A positively charged gold@luminol modified flexible paper substrate and its preparation method and application

Abstract

A positively charged gold@luminol modified flexible paper substrate, its preparation method, and its application are disclosed. The method includes the following steps: CTAB aqueous solution and chloroauric acid aqueous solution are stirred and mixed evenly to obtain mixture A; luminol solution and NaBH4 solution are mixed evenly and then added dropwise to mixture A, and stirred at room temperature until the solution turns light red to obtain the positively charged gold@luminol ((+)Au@luminol NPs) composite material; chitosan is added to ultrapure water and stirred to disperse, then glacial acetic acid is added and stirred to obtain a chitosan solution; filter paper is cut to obtain a bare paper substrate, and the chitosan solution is dropped onto the surface of the bare paper substrate, impregnated, and then dried to obtain the paper substrate; the (+)Au@luminol NPs composite material is dropped onto the paper substrate and dried in the dark to obtain the (+)Au@luminol NPs modified flexible paper substrate, which is initially used for in-situ detection of H2O2 in plants. This method is simple to operate and low in cost.

Description

Technical Field

[0001] The invention relates to the field of flexible paper-based sensing technology, and in particular to a positively charged gold@luminol-modified flexible paper-based material and a preparation method and application thereof. Background Art

[0002] Sensing technology is a platform that is sensitive to target objects and converts their concentration into electrical, electrochemical luminescence or optical signals for detection. It is composed of immobilized target sensitive materials as identification elements, physical and chemical converters and signal amplification devices. Traditional three-electrode electrochemical sensing technology uses glassy carbon, gold or platinum as working electrodes. The electrodes need to be surface treated before each use. There are disadvantages such as easy wear of the electrode surface, accumulation of pollution after long-term use, and high electrode prices. Paper-based analytical devices (PADs) have attracted widespread attention in the development of non-invasive sensors due to their high cost-effectiveness, easy functionalization, low reagent consumption, and good flexibility. In addition, luminol is a classic organic electrochemical luminescence (ECL) luminescence system. Due to its advantages such as low oxidation potential and high luminescence efficiency, luminol has a wide range of applications in the preparation of sensing technology. Luminol composites functionalized with gold or silver nanoparticles significantly enhance the luminescence performance of luminol. Most of the literature reports are about preparing sensing technology for quantitative detection of proteins, nucleic acids, small biological molecules and fungi by modifying gold@luminol through Au-S bonds or directly on the electrode surface. The modification cost is high and the amount is difficult to estimate. Summary of the invention

[0003] The purpose of the present invention is to provide a positively charged gold@luminol modified flexible paper substrate and a preparation method and application thereof. The method is simple and can reduce production time and cost. The prepared flexible paper substrate can achieve in-situ surface high-sensitivity detection of the object to be tested by direct adhesion to the sample surface, and can be preliminarily used for in-situ detection of H2O2 in plants, thereby reducing errors.

[0004] To achieve the above object, the present invention provides a method for preparing a positively charged gold@luminol modified flexible paper substrate, comprising the following steps:

[0005] S1, mixing the hexadecyltrimethylammonium bromide aqueous solution and the chloroauric acid aqueous solution in a molar ratio with stirring to obtain a mixed solution A;

[0006] S2, mixing the luminol solution and the NaBH4 solution evenly, and then adding dropwise to the mixed solution A prepared in step S1, stirring at room temperature until the solution turns light red to obtain a positively charged gold@luminol ((+)Au@luminolNPs) composite material;

[0007] S3, adding chitosan into ultrapure water and stirring to disperse, then adding glacial acetic acid and stirring, and finally dissolving completely to obtain a chitosan solution;

[0008] S4, cutting the filter paper according to the specifications to form a bare paper base, dripping the chitosan solution prepared in step S3 onto the surface of the bare paper base, soaking the bare paper base and drying it to obtain a paper base;

[0009] S5. Add the (+)Au@luminol NPs composite material prepared in step S2 dropwise onto the paper base prepared in step S4, and dry in a dark place to obtain a (+)Au@luminol NPs modified flexible paper base.

[0010] Preferably, in step S1, the concentration of the hexadecyltrimethylammonium bromide aqueous solution is 10 mM, and the concentration of the chloroauric acid aqueous solution is 1 mM; the volume ratio between the hexadecyltrimethylammonium bromide aqueous solution and the chloroauric acid aqueous solution is 2:15; and the mixture is mixed by magnetic stirring for 10-20 min.

[0011] Preferably, in step S2, the concentration of the luminol solution is 10 mM, the concentration of the NaBH4 solution is 5 mM, and the volume ratio between the luminol solution and the NaBH4 solution is 5:1; stirring is performed at room temperature for 0.5-1.5 h.

[0012] Preferably, in step S3, the mass concentration of the chitosan solution is 2%; and the volume percentage concentration of the glacial acetic acid is 1%.

[0013] Preferably, in step S4, a grid of 0.8 cm×1.0 cm is printed on filter paper and cut to form a bare paper base.

[0014] Preferably, in step S4, 5-8 μL of chitosan solution is dripped onto each bare paper base; the bare paper base is soaked and then placed in a 60° C. oven for drying; the process of dripping, soaking and drying is repeated 2-3 times; and the rough surface of the bare paper base is used as the dripping surface.

[0015] Preferably, in step S5, 5-8 μL of (+)Au@luminol NPs composite material is dripped onto each paper substrate; and the dripping and drying process is repeated 2-3 times.

[0016] To achieve the above object, the present invention also provides a (+)Au@luminol NPs modified flexible paper substrate prepared by the above preparation method.

[0017] To achieve the above objectives, the present invention also provides the use of the above (+) Au@luminol NPs modified flexible paper substrate in the in situ detection of plant H2O2.

[0018] Furthermore, 8 μL of 1 nM H2O2 solution was added to the positively charged gold@luminol modified flexible paper substrate for a preliminary H2O2 response. The flexible paper substrate detected H2O2 through the change of the luminol electrochemiluminescence signal caused by the presence of H2O2.

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

[0020] The present invention modifies the surface of the paper chip electrode functionalized with negatively charged materials by electrostatic adsorption, prepares a novel positively charged gold@luminol-modified flexible paper substrate, and preliminarily uses it for in-situ detection of plant H2O2, effectively simplifying the material preparation steps. The flexible paper substrate can realize the quantitative detection of H2O2 through the change of the luminol electrochemical luminescence signal caused by the presence of H2O2. In addition, compared with traditional sensing technologies such as glassy carbon electrodes and gold electrodes, the flexible paper substrate realizes the preparation of disposable electrodes, effectively avoiding the electrode reuse grinding process, the damage and pollution of the electrode, and has great potential in the in-situ and real-time detection of target objects.

[0021] The preparation process of the present invention is simple, which greatly reduces time and cost; the method can accelerate the decomposition of H2O2 by using metal nanoparticles, generate more intermediate reactive oxygen species (ROSs), and thus improve the effectiveness of H2O2 as a co-reactant of luminol. The AuNPs in (+)Au@luminolNPs have good conductivity and electrocatalytic activity, which can promote the reduction of H2O2, thereby generating more O 2- To oxidize luminol, thereby increasing the ECL intensity, and through direct adhesion to the plant surface, high-sensitivity in-situ surface detection of the object to be tested can be achieved, thereby reducing errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The particle size distribution diagram (a) and potential diagram (b) of (+)Au@luminol NPs prepared in step S2 of the embodiment;

[0023] Figure 2 The UV absorption graph (a) and XPS graph (b) of (+)Au@luminol NPs prepared in step S2 of the embodiment;

[0024] Figure 3 This is an elemental analysis diagram of the (+)Au@luminol NPs prepared in step S2 of Example transferred onto a silicon wafer;

[0025] Figure 4 Comparative scanning electron micrographs of the bare paper substrate (a), paper substrate (b), and (+) Au@luminol NPs-modified flexible paper substrate (c) in the examples;

[0026] Figure 5 CV graphs of the bare paper substrate (a), paper substrate (b) and (+) Au@luminolNPs modified flexible paper substrate (c) in the examples;

[0027] Figure 6 Impedance diagrams of bare paper substrate (a), paper substrate (b) and (+) Au@luminol NPs modified flexible paper substrate (c) in the examples;

[0028] Figure 7 Response graphs of the (+)Au@luminol NPs modified flexible paper substrate prepared in the example to 1 nM H2O2 (b) and 0.01 M PBS (a). DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] The raw materials and reagents used in the following examples, unless otherwise specified, are all commercially available.

[0031] Example

[0032] A method for preparing a positively charged gold@luminol modified flexible paper substrate comprises the following steps:

[0033] S1. First, use a pipette to transfer 2 mL of 10 mM hexadecyltrimethylammonium bromide (CTAB) aqueous solution and 15 mL of 1 mM chloroauric acid aqueous solution into a small beaker and mix them evenly. Place the mixture on a magnetic stirrer and stir for 15 min to obtain a mixed solution A.

[0034] S2, 1 ml of 10 mM luminol solution was mixed with 200 μL of 5 mM NaBH4 solution, and after standing for 2 min, the mixture was added dropwise to the mixed solution A prepared in step S1, and stirred at room temperature for 1 h until the solution turned light red to obtain the (+) Au@luminolNPs composite material;

[0035] from Figure 1 It can be seen that the particle size of the (+)Au@luminolNPs composite material is about 10nm and the potential is positive; Figure 2 It can be seen that the (+)Au@luminol NPs composite material has characteristic UV absorption peaks, and the X-ray photoelectron spectroscopy (XPS) survey spectrum shows N1s, O 1s, C 1s and Au4f signals; Figure 3 It can be seen that C, N, O and Au are evenly distributed in the (+)Au@luminolNPs composite material.

[0036] S3, weigh 2g chitosan into a small beaker, add 98mL ultrapure water, stir to disperse, then add 1mL glacial acetic acid and stir, finally dissolve completely to obtain a chitosan (CS) solution with a concentration of 2%;

[0037] S4, print out small squares of 0.8 cm × 1.0 cm on the filter paper and cut them. The cut small squares are bare paper bases, which are placed in a culture dish for later use; use tweezers to take a number of bare paper bases and place them in a small culture dish, with the rough surface of the bare paper bases as the dropping surface, and drop the CS solution prepared in step S3 onto the surface of the bare paper bases, drop 8 μL of each bare paper base, soak the bare paper bases, and then put them in an oven at 60°C for drying, repeat the process of dropping, soaking, and drying 2-3 times to obtain a paper base; Figure 4 (a) and Figure 4 (b) By comparison, it can be found that the original pores on the filter paper have been basically covered by chitosan.

[0038] S5, drop the (+) Au@luminolNPs composite material prepared in step S2 onto the paper base prepared in step S4, drop 8 μL of (+) Au@luminolNPs composite material onto each paper base, dry in dark, repeat the process of dropwise addition and drying 2-3 times, Figure 4 (b) and Figure 4 (c) By comparison, it can be found that the surface is evenly covered with (+)Au@luminol NPs, obtaining a flexible paper substrate modified with (+)Au@luminolNPs.

[0039] from Figure 5 It can be seen that the cyclic voltammetry of bare paper substrate (a) and paper substrate (b) has basically no change, and the redox peak of the cyclic voltammetry of flexible paper substrate modified with (+) Au@luminol NPs (c) is significantly enhanced; Figure 6 It can be seen that the impedance of bare paper substrate (a), paper substrate (b) and (+) Au@luminol NPs modified flexible paper substrate (c) decreases in turn.

[0040] The positively charged gold@luminol modified flexible paper substrate prepared in this example is used in the in situ detection of H2O2 in plants.

[0041] The specific application process is: 8 μL of 1nM H2O2 solution and 8 μL of 0.01M PBS buffer (as a comparison) were added to two (+)Au@luminol NPs-modified flexible paper substrates to perform a preliminary response to H2O2. The flexible paper substrate detects H2O2 through the change in the luminol electrochemiluminescence signal caused by the presence of H2O2. The results are shown in Figure 2. Figure 7As shown in the figure, it can be seen that the electrochemiluminescence intensity of the flexible paper substrate with 1nM H2O2 added is significantly higher than the electrochemiluminescence intensity with 0.01M PBS buffer added. This shows that the flexible paper substrate prepared by the present invention can achieve high-sensitivity in-situ surface detection of the object to be tested by directly adhering to the surface of the plant body, and has potential application value.

Claims

1. A method for preparing a positively charged gold@luminol modified flexible paper substrate, characterized in that: The following steps are involved: S1, mixing the hexadecyltrimethylammonium bromide aqueous solution and the chloroauric acid aqueous solution in a molar ratio with stirring to obtain a mixed solution A; S2, mixing the luminol solution and the NaBH4 solution evenly, and then adding dropwise to the mixed solution A prepared in step S1, stirring at room temperature until the solution turns light red to obtain the (+)Au@luminol NPs composite material; S3, adding chitosan into ultrapure water and stirring to disperse, then adding glacial acetic acid and stirring, and finally dissolving completely to obtain a chitosan solution; S4, cutting the filter paper according to the specifications to form a bare paper base, dripping the chitosan solution prepared in step S3 onto the surface of the bare paper base, soaking the bare paper base and drying it to obtain a paper base; S5. Add the (+)Au@luminol NPs composite material prepared in step S2 dropwise onto the paper base prepared in step S4, and dry in a dark place to obtain a (+)Au@luminol NPs modified flexible paper base.

2. The method for preparing a positively charged gold@luminol modified flexible paper substrate according to claim 1, characterized in that: In step S1, the concentration of the hexadecyltrimethylammonium bromide aqueous solution is 10 mM, and the concentration of the chloroauric acid aqueous solution is 1 mM; the volume ratio between the hexadecyltrimethylammonium bromide aqueous solution and the chloroauric acid aqueous solution is 2:15; and the mixture is stirred magnetically for 10-20 minutes.

3. The method for preparing a positively charged gold@luminol modified flexible paper substrate according to claim 1 or 2, characterized in that: In step S2, the concentration of the luminol solution is 10 mM, the concentration of the NaBH4 solution is 5 mM, and the volume ratio between the luminol solution and the NaBH4 solution is 5:1; stirring is performed at room temperature for 0.5-1.5 h.

4. The method for preparing a positively charged gold@luminol modified flexible paper substrate according to claim 1 or 2, characterized in that: In step S3, the mass concentration of the chitosan solution is 2%; the volume percentage concentration of glacial acetic acid is 1%.

5. The method for preparing a positively charged gold@luminol modified flexible paper substrate according to claim 1 or 2, characterized in that: In step S4, a grid of 0.8 cm×1.0 cm is printed on filter paper and cut to form a bare paper base.

6. The method for preparing a positively charged gold@luminol modified flexible paper substrate according to claim 5, characterized in that: In step S4, 5-8 μL of chitosan solution is dripped onto each bare paper substrate; the bare paper substrate is soaked and then placed in a 60° C. oven for drying; the process of dripping, soaking, and drying is repeated 2-3 times; and the rough surface of the bare paper substrate is used as the dripping surface.

7. The method for preparing a positively charged gold@luminol modified flexible paper substrate according to claim 5, characterized in that: In step S5, 5-8 μL of (+) Au@luminol NPs composite material is dripped onto each paper substrate; the dripping and drying process is repeated 2-3 times.

8. A positively charged gold@luminol modified flexible paper substrate prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the positively charged gold@luminol modified flexible paper substrate as claimed in claim 8 in in-situ detection of H2O2 in plants.

10. The use of the positively charged gold@luminol modified flexible paper substrate in the in-situ detection of H2O2 in plants according to claim 9, characterized in that: 8 μL of 1 nM H2O2 solution was added to the positively charged gold@luminol modified flexible paper substrate for a preliminary H2O2 response. The flexible paper substrate detected H2O2 through the change of the luminol electrochemiluminescence signal caused by the presence of H2O2.

Images