ZnS-TiO2-PVDF sensor for detecting sulfide in diesel fuel, preparation method and application thereof

Abstract

The present invention discloses a ZnS-TiO2-PVDF sensor for detecting sulfides in diesel, as well as its preparation method and application. The sensor includes a substrate, an interdigitated conductive layer is etched on the surface of the substrate, and a ZnS-TiO2-PVDF composite material structure is coated between the interdigitated fingers. The sensor can be used to test the content of thiophene sulfides in diesel. The present invention adopts a spin coating method to prepare the ZnS-TiO2-PVDF sensor, the preparation process is more stable, and the film layer of the sensor sensitive material is more uniform. In the film layer of the sensor sensitive material, the ZnS particles are surrounded by TiO2 particles, and there will be no short circuit between the sensor fingers due to the overlapping of the ZnS particles. The preparation success rate is high; PVDF has an adhesive effect, and the ZnS-TiO2-PVDF composite material is firmly bonded to the surface of the substrate, which reduces the shedding of the sensitive material, and the sensor can exist stably in diesel.

Description

Technical Field

[0001] The present invention belongs to the field of sensor technology, and relates to a sensor for detecting sulfides in diesel, a preparation method and an application thereof, and specifically relates to a ZnS-TiO2-PVDF sensor for detecting thiophene sulfides in diesel, a preparation method and an application thereof. Background Art

[0002] Diesel fuel contains some thiophene-type sulfides. Excessive sulfide content can shorten the lifespan of vehicle engines. The combustion of sulfur-containing organic matter produces gases such as sulfur dioxide, which can then transform into acid rain, harming human health and the natural environment. China, the European Union, and other countries have established sulfur content limits for fuels such as diesel and gasoline. Starting with my country's National V standard, the sulfur content in both gasoline and diesel must not exceed 10 ppm.

[0003] There are currently some methods for testing the sulfur content in diesel. Most of these measurement methods, such as the coulometric method, ultraviolet fluorescence method, and X-ray fluorescence method, require large instruments, have long test cycles, and are less portable. It is necessary to study portable, rapid, highly sensitive, and highly selective sensor detection methods.

[0004] CN116773617A discloses a sensor in which zinc sulfide-zinc oxide core-shell structured nanorods are deposited on FTO conductive glass interdigital electrodes. The sensor is used to detect thiophenes in diesel. The sensor needs to be prepared by a hydrothermal method, which is a complex process. In addition, nanowires are grown in the interdigital region, and the deposited nanowires are not firmly bonded and easily fall off, resulting in a short sensor life. In addition, the nanowires are easily overlapped, causing the sensor to short-circuit and fail to exhibit capacitance. Therefore, the success rate of sensor preparation is low. Summary of the Invention

[0005] The present invention provides a ZnS-TiO2-PVDF sensor for detecting sulfides in diesel, as well as a preparation method and application thereof. A layer of ZnS-TiO2-PVDF composite material is coated on a substrate having an interdigitated conductive layer on the surface to form a sensor for detecting thiophene sulfides in diesel. The sensor can exist stably in diesel. The sensitive material interacts with the thiophene sulfides in diesel, affecting the charge density at the interdigitated positions, thereby generating a change in capacitance. The change in sensor capacitance is detected by a digital bridge measurement (LCR) instrument to thereby detect the concentration of thiophene sulfides in diesel.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A ZnS-TiO2-PVDF sensor for detecting sulfides in diesel comprises a substrate, a surface of the substrate is etched with an interdigitated conductive layer, and a ZnS-TiO2-PVDF composite material structure is coated between the interdigitated layers.

[0008] A method for preparing the above-mentioned ZnS-TiO2-PVDF sensor for detecting sulfides in diesel comprises the following steps:

[0009] Step 1: laser etching the conductive surface of the substrate to produce an interdigitated conductive layer;

[0010] Step 2: Spin coating the ZnS-TiO2-PVDF composite material between the interdigitated conductive layer. The specific steps are as follows:

[0011] Step 21: Add 5-10 mg of nano zinc sulfide particles to 1 ml of titanium dioxide sol and mix them ultrasonically to obtain a ZnS-TiO2 mixed sol system;

[0012] Step 22: Take the prepared ZnS-TiO2 mixed sol system, add PVDF solution, control the volume ratio of the two to be 90-95:5, and ultrasonically mix to obtain a uniformly mixed ZnS-TiO2-PVDF mixed sol system;

[0013] Step 2: Add 15-25 μl of the ZnS-TiO2-PVDF mixed sol system between the interdigitated conductive layer, apply the sol evenly between the interdigitated conductive layer by spin coating, and dry in air to prepare a ZnS-TiO2-PVDF sensor.

[0014] Based on the theory of hard and soft acids and bases, the above-mentioned ZnS-TiO2-PVDF sensor utilizes the sensitive material ZnS as a junction acid, which can undergo chemical adsorption with thiophene molecules as weak bases. The adsorption causes the dielectric constant between the sensor plates to increase, thereby causing the capacitance value of the sensor to increase, generating a capacitive response, which can be used to test the content of thiophene sulfides in diesel.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. During preparation, ZnS is dispersed in TiO2 gel. TiO2 has a film-forming effect, which is beneficial to the dispersion of ZnS particles.

[0017] 2. The spin coating method is used, the preparation process is more stable, and the film layer of the sensor sensitive material is more uniform.

[0018] 3. PVDF has an adhesive effect. The ZnS-TiO2-PVDF composite material is firmly bonded to the substrate surface, reducing the shedding of sensitive materials. The sensor can exist stably in diesel.

[0019] 4. In the sensor sensitive material film layer, ZnS particles are surrounded by TiO2 particles, which will not cause short circuits between sensor fingers due to overlapping of ZnS particles, and the preparation success rate is high.

[0020] 5. The capacitance response of the LCR detection sensor is at the pF level, with fast response and high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of FTO interdigital sensor;

[0022] Figure 2 This is an optical microscopic magnification of the ZnS-TiO2-PVDF composite material on the FTO interdigital electrode of the sensor;

[0023] Figure 3 This is the sensitivity test diagram of ZnS-TiO2-PVDF sensor to different concentrations of benzothiophene in diesel;

[0024] Figure 4 The response curve of the ZnS-TiO2-PVDF sensor in diesel containing 40 ppm benzothiophene and its subsequent recovery curve in blank diesel;

[0025] Figure 5 This is a test chart for the discrimination of benzothiophene, dibenzothiophene, indole, and carbazole at different concentrations. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0027] The present invention provides a ZnS-TiO2-PVDF sensor for detecting sulfides in diesel. The sensor comprises a substrate, a surface of the substrate having an interdigitated conductive layer etched thereon, and a ZnS-TiO2-PVDF composite material structure coated between the interdigitated layers, wherein:

[0028] The substrate is a conductive glass (FTO) substrate;

[0029] The interdigitated conductive layer is made by laser etching a substrate;

[0030] The material of the interdigitated conductive layer is fluorine-doped tin dioxide;

[0031] The interdigitated conductive layer has an interdigitated spacing of 100 μm. If the interdigitated spacing is too large, the sensitivity of the sensor will decrease. If the interdigitated spacing is too small, the sensor manufacturing process will be too demanding, resulting in an increase in manufacturing costs.

[0032] In the present invention, the surface of the sensor is coated with a ZnS-TiO2-PVDF composite material structure. This sensor and its sensitive material can exist stably in diesel. The interaction between its sensitive material and thiophene sulfide will affect the charge density at the interdigital position, thereby causing a change in capacitance. The sensitive material is mainly ZnS material, TiO2 plays a film-forming role, and PVDF plays a bonding role.

[0033] A method for preparing the above-mentioned ZnS-TiO2-PVDF sensor for detecting sulfides in diesel comprises the following steps:

[0034] Step 1: laser etching the conductive surface of the substrate to produce an interdigitated conductive layer;

[0035] Step 2: Spin coating the ZnS-TiO2-PVDF composite material on the sensor surface. The specific steps are as follows:

[0036] Step 21: Prepare PVDF sol with a mass fraction of 1-5%;

[0037] Step 22: Prepare nano zinc sulfide particles by a hydrothermal method: prepare a mixed solution of 0.4 mol / L sodium thiosulfate pentahydrate (Na2S2O3·5H2O) and 0.4 mol / L zinc acetate dihydrate (Zn(CH3COO)2·2H2O), stir for 30 minutes, add 30 ml of the above-prepared solution to a 50 ml reactor, and place the reactor in a blast oven and heat at 150°C for 12 hours. Cool naturally to room temperature, pour out the solid product, wash it with deionized water and ethanol by centrifugation, and dry it in an oven at 80°C to obtain ZnS solid particles;

[0038] Step 2: Prepare titanium dioxide sol: Use chemically pure organic tetrabutyl titanate (Ti(OC4H9)4) as a precursor, dissolve it in anhydrous ethanol, and slowly add water to hydrolyze Ti(OC4H9)4 to obtain a stable TiO2 gel. The molar ratio of the raw materials in the preparation process is: n[Ti(OC4H9)4]:n[EtOH]:n[H2O]=3:4:3.

[0039] Step 24: Add 5-10 mg of nano zinc sulfide particles to 1 ml of titanium dioxide sol and mix by ultrasonication to obtain a ZnS-TiO2 mixed sol system;

[0040] Step 25: Take the prepared ZnS-TiO2 mixed sol system, add PVDF solution, control the volume ratio of the two to be 90-95:5, and ultrasonically mix to obtain a uniformly mixed ZnS-TiO2-PVDF mixed sol system;

[0041] Step 26: Add 15-25 μl of the ZnS-TiO2-PVDF mixed sol system between the interdigitated conductive layer, apply the sol evenly between the interdigitated conductive layer by spin coating, and dry in air to obtain a ZnS-TiO2-PVDF sensor, thereby integrating the sensitive material on the substrate surface.

[0042] The above-mentioned ZnS-TiO2-PVDF sensor can be used to test the content of thiophene sulfides in diesel. The specific testing method is as follows: connect the external wire of the ZnS-TiO2-PVDF sensor to a digital bridge meter (LCR), place the ZnS-TiO2-PVDF sensor in diesel, and test the capacitance change of the ZnS-TiO2-PVDF sensor in diesel samples with different benzothiophene concentrations, wherein: after the ZnS-TiO2-PVDF sensor is connected to the LCR, it is first immersed in a blank diesel sample solution to obtain a baseline value; when testing the capacitance of the ZnS-TiO2-PVDF sensor, the LCR meter is set to a voltage of 1V and a frequency of 10kHz.

[0043] Example 1:

[0044] Step 1: The FTO substrate with the conductive layer laser-etched into an interdigitated shape was first placed in ethanol for ultrasonic cleaning for 10 minutes, then placed in deionized water for ultrasonic cleaning for 10 minutes, and then taken out and dried in an oven at 50°C.

[0045] Step 2: Prepare a mixed solution of 0.4 mol / L sodium thiosulfate pentahydrate and 0.4 mol / L zinc acetate dihydrate and stir for 30 minutes.

[0046] Step 3: Add 30 ml of the solution prepared in step 2 to a 50 ml reactor, and place the reactor in a homogeneous reactor and heat at 150° C. for 12 h.

[0047] Step 4: Cool naturally to room temperature, pour out the solid product, wash it by centrifugation twice with deionized water and ethanol respectively, and then dry it in an oven at 80°C.

[0048] Step 5: Dissolve organic butyl titanate (Ti(OC4H9)4) as a precursor in anhydrous ethanol and slowly add water to hydrolyze the Ti(OC4H9)4 to produce a TiO2 gel. The molar ratio of the raw materials is n[Ti(OC4H9)4]:n[EtOH]:n[H2O] = 3:4:3.

[0049] Step 6: Take 10 mg of zinc sulfide prepared in step 4 and add it to 1 ml of titanium dioxide sol prepared in step 5, and mix by ultrasonic mixing for 30 minutes.

[0050] Step 7: Take the prepared ZnS-TiO2 mixed sol system, add 3% by mass of PVDF sol in a volume ratio of 95:5, and ultrasonically mix for 30 minutes to obtain a uniformly mixed ZnS-TiO2-PVDF mixed sol system.

[0051] Step 8: Take 20 μl of the sol mixture prepared in step 7 and drop it on the FTO surface for spin coating. Control the speed to 400 rpm and the rotation time to 10 min to evenly coat the sol on the FTO surface. Dry it in air for 1 h. After the sol solidifies, it is deposited and fixed on the electrode surface to obtain a ZnS-TiO2-PVDF sensor.

[0052] Step 9: Apply conductive glue to the two conductive ends of the FTO, connect it to the LCR meter with a wire, and set the LCR voltage to 1V and the frequency to 100kHz.

[0053] Step 10: Place the sensor in a blank diesel sample to obtain a stable baseline value. The sensor is then placed in diesel solutions containing benzothiophene at varying concentrations. The sensor will exhibit different capacitive responses in these solutions. The benzothiophene concentration in the diesel can be determined based on the sensor's capacitive responses.

[0054] Step 10: Place the sensor in a blank diesel sample to obtain a stable baseline value. Then, place it in a diesel solution with a 40 ppm benzothiophene concentration, and finally transfer it back to the blank diesel sample. Test the sensor's response in the 40 ppm benzothiophene diesel solution and its recovery in the blank diesel sample.

[0055] The schematic diagram of the sensor with the FTO conductive surface etched into interdigitated shapes is shown in the figure. Figure 1 As shown in Figure 1, the conductive layer is F-doped SnO2, and the finger spacing is 100μm. The microscopic magnification of the ZnS-TiO2-PVDF composite material structure on the FTO substrate of the sensor is shown in Figure 1. Figure 2 As shown by Figure 2 It can be seen that the zinc sulfide particles are evenly distributed in the titanium dioxide gel. The capacitance response test of the ZnS-TiO2-PVDF sensor for diesel samples containing different concentrations of benzothiophene is shown in the figure below. Figure 3 As shown by Figure 3 It can be seen that the sensor produces different capacitance responses in samples with different concentrations of benzothiophene, indicating that the sensor has good sensitivity. The response curves of the ZnS-TiO2-PVDF sensor in diesel containing 40ppm benzothiophene and the recovery curves in blank diesel are shown in Figure 2. Figure 4 As shown by Figure 4It can be seen that when the sensor is transferred from a blank diesel sample to a 40ppm concentration of benzothiophene diesel solution, it takes more than ten seconds to establish a stable capacitive response signal. When the sensor is further transferred to a blank diesel sample, it takes about 500s for the sensor to decrease to a level close to the initial signal, indicating that the thiophene substances bound to the sensor surface need a certain amount of time to return to their initial state.

[0056] Example 2:

[0057] This embodiment differs from embodiment 1 in that 5 mg of ZnS material was added to 1 ml of TiO2 sol when preparing the ZnS-TiO2 mixed sol system, while other conditions remained unchanged. Due to the reduction in the amount of effective sensitive material, the sensor response intensity was weakened.

Claims

1. A method for preparing a ZnS-TiO2-PVDF sensor for detecting sulfides in diesel, characterized in that The method comprises the following steps: Step 1: laser etching the conductive surface of the substrate to produce an interdigitated conductive layer; Step 2: Spin coating the ZnS-TiO2-PVDF composite material between the interdigitated conductive layer. The specific steps are as follows: Step 2:

1. Add 5-10 mg of nano zinc sulfide particles to 1 ml of titanium dioxide sol and mix by ultrasonication to obtain a ZnS-TiO2 mixed sol system; Step 22: Take the prepared ZnS-TiO2 mixed sol system, add PVDF solution, control the volume ratio of the two to be 90-95:5, and ultrasonically mix to obtain a uniformly mixed ZnS-TiO2-PVDF mixed sol system; Step 2 and step 3: add 15-25 μl of the ZnS-TiO2-PVDF mixed sol system between the interdigitated conductive layer, apply the sol evenly between the interdigitated conductive layer by spin coating, and dry in air to prepare a ZnS-TiO2-PVDF sensor.

2. The preparation method of the ZnS-TiO2-PVDF sensor for detecting sulfide in diesel according to claim 1, characterized in that The substrate is a conductive glass substrate.

3. The preparation method of the ZnS-TiO2-PVDF sensor for detecting sulfide in diesel according to claim 1, characterized in that The interdigitated conductive layer is made by laser etching a substrate.

4. The preparation method of the ZnS-TiO2-PVDF sensor for detecting sulfide in diesel according to claim 1 or 3, characterized in that The material of the interdigitated conductive layer is fluorine-doped tin dioxide.

5. The preparation method of the ZnS-TiO2-PVDF sensor for detecting sulfide in diesel according to claim 4, characterized in that The interdigitated conductive layer has an interdigitated distance of 100 μm.

6. A ZnS-TiO2-PVDF sensor prepared by the method according to any one of claims 1 to 5 for measuring the content of thiophene sulfides in diesel.

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