A nanowire-based seawater temperature and salinity sensor and a preparation method thereof

Abstract

The application belongs to the technical field of seawater temperature and salinity sensors, and particularly relates to a seawater temperature and salinity sensor based on nanowires and a preparation method thereof, which comprises a temperature sensing electrode and a conductivity sensing electrode, the temperature sensing electrode uses a grid-shaped platinum resistance film as a temperature sensitive unit, the conductivity sensing electrode comprises seven parallel strip-shaped conductive electrodes, and the temperature sensing electrode and the conductivity sensing electrode are deposited with copper-nickel alloy nanowires on surfaces thereof.The copper-nickel nanowire temperature and salinity electrode has high specific surface area and good thermal conductivity, so that the temperature electrode can instantaneously sense seawater temperature changes and has uniform temperature, and measurement distortion is avoided, and accuracy is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of seawater temperature and salinity sensors, and particularly relates to a seawater temperature and salinity sensor based on nanowires and a preparation method thereof. BACKGROUND

[0002] Temperature and salinity, as core parameters representing the characteristics of the ocean, directly reflect the rules of ocean circulation, water mass movement and air-sea interaction, and play an irreplaceable role in oceanography research, climate prediction and marine resource development. Electrode-type seawater salinity sensors have become the mainstream equipment for salinity detection due to their high measurement accuracy and fast response speed, but they face many technical bottlenecks in harsh marine environments.

[0003] Existing electrode-type sensors generally use platinum black as electrode material. However, such electrodes have significant defects in practical application: first, platinum black is essentially a loose and porous particle accumulation structure, which is prone to coating peeling under the impact of sea currents or biological disturbance, leading to irreversible decay of electrode surface morphology and electrochemical performance. High salt, high pressure, pollutants and microorganisms in the marine environment can cause the platinum black layer to fall off, resulting in physical structure damage and chemical performance degradation of the electrode surface; second, marine microorganisms and organic pollutants are prone to form insulating biofilms on the rough surface, significantly increasing the interface impedance and causing measurement drift and response delay; third, platinum material is expensive, resulting in high sensor manufacturing costs, which makes it difficult to meet the needs of high-density deployment. Data shows that the continuous working life of traditional platinum black electrodes in nearshore environments is usually no more than 12 months, with a precision decay rate of more than 15%, and the life is even shorter in deep-sea environments. These problems seriously restrict the construction and upgrading of the marine salinity monitoring network. SUMMARY

[0004] To address the problems of easy peeling, easy degradation, high cost and short life of traditional platinum black electrodes, the core innovation of the present application is to design a logic with a linear structure as the core, providing a seawater temperature and salinity sensor electrode preparation method based on copper-nickel nanowires.

[0005] A seawater temperature and salinity sensor based on nanowires includes a temperature sensing electrode and a conductivity sensing electrode. The temperature sensing electrode has a grid-shaped platinum resistance film as a temperature sensitive unit, and the conductivity sensing electrode includes seven parallel strip-shaped conductive electrodes. Copper-nickel alloy nanowires are deposited on the surface of the temperature sensing electrode and the conductivity sensing electrode.

[0006] Preferably, the copper-nickel alloy nanowires on the temperature sensing electrode have a diameter ranging from 50 to 500 nm, a length of 2 to 60 microns, and a continuous adjustable copper-nickel atomic ratio of 0.5:1 to 3:1. Silicon dioxide or silicon nitride is deposited on the copper-nickel alloy nanowires and the platinum resistance film at a deposition temperature of 150 to 200 degrees Celsius and a thickness of 100 to 200 nanometers.

[0007] Preferably, the copper-nickel alloy nanowire on the conductivity sensing electrode has a diameter ranging from 50 to 500 nm and a length of 20 to 60 μm, the copper-nickel atomic ratio is continuously adjustable within 0.5:1 to 3:1, the conductive electrode is coated with epoxy resin at the external lead, the coating thickness is 1 to 2 mm, and the curing is performed at 30 to 120°C to insulate and package the welding spot of the sensing electrode.

[0008] A preparation method of a nanowire-based seawater temperature and salinity sensor, comprising the following steps:

[0009] S1, using an anodic aluminum oxide template and a polymer porous membrane to form an electrochemical deposition template, and performing activation pretreatment on the template before deposition;

[0010] S2, using a temperature and salinity sensor electrode covering the electrochemical deposition template as a working electrode, a copper-nickel alloy sheet as a counter electrode, and a saturated calomel electrode as a reference electrode, connecting them according to a three-electrode method and placing them in an electrolyte, and performing copper-nickel nanowire deposition by using a constant current method;

[0011] S3, removing the template after deposition and performing cleaning and activation to obtain a copper-nickel nanowire modified temperature and salinity sensor electrode.

[0012] Preferably, the electrochemical deposition template in step S1 is a "anodic aluminum oxide template-polyether sulfone membrane" composite structure, wherein the anodic aluminum oxide template serves as a main template, has a pore diameter of 50 to 500 nm and a thickness of 20 to 120 μm; and the polyether sulfone membrane serves as a support layer, has a pore diameter of 100 to 800 nm and a thickness of 15 to 80 μm.

[0013] Preferably, the pretreatment of the electrochemical deposition template is as follows: immersing the electrochemical deposition template in a dilute hydrochloric acid solution with a volume fraction of 5% to 10% for 1 to 10 seconds; then sequentially placing the template in deionized water and anhydrous ethanol for ultrasonic cleaning, with an ultrasonic power of 100 to 200 W and a cleaning time of 0.1 to 2 minutes each time; and finally placing the cleaned template in a vacuum drying box and drying it at 40 to 70°C for 3 to 5 hours.

[0014] Preferably, the electrolyte solution in step S2 comprises: nickel sulfate with a concentration of 0.2 to 1.8 M, copper sulfate with a concentration of 0.2 to 1.2 M, and boric acid with a concentration of 0.2 to 2.5 M; and the pH value of the deposition solution is adjusted to 3.5 to 5.5.

[0015] The constant current deposition step is as follows: the first step is a nucleation stage, with a current density of 8 to 15 mA / cm² and a deposition charge of 10 to 40 C; the second step is a main growth stage, with the current density being lowered to 2 to 8 mA / cm², and the required deposition charge being calculated according to the remaining length of the target nanowire by the following formula:

[0016] ;

[0017] wherein, is the density of the deposited material, S is the electrode deposition area, is the porosity of the electrochemical deposition template, F is the Faraday constant, n is the number of electrons, is the molar mass of the deposited material, is the target residual thickness.

[0018] Preferably, step S3, soaking in N,N-dimethylacetamide solution at 50-70℃ for 40-80 minutes, peeling off the polyether sulfone filter membrane; soaking in 10-15wt% sodium hydroxide solution at 40℃ for 0.12-4 hours, dissolving and removing the anodic aluminum template; sequentially using seawater and anhydrous ethanol to clean and remove the residual ions on the surface of the copper-nickel nanowire seawater conductivity sensor electrode and activate the copper-nickel nanowire seawater conductivity sensor electrode.

[0019] Compared with the prior art, the application has the following beneficial effects:

[0020] (1) The electrode material prepared by the application has a linear morphology that can naturally construct a three-dimensional interlaced porous network structure. Compared with the particle accumulation structure of traditional platinum black, the electrode material has a higher specific surface area and more abundant electrochemical reaction active sites. At the same time, the linear structure provides a continuous electron transmission path, effectively reduces the charge transmission impedance, and thus improves the response speed and measurement sensitivity of the sensor.

[0021] (2) The copper-nickel nanowire is formed by a template method, and the nanowire and the unmodified temperature sensing electrode and conductivity sensing electrode form a firm metallurgical bond. The linear structure itself has excellent mechanical flexibility and impact resistance, can effectively resist sea current scouring and pressure fluctuations, solves the problem of easy loosening and peeling of the traditional platinum black electrode layer, and prolongs the working life of the electrode in a complex marine environment.

[0022] (3) The application uses low-cost copper and nickel elements to replace noble metal platinum as the main material, and combines the template electrodeposition and magnetron sputtering process that can be mass-produced, greatly reducing the manufacturing cost of the electrode material.

[0023] (4) The application can realize precise control of the diameter, length and alloy composition of the nanowire by precisely adjusting the composition of the deposition solution, the current density and the charge amount. In addition, the surface can be optionally modified with a thin layer of noble metal, which further enhances the corrosion resistance and anti-biofouling ability of the electrode under the premise of limited cost increase, making it suitable for more severe deep sea and eutrophic sea environments. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The overall scheme flow chart of the method;

[0025] Figure 2 The schematic diagram for in-situ growth and regulation of copper-nickel nanowires based on the AAO template-polyether sulfone membrane composite structure;

[0026] Figure 3 The scanning electron microscope graph of the application;

[0027] Figure 4 The cyclic voltammetry test graph carried out under 35 salinity.

[0028] 1 is an epoxy resin, 2 is a temperature and salinity sensor electrode, 3 is silicon dioxide or silicon nitride, 4 is a shielding electrode 1, 5 is a voltage acquisition electrode, 6 is a voltage acquisition electrode, 7 is an excitation electrode, 8 is a voltage acquisition electrode, 9 is a voltage acquisition electrode, 10 is a shielding electrode 2, and 11 is a grid type platinum resistance film temperature sensitive electrode. DETAILED DESCRIPTION

[0029] The following examples are provided to better further understand the present application and are not limited to the best mode, and do not constitute limitations on the content and protection scope of the present application, and any person under the inspiration of the present application or the combination of the present application with other prior art features obtains any product same or similar to the present application, which falls within the protection scope of the present application.

[0030] The specific experimental steps or conditions are not indicated in the examples, and can be operated according to the conventional experimental steps described in the prior art in the field. The reagents and other instruments not indicated by the manufacturer are all conventional reagent products that can be obtained by purchase.

[0031] A nanowire-based seawater temperature and salinity sensor, comprising a temperature sensing electrode and a conductivity sensing electrode, the temperature sensing electrode is a grid type platinum resistance film as a temperature sensitive unit, the conductivity sensing electrode comprises seven parallel strip-shaped conductive electrodes, which are shielding electrode 1 4, voltage acquisition electrode 5, voltage acquisition electrode 6, excitation electrode 7, voltage acquisition electrode 8, voltage acquisition electrode 9, shielding electrode 2 10 and grid type platinum resistance film temperature sensitive electrode 11 in sequence; the temperature sensing electrode and the conductivity sensing electrode are deposited with copper-nickel alloy nanowires.

[0032] The conductivity measuring unit is a seven-electrode array structure, which is formed by seven parallel strip-shaped conductive electrodes arranged in sequence, and is divided into two shielding electrodes at both ends, an excitation electrode in the middle and four groups of voltage acquisition electrodes between the two, through the cooperative working mechanism of excitation signal input and voltage signal acquisition, the stable detection of seawater conductivity is realized.

[0033] The temperature sensitive electrode and the surface of the conductivity measuring electrode are both deposited with copper-nickel alloy nanowires to increase the contact area of the electrode and the seawater medium, and to enhance the response speed and detection accuracy of the temperature and conductivity measuring signals.

[0034] The nanowire modified conductivity sensing electrode is connected with ground shielding terminals at both ends for shielding electromagnetic interference in the seawater environment to ensure signal stability, and the middle electrode is connected with an excitation source for outputting stable excitation electrical signals.

[0035] The copper-nickel alloy nanowires on the temperature sensing electrode have a diameter range of 50-500nm and a length of 2-60μm, and the copper-nickel atomic ratio is continuously adjustable within 0.5:1 to 3:1, and the nanowires are deposited with silicon dioxide or silicon nitride at a deposition temperature of 150-200℃ and a thickness of 100-200nm for wrapping the copper-nickel alloy nanowires and the platinum resistance thin film.

[0036] The copper-nickel alloy nanowires on the conductivity sensing electrode have a diameter range of 50-500nm and a length of 20-60μm, and the copper-nickel atomic ratio is continuously adjustable within 0.5:1 to 3:1, and the conductive electrode is coated with epoxy resin at the external lead, with a coating thickness of 1-2mm and curing at 30-120℃ for insulating and packaging the welding points of the sensing electrode.

[0037] A preparation method of a seawater temperature and salinity sensor based on nanowires, comprising the following steps:

[0038] S1, using an anodic aluminum oxide template and a polymer porous filter film to form an electrochemical deposition template, and performing activation pretreatment on the template before deposition;

[0039] The electrochemical deposition template in step S1 is a "anodic aluminum oxide template-polyether sulfone film" composite structure, wherein the anodic aluminum oxide template serves as the main template, with a pore diameter of 50-500nm and a thickness of 20-120μm; and the polyether sulfone film serves as the support layer, with a pore diameter of 100-800nm and a thickness of 15-80μm.

[0040] The pretreatment of the electrochemical deposition template specifically includes: immersing the electrochemical deposition template in a dilute hydrochloric acid solution with a volume fraction of 5%-10% for 1-10 seconds; then sequentially placing the template in deionized water and anhydrous ethanol for ultrasonic cleaning, with an ultrasonic power of 100-200W and a cleaning time of 0.1-2 minutes each time; and finally placing the cleaned template in a vacuum drying oven for drying at 40-70℃ for 3-5 hours.

[0041] S2, using the temperature-salt sensor electrode covering the electrochemical deposition template as the working electrode, a copper-nickel alloy sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, connecting and placing the electrodes in an electrolyte solution according to the three-electrode method, and depositing copper-nickel nanowires by using the constant current method.

[0042] The electrolyte solution in step S2 includes: the concentration of nickel sulfate is 0.2-1.8M, the concentration of copper sulfate is 0.2-1.2M, and the concentration of boric acid is 0.2-2.5M; and the pH value of the deposition solution is adjusted to 3.5-5.5.

[0043] The constant current deposition step includes: the first step is a nucleation stage, the current density is 8-15mA / cm², and the deposition charge is 10-40C; and the second step is a main body growth stage, the current density is lowered to 2-8mA / cm², and the charge required for the second step deposition is accurately calculated according to the remaining length of the target nanowire by the following formula:

[0044]

[0045] wherein, is the density of the deposition material, S is the deposition area of the electrode, is the porosity of the electrochemical deposition template, F is the Faraday constant, and n is the number of electrons, is the molar mass of the deposition material, is the target remaining thickness.

[0046] Preferably, during the electrochemical deposition process, the deposition temperature is maintained at 30-75℃, and the stirring speed is 150-350r / min.

[0047] S3, after the deposition is completed, the template is removed, and cleaning and activation are performed to obtain a copper-nickel nanowire modified temperature-salt sensor electrode.

[0048] Step S3, soaking in an N,N-dimethylacetamide solution at 50-70℃ for 40-80 minutes to peel off the polyether sulfone filter film; soaking in a sodium hydroxide solution with a concentration of 10-15wt% at 40℃ for 0.12-4 hours to dissolve and remove the anodic aluminum oxide template; and sequentially cleaning with seawater and anhydrous ethanol to remove residual ions on the surface of the copper-nickel nanowire seawater conductivity sensor electrode and activate the copper-nickel nanowire seawater conductivity sensor electrode.

[0049] Embodiment, the experimental parameters are shown in Table 1.

[0050] Table 1 Experimental parameters

[0051]

[0052] ​​The above describes in detail the electrochemical sensor electrode provided by the present application, the preparation method and application thereof. The principles and implementation manners of the present application are described by using specific examples. The above examples are only used to help understand the method of the present application and the core idea thereof. Meanwhile, for those skilled in the art, the specific implementation manners and application ranges can be changed according to the idea of the present application. In summary, the content of the present description should not be understood as a limitation of the present application.

Claims

1. A method for fabricating a seawater temperature and salinity sensor based on nanowires, characterized in that, Includes the following steps: S1 utilizes an anodic aluminum oxide template and a polymer porous filter membrane to form an electrochemical deposition template. The template is activated and pretreated before deposition. The electrochemical deposition template is a composite structure of "anodic aluminum oxide template-polyethersulfone membrane", in which the anodic aluminum oxide template serves as the main template with a pore size of 50-500 nm and a thickness of 20-120 μm; the polyethersulfone membrane serves as the support layer with a pore size of 100-800 nm and a thickness of 15-80 μm. S2, using a temperature and salinity sensor electrode covered with an electrochemical deposition template as the working electrode, a copper-nickel alloy sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, the electrodes are connected in a three-electrode manner and placed in an electrolyte, and copper-nickel nanowires are deposited using a constant current method. The electrolyte solution includes: nickel sulfate at a concentration of 0.2-1.8M, copper sulfate at a concentration of 0.2-1.2M, and boric acid at a concentration of 0.2-2.5M; the pH of the deposition solution is adjusted to 3.5-5.

5. The constant current deposition process is as follows: The first step is the nucleation stage, with a current density of 8-15 mA / cm². 2 The deposition charge is 10-40C; the second step is the main growth stage, where the current density is reduced to 2-8 mA / cm². 2 The amount of charge required for deposition is calculated based on the remaining length of the target nanowire using the following formula: ； in, Where S is the density of the deposited material, and S is the electrode deposition area. The porosity of the electrochemically deposited template is given by F, where F is the Faraday constant and n is the number of electrons. The molar mass of the deposited material. The target remaining thickness; S3. After deposition, the template is removed and the electrode is cleaned and activated to obtain a copper-nickel nanowire modified temperature and salinity sensor electrode. The polyethersulfone filter membrane is peeled off by immersing it in an N,N-dimethylacetamide solution at 50-70℃ for 40-80 minutes; the anodic aluminum oxide template is dissolved and removed by immersing it in a sodium hydroxide solution at 10-15wt% and 40℃ for 0.12-4 hours; the copper-nickel nanowire seawater conductivity sensor electrode is then cleaned with seawater and anhydrous ethanol in sequence to remove residual ions from the surface of the electrode and to activate the electrode. The copper-nickel alloy nanowires on the temperature sensing electrode have a diameter range of 50-500 nm, a length of 2-60 μm, and a continuously adjustable copper-nickel atomic ratio from 0.5:1 to 3:

1. Silica or silicon nitride is deposited at a deposition temperature of 150-200 °C and a thickness of 100-200 nm. These nanowires are used to encapsulate copper-nickel alloy nanowires and platinum resistance films. The copper-nickel alloy nanowires on the conductivity sensing electrode have a diameter range of 50-500 nm and a length of 20-60 μm. The copper-nickel atomic ratio is continuously adjustable from 0.5:1 to 3:

1. Epoxy resin is applied to the conductive electrode and external leads with a coating thickness of 1-2 mm and cured at 30-120℃ to insulate and encapsulate the solder joints of the sensing electrode.

2. The method for preparing a nanowire-based seawater temperature and salinity sensor according to claim 1, characterized in that, The pretreatment of the electrochemical deposition template is as follows: the electrochemical deposition template is immersed in a 5%-10% (v / v) dilute hydrochloric acid solution for 1-10 seconds; then the template is ultrasonically cleaned in deionized water and anhydrous ethanol in sequence, with an ultrasonic power of 100-200W and a cleaning time of 0.1-2 minutes each time; finally, the cleaned template is placed in a vacuum drying oven and dried at 40-70℃ for 3-5 hours.

3. A nanowire-based seawater temperature and salinity sensor, obtained using the preparation method described in any one of claims 1-2, characterized in that, The temperature sensing electrode uses a grid-type platinum resistance film as the temperature-sensitive unit, and the conductivity sensing electrode includes seven parallel strip-shaped conductive electrodes; copper-nickel alloy nanowires are deposited on the surfaces of the temperature sensing electrode and the conductivity sensing electrode.

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