CN111298828A - Highly dispersed Pt/EMT with Pt nanoparticles on EMT and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of functionalized zeolite materials, in particular to Pt/EMT in which Pt nanoparticles are highly dispersed on EMT and a preparation method and application thereof. In the present invention, Pt NPs (5-8 nm) are uniformly loaded on the ultra-small EMT zeolite (15-20 nm) carrier to prepare a Pt/EMT nanocomposite material with highly dispersed Pt. The Pt/EMT nanomaterials can be well dispersed in water to form a uniform suspension, and then act as a good peroxide-based catalyst in the presence of hydrogen peroxide to oxidize 3,3,5,5-tetramethine benzidine; and used to detect the content of glucose in solution; due to its high selectivity to glucose, it can be used to accurately measure the concentration of glucose in samples including human serum and fruit juice, in clinical diagnosis, pharmaceuticals, food, etc. It has a wide range of applications in the field.

Description

Highly dispersed Pt/EMT with Pt nanoparticles on EMT and its preparation method and application

technical field

The invention belongs to the technical field of functionalized zeolite materials, and in particular relates to a Pt/EMT, a preparation method thereof, and an application as a peroxidase mimic.

Background technique

In 2007, in the first report _on the intrinsic enzymatic activity of _Fe3O4 nanoparticles (NPs), the study of artificial enzyme mimics based on inorganic nanomaterials, due to their clear advantages over natural enzymes, has been recognized in biochemical and There has been widespread interest in bioassay applications, and in the past decade, a large number of inorganic nanomaterials with different structures and compositions, such as metal oxides, noble metals, metal sulfides, etc., have been rationally designed as peroxides Mimic nanozymes in enzyme-like catalytic reactions. As one of the most common precious metals widely used as catalysts in chemical processes, platinum (Pt) is widely regarded as one of the most active peroxidase mimetics. However, the disadvantages of high cost and easy inactivation caused by Pt aggregation greatly limit its applications, and so far, it has not been extensively studied in practical biological applications including biosensing. One strategy to overcome these obstacles is to control the size and structure of Pt nanomaterials to achieve superior enzymatic activity, such as the synthesis of ultrasmall Pt nanoclusters, porous Pt nanotubes, cubic Pt nanocrystals, irregularly shaped Pt NPs, etc. Another strategy is based on the synthesis of Pt/support composite nanomaterials with well-designed stable structures and versatility, usually achieved by uniformly dispersing PtNPs on some suitable supports, including Pt/CeO2 nanocomposite Materials, Au@Pt core-shell nanorods, dumbbell-like PtPd _{- Fe3O4} NPs, ferritin-Pt NPs, dendrimer-wrapped Pt NPs, mesoporous silica-wrapped Pt NPs, etc. Although these Pt-loaded hybrid nanocomposites exhibit satisfactory performance in enzyme-mimicking reactions, it is still difficult to obtain high-quality low-cost carriers and achieve highly uniform dispersion of Pt NPs on/inside the carriers.

Unlike mesoporous materials such as mesoporous SiO ₂ , zeolite is a crystalline aluminosilicate with regular micropores (pore diameter < 2 nm) interconnected with well-developed channels, showing a stable framework structure, good The Bronsted/Lewis acidity and shape selectivity. Generally, most zeolites such as Y (FAU), ZSM-5 (MFI), β (BEA), SSZ-13 (CHA), etc., can be conveniently synthesized by conventional hydrothermal methods and are widely used as low-cost industrial catalysts or large-scale catalyst supports. In recent years, studies on nano- and mesoporous zeolites have attracted considerable attention, mainly because they can overcome diffusion limitations within micropores and improve transport, accessibility of reactants to active sites. Although many nano-sized zeolites have been reported, obtaining ultra-small zeolite nanocrystals (<15 nm) by template-free methods remains a great challenge. Recently, by precisely controlling the nucleation kinetics at low temperature (30 °C), Mintova and co-workers synthesized EMT (10~20 nm) and Y (10~70 nm) from template-free colloidal precursors The ultra-small zeolite materials, all have a 3-dimensional 12-member annular channel system, which can be highly dispersed in water to form a uniform suspension. In addition to its outstanding catalyst performance as zeolite Y in isomerization, alkylation and aromatization reactions, EMT zeolite can also serve as an ideal host for silver nanoparticles through the introduction of silver ions and subsequent reduction reactions, mainly due to Due to their low Si/Al ratio, these nano-sized Ag-EMT zeolites can be stabilized in aqueous suspensions for long-term antimicrobial applications. Nanoscale Pt/EMT zeolites are used as high-performance enzyme mimics due to their inherent surface acidity, low Si/Al ratio, ultra-small particle size of EMT, uniform dispersion of Pt NPs, and uniform suspension in water.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a Pt/EMT with high-performance Pt nanoparticles highly dispersed on ultra-small EMT, its preparation method and its application as a catalase mimetic catalyst.

The invention utilizes the inherent characteristics of EMT zeolite, such as surface acidity, low silicon-aluminum ratio, ultra-small particle size, etc., through the impregnation reduction method, the Pt nano-particles are uniformly dispersed on the surface of the EMT zeolite, and the high-performance Pt/EMT catalyst is prepared; The catalyst can act as a catalase mimetic.

The present invention provides a method for preparing Pt/EMT in which Pt nanoparticles are highly dispersed on ultra-small EMT, and the specific steps are as follows.

(1) Synthesis of ultra-small EMT zeolite:

(1) Dissolve the aluminum source in distilled water under stirring, denoted as solution A; dissolve sodium hydroxide in distilled water under stirring, denoted as solution B; both solutions are fully cooled in an ice bath at 277 K;

(2) Then, slowly pour solution A into solution B under stirring to form a mixed solution, denoted as solution C, and slowly add silicon source under stirring to form a cloudy suspension; the molar amount of each component of the cloudy suspension is The ratio is: Na ₂ O : Al ₂ O ₃ : SiO ₂ : H ₂ O = (18.45-21): (1.0-2.3): (4-5.9): (200-300); under stirring, suspended in a water bath The liquid is hydrothermally crystallized at a temperature of 20-70°C for 30-40 hours;

(3) Centrifuge at 8500-10000r/min for 8-15 minutes, separate the solid product, and then wash with distilled water several times until pH=7.5-8.5 to obtain ultra-small EMT zeolite;

(4) Finally, the solid powder of EMT zeolite is dried at room temperature for at least 24 hours.

(2) Preparation of Pt/EMT complexes using an in-situ reduction method of wet impregnation combined with a reducing agent:

(1) First, 50-150 mg of EMT zeolite solid powder is dispersed in water, and ultrasonically treated for 15-25 minutes to form a uniform suspension;

(2) Then, 1-5mM platinum source was added dropwise under stirring to obtain a mixed solution; 0.2-0.4M reducing agent was added dropwise to the mixed solution at 273 K, and stirred at room temperature for 12-36 h;

(3) Centrifuge at 5500-6500r/min for 4-10 minutes, collect the solid powder, and then wash with water and ethanol for several times respectively; (4) Finally, dry in a vacuum oven at room temperature to obtain the EMT zeolite-loaded Pt complex , denoted as Pt/EMT.

The Pt/EMT prepared by the present invention has ultra-small size, and the general particle size is 15-20 nm, and the Pt particle size is 5-8 nm.

In the Pt/EMT catalyst, since Pt can have different contents, it can be expressed as xPt/EMT catalyst, where x is the mass ratio (%) of Pt to EMT zeolite.

In step (1) of the present invention, the aluminum source used is sodium metaaluminate, and the silicon source used is silica sol (SiO ₂ content is 30%), water glass or white carbon black.

In step (2) of the present invention, the used platinum source is chloroplatinic acid; the used reducing agent is NaHB ₄ .

In the present invention, different concentrations of Pt nanoparticles are supported on the surface of the EMT zeolite to achieve high dispersion of the Pt nanoparticles. As a high performance catalase mimetic catalyst.

As a catalase mimetic catalyst, it can be used for the detection of hydrogen peroxide or glucose; the specific methods are:

Using Pt/EMT as a peroxidase mimetic, ultra-small EMT zeolites with a size of 15–20 nm were synthesized by low-temperature crystallization in a template-free colloidal system, and the zeolite was used to support the surface height of Pt NPs (5–8 nm). Dispersed carrier.

The Pt/EMT nanocomposite can be well dispersed in water to form a uniform suspension; steady-state kinetic analysis shows that the Pt/EMT nanocomposite, in the presence of hydrogen peroxide (H ₂ O ₂ ), acts as a relatively Good peroxide-based catalyst to oxidize _{3,3,5,5 -} tetramethylbenzidine (TMB), with higher affinity for H2O2 and TMB than HRP, allowing a linear range from 3 μM to 30 μM The H ₂ O ₂ concentration was measured, and the detection limit was as low as 1.1 μM; on the other hand, glucose generated hydrogen peroxide under the action of glucose-decomposing enzymes, and the combination of the two could accurately detect the content of glucose in the solution. The catalyst is highly selective for glucose relative to other sugars. It can be used to detect glucose concentration by colorimetry with a detection limit as low as 13.2 μM and a wide linear range (0.08 mM ~ 0.28 mM). More importantly, due to the high selectivity of Pt/EMT nanocomposites for glucose, they can be used as peroxidase catalysts for accurate detection of glucose concentrations in real serum samples and fruit juices, which can be used in clinical diagnosis, food testing, biochemical Analyzing.

Description of drawings

Figure 1 shows the XRD patterns of EMT (a) and Pt/EMT (b) zeolites.

Fig. 2 is the detection limit test of glucose of Pt/EMT catalyst.

Figure 3 shows the glucose selectivity analysis of the Pt/EMT catalyst.

Detailed ways

The present invention will be further elaborated below in conjunction with the accompanying drawings and specific embodiments:

Raw materials: _{sodium metaaluminate} , silica sol ( ₃₀ %), sodium hydroxide, chloroplatinic acid, deionized water, sodium borohydride, EMT zeolite 5.15 SiO ₂ : 240 H ₂ O; in addition, Pt/EMT catalysts with different Pt contents (0.65, 1.3, 1.95, 2.6, 3.25, 3.9 wt% were prepared by impregnation reduction method, denoted as xPt/EMT catalysts, x = Mass ratio (%) of Pt to EMT zeolite).

Example 1: Synthesis of EMT Zeolite

In a typical synthesis of EMT zeolite, Solution A was first prepared by dissolving 2 g of sodium aluminate in 10 mL of distilled water with stirring. Solution B was prepared by dissolving 17 g of sodium hydroxide in 30 mL of distilled water with stirring. Both solutions were well cooled in an ice bath at 277 K. Then, solution A was slowly poured into solution B under vigorous stirring to form mixed solution C, and 10.46 mL of colloidal silica was slowly added under stirring. The final cloudy suspension had the following chemical composition: 18.45 Na2O: 1.0 Al2O3: 5.15 SiO2: 240 H2O. The suspension was continuously stirred for 5 minutes and then kept in a 303K water bath for 36 hours with continuous stirring for hydrothermal crystallization. The solid product was isolated by centrifugation at 8000 r/min for 10 minutes, and then washed several times with distilled water until pH=8. Finally, the solid powder of EMT zeolite was dried at room temperature for at least 24 h.

Example 2: Synthesis of Pt/EMT Zeolite

Pt/EMT catalysts with different Pt contents (0.65, 1.3, 1.95, 2.6, 3.2, 3.9 wt%) were prepared, denoted as xPt/EMT catalyst, x = mass ratio (%) of Pt to EMT zeolite. In a typical 2.6Pt/EMT catalyst synthesis, 100 mg of EMT zeolite was well dispersed in 15 mL of water by sonication for 20 min to form a homogeneous suspension. Then, 7 mL of H ₂ PtCl ₆ solution (2 mM) was added dropwise while stirring for a further 1 h. ₂ mL of freshly prepared NaBH4 solution (0.2 M) was added dropwise to the mixture at 273 K, followed by stirring at room temperature for 12 h. The solid powder was collected by centrifugation at 6000 r/min for 5 min, and then washed with water and ethanol 3 times, respectively. Finally, the 2.6Pt/EMT catalyst was obtained by drying at room temperature overnight.

The XRD patterns of the fully crystallized zeolite are shown in Fig. 1. Fig. 1(A) shows the XRD patterns of the parent EMT zeolite and the Pt/EMT nanocomposite, in which the diffraction peaks appear as those of typical EMT zeolite. The broadening of the Bragg peaks in both samples is very significant, indicating that the synthesized EMT has a small crystallinity, and the average particle size calculated by the Scherrer equation is 13.8 nm. In the Pt/EMT nanocomposites, the diffraction peaks of metallic Pt do not appear (Fig. 1A–b), indicating that the Pt NPs are highly dispersed on the matrix of the EMT zeolite.

For glucose detection, glucose should first be converted into H2O2 and gluconic _acid by the oxidation reaction of glucose oxidase (GOx), and then under the catalysis of Pt/EMT nanocomposites, a colorimetric detection based _on TMB oxidation generated of H ₂ O ₂ , which may be closely related to the concentration of glucose in the solution. The absorbance of the solution gradually increased with the glucose concentration from 0 to 2 mM (Fig. 2), and the glucose concentration-response curve showed a significant linear correlation in the concentration range of 0.08 to 0.28 mM (Fig. 2B). The LOD of glucose on the Pt/EMT nanocomposite was calculated to be about 13.2 μM.

Figure 3 shows the selectivity of the Pt/EMT nanocomposite catalyst for glucose over other sugars, which is a key factor in evaluating whether the material can be used in complex systems. Because the GOx enzyme is highly specific for glucose, the Pt/EMT nanocomposites are very weakly responsive to comparative sugars such as fructose, lactose, and sucrose, showing the Pt/EMT nanocomposite even at high concentrations 10-fold higher than glucose. High selectivity of peroxidase-like catalysts for glucose.

Claims (6)

1. the preparation method of the Pt/EMT that a kind of Pt nano particle is highly dispersed on ultra-small EMT, is characterized in that, concrete steps are as follows: (1) Synthesis of ultra-small EMT zeolite: (1) Dissolve the aluminum source in distilled water under stirring, denoted as solution A; dissolve sodium hydroxide in distilled water under stirring, denoted as solution B; both solutions are fully cooled in an ice bath at 277 K; (2) Then, slowly pour solution A into solution B under stirring to form a mixed solution, denoted as solution C, and slowly add silicon source under stirring to form a turbid suspension; the molar ratio of each component of the turbid suspension is : Na ₂ O : Al ₂ O ₃ : SiO ₂ : H ₂ O = (18.45-21) : (1.0-2.3) : (4-5.9) : (200-300 ); under stirring, the suspension in the water bath was 20-70 ℃ temperature hydrothermal crystallization reaction 30-40 hours; (3) Centrifuge at 8500-10000r/min for 8-15 minutes, separate the solid product, and then wash with distilled water several times until pH=7.5-8.5 to obtain ultra-small EMT zeolite; (4) Finally, dry the solid powder of EMT zeolite at room temperature for at least 24 hours; (2) Preparation of Pt/EMT using the in-situ reduction method of wet impregnation combined with reducing agent: (1) First, 50-150 mg of EMT zeolite solid powder is dispersed in water, and ultrasonically treated for 15-25 minutes to form a uniform suspension; (2) Then, 1-5mM platinum source was added dropwise under stirring to obtain a mixed solution; 0.2-0.4M reducing agent was added dropwise to the mixed solution at 273 K, and stirred at room temperature for 12-36 h; (3) Centrifuge at 5500-6500r/min for 4-10 minutes, collect the solid powder, and then wash with water and ethanol for several times respectively; (4) Finally, dry in a vacuum oven at room temperature to obtain the EMT zeolite-loaded Pt complex , denoted as Pt/EMT; Among them, the particle size of Pt/EMT is 15~20 nm, and the particle size of Pt is 5~8 nm. 2 . The preparation method according to claim 1 , wherein, in step (1), the aluminum source used is sodium metaaluminate, and the silicon source used is silica sol, water glass or white carbon black. 3 . 3. The preparation method according to claim 1, wherein in step (2), the platinum source used is chloroplatinic acid; the reducing agent used is NaHB ₄ . 4. Pt/EMT in which the Pt nanoparticles obtained by the preparation method described in one of claims 1-3 are highly dispersed on ultra-small EMT. 5. Pt nanoparticle as claimed in claim 4 is highly dispersed Pt/EMT on ultra-small EMT, as the application of peroxidase mimic, including: for H ₂ O ₂ Concentration monitoring, detection limit is as low as 1.1 μM; used to detect glucose concentration by colorimetry with a detection limit as low as 13.2 μM and a linear range of 0.08 mM to 0.28 mM. 6. The application according to claim 5, characterized in that it is used to detect the glucose concentration in real serum samples and fruit juices.

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