A three-dimensional doped diamond, its preparation method and application

Abstract

The present invention discloses a three-dimensional doped diamond, a preparation method thereof and an application thereof. The three-dimensional doped diamond comprises a three-dimensional interconnected carbon material with pits on the surface and doped diamond particles disposed in the pits. The three-dimensional interconnected carbon material is formed by three-dimensionally interconnecting a plurality of carbon tubes with hollow cores. The three-dimensional doped diamond provided by the present invention has a high specific surface area, is a fully carbon material, and has a strong interfacial bonding force. In addition, the three-dimensional interpenetrating carbon material is sp<supgt;2< / supgt> carbon, which is beneficial to rapid electron transmission. The diamond is sp<supgt;3< / supgt> carbon, and the doped diamond has good conductivity, so that the fully carbon three-dimensional doped diamond has excellent electron transmission performance. When applied to electrochemical detection, it has excellent linear response and high detection sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond electrode preparation, and particularly relates to a three-dimensional doped diamond, a preparation method thereof, and an application thereof. Background Art

[0002] Pure diamond itself is an excellent insulator. After doping, the resistance of diamond can be greatly reduced, showing electrical conductivity. Boron-doped diamond (BDD) has advantages such as an extremely wide electrochemical window, higher electrochemical stability, and low adsorption characteristics, and is an ideal electrochemical sensing material. However, from the bulk solution to the electrode surface is linear diffusion, so the electrochemical sensing of labeled biomolecules on traditional macroscopic diamond electrodes is poor, resulting in slow kinetics and difficult to meet the actual requirements of high-precision and high-sensitivity micro-biosensing electrode materials.

[0003] Compared with traditional macroscopic electrodes, microelectrodes are small in size, and hemispherical diffusion occurs on the electrode surface, reducing the solution resistance effect and low capacitive current, having a higher signal-to-noise ratio, enhanced mass transfer, and a huge electroactive surface.

[0004] However, diamond is a superhard material and is very difficult to process. It is difficult to fabricate doped diamond electrodes into precisely controlled microarray electrodes, and single electrodes have problems such as low response current. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the first object of the present invention is to provide a three-dimensional doped diamond.

[0006] The second object of the present invention is to provide a preparation method of the three-dimensional doped diamond.

[0007] The third object of the present invention is to provide an application of the three-dimensional doped diamond.

[0008] To achieve the above objects, the present invention adopts the following technical solutions:

[0009] The present invention provides a three-dimensional doped diamond, which comprises a three-dimensional interconnected carbon material with pits on the surface and doped diamond particles arranged in the pits, and the three-dimensional interconnected carbon material is three-dimensionally interconnected by a number of carbon tubes with hollow cores.

[0010] The three-dimensional doped diamond provided by the present invention has a high specific surface area, is a fully carbon material, and has a strong interfacial binding force. In addition, the three-dimensional interpenetrating carbon material is sp 2 carbon, which is beneficial to the rapid transmission of electrons. Diamond is sp 3 carbon, and the doped diamond has good electrical conductivity, making the fully carbon three-dimensional doped diamond have excellent electron transport performance.

[0011] In a preferred embodiment, the wall of the carbon tube consists of an outer carbon layer and an inner tube wall, wherein the outer carbon layer is incompletely crystallized carbon and the inner tube wall is crystallized carbon.

[0012] In a further preferred embodiment, in the carbon tube, the diameter of the hollow core is 5 - 200 nm, and the thickness of the tube wall is 20 nm - 500 μm, wherein the thickness of the outer carbon layer > the thickness of the inner tube wall.

[0013] In a preferred embodiment, in the carbon tube, the hollow core is bamboo - joint - shaped or completely hollow.

[0014] In a preferred embodiment, any one carbon tube contains at least one pit.

[0015] In the present invention, there is no limitation on the shape of the pit, such as including but not limited to circular, rectangular, annular, and the pit is at least one of a closed state and a non - closed state.

[0016] In a preferred embodiment, the doping element in the doped diamond particles is selected from at least one of boron, nitrogen, and phosphorus, preferably boron.

[0017] In a preferred embodiment, the crystal structure of the doped diamond particles is single - crystal or poly - crystal.

[0018] In a preferred embodiment, the particle size of the doped diamond particles is 50 nm - 500 μm.

[0019] In a preferred embodiment, the doping element concentration of the doped diamond particles > 10 18 cm -3 . The inventors found that when the doping element concentration of the doped diamond particles > 10 18 cm -3 , the conductivity of diamond is greatly improved.

[0020] In a preferred embodiment, the doping method of the doped diamond particles is selected from one or a combination of more of constant doping, multi - layer variable doping, and gradient doping.

[0021] In a preferred embodiment, the surface of the doped diamond particles contains a modification layer, and the material of the modification layer is selected from at least one of carbon materials, metals, and polymers.

[0022] In a further preferred embodiment, the carbon material is selected from at least one of microcrystalline graphite, carbon nanotubes, carbon nanofibers, and graphene.

[0023] In a further preferred embodiment, the metal is selected from at least one of iron, copper, platinum, silver, and gold.

[0024] In a further preferred embodiment, the polymer is selected from at least one of poly(N - (2 - hydroxypropyl) methacrylamide) and terminal - alkyne poly(propargyl methacrylamide).

[0025] The present invention provides a method for preparing three-dimensional doped diamond, comprising the following steps:

[0026] Step 1:

[0027] Scheme 1

[0028] Place the catalyst on the surface of the substrate material, then place the substrate material in a chemical vapor deposition furnace, and perform chemical vapor deposition under the assistance of a magnetoelectric coupling field to obtain a three-dimensional interconnected carbon material with pits. During the chemical vapor deposition process, introduce a carbon-containing gas and hydrogen, control the mass flow ratio of the carbon-containing gas to hydrogen to be 10-40:60-90, and control the temperature of the chemical vapor deposition to be 500-700 °C.

[0029] Or

[0030] Scheme 2

[0031] Place the catalyst on the surface of the substrate material, then place the substrate material in a chemical vapor deposition furnace, introduce a carbon-containing gas and hydrogen, control the mass flow ratio of the carbon-containing gas to hydrogen to be 10-40:60-90, perform chemical vapor deposition at 500-700 °C to obtain a three-dimensional interconnected carbon material deposited on the substrate material, and then set pits on the surface of the three-dimensional interconnected carbon material to obtain a three-dimensional interconnected carbon material with pits.

[0032] Step 2

[0033] Directly grow doped diamond particles on the surface of the three-dimensional interconnected carbon material with pits obtained in Step 1 to obtain three-dimensional doped diamond.

[0034] In the preparation method of the present invention, a three-dimensional interconnected carbon material is first obtained through a chemical vapor deposition process. The inventor found that to obtain a three-dimensional interconnected carbon material, it is crucial to use a high-concentration carbon source gas within the scope of the present invention. Because during the carbon deposition process, a part of the catalyst particles are first refined to promote the carbon deposition to grow into tubes, and a high-concentration carbon atmosphere will rapidly grow a thicker carbon layer on the surface of the tubes. Another part of the catalyst particles are gradually refined and grow out of the carbon layer on the tube surface to form tubes, and then cross-link and grow to form an interconnected structure. After setting pits on the surface of the three-dimensional interconnected carbon material, during the chemical vapor deposition process, due to the lack of continuous nucleation sites in the pits, island-shaped doped diamond particles grow at the positions of the pits.

[0035] Regarding the setting of the pits, the inventor unexpectedly found that by performing chemical vapor deposition under the assistance of a magnetoelectric coupling field, a three-dimensional interconnected carbon material with pits can be directly obtained. Of course, it is also possible to first directly prepare a three-dimensional interconnected carbon material by chemical vapor deposition, and then set pits on the surface of the three-dimensional interconnected carbon material to obtain a three-dimensional interconnected carbon material with pits.

[0036] In a preferred embodiment, the base materials in the first and second embodiments are each selected from one of silicon and germanium semiconductors, polyimide, polydimethylsiloxane, and polyethylene terephthalate.

[0037] In a preferred embodiment, the catalysts in the first and second embodiments are each selected from at least one of Ni source, Fe source, Co source, W source, and Mo source.

[0038] More preferably, the Ni source is selected from pure Ni or Ni-containing compounds, the Fe source is selected from pure Fe or Fe-containing compounds, the Co source is selected from pure Co or Co-containing compounds, the W source is selected from pure W or W-containing compounds, and the Mo source is selected from pure Mo or Mo-containing compounds.

[0039] In the actual operation process, the catalyst powder is deposited on the surface of the base material by ultrasonic dispersion method or a film is coated on the surface of the substrate material by magnetron sputtering method.

[0040] In a preferred embodiment, the carbon-containing gases in the first and second embodiments are both methane.

[0041] In a preferred embodiment, the pressures of chemical vapor deposition in the first and second embodiments are both 2 - 7 kPa, and the times of chemical vapor deposition are both 0.5 - 6 h.

[0042] In a preferred embodiment, during the chemical vapor deposition process of the first and second embodiments, a carbon-containing gas and hydrogen are introduced, and the mass flow ratio of the carbon-containing gas to hydrogen is controlled to be 15 - 40:60 - 85.

[0043] In a preferred embodiment, in the first embodiment, the current of the magnetoelectric coupling field is 5 - 80 mA, and the magnetic field intensity is 20 - 10000 Gauss.

[0044] In a preferred embodiment, the method for setting pits on the surface of the three-dimensional interconnected carbon material is selected from at least one of ultrasonic oscillation method and plasma etching.

[0045] The inventors found that when pits are obtained by ultrasonic oscillation, they are hollow pits formed after the carbon nanotubes are damaged, with one pit per carbon nanotube; while when surface pits are obtained by the plasma method, they are nano-walls formed by plasma etching, and the pits are formed between the nano-walls, with multiple pits formed on the surface of each carbon nanotube.

[0046] Further preferably, the specific process of the plasma etching is: placing the base material containing the three-dimensional interconnected carbon material in a magneto-electric coupling field-assisted hot wire chemical vapor deposition device, introducing H2, controlling the hot wire distance to be 6-10 mm, the hot wire temperature to be 1800-2200°C, the H2 etching temperature to be 600-800°C, the H2 flow rate to be 20-100 sccm, the pressure to be 2-5 kPa, the magneto-electric coupling field current to be 10-40 mA, the magnetic field strength to be 80 Guass, and the time to be 10 min to 6 h.

[0047] In a preferred embodiment, the process parameters for directly vapor-depositing boron-doped diamond particles on the surface of the three-dimensional interconnected carbon material containing pits in step 2 are as follows: a growth temperature of 700-850°C, a mass flow ratio of the introduced gas of hydrogen:methane:doping gas source = 99-95:0.5-5:0.1-0.6, a growth pressure of 2-7 kPa, and a time of 0.5-6 h, wherein the doping gas source is selected from at least one of ammonia, phosphine, and borane.

[0048] The present invention also provides an application of the three-dimensional doped diamond, wherein the three-dimensional doped diamond is used for electrochemical detection.

[0049] Beneficial Effects

[0050] (1) The present invention provides a method for preparing three-dimensional doped diamond, which increases the attachment growth sites of boron-doped diamond through three-dimensional interpenetrating carbon materials and achieves a high specific surface area.

[0051] (2) The present invention provides a method for preparing three-dimensional doped diamond, which is the first to use the CVD method to prepare three-dimensional interpenetrating carbon materials with surface pits in one step. Compared with the template method and gel method that require two steps, the preparation steps of the present invention are simpler.

[0052] (3) The three-dimensional interpenetrating carbon material of the present invention has a unique structure, consisting of a hollow core and a tube wall, wherein the tube wall consists of an outer carbon layer with a certain thickness and an inner tube wall. By adjusting the catalyst particle size, carbon material deposition parameters, etc., the core size and structure of the three-dimensional interpenetrating carbon material can be effectively controlled. Surface pits for anchoring boron-doped diamond particles or microneedles can be obtained through ultrasonic oscillation or plasma etching. The method is simple, does not require additional production equipment, and is easy to scale up for production.

[0053] (4) The three-dimensional doped diamond provided by the present invention is a full carbon material with strong interface bonding strength. In addition, the three-dimensional interpenetrating carbon structure is sp 2 Carbon is conducive to rapid electron transmission, diamond is sp 3 Carbon, boron doping concentration> 10 18 cm -3 The conductivity of diamond is greatly improved, making the all-carbon three-dimensional doped diamond have excellent electron transport performance.

[0054] (5) The doped diamond particles in the present invention adopt chemical vapor deposition during the growth process. Taking boron-doped diamond thin film as an example, polycrystalline diamond is prepared by chemical vapor deposition by introducing hydrocarbons such as methane (CH4), acetylene (C2H2), hydrogen (H2), and borane (B2H6) into the reaction chamber. The gas concentration is adjustable and the ratio is uniform. Therefore, the boron-doped diamond thin film prepared by chemical vapor deposition has a high boron doping uniformity, and it is easy to prepare a highly doped thin film. By regulating the pretreatment method, deposition parameters, etc., the present invention can effectively control the crystal structure, size, thickness, and doping amount of the diamond particles, and finally make the performance of the obtained doped diamond particle electrode the most excellent.

[0055] (6) The three-dimensional doped diamond provided by the present invention has good linear response and high detection sensitivity. Description of the Drawings

[0056] Figure 1 Microscopic morphology diagram of the three-dimensional interconnected carbon material with pits on the surface obtained by the one-step method in Example 1.

[0057] Figure 2 Microscopic surface morphology diagram of the three-dimensional doped diamond shown in Example 1.

[0058] Figure 3 Microscopic surface morphology diagram of the pit surface obtained by ultrasonic oscillation of the three-dimensional interconnected carbon material with an average outer diameter of 0.5 μm in Example 2.

[0059] Figure 4 、The sensing performance test diagram of the three-dimensional doped diamond prepared in Example 2 for Pb 2+

[0060] Figure 5 The planar thin film structure shown in Comparative Example 1.

[0061] Figure 6 The structure obtained in Comparative Example 2. Detailed Description of the Invention

[0062] Example 1:

[0063] Preparation of three-dimensional doped diamond:

[0064] (1) Immerse the Si substrate in a mixed solution of NiFe2O4 powder with an average particle size of 6·μm and acetone, ultrasonically oscillate for 30 min, then immerse it in pure water and ultrasonically oscillate for 15 min, and clean and dry.

[0065] (2) A three-dimensional carbon structure with pits is prepared in one step by using a magnetoelectric coupling field-assisted hot-wire chemical vapor deposition equipment. The deposition process parameters are as follows: the distance between the hot wire is 7 mm, the growth temperature is 600 - 650 °C, the hot wire temperature is 2000 °C, the mass flow ratio of the gases is hydrogen:methane = 20:5, the deposition pressure is 2 kPa, the deposition time is 2 h, the current of the magnetoelectric coupling field is 10 mA, and the magnetic field strength is 80 Gauss. A three-dimensional interconnected carbon material with pits on the surface is grown in one step, as shown in Figure 1 .

[0066] (3) Subsequently, the magnetoelectric coupling field is removed, the gas flow is adjusted, 3 sccm of CH4 and 0.1 sccm of B2H6 are introduced, the growth temperature is adjusted to 800 - 850 °C, and boron-doped diamond particles are directly deposited on the surface of the three-dimensional carbon material with pits. The deposition time is 20 min, as shown in Figure 2 . That is, three-dimensional doped diamond is obtained.

[0067] The three-dimensional doped diamond prepared in Example 1 is used as a detection platform for trace Pb in simulated human lymph fluid, and has a good linear response in the concentration range of 0.01 - 4.5 μM. The detection sensitivity is as high as 881 μA·μM 2+ , and its lowest detection limit reaches 0.015 nM. -1

[0068] Example 2:

[0069] Preparation of three-dimensional doped diamond:

[0070] (1) The Si substrate is immersed in an acetone solution and ultrasonically vibrated for 30 min, and then immersed in pure water and ultrasonically vibrated for 15 min, cleaned and dried. Then, an Ni film is deposited on the surface of the Si substrate by magnetron sputtering. The process parameters are as follows: an Ni target with a purity ≥ 99.99% is used, the distance between the substrate and the target is 10 - 15 cm, an argon atmosphere is adopted, the deposition pressure is 0.35 Pa, the sputtering power is 150 W, and the deposition time is 1 min.

[0071] (2) A three-dimensional carbon structure is prepared by using a hot-wire chemical vapor deposition equipment. The process parameters are as follows: the distance between the hot wire is 7 mm, the growth temperature is 600 - 650 °C, the hot wire temperature is 2000 °C, hydrogen:methane = 20:5, the pressure is 3 kPa, and the time is 3 h. A three-dimensional interconnected carbon structure is obtained.

[0072] (3) The sample is placed in a beaker of pure water and ultrasonically vibrated in an ultrasonic cleaner for 10 min to obtain pits at the ends of the three-dimensional carbon structure, as shown in Figure 3 .

[0073] (4) Subsequently, adjust the gas flow rate, introduce 1 sccm of CH4 and 0.1 sccm of B2H6, adjust the growth temperature to 800 - 850 °C, and directly deposit boron-doped diamond particles on the surface of the three-dimensional carbon structure pits for 30 minutes. The three-dimensional doped diamond is thus obtained.

[0074] The three-dimensional doped diamond prepared in Example 2 was used as a detection platform for trace Pb in simulated human lymph fluid 2+ and had a good linear response in the concentration range of 0.005 - 5 μM, with a detection sensitivity as high as 1000 μA·μM -1 , and its lowest detection limit reached 0.01 nM, as Figure 4 shown.

[0075] Comparative Example 1

[0076] Other conditions were the same as in Example 1, except that the pretreatment method was ultrasonic oscillation in a nano-diamond suspension instead of using a mixed solution of NiFe2O4 powder and acetone. A three-dimensional carbon structure could not be prepared, but a planar thin-film structure was obtained, as Figure 5 shown.

[0077] Comparative Example 2

[0078] Other conditions were the same as in Example 2, except that the concentration of the carbon-containing gas was adjusted to hydrogen:methane = 30:1.5. The surface showed a diamond morphology, but a three-dimensional carbon structure could not be prepared, and the pits generated by etching could not be obtained, as Figure 6 shown.

[0079] Using the doped diamond prepared in the above example as the working electrode, trace Pb in simulated human lymph fluid 2+ concentration sensing detection was carried out. The specific test method was as follows:

[0080] 1. Preparation of simulated human lymph fluid:

[0081] Weigh 150 mM KCl, 40 mM NaCl, and 0.02 mM CaCl2 and dissolve them together in ionized water.

[0082] 2. Electrochemical performance test:

[0083] An electrochemical test was carried out using a one-compartment three-electrode device with the prepared three-dimensional doped diamond as the working electrode, platinum as the counter electrode, and Ag / AgCl electrode as the reference electrode. The electrolyte was simulated human lymph fluid, and the detection object was Pb in simulated human lymph fluid 2+ , and the detection method was differential pulse anodic stripping voltammetry (DPASV).

Claims

1. A method for preparing three-dimensional doped diamond, characterized in that: It includes the following steps: Step 1: Scheme 1 Set the catalyst on the surface of the substrate material, then place the substrate material in a chemical vapor deposition furnace, and carry out chemical vapor deposition with the assistance of a magnetoelectric coupling field to obtain a three-dimensional interconnected carbon material with pits. During the chemical vapor deposition process, methane and hydrogen are introduced, the mass flow ratio of methane to hydrogen is controlled to be 10-40:60-90, and the temperature of the chemical vapor deposition is controlled to be 500-700 °C. Or Scheme 2 Set the catalyst on the surface of the substrate material, then place the substrate material in a chemical vapor deposition furnace, introduce methane and hydrogen, control the mass flow ratio of methane to hydrogen to be 10-40:60-90, carry out chemical vapor deposition at 500-700 °C to obtain a three-dimensional interconnected carbon material deposited on the substrate material, and then set pits on the surface of the three-dimensional interconnected carbon material to obtain a three-dimensional interconnected carbon material with pits. The method of setting pits on the surface of the three-dimensional interconnected carbon material is selected from at least one of ultrasonic oscillation method and plasma etching; Step 2 Directly grow doped diamond particles on the surface of the three-dimensional interconnected carbon material with pits obtained in Step 1 to obtain three-dimensional doped diamond; The three-dimensional doped diamond includes a three-dimensional interconnected carbon material with pits on the surface and doped diamond particles arranged in the pits. The three-dimensional interconnected carbon material is three-dimensionally interconnected by a plurality of carbon tubes with hollow cores.

2. The preparation method of a three-dimensional doped diamond according to claim 1, wherein: The substrate materials in Scheme 1 and Scheme 2 are each selected from one of silicon, germanium semiconductors, polyimide, polydimethylsiloxane, and polyethylene terephthalate; The catalysts in Scheme 1 and Scheme 2 are each selected from at least one of Ni source, Fe source, Co source, W source, and Mo source; The pressures during chemical vapor deposition in Scheme 1 and Scheme 2 are both 2-7 kPa, and the chemical vapor deposition times are both 0.5-6 h.

3. The preparation method of a three-dimensional doped diamond according to claim 1, wherein: In Scheme 1, the current of the magnetoelectric coupling field is 5-80 mA, and the magnetic field strength is 40-1000 Gauss.

4. The preparation method of a three-dimensional doped diamond according to claim 1, wherein: The specific process of the plasma etching is as follows: Place the substrate material with the three-dimensional interconnected carbon material in a magnetoelectric coupling field-assisted hot wire chemical vapor deposition device, introduce H2, control the hot wire distance to be 6-10 mm, the hot wire temperature to be 1800-2200 °C, the H2 etching temperature to be 600-800 °C, the H2 flow rate to be 20-100 sccm, the pressure to be 2-5 kPa, the current of the magnetoelectric coupling field to be 10-40 mA, the magnetic field strength to be 80 Gauss, and the time to be 10 min-6 h.

5. The preparation method of a three-dimensional doped diamond according to claim 1, characterized in that: In Step 2, the process parameters for directly growing doped diamond particles on the surface of the three-dimensional interconnected carbon material with pits are: the growth temperature is 700-850 °C, the mass flow ratio of the introduced gases is hydrogen:methane:doping gas source = 99-95:0.5-5:0.1-0.6, the growth pressure is 2-7 kPa, the time is 0.5-6 h, and the doping gas source is selected from at least one of ammonia, phosphine, and borane.

6. According to the method for preparing a three-dimensional doped diamond according to claim 1, characterized in that: The tube wall of the carbon tube is composed of an outer carbon layer and an inner tube wall, wherein the outer carbon layer is incompletely crystallized carbon, and the inner tube wall is crystallized carbon; In the carbon tube, the diameter of the hollow core is 5 to 200 nm, and the thickness of the tube wall is 20 nm to 500 μm, wherein the thickness of the outer carbon layer > the thickness of the inner tube wall; In the carbon tube, the hollow core is bamboo-jointed or completely hollow; Any one carbon tube contains at least one pit.

7. A method for preparing a three-dimensional doped diamond according to claim 1, wherein: The doping element in the doped diamond particles is selected from at least one of boron, nitrogen, and phosphorus; The crystal structure of the doped diamond particles is single crystal or polycrystal; The particle size of the doped diamond particles is 50 nm to 500 μm; The doping element concentration of the doped diamond particles > 10 18 cm -3 .

8. A method for preparing a three-dimensional doped diamond according to claim 1, wherein: The surface of the doped diamond particles contains a modification layer, and the material of the modification layer is selected from at least one of carbon materials, metals, and polymers; the carbon materials are selected from at least one of microcrystalline graphite, carbon nanotubes, carbon nanofibers, and graphene; the metals are selected from at least one of iron, copper, platinum, silver, and gold; the polymers are selected from at least one of poly N-(2-hydroxypropyl) methacrylamide and terminal alkynyl polypropargyl methacrylamide.

9. Use of a three-dimensional doped diamond prepared by the preparation method according to any one of claims 1-8, characterized in that: The three-dimensional doped diamond is used for electrochemical detection.

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