A method for preparing a membrane substrate for real-time analysis of hazards in a flow system

Abstract

The invention discloses a method for preparing a membrane substrate for real-time analysis of hazards in a flow system, wherein silver nitrate and polystyrene PS polyacrylic acid PAA polymer are mixed and dissolved in a mixed solution of ethylene glycol, glycerol, formic acid, and acetic acid; a mixture of cesium chloride and sodium chloride is added dropwise to the mixed solution; the reactant is washed at least 3 times with ethanol or deionized water, and a light yellow solid is obtained after drying; the light yellow solid and the ligand are fully mixed and dissolved in dimethyl sulfoxide; the mixed system is mixed with 20mL of dichloromethane and magnetically stirred to obtain a silvery-gray solid; the silvery-gray solid is redissolved in dimethylformamide, the solution is slowly filtered and flowed through a polytetrafluoroethylene membrane surface, and the filter is repeated more than five times until the filtered solution becomes clear, and finally a membrane substrate is obtained. The above method process is simple, and the yield and performance of the obtained membrane substrate are better.

Description

Technical Field

[0001] The present invention relates to the technical field of metal organic framework materials, and in particular to a method for preparing a membrane substrate for real-time analysis of hazardous substances in a flow system. Background Art

[0002] At present, the analysis of hazardous substances in flowing systems faces bottleneck problems such as many interferences, difficult target identification, and low detection sensitivity. There is no sensing material that can achieve in-situ high-sensitivity detection to realize real-time analysis of trace hazardous substances in flowing systems.

[0003] The existing technology only uses metal-organic framework materials to enrich the target in non-dynamic systems and then perform fluorescence detection. However, due to the interaction between the metal active centers of such materials and the target, the detection sensitivity is not high. Therefore, it is necessary to develop a base material suitable for flow systems to realize real-time analysis of trace hazards in the flow system. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a membrane substrate for real-time analysis of hazardous substances in a flow system. The method has a simple process, and the yield and performance of the obtained membrane substrate are better. The prepared membrane substrate can realize SERS real-time sensing analysis of trace hazardous substances in the flow system, and the substrate material can be reused.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a membrane substrate for real-time analysis of hazards in a flow system, the method comprising:

[0007] Step 1, dissolving silver nitrate and polystyrene PS-polyacrylic acid PAA polymer in a mixed solution of ethylene glycol, glycerol, formic acid, and acetic acid;

[0008] Step 2: Add a mixture of cesium chloride and sodium chloride dropwise to the mixed solution of step 1 within 3 minutes, and heat in an oil bath at 150°C for 2.5 hours;

[0009] Step 3: After the reaction in step 2 is completed, the reactant is washed with ethanol or deionized water at least three times, centrifuged at 5000 rpm for 10 minutes, and then dried at 120° C. to obtain a light yellow solid;

[0010] Step 4: Thoroughly mix the light yellow solid obtained in step 3 and the ligand and dissolve them in dimethyl sulfoxide; wherein the ligand is 6,6',6",6"'-(pyrene-1,3,6,8-tetrasubstituted)tetrakis(2-naphthoic acid), and the amount of the ligand is 150-240 mg;

[0011] Step 5: The mixture obtained in step 4 was mixed with 20 mL of dichloromethane and magnetically stirred at a rate of less than 350 rpm. The mixture was reacted at room temperature for 96 h to obtain a silver-gray solid.

[0012] Step 6: Redissolve the silver-gray solid obtained in dimethylformamide, slowly filter the solution through the surface of the polytetrafluoroethylene membrane, then rotate the polytetrafluoroethylene membrane at a constant speed in a clockwise-counterclockwise order, and repeatedly filter at 1 mL / min for more than five times until the filtered solution becomes clear, thereby obtaining a membrane substrate.

[0013] It can be seen from the technical solution provided by the above invention that the above method has a simple process, the yield and performance of the obtained membrane substrate are better, the prepared membrane substrate can realize SERS real-time sensing analysis of trace hazards in the flow system, and the substrate material can be reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1 A schematic flow chart of a method for preparing a membrane substrate for real-time analysis of hazards in a flow system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments, and do not constitute a limitation of the present invention. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0017] like Figure 1 FIG2 is a flow chart of a method for preparing a membrane substrate for real-time analysis of hazards in a flow system according to an embodiment of the present invention. The method comprises:

[0018] Step 1, dissolving silver nitrate and polystyrene PS-polyacrylic acid PAA polymer in a mixed solution of ethylene glycol, glycerol, formic acid, and acetic acid;

[0019] In this step, the amount of silver nitrate used is 0.064g to 0.128g;

[0020] The amount of the polystyrene PS-polyacrylic acid PAA polymer is 0.064 g to 0.086 g; wherein the average molecular weight ratio of polystyrene PS to polyacrylic acid PAA is 30,000:2,000;

[0021] The amount of the mixed solution of ethylene glycol, glycerol, formic acid and acetic acid is 5 mL; wherein the volume ratio of ethylene glycol, glycerol, formic acid and acetic acid is 8:1:0.5:0.5.

[0022] Step 2: Add a mixture of cesium chloride and sodium chloride dropwise to the mixed solution of step 1 within 3 minutes, and heat in an oil bath at 150°C for 2.5 hours;

[0023] In this step, the volume of cesium chloride added was 60 μL and the concentration was 4.8 mM;

[0024] The volume of sodium chloride added was 60 μL and the concentration was 5.5 mM.

[0025] In the specific implementation, the addition of cesium chloride and sodium chloride is the first invention of this application. When the dosage of the two is 4.8:5.5, the yield of the prepared trimer is above 65%. By adding these two compound compounds, it is beneficial to change the ionic strength of the reaction system and to the growth of porous crystals on the surface of the trimer.

[0026] Step 3: After the reaction in step 2 is completed, the reactant is washed with ethanol or deionized water at least three times, centrifuged at 5000 rpm for 10 minutes, and then dried at 120° C. to obtain a light yellow solid;

[0027] Step 4: The light yellow solid obtained in step 3 and the ligand are thoroughly mixed and dissolved in dimethyl sulfoxide;

[0028] Wherein, the ligand is 6,6',6",6"'-(pyrene-1,3,6,8-tetrasubstituted)tetrakis(2-naphthoic acid), and the amount of the ligand used is 150-240 mg;

[0029] In the specific implementation, the ligand selected in this embodiment, namely 6,6',6",6"'-(pyrene-1,3,6,8-tetrasubstituted)tetra(2-naphthoic acid), is the key to capture trace pollutants and realize SERS real-time analysis. Specifically, the distance between naphthoic acid and the center of the pyrene ring is Optimize the preparation of The crystal has a nanochannel size designed to facilitate the rapid mass transfer of trace pollutants, and is beneficial to the enrichment and in-situ sensing analysis of target pollutants.

[0030] Step 5: The mixture obtained in step 4 was mixed with 20 mL of dichloromethane and magnetically stirred at a rate of less than 350 rpm. The mixture was reacted at room temperature for 96 h to obtain a silver-gray solid.

[0031] In this step, the mixed system obtained in step 4 is transferred to a 25 ml narrow-mouth glass sample bottle, in which a magnetic stirring rotor is placed;

[0032] The solution was then placed in a 500 mL blue-capped bottle, 20 mL of dichloromethane having been previously transferred to the bottom of the blue-capped bottle. The entire system was sealed, the magnetic stirring rate was controlled below 350 rpm, and the reaction was carried out at room temperature for 96 h to finally obtain a silver-gray solid.

[0033] Step 6: The silver-gray solid obtained in step 5 was redissolved in dimethylformamide, and the solution was slowly filtered through the surface of the polytetrafluoroethylene membrane. The polytetrafluoroethylene membrane was then rotated at a constant speed in a clockwise-counterclockwise order and filtered repeatedly at 1 mL / min for more than five times until the filtered solution became clear, thereby obtaining the membrane substrate (Tri-Ag@IQSTAP).

[0034] In this step, the size of the polytetrafluoroethylene membrane is consistent with the size of the bottom of the detection sample cell. In the process of rotating the polytetrafluoroethylene membrane at a constant speed in a clockwise-counterclockwise order, the uniformity of the bonding material on the membrane must be ensured as much as possible.

[0035] In practice, this embodiment uses a clockwise-counterclockwise rotation to ensure uniformity of the membrane substrate (Tri-Ag@IQSTAP), resulting in a SERS sensing RSD of less than 5%, ensuring analytical reliability. Existing nanofabrication methods typically employ etching, chemical deposition, and electron sputtering, which are costly and limit the nanostructures that can be produced. However, this embodiment utilizes a simple rotational method, significantly reducing manufacturing costs while allowing for controlled adjustment of the material growth density on the membrane surface.

[0036] In addition, after obtaining the membrane substrate, the prepared membrane substrate can be soaked in 1 mM sodium borohydride for 5 minutes, and then rinsed with 10 to 15 mL of deionized water 2 to 3 times for repeated use.

[0037] It should be noted that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0038] The present invention utilizes a structured, ordered microporous crystal with large π conjugation and rich carboxylic acid functional groups (abbreviated as "IQSTAP") as the outer layer structure and a membrane substrate (Tri-Ag@IQSTAP) with trimer silver as the inner layer structure as a substrate for surface-enhanced Raman spectroscopy (SERS) analysis. This substrate is used for multi-target analysis of trace hazards in flowing systems (such as flowing water), with a sensitivity of 0.18 to 12.3 ng / mL (ppb). Furthermore, the substrate is reusable (at least 10 times) when cleaned with sodium borohydride.

[0039] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the process method provided by the embodiment of the present invention is described in detail below with reference to specific embodiments:

[0040] Example 1:

[0041] Step A1, preparation of trimer inner layer structure:

[0042] In a three-necked flask equipped with a reflux condenser, silver nitrate (0.064 g) and "polystyrene (PS)-polyacrylic acid (PAA) polymer" (0.064 g, where PS:PAA = 30,000:2,000) were mixed and dissolved in a "ethylene glycol / glycerol / formic acid / acetic acid" mixed solution (5 mL, V:V:V:V = 8:1:0.5:0.5).

[0043] A mixture of cesium chloride (60 μL, 4.8 mM) and sodium chloride (60 μL, 5.5 mM) was added dropwise over 3 minutes. The mixture was heated in an oil bath at 150°C for 2.5 hours. After the reaction, the mixture was washed at least three times with ethanol / deionized water (centrifugation at 5000 rpm for 10 minutes) and dried at 120°C to yield a pale yellow solid.

[0044] Step A2: outer layer microporous crystal coating:

[0045] The obtained light yellow solid and 6,6',6",6"'-(pyrene-1,3,6,8-tetrasubstituted)tetrakis(2-naphthoic acid) (hereinafter referred to as "ligand", 200 mg) were thoroughly mixed and dissolved in dimethyl sulfoxide.

[0046] The above mixed system was transferred to a 25 ml narrow-mouth glass sample bottle (with a magnetic stirring rotor), and then placed in a 500 ml blue-capped bottle. 20 ml of dichloromethane was previously transferred to the bottom of the blue-capped bottle. The entire system was sealed, and the magnetic stirring rate was controlled below 350 rpm. It was placed at room temperature for 96 h to finally obtain a silver-gray solid.

[0047] Step A3, membrane preparation:

[0048] The obtained silver-gray solid was redissolved in dimethylformamide, and the solution was slowly filtered through the surface of the polytetrafluoroethylene membrane (the membrane size was consistent with the bottom size of the detection sample cell), and the membrane was rotated at a constant speed in a clockwise-counterclockwise order to ensure the uniformity of the bonding material on the membrane as much as possible. The filtration was repeated for ≥5 times (1 mL / min) until the filtered solution became clear. The membrane base needed to be stored in a vacuum or nitrogen atmosphere.

[0049] Step A4, membrane recycling and cleaning steps:

[0050] The prepared substrate was soaked in sodium borohydride (1 mM) for 5 min, and then rinsed 2 to 3 times with 10 to 15 mL of deionized water, and then it could be reused.

[0051] Specifically, the material processed in step A3 of Example 1 of the present invention is a structured, ordered microporous crystal with large π conjugation and rich carboxylic acid functional groups (abbreviated as "IQSTAP") as the outer layer structure, and a membrane substrate with trimer silver (Tri-Ag) as the inner layer structure (abbreviated as "Tri-Ag@IQSTAP"). It can be used as a high-performance sensing material for surface enhanced Raman spectroscopy (SERS) analysis, and is used for Raman real-time sensing analysis of trace hazards in flowing systems (such as flowing water bodies).

[0052] Furthermore, the specific surface area and the production yield of the membrane substrate prepared in Example 1 of the present invention were measured, and the results shown in Table 1 below were obtained:

[0053] Table 1

[0054]

[0055] The yield of the membrane substrate (Tri-Ag@IQSTAP) in Example 1 of the present invention was 64.2%, and its specific surface area was 15.88 m 2 ·g -1 .

[0056] Example 2:

[0057] Step A1, preparation of trimer inner layer structure:

[0058] In a three-necked flask equipped with a reflux condenser, silver nitrate (0.128 g) and "polystyrene (PS)-polyacrylic acid (PAA) polymer" (0.086 g, where PS:PAA = 30,000:2,000) were mixed and dissolved in a "ethylene glycol / glycerol / formic acid / acetic acid" mixed solution (5 mL, V:V:V:V = 8:1:0.5:0.5).

[0059] A mixture of cesium chloride (60 μL, 4.8 mM) and sodium chloride (60 μL, 5.5 mM) was added dropwise over 3 minutes. The mixture was heated in an oil bath at 150°C for 2.5 hours. After the reaction, the mixture was washed at least three times with ethanol / deionized water (centrifugation at 5000 rpm for 10 minutes) and dried at 120°C to yield a pale yellow solid.

[0060] Step A2: outer layer microporous crystal coating:

[0061] The obtained light yellow solid and 6,6',6",6"'-(pyrene-1,3,6,8-tetrasubstituted)tetrakis(2-naphthoic acid) (hereinafter referred to as "ligand", 200 mg) were thoroughly mixed and dissolved in dimethyl sulfoxide.

[0062] The above mixed system was transferred to a 25 ml narrow-mouth glass sample bottle (with a magnetic stirring rotor), and then placed in a 500 ml blue-capped bottle. 20 ml of dichloromethane was previously transferred to the bottom of the blue-capped bottle. The entire system was sealed, and the magnetic stirring rate was controlled below 350 rpm. It was placed at room temperature for 96 h to finally obtain a silver-gray solid.

[0063] Step A3, membrane preparation:

[0064] The obtained silver-gray solid was redissolved in dimethylformamide, and the solution was slowly filtered through the surface of the polytetrafluoroethylene membrane (the membrane size was consistent with the bottom size of the detection sample cell), and the membrane was rotated at a constant speed in a clockwise-counterclockwise order to ensure the uniformity of the bonding material on the membrane as much as possible. The filtration was repeated for ≥5 times (1 mL / min) until the filtered solution became clear. The membrane base needed to be stored in a vacuum or nitrogen atmosphere.

[0065] Step A4, membrane recycling and cleaning steps:

[0066] The prepared substrate was soaked in sodium borohydride (1 mM) for 5 min, and then rinsed 2 to 3 times with 10 to 15 mL of deionized water, and then it could be reused.

[0067] Specifically, the material processed in step A3 of Example 2 of the present invention is a membrane substrate (Tri-Ag@IQSTAP) having an IQSTAP porous crystal material as an outer layer structure and a trimer silver (Tri-Ag) as an inner layer structure. By increasing the amount of silver source while keeping other conditions unchanged, the thickness of the outer layer material decreases. The material can be used as a high-performance sensing material for SERS analysis and for Raman real-time sensing analysis of trace hazards in a flowing system (such as flowing water).

[0068] Furthermore, the specific surface area and production yield of the membrane substrate prepared in Example 2 of the present invention were measured, and the results shown in Table 2 below were obtained:

[0069] Table 2

[0070]

[0071] The yield of the membrane substrate (Tri-Ag@IQSTAP) in Example 2 of the present invention was 67.7%, and its specific surface area was 13.36 m 2 ·g -1 .

[0072] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art.

Claims

1. A method for preparing a membrane substrate for real-time analysis of hazards in a flow system, characterized in that: The method comprises: Step 1, dissolving silver nitrate and polystyrene PS-polyacrylic acid PAA polymer in a mixed solution of ethylene glycol, glycerol, formic acid, and acetic acid; Step 2: Add a mixture of cesium chloride and sodium chloride dropwise to the mixed solution of step 1 within 3 minutes, and heat in an oil bath at 150°C for 2.5 hours; Step 3: After the reaction in step 2 is completed, the reactant is washed with ethanol or deionized water at least three times, centrifuged at 5000 rpm for 10 minutes, and then dried at 120° C. to obtain a light yellow solid; Step 4: Thoroughly mix the light yellow solid obtained in step 3 and the ligand and dissolve them in dimethyl sulfoxide; wherein the ligand is 6,6',6",6"'-(pyrene-1,3,6,8-tetrasubstituted)tetrakis(2-naphthoic acid), and the amount of the ligand is 150-240 mg; Step 5: The mixture obtained in step 4 was mixed with 20 mL of dichloromethane and magnetically stirred at a rate of less than 350 rpm. The mixture was reacted at room temperature for 96 h to obtain a silver-gray solid. Step 6: Redissolve the silver-gray solid obtained in dimethylformamide, slowly filter the solution through the surface of the polytetrafluoroethylene membrane, then rotate the polytetrafluoroethylene membrane at a constant speed in a clockwise-counterclockwise order, and repeatedly filter at 1 mL / min for more than five times until the filtered solution becomes clear, thereby obtaining a membrane substrate.

2. The method for preparing a membrane substrate for real-time analysis of hazards in a flow system according to claim 1, characterized in that: In step 1, the amount of silver nitrate used is 0.064g to 0.128g; The amount of the polystyrene PS-polyacrylic acid PAA polymer is 0.064 g to 0.086 g; wherein the average molecular weight ratio of polystyrene PS to polyacrylic acid PAA is 30,000:2,000; The amount of the mixed solution of ethylene glycol, glycerol, formic acid and acetic acid is 5 mL; wherein the volume ratio of ethylene glycol, glycerol, formic acid and acetic acid is 8:1:0.5:0.

5.

3. The method for preparing a membrane substrate for real-time analysis of hazardous substances in a flow system according to claim 1, characterized in that: In step 2, the volume of cesium chloride added was 60 μL and the concentration was 4.8 mM; The volume of sodium chloride added was 60 μL and the concentration was 5.5 mM.

4. The method for preparing a membrane substrate for real-time analysis of hazards in a flow system according to claim 1, characterized in that: The process of step 5 is specifically as follows: The mixed system obtained in step 4 was transferred to a 25 ml narrow-mouth glass sample bottle containing a magnetic stirring rotor; The solution was then placed in a 500 mL blue-capped bottle, 20 mL of dichloromethane having been previously transferred to the bottom of the blue-capped bottle. The magnetic stirring rate was controlled below 350 rpm, and the reaction was carried out at room temperature for 96 h to finally obtain a silver-gray solid.

5. The method for preparing a membrane substrate for real-time analysis of hazards in a flow system according to claim 1, characterized in that: After obtaining the membrane substrate, the prepared membrane substrate was immersed in 1 mM sodium borohydride for 5 minutes, and then rinsed with 10 to 15 mL of deionized water 2 to 3 times for repeated use.

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