Electropolymerization of pyrrole on gold (Au) electrodes

Abstract

A method of forming a polymerized transduction layer on an electrode and an electrode having a polymerized transduction layer. The electrodes are suitable for ion selective applications. The method includes the steps of: (i) forming a combination of an electrode having gold and an electropolymerization mixture. The electropolymerization mixture includes a dopant and a monomer. The dopant comprises benzenesulfonic acid with a benzene ring, and the benzene ring is provided with amido, hydroxyl and / or methyl functional groups and / or derivatives of benzenesulfonic acid. The monomer comprises a cyclic structure comprising at least four carbons (C) and at least one nitrogen (N), sulfur (S) and / or oxygen (O). The method further comprises the step of (ii) treating the assembly formed in step (i) under electropolymerization conditions sufficient to oxidize the monomer and form the polymer on the electrode.

Description

[0001] Cross - reference to related applications This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 425,658, filed on November 15, 2022, which is related to PCT / US2022 / 037198 and PCT / US2022 / 052927, and for all purposes, these applications are incorporated herein by reference. Background of the Invention

[0002] Various polymers have been reported for use in the transducer layer of electrochemical sensors. Polypyrrole (PPy) is often selected because of its preferred properties such as high conductivity, high stability under ambient conditions and at high temperatures, and good redox properties. Multiple electropolymerization methods incorporating different electropolymerization mixtures and different electrode materials have been reported in the literature. The working electrode material affects the formation kinetics and adhesion of the PPy film. Gold (Au) working electrodes have been found to be particularly problematic. Improvements in this field are desired. Summary of the Invention

[0003] The present invention provides a method for forming a polymeric transducer layer on an electrode. The resulting electrode is suitable for ion - selective applications such as ion - selective electrodes and / or sensors. The method includes the step of forming an assembly of an electrode containing gold and an electropolymerization mixture. The electropolymerization mixture contains a dopant and a monomer. The dopant includes benzenesulfonic acid and / or derivatives of benzenesulfonic acid, where the benzene ring has amine, hydroxyl, and / or methyl functional groups. The monomer includes a cyclic structure having at least four carbons (C) and at least one nitrogen (N), sulfur (S), and / or oxygen (O). The method further includes the step of treating the assembly formed in step (i) under electropolymerization conditions sufficient to oxidize the monomer and form a polymer on the electrode. Preferably, an electrode formed by this method is also provided, wherein the transducer layer includes a detectable level of the dopant. Brief Description of the Drawings

[0004] Figure 1 Shows p - The overall reaction scheme for the electrochemical polymerization of TS - doped PPy on a gold substrate.

[0005] Figure 2 Shows CV data from an example of the present invention.

[0006] Figure 3 Shows p - Optical images of a TS - PPy - modified microelectrode shortly after polymer deposition (fresh electrode) and 1 minute after drop - coating THF (after THF exposure).

[0007] Figure 4 Shows pOptical images of the -TS-PPy modified microelectrodes shortly after polymer deposition (fresh electrodes) and after the electrodes were exposed to tape (after tape testing).

[0008] Figure 5 Shows the use of the solution of the present invention and three different methods p Optical images of the -TS-PPy modified gold rod electrodes (such as macroelectrodes (Au-RD)) shortly after polymer deposition (fresh electrodes) and 1 minute after drop-coating THF (after THF exposure). Detailed Description

[0009] It has been found herein that the material of the working electrode affects the electrochemical polymerization kinetics and adhesion of films containing specific polymers (such as PPy). Gold working electrodes have been found to have problems and it is difficult to form thick and mechanically stable polymer layers (such as PPy). Without being bound by a specific mechanism of action, this is thought to be due to: low interfacial adhesion of the polymer (such as PPy) to the underlying gold substrate, inability of the reaction mixture to covalently bond to the gold substrate, relatively low surface energy of gold, and / or electrostatic interactions between the polymer (such as PPy) and the substrate. Prior art solutions enhance adhesion through covalent bonds, such as adding functional groups, such as thiols [1], to the reaction mixture, which is not applicable to some electropolymerization methods because the electrochemical cycling causes the thiol functional groups to be unstable. In addition, it has been found that the improvement in adhesion depends on the anion used, where the initial adsorption of the counterion on the underlying electrode substrate seems to affect the nucleation process.

[0010] The present invention solves the above problems and provides a method and an electropolymerization reaction mixture that enable the formation of a conductive polymer (such as PPy) film with excellent properties and adhesion on the surface of an electrode, where the electrode includes gold. Specifically, the inventors unexpectedly found that, compared with those electropolymerized without a specific combination of monomer / dopant, the electropolymerization of a gold-containing electrode combined with a specific polymerization mixture (which contains a specific monomer and a specific dopant) can prepare an electrode with stable and excellent properties. Specifically, in the absence of a specific dopant, the conductivity of the resulting polymer film is relatively low and it cannot adhere satisfactorily to the gold-containing electrode when exposed to tetrahydrofuran (THF) or subjected to a tape test. In addition, it has been unexpectedly found that the size of the working electrode affects the adhesion of the resulting conductive polymer film. For example, when using microelectrodes, a specific polymer film (such as a p-TS-PPy film) is resistant to THF exposure, while when using macroelectrodes, a specific polymer film (such as p-TS-PPy) obtained by chronoamperometry (CA) and chronopotentiometry (CP) rather than the polymer film obtained by cyclic voltammetry (CV) can withstand the THF test.

[0011] Definition: As used in the specification and claims of this application, the following definitions shall apply.

[0012] "A", "an", and "the" as antecedents refer to singular or plural. For example, "a compound", "a polymer", "a monomer", etc. refer to a single substance or a mixture of the same and / or different substances, unless the context otherwise indicates.

[0013] The electrode preferably comprises gold, consists of gold, or consists mainly of gold. Gold may be present in the electrode / on the electrode as a surface coating, optionally in combination with other materials and / or provided with similar or different conductive materials, and / or the entire electrode may be composed of gold, such as a gold rod or a gold wire, etc.

[0014] The reaction mixture described herein may exist in the form of a mixture or more preferably in the form of a solution. The reaction mixture contains monomers to be polymerized and dopants. The reaction mixture may also contain other components known in the art for promoting chemical reactions or modifying the properties of the resulting polymer or reaction substrate. These other components are not limited herein and include, for example, catalysts, pH regulators, electrolytes, and / or salts (such as KCl, NaCl, etc.), polymer property modifiers, etc.

[0015] "Monomer" includes chemical substances having a cyclic structure, the cyclic structure including at least four carbons (C) and at least one nitrogen (N), and / or sulfur (S), and / or oxygen (O), etc. During the electropolymerization process, the monomer exists in a positively charged oxidized form. Preferred monomers of this application are used to form polymers such as polypyrrole, polyaniline, polythiophene, and poly(3,4-ethylenedioxythiophene). These monomers include, but are not limited to, pyrrole, aniline, thiophene, and 3,4-ethylenedioxythiophene.

[0016] "Dopant" (e.g., preferably p -TS) includes benzenesulfonic acid or its derivatives (such as benzenesulfonic acid in salt form and / or polymer form, etc.). Benzenesulfonic acid preferably includes chemical substances having a benzene ring, and the benzene ring preferably contains any one or a combination of functional groups such as amino group, hydroxyl group, or methyl group. In a preferred embodiment, the dopant includes p-toluenesulfonic acid ( p -TS), and exists in the resulting polymer in the form of p-toluenesulfonic acid ( p -TS).

[0017] "Microelectrode" is an electrode having a planar or three-dimensional surface, with dimensions generally in the range of about 1 μm to 1000 μm, a thickness not higher than about 1000 μm, and a surface area in about 1 μm 2 to 10 6 μm 2The range. Microelectrodes can be obtained on a substrate coated with an electrically insulating material or on an electrically insulating substrate by conventional thin-film preparation techniques, including magnetron sputtering, atomic layer deposition, pulsed laser deposition, chemical vapor deposition, electrospray deposition, electrochemical deposition, sol-gel deposition, deposition based on molecular precursors, etc., with or without an intermediate adhesion-promoting layer between the substrate and the gold, such as chromium, titanium, etc.

[0018] A "macroelectrode" is a planar or three-dimensional electrode, typically in the range of about 1000 μm to 10 cm in size and in the range of about 0.01 cm² to 100 cm² in surface area. The macroelectrode can be a piece of pure gold, mounted on a conductive metal and embedded in an electrically insulating material (such as polycarbonate, polytetrafluoroethylene, etc.).

[0019] "An embodiment", "another embodiment", "one embodiment", "some embodiments", etc. mentioned in the specification refer to specific elements (such as features, structures, properties, and / or characteristics) described in connection with the embodiments being included in at least one of the embodiments described herein, and may or may not be present in other embodiments. In addition, it should be understood that the elements and / or features of any embodiment can be combined with any other described embodiment in any suitable manner.

[0020] The numerical values in the specification and claims of this application reflect average values. In addition, unless otherwise stated, the numerical values should be understood to include the same values when reduced to the same number of significant digits, as well as values that differ from the stated value by less than the experimental error of the conventional measurement techniques described in this application for determining that value.

[0021] Electropolymerization and reaction mixture / method: Electrochemical polymerization (such as electropolymerization) is a well-known coating process in which a conductive polymer is formed from a monomer-containing reaction mixture (such as a polymerization reaction mixture) on a conductive substrate. The applied potential is selected to be high enough to oxidize the monomer for polymerization but low enough to avoid dissolving or corroding the conductive substrate. Electropolymerization is usually carried out in an electrochemical cell, which has a combination of the substrate to be coated as the working electrode and an inert material as the counter electrode. The polymerization reaction mixture usually contains a monomer, a solvent, and a supporting electrolyte. There are at least three different electropolymerization techniques, including potentiodynamic electropolymerization, galvanostatic electropolymerization, and potentiostatic electropolymerization.

[0022] In potentiodynamic electropolymerization (i.e., cyclic voltammetry, CV), a periodic and regular potential scan is performed between the oxidation limit of the monomer and the reduction limit of the polymerized conductive polymer. As the potential cycles back and forth, the growing polymer film continuously changes from a neutral state to a doped (or conductive) state. This process is accompanied by the continuous absorption and desorption of the electrolyte and solvent to stabilize the growing film. When polymerization is carried out by cyclic voltammetry, the following conditions can be adopted: the applied potential range is equal to -10.0 V or +10.0 V or between -10.0 and +10.0 V, for example equal to -2.0 V or +2.0 V or between -2.0 and +2.0 V, more preferably equal to -1.0 V or +1.5 V or between -1.0 and +1.5 V, for example equal to 0.0 V or +1.0 V or between 0.0 and +1.0 V; the number of potential scan cycles ranges from equal to 1 or 1000 or between 1 and 1000, more preferably equal to 1 or 100 or between 1 and 100, for example 3; the potential scan rate ranges from equal to 1 mV / s or 300 mV / s or between 1 and 300 mV / s, more preferably equal to 10 mV / s or 200 mV / s or between 10 and 200 mV / s, for example 100 mV / s.

[0023] In galvanostatic electropolymerization (chronopotentiometry, CP), a constant current is applied to polymerize the conductive polymer at a constant rate. At the beginning of electropolymerization, the potential briefly rises and then drops. The initial rise in potential is due to the formation of redox-active charged oligomers in front of the electrode. The subsequent drop in potential is caused by the catalytic action of the charged oligomers on the oxidized monomer. The measured potential is also related to temperature - the measured potential decreases as the temperature decreases. This can be explained by the decrease in the solvent volume, so the monomer concentration increases as the temperature decreases. When polymerization is carried out by chronopotentiometry, the following conditions can be adopted: the applied current range is equal to 0 mA or 100 mA or between 0 and 100 mA, more preferably in the range of equal to 0 mA or 5 mA or between 0 and 5 mA, for example 0.2 mA; the current application time range is equal to 0 s or 3600 s or between 0 and 3600 s, more preferably in the range of equal to 0 s or 600 s or between 0 and 600 s, for example 10 s.

[0024] In potentiostatic electropolymerization (e.g., chronoamperometry, CA), the applied potential is kept constant and the polymerization rate is controlled according to the applied potential. This method is similar to galvanostatic electropolymerization and different from potentiodynamic electropolymerization because no substances are released from the deposited film during the coating process. When polymerization is carried out by chronoamperometry, the following conditions can be adopted: the range of the applied potential is equal to -10.0 V or +10.0 V or between -10.0 and +10.0 V, for example equal to -2.0 V or +2.5 V or between -2.0 and +2.5 V, more preferably the range is equal to 0.0 V or +1.5 V or between 0.0 and +1.5 V, for example +0.8 V; the range of the potential application time is equal to 0 s or 3600 s or between 0 and 3600 s, more preferably the range is equal to 0 s or 600 s or between 0 and 600 s, for example 20 s.

[0025] Similarly, the electropolymerization of a specific monomer (e.g., pyrrole (Py)) can be promoted by an electrochemical method, where the applied potential oxidizes the monomer and then growth occurs in the form of a polymer on the anode surface (here on the gold electrode). However, the inventors found that during polymerization, adding a dopant containing a larger doped anion molecule (e.g., sulfonate) to the monomer reaction mixture can unexpectedly reduce the distortion of the polymer chains (e.g., polypyrrole (PPy)) and make bipolarons more mobile, and adding these dopants to the reaction mixture can achieve the formation of a stable polymer transducer layer on the gold electrode.

[0026] When the dopant includes p -TS (which is resistant to overoxidation and can be used for electrode applications), a polymer such as p-toluenesulfonic acid-doped polypyrrole ( p -TS-PPy) can be obtained, which is beneficial to obtaining a polymer film with excellent adhesion to the gold electrode. Figure 1 Shows p The overall polymerization scheme of -TS-doped PPy electrochemically polymerized on a gold substrate.

[0027] Without being restricted by a specific mechanism of action, it is believed that during electrochemical polymerization, PPy and negatively charged dopant anions (e.g., preferably p -TS) are formed synchronously. It is further believed that due to the positively charged gold substrate, strong electrostatic interactions occur between it and the negatively charged p -TS anions, thus promoting the adhesion of PPy. The use of these dopants (e.g., p -TS) not only promotes the adhesion of p -TS-PPy to the gold substrate, but also enhances the electron transfer kinetics of the resulting electrode surface.

[0028] The presence of the above dopants (e.g., preferably p -TS) in the reaction mixture and the resulting polymer improves the adhesion to the gold electrode surface. These benefits are not limited to the reaction mixture for the polymerization of pyrrole to form PPy, but may also include polymerization reaction mixtures containing monomers in other electro-polymerized forms, where the monomers include cyclic structures containing at least four carbons (C) and at least one nitrogen (N), and / or sulfur (S), and / or oxygen (O), etc., which generate a positively charged oxidized form during electro-polymerization. Thus, other reaction mixtures (e.g., polymerization mixtures) within the scope of this application include monomers for forming polymers such as polyaniline, polythiophene, and poly(3,4-ethylenedioxythiophene), etc.

[0029] In another embodiment, the resulting electrode has a gold and a polymerized transducer layer, is suitable for ion-selective monitoring and / or detection applications, and preferably has an ion-selective membrane (ISM) disposed on and / or in contact with the transducer layer. In these embodiments, the method further includes the step of forming an ion-selective membrane on the polymerized transducer layer of the electrode. The polymerized ion-selective membrane is integrated in a solid-state ion-selective electrode for generating an electrochemical signal due to the selective ion transport through the ISM. The method of forming and the composition of the ion-selective layer are not particularly limited and are preferably those described in U.S. Provisional Application Serial No. 63 / 291,804, which is incorporated herein by reference for all purposes.

[0030] Transducing layer / polymer layer and formed electrode: The resulting polymer layer formed from the reaction mixtures and methods described herein contains a detectable level of dopants (e.g., preferably p -TS). For example, when the dopant-to-monomer molar ratio is about 2% (e.g., p -TS / Py), a dopant-polymer film (e.g., p -TS-PPy film) with good adhesion to the gold electrode can be prepared when the ratio of dopant (e.g., p -TS) to monomer (e.g., Py) in the electro-polymerization reaction mixture is 1 / 10. These ratios can be determined / estimated using EDX. For example, the ratio of sulfur (S) to nitrogen (N) can be used as a reference since sulfur and nitrogen can only be present in the resulting polymer transducer layer due to the introduction of the dopant and pyrrole monomer, respectively.

[0031] The molar ratio of dopant / monomer (e.g., p -TS / Py) in the electro-polymerization solution can range between 1 / 100 and 10 / 1 p-TS / Py. The detectable level of the dopant in the resulting polymer can be determined by known sample evaluation methods. In a preferred embodiment, the detectable level of the dopant in the resulting polymer prepared from the reaction mixture according to the present invention can be determined by attenuated total reflection - Fourier transform infrared (ATR - FTIR) spectroscopy, ultraviolet absorption spectroscopy, energy - dispersive X - ray (EDX or EDS), X - ray photoelectron spectroscopy (XPS), Raman spectroscopy, gas chromatography, atomic emission spectroscopy, optical emission spectroscopy, and thermogravimetric analysis (TGA).

[0032] The present invention provides a combination of a gold electrode and a polymerization mixture containing a specific monomer and a specific dopant. In the absence of the specific dopant, the conductivity of the resulting polymer film is low and it does not adhere well to the gold working electrode when exposed to tetrahydrofuran (THF) or subjected to a tape test. Additionally, the size of the working electrode affects the adhesion of the resulting conductive polymer film. When using a micro - electrode, p the - TS - PPy film is resistant to THF exposure, while when using a macro - electrode (large - size gold rod electrode), it can withstand the THF test using chronoamperometry (CA) and chronopotentiometry (CP), but the p -TS - PPy obtained by cyclic voltammetry (CV) cannot withstand the THF test.

[0033] In certain embodiments, the polymerized transducer layer can be removed in a solution containing ammonium hydroxide, hydrogen peroxide (active reagent), and water (1:2:10 mL respectively) at 60 °C instead of at room temperature.

[0034] Examples: Without being restricted to a particular mode of operation and not limited to the present invention, the following examples are provided to illustrate the present invention.

[0035] Electropolymerization solution: PPy is typically obtained from a reaction mixture / solution containing a Py monomer in the presence of a supporting electrolyte (such as KCl (potassium chloride) or NaCl (sodium chloride) or tetrabutylammonium perchlorate) in one of the following: 1. Distilled water, or 2. A pH - buffered solution, such as phosphate - buffered solution, or 3. An organic solvent, such as acetonitrile, or 4. A strong acid, such as 1 M HCl.

[0036] The preferred electropolymerization mixture / solution contemplated by the present invention is an aqueous solution and contains a Py monomer, NaCl, and a dopant p -TS.

[0037] Method: Three electropolymerization techniques were used to electrochemically form PPy: potentiodynamic method (cyclic voltammetry, CV); potentiostatic method (chronoamperometry, CA); and galvanostatic method (chronopotentiometry, CP). When using the preferred electropolymerization reaction mixture / solution of the present invention, all three methods can produce p -TS-PPy films with good adhesion to gold microelectrodes, and the latter two techniques can also produce p -TS-PPy films with good adhesion to gold macroelectrodes.

[0038] Chemical substances and electrode: 1. Silver / silver chloride (Ag / AgCl) pseudo-reference electrode (pRE) a. A 1 mm diameter silver wire was incubated in 0.25 M iron(III) chloride (FeCl3) containing 0.20 M hydrochloric acid (HCl) for 16 hours.

[0039] 2. Working electrode a. A gold microelectrode with a thickness of 100 nm was obtained by standard photolithography, which has a chromium (Cr) adhesion layer with a thickness of 10 nm. The width and length of the working electrode are 55 μm and 500 μm respectively. Surface area: 0.0275 mm².

[0040] b. The macroelectrode used was a gold rod electrode (Au-RD), and the diameter of the circular working electrode area was 3 mm. Surface area: 28.3 mm².

[0041] c. Before use, the working electrode was electrochemically cleaned in 0.5 M sulfuric acid (H2SO4).

[0042] 3. Redox mediator a. 5 mM potassium ferricyanide (III) (K3[Fe(CN)6]) prepared in 0.1 M KCl.

[0043] 4. Pyrrole polymerization solution a. The solution of the present invention: an aqueous solution of 10 mM NaCl containing 100 mM pyrrole and 100 mM p-TS.

[0044] b. i. Polymerization method 1. Potentiostatic method (CA): +0.8 V, 20 s.

[0045] 2. Potentiodynamic method (CV) [reference : (-1.0 to +1.0 V), 3 cycles, scan rate 0.1 V / s.

[0046] c. Comparative solution 1 [reference: : 10 mM NaCl solution containing 100 mM pyrrole.

[0047] i. Polymerization method 1. CA: +0.8 V, 20 s.

[0048] 2. CV: (0.0 to +1.1 V), 3 cycles, scan rate 0.1 V / s.

[0049] d. Comparative solution 2 [Reference: : 100 mM Py in 50 mM phosphate buffer (PBS), pH 7.0, containing 0.1 M KCl i. Polymerization method 1. CV: (0.0 to +1.1 V), 3 cycles, scan rate 0.1 V / s, followed by CA at +0.8 V for 20 s.

[0050] 2. CV: (0.0 to +1.1 V), 3 cycles, scan rate 0.1 V / s, followed by CA at +1.0 V for 1 s, repeated 20 times.

[0051] e. Comparative solution 3 [Reference : 100 mM pyrrole in acetonitrile containing 100 mM tetrabutylammonium hexafluorophosphate (TBAPF6), 1% (v / v) HCl and 1% (wt / wt) water.

[0052] i. Polymerization method 1. CA: +0.8 V, 20 s.

[0053] 2. CP: 200 μA, 10 s (200 μA / 2 mC).

[0054] Results: Figure 2 Shows the CV data collected by a gold microelectrode coated with polymer in a [Fe(CN)6] 3- / 4- redox labeling solution when using the solution of the present invention or three different comparative solutions. The CV graphs obtained by a bare gold microelectrode before and after electropolymerization are labeled "a" and "b" respectively.

[0055] Figure 2 A represents p -TS-PPy chronoamperometric signal recorded during the electropolymerization on a gold microelectrode. Using [Fe(CN)6] 3- / 4-Redox and CV techniques were used to analyze the effect of the deposited film on the electrochemical conductivity. In Figure 2 B, a significant increase in the oxidation and reduction peak currents after electropolymerization was clearly observed. p After the deposition of -TS-PPy, the electrode surface turned black.

[0056] When using CV or CA or CP, an electrochemically conductive p -TS-PPy layer can be formed using the solution of the present invention. p The presence of -TS increases the number of available hydrophilic groups (sulfonic acid) at the electrode surface, thereby enabling an increased electron transfer rate, as shown in Figure 2 A and 2B. As shown in Figure 2 C and 2D, regardless of the electropolymerization method used, the electrochemically conductive PPy layer obtained with Comparative Solution 1 was significantly less. It can be concluded that the use of Comparative Solution 2 produced an electrically insulating layer ( Figure 2 E and 2F). The use of Comparative Solution 3 during the implementation of CA produced an insulating layer ( Figure 2 G). Compared with the bare gold microelectrode, the PPy film obtained by using Comparative Solution 3 together with CP had increased oxidation and reduction peak currents. However, Figure 2 the CV curve shown in H indicates that the obtained PPy film had stored capacitive charge, resulting in the formation of a capacitive transducer layer. This type of transducer layer is not suitable for ion-selective potentiometric sensing applications.

[0057] Testing the adhesion of polypyrrole THF is an organic solvent commonly used in the preparation of ion-selective membrane mixtures. Figure 3 Shows p the optical images of the -TS-PPy-coated microelectrode before and after drop-coating THF and wiping the surface with a tissue. The p -TS-PPy obtained when using CV or CA showed excellent adhesion after exposure to THF. The PPy film obtained in Comparative Solution 3 also showed good adhesion when exposed to THF.

[0058] Figure 3 Shows p the optical images of the microelectrode modified with -TS-PPy shortly after polymer deposition (fresh electrode) and 1 minute after drop-coating THF (after THF exposure).

[0059] The second adhesion test was performed by visually inspecting the PPy film after placing and removing tape on the microelectrode surface. As shown in Figure 4 shown, pThe -TS-PPy film is the only polymer film that remains 100% intact after the tape test, while the CA-based PPy film obtained using Comparative Solution 3 remains approximately 30% intact.

[0060] Figure 4 Optical images of the microelectrodes modified with p -TS-PPy are shown shortly after polymer deposition (fresh electrodes) and after the electrodes are exposed to tape (after tape test).

[0061] Effect of working electrode size on the adhesion of p-TS-PPy The influence of working electrode size on the p -TS-PPy adhesion was investigated using gold rod electrodes (Au-RD, 3 mm in diameter) and three electropolymerization methods (CV, CA, CP). When using microelectrodes, polymer films resistant to THF can be formed on gold microelectrodes based on both CV and CA depositions. However, when the working electrode surface area is increased to 28.3 mm², THF-resistant p -TS-PPy films with surface coverages of approximately 99% and approximately 97% after THF exposure are prepared only using CA and CP. As Figure 5 shown, the p -TS-PPy formed based on CV is not sufficient to withstand THF exposure, resulting in approximately 50% of the p -TS-PPy film being removed after THF exposure.

[0062] Generally, increasing the electrode surface area is expected to increase surface roughness, thereby improving polymer adhesion. However, the THF adhesion test using gold macroelectrodes shows that the adhesion of p -TS-PPy obtained using CV is not as good as that of p -TS-PPy formed on gold microelectrodes. This may be because the film thickness obtained at the same number of CV cycles is lower, and thus the proportion of p -TS per unit surface area is lower. The number of CV scans applied is negatively correlated with the polymer film adhesion. This is because during the reverse scan, the polymer reverts to its initial state, and its electrostatic interaction with the negatively charged p -TS is weaker, so its adhesion to the gold surface is poor.

[0063] Conclusion: The overall conclusion is that the proposed method can form conductive p -TS-PPy films with excellent adhesion on gold microelectrodes and macroelectrodes when combined with the proposed electropolymerization solution.

[0064] References: The following references are incorporated herein by reference for all purposes.

[0065]

Claims

1. A method for forming a polymerized transducer layer on an electrode: (i) Forming an assembly of an electrode and an electropolymerization mixture, wherein: the electrode comprises gold (Au), the electropolymerization mixture contains a dopant and a monomer, the dopant comprises benzenesulfonic acid and / or a derivative of benzenesulfonic acid, the benzenesulfonic acid having a benzene ring with amino, hydroxyl, and / or methyl functional groups on the benzene ring, the monomer comprises a cyclic structure, the cyclic structure comprising a cyclic structure of at least four carbons (C) and at least one of nitrogen (N), sulfur (S), and / or oxygen (O), and (ii) Treating the assembly formed in step (i) under electropolymerization conditions sufficient to oxidize the monomer and form a polymer on the electrode, thereby forming a polymerized transducer layer on the electrode.

2. The method according to claim 1, further comprising the following step: (iii) Forming an ion-selective membrane on the polymerized transducer layer on the electrode.

3. The method according to claim 1 or 2, wherein the monomer is selected from the group consisting of pyrrole, aniline, thiophene, and 3,4-ethylenedioxythiophene.

4. The method according to any one of claims 1 to 3, wherein the dopant comprises p -TS, the monomer comprises pyrrole, and the polymer comprises polypyrrole.

5. The method according to any one of claims 1 to 4, wherein the molar ratio of dopant / monomer (e.g., p -TS / pyrrole) in the polymerization mixture ranges from equal to 1 / 100 or 10 / 1 or between 1 / 100 and 10 / 1, preferably ranges from equal to 1 / 50 or 5 / 1 or between 1 / 50 and 5 / 1, more preferably ranges from equal to 1 / 20 or 2 / 1 or between 1 / 20 and 2 / 1, such as 1 / 10.

6. The method according to any one of claims 1 to 5, wherein the electropolymerization conditions are selected from the group consisting of potentiodynamic method (cyclic voltammetry), potentiostatic method (chronopotentiometry), and galvanostatic method (chronoamperometry).

7. The method according to any one of claims 1 to 6, wherein the surface area of the electrode is equal to 1 μm², 10 6 μm² or between 1 μm² and 10 6 μm² (such as a microelectrode), or wherein the surface area of the electrode is equal to 0.01 cm² or 100 cm² or between 0.01 cm² and 100 cm².

8. The method according to any one of claims 1 to 7, wherein the polymerization is carried out by cyclic voltammetry under the following conditions: the applied potential range is equal to -10.0 V or +10.0 V or between -10.0 and +10.0 V, for example equal to -2.0 V or +2.0 V or between -2.0 and +2.0 V, more preferably in the range equal to -1.0 V or +1.5 V or between -1.0 and +1.5 V, for example equal to 0.0 V or +1.0 V or between 0.0 and +1.0 V; the number of potential scan cycles ranges from equal to 1 or 1000 or between 1 and 1000, more preferably in the range equal to 1 or 100 or between 1 and 100, for example 3; the potential scan rate ranges from equal to 1 mV / s or 300 mV / s or between 1 and 300 mV / s, more preferably equal to 10 mV / s or 200 mV / s or between 10 and 200 mV / s, for example 100 mV / s.

9. The method according to any one of claims 1 to 7, wherein the polymerization is carried out by chronoamperometry under the following conditions: the applied potential range is equal to -10.0 V or +10.0 V or between -10.0 and +10.0 V, for example equal to -2.0 V or +2.5 V or between -2.0 and +2.5 V, more preferably in the range equal to 0.0 V or +1.5 V or between 0.0 and +1.5 V, for example +0.8 V; the potential application time ranges from equal to 0 s or 3600 s or between 0 and 3600 s, more preferably in the range equal to 0 s or 600 s or between 0 and 600 s, for example 20 s.

10. The method according to any one of claims 1 to 7, wherein the polymerization is carried out by chronopotentiometry under the following conditions: the applied current ranges from equal to 0 mA or 100 mA or between 0 and 100 mA, more preferably ranges from equal to 0 mA or 5 mA or between 0 and 5 mA, for example 0.2 mA; the current application time ranges from equal to 0 s or 3600 s or between 0 and 3600 s, more preferably ranges from equal to 0 s or 600 s or between 0 and 600 s, for example 10 s.

11. The method according to any one of claims 1 to 7, wherein the surface area of the electrode is equal to 0.01 cm 2 or 100 cm 2 or between 0.01 cm 2 and 100 cm 2 and the polymerization conditions are selected from the group consisting of chronopotentiometry and chronoamperometry.

12. An electrode comprising a polymerized transducer layer, wherein the electrode is prepared by the method according to any one of claims 1 to 11.

13. An electrode comprising a polymeric transducer layer including gold (Au) and a dopant at a detectable level, such as p-toluenesulfonic acid ( p -TS)).

14. The electrode according to claim 12 or 13, wherein the doped agent (e.g., p -TS) contained in the polymerized transducer layer has a molar ratio to the monomer (e.g., pyrrole) equal to 1 / 1000 or 1 / 10 or between 1 / 1000 and 1 / 10, more preferably equal to 1 / 100 or 1 / 25 or between 1 / 100 and 1 / 25, such as 1 / 50.

15. The electrode according to any one of claims 12 to 14, wherein the polymerized transducer layer is resistant to mechanical removal using tape and / or exposure to organic and inorganic solvents selected from the group consisting of tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, ethanol, acetone, and isopropanol at ambient temperature.

16. The electrode according to any one of claims 12 to 15, further comprising: An ion-selective membrane disposed on the polymerized transducer layer of the electrode.

17. The electrode according to any one of claims 12 to 16, wherein the polymer is selected from the group consisting of polypyrrole, polyaniline, polythiophene, and poly(3,4-ethylenedioxythiophene).

18. The electrode according to any one of claims 12 to 17, wherein the dopant comprises p -TS, and the polymer comprises polypyrrole.

19. An ion-selective electrode comprising gold (Au), a polymeric transducer layer having a dopant (e.g., p -toluenesulfonic acid ( p -TS)) at a detectable level, and an ion-selective membrane disposed on the polymeric transducer layer of the electrode.

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