WO2021248669A1

WO2021248669A1 - Cu2+ concentration measurement device and preparation method therefor

Info

Publication number: WO2021248669A1
Application number: PCT/CN2020/107909
Authority: WO
Inventors: 张倩倩; 汤燕梅; 万刘伟; 马正宜; 陈志超
Original assignee: 深圳技术大学
Priority date: 2020-06-12
Filing date: 2020-08-07
Publication date: 2021-12-16
Also published as: CN111650158A

Abstract

Disclosed are a Cu²⁺ concentration measurement device and a preparation method therefor. The device comprises an optical fiber sensor (10), a broadband light source (20) connected to one end of the optical fiber sensor (10) by means of an optical fiber, and an optical fiber spectrometer (30) connected to the other end of the optical fiber sensor (10) by means of an optical fiber, wherein the optical fiber sensor (10) comprises a biconical optical fiber structure (11) and a polymer film layer (12) coating the surface of the biconical optical fiber structure (11), the polymer film layer (12) is an n-layer film of sequentially alternating modified carbon nanotube layers and polyacrylic acid layers, the biconical optical fiber structure (11) is formed by cascading two micro-nano optical fibers, and the micro-nano optical fibers are prepared by tapering single-mode optical fibers. The Cu²⁺ concentration measurement device is easy to carry, and the method for measuring the concentration of Cu²⁺ by using the Cu²⁺ concentration measurement device is simple and convenient to operate, and has low costs and high sensitivity.

Description

A kind of Cu 2+ concentration detection device and preparation method thereof

Technical field

The invention relates to the field of heavy metal ion concentration sensors, in particular to a Cu ²⁺ concentration detection device and a preparation method thereof.

Background technique

Over the years, with the development of industry and technology, the pollution of soil, rivers and even drinking water has become increasingly serious. Wastewater discharged from mining, corrosion, and electronics manufacturing contains large amounts of harmful heavy metal ions and other impurities. Heavy metals are a group of metals with high atomic weight and relatively high density, which are toxic even at low concentrations. The increase in industrial activity has led to heavy metals entering the environment through air, water and soil. Copper is the third most abundant heavy metal necessary for the human body, and it plays an important role in various physiological processes. Copper also has many functions, such as iron absorption, hematopoiesis, various enzyme activities and redox processes. However, excessive intake of copper may cause diarrhea, vomiting, kidney or liver disease. Commonly used Cu ²⁺ detection methods include colorimetry, fluorescence, anodic stripping voltammetry, and atomic absorption. Although these methods usually provide high sensitivity, high selectivity or multi-element analysis, they are time-consuming, complex, and expensive, and require sample preparation and special operational training.

Therefore, the existing technology needs to be improved and developed.

Summary of the invention

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a Cu ²⁺ concentration detection device and a preparation method thereof, aiming to solve the problems of complicated operation, time-consuming and expensive cost of the ^{existing Cu 2+ detection method.}

The technical scheme of the present invention is as follows:

A Cu ²⁺ concentration detection device, which includes an optical fiber sensor, a broadband light source connected to one end of the optical fiber sensor through an optical fiber, and an optical fiber spectrometer connected to the other end of the optical fiber sensor through an optical fiber, and the optical fiber sensor includes a double cone An optical fiber structure and a polymer film layer covering the surface of the biconical optical fiber structure. The polymer film layer is an n-layer film alternately formed by a modified carbon nanotube layer and a polyacrylic acid layer in turn. The biconical optical fiber structure It is composed of two micro-nano optical fibers cascaded, and the micro-nano optical fiber is prepared by tapering a single-mode optical fiber.

In the Cu ²⁺ concentration detection device, 10≤n≤30.

The Cu ²⁺ concentration detection device further includes a fixing clip for fixing the optical fiber.

In the Cu ²⁺ concentration detection device, a glass slide is arranged under the optical fiber sensor.

In the Cu ²⁺ concentration detection device, the wavelength range of the light source of the broadband light source is 1200-1700 nm.

The method for preparing the Cu ²⁺ concentration detection device includes the following steps:

Provide broadband light source and fiber optic spectrometer;

A fiber fusion splicer is used to melt and tap the single-mode optical fiber to obtain a first micro-nano fiber. A second micro-nano fiber with the same parameters is prepared behind the first micro-nano fiber. Two micro-nano fibers are cascaded together to form a double-tapered fiber structure;

Preparing an n-layer film composed of modified carbon nanotube layers and polyacrylic acid layers alternately formed on the surface of the biconical optical fiber structure to obtain an optical fiber sensor;

The two ends of the optical fiber sensor are respectively connected to the broadband light source and the optical fiber spectrometer through optical fibers to prepare the Cu ²⁺ concentration detection device.

The method for preparing the Cu ²⁺ concentration detection device, wherein the step of preparing an n-layer film alternately formed by a modified carbon nanotube layer and a polyacrylic acid layer on the surface of the biconical optical fiber structure to obtain an optical fiber sensor include:

Putting the biconical optical fiber structure into a mixed solution of concentrated sulfuric acid and hydrogen peroxide, and obtaining a pretreated biconical optical fiber structure after heat treatment;

Putting the preprocessed biconical optical fiber structure into a modified carbon nanotube solution, and forming a modified carbon nanotube layer on the surface of the preprocessed biconical optical fiber structure;

Placing the pre-treated biconical optical fiber structure on the surface of the modified carbon nanotube layer into a polyacrylic acid solution to form a polyacrylic acid layer on the surface of the modified carbon nanotube layer;

By repeating the above-mentioned coating process, an n-layer film composed of modified carbon nanotube layers and polyacrylic acid layers alternately formed on the surface of the biconical optical fiber structure after the pretreatment is obtained;

After coating, the pre-processed biconical optical fiber structure is dried, so that the modified carbon nanotube layer and the polyacrylic acid layer are fully reacted and combined to obtain the optical fiber sensor.

In the ^{method for preparing the Cu 2+} concentration detection device, the temperature at which the pre-processed biconical optical fiber structure after coating is dried is 50-80° C., and the time is 3-5 h.

In the ^{preparation method of the Cu 2+} concentration detection device, the preparation of the modified carbon nanotube solution includes the steps:

Add the carbon nanotubes to the concentrated nitric acid solution, treat them at 120°C for 6 hours, cool, filter with suction, wash three times with distilled water, place them in a vacuum drying oven to dry for 8 hours, and grind to obtain modified carbon nanotubes;

The modified carbon nanotubes are added to a 4% acetic acid solution and subjected to ultrasonic treatment, and then magnetically stirred at 80° C. for 2 hours to obtain a modified carbon nanotube solution.

The method for preparing the Cu ²⁺ concentration detection device is characterized in that the concentration of the modified carbon nanotube solution is 1 wt%, and the concentration of the polyacrylic acid solution is 35 wt%.

Beneficial effects: The present invention provides a Cu ²⁺ concentration detection device, which includes a biconical optical fiber structure composed of two micro-nano optical fibers cascaded, and the surface of the biconical optical fiber structure is coated with a modified carbon nanotube layer and The polymer film layer is alternately formed by polyacrylic acid layers, and the biconical optical fiber structure whose surface is covered with the polymer film layer constitutes an optical fiber sensor. When the solution to be tested is dripped onto the surface of the optical fiber sensor, the Cu ^{2+ in} the solution to be tested will cause the volume change of the polymer film on the surface of the optical fiber sensor, resulting in a change in refractive index, thereby causing the optical fiber sensor ^{The intensity of the transmission peak of the interference spectrum changes, and the Cu 2+} concentration in the solution to be tested is obtained according to the intensity change of the transmission peak of the interference spectrum. The method for ^{detecting the Cu 2+} ^{concentration by adopting the Cu 2+} concentration detection device of the present invention has simple operation, low cost, easy portability and high sensitivity.

Description of the drawings

FIG. 1 is a schematic structural diagram of a preferred embodiment of ^{a Cu 2+ concentration detection device of the present invention.}

Figure 2 is a schematic diagram of the structure of the optical fiber sensor of the present invention.

Fig. 3 is a flowchart of a preferred embodiment of a method for preparing ^{a Cu 2+ concentration detection device of the present invention.}

detailed description

The present invention provides a Cu ²⁺ concentration detection device and a preparation method thereof. In order to make the objectives, technical solutions and effects of the present invention clearer and clearer, the present invention will be described in further detail below. It should be understood that the specific embodiments described here are only used to explain the present invention, but not used to limit the present invention.

Fiber optic sensors have the advantages of small size, low cost, anti-electromagnetic interference and multiplexing. Among various types of optical fiber sensors, interferometric sensors have attracted widespread attention due to their advantages of large dynamic range, high sensitivity, and high precision. The most commonly used optical fiber interferometers are Michelson type, Sagnac type, Fabry Perot type and Mach-Zehnder type. Among these interferometers, the Mach-Zehnder interferometer (MZ) configuration has obvious advantages, such as simple manufacturing, direct reading and relatively high sensitivity.

The embodiment of the present invention provides a Cu ²⁺ concentration detection device based on Mach-Zehnder interferometer, as shown in FIG. 1 and FIG. The light source 20, and the optical fiber spectrometer 30 connected to the other end of the optical fiber sensor 10 through an optical fiber. The optical fiber sensor 10 includes a biconical optical fiber structure 11 and a polymer film 12 covering the surface of the biconical optical fiber structure 11, The polymer film layer 12 is an n-layer film formed alternately by a modified carbon nanotube layer and a polyacrylic acid layer. The biconical optical fiber structure 11 is composed of two micro-nano optical fibers cascaded, and the micro-nano optical fiber is composed of a single The optical fiber is made by tapering.

In this embodiment, the broadband light source emits a light source, and the light source is transmitted to the optical fiber sensor through an optical fiber. When the solution to be tested is dripped onto the surface of the optical fiber sensor, the Cu ^{2+ in} the solution to be tested will change The volume of the polymer film on the surface of the optical fiber sensor is changed, and the refractive index is changed, thereby causing the transmission peak intensity of the interference spectrum of the optical fiber sensor to change. The optical fiber spectrometer 30 can change the intensity according to the transmission peak intensity of the interference spectrum. ^{Obtain the Cu 2+} concentration in the solution to be tested. ^{The method for detecting Cu 2+} concentration by adopting the Cu ²⁺ concentration detection device of this embodiment is simple to operate, low in cost, easy to carry, and high in sensitivity.

Since the amino functional groups in the polymer film composed of the modified carbon nanotubes and the polyacrylic acid layer can provide lone pairs of electrons, they can be used as a metal ion chelating agent to ^{complex with Cu 2+} in the solution to be tested, and through coordination The bond forms a stable complex, and the surface of the modified carbon nanotube has a large specific surface area and abundant void structure, which can adsorb Cu ²⁺ solution through electrostatic action. Therefore, when the optical fiber sensor coated with the polymer film layer is used to test the solution to be tested, chelation will cause the refractive index of the polymer film layer to change, which in turn causes a change in the interference spectrum. The optical fiber spectrometer 30 can ^{The Cu 2+} concentration in the solution to be tested is obtained according to the intensity change of the transmission peak of the interference spectrum.

In some embodiments, the broadband light source is a dedicated device in the field of optical fiber sensing and optical fiber communication, which has the advantages of wide wavelength range and high output power, and can provide input light for the M-Z interference optical fiber sensor. As an example, the wavelength range of the light source emitted by the broadband light source is 1200-1700 nm.

In some embodiments, as shown in FIG. 2, the optical fiber sensor 10 includes a double-tapered optical fiber structure 11 and a polymer film 12 covering the surface of the double-tapered optical fiber structure 11, and the double-tapered optical fiber structure 11 is composed of Two micro-nano optical fibers are cascaded, and the micro-nano optical fiber is prepared by tapering a single-mode optical fiber. In this embodiment, when the light emitted by the broadband light source reaches the first micro-nano fiber, part of the fundamental mode in the core of the single-mode fiber will be excited into the fiber cladding and become the fiber cladding mode. At the same time, the remaining part of the fiber core fundamental mode continues to stay in the core for transmission. The middle part of the two micro-nano fibers is used as a sensing interference arm. When the light transmitted in the fiber cladding reaches the second micro-nano fiber, the cladding mode in the fiber cladding will be coupled back into the fiber core and interfere with the fundamental mode transmitted in the core. Because of the phase difference between the fundamental mode in the core and the higher-order modes in the cladding, interference peaks are generated, forming a Mach-Zehnder interferometer. The interference light continues to be transmitted in the fiber core, and finally adjusted and displayed by the fiber spectrometer.

In some embodiments, as shown in FIG. 1, the Cu ²⁺ concentration detection device further includes a fixing clip 40 for fixing the optical fiber, and a carrier glass for carrying the solution to be tested is provided under the optical fiber sensor 10 piece.

In some embodiments, the polymer film layer 12 is a 10-30 layer film formed alternately by a modified carbon nanotube layer and a polyacrylic acid layer. In some specific embodiments, in order to find out the optimal number of coating layers, the surface of the biconical optical fiber structure is coated with polymer coatings of different numbers, and the Mach functionalized with the polymer coatings is used. The Zengde optical fiber sensor was put into Cu ²⁺ solution of different concentration for experimental measurement. Through comparison of experimental results, it is found that the optimal number of layers is 16 layers. At this time, when the concentration of copper ions is between 0.1 and 1.0 mM, the sensitivity of the sensor can reach 18.4598 dB/mM.

In some embodiments, a ^{method for preparing a Cu 2+} concentration detection device is also provided, as shown in FIG. 3, which includes the steps:

S10. Provide broadband light source and optical fiber spectrometer;

S20. Use an optical fiber fusion splicer to melt the single-mode optical fiber to obtain a first micro-nano optical fiber, and prepare a second micro-nano optical fiber with the same parameters behind the first micro-nano optical fiber. The second micro-nano optical fibers are cascaded together to form a double-tapered optical fiber structure;

S30, preparing an n-layer film composed of modified carbon nanotube layers and polyacrylic acid layers alternately formed on the surface of the biconical optical fiber structure to prepare an optical fiber sensor;

S40. Connect both ends of the optical fiber sensor with the broadband light source and the optical fiber spectrometer through optical fibers, to produce the Cu ²⁺ concentration detection device.

In some embodiments, the preparation of the double-tapered optical fiber structure includes the step of preparing the micro-nano fiber by using a polarization-maintaining fiber fusion splicer (FSM-100P+, Fujikura) to prepare a single-mode fiber by fusion and taper. First, remove the coating layer of the ordinary single-mode fiber with a fiber stripper, wipe the surface of the fiber with alcohol, then cut the end face of the single-mode fiber flat with a fiber cleaver, and finally put it into the polarization maintaining fiber fusion splicer for fusion splicing and pulling. Cone. During the preparation process of the micro-nano fiber, the single-mode fiber is heated to a molten state by discharging the two electrode rods of the polarization-maintaining fusion splicer. At the same time, the stepping motor of the polarization-maintaining fusion splicer accelerates the movement to pull the fiber Fine to the diameter you want to prepare. In this process, by adjusting the initial speed and acceleration of the stepping motor, the tapered transition zone of the micro-nano fiber with different degrees of gradual change can be obtained. After setting the acceleration of the stepping motor, micro-nano fibers with different diameters can be obtained by controlling the movement time of the stepping motor. Then, by controlling the stepping motor to draw the fiber at a uniform speed, micro-nano fibers of different lengths are obtained. At the same time, the movement time of the stepping motor is kept consistent with the discharge time of the electrode rod, so that the single-mode fiber is always in a state of heating and melting during the movement of the stepping motor. According to the same method, a micro-nano fiber with the same parameters is prepared behind the prepared micro-nano fiber, so that two cascaded micro-nano fibers are used to form a Mach-Zehnder interferometer (that is, a biconical fiber structure).

In some embodiments, the polymer film layer is formed by alternate self-assembly of modified carbon nanotube layers and polyacrylic acid layers through electrostatic interaction. The steps of the optical fiber sensor include:

S31. Put the double-tapered optical fiber structure into a mixed solution of concentrated sulfuric acid and hydrogen peroxide, and obtain a pre-processed double-tapered optical fiber structure after heat treatment;

S32. Put the pre-processed biconical optical fiber structure into a modified carbon nanotube solution, and form a modified carbon nanotube layer on the surface of the pre-processed biconical optical fiber structure;

S33. Put the pre-treated biconical optical fiber structure on the surface of the modified carbon nanotube layer into a polyacrylic acid solution to form a polyacrylic acid layer on the surface of the modified carbon nanotube layer;

S34. By repeating the above-mentioned coating process, after the pretreatment, an n-layer film formed alternately by a modified carbon nanotube layer and a polyacrylic acid layer is obtained on the surface of the biconical optical fiber structure after the pretreatment;

S35. Drying the pre-processed biconical optical fiber structure after the coating is completed, so that the modified carbon nanotube layer and the polyacrylic acid layer are fully reacted and combined to obtain the optical fiber sensor.

The optical fiber sensor prepared by this embodiment has the advantages of simple preparation, easy signal light transmission, high stability, strong anti-electromagnetic interference ability, corrosion resistance, and high sensitivity. It also has the advantages of low cost, light weight, small size, simple structure, and mechanical High strength and other advantages, thereby reducing measurement equipment and expenses, can be widely used in water quality testing, environmental monitoring and other fields.

Specifically, in this embodiment, a modified carbon nanotube solution and a polyacrylic acid solution are pre-configured, wherein the preparation of the modified carbon nanotube solution includes the steps of adding carbon nanotubes to a certain amount of concentrated nitric acid solution, 120 Treated at ℃ for 6 hours, cooled, filtered, washed with distilled water three times, placed in a vacuum drying oven for 8 hours, and ground to obtain modified carbon nanotubes; add 50g of modified carbon nanotubes to 50ml of 4% acetic acid solution , Ultrasonic treatment for 3 min, and then magnetic stirring at 80°C for 2 h to obtain a modified carbon nanotube solution with a concentration of 1 wt%; the surface of the modified carbon nanotube contains functional groups such as hydroxyl, amino, and carbonyl. Protonation is positively charged; the preparation of the polyacrylic acid solution includes the steps of: diluting the polyacrylic acid with deionized water to obtain a polyacrylic acid solution with a concentration of 35 wt%, and the carboxyl groups in the polyacrylic acid solution will be deprotonated and negatively charged.

Secondly, put the fabricated biconical fiber structure into a piranha solution (98% concentrated sulfuric acid and 30% hydrogen peroxide), and heat it at 80°C for 1 hour to remove organic residues on the surface of the fiber structure and remove the hydroxyl groups on the surface of the fiber structure. Then, it is thoroughly cleaned several times with deionized water and ethanol, and dried in a drying box to obtain the pre-treated biconical optical fiber structure.

Next, put the pretreated optical fiber sensor into the 1wt% modified carbon nanotube solution and fully react for 2 minutes, then slowly take it out, and dry it in air for 1 minute. After the pretreatment, the surface of the biconical optical fiber structure is formed. Modified carbon nanotube layer; then put it into a 35wt% polyacrylic acid solution, slowly take it out after 2 minutes, and dry in the air for 1 minute to form a polyacrylic acid layer on the surface of the modified carbon nanotube layer; finally, once again Put it in deionized water for 2 minutes to remove the weakly bound molecules, and then slowly take it out and dry it in the air for 1 minute. Since the modified carbon nanotube layer is positively charged and the polyacrylic acid layer is negatively charged, the two can be assembled layer by layer through electrostatic adsorption to form a uniform polymer film layer. By repeating the above coating process, a complete multi-layer polymer film can be obtained. After the coating, the optical fiber sensor is placed in a constant temperature drying oven at 50-80°C for 3-5 hours to make the modified carbon nanotubes and polyacrylic acid Fully react and combine.

In the present invention, since the amino functional group in the polymer film layer composed of the modified carbon nanotube and the polyacrylic acid layer can provide a lone pair of electrons, it can be used as a metal ion chelating agent to complex ^{with Cu 2+ in the solution to be tested} It can form stable complexes through coordination bonds, and the surface of the modified carbon nanotubes has a large specific surface area and abundant void structure, which can adsorb Cu ²⁺ solution through electrostatic effect. Therefore, when the optical fiber sensor coated with the polymer film layer is used to test the solution to be tested, chelation will cause the refractive index of the polymer film layer to change, which in turn causes a change in the interference spectrum. The optical fiber spectrometer 30 can ^{The Cu 2+} concentration in the solution to be tested is obtained according to the intensity change of the transmission peak of the interference spectrum.

In summary, the present invention provides a Cu ²⁺ concentration detection device, which includes a biconical optical fiber structure composed of two micro-nano optical fibers cascaded, and the surface of the biconical optical fiber structure is coated with modified carbon nanotubes. The polymer film layer is alternately formed by the polyacrylic acid layer and the polyacrylic acid layer in turn, and the biconical optical fiber structure whose surface is covered with the polymer film layer constitutes an optical fiber sensor. When the solution to be tested is dripped onto the surface of the optical fiber sensor, the Cu ^{2+ in} the solution to be tested will cause the volume change of the polymer film on the surface of the optical fiber sensor, resulting in a change in refractive index, thereby causing the optical fiber sensor ^{The intensity of the transmission peak of the interference spectrum changes, and the Cu 2+} concentration in the solution to be tested is obtained according to the intensity change of the transmission peak of the interference spectrum. The method for ^{detecting the Cu 2+} ^{concentration by adopting the Cu 2+} concentration detection device of the present invention has simple operation, low cost, easy portability and high sensitivity.

It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or changes can be made based on the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims

A Cu 2+ concentration detection device, which is characterized in that it comprises an optical fiber sensor, a broadband light source connected to one end of the optical fiber sensor through an optical fiber, and an optical fiber spectrometer connected to the other end of the optical fiber sensor through an optical fiber, and the optical fiber sensor includes A biconical optical fiber structure and a polymer film layer covering the surface of the biconical optical fiber structure. The polymer film is an n-layer film formed alternately by a modified carbon nanotube layer and a polyacrylic acid layer. The optical fiber structure is formed by cascading two micro-nano optical fibers, and the micro-nano optical fibers are prepared by tapering a single-mode optical fiber.
The Cu 2+ concentration detection device according to claim 1, wherein 10≤n≤30.
The Cu 2+ concentration detection device according to claim 1, further comprising a fixing clip for fixing the optical fiber.
The Cu 2+ concentration detection device according to claim 1, wherein a glass slide is arranged under the optical fiber sensor.
The Cu 2+ concentration detection device according to claim 1, wherein the wavelength range of the light source of the broadband light source is 1200-1700 nm.
A method for preparing the Cu 2+ concentration detection device according to any one of claims 1 to 5, characterized in that it comprises the steps of:

Provide broadband light source and fiber optic spectrometer;

A fiber fusion splicer is used to melt and tap the single-mode optical fiber to obtain a first micro-nano fiber. A second micro-nano fiber with the same parameters is prepared behind the first micro-nano fiber. Two micro-nano fibers are cascaded together to form a double-tapered fiber structure;

Preparing an n-layer film composed of modified carbon nanotube layers and polyacrylic acid layers alternately formed on the surface of the biconical optical fiber structure to obtain an optical fiber sensor;

The two ends of the optical fiber sensor are respectively connected to the broadband light source and the optical fiber spectrometer through optical fibers to prepare the Cu 2+ concentration detection device.
The method for preparing a Cu 2+ concentration detection device according to claim 6, characterized in that, on the surface of the biconical optical fiber structure, an n-layer film composed of modified carbon nanotube layers and polyacrylic acid layers alternately formed in turn is prepared on the surface of the biconical fiber structure, The steps to make a fiber optic sensor include:

Putting the biconical optical fiber structure into a mixed solution of concentrated sulfuric acid and hydrogen peroxide, and obtaining a pretreated biconical optical fiber structure after heat treatment;

Putting the preprocessed biconical optical fiber structure into a modified carbon nanotube solution, and forming a modified carbon nanotube layer on the surface of the preprocessed biconical optical fiber structure;

Placing the pre-treated biconical optical fiber structure on the surface of the modified carbon nanotube layer into a polyacrylic acid solution to form a polyacrylic acid layer on the surface of the modified carbon nanotube layer;

By repeating the above-mentioned coating process, an n-layer film composed of modified carbon nanotube layers and polyacrylic acid layers alternately formed on the surface of the biconical optical fiber structure after the pretreatment is obtained;

After coating, the pre-processed biconical optical fiber structure is dried, so that the modified carbon nanotube layer and the polyacrylic acid layer are fully reacted and combined to obtain the optical fiber sensor.
The method for preparing the Cu 2+ concentration detection device according to claim 7, wherein the temperature at which the pre-processed biconical optical fiber structure after coating is dried is 50-80°C, and the time is 3 -5h.
7. The method for preparing a Cu 2+ concentration detection device according to claim 7, wherein the preparation of the modified carbon nanotube solution comprises the following steps:

Add the carbon nanotubes to the concentrated nitric acid solution, treat them at 120°C for 6 hours, cool, filter with suction, wash three times with distilled water, place them in a vacuum drying oven to dry for 8 hours, and grind to obtain modified carbon nanotubes;

The modified carbon nanotubes are added to a 4% acetic acid solution and subjected to ultrasonic treatment, and then magnetically stirred at 80° C. for 2 hours to obtain a modified carbon nanotube solution.
The method for preparing a Cu 2+ concentration detection device according to claim 7, characterized in that:

The concentration of the modified carbon nanotube solution is 1 wt%, and the concentration of the polyacrylic acid solution is 35 wt%.