Preparation method of nanograss diamond film and application as high-sensitivity electrochemical electrode

Abstract

This invention describes a method for preparing nano-grass diamond / non-diamond carbon composite structures by etching away the non-diamond carbon portion through high-temperature annealing in air, thus forming nano-grass diamond. This belongs to the technical field of functional nanostructures and their preparation. Nitrogen is crucial in the preparation of boron-nitrogen co-doped diamond / non-diamond composite films. Nitrogen doping leads to columnar diamond growth, and the high methane concentration and nitrogen addition intensify secondary diamond nucleation, resulting in very small diamond grains containing a large amount of non-diamond carbon—precisely the desired outcome. Removing the non-diamond carbon significantly increases the surface area of ​​the electrode in this diamond sensor's high-density nanograss structure, providing more reaction sites for detecting trace molecules. Taking cadmium ions as an example, in the range of 1–100 μg / L… ‑1 It exhibits good linearity in solutions, achieving a concentration of 0.28 μg / L. ‑1 The nanograss diamond sensor exhibits a low detection limit. It demonstrates good stability and reusability, and its fabrication method is simple and suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the technical field of diamond nanostructures and their preparation, and relates to a novel method for preparing a nanostructured diamond film and its application as a high-sensitivity electrochemical electrode. Background Technology

[0002] Diamond is a functional material with excellent properties such as ultra-hardness, high thermal conductivity, chemical inertness, and stability. High-performance electrochemical electrodes can be fabricated by incorporating impurities (such as boron) to make it conductive. Furthermore, functional electrodes can benefit from improved performance through the nanostructures of diamond (e.g., nanotextures, nanowires, and porous diamond). However, due to its extremely high hardness and chemical inertness, the morphology of diamond cannot be easily altered through machining or wet chemical etching. Diamond nanostructures can be achieved through plasma etching, which increases the surface area by creating surface nanostructures. Chinese invention patent application CN 104709872A discloses a diamond nanowire array, its preparation method, and an electrode for electrochemical analysis. The disclosed preparation method involves setting a mask layer on the surface of a diamond film to expose the tips of the nanowires to be formed. Inductively coupled plasma etching is then used to form columnar diamond nanowires. Removing the top mask material yields a diamond nanowire array with a higher aspect ratio. However, this method for preparing nanostructured diamond suffers from high costs. Summary of the Invention

[0003] To address the aforementioned problems, this invention employs high-temperature annealing in air to etch away the non-diamond carbon portion of the nano-grass diamond / non-diamond carbon composite structure, thereby obtaining nano-grass diamond.

[0004] The technical solution adopted in this invention is as follows:

[0005] A method for preparing a nano-grass diamond film, comprising the following steps:

[0006] 1) Preparation of boron-nitrogen co-doped diamond / non-diamond composite thin films using chemical vapor deposition (CVD):

[0007] Hydrogen, methane, trimethyl borate, and nitrogen were used as the preparation gases. Trimethyl borate was carried into the chamber by hydrogen. The hydrogen flow rate was set to 150–200 sccm; the methane flow rate was 15–20 sccm; the hydrogen flow rate carrying trimethyl borate was 2–5 sccm; and the nitrogen flow rate was 0.5–1 sccm. The working pressure of the chamber was 7–8 kPa. A boron-nitrogen co-doped diamond / non-diamond composite film was grown on the substrate.

[0008] 2) The boron-nitrogen co-doped diamond / non-diamond composite film obtained in step 1) is placed in a tube furnace and annealed at 800°C for 15-20 minutes in an air atmosphere to etch away the non-diamond part and form nano-diamond.

[0009] The chemical vapor deposition methods include microwave plasma chemical vapor deposition (MPCVD), hot filament chemical vapor deposition (HFCVD), and hot cathode direct current plasma chemical vapor deposition (DCCVD). In the microwave plasma chemical vapor deposition method, the microwave power is set to 350–400 W.

[0010] It can be a heteroepitaxial growth of polycrystalline thin films on substrates such as silicon and titanium, and the thin films must be nitrogen-doped.

[0011] The nano-grass diamond film prepared by this invention can be used as an electrochemical electrode for a high-sensitivity detector.

[0012] The beneficial effects of this invention are:

[0013] This invention prepares a high-density nano-grass diamond by etching away the non-diamond carbon portion in a nano-grass diamond / non-diamond carbon composite structure through high-temperature annealing in air.

[0014] It is used in the electrochemical electrode of the detector. The high-density nanostructure of this detector greatly increases the surface area of ​​the electrode, providing more reaction sites for the detection of trace molecules, which can significantly improve the performance of heavy metal ion detection. Taking cadmium ions as an example, in the range of 1 to 100 g·L⁻¹, the detection performance is significantly improved. -1 It exhibits good linearity in solutions, achieving a linearity of 0.28 g·L⁻¹. -1 It exhibits a low detection limit and excellent stability and repeatability. This is significant for the application of diamond sensors in a wide range of industrial fields for detecting low concentrations and trace amounts of chemical and biomolecules.

[0015] The preparation method of this invention is simple and easy to prepare on a large scale. Attached Figure Description

[0016] Figure 1 (a) shows the boron-nitrogen co-doped diamond / non-diamond composite film, (b) shows the morphology of nano-grass diamond, and (c) and (d) are high-magnification images of (a) and (b), respectively.

[0017] Figure 2 (a) is from 1 to 100 g·L -1 (a) Differential conventional pulse voltammetry plots of cadmium ion solutions with different concentrations. (b) A plot showing the fitted linear relationship between the oxidation peak current and the cadmium ion concentration.

[0018] Figure 3 Bar chart of selectivity of nanograss diamond electrode. Detailed Implementation

[0019] The present application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present application and are not intended to limit it in any way.

[0020] Example 1: Preparation of boron-nitrogen co-doped diamond / non-diamond composite thin films on silicon wafer substrates

[0021] A 1cm × 1cm silicon wafer was selected as the growth substrate. First, the wafer was cleaned to remove surface contaminants. To improve the nucleation density during growth, the growth surface was ground on sandpaper containing diamond powder for 15 minutes, then ultrasonically treated in alcohol containing diamond powder for 1 hour. Finally, it was ultrasonically cleaned sequentially with acetone, alcohol, and deionized water, dried with nitrogen, and placed in a CVD reaction chamber to deposit a diamond film. During vapor deposition, hydrogen, methane, hydrogen carrying trimethyl borate, and nitrogen were used as reactant gases, with corresponding flow rates of 200 sccm, 20 sccm, 2 sccm, and 1 sccm, respectively. The microwave power was 350W, the chamber pressure was 8 kPa, and the growth time was 6 hours. The composite film deposition thickness was approximately 15 μm.

[0022] Nitrogen is crucial in the preparation of boron-nitrogen co-doped diamond / non-diamond composite films. Nitrogen doping leads to columnar growth of diamond, while the high methane concentration and the addition of nitrogen intensify secondary nucleation of diamond, resulting in very small diamond grains containing a large amount of non-diamond carbon, which is exactly the result we want.

[0023] Example 2: Preparation of nano-grass diamond structure

[0024] The boron-nitrogen co-doped diamond / non-diamond composite film was placed in a tube furnace and annealed in air at 800°C for 15 minutes. It was then quickly removed. The non-diamond carbon was rapidly oxidized and disappeared in the air, leaving the diamond phase. At the same time, due to the addition of nitrogen in Example 1, the diamond nanograss exhibited an upright columnar growth, thus preparing high-density boron-nitrogen co-doped nanograss diamond.

[0025] Example 3: Electrochemical test for detecting cadmium ions

[0026] Cadmium ions were diluted to different concentrations using acetate buffer solution at pH 5.5 for analysis. Under optimal deposition conditions (deposition time 270 s, deposition potential -1.0 V), Figure 2 (a) is from 1 to 100 g·L -1 Differential pulse anodic stripping voltammograms of cadmium ion solutions with different concentrations are shown. Clearly, the oxidation peak current increases with increasing cadmium ion concentration, indicating that the peak current is sensitive to low concentrations of cadmium ions. Figure 2 (b) revealed a fitted linear relationship between the peak oxidation current and the cadmium ion concentration, where the correlation coefficient (R0) was [missing information]. 2 The signal-to-noise ratio (SNR) is 0.998. Based on a three-fold SNR, the calculated detection limit is 0.28 g·L⁻¹. -1 It is lower than the EU recommended standard for cadmium ions (not exceeding 3 g / L in water). -1 The superior detection capability is attributed to the abundance of reaction sites, excellent electrocatalytic activity, and high signal-to-noise ratio in the boron-nitrogen co-doped nanofiber diamond. Furthermore, compared to other related diamond materials such as boron-doped diamond, nitrogen-doped diamond, metal particle-modified diamond, and graphite-modified diamond electrodes, its detection limits are 1.6, 1.1, 0.51, and 0.47 g·L⁻¹, respectively. -1 The detection limit of the nano-grass boron nitrogen co-doped diamond electrode is smaller than that of the electrode materials reported above. Therefore, nano-grass boron nitrogen co-doped diamond is a promising electrode material for constructing high-performance electrochemical sensors.

[0027] Example 4: Used for detecting cadmium ions (Cd) 2+ Selectivity testing of nanograss diamond electrodes

[0028] Figure 3 This demonstrates that nano-boron-nitrogen co-doped diamond electrodes will include Pb 2+ Zn 2+ Ca 2+ Cu 2+ Mg 2+ and Na + Several interfering ions, including those mentioned above, were added to a solution containing ten times the Cd content. 2+ Cd concentration 2+ In standard solutions. For example... Figure 3 As shown, when Pb is added 2 + Zn 2+ Ca 2+ Cu 2+ Mg 2+ and Na + When ions are present, Cd 2+ The signal changed slightly. This indicates that the nano-boron-nitrogen co-doped diamond electrode has good anti-interference performance against the above six ions.

Claims

1. A method for preparing a nano-grass diamond film, characterized in that, The specific steps of this method are as follows: 1) Preparation of boron-nitrogen co-doped diamond / non-diamond composite thin films using chemical vapor deposition: Hydrogen, methane, trimethyl borate, and nitrogen were used as the preparation gases. Trimethyl borate was carried into the chamber by hydrogen. The hydrogen flow rate was set to 150–200 sccm; the methane flow rate was 15–20 sccm; the hydrogen flow rate carrying trimethyl borate was 2–5 sccm; and the nitrogen flow rate was 0.5–1 sccm. The working pressure of the chamber was 7–8 kPa. A boron-nitrogen co-doped diamond / non-diamond composite film was grown on the substrate. 2) The boron-nitrogen co-doped diamond / non-diamond composite film obtained in step 1) is placed in a tube furnace and annealed at 800°C for 15-20 minutes in an air atmosphere to etch away the non-diamond part and form nano-diamond.

2. The method for preparing the nano-grass diamond film according to claim 1, characterized in that, The chemical vapor deposition methods include: microwave plasma chemical vapor deposition, hot filament chemical vapor deposition, and hot cathode direct current plasma chemical vapor deposition.

3. The method for preparing the nano-grass diamond film according to claim 2, characterized in that, In microwave plasma chemical vapor deposition, the microwave power is set to 350–400 W.

4. The method for preparing the nano-grass diamond film according to claim 1, characterized in that, The substrate is made of silicon or titanium.

5. The method for preparing the nano-grass diamond film according to claim 1, characterized in that, The gas flow rates of hydrogen, methane, hydrogen carrying trimethyl borate, and nitrogen were 200 sccm, 20 sccm, 2 sccm, and 1 sccm, respectively.

6. A nano-grass diamond film prepared by the method according to any one of claims 1 to 5.

7. The use of the nano-grass diamond film as described in claim 6 as an electrochemical electrode for a high-sensitivity detector.

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