A soil carbonate ion sensor based on CuO-Cu2O heterojunction nanowires, a preparation method thereof and a real-time monitoring device thereof
A sensor based on CuO-Cu2O heterojunction nanowires fabricated on a copper foam substrate solves the selectivity and stability problems of soil CO32− detection in existing technologies, achieving high sensitivity and portable real-time monitoring, suitable for in-situ detection of saline-alkali soils.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHENGZHOU UNIV
- Filing Date
- 2026-04-29
- Publication Date
- 2026-07-24
AI Technical Summary
Existing electrochemical sensors suffer from poor selectivity, instability, and inability to achieve in-situ real-time monitoring when detecting carbonate ions (CO32−) in soil, especially in saline-alkali soils where they are affected by interference from coexisting ions.
Using CuO-Cu2O heterojunction nanowires as the sensing material, Cu(OH)2 nanowires were grown in situ on a copper foam substrate and calcined to form a CuO-Cu2O heterojunction. Combined with a portable electrochemical workstation and wireless communication technology, a portable sensor was constructed to achieve high sensitivity and selectivity for CO32− detection.
It achieves high sensitivity, low detection limit and good selectivity for detecting CO32− in soil, supports rapid on-site detection and remote data transmission, and is suitable for field applications.
Smart Images
Figure CN122448934A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical sensor and soil analysis technology, specifically relating to a soil carbonate ion sensor based on CuO-Cu2O heterojunction nanowires, its preparation method and real-time monitoring device, and applied to in-situ real-time monitoring of soil salinization. Background Technology
[0002] Soil salinization is a significant global problem that restricts agricultural production and damages the ecological environment. Carbonate ions (CO3-) 2− CO32- is a typical alkaline salt in saline-alkali soils, and its content is a key indicator for assessing the degree of soil alkalization and salt composition. Accurate, rapid, and in-situ detection of free CO32- in soil is crucial. 2− Real-time CO3 concentration is of great significance for guiding agricultural irrigation, improving saline-alkali land, assessing ecological environment quality, and studying carbon cycle processes. This is especially true in precision agriculture practices, where real-time acquisition of soil CO3 levels is crucial. 2− Dynamically changing data is an important prerequisite for implementing variable management and precise improvement measures.
[0003] Currently, CO3 in the soil 2− Conventional determinations of CO3 in soil primarily rely on laboratory analysis, such as dual-indicator neutralization titration. While accurate, these methods suffer from inherent drawbacks, including complex sample pretreatment, time-consuming and labor-intensive processes, and the inability to achieve in-situ real-time monitoring. Electrochemical sensing technology, particularly ion-selective electrodes based on potentiometry or amperometric analysis (current detection), demonstrates significant potential in in-situ ion detection due to its advantages such as rapid response, ease of operation, and suitability for miniaturization and integration. However, for CO3 in soil... 2− Direct, highly selective electrochemical sensing remains a challenge. This is due to the lack of specific targets for CO3. 2− Sensitive membrane materials with highly specific recognition sites often face challenges from coexisting ions in the soil (such as Cl-). − SO4 2− HCO3 − It suffers from severe interference from (etc.), as well as problems such as poor stability and short service life in complex soil media.
[0004] In recent years, the rapid development of nanomaterials has provided new ideas for improving the performance of electrochemical sensors. Transition metal oxide nanomaterials, in particular, have attracted widespread attention for constructing highly sensitive and stable electrochemical sensing interfaces due to their tunable electronic structure, high specific surface area, and good chemical stability. Among them, copper oxide (CuO) and cuprous oxide (Cu2O), as two typical p-type semiconductor materials, have been extensively studied in the fields of gas sensing and electrochemical catalysis. Research shows that by constructing CuO-Cu2O heterojunctions at the nanoscale, the charge transfer behavior at the interface can be effectively controlled, significantly enhancing the chemical reactivity of the material surface. This provides a possibility for designing highly sensitive electrochemical interfaces.
[0005] By combining modern Internet of Things (IoT) and wireless communication technologies, and integrating high-performance electrochemical sensors with portable, intelligent data acquisition and transmission modules, it is possible to monitor soil CO3 levels. 2− The gridded, continuous, and remote monitoring of concentrations demonstrates significant application value and broad prospects in building a smart agricultural Internet of Things, achieving dynamic and precise management of saline-alkali land, and conducting large-scale environmental science research. Summary of the Invention
[0006] The purpose of this invention is to provide a soil carbonate (CO3) ion exchanger based on CuO-Cu2O heterojunction nanowires with excellent electrochemical properties. 2− This study utilizes a sensing material to fabricate a highly sensitive and selective electrochemical sensor and an in-situ real-time monitoring device. CuO-Cu2O nanowires with a specific heterostructure are grown in situ on a substrate through chemical oxidation and controlled-temperature calcination of copper foam, serving as the working electrode. The fabricated sensor probe is combined with a circuit module integrating signal acquisition, data processing, and wireless transmission functions to construct a portable monitoring device. This device can detect CO3... 2− When the concentration is abnormal, remote early warning can be achieved through wireless communication.
[0007] To achieve the above objectives, the present invention employs the following technical solution:
[0008] The first step is to clean the foamed copper substrate: commercial foamed copper is placed in ethanol, 0.1 M hydrochloric acid solution and deionized water in sequence, and ultrasonically cleaned to remove surface impurities, and then dried for later use.
[0009] The second step is to synthesize Cu(OH)2 nanowire precursors: the cleaned copper foam is immersed in a mixed aqueous solution containing 2.67M sodium hydroxide (NaOH) and 0.13M ammonium persulfate ((NH4)2S2O8) and reacted at room temperature for 20 minutes to grow Cu(OH)2 nanowires in situ on its surface.
[0010] The third step is the cleaning and drying of the precursor: the sample loaded with Cu(OH)2 nanowires obtained in the second step is taken out and washed several times with deionized water and ethanol alternately, and then placed in a vacuum drying oven at 60°C for 10 hours.
[0011] The fourth step is calcination to construct a heterojunction: the dried sample is placed in a tube furnace and heated to a set temperature (such as 100°C, 200°C or 300°C) at a heating rate of 5°C / min under an air atmosphere, and calcined at this temperature for 4 hours, and then naturally cooled to room temperature; among them, the product obtained by calcination at 300°C is a heterojunction nanowire of CuO and Cu2O, which is the sensitive material required by the present invention;
[0012] After the above steps, the material to which this invention pertains is obtained.
[0013] The soil carbonate ion (CO3) based on CuO-Cu2O heterojunction nanowires described in this invention 2− The preparation method of the electrochemical sensor is as follows:
[0014] (1) Preparation of working electrode: The prepared copper foam material with CuO-Cu2O heterostructure nanowires was cut into a sheet with an area of about 1cm × 1cm to serve as the working electrode and reliably connected to the wire.
[0015] (2) Counter electrode treatment: The carbon rod is polished and cleaned and then used as the counter electrode;
[0016] (3) Sensor probe assembly: Fix the above working electrode and carbon rod counter electrode in parallel relative to each other in the insulating shell, keeping the distance between the two electrodes about 3-5 mm, so that the working surface of the electrode is exposed so that it can be inserted into the soil medium to be tested;
[0017] (4) Circuit connection and system integration: Connect the leads of the working electrode and the counter electrode to the corresponding interfaces of the self-developed portable electrochemical workstation. The workstation uses the ESP32 module as the core controller and integrates a 12-bit precision DAC, operational amplifier filter circuit and a 4-inch capacitive touch screen. It can accurately output the excitation potential from -2.5 V to +2.5 V and collect the micro-current response signal in real time.
[0018] (5) Communication and monitoring functions: Through the dual-band Wi-Fi and Bluetooth communication capabilities of the ESP32 module, the collected current data is uploaded to a mobile phone, computer or cloud server in real time, and the measurement curve is displayed on the touch screen in real time; by setting an appropriate working potential (E0), the amperometric method is used to monitor CO3 in the soil. 2− Quantitative measurement of concentration, obtaining current change (Δi) and CO3. 2−The positive correlation between concentration changes (Δc) is used to complete the sensor fabrication and system integration.
[0019] The soil carbonate ions (CO3-) prepared by this invention based on CuO-Cu2O heterostructured nanowires 2− Electrochemical sensors have the following advantages:
[0020] 1. The preparation process of the sensitive material is simple and the conditions are mild. The precursor can be obtained by one-step oxidation of copper foam in an alkaline oxidizing solution, and then a heterojunction can be formed by a single-temperature calcination step. No complex templates or expensive equipment are required, the cost is low, the reproducibility is good, and it is suitable for large-scale preparation.
[0021] 2. By precisely controlling the calcination temperature, the controllable transformation of Cu(OH)₂ precursor into CuO-Cu₂O heterojunction nanowires was achieved. This heterojunction structure can effectively regulate interfacial charge transfer and significantly enhance the resistance to CO₃²⁻. 2− Its electrochemical responsiveness enables the sensor to possess high sensitivity, low detection limit, and good selectivity, thus achieving the detection of trace CO3 in soil. 2− Rapid and accurate detection;
[0022] 3. The sensor uses copper foam with the sensitive material grown on it directly as the working electrode, avoiding the use of conductive binders and ensuring good electronic conduction and mechanical stability. The entire detection device is centered on a highly integrated portable electrochemical workstation, which is small in size, low in power consumption, and easy to operate. It supports rapid on-site detection and remote data transmission, making it very suitable for field environments and large-scale deployment applications. Attached Figure Description
[0023] Figure 1 Microscopic morphology characterization diagram of sensitive materials.
[0024] Figure 2 XRD patterns of samples from each embodiment.
[0025] Figure 3 Sensors at different CO3 concentrations 2− Current response (It) curve in solution and its calibration curve.
[0026] Figure 4 Selectivity evaluation diagram of the sensor.
[0027] Figure 5 : Long-term stability test diagram of the sensor.
[0028] Figure 6 Schematic diagram of the composition and working principle of a portable monitoring system. Detailed Implementation
[0029] Comparative example:
[0030] The first step involves placing commercial copper foam in ethanol, 0.1 M hydrochloric acid solution, and deionized water in sequence for ultrasonic cleaning to remove surface impurities, followed by drying for later use.
[0031] The second step involves immersing the cleaned copper foam in a mixed aqueous solution containing 2.67 M sodium hydroxide (NaOH) and 0.13 M ammonium persulfate ((NH4)2S2O8) and reacting it at room temperature for 20 minutes.
[0032] The third step is to take out the reacted sample and then place it in a vacuum drying oven at 60°C for 10 hours.
[0033] After the above steps, Cu(OH)2 nanowires, the comparative material, were obtained.
[0034] The soil carbonate ions (CO3-) based on Cu(OH)2 nanowire material described in this invention 2− The preparation method of the electrochemical sensor is as follows:
[0035] (1) The prepared copper foam material with Cu(OH)2 nanowires was cut into sheets with an area of approximately 1.0 cm × 1.0 cm and used as working electrodes. A reliable electrical connection was achieved with it using conductive silver paste and wires;
[0036] (2) Polish a carbon rod with sandpaper until smooth, then clean it with deionized water and ethanol in sequence by ultrasonic cleaning, and dry it to use as a counter electrode.
[0037] (3) Fix the above working electrode and the carbon rod counter electrode in an insulated sensor housing in a parallel and opposite manner, ensuring that the active working surfaces of the two electrodes are exposed, and adjust the distance to 3-5 mm to form a probe that can be directly inserted into the soil medium for detection.
[0038] (4) Connect the leads of the working electrode and the counter electrode to the corresponding interfaces of the self-developed portable electrochemical workstation. The workstation is based on the ESP32 module and has the functions of constant potential application and microcurrent signal acquisition;
[0039] (5) Through the dual-band Wi-Fi and Bluetooth communication functions of the ESP32 module, the collected real-time current data is wirelessly transmitted to a mobile phone, computer or cloud server to realize soil CO3. 2− The remote, real-time monitoring and display of concentration yields the complete sensor monitoring system described in this invention.
[0040] Comparative Example 2:
[0041] The first step involves placing commercial copper foam in ethanol, 0.1 M hydrochloric acid solution, and deionized water in sequence for ultrasonic cleaning to remove surface impurities, followed by drying for later use.
[0042] The second step involves immersing the cleaned copper foam in a mixed aqueous solution containing 2.67 M sodium hydroxide (NaOH) and 0.13 M ammonium persulfate ((NH4)2S2O8) and reacting it at room temperature for 20 minutes.
[0043] The third step is to take out the reacted sample and then place it in a vacuum drying oven at 60°C for 10 hours.
[0044] The fourth step involves placing the dried sample in a tube furnace and heating it to 100°C at a rate of 5°C / min in air atmosphere. The sample is then calcined at this temperature for 4 hours and subsequently cooled naturally to room temperature to obtain nanowire materials mainly composed of CuO-100.
[0045] After the above steps, the material to which this invention pertains is obtained.
[0046] The soil carbonate ion (CO3) based on CuO-100 nanowires described in this invention 2− The preparation method of the electrochemical sensor is as follows:
[0047] (1) The prepared copper foam material with CuO-100 nanowires was cut into sheets with an area of approximately 1.0 cm × 1.0 cm and used as working electrodes. Reliable electrical connection was achieved with it using conductive silver paste and wires;
[0048] (2) Polish a carbon rod with sandpaper until smooth, then clean it with deionized water and ethanol in sequence by ultrasonic cleaning, and dry it to use as a counter electrode.
[0049] (3) Fix the above working electrode and the carbon rod counter electrode in an insulated sensor housing in a parallel and opposite manner, ensuring that the active working surfaces of the two electrodes are exposed, and adjust the distance to 3-5 mm to form a probe that can be directly inserted into the soil medium for detection.
[0050] (4) Connect the leads of the working electrode and the counter electrode to the corresponding interfaces of the self-developed portable electrochemical workstation. The workstation is based on the ESP32 module and has the functions of constant potential application and microcurrent signal acquisition;
[0051] (5) Through the dual-band Wi-Fi and Bluetooth communication functions of the ESP32 module, the collected real-time current data is wirelessly transmitted to a mobile phone, computer or cloud server to realize soil CO3. 2− The remote, real-time monitoring and display of concentration yields the complete sensor monitoring system described in this invention.
[0052] Comparative Example 3:
[0053] The first step involves placing commercial copper foam in ethanol, 0.1 M hydrochloric acid solution, and deionized water in sequence for ultrasonic cleaning to remove surface impurities, followed by drying for later use.
[0054] The second step involves immersing the cleaned copper foam in a mixed aqueous solution containing 2.67 M sodium hydroxide (NaOH) and 0.13 M ammonium persulfate ((NH4)2S2O8) and reacting it at room temperature for 20 minutes.
[0055] The third step is to take out the reacted sample and then place it in a vacuum drying oven at 60°C for 10 hours.
[0056] The fourth step involves placing the dried sample in a tube furnace and heating it to 200°C at a rate of 5°C / min in air atmosphere. The sample is then calcined at this temperature for 4 hours and subsequently cooled naturally to room temperature to obtain nanowire materials mainly composed of CuO-200.
[0057] After the above steps, the material to which this invention pertains is obtained.
[0058] The soil carbonate ion (CO3) based on CuO-200 nanowires described in this invention 2− The preparation method of the electrochemical sensor is as follows:
[0059] (1) The prepared copper foam material with CuO-200 nanowires was cut into sheets with an area of approximately 1.0 cm × 1.0 cm and used as working electrodes. Reliable electrical connection was achieved with conductive silver paste and wires.
[0060] (2) Polish a carbon rod with sandpaper until smooth, then clean it with deionized water and ethanol in sequence by ultrasonic cleaning, and dry it to use as a counter electrode.
[0061] (3) Fix the above working electrode and the carbon rod counter electrode in an insulated sensor housing in a parallel and opposite manner, ensuring that the active working surfaces of the two electrodes are exposed, and adjust the distance to 3-5 mm to form a probe that can be directly inserted into the soil medium for detection.
[0062] (4) Connect the leads of the working electrode and the counter electrode to the corresponding interfaces of the self-developed portable electrochemical workstation. The workstation is based on the ESP32 module and has the functions of constant potential application and microcurrent signal acquisition;
[0063] (5) Through the dual-band Wi-Fi and Bluetooth communication functions of the ESP32 module, the collected real-time current data is wirelessly transmitted to a mobile phone, computer or cloud server to realize soil CO3. 2−The remote, real-time monitoring and display of concentration yields the complete sensor monitoring system described in this invention.
[0064] Example 1:
[0065] The first step involves placing commercial copper foam in ethanol, 0.1 M hydrochloric acid solution, and deionized water in sequence for ultrasonic cleaning to remove surface impurities, followed by drying for later use.
[0066] The second step involves immersing the cleaned copper foam in a mixed aqueous solution containing 2.67 M sodium hydroxide (NaOH) and 0.13 M ammonium persulfate ((NH4)2S2O8) and reacting it at room temperature for 20 minutes.
[0067] The third step is to take out the reacted sample and then place it in a vacuum drying oven at 60°C for 10 hours.
[0068] The fourth step involves placing the dried sample in a tube furnace and heating it to 300°C at a rate of 5°C / min in air atmosphere. The sample is then calcined at this temperature for 4 hours and subsequently cooled naturally to room temperature to obtain a heterojunction nanowire material mainly composed of CuO-Cu2O.
[0069] After the above steps, the material to which this invention pertains is obtained.
[0070] The soil carbonate ion (CO3) based on CuO-Cu2O heterojunction nanowires described in this invention 2− The preparation method of the electrochemical sensor is as follows:
[0071] (1) The prepared copper foam material with CuO-Cu2O heterojunction nanowires was cut into sheets with an area of approximately 1.0 cm × 1.0 cm and used as working electrodes. Reliable electrical connection was achieved with it using conductive silver paste and wires;
[0072] (2) Polish a carbon rod with sandpaper until smooth, then clean it with deionized water and ethanol in sequence by ultrasonic cleaning, and dry it to use as a counter electrode.
[0073] (3) Fix the above working electrode and the carbon rod counter electrode in an insulated sensor housing in a parallel and opposite manner, ensuring that the active working surfaces of the two electrodes are exposed, and adjust the distance to 3-5 mm to form a probe that can be directly inserted into the soil medium for detection.
[0074] (4) Connect the leads of the working electrode and the counter electrode to the corresponding interfaces of the self-developed portable electrochemical workstation. The workstation is based on the ESP32 module and has the functions of constant potential application and microcurrent signal acquisition;
[0075] (5) Through the dual-band Wi-Fi and Bluetooth communication functions of the ESP32 module, the collected real-time current data is wirelessly transmitted to a mobile phone, computer or cloud server to realize soil CO3. 2− The remote, real-time monitoring and display of concentration yields the complete sensor monitoring system described in this invention.
Claims
1. This invention provides a soil carbonate ion sensor based on CuO-Cu2O heterojunction nanowires, its preparation method, and a real-time monitoring device. Its features are: The sensor includes an electrochemical sensing unit with CuO-Cu2O heterojunction nanowires grown in situ on a copper foam substrate as the working electrode. The preparation method of the CuO-Cu2O heterojunction nanowire sensing material includes the following steps: S1: The foamed copper substrate is pretreated by ultrasonic cleaning in dilute acid, acetone, ethanol and deionized water in sequence, and then dried for later use. S2: The pretreated copper foam is immersed in a mixed aqueous solution containing sodium hydroxide (NaOH) and ammonium persulfate ((NH4)2S2O8) and reacted at room temperature for a period of time to generate Cu(OH)2 nanowire precursors in situ on the surface of the copper foam; S3: Take out the copper foam loaded with Cu(OH)2 nanowire precursor obtained in step S2, clean and dry it, and then perform programmed temperature calcination in air atmosphere. By controlling the calcination temperature, the Cu(OH)2 nanowires are transformed into heterojunction nanowires with different CuO and Cu2O ratios, thus obtaining the sensitive material.
2. The preparation method according to claim 1, characterized in that, In step S2, the concentration of NaOH in the mixed aqueous solution is 2.67 M, the concentration of (NH4)2S2O8 is 0.13 M, and the impregnation reaction time of the copper foam is 20 minutes.
3. The preparation method according to claim 1, characterized in that, In step S3, the preferred calcination conditions are: heating to 300°C at a rate of 5°C / min in an air atmosphere and holding for 4 hours to obtain CuO-Cu2O heterojunction nanowire sensitive material.
4. A type of soil carbonate ion (CO3) 2− The working electrode of the electrochemical sensor is characterized in that, The working electrode is composed of a copper foam substrate and a sensitive material layer grown in situ on its surface, wherein the sensitive material layer is a CuO-Cu2O heterojunction nanowire prepared by the method of any one of claims 1-3.
5. A type of soil carbonate ion (CO3) 2− An electrochemical sensor, characterized in that, include: The working electrode as described in claim 4; Together with the counter electrode and reference electrode that match the working electrode, they are integrated into a three-electrode sensing unit.
6. A method for fabricating a soil carbonate ion electrochemical sensor as described in claim 5, characterized in that, Includes the following steps: S1: The working electrode as described in claim 4 is connected to the counter electrode and the reference electrode by a wire and integrated and fixed in an insulating shell, so that the sensitive surface of the working electrode is exposed. S2: Connect the integrated electrode system to the signal lead terminal to form a complete sensor probe.
7. A portable soil carbonate ion monitoring device, characterized in that, include: S1: Soil carbonate ion electrochemical sensor as described in claim 5 or 6; S2: Electrochemical detection and signal acquisition module, connected to the sensor, used to apply a constant potential to the sensor, acquire current response signals, and perform processing and analog-to-digital conversion; S3: Microcontroller module, used to control the detection process, process sensor data and calculate carbonate ion concentration; S4: Wireless communication module, used to upload concentration data and equipment information to a cloud platform or remote server; S5: Power module, which supplies power to the entire device; The sensor, electrochemical detection and signal acquisition module, microcontroller module, wireless communication module and power supply module are integrated and packaged to form an integrated monitoring device.
8. The portable real-time soil carbonate ion monitoring device according to claim 7, characterized in that, The microcontroller module uses an ESP32 chip, and the wireless communication module includes a Wi-Fi and / or Bluetooth unit.