate being 8:2:1:28, the rest was consistent with Example 1. The resulting fiber membrane exhibited a linear fluorescence response range of 0.60 nM to 44.0 nM, with a detection limit of 0.19 nM.

[0052] Comparative Example 1

[0053] The carbon source was changed to *Achnatherum gracile*, and carbon quantum dots were prepared according to Example 1. The method of detecting hypochlorite in the carbon quantum dot solution was tested according to Example 1. The results showed that the limit of detection was 70.02 nM.

[0054] Comparative Example 2

[0055] The carbon source was changed to rapeseed straw, and carbon quantum dots were prepared according to Example 1. The carbon quantum dot solution was then tested for hypochlorite ions using the method described in Example 1. The results showed that the limit of detection was 53.06 nM.

[0056] Comparative Example 3

[0057] Carbon quantum dots were prepared according to Example 1, but nano-silica and nano-titanium dioxide were not added during the preparation of electrospun fibers. The method for detecting hypochlorite in the fiber membrane was tested according to the method in Example 1. The results showed that the limit of detection was 37.65 nM, and the fluorescence response linear range was narrow, from 120 nM to 620 nM. After repeated use three times, the limit of detection exceeded 150 nM.

[0058] Comparative Example 4

[0059] Except for not mixing the supernatant after centrifugation with the polyvinylpyrrolidone aqueous solution, carbon quantum dots were prepared according to Example 1, and fiber membranes were prepared according to the method of Example 1. The scheme for detecting hypochlorite using the fiber membrane was tested according to the method of Example 1. The results showed that the limit of detection was 15.24 nM, and the fluorescence response range was narrow, from 50 nM to 350 nM. After four repetitions, the limit of detection exceeded 100 nM.

Claims

1. A method for preparing a fiber membrane for repeatable and highly sensitive detection of hypochlorite, characterized in that, The preparation method includes the following steps: (1) Take Reed and rape straw at a weight ratio of 5:1, crush them, heat them at 180~200℃ for 6~8 hours, then centrifuge to obtain the supernatant; mix the supernatant with a 1.2wt% polyvinylpyrrolidone aqueous solution, stir and react for 4~5 hours, then perform membrane dialysis, and freeze-dry the dialysate; (2) The product obtained in step (1), nano silica, nano titanium dioxide and polymethyl methacrylate are placed in dimethylformamide, and the weight fraction of the solute is 5~6%; then an electrospun fiber membrane is prepared by electrospinning, and then the residual solvent dimethylformamide in the electrospun fiber membrane is dried to obtain the product; wherein, the weight ratio of the product obtained in step (1), nano silica, nano titanium dioxide and polymethyl methacrylate is 8:2:1:25~30; when preparing the electrospun fiber membrane, the spinning parameters are: the feed speed is 0.2mL / h, the voltage is 10kV, the ambient temperature is 30℃, the aluminum foil is used as the receiving plate, and the distance between the receiving plate and the needle tip is 15cm.

2. The preparation method according to claim 1, characterized in that, The heat treatment is carried out at a temperature of 180℃ for 8 hours.

3. The preparation method according to claim 1, characterized in that, When performing membrane dialysis, a 0.2 μm membrane is used for dialysis for 24 hours.

4. The preparation method according to claim 1, characterized in that, The weight ratio of the product obtained in step (1), nano silica, nano titanium dioxide and polymethyl methacrylate is 8:2:1:

30.

5. The preparation method according to claim 4, characterized in that, When preparing the electrospinning solution, the weight fraction of the solute is 5.5%.

6. The preparation method according to claim 1 or 4, characterized in that, When drying electrospun fiber membranes, the membranes are placed in a container that has been vacuum-treated for drying.

7. A fiber membrane for repeatable and highly sensitive detection of hypochlorite, characterized in that, The fiber membrane is prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the fiber membrane according to claim 7 in the detection of hypochlorite, characterized in that, The hypochlorite ion includes hypochlorite; the hypochlorite includes sodium hypochlorite.

Images