A method for preparing narrow diameter distribution semiconductive single-walled carbon nanotubes and applications thereof

Abstract

The application discloses a method for preparing semiconductor single-wall carbon nanotubes with narrow diameter distribution and application, and steps of the method are as follows: first, a non-metal catalyst foam skeleton is prepared; the non-metal catalyst foam skeleton is placed into a conveyor; a reaction chamber and a collection chamber are vacuumized to remove air; inert gas is introduced to make the reaction chamber and the collection chamber reach normal pressure; the reaction chamber is heated to a specified temperature range; a preheater is started to preheat carbon source mixed gas and then the carbon source mixed gas is sent into the reaction chamber; the non-metal catalyst foam skeleton is sent into the reaction chamber through the conveyor; the non-metal catalyst foam skeleton and the carbon source mixed gas are catalytically cracked to generate SWCNT products without metal catalyst; after collection, the semiconductor high-purity SWCNT with a diameter of 1.3-1.8 nm, a G / D ratio of more than 200 and a diameter distribution ratio of more than 99% and containing only carbon elements is obtained. The obtained product can be used to manufacture SWCNT-based flexible electronic devices and logic circuits.

Description

Technical Field

[0001] This invention relates to the preparation of nanomaterials, and more particularly to a method for preparing narrow-diameter-distributed semiconductor single-walled carbon nanotubes and their applications. Background Technology

[0002] Currently, single-walled carbon nanotubes (SWCNTs) have attracted much attention due to their outstanding performance, with a theoretical carrier mobility exceeding 2000 cm⁻¹. 2 Its spectral density (VS) is more than 10 times that of silicon. Therefore, it has attracted considerable attention from scientists both domestically and internationally in flexible electronic devices and field-effect transistors. The preparation of SWCNTs will determine the future; however, experimentally synthesized SWCNTs often fall short of expectations. Because the crystallinity of single-walled carbon nanotubes is highly correlated with their electrical, thermal, and mechanical properties, how to prepare high-purity, highly crystalline single-walled carbon nanotubes is of great significance for the large-scale preparation of single-walled carbon nanotubes and their killer applications, especially in the field of optoelectronic information.

[0003] To obtain highly crystalline single-walled carbon nanotubes (SWCNTs), high temperatures are typically used to overcome the activation energy required for defect healing during SWCNT growth, thus producing SWCNTs with higher crystallinity. As growth temperatures increase, selecting catalyst nanoparticles with high-temperature stability is essential for synthesizing highly crystalline SWCNTs. However, traditional metal catalysts such as Fe, Ni, Co, and related alloys, due to their moderate melting points, inevitably aggregate and deactivate, limiting the quality and yield of SWCNTs at high temperatures. Furthermore, while some high-melting-point metals, such as W, Mo, Re, and TiC, can be used as catalysts, metal nanoparticles are considered impurities in some applications and must be removed through post-processing. High-melting-point metal impurities are difficult to remove easily, and purification processes often introduce additional defects that affect their physical properties. Simultaneously, the preparation processes for high-melting-point catalysts are generally extremely complex, requiring sophisticated equipment and exhibiting low reproducibility (J. Phys. Chem. Lett. 2010, 1, 918–922). These molten nano-metal catalysts are prone to deformation during the high-temperature synthesis of carbon nanotubes, and cannot form regular five- or six-membered ring structures. This is considered to be one of the main sources of defects in carbon nanotubes.

[0004] Existing technologies include chemical vapor deposition (CVD) to synthesize carbon nanotubes without metal catalysts. This method involves depositing carbon source gas onto a substrate such as corundum, quartz, silicon, or alumina in a CVD furnace to grow carbon nanotubes. While this method allows for the growth of carbon nanotubes on non-metallic substrates, it is difficult to continuously supply catalysts, limiting its large-scale growth. Results show that the products prepared by this method are gaseous carbon fibers and multi-walled carbon nanotubes with a diameter of 50 nm, rather than single-walled carbon nanotubes. Furthermore, these products have numerous defects and low yields, thus limiting their application scope.

[0005] Another method uses non-metallic silica as a catalyst to preferentially grow metallic single-walled carbon nanotubes (SWCNTs). Although the sample does not contain metallic impurities, the non-metallic element silicon remains in the SWCNTs, reducing conductivity and making them difficult to remove. Removing them with strong acids will damage the crystallinity of the SWCNTs themselves, introducing new defects and limiting their application range. Another method uses carbon-coated boron-doped silica nanomaterials as a catalyst to prepare carbon nanotubes in concentrated sulfuric acid and hydrochloric acid environments. Although it also does not contain metallic elements, the prepared products contain difficult-to-remove silicon and boron non-metallic elements, and the tube diameter distribution ranges from 15 to 20 nm. Because the reaction requires strong acid, there are many defects, which can also be seen from TEM images, showing localized bending and twisting at the nanoscale, indicating numerous defects.

[0006] To overcome the shortcomings of existing low-melting-point and high-melting-point metal catalysts, one possible solution is to prepare non-metallic nanocatalysts by growing highly crystalline SWCNTs. However, how to deliver nanoscale non-metallic nanoparticles into the reaction chamber is a problem. One technical problem solved by this invention is to overcome the problem that existing catalysts are mostly metal nanoparticles with low melting points, and their structures are unstable at high temperatures.

[0007] Meanwhile, it overcomes the problems that ordinary pretreatment methods can only obtain non-metallic catalysts with a wide particle size distribution and the particle size is difficult to control; another technical problem solved by this invention is to overcome the problem that existing semiconducting single-walled carbon nanotubes are difficult to selectively prepare, and subsequent processing can usually only etch them to obtain semiconducting single-walled carbon nanotubes. At the same time, not introducing new metal elements is an urgent problem to be solved. Summary of the Invention

[0008] This invention discloses a method for preparing diameter-distributed semiconducting single-walled carbon nanotubes and their applications, in order to solve any of the above-mentioned and other potential problems in the prior art.

[0009] To address the problems existing in the prior art, the technical solution adopted in this invention is: a method for preparing narrow-diameter distributed semiconducting single-walled carbon nanotubes, which specifically includes the following steps:

[0010] S1) Prepare a non-metallic catalyst foam framework for later use;

[0011] S2) The non-metallic catalyst foam skeleton obtained in S1) is placed into the conveyor, and the reaction chamber and collection chamber are evacuated to remove the air atmosphere. Then, inert gas is introduced to bring the reaction chamber and collection chamber to atmospheric pressure.

[0012] S3) Heat the reaction chamber to the specified temperature range and start the preheater to preheat the carbon source mixture;

[0013] S4) A certain amount of non-metallic catalyst foam skeleton is sent into the reaction chamber through a conveyor, and at the same time, the preheated carbon source mixed gas is sent into the reaction chamber. The non-metallic catalyst foam skeleton is catalytically decomposed with the carbon source mixed gas to generate metal-free single-walled carbon nanotube products. The products fall into the collection chamber with the gas flow and are collected, thus obtaining narrow diameter distributed semiconductor single-walled carbon nanotubes.

[0014] Furthermore, the specific steps of S1) are as follows:

[0015] S1.1) First, non-metallic catalyst nanoparticles are dispersed in an organic solvent in a certain proportion to form a non-metallic catalyst nanoparticle solution. Then, the non-metallic catalyst nanoparticle diamond solution and liquid hydrocarbons are mixed in a certain proportion to form a non-metallic catalyst pre-dispersion.

[0016] S1.2) Place the non-metallic catalyst pre-dispersion solution into the reaction vessel, ensuring that the solution is spread evenly in the reaction vessel with a height not exceeding 15 mm; process it using a three-step gradient heating method to form a uniformly loaded non-metallic catalyst foam skeleton;

[0017] S1.3) Finally, the non-metallic catalyst foam skeleton is crushed, ground, and sieved to obtain particles of 20-800 mesh, which is the prepared non-metallic catalyst foam skeleton.

[0018] Furthermore, in S1.1), the proportion of non-metallic catalyst nanoparticles to organic solvent is 0.3-6 wt%, and the proportion of liquid hydrocarbons to non-metallic catalyst predispersant is 3-35 wt%.

[0019] Furthermore, the organic solvent is styrene, perchloroethylene, trichloroethylene and ethylene glycol ether, acetone, anhydrous ethanol or toluene;

[0020] The non-metallic catalyst nanoparticles are diamond nanoparticles with a particle size of 3-35 nm.

[0021] The hydrocarbon is any one or a mixture of sucrose, glucose, maltose, lactose and complex sugars, water-soluble starch and water-soluble chitosan.

[0022] Furthermore, the three-step gradient heating method in S1.2) specifically comprises: First, heating to 60-95℃ and performing low-temperature heat treatment for 1-6 hours;

[0023] The second step is to continue heating to 100-180℃ and perform medium-temperature treatment for 1-20 hours.

[0024] The third step is to continue heating to 300-700℃ and perform high-temperature heat treatment for 0.5-10 hours;

[0025] The reaction vessel is made of high-temperature resistant non-metallic materials such as quartz, graphite, or corundum.

[0026] Furthermore, the reaction chamber in S3) is heated to 900-3000°C by fixed-bed CVD, fluidized-bed CVD, DC arc discharge, AC arc discharge, plasma torch, radio frequency induction plasma, or microwave discharge plasma.

[0027] Furthermore, the powder feeding rate of the non-metallic catalyst foam skeleton in S4) is 0.1-30 g / min;

[0028] The preheating temperature of the carbon source mixed gas is 200-650℃;

[0029] The carbon source mixed gas includes a carbon source gas, a mild etching gas, and a carrier gas;

[0030] The flow rate of the carbon source gas is 0.5-30 L / min;

[0031] The rate of mild etching gas is 0.1-125 L / min;

[0032] The carrier gas flow rate is 5-200 L / min.

[0033] Furthermore, the mild etching gas is one or more of carbon monoxide, carbon dioxide, ammonia, water vapor, and hydrogen gas;

[0034] The carrier gas is at least one of argon, nitrogen, and helium.

[0035] Furthermore, the narrow-diameter-distribution semiconducting single-walled carbon nanotubes prepared by the method have a purity of not less than 99.9% and a G / D greater than 200. The chiral indices (12,7), (14,6), and (14,10) account for 51.60%, 21.77%, and 25.66% of the carbon nanotubes, respectively, which means that more than 99% of the semiconducting single-walled carbon nanotubes have a narrow diameter distribution of 1.3-1.8 nm.

[0036] A diameter-distributed semiconducting single-walled carbon nanotube is prepared by the method described above.

[0037] The single-walled carbon nanotubes prepared by the above method have applications in optoelectronic devices, logic circuits, flexible displays, and quantum light sources.

[0038] The beneficial effects of this invention are as follows: By preparing a non-metallic catalyst as a catalyst for growing single-walled carbon nanotubes, and by controlling the growth conditions, this invention successfully prepared high-quality single-walled carbon nanotubes with a product G / D ratio exceeding 200. The chiral indices (12,7), (14,6), and (14,10) accounted for 51.60%, 21.77%, and 25.66% of the carbon nanotubes, respectively, which is more than 99%. These are semiconducting single-walled carbon nanotubes with a narrow diameter distribution of 1.3-1.8 nm, containing only carbon elements.

[0039] It is difficult to continuously introduce nanodiamond catalysts into the reaction chamber. By uniformly mixing selected 3-15nm diamond particles with liquid hydrocarbons, a uniform non-metallic catalyst foam framework is formed through a three-step slow evaporation and carbonization process: low-temperature evaporation of organic solvent, medium-temperature evaporation of hydrocarbons, and high-temperature carbonization of hydrocarbons. This process forms a uniformly loaded hydrocarbon foam framework, avoiding the formation of agglomerates that inhibit the catalytic activity of diamond nanocatalysts through direct carbonization. It also facilitates the formation of chiral, concentrated, semiconducting single-walled carbon nanotubes, which can improve catalytic efficiency and increase yield.

[0040] This type of supported non-metallic catalyst can be continuously fed into the reaction chamber for catalytic cracking by powder feeding or spraying, which helps to improve the yield. 0.5 to 15 g of high-quality single-walled carbon nanotubes can be obtained per hour, which is conducive to large-scale preparation.

[0041] By introducing an appropriate amount of mild etching gas, the activity and lifetime of the non-metallic catalyst are improved. In the large-scale production process of carbon nanotubes, the etching and protection of carbon nanotubes from damage are balanced, which helps to obtain high-quality single-walled carbon nanotubes with a purity of over 99.9%, containing no other impurities and only carbon. Attached Figure Description

[0042] Figure 1 This is a schematic flowchart of a method for preparing narrow-diameter-distributed semiconductor single-walled carbon nanotubes according to the present invention.

[0043] Figure 2 This is a process flow diagram for preparing the non-metallic catalyst foam skeleton of the present invention.

[0044] Figure 3 This is a schematic diagram illustrating the process of growing single-walled carbon nanotubes using nanodiamond "growth seeds" according to the present invention.

[0045] Figure 4 This is a schematic diagram of the resistivity of the single-walled carbon nanotube powder prepared in Example 1 of the present invention as a function of pressure.

[0046] Figure 5This is a scanning electron microscope (SEM) schematic diagram of the single-walled carbon nanotubes prepared in Example 2 of the present invention.

[0047] Figure 6 This is a schematic diagram of the thermogravimetric characterization of single-walled carbon nanotubes prepared in Example 4 of the present invention.

[0048] Figure 7 This is a schematic diagram of the Raman spectrum of the single-walled carbon nanotubes prepared in Example 3 of the present invention.

[0049] Figure 8 This is a locally magnified schematic diagram of the Raman spectrum RBM peak of the single-walled carbon nanotubes prepared in Example 3 of the present invention.

[0050] Figure 9 This is a transmission electron microscope (TEM) schematic diagram of the single-walled carbon nanotubes prepared in Example 3 of the present invention.

[0051] Figure 10 This is a transmission electron microscope (TEM) schematic diagram of the single-walled carbon nanotubes prepared in Example 3 of the present invention.

[0052] Figure 11 This is a locally magnified schematic diagram of the Raman spectrum RBM peak of the single-walled carbon nanotube prepared in Comparative Example 1 of the present invention.

[0053] Figure 12 This is an atomic force microscope schematic diagram of the thin film deposition of single-walled carbon nanotubes prepared in Example 5 of the present invention. Detailed Implementation

[0054] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0055] like Figure 1 As shown, this invention discloses a method for preparing narrow-diameter-distribution semiconducting single-walled carbon nanotubes using a non-metallic catalyst. The method specifically includes the following steps:

[0056] S1) Preparation of non-metallic catalyst foam framework;

[0057] The specific steps are as follows:

[0058] S1.1) First, non-metallic catalyst nanoparticles of 3-35 nm are dispersed in an organic solvent at a ratio of 0.3-6 wt% of non-metallic catalyst nanoparticles to organic solvent to form a non-metallic catalyst nanoparticle solution. Then, nanodiamond solution and liquid hydrocarbons are mixed at a ratio of 3-35 wt% of liquid hydrocarbons to non-metallic catalyst pre-dispersion to form a non-metallic catalyst pre-dispersion.

[0059] S1.2) Place the non-metallic catalyst pre-dispersion solution into the reaction vessel, ensuring that the solution is spread evenly in the reaction vessel with a height not exceeding 15 mm; process it using a three-step gradient heating method, specifically the first step, heating to 60-95℃ and internally performing low-temperature heat treatment for 1-6 hours;

[0060] The second step is to continue heating to 100-180℃ and treat at a medium temperature for 1-20 hours.

[0061] The third step is to continue heating to 300-700℃ and perform high-temperature heat treatment for 0.5-10 hours to form a uniformly loaded non-metallic catalyst foam skeleton.

[0062] S1.3) Finally, the non-metallic catalyst foam skeleton is crushed, ground, and sieved to obtain particles of 20-800 mesh, which is the non-metallic catalyst foam skeleton. Refer to the preparation process flow diagram. Figure 2 As shown;

[0063] S2) The non-metallic catalyst obtained in S1) is placed into the conveyor, and the reaction chamber and collection chamber are evacuated to remove the air atmosphere, so that the vacuum degree is no more than 10 kPa and is maintained for more than 12 hours. Then, inert gas is introduced to bring the reaction chamber and collection chamber to normal pressure.

[0064] S3) Heat the reaction chamber to 900-3000℃, and start the preheater to preheat the carbon source mixture to 200-650℃;

[0065] S4) The non-metallic catalyst foam framework is fed into the reaction chamber at a powder feeding rate of 0.1-30 g / min. At the same time, a carbon source mixture consisting of carbon source gas, mild etching gas and carrier gas is fed into the reaction chamber at a flow rate of 0.5-30 L / min for carbon source gas, 0.1-125 L / min for mild etching gas and 5-200 L / min for carrier gas. The non-metallic catalyst is catalytically decomposed with the carbon source mixture to generate metal-free single-walled carbon nanotube products, which are collected in the collection chamber by the gas flow.

[0066] Preferably, the organic solvent is one of styrene, perchloroethylene, trichloroethylene and ethylene glycol ether, acetone, anhydrous ethanol or toluene;

[0067] The non-metallic catalyst nanoparticles are diamond nanoparticles.

[0068] The hydrocarbon is any one or a mixture of sucrose, glucose, maltose, lactose and complex sugars, water-soluble starch and water-soluble chitosan.

[0069] The reaction vessel is made of high-temperature resistant non-metallic materials such as quartz, graphite, or corundum.

[0070] Preferably, the heating method in S3) is through fixed bed CVD, fluidized bed CVD, DC arc discharge, AC arc discharge, plasma torch, radio frequency induction plasma, or microwave discharge induction plasma.

[0071] Preferably, the carbon source gas is at least one of natural gas, methane, ethane, propane, butane, pentane, hexane, ethylene, propylene, and aliphatic hydrocarbons;

[0072] The mild etching gas is one or more of carbon monoxide, carbon dioxide, ammonia, water vapor, and hydrogen gas;

[0073] The carrier gas is at least one of argon, nitrogen, and helium.

[0074] The single-walled carbon nanotubes prepared by the method have a purity of not less than 99.9%, as shown in the thermogravimetric characterization results in Table 2, and a G / D ratio exceeding 200. Figure 7 As shown in Table 2, the chiral indices (12,7), (14,6), and (14,10) account for 51.60%, 21.77%, and 25.66% of the carbon nanoparticles, respectively. Refer to the calculations of Raman peak positions and diameters in Table 2. Figure 8 The magnified image of the Raman spectrum shows that more than 99% of the nanotubes are semiconducting single-walled carbon nanotubes with a narrow diameter distribution of 1.3-1.8 nanometers.

[0075] The single-walled carbon nanotubes prepared by the above method have applications in optoelectronic devices, logic circuits, flexible displays, and quantum light sources.

[0076] For the Raman spectroscopy, thermogravimetric characterization, scanning electron microscopy and energy-dispersive X-ray spectroscopy, transmission electron microscopy and ultraviolet-visible-near-infrared absorption spectroscopy characterization methods for high-quality single-walled carbon nanotube samples, please refer to GB / T 32871-2016, GB / T 24490-2009, GB / T 32869-2016, GB / T 30534-2014 and GB / T39114-2020 standards.

[0077] The diameter distribution of single-walled carbon nanotubes in the product obtained by the method of this invention ranges from 1.3 to 1.8 nm. This diameter distribution was obtained by statistically analyzing more than 150 carbon nanotubes using high-resolution transmission electron microscopy images, and this diameter distribution range is basically consistent with the diameter distribution calculated from Raman spectroscopy.

[0078] The relationship between the diameter of single-walled carbon nanotubes and the respiratory mode frequency shift is shown in Equation 1.

[0079] ωRBM=A / d+B Equation 1

[0080] ωRBM is the respiratory mode shift, expressed in centimeters (cm).-1 );

[0081] d is the diameter of a single-walled carbon nanotube, in nanometers (nm).

[0082] A constant, with units of nanometers per centimeter (cm). -1 nm);

[0083] B is a constant, with units of per centimeter (cm). -1 The chiral indices of single-walled carbon nanotubes (SUVs) in different dielectric environments show slight differences in parameters A and B. Although the A and B parameters vary between different samples, the differences in the given SUV diameter are generally within ±0.05 nm. For untreated SUV samples, it is recommended to use A = 234 and B = 10. The chiral index of SUVs is obtained from the Kataura diagram.

[0084] Since its discovery, SWCNTs have attracted widespread attention from researchers due to their unique structure and electronic properties, and are considered a core material for the channel of next-generation electronic devices. After more than two decades of development, SWCNTs have been applied to the fabrication of functional devices such as field-effect transistors, infrared detectors, flexible displays, radio frequency devices, and chemical and biological sensors. The application of carbon nanotubes continues to advance, starting from material preparation, device performance optimization, and device structure design. To achieve large-area, highly uniform, and high-performance device fabrication, the material itself, device design, and processes are all crucial. First, a high-purity, low-defect semiconductor single-walled carbon nanotube solution was obtained, which was further purified to obtain an ultra-high-purity semiconductor single-walled carbon nanotube solution. Based on this, a uniform carbon nanotube thin film was prepared, and the electrical performance of the separated carbon nanotubes was verified by fabricating semiconductor carbon nanotube field-effect transistors. Furthermore, by optimizing the fabrication process of the field-effect transistors and improving the contact between the electrodes and the carbon nanotubes, the performance was significantly improved.

[0085] Explanation of the principle:

[0086] Since the growth of SWCNTs originates from the formation of single-walled carbon nanotubes (SUCs), optimizing the SUC formation conditions is crucial for improving SUC yield and achieving higher nucleation efficiency. Nanodiamonds, due to their non-fusion properties, prevent nanoparticle aggregation or sintering even at high growth temperatures, enabling the formation of regular five- or six-membered ring structures and readily producing highly crystalline SWCNTs, making them a promising "growth seed." Furthermore, SWCNTs grown from nanodiamond nanoparticles exhibit high purity, reducing the need for post-growth purification.

[0087] Since carbon diffusion in diamond is negligible compared to some metals such as Fe, bulk carbon diffusion is unlikely to promote carbon nanotube growth. Therefore, carbon nanotube growth in nanodiamonds must be driven by surface diffusion of carbon, a mechanism known as the gas-solid surface-solid mechanism. The limited catalytic activity and narrow growth window of nanodiamonds result in low CNT growth yields.

[0088] like Figure 3 A schematic diagram illustrating the process of growing single-walled carbon nanotubes (SWCNTs) from diamond "seeds." On these carbon-saturated surfaces, SWCNTs grow on SP... 2 A schematic diagram of surface growth shows a SWCNT "seed" with a graphene bud. During growth, carbon atoms from the decomposition of the carbon source molecule bond together on a suitable growth seed. This growth seed is a nanoparticle that serves as a template, initially forming a hemispherical graphite structure called a carbon cap structure, such as... Figure 3 As shown, the nanoscale curved surface provides a template for the formation of carbon nanotube caps. With the attachment of carbon atoms at the tubular edges and the seed interface, the tubular structure gradually elongates, forming a relatively perfect single-walled carbon nanotube structure composed of five-membered and six-membered rings. This achieves efficient growth of high-quality, structurally controllable single-walled carbon nanotubes. By introducing a mild etchant, highly crystalline, impurity-free SWCNTs were obtained, and the yield was improved. This supported non-metallic catalyst can be continuously fed into the reaction chamber via powder feeding, facilitating continuous preparation and enabling its large-scale production.

[0089] Example 1

[0090] S1) Prepare a non-metallic catalyst foam framework for later use;

[0091] The specific steps for using non-metallic catalysts are as follows:

[0092] S1.1) First, 3-18nm non-metallic catalyst nanoparticles are dispersed in anhydrous ethanol at a ratio of 1.2wt% of non-metallic catalyst nanoparticles to organic solvent to form a non-metallic catalyst nanoparticle solution. Then, the non-metallic catalyst nanoparticle diamond solution, liquid hydrocarbon maltose, water-soluble starch, and water-soluble chitosan are mixed together at a ratio of 7.5wt% of liquid hydrocarbons to non-metallic catalyst pre-dispersion to form a non-metallic catalyst pre-dispersion.

[0093] S1.2) The pre-dispersion solution of the non-metallic catalyst is placed in a quartz reaction vessel, ensuring that the solution level in the vessel does not exceed 15 mm. A uniformly loaded non-metallic catalyst foam skeleton is formed through a three-step gradient heating method. The three-step gradient heating method is as follows:

[0094] The first step is to heat to 65°C and perform internal low-temperature heat treatment for 1.5 hours;

[0095] The second step is to continue heating to 120℃ and treat at a medium temperature for 3 hours.

[0096] The third step is to continue heating to 320℃ and perform high-temperature heat treatment for 3 hours.

[0097] S1.3) Finally, the non-metallic catalyst foam skeleton is crushed, ground, and sieved to obtain 60-600 mesh particles, which are the non-metallic catalysts with single-walled carbon nanotubes prepared.

[0098] S2) The non-metallic catalyst obtained in S1) is placed into the conveyor, and the reaction chamber and collection chamber are evacuated to remove the air atmosphere. The vacuum degree is no more than 10 kPa and is maintained for more than 12 hours. Then, inert gas is introduced to bring the reaction chamber and collection chamber to normal pressure.

[0099] S3) The reaction chamber is heated to 1200°C by DC arc discharge; the preheater is started to preheat the carbon source mixture to 350°C;

[0100] S4) The non-metallic catalyst powder is fed into the reaction chamber at a rate of 3 g / min through a conveyor, and the preheated carbon source mixed gas is also fed into the reaction chamber. The non-metallic catalyst is catalytically decomposed with the carbon source mixed gas to generate metal-free single-walled carbon nanotube products, which are then collected in the collection chamber by the gas flow.

[0101] The carbon source mixed gas includes 1.5 L / min natural gas as the carbon source gas, 5 L / min carbon monoxide as a mild etching gas, 3 L / min water vapor as a ...

[0102] Table 3 shows that the I of the initial product obtained in Example 1 G / I D The ratio was 208, indicating good crystallinity and high-quality single-walled carbon nanotubes. The initial product yield was 1.73 g / h, and the residual TG in the product was 0.01%, which may be due to contamination from the quartz reaction vessel used or testing errors caused by dust in the air. The resistivity curve of the single-walled carbon nanotube powder prepared in Example 1 as a function of pressure is shown in the figure. Figure 4 As shown, the powder resistivity of the products prepared by this invention is low, ranging from 3.4 to 1.1 mΩ·cm in the range of 2-18 MPa. Figure 4 It can be seen that the resistivity of the single-walled carbon nanotubes GNH-1000 prepared by Beijing Beifang Guoneng Technology Co., Ltd. using metal-based catalysts is 71.8-16.6 mΩ·cm in the range of 2-18 MPa, indicating that the single-walled carbon nanotubes prepared by the non-metallic diamond catalyst of this invention have significant advantages in conductivity.

[0103] Example 2

[0104] The difference between the preparation method and steps in Example 1 is that the preferred non-metallic catalyst nanoparticles have a particle size distribution of 3-15 nm, the liquid hydrocarbon is glucose, and the non-metallic catalyst nanoparticles are dispersed in toluene solution at a ratio of 2.4 wt% of the organic solvent; the liquid hydrocarbon is mixed with the non-metallic catalyst pre-dispersion at a ratio of 15 wt% to form the non-metallic catalyst pre-dispersion.

[0105] The solution layer in the quartz reaction vessel should be no higher than 12 mm in height. A uniformly loaded non-metallic catalyst foam framework is formed through a three-step gradient heating method. The three-step gradient heating method is as follows:

[0106] The first step is to heat to 75°C and perform internal low-temperature heat treatment for 2.5 hours;

[0107] The second step is to continue heating to 150℃ and treat at a medium temperature for 8 hours.

[0108] The third step is to continue heating to 430℃ and perform high-temperature heat treatment for 6 hours.

[0109] The non-metallic catalyst foam skeleton is crushed, ground, and sieved to obtain particles of 80-500 mesh, which are the single-walled carbon nanotubes of the non-metallic catalyst.

[0110] The reaction chamber is heated to 1470°C using an alternating electric arc discharge method; the preheater is then started to preheat the carbon source mixture to 385°C.

[0111] The non-metallic catalyst feed rate is 7.5 g / min. The carbon source mixed gas includes 3.5 L / min methane as the carbon source gas, 8 L / min carbon dioxide, 5 L / min water vapor and 25 L / min hydrogen as mild etching gases, and 12 L / min argon as the carrier gas.

[0112] Table 3 shows that the I of the initial product obtained in Example 2 G / I D The ratio was 238, indicating high-quality single-walled carbon nanotubes. The initial product yield was 3.16 g / h, and the residual TG in the product was 0, indicating that the product contained only carbon and was free from contamination by other metal catalysts. Due to the limitation of the thermogravimetric instrument's measurement limit, inductively coupled plasma atomic emission spectrometry (ICP-AES) characterization was further performed, as shown in Table 1. The results showed that the metal content in the product was generally less than 20 PPM, which is basically consistent with the results of TG characterization analysis in Table 2. Figure 5 Scanning electron microscopy showed that the surface purity of the product was consistent with the thermogravimetric characterization results.

[0113] Example 3

[0114] The difference between the preparation method and steps of Example 2 is that the liquid hydrocarbon is water-soluble starch, the non-metallic catalyst nanoparticles are dispersed in a styrene solution at a ratio of 3.6 wt% of the organic solvent, and the liquid hydrocarbon is mixed with the non-metallic catalyst pre-dispersion at a ratio of 21 wt% to form the non-metallic catalyst pre-dispersion.

[0115] The solution in the corundum reaction vessel is spread to a height not exceeding 10 mm; a uniformly loaded non-metallic catalyst foam skeleton is formed through a three-step gradient heating method; the three-step gradient heating method is as follows:

[0116] The first step is to heat to 87°C and perform internal low-temperature heat treatment for 3.5 hours.

[0117] The second step is to continue heating to 160℃ and treat at a medium temperature for 10 hours.

[0118] The third step is to continue heating to 460℃ and perform high-temperature heat treatment for 2 hours.

[0119] The non-metallic catalyst foam skeleton is crushed, ground, and sieved to obtain particles of 80-325 mesh, which are the single-walled carbon nanotubes of the non-metallic catalyst.

[0120] The reaction chamber was heated to 1780°C using radio frequency induction plasma method; the preheater was started to preheat the carbon source mixture to 435°C.

[0121] The non-metallic catalyst feed rate is 12.5 g / min. The carbon source mixed gas includes 5.5 L / min methane as the carbon source gas, 3 L / min ammonia as a mild etching gas, 12 L / min water vapor and 35 L / min hydrogen as the mild etching gas, and 28 L / min argon as the carrier gas.

[0122] As shown in Table 3, the yield of the initial product obtained in Example 3 was 5.66 g / h, the residual TG in the product was 0, and it contained only carbon. Figure 7 The Raman spectrum of the sample prepared in Example 3 was obtained at 180 cm⁻¹. -1 The product exhibits distinct and sharp RBM characteristic absorption peaks on both sides, indicating the presence of single-walled carbon nanotubes. Under the test condition of an excitation wavelength of 532 nm, the product I was calculated using the classical formula in Equation 1. G / I D The ratio is 257, indicating that the prepared product contains high-quality single-walled carbon nanotubes. Statistical calculation of the integrated intensity of the breathing mode (RBM peak) in Raman spectroscopy shows that the percentage of semiconductor-grade single-walled carbon nanotubes is 99%. Table 3 shows that the initial product has 0% TG residue, indicating that the product contains only carbon and is free from contamination by other metal catalysts.

[0123] The diameter and chiral distribution of the single-walled carbon nanotubes prepared in Example 3 and Comparative Example 1 are shown in Table 2. It can be seen that the diameter distribution range of Example 1 is relatively narrow, from 1.3 to 1.8 nm, while that of Comparative Example 1 is a wider diameter range of 1.0 to 2.4 nm. Figure 8 The calculated magnified images of the Raman spectra are shown in Table 2. In Example 3, the chiral indices (12,7), (14,6), and (14,10) accounted for 51.60%, 21.77%, and 25.66% of the carbon nanotubes, respectively, representing over 99% of the narrow diameter distribution of the 1.3-1.8 nm semiconducting single-walled carbon nanotubes. Comparative Example 1, with chiral indices including (19,9), (20,6), (17,9), (16,8), (14,10), (15,4), (14,4), (13,2), and (11,6), also showed semiconducting single-walled carbon nanotubes with a wider chiral distribution. This indicates that compared to the single-walled carbon nanotubes prepared in Comparative Example 1, the diameter and chiral distribution of the single-walled carbon nanotubes prepared in Example 3 are more concentrated. This provides a significant advantage for the subsequent application of single-walled carbon nanotubes. Figure 8 and Figure 11 It's more intuitive to see.

[0124] Figure 9 and Figure 10 The transmission electron microscopy characterization of the coking products collected in Example 3 further verifies that the products do not contain some non-carbon elements and have no obvious impurities at the microscopic level. Figure 9 The SWCNTs in the product had a diameter of 1.65 nm. The diameters of more than 150 single-walled carbon nanotubes were measured and statistically analyzed under a transmission electron microscope, and their diameter distribution ranged from 1.3 to 1.8 nm. This diameter distribution range is basically consistent with the diameter distribution calculated from Raman spectroscopy.

[0125] Example 4

[0126] The difference between the preparation method and steps in Example 3 is that the liquid hydrocarbon is water-soluble chitosan, the non-metallic catalyst nanoparticles are dispersed in trichloroethylene solution at a ratio of 4.3 wt% of the organic solvent, and the liquid hydrocarbon is mixed with the non-metallic catalyst pre-dispersion at a ratio of 32 wt% to form the non-metallic catalyst pre-dispersion.

[0127] The solution in the corundum reaction vessel is spread evenly to a height of no more than 8 mm; a three-step gradient heating method is used to form a uniformly loaded non-metallic catalyst foam skeleton.

[0128] The non-metallic catalyst foam skeleton is crushed, ground, and sieved to obtain particles of 150-325 mesh, which are the single-walled carbon nanotubes of the non-metallic catalyst.

[0129] The reaction chamber is heated to 1880°C using radio frequency induction plasma method; the preheater is started to preheat the carbon source mixture to 465°C.

[0130] The non-metallic catalyst feed rate is 18.5 g / min. The carbon source mixed gas includes 10.5 L / min methane as the carbon source gas, 15 L / min carbon monoxide as a mild etching gas, 18 L / min water vapor as a mild etching gas, and 65 L / min hydrogen as a hydrogen gas; and 88 L / min argon as the carrier gas.

[0131] Table 3 shows that the I of the initial product obtained in Example 5 G / I D The ratio is 215, indicating high-quality single-walled carbon nanotubes. The initial product yield is 10.38 g / h. Figure 6 Thermogravimetric analysis revealed that the residual TG in the product was 0.03, which may be due to contamination from the corundum material of the container or contamination from elements contained in the dust in the air.

[0132] Example 5

[0133] The difference between the preparation method and steps of Example 4 is that the liquid hydrocarbon is a complex sugar, the non-metallic catalyst nanoparticles are dispersed in anhydrous ethanol solution at a ratio of 5.8 wt% of the organic solvent, and the liquid hydrocarbon is mixed with the non-metallic catalyst pre-dispersion at a ratio of 25 wt% to form the non-metallic catalyst pre-dispersion.

[0134] The solution is spread evenly in the graphite reaction vessel to a height not exceeding 5 mm; a three-step gradient heating method is used to form a uniformly loaded non-metallic catalyst foam skeleton.

[0135] The non-metallic catalyst foam skeleton is crushed, ground, and sieved to obtain particles of 150-250 mesh, which are the single-walled carbon nanotubes of the non-metallic catalyst.

[0136] The preheater is started to preheat the carbon source mixture to a temperature of 565℃;

[0137] The non-metallic catalyst feed rate is 25.5 g / min. The carbon source mixed gas includes 24 L / min methane as the carbon source gas, 25 L / min carbon monoxide as a mild etching gas, 28 L / min water vapor and 90 L / min hydrogen as the mild etching gas, and 150 L / min argon as the carrier gas.

[0138] Table 3 shows that the I of the initial product obtained in Example 5 G / I DThe ratio is 272, indicating high-quality single-walled carbon nanotubes. The initial product yield is 14.75 g / h, so the residual TG in the product is 0, and the G / D ratio in the product is greater than 200. The product of Example 5 is made into a nanoscale thickness film, such as... Figure 12 As shown, the thickness difference is between -2 and 3.6 nm under an atomic force microscope, which can be used to fabricate functional devices such as field-effect transistors, infrared detectors, flexible displays, radio frequency devices, and chemical and biological sensors.

[0139] Comparative Example 1

[0140] The difference between the preparation method and steps of Example 5 is that the three-step drying method was not used. Instead, the product was directly carbonized at 456°C for 3 hours and then dried. As shown in Table 3, the G / D ratio of the product was 78. Compared with the product of Example 5, the crystallinity was lower and there were more defects. The initial product yield was 2.35 g / h, which was a significant decrease in yield. The thermogravimetric analysis showed that the residual was 0.05 wt%, which was also significantly increased.

[0141] Depend on Figure 11 The calculated RBM amplification peaks of the Raman spectra are shown in Table 2. It can be seen that the SWCNTs of Comparative Example 1 have a wider chiral distribution and a wider diameter distribution. The chiral indices of Comparative Example 1 include (19,9), (20,6), (17,9), (16,8), (14,10), (15,4), (14,4), (13,2), and (11,6), etc. Although they are also semiconducting single-walled carbon nanotubes, their chiral distribution is wider. Compared to Example 3, Comparative Example 1 has a wider diameter distribution range of 1.0–2.4 nm. Figure 11 and Figure 8 The magnified schematic diagram of the RBM peak in the Raman spectrum provides a clearer view of the distribution of semiconducting single-walled carbon nanotubes in Example 3, which is more concentrated than that in Comparative Example 1.

[0142] Table 1. Inductively Coupled Plasma-Atomic Emission Spectroscopy Characterization of the Products Prepared in Example 2

[0143]

[0144] Table 2. Diameter and chiral distribution of single-walled carbon nanotubes in Example 3 and Comparative Example 1.

[0145]

[0146]

[0147] Table 3 Product Indicators in Examples

[0148]

[0149] The characterization techniques for evaluating the metallic and semiconductor properties of single-walled carbon nanotubes in the product obtained by the method of this invention include Raman spectroscopy and temperature-dependent resistance testing. The content of single-walled carbon nanotubes is calculated using Raman spectroscopy as follows: Raman spectroscopy is performed on a silicon substrate at a depth of 303 cm⁻¹. -1 The signal is normalized, the average breathing modulus is statistically analyzed, and the percentage of single-walled carbon nanotubes (SUVs) relative to the total number of SUVs is calculated based on the peak area integral. (n, m) is called the chiral index of the carbon nanotube; SUVs can exhibit both semiconductor and metallic properties. When nm is an integer multiple of 3, the density of states at the Fermi level of the SUV is not zero, exhibiting metallic properties; when nm is a non-integer multiple of 3, the density of states near the Fermi level is zero, exhibiting semiconductor properties.

[0150] The foregoing has provided a detailed description of a method for preparing narrow-diameter distributed semiconducting single-walled carbon nanotubes and its applications, as provided in the embodiments of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and its core ideas; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

[0151] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0152] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0153] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0154] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A method for preparing narrow-diameter-distribution semiconducting single-walled carbon nanotubes, characterized in that, The method specifically includes the following steps: S1) Prepare a non-metallic catalyst foam framework for later use; The specific steps are as follows: S1.1) First, non-metallic catalyst nanoparticles are dispersed in an organic solvent in a certain proportion to form a non-metallic catalyst nanoparticle solution. Then, the non-metallic catalyst nanoparticle diamond solution and liquid hydrocarbons are mixed in a certain proportion to form a non-metallic catalyst pre-dispersion. S1.2) Place the non-metallic catalyst pre-dispersion solution into the reaction vessel, ensuring the solution is spread evenly within the vessel to a height not exceeding 15 mm; then, use a three-step gradient heating method to form a uniformly loaded non-metallic catalyst foam skeleton. S1.3) Finally, the non-metallic catalyst foam skeleton is crushed, ground, and sieved to obtain particles of 20-800 mesh, which is the prepared non-metallic catalyst foam skeleton. S2) The non-metallic catalyst foam skeleton obtained in S1) is placed into the conveyor, and the reaction chamber and collection chamber are evacuated to remove the air atmosphere. Then, inert gas is introduced to bring the reaction chamber and collection chamber to atmospheric pressure. S3) Heat the reaction chamber to the specified temperature range and start the preheater to preheat the carbon source mixture; S4) A certain amount of non-metallic catalyst foam skeleton is sent into the reaction chamber through a conveyor, and at the same time, the preheated carbon source mixed gas is sent into the reaction chamber. The non-metallic catalyst foam skeleton is catalytically decomposed with the carbon source mixed gas to generate metal catalyst-free single-walled carbon nanotube products. The products fall into the collection chamber with the airflow and are collected, thus obtaining narrow diameter distributed semiconductor single-walled carbon nanotubes.

2. The method according to claim 1, characterized in that, The proportion of non-metallic catalyst nanoparticles to organic solvent in S1.1) is 0.3-6 wt%, and the proportion of liquid hydrocarbons to non-metallic catalyst predispersants is 3-35 wt%.

3. The method according to claim 2, characterized in that, The organic solvent is styrene, perchloroethylene, trichloroethylene and ethylene glycol ether, acetone, anhydrous ethanol or toluene; The non-metallic catalyst nanoparticles are diamond nanoparticles with a particle size of 3-35 nm. The hydrocarbon is any one or a mixture of sucrose, glucose, maltose, lactose and complex sugars, water-soluble starch and water-soluble chitosan.

4. The method according to claim 1, characterized in that, The process of the three-step gradient heating method in S1.2) is as follows: First, heat to 60-95℃ and perform low-temperature heat treatment for 1-6 hours; The second step is to continue heating to 100-180℃ and perform medium-temperature treatment for 1-20 hours. The third step is to continue heating to 300-700℃ and perform high-temperature heat treatment for 0.5-10 hours; The reaction vessel is made of quartz, graphite, or corundum.

5. The method according to claim 1, characterized in that, The reaction chamber in S3) is heated to 900-3000℃ by fixed-bed CVD, fluidized-bed CVD, DC arc discharge, AC arc discharge, plasma torch, radio frequency induction plasma, or microwave discharge plasma.

6. The method according to claim 1, characterized in that, The powder feeding rate of the non-metallic catalyst foam skeleton in S4) is 0.1-30 g / min; The preheating temperature of the carbon source mixed gas is 200-650℃; The carbon source mixed gas includes a carbon source gas, a mild etching gas, and a carrier gas; The flow rate of the carbon source gas is 0.5-30 L / min; The range of mild etching gas is 0.1-125 L / min; The carrier gas flow rate is 5-200 L / min.

7. The method according to claim 1, characterized in that, The narrow-diameter-distribution semiconducting single-walled carbon nanotubes prepared by the method have a purity of not less than 99.9% and a G / D greater than 200. The chiral indices (12,7), (14,6), and (14,10) account for 51.60%, 21.77%, and 25.66% of the carbon nanotubes, respectively, which means that more than 99% of the semiconducting single-walled carbon nanotubes have a narrow diameter distribution of 1.3-1.8 nm.

8. A single-walled carbon nanotube with a diameter distribution that exhibits semiconducting properties, characterized in that, The diameter-distributed semiconducting single-walled carbon nanotubes are prepared by the method described in any one of claims 1-7.

9. Application of a single-walled carbon nanotube prepared by the method according to any one of claims 1-7 in optoelectronic devices, logic circuits, flexible displays and quantum light sources.

Images