Cationic polythiophene derivatives for detecting and removing cr(vi) and methods thereof

Abstract

The present application relates to the technical field of inorganic anion pollutant detection, and particularly relates to a cationic polythiophene derivative for detecting and removing Cr(VI) and a method thereof.The cationic polythiophene derivative has good water solubility, and presents obvious specificity in detection, and can sensitively detect Cr(VI).The compound with the structure exhibits different states to external stimulation in the conformation and aggregation state in the solution, and further causes the change of optical properties.The method utilizes the color change and fluorescence intensity change of the solution caused by the reaction of the polythiophene and Cr(VI) to detect Cr(VI), and removes the polythiophene derivative-Cr(VI) compound after the reaction through a removal system.The detection method has high specificity and sensitivity, supports visual detection, the recovery method provided is simple to operate, has wide application range, and can realize synchronous double-mode detection and removal of Cr(VI) in water.

Description

TECHNICAL FIELD

[0001] The present application 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

[0002] Chromium (Cr) is one of the 45 heavy metal elements, belonging to the VIB group, which has a silver-white luster and high corrosion resistance. In nature, chromium mainly exists in two oxidation states: trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)). Among them, Cr(VI) is a strong oxidizing agent with high solubility, usually in the form of chromate and dichromate (CrO4 2- and Cr2O7 2- ). Cr(VI) compounds have the characteristics of teratogenic, carcinogenic and mutagenic, which are not only harmful to mammals and aquatic organisms, but also cause damage to water bodies, algae and soil. Studies have shown that Cr(VI) can enter the human body through skin wounds, causing chromium ulcers, and long-term contact may cause nasal septum membrane bleeding and perforation, and even severe corrosion of internal organs and gastric ulcers. In addition, Cr(VI) can induce mutations in human peripheral blood lymphocytes, increasing the risk of lung cancer, respiratory cancer and bronchial cancer. The national implementation of the "GB5749-2022 Drinking Water Health Standards" stipulates that the limit of Cr(VI) in drinking water is 0.05mg / L, in order to ensure the safety of drinking water.

[0003] Currently, the methods for detecting Cr(VI) include spectrophotometry, atomic absorption spectrometry, electrochemical method and chromatography, etc. 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, which have high selectivity and sensitivity to Cr(VI) and can quickly and accurately detect the presence of Cr(VI) in the water environment. The existing detection methods are mainly based on fluorescence sensing, in order to overcome the problems of strong background interference of single sensing and limited application, a method of developing ultraviolet / fluorescence dual-mode sensing technology for detecting Cr(VI) is proposed.

[0004] Because the existence of Cr(VI) has serious harm to human body and water quality, scientists have developed a series of methods for removing Cr(VI): chemical precipitation, ion exchange, membrane separation technology, electrochemical method, bioremediation and so on. The existing methods need a large amount of chemical reagents, high removal cost, long removal period, secondary pollution and other problems. Therefore, it is of great significance to establish a simple, rapid, high-sensitivity, environment-friendly new method for simultaneously detecting and removing Cr(VI). SUMMARY

[0005] The purpose of the present application 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 application, 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) or formula (II):

[0008]

[0009] Formula (I) is a homopolymer structure, R1 is H or CH3; R2 is O or CH2; R3 is an alkyl group with an integer 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 0.3 to 5 million;

[0010] Formula (II) is composed of thiophene units connected by 2,5 positions to form a conjugated main chain, and its structural formula is as follows:

[0011]

[0012] 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# , 2# , 3# , 4# is selected from R # in formula (I) above, wherein R3 is an alkyl group with an integer 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 R 1# ≠R 2# ≠R 3# ≠R 4#; n1, n2, n3, n4 are integers between 1-500, and the average molecular weight of the polythiophene derivative is 0.3-10 million.

[0013] A method for detecting Cr(VI) by using the cationic polythiophene derivative, comprising the following steps:

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

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

[0016] (3) adding Cr(VI) standard solution into the colorimetric cell gradually, and measuring the change of ultraviolet-visible absorption spectrum and fluorescence spectrum;

[0017] (4) analyzing the relationship between the absorbance ratio and the Cr(VI) concentration, and the relationship between the fluorescence intensity and the Cr(VI) concentration, and performing quantitative and specific detection of Cr(VI) in the solution.

[0018] Further, 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℃, and the reaction system is ultrapure water, buffer solution HEPES, or an aqueous solution containing organic solvents such as methanol, ethanol, and acetonitrile.

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

[0020] The step of removing Cr(VI) by using the probe molecule:

[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) into water containing Cr(VI) to perform a reaction;

[0023] (3) after the reaction is completed, adding the solution into a removal system to perform separation and removal, and analyzing the removed sample to obtain the efficiency of removing Cr(VI) by using the probe molecule;

[0024] Further, when the concentration of Cr(VI) is 0.1-100 mM, precipitation is used for separation and removal.

[0025] Furthermore, when the Cr(VI) concentration is between 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, and Nylon66; the pore size of the filter membrane includes, but is not limited to, 0.2-0.45 μm.

[0026] Furthermore, when the Cr(VI) concentration is 20-200 μM, an ultrafiltration system is used for separation and removal. The pore size of the ultrafiltration system includes, but is not limited to, 3-300 kDa.

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

[0028] The beneficial effects of this invention are reflected in:

[0029] This invention provides a method for detecting and removing hexavalent chromium using cationic polythiophene derivatives. The method utilizes the color and fluorescence intensity changes in the solution caused by the reaction of polythiophene with Cr(VI) to detect Cr(VI), and then removes the resulting polythiophene derivative-Cr(VI) complex using a removal system. The detection method of this invention has high specificity and sensitivity, supports visual detection, and the provided recovery method is simple to operate and has a wide range of applications, enabling simultaneous dual-mode detection and removal of Cr(VI) in water. Attached Figure Description

[0030] Figure 1 In Embodiment 1 of the present invention, different R values ​​are changed. 1 The effect diagram of the detection of Cr(VI) by the substituent formula (Ⅰ) probe molecule, A) shows the different PT names and different R 1 A) Structural differences of substituents; B) Schematic diagram of colorimetric and absorption spectroscopy sensing; C) Schematic diagram of fluorescence colorimetric and fluorescence spectroscopy sensing.

[0031] Figure 2 The image shows the effect of detecting Cr(VI) by the probe molecule of formula (Ⅰ) with different carbon chain lengths m in Example 1 of the present invention. A) shows the differences between different PT names and different carbon chain lengths m; B) shows the schematic diagram of colorimetric and absorption spectral sensing; C) shows the schematic diagram of fluorescence colorimetric and fluorescence spectral sensing.

[0032] Figure 3 In Embodiment 1 of the present invention, different R values ​​are changed. # The effect diagram of the detection of Cr(VI) by the substituent formula (Ⅰ) probe molecule, A) shows the different PT names and different R #Structure difference of substituent; B) is colorimetric and absorption spectrum sensing diagram; C) is fluorescence colorimetric and fluorescence spectrum sensing diagram.

[0033] Figure 4 Effect diagram of detecting Cr(VI) by using probe molecule formula (II) with different structures in embodiment 1 of the present application, A) is difference of different PT names and different monomer, polymerization ratio; B) is colorimetric and absorption spectrum sensing diagram; C) is fluorescence colorimetric and fluorescence spectrum sensing diagram.

[0034] Figure 5 Effect diagram of detecting Cr(VI) under different PT concentration conditions in embodiment 2 of the present application, A) is different PT concentration; B) is colorimetric and absorption spectrum sensing diagram; C) is fluorescence colorimetric and fluorescence spectrum sensing diagram.

[0035] Figure 6 Effect diagram of detecting Cr(VI) under different solvent conditions in embodiment 2 of the present application, A) is different solvent; B) is colorimetric and absorption spectrum sensing diagram; C) is fluorescence colorimetric and fluorescence spectrum sensing diagram.

[0036] Figure 7 Effect diagram of detecting Cr(VI) under different pH conditions in embodiment 2 of the present application, A) is different pH; B) is colorimetric and absorption spectrum sensing diagram; C) is fluorescence colorimetric and fluorescence spectrum sensing diagram.

[0037] Figure 8 Effect diagram of detecting CrO4 2- and Cr2O7 2- in embodiment 2 of the present application, A) is visual colorimetric diagram; B) is fluorescence colorimetric diagram; C) is ultraviolet absorption spectrum diagram; D) is fluorescence spectrum diagram.

[0038] Figure 9 Effect diagram of ultraviolet sensing of probe molecule and Cr(VI) in embodiment 3 of the present application, A) is relationship diagram between Cr(VI) concentration change and PT absorption spectrum change; B) is relationship diagram between Cr(VI) concentration change and PT absorbance ratio change; interpolation diagram is linear relationship between absorbance ratio and Cr(VI) concentration; C) is relationship diagram between Cr(VI) concentration change and its own absorption spectrum; D) is relationship diagram between Cr(VI) concentration change and its own absorbance ratio change; E) is colorimetric visualization diagram of probe molecule and different concentration Cr(VI); F) is colorimetric change diagram of R / (G+B) value of different concentration Cr(VI) and probe molecule.

[0039] Figure 10Figure A) Color change chart of different ions after reaction with PT; Figure B) Absorbance ratio change chart of different ions after reaction with PT. 525nm / A 400nm .

[0040] Figure 11 Figure A) Relationship chart between Cr(VI) concentration change and PT fluorescence emission spectrum change; Figure B) Relationship chart between Cr(VI) concentration change and fluorescence quenching rate change; Figure C) Fluorescence visualization chart of probe molecules and different concentrations of Cr(VI) under blue light irradiation; Figure D) R / (G+B) value change chart of different concentrations of Cr(VI) and probe molecules under blue light irradiation.

[0041] Figure 12 Figure A) Fluorescence color change chart of different ions after reaction with PT under 420nm blue light excitation; Figure B) Fluorescence quenching rate change chart of different ions after reaction with PT.

[0042] Figure 13 Figure A-B is precipitate removal (Figure A: flowchart, Figure B: Cr(VI) removal effect chart of precipitate removal); Figure C-D is microfiltration removal of Cr(VI) (Figure C: flowchart, Figure D: Cr(VI) removal effect chart of microfiltration); Figure E-F is ultrafiltration removal of Cr(VI) (Figure E: flowchart, Figure F: Cr(VI) removal effect chart of ultrafiltration); Figure G-H is dialysis removal of Cr(VI) (Figure G: flowchart, Figure H: Cr(VI) removal effect chart of dialysis).

[0043] Figure 14 Figure A) Recycling principle schematic diagram of probe; Figure B) Recycling effect chart of probe molecules. DETAILED DESCRIPTION

[0044] In order to deepen the understanding of the present application, the following embodiments are further described in detail in combination with the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and are not a limitation on the present application.

[0045] Firstly, the present application provides a cationic polythiophene derivative represented by formula (I) and formula (II).

[0046]

[0047] Formula (I) is a homopolymer structure, R1 is H or CH3; R2 is O or CH2; R3 is alkyl with an integer between 1-6 carbon number 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 to 15; M is Cl or Br; n is a positive integer, and the weight average molecular weight of the polythiophene derivative is 0.3 to 50,000.

[0048] Formula (II) is composed of conjugated main chain which can be connected by each thiophene unit through 2,5 position, and its structural formula is shown as follows:

[0049]

[0050] Formula (II) is a copolymer structure, R1 is H or CH3; R2 is O or CH2; m is an integer between 0 to 15; M is Cl or Br; R 1# , 2# , 3# , 4# , is selected from R # in formula (I) above, wherein R3 is alkyl with an integer between 1-6 carbon number 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 1-500, and the weight average molecular weight of the polythiophene derivative is 0.3 to 100,000.

[0051] The cationic polythiophene derivative represented by the above formula (I) and formula (II) has good water solubility, and shows obvious specificity in detection, and can sensitively detect Cr(VI). The conformation and aggregation state of the compound represented by the above formula (I) and formula (II) in solution exhibit different states to external stimulation, thereby causing changes in its optical properties.

[0052] Secondly, the application provides a visual bimodal probe molecule for detecting 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 the probe molecule for rapidly detecting Cr(VI) according to the application are as follows:

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

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

[0057] (3) the Cr(VI) standard solution is gradually added to the cuvette, and the change in the ultraviolet-visible absorption spectrum and the fluorescence spectrum are measured;

[0058] (4) the relationship between the absorbance ratio and the Cr(VI) concentration and the relationship between the fluorescence intensity and the Cr(VI) concentration are analyzed to quantitatively and specifically detect the Cr(VI) in the solution.

[0059] Preferably, the conditions of the reaction include: (1) the volume of the reaction system is 200-3000 μL, and the reaction volume is further preferably 2000 μL; (2) the reaction temperature of the reaction system is 4-40°C, and the reaction temperature is further preferably 25°C; (3) the pH value of the reaction system is 3-13, and the pH value is further preferably pH=7; (4) the concentration of the polythiophene derivative is 10-150 μM, and the concentration is further preferably 50 μM.

[0060] Thirdly, the application provides a method for removing Cr(VI) in water, in order to achieve the purpose of removing Cr(VI);

[0061] The probe molecule provided by the application removes Cr(VI) in the following steps:

[0062] (1) formula I / formula II is dissolved in ultrapure water to obtain a probe molecule solution;

[0063] (2) the probe molecule prepared in step (1) is added to water containing Cr(VI) to react;

[0064] (3) after the reaction is completed, the solution is added to a removal system for separation and removal, and the removed sample is analyzed to obtain the efficiency of the probe molecule in removing Cr(VI);

[0065] Preferably, the removal reaction provided by the application can be separated and removed by different systems:

[0066] (1) precipitation removal, when the concentration of Cr(VI) is 0.1-100 mM, precipitation is used for separation and removal;

[0067] (2) microfiltration removal, preferably 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;

[0068] (3) Ultrafiltration removal, preferably when the Cr(VI) concentration 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;

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

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

[0071] Homopolymer PT1-PT18 was synthesized according to the reference (Chinese Patent: CN118480172A).

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

[0073] The changes in ultraviolet-visible absorption spectrum, fluorescence spectrum, visual color change, and fluorescence color change were measured by adding Cr(VI) standard solution to a cuvette.

[0074] like Figure 1 As shown, in the regulatory formula (Ⅰ) molecule, R 1 After the substituent is added, the probe molecule exhibits a signal output response to Cr(VI), specifically manifested as changes in the UV-Vis absorption spectrum and color, and fluorescence quenching accompanied by a change in fluorescence color, indicating that the synthesized probe molecule is (I)thiophene 4-R 1 When the structure is CH3 and H, it can be used for UV / fluorescence dual-mode detection of Cr(VI).

[0075] like Figure 2 As shown, after adjusting the length of the m carbon chain in the (Ⅰ) molecule, the probe molecules all showed good signal output response to Cr(VI), indicating that the synthesized probe molecules with m carbon chain lengths of 1-15 in the (Ⅰ) molecule can all be used for UV / fluorescence dual-mode detection of Cr(VI).

[0076] like Figure 3 As shown, in the regulatory formula (Ⅰ) molecule, R # After the substituents were added, all probe molecules showed good signal output response to Cr(VI), indicating that the synthesized probe molecules with the 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 4As shown, after adjusting the structure and polymerization ratio of the monomers in formula (II), the probe molecules all showed good signal output response to Cr(VI), indicating that the synthesized probe molecule (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 recognizing Cr(VI) ions

[0079] The prepared probe molecules were added to a cuvette to obtain the Cr(VI) detection reagent.

[0080] By changing the experimental conditions, Cr(VI) standard solution was added to a cuvette and the changes in ultraviolet-visible absorption spectrum, fluorescence spectrum, visual color change, and fluorescence color change were measured.

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

[0082] like Figure 6 As shown, the probe molecule exhibits a signal output response to Cr(VI) after changing different solvents, 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 7 As shown, after changing the pH value of the reaction system, the probe molecules all showed a signal output response 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, different Cr(VI) compounds CrO4 were added. 2- and Cr2O7 2- The UV-Vis spectra of both molecules changed, and their fluorescence was quenched. The probe molecules showed a change in their response to CrO4. 2- and Cr2O7 2- All samples showed signal output responses, indicating that the probe molecules can detect different compound forms of Cr(VI).

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

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

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

[0088] The ultraviolet-visible absorption spectrum of the probe molecule was scanned, and then a certain concentration of Cr(VI) standard solution was gradually added into the cuvette. After mixing, the ultraviolet-visible absorption spectrum was measured, and the peak values at 400 nm and 525 nm were read. The results are shown in Figure 9 A). Figure 9 A) shows that the absorbance of the aforementioned probe molecule at 400 nm gradually decreases with the addition of Cr(VI). With the increase of Cr(VI) concentration, the peak value at 525 nm gradually increases, and the peak value at 400 nm gradually decreases. The absorbance ratio A 525nm / A 400nm has 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] A certain concentration of Cr(VI) standard solution was gradually added into the cuvette, and after mixing, the ultraviolet-visible absorption spectrum was measured. As shown in Figure 9 C), the color of Cr(VI) itself increases with the increase of absorbance value. The peak values at 400 nm and 525 nm were read and the results are shown in Figure 9 D). The relationship between the absorbance ratio A525 nm / A400 nm of Cr(VI) itself and the concentration of Cr(VI) is a straight line, which indicates that the color of Cr(VI) does not affect the detection of the probe.

[0090] Different concentrations of Cr(VI) standard solution were added into small bottles, and after mixing, the photos were taken under indoor natural light. The RGB values of each small bottle were extracted using the software Color Grab. As shown in Figure 9 E), the results show that with the increase of the concentration of Cr(VI), the color of the probe molecule solution gradually changes from yellow to red, and the detection limit of the naked eye is 8 μmol / L. As shown in Figure 9 F), the R value / (G+B) value obtained by software reading has a linear relationship with the concentration of Cr(VI), and the correlation coefficient R 2 = 0.96549, and the detection limit is 4 μmol / L.

[0091] 2. Specificity of colorimetric and ultraviolet spectral sensing detection of Cr(VI)

[0092] Common ions were selected as interference ions for detecting Cr(VI). The concentration of the aforementioned polythiophene derivative was 50 μmol / L, the concentration of all ions was 100 μmol / L, and 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 interference was used as a parameter to measure the influence of the probe on the measured substance.

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

[0094] Example 4: Cationic polythiophene probe for fluorescence colorimetric and fluorescence spectral sensing detection of Cr(VI) ions

[0095] 1. Fluorescence colorimetric and fluorescence spectral method for quantitative detection of Cr(VI)

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

[0097] Cr(VI) was added dropwise, mixed, and its fluorescence spectrum was measured, as shown in Figure 11 A), the probe molecule has an emission peak at 540 nm under 420 nm excitation, and with the addition of Cr(VI), the emission peak of the aforementioned probe molecule gradually decreases. As shown in Figure 11 B), the addition of Cr(VI) causes the fluorescence quenching rate to continuously increase, and the detection limit is 0.25 μmol / L according to the degree of fluorescence quenching.

[0098] Different concentrations of Cr(VI) standard solution were added to a vial, mixed, and a photo was taken under blue light excitation. The RGB value of each vial was extracted using the software Color Grab. As shown in Figure 11 C), the results show that with the increase of the concentration of Cr(VI), the yellow fluorescence of the probe molecule solution is gradually quenched, and the detection limit is 10 μmol / L with the naked eye; as shown in Figure 11 D), the R value / (G+B) value obtained by software reading and the concentration of Cr(VI) show a linear relationship, and the correlation coefficient R 2 = 0.97548, and the detection limit is 6 μmol / L.

[0099] 2. Specificity of fluorescence colorimetric and fluorescence spectral sensing detection of Cr(VI)

[0100] Common ions were selected as interference ions for detecting Cr(VI). The concentration of the aforementioned polythiophene derivative was 50 μmol / L, the concentration of all ions was 100 μmol / L, and the fluorescence spectrum was tested under the same test conditions. The fluorescence quenching rate ((I0-I) / I0) of the probe before and after the addition of the interference was used as a parameter for measuring the influence of the probe on the measured substance.

[0101] As Figure 12 A) is the fluorescence change of the probe molecule under 420 nm blue light irradiation before and after the addition of Cr(VI) and other ions. The probe molecule itself presents yellow fluorescence, and after the addition of Cr(VI), significant fluorescence quenching and color change from yellow to red occur, which can be observed by the naked eye. After the addition of other ions, the fluorescence of the probe molecule does not change significantly.

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

[0103] Example 5: Cationic polythiophene probe molecule for removing Cr(VI) ions

[0104] 1. Removing Cr(VI) ions

[0105] For water samples contaminated with Cr(VI), precipitation can be used for removal. The probe molecule is added, and the probe molecule is aggregated due to Cr(VI), and the effect of precipitation removal is shown in Figure 13 A). As can be seen, the addition of Cr(VI) changes the structure of the probe molecule, and the probe molecule can be precipitated under static conditions. After centrifugation for 30 min, the supernatant was collected, diluted 50 times, and then the probe molecule was added again for UV-visible absorption spectrum scanning. The absorbance ratio at 525 nm to the absorbance at 400 nm was used as an important parameter for measuring the removal effect.

[0106] The results are shown in Figure 13 B). As the concentration of the probe molecule increases, the Cr(VI) content in the supernatant decreases significantly, and the removal rate of the probe molecule for Cr(VI) reaches 99.75% according to the absorbance ratio. The range of Cr(VI) removal by precipitation is 0.1-100 mM.

[0107] The probe molecule was added to the solution containing Cr(VI) (200 μM) and shaken for 5 min, and then absorbed into a needle filter. Microfiltration was performed using a 0.22 μm PES membrane. The filtrate was added with the probe molecule again for UV-visible absorption spectrum scanning. The flow chart is shown in Figure 13 C) shows that the absorbance value at 525 nm was read and compared with the absorbance value at 400 nm as an important parameter for measuring the removal effect.

[0108] The results are shown in Figure 13 D) shows that after membrane filtration, the complex formed by the probe molecule and Cr(VI) was effectively retained on the microporous filter, resulting in a decrease in the Cr(VI) concentration in the filtrate, thereby achieving rapid on-site removal of Cr(VI). With the increase of the amount of probe molecule, a removal rate of 97.50% can be achieved. The range of Cr(VI) removal by membrane filtration is 5-500;

[0109] The probe molecule was mixed with Cr(VI) (100 μM) and added to an ultrafiltration tube. Ultrafiltration centrifugation was performed at 5000 g for 10 min. The lower layer of the permeate was taken for UV-visible absorption spectrum scanning. The operation flow chart is shown in Figure 13 E) shows that the absorbance value at 525 nm was read and compared with the absorbance value at 400 nm as an important parameter for measuring the removal effect.

[0110] The results are shown in Figure 13 F) shows that after the addition of 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 Cr(VI) removal by ultrafiltration is 20-200 μM, and the removal rate is 89.9%.

[0111] 100 μM of the probe molecule was loaded into an 8 kDa dialysis bag. The dialysis bag was placed in 50 mL of Cr(VI) (150 μM) solution and magnetically stirred for 12 h. The flow chart is shown in Figure 13 G) shows that the absorbance value at 545 nm was read and compared with the absorbance value at 410 nm as an important parameter for measuring the effect of the probe molecule on Cr(VI).

[0112] As shown in Figure 14H)As shown in Fig. 1H, because the dialysis bag has the property of semi-permeable membrane, Cr(VI) can diffuse in and out of the dialysis bag. When the dialysis bag containing the probe molecules is immersed in a solution containing Cr(VI), the diffusion of Cr(VI) into the dialysis bag will be combined with the probe molecules in the bag to form a complex, resulting in a change in the color of the probe molecules in the bag, and the absorbance ratio also increases significantly. With the increase of the amount of probe molecules, the removal rate of Cr(VI) gradually increases, and large volume of Cr(VI) can be removed, and the removal rate is 73.51%. The concentration range of Cr(VI) removed by dialysis is 50-300 μM.

[0113] 2. Recovery of cationic polythiophene probe molecules

[0114] The cationic polythiophene probe molecules are combined with Cr(VI), and after the combination is completed, NaCl (20 mM) solution is added and shaken for 5 min. After shaking, the solution is placed in an ultrafiltration tube for ultrafiltration at 14000 rpm for 10 min. Because a high concentration of salt solution can destroy the combined state of Cr(VI) and the probe molecules, ultrafiltration can separate small particle size Cr(VI) and chloride ions from the probe molecules to realize the recovery of the probe molecules. The cut-off liquid is used again to add Cr(VI) for ultraviolet-visible absorption spectrum detection to determine the recycling effect of the probe molecules. The principle diagram is shown in Fig. 2A. Figure 14 A) After detection, NaCl (20 mM) solution is added again to repeat the above steps four times, and the absorbance value at 525 nm is read and compared with the absorbance value at 400 nm as an important parameter for measuring the recovery effect of the probe molecules. ​ B) The results show that even after four cycles, the probe molecules still have good detection performance for Cr(VI), and the repeated utilization rate is 87.69%.

[0115] The remaining matters of the present application are known technologies.

[0116] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable personnel familiar with this technology to understand the content of the present application and implement it, and it cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application should be covered within the protection scope of the present application.

Claims

1. A method for detecting Cr(VI) using a cationic polythiophene derivative of Cr(VI), characterized by: The cationic polythiophene derivative structure is shown as formula (I) or formula (II): Formula (I) Formula (I) is a homopolymer structure, R1 is H or CH3; R2 is O or CH2; R3 is an alkyl group with an integer between 1-6 carbon numbers and its isomers: methyl, ethyl, propyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, isopentyl, n-hexyl, isohexyl; R4 is H or CH3; m is an integer between 0-15; M is Cl or Br; n is a positive integer, and the weight average molecular weight of the polythiophene derivative is 0.3-5 million; Formula (II) is composed of a conjugated main chain by connecting each thiophene unit through 2,5 positions, and the structure formula is as follows: Formula (II) 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# , are selected from the R # substituents in Formula (I) above, wherein R3 is selected from alkyl groups with an integer number of carbons between 1 and 6 and their isomers: methyl, ethyl, propyl, n-butyl, isobutyl, sec-butyl, t-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 such that the average molecular weight of the polythiophene derivative is between 3,000 and 100,000; The detection method comprises the following steps: (1) Dissolving the cationic polythiophene derivative shown as formula (I) or formula (II) in water to prepare a probe molecule; (2) Adding the probe molecule obtained in step (1) into a quartz cuvette to obtain a detection reagent; (3) Gradually adding a Cr(VI) standard solution into the cuvette to measure the change of the ultraviolet-visible absorption spectrum and the fluorescence spectrum; (4) Analyzing the relationship between the absorbance ratio and the Cr(VI) concentration and the relationship between the fluorescence intensity and the Cr(VI) concentration to quantitatively and specifically detect Cr(VI) in the solution; 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 ℃, and the reaction system is selected from ultrapure water, a buffer solution HEPES, and an aqueous solution containing an organic solvent.

2. A method for removing Cr(VI) from a cationic polythiophene derivative of Cr(VI) characterized by: The cationic polythiophene derivative structure is shown as formula (I) or formula (II): Formula (I) Formula (I) is a homopolymer structure, R1 is H or CH3; R2 is O or CH2; R3 is an alkyl group with an integer between 1-6 carbon numbers and its isomers: methyl, ethyl, propyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, isopentyl, n-hexyl, isohexyl; R4 is H or CH3; m is an integer between 0-15; M is Cl or Br; n is a positive integer, and the weight average molecular weight of the polythiophene derivative is 0.3-5 million; Formula (II) is composed of a conjugated main chain by connecting each thiophene unit through 2,5 positions, and the structure formula is as follows: Formula (II) 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# , are selected from the R # substituents in Formula (I) above, wherein R3 is selected from alkyl groups with an integer number of carbons between 1 and 6 and their isomers: methyl, ethyl, propyl, n-butyl, isobutyl, sec-butyl, t-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 such that the average molecular weight of the polythiophene derivative is between 3,000 and 100,000; The removal method comprises the following steps: (1) Dissolving the cationic polythiophene derivative shown as formula (I) or formula (II) in ultrapure water to obtain a probe molecule solution; (2) Adding the probe molecule prepared in step (1) into water containing Cr(VI) to react; (3) After the reaction is completed, the solution is added into a removal system for separation and removal, and the removed sample is analyzed to obtain the efficiency of removing Cr(VI) by the probe molecule; When the Cr(VI) concentration is 0.1-100 mM, precipitation is used for separation and removal; When the Cr(VI) concentration is 5-500 μM, microfiltration is used for separation and removal, and the type of filter membrane is selected from PES, PVDF, PTFE, PC, PP, and Nylon 66, and the pore size of the filter membrane is 0.2-0.45 μm; when the Cr(VI) concentration is in the range of 20-200 μM, the removal is performed by ultrafiltration with a pore size in the range of 3-300 kDa; when the Cr(VI) concentration is in the range of 50-300 μM, the removal is performed by dialysis with a pore size in the range of 8-50 kDa and a material selected from cellulose ester CE, regenerated cellulose RC, PVDF.

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