A molecular imprinting sensor based on β-CD modified graphene quantum dots and its preparation method and application

Abstract

The present invention provides a molecular imprinting sensor based on β-CD modified graphene quantum dots and its preparation method and application, which belongs to the field of electrochemical technology. The preparation method comprises the following steps: using citric acid as a carbon source, preparing graphene quantum dots by pyrolysis; mixing graphene quantum dots, β-cyclodextrin and water evenly to obtain a GQDs / β-CD composite material dispersion; applying the GQDs / β-CD composite material dispersion dropwise to the electrode surface to obtain a GQDs / β-CD modified electrode; placing the GQDs / β-CD modified electrode in a polymembrane solution for electropolymerization to obtain a MIPs / (GQDs / β-CD) modified electrode, and then eluting to remove the imprinted molecules to obtain the molecular imprinting sensor. The molecular imprinting sensor provided by the present invention has high selectivity for D-carnitine, low detection limit, excellent detection performance and high stability.

Description

Technical Field

[0001] The invention relates to the field of electrochemical technology, and in particular to a molecular imprinting sensor based on β-CD modified graphene quantum dots and a preparation method and application thereof. Background Art

[0002] Enantiomers refer to a pair of isomers that are mirror images of each other, just like the left hand and the right hand, which are symmetrical but cannot overlap in structure. According to statistics, among the 500 best-selling drugs in the world, drugs sold as a single enantiomer account for more than half of the total, accounting for 52% of the total sales. However, the enantiomers of most chiral drugs have completely different pharmacological effects under physiological conditions. They can be divided into four categories based on pharmacological effects: (1) Only one enantiomer has pharmacological activity, such as levetiracetam has anti-epileptic effects, while its enantiomer ethiracetam has no pharmacological activity. (2) One enantiomer of a chiral drug will produce toxic side effects, such as D-penicillamine can be used to treat arthritis and cystinuria, while L-penicillamine is toxic in humans. (3) The two enantiomers of a chiral drug have two completely different pharmacological effects, such as levomethoxazole has analgesic activity, while dextromethorphan has central antitussive activity. (4) One enantiomer has higher pharmacological activity than the other enantiomer. For example, the analgesic and anti-inflammatory effects of S-ibuprofen are more than 100 times higher than those of R-ibuprofen, and the antibacterial activity of S-ofloxacin is more than 2 times that of R-ofloxacin. The use of single enantiomer drugs can not only avoid the harm caused by the different pharmacological properties of enantiomer drugs, but also significantly improve the utilization rate of drugs. Therefore, the detection of enantiomers in drugs is of great significance.

[0003] Carnitine is one of the commonly used chiral drugs, among which L-carnitine can shuttle long-chain fatty acids from the cytoplasm through the mitochondrial membrane to the mitochondrial matrix for β-oxidation, thereby generating cellular energy and promoting cellular metabolism. L-carnitine is often used as a drug additive in industry and applied in clinical practice, but industrially produced L-carnitine is often accompanied by D-carnitine, and the presence of D-carnitine inhibits the physiological effects of L-carnitine, thereby inhibiting cell metabolism and causing symptoms such as muscle weakness in the human body. Therefore, the specific detection of D-carnitine is of great significance. At present, the detection methods of D-carnitine mainly include chiral high-performance phase chromatography, high-performance liquid chromatography-fluorescence detection, capillary electrophoresis-tandem mass spectrometry, biosensor method, etc. However, these detection methods are not only expensive in instruments, cumbersome in detection operation, but also require professional personnel to operate, so it is of great significance to develop an easy-to-operate, highly sensitive and highly selective detection method.

[0004] Molecular Imprinting Technology (MIT) is the design of a robust recognition material that can mimic the receptors of biological or chemical molecules. Molecular imprinting technology is based on the principle of molecular recognition. It pre-fixes the template molecule in the polymer matrix through a series of chemical reactions, and then dissociates the template molecule from the polymer, leaving behind a specific cavity with the greatest affinity for the template molecule. These specific cavities have similar structure, shape, charge, environment and other characteristics to the target molecule, so that the target molecule can be selectively captured and separated. MIPs prepared using MIT have developed into an important separation, recognition and detection method, and are widely used in food safety, environmental monitoring, life sciences, medicine and drug research. Auxiliary recognition elements can also be introduced on the basis of MIPs to improve the specific recognition ability of MIPs. Summary of the invention

[0005] Based on the above content, the purpose of the present invention is to provide a molecular imprinting sensor based on β-CD modified graphene quantum dots and its preparation method and application.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention is a method for preparing a molecular imprinting sensor based on β-CD modified graphene quantum dots, comprising the following steps:

[0008] Graphene quantum dots were prepared by pyrolysis using citric acid as the carbon source;

[0009] The graphene quantum dots, β-cyclodextrin and water are uniformly mixed to obtain a GQDs / β-CD composite material dispersion;

[0010] Applying the GQDs / β-CD composite material dispersion droplets to the electrode surface to obtain a GQDs / β-CD modified electrode;

[0011] placing the GQDs / β-CD modified electrode in a polymerizing solution for electropolymerization to obtain a MIPs / (GQDs / β-CD) modified electrode;

[0012] The MIPs / (GQDs / β-CD) modified electrode is eluted to remove the imprinted molecules, thereby obtaining the molecular imprinted sensor.

[0013] The second technical solution of the present invention is a molecular imprinting sensor based on β-CD modified graphene quantum dots prepared by the above preparation method.

[0014] The third technical solution of the present invention is an application of the above-mentioned molecular imprinting sensor based on β-CD modified graphene quantum dots in the detection of chiral molecules.

[0015] The present invention discloses the following technical effects:

[0016] The molecular imprinting sensor material based on β-CD modified graphene quantum dots provided by the present invention is a uniform surface of GQDs functionalized with β-CD, with uniform size and good conductivity, which can provide abundant holes for the detected molecules. The results show that the molecular imprinting sensor based on β-CD modified graphene quantum dots provided by the present invention has a detection limit of D-carnitine as low as 2.35×10 -13 mol / L, the selectivity of identifying D-carnitine increased by 7.15 times. The recovery rate of spiked solution was 98.0% to 106.4% when determining the content of D-carnitine in actual samples.

[0017] The sensor preparation method provided by the present invention is simple and easy to operate, and when used as a sensor, it has excellent detection performance and high stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 This is a scanning electron microscopy image of the GQDs / β-CD prepared in Example 1;

[0020] Figure 2 This is a transmission electron microscopy image of GQDs / β-CD prepared in Example 1;

[0021] Figure 3 It is the UV-visible absorption spectrum of GQDs / β-CD+D-carnitine in Example 1;

[0022] Figure 4 The pulse voltammogram A and cyclic voltammogram B of the MIPs / (GQDs / β-CD) molecular imprinting sensor under different conditions in Application Example 1;

[0023] Figure 5 Electrochemical impedance spectroscopy of the MIPs / (GQDs / β-CD) molecular imprinting sensor under different conditions in Application Example 1;

[0024] Figure 6The DPV signal response A and working curve B of the MIPs / (GQDs / β-CD) molecular imprinting sensor to different concentrations of D-carnitine in application example 1;

[0025] Figure 7 The selectivity DPV diagram of the MIPs / (GQDs / β-CD) molecular imprinting sensor in Application Example 2;

[0026] Figure 8 The anti-interference experimental results of the MIPs / (GQDs / β-CD) molecular imprinting sensor in Application Example 2;

[0027] Fig. 9 The stability bar graph A and reproducibility bar graph B of the MIPs / (GQDs / β-CD) molecular imprinting sensor in Application Example 2. DETAILED DESCRIPTION

[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0029] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0030] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0031] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0032] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0033] The present invention provides a method for preparing a molecular imprinting sensor based on β-CD modified graphene quantum dots, comprising the following steps:

[0034] Graphene quantum dots were prepared by pyrolysis using citric acid as the carbon source;

[0035] The graphene quantum dots, β-cyclodextrin and water are uniformly mixed to obtain a GQDs / β-CD composite material dispersion;

[0036] Applying the GQDs / β-CD composite material dispersion droplets to the electrode surface to obtain a GQDs / β-CD modified electrode;

[0037] placing the GQDs / β-CD modified electrode in a polymerizing solution for electropolymerization to obtain a MIPs / (GQDs / β-CD) modified electrode;

[0038] The MIPs / (GQDs / β-CD) modified electrode is eluted to remove the imprinted molecules, thereby obtaining the molecular imprinted sensor.

[0039] β-cyclodextrin (β-CD) is an oligosaccharide composed of seven glucose units, containing a hydrophobic cavity with a large number of hydrophilic hydroxyl groups on the outside. It can form inclusion complexes with many organic molecules, so drugs can be stored in the cavity through hydrophobic interactions. Guest molecules containing hydroxyl, amino, carboxyl and other groups can form host-guest complexes with β-CD through electrostatic interactions, dipole-dipole interactions and intermolecular hydrogen bonds. Its excellent molecular spatial recognition properties give it a high chiral recognition ability and can be used for the recognition and detection of chiral enantiomers.

[0040] Graphene Quantum Dots (GQDs) is a new type of zero-dimensional nanomaterial. It is usually prepared by high-temperature treatment and chemical modification of graphene. Compared with traditional graphene materials, graphene quantum dots have smaller particle size, higher surface area, and excellent physical, chemical, optical and electrochemical properties. Its high specific surface area, excellent electrochemical properties and abundant carboxyl groups on its surface make it have a wide range of application prospects in electrochemical sensors. Due to its excellent conductivity, specific surface area and abundant carboxyl groups, it can improve the sensitivity and detection limit of electrochemical sensors.

[0041] The present invention introduces a GQDs / β-CD composite material bonded by hydrogen bonding as an auxiliary recognition element into the preparation of MIPs. The GQDs / β-CD composite material is negatively charged due to the ionization of the GQDs carboxyl group, which can effectively fix the GQDs / β-CD composite material on the electrode surface, and its excellent electron transmission performance enables the prepared sensor to have a lower detection limit; at the same time, β-CD with chiral recognition performance is introduced, and the host-guest recognition mechanism of its cavity structure is utilized to improve the recognition ability of the imprinted pores and enhance the chiral recognition ability of the MIPs material to the enantiomer. The GQDs / β-CD composite material is drop-coated on the surface of the polished and cleaned glassy carbon electrode, and D-carnitine is used as the imprinted molecule, and electropolymerization is performed to form a MIPs / (GQDs / β-CD) film. After eluting and removing the imprinted molecule D-carnitine, an imprinted pore that can specifically recognize D-carnitine is formed.

[0042] The present invention first uses citric acid as a carbon source and prepares graphene quantum dots through a pyrolysis method.

[0043] In some embodiments of the present invention, the thermal decomposition method is specifically as follows: citric acid is heated to generate a yellow viscous substance, which is then evenly mixed with a sodium hydroxide solution, and then the resulting dispersion is centrifuged to collect the precipitate, which is the graphene quantum dots.

[0044] In some embodiments of the present invention, the heating temperature is 120°C to 280°C, preferably 200°C, and the heating time is 10min to 120min, preferably 30min. The heating device in the present invention can be any heating device commonly used by those skilled in the art, such as an oven, a muffle furnace or a tubular furnace.

[0045] The concentration of the sodium hydroxide solution is 0.2 mg / mL-2.0 mg / mL, preferably 1.0 mg / mL.

[0046] After obtaining the graphene quantum dots, the present invention uniformly mixes the graphene quantum dots, β-cyclodextrin and water to obtain a GQDs / β-CD composite material dispersion.

[0047] In the present invention, since the carboxyl groups of GQDs are ionized and negatively charged, the GQDs / β-CD composite material can be effectively fixed on the electrode surface, and its excellent electron transport performance enables the prepared sensor to have a lower detection limit; at the same time, β-CD with chiral recognition performance is introduced, and the host-guest recognition mechanism of its cavity structure is utilized to improve the recognition ability of the imprinted pores, enhance the chiral recognition ability of the MIPs material to the enantiomers, and use GQDs / β-CD as a sensor modification material to improve the sensitivity and expand the detection range.

[0048] In some embodiments of the present invention, in the GQDs / β-CD composite material dispersion, the amount ratio of the graphene quantum dots, β-cyclodextrin and water is (2-60) mg: (1×10 -6 -30×10 -6 )mol:50mL, preferably (5-20)mg:(2.5×10 -6 -10×10 -6 )mol:50mL, more preferably 10mg:5×10 -6 mol:50mL.

[0049] In the present invention, if the ratio of graphene quantum dots to β-cyclodextrin is not within the above parameter range, the current signal will be weaker and the detection parameters during electrochemical detection will be poor.

[0050] In some embodiments of the present invention, the particle size of GQDs / β-CD in the GQDs / β-CD composite material dispersion is 5-10 nm.

[0051] After obtaining the GQDs / β-CD composite material dispersion, the present invention applies the GQDs / β-CD composite material dispersion dropwise to the electrode surface to obtain a GQDs / β-CD modified electrode.

[0052] In some embodiments of the present invention, before the GQDs / β-CD composite material dispersion is drop-coated onto the electrode surface, the electrode surface is polished and cleaned; after the GQDs / β-CD composite material dispersion is drop-coated onto the electrode surface, the electrode surface is naturally dried.

[0053] In some embodiments of the present invention, the electrode comprises a glassy carbon electrode, a gold electrode or a carbon paste electrode, preferably a carbon paste electrode.

[0054] In some embodiments of the present invention, in the process of drop-coating the GQDs / β-CD composite material dispersion onto the electrode surface, the amount of the GQDs / β-CD composite material dispersion used is 2-8 μL, preferably 6 μL.

[0055] In the present invention, if the amount of GQDs / β-CD composite material dispersion is too much, the material will completely cover the electrode surface, affecting the electron transmission on the electrode surface, resulting in a weak current signal; if the amount is too little, less material is dispersed on the electrode surface, and the current signal generated by itself will also be weak. Only when the amount is within the appropriate range can a strong current signal be generated.

[0056] After obtaining the GQDs / β-CD modified electrode, the present invention places the GQDs / β-CD modified electrode in a polyfilm solution for electropolymerization to obtain a MIPs / (GQDs / β-CD) modified electrode.

[0057] In some embodiments of the present invention, the polymembrane solution contains D-carnitine and o-phenylenediamine (o-PD).

[0058] In some embodiments of the present invention, the concentration of D-carnitine in the polymembrane solution is 1.0×10 -4 mol / L, the concentration of o-phenylenediamine is 4.0×10 -4 mol / L.

[0059] In some embodiments of the present invention, the number of cycles of electropolymerization is 10-50 cycles, preferably 20 cycles.

[0060] In the present invention, too many electropolymerization cycles will make the polymer film covering the electrode surface too thick, affecting the current. If the number of electropolymerization cycles is too small, the polymer film at the interface is too thin and a good imprint cannot be formed. During detection, the detected molecule and the imprint may not be well combined.

[0061] After obtaining the MIPs / (GQDs / β-CD) modified electrode, the present invention elutes the MIPs / (GQDs / β-CD) modified electrode to remove the imprinted molecules, thereby obtaining the molecular imprinted sensor.

[0062] The present invention drips a GQDs / β-CD composite material onto an electrode surface, uses D-carnitine as an imprinting molecule, and forms an MIPs / (GQDs / β-CD) membrane by electropolymerization. After the imprinting molecule D-carnitine is removed by elution, imprinting holes that can specifically recognize D-carnitine are formed.

[0063] In some embodiments of the present invention, the solution used for elution is an alcohol-organic acid mixed solution, preferably an ethanol-acetic acid mixed solution; the volume ratio of ethanol to acetic acid is 4:1.

[0064] The present invention also provides a molecular imprinting sensor based on β-CD modified graphene quantum dots prepared by the preparation method described in the above technical solution.

[0065] The present invention also provides the application of the molecular imprinting sensor based on β-CD modified graphene quantum dots described in the above technical solution in the detection of chiral molecules.

[0066] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0067] Unless otherwise specified, the raw materials and reagents used in the examples can be obtained through commercial channels.

[0068] Example 1

[0069] This embodiment provides a molecular imprinting sensor based on β-CD modified graphene quantum dots, and the preparation steps are as follows:

[0070] Step 1. Take 0.5000g of citric acid in a crucible and heat it in a muffle furnace at 200℃ for 30.0min. After the reaction, a brown-yellow viscous substance is generated. After cooling to room temperature, mix it evenly with 15.00mL of 1.0mg / mL NaOH solution. Then, centrifuge the resulting dispersion at 3500r / min for 20.0min, collect the precipitate, remove large particle impurities, and obtain graphene quantum dots (GQDs). Weigh the GQDs and dissolve them in ultrapure water to prepare a 2.0mg / mL GQDs solution, which is refrigerated at -4℃ for later use.

[0071] Step 2. Accurately weigh 0.1135 g of β-CD and dissolve it in ultrapure water to prepare 1.0×10 -3 The 1 mol / L β-CD solution was refrigerated at -4°C until use.

[0072] Step 3. Take 5.00 mL of GQDs solution and 5.00 mL of β-CD solution in a 50.0 mL volumetric flask respectively, make up to volume, prepare a GQDs / β-CD composite material dispersion, and refrigerate at -4°C for later use.

[0073] Step 4. After polishing the surface of the glassy carbon electrode with 0.05 μm Al2O3 powder on suede, it was cleaned with ultrapure water to remove impurities and dried for later use. 6.0 μL of GQDs / β-CD composite dispersion was dropped onto the polished and cleaned surface of the glassy carbon electrode and dried naturally for 30.0 min to obtain a GQDs / β-CD modified electrode.

[0074] Step 5. Place the GQDs / β-CD modified electrode in a poly film solution (containing 1.0×10 -4 mol / LD-carnitine and 4.0×10 -4 mol / L o-PD) was electropolymerized for 20 cycles to form a MIPs / (GQDs / β-CD) film on the electrode surface to prepare a MIPs / (GQDs / β-CD) modified electrode.

[0075] Step 6. The MIPs / (GQDs / β-CD) modified electrode was immersed in a mixed solution of ethanol and acetic acid with a volume ratio of 4:1 for 120 seconds. After eluting and removing the imprinted molecule D-carnitine, the formed imprinted pores can be used to specifically recognize D-carnitine, thereby preparing a molecular imprinting sensor for specifically recognizing D-carnitine (denoted as MIPs / (GQDs / β-CD) molecular imprinting sensor).

[0076] Figure 1 This is a scanning electron microscope image of the GQDs / β-CD prepared in Example 1. It can be clearly seen from the image that the prepared GQDs / β-CD is uniformly spherical and has a uniform size distribution.

[0077] Figure 2 This is a transmission electron microscopy image of GQDs / β-CD prepared in Example 1. It can be seen from the image that the size of the GQDs / β-CD quantum dots is about 5-10 nm, they are evenly dispersed, and no aggregation occurs.

[0078] Figure 3 This is the UV-visible absorption spectrum of GQDs / β-CD+D-carnitine prepared in Example 1 (i.e., simply mixing the GQDs / β-CD material and D-carnitine to examine the mutual influence between the two); after the interaction between GQDs / β-CD and D-carnitine, the absorption peak at 218.4nm belonging to GQDs / β-CD disappears, and it is possible that D-carnitine enters the hydrophobic cavity of the GQDs / β-CD composite material and combines through intermolecular hydrogen bonds and electrostatic interactions.

[0079] Application Example 1

[0080] The MIPs / (GQDs / β-CD) molecular imprinting sensor prepared in Example 1 was used for D-carnitine detection.

[0081] Figure 4 The pulse voltammogram and cyclic voltammogram of the MIPs / (GQDs / β-CD) molecular imprinting sensor prepared in Example 1; Figure 4 As can be seen in (A), the peak current intensity of the bare glassy carbon electrode at 0.2V is the largest when measured by DPV (curve a). After the GQDs / β-CD composite material is drop-coated, the electron transfer is hindered, and the peak current intensity decreases (curve b). After electropolymerization, a compact and poorly conductive MIPs film is formed on the electrode surface, which increases the resistance and the DPV peak current intensity is close to 0 (curve c). After the electrode is placed in a mixed solution of ethanol and acetic acid with a volume ratio of 4:1 and eluted for 120s to remove D-carnitine, the current intensity increases again (curve d). This is because D-carnitine imprinted holes are formed on the MIPs film, and electrons can be transferred from the holes, which increases the current intensity. The electrode is placed in a 1.0×10 -9After 25.0 min of re-adsorption of mol / L D-carnitine solution, the imprinted holes were filled with D-carnitine, which hindered the transfer of electrons and reduced the current intensity (curve e). The results showed that the MIPs / (GQDs / β-CD) sensor had a recognition effect on D-carnitine. CV measurement results ( Figure 4 (B)) and DPV determination results ( Figure 4 (A) is consistent with the above.

[0082] Figure 5 The electrochemical impedance spectroscopy of the MIPs / (GQDs / β-CD) molecular imprinting sensor prepared in Example 1 is shown in FIG. Figure 5 As shown in the figure, the initial impedance value of the bare glassy carbon electrode is the smallest (curve a, 129.7Ω). After the GQDs / β-CD composite material is drop-coated, the GQDs / β-CD composite material on the electrode surface hinders the transmission of electrons, causing the impedance value to increase slightly (curve b, 380.8Ω). After the electrode forms a compact MIPs (GQDs / β-CD) film on the surface through electropolymerization, it is difficult for electrons to pass through the MIPs (GQDs / β-CD) film, so the impedance value of the electrode increases significantly (curve c, 6633.1Ω). After the electrode is placed in a mixed solution of ethanol and acetic acid with a volume ratio of 4:1 and eluted for 120s to remove D-carnitine, D-carnitine imprinted holes are formed, and electrons can pass through the holes, so that the impedance value of the electrode is reduced (curve c, 1189.3Ω); the electrode is placed in a 1.0×10 -9 After re-adsorption of mol / L D-carnitine solution for 25.0 min, the impedance value of the electrode increased again (curve e, 1379.7Ω) because the imprinted pores were filled with D-carnitine, indicating that the prepared MIPs / (GQDs / β-CD) molecular imprinting sensor can recognize and bind to D-carnitine molecules.

[0083] Figure 6 The DPV signal response (A) and working curve (B) of the MIPs / (GQDs / β-CD) molecular imprinting sensor prepared in Example 1 to different concentrations of D-carnitine; Figure 6 As shown in Figure A, the DPV peak current gradually decreases with the increase of the concentration of D-carnitine re-adsorbed by the sensor. This is because the recognition of D-carnitine by the MIPs / (GQDs / β-CD) molecular imprinting sensor gradually increases, blocking the electron transfer channel and reducing the DPV peak current intensity. Studies have shown that the DPV response signal change Δi of the MIPs / (GQDs / β-CD) molecular imprinting sensor and the logarithm of the D-carnitine concentration lgC are 1.0×10-12 mol / L~1.0×10 -9 The relationship is linear in the range of mol / L ( Figure 6 B), the linear equation is Δi(A)=8.9×10 -6 lg(C / (mol / L))+1.1×10 -4 (r=0.9899), detection limit DL(3δ b / K)=2.35×10 - 13 mol / L.

[0084] Example 2

[0085] This embodiment provides a molecular imprinting sensor based on β-CD modified graphene quantum dots, and the preparation steps are as follows:

[0086] Step 1. Take 0.5000g of citric acid in a crucible and heat it in a tube furnace at 180°C for 40.0min. After the reaction, a brown-yellow viscous substance is generated. After cooling to room temperature, mix it evenly with 15.00mL of 1.0mg / mL NaOH solution. Then, centrifuge the resulting dispersion at 3500r / min for 20.0min, collect the precipitate, remove large particle impurities, and obtain graphene quantum dots (GQDs). Weigh the GQDs and dissolve them in ultrapure water to prepare a 2.0mg / mL GQDs solution, which is refrigerated at -4°C for later use.

[0087] Step 2. Accurately weigh 0.1135 g of β-CD and dissolve it in ultrapure water to prepare 1.0×10 -3 The 1 mol / L β-CD solution was refrigerated at -4°C until use.

[0088] Step 3. Take 5.00 mL of GQDs solution and 8.00 mL of β-CD solution in a 50.0 mL volumetric flask, make up to volume, prepare a GQDs / β-CD composite material dispersion, and refrigerate at -4°C for later use.

[0089] Step 4. After polishing the surface of the glassy carbon electrode with 0.05 μm Al2O3 powder on suede, it was cleaned with ultrapure water to remove impurities and dried for later use. 6.0 μL of GQDs / β-CD composite dispersion was dropped onto the polished and cleaned surface of the glassy carbon electrode and dried naturally for 30.0 min to obtain a GQDs / β-CD modified electrode.

[0090] Step 5. Place the GQDs / β-CD modified electrode in a poly film solution (containing 1.0×10 -4 mol / LD-carnitine and 4.0×10 -4mol / L o-PD) was electropolymerized for 20 cycles to form a MIPs / (GQDs / β-CD) film on the electrode surface to prepare a MIPs / (GQDs / β-CD) modified electrode.

[0091] Step 6. The MIPs / (GQDs / β-CD) modified electrode was immersed in a mixed solution of ethanol and acetic acid with a volume ratio of 4:1 for 120 seconds. After eluting and removing the imprinted molecule D-carnitine, the formed imprinted pores can be used to specifically recognize D-carnitine, thereby preparing a molecular imprinting sensor for specifically recognizing D-carnitine (denoted as MIPs / (GQDs / β-CD) molecular imprinting sensor).

[0092] Application Example 2

[0093] The MIPs / (GQDs / β-CD) molecular imprinting sensor prepared in Example 2 was used for D-carnitin detection, and its selectivity, anti-interference ability, etc. were studied.

[0094] Figure 7 The selectivity DPV diagram of the MIPs / (GQDs / β-CD) molecular imprinting sensor of Example 2 is shown in FIG. -9 mol / L L-carnitine, D / L-carnitine, and D-carnitine were identified by eluting I p The intensity (curve a') is the blank control, and the sensor recognizes L-carnitine. p The intensity (curve b') decreased by 8.91%. After the identification of D / L-carnitine (curve c'), I p The intensity decreased by 31.73% in the identification of D-carnitine (curve d'). p The intensity decreased by 59.36%. The results show that the recognition ability of MIPs / (GQDs / β-CD) molecular imprinting sensor for L-carnitine is 21.92% of that of D-carnitine at the same concentration, indicating that the introduction of GQDs / β-CD composite material as an auxiliary element in the sensor significantly improves the ability of the sensor to recognize a single enantiomer.

[0095] Figure 8The anti-interference experimental results of the MIPs / (GQDs / β-CD) molecular imprinting sensor of Example 2; the anti-interference performance of the MIPs / (GQDs / β-CD) molecular imprinting sensor was studied using six amino acids (D-Thr, D-Ser, D-Val, L-Thr, L-Ser, L-Val) with similar structures to D-carnitine as interferents. The DPV was used to measure the re-adsorption of the six amino acids with 1000 times concentration (1.0×10 -6 mol / L) of amino acid interfering substance D-carnitine solution (1.0×10 -9 mol / L), compared with the single adsorption of D-carnitine (1.0×10 -9 mol / L) solution, I p Current signal such as Fig. 9 The I of MIPs / (GQDs / β-CD) molecular imprinting sensor after adding 6 amino acid interfering substances at 1000 times the concentration after recognizing D-carnitine p The current signal Δi does not exceed 10%, and the largest interferent is D-Val, which exceeds the D-carnitine signal measured alone by 7.32%. The above results show that the MIPs / (GQDs / β-CD) molecular imprinting sensor has good anti-interference ability.

[0096] Fig. 9 The stability and reproducibility bar graph of the MIPs / (GQDs / β-CD) molecular imprinting sensor of Example 2; a MIPs / (GQDs / β-CD electrode pair with a concentration of 1.0×10 -9 After re-adsorption of mol / L D-carnitine for 25 min, the DPV response signal was measured 9 times ( Fig. 9 The RSD% is 1.91%, which shows that the MIPs / (GQDs / β-CD) sensor has good stability. Five MIPs / (GQDs / β-CD) electrodes were prepared in the same way, and the recognition concentration was 1.0×10 -9 mol / L D-carnitine after 25.0 min. Fig. 9 In B), the RSD% is 3.12%, indicating that the MIPs / (GQDs / β-CD) molecular imprinting sensor has good reproducibility. After the electrode was placed in a dust-proof and refrigerated place for 7 days, the measured DPV current response intensity only decreased by 1.69%, indicating that the prepared MIPs / (GQDs / β-CD) molecular imprinting sensor has a long service life.

[0097] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. Application of a molecular imprinting sensor based on β-CD modified graphene quantum dots in the detection of chiral molecules, characterized in that: The chiral molecule is D-carnitine; The preparation method of the molecular imprinting sensor based on β-CD modified graphene quantum dots comprises the following steps: Graphene quantum dots were prepared by pyrolysis using citric acid as the carbon source; The graphene quantum dots, β-cyclodextrin and water are uniformly mixed to obtain a GQDs / β-CD composite material dispersion; Applying the GQDs / β-CD composite material dispersion droplets to the electrode surface to obtain a GQDs / β-CD modified electrode; placing the GQDs / β-CD modified electrode in a polymerizing solution for electropolymerization to obtain a MIPs / (GQDs / β-CD) modified electrode; The MIPs / (GQDs / β-CD) modified electrode is eluted to remove the imprinted molecules, thereby obtaining the molecular imprinted sensor; In the GQDs / β-CD composite material dispersion, the amount ratio of the graphene quantum dots, β-cyclodextrin and water is (2-60) mg:(1×10 -6 -30×10 -6 )mol:50mL; The polymembrane solution contains D-carnitine and o-phenylenediamine; In the polymembrane solution, the concentration of D-carnitine is 1.0×10 -4 mol / L, the concentration of o-phenylenediamine is 4.0×10 -4 mol / L; The number of cycles of the electropolymerization is 10-50; In the process of drop-coating the GQDs / β-CD composite material dispersion onto the electrode surface, the amount of the GQDs / β-CD composite material dispersion used is 2-8 μL.

2. The use of the molecular imprinting sensor based on β-CD modified graphene quantum dots in chiral molecule detection according to claim 1, characterized in that: The thermal decomposition method is specifically as follows: citric acid is heated to generate a yellow viscous substance, which is then evenly mixed with a sodium hydroxide solution, and then the resulting dispersion is centrifuged to separate the precipitate, which is the graphene quantum dots.

3. The use of the molecular imprinting sensor based on β-CD modified graphene quantum dots in chiral molecule detection according to claim 1, characterized in that: The particle size of GQDs / β-CD in the GQDs / β-CD composite material dispersion is 5-10 nm.

4. The use of a molecular imprinting sensor based on β-CD modified graphene quantum dots in chiral molecule detection according to claim 1, characterized in that: Before applying the GQDs / β-CD composite material dispersion droplets to the electrode surface, the electrode surface is polished and cleaned; after applying the GQDs / β-CD composite material dispersion droplets to the electrode surface, the electrode surface is naturally dried.

Images