CN111440439B

CN111440439B - Solid ionophore and preparation method and application thereof

Info

Publication number: CN111440439B
Application number: CN201910043923.8A
Authority: CN
Inventors: 李新贵; 黄美荣; 范武略
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2019-01-17
Filing date: 2019-01-17
Publication date: 2021-09-03
Anticipated expiration: 2039-01-17
Also published as: CN111440439A

Abstract

The invention relates to a solid ionophore, a preparation method and application thereof. The preparation method comprises the following steps of stirring graphene nanosheets, conductive polymer monomers and conductive polymer monomers containing multiple functional groups, carrying out ultrasonic treatment, adding an oxidant, carrying out polymerization reaction under the condition of water bath, and carrying out in-situ polymerization on the conductive polymer monomers and the conductive polymer monomers containing the multiple functional groups on the graphene nanosheets to form a nano-composite, namely a solid ionic carrier, which is composed of the conductive polymer nanoparticles rich in the functional groups and the graphene nanosheets, wherein the nano-composite is mainly used as a lead ionic carrier. The active functional group in the ionic carrier is easier to expose, and the complexing sites of the solid carrier are increased; the graphene can endow the ion carrier with electron conduction and ion conduction capability and the conversion between the electron conduction and the ion conduction capability, and the problem of difficulty in electric signal transmission in the existing all-solid-state sensing film is solved. The synergistic effect between the two makes the sensing film have fast and stable signal response.

Description

Solid ionophore and preparation method and application thereof

Technical Field

The invention relates to the technical field of preparation and application of an ionic carrier, in particular to a solid ionic carrier and a preparation method and application thereof.

Background

Lead ions, one of the most serious environmental pollutants, may cause a series of diseases such as anemia, mental disorders, and permanent nerve damage to the human body. Thus, accurate measurement of Pb in the environment²⁺The content of (A) is particularly important for the overall health growth of human beings. And the traditional detection of trace Pb by Atomic Absorption Spectrometry (AAS), inductively coupled plasma mass spectrometry (ICP-MS) and the like²⁺The method has the disadvantages of high equipment cost, need of professional operators and the like, and can only be used for detection under laboratory conditions. But the method of the ion selective electrode can well meet the requirements of outdoor operation and on-line detection of ion concentration by the advantages of simple operation, quick response, low cost, environmental protection, safety, and the like.

For ion-selective electrodes, the ionophore in their sensing membrane is one of the key components that determines their performance. The research on lead ion selective carriers at home and abroad mainly focuses on organic compound neutral carriersExamples of these are thioethers (Guzinski, M.; Lisak, G.; Kupis, J.; Jasinski, A. Bochenska M.lead (II) -Selective Ionophores for Ion-Selective Electrodes: A Review. An. Chim. acta 2013,791:1-12), crown ethers (Kazemi, S.Y.; Shamsipur, M.; Sharghi, H.lead-Selective poly (vinyl chloride) electron-based nanoparticles on synthesis of fused benzene-based nanoparticles, Mater.2009,172(1):68-73), calixarenes (Yaftarene, M.R.; Rayanti, S.tyc. aromatic copolymers, J.Hazard. matrix, D.A. green-derived electron-beam [4 ] electron-derived electron-electron]arene derivative scientific 2006,22(8): 1075-; rani, g.; singh, g.; agarwal, H.comprehensive Study of Lead (II) Selective Poly (vinyl chloride) membranes Based on + depletion Derivatives as Ionophores. electroanalysis 2013,25(2): 475-; jiang, x.; zhao, y.; jiang, w.; zhang, z.; yu, L.A solid-contact Pb²⁺-selective electrode based on electrophoretic polysaccharide membranes as on-to-electron driver. electrochemical Acta 2017,231: 53-60). However, neutral organic molecular carriers have the disadvantages of complicated synthesis method and the like. Recently, inorganic substances such as PbS have also been used as lead ion carriers, but their lower limit of detection is only 10 by plasticizing PVC sensor films to a thickness of up to 1mm^-2～10^-4mol/L, narrow detection range, and a lifetime of only 44 days (Ajadi, A.A.; Shuaib, N.M.; Shoukry, A.F. depth profiling X-ray photoelectron spectroscopy and atomic force microscopy of Cd (II) -and Pb (II) -selective electronics based on nano metal filters RSC adv.2018,8: 3574-. Clearly, pure inorganic materials are not the first choice for lead ionophores.

In recent years, tin (IV) tungstate (Khan, A.A.; Alam, M.M.Synthesis, conversion and analytical applications of a new and novel 'organic' composite materials a present exchange and Cd (II) ion-selective membrane electrode: polyaniline Sn (IV) longitudinal storage. reaction.Funct.Polymer.2003, 55(3) 277-ion and separation of Pb²⁺From an aqueous solution using a fibrous type organic-inorganic hybrid location-exchange material polypyrole sodium (IV) phosphate. react. Funct. Polymer.2005, 63(2) 119-; khan, m.q.; shaheen, S.Synthesis, chromatography, and electrochemical students of Pb²⁺-selective polypyrrole-Zr (IV) phosphate ion exchange membrane. J. solid State electrochem.2016,20(7) 2079-2091. Inamudin; rangrez, t.a.; mu, N.; ahmad, A.Synthesis and catalysis of poly (3,4-ethylenedioxythiophene) -poly (phenylenesulfonato) (PEDOT: PSS) Zr (IV) monophosphosphosphosphonium complex exchange, inorganic application of organic membrane electrode, Intern.J.Environ.Anal.chem.2015,95(4) 312-323) and other such quaternary transition metals, through the interaction between the transition metal empty-d orbital and the lone pair on the nitrogen atom in the conductive polymer, the formed organic-inorganic composite is used as lead ion carrier, the lower limit of detection of the electrode can reach 10^-7mol/L, but the selectivity is not ideal. With (PEDOT: PSS) -Zr (HPO)₃S)₂For example, many heavy divalent and trivalent metal ions such as Cu (II), Cd (II), Zn (II), Al (III), Fe (III) and Cr (III) interfere with the detection of Pb (II) to some extent. In addition to complexing with conducting polymers, transition metal salts are also used as lead ionophores in combination with natural polymers, such as tin (IV) phosphate-poly (gelatin-cl-alginate) nanocomposites, except that the response slope of the electrode is only 20.28mV/dec (Pathania, D.; Thakur, M.; Sharma, G.; Mishra, A.K. tin (IV) phosphate/poly (geltin-cl-alginate) nanocomposite: photocatalytic and purification of pore-measuring sensors for Pb (II). Materials day Communications 2018,14:282-293), much lower than the nerstrian slope. It can be seen that the performance of the composite carrier is to be improved.

Another key component in the sensing film is the base film. The base film material for conventional ion selective electrodes is polyvinyl chloride (PVC). However, the PVC must be added with about 2 times of plasticizer to form a flexible film, and the plasticizer is addedMigration in the polymer membrane, eventually leakage loss, and leakage out together with the ion carriers, ion exchangers, etc. dissolved therein, seriously affect the service life of the ion selective electrode. Another drawback of the PVC-based membrane is that in the constructed liquid-connection ion selective electrode, sensitive detection of target ions cannot be realized due to the membrane ion current existing on two sides of the membrane, and the detection lower limit is generally only 1 x 10^-6The mol/L concentration level obviously cannot meet the detection of high-standard water samples such as drinking water and the like. In addition, plasticizers also tend to extract lipid components from the sample being tested, causing the response potential of the sensing membrane to drift and lose selectivity (Mikhelson, K.N. ion-selective electrolytes with sensitivity in linear concentrations. J.Anal. chem.2010,65(2): 112-.

In order to avoid the above-mentioned drawbacks of PVC films, some base films with little or no plasticizer have been proposed in recent years for use in ion selective electrodes. Representative base film materials include polyimide (Cha, G.S.; Brown, R.B.Polymer-matrix-selective membranes, sensor Acuat B1990, 1(1):281-285), room temperature vulcanized rubber (Oh, B.K.; Kim, C.Y.; Lee, H.J.; Rho, K.L.; Cha, G.S.; Nam, H.one-component-temperature vulcanized rubber-like rubber-like rubber, 68 (3); 503-508. Lindforms, T.; Sz Sz, J.; Sundfors, F. G.n.S. and R.E.S. polyurethane-like, R.E.S. polyurethane-like rubber-like, rubber-like, rubber-2, rubber-like, rubber-like, rubber-2, rubber as a membrane matrix, Talanata 2001,55(3):449-457.Qin, Y.; peper, s.; bakker, E.Plastic-free polymer membrane ion-selective electron condensation a methacrylic copolymer matrix. Electrical. 2002,14(14): 1375-; feng, h.; huang, m.r.; gu, g.l.; moloney, M.G.ultrasensive Pb (II) positional Sensor Based on polyaniline Nanoparticles in a Plastic-Free Membrane with a Long lifetime, anal.Chem.2012,84(1): 134-. The former two are films formed by polymer dissolution casting, and the plasticizer is not separated, but the dosage is much less than that of PVC; the polyacrylate base film and the vinyl resin base film which are polymerized in situ by the acrylic acid monomer through illumination do not need a plasticizer. These plasticizer-free polymer-based films have electroactive species that are only incorporated into the polymer film and are not soluble in molecular form, which in turn raises another problem of greatly increased film resistance, resulting in unstable response potential readings. This problem of non-plasticized PVC films has hitherto been difficult to completely solve. For example, 1 wt% of nano-Pt is introduced into a polyacrylic acid solid film based potassium ion sensing film fixedly connected with polythiophene POT, and the film resistance can be reduced from 2.5M omega to 0.097M omega (Jaworska, E.; Kisiel, A.; Maksymuk, K.; Michalska, A. Lowering the resistance of polyacrylic acid-selective membrane by nano particulate addition. Anal. chem.2011,83 (1)), 438K.; is reduced by 26 times, while in a polyacrylic acid solid film based calcium ion selective electrode which is also in contact with POT solid, the resistance is reduced by more times after the same amount of nano-Pt is used, and the resistance is reduced from 20M omega to 0.6M omega, so that the potential reading deviation value of the electrode is reduced from 2mV to 7mV to 2mV or less. But this fluctuation is still greater than plasticized PVC films.

Therefore, the plasticizer-free all-solid-state sensing membrane electrode with high response speed and stable response potential is not realized at present. The research on how to find a sensing membrane material which is non-toxic, environment-friendly and can tolerate the embedding of active component particles from a plurality of organic materials so as to realize the stable detection of lead ions is not reported.

Disclosure of Invention

The invention aims to solve the defects in the prior art and provides a solid ionophore, a preparation method and application thereof. The invention also provides a preparation method and application of the plasticizer-free environment-friendly waterborne polyurethane flexible sensing film.

The purpose of the invention can be realized by the following technical scheme:

the first technical scheme is as follows:

provided is a solid ionic carrier which is a nano-composite formed by compounding conductive polymer nano-particles rich in functional groups and graphene nano-sheets.

Further, the solid ionophore is a lead ionophore.

In the solid ionophore, the weight ratio of the conductive polymer to the graphene is 90/10-99.9/0.1, and the preferable ratio is 98/2-99/1.

Preferably, the solid ionophore may be a polyaniline/graphene nanocomposite.

In the nano composite formed by compounding the conductive polymer nano particles rich in functional groups and the graphene nano sheets, the conductive polymer is a lead ion carrier, but the electronic conduction capability, particularly the ion conduction capability, of the conductive polymer is limited, the graphene sheets dispersed in the conductive polymer nano particles can realize both electronic conduction and ion conduction, and a bridge can be built for the conduction among the conductive polymer particles, so that the electric signal conduction performance among the carrier particles is greatly increased, the electric signal conduction function of the solid carrier is endowed, and the response and feedback of electric signals are facilitated. On the other hand, the planar graphene also helps to prevent soft agglomeration of the granular conductive polymer, further separate the nanoparticles, achieve finer-layer dispersion, and finally enable the functional group-NH on the molecular chain₂、-NH-、OH-、-SO₃H, etc. are sufficiently exposed. The synergistic effect between the conduction function and the fine dispersion structure achieves the sensitive response function of the nano composite to lead ions. The schematic diagram of the aggregate structure of such solid ionophores is shown in fig. 1.

That is, the active functional group in the ionic carrier is easier to expose, and the complexing site of the solid carrier is undoubtedly enhanced, so that the complexing function of the solid carrier is enhanced; on the other hand, in the process of selective complexation between the ion carrier and target ions, the graphene in the compound can provide and enhance the electron conduction and ion conduction capability of the ion carrier and the conversion between the electron conduction and the ion conduction capability, and promote the complexation between the carrier and ions, so that the problem of difficulty in carrier transfer in the existing all-solid sensing membrane is solved, the potential response of the electrode of the solid ion carrier applying the technical scheme is more stable compared with other all-solid membrane ion selection electrodes, and meanwhile, the response time is obviously shorter than that of other all-solid membrane ion selection electrodes.

The second technical scheme is as follows:

preparation method for providing the solid ionophore

A method for preparing a solid ionophore: the preparation method comprises the following steps of carrying out chemical oxidative polymerization on graphene nanosheets, conductive polymer monomers and conductive polymer monomers containing multiple functional groups, so that the conductive polymer monomers and the conductive polymer monomers containing the multiple functional groups are polymerized on the graphene nanosheets in situ to form a nano-composite, namely a solid ionic carrier, consisting of the conductive polymer nanoparticles rich in the functional groups and the graphene nanosheets.

The preparation method of the solid ionophore specifically comprises the following steps:

mixing the graphene nanosheets, the conductive polymer monomer and the conductive polymer monomer containing various functional groups, stirring, performing ultrasonic treatment, adding an oxidant, performing polymerization reaction under the condition of water bath, performing centrifugal treatment after the reaction is finished, and washing the obtained product to obtain a nano compound, namely the solid ionic carrier, which is composed of the conductive polymer nanoparticles rich in the functional groups and the graphene nanosheets.

Further, the graphene nanosheet and the conductive polymer monomer are mixed firstly and then subjected to ultrasonic treatment, and then the conductive polymer monomer containing multiple functional groups is added and mixed.

Further, mixing graphite and a conductive polymer monomer, performing ultrasonic treatment to obtain a blending system of the graphene nanosheet and the conductive polymer monomer, and then adding the conductive polymer monomer containing multiple functional groups for mixing.

The blending system of the graphene nanosheets and the conductive polymer monomer is equivalent to a mixing system of the graphene nanosheets and the conductive polymer monomer.

Further, the conductive polymer monomer is selected from one or more of aniline, methylaniline, ethylaniline, propylaniline, N-methylaniline, N-ethylaniline or N-propylaniline.

The conductive polymer monomer is used as a polymerization monomer and also used as a liquid-phase ultrasonic medium.

Further, the conductive polymer monomer containing multiple functional groups is an aniline derivative containing one or more of amino groups, sulfonic acid groups, hydroxyl groups or alkoxy groups, and has the following structural general formula:

in the formula, R₁And R₂Each independently selected from-H, -NH₂、-OH、-SO₃H、-OCH₃or-OCH₂CH₃；

The conductive polymer monomer having various functional groups is preferably as follows:

the oxidant is selected from ammonium persulfate or ferric trichloride.

The oxidant is added in the form of being prepared in an acid solution, and the acid solution for preparing the oxidant solution can be selected from 0.5-1 mol/L hydrochloric acid, nitric acid, sulfuric acid, perchloric acid and the like.

When the oxidant is selected from ammonium persulfate, the molar concentration of the ammonium persulfate is 50-500 mmol/L, and the preferred molar concentration of the ammonium persulfate is 100-300 mmol/L.

When the oxidant is selected from ferric trichloride, the molar concentration of the ferric trichloride is 100 mmol/L-500 mmol/L, and the molar concentration of the ferric trichloride is preferably 200-300 mmol/L.

The molar ratio of the oxidant to the comonomer is 1/2-3/1, preferably 1/1, and the molar weight of the comonomer is the sum of the molar weight of the conductive polymer monomer and the molar weight of the conductive polymer monomer containing various functional groups.

Further, the temperature of the polymerization reaction is 0-50 ℃, preferably 10 ℃, and the time of the polymerization reaction is 6-48 hours, preferably 24 hours.

Further, the preparation method of the solid ionophore directly takes graphite as an initial raw material to prepare, and specifically comprises the following steps:

1) preparation of expanded graphite using a thermal expansion process: and uniformly scattering graphite into a stainless steel disc in a high-temperature muffle furnace, and taking out after a certain time. And (3) placing the graphite on a temperature-resistant experiment table, covering the experiment table with a cover, cooling to be close to room temperature, and then placing the graphite in a dryer filled with blue silica gel for cooling to obtain the expanded graphite.

2) Preparing graphene nanosheets by using expanded graphite through a liquid phase stripping method: dispersing the expanded graphite obtained in the step 1) in a conductive polymer monomer according to a certain amount, taking the conductive polymer monomer as a liquid phase medium, performing ultrasonic treatment at a certain frequency and power for a certain time, performing centrifugal separation, and removing redundant conductive polymer monomer.

3) Preparing a solid ionophore by using an in-situ chemical oxidative polymerization method: centrifuging the graphene subjected to the ultrasound in the step 2) at a high speed for a certain time to ensure that all graphene nanosheets can be settled, and during the centrifuging, checking whether the supernatant liquid contains graphene or not by using an ultraviolet spectrophotometer, if so, prolonging the centrifuging time, and if not, stopping centrifuging. Excess supernatant liquid was carefully aspirated until the amount of conductive polymer monomer remaining in the bottle reached the set amount. Then adding a conductive polymer monomer containing multiple functional groups, stirring for several minutes by strong magnetic force, immediately transferring to a water bath for ultrasonic treatment, and then dropwise adding a certain amount of oxidant solution into the blending system at a dropwise adding speed of 1 drop/3 s for about 40 min; and then transferring the mixture to a magnetic stirrer, stirring and reacting in a water bath at a certain temperature, finishing the reaction after a certain time to obtain a dark black suspension, centrifuging at 4000rpm for at least 90min, repeatedly washing the obtained product with 1mol/L HCl for 5-6 times to remove by-products, finally transferring the obtained lead ion carrier nano-composite to a watch glass, freeze-drying for 48h to constant weight, and calculating the yield of the conductive polymer and the weight ratio of the conductive polymer to the nano-composite.

The graphite is natural crystalline flake graphite or expandable graphite, and preferably expandable graphite.

The expansion process of the graphite is different according to the graphite raw materials, the thermal expansion temperature of the graphite is generally 600-1200 ℃, the preferred temperature and time are 950 ℃, and the expansion time is tens of seconds.

When the expanded graphite is subjected to liquid phase stripping, the expanded graphite needs to be subjected to ultrasonic treatment, and the solid content of the graphite during ultrasonic treatment is less than 2mg/mL, preferably less than 1mg/mL, and the optimal content is less than 0.5 mg/mL.

The ultrasound is selected from water bath ultrasound or needle ultrasound, the process conditions of the water bath ultrasound are ultrasound for 24h to 72h under the acoustic frequency of 40kHz to 60kHz and the acoustic power of 50W to 200W, and ultrasound for 48h under 180W is preferred; the needle type ultrasound process conditions are 20kHz sound frequency and 200W to 600W sound power, ultrasound lasts for 2h to 6h, and ultrasound lasts for 3h under 400W is preferred.

The centrifugation condition after the ultrasonic treatment is that the centrifugation is carried out for 20min to 90min at 5000rpm to 2000rpm, and the centrifugation is preferably carried out for 90min at 3000 rpm.

By using the preparation method of the solid-state ionophore, the actual yield and the actual weight percentage calculation formula of graphene in the solid-state ionophore are derived in detail as follows:

since the oxidant is added in the form of being prepared in the acid solution, namely the polymerization system is carried out under the acidic condition, the added acid is sulfate radical which is a reaction by-product when ammonium persulfate is used as the oxidant, and the whole polymerization system is always kept acidic along with the removal of the acid in the polymerization process, the generated conductive polymer is in a doped state, and the doping protonic acid of the conductive polymer is determined by the acid medium. The specific acid anion to be incorporated depends on the acid used. Thus, the yield Y of the conductive polymer_CPThe calculation formula is as follows:

Y_CP＝(W_Total–W_G)/W_T……………………………(1)

W_Total: total weight of the resulting nanocompositeMeasurement of

W_G: graphene input weight

W_T: theoretical weight of doped conducting polymer

Actual weight ratio R of conductive polymer to graphene in solid ionophore_CP/GThe calculation formula is as follows:

R_CP/G＝(W_Total–W_G)/W_G……………………………(2)

the third technical scheme is as follows:

provides an environment-friendly waterborne polyurethane flexible sensing film without plasticizer

The plasticizer-free environment-friendly waterborne polyurethane flexible sensing film comprises a continuous phase film matrix, and a solid ionic carrier and an ion exchanger embedded in the continuous phase film matrix, wherein the continuous phase film matrix is Waterborne Polyurethane (WPU), and the solid ionic carrier is a nano compound formed by compounding conductive polymer nano particles rich in functional groups and graphene nano sheets.

The solid ionophore can be prepared by the above technical scheme two as described in the above technical scheme one.

The content of the solid ionophore is 1 wt% to 8 wt%, preferably 3 wt%. The solid ionophore is mainly used for lead ionophores.

The ion exchanger is selected from one of NaTPB, NaFTPB, KTClPB or KClTPB and the like.

The content of the ion exchanger is 0 to 10 weight percent, and 3 weight percent is preferred.

The water-based polyurethane is water-dispersed polyurethane or water-based polyurethane without organic solvent, and can be one or a mixture of more of polyurethane water-based emulsion, vinyl polyurethane water-based emulsion or polyisocyanate water-based emulsion.

The WPU base film is environment-friendly and non-toxic, has excellent flexibility and moderate elasticity, can enable the mechanical property of the WPU base film to completely meet the use requirement of an electrode film without using any plasticizer, and can tolerate the situation that a small amount of nano-particles or even micro-particles are embedded in the WPU base film and still maintain a good compact structure without generating defects.The base membrane can block transmembrane ion circulation on two sides of the membrane so that the lower detection limit of the base membrane breaks through 10 of a PVC membrane ion electrode^-6Bottleneck of mol/L. The plasticizer-free environment-friendly waterborne polyurethane flexible sensing film can also obtain a calibration-free ion selective electrode, and the response potential curve of the plasticizer-free environment-friendly waterborne polyurethane flexible sensing film does not drift in 2 months of use.

The technical scheme is as follows:

provides a method for preparing an environment-friendly waterborne polyurethane flexible sensing film without a plasticizer

Firstly, carrying out ultrasonic dispersion on a solid ion carrier and an ion exchanger in an organic phase, then adding the solid ion carrier and the ion exchanger into a certain amount of aqueous polyurethane emulsion in batches, finally forming a film by a solution method, drying for a certain time at a certain temperature, and removing the film by buoyancy in water to obtain the plasticizer-free aqueous polyurethane flexible sensing film.

The solution method film forming can adopt a method of solution casting film forming and a method of solution wire rod scraping film forming, and preferably the wire rod scraping film forming.

The film forming and drying temperature is 0-100 ℃, and preferably 50 ℃.

The film-forming drying time is 1 min-48 h, preferably 24 h.

The technical scheme is as follows:

provides application of plasticizer-free environment-friendly waterborne polyurethane flexible sensing film

The plasticizer-free environment-friendly waterborne polyurethane flexible sensing film is applied to a sensing film in an ion selective electrode, and corresponding sensing ions are lead ions. Or be assembled on a potential sensor to be applied to the detection of lead ions.

The internal filling liquid used in the ion selective electrode is 1.00 multiplied by 10^-5～1.00×10^-2mol/L Pb(NO₃)₂Solutions, preferably 1.00X 10^-4mol/L。

The preparation solution used in the ion selective electrode is 1.00X 10^-5～1.00×10^-2mol/L Pb(NO₃)₂Solutions, preferably 1.00X 10^-4mol/L, the preparation time is 1 to 3 days, preferably 1 day。

The specific operation that the plasticizer-free environment-friendly waterborne polyurethane flexible sensing film has an excellent lead ion sensing effect is as follows: preparing a certain amount of Pb (NO) with a certain concentration₃)₂And (3) inserting the prepared electrode into a standard solution, taking the Shanghai Lei magnet 232-01 single-salt bridge saturated calomel electrode as an external reference electrode, and testing the response potential of the WPU sensing membrane by adopting a PXSJ-216F type ion meter produced by Shanghai Lei magnet company. The electrochemical cell structure is as follows:

The technical scheme is six:

the lead ion selective electrode is provided, and the environment-friendly water-based polyurethane flexible sensing film without the plasticizer is used as the sensing film in the technical scheme V.

The invention has the following benefits:

a very small amount of graphene nanosheets are introduced into conductive polymer (such as copolyalniline) nanoparticles, so that the graphene nanosheets are dispersed in the conductive polymer nanoparticles, and a bridge is built for electronic conduction and ionic conduction among particles. Due to the specific fine composite structure and the synergistic effect of the two, when the nano composite is used as a lead ion carrier, not only can the functional groups on the molecular chain of the conductive polymer be more effectively exposed, but also the sensitive response function to lead ions can be further improved. The sensor is embedded into a water-based polyurethane base film without a plasticizer, and the constructed all-solid-state sensing film can also obtain the functions of electronic conduction and ion conduction, so that the potential response of the electrode is more stable and the response speed is faster compared with other solid-state film ion-selective electrodes. The method retains the inherent advantages of the non-plasticized solid sensing membrane, overcomes the common defect of unstable potential response reading of the solid sensing membrane, and is expected to be developed into a new generation of lead ion selective electrode following the conventional plasticized PVC base membrane.

The waterborne polyurethane without the plasticizer is used as a film matrix material, so that the defects of the traditional plasticized PVC base film are overcome, and the waterborne polyurethane has excellent environmental friendliness compared with other non-plasticized PVC films. The waterborne polyurethane is an environment-friendly high polymer material which is expected to replace toxic organic solvent system polyurethane and developed in recent years, is a binary colloid system formed by uniformly dispersing polyurethane nanoparticles in a water system, and has the advantages of no free isocyanate group (-NCO), low VOC content, easiness in cleaning, non-flammability and the like. The flexible and elastic sensing film can be obtained by using the self-prepared polyurethane as a sensing film substrate and embedding active components such as an ionophore and the like into the sensing film substrate by virtue of the excellent film-forming property of the waterborne polyurethane. The method not only widens the application field of the waterborne polyurethane, but also develops a new class of environment-friendly base film materials for the sensing film, and makes the preparation of the sensing film step on a new step of removing the organic solvent. Related studies have not been reported.

Compared with the lead ion selective electrode reported in the prior art, the lead ion selective electrode taking the conductive polymer/graphene nano composite as the carrier has the following advantages:

(1) the conductive polymer/graphene nano-composite has the advantages of simple synthesis method, high yield and rich monomer sources, and compared with the traditional neutral molecular carrier, the conductive polymer/graphene nano-composite has low price and is embedded in the sensing membrane in a solid state and not easy to run off;

(2) compared with the lower detection limit of a plasticized PVC membrane electrode, the lower detection limit of the lead ion selective electrode is expanded by 2 orders of magnitude to 10^-8The membrane is in a mol/L level, the response potential is stable, the response time is extremely short and generally does not exceed 10s, and the potential stability is obviously superior to other all-solid-state membranes reported.

(3) The plasticizer-free environment-friendly water-based polyurethane flexible sensing film serving as the lead ion selective electrode is a long-life calibration-free electrode, the response potential curve of the electrode does not drift in 2-month use, and the service life of the electrode can reach at least 4.5 months (18 weeks).

Drawings

FIG. 1 is a schematic diagram of the aggregate structure of a lead ionophore nanocomposite;

FIG. 2 is the ultraviolet absorption spectrum and the Tyndall phenomenon of the graphene nanosheet obtained by ultrasonic treatment in example 4;

FIG. 3 is the infrared absorption spectrum of the polyaniline/graphene nanocomposite obtained in examples 6 and 7;

FIG. 4 is a scanning electron micrograph of the polyaniline/graphene nanocomposite obtained in example 6;

FIG. 5 is a potential response curve of a sensing membrane electrode prepared in example 11 to lead ions;

FIG. 6 is a graph showing the potential response of a sensing membrane electrode prepared in example 12 to lead ions;

FIG. 7 is a graph showing the potential response of a sensing membrane electrode prepared in example 13 to lead ions;

FIG. 8 is the response time of the sensing membrane electrode prepared in example 11 to the potential of lead ions;

FIG. 9 is the pH window of the sensor film electrode prepared in example 11;

FIG. 10 is a potential response curve of the sensor film electrode prepared in example 11 for the first 8 weeks;

FIG. 11 is an electrochemical impedance spectrum of a sensor film electrode prepared in example 11;

FIG. 12 is an equivalent circuit diagram used in the simulation of the EIS;

FIG. 13 is an infrared spectrum of expandable graphite, expanded graphite, and ultrasonically exfoliated graphene thereof;

FIG. 14 thermogravimetric plot of graphene after ultrasonic exfoliation of expanded graphite in aniline;

FIG. 15 is a thermogravimetric plot of a nascent sensing membrane;

FIG. 16 thermogravimetric curves of the sensor film modulated and used.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Examples 1-2 preparation of expanded graphite by thermal expansion method

Example 1

0.5g of graphite is weighed in a ceramic crucible, scattered in a disc placed in a muffle furnace at 800 ℃, taken out after 20s, placed on a temperature-resistant experiment table, covered with a cover, cooled to the temperature close to room temperature and then placed in a dryer filled with blue silica gel for cooling. The expanded graphite is obtained, weighed, measured for volume, and the expansion rate can be calculated to be 365 mL/g.

Example 2

The other conditions were the same as in example 1, except that a muffle furnace at 1200 ℃ was used, and the swelling ratio was 331 mL/g.

Example 3-5 preparation of graphene nanoplate by ultrasonic method

Example 3

Adding 13mg of graphite and 20mL of aniline into a glass test tube, performing rod type ultrasonic treatment at 40% power by using a JY92-IIN ultrasonic cell crusher (650W, 20-25 kHz), stopping for 1s every 3s, and performing ultrasonic treatment for 1h in total to obtain graphene dispersion liquid with the appearance like ink, wherein the ultraviolet spectrum of the graphene dispersion liquid generates obvious absorption on 660nm light waves, but a small amount of particles are observed to be settled after standing overnight.

Example 4

The other conditions were the same as example 3, except that an SK3300HP ultrasonic cleaner (180W,53kHz) was used, and ultrasonic cleaning was carried out in a water bath at a power of 180W for 48 hours. The graphene dispersion liquid with the appearance like ink is obtained, the ultraviolet spectrum of the graphene dispersion liquid generates obvious absorption on light waves with the wavelength of 660nm, and basically no precipitate is generated after standing overnight. The ultraviolet spectrum of the obtained graphene dispersion liquid after 5-time dilution is shown in figure 2, the Tyndall photo is shown in an inset of figure 2, and a scattering light path cannot be observed due to high graphene concentration.

Example 5

The other conditions were the same as in example 4, but 13mg of graphite was soaked in 20mL of aniline for 4 weeks before sonication, and the resulting graphene dispersion was more stable.

Example 6 in situ polymerization 1

The graphene dispersion prepared in example 4 was centrifuged at 3000rpm for 90min and the supernatant gradually removed by aspiration to give a weight of just 757.8mg of the remaining material in the vial, yielding a blend of 13mg of graphene and 744.8mg of aniline. Quickly adding 378.4mg of o-aminophenol sulfonic acid 100mL of 1mol/L HCl solution, stirring for 5min by strong magnetic force, immediately transferring to water bath ultrasound (53kHz,180W, 100%), and then dripping 50mL of 0.2mol/L ammonium persulfate 1mol/L HCl aqueous solution at a dripping speed of 1 drop/3 s for about 40 min; then transferring it into magnetStirring in a water bath on a force stirrer for 24 hours, repeatedly washing by using 1mol/L HCl after the reaction is finished to remove byproducts, and centrifugally separating and removing supernatant; and finally, transferring the obtained copolyalniline/graphene nano composite into a watch glass, and freeze-drying for 48 hours until the weight is constant to obtain the powder of the copolyalniline/graphene nano composite, wherein the polymerization yield is 50.21%, and the mass ratio of the copolyalniline to the graphene is about 98: 2. The conductivity of the composite measured by the powder tabletting four-probe method is 9.73 multiplied by 10^-2S/cm。

The infrared spectrum of the resulting composite is shown in fig. 3 as the absorption spectrum labeled "ultrasound aniline copolymer/graphene nanocomposite". 2800 to 3400cm in a high-band region^-1A broad absorption peak appears in the range, which is an-NH-stretching vibration absorption peak of amino and imino, particularly 3200cm^-1A small distinct absorption peak based on the broad absorption peak was observed indicating significant exposure of the amino groups in the copolymer. 2950cm at a slightly lower band^-1Also appear as weaker peak-CH-characteristic absorption peak. Combined 1580, 1500cm^-1Typical vibration characteristic peaks of the benzene ring skeleton correspond to stretching vibration of a quinoid (C ═ C) and a benzene (C-C) in a molecular chain of the copolymer, respectively, and illustrate formation of the aniline copolymer.

The scanning electron micrograph of the resulting composite is shown in FIG. 4. It can be seen that the copolymerized aniline particles of submicron level formed by the agglomeration of the primary particles of nanometer level are attached to the graphene nanosheets, and particularly, the particles of the copolymerized aniline particles are hidden and visible between the layers of the graphene nanosheets, so that a composite structure coated with the graphene wafers is formed.

Example 7 in situ polymerization 2 raw, un-sonicated aniline control experiment

The graphene dispersion obtained by stripping in example 4 was centrifuged at 3000rpm for 90min and the supernatant was completely removed leaving only the sonicated graphite in the bottle. Then 0.73mL of fresh aniline was added, and 378.4mg of o-aminophenol sulfonic acid in 100mL of 1mol/L HCl solution prepared in advance was added rapidly. The rest of the procedure was the same as in example 6. Finally, freeze drying for 48h to constant weight to obtain the powder of the copolyalniline/graphene nano composite, wherein the polymerization yield is 40.62 percent, and the copolyalniline isThe mass ratio to graphene was 98: 2. The conductivity of the compound measured by the powder tabletting four-probe method is 3.06 multiplied by 10^-3S/cm. 1/32 for the resulting composite was only interpolymerized with aniline monomer that underwent sonication. The infrared spectrum of the resulting composite is shown in fig. 3 as the absorption spectrum of the "pristine aniline copolymer/graphene nanocomposite". Compared with the absorption spectrum of the ultrasonic aniline copolymer/graphene nano composite, the biggest difference is 3200cm^-1The small nearby absorption peaks are attenuated, indicating a reduced exposure of the amino groups in the copolymer.

Example 8 in situ polymerization 3

6.5mg of graphite and 20mL of ethylaniline were added to a glass test tube, subjected to ultrasonic bath for 48 hours using an SK3300HP ultrasonic cleaner (180W,53kHz) at a power of 180W, the resulting dispersion was centrifuged at 3000rpm for 90 minutes, and the supernatant was gradually removed by pipetting to give a weight of just 998.3mg of the remaining material in the bottle, yielding a blend of 6.3mg of graphene and 992mg of ethylaniline. Prepared 100mL of 1mol/L HNO containing 246mg of o-anisidine₃The solution was added rapidly and the subsequent polymerization procedure was the same as in example 6 to obtain the copolyalniline/graphene nanocomposite powder with a polymerization yield of 45.98% and a mass ratio of copolyalniline to graphene of about 99: 1.

Example 9 in situ polymerization 4

15mg of graphite and 20mL of N-methylaniline were added to a glass test tube, subjected to ultrasonic bath for 48 hours using an SK3300HP ultrasonic cleaner (180W,53kHz) at a power of 180W, the resulting dispersion was centrifuged at 3000rpm for 90 minutes, and the supernatant was gradually removed by pipetting to give a weight of just 998.3mg of the remaining material in the bottle, to give a blend of 6.3mg of graphene and 992mg of ethylaniline. 100mL of 0.5mol/L H of 346.4mg m-aminobenzenesulfonic acid prepared in advance₂SO₄The solution was added rapidly and the subsequent polymerization procedure was the same as in example 6 to obtain a powder of the copolyalniline/graphene nanocomposite with a polymerization yield of 67.81% and a mass ratio of copolyalniline to graphene of about 94: 6.

Example 10 in situ polymerization 5

The graphene dispersion obtained by stripping after soaking for 4 weeks in example 5 was subjected to in-situ polymerization as in example 6, but the obtained copolyalniline/graphene composite was not dried after being washed, but was dispersed in 64.5mL of a mixed medium of ethanol and water in a volume ratio of 1: 1.

Examples 11-12 preparation of sensing films from composite powders

30.6mg of the copolyalniline/graphene nanocomposite obtained in example 6 and example 7 were weighed into a weighing bottle, 3mL of a blending solvent of ethanol and water (volume ratio 1:1) was added, water bath sonication (60kHz, 100%) was performed for 30min, then the mixture was vigorously stirred at 800rpm by a homogenizer for 10min, and then the mixture was transferred to the water bath sonication (60kHz, 100%) for 10min, and the above cycle was repeated for 5 times. 2.6mL of aqueous solution of waterborne polyurethane (R974) with the solid content of 35 percent is measured, the aqueous solution is put into another weighing bottle, the strong stirring is carried out by a homogenizer at 800rpm, the nano-composite dispersion liquid is slowly added, 200 mu L of the aqueous solution is added at one time, the strong stirring is carried out while the addition is carried out, the time interval of each addition is 20min, and the stirring is carried out for about 150min in total. The entire casting solution was poured onto an OPP film, and the film was scraped into a film using a RK stamp press and a 100 μm wire bar. And (3) drying the wet film in an oven at 50 ℃ for 24 hours, taking out, naturally cooling to room temperature, putting the film into clear water of about 3cm for demoulding, taking out and drying in the air, wherein the thicknesses are 35-46 mu m and 44-53 mu m respectively.

EXAMPLE 13 preparation of sensing membranes from Complex dispersions

Weighing 3mL of the graphene dispersion liquid prepared in the example 10 into a weighing bottle, strongly stirring the graphene dispersion liquid for 10min at 800rpm by using a homogenizer, transferring the graphene dispersion liquid into a water bath at 60kHz and carrying out ultrasonic treatment for 10min at 100% power, circulating the steps for 5 times in the way, and then blending the graphene dispersion liquid with polyurethane, wherein the specific operation is the same as that of the examples 10-11, and the thickness of the obtained film is 30-38 micrometers.

Examples 14-16 Assembly of lead ion electrodes

The sensor films obtained in examples 11 to 13 were cut into disks 12mm in diameter, adhered to the ends of plastic tubes with glue, and after they were naturally dried, 10 pieces of adhesive were inserted into the tubes^-4And (3) mol/L lead nitrate solution. Warp 10^-4And testing the response performance of the lead nitrate in mol/L to lead ions after being modulated for 24 hours and activated. See fig. 5-7 for details. It can be seen that when the polyaniline/graphene nanocomposite obtained in example 6 is used as a carrier, the lower limit of electrode detection is minimizedValue of 10^-8mol/L，Pb²⁺Activity linear range 10^-2.27～10^- ^7.98M, the response slope is 27.84 mV/dec; when the copolyalniline/graphene nanocomposite in example 9 is used as a carrier, the lower limit of electrode detection is 10^-6.31mol/L，Pb²⁺Activity linear range 10^-1.59～10^-6.31M, the response slope is 32.99 mV/dec; when the copolyalniline/graphene nanocomposite in example 9 is used as a carrier, the lower limit of electrode detection is 10^-6.82mol/L，Pb²⁺Activity linear range 10^-2.27～10^-6.82M, the response slope is 29.43 mV/dec;

it can be seen that, comparing the sensing membranes prepared from the nanocomposite lead ion carriers prepared in examples 6 and 7, it is found that the nanocomposite carrier obtained by in-situ copolymerization of the monomers left after the graphite ultrasonication is easier to obtain a more excellent lower detection limit and a more ideal Nernstian slope than the nanocomposite carrier obtained from the original monomers without being subjected to ultrasonication, and thus there is more chance that the monomers subjected to the common ultrasonication interact with the graphite and the graphene. The monomer is easier to wet graphite and even to insert into graphite layers in the ultrasonic process according to the moderate surface tension and similar benzene ring pi planes, in the process of ultrasonic stripping of graphite, the graphite enters a certain non-equilibrium state at a certain moment under the action of strong sound wave power, and the graphite flake layers have a slight opening tendency, at the moment, monomer molecules wetted on the graphite flake can be inserted between graphene planes while the graphite flake is still in contact with the graphene, so that, the graphene surface modification agent promotes graphite stripping, and simultaneously adsorbs on a graphene plane by virtue of pi-pi action, so that the monomer is easy to nucleate and grow on the graphene surface during subsequent copolymerization, and the two components are easy to be hybridized and compounded with each other, and finally a deeper and finer composite structure is achieved, so that more functional groups in the copolyalniline are exposed, and the effect of sensing target ions is exerted, wherein the infrared spectrum is 3200 cm.^-1This is evidenced by the apparent enhancement of the absorption peaks on the left and right representing amino groups. And the original monomer is supplemented after the graphite is subjected to ultrasonic treatment, so that the monomer molecules and the graphene are not fully utilizedWith this, polymerization thereof more easily occurs in the aqueous phase, and isolated nucleation growth proceeds. Therefore, fresh monomers that have not been subjected to ultrasound with graphite cannot achieve a fine composite structure.

Example 17 response time of electrodes

The response time of an electrode refers to the time that the electrode takes from contacting the test solution to obtaining a relatively stable value. The potential response of the sensing membrane electrode prepared in example 11 in six different concentrations of lead solution versus time is shown in fig. 8. It can be seen that for 10^-2～10^-8The response time of the electrode does not exceed 10s for mol/L lead solution.

Example 18pH Window

The potential response of the sensing membrane electrode prepared in example 11 in two lead solutions with different concentrations is related to the pH value as shown in FIG. 9. It can be seen that for 1.0 × 10^-3And 1.0X 10^-4In the pH range to be considered, the potential response of the electrode of two mol/L lead standard solutions is divided into three stages, wherein the middle section 5.0-7.0 is a horizontal line, the potential change along with the pH is small and corresponds to 1.0 multiplied by 10^-3mol/L and 1.0X 10^-4The potential reading values of the two kinds of lead standard solutions of mol/L are respectively in the ranges of-54.8 mV to-56.2 mV and-83.9 mV to-84.4 mV, and the fluctuation ranges are respectively 1.4mV and 0.5 mV. Therefore, the pH potential platform window of the electrode is 5.0-7.0.

EXAMPLE 19 electrode Selectivity

The selectivity of the electrode to lead ions was evaluated by a modified separate solution method, so that a non-biased selectivity coefficient could be obtained. 13 possible interference ions are selected, the selection coefficient of each interference ion is tested by using 13 rod electrodes respectively, and the electrodes cannot contact the main ions and other interference ions from beginning to end so as to ensure that a real selectivity coefficient is obtained. Reading the specific potential difference of i ions and j ions corresponding to the potential response curve of each interference ion when the activity is extrapolated to 1mol/L by adopting an equipotential processing method

Substituting into formula (3) to calculate the selection coefficient. Is thus measuredThe selection coefficients are listed in table 1. Therefore, the electrode has better anti-interference capability on divalent ions and certain anti-interference capability on monovalent ions.

TABLE 1 Selectivity coefficients of lead ion-selective electrodes

EXAMPLE 20 service life of the electrode

The service life of the electrode is evaluated by electric polarity energy parameters such as the response slope, linear range, response time, and detection lower limit of the electrode. According to IUPAC regulations, an electrode is considered to be failed when the response slope for evaluating electrode life is less than 95% of the initial electrode test parameters. The electrodes were tested twice a week for the first month, once a week for the second month, and once every two weeks for the third month and thereafter. After each test, the electrode is washed, the internal filling liquid is poured out, and the electrode is placed in a cool and dry place for storage. Refill 10 for lower wheel test^-4The solution was poured into a flask of mol/L and mixed with a lead nitrate solution of the same concentration for 24 hours. The potential response curve parameters of the sensor film electrode prepared in example 11 during the examination are shown in table 2. It can be seen that the electrode can maintain good lead ion linear responsiveness in the investigated 22 weeks, and the detection lower limit is basically kept unchanged, especially the response slope approaches to the Nernst slope in the first 18 weeks. It is particularly noted that the response curve of the first 8 weeks hardly changed (fig. 10), and not only the slope hardly decreased cracking, but also the response potential of each concentration point in its linear range did not drift so much that the entire response curve was fixed at the response potential level of the initial stage. This property confers on the electrode a calibration-free capability, and ion-selective electrodes capable of sustaining for 2 months without calibration have not been reported.

Table 2 change of potential response curve at each stage of sensor film electrode prepared in example 11

EXAMPLE 21 application of the electrode

The actual samples were taken from tap water in the laboratories of the ecological buildings of the university of Tongji, 10 months of rainwater in Shanghai City, and river water under the administrative road and bridge in the Yanpu area of Shanghai city, respectively. The actual samples were filtered using a 0.22 μm filter to remove insoluble solid particles from the water prior to testing. The pH of all three water samples was near neutral. The lead content of the pretreated sample and the contents of other common metal ions were measured by an Agilent ICPMS7700 inductively coupled plasma mass spectrometer, and the results are shown in Table 3. It can be seen that the lead content of three actual water samples ranges from several ppb to tens of ppb. Because the concentration of lead ions is too low, the response potential of the electrode adopting the direct potential method is not in a linear range, and the lead content cannot be accurately detected.

TABLE 3 pH of three actual water samples and several metal ion contents (mol/L)

Then, three actual water samples are subjected to the standard addition recovery experiment, and 1.00 multiplied by 10 are accurately transferred into 40mL of water samples ^-3200 mu L of lead standard solution of mol/L, and the lead content can be obtained after shaking up to 5.00 multiplied by 10^-6And adding a standard water sample in mol/L. The electrode of the invention is passed through a screen of 1.00X 10^-4And (3) modulating and activating for 24 hours in mol/L lead standard solution, washing the lead standard solution to a stable potential by using ultrapure water, and directly measuring the lead content of three standard water samples, wherein each water sample is repeatedly tested for 3 times, and the electrode after each test needs to be repeatedly cleaned for 5-6 times by using the ultrapure water, so that the potential is recovered or is close to the initial potential and then used for the next test. The results of such tests are shown in Table 4. Therefore, the recovery rate of each water sample measured by the direct potentiometry is within the range of 93-107%, and the test accuracy and precision are better.

TABLE 4 lead content (mol/L) recovery experiments using lead ion selective electrodes to test three actual spiked water samples

Example 22EIS testing

Using the sensor membrane electrode prepared in example 11 as a working electrode, a platinum electrode as a counter electrode, and a saturated calomel electrode as a reference electrode, a three-electrode system was constructed at 1.0X 10^-4And (3) performing Electrochemical Impedance Spectroscopy (EIS) determination after the open-circuit potential in the lead nitrate solution of mol/L is stable, wherein the tested voltage amplitude is 5mV, the tested frequency is 0.01 Hz-100 kHz, and the obtained Bode graph and the Nyquist graph are shown in a figure 11. Fitting the obtained EIS atlas with ZsimWin software according to the equivalent circuit shown in FIG. 12, wherein the parameters used in the fitting process include the thickness of the sensing film being about 35 μm, the effective radius of the sensing film being 0.8cm, and the effective area being 2cm²The parameters of each element obtained by fitting are that the series resistance Rs is 2.45 multiplied by 10⁴Ω/cm²Membrane resistance R_bIs 1.59X 10⁶Ω/cm²Conductivity 1.3X 10^-9S/cm, geometric capacitance C_gIs 1.25X 10^-10F/cm²Warburg impedance coefficient 6.67 x 10⁴Ω·s^-1/2. Therefore, the graphene in the composite carrier has an ion and electron conduction function, so that the conduction capability of the membrane is obviously improved, and the ion selective electrode is endowed with excellent potential response performance.

Example 23

The graphene dispersion prepared in example 4 by ultrasonic exfoliation was washed centrifugally with 1mol/L HCl at 4000rpm for a total of 6 washes, trying to wash away all aniline medium. The cleaned graphene was dried in an oven at 80 ℃, and the infrared spectrum of the powder sample is shown in fig. 13. For illustrative purposes, expandable graphite, as well as expanded graphite, are also provided. The analysis map shows that the expandable graphite is 1632cm^-1,1171cm^-1And 1069cm^-1The absorption peak can be attributed to the stretching vibration of the graphite carbon skeleton, and the absorption peak of the fingerprint area is related to the substitution structure of the graphite aromatic ring. And is at 3390cm^-1A strong and wide suction appearsThe contraction band belongs to the stretching vibration of hydroxyl O-H, which indicates that a certain amount of hydroxyl oxygen-containing groups exist in the expandable graphite and the length of the contraction band is 1724cm^-1A fusion appears at 1632cm^-1A shoulder on the main peak, which is the characteristic stretching vibration absorption peak of the sharp carbonyl group C ═ O, indicating the presence of a certain amount of two other oxygen-containing groups such as carbonyl or carboxyl groups. After high temperature expansion, the absorption peaks at both parts are weakened, especially 3390cm^-1The absorption peak is greatly reduced, which shows that the oxygen-containing groups are basically removed, and the graphite is still 2916cm after expansion^-1Symmetric stretching vibration of aromatic hydrocarbon (C-H) appears, which indicates that a small amount of hydrogen is bonded to a fused ring aromatic hydrocarbon carbon skeleton in the deoxidation expansion process. It is worth noting that the graphite after expansion is restored to 3390cm after ultrasonic liquid phase stripping in aniline for 48 hours^-1Strong and wide absorption band at 3230cm with only a red shift of the vibration frequency (wave number reduction)^-1A strong absorption peak is highlighted, which is attributed to the stretching vibration of amino N-H, indicating the existence of aniline in the ultrasonic graphene. Even more clearly 1450cm^-1The absorption peak is the stretching vibration of the C-N group, the peak only appears in the graphite subjected to aniline ultrasonic liquid phase stripping, but does not appear in the expandable graphite and the expanded graphite, and further proves that aniline exists in the graphite after ultrasonic stripping, and as the ultrasonic graphite is washed for multiple times by 1mol/L HCl, the aniline can be inferred not to be simply blended in free aniline among graphite particles, but is aniline which is inserted among graphite wafers and is difficult to wash away, obviously, the aniline remained in the way is favorable for forming an intercalation composite structure during subsequent in-situ polymerization.

Example 24

The graphene dispersion prepared in example 4 by ultrasonic exfoliation was washed centrifugally with 1mol/L HCl at 4000rpm for a total of 6 washes, trying to wash away all aniline medium. The cleaned graphene is put into an oven at 80 ℃ for drying, and the thermogravimetric curve TG and the differential curve DTG of the powder sample in the air are shown in figure 14. It can be seen that the maximum decomposition rate is at 650 ℃, due to the decomposition weight loss of graphene. Also of particular note here is the apparent weight loss peak at around 184 c, which is known to correspond to the boiling point of 184 c for aniline, which apparently corresponds to the weight loss of aniline, which is known to be about 5 wt% from the weight loss value. It can be seen that although the graphene is strongly washed, a small amount of aniline which is not easy to wash away still exists, and it can be concluded that the remaining aniline which is not easy to wash away is intercalated between wafer layers of the graphene, which lays a foundation for preparing the polyaniline-graphene nanocomposite through subsequent in-situ polymerization.

Example 25

The thermogravimetric curves TG and DTG of the primary sensor film prepared in example 11 and 2.77mg of the conditioned and used sensor film were measured at a temperature rise rate of 10 ℃/min in a synthetic air atmosphere, respectively, and the results are shown in fig. 15 and fig. 16. The analysis of DTG shows that the primary film is basically free from equilibrium hygroscopic water peaks, which indicates that the surface and the inside of the base film do not contain water, and the base film can prove to be difficult to absorb water and can block water from penetrating, namely can effectively block ion flow. The main peak of the maximum decomposition rate is 341 ℃ at high temperature, 2-4 shoulder peaks are arranged on the main peak, which is the characteristic expression of the multi-component aliphatic polyurethane, each degradation peak is corresponding to the degradation of one chain link component until all soft segments and hard segments in a polyurethane molecular chain are completely degraded at 600 ℃, only graphene and partial aniline copolymer in the active carrier compound are remained, and the residual coke content is about 0.9 wt%. However, although the maximum thermal decomposition rate of the thermogravimetric curve of the sensing film subjected to lead ion modulation and lead ion response curve test is-1.5 wt%/° c without any change, the thermal stability of the sensing film is obviously improved, and the weight loss peak attributed to soft segment degradation at about 214 ℃ basically disappears, the initial decomposition temperature is improved to 291 ℃ from about 161 ℃, the temperature at the maximum thermal decomposition rate is improved to 356 ℃ from 341 ℃, the temperature is respectively improved by 130 ℃ and 15 ℃, the residual coke content is also improved to 2.8 wt% from 0.9 wt%, and the residual coke content is increased by 3.1 times. Meanwhile, multiple degradation peaks tend to be fused, the peak width becomes narrow and small, the spike shape becomes sharp, and the improvement of the possible thermal performance and the increase of the residual weight are reflected by the fact that lead salt enters a membrane phase. It can be seen that after the sensing film is contacted with the lead ion solution, the active carrier on the sensing film can introduce the lead ions in the solution into the sensing film through complexation and anchor the lead ions in the sensing film.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. The application of the solid ionophore is characterized in that the solid ionophore is embedded into a water-based polyurethane base film without a plasticizer to construct an all-solid sensing film; or, the all-solid-state sensing film is used as a lead ion selective electrode;

the solid ionic carrier is a nano composite formed by compounding conductive polymer nano particles rich in functional groups and graphene nano sheets;

in the solid ionophore, the weight ratio of the conductive polymer to the graphene is 90/10-99.9/0.1,

the conductive polymer is formed by polymerizing a conductive polymer monomer and a conductive polymer monomer containing various functional groups,

the conductive polymer monomer is selected from one or more of aniline, methylaniline, ethylaniline, propylaniline, N-methylaniline, N-ethylaniline or N-propylaniline;

the conductive polymer monomer containing multiple functional groups is an aniline derivative containing one or more of amino groups, sulfonic acid groups, hydroxyl groups or alkoxy groups, and has the following structural general formula:

in the formula, R₁And R₂Each independently selected from-H, -NH₂、-OH、-SO₃H、-OCH₃or-OCH₂CH₃。

2. The use of a solid ionophore according to claim 1 wherein said solid ionophore is a lead ionophore.

3. The use of the solid ionophore according to claim 1, wherein the weight ratio of the conductive polymer to the graphene in the solid ionophore is 98/2-99/1.

4. The use of the solid ionophore according to claim 1, wherein the plurality of functional groups of the conductive polymer monomers are selected from the group consisting of:

5. the use of the solid ionophore according to claim 1, wherein the solid ionophore is prepared by a method comprising:

the preparation method comprises the following steps of carrying out chemical oxidative polymerization on graphene nanosheets, conductive polymer monomers and conductive polymer monomers containing multiple functional groups, so that the conductive polymer monomers and the conductive polymer monomers containing the multiple functional groups are polymerized on the graphene nanosheets in situ to form a nano-composite, namely a solid ionic carrier, consisting of the conductive polymer nanoparticles rich in the functional groups and the graphene nanosheets.

6. Use of a solid ionophore according to claim 5, characterised in that it comprises the steps of: mixing the graphene nanosheets, the conductive polymer monomer and the conductive polymer monomer containing various functional groups, stirring, performing ultrasonic treatment, adding an oxidant, and performing polymerization reaction in a water bath condition to obtain a nano compound, namely a solid ionic carrier, consisting of the conductive polymer nanoparticles rich in the functional groups and the graphene nanosheets.

7. The application of the solid ionic carrier according to claim 6, wherein the graphene nanoplatelets and the conductive polymer monomer are mixed and then subjected to ultrasonic treatment, and then the conductive polymer monomer containing multiple functional groups is added and mixed, or,

mixing graphite and a conductive polymer monomer, carrying out ultrasonic treatment to obtain a blending system of the graphene nanosheet and the conductive polymer monomer, and then adding the conductive polymer monomer containing multiple functional groups for mixing.

8. The use of a solid ionophore according to claim 6 wherein said oxidant is selected from ammonium persulfate and ferric trichloride.

9. The use of the solid ionophore according to claim 6, wherein the oxidant is added in the form of an acid solution, and the acid solution for preparing the oxidant solution is selected from 0.5-1 mol/L hydrochloric acid, nitric acid, sulfuric acid, perchloric acid;

when the oxidant is selected from ammonium persulfate, the molar concentration of the ammonium persulfate is 50 mmol/L-500 mmol/L,

when the oxidant is selected from ferric trichloride, the molar concentration of the ferric trichloride is 100 mmol/L-500 mmol/L,

the molar ratio of the oxidant to the comonomer is 1/2-3/1, and the molar weight of the comonomer is the sum of the molar weight of the conductive polymer monomer and the molar weight of the conductive polymer monomer containing various functional groups.

10. The use of the solid ionophore according to claim 9, wherein when the oxidant is selected from ammonium persulfate, the molar concentration of ammonium persulfate is 100-300 mmol/L;

when the oxidant is selected from ferric trichloride, the molar concentration of the ferric trichloride is 200-300 mmol/L;

the molar ratio of oxidant to comonomer was 1/1.

11. The use of the solid ionophore according to claim 6, wherein the polymerization temperature is 0-50 ℃ and the polymerization time is 6-48 h;

the ultrasound is selected from water bath ultrasound or needle ultrasound, and the process conditions of the water bath ultrasound are 40 kHz-60 kHz acoustic frequency and ultrasound for 24 h-72 h under 50W-200W acoustic power; and the needle type ultrasonic process conditions are 20kHz acoustic frequency and ultrasonic treatment for 2 to 6 hours under 200 to 600W acoustic power.

12. The use of a solid ionophore according to claim 11 wherein the polymerization temperature is 10 ℃ and the polymerization time is 24 h;

the ultrasound is selected from water bath ultrasound or needle ultrasound, and the process conditions of the water bath ultrasound are 40 kHz-60 kHz acoustic frequency and ultrasound under 180W for 48 hours; and the process conditions of the needle type ultrasound are 20kHz acoustic frequency and ultrasound under 400W for 3 h.