CN113567531B - Composite material N-Co-MOF@PDA-Ag and preparation method and application thereof - Google Patents
Composite material N-Co-MOF@PDA-Ag and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of metal organic materials, and particularly relates to a composite material N-Co-MOF@PDA-Ag, and a preparation method and application thereof. N-doped Co-MOF@polydopamine (N-Co-MOF@PDA) is then wrapped by in-situ reduced Ag nanoparticles (Ag NPs) to prepare the final target N-Co-MOF@PDa-Ag composite material. In the synthesis process, dopamine (DA) is added into Tris buffer solution in which N-Co-MOF nano sheets are uniformly dispersed, and the N-Co-MOF nano sheets can effectively promote DA polymerization. The novel non-enzymatic glucose sensor based on the N-Co-MOF@PDA-Ag composite material is developed, has the advantages of wide linear range, low detection limit, good selectivity and the like, and can be used for detecting glucose in various solutions.
Description
Technical Field
The invention belongs to the technical field of metal organic materials, and particularly relates to a composite material N-Co-MOF@PDA-Ag, and a preparation method and application thereof.
Background
Glucose is the main source of energy molecule adenosine triphosphate produced by the human body. However, excessive levels of glucose in the human blood may lead to some metabolic disorders. Therefore, it is particularly important to be able to reliably and sensitively analyze and detect glucose in food processing and clinical diagnosis. Currently, methods for measuring glucose include colorimetry, fluorescence, capacitance, acoustic, electrochemical methods, and the like. Among them, electrochemical glucose sensors are attracting attention due to their good response performance and easy operation, and generally fall into two main categories: enzyme sensor and non-enzyme sensor. However, these enzyme-based electrochemical sensors have disadvantages of high cost, strict operating conditions, unstable long-term, complicated immobilization process, and the like. Non-enzymatic glucose sensors can overcome the drawbacks of enzymatic glucose sensors to some extent, and thus, a great deal of research has been conducted on non-enzymatic glucose sensors in recent years.
Metal-organic frameworks (met)al-organic frameworks, MOF) is an organic-inorganic hybrid material formed from organic ligands and metal ions through coordination bonds. The material has been paid attention to because of its unique advantages of large specific surface area, diverse structures, high porosity, and abundant active sites. However, poor electrical conductivity is a major obstacle to the use of MOFs in the field of electrochemical sensors. Therefore, it would be of great interest to develop new strategies to improve the conductivity and sensing performance of non-enzymatic sensors based on MOFs, such as Co-MOFs. In addition, the Co-MOF non-enzyme sensor based on modification, which is developed in literature, has excellent peroxidase-like activity and can be used as an electrocatalyst for glucose and H 2 O 2 And non-enzymatic detection of zearalenone.
Dopamine (DA) is a Polydopamine (PDA) monomer containing catechol and amino functional groups, which can show strong adhesion on almost any material surface after oxidative self-polymerization under alkaline conditions, and is receiving a great deal of attention as a potential material. In 2018 Liu subject group, PDA-coated polyvinyl alcohol-ethylene copolymer nanofiber membrane is prepared by adopting in-situ polymerization method, and then the prepared PDA-nanofiber membrane is used as in-situ reducing agent to capture Ag + And reduced to Ag NPs (Composit. Commun.9 (2018) 11-16.).
Disclosure of Invention
According to the defects existing in the prior art, the invention provides a composite material N-Co-MOF@PDA-Ag, a preparation method and application thereof, solves the problem of low self-polymerization speed of the existing dopamine, and provides a novel non-enzymatic glucose sensor with good catalytic performance.
The invention is realized by adopting the following technical scheme:
the invention provides a preparation method of silver nanoparticle-coated and rapidly polymerized core-shell material nitrogen-doped Co-MOF@polydopamine, which is characterized by comprising the following steps of:
(1) N-Co-MOF preparation:
Co(Ac) 2 ·4H 2 o and polyvinylpyrrolidone according to 0.6-0.7: 1 in 20mL DMF as a solutionA, A is as follows; 1, 4-terephthalic acid is dissolved in DMF to form solution B with the mass concentration of 10-11 mg/mL; then, dropwise adding the solution B into the solution A, uniformly stirring, transferring into a high-pressure reaction kettle, reacting for 20 hours at 105 ℃, centrifugally separating the obtained product, washing for multiple times by using DMF and ethanol respectively, and drying;
(2) Preparation of N-Co-MOF@PDA-Ag:
ultrasonically dispersing the N-Co-MOF nanosheets synthesized in the step (1) in Tris buffer (pH 8.5,10 mM), wherein the mass concentration is 2mg/mL, then adding 2mg/mL of dopamine, and stirring for 1h at room temperature; centrifugally filtering the obtained product, and cleaning the product by using ultrapure water to obtain a core-shell material N-Co-MOF@PDA;
N-Co-MOF@PDA was then sonicated to freshly formulated [ Ag (NH) 3 ) 2 ] + In the solution, the mass concentration ratio is N-Co-MOF@PDA: [ Ag (NH) 3 ) 2 ] + =1.5 to 2:5, stirring for 10-12 h in the dark; and (3) after centrifugation, collecting the obtained composite material N-Co-MOF@PDA-Ag, washing the composite material N-Co-MOF@PDA-Ag with ultrapure water and ethanol for multiple times, and drying the composite material in vacuum.
The invention also provides a composite material N-Co-MOF@PDA-Ag prepared by the preparation method, and the rapidly polymerized core-shell material nitrogen-doped Co-MOF@polydopamine is coated by silver nano particles which are reduced in situ outside the composite material N-Co-MOF@PDA-Ag.
The invention also provides application of the composite material N-Co-MOF@PDA-Ag, which is used for preparing a glucose electrochemical sensor, and detecting the linear range of glucose in a glucose-containing solution to be 1 mu M-2 mM, wherein the detection limit is 0.5 mu M (S/N=3).
The preparation method of the electrode of the glucose electrochemical sensor comprises the following steps: adding the N-Co-MOF@PDA-Ag composite material into ethanol, and performing ultrasonic diffusion to obtain a black suspension with 2mg/mL of uniformly dispersed particles; transferring 3-5 mu L N-Co-MOF@PDA-Ag suspension drops on the surface of a pretreated clean Glassy Carbon (GC) electrode, and airing; then 2-3 mu L of Nafion solution (0.05 wt%) is dripped on the surface of the electrode as a binder, and the electrode is obtained after drying.
Specifically, the electrode was scanned from-0.2 to 0.6V using a potential in a 0.1M NaOH solution at a scan rate of 50 mV/s.
Preferably, the glucose-containing solution comprises human serum, and the linear range of detecting glucose in the human serum is 5 mu M-2.6 mM, and the detection limit is 2.0 mu M.
Preferably, the glucose-containing solution comprises a glucose-containing juice, and the linear range of detecting glucose in the glucose-containing juice is 5 mu M-2.0 mM, and the detection limit is 2.5 mu M.
Compared with the prior art, the invention has the beneficial effects that:
as shown in FIG. 1, a rapidly polymerized core-shell material N-Co-MOF@PDA was prepared and coated with in-situ reduced Ag NPs. In the synthesis process, DA is added into Tris buffer solution in which N-Co-MOF nano sheets are uniformly dispersed, and the N-Co-MOF can effectively improve the polymerization speed of DA, so that the preparation time of PDA can be greatly shortened compared with the traditional DA self-polymerization method. PDA in the core-shell material N-Co-MOF@PDA can be used for preparing Ag without adding other reducing agents + In-situ reducing to silver nano particles (Ag NPs) to prepare the target composite material N-Co-MOF@PDa-Ag. Because the N-Co-MOF and Ag NPs have the performance of synergetic electrocatalytic oxidation of glucose, a novel non-enzymatic glucose sensor with good catalytic performance based on the N-Co-MOF@PDa-Ag composite material is developed. The linear range of glucose detection by the sensor based on the N-Co-MOF@PDA-Ag composite material is as follows: 1. Mu.M to 2mM, the limit of detection is 0.5. Mu.M (S/N=3), and furthermore, has good selectivity, long-term stability and good reproducibility. The sensor verifies the feasibility of detecting glucose in actual sample fruit juice and human serum, and achieves satisfactory results. The above results indicate that the N-Co-MOF@PDA-Ag composite material provided by the invention is a very promising non-enzyme sensor candidate material.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention.
In the drawings:
FIG. 1 is a schematic diagram of a sensing mechanism of a preparation and modification electrode of an N-Co-MOF@PDA-Ag composite material of the invention;
FIG. 2 is a photograph showing the synthesis process of example 1 of the present invention; wherein, the photographs of different reaction times in the preparation process of the PDA in the figure 2 (A) and the N-Co-MOF@PDA in the figure 2 (B) are shown;
FIG. 3 is an SEM image of a composite material of the present invention; wherein, the SEM images and partial enlargement of FIG. 3 (A) N-Co-MOF, FIG. 3 (B) N-Co-MOF@PDA and FIG. 3 (C) N-Co-MOF@PDA-Ag, and the TEM images of corresponding FIG. 3 (D) N-Co-MOF, FIG. 3 (E) N-Co-MOF@PDA and FIG. 3 (F) N-Co-MOF@PDA-Ag; FIG. 3 (G) SEM image of N-Co-MOF@PDA-Ag and a Co, ag, C, N, O element distribution diagram thereof;
FIG. 4 is a topographical view of a composite material of the present invention; SEM pictures of 4 (A) Co-MOF and 4 (B) N-Co-MOF and related photographs 4 (C) and 4 (D).
FIG. 5 is an XRD pattern and XPS pattern of a composite material of the present invention; wherein the XRD pattern of the N-Co-MOF@PDa-Ag composite material of FIG. 5 (A), the XPS full spectrum of the N-Co-MOF@PDa-Ag composite material of FIG. 5 (B), the high resolution XPS spectrum of Co 2p of FIG. 5 (C) and Ag 3D of FIG. 5 (D);
FIG. 6 is a cyclic voltammogram and amperometric response curve of a composite material of the invention; wherein, FIG. 6 (A) is a cyclic voltammogram of bare GC, FIG. 6 (B) is an N-Co-MOF@PDA and FIG. 6 (C) is an N-Co-MOF@PDA-Ag modified electrode without addition (dotted line) and with addition of 0.5mM glucose (solid line) in 0.1M NaOH solution at a scan rate of 50 mV/s; FIG. 6 (D) amperometric responses of bare GC, N-Co-MOF@PDA and N-Co-MOF@PDA-Ag modified electrodes at an applied potential of 0.55V with 6. Mu.M glucose added continuously to a 0.1M NaOH solution;
FIG. 7 is a plot of cyclic voltammograms and peak current versus scan rate for a composite material of the present invention; wherein FIG. 7 (A) is a cyclic voltammogram of 0, 0.5, 1, 1.5, 2.0 and 2.5mM glucose in a 0.1M NaOH solution at a 50mV/s sweep rate based on an N-Co-MOF@PDA-Ag sensor; FIG. 7 (B) cyclic voltammograms at different scan rates (30, 60, 90, 120, 150, 180 and 210 mV/s) after addition of 0.5mM glucose to a 0.1M NaOH solution based on an N-Co-MOF@PDA-Ag sensor; FIG. 7 (C) is a linear plot of peak redox current versus scan rate;
FIG. 8 is a graph showing the response of the applied potential and ion concentration to current flow in accordance with the present inventionSounding; wherein FIG. 8 (A) applies a potential and FIG. 8 (B) Ag + Effect of ion concentration on response to detecting 100 μm glucose current based on N-Co-mof@pdA-Ag sensor;
FIG. 9 is an ampere-current response curve and a linear relationship between ampere-current and glucose concentration for a composite material of the present invention; wherein, FIG. 9 (A) and FIG. 9 (B) are based on the amperometric response of an N-Co-MOF@PDA-Ag sensor with glucose added continuously to a 0.1M NaOH solution; FIG. 9 (C) is a linear plot of amperometric current versus glucose concentration; FIG. 9 (D) amperometric responses of 100. Mu.M glucose, 20. Mu.M fructose, 20. Mu.M ascorbic acid, 20. Mu.M uric acid and 100. Mu.M glucose were continuously added to a 0.1M NaOH solution based on an N-Co-MOF@PDA-Ag sensor at an applied potential of 0.55V;
FIG. 10 is a reproducibility study (FIG. 10 (A)) and a stability study (FIG. 10 (B)) of the electrochemical detection of 100. Mu.M glucose assay of the synthetic material of the present invention.
FIG. 11 is a graph showing amperometric current response and a linear relationship between amperometric current and glucose concentration for a synthetic material of the invention in an actual sample; wherein glucose was continuously added to the actual samples of FIG. 11 (A) human serum and FIG. 11 (C) juice based on the amperometric response of the N-Co-MOF@PDA-Ag sensor; the amperometric current of the response was plotted against the concentration of glucose in the human serum of FIG. 11 (B) and the juice of FIG. 11 (D).
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings, in order to make the objects and technical solutions of the present invention more apparent. The experimental methods described in the following examples are all conventional methods unless otherwise specified; the specific techniques or conditions are not identified in the examples and are performed according to techniques or conditions described in the literature in this field or according to product specifications; the reagents and materials, unless otherwise specified, are commercially available.
1. Reagents and materials
Cobalt acetate tetrahydrate (Co (Ac) 2 ·4H 2 O), sodium hydroxide (NaOH), polyvinylpyrrolidone (PVP, average molecular weight 24,000 g/mol), 1, 4-terephthalic acid (H) 2 BDC), N-Dimethylformamide (DM)F) Silver nitrate (AgNO) 3 ) Dopamine hydrochloride, glucose, urea, uric acid, and antioxidant blood acid were all purchased from national pharmaceutical chemicals, inc. Nafion was purchased from Sigma-Aldrich. The electrolyte is 0.1M NaOH solution. All reagents were analytical grade reagents. During the experiment, all solutions were prepared with ultra pure water (18.2 M.OMEGA.cm, millipore).
2. Instrument for measuring and controlling the intensity of light
The morphology of the material was characterized by means of a field emission scanning electron microscope (FE-SEM, zeiss Sigma 500/VP, germany) and a transmission electron microscope (TEM, JEM-2100F). The phase structure of the material was analyzed by X-ray diffractometer (XRD, bruker D8 Advanced, germany). The elemental valence state was analyzed by X-ray photoelectron spectroscopy (XPS, perkinElmer-5000C, USA). All electrochemical measurements were performed on an electrochemical workstation (CHI 760E, china). A standard three-electrode system is adopted, wherein a Glassy Carbon (GC) electrode with the diameter of 3mm is used as a working electrode, a platinum wire is used as a counter electrode, and an Ag/AgCl electrode (3M KCl) is used as a reference electrode.
1. Preparing an N-Co-MOF@PDA-Ag composite material and modifying a GC electrode:
example 1
(1) PVP is adopted to assist in synthesizing N-doped Co-MOF (N-Co-MOF):
0.642g Co(Ac) 2 ·4H 2 o and 1.0g PVP were dissolved in 20mL DMF as solution A.0.418g H 2 BDC was dissolved in 40mL DMF as solution B. Subsequently, solution B was added dropwise to solution A, stirred for 10 minutes, transferred to a 100mL autoclave, reacted at 105℃for 20 hours, and the resultant product was centrifuged, washed 3 times with DMF and ethanol, respectively, and dried overnight at 60 ℃.
(2) Synthesis of N-Co-MOF@PDA-Ag composite material
The 40mg N-Co-MOF nanoplatelets synthesized in step (1) were sonicated in 20mL Tris buffer (pH 8.5,10 mM), then 2mg/mL DA was added and stirred at room temperature for 1h. The obtained product is centrifugally filtered and washed by ultrapure water for 3 times to obtain the core-shell material N-Co-MOF@PDA. Then 2mg/mL of N-Co-MOF@PDA was ultrasonically dispersed to a newly formulated 5mg/mL [ Ag (NH) 3 ) 2 ] + The solution was stirred in the dark for 12h. Collecting after centrifugationThe target composite material N-Co-MOF@PDA-Ag was washed three times with ultrapure water and ethanol, and dried under vacuum overnight.
Comparative example 1
To investigate the effect of PVP on Co-MOF morphology, co-MOF was synthesized following the procedure of example 1, except that PVP was not added.
Comparative example 2
Traditional DA polymerization methods, self-polymerization in Tris buffer:
40mg of DA was dispersed in 20mL of Tris buffer (pH 8.5,10 mM) and stirred at room temperature for 12h. The obtained product was centrifugally filtered, washed with ultrapure water 3 times, and dried to obtain PDA.
Example 2
10mg of the N-Co-MOF@PDA-Ag composite material prepared in example 1 was added to 5mL of ethanol, and subjected to ultrasonic diffusion for 20 minutes to obtain 2mg/mL of a uniformly dispersed black suspension. And transferring 5 mu L of the N-Co-MOF@PDA-Ag suspension drops to the surface of the pretreated clean GC electrode, and naturally airing. Then 3. Mu.L of Nafion solution (0.05 wt%) was added dropwise as a binder to the electrode surface, and the mixture was dried for use.
Comparative example 3
For comparison, a GC electrode modified with a core-shell material N-Co-MOF@PDA was prepared using the method of example 2.
2. Characterization of N-Co-MOF@PDA-Ag composite material
1. FIG. 2 depicts the synthesis process of the N-Co-MOF@PDA-Ag composite material and the detection mechanism of the prepared glucose sensor. Firstly, in Tris buffer solution, DA is oxidized and polymerized on the surface of an N-Co-MOF nanosheet to prepare the core-shell material N-Co-MOF@PDA. The conventional DA polymerization method used in comparative example 2 was self-polymerization in an alkaline solution, but the reaction rate was very slow, and it generally took about 12 hours (fig. 2 (a)), which is in accordance with the literature report (Carbon 46 (2008) 1792-1828; ACS appl. Mater. Interfaces 5 (2013) 9167-9171.). Notably, in example 1, the polymerization rate of DA was greatly increased after adding the N-Co-MOF nanoplatelets to the buffer solution, and the polymerization was completed in about 1 hour (FIG. 2 (B)), and the thickness of PDA was about 20nm (FIG. 3 (F)). Then, since PDA contains active amino and catechol functional groups, [ Ag (NH) 3 ) 2 ] + Can be effectively adsorbed on the outer layer of the N-Co-MOF@PDA and can be reduced to Ag NPs in situ. And finally, uniformly dispersed N-Co-MOF@PDA-Ag suspension is dripped on the surface of the GC electrode to construct the electrochemical sensor. Notably, the anodic current of the cyclic voltammogram increases significantly after glucose addition, which confirms that the prepared sensor has good catalytic activity for glucose oxidation.
2. The microstructure of the composite material was analyzed by SEM and TEM. As can be seen from FIGS. 3 (A) and 3 (D), the synthesized N-Co-MOF nanoplatelets have smooth surfaces and a two-dimensional layered structure, and the average thickness of the single nanoplatelets is about 19nm. In contrast, co-MOFs synthesized without PVP were large and prone to agglomeration, and the shape of the nanoplatelets was only marginally observed (fig. 4 (a) and fig. 4 (B)). In addition, the color of the N-Co-MOF was light purple, unlike the dark purple of the Co-MOF (FIG. 4 (D) and FIG. 4 (C)). The conclusion above shows that PVP plays an important role in morphology control in the synthesis of N-Co-MOF nanoplatelets. As shown in FIG. 3 (B) and FIG. 3 (E), the N-Co-MOF@PDA composite material which has an obvious core-shell structure, a rough surface and uniform morphology is successfully synthesized, namely, an N-Co-MOF nano sheet is used as a core layer, and a PDA thin shell layer with the thickness of about 20nm is successfully coated. As shown in FIG. 3 (C) and FIG. 3 (F), a large number of uniformly dispersed spherical Ag NPs were deposited on the surface of the N-Co-MOF@PDA, with an average diameter of about 23nm, indicating that the PDA successfully formed Ag (NH) 3 ) 2 ] + Reduced to Ag NPs. As shown in FIG. 3 (G), EDS analysis confirmed that the Co, ag, C, N, O element was uniformly distributed throughout the N-Co-MOF@PDA-Ag composite material.
The XRD spectrum of the synthetic material is shown in FIG. 5 (A). The characteristic diffraction peaks of the synthesized N-Co-MOF all conform to the standard chart of MOF-71 (CCDC-265092) (J.solid State chem.242 (2016) 71-76.; J.am.chem.Soc.127 (2005) 1504-1518.) which demonstrates successful preparation of the N-Co-MOF. Peaks in the XRD patterns of Co-MOFs without PVP assistance were also consistent with simulation results. For N-Co-MOF@PDA, the main characteristic peak of N-Co-MOF can be well identified, which shows that the original structure is maintained after the surface of the N-Co-MOF is wrapped with the PDA. In addition, there are three characteristic diffraction peaks at 38.1 °, 44.3 ° and 77.4 ° in the XRD spectrum of the N-Co-mof@pda-Ag composite material, which respectively belong to the (1 1 1), (2 0) and (3 1) crystal planes (jcpds#65-2871) of Ag metal (anal. Chim. Acta 1152 (2021) 338285).
The elemental composition and chemical valence of the N-Co-MOF@PDA-Ag composite material were analyzed according to XPS spectral data. The XPS spectrum holomogram confirms the presence of C, ag, N, O, co element (FIG. 5 (B)), which is consistent with the elemental analysis results of EDS. As can be seen from FIG. 5 (C), the peaks at 781.0 and 796.6eV correspond to Co 2p of Co element, respectively 3/2 And Co 2p 1/2 (J.am.chem.Soc.142 (2020) 19198-19208.). The two peaks at binding energies 786.0eV and 803.5eV are coincident with the two satellite peaks of Co element (sens. Insulators, B278 (2019) 126-132.). These results indicate that Co element is Co 2+ Is present. As can be seen from FIG. 5 (D), the binding energy has two separate peaks at 368.1 and 374.2eV, respectively, with Ag 3D 5/2 And Ag 3d 3/2 Identical, indicating the presence of elemental Ag (sens. Operators, B260 (2018) 852-860; ACS appl. Mater. Interfaces 8 (2016) 17060-17067.).
3. Electroanalytical performance of N-Co-MOF@PDA-Ag glucose sensor
The performance of the sensor as a non-enzymatic glucose sensor was analyzed in FIGS. 6-8 due to the excellent conductivity, high electrocatalytic activity and outstanding synergistic effect of the sensor based on the N-Co-MOF@PDA-Ag composite material. The electrochemical performance of the N-Co-MOF@PDA-Ag modified electrode was first analyzed by cyclic voltammetry in a 0.1M NaOH solution at a scan rate of 50mV/s with a potential of from-0.2 to 0.6V. Meanwhile, the electrochemical behaviors of the bare GC electrode and the N-Co-MOF@PDA modified electrode are compared. As shown in fig. 6 (a), a cyclic voltammogram was obtained for the bare GC electrode without addition (dotted line) and with addition of 0.5mM glucose (solid line), and no change in current was observed after glucose was added, indicating that the bare GC electrode had no electrocatalytic performance for glucose. As can be seen from FIG. 6 (B), the N-Co-MOF@PDA modified electrode had a pair of redox peaks in the absence of added glucose due to Co generation 2+ And Co 3+ And oxidation-reduction reaction between the two. The oxidation current increased after the addition of 0.5mM glucose (FIG. 6B, solid line), indicating that the N-Co-MOF@PDA material has electrochemically catalyzed oxygenGlucose-converting properties. As shown in FIG. 6 (C), since the N-Co-MOF@PDA-Ag composite material has the most effective electron transfer capability, the redox current of the modified electrode based on N-Co-MOF@PDA-Ag is obviously improved compared with that of the modified electrode based on the naked GC electrode and the modified electrode based on N-Co-MOF@PDA when no glucose is added. After the addition of 0.5mM glucose (solid line in FIG. 6 (C)), the current based on the N-Co-MOF@PDA-Ag sensor was higher than that of the N-Co-MOF@PDA. The above phenomenon shows that the N-Co-MOF@PDa-Ag composite material has the highest activity of catalyzing and oxidizing glucose, which is attributed to the synergistic effect of catalyzing glucose between N-Co-MOF and Ag NPs. FIG. 6 (D) shows the amperometric response of a different sensor with a continuous addition of 6. Mu.M glucose to a 0.1M NaOH solution at an applied potential of 0.55V. The N-Co-MOF@PDA-Ag based sensor has the highest amperometric current response, and the fastest response time (less than 5 s) compared to other sensors. The above results further demonstrate that the target composite N-Co-MOF@PDA-Ag has the most effective electrocatalytic glucose properties.
FIG. 7 (A) is a cyclic voltammogram based on the addition of different concentrations of glucose to a 0.1M NaOH solution using an N-Co-MOF@PDA-Ag sensor. After continuous addition of glucose, in the range of 0-2.5 mM, the anodic current increases significantly with increasing glucose concentration, due to the superior electrocatalytic oxidation activity for glucose based on the N-Co-MOF@PDA-Ag sensor. After adding 0.5mM glucose to 0.1M NaOH solution, the effect of scan rate on glucose sensor performance was studied. As can be seen from FIG. 7 (B), in the range of 30 to 210mV/s, the peak current increases with increasing scan rate. As shown in fig. 7 (C), there is a good linear relationship between anode and cathode peak currents and scan rates, which illustrates that this process is a fast surface control process.
The applied potential and Ag was studied by adding 100. Mu.M glucose amperometric signal response + Influence of main conditions such as ion concentration on the inductive glucose electroanalytical performance of the constructed sensor based on N-Co-MOF@PDA-Ag (FIG. 8). In the range of 0.40-0.60V, the different applied potentials have different effects on the measurement. As shown in fig. 8 (a), the maximum response current is obtained at 0.55V, and thus 0.55V is selected as the optimum application potential.In addition, also examine Ag + The effect of ion concentration on the experiment in the range of 2.5-10mg/mL, with maximum amperometric current response at a concentration of 5mg/mL (FIG. 8 (B)), which may be due to: ag (silver) + Lower ion concentrations may result in lower amounts of Ag NPs in the target composite; while too high a concentration may result in Ag NPs not being deposited firmly on the target composite. Thus Ag + As the optimal concentration for the experiment, 5mg/mL of ion was selected.
FIGS. 9 (A) and 9 (B) are the amperometric responses of glucose based on an N-Co-MOF@PDA-Ag sensor with continuous addition of 0.1M NaOH solution, and a steady and rapid amperometric response was seen. FIG. 9 (C) shows a standard curve between amperometric current and glucose concentration in response, with a linear regression equation of Y= 12.971X-0.216, a linear range of 1. Mu.M to 2mM, and a detection limit of 0.5. Mu.M (S/N=3).
The anti-interference performance is an important index for evaluating the application performance of the electroanalysis. FIG. 9 (D) is an amperometric response curve based on an N-Co-MOF@PDA-Ag sensor with the sequential addition of 100. Mu.M glucose, 20. Mu.M fructose, 20. Mu.M ascorbic acid, 20. Mu.M uric acid and 100. Mu.M glucose in a 0.1M NaOH solution. The results show that the current response of fructose, ascorbic acid and uric acid to glucose is negligible, which indicates that the prepared sensor has good anti-interference capability to common interference species.
Five different N-Co-MOF@PDA-Ag based sensors were analyzed for amperometric responses to 100. Mu.M glucose in 0.1M NaOH solution under the same experimental conditions, resulting in a Relative Standard Deviation (RSD) of 4.6%, which demonstrated good reproducibility of glucose detection by the developed sensors (FIG. 10 (A)). In addition, the long-term stability of the sensor based on the N-Co-MOF@PDA-Ag is also examined, and the electrochemical sensing performance of the sensor is further evaluated. As shown in FIG. 10 (B), after adding 1mM glucose and continuously detecting for 3600 seconds, the response value remained around 96.2% of the original value, which indicates good stability.
4. Electrochemical analysis of glucose in actual samples
To further verify the practical application potential of the N-Co-mof@pdA-Ag based sensor, it was used for glucose detection in practical samples such as serum and juice. Human serum was purchased from the chinese strong tech company, and juice was purchased from a local supermarket, diluted 40-fold with 0.1M NaOH solution prior to testing. The amperometric response curves of the glucose added to human serum and juice at different concentrations are shown in fig. 11 (a) and 11 (B), respectively, and a rapid and stable amperometric response was observed after each glucose addition. In human serum and juice, the linear range of glucose detection based on the N-Co-MOF@PDA-Ag sensor is respectively as follows: 5. Mu.M to 2.6mM and 5. Mu.M to 2.0mM (see FIG. 11 (C) and FIG. 11 (D)), the detection limits were 2.0. Mu.M and 2.5. Mu.M, respectively. Thus, the electrochemical sensor can be used for the detection of glucose in an actual sample.
It should be understood that the foregoing description is only a preferred embodiment of the present invention, and the present invention is not limited to the above-described embodiment, but may be modified or substituted for some of the features described in the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. The application of the composite material N-Co-MOF@PDA-Ag is characterized in that the composite material N-Co-MOF@PDA-Ag is used for preparing a glucose electrochemical sensor, the linear range of detecting glucose in a glucose-containing solution is 1 mu M-2 mM, the detection limit is 0.5 mu M, and S/N=3;
the preparation method of the electrode of the glucose electrochemical sensor comprises the following steps: adding the N-Co-MOF@PDA-Ag composite material into ethanol, and performing ultrasonic dispersion to obtain a black suspension with 2mg/mL of uniformly dispersed particles; transferring 3-5 mu LN-Co-MOF@PDA-Ag suspension drops on the surface of the pretreated clean glassy carbon electrode, and airing; then 2-3 mu LNafion solution is dripped on the surface of the electrode as a binder, and the modified electrode is obtained after drying, wherein the concentration of the Nafion solution is 0.05wt%;
the preparation method of the composite material N-Co-MOF@PDA-Ag comprises the following steps:
(1) N-Co-MOF preparation:
Co(Ac) 2 ·4H 2 o and polyvinylpyrrolidone according to 0.6-0.7: 1 in a mass ratio of 20ml dmf to solution a;1, 4-terephthalic acid is dissolved in DMF to form solution B with the mass concentration of 10-11 mg/mL; then, dropwise adding the solution B into the solution A, uniformly stirring, transferring into a high-pressure reaction kettle, reacting for 20 hours at 105 ℃, centrifugally separating the obtained product, washing for multiple times by using DMF and ethanol respectively, and drying;
(2) Preparation of N-Co-MOF@PDA-Ag:
ultrasonically dispersing the N-Co-MOF nanosheets synthesized in the step (1) in Tris buffer, wherein the mass concentration is 2mg/mL, then adding 2mg/mL of dopamine, and stirring for 1h at room temperature; centrifugally filtering the obtained product, and cleaning the product by using ultrapure water to obtain a core-shell material N-Co-MOF@PDA, wherein the pH of a Tris buffer solution is 8.5, and the concentration is 10mM;
N-Co-MOF@PDA was then sonicated to freshly formulated [ Ag (NH) 3 ) 2 ] + In the solution, the mass concentration ratio is N-Co-MOF@PDA: [ Ag (NH) 3 ) 2 ] + =1.5 to 2:5, stirring for 10-12 h in the dark; and (3) after centrifugation, collecting the obtained composite material N-Co-MOF@PDA-Ag, washing the composite material N-Co-MOF@PDA-Ag with ultrapure water and ethanol for multiple times, and drying the composite material in vacuum.
2. The use according to claim 1, characterized in that the rapidly polymerized core-shell material nitrogen doped Co-mof@polydopamine is externally encapsulated by silver nanoparticles reduced in situ thereof.
3. The use according to claim 1, wherein the modified electrode is scanned from-0.2 to 0.6V in a 0.1m naoh solution at a scan rate of 50 mV/s.
4. The use according to claim 1, wherein the glucose-containing solution comprises human serum, and the linear range of glucose in human serum is 5 μm to 2.6mM, and the limit of detection is 2.0 μm.
5. The use according to claim 1, wherein the glucose-containing solution comprises a glucose-containing juice, the linear range of glucose detected in the glucose-containing juice being 5 μm to 2.0mM and the limit of detection being 2.5 μm.
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