Lead ion high-sensitivity detection method and sensor

Abstract

The invention is suitable for the technical field of nanometer electrochemical sensing, and provides a lead ion high-sensitivity detection method and a sensor, the detection sensor comprises a PET nanometer channel film and a tannic acid-based poly (N-(6-aminohexyl) methacrylamide) hydrogel heterogeneous layer covering the outer surface of the PET nanometer channel film; the hydrogel is formed by cross-linking tannic acid (TA) and poly (N-(6-aminohexyl) methacrylamide) (PMAM) through a Michael addition reaction. The detection method comprises the following steps: adsorbing Pb by the pretreated tannic acid-based poly (N-(6-aminohexyl) methacrylamide) hydrogel, attaching the pretreated tannic acid-based poly (N-(6-aminohexyl) methacrylamide) hydrogel to the outer surface of the PET nano-channel film, and detecting the change of a current signal of a system under the condition of applying + / -2V voltage scanning, so as to realize the quantitative detection of lead ions. By constructing a hydrogel functionalized nano-channel heterogeneous membrane structure, high-sensitivity and high-specificity instant detection on lead ions is realized, and the hydrogel functionalized nano-channel heterogeneous membrane has the advantages of low cost, simplicity and convenience in operation, quick response and the like.

Description

Technical Field

[0001] This invention belongs to the field of nano-electrochemical sensing technology, and particularly relates to a highly sensitive method and sensor for detecting lead ions. Background Technology

[0002] Developing a series of simple, low-cost, and highly sensitive instant detection technologies is of great significance for ensuring water quality safety and protecting public health.

[0003] Currently, the detection of pollutants such as heavy metals in water mainly relies on spectroscopic, chromatographic, and mass spectrometric methods. However, these methods have several significant drawbacks: First, sample pretreatment is complex, time-consuming, and requires substantial manpower and reagents; second, these techniques typically require samples to be sent to a laboratory for analysis, making rapid on-site detection difficult; third, the related precision instruments, such as solid-phase extraction instruments and inductively coupled plasma mass spectrometers, are expensive, and their maintenance costs are also high. Therefore, achieving highly sensitive, rapid, accurate, real-time, and specific detection of pollutants in water remains a key research focus both domestically and internationally.

[0005] Electrochemical sensors are devices or instruments that react with a target substance through a sensitive element and convert the reaction signal into a recognizable electrical signal. They have advantages such as simple operation, fast response speed, high sensitivity, and small and portable size, and show broad application prospects in online monitoring of water pollution.

[0006] In electrochemical sensors, nanochannels have attracted widespread attention due to their applications in molecular filters, biosensors, nanofluidic logic devices, and energy conversion. Probe-modified nanochannels have become a powerful platform for detecting various target substances, such as metal ions, anions, small molecules, and biomolecules. When a target substance passes through a nanochannel or binds to a probe modified on the channel surface, it induces a change in ion current. Typically, the probe is modified on the inner wall of the nanochannel. However, due to the limited space inside the channel, target molecules have difficulty effectively approaching the probe, resulting in low recognition efficiency. In contrast, by modifying the outer surface of the nanochannel, the probe binds to the target, which is not limited by pore size and can achieve multi-scale recognition from the ion to the cell scale. Furthermore, the outer surface is more easily exposed to the target solution, thereby improving the recognition efficiency between the probe and the target.

[0007] Recent studies have attempted to modify external surfaces using metal deposition or spin coating methods, but these methods still face challenges such as complex processes and the easy introduction of air bubbles. Therefore, there is an urgent need to develop a highly sensitive method and sensor for lead ion detection to overcome the shortcomings in current practical applications. Summary of the Invention

[0008] The purpose of this invention is to provide a highly sensitive method and sensor for detecting lead ions, which can rapidly detect Pb²⁺ in water on-site, solving the problems of expensive equipment, complex operation, and low recognition efficiency of existing nanochannel sensors.

[0009] The present invention is implemented as follows: a highly sensitive lead ion detection sensor includes a PET nanochannel membrane and a tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel heterolayer covering the outer surface of the PET nanochannel membrane; The hydrogel comprises tannic acid and poly(N-(6-aminohexyl)methacrylamide) and is cross-linked by Michael addition reaction.

[0010] A further technical solution is that the PET nanochannel membrane has a pore size of 30 nm and a pore density of 5 × 10⁻⁶. 7 / cm², with a thickness of 12μm.

[0011] In a further technical solution, the thickness of the hydrogel heterolayer is 200 μm.

[0012] A further technical solution is that the raw materials for preparing poly(N-(6-aminohexyl)methacrylamide) include N-(6-aminohexyl)methacrylamide monomer, acrylamide, N,N'-methylenebisacrylamide and ammonium persulfate; The N-(6-aminohexyl)methacrylamide monomer is synthesized from methacrylic anhydride and 1,6-hexanediamine via an amidation reaction.

[0013] A further technical solution is provided, wherein the preparation conditions for the poly(N-(6-aminohexyl)methacrylamide) are as follows: Under nitrogen protection, 500 mg of N-(6-aminohexyl)methacrylamide monomer, 500 mg of acrylamide, 1 mg of N,N'-methylenebisacrylamide and 15 mg of ammonium persulfate were dissolved in 5 mL of deionized water and reacted at 70 °C for 10 hours.

[0014] Another object of the present invention is a highly sensitive method for detecting lead ions, comprising the following steps: Pb²⁺ was adsorbed onto the outer surface of a PET nanochannel membrane after pretreated tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel. The changes in the current signal of the system were detected under ±2V voltage scanning conditions to achieve quantitative detection of lead ions.

[0015] A further technical solution is that the PET nanochannel membrane has a pore size of 30 nm and a pore density of 5 × 10⁻⁶. 7 / cm², with a thickness of 12μm.

[0016] A further technical solution is that the pretreatment of the tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel includes: Soak in 1 mmol / L NaCl solution for 24 hours, absorb the surface moisture, and then air dry naturally to the initial weight.

[0017] In a further technical solution, the voltage scan range is −2V to +2V, with a period of 40 seconds; the electrolyte solution of the detection system is 1mmol / L KCl, and the experimental temperature is controlled at 25℃.

[0018] A further technical solution involves preparing the tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel, including: The freeze-dried poly(N-(6-aminohexyl)methacrylamide) was placed in an aqueous solution of tannic acid at pH 8.5 and a concentration of 500 mg / mL, and a Michael addition reaction was carried out at room temperature for 24 hours.

[0019] The present invention provides a highly sensitive method and sensor for detecting lead ions, which has the following beneficial effects: By constructing a heterogeneous membrane structure on the outer surface of hydrogel-functionalized nanochannels, this method overcomes the spatial limitations of traditional inner wall modification, achieving rapid, highly sensitive, and highly specific detection of lead ions in water. The sensor utilizes the charge change induced by the specific binding of tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel with Pb²⁺ to modulate the double-layer structure of the nanochannels, generating a significant current response. The detection limit is as low as 0.03 ppb, exhibiting high sensitivity and strong selectivity, maintaining a selectivity advantage of over 20 times even in the presence of multiple metal ions. Furthermore, the externally attached, detachable hydrogel design eliminates the need for complex modification processes, making operation simple, reusable, and requiring only 3 minutes for the entire detection process (including pre-adsorption). It can be rapidly screened on-site using simple electrochemical equipment, with equipment costs only one percent of traditional methods. This solves the problems of expensive equipment, complex processes, and low identification efficiency of existing methods, providing a practical and feasible technical solution for efficient, low-cost, and real-time monitoring of lead pollution in aquatic environments, with broad application prospects.

[0020] In summary, this invention achieves highly sensitive and specific real-time detection of lead ions by constructing a hydrogel-functionalized nanochannel heterogeneous membrane structure. It has advantages such as low cost, simple operation, and rapid response, and is suitable for on-site water quality monitoring applications. Attached Figure Description

[0021] Figure 1 A schematic diagram illustrating the preparation of tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel and its specific adsorption principle for lead ions, provided in an embodiment of the present invention. Figure 2A schematic diagram showing the detection of Pb²⁺ by an electrochemical sensor after adsorption of tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel. Figure 3 A schematic diagram of the bonding of a tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel with a PET film after adsorbing Pb²⁺. Figure 4 This is a schematic diagram of the detection of Pb²⁺ concentration using an electrochemical sensor. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0024] Example 1

[0025] An embodiment of the present invention provides a highly sensitive lead ion detection sensor, comprising a polyethylene terephthalate (PET) nanochannel membrane and a tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel (i.e., TA / PMAM hydrogel) heterolayer covering the outer surface of the PET nanochannel membrane; wherein the hydrogel comprises tannic acid and poly(N-(6-aminohexyl)methacrylamide), and is cross-linked through a Michael addition reaction to form ( Figure 1 ).

[0026] Preferably, the PET nanochannel membrane has a pore size of 30 nm and the hydrogel heterolayer has a thickness of approximately 200 μm.

[0027] Example 2

[0028] An embodiment of the present invention also provides a highly sensitive method for detecting lead ions, comprising the following steps: Pretreated tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel was adsorbed with Pb²⁺ and then attached to the outer surface of a PET nanochannel membrane. Figure 2 By applying a ±2V voltage scan, changes in the current signal of the detection system are measured, thereby achieving quantitative detection of lead ions. Figure 3 That is, detection is achieved by regulating the ion current through the charge change caused by the specific binding of Pb²⁺ to the phenolic hydroxyl group. Figure 4 ).

[0029] In practical implementation, a device is provided to achieve highly sensitive detection of lead ions (Pb²⁺) by functionalizing the outer surface of nanochannels with hydrogel. This device utilizes hydrogels with lead-responsive properties to construct a stable covalent cross-linked structure between tannic acid and poly(N-(6-aminohexyl)methacrylamide) based on Schiff base bonds through a simple Michael addition reaction synthesis pathway.

[0030] During the detection process, Pb²⁺ can specifically bind to the phenolic hydroxyl and carbonyl groups in tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel, thereby changing the charge distribution state inside the hydrogel and further regulating the double layer characteristics of the nanochannel surface, resulting in a significant decrease in ion current and achieving high-sensitivity detection of Pb²⁺.

[0031] In a further technical solution: the nanochannel uses a polyethylene terephthalate (PET) membrane as the substrate material, with a pore size of 30 nm and a pore density of 5 × 10⁻⁶. 7 / cm², with a thickness of 12μm.

[0032] The preparation method of the hydrogel is as follows: using methacrylic anhydride and 1,6-hexanediamine as raw materials, a functional monomer N-(6-aminohexyl)methacrylamide (MAM) containing a primary amine group at one end is synthesized through the amidation reaction of amino groups and acid anhydrides.

[0033] Under a nitrogen atmosphere, 500 mg of MAM monomer (2.71 mmol) was dissolved in 5 mL of deionized water. Then, 500 mg of acrylamide (7.03 mmol), 1 mg of N,N'-methylenebisacrylamide (0.00649 mmol, as a crosslinking agent), and 15 mg of ammonium persulfate (0.0657 mmol, as an initiator) were added. After thorough mixing, the mixture was reacted at 70 °C for 10 hours to obtain the polymer PMAM.

[0034] After freeze-drying, the reaction product was placed in an aqueous solution of tannic acid at pH 8.5 and a concentration of 500 mg / mL, and Michael addition reaction was carried out at room temperature for 24 hours to finally obtain tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel.

[0035] The specific construction steps of the detection device are as follows: The prepared hydrogel was pretreated by soaking it in 1 mmol / L NaCl solution for 24 hours; after taking it out, the surface moisture was absorbed with filter paper and air-dried naturally to the initial mass; then the hydrogel was immersed in Pb²⁺ solution for 120 minutes to simulate interference testing under oxidative environment; after being absorbed and air-dried, it was attached to the outer surface of PET nanochannel membrane to form a heterogeneous membrane structure.

[0036] The hydrogel has a thickness of 200 μm, and the PET film has a thickness of 12 μm.

[0037] Composition and operation of the detection system: The heterogeneous membrane described above is installed between the two electrolytic cells of an electrochemical cell. A voltage is applied to the membrane using a self-made Ag / AgCl electrode, and the current and voltage signals are acquired using a Keithley 6485 sensor.

[0038] The forward voltage was defined as the potential applied to the hydrogel side, with a scan range of −2V to +2V and a period of 40 seconds. The electrolyte solution was 1 mmol / L KCl, and each sample was tested three times. The experimental temperature was controlled at 25℃.

[0039] The above embodiments of the present invention provide a highly sensitive method and sensor for detecting lead ions. By constructing a heterogeneous membrane structure on the outer surface of a hydrogel-functionalized nanochannel, the spatial limitations of traditional nanochannel inner wall modification are overcome, achieving rapid, highly sensitive, and highly specific detection of lead ions in water. It has the following significant advantages: 1) Based on a heterogeneous membrane structure design, this sensor utilizes the charge change induced by Pb²⁺ adsorption on a hydrogel to modulate the double-layer properties of the nanochannel, thereby achieving a significant response to the current signal. The sensor has a detection limit for lead ions as low as 0.03 ppb, achieving trace detection levels, and its equipment cost is only one percent of that of traditional spectroscopic / mass spectrometry methods, making it a potential candidate for portable field applications.

[0040] 2) Employing an external hydrogel heterogeneous membrane structure, nanochannel functionalization can be achieved without complex chemical modification processes. The hydrogel can be easily peeled off and replaced after detection, while the PET substrate maintains structural stability, greatly simplifying the sensor's operation and subsequent maintenance, making it suitable for operation by non-professionals.

[0041] 3) The hydrogel is formed by crosslinking tannic acid (TA) and poly(N-(6-aminohexyl)methacrylamide) (PMAM) via Michael addition reaction. It has a stable structure and good mechanical properties and chemical resistance. The abundant phenolic hydroxyl groups in TA have a highly specific binding ability with Pb²⁺, and still show a selectivity advantage of more than 20 times in the presence of multiple coexisting metal ions, which significantly improves the anti-interference performance.

[0042] 4) The entire detection process can be completed within 3 minutes (excluding the 120-minute pre-adsorption step), suitable for rapid on-site screening needs. The sensor can acquire signals through a simple electrochemical device (such as an Ag / AgCl electrode + picoammeter), making it suitable for real-time monitoring of various water quality samples such as surface water and drinking water.

[0043] 5) The detection principle is based on the specific binding of Pb²⁺ with phenolic hydroxyl and carbonyl groups in tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel → change of charge state → regulation of the double electric layer structure of nanochannel → causing a decrease in ion current through a multi-level amplification mechanism, which enables weak changes in target concentration to be converted into significant electrical signal output, thereby improving detection reliability.

[0044] In summary, this invention not only solves the problems of expensive equipment and complicated operation in traditional heavy metal detection methods, but also overcomes the bottlenecks of low recognition efficiency and cumbersome modification processes of existing nanochannel sensors. It provides a practical and feasible technical path for efficient, low-cost, and real-time detection of lead ions in the water environment, and has broad application prospects and promotional value.

[0045] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0046] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A highly sensitive lead ion detection sensor, characterized in that, It includes a PET nanochannel membrane and a tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel heterolayer covering the outer surface of the PET nanochannel membrane; The hydrogel comprises tannic acid and poly(N-(6-aminohexyl)methacrylamide) and is cross-linked by Michael addition reaction.

2. The high-sensitivity lead ion detection sensor according to claim 1, characterized in that, The PET nanochannel membrane has a pore size of 30 nm and a pore density of 5 × 10⁻⁶. 7 / cm², with a thickness of 12μm.

3. The high-sensitivity lead ion detection sensor according to claim 1, characterized in that, The thickness of the hydrogel heterolayer is 200 μm.

4. The high-sensitivity lead ion detection sensor according to claim 1, characterized in that, The raw materials for preparing poly(N-(6-aminohexyl)methacrylamide) include N-(6-aminohexyl)methacrylamide monomer, acrylamide, N,N'-methylenebisacrylamide and ammonium persulfate; The N-(6-aminohexyl)methacrylamide monomer is synthesized from methacrylic anhydride and 1,6-hexanediamine via an amidation reaction.

5. The high-sensitivity lead ion detection sensor according to claim 4, characterized in that, The preparation conditions for the poly(N-(6-aminohexyl)methacrylamide) are as follows: Under nitrogen protection, 500 mg of N-(6-aminohexyl)methacrylamide monomer, 500 mg of acrylamide, 1 mg of N,N'-methylenebisacrylamide and 15 mg of ammonium persulfate were dissolved in 5 mL of deionized water and reacted at 70 °C for 10 hours.

6. A highly sensitive method for detecting lead ions, characterized in that, The following steps are involved: Pb²⁺ was adsorbed onto the outer surface of a PET nanochannel membrane after pretreated tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel. The changes in the current signal of the system were detected under ±2V voltage scanning conditions to achieve quantitative detection of lead ions.

7. The highly sensitive lead ion detection method according to claim 6, characterized in that, The PET nanochannel membrane has a pore size of 30 nm and a pore density of 5 × 10⁻⁶. 7 / cm², with a thickness of 12μm.

8. The highly sensitive lead ion detection method according to claim 6, characterized in that, The pretreatment of the tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel includes: Soak in 1 mmol / L NaCl solution for 24 hours, absorb the surface moisture, and air dry naturally to the initial mass for comparative testing.

9. The highly sensitive lead ion detection method according to claim 6, characterized in that, The voltage scan ranges from −2V to +2V, with a period of 40 seconds; The electrolyte solution for the detection system was 1 mmol / L KCl, and the experimental temperature was controlled at 25℃.

10. The highly sensitive lead ion detection method according to claim 8, characterized in that, The preparation of the tannic acid-based poly(N-(6-aminohexyl)methacrylamide) hydrogel includes: The freeze-dried poly(N-(6-aminohexyl)methacrylamide) was placed in an aqueous solution of tannic acid at pH 8.5 and a concentration of 500 mg / mL, and Michael addition reaction was carried out at room temperature for 24 hours.

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