CN113640358A - MXene composite membrane modified electrode and electrochemical identification of methionine enantiomer thereof - Google Patents

MXene composite membrane modified electrode and electrochemical identification of methionine enantiomer thereof Download PDF

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CN113640358A
CN113640358A CN202110928461.5A CN202110928461A CN113640358A CN 113640358 A CN113640358 A CN 113640358A CN 202110928461 A CN202110928461 A CN 202110928461A CN 113640358 A CN113640358 A CN 113640358A
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mxene
ldhns
methionine
cmcd
gce
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詹天荣
王军
王闰夏
钱星
王超
王磊
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Qingdao University of Science and Technology
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Abstract

The invention discloses a transition metal carbonitride @ cobalt aluminum hydrotalcite-like nanosheet/carboxymethyl-beta-cyclodextrin composite membrane modified electrode, a preparation method thereof and application of the modified electrode in identification and detection of methionine enantiomer. Preparing MXene by using a fluorite etching method, and growing hydrotalcite-like nano-sheets on the surface of the MXene in situ; modifying carboxymethyl-beta-cyclodextrin to the surface of MXene @ LDHNS by utilizing electrostatic adsorption to prepare the MXene @ LDHNS/CMCD nano composite material, and preparing a corresponding composite film modified electrode by adopting a dropping coating method. The obtained modified electrode plays a synergistic effect of MXene, hydrotalcite-like nano-sheets and carboxymethyl-beta-cyclodextrin, and realizes the identification and high-sensitivity detection of methionine enantiomer, wherein the linear range of L-methionine detection is 2 multiplied by 10‑8～2.5×10‑5mol/L, the detection limit is 9.6 nmol/L; the linear range of D-methionine detection is 1X 10‑7～2.5×10‑5mol/L, limit of detectionWas 39 nmol/L. The modified electrode provided by the invention is simple in preparation method, and can realize high-sensitivity identification and detection of methionine chiral enantiomers.

Description

MXene composite membrane modified electrode and electrochemical identification of methionine enantiomer thereof
The technical field is as follows:
the invention relates to an MXene @ cobalt-aluminum hydrotalcite nanosheet/carboxymethyl-beta-cyclodextrin modified electrode; the invention also relates to a preparation method of the modified electrode and an application of the modified electrode in electrochemical identification of amino acid enantiomers.
Background art:
chiral molecules, also known as enantiomers, have the same elemental composition and major physicochemical properties, but differ greatly in metabolic processes, physiological toxicity and pharmacological activity. Usually, only one chiral molecule is effective, while the other chiral molecule is ineffective, or even exhibits the opposite effect. Methionine is essential amino acid of animal body, and can maintain growth and nitrogen balance of animal body, prevent and treat liver diseases and poisoning caused by arsenic and benzene, and lack of methionine in livestock and poultry can cause dysplasia, weight loss, liver and kidney function reduction, muscle atrophy, fur deterioration, etc. Methionine is an optically active compound, and is classified into D-form and L-form. The L form is easy to be absorbed in animal body, and the D form can participate in the synthesis of protein only after being converted into the L form by enzyme. Therefore, establishing a method for identifying and detecting D/L methionine enantiomer with good stability and high sensitivity is particularly important. In order to solve the problem, various analysis methods such as capillary electrophoresis, high performance liquid chromatography, circular dichroism, colorimetry, fluorescence and the like are established to realize sensitive identification and detection of enantiomers. However, these methods have limited their use due to time consuming, expensive instruments and reagents, and complicated procedures performed by skilled technicians. The electrochemical method has the advantages of quick response, high sensitivity, good selectivity, low cost, simple and convenient operation, time saving and the like, provides selection for identifying and detecting enantiomers, and therefore, the method for finding the electrode suitable for modifying the nano composite membrane is an effective method for improving the sensitivity and the stability of the electrode.
Cyclodextrin (CD) is a natural macrocyclic oligosaccharide with a hydrophobic inner cavity and a hydrophilic outer cavity. The CD has lower cost and excellent performance, and can effectively adsorb enantiomers selectively into hydrophobic cavities thereof to form a host-guest inclusion compound. Due to the poor conductivity of CD, the direct construction of electrochemical sensors using it does not achieve good results. Efficient electrochemical chiral sensors not only require the identification of each enantiomer, but also require improved response signals, and thus the construction of chiral sensors using conjugated materials through the combination of enantioselectivity and electrochemical properties has become an option. Carboxymethyl-beta-cyclodextrin (CMCD) is a derivative of CD, has stronger compatibilization capacity and higher stability, and is generally used for compounding with other nano materials to form conjugated materials.
Hydrotalcite-like compounds (LDHs) are two-dimensional layered nanomaterials, which have a positive sheet charge and are widely used in recent years to immobilize negatively charged biomolecules. Compared with other inorganic matrixes, LDH has abundant chemical components, adjustable structural characteristics and intercalation performance, and is an effective host nanostructure for fixing guest molecules. However, LDH has the defects of easy aggregation, poor conductivity, insufficient exposure of catalytic active sites and the like, and the specific surface area of the LDH can be improved by stripping the LDH into LDH ultrathin nano sheets, and the catalytic sites of the LDH ultrathin nano sheets can be fully exposed, so that the electrochemical catalytic performance of the LDH can be improved. However, the LDH ultrathin nanosheets in the exfoliated state are easy to aggregate and recover into LDH bulk states in an aqueous medium, and can only be used in the form of colloidal solution, so that the deep development of hydrotalcite-like compounds in the electrochemical field is greatly limited. MXene has excellent conductivity and abundant surface groups, and is a promising substrate. The end groups have a large number of negatively charged-F and-OH surfaces, which are favorable for electroactive growth. Constructing three-dimensional interconnected morphology and introducing spacer material are effective strategies to address the inherent stacking deficiency of two-dimensional materials. In previous researches, MXene and LDH can be used as carriers to load a large number of electrochemical species so as to integrate respective advantages and realize new characteristics.
In order to solve the defects existing when the materials are used independently, hydrotalcite is synthesized in situ on an MXene material to compound the two materials, then the hydrotalcite is combined with carboxymethyl-beta-cyclodextrin (CMCD) to obtain a target material MXene @ LDH/CMCD nano compound, the compound is adopted to modify a Glassy Carbon Electrode (GCE), the synergistic effect of the modified electrode material is fully exerted by utilizing the difference of the affinities of the CMCD and different amino acid enantiomers and utilizing the advantages of larger specific surface areas of the MXene material and the hydrotalcite material and the like, the conductivity is improved, the active site of an electrocatalyst is fully exposed, the qualitative and quantitative detection of D-/L-methionine (D-/L-Met) is realized, the linear detection range is further widened, the detection limit is reduced, and the stability and the sensitivity are improved.
The invention content is as follows:
aiming at the defects of the prior art and the requirements of research and application in the field, one of the purposes of the invention is to provide a transition metal carbonitride @ hydrotalcite-like nanosheet/carboxymethyl-beta-cyclodextrin composite modified electrode, namely, a corresponding modified electrode prepared from MXene @ LDHNS/CMCD composite membrane.
The invention also aims to provide a preparation method of the electrode modified by the MXene @ hydrotalcite-like nano-sheet/carboxymethyl-beta-cyclodextrin composite material, which comprises the following specific steps:
(a) preparation of MXene material
Adding 1.98g LiF into a polytetrafluoroethylene beaker containing 30mL of 6M HCl solution, and stirring and mixing uniformly; then 3g of Ti were slowly added under stirring3AlC2Powder, reaction mixed solution is kept stirring at 40 ℃ for 45 hours of reaction, and centrifugal washing is carried out until the pH value of supernatant fluid is 6; obtaining MXene by freeze drying;
(b) preparation of MXene @ LDHNS
Dispersing 0.04g of MXene powder into 10mL of deionized water, ultrasonically stripping the MXene powder for 2h, centrifuging at 3500rpm for 1h, and discarding the precipitate to obtain an upper solution; the upper solution was mixed with 291mg of Co (NO)3)2·6H2O187.5 mg of Al (NO)3)3·9H2Dispersing O and 167.5mg of ammonium fluoride into 55mL of deionized water, and uniformly stirring; dropwise adding 4.5mL of 1M ammonia water into the mixed solution, stirring at room temperature for reaction for 1.5h, aging for 2.5h, washing the MXene @ LDHNS with distilled water and ethanol, and freeze-drying to obtain MXene @ LDHNS;
(c) preparation of MXene @ LDHNS/CMCD
Weighing 15mg of the MXene @ LDHNS material prepared above, ultrasonically dispersing the MXene @ LDHNS material in 10mL of deionized water, adding 60mg of CMCD, stirring for 12 hours, washing the obtained black slurry with ethanol and deionized water for three times, and freeze-drying to obtain MXene @ LDHNS/CMCD;
(d) preparation of MXene @ LDHNS/CMCD composite film modified GCE
Polishing the substrate electrode into a mirror surface, ultrasonically cleaning the mirror surface by using ultrapure water, and naturally drying the mirror surface at room temperature to obtain the well-treated GCE; ultrasonically dispersing the MXene @ LDHNS/CMCD composite material prepared in the step (c) in deionized water to prepare a dispersion liquid with the concentration of 1mg/mL, dropwise coating 2-20 mu L of the dispersion liquid on the surface of the GCE treated in the step (d), and naturally drying at room temperature to obtain the MXene @ LDHNS/CMCD composite film modified GCE.
Wherein in step (a) of the preparation method, Ti is added3AlC2In the case of powder, in order to prevent local reaction overheating, the powder must be kept in a stirring state all the time; said Co (NO) in step (b)3)2·6H2O and Al (NO)3)3·9H2The molar ratio of O is 2: 1; in the MXene @ LDHNS/CMCD, MXene has an obvious lamellar structure, and after the MXene is ultrasonically stripped into a single MXene, the LDHNS grows on the surface of the MXene in situ so that the ultrathin LDHNS is uniformly attached to the surface of the MXene; in the step (d), the polishing of the substrate electrode adopts aluminum oxide powder on chamois to polish in sequence, and the time of ultrasonic cleaning is 30 s.
The third purpose of the invention is to provide the application of the modified electrode of the transition metal carbonitride @ hydrotalcite-like nano-sheet/carboxymethyl-beta-cyclodextrin composite material in the identification and detection of the methionine chiral enantiomer, it is characterized in that 0.1mol/L phosphate buffer solution with pH 6.0 is used as supporting electrolyte, the modified electrode is added into an electrolytic cell after being incubated in electrolyte solution containing different amounts of L-methionine and D-methionine, and (3) taking the modified electrode as a working electrode, detecting by using a differential pulse voltammetry to respectively obtain linear regression equations of the oxidation peak currents and the concentrations of the oxidation peak currents of the L-methionine and the D-methionine, measuring the oxidation peak currents of the L-methionine and the D-methionine in the sample to be detected by using the same method, and substituting the oxidation peak currents into the linear regression equations to obtain the contents of the L-methionine and the D-methionine in the sample to be detected.
Compared with the prior art, the invention has the following beneficial effects:
(a) the MXene @ hydrotalcite-like nanosheet/carboxymethyl-beta-cyclodextrin composite material modified electrode provided by the invention exerts the synergistic effect of the components in the aspect of electrocatalysis of L-methionine and D-methionine: the carboxymethyl-beta-cyclodextrin can effectively and selectively adsorb various compounds into a hydrophobic cavity of the carboxymethyl-beta-cyclodextrin to form a host-guest inclusion compound, the possibility is provided for the recognition and detection of D-/L-Met due to the difference of the binding affinity of amino acid enantiomers, the MXene @ LDNS material counteracts the defects of CMCD in electron transfer, compared with the common GCE surface, the MXene @ LDHNS has higher specific surface area, loads more CMCD, effectively increases the active interface sites of chiral recognition, and has better selectivity, thereby providing an acceptable conductivity to ensure the sensitivity; and the MXene @ LDHNS/CMCD composite material has high asymmetry and more complex spatial difference, fully exerts the synergistic effect among different materials and realizes the qualitative and quantitative detection of D-/L-Met. The obtained electrochemical sensor can realize the identification and detection of the enantiomer, improve the response signal and improve the electrochemical performance.
(b) The MXene @ hydrotalcite-like nano-sheet/carboxymethyl-beta-cyclodextrin composite material modified electrode obtains a wider linear range (L-methionine 2 multiplied by 10) in the aspect of detecting D-/L-methionine enantiomer-8～2.5×10-5mol/L, D-methionine 1X 10-7～2.5×10-5mol/L) and lower detection limit (L-methionine 9.6nmol/L, D-methionine 39nmol/L), so that the chiral recognition of methionine enantiomer can be well realized, and the detection method has good stability and high sensitivity.
Description of the drawings:
FIG. 1 is an SEM image of the compound MXene, MXene @ LDHNS/CMCD obtained in example 1.
FIG. 2 shows the results of differential pulse voltammetry for GCE (A) corresponding to comparative example 1, CMCD/GCE (B) corresponding to comparative example 2, LDHNS/GCE (C) corresponding to comparative example 3, MXene @ LDHNS/GCE (D) corresponding to comparative example 4, and MXene @ LDHNS/CMCD/GCE (E) corresponding to example 1 in 0.1mol/L phosphate buffer pH 6.0 containing a mixture of 0.1mmol/L L-methionine and D-methionine, wherein a curve corresponds to L-methionine, and b curve corresponds to D-methionine.
FIG. 3 shows GCE (a), CMCD/GC for comparative examples 1 to 4 and example 1E (b), LDHNS/GCE (c), MXene @ LDHNS/GCE (d) and MXene @ LDHNS/CMCD/GCE (e) in a solution containing 10.0mmol/L [ Fe (CN)6]-3/-4And electrochemical impedance plot in 0.1mol/L KCl solution.
FIG. 4 is a differential pulse voltammogram of the L-methionine enantiomer at different concentrations, sequentially at 2X 10, on MXene @ LDHNS/CMCD/GCE corresponding to example 1-8、5×10-8、1×10-7、5×10-7、1×10-6、5×10-6、1×10-5、1.5×10-5、2×10-5、2.5×10-5mol/L(a～j)。
FIG. 5 is a differential pulse voltammogram of D-methionine enantiomer at different concentrations on MXene @ LDHNS/CMCD/GCE corresponding to example 1, with D-methionine concentration being 1X 10 in order-7、5×10-7、1×10-6、5×10-6、1×10-5、1.5×10-5、2×10-5、1.5×10-5mol/L(a～h)。
FIG. 6 is a graph showing the linear relationship between L-methionine concentration and peak current.
FIG. 7 is a graph showing the linear relationship between the D-methionine concentration and the peak current.
The specific implementation mode is as follows:
for a further understanding of the invention, reference will now be made to the following examples and drawings, which are not intended to limit the invention in any way.
Example 1:
(a) preparation of MXene material
Preparing 30mL of 6M HCl solution in a polytetrafluoroethylene beaker, adding 1.98g LiF, and uniformly mixing; slowly add 3g Ti3AlC2Powder, which is always kept in a stirring state in the adding process; after keeping the reaction mixture at 40 ℃ for 45h, centrifugally washing until the pH of the supernatant is 6; freeze drying to obtain Ti3C2TxMXene, hereinafter referred to as MXene;
(b) preparation of MXene @ LDHNS
Dispersing MXene (0.04g) into 10mL deionized water, ultrasonic stripping for 2h, centrifuging at 3500rpm for one hour, discarding precipitate to obtainWith Co (NO)3)2·6H2O(0.291g)、Al(NO3)3·9H2O (0.1875g) and ammonium fluoride (0.1675g) are dispersed in 55mL deionized water and stirred uniformly; 1M ammonia water (4.5mL) is added into the mixed solution dropwise; stirring the suspension at room temperature for 1.5h, aging for 2.5h to obtain MXene @ LDHNS, washing with distilled water and ethanol, and freeze-drying to obtain MXene @ LDHNS;
(c) preparation of MXene @ LDHNS/CMCD
Weighing 15mg of the MXene @ LDH material prepared above, ultrasonically dispersing the MXene @ LDH material into 10mL of deionized water, adding 60mg of CMCD, slowly stirring for 12h, washing the obtained black solid slurry with ethanol and deionized water for three times, and freeze-drying to obtain MXene @ LDH/CMCD;
(d) preparation of MXene @ LDHNS/CMCD composite film modified GCE
Polishing the substrate electrode into a mirror surface, ultrasonically cleaning the mirror surface by using ultrapure water, and naturally drying the mirror surface at room temperature to obtain the well-treated GCE; ultrasonically dispersing the MXene @ LDHNS/CMCD composite material prepared in the step (c) into deionized water to prepare a dispersion liquid with the concentration of 1mg/mL, dropwise coating 5 mu L of the dispersion liquid on the surface of the GCE treated in the step (d), and naturally drying at room temperature to obtain the MXene @ LDHNS/CMCD composite film modified GCE.
Example 2:
(a) preparation of MXene material
Prepared according to the method and conditions of step (a) in example 1;
(b) preparation of MXene @ LDHNS
Prepared according to the method and conditions of step (b) in example 1;
(c) preparation of MXene @ LDHNS/CMCD
Prepared according to the method and conditions of step (c) in example 1
(c) Preparation of MXene @ LDHNS/CMCD composite material modified GCE
Polishing the substrate electrode into a mirror surface, ultrasonically cleaning the mirror surface by using ultrapure water, and naturally drying the mirror surface at room temperature to obtain the well-treated GCE; ultrasonically dispersing the MXene @ LDHNS/CMCD composite material prepared in the step (c) into deionized water to prepare a dispersion liquid with the concentration of 1mg/mL, dropwise coating 2 muL of the dispersion liquid on the surface of the GCE treated in the step (d), and naturally drying at room temperature to obtain the MXene @ LDHNS/CMCD composite film modified GCE.
Example 3:
(a) preparation of MXene material
Prepared according to the method and conditions of step (a) in example 1;
(b) preparation of MXene @ LDHNS
Prepared according to the method and conditions of step (b) in example 1;
(c) preparation of MXene @ LDHNS/CMCD
Prepared according to the method and conditions of step (c) in example 1
(c) Preparation of MXene @ LDHNS/CMCD composite material modified GCE
Polishing the substrate electrode into a mirror surface, ultrasonically cleaning the mirror surface by using ultrapure water, and naturally drying the mirror surface at room temperature to obtain the well-treated GCE; ultrasonically dispersing the MXene @ LDHNS/CMCD composite material prepared in the step (c) into deionized water to prepare a dispersion liquid with the concentration of 1mg/mL, dropwise coating 8 muL of the dispersion liquid on the surface of the GCE treated in the step (d), and naturally drying at room temperature to obtain the MXene @ LDHNS/CMCD composite film modified GCE.
Example 4:
(a) preparation of MXene material
Prepared according to the method and conditions of step (a) in example 1;
(b) preparation of MXene @ LDHNS
Prepared according to the method and conditions of step (b) in example 1;
(c) preparation of MXene @ LDHNS/CMCD
Prepared according to the method and conditions of step (c) in example 1
(c) Preparation of MXene @ LDHNS/CMCD composite material modified GCE
Polishing the substrate electrode into a mirror surface, ultrasonically cleaning the mirror surface by using ultrapure water, and naturally drying the mirror surface at room temperature to obtain the well-treated GCE; ultrasonically dispersing the MXene @ LDHNS/CMCD composite material prepared in the step (c) into deionized water to prepare a dispersion liquid with the concentration of 1mg/mL, dropwise coating 10 mu L of the dispersion liquid on the surface of the GCE treated in the step (d), and naturally drying at room temperature to obtain the MXene @ LDHNS/CMCD composite film modified GCE.
Example 5:
(a) preparation of MXene material
Prepared according to the method and conditions of step (a) in example 1;
(b) preparation of MXene @ LDHNS
Prepared according to the method and conditions of step (b) in example 1;
(c) preparation of MXene @ LDHNS/CMCD
Prepared according to the method and conditions of step (c) in example 1
(c) Preparation of MXene @ LDHNS/CMCD composite material modified GCE
Polishing the substrate electrode into a mirror surface, ultrasonically cleaning the mirror surface by using ultrapure water, and naturally drying the mirror surface at room temperature to obtain the well-treated GCE; ultrasonically dispersing the MXene @ LDHNS/CMCD composite material prepared in the step (c) into deionized water to prepare a dispersion liquid with the concentration of 1mg/mL, dropwise coating 12 mu L of the dispersion liquid on the surface of the GCE treated in the step (d), and naturally drying at room temperature to obtain the MXene @ LDHNS/CMCD composite film modified GCE.
Comparative example 1:
directly using naked GCE.
Comparative example 2:
polishing the substrate electrode into a mirror surface, ultrasonically cleaning the mirror surface by using ultrapure water, and naturally drying the mirror surface at room temperature to obtain the well-treated GCE; ultrasonically dispersing analytically pure CMCD in deionized water to prepare a dispersion liquid with the concentration of 1mg/mL, dropwise coating 5 mu L of the dispersion liquid on the surface of the treated GCE, and naturally drying at room temperature to obtain CMCD/GCE;
comparative example 3:
(a) preparation of LDHNS material
Mixing Co (NO)3)2·6H2O(0.291g)、Al(NO3)3·9H2O (0.1875g) and ammonium fluoride (0.1675g) were added to 55mL of distilled water, and stirred well. 1M aqueous ammonia (4.5mL) was added dropwise to the mixed solution. Stirring the suspension at room temperature for 1.5h, aging for 2.5h, washing the obtained LDH with deionized water and ethanol, and freeze-drying to obtain LDH;
(b) preparation of LDHNS composite material modified GCE
Polishing the substrate electrode into a mirror surface, ultrasonically cleaning the mirror surface by using ultrapure water, and naturally drying the mirror surface at room temperature to obtain the well-treated GCE; ultrasonically dispersing the LDHNS material prepared in the step (a) in deionized water to prepare dispersion liquid with the concentration of 1mg/mL, dropwise coating 5 mu L of the dispersion liquid on the surface of the GCE treated in the step (b), and naturally drying at room temperature to obtain the GCE modified by the LDHNS composite membrane.
Comparative example 4:
(a) preparation of MXene material
Prepared according to the method and conditions of step (a) in example 1;
(b) preparation of MXene @ LDHNS
Prepared according to the method and conditions of step (b) in example 1;
(c) preparation of MXene @ LDHNS composite material modified GCE
Polishing the substrate electrode into a mirror surface, ultrasonically cleaning the mirror surface by using ultrapure water, and naturally drying the mirror surface at room temperature to obtain the well-treated GCE; ultrasonically dispersing the MXene @ LDHNS composite material prepared in the step (b) in deionized water to prepare a dispersion liquid with the concentration of 1mg/mL, dropwise coating 5 mu L of the dispersion liquid on the surface of the GCE treated in the step (c), and naturally drying at room temperature to obtain the MXene @ LDHNS composite film modified GCE.
FIG. 1 is an SEM image of the MXene, MXene @ LDHNS/CMCD composite of the present invention. The multi-slice structure of MXene is clearly observed in FIG. A. After MXene is ultrasonically stripped into single MXene, LDHNS grows on the MXene surface in situ, so that a layer of single-sheet hydrotalcite is uniformly adhered to the MXene surface, as shown in a diagram B. The CMCD can be adsorbed on the surface of the LDHNS through electrostatic adsorption, the uniform adhesion of the LDHNS provides a large number of attachment sites for the CMCD, and the adhesion of the CMCD also makes the surface of the MXene @ LDH material quite rough, as shown in a graph C.
Example 6:
by using MXene @ LDHNS/CMCD/GCE prepared in example 1 as a working electrode, a platinum wire as a counter electrode and an Ag/AgCl electrode as a reference electrode, GCE, CMCD/GCE, LDHNS/GCE, MXene @ LDHNH @ LDH corresponding to comparative example 1, comparative example 2, comparative example 3, comparative example 4 and comparative example 1 as comparisonNS/CMCD/GCE was used as the working electrode, and then differential pulse voltammetry was performed in 0.1mol/L phosphate buffer pH 6.0 containing 0.1mmol/L L-methionine and D-methionine, respectively (curve a is L-methionine, and curve b is D-methionine), and the results are shown in FIG. 2. As shown in panel A, the DPV peaks of L-Met and D-Met showed little difference in current at the 0.47V oxidation peak on the blank control naked GCE, indicating that the naked GCE did not have chiral recognition ability. In the DPV response of D-/L-Met at CMCD/GCE in FIG. B, although both L-Met and D-Met can bind to the cavity of CMCD to form a host-guest coating structure, CMCD as a chiral agent exhibits different binding affinities to D-/L-Met, and significantly stronger binding affinity to L-Met than to D-Met, so that although no significant difference in oxidation peak potential is exhibited, the oxidation peak current is significantly increased to different degrees compared to naked GCE, IL/IDAbout 1.35, which indicates that the CMCD modified electrode has certain ability for detecting and identifying Met chiral isomer, but the identification efficiency is not ideal due to small current ratio, probably because the CMCD amount adsorbed by GCE is too small to effectively identify L-Met and D-Met. Panel C and D are the DPV responses of D-/L-Met at LDHNS/GCE and MXene @ LDHNS/GCE, respectively. Compared with naked GCE, the oxidation peak current of D-/L-Met is obviously improved, the difference of the improvement amplitude of the current is small and almost negligible, and the results show that the LDHNS/GCE and MXene @ LDHNS/GCE have no capacity of distinguishing L-Met from D-Met. As shown in FIG. E, detection of L/D-Met, I was performed using MXene @ LDHNS/CMCD/GCEL/IDAt 1.81, the difference increased significantly. According to our conjecture, there are three major influencing factors that support the expected results of nanocomposites. Firstly, the difference of the binding affinity of CMCD to the amino acid enantiomer provides the possibility for the identification and detection of D-/L-Met; secondly, the MXene @ LDHNS material offsets the defects of the CMCD in the aspect of electron transfer, and compared with the surface of the common GCE, the MXene @ LDHNS material has a higher specific surface area and loads more CMCDs, so that the active interface sites of chiral recognition are effectively increased, and the selectivity is better, and therefore, the acceptable conductivity is provided to ensure the sensitivity; thirdly, the MXene @ LDHNS/CMCD composite material has high asymmetry and more complex spatial difference, and gives full play to different materialsRealizes the qualitative and quantitative detection of D-/L-Met by the synergistic effect. In conclusion, the feasibility of chiral recognition of the MXene @ LDHNS/CMCD nanocomposite is clearly proved by the research results, and the great potential of chiral sensing is shown by the effective synergistic effect of the asymmetric mixed sensing interface.
FIG. 3 shows GCE (a), CMCD/GCE (b), LDHNS/GCE (c), MXene @ LDHNS/GCE (d) and MXene @ LDHNS/CMCD/GCE (d) in the amounts of 10.0mmol/L [ Fe (CN)6]-3/-4And electrochemical impedance plot in 0.1mol/L KCl solution. As can be seen from the figure, the spectrum is divided into two parts, where a semicircle under high frequency corresponds to the effective electron transfer control process, and the diameter of the semicircle represents the electron transfer resistance (Ret); while the linear part of the lower frequency band corresponds to the solute diffusion control process. The fitted charge transfer resistance (R) of comparative example 2 to CMCD/GCE (curve b, 780 Ω) due to poor CMCD conductivityct) Only superior to the bare-board GCE of comparative example 1 (curve a, 1300. omega.), the LDHNS-modified electrode of comparative example 3 alone and the R of CMCD/GCEctThe difference is not very large, about 770 Ω. Compared with MXene @ LDHNS/GCE in the comparative example 4, the conductivity of the modified electrode is improved, the electron transfer is promoted, and RctThe value is smaller about 460 Ω, which is significantly lower than the first three. Example 1R of MXene @ LDHNS/CMCD/GCEctThe value is slightly increased compared with MXene @ LDHNS/GCE, but the performance is obviously improved compared with CMCD/GCE, and the purposes of improving the conductivity of the modified electrode and promoting electron transfer are achieved. The result is well matched with the CV result, and the successful preparation of the MXene @ LDHNS/CMCD nano composite electrochemical sensor is verified again.
Increasing the concentration of L-methionine and D-methionine, increasing the current of oxidation peak, obtaining the linear relation curve of the concentration of L-methionine and D-methionine and the current of oxidation peak, and determining the detection limit of L-methionine and D-methionine according to the related sensitivity determination rule. The optimal condition for measuring the L-methionine and the D-methionine is phosphate buffer solution with pH of 6.0, and the concentrations of the L-methionine and the D-methionine measured by differential pulse voltammetry are in a good linear relation with oxidation peak current within a certain range.
FIG. 4 is a differential pulse voltammogram of L-methionine at various concentrations on MXene @ LDHNS/CMCD/GCE corresponding to example 1. It can be seen that the response value current of L-methionine is gradually increased along with the increase of the concentration in the concentration range of the experiment, which indicates that the modified electrode prepared by the invention can realize the quantitative detection of L-methionine.
FIG. 5 is a differential pulse voltammogram of D-methionine at various concentrations on the corresponding MXene @ LDHNS/CMCD/GCE of example 1. It can be seen that the response value current of D-methionine is gradually increased along with the increase of the concentration in the concentration range of the experiment, which shows that the modified electrode prepared by the invention can realize the quantitative detection of D-methionine.
As shown in FIG. 6, L-methionine has different linear relations in the range of 0.02 to 0.5. mu.M and in the range of 0.5 to 25. mu.M, respectively, and is I (. mu.A) ═ 1.62212c (. mu.M) -0.83914 (R)20.98763) and I (μ a) -0.25643c (μ M) -1.49803 (R)20.99471) with a detection limit of 9.6 nM.
As shown in FIG. 7, D-methionine has a good linear relationship in the range of 0.1-25 μ M, I (μ A) ═ 0.17741c (μ M) -0.6858 (R)20.99391) with a detection limit of 39 nM.
As can be seen from Table 1, after the MXene @ LDHNS/CMCD nano composite is adopted to modify the substrate electrode, the linear range of the MXene @ LDHNS/CMCD nano composite in the identification and detection of L-methionine and D-methionine is close to or superior to that of the existing modified electrode, but the detection limit is obviously lower than that of the existing modified electrode, so that the MXene @ LDHNS/CMCD composite membrane modified electrode has sensitive electrocatalytic performance on L-methionine and D-methionine, and therefore better stability and sensitivity are shown.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Table 1 shows the comparison of the performance of MXene @ LDHNS/CMCD/GCE for detecting L-methionine and D-methionine in the invention with other electroanalysis methods
Figure BDA0003210057640000101

Claims (3)

1. A transition metal carbonitride @ hydrotalcite-like nano sheet/carboxymethyl-beta-cyclodextrin composite film modified electrode is characterized in that the composite film modified electrode is composed of a glassy carbon electrode as a substrate electrode and transition metal carbonitride @ hydrotalcite-like nano sheet/carboxymethyl-beta-cyclodextrin as an electrode modification material; the transition metal carbonitride @ hydrotalcite-like nanosheet/carboxymethyl-beta-cyclodextrin is obtained by preparing MXene by using a fluoride salt etching method, growing the hydrotalcite-like nanosheet on the surface of the MXene in situ, and modifying the carboxymethyl-beta-cyclodextrin to the surface of the MXene @ hydrotalcite-like nanosheet by using electrostatic adsorption; the glassy carbon electrode is marked as GCE; the MXene is transition metal carbonitride; the hydrotalcite-like nano-sheet is a cobalt-aluminum hydrotalcite-like nano-sheet and is marked as LDHNS; the carboxymethyl-beta-cyclodextrin is marked as CMCD;
the preparation method of the transition metal carbonitride @ hydrotalcite nanosheet/carboxymethyl-beta-cyclodextrin composite membrane modified electrode comprises the following specific steps:
(a) preparation of MXene material
Adding 1.98g LiF into a polytetrafluoroethylene beaker containing 30mL of 6M HCl solution, and stirring and mixing uniformly; then 3g of Ti were slowly added under stirring3AlC2Powder, reaction mixed solution is kept stirring at 40 ℃ for 45 hours of reaction, and centrifugal washing is carried out until the pH value of supernatant fluid is 6; obtaining MXene by freeze drying;
(b) preparation of MXene @ LDHNS
Dispersing 0.04g of MXene powder into 10mL of deionized water, ultrasonically stripping the MXene powder for 2h, centrifuging at 3500rpm for 1h, and discarding the precipitate to obtain an upper solution; the upper solution was mixed with 291mg of Co (NO)3)2·6H2O187.5 mg of Al (NO)3)3·9H2Dispersing O and 167.5mg of ammonium fluoride into 55mL of deionized water, and uniformly stirring; 4.5mL of 1M ammonia water is added into the mixed solution dropwise, stirred at room temperature for reaction for 1.5h, and then aged for 2.5h to obtainWashing MXene @ LDHNS with distilled water and ethanol, and freeze-drying to obtain MXene @ LDHNS;
(c) preparation of MXene @ LDHNS/CMCD
Weighing 15mg of the MXene @ LDHNS material prepared above, ultrasonically dispersing the MXene @ LDHNS material in 10mL of deionized water, adding 60mg of CMCD, stirring for 12 hours, washing the obtained black slurry with ethanol and deionized water for three times, and freeze-drying to obtain MXene @ LDHNS/CMCD;
(d) preparation of MXene @ LDHNS/CMCD composite film modified GCE
Polishing the substrate electrode into a mirror surface, ultrasonically cleaning the mirror surface by using ultrapure water, and naturally drying the mirror surface at room temperature to obtain the well-treated GCE; ultrasonically dispersing the MXene @ LDHNS/CMCD composite material prepared in the step (c) in deionized water to prepare a dispersion liquid with the concentration of 1mg/mL, dropwise coating 2-20 mu L of the dispersion liquid on the surface of the GCE treated in the step (d), and naturally drying at room temperature to obtain the MXene @ LDHNS/CMCD composite film modified GCE.
2. The transition metal carbonitride @ hydrotalcite-like nanosheet/carboxymethyl-beta-cyclodextrin composite film modified electrode according to claim 1, wherein Ti is added in the step (a) of the preparation method3AlC2In the case of powder, in order to prevent local reaction overheating, the powder must be kept in a stirring state all the time; said Co (NO) in step (b)3)2·6H2O and Al (NO)3)3·9H2The molar ratio of O is 2: 1; in the MXene @ LDHNS/CMCD, MXene has an obvious lamellar structure, and after the MXene is ultrasonically stripped into a single MXene, the LDHNS grows on the surface of the MXene in situ so that the ultrathin LDHNS is uniformly attached to the surface of the MXene; in the step (d), the polishing of the substrate electrode adopts aluminum oxide powder on chamois to polish in sequence, and the time of ultrasonic cleaning is 30 s.
3. The transition metal carbonitride @ hydrotalcite-like nanosheet/carboxymethyl-beta-cyclodextrin composite membrane modified electrode of claim 1 or 2, used for identifying and detecting methionine chiral enantiomer, it is characterized in that 0.1mol/L phosphate buffer solution with pH 6.0 is used as supporting electrolyte, the modified electrode is added into an electrolytic cell after being incubated in electrolyte solution containing different amounts of L-methionine and D-methionine, and (3) taking the modified electrode as a working electrode, detecting by using a differential pulse voltammetry to respectively obtain linear regression equations of the oxidation peak currents and the concentrations of the oxidation peak currents of the L-methionine and the D-methionine, measuring the oxidation peak currents of the L-methionine and the D-methionine in the sample to be detected by using the same method, and substituting the oxidation peak currents into the linear regression equations to obtain the contents of the L-methionine and the D-methionine in the sample to be detected.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114381023A (en) * 2021-12-17 2022-04-22 武汉工程大学 MXene film crosslinked with beta-cyclodextrin, and preparation method and application thereof
CN115403832A (en) * 2022-01-11 2022-11-29 贵州大学 Preparation method and application of anti-oxidation MXene based on cyclodextrin encapsulation

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114381023A (en) * 2021-12-17 2022-04-22 武汉工程大学 MXene film crosslinked with beta-cyclodextrin, and preparation method and application thereof
CN114381023B (en) * 2021-12-17 2023-12-12 武汉工程大学 MXene film of crosslinked beta-cyclodextrin and preparation method and application thereof
CN115403832A (en) * 2022-01-11 2022-11-29 贵州大学 Preparation method and application of anti-oxidation MXene based on cyclodextrin encapsulation
CN115403832B (en) * 2022-01-11 2023-05-30 贵州大学 Preparation method and application of cyclodextrin encapsulation-based antioxidant MXene

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