Self-generating water ion detector and preparation method and application thereof

Abstract

The invention discloses a self-power-generation water body ion detector and a preparation method and application thereof, and relates to the technical field of environmental monitoring and electronics, a silk fibroin coating is combined to a ZnO nano array, the cooperation of ion selectivity enhancement and self-power-generation effect is effectively realized, and the ion detection sensitivity and stability are remarkably improved. The self-generating water ion detector sequentially comprises a substrate, a ZnO nano array, a silk fibroin coating and a packaging protection layer from bottom to top, the edge of the ZnO nano array is connected with a copper foil lead through a conductive silver adhesive to form a piezoelectric output electrode. According to the invention, an ion concentration signal is converted into a stable electric signal by utilizing a water photovoltaic effect, the detection of ions in a self-powered water body without an external power supply is realized, and meanwhile, the equipment has the advantages of high sensitivity, long endurance time, stable mechanical property and the like, and has important application value in remote water quality monitoring.

Description

Technical Field

[0001] The present invention relates to the field of environmental monitoring and electronic technology, and in particular to a self-generating water ion detector and a preparation method and application thereof. Background Art

[0002] Real-time monitoring of ion concentrations in water is a core requirement for environmental governance, industrial process control, and public health safety. Existing monitoring technologies primarily rely on electrochemical sensors and spectral analysis devices, but these devices suffer from a series of significant drawbacks in practical applications: First, they require continuous external power, making deployment in remote areas expensive and unstable. Second, traditional detectors in complex water bodies are not very durable, require frequent calibration, and are easily damaged by water erosion or physical impact, resulting in high replacement and maintenance costs. Third, their low sensitivity makes it difficult to meet trace detection requirements, making real-time monitoring impossible and making it difficult to capture sudden events. Therefore, there is an urgent need for a self-generating sensor device that does not require an external power source, can achieve high sensitivity, and operates stably over a long period of time, to enable real-time monitoring of ions in water.

[0003] Hydrovoltaic technology is an emerging energy technology that uses the interaction between water and materials to generate electricity. Its core lies in converting natural processes such as water flow, evaporation, humidity changes or capillary action into electricity. This technology breaks through the limitations of traditional hydropower generation and is particularly suitable for nanoscale energy collection. λ D ) is the core parameter that describes the thickness of the double layer, indicating the range of ion shielding on surface charges and is mainly determined by the ionic strength. When the diameter of the nanochannel is the same as the Debye length, the double layer will overlap, allowing ions to pass selectively, resulting in a potential difference before and after the channel, thereby generating a voltage. Based on this, according to the relationship between voltage and ionic strength changes, the characteristic of hydrovoltaic technology that can spontaneously generate electricity can be used to select suitable materials to make ion detectors. However, the existing hydrovoltaic effect ion detectors generally have the following shortcomings: the materials used are single, mainly simple nanomaterials, and the synergistic effect of materials is not achieved; the structural design of the device is mostly a single planar structure, and a macroscopic three-dimensional structural system has not been formed, making it difficult to simultaneously meet the requirements of high sensitivity, high output power and long-term stability; the lack of effective packaging and protection technology makes the device less stable in complex natural environments and long-term use, and its application range is significantly limited.

[0004] In summary, in view of the problems of single material, simple structure, limited performance and difficulty in application in the prior art, it is expected in the field to develop a device which is based on the synergistic combination of multiple materials and simultaneously realizes efficient self-power generation and high-sensitivity ion concentration detection by using the water-induced effect. The device not only breaks away from the shackles of external power supply, but also realizes a breakthrough in detection sensitivity, response speed and long-term stability, and is especially suitable for remote real-time monitoring of water environment in remote areas. SUMMARY

[0005] The present application aims to overcome the deficiencies of the prior art, and provides a self-power generation water body ion detector, a preparation method and application thereof. The present application proposes a self-power generation water body ion detector which combines a silk fibroin functional coating and a ZnO nano array. The device significantly improves the ion detection sensitivity, response speed and environmental adaptability by using an innovative multi-scale structure and material combination, converts the ion concentration into an electrical signal by using the water-induced effect, and realizes the detection of ions in the water body. At the same time, the device has the advantages of high sensitivity, long endurance time and stable mechanical properties, and has important application value in water body ion monitoring.

[0006] The technical scheme for solving the above technical problems is as follows: a self-power generation water body ion detector is provided, which comprises, from bottom to top, a substrate, a ZnO nano array, a silk fibroin coating and a packaging protective layer; the edge of the ZnO nano array is connected to a copper foil lead by conductive silver glue to form a piezoelectric output electrode.

[0007] The beneficial effects of the technical scheme of the present application are as follows: the ZnO nanowire array utilizes the mechanical deformation caused by water flow impact to output an alternating voltage of 1-3 V by using the water-induced effect. The silk fibroin coating is used as a functional layer, and a controllable gradient nano channel structure is adopted, and the channel size is accurately matched with the Debye length: the double-layer overlap is enhanced at low concentration to improve selectivity, and the ion shielding effect is dominant at high concentration. By combining the silk fibroin coating with the ZnO nano array, the ion selectivity enhancement and the self-power generation effect are effectively realized, and the detection sensitivity and stability are significantly improved. The integrated structure of the nano array + silk fibroin coating + micro channel realizes the detection of ion concentration of 10 -8 -10 0 M full-coverage high-sensitivity monitoring. The device integrates multiple advanced processes such as hydrothermal growth, pressure embedding into PDMS, laser etching micro channel and hot-pressing FEP packaging, and effectively ensures the integrity of the device structure.

[0008] Further, the material of the substrate is polydimethylsiloxane (PDMS); and the material of the packaging protective layer is fluorinated ethylene propylene copolymer (FEP).

[0009] Further, the density of the ZnO nano array is 2.5 g / cm 3wherein the nanowire has a diameter of 100 nm and a length of 3 μm.

[0010] Further, the silk fibroin coating is aligned with the ZnO nanowire array region.

[0011] Further, the piezoelectric output electrode is connected to a flexible circuit board, and the flexible circuit board is integrated with a Bluetooth transmission module and an energy management unit. The energy management unit rectifies the alternating current output by the ZnO and stores the alternating current into a capacitor. The Bluetooth transmission module wirelessly transmits ion concentration data.

[0012] The beneficial effects of the technical scheme of the present application are as follows: the alternating current generated by the ZnO nanowire array is converted by the rectifier circuit and stored into a 10 F capacitor, which can support the operation of the detection circuit and the Bluetooth module, and the endurance time of the system is significantly better than that of a traditional electrochemical sensor; the Bluetooth module sends the measured data at a certain frequency (for example, once every 10 seconds), so that the data is not missing or omitted, and a wide-area monitoring network can be constructed by connecting a satellite repeater, and a cloud platform generates a ion distribution thermal map and a pollution early warning model in real time.

[0013] Further, a packaging protective layer covers all regions except the electrode contact region.

[0014] The present application also provides a preparation method of the self-powered water body ion detector. (1) etching a titanium foil with hydrofluoric acid, placing the titanium foil in a reaction kettle, adding a growth solution to perform vertical hydrothermal reaction of the titanium foil, and after washing and drying, obtaining a ZnO nanowire array; (2) adhering the ZnO nanowire array obtained in step (1) to a substrate, pressing to embed the ZnO nanowire array into the substrate, and then peeling off the titanium foil to obtain a nanowire substrate; (3) applying silk fibroin on the nanowire substrate obtained in step (2), and then etching a microchannel by laser micromachining technology, aligning with the ZnO nanowire array region, and coating conductive silver glue on the edge of the ZnO nanowire array to connect to a copper foil lead to form a piezoelectric output electrode; (4) covering the regions except the electrode contact region with a packaging protective layer, and then thermal compression bonding.

[0015] Further, in step (1), the growth solution is prepared by dissolving zinc nitrate and hexamethylenetetramine in ammonia water.

[0016] Further, in step (1), the concentration of zinc nitrate is 0.08-0.12 mol / L, and the concentration of hexamethylenetetramine is 0.08-0.12 mol / L.

[0017] Further, in step (1), the pH of the growth solution is 10-12.

[0018] Further, in step (1), the thickness of the titanium foil is 0.1 mm, and the purity is 99%. The titanium foil is cleaned by ultrasonic before use.

[0019] Further, in step (1), the temperature of the titanium foil in the hydrothermal reaction is 80-100℃, and the time is 4-8 h. Water is added regularly during the reaction.

[0020] Further, in step (1), the substrate is PDMS, which is prepared by mixing PDMS prepolymer A component and B component at a mass ratio of 10:1, adding a diluent, stirring, pouring into a mold, curing to form a semi-cured film, and then performing oxygen plasma treatment and cooling.

[0021] Further, the diluent is n-hexane.

[0022] Further, in step (2), the pressure is 0.8-1.2 MPa for 4-6 min.

[0023] Further, in step (3), the silk fibroin is coated 3-5 times.

[0024] Further, in step (3), the silk fibroin is coated using a silk fibroin solution with a concentration of 200 mL and a concentration of 0.01wt%.

[0025] Further, in step (3), the silk fibroin is coated to a thickness of 10 nm.

[0026] Further, in step (3), the piezoelectric output electrode is connected to a flexible circuit board.

[0027] Further, in step (4), the hot pressing is performed at 220-280℃ for 8-12 min.

[0028] Further, in step (4), the interface is coated with liquid silicone, and the silicone is cured at 50-70℃ for 1-3 h.

[0029] The application also provides the use of the self-generating water ion detector in water ion detection.

[0030] The application has the following advantages: 1. The application uses ZnO piezoelectric nanowire array as the core of the electric sensor device, which significantly improves the storage of electric energy and accelerates the transmission efficiency of electric charge through the piezoelectric properties of the ZnO array; the functional layer is made of silk fibroin (SF), which can well regulate the formed nanochannel, the channel size is smaller than the Debye length of the solution, and an overlapping double electric layer is formed; finally, fluorinated ethylene propylene (FEP) is selected as the packaging protective layer of the device, which can ensure that the device can still operate stably for a long time in complex natural environment.

[0031] 2、The device of the application utilizes the water-induced effect to convert the output voltage value into the corresponding ion concentration value, realizes real-time monitoring of the ion concentration of the water body, and at the same time, the generated electric energy can be stored, which makes up for the shortcomings of the existing detector, such as unstable output value, easy data loss and difficult to work in harsh environment, thereby significantly improving the performance of the device, and is expected to meet the remote detection of water ions.

[0032] 3、The device of the application flexibly combines the PDMS substrate (Young's modulus 1 MPa) with the ZnO nanowire array, and can still maintain stable performance after more than 50% tensile deformation and 1000 bending cycles; at the same time, the FEP film is combined with the functional layer by using a thermal compression bonding process, the interface strength is high, and more complex water areas can be measured; in addition, laser micromachining microchannels are used to guide the water flow to pass through the detection area in a direction, reduce the damage of water flow impact, and further improve the stability and service life of the device; the total thickness of the device is less than 5cm, and the weight is less than 10g, which is convenient for carrying and installation, and can be used for long-term monitoring in the field and remote areas. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of the self-powered water body ion detector of example 1; Figure 2 It is a simulation operation diagram of the self-powered water body ion detector; Figure 3 It is a deionized water detection result diagram of the device prepared by different silk fibroin coating layer numbers; Figure 4 It is a voltage response diagram of the self-powered water body ion detector to different concentrations of NaCl solution; Figure 5 It is a voltage response diagram of the self-powered water body ion detector to ion solutions of different valence states; Figure 6 It is a real-time voltage curve diagram of the self-powered water body ion detector under different mechanical damage. DETAILED DESCRIPTION

[0034] The principles and characteristics of the application are described below, and the examples are only used to explain the application and not to limit the scope of the application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0035] Example 1 A self-powered water body ion detector, the structural schematic diagram is as Figure 1As shown, from bottom to top, it includes PDMS substrate, zinc oxide (ZnO) nanometer array, silk fibroin (SF) coating and FEP encapsulation protection layer in turn; the edge of the ZnO nanometer array is connected to copper foil lead through conductive silver glue to form a piezoelectric output electrode; the piezoelectric output electrode is connected to a flexible circuit board, and the flexible circuit board is integrated with a Bluetooth transmission module and an energy management unit.

[0036] The preparation method thereof comprises the following steps in turn: (1) after etching the titanium foil (thickness of 0.1 mm, purity of 99%) with hydrofluoric acid, it is placed in a reaction kettle, and a growth solution is added to carry out vertical hydrothermal reaction of titanium foil (90℃, 6 h, regular water supplement), after washing and drying, ZnO nanometer array is obtained; the growth solution is composed of 0.1 mol / L zinc nitrate, 0.1 mol / L hexamethylene tetramine and ammonia water, and the pH is 10.5; (2) the ZnO nanometer array obtained in step (1) is attached to the PDMS substrate, 1 MPa pressure for 5 min, the ZnO nanometer array is embedded in the PDMS substrate, then the titanium foil is peeled off, and the nanometer wire substrate is obtained; (3) silk fibroin is applied on the nanometer wire substrate obtained in step (2), and the silk fibroin is applied for 3 times, then laser micro machining technology is used to etch micro channel, which is aligned with the ZnO nanometer array area, and conductive silver glue is coated on the edge of the ZnO nanometer array to connect to the copper foil lead to form a piezoelectric output electrode; the piezoelectric output electrode is connected to a flexible circuit board; (4) use the encapsulation protection layer to cover the area except the electrode contact area, then heat press at 250℃ for 10 min, and then use liquid silicone to cover the interface, and solidify at 60℃ for 2 h.

[0037] Example 2 A self-powered water ion detector, from bottom to top, it includes PDMS substrate, ZnO nanometer array, silk fibroin coating and FEP encapsulation protection layer in turn; the edge of the ZnO nanometer array is connected to copper foil lead through conductive silver glue to form a piezoelectric output electrode; the piezoelectric output electrode is connected to a flexible circuit board, and the flexible circuit board is integrated with a Bluetooth transmission module and an energy management unit.

[0038] The preparation method thereof comprises the following steps in turn: (1) after etching the titanium foil with hydrofluoric acid, it is placed in a reaction kettle, and a growth solution is added to carry out vertical hydrothermal reaction of titanium foil (80℃, 8 h, regular water supplement), after washing and drying, ZnO nanometer array is obtained; the growth solution is composed of 0.08 mol / L zinc nitrate, 0.08 mol / L hexamethylene tetramine and ammonia water, and the pH is 10; (2) The ZnO nanowire array obtained in step (1) is attached to a PDMS substrate, and the ZnO nanowire array is embedded in the PDMS substrate under a pressure of 0.8 MPa for 6 min, and then the titanium foil is peeled off to obtain a nanowire substrate; (3) The nanowire substrate obtained in step (2) is coated with silk fibroin for 4 times, and then a microchannel is etched by using a laser microprocessing technology to align with the ZnO nanowire array region, and a conductive silver glue is coated on the edge of the ZnO nanowire array to be connected to a copper foil lead to form a piezoelectric output electrode; the piezoelectric output electrode is connected to a flexible circuit board; (4) An encapsulation protective layer is used to cover the area except the electrode contact area, and then hot pressing is performed at 220℃ for 8 min, and then a liquid silicone is used to coat the interface and is cured at 50℃ for 3 h.

[0039] Example 3 A self-powered water ion detector includes, from bottom to top, a PDMS substrate, a ZnO nanowire array, a silk fibroin coating layer, and a FEP encapsulation protective layer; the edge of the ZnO nanowire array is connected to a copper foil lead through a conductive silver glue to form a piezoelectric output electrode; the piezoelectric output electrode is connected to a flexible circuit board, and the flexible circuit board is integrated with a Bluetooth transmission module and an energy management unit.

[0040] The preparation method thereof comprises the following steps in sequence: (1) The titanium foil is etched with hydrofluoric acid and then placed in a reaction kettle, and a growth solution is added to perform vertical hydrothermal reaction of the titanium foil (100℃, 4 h, and water is supplemented regularly); after washing and drying, a ZnO nanowire array is obtained; the growth solution is composed of 0.12 mol / L zinc nitrate, 0.12 mol / L hexamethylenetetramine, and ammonia water, and the pH is 12; (2) The ZnO nanowire array obtained in step (1) is attached to a PDMS substrate, and the ZnO nanowire array is embedded in the PDMS substrate under a pressure of 1.2 MPa for 4 min, and then the titanium foil is peeled off to obtain a nanowire substrate; (3) The nanowire substrate obtained in step (2) is coated with silk fibroin for 5 times, and then a microchannel is etched by using a laser microprocessing technology to align with the ZnO nanowire array region, and a conductive silver glue is coated on the edge of the ZnO nanowire array to be connected to a copper foil lead to form a piezoelectric output electrode; the piezoelectric output electrode is connected to a flexible circuit board; (4) An encapsulation protective layer is used to cover the area except the electrode contact area, and then hot pressing is performed at 280℃ for 12 min, and then a liquid silicone is used to coat the interface and is cured at 70℃ for 1 h.

[0041] Test Example 1 The self-powered water ion detectors with different coating layers are prepared by referring to the preparation method in Example 1, and then voltage and current value tests are performed, and a simulation operation graph is shown in Figure 2 .

[0042] The 500 mL deionized water was measured into a beaker, the prepared device was put into the water and ensured that the conductive silver paste was completely covered by the deionized water, the Bluetooth was connected to the computer system, the voltage and current were observed in real time, and the data were recorded after stabilization, and the results are shown in Figure 3 .

[0043] It can be seen from Figure 3 that as the number of coating layers gradually increases, the voltage value of the device increases from 0.32 V to 3.48 V, and then decreases to 1.87 V; the current value increases from 30 nA to 122 nA, and then decreases to 86 nA. It is observed that the voltage reaches a peak when the number of coating layers is 3. The results show that the nanopore aperture size of the device is optimized at this number of coating layers.

[0044] Test Example 2 A series of concentration gradients of sodium chloride (NaCl) were configured as test reagents, and the spontaneous electric water ion detector of Example 1 was used for measurement, and a linear fitting was performed on the curve of voltage change with concentration, and the results are shown in Figure 4 .

[0045] It can be seen from Figure 4 that the correlation R 2 is 0.99, and the voltage value of the device changes obviously linearly with different concentrations of ions. According to the equation, the relationship between voltage and concentration can be established, and the ion concentration in the solution can be calculated by the indication of the voltage. According to the equation, it can be seen that the device has a sensitivity of up to 0.389 Vdec -8 in the NaCl concentration range of 10 -1 -10 -1 M. The response speed of the device is fast enough, and the conclusion can be drawn in a short time, avoiding data omission caused by sudden situations.

[0046] Test Example 3 In order to more clearly understand the sensing characteristics of the device and whether it will affect the transmission performance and sensing signal in complex water environment, ion solutions with different valence states were selected, and the voltage of the spontaneous electric water ion detector of Example 1 was detected, and the results are shown in Figure 5 .

[0047] It can be seen from Figure 5 that for monovalent ions, the voltage change amplitude is not very large, and the overall voltage can be maintained above 3 V; when the ion valence state increases to divalent, the generated voltage value decreases significantly to below 2 V; when the ion valence state is trivalent, the generated voltage decreases again.

[0048] Test Example 4 In order to explore whether the device can still maintain the function of outputting signals after being hit in a complex natural environment, the self-generating water ion detector of Example 1 was used as a test device to artificially simulate three types of damage. They are: (1) placing the device in a stirrer with a speed of 1500 rpm for 30 minutes; (2) rubbing the device back and forth by hand for about 150 times; (3) applying a force of 200 N in the four directions of the device for 30 minutes. The test results are shown in Figure 2. Figure 6 shown.

[0049] Depend on Figure 6 It can be seen that although the output signal of the device fluctuates slightly after the three types of damage, it generally remains at around 3 V, indicating that the mechanical properties of the device are good and it can adapt to complex environments.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A self-generating water ion detector, characterized in that: From bottom to top, it includes a substrate, a ZnO nanoarray, a silk fibroin coating and an encapsulation protection layer; the edge of the ZnO nanoarray is connected to a copper foil lead through conductive silver glue to form a piezoelectric output electrode.

2. The self-generating water ion detector according to claim 1, characterized in that: The material of the substrate is polydimethylsiloxane; the material of the encapsulation protection layer is fluorinated ethylene propylene copolymer.

3. The self-generating water ion detector according to claim 1, characterized in that: The piezoelectric output electrode is connected to a flexible circuit board, and a Bluetooth transmission module and an energy management unit are integrated into the flexible circuit board.

4. The method for preparing the self-generating water ion detector according to any one of claims 1 to 3, characterized in that: The following steps are included in sequence: (1) The titanium foil is etched with hydrofluoric acid and placed in a reactor. A growth liquid is added to perform a vertical hydrothermal reaction on the titanium foil. After washing and drying, a ZnO nanoarray is obtained. (2) laminating the ZnO nanoarray obtained in step (1) to a substrate, applying pressure to embed the ZnO nanoarray into the substrate, and then peeling off the titanium foil to obtain a nanowire substrate; (3) applying silk fibroin onto the nanowire substrate obtained in step (2), then etching a microchannel using laser micromachining technology to align it with the ZnO nanoarray area, and then coating the edge of the ZnO nanoarray with conductive silver glue to connect it to the copper foil lead to form a piezoelectric output electrode; (4) Use a packaging protective layer to cover the area except the electrode contact area, and then perform thermal compression bonding.

5. The method for preparing the self-generating water ion detector according to claim 4, wherein: In step (1), the growth solution is prepared by dissolving zinc nitrate and hexamethylenetetramine in ammonia water.

6. The method for preparing the self-generating water ion detector according to claim 4, wherein: In step (1), the temperature of the vertical hydrothermal reaction of the titanium foil is 80-100°C and the time is 4-8 hours.

7. The method for preparing the self-generating water ion detector according to claim 4, wherein: In step (2), pressurize at 0.8-1.2 MPa for 4-6 min.

8. The method for preparing the self-generating water ion detector according to claim 4, wherein: In step (3), the silk fibroin is applied 3-5 times.

9. The method for preparing the self-generating water ion detector according to claim 4, wherein: In step (4), hot pressing is performed at 220-280°C for 8-12 min.

10. Use of the self-generating water ion detector according to any one of claims 1 to 3 in water ion detection.

Images