CN114042450A - Core-shell palladium-platinum composite nano porous material and preparation method and application thereof - Google Patents
Core-shell palladium-platinum composite nano porous material and preparation method and application thereof Download PDFInfo
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/44—Palladium
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- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
- B01J35/396—Distribution of the active metal ingredient
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- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
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- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
- B01J35/61—Surface area
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/16—Reducing
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Abstract
The invention provides a preparation method of a core-shell palladium-platinum composite nano porous material, belonging to the field of porous materials. According to the method, a platinum-nitrogen-doped carbon quantum dot composite intermediate generated by a platinum source and nitrogen-doped carbon quantum dots is used as a nucleation site, palladium ions are reduced on the surface of the intermediate to form smaller palladium particles, then the smaller palladium particles are gathered to form larger palladium particles, the platinum ions in the intermediate are slowly reduced on the palladium particles to form platinum particles, and the nitrogen-doped carbon quantum dots are discharged, so that the core-shell type palladium-platinum composite nano-porous material with extremely high specific surface area and extremely high simulated oxidase activity is finally formed. The preparation method of the material omits the use of a template agent, and is beneficial to increasing the specific surface area, thereby being beneficial to improving the catalytic activity of the material. Preparation of the applicationmPd @ Pt NSs has a specific surface area of up to 210m2·g‑1，Vmax0.05. mu.M.s‑1，Km68.55 μ M, KcatIs 2.1 × 103s‑1。
Description
Technical Field
The invention relates to the field of porous materials, in particular to a preparation method of a core-shell palladium-platinum composite nano porous material.
Background
The nano enzyme is a mimic enzyme which not only has the unique performance of nano materials, but also has a catalytic function. The nano enzyme has the characteristics of simple preparation, stable property, reusability and strong environmental tolerance, and is widely applied to the fields of medicine, chemical industry, food, agriculture, environment and the like. Among many mimetic enzyme studies, peroxidase mimetic activity is studied more often, and the application range of mimetic peroxidase is very wide, for example, it is used to couple with antibody or other biomolecules for signal amplification and form detectable electric signal or color signal for blood sugar detection, serum immunodetection, disease detection, etc. However, in the color development application of the mimic peroxidase, additional hydrogen peroxide is required to be added, and the hydrogen peroxide is unstable in air, so that the application of the peroxidase is influenced. The oxidase does not need to additionally add hydrogen peroxide, and the color of the chromogenic substrate can be catalyzed by utilizing dissolved oxygen in the system, so that the oxidase is more convenient to use, and the influence on the application such as measurement and the like due to the instability of the hydrogen peroxide is eliminated.
The nano enzyme has the size effect of a common nano material, when the particle size of the nano material is reduced, the specific surface area is increased, the surface atomic number is multiplied, and the coordination number of the surface atomic number is seriously insufficient, so that the surface active site is increased, and the catalytic efficiency of the nano catalyst is improved. However, the nano-enzyme prepared by the prior art still has the problems of small specific surface area and low enzyme activity. Therefore, how to prepare nanoenzymes with large specific surface area and more catalytic active sites to improve the catalytic activity and the rate of catalytic reaction thereof is a technical problem which needs to be solved at present.
Disclosure of Invention
The core-shell palladium-platinum composite nano-porous material prepared by the method has the advantages of large specific surface area, high activity of oxide mimic enzyme and excellent catalytic performance.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a core-shell palladium-platinum composite nano porous material, which comprises the following steps:
(1) mixing a platinum source, nitrogen-doped carbon quantum dots, a reducing agent and water, and then carrying out primary incubation to obtain an incubation liquid;
the temperature of the first incubation is 30-40 ℃, and the time of the first incubation is 0.5-3 h;
(2) and (2) mixing the incubation liquid obtained in the step (1) with a palladium source and a reducing agent, and then carrying out secondary incubation to obtain the core-shell type palladium-platinum composite nano-porous material.
The temperature of the second incubation is 30-40 ℃, and the time of the second incubation is 0.5-3 h.
Preferably, the platinum source in step (1) comprises one or more of chloroplatinic acid, sodium chloroplatinate and platinum tetrachloride.
Preferably, the palladium source in step (2) comprises one or more of palladium chloride, potassium chloropalladate and chloropalladate.
Preferably, the molar concentration of platinum atoms in the incubation liquid in the step (1), the mass concentration of nitrogen-doped carbon quantum dots, and the molar concentration of palladium atoms in the palladium source in the step (2) are in a ratio of: (1) mmol: (2.6-130) ug/mL: (0.1-10) mmol.
Preferably, the ratio of the amounts of the platinum atoms in the platinum source and the substance of the reducing agent in the step (1) is 1: 6.
preferably, the temperature of the first incubation in the step (1) is 30-40 ℃, and the time of the first incubation is 0.5-3 h.
Preferably, the ratio of the amounts of the palladium atom in the palladium source and the substance of the reducing agent in the step (2) is 1: 6.
preferably, the temperature of the second incubation in the step (2) is 30-40 ℃, and the time of the second incubation is 0.5-3 h.
The invention also provides the core-shell palladium-platinum composite nano-porous material prepared by the preparation method of the technical scheme.
The invention also provides application of the core-shell palladium-platinum composite nano-porous material in enzyme catalysis.
The invention provides a preparation method of a core-shell palladium-platinum composite nano porous material, which comprises the steps of mixing a platinum source, nitrogen-doped carbon quantum dots, a reducing agent and water, incubating for the first time at 30-40 ℃ for 0.5-3 h, adding a palladium source and a reducing agent, and incubating for the second time at 30-40 ℃ for 0.5-3 h to obtain the core-shell palladium-platinum composite nano porous material. According to the method, a certain amount of platinum source and nitrogen-doped carbon quantum dots are firstly reacted at a certain reaction temperature and within a certain reaction time to form a platinum-nitrogen-doped carbon quantum dot composite intermediate, the intermediate is formed to remarkably reduce the speed of reducing platinum ions in the platinum source, after a palladium source and a reducing agent are added, palladium ions are reduced on the surface of the intermediate to form smaller palladium particles, then in order to reduce the surface energy of a reaction system, the smaller palladium particles are aggregated into larger palladium particles, and along with the reduction of the platinum ions in the intermediate on the surface of the palladium particles and the discharge of the nitrogen-doped carbon quantum dots, components with palladium shells as platinum are formed as cores, and a pore structure is formed, and finally the nano-porous material (mPd @ Pt NSs) is formed.
In the process, the intermediate can be used as a nucleation site, so that the use of a template agent is omitted, and the surface roughness of the nano porous material obtained by subsequent preparation is increased, so that the specific surface area of the nano porous material obtained by subsequent preparation is obviously increased. Because the nano-porous material has high specific surface area, the activity of the oxide mimic enzyme is greatly improved, and the catalytic performance is excellent. The results of the examples show that the specific surface area of the core-shell type palladium-platinum composite nano-porous material mPd @ Pt NSs prepared by the method is as high as 210m2·g-1V as a mimic oxidase for catalytically oxidizing TMBmax0.05. mu.M.s-1，Km68.55 μ M, Kcat 2.1X 103s-1(Kcat＝Vmax/[ nanoenzymes]) And K of mPd @ Pt NSscat(2.1×103s-1) With horseradish peroxidase (K)cat＝4.3×103s-1) On the same order of magnitude; compared with the currently reported nano-oxide mimic enzyme, the nano-oxide mimic enzyme is improved by 5 times.
The method provided by the invention adopts a two-step method to prepare the core-shell type palladium-platinum composite nano porous material, has mild reaction conditions and simple operation, does not use organic solvents and templates, and is green and environment-friendly. Compared with the existing unsupported platinum-based nano material, the surface area of the material is greatly improved, and the activity of the oxide mimic enzyme is excellent.
Drawings
FIG. 1 is photographs of mixed solutions of nitrogen-doped carbon quantum dots, chloroplatinic acid (final concentration: 1mmol) and ascorbic acid (final concentration: 6mmol) at different concentrations, taken at different reaction times. The final concentrations of the nitrogen-doped carbon quantum dots are respectively as follows: (a) 0. mu.g/mL-1,(b)5μg·mL-1,(c)26μg·mL-1,(d)52μg·mL-1,and(e)130μg·mL-1。
FIG. 2 is a TEM image of mPd @ Pt NSs (1:1) core-shell type Pd/Pt composite nano-porous material prepared in example 1 of the present invention, wherein the inset is (electron diffraction picture thereof);
FIG. 3 is a transmission diagram of high angle annular dark field scanning and EDS element scanning of mPd @ Pt NSs (1:1) core-shell palladium-platinum composite nanoporous material prepared in example 1 of the present invention, wherein green is platinum and red is palladium;
FIG. 4 is a high resolution electron microscope image of mPd @ Pt NSs (1:1) core-shell palladium-platinum composite nanoporous material prepared in example 1 of the invention;
FIG. 5 is an EDS line scan graph of the core-shell palladium platinum composite nanoporous material mPd @ Pt NSs (1:1) prepared in example 1 of the present invention;
FIG. 6 is an XRD pattern of mPd @ Pt NSs (1:1) core-shell palladium-platinum composite nanoporous material prepared in example 1 of the invention;
FIG. 7 shows N of mPd @ Pt NSs (1:1) core-shell type Pd/Pt composite nano-porous material prepared in example 1 of the present invention2Adsorption and desorption isotherms;
FIG. 8 is a graph showing the UV-visible absorption curve and the corresponding color rendering photograph (reaction condition: 20mM, PB buffer solution with pH 4.0, room temperature reaction for 5 minutes) of the core-shell type Pd/Pt composite nano-porous material mPd @ Pt NSs (1:1) prepared in example 1 of the present invention catalyzing oxidation of TMB, wherein the left graph of the solid line and the inset is control TMB, and the right graph of the dotted line and the inset is experimental TMB and mPd @ Pt NSs (1: 1);
FIG. 9 is a graph of the equation of the reciprocal curve of the catalysis oxidation of TMB by mPd @ Pt NSs (1:1) of the core-shell type palladium-platinum composite nano-porous material prepared in example 1 of the invention;
FIG. 10 is a comparison graph of the activity of an oxide mimic enzyme of the core-shell palladium-platinum composite nanoporous material mPd @ Pt NSs prepared in embodiments 1 to 6 of the present invention, wherein the reaction conditions are as follows: 20mM PB buffer solution with pH 4.0 and a chromogenic substrate TMB, reacting for 5 minutes at room temperature, and detecting the wavelength lambda which is 652 nm;
FIG. 11 is a comparison graph of the activity of an oxide mimic enzyme of the core-shell palladium-platinum composite nanoporous material mPd @ Pt NSs prepared in embodiments 1, 7 to 12 of the present invention, wherein the reaction conditions are as follows: 20mM PB buffer solution with pH 4.0 and a chromogenic substrate TMB, reacting for 5 minutes at room temperature, and detecting the wavelength lambda which is 652 nm;
FIG. 12 is a TEM image of a palladium-platinum composite nanomaterial Pt @ Pd NPs prepared in comparative example 1 of the present invention;
FIG. 13 is a TEM image of the platinum nanomaterials NCDs-Pt NDs prepared in comparative example 2 of the present invention;
FIG. 14 is a TEM image of the palladium nanomaterials NCDs-Pd NSs prepared by comparative example 3 of the present invention;
FIG. 15 is a TEM image of Pt NDs, which are platinum nanomaterials prepared by comparative example 4 of the present invention;
FIG. 16 is a TEM image of Pd NPs as a palladium nanomaterial prepared according to comparative example 5 of the present invention;
FIG. 17 is a graph showing the comparison of the activity of the oxidase mimics of the nanomaterials prepared in example 1 of the present invention and comparative examples 1 to 5. The inset is a color picture of a solution with TMB free and containing nitrogen-doped carbon quantum dots reacted for five minutes at room temperature. Reaction conditions are as follows: 20mM PB buffer solution with pH 4.0 and a chromogenic substrate TMB, reacting for 5 minutes at room temperature, and detecting the wavelength lambda which is 652 nm;
FIG. 18 is a graph comparing the absorbance (. lamda. 652nm) of oxidized TMB in the presence and absence of hydrogen peroxide with time for example 1 of the present invention and a commercially available horseradish peroxidase (HRP).
Detailed Description
The invention provides a preparation method of a core-shell palladium-platinum composite nano porous material, which comprises the following steps:
(1) mixing a platinum source, nitrogen-doped carbon quantum dots, a reducing agent and water, and then carrying out primary incubation to obtain an incubation liquid;
the temperature of the first incubation is 30-40 ℃, and the time of the first incubation is 0.5-3 h;
(2) and (2) mixing the incubation liquid obtained in the step (1) with a palladium source and a reducing agent, and then carrying out secondary incubation to obtain the core-shell type palladium-platinum composite nano-porous material.
The temperature of the second incubation is 30-40 ℃, and the time of the second incubation is 0.5-3 h.
In the present invention, the raw materials used are all commercial products which are conventional in the art, unless otherwise specified.
According to the invention, a platinum source, nitrogen-doped carbon quantum dots, a reducing agent and water are mixed and then incubated for the first time to obtain an incubation liquid.
In the present invention, the platinum source preferably includes one or more of chloroplatinic acid, sodium chloroplatinate, and platinum tetrachloride. In an embodiment of the invention, the platinum source may specifically be chloroplatinic acid.
In the present invention, the nitrogen-doped carbon quantum dot preferably has a particle size of less than 10 nm. In the invention, the preparation method of the nitrogen-doped carbon quantum dot preferably comprises a microwave method, a glucose cracking method or other methods known in the art, and more preferably comprises the microwave method.
In the invention, the microwave method is used for preparing the nitrogen-doped carbon quantum dots: mixing sodium citrate, glycine and water, and carrying out microwave reaction to obtain the nitrogen-doped carbon quantum dot aqueous solution.
In the invention, the sodium citrate, the glycine and the water are preferably mixed to respectively prepare a sodium citrate solution with the concentration of 0.34mol/L and a glycine solution with the concentration of 2.0mol/L with the sodium citrate and the glycine; and mixing the sodium citrate solution and the glycine solution to obtain a mixed solution. After the mixed solution is obtained, the mixed solution is preferably subjected to microwave reaction in a microwave oven for 3 minutes to obtain the nitrogen-doped carbon quantum dot aqueous solution.
In the present invention, it is preferable that the microwave reaction further comprises: dialyzing the product of the microwave reaction. The solvent used for dialysis in the present invention is preferably ultrapure water. In the invention, a double-layer dialysis method is selected for dialysis: the inner dialysis bag (molecular weight cut-off 3500Da) and the outer dialysis bag (molecular weight cut-off 500 Da). After 72 hours of dialysis, the carbon quantum dot solution in the interlayer of the dialysis bag is taken for subsequent experiments. After dialysis and purification, the average grain size of the nitrogen-doped carbon quantum dots is 4 nm.
In the present invention, the nitrogen-doped carbon quantum dots are preferably added in the form of an aqueous solution of nitrogen-doped carbon quantum dots; the mass concentration of the nitrogen-doped carbon quantum dot aqueous solution is preferably 26-52 ug/mL, and more preferably 26 ug/mL.
In the present invention, the reducing agent is preferably one or more of ascorbic acid and sodium citrate. In an embodiment of the present invention, the reducing agent may be specifically ascorbic acid.
In the present invention, the ratio of the amount of the platinum atom and the substance of the reducing agent in the platinum source is preferably 1: 6.
in the invention, the mixing of the platinum source, the nitrogen-doped carbon quantum dot, the reducing agent and the water is preferably to mix the platinum source and the water to prepare a platinum source solution; and mixing the platinum source solution and the nitrogen-doped carbon quantum dot aqueous solution, and then mixing with a reducing agent.
In the present invention, the first incubation is preferably carried out on a shaker at a rotation speed of 220 rpm. The present invention is not particularly limited to such a rocking bed, and may be carried out by using an apparatus known in the art. According to the invention, the first incubation is carried out on the shaking table, so that all components and the generated intermediate are always in a dynamic state, the uniform mixing of all components and the generated intermediate is facilitated, and the particle size of the generated intermediate is reduced.
In the invention, the temperature of the first incubation is 30-40 ℃, and more preferably 37 ℃. In the invention, the time of the first incubation is 1-3 h, and more preferably 2 h. According to the invention, the temperature and time of the first incubation are controlled within the above ranges, which is beneficial to the conversion of the platinum source and the nitrogen-doped quantum into the compound intermediate of the platinum source and the nitrogen-doped carbon quantum dot, so that the reduction speed of platinum ions is reduced, and the platinum ions are used as nucleation sites, so that the template agent is omitted, the surface roughness of the nano porous material obtained by the subsequent preparation is increased, and the specific surface area of the nano porous material obtained by the subsequent preparation is obviously increased.
After obtaining the incubation liquid, mixing the incubation liquid with a palladium source and a reducing agent, and carrying out secondary incubation to obtain the core-shell type palladium-platinum composite nano porous material.
In the present invention, the palladium source preferably includes one or more of palladium chloride, potassium chloropalladate and chloropalladate. In an embodiment of the present invention, the palladium source may be specifically palladium chloride.
In the present invention, the ratio of the amount of the substance of the palladium atom and the reducing agent in the palladium source is preferably 1 mmol: 6 mmol.
In the present invention, the second incubation is preferably performed on a shaker at a shaker speed of 220 rpm. The present invention is not particularly limited to such a rocking bed, and may be carried out by using an apparatus known in the art. According to the invention, the second incubation is carried out on the shaking table, so that all components and various generated particles are always in a dynamic state, the components and the various generated particles are uniformly mixed, the particle sizes of the various generated particles are reduced, and the product is aged in such a way to obtain pure particles.
In the invention, the temperature of the second incubation is 30-40 ℃, and more preferably 37 ℃. In the invention, the time of the second incubation is 1-3 h, and more preferably 2 h. The temperature and time of the second incubation are controlled in the range, so that the pure core-shell type palladium-platinum composite nano-porous material is obtained.
In the present invention, the ratio of the molar concentration of platinum atoms in the platinum source to the molar concentration of palladium atoms in the palladium source is preferably 1 mmol: (0.1 to 10) mmol, more preferably 1 mmol: 0.5 to 2mmol, more preferably 1 mmol: 1 mmol.
In the present invention, the mass concentration of nitrogen-doped carbon quantum dots (2.6. mu.g. mL)-1～130μg·mL-1) More preferably (26. mu.g.mL)-1～52μg·mL-1) More preferably 26. mu.g/mL-1。
In the invention, the core-shell type palladium-platinum composite nano-porous material which has high specific surface area, more active sites and high activity of the oxide mimic enzyme can be obtained by controlling the mass ratio of platinum atoms in the platinum source to palladium atoms in the palladium source and the mass concentration of the nitrogen-doped carbon quantum dots within the range; the method has the advantages that the situation that the nitrogen-doped carbon quantum dots are too small in dosage, sufficient intermediate nucleation sites cannot be formed, the specific surface area of the prepared nano porous material is not favorably improved, the activity of the oxide simulation enzyme of the prepared nano porous material is low, and the situation that the nitrogen-doped carbon quantum dots are too large in dosage, the active sites of the nano porous material are sealed, and the activity of the oxide simulation enzyme of the prepared nano porous material is reduced is avoided. In the embodiment, the concentration of the platinum source in the fixed reaction system is 1mmol, and the concentration of the palladium source is changed from 0.1 to 10mmol, so that the conditions that the ratio of the amounts of the platinum atom to the palladium atom in the palladium source is too large and too small are not favorable for improving the specific surface area and the activity of the oxide mimic enzyme of the prepared nano-porous material.
After the second incubation is completed, the product of the second incubation is preferably washed to obtain the core-shell palladium-platinum composite nano-porous material, and then dispersed in ultrapure water for standby.
In the present invention, the solvent used for the washing is preferably ultrapure water. In the present invention, the washing means is preferably ultrasonic centrifugal washing. In the present invention, the number of washing is preferably 2 to 4.
The invention also provides the core-shell palladium-platinum composite nano-porous material prepared by the preparation method of the technical scheme. In the present invention, the core-shell type palladium platinum composite nanoporous material preferably includes palladium particles concentrated in the inner core and platinum particles concentrated in the outer shell.
The invention also provides application of the core-shell palladium-platinum composite nano-porous material in enzyme catalysis. In the invention, the core-shell palladium-platinum composite nano-porous material can be used as an oxide mimic enzyme for oxidation catalysis.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Preparation method of core-shell type palladium-platinum composite nano porous material
(1) Mixing 560 mu L of 93 mu g/mL nitrogen-doped carbon quantum dot aqueous solution, 200 mu L of 10mmol chloroplatinic acid solution and 120 mu L of 100mmol ascorbic acid, and performing primary incubation on a shaking table (the rotating speed is 220rpm) at constant temperature of 37 ℃ for 2h to obtain an incubation solution;
wherein, the nitrogen-doped carbon quantum dots in the step (1) are prepared by a microwave method and purified by ultrapure water dialysis;
the molar concentration ratio of platinum atoms in chloroplatinic acid to ascorbic acid in the step (1) is (1: 6);
(2) mixing the incubation liquid obtained in the step (1) with 1mL of 2mmol palladium chloride solution and 120 mu L of 100mmol ascorbic acid, then carrying out secondary incubation for 2h on a shaking table at constant temperature of 37 ℃, collecting a product, and carrying out ultrasonic dispersion and centrifugal washing for three times by using ultrapure water to obtain a material, wherein the label is as follows: mPd @ Pt NSs (1:1), dried and weighed, and then dispersed in ultrapure water for use;
wherein the molar concentration ratio of palladium atoms in the palladium chloride to the ascorbic acid in the step (2) is (1: 6);
the ratio of the molar concentration of platinum atoms in the chloroplatinic acid to palladium atoms in the palladium chloride is preferably 1 mmol: 1mmol of the active component; the mass concentration of the nitrogen-doped carbon quantum dots is 26 mug/mL.
FIG. 1 is photographs of mixed solutions of nitrogen-doped carbon quantum dots, chloroplatinic acid (final concentration: 1mmol) and ascorbic acid (final concentration: 6mmol) at different concentrations, taken at different reaction times. As can be seen from fig. 1, as the concentration of the nitrogen-doped carbon quantum dots increases, the time for the solution to form a brownish black precipitate is prolonged, and it can be seen that the nitrogen-doped carbon quantum dots strongly interact with platinum in chloroplatinic acid, so that the reduction rate of platinum is reduced.
FIG. 2 is a TEM image of the core-shell palladium-platinum composite nanoporous material mPd @ Pt NSs (1:1) prepared in example 1, wherein the inset is an electron diffraction image thereof. As can be seen from the figure, the surface of the core-shell type palladium-platinum composite nano-porous material mPd @ Pt NSs (1:1) prepared in example 1 is rough and spherical, and the average particle size is 63 nm. The material is polycrystalline as seen from the electron diffraction pattern.
Fig. 3 is a transmission diagram of high-angle annular dark field scanning and an EDS element scanning image of mPd @ Pt NSs (1:1) core-shell type palladium-platinum composite nanoporous material prepared in example 1, wherein green is platinum and red is palladium, and it can be seen that mPd @ Pt NSs (1:1) prepared in example 1 is a nanomaterial and the material is composed of a plurality of small particle units, a plurality of pores are formed between the small particles, and further, it can be seen from element distribution that palladium is concentrated in the core platinum at the outer shell.
Fig. 4 is a high resolution electron microscope image of mPd @ Pt NSs (1:1) of the core-shell type palladium-platinum composite nano-porous material prepared in example 1, and it can be seen that mPd @ Pt NSs (1:1) of the core-shell type palladium-platinum composite nano-porous material prepared in example 1 has clearly visible lattice stripes on the surface, and the interplanar spacing is 0.23nm, which corresponds to the interplanar spacing of platinum (111).
FIG. 5 is an EDS line scan graph of the core-shell type Pd/Pt composite nano-porous material mPd @ Pt NSs (1:1) prepared in example 1, and it can be seen that the palladium is concentrated in the core and the shell layer is mainly composed of platinum in the composite nano-porous material mPd @ Pt NSs (1:1) prepared in example 1, and the material is further confirmed to be the core-shell type Pd/Pt composite nano-material.
FIG. 6 is an XRD pattern of mPd @ Pt NSs (1:1) of the core-shell type palladium-platinum composite nano-porous material prepared in example 1, and it can be seen that mPd @ Pt NSs (1:1) of the material prepared in example 1 is made of a platinum-palladium alloy.
Two and N2Adsorption and desorption
FIG. 7 is the N of the core-shell palladium-platinum composite nanoporous material mPd @ Pt NSs (1:1) prepared in example 12Adsorption and desorption isothermAs can be seen from the figure, N of the core-shell type palladium-platinum composite nano-porous material mPd @ Pt NSs (1:1) prepared in example 12The adsorption and desorption isotherm is a type IV isotherm. The BET surface area obtained was 210.4m2·g-1The BET surface area is 10 times of that of the commercially available platinum black, and is greatly improved compared with other unsupported platinum-based nano materials.
Third, the detection of the activity of the mimic oxidase
The mimic oxidase activity of the mPd @ Pt NSs (1:1) prepared as described above was tested using TMB as a color developer, and normally TMB was colorless in water, but in the presence of an oxidase, the oxidase oxidized the colorless TMB to a blue color (oxidation state of TMB).
And (3) detection process:
control group: preparing 3mL of 20mM PB buffer solution (pH 4.0) containing 0.3mM TMB, and detecting the ultraviolet-visible absorption curve;
experimental groups: 3mL of 20mM PB buffer solution (pH 4.0) containing 0.3mM TMB was prepared, and then (15. mu.g mPD @ Pt NS (1:1) was added thereto, and after mixing uniformly, the mixture was reacted at room temperature for 5 minutes to obtain a mixed system, and the UV-visible absorption curve of the mixed system was examined.
FIG. 8 is a UV-visible absorption curve of the catalyzed TMB oxidation of the core-shell palladium-platinum composite nanoporous material mPd @ Pt NSs (1:1) prepared in example 1, wherein the solid line is the control TMB and the dashed lines are the experimental TMB and mPd @ Pt NSs (1: 1). As can be seen, the core-shell palladium-platinum composite nanoporous material mPd @ Pt NSs (1:1) prepared in example 1 can directly oxidize the colorless TMB (inset left) to its oxidation state and turn the solution blue (inset right) in the absence of hydrogen peroxide; it can be seen that the core-shell palladium-platinum composite nano-porous material mPd @ Pt NSs (1:1) prepared in example 1 has good oxidase activity.
III mPd @ Pt NSs (1:1) oxidase-mimicking Vmax、KmAnd Kcat
And (3) detection process: firstly, preparing PB buffer solution (20mM, pH 4.0) containing TMB with different concentrations (the TMB concentrations are respectively 60 muM, 80 muM, 100 muM, 120 muM, 140 muM, 160 muM and 180 muM), adding mPd @ Pt NSs (1:1) nano enzyme with fixed concentration, measuring the change of the absorbance value of the system along with time after the nano enzyme is added at 652nm to obtain the relation between the initial rate and the TMB concentration, drawing through the following Mie's equation to obtain steady-state kinetic curves under different TMB concentrations, and calculating to obtain a corresponding double reciprocal curve equation as follows;
the equation of mie:
wherein V is the initial velocity, VmaxTo maximize the reaction rate, KmIs the Michaelis constant, [ S ]]Is the TMB concentration.
FIG. 9 is a double reciprocal curve equation of TMB catalyzed oxidation of mPd @ Pt NSs (1:1) of the core-shell type Pd/Pt composite nano-porous material prepared in example 1, and it can be seen that the TMB catalyzed oxidation of mPd @ Pt NSs (1:1) of the core-shell type Pd/Pt composite nano-porous material prepared in example 1 conforms to the Mie's equation. The V of mPd @ Pt NSs (1:1) was calculatedmax0.05. mu.M.s-1，Km68.55 μ M, Kcat 2.1X 103s-1(Kcat＝Vmax/[ nanoenzymes]) And mPd @ Pt NSsI Kcat(2.1×103s-1) With horseradish peroxidase (K)cat＝4.3×103s-1) On the same order of magnitude, mPd @ Pt NSs (1:1) is shown to have excellent catalytic efficiency of mimic oxidase, and the generated peroxy radical intermediate O in the presence of oxygen2-The method can catalyze, oxidize and color-develop a substrate TMB for color development, so that the method has higher affinity and catalytic performance for the TMB, greatly improves the utilization efficiency of platinum atoms due to the high surface area, the core-shell structure of palladium and platinum and the good enzyme catalytic activity of platinum, and greatly improves the activity of mimic enzyme of the platinum atoms.
Example 2
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (0.1:1), and tested for mimic oxidase activity using the same method;
unlike example 1, the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots, and the molar concentration of palladium atoms in palladium chloride are preferably 1 mmol: 26. mu.g/mL: 0.1 mmol.
Example 3
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (0.5:1), and tested for mimic oxidase activity using the same method;
unlike example 1, the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots, and the molar concentration of palladium atoms in palladium chloride are preferably 1 mmol: 26. mu.g/mL: 0.5 mmol.
Example 4
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (2.5:1), and tested for mimic oxidase activity using the same method;
unlike example 1, the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots, and the molar concentration of palladium atoms in palladium chloride are preferably 1 mmol: 26. mu.g/mL: 2.5 mmol.
Example 5
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (5:1), and tested for mimic oxidase activity using the same method;
unlike example 1, the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots, and the molar concentration of palladium atoms in palladium chloride are preferably 1 mmol: 26. mu.g/mL: 5 mmol.
Example 6
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (10:1), and tested for mimic oxidase activity using the same method;
unlike example 1, the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots, and the molar concentration of palladium atoms in palladium chloride are preferably 1 mmol: 26. mu.g/mL: 10 mmol.
Fig. 10 is a comparison graph of the activity of the simulated enzyme of the mPd @ Pt NSs oxide of the core-shell type palladium-platinum composite nanoporous material prepared in examples 1 to 6, and it can be seen from the graph that when the molar concentrations of the platinum atom and the palladium atom in the feed are both 1mmol, the obtained material oxidizes TMB to make the relative absorbance of the product of the color change highest, and thus the activity of the simulated enzyme of the oxide is the best.
Example 7
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (NCDs-2.6), and tested for mimic oxidase activity using the same method;
different from the embodiment 1, the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots and the molar concentration of palladium atoms in palladium chloride are respectively preferably 1mmol and 2.6 mu g/mL-1、1mmol。
Example 8
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (NCDs-13), and tested for mimic oxidase activity using the same method;
wherein the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots, and the molar concentration of palladium atoms in palladium chloride are preferably 1mmol and 13. mu.g.mL, respectively-1、1mmol。
Example 9
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (NCDs-26), and tested for mimic oxidase activity using the same method;
unlike example 1, the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots, and the molar concentration of palladium atoms in palladium chloride are preferably 1mmol and 26 μ g · mL, respectively-1、1mmol。
Example 10
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (NCDs-52), and tested for mimic oxidase activity using the same method;
different from the embodiment 1, the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots and the molar concentration of palladium atoms in palladium chloride are respectively preferably 1mmol and 52 mu g/mL-1、1mmol。
Example 11
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (NCDs-78), and tested for mimic oxidase activity using the same method;
different from the embodiment 1, the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots and the molar concentration of palladium atoms in palladium chloride are respectively preferably 1mmol and 78 mug-mL-1、1mmol。
Example 12
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (NCDs-104), and tested for mimic oxidase activity using the same method;
different from the embodiment 1, the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots and the molar concentration of palladium atoms in palladium chloride are respectively preferably 1mmol and 104 mug-mL-1、1mmol。
Example 13
Core-shell palladium-platinum composite nanoporous materials were prepared according to the method of example 1, labeled: mPd @ Pt NSs (NCDs-130), and tested for mimic oxidase activity using the same method;
different from the embodiment 1, the molar concentration of platinum atoms in chloroplatinic acid, the mass concentration of nitrogen-doped carbon quantum dots and the molar concentration of palladium atoms in palladium chloride are respectively preferably 1mmol and 130 mug-mL-1、1mmol。
FIG. 11 is a comparison graph of the activity of the oxide mimic enzymes of the core-shell palladium-platinum composite nanoporous material mPd @ Pt NSs prepared in examples 1, 7 to 13 of the present invention. By fixing the ratio of the molar concentration of platinum atoms in the platinum source to the molar concentration of palladium atoms in the palladium source to each other to 1 mmol: 1mmoAnd l, investigating the influence of the nitrogen-doped carbon quantum dot concentration on the activity of the prepared material simulation oxidase. The result shows that the mass concentration of the nitrogen-doped carbon quantum dots is 26 mu g/mL-1The oxide mimic enzyme activity of the obtained material is highest.
Comparative example 1
Preparation of platinum-palladium core-shell nano material (Pt @ Pd NPs)
The procedure of example 1 was followed except that in the first step 560. mu.L of test water was substituted for 560. mu.L of an aqueous solution of 93. mu.g/mL nitrogen-doped carbon quantum dots; preparing the palladium-platinum composite nano material, and marking as: pt @ Pd NPs and tested for mimic oxidase activity using the same method.
Comparative example 2
Preparation of platinum nanoporous materials (NCDs-Pt NDs):
the procedure of example 1 was followed, but in the second step, the nanomaterial was prepared using 1mL of experimental water instead of 1mL of 2mmol of palladium chloride, labeled: NCDs-Pt NDs, and their mimic oxidase activity were tested using the same method.
Comparative example 3
Preparation of palladium nanoporous materials (NCDs-Pd NSs):
the procedure of example 1 was followed, but in the first step, the nanomaterial was prepared using 200. mu.L of test water instead of 200. mu.L of 10mmol chloroplatinic acid, labeled: NCDs-Pd NSs and tested for mimic oxidase activity using the same method.
Comparative example 4
Preparation of platinum nanomaterials (Pt NDs):
following the procedure of example 1, in a first step, 560. mu.L of test water was substituted for 560. mu.L of an aqueous solution of 93. mu.g/mL nitrogen-doped carbon quantum dots; in the second step, 1mL of test water was used instead of 1mL of 2mmol of palladium chloride to prepare the nanomaterial, labeled: pt NDs and tested for mimic oxidase activity using the same method.
Comparative example 5
Preparation of palladium nanomaterials (Pd NPs):
the procedure of example 1 was followed except that in the first step 560. mu.L of test water was substituted for 560. mu.L of an aqueous solution of 93. mu.g/mL nitrogen-doped carbon quantum dots; in the second step, 1mL of test water was used instead of 1mL of 2mmol of palladium chloride to prepare the nanomaterial, labeled: pd NPs and tested for mimic oxidase activity using the same method.
FIG. 12 is a TEM image of Pt @ Pd NPs of the palladium-platinum composite nanomaterial prepared in comparative example 1, and it can be seen that the surface roughness of the material is obviously reduced and the degree of surface branching is reduced compared with mPd @ Pt NSs (1: 1).
FIG. 13 is a TEM image of the platinum nanomaterials NCDs-Pt NDs prepared in comparative example 2, which shows that the NCDs-Pt NDs are large particles composed of several smaller platinum particles connected together, and have a nearly spherical shape and a particle size, and the materials have high surface roughness and high surface branching degree.
FIG. 14 is a TEM image of the palladium nano-material NCDs-Pd NSs prepared in comparative example 3, from which it can be seen that NCDs-Pd NSs are large particles composed of some smaller palladium particles connected, and the material has high surface roughness and high degree of surface branching.
Fig. 15 is a TEM image of the Pt NDs as the platinum nanomaterial prepared in comparative example 4, and it can be seen that the material has a high degree of surface branching, but the particle density is large as seen from the image.
Fig. 16 is a TEM image of Pd NPs of the palladium nanomaterial prepared in comparative example 5, and it can be seen that the surface roughness of the material is significantly reduced compared to the surface roughness of the previously described material.
Compared with the graph 1 and the graph 11-15, firstly, the nitrogen-doped carbon quantum dots are added in the sample preparation, so that the preparation of the material with higher surface roughness and higher surface branching degree is facilitated, namely the nitrogen-doped carbon quantum dots are beneficial to the formation of the porous nano material; mPd @ Pt NSs (1:1) particles have large surface roughness and high surface branching degree, and the shells of the particles mainly comprise platinum, which is mainly beneficial to maintaining or improving the performance of the platinum and reducing the consumption of the platinum.
FIG. 17 is a comparison of the activities of the oxidate-mimic enzymes of the nanomaterials prepared in example 1 and comparative examples 1-5, which shows that the nitrogen-doped carbon quantum dots themselves have no mimic oxidase activity (shown in the figure), but the samples prepared from the nitrogen-doped carbon quantum dots have better mimic oxidase activity, wherein the oxidase activity of mPd @ Pt NSs (1:1) is the highest, and the NCDs-Pt NDs are the second order.
FIG. 18 is a graph showing the change in absorbance (. lamda. 652nm) of oxidized TMB with time in the presence and absence of hydrogen peroxide in example 1 and a commercially available horseradish peroxidase. As can be seen from FIG. 18, in the absence of hydrogen peroxide, mPd @ Pt NSs (1:1) exhibited comparable catalytic rates to the commercial horseradish peroxidase, but, if hydrogen peroxide was added to the system, mPd @ Pt NSs (1:1) exhibited a catalytic rate that was-5 times that of the commercial horseradish peroxidase.
As can be seen from the above examples and comparative examples, the specific surface area of the core-shell type palladium-platinum composite nano-porous material mPd @ Pt NSs (1:1) prepared by the method is as high as 210m2·g-1V as a mimic oxidase for catalytically oxidizing TMBmax0.05. mu.M.s-1，Km68.55 μ M, Kcat 2.1X 103s-1(Kcat＝Vmax/[ nanoenzymes]) And K of mPd @ Pt NSscat(2.1×103s-1) With horseradish peroxidase (K)cat＝4.3×103s-1) In the same order of magnitude; if hydrogen peroxide is added into the system, mPd @ Pt NSs (1:1) shows peroxidase mimic activity, and under the condition of the same order of enzyme molar concentration, mPd @ Pt NSs (1:1) has peroxidase activity which is higher than that of the commercial horseradish peroxidase, the rate is about 5 times, and the catalytic performance is excellent. According to the method, a certain amount of platinum source and nitrogen-doped carbon quantum dots are converted into a platinum-nitrogen-doped carbon quantum dot intermediate at a certain reaction temperature within a certain reaction time, the reduction speed of platinum in the platinum source is reduced, the intermediate can serve as a nucleation site, palladium ions in the palladium source are reduced to form small palladium particles on the surface of the intermediate after the palladium source and a reducing agent are added in the second step, then the small palladium particles are gathered to form large palladium particles in order to reduce the surface energy of a reaction system, and the small palladium particles are gradually reduced out and the nitrogen-doped carbon quantum dots are discharged out along with the platinum ions in the intermediate on the surface of the palladium particles to form a core-shell structure with palladium as a core and platinum as a shell, channels are formed in the process of discharging the nitrogen-doped carbon quantum dots, the specific surface area of the prepared nano porous material is increased, and finally a core-shell structure is formedType palladium platinum composite nanoporous materials (mPd @ Pt NSs). The nano-porous material has high specific surface area and platinum with good catalytic activity is positioned on the surface of the particles, so that the activity of the oxide mimic enzyme is greatly improved and the catalytic performance is excellent.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A preparation method of a core-shell palladium-platinum composite nano-porous material comprises the following steps:
(1) mixing a platinum source, nitrogen-doped carbon quantum dots, a reducing agent and water, and then carrying out primary incubation to obtain an incubation liquid;
the temperature of the first incubation is 30-40 ℃, and the time of the first incubation is 0.5-3 h;
(2) and (2) mixing the incubation liquid obtained in the step (1) with a palladium source and a reducing agent, and then carrying out secondary incubation to obtain the core-shell type palladium-platinum composite nano-porous material.
The temperature of the second incubation is 30-40 ℃, and the time of the second incubation is 0.5-3 h.
2. The method according to claim 1, wherein the source of platinum in step (1) comprises one or more of chloroplatinic acid, sodium chloroplatinate, and platinum tetrachloride.
3. The method according to claim 1, wherein the palladium source in the step (2) includes one or more of palladium chloride, potassium chloropalladate and chloropalladate.
4. The method according to claim 1, wherein the ratio of the molar concentration of the platinum atoms in the incubation liquid in the step (1), the mass concentration of the nitrogen-doped carbon quantum dots, and the molar concentration of the palladium atoms in the palladium source in the step (2) is (1) mmol: (2.6-130) ug/mL: (0.1-10) mol.
5. The production method according to claim 1, wherein the ratio of the amounts of the platinum atom in the platinum source and the substance of the reducing agent in the step (1) is 1: 6.
6. the preparation method according to claim 1, wherein the temperature of the first incubation in the step (1) is 30-40 ℃, and the time of the first incubation is 0.5-3 h.
7. The production method according to claim 1, wherein the ratio of the amounts of the substance of the palladium atom and the reducing agent in the palladium source in the step (2) is 1: 6.
8. the preparation method according to claim 1, wherein the temperature of the second incubation in the step (2) is 30-40 ℃, and the time of the second incubation is 0.5-3 h.
9. The core-shell palladium-platinum composite nano-porous material prepared by the preparation method of any one of claims 1 to 8.
10. Use of the core-shell palladium platinum composite nanoporous material according to claim 9 in enzymatic catalysis.
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| CN110841632A (en) * | 2019-11-18 | 2020-02-28 | 湖北大学 | Controllable synthesis method and application of novel palladium-carbon nano composite catalyst |
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