A flexible solid-state hydrogen ion sensor and its preparation method

Abstract

The present invention discloses a flexible solid-state hydrogen ion sensor and a preparation method thereof. The preparation method of the flexible solid-state hydrogen ion sensor comprises the following steps: (1) adding Ti3AlC2 into a hydrofluoric acid solution, stirring, centrifugally washing, drying to obtain HF-Ti3C2T x ; (2) weighing HF-Ti3C2T x , measuring a Nafion solution, dispersing it in water to obtain a mixed system A; (3) cleaning a PET sheet, performing plasma cleaning again, drying, magnetron sputtering a metal on the PET sheet, coating a layer of PDMS and drying to obtain a flexible solid-state electrode; (4) drop-coating the mixed system A on the surface of the flexible solid-state electrode and drying to obtain a flexible solid-state hydrogen ion sensor. The preparation method of the present invention is simple, and the prepared flexible solid-state hydrogen ion sensor has the advantages of low cost, high sensitivity, high selectivity, etc., and can monitor the hydrogen ion concentration in sweat excreted during human movement in real time.

Description

Technical Field

[0001] The present invention relates to the field of ion analysis sensors, and particularly relates to a flexible solid-state hydrogen ion sensor and a preparation method thereof. Background Art

[0002] The detection of hydrogen ion concentration is one of the important contents of ion detection in analytical chemistry. The concentration of hydrogen ions in physiological body fluids such as human sweat, saliva, and urine is closely related to various physiological diseases. Secondly, real-time monitoring of the hydrogen ion concentration in soil is beneficial to the healthy growth of plants. Currently, the most widely used method for detecting hydrogen ion concentration is the glass electrode, but it has defects such as poor potential stability, high resistance, and easy damage, which limit its further application. Flexible electrodes have the characteristics of easy miniaturization, low cost, and strong flexibility, and have been widely used in wearable devices.

[0003] All-solid-state ion-selective electrodes (SC-ISEs) are the core components of wearable ion sensors, which consist of two core components: a solid contact layer and an ion-selective membrane. The solid contact layer plays an important role in ion-electron conduction, while the ion-selective membrane plays an important role in the recognition of target ions. Currently, hydrogen ion carriers are the most widely used pH-sensitive materials in the early stage. However, due to the high cost of membrane electrodes using hydrogen ion carriers and the easy leakage of toxic substances, researchers have gradually started to study other alternative materials. Among them, the most widely studied are organic polymers represented by polyaniline (such as the literature Tom Lindfors et.al., Journal of Electroanalytical Chemistry, 2002, 531(1), 43-52) and inorganic metal oxides represented by iridium oxide (such as the literature Sayed A.M. Marzouk et.al., Analytical Chemistry, 1998, 70(23), 5054-5061). And research shows that substances with oxygen-containing functional groups such as hydroxyl and carbonyl groups on the surface can also be used as hydrogen ion-sensitive materials, such as carbon nanotubes (such as the literature Dongjin Lee et.al., Microelectronic Engineering, 2012, 93, 39-42) and graphene (such as the literature Selvaraj Chinnathambi et.al., Journal of Electroanalytical Chemistry, 2021, 895(1), 115530), etc. However, in the prior art, there is still a lack of a material guideline that emphasizes the direct use of surface functional groups as hydrogen ion-sensitive elementary units in the field of SC-ISEs. Summary of the Invention

[0004] In view of the above-mentioned defects of the prior art, the object of the present invention is to provide a flexible solid-state hydrogen ion sensor and a preparation method thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] In the first aspect, the present invention provides a preparation method of a flexible solid-state hydrogen ion sensor, and the preparation steps of the method are as follows:

[0007] (1) Add Ti3AlC2 to a hydrofluoric acid solution, stir, centrifuge and wash, and dry to obtain HF-Ti3C2T x ;

[0008] (2) Weigh HF-Ti3C2T x , measure Nafion solution, disperse it in water to obtain a mixed system A;

[0009] (3) After cleaning the PET sheet, perform plasma cleaning again, dry it, magnetron sputter metal on the PET sheet, coat a layer of PDMS and dry it to obtain a flexible solid-state electrode;

[0010] (4) Drop the mixed system A on the surface of the flexible solid-state electrode, dry it to obtain a flexible solid-state hydrogen ion sensor.

[0011] Preferably, in step (1), the hydrofluoric acid solution is a 20-49 wt% hydrofluoric acid solution, and the dosage is 5-40 mL.

[0012] More preferably, in step (1), the concentration of the hydrofluoric acid solution is 49 wt%, and the dosage is 20 mL.

[0013] Preferably, in step (1), the mass of the Ti3AlC2 is 0.5-2 g.

[0014] More preferably, in step (1), the mass of the Ti3AlC2 is 1 g.

[0015] Preferably, in step (1), the stirring time is 24 h.

[0016] Preferably, in step (1), deionized water is used for centrifugal cleaning, the rotation speed per minute of centrifugation is 3500 rpm, the centrifugation time is 5 min, and the centrifugal cleaning process is repeated until the pH of the supernatant is greater than or equal to 6.

[0017] Preferably, in step (1), drying is carried out in a vacuum environment, the drying temperature is 60 °C, and the drying time is 12 h.

[0018] Preferably, in step (2), the HF-Ti3C2T xThe mass is 5 - 20 mg, and the dosage of the Nafion solution is 50 - 400 μL.

[0019] More preferably, in step (2), the HF-Ti3C2T x The mass is 10 mg, and the dosage of the Nafion solution is 200 μL.

[0020] Preferably, in step (2), the dispersion is ultrasonic dispersion, and the dispersion time is 1 h.

[0021] Preferably, in step (2), the water is deionized water, and the dosage is 600 - 950 μL.

[0022] More preferably, in step (2), the dosage of the water is 800 μL.

[0023] Preferably, in step (3), the size of the PET sheet is 7 cm × 7 cm - 8 cm × 8 cm.

[0024] More preferably, in step (3), the size of the PET sheet is 8 cm × 8 cm.

[0025] Preferably, in step (3), the cleaning process of the PET sheet is to ultrasonically clean the PET sheet in isopropanol, ethanol, and deionized water in sequence, and the ultrasonic cleaning time is 10 min each time.

[0026] Preferably, in step (3), the plasma re-cleaning is carried out in a plasma cleaner for 5 min.

[0027] Preferably, in step (3), the drying gas is N2.

[0028] Preferably, in step (3), the metals are Cr and Ag. First, Cr is sputtered, and then Ag is sputtered. The thickness of Cr is 5 - 30 nm, and the thickness of Ag is 100 - 300 nm.

[0029] More preferably, in step (3), the thickness of Cr is 30 nm, and the thickness of Ag is 300 nm.

[0030] Preferably, in step (3), the drying temperature is 90 °C, and the drying time is 40 min.

[0031] Preferably, in step (4), the dosage of the mixed system A is 5 - 20 μL.

[0032] More preferably, in step (4), the dosage of the mixed system A is 10 μL.

[0033] Preferably, in step (4), the drying is carried out in a vacuum environment. The drying temperature is 60 °C, and the drying time is 1 h.

[0034] In a second aspect, the present invention also provides a flexible solid-state hydrogen ion sensor prepared by the method described above.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) In the method for preparing a flexible solid-state hydrogen ion sensor according to the present invention, a large number of oxygen-containing functional groups will be generated on the surface of HF-Ti3C2T after etching with hydrofluoric acid. After the peeling treatment, HF-Ti3C2T x has a large specific surface area. Therefore, HF-Ti3C2T x has conductivity similar to that of a metal. The flexible solid-state hydrogen ion sensor prepared by this method has strong potential stability and can effectively monitor the hydrogen ion concentration in human sweat in real time. x

[0037] (2) For the flexible solid-state hydrogen ion sensor according to the present invention, the solid-state hydrogen ion selective electrode based on the emerging two-dimensional carbon material Ti3C2T x has high selectivity and anti-interference ability. The flexible solid-state hydrogen ion sensor integrated with the solid-state hydrogen ion selective electrode can monitor the hydrogen ion concentration in the sweat excreted during human movement in real time. This sensor has the advantages of low cost, high sensitivity, high selectivity, etc., and has great application potential and commercial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 X-ray diffraction pattern of HF-Ti3C2T prepared in Example 1; x

[0039] Figure 2 In (a) is the scanning electron microscope image of Ti3AlC2 in Example 1, (b) is the elemental distribution map of Ti3AlC2 in Example 1, (c) is the Ti elemental distribution map of Ti3AlC2 in Example 1, (d) is the C elemental distribution map of Ti3AlC2 in Example 1, and (e) is the distribution map of the Al element of Ti3AlC2 in Example 1;

[0040] Figure 3 Scanning electron microscope image of HF-Ti3C2T prepared in Example 1; x

[0041] Figure 4 In (a) is the elemental composition and distribution map of HF-Ti3C2T prepared in Example 1, (b) is the Ti elemental distribution map of HF-Ti3C2T prepared in Example 1, and (c) is the HF-Ti3C2T prepared in Example 1 x x ​x Distribution map of F element, (d) is HF-Ti3C2T prepared in Example 1 x Distribution map of C element, (e) is HF-Ti3C2T prepared in Example 1 x Distribution map of Al element, (e) is HF-Ti3C2T prepared in Example 1 x Distribution map of O element;

[0042] Figure 5 For Ti3AlC2 in Example 1 and HF-Ti3C2T prepared in Example 1 x Element composition comparison chart;

[0043] Figure 6 In (a) is the preparation schematic diagram of the flexible solid-state hydrogen ion sensor prepared in Example 5, (b) is the image diagram of the flexible solid-state hydrogen ion sensor prepared in Example 5;

[0044] Figure 7 In (a) is the potential response curve of the solid-state hydrogen ion selective electrode prepared in Example 2, (b) is the potential-hydrogen ion activity calibration curve of the solid-state hydrogen ion selective electrode prepared in Example 2;

[0045] Figure 8 For the anti-interference test of the solid-state hydrogen ion selective electrode prepared in Example 2;

[0046] Figure 9 For the selectivity test of the solid-state hydrogen ion selective electrode prepared in Example 2 for H + Selectivity test;

[0047] Figure 10 In (a) are the potential response curves of the flexible solid-state hydrogen ion sensor in the normal state and the flexible solid-state hydrogen ion sensor in the bent 120° state, (b) are the potential response calibration curves of the flexible solid-state hydrogen ion sensor in the normal state and the flexible solid-state hydrogen ion sensor in the bent 120° state;

[0048] Figure 11 In (a) is the real-time potential map of the human sweat test, (b) is the potential response curve of the flexible solid-state hydrogen ion sensor before and after the sweat test, (c) is the potential-hydrogen ion activity calibration curve before and after the sweat test, (d) is the sensor test result and the result of the precision pH test paper during the sweat test. Detailed implementation manners

[0049] The following further describes the specific embodiments of the present invention in conjunction with the accompanying drawings. It should be noted here that the description of these embodiments is used to assist in understanding the present invention, but does not constitute a limitation on the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0050] Example 1

[0051] A preparation method of HF-Ti3C2T x The method includes the following steps:

[0052] Add 1 g of Ti3AlC2 to 20 mL of 49 wt% hydrofluoric acid solution, stir for 24 h, perform centrifugal washing with deionized water, the rotation speed per minute of centrifugation is 3500 rpm, the centrifugation time is 5 min, repeat the centrifugal washing process until the pH of the supernatant is greater than or equal to 6, and dry at 60 °C in a vacuum environment for 12 h to obtain HF-Ti3C2T x .

[0053] Example 2

[0054] A preparation method of a solid-state hydrogen ion selective electrode, the method includes the following steps:

[0055] (1) Add 1 g of Ti3AlC2 to 20 mL of 49 wt% hydrofluoric acid solution, stir for 24 h, perform centrifugal washing with deionized water, the rotation speed per minute of centrifugation is 3500 rpm, the centrifugation time is 5 min, repeat the centrifugal washing process until the pH of the supernatant is greater than or equal to 6, and dry at 60 °C in a vacuum environment for 12 h to obtain HF-Ti3C2T x ;

[0056] (2) Weigh 10 mg of HF-Ti3C2T x , measure 200 μL of Nafion solution, disperse it in 800 μL of deionized water, and ultrasonically disperse for 1 h to obtain a mixed system A;

[0057] (3) Use a glassy carbon electrode with a diameter of 5 mm, first polish the glassy carbon electrode with 0.3 μm Al2O3 powder on suede, wash it with deionized water and then polish the glassy carbon electrode with 0.05 μm Al2O3 powder on suede, and then ultrasonically wash it several times with deionized water, ethanol, and deionized water in sequence to obtain a polished glassy carbon electrode;

[0058] (4) Drop 10 μL of the mixed system A on the surface of the polished glassy carbon electrode, and dry it in a vacuum at 60 °C for 1 h to obtain a solid-state hydrogen ion selective electrode.

[0059] Example 3

[0060] A preparation method of a flexible solid-state hydrogen ion sensor, the method comprising the following steps:

[0061] (1) Add 0.5 g of Ti3AlC2 to 10 mL of 49 wt% hydrofluoric acid solution and stir for 24 h. Centrifuge and wash with deionized water at a rotation speed of 3500 rpm per minute for 5 min. Repeat the centrifugation and washing process until the pH of the supernatant is greater than or equal to 6. Dry at 60 °C in a vacuum environment for 12 h to obtain HF-Ti3C2T x .

[0062] (2) Weigh 5 mg of HF-Ti3C2T x , measure 50 μL of Nafion solution, disperse it in 600 μL of deionized water, and ultrasonically disperse for 1 h to obtain a mixed system A;

[0063] (3) Cut the PET sheet into a size of 7 cm × 7 cm, ultrasonically clean it in isopropanol, ethanol, and deionized water in sequence, ultrasonically clean for 10 min each time, then clean it in a plasma cleaner for 5 min and dry with N2. Plasma clean and dry again. Magnetron sputter 5 nm of Cr and 100 nm of Ag on the PET sheet, coat a layer of PDMS and dry at 90 °C for 40 min to obtain a flexible solid-state electrode based on HF-Ti3C2T x ;

[0064] (4) Measure 5 μL of the mixed system A and drop-coat it on the surface of the flexible solid-state electrode, and dry it in a vacuum at 60 °C for 1 h to obtain a flexible solid-state hydrogen ion sensor.

[0065] Example 4

[0066] A preparation method of a flexible solid-state hydrogen ion sensor, the method comprising the following steps:

[0067] (1) Add 2 g of Ti3AlC2 to 40 mL of 49 wt% hydrofluoric acid solution and stir for 24 h. Centrifuge and wash with deionized water at a rotation speed of 3500 rpm per minute for 5 min. Repeat the centrifugation and washing process until the pH of the supernatant is greater than or equal to 6. Dry at 60 °C in a vacuum environment for 12 h to obtain HF-Ti3C2T x .

[0068] (2) Weigh 20 mg of HF-Ti3C2T x , measure 400 μL of Nafion solution, disperse it in 950 μL of deionized water, and ultrasonically disperse for 1 h to obtain a mixed system A;

[0069] (3) Cut the PET sheet into a size of 8 cm × 8 cm, ultrasonically clean it successively in isopropanol, ethanol, and deionized water for 2 min each time, then clean it in a plasma cleaner for 5 min and dry it with N2, perform plasma cleaning and drying again, magnetron sputter 30 nm of Cr and 300 nm of Ag on the PET sheet, coat a layer of PDMS and dry it at 90 °C for 40 min to obtain a flexible solid-state electrode based on HF-Ti3C2T x ;

[0070] (4) Measure 20 μL of the mixed system A and drop-coat it on the surface of the flexible solid-state electrode, and vacuum-dry it at 60 °C for 1 h to obtain a flexible solid-state hydrogen ion sensor.

[0071] Example 5

[0072] A preparation method of a flexible solid-state hydrogen ion sensor, the method comprising the following steps:

[0073] (1) Add 1 g of Ti3AlC2 to 20 mL of 49 wt% hydrofluoric acid solution, stir for 24 h, perform centrifugal cleaning with deionized water, the rotation speed per minute of centrifugation is 3500 rpm, and the centrifugation time is 5 min. Repeat the centrifugal cleaning process until the pH of the supernatant is greater than or equal to 6, and vacuum-dry it at 60 °C for 12 h to obtain HF-Ti3C2T x ;

[0074] (2) Weigh 10 mg of HF-Ti3C2T x , measure 200 μL of Nafion solution, disperse it in 800 μL of deionized water, and ultrasonically disperse it for 1 h to obtain a mixed system A;

[0075] (3) Cut the PET sheet into a size of 8 cm × 8 cm, ultrasonically clean it successively in isopropanol, ethanol, and deionized water for 2 min each time, then clean it in a plasma cleaner for 5 min and dry it with N2, magnetron sputter 30 nm of Cr and 300 nm of Ag on the PET sheet, coat a layer of PDMS and dry it at 90 °C for 40 min to obtain a flexible solid-state electrode based on HF-Ti3C2T x ;

[0076] (4) Measure 10 μL of the mixed system A and drop-coat it on the surface of the flexible solid-state electrode, and vacuum-dry it at 60 °C for 1 h to obtain a flexible solid-state hydrogen ion sensor.

[0077] Figure 6 In (a) is the preparation schematic diagram of the flexible solid-state hydrogen ion sensor prepared in Example 5, and (b) is the image diagram of the flexible solid-state hydrogen ion sensor prepared in Example 5.

[0078] Experimental Example 1

[0079] In this experimental example, the morphology and properties of HF-Ti3C2T prepared in Example 1 were investigated. x For HF-Ti3C2T prepared in Example 1, x X-ray diffraction was performed to characterize the crystal structure. As Figure 1 shown, it is the X-ray diffraction pattern of HF-Ti3C2T prepared in Example 1. x It can be seen from Figure 1 that the characteristic peak at 2θ = 10° is the (001) peak of HF-Ti3C2T, and the characteristic peak at 2θ = 39° is the characteristic peak of Al atoms. The weak intensity of this peak indicates that the Al atoms in HF-Ti3C2T x are almost completely etched. x

[0080] Scanning electron microscopy (SEM) characterization was performed on Ti3AlC2 in Example 1. As Figure 2 (a) shows, scanning electron microscopy (SEM) characterization was performed on HF-Ti3C2T prepared in Example 1. x As Figure 3 shown, it is the SEM image of HF-Ti3C2T prepared in Example 1. x It can be seen from Figure 2 (a) and Figure 3 that the unetched Ti3AlC2 exhibits a closely stacked layered structure, while the microscopic morphology of HF-Ti3C2T x obtained after HF etching is an accordion-like layered structure.

[0081] Elemental imaging analysis (MAPPING) was performed on Ti3AlC2 in Example 1. The results are as Figure 2 (b), Figure 2 (c), Figure 2 (d), Figure 2 (e) shown. Figure 2 Among them, (b) is the elemental distribution map of Ti3AlC2 in Example 1, (c) is the Ti elemental distribution map of Ti3AlC2 in Example 1, (d) is the C elemental distribution map of Ti3AlC2 in Example 1, and (e) is the Al elemental distribution map of Ti3AlC2 in Example 1. As Figure 2 (b), Figure 2 (c), Figure 2 (d), Figure 2 (e) can be seen, Ti3AlC2 is mainly composed of three elements: Ti, C, and Al.

[0082] Elemental imaging analysis (MAPPING) was performed on HF-Ti3C2T prepared in Example 1. The results are as x follows.Figure 4 As shown Figure 4 in the elemental distribution map of HF-Ti3C2T prepared in Example 1(a), x and (b) is the elemental distribution map of Ti in HF-Ti3C2T prepared in Example 1, x and (c) is the elemental distribution map of F in HF-Ti3C2T prepared in Example 1, x and (d) is the elemental map of C in HF-Ti3C2T prepared in Example 1, x and (e) is the elemental distribution map of Al in HF-Ti3C2T prepared in Example 1, x and (f) is the elemental distribution map of O in HF-Ti3C2T prepared in Example 1. It can be seen from x that HF-Ti3C2T Figure 4 is mainly composed of Ti, F, C, O and a small amount of residual Al elements. x

[0083] The elemental composition and content of Ti3AlC2 in Example 1 and HF-Ti3C2T prepared in Example 1 x were compared. The results are as Figure 5 shown. It can be seen from Figure 5 that Ti3AlC2 in Example 1 is composed of three elements, Ti, Al, and C, while HF-Ti3C2T x prepared in Example 1 is composed of five elements, Ti, Al, C, O, and F. After etching, O and F in HF-Ti3C2T x exist in the forms of -OH, =O and -F functional groups respectively. At the same time, the Al content in HF-Ti3C2T x is significantly lower than that in Ti3AlC2, indicating that the Al atoms in HF-Ti3C2T x are almost completely etched.

[0084] Experimental Example 2

[0085] In this experimental example, the potential response of the solid-state hydrogen ion selective electrode prepared in Example 2 to H + was investigated. Using the solid-state hydrogen ion selective electrode prepared in Example 2 as the working electrode and the saturated calomel electrode as the reference electrode, the potential response ability and response time of the solid-state hydrogen ion selective electrode prepared in Example 2 were tested by the electrochemical open circuit potential method using an EMF6 multi-channel potentiometer. The results are as Figure 7 shown. Figure 7 In (a) is the potential response curve of the solid-state hydrogen ion selective electrode prepared in Example 2, and (b) is the potential-hydrogen ion activity calibration curve of the solid-state hydrogen ion selective electrode prepared in Example 2. From​Figure 7 (a) It can be seen that the solid-state hydrogen ion selective electrode has good potential cycling stability. Figure 7 (b) It can be seen that the solid-state hydrogen ion selective electrode has a good sensitivity to H in the pH range of 1 to 11. + The sensitivity is -43.51mV·pH -1 , indicating that the solid hydrogen ion selective electrode prepared in Example 2 can meet the needs of real-time testing of human sweat.

[0086] Experimental Example 3

[0087] In this experimental example, the anti-interference performance of the solid hydrogen ion selective electrode prepared in Example 2 was investigated, and the steps were as follows:

[0088] (1) preparing a mixed solution of 0.04 M phosphoric acid, 0.04 M boric acid and 0.04 M acetic acid, adding 0.02 M NaOH solution, and adjusting the pH background to 7 to obtain a pH buffer solution;

[0089] (2) The solid hydrogen ion selective electrode prepared in Example 2 was used as the working electrode, and the saturated calomel electrode was used as the reference electrode. 10 mM Na + , K + NH4 + , Li + and Mg 2+ After the five interfering ions were detected, the potential changes were recorded by the electrochemical open circuit potential method using an EMF6 multi-channel potentiometer.

[0090] The results are as follows Figure 8 As shown, the anti-interference test of the solid hydrogen ion selective electrode prepared in Example 2 is shown. Figure 8 It can be seen that the solid hydrogen ion selective electrode was added with 10mM Na + , K + NH4 + , Li + and Mg 2+ There was no obvious drift in the potential after the five interfering ions, indicating that the solid hydrogen ion selective electrode prepared in Example 2 has a certain anti-interference ability.

[0091] Experimental Example 4

[0092] In this experimental example, the solid hydrogen ion selective electrode prepared in Example 2 was investigated for H + The selectivity of the solid hydrogen ion selective electrode was tested using the electrochemical open circuit potential test method. -1 ~10 -5 The interfering ions (Na + , K+ , NH4 + , Li + and Mg 2+ ), and the target ion H + 's potential response. The results are as Figure 9 shown, which is the selectivity test of the solid-state hydrogen ion selective electrode prepared in Example 2 for H + . It can be seen from Figure 9 that the potentials of all interfering ions are below the potential of the target ion H + , indicating that the solid-state hydrogen ion selective electrode prepared in Example 2 has a certain selectivity for H + .

[0093] Experimental Example 5

[0094] In this experimental example, the bending resistance of the flexible solid-state hydrogen ion sensor prepared in Example 5 was investigated. Using the flexible solid-state hydrogen ion sensor and the flexible solid-state hydrogen ion sensor in the bent 120° state as the working electrodes, and the saturated calomel electrode as the reference electrode, the open-circuit potentials of the flexible solid-state hydrogen ion sensor in the normal state and the flexible solid-state hydrogen ion sensor in the bent 120° state at pH values between 4 and 8 were measured by the electrochemical open-circuit potential test using a self-made small multi-channel potentiometer. The results are as Figure 10 shown. Figure 10 In (a), the potential response curves of the flexible solid-state hydrogen ion sensor in the normal state and the flexible solid-state hydrogen ion sensor in the bent 120° state are shown. In (b), the potential response correction curves of the flexible solid-state hydrogen ion sensor in the normal state and the flexible solid-state hydrogen ion sensor in the bent 120° state are shown. Figure 10 Comparing (a) and (b), it can be seen that the potential response difference between the flexible solid-state hydrogen ion sensor in the normal state and the flexible solid-state hydrogen ion sensor in the bent 120° state at pH values between 4 and 8 is about 10 mV, and the slope has no obvious decrease, indicating that the flexible solid-state hydrogen ion sensor prepared in Example 5 has good bending resistance.

[0095] Experimental Example 6

[0096] This experimental example is a sweat test to investigate the detection effect of the flexible solid-state hydrogen ion sensor prepared in Example 5 on H + in human sweat. Using the flexible solid-state hydrogen ion sensor as the working electrode and the saturated calomel electrode as the reference electrode, the real-time concentration of H + in human sweat was detected by the electrochemical open-circuit potential test method using a self-made small multi-channel potentiometer when the volunteer was running. During the test, the sweat secreted by the volunteer would flow through the flexible solid-state hydrogen ion sensor attached to the human skin. The results are as Figure 11 shown. Figure 11(a) shows the real-time potential diagram of human sweat test, (b) shows the potential response curves of the flexible solid-state hydrogen ion sensor before and after sweat test, (c) shows the potential-hydrogen ion activity calibration curves before and after sweat test, and (d) shows the test results of the sensor and the results of the precision pH test paper during sweat test. From Figure 11 (a), it can be seen that at the beginning of the test, since there was not enough sweat in contact with the electrode surface, the potential fluctuated irregularly. At about 820 seconds, the volunteer started to sweat and the potential tended to be stable. From Figure 11 (b), it can be seen that the potential response of the flexible solid-state hydrogen ion sensor to H + before and after the sweat test differed by 15 mV, and the slope decreased from -42.64 mV / pH to -39.65 mV / pH. The reason for the slight decrease in performance may be that there was excessive wear between the electrode surface and the skin during the sweat test, resulting in a decrease in the performance of the working electrode and the reference electrode. From Figure 11 (d), it can be seen that by testing the sweat secreted during the test with a precision pH test paper, it can be obtained from the figure that the result obtained by the precision pH test paper is pH equal to 6.4, while the result measured by the sensor is 6.5. Therefore, it can be obtained that the measurement accuracy of the sensor is as high as 98%, indicating that the sensor has good detection performance and has great prospects for further commercial application.

[0097] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions, and variations to these embodiments still fall within the protection scope of the present invention.

Claims

1. A preparation method of a flexible solid hydrogen ion sensor, characterized in that, The method comprises the following steps: (1) Add Ti3AlC2 to a hydrofluoric acid solution, stir, centrifuge and wash, and dry to obtain HF-Ti3C2T x ; (2) Weigh HF-Ti3C2T x , measure Nafion solution, disperse it in water to obtain a mixed system A; (3) After cleaning the PET sheet, performing plasma re-cleaning, drying, magnetron sputtering metal on the PET sheet, coating a layer of PDMS and drying to obtain a flexible solid-state electrode; (4) Drop-coating the mixed system A on the surface of the flexible solid-state electrode and drying to obtain a flexible solid-state hydrogen ion sensor.

2. The preparation method of the flexible solid-state hydrogen ion sensor according to claim 1, wherein, The hydrofluoric acid solution is a 20-49 wt% hydrofluoric acid solution, and the water is deionized water.

3. The preparation method of the flexible solid-state hydrogen ion sensor according to claim 1, characterized in that, The dosage of the hydrofluoric acid solution is 5 to 40 mL; the mass of the Ti3AlC2 is 0.5 to 2 g; the mass of the HF-Ti3C2T x is 5 to 20 mg; the dosage of the Nafion solution is 50 to 400 μL; the water dosage is 600 to 950 μL; the size of the PET thin sheet is 7 cm × 7 cm to 8 cm × 8 cm; the metals are Cr and Ag.

4. The preparation method of the flexible solid-state hydrogen ion sensor according to claim 1, characterized in that, In step (1), the stirring time is 24 h, centrifugal cleaning is performed using deionized water, the rotation speed per minute of centrifugation is 3500 rpm, the centrifugation time is 5 min, and the centrifugal cleaning process is repeated until the pH of the supernatant is greater than or equal to 6.

5. The preparation method of the flexible solid-state hydrogen ion sensor according to claim 1, characterized in that, In step (1), drying is carried out in a vacuum environment, the drying temperature is 60 °C, and the drying time is 12 h.

6. The preparation method of the flexible solid-state hydrogen ion sensor according to claim 1, characterized in that, In step (2), the dispersion is ultrasonic dispersion, and the dispersion time is 1 h.

7. The preparation method of the flexible solid-state hydrogen ion sensor according to claim 1, wherein In step (3), the cleaning process of the PET sheet is to ultrasonically clean the PET sheet in isopropanol, ethanol, and deionized water in sequence, with each ultrasonic cleaning time being 2 min. The plasma re-cleaning is carried out in a plasma cleaner for 5 min, and the drying gas is N2.

8. The preparation method of the flexible solid-state hydrogen ion sensor according to claim 1, characterized in that, In step (3), Cr is sputtered first, and then Ag is sputtered. The thickness of Cr is 5-30 nm, the thickness of Ag is 100-300 nm, the drying temperature is 90 °C, and the drying time is 40 min.

9. The preparation method of the flexible solid-state hydrogen ion sensor according to claim 1, wherein In step (4), the dosage of the mixed system A is 5-20 μL, drying is carried out in a vacuum environment, the drying temperature is 60 °C, and the drying time is 1 h.

10. A flexible solid-state hydrogen ion sensor prepared by the preparation method according to any one of claims 1-9.

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