Preparation and application of dandelion-like cerium-zinc oxide / reduced graphene oxide composite material

Abstract

This invention belongs to the field of novel nanomaterials and electrochemical biosensor detection technology, and discloses the preparation of a dandelion-shaped cerium-zinc oxide / reduced graphene oxide composite material. The purpose of this invention is to solve the problems of low sensitivity, baseline drift, and poor stability in existing materials for dopamine detection. The main preparation method of this invention is as follows: 1. Preparation of a dandelion-shaped cerium-zinc bimetallic organic framework using a hydrothermal synthesis method; 2. Preparation of a dandelion-shaped cerium-zinc bimetallic organic framework / reduced graphene oxide composite material using a one-step hydrothermal synthesis method; 3. Preparation of a cerium-zinc bimetallic organic framework / reduced graphene oxide / ITO electrode using an automated spraying method; 4. Conversion of the electrode to a cerium-zinc oxide / reduced graphene oxide / ITO electrode by high-temperature annealing. The cerium-zinc oxide / reduced graphene oxide / ITO electrode exhibits excellent sensitivity of 17.67 μA·μM when detecting dopamine in the range of 0~10 μM. ‑1 ·cm ‑2 Furthermore, the detection limit for dopamine is 2.1 nM.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation and relates to a dandelion-like cerium-zinc metal oxide / reduced graphene oxide composite material as an electrode for high-sensitivity electrochemical detection of dopamine. Background Technology

[0002] Parkinson's disease is the second most common neurodegenerative disease among the elderly. It is estimated that approximately six million people worldwide suffer from Parkinson's disease, and the rate of increase has been rising in recent decades. Dopamine is an important neurotransmitter that is normally maintained within a certain concentration range in the body. An imbalance in the substantia nigra of the brainstem leads to a decrease in dopamine synthesis, and low levels of dopamine in the body contribute to the development of Parkinson's disease. Therefore, rapid, simple, and highly sensitive dopamine measurement is crucial for the early diagnosis of Parkinson's disease and the adjustment of drug dosage, possessing significant clinical and pharmacological value.

[0003] Cerium oxide, a rare-earth metal oxide, has been widely used in catalysis and biosensing due to its ability to freely change the valence state of cerium ions, abundant oxygen vacancies, and excellent redox capabilities. Zinc oxide possesses unique electron transfer properties and good chemical stability, and its energy state is very similar to that of cerium oxide. Heterogeneous structures based on cerium-zinc metal oxides can utilize synergistic effects to achieve better sensing performance than pure cerium oxide. The sensing performance of cerium-zinc metal oxides is greatly influenced by the synthesis method and morphology. To date, several synthetic methods have been developed, including co-precipitation, sol-gel, and hydrothermal synthesis, which produce different morphologies such as nanorods and nanospheres. However, developing new morphological strategies to address diverse needs remains crucial.

[0004] Metal-organic frameworks (MOFs) are ligand complexes with tunable structures, uniform pore sizes, and large specific surface areas. Metal oxides derived from MOFs through heat treatment can inherit their favorable morphology and large surface area, making them widely used in sensing applications. More importantly, during the release of organic ligands via calcination, certain defects can be introduced into the metal oxides, significantly increasing their catalytic activity. Therefore, this provides an effective method for preparing cerium-zinc metal oxides with different morphologies and high properties. Furthermore, reduced graphene oxide, with its high conductivity and biocompatibility, is considered an excellent material that can further enhance the conductivity of cerium-zinc metal oxides, making them more suitable for electrochemical sensing.

[0005] In summary, this invention utilizes a one-step hydrothermal method to prepare dandelion-like cerium-zinc metal oxide / reduced graphene oxide composite material, leveraging the synergistic effect of both materials. When used for dopamine detection, this electrode exhibits ultra-high sensitivity and a low detection limit, showing promising clinical application prospects. Summary of the Invention

[0006] This invention aims to address the problems of low sensitivity, baseline drift, and poor stability in existing materials for dopamine detection. It develops a dandelion-shaped cerium-zinc metal oxide / reduced graphene oxide composite electrode, thereby providing a method for preparing the dandelion-shaped cerium-zinc metal oxide / reduced graphene oxide composite electrode.

[0007] I. Preparation of Cerium-Zinc Bimetallic Organic Frameworks

[0008] 1) Weigh 10-25 mL of dimethylformamide solution, add 0.2-0.3 g of cerium nitrate and 0.05-0.15 g of zinc nitrate in sequence, and stir vigorously for 10-45 min to obtain solution A;

[0009] 2) Weigh 0.3-0.45g of benzotriic acid and add it to 10-30mL of anhydrous ethanol, and stir vigorously for 10-45min to obtain solution B;

[0010] 3) After the reagents are evenly dispersed in the solvent, quickly mix solutions A and B, add 0.1-0.4 g of polyvinylpyrrolidone, stir for 1-2 h, then transfer to a 50 mL reaction vessel, keep the temperature at 170-180°C for 10-12 h, and after the reaction is completed and cooled, wash the product with dimethylformamide and anhydrous ethanol, centrifuge and dry to obtain gray cerium-zinc bimetallic organic framework powder;

[0011] II. Cerium-Zinc Bimetallic Organic Framework / Reduced Graphene Oxide Composite Material

[0012] Add 10-50 mg of graphene oxide to the mixed solution in step 1(3), stir for 2-5 h, then transfer to a 50 mL reaction vessel, keep the temperature at 170-180°C for 10-12 h, and after the reaction is completed and cooled, wash the product with dimethylformamide and anhydrous ethanol, centrifuge and dry to obtain black cerium-zinc bimetallic organic framework / reduced graphene oxide composite powder.

[0013] III. Preparation of Cerium-Zinc Bimetallic Organic Framework / Reduced Graphene Oxide / ITO Electrode by Automated Spray Coating Method

[0014] Cerium-zinc bimetallic organic framework / reduced graphene oxide powder was prepared into a suspension of 1-5 mg / mL, and the mixed suspension was sprayed onto ITO glass with a spray gun to obtain a cerium-zinc bimetallic organic framework / reduced graphene oxide / ITO electrode.

[0015] IV. Preparation of Cerium-Zinc Metal Oxide / Reduced Graphene Oxide / ITO Electrodes by Heat Treatment

[0016] The electrode obtained in step three is placed in a tube furnace and heat-treated at 300-500°C under the protection of argon to obtain a cerium-zinc metal oxide / reduced graphene oxide / ITO electrode; wherein the heating rate is 5-15°C / min and the holding time is 1-3h.

[0017] Compared with existing technologies, the present invention has the following advantages:

[0018] 1. The process of this invention is simple and can be prepared on a large scale. The addition of graphene oxide to the solution improves the conductivity of the composite material. Furthermore, the dandelion-like cerium-zinc metal oxide possesses abundant active sites, excellent redox activity, high specific surface area, and stability, which are beneficial for improving the electrochemical performance of the composite material.

[0019] 2. This invention utilizes a composite of dandelion-like cerium-zinc metal oxide and two-dimensional nanosheet-like reduced graphene oxide to significantly increase the contact area with the electrolyte, thereby greatly improving the electrochemical performance of the composite material. The sensitivity for electrochemical detection of dopamine in the 0–10 μM range is 17.67 μA·μM. -1 ·cm -2 Furthermore, the detection limit for dopamine was 2.1 nM in the range of 0–60 μM. Attached Figure Description

[0020] Figure 1 Morphological characterization of dandelion-like cerium-zinc metal oxide / reduced graphene oxide;

[0021] Figure 2 Structural characterization diagram of dandelion-shaped cerium-zinc metal oxide / reduced graphene oxide;

[0022] Figure 3 Electrochemical performance testing of dandelion-shaped cerium-zinc metal oxide / reduced graphene oxide;

[0023] Figure 4 The cerium-zinc bimetallic organic framework synthesized by hydrothermal method consists of nanorods with a length of 2 μm and a diameter of 50 nm, and the entire dandelion-shaped cerium-zinc bimetallic organic framework has a diameter of approximately 4 μm. Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the examples described below are intended to facilitate the understanding of the present invention and do not constitute any limitation thereof.

[0025] Specific Embodiment 1: A method for preparing a dandelion-like cerium-zinc metal oxide / reduced graphene oxide composite material, comprising the following steps:

[0026] I. Preparation of Cerium-Zinc Bimetallic Organic Frameworks

[0027] 1) Weigh 10-25 mL of dimethylformamide solution, add 0.2-0.3 g of cerium nitrate and 0.05-0.15 g of zinc nitrate in sequence, and stir vigorously for 10-45 min to obtain solution A;

[0028] 2) Weigh 0.3-0.45g of benzotriic acid and add it to 10-30mL of anhydrous ethanol, and stir vigorously for 10-45min to obtain solution B;

[0029] 3) After the reagents are evenly dispersed in the solvent, quickly mix solutions A and B, add 0.1-0.4 g of polyvinylpyrrolidone, stir for 1-2 h, then transfer to a 50 mL reaction vessel, keep the temperature at 170-180°C for 10-12 h, and after the reaction is completed and cooled, wash the product with dimethylformamide and anhydrous ethanol, centrifuge and dry to obtain gray cerium-zinc bimetallic organic framework powder;

[0030] II. Cerium-Zinc Bimetallic Organic Framework / Reduced Graphene Oxide Composite Material

[0031] Add 10-50 mg of graphene oxide to the mixed solution in step 1(3), stir for 2-5 h, then transfer to a 50 mL reaction vessel, keep the temperature at 170-180°C for 10-12 h, and after the reaction is completed and cooled, wash the product with dimethylformamide and anhydrous ethanol, centrifuge and dry to obtain black cerium-zinc bimetallic organic framework / reduced graphene oxide composite powder.

[0032] III. Preparation of Cerium-Zinc Bimetallic Organic Framework / Reduced Graphene Oxide / ITO Electrode by Automated Spray Coating Method

[0033] Cerium-zinc bimetallic organic framework / reduced graphene oxide powder was prepared into a suspension of 1-5 mg / mL, and the mixed suspension was sprayed onto ITO glass with a spray gun to obtain a cerium-zinc bimetallic organic framework / reduced graphene oxide / ITO electrode.

[0034] IV. Preparation of Cerium-Zinc Metal Oxide / Reduced Graphene Oxide / ITO Electrodes by Heat Treatment

[0035] The electrode obtained in step three is placed in a tube furnace and heat-treated at 300-500°C under the protection of argon to obtain a cerium-zinc metal oxide / reduced graphene oxide / ITO electrode; wherein the heating rate is 5-15°C / min and the holding time is 1-3h.

[0036] Specific Embodiment 2: A method for preparing a dandelion-like cerium-zinc metal oxide / reduced graphene oxide composite material, comprising the following steps:

[0037] The difference between this embodiment and Example 1 is that the mass of graphene oxide added to the mixed solution in step 2 is 30-50 mg, while the rest is the same as in Example 1.

[0038] Specific Embodiment 3: A method for preparing a dandelion-like cerium-zinc metal oxide / reduced graphene oxide composite material, comprising the following steps:

[0039] The difference between this embodiment and one of Examples 1 or 2 is that the mass of polyvinylpyrrolidone added in step 1, 3) is 0.3~0.4 g, while the rest is the same as in Example 1 or 2.

[0040] Specific Embodiment 4: A method for preparing a dandelion-like cerium-zinc metal oxide / reduced graphene oxide composite material, comprising the following steps:

[0041] The difference between this embodiment and any one of Examples 1 to 3 is that the cerium-zinc metal oxide / reduced graphene oxide composite powder in step 3 is prepared as a suspension solution of 3-5 mg / mL, and the mixed suspension is sprayed onto ITO glass with a spray gun to obtain a cerium-zinc metal oxide / reduced graphene oxide / ITO electrode. The rest is the same as any one of Examples 1 to 3.

[0042] The effectiveness of the present invention was verified by the following experiments:

[0043] This experiment describes a method for preparing a dandelion-like cerium-zinc metal oxide / reduced graphene oxide composite material, comprising the following steps:

[0044] I. Preparation of Cerium-Zinc Bimetallic Organic Frameworks

[0045] 1) Weigh 15 mL of dimethylformamide solution, add 0.25 g of cerium nitrate and 0.1 g of zinc nitrate in sequence, and stir vigorously for 30 min to obtain solution A;

[0046] 2) Weigh 0.35g of benzotriic acid and add it to 20mL of anhydrous ethanol, and stir vigorously for 30min to obtain solution B;

[0047] 3) After the reagents are evenly dispersed in the solvent, solutions A and B are quickly mixed and 0.2g of polyvinylpyrrolidone is added. After stirring for 1 hour, the mixture is transferred to a 50 mL reaction vessel and kept at 180°C for 12 hours. After the reaction is completed and cooled, the product is washed with dimethylformamide and anhydrous ethanol, and then centrifuged and dried to obtain gray cerium-zinc bimetallic organic framework powder.

[0048] II. Cerium-Zinc Bimetallic Organic Framework / Reduced Graphene Oxide Composite Material

[0049] Add 30 mg of graphene oxide to the mixed solution in step 1(3), stir for 3 h, then transfer to a 50 mL reaction vessel, keep the temperature at 180°C for 12 h, and after the reaction is completed and cooled, wash the product with dimethylformamide and anhydrous ethanol, centrifuge and dry to obtain black cerium-zinc bimetallic organic framework / reduced graphene oxide composite powder.

[0050] III. Preparation of Cerium-Zinc Bimetallic Organic Framework / Reduced Graphene Oxide / ITO Electrode by Automated Spray Coating Method

[0051] Cerium-zinc bimetallic organic framework / reduced graphene oxide powder was prepared into a 3 mg / mL suspension, and the mixed suspension was sprayed onto ITO glass with a spray gun to obtain a cerium-zinc bimetallic organic framework / reduced graphene oxide / ITO electrode.

[0052] IV. Preparation of Cerium-Zinc Metal Oxide / Reduced Graphene Oxide / ITO Electrodes by Heat Treatment

[0053] The electrode obtained in step three was placed in a tube furnace and heat-treated at 450°C under argon protection to obtain a cerium-zinc metal oxide / reduced graphene oxide / ITO electrode; wherein the heating rate was 10°C / min and the holding time was 2h.

[0054] This invention uses a three-electrode testing system to study the electrochemical performance of materials. A platinum sheet is used as the counter electrode, a silver / silver chloride electrode as the reference electrode, and a 1 mol / L phosphate solution is used as the electrolyte for testing.

[0055] Figure 1 Scanning electron microscopy and transmission electron microscopy images of cerium-zinc metal oxide / reduced graphene oxide composites are shown. Figure 1 Image a shows a scanning electron micrograph of a cerium-zinc bimetallic organic framework at low magnification, in which the size of the cerium-zinc bimetallic organic framework can be observed to be approximately 4 μm. Figure 1 b shows a high-magnification scanning electron micrograph of the cerium-zinc bimetallic organic framework, in which the unique hollow dandelion-like morphology can be observed, providing a large surface area that is more conducive to capturing biomolecules. After high-temperature annealing, the cerium-zinc bimetallic organic framework is derived into cerium-zinc metal oxides without significant changes in morphology. Figure 1 c). Figure 1The image shows scanning electron micrographs of cerium-zinc metal oxide / reduced graphene oxide prepared with different amounts of graphene oxide. When the cerium-zinc bimetallic organic framework was bound to graphene oxide, the size of the cerium-zinc bimetallic organic framework decreased slightly, which may be due to the functional groups of graphene oxide hindering the growth of the cerium-zinc bimetallic organic framework. Graphene oxide exhibited curling at low concentrations, but became flatter and less curled with increasing concentration, which is due to the presence of Zn. 2+ and Ce 3+ The surface potential changes caused by ion attachment on the graphene oxide surface. However, when the graphene oxide content is too high, strong π-π bond interactions lead to graphene oxide aggregation and repackaging, reducing the number of exposed active sites. Transmission electron microscopy images show that in cerium-zinc metal oxide / reduced graphene oxide, cerium-zinc metal oxide is well bound to graphene oxide (…). Figure 1 The diameter of the cerium-zinc metal oxide nanorods is approximately 50 nm. Furthermore, the lattice spacings of 0.26 nm and 0.31 nm in the figure correspond to the (002) crystal plane of zinc oxide and the (111) crystal plane of cerium oxide, respectively. Figure 1 i).

[0056] The structure and surface chemistry of cerium-zinc metal oxide / reduced graphene oxide are shown in Figure 2 In the middle. For example Figure 2 As shown in Figure a, the diffraction peaks of the cerium-zinc bimetallic organic framework at 28.54° and 33.08° correspond to the (111) and (200) crystal planes of cerium oxide, while the peaks at 32.0° and 36.53° correspond to the (100) and (101) crystal planes of zinc oxide. The peaks at 47.84°, 56.64°, and 77.5° are considered to be caused by the simultaneous presence of cerium oxide and zinc oxide. Meanwhile, no obvious characteristic peaks of reduced graphene oxide were observed, which may be due to the low content of reduced graphene oxide and the high intensity of other characteristic peaks. Figure 2 As shown in b, 1342 cm -1 and 1590 cm -1 The characteristic peaks originate from the D and G bands of reduced graphene oxide, corresponding to disordered and ordered carbons, respectively. Higher I... D / I G The ratio indicates a strong interaction between cerium-zinc metal oxide and reduced graphene oxide, and a high degree of reduction in graphene oxide. Located at 457 cm⁻¹ -1 The peak value confirms the cubic fluorite crystal structure of cerium oxide, while the 438 cm⁻¹ peak value confirms the cubic fluorite crystal structure of cerium oxide. -1The peak values ​​can be attributed to the Woolst-like hexagonal phase of zinc oxide. To further investigate the changes in elemental valence states and bonding energies, XPS spectral analysis was performed. Four distinct peak values, primarily composed of C, O, Ce, and Zn, were observed in the investigated spectra. Figure 2 c). High-resolution spectra of Zn 2p show Zn 2p observed at 1020.77 eV and 1043.88 eV. 3 / 2 and Zn 2p 1 / 2 The two characteristic peaks of the signal indicate that Zn 2+ The existence of form ( Figure 2 d). The diffraction peaks at 880.76 eV and 884.81 eV are Ce. 3+ In Ce 3d 5 / 2 The orbital results show peaks at 882.23 eV, 887.39 eV, and 898.06 eV, which are Ce... 4+ In Ce 3d 5 / 2 The results of the orbit ( Figure 2 e). The diffraction peaks at 900.24 eV and 903.75 eV are attributed to Ce. 3+ In Ce 3d 3 / 2 On the orbital, the diffraction peaks at 900.97 eV, 907.01 eV, and 916.47 eV are attributed to Ce. 4+ In Ce 3d 3 / 2 On the orbit. This indicates the simultaneous presence of Ce in cerium-zinc metal oxide / reduced graphene oxide. 4+ and Ce 3+ . Figure 2 f shows the high-resolution spectrum of the O 1s orbital, with the characteristic peak at a binding energy of 528.65 eV attributed to O. 2- The lattice oxygen in the sample may originate from Zn-O and Ce-O bonds. The peak at 530.7 eV is mainly caused by defects in low-oxygen coordination. The characteristic peak at 532.05 eV is mainly caused by hydroxyl groups (-OH) resulting from water adsorption on the surface of cerium-zinc metal oxide / reduced graphene oxide. Figure 2 The high-resolution spectrum of the C 1s orbitals of cerium-zinc metal oxide / reduced graphene oxide was displayed. The characteristic peaks at 284.0 eV, 285.01 eV, 287.27 eV, and 288.42 eV are attributed to the CC / C=C, CO, C=O, and OC=O bonds in the reduced graphene oxide, respectively. All these results indicate that the synthesis of cerium-zinc metal oxide / reduced graphene oxide was successful.

[0057] A more sensitive differential pulse voltammetry method was used to further examine the electrochemical response of dopamine to a cerium-zinc oxide / reduced graphene oxide / ITO electrode, such as... Figure 3As shown, the electrode exhibits a gradually increasing oxidation peak current for dopamine at a potential of 0.22 V at different dopamine concentrations ranging from 0 to 60 μM, with a stronger current response at low dopamine concentrations. Figure 3 a). The corresponding regression equation is Ipa = 17.67C + 3.06 (R²). 2 =0.9999), Ipa=6.79C+129.06 (R 2 =0.9999) Figure 3 d). This indicates that the electrode has a sensitivity of 17.67 μA·μM for detecting dopamine. -1 ·cm -2 (0-10 μM) and 6.79 μA·μM -1 ·cm -2 (10-60 μM), detection limit was 2.1 nM (S / N=3). Furthermore, uric acid is widely present in body fluids and has a very important impact on human health. Its oxidation potential is similar to that of dopamine, so the electrode's resistance to interference with uric acid was investigated. The oxidation peak of uric acid by the electrode is at a potential of 0.35 V. The current change for detecting uric acid concentrations from 0-60 μM is shown below. Figure 3 As shown in b and 3e, this corresponds to the regression equation Ipa = 6.10C + 1.15 (R²). 2 =0.9999) and Ipa=2.62C+39.33 (R 2 =0.9999). Differential pulse voltammetry of the electrode was also performed in the presence of 20 μM uric acid at different concentrations of dopamine. Figure 3 c). Two distinct oxidation peaks can be clearly observed, belonging to dopamine and uric acid. The peak current of dopamine tends to increase with increasing dopamine concentration, but the peak current of uric acid remains unchanged. Figure 3 f shows the regression equation for peak current versus dopamine concentration: Ipa = 17.66C + 2.35(R) 2 =0.9999) and Ipa=6.77C+123.27 (R 2 =0.9999). The results show that the addition of uric acid has no significant effect on the detection of dopamine, and the cerium-zinc metal oxide / reduced graphene oxide / ITO electrode has good selectivity for dopamine.

Claims

1. The application of a dandelion-shaped cerium-zinc oxide / reduced graphene oxide composite electrode in the field of dopamine detection, characterized in that... The preparation method of the dandelion-shaped cerium-zinc oxide / reduced graphene oxide composite electrode is carried out according to the following steps: I. Preparation of Cerium-Zinc Bimetallic Organic Frameworks 1) Weigh 10-25 mL of dimethylformamide solution, add 0.2-0.3 g of cerium nitrate and 0.05-0.15 g of zinc nitrate in sequence, and stir vigorously for 10-45 min to obtain solution A; 2) Weigh 0.3-0.45g of benzotriic acid and add it to 10-30mL of anhydrous ethanol, and stir vigorously for 10-45min to obtain solution B; 3) After the reagents are evenly dispersed in the solvent, quickly mix solutions A and B, add 0.1-0.4 g of polyvinylpyrrolidone, stir for 1-2 h, then transfer to a 50 mL reaction vessel, keep the temperature at 170-180°C for 10-12 h, and after the reaction is completed and cooled, wash the product with dimethylformamide and anhydrous ethanol, centrifuge and dry to obtain gray cerium-zinc bimetallic organic framework powder; II. Cerium-Zinc Bimetallic Organic Framework / Reduced Graphene Oxide Composite Material Add 10-50 mg of graphene oxide to the mixed solution in step 1(3), stir for 2-5 h, then transfer to a 50 mL reaction vessel, keep the temperature at 170-180°C for 10-12 h, and after the reaction is completed and cooled, wash the product with dimethylformamide and anhydrous ethanol, centrifuge and dry to obtain black cerium-zinc bimetallic organic framework / reduced graphene oxide composite powder. III. Preparation of Cerium-Zinc Bimetallic Organic Framework / Reduced Graphene Oxide / ITO Electrode by Automated Spray Coating Method Cerium-zinc bimetallic organic framework / reduced graphene oxide powder was prepared into a suspension of 1-5 mg / mL, and the mixed suspension was sprayed onto ITO glass with a spray gun to obtain a cerium-zinc bimetallic organic framework / reduced graphene oxide / ITO electrode. IV. Preparation of Cerium-Zinc Metal Oxide / Reduced Graphene Oxide / ITO Electrodes by Heat Treatment The electrode obtained in step three is placed in a tube furnace and heat-treated at 300-500°C under the protection of argon to obtain a cerium-zinc metal oxide / reduced graphene oxide / ITO electrode; wherein the heating rate is 5-15°C / min and the holding time is 1-3h.

2. The application of the dandelion-shaped cerium-zinc metal oxide / reduced graphene oxide composite electrode according to claim 1 in the field of dopamine detection, characterized in that: The cerium-zinc metal oxide / reduced graphene oxide composite material is used as the working electrode of an electrochemical biosensor for highly sensitive detection of dopamine.

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