Cationic polythiophene derivative for detecting and removing Cr (VI) and method thereof

Abstract

The invention relates to the technical field of inorganic anion pollutant detection, in particular to a cationic polythiophene derivative for detecting and removing Cr (VI) and a method thereof. The cationic polythiophene derivative has good water solubility, shows obvious specificity in detection, and can sensitively detect Cr (VI). The conformation and aggregation states of the compound with the structure in a solution show different states to external stimulation, so that the optical characteristics of the compound are changed. According to the method, Cr (VI) is detected by utilizing solution color change and fluorescence intensity change caused by reaction of polythiophene and Cr (VI), and a polythiophene derivative-Cr (VI) compound after reaction is removed through a removal system. The detection method has high specificity and sensitivity and supports visual detection, the provided recovery method is easy and convenient to operate and wide in application range, and synchronous dual-mode detection and removal of Cr (VI) in water can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic anion pollutant detection, and in particular to a cationic polythiophene derivative for detecting and removing Cr(VI) and a method thereof. Background Art

[0002] Chromium (Cr) is one of the 45 heavy metal elements belonging to the VIB group. It has a silvery white luster and high corrosion resistance. In nature, chromium exists mainly in two oxidation states: trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)). Cr(VI) is a strong oxidant with high solubility and is usually present in the form of chromate and dichromate (CrO 4 2- and Cr 2 O 7 2- ), Cr(VI) compounds have teratogenic, carcinogenic and mutagenic properties. It is not only harmful to mammals and aquatic organisms, but also causes damage to water bodies, algae and soil. Studies have shown that Cr(VI) can enter the human body through skin wounds and cause chromium ulcers. Long-term contact may also cause bleeding and perforation of the nasal septum. In severe cases, it may even corrode internal organs and cause gastric ulcers. In addition, Cr(VI) can also induce mutations in human peripheral blood lymphocytes and increase the risk of lung cancer, respiratory cancer and bronchial cancer. The "GB5749-2022 Drinking Water Hygiene Standard" implemented by the state stipulates that the limit of Cr(VI) in drinking water is 0.05 mg / L to ensure the safety of drinking water.

[0003] At present, the methods for detecting Cr(VI) include spectrophotometry, atomic absorption spectroscopy, electrochemical method and chromatography. Xie Lijun et al. (Chinese patent: CN118546673A) developed a fluorescent probe based on metal organic frameworks (MOFs) for efficient and sensitive detection of Cr(VI) ions in water. Ning Zhanglei et al. (Chinese patent: CN118599527A) disclosed a multi-channel fluorescence sensor array for detecting Cr(VI) in water. The sensor array uses covalent organic framework materials (COFs) as fluorescent probes. The material has a highly selective and sensitive fluorescence response to Cr(VI) and can quickly and accurately detect the presence of Cr(VI) in water environments. Most of the existing detection methods are based on fluorescence sensing. In order to overcome the problems of strong background interference of single sensing and limited application, a method for developing ultraviolet / fluorescence dual-mode sensing technology to detect Cr(VI) is proposed.

[0004] Since the presence of Cr(VI) is seriously harmful to human body and water quality, scientists have developed a series of methods to remove Cr(VI): chemical precipitation, ion exchange, membrane separation technology, electrochemical method, bioremediation, etc. Existing methods require a large amount of chemical reagents, high removal cost, long removal cycle, secondary pollution and other problems. Therefore, it is of great significance to establish a simple, rapid, highly sensitive and environmentally friendly new method for simultaneous detection and removal of Cr(VI). Summary of the invention

[0005] The object of the present invention is to provide a method for detecting and removing hexavalent chromium by using cationic polythiophene derivatives.

[0006] In order to achieve the purpose of the present invention, the following technical solutions are provided:

[0007] A cationic polythiophene derivative for detecting and removing Cr(VI) has a structure as shown in formula (I) and formula (II):

[0008]

[0009] Formula (I) is a homopolymer structure, R 1 H or CH 3 ; R 2 O or CH 2 ; R 3 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; R 4 H or CH 3 ; 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;

[0010] 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:

[0011]

[0012] Formula (II) is a copolymer structure, R 1 H or CH 3 ; R 2 O or CH 2 ; 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, where R 3is 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; R 4 H or CH 3 ; and satisfy R 1# ≠R 2# ≠R 3# ≠R 4# ;n 1 , n 2 , n 3 , n 4 is an integer between 1 and 500, and makes the weight-average molecular weight of the polythiophene derivative be between 3,000 and 100,000.

[0013] A method for detecting Cr(VI) using a cationic polythiophene derivative comprises the following steps:

[0014] (1) dissolving the cationic polythiophene derivative in water to prepare a probe molecule;

[0015] (2) adding the probe molecule obtained in step (1) into a quartz cuvette to obtain a detection reagent;

[0016] (3) gradually adding the Cr(VI) standard solution into the cuvette and measuring the changes in its UV-visible absorption spectrum and fluorescence spectrum;

[0017] (4) The relationship between the absorbance ratio and the change of Cr(VI) concentration and the relationship between the fluorescence intensity and the change of Cr(VI) concentration were analyzed to perform quantitative and specific detection of Cr(VI) in the solution.

[0018] Furthermore, the concentration of the cationic polythiophene derivative is 10-150 μM, the reaction volume is 200-3000 μL, the reaction pH is 3-13, the reaction temperature is 4-35° C., and the reaction system is ultrapure water, buffer solution HEPES, or an aqueous solution containing an organic solvent such as methanol, ethanol, or acetonitrile.

[0019] A method for removing Cr(VI) using the cationic polythiophene derivative, in order to achieve the purpose of removing Cr(VI);

[0020] The steps of removing Cr(VI) by the probe molecule of the present invention are as follows:

[0021] (1) dissolving Formula I / Formula II in ultrapure water to obtain a probe molecule solution;

[0022] (2) adding the probe molecule prepared in step (1) to water containing Cr(VI) for reaction;

[0023] (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 Cr(VI);

[0024] Furthermore, Cr(VI) was separated and removed using precipitation when the concentration was 0.1-100 mM.

[0025] Furthermore, when the concentration of Cr(VI) is 5-500 μM, microfiltration is used for separation and removal, and the types of filter membranes include but are not limited to: PES, PVDF, PTFE, PC, PP, Nylon66; the pore size of the filter membrane includes but is not limited to 0.2-0.45 μm.

[0026] Furthermore, when the concentration of Cr(VI) is 20-200 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.

[0027] Furthermore, when the concentration of Cr(VI) is 50-300 μM, a dialysis bag is used for separation and removal, and the pore size of the dialysis bag includes but is not limited to 8-50 kDa; the material of the dialysis bag includes but is not limited to cellulose ester CE, regenerated cellulose RC, and PVDF.

[0028] The beneficial effects of the present invention are embodied in:

[0029] The present invention provides a method for detecting and removing hexavalent chromium using a cationic polythiophene derivative. The method detects Cr(VI) by using the solution color change and fluorescence intensity change caused by the reaction of polythiophene with Cr(VI), and removes the polythiophene derivative-Cr(VI) complex after the reaction through a removal system. The detection method of the present invention has high specificity and sensitivity, supports visual detection, and the recovery method provided is simple to operate and has a wide range of applications, and can realize synchronous dual-mode detection and removal of Cr(VI) in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 In Example 1 of the present invention, different R 1 The effect diagram of the probe molecule of formula (I) with substituents for detecting Cr(VI), A) is listed as different PT names and different R 1 Structural differences of substituents; B) is a schematic diagram of colorimetry and absorption spectrum sensing; C) is a schematic diagram of fluorescence colorimetry and fluorescence spectrum sensing.

[0031] Figure 2 This is a diagram showing the effect of detecting Cr(VI) by using the probe molecule of formula (I) with different carbon chain lengths m in Example 1 of the present invention, wherein A) lists different PT names 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.

[0032] Figure 3 In Example 1 of the present invention, different R # The effect diagram of the probe molecule of formula (I) with substituents for detecting Cr(VI), A) is listed as different PT names and different R # Structural differences of substituents; 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 4 The effect diagram of using probe molecular formula (II) with different structures to detect Cr(VI) in Example 1 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.

[0034] Figure 5 The effect diagram of detecting Cr(VI) under different PT concentration conditions in Example 2 of the present invention, A) is a diagram of different PT concentrations; B) is a schematic diagram of colorimetry and absorption spectrum sensing; C) is a schematic diagram of fluorescence colorimetry and fluorescence spectrum sensing.

[0035] Figure 6 The effect diagram of detecting Cr(VI) under different solvent conditions in Example 2 of the present invention, A) is a diagram of different solvents; B) is a schematic diagram of colorimetry and absorption spectrum sensing; C) is a schematic diagram of fluorescence colorimetry and fluorescence spectrum sensing.

[0036] Figure 7 The effect diagram of detecting Cr(VI) under different pH conditions in Example 2 of the present invention, A) is a diagram of different pH; B) is a schematic diagram of colorimetry and absorption spectrum sensing; C) is a schematic diagram of fluorescence colorimetry and fluorescence spectrum sensing.

[0037] Figure 8 For detecting CrO in Example 2 of the present invention 4 2- and Cr 2 O 7 2- Comparison diagram, A) is the visual colorimetric diagram; B) is the fluorescence colorimetric diagram; C) is the ultraviolet absorption spectrum diagram; D) is the fluorescence spectrum diagram.

[0038] Fig. 9The diagram is a diagram of the probe molecule and the Cr(VI) ultraviolet sensing effect in Example 3 of the present invention, wherein A) is a diagram showing the relationship between the change in Cr(VI) concentration and the change in PT absorption spectrum; B) is a diagram showing the relationship between the change in Cr(VI) concentration and the change in PT absorbance ratio; the inset diagram shows the linear relationship between the absorbance ratio and the Cr(VI) concentration; C) is a diagram showing the relationship between the change in Cr(VI) concentration and its own absorption spectrum; D) is a diagram showing the relationship between the change in Cr(VI) concentration and the change in its own absorbance ratio; E) a colorimetric visualization diagram of the probe molecule and different concentrations of Cr(VI); F) a colorimetric change diagram of different concentrations of Cr(VI) and the R / (G+B) value of the probe molecule.

[0039] Fig.10 The colorimetric effect diagram of the probe molecule specifically identifying Cr(VI) in Example 3 of the present invention, A) the color change diagram after different ions react with PT; B) the absorbance ratio A after different ions react with PT 525nm / A 400nm 's change graph.

[0040] Fig.11 The diagram is a fluorescence sensing effect diagram of the probe molecule and Cr(VI) in Example 4 of the present invention, wherein A) is a relationship diagram between the change in Cr(VI) concentration and the change in PT fluorescence emission spectrum; B) is a relationship diagram between the change in Cr(VI) concentration and the change in fluorescence quenching rate; C) fluorescence visualization diagram of the probe molecule and different concentrations of Cr(VI) under blue light irradiation; D) a diagram of the change in R / (G+B) values ​​of different concentrations of Cr(VI) and the probe molecule under blue light irradiation.

[0041] Fig.12 The fluorescence effect diagram of the probe molecule specifically identifying Cr(VI) in Example 4 of the present invention is shown in Figure 4. A) The fluorescence color change diagram after different ions react with PT under 420nm blue light excitation; B) The fluorescence quenching rate change diagram after different ions react with PT.

[0042] Fig.13 This is a diagram showing the effect of the probe molecule in Example 5 of the present invention on the removal of Cr(VI), AB is precipitation removal (Figure A: flow chart, Figure B: effect diagram of precipitation removal of Cr(VI)); CD is microfiltration removal of Cr(VI) (Figure C: flow chart, Figure D: effect diagram of microfiltration removal of Cr(VI)); EF is ultrafiltration removal of Cr(VI) (Figure E: flow chart, Figure F: effect diagram of ultrafiltration removal of Cr(VI)); GH is dialysis removal of Cr(VI) (Figure G: flow chart, Figure H: effect diagram of dialysis removal of Cr(VI)).

[0043] Fig.14 Effect diagram of recycling probe molecules in Example 5 of the present invention, A) schematic diagram of the principle of recycling probes; B) effect diagram of recycling probe molecules. DETAILED DESCRIPTION

[0044] In order to deepen the understanding of the present invention, the following is a further detailed description of the embodiments in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, but are not intended to limit the present invention.

[0045] First, the present invention provides cationic polythiophene derivatives represented by formula (I) and formula (II).

[0046]

[0047] Formula (I) is a homopolymer structure, R 1 H or CH 3 ; R 2 O or CH 2 ; R 3 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); R 4 H or CH 3 ; 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.

[0048] 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:

[0049]

[0050] Formula (II) is a copolymer structure, R 1 H or CH 3 ; R 2 O or CH 2 ; 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, where R 3 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); R 4 H or CH 3 ; and satisfy R 1# ≠R 2# ≠R 3# ≠R 4# ;n 1 , n 2 , n 3 , n4 is an integer between 1 and 500, and makes the weight-average molecular weight of the polythiophene derivative be between 3,000 and 100,000.

[0051] 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 Cr(VI). The conformation and aggregation state of the compounds of the structures shown in the above formula (I) and formula (II) in the solution show different states to external stimuli, thereby causing changes in their optical properties.

[0052] Second, the present invention provides a probe molecule for visual dual-mode detection of Cr(VI) ions, which can be used for rapid, quantitative and specific detection of Cr(VI);

[0053] In order to achieve the purpose of detecting Cr(VI);

[0054] The steps of rapid detection of Cr(VI) by the probe molecule of the present invention are as follows:

[0055] (1) dissolving the cationic polythiophene derivative in water to prepare a probe molecule;

[0056] (2) adding the probe molecule obtained in step (1) into a quartz cuvette to obtain a detection reagent;

[0057] (3) gradually adding the Cr(VI) standard solution into the cuvette and measuring the changes in its UV-visible absorption spectrum and fluorescence spectrum;

[0058] (4) Analyze the relationship between the absorbance ratio and the change of Cr(VI) concentration and the relationship between the fluorescence intensity and the change of Cr(VI) concentration, and perform quantitative and specific detection of Cr(VI) in the solution.

[0059] Preferably, 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 3-13, and more preferably pH=7; (4) the concentration of the polythiophene derivative is 10-150 μM, and more preferably 50 μM.

[0060] Third: The present invention provides a method for removing Cr(VI) from water, in order to achieve the purpose of removing Cr(VI);

[0061] The steps of removing Cr(VI) by the probe molecule of the present invention are as follows:

[0062] (1) dissolving Formula I / Formula II in ultrapure water to obtain a probe molecule solution;

[0063] (2) adding the probe molecule prepared in step (1) to water containing Cr(VI) for reaction;

[0064] (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 Cr(VI);

[0065] Preferably, the removal reaction of the present invention can be separated and removed using different systems:

[0066] (1) Precipitation removal: Cr(VI) is separated and removed by precipitation when the concentration is 0.1-100 mM;

[0067] (2) microfiltration removal, preferably using microfiltration for separation and removal when the Cr(VI) concentration is 5-500 μM, the types of filter membranes include but are not limited to: PES, PVDF, PTFE, PC, PP, Nylon66; the pore size of the filter membrane includes but is not limited to 0.2-0.45 μm;

[0068] (3) ultrafiltration removal, preferably using an ultrafiltration system for separation and removal when the Cr(VI) concentration is 20-200 μM, and the pore size of the ultrafiltration system includes but is not limited to: 3-300 kDa;

[0069] (4) Dialysis removal, preferably using a dialysis bag for separation and removal when the Cr(VI) concentration is 50-300 μM, the pore size of the dialysis bag includes but is not limited to 8-50 kDa; the material of the dialysis bag includes but is not limited to cellulose ester CE, regenerated cellulose RC, and PVDF.

[0070] Example 1: Structural characteristics of cationic polythiophene probes for recognizing Cr(VI) ions

[0071] Homopolymer PT1-PT18 was synthesized by referring to the literature (Chinese patent: CN118480172A).

[0072] The prepared probe molecules with different structures (Formula I and Formula II) are added into the cuvettes respectively to obtain the Cr(VI) detection reagents;

[0073] The Cr(VI) standard solution was added into the cuvette to measure the changes in UV-visible absorption spectrum, fluorescence spectrum, visual color and fluorescence color.

[0074] like Figure 1 As shown, in the molecule of the regulating formula (I), R 1 After the structure of the substituent group, the probe molecule has a signal output response to Cr(VI), 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) is R1 The structure is CH 3 When H and Cr(VI) are used, it can be used for UV / fluorescence dual-mode detection.

[0075] like Figure 2 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 Cr(VI), 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 Cr(VI).

[0076] like Figure 3 As shown, in the molecule of the regulating formula (I), R # After the structure of the substituent group, the probe molecules all have a good signal output response to Cr(VI), indicating that the synthesized probe molecule formula (I) R # Substituents such as quaternary ammonium salt substituents (methyl, ethyl, propyl, butyl, hexyl), 1-methylimidazole, and 1,2-dimethylimidazole structures can all be used for UV / fluorescence dual-mode detection of Cr(VI).

[0077] like Figure 4 As shown, after adjusting the structure and polymerization ratio of the monomers in the molecule of formula (II), the probe molecules have a good signal output response to Cr(VI), indicating that the synthesized probe molecule of formula (II) can be used for UV / fluorescence dual-mode detection of Cr(VI) after adjusting the structure and polymerization ratio of the monomers.

[0078] Example 2: Experimental conditions for identifying Cr(VI) ions

[0079] Adding the prepared probe molecule into a cuvette to obtain a Cr(VI) detection reagent;

[0080] The experimental conditions were changed, and the Cr(VI) standard solution was added into the cuvette to measure the changes in UV-visible absorption spectrum, fluorescence spectrum, visual color and fluorescence color.

[0081] like Figure 5 As shown, after adjusting the concentration of the probe molecule, it still has a signal output response to Cr(VI), indicating that the probe molecule can be used for UV / fluorescence dual-mode detection of Cr(VI) when the concentration is 10-150 μM.

[0082] like Figure 6 As shown, after changing different solvents, the probe molecule has a signal output response to Cr(VI), indicating that the probe molecule can be used for UV / fluorescence dual-mode detection of Cr(VI) in methanol / water (10:90, V / V), ethanol / water (10:90, V / V), acetonitrile / water (10:90, V / V), and HEPES buffer.

[0083] like Figure 7As shown, after changing the pH value of the reaction system, the probe molecules all have signal output responses to Cr(VI), indicating that the probe molecules can be used for UV / fluorescence dual-mode detection of Cr(VI) at pH values ​​of 3-13.

[0084] like Figure 8 As shown, adding different Cr(VI) compounds CrO 4 2- and Cr 2 O 7 2- The UV-visible spectra of both of them changed, and the fluorescence was quenched. The probe molecule was sensitive to CrO 4 2- and Cr 2 O 7 2- All of them had signal output responses, indicating that the probe molecule can detect different compound forms of Cr(VI).

[0085] Example 3: Cationic polythiophene probe for colorimetric and ultraviolet spectroscopy sensing of Cr(VI) ions

[0086] 1. Quantitative detection of Cr(VI) by colorimetry and UV-visible absorption spectroscopy

[0087] The probe mother solution was dissolved in ultrapure water to obtain a probe molecule solution, and 2 mL of the obtained probe molecule solution was added to a cuvette of uniform volume as a reagent for detecting Cr(VI).

[0088] Scan the UV-visible absorption spectrum of the probe molecule, then gradually add a certain concentration of Cr(VI) standard solution into the cuvette, mix evenly, measure its UV-visible absorption spectrum, and read the peaks at 400nm and 525nm. The results are as follows: Fig. 9 show, Fig. 9 A) shows that the absorbance of the aforementioned probe molecule at 400nm gradually decreases with the addition of Cr(VI). As the concentration of Cr(VI) increases, the peak at 525nm gradually increases, while the peak at 400nm gradually decreases. 525nm / A 400nm There is a good linear correlation with the concentration of Cr(VI), R 2 =0.98775. According to the detection limit calculation method, the detection limit of the probe molecule for Cr(VI) is 0.38 μmol / L.

[0089] Gradually add a certain concentration of Cr(VI) standard solution into the cuvette, mix well and measure its UV-visible absorption spectrum, such as Fig. 9 C) As shown in Figure 1, the color of Cr(VI) itself will increase with the increase of concentration. Read the peak values ​​at 400nm and 525nm and make a ratio. The result is as follows: Fig. 9 As shown in D), the relationship between the absorbance ratio of Cr(VI) itself, A525 nm / A400 nm, and the concentration of Cr(VI) is a constant straight line, indicating that the color of Cr(VI) will not affect the detection of the probe.

[0090] Add different concentrations of Cr(VI) standard solutions into vials, mix well, take photos under natural light, and use Color Grab software to extract the RGB value of each vial. Fig. 9 E) The results show that as the concentration of Cr(VI) increases, the solution color of the probe molecule gradually changes from yellow to red, and the visible detection limit is 8μmol / L; Fig. 9 F), the R value / (G+B) value obtained by the software is linearly related to the concentration of Cr(VI), and the correlation coefficient R 2 =0.96549, detection limit 4μmol / L.

[0091] 2. Specificity of colorimetric and UV spectroscopy sensing for detecting Cr(VI)

[0092] Common ions were selected as interfering ions for the detection of Cr(VI). In the test, the concentration of the aforementioned polythiophene derivative was 50 μmol / L, and the concentration of all ions was 100 μmol / L. The UV-visible absorption spectrum was tested under the same test conditions. The absorbance ratio of the probe before and after the addition of the interfering substance was used as a parameter to measure the influence of the probe on the analyte.

[0093] like Fig.10 As shown in the figure, the results show that when different ions are added to the probe molecule solution, only when Cr(VI) is added, the solution color changes from yellow to pink, and the absorbance ratio A 525nm / A 400nm It is significantly higher than other ions, so the probe molecule can specifically detect Cr(VI).

[0094] Example 4: Cationic polythiophene probe for fluorescence colorimetry and fluorescence spectroscopy sensing of Cr(VI) ions

[0095] 1. Quantitative detection of Cr(VI) by fluorescence colorimetry and fluorescence spectroscopy

[0096] The probe mother solution was dissolved in ultrapure water to obtain a probe molecule solution, and 2 mL of the obtained probe molecule solution was added to a cuvette of uniform volume as a reagent for detecting Cr(VI).

[0097] Add Cr(VI) dropwise, mix well and measure its fluorescence spectrum respectively, such as Fig.11 As shown in Figure A), the probe molecule has an emission peak of 540nm under 420nm excitation. With the addition of Cr(VI), the emission peak of the probe molecule gradually decreases. Fig.11 As shown in Figure B), the addition of Cr(VI) caused the fluorescence quenching rate to increase continuously, and the detection limit was 0.25 μmol / L based on the degree of fluorescence quenching.

[0098] Add different concentrations of Cr(VI) standard solutions into vials, mix well, take photos under blue light excitation, and use Color Grab software to extract the RGB value of each vial. Fig.11 C) The results show that as the concentration of Cr(VI) increases, the yellow fluorescence of the probe molecule solution gradually quenches, and the visible detection limit is 10 μmol / L; Fig.11 D), the R value / (G+B) value obtained by the software is linearly related to the concentration of Cr(VI), and the correlation coefficient R 2 =0.97548, detection limit 6μmol / L.

[0099] 2. Specificity of fluorescence colorimetry and fluorescence spectroscopy in detecting Cr(VI)

[0100] Common ions were selected as interfering ions for the detection of Cr(VI). In the test, the concentration of the polythiophene derivative was 50 μmol / L, and the concentration of all ions was 100 μmol / L. The fluorescence spectrum was tested under the same test conditions. The fluorescence quenching rate (I 0 -I) / I 0 ) is used as a parameter to measure the influence of the probe on the analyte.

[0101] like Fig.12 A) is the fluorescence change of the probe molecule under 420nm blue light before and after the addition of Cr(VI) and other ions. The probe molecule itself exhibits yellow fluorescence, and after the addition of Cr(VI), the fluorescence is significantly quenched and the fluorescence color gradually changes from yellow to red. This result can be observed by the naked eye. After the addition of other ions, the fluorescence of the probe molecule does not undergo obvious quenching and color change.

[0102] The fluorescence spectrum was tested under the same test conditions. The ratio of the red-shifted emission peak after adding ions to the emission peak of the polythiophene derivative was used as a parameter to measure the influence of the probe on Cr(VI). The results are shown in Figure 2. Fig.12 As shown in Figure B), after the aforementioned probe molecule interacted with Cr(VI) and other ions, the fluorescence quenching rate of Cr(VI) increased significantly compared with other ions, indicating that the probe molecule has good specificity for Cr(VI).

[0103] Example 5: Cationic polythiophene probe molecules for removal of Cr(VI) ions

[0104] 1. Removal of Cr(VI) ions

[0105] For water samples contaminated with Cr(VI), precipitation can be used to remove it. Probe molecules are added. Since Cr(VI) causes probe molecules to aggregate, the effect of precipitation removal is shown in the figure below. Fig.13 As shown in A), it can be seen that the addition of Cr(VI) will change the structure of the probe molecule, and a precipitation effect will occur when it is left to stand. The precipitation is visible to the naked eye. The precipitate is placed for 30 minutes and then centrifuged to obtain the supernatant. The supernatant is diluted 50 times and the probe molecule is added again for UV-visible absorption spectrum scanning. The absorbance value at 525nm is read and the ratio of the absorbance value at 400nm is taken as an important parameter to measure the removal effect;

[0106] The results are as follows Fig.13 As shown in Figure B, with the increase of the probe molecule concentration, the Cr(VI) content in the supernatant decreased significantly. According to the absorbance ratio, the removal rate of Cr(VI) by the probe molecule reached 99.75%, and the range of Cr(VI) removal by precipitation was 0.1-100 mM.

[0107] The probe molecule was added to a solution containing Cr(VI) (200 μM) and shaken for 5 min. The solution was then sucked into a needle filter and microfiltered using a 0.22 μm PES membrane. The probe molecule was added to the filtrate again and the UV-visible absorption spectrum was scanned. The flow chart is shown in the following figure. Fig.13 C), the absorbance value at 525 nm is read and compared with the absorbance value at 400 nm, which is used as an important parameter to measure the removal effect;

[0108] The results are as follows Fig.13 D) As shown, after filtration with a membrane, the complex formed by the probe molecule and Cr(VI) is effectively retained on the microporous membrane, resulting in a reduction in the concentration of Cr(VI) in the filtrate, achieving rapid on-site removal of Cr(VI). As the amount of probe molecules increases, a removal rate of 97.50% can be achieved, and the range of Cr(VI) removal by membrane filtration is 5-500;

[0109] The probe molecule and Cr(VI) (100 μM) were mixed and added to the ultrafiltration tube, and ultrafiltration was centrifuged at 5000 g for 10 min. The permeate layer was taken for UV-visible absorption spectrum scanning. The operation flow chart is shown in the figure. Fig.13 E) as shown, read the absorbance value at 525nm and the absorbance value at 400nm and make a ratio as an important parameter to measure the removal effect;

[0110] The results are as follows Fig.13 F) shows that after adding the probe solution, the absorbance ratio of Cr(VI) in the permeate decreased significantly. This method can effectively remove low-concentration Cr(VI) in water. The range of ultrafiltration removal of Cr(VI) is 20-200 μM, and the removal rate is 89.9%.

[0111] 100 μM probe molecules were loaded into an 8 kDa dialysis bag, which was then placed in 50 mL of Cr(VI) (150 μM) solution and magnetically stirred for 12 h. The schematic diagram of the process is shown in Fig.13 G) shows that the absorbance value at 545 nm is read as a ratio to the absorbance value at 410 nm, which is used as an important parameter to measure the effect of the probe molecule binding to Cr(VI);

[0112] like Fig.13 H), since the dialysis bag has the properties of a semipermeable membrane, Cr(VI) can diffuse inside and outside the dialysis bag. When the dialysis bag containing the probe molecules is immersed in a solution containing Cr(VI), the Cr(VI) diffuses into the dialysis bag and is combined with the probe molecules in the bag to form a complex, which causes the color of the probe molecules in the bag to change, and the absorbance ratio also increases significantly. As the amount of probe molecules increases, the removal rate of Cr(VI) gradually increases, and a large volume of Cr(VI) can be removed, with a removal rate of 73.51%. The concentration range of Cr(VI) removed by dialysis is 50-300μM.

[0113] 2. Cationic polythiophene probe molecule recovery

[0114] The cationic polythiophene probe molecule is combined with Cr(VI). After the combination is completed, NaCl (20mM) solution is added and shaken for 5 minutes. After the shaking is completed, the solution is placed in an ultrafiltration tube for ultrafiltration at 14000rpm and centrifuged for 10 minutes. Since the high concentration of salt solution will destroy the binding state of Cr(VI) and probe molecules, small-sized Cr(VI) and chloride ions can be separated from the probe molecules by ultrafiltration to achieve probe molecule recovery. The retentate is used to add Cr(VI) again for UV-visible absorption spectrum detection to determine the recycling effect of the probe molecules. The principle diagram is shown in the figure. Fig.14 After the detection is completed, NaCl (20mM) solution is added again and the above steps are repeated four times. The absorbance value at 525nm is read and the ratio of the absorbance value at 400nm is taken as an important parameter to measure the recovery effect of the probe molecule; Fig.14 B) The results show that the probe molecule still maintains good detection performance for Cr(VI) even after four cycles, with a reuse rate of 87.69%.

[0115] Matters not covered by the present invention are known technologies.

[0116] 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 Cr(VI), 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 at 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. A method for detecting Cr(VI) 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 the Cr(VI) standard solution into the cuvette and measuring the changes in its UV-visible absorption spectrum and fluorescence spectrum; (4) The relationship between the absorbance ratio and the change of Cr(VI) concentration and the relationship between the fluorescence intensity and the change of Cr(VI) concentration were analyzed to perform quantitative and specific detection of Cr(VI) in the solution.

3. The method for detecting Cr(VI) using a cationic polythiophene derivative according to claim 2, characterized in that: The concentration of the cationic polythiophene derivative in the detection system is 10-150 μM, the reaction volume is 200-3000 μL, the reaction pH is 3-13, the reaction temperature is 4-35° C., and the reaction system is ultrapure water, buffer solution HEPES, or an aqueous solution containing organic solvents such as methanol, ethanol, acetonitrile, etc.

4. A method for removing Cr(VI) 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) to water containing Cr(VI) for reaction; (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 Cr(VI).

5. The method for removing Cr(VI) from a cationic polythiophene derivative according to claim 4, characterized in that: The Cr(VI) is separated and removed by precipitation when the concentration is 0.1-100 mM.

6. The method for removing Cr(VI) from a cationic polythiophene derivative according to claim 4, characterized in that: When the concentration of Cr(VI) is 5-500 μM, microfiltration is used for separation and removal. The types of filter membranes include but are not limited to: PES, PVDF, PTFE, PC, PP, Nylon66; the pore size of the filter membrane includes but is not limited to 0.2-0.45 μm.

7. The method for removing Cr(VI) from a cationic polythiophene derivative according to claim 4, characterized in that: When the concentration of Cr(VI) is 20-200 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.

8. The method for removing Cr(VI) from a cationic polythiophene derivative according to claim 4, characterized in that: When the concentration of Cr(VI) is 50-300 μM, a dialysis bag is used for separation and removal. The pore size of the dialysis bag includes but is not limited to 8-50 kDa; the material of the dialysis bag includes but is not limited to cellulose ester CE, regenerated cellulose RC, and PVDF.

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