Heavy metal ion detection device based on nanoparticle-polyelectrolyte ion diode and preparation method of heavy metal ion detection device

Abstract

The invention provides a heavy metal ion detection device based on a nanoparticle-polyelectrolyte ion diode and a preparation method, and belongs to the technical field of heavy metal detection. The device comprises a micro-fluidic chip, a power supply unit, a fluorescence detection unit and a control and display unit, the micro-fluidic chip comprises a PDMS cover plate which is bonded with a glass substrate, a working channel, a straight channel, a side channel and a plurality of sample feeding / discharging ports are formed in the micro-fluidic chip, and an ion diode is formed in the working channel through directional electric field induction polycationic electrolyte (PDAC) and nanoparticles (polystyrene); the power supply unit provides adjustable direct current to achieve heavy metal ion convergence and concentration, the fluorescence detection unit excites a fluorescence probe, collects characteristic fluorescence signals and converts the characteristic fluorescence signals into digital signals, and the control and display unit processes the signals and calculates and displays the heavy metal ion concentration. The device is compact in structure, easy and convenient to operate, high in detection efficiency, high in specificity and suitable for rapid and accurate detection of heavy metal ions in an environmental water sample.

Description

Technical Field

[0001] This invention relates to the field of heavy metal detection technology, and more particularly to a heavy metal ion detection device based on nanoparticle-polyelectrolyte ion diode and its preparation method. Background Technology

[0002] Heavy metals in water bodies are highly toxic, persistent, and bioaccumulative, easily accumulating through the food chain and causing irreversible damage to the structure and function of aquatic ecosystems. They can also enter the human body through drinking contaminated water or consuming seafood enriched with heavy metals, posing a sustained threat to human health with long-term exposure. Furthermore, water bodies contaminated with heavy metals are difficult to restore naturally, not only restricting the sustainable use of water resources but also having a chain of negative impacts on agricultural irrigation and industrial water use, resulting in significant ecological and economic losses.

[0003] Currently, commonly used methods for heavy metal ion detection include atomic absorption spectrometry, inductively coupled plasma mass spectrometry, and colorimetry. Atomic absorption spectrometry converts heavy metal ions into atomic vapor, which then selectively absorbs light at specific wavelengths. Quantitative detection is achieved by comparing absorbance with a standard curve. However, this method involves expensive and bulky instruments, making rapid on-site detection impossible. Furthermore, sample pretreatment is complex and time-consuming, and there is still room for improvement in detecting low-concentration ions.

[0004] In addition, inductively coupled plasma mass spectrometry (ICP-MS) involves ionizing heavy metal ions with plasma and then quantitatively detecting them based on ion abundance using a mass analysis instrument. However, this method involves expensive instruments, a matrix that is susceptible to interference, a complex sample pretreatment process, and detection that depends on specialized laboratory conditions, making it unsuitable for on-site emergency testing needs.

[0005] In addition, colorimetric methods utilize the reaction of heavy metal ions with specific colorimetric reagents to generate colored compounds, achieving detection through absorbance or color changes. However, this method has low sensitivity, poor selectivity, and is easily interfered with by other ions and organic matter in the water, making it difficult to meet the requirements for accurate detection of trace pollution. Therefore, developing a simple, portable, and highly sensitive heavy metal detection device is of significant practical importance. Summary of the Invention

[0006] In view of the technical problems mentioned in the background section, a heavy metal ion detection device based on nanoparticle-polyelectrolyte ion diode and its preparation method are provided.

[0007] The technical means employed in this invention are as follows: A heavy metal ion detection device based on nanoparticle-polyelectrolyte ion diode includes: a microfluidic chip, a power supply unit, a fluorescence detection unit, and a control and display unit; The microfluidic chip includes: a PDMS cover plate and a substrate that are bonded and sealed; the groove on the lower surface of the PDMS cover plate and the substrate enclose a working channel, a first straight channel, a second straight channel, and a side channel, as well as a first sample inlet, a first sample outlet, a second sample inlet, a second sample outlet, and a detection sample inlet that are respectively connected to each channel; a nanoparticle-polyelectrolyte ion diode is provided in the working channel. The power supply unit is electrically connected to the first and second sample inlets via wires to provide adjustable DC power to form a controllable DC electric field within the microchannel. The fluorescence detection unit includes: an excitation light source, an optical collection system, a photoelectric conversion module, and a signal processing circuit; the fluorescence detection unit is used to excite and collect the characteristic fluorescence signal of the fluorescent probe in the pores of the nanoparticle-polyelectrolyte ion diode, and convert it into a digital signal; The control and display unit includes a control circuit and a liquid crystal display. The control circuit is electrically connected to the power supply unit and the fluorescence detection unit, respectively, and is used to control the output voltage of the power supply unit, process the digital signal of the fluorescence detection unit and calculate the concentration of heavy metal ions. The liquid crystal display is used to display the detection results.

[0008] Furthermore, the substrate is made of glass and its size is larger than that of the PDMS cover plate.

[0009] Furthermore, the nanoparticle-polyelectrolyte ion diode comprises: a polycationic electrolyte and nanoparticles combined in the working channel under the action of a directional electric field, wherein one end of the nanoparticle-polyelectrolyte ion diode is modified with a positive charge by the polycationic electrolyte, and the other end is modified with nanoparticles to carry a negative charge.

[0010] Furthermore, the polycationic electrolyte is PDAC, the nanoparticles are polystyrene, and the concentrations of both the polycationic electrolyte solution and the nanoparticle solution are 1%.

[0011] Furthermore, the excitation light source of the fluorescence detection unit emits excitation light of a specific wavelength, the optical collection system is used to separate characteristic fluorescence signals, the photoelectric conversion module converts the fluorescence signal into a current or voltage signal, and the signal processing circuit amplifies and filters the electrical signal before converting it into a digital signal.

[0012] Furthermore, the control circuit outputs a control signal to adjust the applied voltage of the power supply unit, thereby achieving the aggregation and concentration of heavy metal ions. At the same time, it receives and saves the digital signal from the fluorescence detection unit, and calculates the concentration of heavy metal ions based on the intensity of the fluorescence signal.

[0013] This invention also includes a method for preparing a heavy metal ion detection device based on nanoparticle-polyelectrolyte ion diode, comprising the following steps: Step 1: Microchannel fabrication; Using a silicon substrate as the base, after photoresist spin coating, pre-baking, mask exposure, post-baking, development, cleaning and drying, PDMS is poured and cured in an 80℃ oven for 1 hour. After cutting, holes are drilled to form each sample inlet and outlet. The PDMS cover plate is bonded to the glass substrate after plasma cleaning for 1 minute. Step 2: Formation of nanoparticle-polyelectrolyte ion diode; Deionized water and 0.1M NaOH solution are sequentially added to each inlet and outlet to rinse the channel. Then, polycationic electrolyte solution and nanoparticle solution are added to the first and second inlets respectively. DC power is applied through the power supply unit to make the two recombine in the working channel to form an ion diode. Step 3, Circuit Connection: Connect the microfluidic chip to the fluorescence detection unit, and connect the fluorescence detection unit to the control and display unit to complete the device construction.

[0014] Furthermore, the photolithography process in step 1 is performed in two steps: the first exposure uses a working channel mask, and the second exposure uses masks for the first straight channel, the second straight channel, and the side channel. After each exposure, post-baking, development, and cleaning are performed.

[0015] Furthermore, step 2 includes the following steps: Step 21: Use a pipette to add deionized water to the inlet and outlet to rinse the channels; then aspirate the deionized water from the reservoir and continue to add 0.01-0.5M NaOH solution, soaking for 30 minutes; then rinse with clean water to remove any remaining NaOH from the channels. Step 22: Add a polycationic electrolyte solution with a concentration of 0.2%-2% and nanoparticles with a concentration of 0.2%-2% to the first and second injection ports. The power supply unit provides DC power to the first and second injection ports. A positive voltage is applied to the injection port where the polycationic electrolyte solution is added, and the injection port where the nanoparticles are added is grounded. Step 23: After the microfluidic chip is connected to the power supply unit, an electric field is generated in the microchannel. The direction of the electric field is from the positive electrode to the negative electrode. Under the action of the directional electric field force, the polycationic electrolyte solution and nanoparticles move in the microchannel and eventually meet in the working channel. One end is modified by the polycationic electrolyte solution and carries a positive charge, while the other end is modified by the nanoparticles and carries a negative charge, thus forming a microfluidic chip integrating nanoparticle-polyelectrolyte ion diode.

[0016] Furthermore, the applied positive voltage range is 1-5V.

[0017] Compared with the prior art, the present invention has the following advantages: 1. The heavy metal ion detection device based on nanoparticle-polyelectrolyte ion diode provided by the present invention has the advantages of simple operation, portability, and high sensitivity. Moreover, the sample volume required for detection is small, and the entire detection process does not rely on large instruments or complex reagents, making it suitable for on-site detection of trace heavy metal ions in the environment.

[0018] 2. The heavy metal ion detection device based on nanoparticle-polyelectrolyte ion diode provided by the present invention can effectively utilize the ion aggregation effect of the ion diode under the action of an electric field to achieve efficient enrichment of trace heavy metal ions in the detection area, thereby significantly improving detection sensitivity and accuracy. This method avoids the complicated sample enrichment steps in traditional pretreatment, greatly shortens the detection time and reduces operating costs, and has good practicality and promotion potential. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the detection device of the present invention.

[0021] Figure 2 This is a schematic diagram of the microfluidic chip of the present invention.

[0022] Figure 3 This is a schematic diagram of the nanoparticle-polyelectrolyte ion diode structure of the present invention.

[0023] Figure 4 This is a schematic diagram illustrating the working principle of the nanoparticle-polyelectrolyte ion diode of the present invention.

[0024] Figure 5 This is a graph showing the change in fluorescence intensity as a function of heavy metal ion concentration according to the present invention.

[0025] In the diagram: 1. Microfluidic chip; 11. PDMS cover plate; 12. Working channel; 13. First straight channel; 14. Second straight channel; 15. Side channel; 16. First sample inlet; 17. First sample outlet; 18. Second sample inlet; 19. Second sample outlet; 110. Detection sample inlet; 111. Nanoparticle-polyelectrolyte ion diode; 112. Substrate; 2. Power supply unit; 3. Fluorescent display unit; 4. Control and display unit. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] like Figure 1 As shown, the present invention provides a heavy metal ion detection device based on nanoparticle-polyelectrolyte ion diode, comprising: a microfluidic chip 1, a power supply unit 2, a fluorescence detection unit 3, and a control and display unit 4.

[0029] like Figure 2As shown, the microfluidic chip 1 includes: a PDMS cover plate 11, a working channel 12, a first straight channel 13, a second straight channel 14, a side channel 15, a first sample inlet 16, a first sample outlet 17, a second sample inlet 18, a second sample outlet 19, a detection sample inlet 110, a nanoparticle-polyelectrolyte ion diode 111, and a substrate 112. The PDMS cover plate 11 is a cuboid with a length of 5cm, a width of 3.5cm, and a thickness of 5mm. Its lower surface is attached to and sealed with the upper surface of the substrate 112. The substrate 112 is made of glass and is larger than the PDMS cover plate 11. A groove is formed on the lower surface of the PDMS cover plate 11, forming a closed working channel 1 with the substrate 110. 2. A first straight channel 13, a second straight channel 14, a side channel 15, a first sample inlet 16, a first sample outlet 17, a second sample inlet 18, a second sample outlet 19, and a detection sample inlet 110. Among them, the working channel 12 has a length of 400μm, a width of 20μm, and a height of 5μm; the first straight channel 13 and the second straight channel 14 have a length of 1mm, a width of 200μm, and a height of 30μm; the side channel 15 has a length of 500μm, a width of 200μm, and a height of 30μm; and the first sample inlet 16, the first sample outlet 17, the second sample inlet 18, the second sample outlet 19, and the detection sample inlet 110 have a diameter of 6mm and a height of 5mm.

[0030] like Figure 1 As shown, the power supply unit 2 is used to provide direct current and is connected to the first sample inlet 16 and the second sample inlet 18 through wires, so that a controllable direct current electric field is formed in the microchannel. The voltage of the power supply unit 2 is adjustable, and the electric field strength in the microchannel can be controlled by changing the applied voltage.

[0031] like Figure 1 As shown, the fluorescence detection unit 3 includes an excitation light source, an optical collection system, a photoelectric conversion module, and a signal processing circuit, used to detect fluorescence signals in the microfluidic chip. The excitation light source emits excitation light of a specific wavelength to irradiate the nanoparticle-polyelectrolyte ion diode in the working channel of the microfluidic chip, exciting the fluorescent probes bound to heavy metal ions in their pores to emit fluorescence. The optical collection system efficiently collects and separates the characteristic fluorescence signals emitted by the excited fluorescent probes. The photoelectric conversion module converts the received fluorescence signals into corresponding current or voltage signals. The signal processing circuit amplifies and filters the electrical signals and converts the fluorescence intensity into a digital signal, which is then transmitted to the control and display unit 4 for analysis and display.

[0032] like Figure 1As shown, the control and display unit 4 includes a control circuit and a liquid crystal display. The control circuit is a single-chip microcomputer circuit with a built-in control and processing program, which is connected to the power supply unit and the fluorescence detection unit. It is used to output control signals to the power supply unit to control the voltage applied to the microfluidic chip, thereby realizing the aggregation and concentration of heavy metal ions, and to receive and store the signals input by the fluorescence detection unit. Based on the intensity of the fluorescence signal, the concentration of heavy metal ions in the sample is calculated. The liquid crystal display is connected to the control circuit and is used to display the measurement results.

[0033] This invention provides a method for preparing a heavy metal ion detection device based on a nanoparticle-polyelectrolyte ion diode, comprising the following steps: Step 1, Microchannel preparation, specifically: Step 11: Using a silicon substrate as a base, spin-coat photoresist onto the silicon substrate and pre-bake it; place the working channel mask on the treated silicon substrate and expose it under a UV lamp, then post-bake it, and then immerse it in a developer solution and clean it; after cleaning and drying the silicon substrate, spin-coat photoresist again and pre-bake it; after the treatment, place the masks for the two straight channels and the side channels on the silicon substrate and continue to expose them under a UV lamp.

[0034] Step 12: Perform post-baking treatment on the exposed silicon substrate. After treatment, the silicon substrate is immersed in the developer and cleaned, and then purged with nitrogen to dry. After drying, PDMS is poured onto the silicon substrate and cured by heating in an oven at 80°C for 1 hour.

[0035] Step 13: Use a punch to punch holes in the cut microfluidic chip to form a first sample inlet 16, a first sample outlet 17, a second sample inlet 18, a second sample outlet 19, and a detection sample inlet 110. The hole diameter is 6mm. Place the punched microfluidic chip and the substrate into a plasma cleaner for 1 minute. Then bond the processed microfluidic chip onto the glass substrate.

[0036] Step 2, formation of nanoparticle-polyelectrolyte ion diode, specifically: Step 21: Use a pipette to add deionized water to the first inlet 16, the first outlet 17, the second inlet 18, the second outlet 19, and the detection inlet 110 to rinse the channels; then aspirate the deionized water from the storage tank and continue to add 0.1M NaOH solution, soaking for 30 minutes; then rinse with clean water to remove any remaining NaOH from the channels; Step 22: Add a 1% polycationic electrolyte solution and a 1% nanoparticle to the first injection port 16 and the second injection port 18. The power supply unit 2 applies DC power to the first injection port 16 and the second injection port 18. The positive terminal is connected to the injection port where the polycationic electrolyte solution is added, and the negative terminal is connected to the injection port where the nanoparticle is added. Step 23: After the microfluidic chip 1 is connected to the power supply unit 2, an electric field is generated in the microchannel. The direction of the electric field is from the positive electrode to the negative electrode. Under the action of the directional electric field force, the polycationic electrolyte solution PDAC and the nanoparticle polystyrene move in the microchannel and eventually meet in the working channel 12. One end of the chip is modified with the polycationic electrolyte solution PDAC and carries a positive charge, while the other end is modified with the nanoparticle polystyrene and carries a negative charge, forming a microfluidic chip integrating a nanoparticle-polyelectrolyte ion diode. The working principle of the nanoparticle-polyelectrolyte ion diode is as follows: Figure 4 As shown; Step 3, connect the control circuit, specifically: Connect the microfluidic chip 1 obtained in step 2 to the fluorescence detection unit 3. The fluorescence detection unit 3 converts the obtained fluorescence signal into a digital signal and transmits it to the control and display unit 4 to display the measurement results. After the connection is completed, a heavy metal ion detection device based on nanoparticle-polyelectrolyte ion diode is obtained.

[0037] Example 1: This invention also provides a method for using a heavy metal ion detection device based on nanoparticle-polyelectrolyte ion diode, specifically for Cu. 2+ The detection process includes the following steps: S11. Microchannels are prepared using a silicon substrate, and holes are punched to form an inlet and an outlet. The processed microfluidic chip is then bonded to a glass substrate 112. S12. Rinse the channel by adding deionized water, 0.1M NaOH solution, and clean water to the inlet and outlet of the sample outlet one after another using a pipette, and rinse three times. S13. A 1% polycationic electrolyte solution PDAC is added to the first injection port 16, and a 1% nanoparticle polystyrene is added to the second injection port 18. DC power is provided by the power supply unit 2, and a 5V positive voltage is applied to the first injection port 16. The second injection port 18 is grounded. Under the action of the directional electric field, a microfluidic chip 1 integrating a nanoparticle-polyelectrolyte ion diode 111 is formed. S14. Take a water sample from the environment to be tested, add the fluorescent probe N-Aminofluorescein, and the Cu in the water sample... 2+The fluorescent probe N-Aminofluorescein was reacted with the fluorescent probe in 0.01 M Tris-HCl buffer solution at 80 °C for 6 h. The concentration of the fluorescent probe was 1.5 mM Cu. 2+ The concentration should not exceed the concentration of the fluorescent probe N-Aminofluorescein; Cu 2+ After binding with the fluorescent probe N-Aminofluorescein, Cu 2+ The complexation promotes the hydrolysis of amide bonds, leading to the release of fluorophores (fluorescein), thereby amplifying the fluorescence signal. Fluorescent powder carries one unit of negative charge. S15, Add Cu to the detection inlet 110 2+ The mixed solution reacted with the fluorescent probe N-Aminofluorescein, and then a 24V positive voltage was applied to the microfluidic chip 1 for 10 minutes. The fluorescence detection unit 3 converted the detected fluorescence intensity into a digital signal, which was transmitted to the control and display unit 4 to analyze the Cu content in the water sample. 2+ Concentration; Fluorescence intensity as a function of heavy metal ion concentration is shown in the graph. Figure 5 As shown.

[0038] Example 2: This invention also provides a method for using a heavy metal ion detection device based on nanoparticle-polyelectrolyte ion diode, specifically for Hg. 2+ The detection process includes the following steps: S21. Microchannels are prepared using a silicon substrate, and holes are punched to form an inlet and an outlet. The processed microfluidic chip is then bonded to a glass substrate 112. S22. Rinse the channel by adding deionized water, 0.1M NaOH solution, and clean water to the inlet and outlet of the sample outlet one after another using a pipette, and rinse three times. S23. Add 1% concentration of nanoparticle polystyrene to the first injection port 16, add 1% concentration of polycationic electrolyte solution PDAC to the second injection port 18, provide DC power from the power supply unit 2, apply a 5V positive voltage to the second injection port 18, and ground the first injection port 16. Under the action of the directional electric field, a microfluidic chip 1 integrating nanoparticle-polyelectrolyte ion diode 111 is formed. S24. Take a water sample from the environment to be tested, add the fluorescent probe rhodamine B hydrazide, and the Hg in the water sample... 2+ The fluorescent probe rhodamine B hydrazide was reacted with a MeOH:H2O (10:90 v / v) buffer solution, wherein the concentration of the fluorescent probe was 20 μM and Hg 2+ The concentration should not exceed the concentration of the fluorescent probe rhodamine B hydrazide; Hg 2+Upon binding with the fluorescent probe rhodamine B hydrazide, a cyclization reaction of rhodamine B hydrazide is initiated, leading to the release of a fluorophore (luciferin), thereby amplifying the fluorescence signal. The luciferin carries one unit of positive charge. S25. Add Hg to the detection inlet 110. 2+ The mixed solution after reaction with the fluorescent probe rhodamine B hydrazide was then subjected to a 24V positive voltage applied to the microfluidic chip 1 for 10 minutes. The fluorescence detection unit 3 converted the detected fluorescence intensity into a digital signal, which was transmitted to the control and display unit 4 to analyze the Hg content in the water sample. 2+ concentration.

[0039] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. In the above embodiments of the present invention, the descriptions of each embodiment have their own emphasis; parts not described in detail in a certain embodiment can be referred to in the relevant descriptions of other embodiments. It should be understood that the disclosed technical content in the several embodiments provided in this application can be implemented in other ways.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A nanoparticle-polyelectrolyte ionic diode based heavy metal ion detection device, characterized by, The application relates to a microfluidic chip (1), a power supply unit (2), a fluorescence detection unit (3) and a control and display unit (4). The microfluidic chip (1) comprises a tightly sealed PDMS cover plate (11) and a substrate (112); a groove on the lower surface of the PDMS cover plate (11) and the substrate (112) form a working channel (12), a first straight channel (13), a second straight channel (14), a side channel (15), and a first sample inlet (16), a first sample outlet (17), a second sample inlet (18), a second sample outlet (19) and a detection sample inlet (110) which are respectively connected with the channels; a nano-particle-polyelectrolyte ion diode (111) is arranged in the working channel (12). The power supply unit (2) is electrically connected with the first sample inlet (16) and the second sample inlet (18) through wires and is used for providing adjustable direct current to form a controllable direct current field in the micro channel. The fluorescence detection unit (3) comprises an excitation light source, an optical collection system, a photoelectric conversion module and a signal processing circuit; the fluorescence detection unit (3) is used for exciting and collecting characteristic fluorescence signals of a fluorescent probe in the nano-particle-polyelectrolyte ion diode (111) aperture, converting the signals into digital signals. The control and display unit (4) comprises a control circuit and a liquid crystal display; the control circuit is electrically connected with the power supply unit (2) and the fluorescence detection unit (3) and is used for controlling the output voltage of the power supply unit (2), processing the digital signals of the fluorescence detection unit (3) and calculating the heavy metal ion concentration; and the liquid crystal display is used for displaying the detection results. The substrate (112) is made of glass and has a size larger than that of the PDMS cover plate (11).

2. The nanoparticle-polyelectrolyte ion diode based heavy metal ion detection device according to claim 1, wherein, The nano-particle-polyelectrolyte ion diode (111) comprises polycation electrolyte and nano-particles which are compounded in the working channel (12) under the action of directional electric field force; one end of the nano-particle-polyelectrolyte ion diode (111) is modified by the polycation electrolyte and is positively charged, and the other end is modified by the nano-particles and is negatively charged.

3. The nanoparticle-polyelectrolyte ion diode based heavy metal ion detection device according to claim 1, wherein, The polycation electrolyte is PDAC, the nano-particles are polystyrene, and the concentration of the polycation electrolyte solution and the nano-particle solution is 1%.

4. The nanoparticle-polyelectrolyte ion diode-based heavy metal ion detection device according to claim 3, wherein, The excitation light source of the fluorescence detection unit (3) emits excitation light of a specific wavelength, the optical collection system is used for separating characteristic fluorescence signals, the photoelectric conversion module converts the fluorescence signals into current or voltage signals, and the signal processing circuit amplifies and filters the electric signals and then converts the signals into digital signals.

5. The nanoparticle-polyelectrolyte ion diode based heavy metal ion detection device according to claim 1, wherein, The control circuit outputs a control signal to adjust the applied voltage of the power supply unit (2), realizes the gathering and concentration of heavy metal ions, receives and saves the digital signals of the fluorescence detection unit (3) and calculates the heavy metal ion concentration based on the fluorescence signal strength.

6. The nanoparticle-polyelectrolyte ion diode based heavy metal ion detection device according to claim 1, wherein, The application further discloses a detection method of heavy metal ions.

7. A method for the preparation of a nanoparticle-polyelectrolyte ionic diode based heavy metal ion detection device, using the device of any one of claims 1-6, wherein, ​ Step 1, microchannel preparation; after spin coating, pre-baking, mask exposure, post-baking, developing, cleaning and drying of photoresist, pouring PDMS and curing in 80℃ oven for 1h, punching after cutting to form each inlet and outlet, bonding the PDMS cover plate (11) and the glass substrate (112) after plasma cleaning for 1min; Step 2, nanoparticle-polyelectrolyte ion diode formation; adding deionized water, 0.1M NaOH solution to each inlet and outlet in turn, then adding polycationic electrolyte solution and nanoparticle solution to the first inlet (16) and the second inlet (18) respectively, and applying direct current through the power supply unit (2) to make the two compounds form an ion diode in the working channel (12); Step 3, circuit connection: connecting the microfluidic chip (1) with the fluorescence detection unit (3), connecting the fluorescence detection unit (3) with the control and display unit (4), and completing the device construction.

8. The method of claim 7, wherein the method comprises the steps of: (a) mixing the nanoparticles and the polyelectrolyte to form a mixture; (b) adding the mixture to the substrate to form a layer of the mixture on the substrate; and (c) drying the layer of the mixture on the substrate to form the device. The photoetching process in step 1 is carried out twice: the first time is to use the working channel mask to expose, and the second time is to use the first straight channel, the second straight channel and the side channel mask to expose, and after each exposure, post-baking, developing and cleaning are carried out.

9. The method of claim 7, wherein the method comprises the steps of: (a) mixing the nanoparticles and the polyelectrolyte to form a mixture; (b) adding the mixture to the solution; and (c) allowing the mixture to react with the solution to form the device. The step 2 includes the following steps: Step 21, adding deionized water to the inlets and outlets with a pipette to flush the channels; then, absorbing the deionized water in the reservoir, continuing to add 0.01-0.5M NaOH solution, and soaking for 30min; then, flushing with water to flush the residual NaOH in the channel; Step 22, adding polycationic electrolyte solution with a concentration of 0.2%-2% and nanoparticles with a concentration of 0.2%-2% to the first inlet and the second inlet, and providing direct current to the first inlet and the second inlet by the power supply unit, applying positive voltage to the inlet where the polycationic electrolyte solution is added, and grounding the inlet where the nanoparticles are added; Step 23, after connecting the microfluidic chip with the power supply unit, an electric field is generated in the microchannel, the direction of the electric field is from the positive electrode to the negative electrode, under the action of the directional electric force, the polycationic electrolyte solution and the nanoparticles move in the microchannel, finally meet in the working channel, one end is modified by the polycationic electrolyte solution and carries positive charge, the other end is modified by the nanoparticles and carries negative charge, thus forming a microfluidic chip integrated with nanoparticle-polyelectrolyte ion diode.

10. The method of claim 9, wherein the method comprises the steps of: (a) mixing the nanoparticles and the polyelectrolyte to form a mixture; (b) adding the mixture to the solution; and (c) allowing the mixture to react with the solution to form the device. The range of the applied positive voltage is 1-5V.

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