Cationic polythiophene derivative and method for detecting and removing anionic surfactant

Abstract

The invention relates to the technical field of pollutant detection, in particular to a cationic polythiophene derivative for detecting and removing an anionic surfactant and a method thereof. Probe molecules prepared from the cationic polythiophene derivative provided by the invention can be combined with an anionic surfactant to cause the change of solution color and optical properties, and can directly perform specific and sensitive colorimetric and fluorescence sensing on the anionic surfactant. And meanwhile, the removal of the anionic surfactant in water is realized by molecular structure aggregation after the probe molecules are combined with the anionic surfactant. The probe molecule developed by the invention has the advantages of stable structure, good water solubility, rapid response and the like, and can realize synchronous dual-mode detection and removal of anions in water.

Description

Technical Field

[0001] The present invention relates to the technical field of pollutant detection, and in particular to a cationic polythiophene derivative and a method for detecting and removing anionic surfactants. Background Art

[0002] Anionic surfactants have high cleaning, foaming, dispersing and emulsifying abilities and are widely used in the production of industrial detergents. However, anionic surfactants are extremely harmful. It is difficult for them to be naturally degraded in the environment if they are discharged into natural water bodies at will, which has adverse effects on aquatic organisms. The toxicity of anionic surfactants can also enter the human body through the food chain, affecting the activity of various enzymes in the human body and reducing the body's resistance. In addition, anionic surfactants can synergize with some other toxic chemicals in wastewater, and can stimulate weight gain and accelerate the synthesis of cholesterol in the liver when entering the human body with drinking water. Therefore, the detection of anionic surfactants in environmental water samples has become a basic task of environmental monitoring. The "GB5479-2022 Drinking Water Hygiene Standard" implemented by the state on April 1, 2023 stipulates that the residual amount of anionic synthetic detergents in water is 0.3 mg / L to ensure the safety of drinking water resources and food.

[0003] At present, the methods developed for detecting anionic surfactants include flow injection method, two-phase titration method, high performance liquid chromatography, etc. However, these detection methods generally have cumbersome operation processes, use reagents with relatively high toxicity, and cause certain harm to the human body and the environment when used in large quantities. They are not suitable for the current needs of instant detection, rapid green environmental protection.

[0004] Water-soluble polythiophene is used in optical devices because its chain conformation and photophysical properties are sensitive to external stimuli such as heat or light treatment, changes in solvent composition, and the introduction of chemical and biochemical targets. It also has good thermal stability and biocompatibility. Some researchers have applied water-soluble polythiophene to the detection of anionic surfactants. Yao et al. (Chem. Commun., 2010, 46, 8639) used aromatic 2-naphthalenesulfonate (NS) to induce water-soluble polythiophene (PMTPA) to aggregate in HEPES buffer to form a PMTPA-NS complex. After adding anionic surfactants, the aggregates dissociated. The complex can be used as a promising colorimetric detection probe for anionic surfactants. An et al. (Soft Matter 2011, 7, 6873-6877.) prepared anionic dyes (HPTS), introduced HPTS into polythiophene (PMTPA) aqueous solution to form a complex, and then used the complex as a colorimetric and fluorescent dual-mode probe for detecting anionic surfactants, which has good selectivity and sensitivity.

[0005] In the above method, after preparing the water-soluble polythiophene, other components need to be introduced and aggregated into a complex before it can be used for the detection of anionic surfactants. The steps are cumbersome and inconvenient to use. Summary of the invention

[0006] The present invention aims to solve the problem of lack of high-sensitivity selective identification materials for anionic surfactants, and provides a cationic polythiophene derivative and a method for detecting and removing anionic surfactants.

[0007] The technical solution of the present invention is as follows:

[0008] A cationic polythiophene derivative for detecting and removing anionic surfactants, the structures of which are shown in formula (I) and formula (II):

[0009]

[0010] Formula (I) is a homopolymer structure, R1 is H or CH3; R2 is O or CH2; R3 is an alkyl group with an integer of carbon number between 1 and 6 and its isomers: methyl, ethyl, propyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, isohexyl; R4 is H or CH3; m is an integer between 0 and 15; M is Cl or Br; n is a positive integer, and the weight average molecular weight of the polythiophene derivative is 3,000 to 50,000;

[0011] Formula (II) is composed of thiophene units connected at the 2 and 5 positions to form a conjugated main chain, and its structural formula is shown below:

[0012]

[0013] Formula (II) is a copolymer structure, R1 is H or CH3; R2 is O or CH2; m is an integer between 0 and 15; M is Cl or Br; R 1# ,R 2# ,R 3# ,R 4# , selected from R in the above formula (I) # Substituents, wherein R3 is an alkyl group with an integer carbon number between 1 and 6 and its isomers: methyl, ethyl, propyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, isohexyl; R4 is H or CH3; and satisfies R 1# ≠R 2# ≠R 3# ≠R 4# ; n1, n2, n3, n4 are integers between 1 and 500, and make the weight-average molecular weight of the polythiophene derivative be between 3,000 and 100,000.

[0014] Furthermore, the types of anionic surfactants detected and removed include alkyl carboxylic acids: sodium dodecyl carboxylate SDC, alkyl sulfonic acids: sodium octyl sulfonate OS, alkyl benzene sulfonic acids: sodium dodecyl benzene sulfonate SDBS, alkyl sulfuric acids: sodium octyl sulfate SOS, sodium dodecyl sulfate SDS.

[0015] A method for detecting anionic surfactants using the cationic polythiophene derivative comprises the following steps:

[0016] (1) dissolving the cationic polythiophene derivatives represented by formula (I) and formula (II) in water to prepare probe molecules;

[0017] (2) adding the probe molecule obtained in step (1) into a quartz cuvette to obtain a detection reagent;

[0018] (3) gradually adding anionic surfactant standard solution into the cuvette, and measuring the change of its UV-visible absorption spectrum and fluorescence spectrum;

[0019] (4) Analyze the relationship between the absorbance ratio and the change in the concentration of the specific anionic surfactant and the relationship between the fluorescence intensity and the change in the concentration of the specific anionic surfactant to perform quantitative specific detection of the anionic surfactant in the solution.

[0020] Furthermore, the concentration of the cationic polythiophene derivative in the detection system is 0.1-100 μM, the reaction volume is 200-3000 μL, the reaction pH is 4-14, the reaction temperature is 4-40° C., and the reaction system is ultrapure water and HEPES buffer solution.

[0021] A method for removing anionic surfactants using the cationic polythiophene derivative comprises the following steps:

[0022] (1) dissolving the cationic polythiophene derivative represented by formula (I) / formula (II) in ultrapure water to obtain a probe molecule solution;

[0023] (2) adding the probe molecule prepared in step (1) into water containing anionic surfactant for reaction;

[0024] (3) After the reaction is completed, the solution is added to a removal system for separation and removal, and the sample after removal is analyzed to obtain the efficiency of the probe molecule in removing the corresponding anionic surfactant.

[0025] Furthermore, when the concentration of the anionic surfactant is 0.1-20 μM, an ultrafiltration system is used for separation and removal, and the pore size of the ultrafiltration system includes but is not limited to: 3-300 kDa.

[0026] The beneficial effects of the present invention are embodied in:

[0027] The probe molecules made of cationic polythiophene derivatives provided by the present invention can combine with anionic surfactants to cause changes in solution color and optical properties, and can directly perform specific and sensitive colorimetric and fluorescence sensing on anionic surfactants. At the same time, the molecular structure aggregation after the probe molecules combine with the anionic surfactants is used to achieve the removal of anionic surfactants in water. The probe molecules developed by the present invention have the advantages of stable structure, good water solubility, rapid response, etc., and can achieve synchronous dual-mode detection and removal of anions in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the principle of detecting anionic surfactants by cationic polythiophene in Example 1 of the present invention.

[0029] Figure 2 This is a diagram showing the effect of the probe molecule of formula (I) detecting SDS when R1 of the dissociated probe in Example 1 of the present invention is CH3 or H. A) lists different PT names and different R1 distinctions; B) lists colorimetric and absorption spectrum sensing schematics; C) is a fluorescence colorimetric and fluorescence spectrum sensing schematic.

[0030] Figure 3 This is a diagram showing the effect of the depolymerized probe in Example 1 of the present invention on detecting SDS by changing the length of the probe molecule of formula (I) with different carbon chains m, wherein A) lists the names of different PTs and the lengths of different carbon chains m; B) is a schematic diagram of colorimetry and absorption spectrum sensing; and C) is a schematic diagram of fluorescence colorimetry and fluorescence spectrum sensing.

[0031] Figure 4 The dissociation type probes in Example 2 of the present invention have different R # The effect diagram of the probe molecule of formula (I) for detecting SDS, A) is listed as different PT names and different R # The length of the substituent differs; B) is a schematic diagram of colorimetry and absorption spectrum sensing; C) is a schematic diagram of fluorescence colorimetry and fluorescence spectrum sensing.

[0032] Figure 5 The effect diagram of using different structures of dissociated probe molecular formula (II) to detect SDS in Example 2 of the present invention, A) lists the names of different PTs and the differences between different monomers and polymerization ratios; B) is a schematic diagram of colorimetry and absorption spectrum sensing; C) is a schematic diagram of fluorescence colorimetry and fluorescence spectrum sensing.

[0033] Figure 6The effect diagram of the dissociated probe molecule and SDS ultraviolet-visible absorption and fluorescence dual-mode sensing in Example 2 of the present invention, A) is a relationship diagram between the change in SDS concentration and the change in the absorption spectrum of the probe molecule; B) is a linear relationship between the SDS concentration and the absorbance ratio of the probe molecule; C) is a colorimetric visualization diagram of the probe molecule and different concentrations of SDS; D) is a diagram of the change in G value of different concentrations of SDS and the probe molecule under fluorescent light irradiation; E) is a diagram of the relationship between the change in SDS concentration and the change in the emission spectrum of the probe molecule; F) is a diagram of the relationship between the fluorescence intensity and the increase in SDS concentration (where I0 is the initial fluorescence intensity of the probe molecule at 600nm, and I is the fluorescence intensity at 600nm after the addition of SDS).

[0034] Figure 7 The effect diagram of the dissociation probe molecule specifically recognizing anionic surfactants in Example 2 of the present invention, A) is a color change diagram after different ions react with the dissociation probe molecule (sequence numbers in the figure: 1PT, 2Cl - 、3ClO3 - 4CO3 2- , 5HCO3 - 6NO3 - ,7SO4 2- , 8F - 、9PO4 3- 、10HPO4 2- 、11H2PO4 - , 12Tween-20, 13Triton X-100, 14CTAB, 15SDS, 16SDBS, the same below); B) absorbance ratio A after different ions react with the depolymerized probe molecule 392nm / A 535nm C) is a graph showing the fluorescence color change of different ions after reaction with the disaggregated probe molecule under 470nm blue light excitation; D) fluorescence intensity ratio of different ions after reaction with the disaggregated probe molecule I 550nm / I 610nm 's change graph.

[0035] Figure 8 This is a diagram showing the effect of detecting SDS by changing the R3 substituent of the aggregation probe of Example 3 of the present invention to a probe molecule of formula (I), wherein A) lists different PT names and different R3 distinctions; B) is a schematic diagram of colorimetry and absorption spectrum sensing; and C) is a schematic diagram of fluorescence colorimetry and fluorescence spectrum sensing.

[0036] Fig. 9 The effect diagram of using different structures of aggregation probe molecular formula (II) to detect SDS in Example 3 of the present invention, A) lists the differences between different PT names and different monomers and polymerization ratios; B) is a schematic diagram of colorimetry and absorption spectrum sensing; C) is a schematic diagram of fluorescence colorimetry and fluorescence spectrum sensing.

[0037] Fig.10 The effect diagram of the dual-mode sensing of ultraviolet-visible absorption and fluorescence of the aggregated probe molecules and SDS in Example 3 of the present invention, A) is a diagram showing the relationship between the change in SDS concentration and the change in the absorption spectrum of the probe molecules; B) is a linear relationship between the SDS concentration and the absorbance ratio of the probe molecules; C) is a colorimetric visualization diagram of the probe molecules and different concentrations of SDS; D) is a diagram showing the change in R / (G+B) values ​​of different concentrations of SDS and probe molecules under fluorescent light irradiation; E) is a diagram showing the relationship between the change in SDS concentration and the change in the emission spectrum of the probe molecules; F) is a diagram showing the relationship between the fluorescence intensity as the SDS concentration increases.

[0038] Fig.11 The effect diagram of the specific recognition of anionic surfactants by the aggregating probe molecules in Example 3 of the present invention, A) is a color change diagram after the reaction of different ions with the aggregating probe molecules (sequence numbers in the figure: 1PT, 2Cl - 、3ClO3 - 4CO3 2- , 5HCO3 - 6NO3 - ,7SO4 2- , 8F - 、9PO4 3- 、10HPO4 2- 、11H2PO4 - , 12Tween-20, 13Triton X-100, 14CTAB, 15SDS, 16SDBS, the same below); B) absorbance ratio A after different ions react with aggregated probe molecules 525nm / A 405nm C) is a graph showing the fluorescence color change of different ions after reaction with aggregated probe molecules under 470nm blue light excitation; D) fluorescence intensity ratio of different ions after reaction with aggregated probe molecules I 655nm / I 520nm 's change graph.

[0039] Fig.12 Effect diagram of the probe molecule detecting different anionic surfactants in Example 4 of the present invention, A) is the absorption spectrum diagram after the reaction of different anionic surfactants with the probe molecule; B) is the absorbance ratio A after the reaction of different anionic surfactants with the probe molecule 525nm / A 405nm Change diagram (sequence numbers in the figure: 1PT, 2OS, 3SOS, 4SDC, 5SDBS, 6SDS)

[0040] Fig.13 A diagram showing the effect of the probe molecule in Example 5 of the present invention on the ultrafiltration (UF) removal of anionic surfactants. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The embodiments are only used to explain the present invention rather than to limit the present invention.

[0042] First, the structure of the cationic polythiophene derivative provided by the present invention is shown in the figure:

[0043]

[0044] Formula (I) is a homopolymer structure, R1 is H or CH3; R2 is O or CH2; R3 is an alkyl group with an integer carbon number between 1 and 6 and its isomers (methyl, ethyl, propyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, isohexyl); R4 is H or CH3; m is an integer between 0 and 15; M is Cl or Br; n is a positive integer, and the weight average molecular weight of the polythiophene derivative is between 3,000 and 50,000.

[0045] Formula (II) consists of thiophene units connected at the 2 and 5 positions to form a conjugated main chain, and its structural formula is shown below:

[0046]

[0047] Formula (II) is a copolymer structure, R1 is H or CH3; R2 is O or CH2; m is an integer between 0 and 15; M is Cl or Br; R 1# ,R 2# ,R 3# ,R 4# , selected from R in the above formula (I) # Substituents, wherein R3 is an alkyl group having an integer of 1 to 6 carbon atoms and its isomers (methyl, ethyl, propyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, isohexyl); R4 is H or CH3; and R 1# ≠R 2# ≠R 3# ≠R 4# ; n1, n2, n3, n4 are integers between 1 and 500, and make the weight-average molecular weight of the polythiophene derivative be between 3,000 and 100,000.

[0048] The cationic polythiophene derivatives of the structures shown in the above formula (I) and formula (II) have good water solubility and show obvious specificity in detection, and can sensitively detect anionic surfactants. The polythiophene derivatives of the structures shown in the above can be divided into two types: depolymerized type and aggregated type according to the conformation and aggregation state in the solution.

[0049] Figure 1 Schematic diagram of the probe molecule detecting anionic surfactants. Figure 1As shown in Figure A, the depolymerized polythiophene probe is purple-red and has red fluorescence. When anionic surfactants are added, the aggregates formed by the probe molecules themselves in water are dispersed, and the color of the solution changes from purple-red to yellow accordingly; Figure 1 As shown in Figure B, the aggregated polythiophene probe is light yellow and has yellow fluorescence. It is uniformly dispersed in the aqueous solution. When an anionic surfactant is added, a cationic polythiophene-anionic surfactant complex is formed, and the color of the solution changes from yellow to purple red accordingly. In the presence of anionic surfactants, both types of probe molecules have obvious fluorescence changes. Highly sensitive and specific qualitative and quantitative detection of anionic surfactants can be achieved through changes in absorption spectra, fluorescence spectra and intensity.

[0050] Second, the present invention provides a probe molecule for visual dual-mode detection of anionic surfactants, which can be used for rapid, quantitative and specific detection of anionic surfactants; in order to achieve the purpose of detecting anionic surfactants;

[0051] The steps of the probe molecule of the present invention for rapid detection of anionic surfactants are as follows (taking SDS as an example):

[0052] (1) Dissolve 5 μmol of probe in 100 mL of ultrapure water to obtain a probe molecule solution;

[0053] (2) adding the probe obtained in step (1) into a cuvette of uniform volume to obtain a detection reagent;

[0054] (3) After the SDS standard solution reacts with the reagent obtained in step (2), the changes in the UV-visible absorption spectrum and the fluorescence spectrum are measured. The linear relationship between the peak value change and the SDS concentration value can be used for quantitative analysis;

[0055] (4) After adding SDS to the detection reagent of step (2), the absorbance of the disaggregated probe molecule at 537 nm gradually decreases, while the absorbance at 395 nm gradually increases. At the same time, the fluorescence of the probe molecule is enhanced and the characteristic absorption peak undergoes a blue shift. The absorbance of the aggregated probe molecule at 405 nm gradually decreases, while the absorbance at 535 nm gradually increases. At the same time, the fluorescence of the probe molecule is quenched and the characteristic absorption peak undergoes a red shift. The overall detection time is less than 10 s.

[0056] The probe molecule of the present invention can detect SDS in a concentration range of 0.1-5×10 5 The concentration of the probe molecule is in the range of 0.1-100 μM, preferably 50 μM.

[0057] The reaction conditions include: (1) the volume of the reaction system is 200-3000 μL, and the reaction volume is more preferably 2000 μL; (2) the reaction temperature of the reaction system is 4-40° C., and the reaction temperature is more preferably 25° C.; (3) the pH value of the reaction system is 4-14, and more preferably pH=7;

[0058] Thirdly, the present invention provides a probe molecule for removing anionic surfactants from water, in order to achieve the purpose of removing anionic surfactants;

[0059] The steps of removing anionic surfactants by the probe molecule of the present invention are as follows (taking SDBS as an example):

[0060] (1) dissolving Formula I / Formula II in ultrapure water to obtain a probe molecule solution;

[0061] (2) adding the probe molecule prepared in step (1) into water containing SDBS for reaction;

[0062] (3) After the reaction is completed, the solution is added to an ultrafiltration removal system for separation and removal, and the sample after removal is analyzed to obtain the efficiency of the probe molecule in removing SDBS;

[0063] The pore size of the ultrafiltration system includes but is not limited to: 3-300 kDa; preferably, the ultrafiltration system can be used for separation and removal when the SDBS concentration is 0.1-20 μM;

[0064] Preparation of probe mother solution: weigh the solid and prepare a mother solution with a concentration of 5 μmol using ultrapure water. When testing, use ultrapure water to dilute to a certain concentration for testing.

[0065] Preparation of anionic surfactant standard solution: Prepare the purchased anionic surfactant standard solution and powder into a 10 mM solution, divide the solution into small bottles of equal volume for later use, and store in a refrigerator at 4°C.

[0066] Preparation of interfering substances: Prepare the purchased standard solution and powder into a 10 mM solution, divide it into small bottles of equal volume for later use, and store it in a refrigerator at 4°C.

[0067] Fourth, the types of anionic surfactants detected and removed include but are not limited to alkyl carboxylic acids (sodium dodecyl carboxylate SDC), alkyl sulfonic acids (sodium octyl sulfonate OS), alkyl benzene sulfonic acids (sodium dodecyl benzene sulfonate SDBS), and alkyl sulfates (sodium octyl sulfate SOS, sodium dodecyl sulfate SDS).

[0068] Example 1: Detection effect of cationic polythiophene on anionic surfactants

[0069] 1. Principle of cationic polythiophene probe for detecting anionic surfactants

[0070] Referring to the literature (Chinese patent: CN118480172A), homopolymers PT1-PT17 and PT29, copolymers PT18-20 and PTC-PTF were synthesized. According to the conformation and aggregation state in the solution, the cationic polythiophene probes can be divided into two types: depolymerization type and aggregation type.

[0071] Figure 1 Schematic diagram of the principle of using cationic polythiophene probe to detect anionic surfactants. Figure 1 As shown in Figure A, the depolymerized polythiophene probe is purple-red and has red fluorescence. When anionic surfactants are added, the aggregates formed by the probe molecules themselves in water are dispersed, and the color of the solution changes from purple-red to yellow accordingly; Figure 1 As shown in B, the aggregated polythiophene probe is light yellow and has yellow fluorescence. It is evenly dispersed in the aqueous solution. When an anionic surfactant is added, a cationic polythiophene-anionic surfactant complex is formed, and the color of the solution changes from yellow to purple-red accordingly.

[0072] 2. Structural characteristics of cationic polythiophene probes for identifying anionic surfactants

[0073] The prepared probe molecules with different structures are respectively added into a colorimetric cell with uniform volume to obtain a detection reagent for detecting anionic surfactant (SDS);

[0074] Add the SDS standard solution into the colorimetric cell to measure the changes in UV-visible absorption spectrum, fluorescence spectrum, visual color and fluorescence color;

[0075] like Figure 2 As shown, after adjusting the structure of the R1 substituent in the molecule of formula (I), the probe molecule has a signal output response to the anionic surfactant, which is specifically manifested as: UV-visible absorption spectrum and color change, fluorescence quenching of the fluorescence spectrum accompanied by a change in fluorescence color, indicating that the synthesized probe molecule formula (I) can be used for UV / fluorescence dual-mode detection of anionic surfactants when the R1 structure at position 4 of thiophene is CH3 or H.

[0076] like Figure 3 As shown, after adjusting the length of the carbon chain m in the molecule of formula (Ⅰ), the probe molecules all have a good signal output response to the anionic surfactant, indicating that the synthesized probe molecules of formula (Ⅰ) with a carbon chain length of 1-15 can be used for UV / fluorescence dual-mode detection of anionic surfactants.

[0077] Example 2: Visualized dual-mode detection of depolymerized cationic polythiophene for anionic surfactants

[0078] 1. Structural characteristics of depolymerized cationic polythiophene probes for identifying anionic surfactants

[0079] By adjusting R # Substituents can be used to prepare depolymerized cationic polythiophene probes with different structures. The depolymerized probe molecules are added to a colorimetric cell of uniform volume to obtain a detection reagent for detecting anionic surfactant (SDS);

[0080] Add the SDS standard solution into the colorimetric cell to measure the changes in UV-visible absorption spectrum, fluorescence spectrum, visual color and fluorescence color;

[0081] like Figure 4 As shown, in the molecule of the regulating formula (I), R # After the structure of the substituent group, the depolymerized probe molecules all have a good signal output response to the anionic surfactant, indicating that the synthesized depolymerized probe molecule formula (I) R # Substituents such as quaternary ammonium salt substituents (methyl, ethyl), 1-methylimidazole, and 1,2-dimethylimidazole structures can all be used for UV / fluorescence dual-mode detection of anionic surfactants.

[0082] like Figure 5 As shown, after adjusting the structure and polymerization ratio of the monomers in the molecule of formula (II), the depolymerized probe molecules all have good signal output responses to anionic surfactants, indicating that the synthesized depolymerized probe molecules of formula (II) can be used for UV / fluorescence dual-mode detection of anionic surfactants after adjusting the structure and polymerization ratio of the monomers.

[0083] 2. Depolymerized cationic polythiophene probe for UV spectroscopy sensing of anionic surfactants

[0084] The probe mother solution is dissolved in ultrapure water to obtain a probe molecule solution, and 2 mL of the obtained probe molecule solution is added to a colorimetric cell of uniform volume as a reagent for detecting SDS;

[0085] Scan the UV-visible absorption spectrum of the probe molecule, then gradually add a certain concentration of SDS standard solution into the colorimetric cell, mix well, measure its UV-visible absorption spectrum, and read the peaks at 395nm and 537nm;

[0086] The results are as follows Figure 6 show, Figure 6 A shows that the absorbance of the aforementioned dissociated probe molecule at 537 nm gradually decreases with the addition of SDS, while the absorbance at 395 nm gradually increases. Figure 6 B shows the relationship between the absorbance ratio and the SDS concentration. As the SDS concentration increases, the absorbance ratio A 395nm / A 537nmGradually increasing, quantitative detection can be achieved between 0-10μM with good linear relationship (R 2 =0.97198). According to the calculation method of the detection limit, the detection limit of the probe molecule for SDS is 0.209 μmol / L.

[0087] 3. Depolymerized cationic polythiophene probe for colorimetric sensing of anionic surfactants

[0088] The probe mother solution was dissolved in ultrapure water to obtain a probe molecule solution, and 1 mL of the obtained probe molecule solution was added to a glass vial as a reagent for detecting SDS;

[0089] Add SDS standard solutions of different concentrations into the vials, mix well and take photos under natural light indoors ( Figure 6 C) Use Color Grab software to extract the RGB value of each vial ( Figure 6 D)

[0090] Figure 6 The results of C and D show that the solution color of the probe molecule gradually changes from purple to yellow with the increase of SDS concentration. The visible detection limit is 5 μmol / L. The G value obtained by the software is linearly related to the SDS concentration, and the correlation coefficient R 2 It is 0.99148, and the detection limit is 2.5μmol / L.

[0091] 4. Depolymerized cationic polythiophene probe for fluorescence sensing of anionic surfactants

[0092] The probe mother solution is dissolved in ultrapure water to obtain a probe molecule solution, and 2 mL of the obtained probe molecule solution is added to a fluorescent cell of uniform volume as a reagent for detecting SDS;

[0093] The fluorescence spectrum of the disaggregated probe molecule was measured, and the fluorescence intensity at a wavelength of 590 nm was recorded as I0. Subsequently, a certain concentration of SDS standard solution was gradually added to the fluorescence pool, and the corresponding fluorescence spectrum was measured after mixing evenly, and the fluorescence intensity at a wavelength of 590 nm was recorded as I;

[0094] The results are as follows Figure 6 As shown in Figure E, the probe molecule is excited at an excitation wavelength of 420 nm, has a maximum absorption peak at 590 nm, and emits strong yellow fluorescence in aqueous solution. With the addition of SDS, the fluorescence intensity of the probe molecule gradually increases. Figure 6 F indicates the relationship between fluorescence enhancement and SDS concentration. As the SDS concentration increases, the fluorescence intensity ratio I / I0 gradually increases. According to the calculation method of the detection limit, the detection limit of the dissociated probe molecule for SDS is 0.026μmol / L.

[0095] 5. Specificity of depolymerized cationic polythiophene probe for colorimetric and UV spectroscopy sensing of anionic surfactants

[0096] Common anions in water include (Cl - 、ClO3 - 、CO3 2- 、HCO3 - 、NO3 - 、SO4 2- 、F - PO4 3- 、HPO4 2- 、H2PO4 - ), nonionic surfactants (Tween-20, Triton X-100), and cationic surfactant CTAB as interfering substances in the detection of anionic surfactants (SDS, SDBS);

[0097] In order to more intuitively observe the effect of the interaction between the probe molecule and the anionic surfactant, the color change of the solution was observed under a fluorescent lamp and photographed with a camera;

[0098] like Figure 7 As shown in A, when interference substances are added to the dissociated probe molecules, the color of the solution does not change or turns purple-red, while when SDS and SDBS are added, the color of the solution turns yellow.

[0099] The probe mother solution was dissolved in ultrapure water to obtain a probe molecule solution. 2 mL of the obtained probe molecule solution was added to a uniform volume colorimetric cell as a reagent for detecting anionic surfactants. Under the same conditions, a UV-visible absorption spectrum was scanned, and the absorbance at 392 nm was compared with the absorbance at 535 nm. 392nm / A 535nm As a parameter to measure the response of the probe molecule to the substance to be tested;

[0100] The results are as follows Figure 7 As shown in B, except for SDS and SDBS, the A 392nm / A 535nm The ratio is <0.82, while the A 392nm / A 537nm The ratio was >5.8, indicating that the dissociated probe molecule had good selectivity when detecting anionic surfactants using UV-visible absorption spectroscopy;

[0101] 6. Specificity of depolymerized cationic polythiophene probes for fluorescence colorimetry and fluorescence spectroscopy sensing of anionic surfactants

[0102] Common anions in water include (Cl -、ClO3 - 、CO3 2- 、HCO3 - 、NO3 - 、SO4 2- 、F - PO4 3- 、HPO4 2- 、H2PO4 - ), nonionic surfactants (Tween-20, Triton X-100), and cationic surfactant CTAB as interfering substances in the detection of anionic surfactants (SDS, SDBS);

[0103] In order to more intuitively observe the effect of the interaction between the probe molecule and the anionic surfactant and other interfering substances, the change of solution fluorescence during the selective investigation of the probe molecule on the anionic surfactant was observed under blue light (470nm);

[0104] like Figure 7 As shown in C, when interference substances are added to the dissociated probe molecule, the fluorescence color does not change or the fluorescence is quenched, but when SDS and SDBS are added, the fluorescence color turns yellow and a certain degree of fluorescence enhancement and fluorescence blue shift occur;

[0105] The probe mother solution is dissolved in ultrapure water to obtain a probe molecule solution, and 2 mL of the obtained probe molecule solution is added into a fluorescence cell of uniform volume as a reagent for detecting anionic surfactants (SDS, SDBS);

[0106] Under the same conditions, the fluorescence spectrum was scanned and the fluorescence intensity value at 550nm was compared with the fluorescence intensity value at 610nm. 550nm / I 610nm As a parameter to measure the response of the probe molecule to the substance to be tested;

[0107] The results are as follows Figure 7 D shows that the I of the substances except SDS and SDBS 550nm / I 610nm The ratio is <0.8, while the I 655nm / I 520nm The ratio>1.5 indicates that the dissociated probe molecule can specifically detect anionic surfactants.

[0108] Example 3: Visualized dual-mode detection of anionic surfactants by aggregated cationic polythiophenes

[0109] 1. Structural characteristics of aggregated cationic polythiophene probes for identifying anionic surfactants

[0110] By adjusting R # Substituents can be used to prepare aggregated cationic polythiophene probes with different structures. Aggregated probe molecules are added to a colorimetric cell of uniform volume to obtain a detection reagent for detecting anionic surfactant (SDS);

[0111] Add the SDS standard solution into the colorimetric cell to measure the changes in UV-visible absorption spectrum, fluorescence spectrum, visual color and fluorescence color;

[0112] like Figure 8 As shown, after adjusting the structure of the R3 substituent in the molecule of formula (Ⅰ), the aggregation probe molecules all have a good signal output response to the anionic surfactant, indicating that the synthesized aggregation probe molecule formula (Ⅰ) with the R3 substituent being a quaternary ammonium salt substituent (propyl, butyl, hexyl) can be used for UV / fluorescence dual-mode detection of anionic surfactants.

[0113] like Fig. 9 As shown, after adjusting the structure and polymerization ratio of the monomers in the molecule of formula (II), the aggregation probe molecules have a good signal output response to the anionic surfactant, indicating that the synthesized aggregation probe molecule formula (II) can be used for UV / fluorescence dual-mode detection of anionic surfactants after adjusting the structure and polymerization ratio of the monomers.

[0114] 2. Aggregated cationic polythiophene probes for UV spectroscopy sensing of anionic surfactants

[0115] The probe mother solution is dissolved in ultrapure water to obtain a probe molecule solution, and 2 mL of the obtained probe molecule solution is added to a colorimetric cell of uniform volume as a reagent for detecting SDS;

[0116] Scan the UV-visible absorption spectrum of the probe molecule, then gradually add a certain concentration of SDS standard solution into the colorimetric cell, mix well, measure its UV-visible absorption spectrum, and read the peaks at 535nm and 405nm;

[0117] The results are as follows Fig.10 show, Fig.10 A shows that the absorbance of the aforementioned aggregated probe molecules at 405 nm gradually decreases with the addition of SDS, while the absorbance at 535 nm gradually increases. Fig.10 B shows the relationship between the absorbance ratio and the SDS concentration. As the SDS concentration increases, the absorbance ratio A 535nm / A 405nm Gradually increasing, quantitative detection can be achieved between 0-20μM with good linear relationship (R 2 =0.99888). According to the calculation method of the detection limit, the detection limit of the probe molecule for SDS is 0.0896 μmol / L.

[0118] 3. Aggregated cationic polythiophene probes for colorimetric sensing of anionic surfactants

[0119] The probe mother solution was dissolved in ultrapure water to obtain a probe molecule solution, and 1 mL of the obtained probe molecule solution was added to a glass vial as a reagent for detecting SDS;

[0120] Add SDS standard solutions of different concentrations into the vials, mix well and take photos under natural light indoors ( Fig.10 C) Use Color Grab software to extract the RGB value of each vial ( Fig.10 D)

[0121] Fig.10 The results of C and D show that the color of the probe molecule solution gradually changes from yellow to red with the increase of SDS concentration. The visible detection limit is 5 μmol / L. The R / (G+B) value obtained by the software is linearly related to the SDS concentration, and the correlation coefficient R 2 It is 0.99554, and the detection limit is 1.90μmol / L.

[0122] 4. Aggregated cationic polythiophene probes for fluorescence sensing of anionic surfactants

[0123] The probe mother solution is dissolved in ultrapure water to obtain a probe molecule solution, and 2 mL of the obtained probe molecule solution is added to a fluorescent cell of uniform volume as a reagent for detecting SDS;

[0124] The fluorescence spectrum of the aggregated probe molecule was measured, and the fluorescence intensity at a wavelength of 525 nm was recorded as I 525nm Then, a certain concentration of SDS standard solution was gradually added to the fluorescence pool, and the corresponding fluorescence spectrum was measured after mixing evenly, and the fluorescence intensity at a wavelength of 650nm was recorded as I 650nm ;

[0125] The results are as follows Fig.10 As shown in Figure E, the probe molecule is excited at an excitation wavelength of 420 nm, has a maximum absorption peak at 525 nm, and emits strong yellow fluorescence in aqueous solution. With the addition of SDS, the fluorescence intensity of the probe molecule is gradually quenched, and the maximum absorption peak of the fluorescence is red-shifted. Fig.10 F shows the relationship between the red shift of the maximum absorption peak and the SDS concentration. As the SDS concentration increases, I 650nm / I 525nm The fluorescence intensity ratio gradually increased. According to the calculation method of the detection limit, the detection limit of the probe molecule for SDS is 0.2μmol / L.

[0126] 5. Specificity of Aggregated Cationic Polythiophene Probes for Colorimetric and UV Spectroscopic Sensing of Anionic Surfactants

[0127] Common anions in water include (Cl - 、ClO3 - 、CO3 2- 、HCO3 - 、NO3 - 、SO4 2- 、F - PO4 3- 、HPO4 2- 、H2PO4 - ), nonionic surfactants (Tween-20, Triton X-100), and cationic surfactant CTAB as interfering substances in the detection of anionic surfactants (SDS, SDBS);

[0128] In order to more intuitively observe the effect of the interaction between the probe molecule and the anionic surfactant, the color change of the solution was observed under a fluorescent lamp and photographed with a camera;

[0129] like Fig.11 As shown in A, when interfering substances are added to the aggregated probe molecules, the color of the solution does not change, but when SDS and SDBS are added, the color of the solution turns red.

[0130] The probe mother solution was dissolved in ultrapure water to obtain a probe molecule solution. 2 mL of the obtained probe molecule solution was added to a colorimetric cell of uniform volume as a reagent for detecting anionic surfactants. Under the same conditions, a UV-visible absorption spectrum was scanned, and the absorbance value at 525 nm was compared with the absorbance value at 405 nm. 525nm / A 405nm As a parameter to measure the response of the probe molecule to the substance to be tested;

[0131] The results are as follows Fig.11 As shown in B, except for SDS and SDBS, the A 525nm / A 405nm The ratio is <0.3, while the A 525nm / A 405nm The ratio was >1.7, indicating that the aggregated probe molecules also had good selectivity when detecting anionic surfactants using UV-visible absorption spectroscopy;

[0132] 6. Aggregated cationic polythiophene probes for specific detection of anionic surfactants by fluorescence colorimetry and fluorescence spectroscopy

[0133] Common anions in water including (Cl, ClO3, CO32, HCO3, NO3, SO42, F-, PO43-, HPO42, H2PO4), non-ionic surfactants (Tween-20, Triton X-100), and cationic surfactant CTAB were selected as interfering substances in the detection of anionic surfactants (SDS, SDBS);

[0134] In order to more intuitively observe the effect of the interaction between the probe molecule and the anionic surfactant and other interfering substances, the change of solution fluorescence during the selective investigation of the probe molecule on the anionic surfactant was observed under blue light (470nm);

[0135] like Fig.11 As shown in C, when interference substances are added to the aggregated probe molecules, the fluorescence color does not change, but when SDS and SDBS are added, the fluorescence color turns red and a certain degree of fluorescence quenching occurs;

[0136] The probe mother solution was dissolved in ultrapure water to obtain a probe molecule solution. 2 mL of the obtained probe molecule solution was added to a fluorescence cell of uniform volume as a reagent for detecting anionic surfactants (SDS, SDBS). Fluorescence spectrum scanning was performed under the same conditions, and the fluorescence value at 655 nm was compared with the fluorescence value at 520 nm. 655nm / I 520nm As a parameter to measure the response of the probe molecule to the substance to be tested;

[0137] The results are as follows Fig.11 D shows that the I of the substances except SDS and SDBS 655nm / I 520nm The ratio is <2, while the I 655nm / I 520nm The ratio was >38, indicating that the aggregated probe molecules could also specifically detect anionic surfactants.

[0138] Example 4: Detection of various anionic surfactants using polythiophene probes

[0139] In order to prove whether the SDS detection method has universal practicability for the detection of anionic surfactants with different alkyl chain lengths and functional groups. Anionic surfactants with different carbon chain lengths (C8: OS, SOS; C12: SDC, SDS, SDBS) and different head groups (carboxylic acid group: SDC; sulfonic acid group: OS; benzenesulfonic acid group: SDBS; sulfate group: SOS, SDS) were selected to investigate the detection effect of polythiophene probe on different anionic surfactants.

[0140] The probe mother solution was dissolved in ultrapure water to obtain a probe molecule solution. 2 mL of the obtained probe molecule solution was added to a colorimetric cell of uniform volume as a reagent for detecting anionic surfactants. Under the same conditions, a UV-visible absorption spectrum was scanned, and the absorbance value at 525 nm was compared with the absorbance value at 405 nm. 525nm / A 405nm As a parameter to measure the response of the probe molecule to the substance to be tested;

[0141] The results are as follows Fig.12 show, Fig.12 A shows that after adding anionic surfactant, the absorbance of the probe molecule at 405nm decreases, while the absorbance at 525nm increases. Fig.12 B shows the absorbance ratio of A 525nm / A 405nm The relationship between different anionic surfactants shows that when the head groups of anionic surfactants are the same, the detection effect of 12 carbon chain lengths is better than that of 8 carbon chain lengths; and among different head groups of anionic surfactants, the detection effect is sulfate group>benzenesulfonic acid group>sulfonic acid group>carboxylic acid group.

[0142] Example 5: Removal of anionic surfactants by cationic polythiophene probe molecules

[0143] The probe molecule and a trace amount of anionic surfactant were mixed and added to the ultrafiltration tube, and ultrafiltration was centrifuged at 5000g for 10 minutes. The permeate was taken out and evaporated and concentrated to 2 mL. After concentration, the probe molecule was added again for UV-visible absorption spectrum scanning. The absorbance value at 535nm was read and the ratio of the absorbance value at 405nm was taken as an important parameter to measure the removal effect.

[0144] The results are as follows Fig.12 As shown, after adding the probe solution (PT), the absorbance ratio of the anionic surfactant in the permeate decreased significantly. This method can effectively remove low-concentration anionic surfactants in water. The range of ultrafiltration removal of anionic surfactants is 0.1-20μM, and the removal rate can reach 97%.

[0145] Matters not covered in the present invention are known technologies. The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A cationic polythiophene derivative for detecting and removing anionic surfactants, characterized in that: The structure is shown in formula (I) and formula (II): Formula (I) is a homopolymer structure, R1 is H or CH3; R2 is O or CH2; R3 is an alkyl group with an integer of carbon number between 1 and 6 and its isomers: methyl, ethyl, propyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, isohexyl; R4 is H or CH3; m is an integer between 0 and 15; M is Cl or Br; n is a positive integer, and the weight average molecular weight of the polythiophene derivative is 3,000 to 50,000; Formula (II) is composed of thiophene units connected through the 2 and 5 positions to form a conjugated main chain, and its structural formula is shown below: Formula (II) is a copolymer structure, R1 is H or CH3; R2 is O or CH2; m is an integer between 0 and 15; M is Cl or Br; R 1# ,R 2# ,R 3# ,R 4# , selected from R in the above formula (I) # Substituents, wherein R3 is an alkyl group with an integer carbon number between 1 and 6 and its isomers: methyl, ethyl, propyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, isohexyl; R4 is H or CH3; and satisfies R 1# ≠R 2# ≠R 3# ≠R 4# ; n1, n2, n3, n4 are integers between 1 and 500, and make the weight-average molecular weight of the polythiophene derivative be between 3,000 and 100,000.

2. The cationic polythiophene derivative for detecting and removing anionic surfactants according to claim 1, characterized in that: The types of anionic surfactants detected and removed include alkyl carboxylic acids: sodium dodecyl carboxylate SDC, alkyl sulfonic acids: sodium octyl sulfonate OS, alkyl benzene sulfonic acids: sodium dodecyl benzene sulfonate SDBS, alkyl sulfates: sodium octyl sulfate SOS, sodium dodecyl sulfate SDS.

3. A method for detecting anionic surfactants using the cationic polythiophene derivative according to claim 1, characterized in that: The following steps are involved: (1) dissolving the cationic polythiophene derivatives represented by formula (I) and formula (II) in water to prepare probe molecules; (2) adding the probe molecule obtained in step (1) into a quartz cuvette to obtain a detection reagent; (3) gradually adding anionic surfactant standard solution into the cuvette, and measuring the change of its UV-visible absorption spectrum and fluorescence spectrum; (4) Analyze the relationship between the absorbance ratio and the change in the concentration of the specific anionic surfactant and the relationship between the fluorescence intensity and the change in the concentration of the specific anionic surfactant to perform quantitative specific detection of the anionic surfactant in the solution.

4. The method for detecting anionic surfactants using cationic polythiophene derivatives according to claim 3, characterized in that: The concentration of the cationic polythiophene derivative in the detection system is 0.1-100 μM, the reaction volume is 200-3000 μL, the reaction pH is 4-14, the reaction temperature is 4-40° C., and the reaction system is ultrapure water and HEPES buffer solution.

5. A method for removing anionic surfactants using the cationic polythiophene derivative according to claim 1, characterized in that: The following steps are involved: (1) dissolving the cationic polythiophene derivative represented by formula (I) / formula (II) in ultrapure water to obtain a probe molecule solution; (2) adding the probe molecule prepared in step (1) into water containing anionic surfactant to react; (3) After the reaction is completed, the solution is added to a removal system for separation and removal, and the sample after removal is analyzed to obtain the efficiency of the probe molecule in removing the corresponding anionic surfactant.

6. The method for removing anionic surfactants using a cationic polythiophene derivative according to claim 5, characterized in that: When the concentration of the anionic surfactant is 0.1-20 μM, an ultrafiltration system is used for separation and removal, and the pore size of the ultrafiltration system includes but is not limited to: 3-300 kDa.

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