An electrochemical NO sensor based on a platinum-iridium mesoporous alloy and its preparation method

Abstract

This paper presents an electrochemical NO sensor based on a platinum-iridium mesoporous alloy and its fabrication method, belonging to the field of electrochemical sensor technology. The method involves in-situ generation of mesoporous platinum-iridium alloy nanoparticles (Pt-Ir NPs) on the electrode surface using electrochemical deposition, enabling accurate and rapid NO detection under physiological conditions. The mesopores are constructed by adding an auxiliary surfactant to the electrolyte. Furthermore, this sensor exhibits advantages such as a wide linear range, high sensitivity, low detection limit, short response time, and strong anti-interference capability, showing promise for playing a significant role in biomedical analytical detection and possessing commercial potential.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical sensor technology, specifically relating to the application of platinum-iridium mesoporous alloy nanomaterials in the construction of NO electrochemical sensors. Background Technology

[0002] In vivo, nitrogen (NO) is a crucial component of nitrosation stress and plays a negative role in many injuries and diseases. Therefore, exploring the changes in NO production levels and the mechanisms of transformation in cells has attracted widespread attention. NO primarily originates from mitochondria and is typically produced in a burst, characterized by high activity and a short half-life. Subsequently, NO undergoes a series of reactions, transfers, and leakages from the cell membrane. Due to its transient nature and short diffusion distance, achieving in-situ real-time monitoring of NO is challenging.

[0003] Methods for NO detection mainly include colorimetry, spectrophotometry, spectroscopy, fluorescence, and electrochemical methods. Among these, electrochemical methods offer advantages such as sensitivity, specificity, simplicity, and low cost, making them suitable for real-time detection of NO molecules using electrochemical sensors. In the construction of NO sensors, mesoporous materials exhibit adsorption and highly efficient electrocatalytic activity for gaseous small molecule NO; therefore, NO electrochemical sensors based on mesoporous nanomaterials hold great potential. Specifically, the outermost d-electron orbitals of platinum group metals (PGMs) can coordinate with the lone electrons of NO, achieving adsorption. Furthermore, PGMs possess valuable physical and chemical properties, such as high-temperature stability, low electrical impedance, and high corrosion resistance. Based on these characteristics, PGMs and their alloys can demonstrate excellent NO electrocatalytic sensing performance.

[0004] Based on this, our research group, with the support of the National Natural Science Foundation of China (No. 21876005, 21936001, 21625501) and the Beijing Outstanding Young Scientists Program (BJJWZYJH01201910005017), has developed an electrochemical sensor that enables direct real-time detection of NO. This sensor has a simple preparation method and good performance, and is expected to play an important role in the field of biomedical analysis and detection. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide the application of platinum-based nanomaterials in the construction of nitric oxide electrochemical sensors.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An electrochemical NO sensor based on a platinum-iridium mesoporous alloy and its preparation method.

[0008] Preferably, the nitric oxide electrochemical sensor includes an electrochemical workstation, a working electrode with a surface modified with mesoporous platinum-iridium alloy nanomaterials, a counter electrode, a reference electrode, an electrolytic cell, and an electrolyte.

[0009] Preferably, the working electrode with the surface modified with mesoporous platinum-iridium alloy nanomaterial is prepared by the following method: the electrode is immersed in an electrolyte containing platinum chloride, iridium chloride, and a nonionic surfactant; a constant potential is applied to the working electrode; under the drive of the applied potential, the metal ion precursor is reduced to metal atoms on the electrode surface. Subsequently, the electrode is immersed in an organic solvent to remove surfactant molecules and then dried.

[0010] Preferably, the working electrode is one of a glassy carbon electrode and a platinum electrode.

[0011] Preferably, the electrolyte is prepared by dissolving a triblock copolymer surfactant in a mixed solution of tetrahydrofuran (THF) and ethanol, and then mixing it with a solution of platinum chloride and iridium chloride. The electrolyte is stored at 4°C in the dark.

[0012] Preferably, the molar ratio of platinum chloride to iridium chloride in the electrolyte varies within the range of 100:0 to 0:100.

[0013] Preferably, the platinum chloride is one of chloroplatinic acid or potassium chloroplatinate, and the iridium chloride is one of chloroiridium acid, iridium chloride, or potassium chloroiridium.

[0014] Preferably, the organic solvent is a mixed solution of ethanol and tetrahydrofuran (THF).

[0015] Secondly, the present invention provides an electrochemical sensor for direct real-time detection of NO, which is prepared using the above-described method.

[0016] Thirdly, the present invention provides the application of the above-mentioned electrochemical sensor for direct real-time detection of NO in the detection of NO concentration.

[0017] Furthermore, the electrochemical sensor can realize direct real-time detection of NO in the liquid phase. The specific steps are as follows: (1) Using a silver / silver chloride electrode as the reference electrode, a platinum wire electrode as the counter electrode, and the prepared electrochemical sensor as the working electrode, a three-electrode system is constructed; (2) The three-electrode system is placed in a 0.1 mol / L phosphate buffer solution (pH value 7.4); (3) Using 0.75V as the working potential, the chronoamperometry is used for determination; (4) The sample is added to the base liquid, and the NO in the sample is quantitatively analyzed by the current step; (5) If the solution contains NO, a current step will appear. If the sample does not contain NO, the current step cannot be observed. This is used to perform qualitative analysis of NO. In addition, the size of the current step is proportional to the concentration of NO in the solution, so the NO in the sample can be quantitatively analyzed; (6) The pulse voltammetry is used for determination in the potential range of 0.4V-1V; (7) The sample is added to the base liquid, and the NO in the sample is quantitatively analyzed by the current peak. If the solution contains NO, an oxidation peak will be observed at around 0.75V. If the sample does not contain NO, no oxidation peak will be observed, thus enabling qualitative analysis of NO. Furthermore, the magnitude of the current peak is directly proportional to the concentration of NO in the solution, allowing for quantitative analysis of NO in the sample.

[0018] An electrochemical sensor was applied to the detection of NO using chronoamperometry, exhibiting a wide linear range of 1.8 nM–6.5 μmol / L and 6.5–179 μmol / L. Within the concentration range of 1.8 nM–6.5 μmol / L, the sensor's sensitivity was 1.189 μA / μM, and the detection limit was 0.861 ± 0.029 nM. Similarly, an electrochemical sensor was applied to the detection of NO using pulse voltammetry, also showing a wide linear range of 1.8 nM–6.1 μM and 6.1 μM–179 μM. Within the concentration range of 1.8 nM–6.1 μmol / L, the sensor's sensitivity was 3.853 μA / μM, and the detection limit was 0.857 ± 0.022 nM.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) This invention provides a method for preparing mesoporous platinum-iridium alloys by surfactant-assisted electrodeposition, using an amphiphilic triblock copolymer as a soft template to form a uniform mesoporous structure on the electrode surface. This surfactant-assisted electrodeposition method can controllably construct mesoporous structures and can be extended to other types of metallic materials.

[0021] (2) This invention provides the application of mesoporous platinum-iridium alloy nanomaterials in the construction of an electrochemical nitric oxide sensor. The prepared mesoporous platinum-iridium alloy nanoparticles were applied for the first time in the electrochemical detection of NO, exhibiting high sensitivity to low concentrations of NO and a stronger oxidation current compared to single-metal platinum nanoparticles. This can be attributed to the alloying effect between the platinum and iridium bimetals on the regulation of surface properties, as well as the adsorption effect of the nanoporous structure on NO. In practical detection, the sensor exhibits a low detection limit and high selectivity, and its electrochemical performance is stable with a long cycle life, making it suitable for commercial application. Attached Figure Description

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0023] Figure 1 This is a transmission electron microscope (TEM) image of the electrolyte used for electrodeposition prepared in Example 1.

[0024] Figure 2 This is a scanning electron microscope image of the platinum-iridium mesoporous alloy nanoparticles prepared in Example 1.

[0025] Figure 3 The image shows the X-ray diffraction pattern of the platinum-iridium mesoporous alloy nanoparticles prepared in Example 1.

[0026] Figure 4 The image shows the X-ray photoelectron spectrum of the platinum-iridium mesoporous alloy nanoparticles prepared in Example 1.

[0027] Figure 5 A and B represent the electrodes prepared in Examples 1, 2, 3, and 4, respectively, in 5 mM [Fe(CN)6]. 3- / 4- Cyclic voltammetry and electrochemical impedance spectroscopy.

[0028] Figure 6 A and B represent the differential pulse voltammogram and cyclic voltammogram of the bare electrode and the electrodes prepared in Examples 1, 2, and 3, respectively, in 10 μM NO.

[0029] Figure 7 A represents the cyclic voltammograms of the sensor prepared in Example 1 at different scan rates in 10 μM NO. Figure 7 BC are the linear relationship curves between current and sweep speed and the square root of sweep speed, respectively.

[0030] Figure 8 A represents the differential pulse voltammograms of the sensor prepared in Example 1 in different concentrations of NO (1.8 nM-179 μM). Figure 8 B represents the corresponding linear relationship curve.

[0031] Figure 9A represents the chronocurrent response of the sensor prepared in Example 1 in different concentrations of NO (1.8 nM-179 μM). Figure 9 B represents the corresponding linear relationship curve.

[0032] Figure 10 This is a graph showing the results of selective testing of different interference components by the sensor constructed in Example 1.

[0033] Figure 11 The graph shows the reproducibility test results of the sensor constructed in Example 1.

[0034] Figure 12 The graph shows the stability test results of the sensor constructed in Example 1. Detailed Implementation

[0035] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] A nitric oxide electrochemical sensor was constructed and prepared according to the following method:

[0038] (1) Preparation of metal precursor electrolyte

[0039] An amphiphilic surfactant—polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123)—was dissolved in a mixture of THF and ethanol (1:1) to a mass fraction of 2 wt%. Then, 1.24 mL of potassium chloroplatinate solution (20 mM) and 0.76 mL of potassium chloroiridium solution (20 mM) were added dropwise and mixed thoroughly to achieve platinum ion concentrations of 3.8 mM and iridium ion concentrations of 6.2 mM in the electrolyte. This mixed solution is the electrolyte and should be stored at 4°C protected from light. Nitrogen purging for 5 minutes is required before use.

[0040] (2) Electrochemical deposition preparation of platinum-iridium mesoporous alloy modified electrodes

[0041] Using an electrochemical workstation (CHI 660E, CHI Instrument, US), a standard three-electrode system was employed, including an Ag / AgCl (saturated KCl) electrode as the reference electrode, a platinum wire as the counter electrode, and a platinum disk electrode or a glassy carbon electrode as the working electrode. Electrodeposition was performed at a constant potential of -0.25 V at room temperature. The working electrode was then placed in a 1:1 mixture of THF and ethanol for 12 hours to extract P123. The electrode was then thoroughly rinsed with deionized water and air-dried.

[0042] (3) Assemble a nitric oxide electrochemical sensor

[0043] The modified electrode obtained in step (2) was assembled together with an electrochemical workstation, a counter electrode (platinum wire electrode), a reference electrode (Ag / AgCl electrode), an electrolytic cell, and an electrolyte (0.1 mol / L, pH=7.4 phosphate buffer solution) to form a NO electrochemical sensor.

[0044] Example 2

[0045] A nitric oxide electrochemical sensor was constructed and prepared according to the following method:

[0046] (1) Preparation of metal precursor electrolyte

[0047] The amphiphilic surfactant—polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123)—was dissolved in a mixture of THF and ethanol (1:1) to a mass fraction of 2 wt%. 2 mL of potassium chloroplatinate solution (20 mM) was added dropwise to the solution. This mixture constitutes the electrolyte and should be stored at 4°C protected from light. Nitrogen purging for 5 minutes is required before use.

[0048] (2) Electrochemical deposition preparation of mesoporous platinum-modified electrodes

[0049] Using an electrochemical workstation (CHI 660E, CHI Instrument, US), a standard three-electrode system was employed, including an Ag / AgCl (saturated KCl) electrode as the reference electrode, a platinum wire as the counter electrode, and a platinum disk electrode or a glassy carbon electrode as the working electrode. Electrodeposition was performed at a constant potential of -0.25 V at room temperature. The working electrode was then placed in a 1:1 mixture of THF and ethanol for 12 hours to extract P123. The electrode was then thoroughly rinsed with deionized water and air-dried.

[0050] (3) Assemble a nitric oxide electrochemical sensor

[0051] The modified electrode obtained in step (2) was assembled together with an electrochemical workstation, a counter electrode (platinum wire electrode), a reference electrode (Ag / AgCl electrode), an electrolytic cell, and an electrolyte (0.1 mol / L, pH=7.4 phosphate buffer solution) to form a NO electrochemical sensor.

[0052] Example 3

[0053] A nitric oxide electrochemical sensor was constructed and prepared according to the following method:

[0054] (1) Preparation of metal precursor electrolyte

[0055] The amphiphilic surfactant—polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123)—was dissolved in a mixture of THF and ethanol (1:1) to a mass fraction of 2 wt%. 2 mL of potassium chloroiridium solution (20 mM) was added dropwise to the solution; this mixture constitutes the electrolyte. The electrolyte was stored at 4°C protected from light. Nitrogen was purged for 5 minutes before use to remove oxygen.

[0056] (2) Electrochemical deposition to prepare mesoporous iridium-modified electrodes

[0057] Using an electrochemical workstation (CHI 660E, CHI Instrument, US), a standard three-electrode system was employed, including an Ag / AgCl (saturated KCl) electrode as the reference electrode, a platinum wire as the counter electrode, and a platinum disk electrode or a glassy carbon electrode as the working electrode. Electrodeposition was performed at a constant potential of -0.25 V at room temperature. The working electrode was then placed in a 1:1 mixture of THF and ethanol for 12 hours to extract P123. The electrode was then thoroughly rinsed with deionized water and air-dried.

[0058] (3) Assemble a nitric oxide electrochemical sensor

[0059] The modified electrode obtained in step (2) was assembled together with an electrochemical workstation, a counter electrode (platinum wire electrode), a reference electrode (Ag / AgCl electrode), an electrolytic cell, and an electrolyte (0.1 mol / L, pH=7.4 phosphate buffer solution) to form a NO electrochemical sensor.

[0060] Example 4

[0061] A nitric oxide electrochemical sensor was constructed and prepared according to the following method:

[0062] (1) Preparation of metal precursor electrolyte

[0063] Mix 0.76 mL of potassium chloroplatinate solution (10 mM) with 1.24 mL of potassium chloroiridium solution (10 mM) to achieve platinum ion concentrations of 3.8 mM and iridium ion concentrations of 6.2 mM. This mixed solution is the electrolyte and should be stored at 4°C protected from light. Nitrogen should be purged for 5 minutes before use to remove oxygen.

[0064] (2) Electrochemical deposition preparation of non-porous platinum-iridium alloy modified electrodes

[0065] Using an electrochemical workstation (CHI 660E, CHI Instrument, US), a standard three-electrode system was employed, including an Ag / AgCl (saturated KCl) electrode as the reference electrode, a platinum wire as the counter electrode, and a platinum disk electrode or a glassy carbon electrode as the working electrode. Electrodeposition was performed at a constant potential of -0.25 V at room temperature. The working electrode was then placed in a 1:1 mixture of THF and ethanol for 12 hours to extract P123. The electrode was then thoroughly rinsed with deionized water and air-dried.

[0066] (3) Assemble a nitric oxide electrochemical sensor

[0067] The modified electrode obtained in step (2) was assembled together with an electrochemical workstation, a counter electrode (platinum wire electrode), a reference electrode (Ag / AgCl electrode), an electrolytic cell, and an electrolyte (0.1 mol / L, pH=7.4 phosphate buffer solution) to form a NO electrochemical sensor.

[0068] Figure 1 This is a transmission electron microscope (TEM) image of the metal precursor electrolyte prepared in Example 1. Figure 1 It is known that spherical micelle structures with a diameter of about 10-20 nanometers exist in the electrolyte.

[0069] Figure 2 This is a scanning electron microscope (SEM) image of the platinum-iridium mesoporous alloy nanoparticles prepared in Example 1. Figure 2 It can be seen that the alloy nanoparticles have a mesoporous morphology.

[0070] Figure 3 The image shows the X-ray diffraction pattern of the platinum-iridium mesoporous alloy nanoparticles prepared in Example 1. Figure 3 It can be seen that the alloy nanoparticles expose the crystal planes of platinum and iridium, among which the (111) plane plays a major role. The platinum-iridium mesoporous alloy nanoparticles have a good crystal lattice structure.

[0071] Figure 4 The image shows the X-ray photoelectron spectrum of the platinum-iridium mesoporous alloy nanoparticles prepared in Example 1. Figure 4 It can be seen that the peaks of Pt 4f (70-75eV) and Ir 4f (60-64eV) are shown, indicating the presence of these two metal atoms.

[0072] Figure 5 The electrodes prepared in Examples 1, 2, 3, and 4 were subjected to 5 mM [Fe(CN)6] 3- / 4- The cyclic voltammograms and electrochemical impedance spectroscopy in the data are derived from... Figure 5 It can be seen that the mesoporous platinum-iridium alloy sensor has the highest current response and the lowest electrode resistance, indicating that the mesopores increase the electrochemical active surface area of ​​the electrode, and the platinum-iridium bimetallic alloy further improves the conductivity of the electrode.

[0073] Figure 6 The differential pulse voltammograms and cyclic voltammograms of the bare electrode and the electrodes prepared in Examples 1, 2, and 3 in 10 μM NO are provided by [the relevant authority / organization]. Figure 6 It can be seen that the mesoporous platinum-iridium alloy sensor has the highest oxidation current and the lowest oxidation potential, demonstrating high electrochemical sensing performance for NO.

[0074] Figure 7 The cyclic voltammograms of the sensor prepared in Example 1 at different scan rates in 10 μM NO are obtained from... Figure 7 It can be seen that there is a linear relationship between the anode peak current and the sweep rate (Ra). 2 =0.991), and there is also a linear relationship between it and the square root of the scan rate (R). 2 =0.992), which indicates that NO is simultaneously regulated by adsorption and diffusion kinetics on the surface of platinum-iridium mesoporous alloy.

[0075] Example 5

[0076] The differential pulse voltammetric response was tested using the sensor prepared in Example 1 in different concentrations of NO (1.8 nM-179 μM), and the results are as follows. Figure 8 As shown. By Figure 8 It can be seen that the oxidation peak at 0.68 V increases continuously with increasing NO concentration. The oxidation current exhibits a good linear relationship with NO concentration in two ranges: 1.8 nM to 6.1 μM, and 6.1 μM to 179 μM. This sensor is more sensitive to the determination of low concentrations of NO, yielding I(μA) = 3.853 C. NO +0.227(R 2 Using a linear equation with a sensitivity of 3.853 μA / μM and a detection limit of 0.857 ± 0.022 nM, the improved sensor interface exhibits high sensitivity and a low detection limit, making it suitable for trace NO detection.

[0077] Example 6

[0078] The chronocurrent response was tested using the sensor prepared in Example 1 in different concentrations of NO (1.8 nM-179 μM) with a constant potential of +0.75 V. The results are as follows: Figure 9 As shown. By Figure 9 It can be seen that the current increases continuously with the successive addition of NO. The oxidation current and NO concentration exhibit a good linear relationship in two ranges: 1.8 nM to 6.5 μM, and 6.5 μM to 179 μM. The sensor is more sensitive to the determination of low concentrations of NO, and I(μA) = 1.189 C can be obtained. NO +0.071(R 2 Using a linear equation (=0.992), the sensitivity was calculated to be 1.189 μA / μM, and the detection limit was 0.861 ± 0.029 nM. This also demonstrates that the improved sensor interface has high sensitivity and a low detection limit, making it suitable for trace NO detection.

[0079] Example 7

[0080] Solutions of different substances were sequentially added to the electrolyte of the sensor constructed in Example 1, and the chronocurrent response of the sensor to different interfering components was tested. The test voltage was 0.75V, and the time interval between adding different interfering substances was 60s. The amperometric response curves of the sensor to selectively test different interfering components were obtained, and the results are as follows. Figure 10 As shown. By Figure 10 It can be seen that the sensor has good selectivity for NO.

[0081] Example 8

[0082] The differential pulse volt-ampere response of five different batches of sensors constructed in Example 1 in 10 μM NO was tested with an applied voltage of 0.75 V. The results are as follows. Figure 11 As shown. By Figure 11 It can be seen that the sensor has good test reproducibility.

[0083] Example 9

[0084] The differential pulse voltammetric response of the sensor constructed in Example 1 in 10 μM NO was tested after 0, 2, 4, 6, 8, and 10 days. The results are as follows: Figure 12 As shown. By Figure 12 It can be seen that the sensor has good testing stability.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a NO electrochemical sensor based on a platinum-iridium mesoporous alloy, characterized in that, The nitric oxide electrochemical sensor includes an electrochemical workstation, a working electrode with a surface modified with mesoporous platinum-iridium alloy nanomaterials, a counter electrode, a reference electrode, an electrolytic cell, and an electrolyte; The working electrode with the surface modified with mesoporous platinum-iridium alloy nanomaterial is prepared by the following method: the electrode is immersed in an electrolyte containing platinum chloride, iridium chloride, and nonionic surfactant; a constant potential is applied to the working electrode; under the drive of the applied potential, the metal ion precursor is reduced to metal atoms on the electrode surface; then the electrode is immersed in an organic solvent to remove surfactant molecules and dried. The electrolyte is prepared as follows: First, a nonionic surfactant is dissolved in a mixed solution of tetrahydrofuran and ethanol in a volume ratio of 1:

1. Then, a mixture of a 10 mM platinum chloride solution and a 10 mM iridium chloride solution in a volume ratio of 38:62 is added dropwise to obtain a mixed solution with a total metal concentration of 10 mM. This mixed solution is the electrolyte and is stored at 4°C in the dark. The working electrode is either a glassy carbon electrode or a platinum electrode, and the nonionic surfactant is a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer P123.

2. The method as described in claim 1, characterized in that, The molar ratio of platinum ions to iridium ions in the electrolyte varies within the range of 100:0 to 0:

100.

3. The method as described in claim 1, characterized in that, The platinum chloride is one of chloroplatinic acid or potassium chloroplatinate, and the iridium chloride is one of chloroiridium acid, iridium chloride, or potassium chloroiridium.

4. The method as described in claim 1, characterized in that, The organic solvent is ethanol or a mixture of ethanol and tetrahydrofuran.

5. The NO electrochemical sensor obtained by any of the preparation methods described in claims 1 to 4.

6. The application of the NO electrochemical sensor as described in claim 5, characterized in that, The electrochemical sensor was applied to the detection of NO in the liquid phase.

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