Method for electrochemical synthesis of cf and composites thereof and use thereof

Abstract

The application discloses a method for electrochemically synthesizing CF (carbonaceous fragment) and a composite material thereof and application thereof. The synthesis of CF is realized through electrochemical stripping and cutting effect by taking conventional carbon materials as raw materials, and the CF has a PCET active CF sheet structure. Meanwhile, the controllable CF synthesis with accurate control of the density of active groups on the CF surface is realized by adjusting electrochemical parameters and / or using auxiliary reagents, so that the electrochemical calibration-free pH sensing material can meet the requirements of different pH quantitative analysis scenes, and is particularly suitable for application scenes which need to meet the requirements of high accuracy, high stability, continuity, in-situ quantitative analysis and combination thereof.

Description

Technical Field

[0001] This invention belongs to the fields of electrochemical detection and analysis, chemiluminescence technology and nanomaterials, and relates to a method for electrochemical synthesis of CF and its composite materials and their applications. Background Technology

[0002] pH is an essential chemical indicator in many fields, and accurate, continuous, and in-situ quantitative analysis of pH is indispensable in various high-value-added applications. However, currently, there are extremely limited pH sensors that can simultaneously meet these functions, mainly because such sensors struggle to overcome the problem of continuously increasing measurement errors in complex environments. Novel electrochemical pH sensing technology based on dynamic current technology can dynamically and in real-time correct signal drift caused by changes in electrode interface states, thus effectively solving this problem. However, this technology relies on precise and stable sensor interface modification techniques, and therefore typically faces technical challenges such as high processing difficulty, high production costs, low yield, and the need to sacrifice response rate to ensure stability.

[0003] Carbon fragments (CFs) are a new type of carbon nanomaterial, with sizes close to or exceeding those of carbon quantum dots (CQDs), primarily concentrated in the finite range of several nanometers to tens of nanometers. Typically, they exhibit optical and electrochemical activities similar to CQDs, and their physicochemical properties are also quite similar. Their surfaces can carry a variety of chemical functional groups, and they possess excellent biocompatibility. However, unlike CQDs, CFs generally do not possess diverse fluorescent activities; their solubility offers greater controllability compared to CQDs. CFs were first reported as an impurity component in carbon nanomaterials such as carbon nanotubes or graphene, but their discovery was relatively recent, and their applications have been quite limited to date, which is regrettable.

[0004] A key electrochemical characteristic of graphene cellulose (CF) is that its surface carries a large number of diverse chemical functional groups, such as hydroxyl, ketone, ether, carboxyl, ester, aryl, and epoxy groups, depending on the generation strategy employed. These, along with the large π-bond structure of the graphene-like host sheet, form the basis for the complex surface chemistry and electrochemical activity of CF. Among these, the electrochemical voltage-response activity of CF due to the presence of some of these unique structures is a crucial electrochemical characteristic. Fortunately, this activity of CF is proton-coupled electron transfer (PCET) activity, meaning that the heterogeneous electron transfer reaction process generated by CF under voltage excitation involves protons (or hydrogen ions, H+) in the solvent environment. + This is a process dependent on [the solvent environment]. Therefore, the quantitative relationship between the electrochemical reaction rate and the proton activity in the solvent environment during this process can be measured by dynamic current analysis, enabling accurate measurement of the pH of the software environment. Summary of the Invention

[0005] This invention proposes a technical solution using carbon nanomaterials as electrochemical probes for dynamic current-based pH sensors. In this solution, the inherent pH electrochemical responsiveness of specific carbon nanomaterials is utilized as a pH indicator. In addition to its electrochemical pH responsiveness, carbon nanomaterials are also excellent current collectors; therefore, sensors using them as the pH electrochemical sensitive interface do not require special chemical modification of the sensor interface, resulting in multiple performance advantages.

[0006] The purpose of this invention is to provide a method for electrochemical synthesis of CF.

[0007] Another object of the present invention is to provide the application of the above-mentioned CF in the preparation of CF composite materials.

[0008] Another object of the present invention is to provide a method for preparing CF composite materials using the above-mentioned CF.

[0009] An electrochemical synthesis method for CF includes the following steps:

[0010] (1) Use carbon materials as the working electrode and counter electrode to form a three-electrode system;

[0011] (2) Place the three-electrode system in an aqueous or lipid-phase solution and apply a constant voltage;

[0012] When the three-electrode system is placed in an aqueous solution

[0013] (3) Remove the working electrode and place it in an aqueous solution containing carbonate and glycerol, then heat it to 80-110°C to react and obtain CF;

[0014] When the three-electrode system is placed in a lipid phase solution

[0015] (3) Remove the working electrode and place it in a mixed solution of DMSO-ethanol, and then microwave or heat it to obtain CF.

[0016] Furthermore, the carbon material mentioned in step (1) includes, but is not limited to, at least one of the following: natural graphite, synthetic flake graphite, high-order pyrolytic graphite, carbon black, carbon fiber, glassy carbon, amorphous carbon, carbon nanotubes, carbon nanotubes, graphene and its derivatives.

[0017] Furthermore, the electrode in step (1) can be in any form, such as sheet, rod, plate, or wire.

[0018] Furthermore, in the three-electrode system described in step (1), the reference electrode is at least one of Al, Ag, Ag / AgCl, Cu, Au, Sn, and C.

[0019] Further, the aqueous solution in step (2) is at least one of NaNO3 solution, KCl solution, NaCl solution, NaH2PO4-NaOH solution, NaH2PO4-Na2HPO4 solution, H3PO4 solution, H2SO4 solution, NaOH solution, and KOH solution; the concentration is 0.05-0.5M, preferably 0.08-0.2M, and more preferably 0.1M.

[0020] Further, the solute in the lipid phase solution of step (2) is at least one selected from tetrabutylamine hexafluorophosphate, tetrabutylammonium tetrafluoroborate, tributylmethylammonium bis(trifluoromethanesulfonyl)imide, tetrabutylphosphine chloride, 1-butyl-3-methylimidazolium, N-butylpyridine, N-butylmethylpiperidine, and N-ethylmethylpyrrolidine, and the solvent is at least one selected from acetonitrile, N,N-dimethylformamide, tetrahydrofuran, and dimethyl sulfoxide. The concentration of the above lipid phase solution is 2-20 M, preferably 5-15 M, and more preferably 10 M.

[0021] Furthermore, the constant voltage in step (2) can be in the form of alternating current or direct current and any combination thereof, and the excitation waveform includes, but is not limited to, linear volt-ampere type, pulse volt-ampere type, nonlinear volt-ampere type, constant potential type, DC pulse type, etc.

[0022] Furthermore, the constant potential in step (2) is 0.1–10V, preferably 0.5–5V, and more preferably 1–2V. The time for applying the constant voltage is 5–60 min; preferably 10–40 min; and more preferably 15–30 min.

[0023] Further, an auxiliary reagent is added to the aqueous solution in step (2). The auxiliary reagent includes, but is not limited to, at least one of sulfuric acid, phosphoric acid, nitric acid, perchloric acid, sodium dodecyl sulfate, trifluoromethanesulfonic acid, Triton X-100, potassium permanganate, hydrogen peroxide, sodium hydroxide, potassium hydroxide, periodic acid, periodate, 3-methylimidazole, N-propylmethylpiperidine bis(trifluoromethanesulfonyl)imide, and tetrabutylammonium tetrafluoroborate. The concentration of the auxiliary reagent in the aqueous solution is 0-30M, not 0; preferably 0-20M, not 0; more preferably, phosphoric acid is used at a concentration of 0-15M, and sulfuric acid is used at a concentration of 0-18M.

[0024] Furthermore, when the three-electrode system is placed in an aqueous solution, the carbonate in the aqueous solution of step (3) is at least one of K2CO3, sodium carbonate, etc., and the concentration of the carbonate is 0.1-5M, preferably 0.1-2M, more preferably 0.5M; the concentration of glycerol in the aqueous solution is 5-40m:m%, preferably 10-30m:m%, more preferably 25m:m%.

[0025] Furthermore, the heating reaction temperature in step (3) is 90-100°C, preferably 95°C; the reaction time is 1-10 min, preferably 2-8 min, and more preferably 5 min.

[0026] Furthermore, by taking the working electrode processed in step (3) as the working electrode and repeating steps (1)-(3) 2 to 10 times, a large amount of CF can be obtained.

[0027] Furthermore, when the three-electrode system is placed in a lipid phase solution, the volume ratio of DMSO to ethanol is 1–10:1, preferably 5:1; the microwave treatment power is 1–8W, preferably 2–6W, more preferably 4W; and the microwave treatment time is 1–10 min, preferably 2–8 min, more preferably 5 min. The heating reaction temperature is 90–100℃, preferably 95℃; and the reaction time is 1–10 min, preferably 2–8 min, more preferably 5 min.

[0028] Furthermore, the microwave treatment specifically involves first placing the device in a 4W microwave treatment environment for 5 minutes; then pausing for 30 seconds before continuing the treatment for another 5 minutes.

[0029] The above-mentioned application of CF in the preparation of CF composite materials. Combining electrochemically synthesized CF with polymer materials, the resulting composite materials can compensate for the limitations of the intrinsic chemical properties of CF in specific pH quantitative analysis scenarios.

[0030] Furthermore, the other host materials used in the composite material for compounding with CF include, but are not limited to, nanomaterials such as graphene, carbon nanotubes, carbon nanoribbons, gold nanoparticles, etc.; and at least one of functional polymers such as PVP, PU, ​​electrochemically active polymers, natural polymers, polycations, polyanions, polyionic liquids, covalent organic frameworks, metal-organic frameworks, supramolecular bodies, etc.

[0031] A method for preparing CF composite materials using the above-mentioned CF includes the following steps:

[0032] The CF-polymer composite material CF@pFc was obtained by mixing CF dispersion, benzoyl peroxide and DMSO solution of vinyl ferrocene.

[0033] Furthermore, the CF dispersion is obtained by dispersing CF in DMSO, with a concentration of 0.1–2 mg / mL, preferably 0.5–1.5 mg / mL, and more preferably 1 mg / mL.

[0034] Furthermore, the concentration of the vinyl ferrocene DMSO solution is 0.5–5 mM, preferably 1–3 mM, and more preferably 2 mM.

[0035] The ratio of the CF dispersion, benzoyl peroxide and vinyl ferrocene DMSO solution is 50-90 mL: 1.2 g: 60-100 mL; preferably 60-80 mL: 1.2 g: 70-90 mL, and more preferably 70 mL: 1.2 g: 80 mL.

[0036] The reaction temperature is 70–100°C, preferably 75–95°C, and more preferably 80–90°C. The reaction time is 1–8 hours, preferably 2–6 hours.

[0037] Furthermore, after the reaction is complete, allow the mixture to stand until the precipitate forms, and then wash the product with an ethanol solution.

[0038] This example is presented merely as an illustrative case to demonstrate the enormous potential for CF to be combined with other functional materials, and the possibility of obtaining more powerful and complex material properties, rather than to illustrate the limited scope of protecting CF-polymer composites.

[0039] A method for preparing an electrochemical pH sensor using the above-mentioned CF or CF composite material includes the following steps:

[0040] A mixed solution is obtained by dispersing CF or CF composite material in DMSO. The end of the substrate electrode is connected to a wire with a gold-plated copper tube socket to form an electrode CRE. Then, the working surface of the electrode CRE is dropped or immersed in the mixed solution. After drying, an electrochemical pH sensor can be obtained.

[0041] Further, weigh the above CF@pFc and dissolve it in DMSO to prepare a 1wt% mixed solution. Connect the end of the graphite rod with a gold-plated copper tube socket to form an electrode CRE. Add the CF@pFc solution to the working surface of the electrode CRE and dry it to prepare the CF@pFc-CRE electrode.

[0042] Furthermore, the concentration of CF or CF@pFc in the mixed solution is 0.1–10 wt%, preferably 0.5–5 wt%, and more preferably 1 wt%.

[0043] Furthermore, a graphite rod with a diameter of 3.0 mm is cut into a cylinder with a length of 10.0 mm. The end face is polished flat to serve as the working surface. The sides are sealed with insulating varnish. The end is connected to a wire with a gold-plated copper tube socket to form an electrode CRE. 2.5 μL of CF@pFc solution is dropped onto the working surface of the CRE electrode and evaporated under an infrared lamp until the electrode surface is completely dry, thus producing a CF@pFc-CRE electrode.

[0044] Compared with the prior art, the present invention has the following technical effects:

[0045] 1. This invention uses conventional carbon materials as raw materials to synthesize CF through electrochemical stripping and cutting.

[0046] 2. This invention uses electrochemical energy as the driving force and oxidant, and also uses common carbon materials as raw materials to synthesize CF sheet structures with PCET activity;

[0047] 3. This invention enables controllable synthesis of CF by adjusting electrochemical parameters and / or using auxiliary reagents to achieve precise control of the density of CF surface active groups, thereby serving as an electrochemical calibration-free pH sensing material that meets the needs of pH quantitative analysis scenarios with different requirements.

[0048] 4. This invention uses CF as a pH-specific electrochemical probe and its dynamic current signal based on PECT activity as a primary sensing signal to achieve pH quantification. pH sensing based on this mode enables calibration-free analysis and is particularly suitable for applications requiring high accuracy, high stability, continuous, in-situ quantitative analysis, and their combinatorial capabilities. Attached Figure Description

[0049] Figure 1 The images show the HRTEM image and SAED photograph of the aqueous electrochemical synthesis of CF in Example 1.

[0050] Figure 2 The image shows the Raman spectrum of CF synthesized by the lipid phase electrochemical method in Example 2.

[0051] Figure 3 The LSV curve results for Example 3 are obtained by controlling the peak shape characteristics of the electrode target through CF synthesis parameters.

[0052] Figure 4 The LSV measurement results for Example 4 CF@pFc-CRE in standard solutions at pH 4.01, 6.86, and 9.18 are shown.

[0053] Figure 5 LSV response curves of cCF-CRE prepared by chemical method in Comparative Example 1 at different pH values.

[0054] Figure 6 Square pulse voltammetry (a) of the oCF-CRE electrode in Britton-Robinson buffer at pH 2-12 in Comparative Example 2 and au-pH regression curve (b) after converting the result to au value.

[0055] Figure 7 The results show the long-term measurement results of oCF-CRE and DRP-110PANI in standard pH solution in Comparative Example 2. The solid dot group represents the test results of oCF-CRE, and the dashed square dot group represents the test results of DRP-110PANI. Detailed Implementation

[0056] Example 1: Electrochemical Aqueous Phase Synthesis of CF

[0057] A 100×100×4mm graphite plate was used as the electrode material. Two graphite plates were arranged parallel to each other with a 10mm gap, one as the working electrode (WE) and the other as the counter electrode (CE). A 100×100mm silver wire mesh was placed at equal intervals in between as the reference electrode (RE), thus constructing a three-electrode reaction system. The three-electrode system was placed in a 0.1M NaNO3 solution, and a constant potential of 1.5V was continuously applied to the electrode system for 20 minutes. Subsequently, the WE portion was removed, rinsed with pure water, and placed in an aqueous solution containing 0.5M K2CO3 and 25m:m% glycerol. The solution was heated to 95℃ and treated for 5 minutes before removal. The WE was removed, rinsed, and placed in a 0.1M NaNO3 solution again for electrochemical treatment, and the subsequent steps were repeated. After multiple treatments, the treated solution after constant potential treatment was collected, at which point the solution changed from colorless and transparent to dark yellow. The solution was filtered through qualitative filter paper and centrifuged at 18,000 rpm for 30 min. The concentrated yellow liquid fraction at the bottom was collected.

[0058] HRTEM microscopy was performed on samples prepared using carbon-based copper mesh. The results are shown in the appendix. Figure 1 It can be clearly observed that a large number of tiny sheet structures, mainly with a size of ~10 nm, exist in the concentrated solution. Further magnified observation reveals a graphene-like lattice structure. A distinct hexagonal lattice distribution is observed in the micro-area electron diffraction pattern. These facts fully demonstrate that this sheet structure is a graphene-like carbon nanostructure. Furthermore, it exhibits classic oligolayer graphene-like diffraction fringes, i.e., microscopic morphological characteristics, indicating that this material is CF.

[0059] Example 2 Electrochemical lipid phase synthesis

[0060] Carbon cloth was cut into strips of 200×40×0.4mm to serve as the electrode reaction (WE) and electrode assembly (CE). A 200×40mm silver wire mesh was placed at equal intervals in the middle to serve as the electrode reaction (RE), and a three-electrode reaction system was constructed using these strips. First, the three-electrode system was placed in acetonitrile containing 0.05M tetrabutylammonium hexafluorophosphate and allowed to stand for 30 minutes to equilibrate. A constant potential of 1.8V was continuously applied to the electrode system for 30 minutes. Second, the WE was removed, rinsed sequentially with acetonitrile and ethanol, and then transferred to a mixed solution of DMSO-ethanol (v:v = 5:1). The solution was then microwaved at 4W for 5 minutes, paused for 30 seconds, and then microwaved for another 5 minutes. This process was repeated 6–10 times. After rinsing the WE with acetonitrile, the first and second steps were repeated sequentially until the solution used in the second step turned yellow. This solution was then centrifuged at 20,000 rpm for 40 minutes, and the concentrated dark yellow liquid at the bottom was collected.

[0061] The carbon cloth and the collected concentrate samples were prepared and subjected to Raman spectral analysis. The results are shown in the attached figure. Figure 2 As shown in the figure, the black curve represents the Raman spectral line of the carbon cloth sample, and the red curve represents the CF concentrate sample. It is clear that the carbon cloth only exhibits its characteristic spectral line at 1580 cm⁻¹. -1 and 1323cm -1 Two strong G peaks and a weak D peak appear, which are SP peaks in carbon materials, respectively. 2 The CF sample exhibits characteristic peaks of in-plane vibration and in-plane defects; however, in the CF sample spectrum, both the D and G peaks are strong signal peaks. This difference indicates that the density of in-plane defect sites in the CF sample is much greater than that in the raw carbon cloth. Furthermore, this spectral line is located at ~2700 cm⁻¹. -1 and ~2910cm -1 A strong peak signal appears at each location, representing the 2D peak and G+D peak signal of carbon materials, respectively. This is a characteristic Raman feature of graphene-like structures exhibiting carbon quantum dot-like structures. Based on the above information, CF can be effectively generated using the method described in this example.

[0062] Example 3: Controlling the peak shape characteristics of the electrode target using CF synthesis parameters

[0063] The CF electrode CF-CRE was prepared using a 0.1 mg / mL CF dispersion solution prepared according to the method described in Example 1. Seven control analysis groups were set up to compare the target signal resolution effects of different auxiliary reagent formulations. The difference was that different amounts of auxiliary reagents (specific formulations are shown in Table 1) were added to the NaNO3 supporting electrolyte solution used in each group to control the total surface oxygen content of the synthesized CF. The electrode preparation method was as follows: a graphite rod with a diameter of 3.0 mm was cut into a cylinder with a length of 10.0 mm. The end face was polished smooth with 800-grit sandpaper to form the working surface. The sides were sealed with insulating varnish. The end was connected to the wire with a gold-plated copper tube socket to form the electrode CRE. 6 μL of CF dispersion solution was dropped onto the working surface of the electrode. After the solvent completely evaporated, it was then used as a Pt electrode. A three-electrode system was formed using an Ag / AgCl reference electrode (3M KCl). The electrode system was immersed in an aqueous solution containing 0.1M NaNO3 and 0.1wt% polyacrylamide, and a DC square wave pulse excitation potential (frequency = 0.1Hz) of ±1.0V was applied for 100s before removal to prepare CF-CRE. The CF-CRE was then subjected to linear voltammetry (LSV) scans of 1.0–0V at a rate of 0.05V / s in a 0.05M citrate-sodium hydroxide solution at pH 2.0. Table 1 records the test results for each electrode.

[0064] Table 1. Peak shape characteristics of CF-CRE targets corresponding to different CF synthesis parameters.

[0065]

[0066] From the appendix Figure 3 As shown in Table 1, different CF synthesis methods significantly affect the target peak shape and characteristic values ​​of CF-CRE. The curve shape provides a clear indication: with almost no auxiliary reagents added, the target peak shape of CF-CRE is relatively smooth. Such a peak shape is prone to multiple peak points or regional clutter, easily leading to errors in computer-generated peak characteristic values, insufficient accuracy, or significantly increasing the design complexity of the peak characteristic value extraction algorithm. However, with the help of auxiliary reagents, the target peak shape of CF-CRE can become sharp and prominent, making it easier to accurately extract its peak characteristic value data using simple algorithms. It can also be seen that different amounts of auxiliary reagents can cause regular changes in the peak shape, allowing for targeted optimization of the peak shape and peak characteristic values. This will greatly simplify the design of the sensor's accompanying analysis software and significantly improve the sensor's overall performance, including sensitivity, effective resolution, and response time.

[0067] Example 4: Electrochemical Synthesis of CF-Polymer Composite Materials

[0068] Two 100×100×4mm graphite plates were used as the electrochemical reaction (WE) and electrochemical reaction (CE), respectively. The two graphite plates were arranged parallel to each other with a 10mm gap, and a 100×100mm silver wire mesh was placed at equal intervals in the middle as the electrochemical reaction (RE), constructing a three-electrode reaction system. The three-electrode system was placed in a 0.1M NaNO3 solution containing 3000mM H3PO4 and 1wt% Triton X-100, and a constant potential of 1.5V was continuously applied to the electrode system for 40 min. Subsequently, the WE portion was removed, rinsed with pure water, and placed in an aqueous solution containing 0.5M K2CO3 and 25m:m% glycerol. The solution was heated to 95℃ and treated for 5 min before removal. The WE portion was then rinsed again and placed in a 0.1M NaNO3 solution for electrochemical treatment, and the subsequent steps were repeated. After multiple treatments, the second-step treatment solution was collected. The solution was filtered through qualitative filter paper and centrifuged at 18000rpm for 30 min, collecting the concentrated yellow liquid at the bottom. Dilute the concentrated solution with DMSO to a concentration of ~1 mg / mL in 70 mL of CF dispersion. Prepare 80 mL of DMSO solution containing 2 mM vinyl ferrocene. Add the CF dispersion dropwise through a separatory funnel and stir for 15 min under nitrogen protection. Then add 1.2 g of benzoyl peroxide, stir thoroughly for 10 min, and then heat the reaction system to 85 °C and continue the reaction for 4 h, during which an orange-red precipitate gradually forms. Allow the precipitate to stand for 20 min and then decant to concentrate it. Then filter the precipitate under negative pressure. Wash the solid with ethanol and dry under vacuum to obtain the CF-polymer composite material CF@pFc. Weigh CF@pFc and dissolve it in DMSO to prepare a 1 wt% solution.

[0069] A 3.0 mm diameter graphite rod was cut into 10.0 mm long cylinders. The end face was polished smooth with 800-grit sandpaper to form the working surface. The sides were sealed with insulating varnish, and the end was connected to a gold-plated copper tube socket to form an electrode CRE. 2.5 μL of CF@pFc solution was dropped onto the electrode working surface and allowed to evaporate under an infrared lamp until the electrode surface was completely dry, thus fabricating the CF@pFc-CRE electrode. Subsequently, a Pt counter electrode was formed. A three-electrode system was constructed using an Ag / AgCl reference electrode (3M KCl). Standard solutions with pH values ​​(25℃) of 4.01, 6.86, and 9.18 were prepared according to the method described in GB / T 27501-2011, "Preparation Method of Buffer Solutions for pH Determination". LSV measurements were performed using the above three-electrode system in the standard solutions at different pH values. The measurement parameters were set as follows: scan potential -400 to 800 mV, scan rate 100 mV / s. The measurement results are shown in the appendix. Figure 4In standard solutions at pH 4.01, 6.86, and 9.18, CF@pFc-CRE showed two distinct LSV peaks. The characteristic peak of ferrocene (Fc) at ~300 mV did not change significantly with the pH of the solution. The characteristic peak appearing in the range of -100 to 200 mV was the CF peak shape, and its potential and peak current intensity changed with pH.

[0070] Comparative Example 1: pH sensing performance comparison between electrochemically synthesized CF and chemically synthesized CF

[0071] CF can also be obtained using chemical methods, and its optical activity is similar to that of the electrochemically synthesized CF of this invention, but there are significant differences in electrochemical characteristics.

[0072] Two g of multi-walled carbon nanotubes were placed in a round-bottom flask, and 100 mL of 20 wt% sulfuric acid aqueous solution was added. The solution was dispersed by ultrasonic treatment at 40 W for 30 min. Subsequently, the flask was transferred to a heating mantle and heated to 98 °C, then refluxed for 2 h, during which the solution changed from a black, semi-transparent state to a deep black, opaque state. After cooling to room temperature, the reaction solution was neutralized with sodium hydroxide to a pH of 6–7, and centrifuged at 6000 rpm for 15 min, collecting the black precipitate. This precipitate was redispersed in a flask with 0.1 M NaOH aqueous solution and refluxed at 100 °C for 25 min. After cooling to room temperature, the reaction solution was centrifuged at 15000 rpm for 30 min, collecting the yellowish-brown portion at the bottom. A large amount of water was added, and the same centrifugation process was repeated until the pH of the collected bottom solution was 6–7. A CF-modified electrode, denoted as cCF-CRE, was prepared using the method described in Example 3. Standard solutions with pH values ​​(25℃) of 4.01, 6.86, and 9.18 were prepared. LSV measurements were performed in these standard solutions at different pH values ​​using the aforementioned three-electrode system. Measurement parameters were set as follows: scan potential -400 to 800 mV, scan rate 100 mV / s. Measurement results are attached. Figure 5 The results showed that under different pH conditions, the redox peaks exhibited by cCF-CRE were extremely weak, and the peak shapes were rounded, flat, and difficult to accurately identify. Furthermore, under weakly alkaline conditions, the voltammetric peak shape of cCF-CRE was no longer a single peak. This indicates that when the chemically synthesized CF is used on the electrode surface, the kinetics of its surface electrochemically active functional groups are slow, and the PCET reaction becomes a stepwise reaction under weakly alkaline conditions. This makes it impossible to accurately pinpoint the characteristic peak parameters used for pH quantification. A comparison with the analytical results of Examples 3 and 4 shows that chemically synthesized CF is difficult to directly apply to the preparation of electrochemical pH sensors.

[0073] Comparative Example 2: Stability Comparison with Mainstream Solid-State Electrodes (pANI)

[0074] Carbon cloth was cut into 100×50mm pieces to serve as the electrode reaction (WE) and electrode reaction (CE). Silver wire mesh of the same size was placed at equidistant positions in the middle to serve as the electrode reaction (RE), thus constructing a three-electrode reaction system. The three-electrode system was placed in DMF containing 0.05M tetrabutylammonium hexafluorophosphate and allowed to stand for equilibration for 10 min. Then, a potential of 1.8V was continuously applied to the electrode system for 30 min. Subsequently, the WE was removed and transferred to a DMF solution containing 0.02M triethylamine. The solution was heated to 95℃ for 15 min under stirring. This electrochemical and solvothermal treatment was repeated 10 times. The brownish-red solution fraction was collected. This solution was centrifuged at 20000 rpm for 40 min, and the concentrated dark liquid fraction at the bottom was collected. This was diluted with DMF to 0.1 mg / mL and 0.025M 1-allyl-3-methylimidazolium chloride was added to prepare a mixture. A 3.0mm diameter graphite rod is cut into 10.0mm long cylinders. The end face is polished smooth with 800-grit sandpaper to form the working surface. The sides are sealed with insulating varnish. The end is connected to a gold-plated copper tube socket to form an electrode CRE. The CRE is then used as a Pt counter electrode. A three-electrode system was formed by combining the CRE with an Ag / AgCl reference electrode (3M KCl). The CRE was immersed in the mixture, and a constant potential of 0.55V was applied to it for 25 minutes. After treatment, the CRE was removed and rinsed with ethanol. The ethanol was then evaporated under an infrared lamp until the electrode surface was completely dry, thus preparing the oCF-CRE electrode.

[0075] oCF-CRE was used as the WE and Pt counter electrode. A three-electrode system was formed using an Ag / AgCl reference electrode (3MKCl). A 40mM Britton-Robinson standard buffer solution was used, and the pH of the buffer was adjusted to 2-12 using 0.5M standard hydrochloric acid and potassium hydroxide. Differential pulse voltammetry (scanning potential from 800 to -500mV, pulse potential increment of 5mV, pulse amplitude of 50mV, pulse frequency of 20Hz) was used to measure the changes in current and potential of the oCF-CRE electrode with pH in the buffer sample. The pH response curve was recorded, and the microcontroller software automatically calculated E based on the curve results. f The values ​​of HWHM, ΔI1, ΔI2, a, and au, where au is defined as... Where E f ΔI0 represents the peak potential, HWHM represents the half-peak-half-width potential, ΔI1 and ΔI2 represent the peak current intensities corresponding to the pH-sensitive and pH-insensitive probes, respectively, and a is the electrode constant. A regression curve is generated based on the relationship between au value and the pH value of the standard buffer solution, as shown below. Figure 6As shown, the pH value was calculated based on the au value during actual testing. pH measurements were recorded every 8 hours. The DPV response of the three-electrode system was continuously recorded in standard solutions containing 0.1 mM ferrohydroxyol at pH 4.01 and 9.18 (DPV parameters were set as follows: scan potential 600–400 mV, increment potential 5 mV, pulse potential amplification 50 mV, pulse width 50 ms, sampling period 500 ms). Simultaneously, the pH values ​​of the same samples measured using the DropSens DRP-110PANI polyaniline-based solid pH electrode (a gold standard brand) were compared with those measured in OCP mode according to the sensor's product instructions. Results are attached. Figure 7 As shown. During continuous 96 hours of measurement, the oCF-CRE had a measurement error of <0.1 pH and a pH drift of <0.4; while the control group's polyaniline solid pH electrode had a measurement error of ≥0.75 and a pH drift of >2.4.

[0076] Table 2 shows the measurement results of oCF-CRE and DRP-110PANI in standard pH solutions.

[0077]

[0078]

Claims

1. A method for electrochemically synthesizing carbonaceous fragments, characterized in that... Includes the following steps: (1) Using carbon materials as the working electrode and the counter electrode to form a three-electrode system; (2) Place the three-electrode system in an aqueous or lipid-phase solution and apply a constant voltage; When the three-electrode system is placed in an aqueous solution (3) Remove the working electrode and place it in an aqueous solution containing carbonate and glycerol, and heat it to 80~110℃ to react and obtain carbonaceous fragments; When the three-electrode system is placed in a lipid phase solution (3) Remove the working electrode and place it in a mixed solution of DMSO-ethanol, then microwave or heat it to obtain carbonaceous fragments. The carbon material mentioned in step (1) includes, but is not limited to, at least one of natural graphite, synthetic flake graphite, high-order pyrolytic graphite, carbon black, carbon fiber, glassy carbon, carbon nanotubes, carbon nanotubes, graphene and its derivatives. Add auxiliary reagents to the aqueous solution in step (2). The auxiliary reagents include, but are not limited to, at least one of sulfuric acid, phosphoric acid, nitric acid, perchloric acid, sodium dodecyl sulfate, trifluoromethanesulfonic acid, Triton X-100, potassium permanganate, hydrogen peroxide, sodium hydroxide, potassium hydroxide, periodic acid, periodate, 3-methylimidazolium, N-propylmethylpiperidine bis(trifluoromethanesulfonyl)imide, and tetrabutylammonium tetrafluoroborate. The aqueous phase solution in step (2) is at least one of NaNO3 solution, KCl solution, NaCl solution, NaH2PO4-NaOH solution, NaH2PO4-Na2HPO4 solution, H3PO4 solution, H2SO4 solution, NaOH solution, and KOH solution; the solute in the lipid phase solution in step (2) is at least one of tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate, tributylmethylammonium bis(trifluoromethanesulfonyl)imide, tetrabutylphosphine chloride, 1-butyl-3-methylimidazolium, N-butylpyridine, N-butylmethylpiperidine, and N-ethylmethylpyrrolidine; and the solvent is at least one of acetonitrile, N,N-dimethylformamide, tetrahydrofuran, and dimethyl sulfoxide. The aqueous phase solution in step (2) has a concentration of 0.05~0.5 M; the lipid phase solution has a concentration of 2~20 M. The constant voltage in step (2) is 0.1~10 V; the time for applying the constant voltage is 5~60 min.

2. The method according to claim 1, characterized in that: The concentration of the auxiliary reagent in the aqueous solution is 0~30M, not 0.

3. The method according to claim 1, characterized in that: In step (3), the carbonate in the aqueous solution is at least one of K2CO3 and sodium carbonate; the concentration of the carbonate is 0.1~5 M; and the concentration of glycerol in the aqueous solution is 5~40 m:m.

4. The method according to claim 1, characterized in that: When the three-electrode system is placed in a lipid phase solution, the volume ratio of DMSO to ethanol is 1~10:1; the power of microwave treatment is 1~8 W; and the heating temperature is 90~100 ℃.

5. The use of carbonaceous fragments obtained by the method according to any one of claims 1-4 in the preparation of carbonaceous fragment composite materials.

6. A method for preparing carbonaceous fragment composite materials using carbonaceous fragments obtained by the method according to any one of claims 1-4, characterized in that... Includes the following steps: Carbonaceous fragments were mixed with benzoyl peroxide and DMSO solution to obtain carbonaceous fragment composite material.

7. The method according to claim 6, characterized in that: The carbonaceous fragment dispersion is obtained by dispersing carbonaceous fragments in DMSO with a concentration of 0.1~2 mg / mL; the concentration of the vinyl ferrocene DMSO solution is 0.5~5 mM; the volume ratio of the carbonaceous fragment dispersion, benzoyl peroxide and vinyl ferrocene DMSO solution is 50~90 mL:1.2 g:60~100 mL.

8. A method for preparing an electrochemical pH sensor using carbonaceous fragments obtained by the method according to any one of claims 1 to 4 or carbonaceous fragment composite materials obtained by the method according to any one of claims 6 to 7, characterized in that... Includes the following steps: A mixed solution is obtained by dispersing carbonaceous fragments or carbonaceous fragment composites in DMSO. The end of the substrate electrode is connected to a wire with a gold-plated copper tube socket to form an electrode CRE. Then, the working surface of the electrode CRE is dropped or immersed in the mixed solution. After drying, an electrochemical pH sensor can be obtained.

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