Method for manufacturing nanodiamonds, and nanodiamond structure

Abstract

This invention provides a novel method for manufacturing nanodiamonds that can be produced at a lower cost and in a milder environment than conventional methods. [Solution] A method for producing nanodiamonds is a method for producing nanodiamonds from a cyclic aliphatic hydrocarbon compound by irradiating the cyclic aliphatic hydrocarbon compound with an electron beam, wherein the cyclic aliphatic hydrocarbon compound is sp 3 It contains carbon.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing nanodiamonds and a nanodiamond structure

Background Art

[0002] Various methods such as high temperature and high pressure method, chemical vapor deposition (CVD) method, explosion method, and laser ablation method have been developed for the synthesis of nanodiamonds, starting from the synthesis method described in Non-Patent Document 1

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Nanodiamonds have excellent mechanical strength, high thermal conductivity, electrical insulation, chemical stability, and excellent optical properties, and thus are attracting attention as promising materials in many advanced technical fields such as electronics, optics, biomedical, and quantum devices

[0005] The high temperature and high pressure method is a method of converting carbon into diamond in a high temperature and high pressure environment that mimics the formation conditions of natural diamonds, and it is possible to obtain high-quality nanodiamonds. However, there is a problem that the manufacturing cost of nanodiamonds becomes very high because the equipment is huge and expensive, and a huge amount of energy is required to maintain the high temperature and high pressure conditions

[0006] Chemical vapor deposition (CVD) is a method of depositing a diamond thin film onto a substrate by decomposing a source gas containing hydrocarbon gases at high temperatures. CVD allows for the synthesis of diamond thin films under relatively low-temperature conditions and enables film deposition on large-area substrates. However, CVD suffers from high costs due to the complexity of the process.

[0007] The explosive method is a technique for producing nanodiamonds using the explosive energy of explosives. While this method can synthesize large quantities of nanodiamonds relatively inexpensively, it has a high environmental impact and concerns about the safety of the manufacturing process.

[0008] Laser ablation is a method of generating nanodiamonds by irradiating a target material with a high-energy laser. While laser ablation can produce high-purity nanodiamonds, it has drawbacks such as high equipment costs and difficulty in controlling the generation process.

[0009] One aspect of this disclosure has been made in view of the above-mentioned problems, and its purpose is to provide a novel method for manufacturing nanodiamonds, and related technologies, which can be manufactured at a lower cost in a milder environment than conventional manufacturing methods. [Means for solving the problem]

[0010] To solve the above problems, a method for producing nanodiamonds according to one aspect of the present disclosure involves irradiating a cyclic aliphatic hydrocarbon compound with an electron beam, wherein the cyclic aliphatic hydrocarbon compound is sp 3 It is a cyclic aliphatic hydrocarbon compound that contains carbon.

[0011] Nanodiamonds according to one aspect of this disclosure are formed by the polymerization of structural units consisting of adamantane-based compounds.

[0012] A nanodiamond thin film according to one aspect of the present disclosure is a nanodiamond thin film comprising nanodiamonds according to one aspect of the present disclosure, comprising isolated nanodiamond particles or aggregates of such isolated particles, wherein the grain size of the nanodiamond thin film is from 1 nm to 1000 nm, the crystallinity of the nanodiamond thin film is from 60% to 100%, and the surface roughness of the nanodiamond thin film is from 0.1 nm to 100 nm. [Effects of the Invention]

[0013] According to one aspect of this disclosure, the objective is to provide a novel method for manufacturing nanodiamonds, and related technologies, which can be manufactured at a lower cost in a milder environment compared to conventional manufacturing methods. [Brief explanation of the drawing]

[0014] [Figure 1] This diagram illustrates the growth scheme for diamond skeletons from adamantane and diamantane via CH / CH coupling. [Figure 2] This paper demonstrates a scheme for generating oligomers from adamantane crystals and growing them into nanodiamonds via electron beam propagation. [Figure 3] The images show electron diffraction (ED) patterns obtained from adamantane crystals, amorphous materials, and nanodiamond particles under experimental conditions of 200 keV and 100 K. TED50 indicates the total electron dose (TED) required to halve the ED intensity at each stage. [Figure 4] This is a TEM image of nanodiamond acquired at low magnification. The scale bar in the figure represents 100 nm. [Figure 5] This shows TEM images of nanodiamonds acquired at high magnification, along with their crystal structure orientation and structural model. [Figure 6] This paper presents time evolution and structural analyses related to the growth of nanodiamonds. It also includes statistical analysis of circularity. In Figure 6, MP refers to the mirror plane. [Figure 7] This is a SEM image of nanodiamonds produced at 1kV. [Figure 8] This is a SEM image of nanodiamonds produced at 15kV. [Figure 9] Figure 9A shows the total electron dose (TED50) required to convert 50% of adamantane under conditions of 200 keV and 100 K, and Figure 9B shows a plot of normalized particle number and diameter against the reaction progress in a study using adamantane as a precursor. [Figure 10] Figure 10 shows the relative standard distribution of particle size against the normalized reaction progress in studies using adamantane as a precursor. [Figure 11] Figures 11A and 11B show the results of the analysis of the temperature dependence of the rate constant in the adamantane polymerization reaction under 200 keV and 80 keV conditions. [Figure 12] Under 200 keV and 80 keV conditions, the Arrhenius activity energy Ea = 0.40 and 1.68 kJ / mol, along with the frequency factor A or PEF, are shown as an analysis using an Arrhenius plot. [Figure 13] Figures 13A and 13B show the analysis results regarding the temperature dependence of the rate constants in the polymerization reactions of adamantane and adamantane-D16 under 200 keV and 80 keV conditions. [Figure 14] This shows the presumed sequential reaction mechanism in the polymerization reaction of adamantane. [Modes for carrying out the invention]

[0015] One embodiment of this disclosure will be described in detail below.

[0016] <1> Method for manufacturing nanodiamonds The method for manufacturing nanodiamonds may include the presence of heteroatoms. 3The method includes a step of producing nanodiamonds by irradiating a carbon-containing cyclic aliphatic hydrocarbon compound with an electron beam under high vacuum. This allows the cyclic aliphatic hydrocarbon compound to be polymerized, and nanodiamonds having structural units derived from the cyclic aliphatic hydrocarbon compound (for example, an adamantane-based compound which may have heteroatoms) can be produced.

[0017] Since nanodiamonds can be produced by irradiating the cyclic aliphatic hydrocarbon compound (for example, an adamantane-based compound which may have heteroatoms) with an electron beam, it does not require the use of reagents that have been essential for conventional nanodiamond synthesis, such as metal catalysts for hydrogen removal and explosive organic compounds. Therefore, the nanodiamonds are not contaminated with impurities derived from metal catalysts and explosive organic compounds.

[0018] Methods for producing nanodiamonds include conductive substrates (e.g., ITO substrates, ETO substrates, graphite substrates, etc.), highly conductive substrates (glass substrates, silicon substrates), metal substrates (Au substrates, Pt substrates, Al substrates, etc.), coated insulating substrates (silicon oxide substrates, alumina substrates, etc.), coated polymer substrates (polycarbonate substrates, polyimide substrates, etc.), and special substrates (single crystal substrates, carbon-coded copper grids, silicon nitride substrates, etc.). For coatings, Au, Pt, carbon, and Pd are preferred to prevent charge buildup. A thin film of the cyclic aliphatic hydrocarbon compound (e.g., an adamantane-based compound which may have heteroatoms) formed on these substrates is irradiated with an electron beam under high vacuum. This makes it possible to produce a nanodiamond thin film containing isolated nanodiamond particles and aggregates of such isolated particles on the substrate. In this invention, a thin film refers to a film-like structure having a thickness of 1 nm to 10 μm, and includes amorphous, crystalline, and intermediate structures. The morphology of a film does not necessarily have to be continuous; films with locally grown island structures are also included in the definition of a thin film. The film can be formed on a substrate or independently, regardless of whether it is single-layer or multi-layered. Furthermore, multilayer films and films with added functionality are also included in this definition.

[0019] In nanodiamonds, isolated particles refer to single crystals and twins with a size of 10 nm or less that do not spatially interact with other particles, while an aggregate of isolated particles refers to a thin film formed by the aggregation of isolated particles, and is not limited to whether or not the isolated particles are aggregated.

[0020] A method for producing nanodiamonds according to one embodiment can be incorporated into manufacturing methods for various device applications, including a step for producing a nanodiamond thin film. That is, the method for producing nanodiamonds according to one embodiment can be used to produce nanodiamonds using a known semiconductor manufacturing apparatus equipped with an electron beam irradiation apparatus and a coating apparatus such as a spin coater. Therefore, the cost required to prepare an apparatus for producing nanodiamonds can be eliminated.

[0021] <1-1> Irradiation with electron beam The temperature conditions when irradiating the cyclic aliphatic hydrocarbon compound (e.g., an adamantane-based compound which may have heteroatoms) with an electron beam are preferably higher than absolute zero and 200°C or lower, more preferably between -269°C and 200°C, even more preferably between -100°C and 100°C, and particularly preferably within the range of 10°C and 30°C. Furthermore, from the viewpoint that increasing the crystallinity of the cyclic aliphatic hydrocarbon compound before electron beam irradiation contributes to improving the purity of nanodiamonds, the electron beam irradiation temperature conditions are preferably near absolute zero. The upper limit is preferred from the viewpoint of preventing sublimation of the cyclic aliphatic hydrocarbon compound (e.g., an adamantane-based compound which may have heteroatoms), and the lower limit is preferred from the viewpoint of improving repeatability. This makes it possible to significantly reduce energy consumption compared to other manufacturing methods such as the high-temperature, high-pressure method. The electron beam irradiation of the cyclic aliphatic hydrocarbon compound (for example, an adamantane-based compound which may have heteroatoms) can be carried out under temperature conditions in the range of absolute zero to 200°C, but one of the advantages of the present invention is that nanodiamonds can be produced under extremely mild reaction conditions, for example, 20°C.

[0022] The vacuum level when irradiating the cyclic aliphatic hydrocarbon compound (for example, an adamantane-based compound which may have heteroatoms) with an electron beam is 10 -8 Pa~10 -2It is preferably within the range of Pa. The lower limit value is better as the degree of vacuum increases with the ability of a vacuum pump such as a cryopump. However, the upper limit value needs to reduce the coexistence of molecules that inhibit reactions by electron beams, such as nitrogen, in the system, and is about 10 -2 Pa. From the perspective of efficient and repetitive production, it is more preferably within the range of 10 -5 Pa to 10 -3 Pa.

[0023] When irradiating the cycloaliphatic hydrocarbon compound (for example, an adamantane-based compound that may have heteroatoms) with an electron beam, the energy range of the electron beam may be designed according to the thickness of the thin film of the cycloaliphatic hydrocarbon compound (for example, an adamantane-based compound that may have heteroatoms) to be irradiated with the electron beam, and should not be limited, but it is preferably within the range of 1 eV to 500 keV, more preferably 30 eV to 150 keV, and even more preferably within the range of 50 eV to 80 keV. In order to efficiently perform the conversion to nanodiamond, more than about this lower limit value is preferable. The upper limit value is because if the electron beam is too strong, the conversion rate becomes fast and the structural conversion to nanodiamond is inhibited.

[0024] When irradiating the cycloaliphatic hydrocarbon compound (for example, an adamantane-based compound that may have heteroatoms) with an electron beam, the current density may be designed according to the thickness of the thin film of the cycloaliphatic hydrocarbon compound (for example, an adamantane-based compound that may have heteroatoms) to be irradiated with the electron beam, and is preferably within the range of 10 -3 A / cm 2 to 10 5 A / cm 2 and more preferably within the range of 10 1 A / cm 2 to 10 3 A / cm 2 The current density when irradiating the cycloaliphatic hydrocarbon compound (for example, an adamantane-based compound that may have heteroatoms) with an electron beam may be calculated from the irradiation electron dose (EDR) and the irradiation time. For example, when EDR is 10 4 to 106 e - nm -2 s -1 Under these conditions, it is preferable to irradiate with an electron beam for a time range of 1 second to 1 hour.

[0025] The acceleration voltage when irradiating the cyclic aliphatic hydrocarbon compound (for example, an adamantane-based compound which may have heteroatoms) with an electron beam should be designed according to the thickness of the thin film of the cyclic aliphatic hydrocarbon compound (for example, an adamantane-based compound which may have heteroatoms), and it is preferable that the acceleration voltage of the electron beam is in the range of 10V to 300kV.

[0026] Furthermore, the total electron dose (TED) of the irradiated electron beam is 10 2 ~10 10 e - nm -2 The higher the value, the higher the conversion rate of the cyclic aliphatic hydrocarbon compound to nanodiamonds.

[0027] The beam diameter when irradiating the cyclic aliphatic hydrocarbon compound (for example, an adamantane-based compound which may have heteroatoms) with an electron beam can be appropriately designed within the range of 1 nm to 3 cm and is not limited thereto. Furthermore, the irradiation angle of the electron beam can be appropriately designed within the range of 0 degrees to 90 degrees.

[0028] The cyclic aliphatic hydrocarbon compound and the compound having a polycyclic hydrocarbon skeleton are compounds that can produce nanodiamonds when irradiated with an electron beam, and these compounds have carbon-hydrogen bonds and sp 3 It has a three-dimensional structure containing a six-membered ring comprising carbon atoms, or three or more six-membered rings are sp 3 These compounds have a polycyclic hydrocarbon skeleton formed by condensation through carbon linkage, and these cyclic aliphatic hydrocarbon compounds may also contain heteroatoms.

[0029] Cyclic aliphatic hydrocarbon compounds (e.g., adamantane compounds which may have heteroatoms) are sp 3It has a three-dimensional structure including a condensed six-membered ring. The cyclic aliphatic hydrocarbon compound (for example, an adamantane compound which may have heteroatoms) polymerizes due to the presence of the condensed six-membered ring, and when hydrogen is removed, the carbon sp 3 It is believed that nanodiamonds are generated from the structure. The nanodiamonds have a crystalline structure which is a structural unit derived from the cyclic aliphatic hydrocarbon compound (e.g., an adamantane compound which may have heteroatoms). In this specification, unless otherwise specified, for convenience, the cyclic aliphatic hydrocarbon compound (e.g., an adamantane compound which may have heteroatoms) includes adamantane compounds and their derivatives.

[0030] In the cyclic aliphatic hydrocarbon compounds (e.g., adamantane compounds which may have heteroatoms) for generating nanodiamonds, for example, adamantane compounds include adamantane compounds and their derivatives. The cyclic aliphatic hydrocarbon compounds include (i) a group of 6-membered ring compounds having a three-dimensional stereostructure, (ii) polycyclic compounds containing atoms other than carbon as heteroatoms, and (iii) sp compounds containing a 6-membered ring. 3 Examples include compounds with a structure composed of carbon.

[0031] (i) The group of 6-membered ring compounds having a three-dimensional stereostructure includes adamantane compounds, such as adamantane, diamantane, triamantane, tetraamantane, pentaamantane, and hexaamantane. Derivatives may have any substituents, but specific examples of substituents include hydroxyl groups, hydroxycarbonyl groups, amino groups which may have any substituents, alkyl groups such as methyl groups, aryl groups such as phenyl groups, and halogen atoms. Phenyl groups and amino groups may further have any substituents. Adamantane compounds are preferred from the viewpoint of being able to produce nanodiamonds with high crystallinity and high conversion rates.

[0032] (ii) Polycyclic compounds containing heteroatoms are derivatives of adamantane compounds in which at least one carbon atom and one hydrogen atom are substituted with a heteroatom. Examples of heteroatoms include nitrogen, phosphorus, silicon, sulfur, oxygen, and boron. Examples of polycyclic aliphatic hydrocarbon compounds containing heteroatoms include tetraadamantane, triadamantane, oxadamantane, diaadamantane, siladamantane, and boroadamantane. Examples of compounds with substituents include phenoxyadamantane, tetramethyladamantane, piperazineadamantane, and dioxadamantane. These polycyclic aliphatic hydrocarbon compounds are spliced ​​with adamantane compounds. 3 These compounds have a three-dimensional structure in which some of the carbon atoms are replaced by heteroatoms.

[0033] (iii) The cyclic aliphatic hydrocarbon compound contains sp 3 This group of compounds may have a carbon-based structure, and examples of such compounds include diamantane, tryptamantane, karan, coran, samantane, cholestane, flulanoadamantane, isoadamantane, tetramethyladamantane, and akamantane, and these compounds are also included in the derivatives of adamantane compounds.

[0034] Furthermore, as mentioned above, cyclic aliphatic hydrocarbon compounds have three or more 6-membered rings sp 3 Examples include compounds having a polycyclic hydrocarbon skeleton formed by condensation through carbon linkage. By crystallizing the compound and irradiating it with an electron beam, three or more 6-membered rings are formed sp 3 Nanodiamonds are generated from polycyclic hydrocarbon skeletons formed by condensation through carbon linkage. These compounds include cholestane, androstan, pregnane, cholestanol, estran, gonan, hopanane, campstan, ergostan, and stanol, as well as sp2 compounds with polycyclic structures found in nature and synthetic chemistry. 3Examples include carbon compounds, hopane, caran, acramantane, alkane polycyclo compounds, decahydroquinarine, quantheine, norbornane, pentamethylhexahydroadamantane, octamethyldiamantane, and trianthracene, which may include derivatives of adamantane compounds.

[0035] <Nanodiamonds and nanodiamond thin films> The nanodiamond thin film produced by irradiating the cyclic aliphatic hydrocarbon compound with an electron beam contains nanodiamonds with a grain size of approximately 1 nm to 1000 nm, preferably 5 to 100 nm. Furthermore, if the nanodiamonds have a grain size of approximately 2 nm to 5 nm, they can be used as quantum dots. The grain size of the nanodiamonds contained in the nanodiamond thin film can be calculated as the average grain size of the nanodiamond particles using TEM. The volume of the nanodiamond particles can be calculated as the volume of a sphere calculated from the area of ​​the particles in the TEM image.

[0036] The nanodiamond thin film is constructed from cubic nanodiamonds. Preferably, the crystallinity of the nanodiamond thin film is in the range of 60% to 100%. For example, when adamantane is used as the cyclic aliphatic hydrocarbon compound, the crystallinity of the nanodiamond can be qualitatively determined.

[0037] Furthermore, the nanodiamond crystals in the nanodiamond thin film are oriented such that the preferred orientation direction is (100), (110), or (111).

[0038] A characteristic feature of the nanodiamonds contained in the nanodiamond thin film produced by the manufacturing method according to one embodiment is that the particle shape is spherical and the roundness is in the range of 70 to 100%.

[0039] Furthermore, the film thickness of the adamantane-based compound can be set as appropriate and is not limited, but it is preferably about 1 nm to 1 μm. The surface roughness of the converted nanodiamond thin film is preferably about 0.1 nm to 100 nm.

[0040] Furthermore, the nanodiamonds contained in the nanodiamond thin film preferably have a conversion rate from adamantane-based compounds of 80% or more, more preferably 90% or more, and particularly preferably 95% or more. For example, if adamantane is used as the adamantane-based compound, nanodiamonds with a quantitative conversion rate of 100% are obtained.

[0041] In addition, the nanodiamonds contained in the nanodiamond thin film may also contain p-type dopants such as nitrogen atoms and boron atoms.

[0042] <1-2> Step of applying the cyclic aliphatic hydrocarbon compound Using a preferred adamantane-based compound as the cyclic aliphatic hydrocarbon compound, the method for producing nanodiamonds preferably includes a step of coating the substrate with the adamantane-based compound before irradiation with an electron beam. Furthermore, the method for producing nanodiamonds according to one embodiment of this disclosure may include a step of treating the surface of the substrate. This allows the surface roughness of the substrate to which the adamantane-based compound is coated to be controlled to approximately 0.1 nm to 100 nm. By adjusting the surface roughness of the substrate through surface treatment, the surface roughness of the nanodiamond thin film formed on the substrate can be controlled to approximately 0.1 nm to 100 nm. In addition, the degree of nanodiamond orientation in the nanodiamond thin film formed on the substrate can be increased to 80% or more, enabling the preparation of a homogeneous thin film. The degree of nanodiamond orientation can be analyzed not only from the acquired TEM image but also by performing a fast Fourier transform (FFT) on the region corresponding to the nanodiamonds.

[0043] In this specification, nanodiamonds with uniform orientation are referred to as oriented nanodiamond thin films. Most preferably, the degree of orientation of the nanodiamonds is 90% or higher.

[0044] The surface treatment process for the substrate should be appropriately selected depending on the type of substrate to which the adamantane-based compound is applied. Specifically, this includes cleaning, polishing, chemical conversion treatment, plasma treatment, chemical etching, and heat treatment.

[0045] The process of coating an adamantane compound is carried out by coating the composition onto a substrate. The composition consists of an adamantane compound and a solvent. The solvent can be selected according to the type of adamantane compound, and examples include: aliphatic hydrocarbon solvents: pentane, hexane, cyclohexane, and butane; aromatic hydrocarbon solvents: toluene, chlorobenzene, fluorobenzene, xylene, etc.; ether solvents: dibutyl ether, tetrahydrofuran, dioxane, etc.; and halogenated solvents: chloroform, dichloroethane, dichloromethane, etc. To form a thin film with good film properties, the boiling point of the solvent is preferably 55°C or higher, more preferably 80°C or higher, and particularly preferably 100°C or higher. The boiling point of the solvent during coating may be 0°C or higher, and there is no particular upper limit to the boiling point. From a coating perspective, examples include petroleum-based hydrocarbon solvents such as kerosene, mineral spirits, and IP solvents, as well as polar solvents such as N-methylpyrrolidone (NMP) and propylene glycol monomethyl ether acetate (PEGMEA). The composition may contain two or more solvents.

[0046] In the process of coating an adamantane-based compound, the method of coating the adamantane-based compound can be selected from known coating methods such as spin coating, dip coating, spray coating, and vacuum deposition, but is not limited to these.

[0047] One of the features of a method for manufacturing a nanodiamond thin film according to one embodiment of this disclosure is that a thin film of a cyclic aliphatic hydrocarbon compound, such as an adamantane-based compound, can be created by a simple coating method, and a nanodiamond thin film can be formed on a substrate. Furthermore, compared to high-temperature and high-pressure methods, explosion methods, and laser ablation methods, the method for manufacturing a nanodiamond thin film according to one embodiment of this disclosure can be manufactured in a mild temperature environment with low load. As a result, nanodiamonds with a particle size distribution with less variation can be manufactured.

[0048] Examples of substrates include those selected from those described above. For example, if the substrate is a conductive substrate, it is preferable that the substrate contains a conductive material selected from metals and carbon, etc.

[0049] The substrate may be a substrate for forming various devices, for example, a circuit including a transistor may be pre-patterned on it, and electrodes and wiring for conducting current in part of the circuit may be formed on the surface on which the nanodiamond thin film is formed. The thickness of the substrate can be appropriately selected depending on the size of the device, and is generally about 10 μm to 10 mm, but is not limited to that.

[0050] Nanodiamond thin films with patterns on a substrate may be implanted with dopants such as nitrogen, boron, or phosphorus, as needed, through the use of additives or post-modification. This makes it possible to manufacture devices with nanodiamond semiconductor thin films.

[0051] 〔summary〕 As described above, a method for producing nanodiamonds according to an aspect [1] of the present disclosure is a method for producing nanodiamonds from a cyclic aliphatic hydrocarbon compound by irradiating the cyclic aliphatic hydrocarbon compound with an electron beam, wherein the cyclic aliphatic hydrocarbon compound is sp 3 It is a cyclic aliphatic hydrocarbon compound containing carbon.

[0052] Furthermore, in the method for producing nanodiamonds according to aspect [2] of the present disclosure, in aspect [1], the cyclic aliphatic hydrocarbon compound is sp 3 It has a three-dimensional structure containing carbon and a 6-membered ring, or three or more 6-membered rings are sp 3 It is preferable that the compound has a polycyclic hydrocarbon skeleton formed by condensation through carbon linkage.

[0053] Furthermore, in the method for producing nanodiamonds according to aspect [3] of the present disclosure, it is preferable that nanodiamonds are produced from a cyclic aliphatic hydrocarbon compound by irradiating it with an electron beam in an energy range of 1 eV to 500 keV, as described in aspect [1] or [2].

[0054] Furthermore, in the method for producing nanodiamonds according to aspect [4] of this disclosure, in aspects [1] to [3], the current density of the electron beam is 10 -3 A / cm 2 ~10 5 A / cm 2 It is preferable that this be the case.

[0055] Furthermore, in the method for producing nanodiamonds according to aspect [5] of this disclosure, in aspects [1] to [4], the total electron dose (TED) of the irradiated electron beam is 10 2 ~10 10 e - nm -2 It is preferable that this be the case.

[0056] Furthermore, in the method for producing nanodiamonds according to aspects [6] of the present disclosure, it is more preferable that the cyclic aliphatic hydrocarbon compound is an adamantane-based compound in aspects [1] to [5].

[0057] Furthermore, in the method for producing nanodiamonds according to an aspect [7] of the present disclosure, in the aspect [6], the adamantane compound is preferably selected from the group consisting of adamantane, diamantane, triamantane, and their derivatives, and combinations thereof, wherein the derivative is selected from derivatives in which at least one of the carbon atoms and hydrogen atoms of the adamantane compound is substituted with a heteroatom, and derivatives having substituents, wherein the heteroatom is selected from nitrogen, phosphorus, silicon, sulfur, oxygen, and boron, and the substituent is preferably selected from an aryl group, a hydroxycarbonyl group, an amino group, and a halogen atom, wherein the aryl group and the amino group may or may not have substituents.

[0058] In any of the embodiments [8] of the present disclosure, it is more preferable that the cyclic aliphatic hydrocarbon compound is irradiated with the electron beam at a temperature of 200°C or less.

[0059] A method for producing nanodiamonds according to an aspect of this disclosure [9] is provided in any of the above aspects [1] to [8], where 10 -8 Pa~10 -2 It is more preferable to irradiate with the electron beam for 1 second to 1 hour under a vacuum of Pa.

[0060] In any of the embodiments

[10] of the present disclosure, the method for producing nanodiamonds is more preferably such that the acceleration voltage of the electron beam is 10V to 300kV.

[0061] A method for producing nanodiamonds according to an aspect of the present disclosure

[11] includes, in any of the aspects [1] to

[10] above, a step of coating the cyclic aliphatic hydrocarbon compound onto a substrate before irradiation with the electron beam, and by irradiating with the electron beam, a nanodiamond thin film containing at least one of the solitary nanodiamond particles or aggregates of the solitary particles is formed on the substrate.

[0062] In the method for producing nanodiamonds according to an aspect

[12] of the present disclosure, it is more preferable that, in the aspect

[11] , the grain size of the nanodiamonds contained in the nanodiamond thin film is 1 nm or more and less than 1000 nm, and the crystallinity of the nanodiamond thin film is 60% to 100%.

[0063] In the method for producing nanodiamonds according to an aspect of the present disclosure

[13] , it is more preferable that the surface roughness of the nanodiamond thin film is 0.1 nm to 100.0 nm, in the aspect

[11] or

[12] .

[0064] In any of the embodiments

[11] to

[13] of the present disclosure, the method for producing nanodiamonds according to the present disclosure

[14] is more preferably such that the thickness of the nanodiamond thin film is 1 nm to 1 μm.

[0065] A method for producing nanodiamonds according to an aspect of the present disclosure

[15] may include a step of doping the nanodiamonds by using an additive or by post-modification in any of the aspects

[11] to

[14] .

[0066] The nanodiamonds according to an aspect of this disclosure

[16] are nanodiamonds formed by the polymerization of structural units consisting of adamantane compounds.

[0067] In the embodiment of the present disclosure

[17] , the nanodiamonds in the embodiment

[16] are more preferably spherical in shape and have a roundness in the range of 70 to 100%.

[0068] In the embodiments of the present disclosure

[18] , it is more preferable that the conversion rate of the adamantane-based compound to the nanodiamond is 90% or more in embodiments

[16] or

[17] .

[0069] A nanodiamond according to an aspect of the present disclosure

[19] may have a carbon-hydrogen covalent bond on the surface of the nanodiamond in any of the aspects

[16] to

[18] .

[0070] A nanodiamond thin film according to an aspect of the present disclosure

[20] is a nanodiamond thin film comprising any of the nanodiamonds of aspects

[16] to

[19] , comprising solitary nanodiamond particles or aggregates of such solitary particles, wherein the grain size of the nanodiamond thin film is from 1 nm to 1000 nm, the crystallinity of the nanodiamond thin film is from 60% to 100%, and the surface roughness of the nanodiamond thin film is from 0.1 nm to 100 nm.

[0071] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure. [Examples]

[0072] An embodiment of this disclosure is described below, but this disclosure is not limited to such embodiments unless it exceeds its gist.

[0073] <1> Sample preparation For the samples, adamantane compounds were selected, including adamantane, adamantane-D16, diamantane, 1-ethyladamantane, 1-phenyladamantane, 1-chloroadamantane, 1-bromoadamantane, 1-iodoadamantane, 2-bromoadamantane, and 1-adamantanecarboxylic acid. Each of these adamantane compounds was placed in a separate vial and dissolved in pentane, a suitable solvent. By rapidly evaporating the solvent, a thin film of the adamantane compound was formed on the inner wall of the vial. These films were scraped off the inner wall of the vial with a spatula to obtain fine particles of the adamantane compound. The adamantane compounds used for the samples were from Tokyo Chemical Industry Co., Ltd., CIL (Cambridge Isotope Laboratories), and Sigma-Aldrich.

[0074] <1-1> Samples for electron beam irradiation (EB) processing Fine particles of an adamantane-based compound formed in a vial were scattered onto a conductive carbon tape (Nisshin EM Co., Ltd., Cat. No. 731) to obtain a sample for electron beam irradiation (EB) processing.

[0075] <1-2> Samples for Scanning Electron Microscope (SEM) Fine particles of an adamantane-based compound formed in a vial were scattered onto a conductive carbon tape to obtain a sample for scanning electron microscopy (SEM). <1-3> Samples for transmission electron microscopy (TEM) A C-flat TEM grid (CF-1.2 / 1.3-3C, ElectronMicroscopySciences, 20 nm thick, amorphous carbon film) was placed in a vial containing microparticles of each adamantane compound and shaken. The grid was uniformly coated with the microparticles of the adamantane compounds to obtain a sample for transmission electron microscopy (TEM).

[0076] <2> Electron beam irradiation experiment Electron beam irradiation was performed using EB, SEM, and TEM. [Examples]

[0077] Experiments using EB were conducted using the EC250 / 15 / 180L (I-Electron Beam) instrument, with 10 -4 Under a vacuum of Pa, the sample was placed in a 15cm x 20cm tray with a beam width of 100mm and irradiated with an electron beam for 1 hour at 200kV and 296K. [Examples]

[0078] The SEM experiment was conducted using the JSM-IT800SHL (manufactured by JEOL) instrument, with 10 -4 Under a vacuum of Pa, electron beam irradiation was performed for 30 minutes at 1kV and 296K. [Examples]

[0079] The procedure was the same as in Example 2, except that the voltage was changed to 15kV. [Examples]

[0080] The TEM experiment was conducted using the JEM-ARM200F instrument (manufactured by JEOL Corporation) for 10 -5 Under a vacuum of Pa, electron beam irradiation was performed at 200kV and 100K for 30 minutes. [Examples]

[0081] The procedure was the same as in Example 4, except that the voltage was changed to 80kV. [Examples]

[0082] The procedure was the same as in Example 4, except that the temperature was changed to 296K. [Examples]

[0083] The procedure was the same as in Example 4, except that the temperature was changed to 296K.

[0084] TEM and ED measurements of the nanodiamonds obtained in Examples 1 to 7 all showed results consistent with known structural information specific to nanodiamonds.

[0085] <2-1> "Analysis, Identification, and Examples of Analysis" When the Raman spectra of the nanodiamonds obtained in Examples 1 to 7 were measured, they all showed peaks characteristic of known nanodiamonds.

[0086] ≪Analysis using TEM≫ For TEM reaction analysis, a CMOS camera (OneView, 4096×4096 pixels, Gatan / AMETEK) was used to continuously capture images at frame rates of 2, 25, and / or 50 frames / second. TEM reaction analysis was performed at low magnification (80k~300k), with an electron dose rate (EDR) of 4.0×10⁻¹⁰. 4 ~8.0×10 5 e - nm -2 s -1 That's what I decided.

[0087] At 100K, a cryo-TEM holder using liquid nitrogen (Gatan626 Cryo-holder) was employed. TEM images were analyzed using digital micrograph software (Gatan) and ImageJ software.

[0088] ≪Reaction Analysis≫ For the reaction rate analysis, the area and volume of diamond particles were analyzed from TEM image data using ImageJ software. The analysis procedure is shown in (I) to (VI) below. (I) Images from frames 2-5 were combined, and the image contrast was adjusted. (II) Bandpass filtering was applied (filtering structures with more than 40 pixels and less than 3 pixels). (III) The images were binarized by thresholding based on the size of the diamond particles in each frame. (IV) The area of ​​each particle was measured using the "Analyze Particles" function. In the figure, N refers to the number of particles measured. (V) The volume of the sphere was calculated based on the area of ​​each particle. (VI) The volume in each frame was normalized using the last frame captured as the maximum value, and the size of the diamond was evaluated. The reaction rate constant was determined by linear fitting of the data in the nucleation stage. Representative examples are shown for conversion rates of 10% and 100%.

[0089] The roundness of the nanodiamonds in Example 7, as determined from TEM images, was approximately 85-98%.

[0090] ≪Structural analysis≫ Structural analysis was performed using TEM at high magnification (1M-2M), with an electron dose rate (EDR) of 1.0 × 10⁻¹⁴. 6 ~8.0×10 7 e - nm -2 s -1 The range was set to this extent. This allowed for structural analysis of nanodiamonds in both real lattice space and reciprocal lattice space (Figure 5).

[0091] In electron diffraction, the intensity of the diffraction spot was measured using the "Measure Stack" function in ImageJ. The background intensity was manually subtracted, and the decay rate constant was determined by linear fitting. The activation energy (Ea) and frequency factor (ln(A)) were calculated from the Arrhenius plot.

[0092] <3> Electron-mediated CH / CH coupling of adamantane TEM analysis suggests that the adamantane-nanodiamond reaction can be divided into two stages: (1) a nucleation stage dominated by the adamantane-adamantane reaction, and (2) a growth stage in which nanodiamonds are formed. The reaction kinetic analysis was limited to the first stage, the nucleation stage.

[0093] Temperature conditions of 100K, 10 -5 The results of electron-mediated CH / CH coupling of adamantane under vacuum conditions below Pa are shown below.

[0094] As a scheme for electron beam-mediated CH / CH coupling of adamantane molecules to nanodiamonds, Figure 1 shows the formation of oligomers from adamantane or didamantane, and Figure 2 shows the growth of progressively larger nanodiamonds from left to right.

[0095] The product was analyzed using aberration-corrected TEM for atomic resolution analysis, revealing the nanodiamond structure. Figure 2 (left) shows a TEM image of a defect-free nanodiamond composed of approximately 20 adamantane molecules, obtained by irradiating an adamantane crystal (Ad Crystals) with an electron beam. Figure 2 (center) shows a nanodiamond composed of approximately 2000 adamantane molecules (Ad~ 2000 TEM images of nanodiamonds synthesized from ) are shown.

[0096] Unlike nanodiamonds synthesized from approximately 2000 adamantane molecules, Figure 2 (right) shows a TEM image of twins constructed from a cubic crystal.

[0097] Figure 3 shows ED images of adamantane crystal, amorphous adamantane, and nanodiamond under an accelerating voltage of 200 kV. The ED measurements showed that the obtained nanodiamonds were identical to the macroscopic nanodiamond sample down to the {135} diffraction pattern. In this application, half-life refers to the electron dose at which the intensity drops to half of the initial intensity in electron diffraction, and to the electron dose at which half the time has passed since the raw material was completely consumed in real-time TEM analysis.

[0098] Figure 4 shows an image taken by TEM 114 seconds after the start of electron beam irradiation. The three-dimensional structure of the nanodiamonds is clearly visible.

[0099] Figure 5 shows a TEM image and structural model of a single crystal of nanodiamond. The {100}, {101}, and {121} lattice planes of the nanodiamond are shown in the TEM image.

[0100] Figure 6 shows a TEM image of the bonding growth of nanodiamond single crystals. Figure 6A shows the image taken by TEM 15 seconds after the start of electron beam irradiation. Figure 6B shows the FFT image of the region corresponding to the dotted line in Figure 6A. Figure 6C shows the time dependence of the angle in the FFT image obtained in Figure 6B. Figure 6D shows the circularity of the nanodiamond particles observed by TEM.

[0101] Figure 7 shows an SEM image of nanodiamond obtained at 1 kV.

[0102] Figure 8 shows an SEM image of nanodiamonds obtained at 15kV.

[0103] As shown in Figures 7 and 8, as the nanodiamond crystal growth neared its end, some of the nanodiamonds aggregated into spherical twins with a diameter of 20 nm or less, until all the adamantane molecules were consumed. When deuterated adamantane-D16 was used, kinetic isotope effects were observed.

[0104] As shown in Figure 9A, the total electron dose (TED50) required to convert 50% of adamantane is equivalent to the 10 required for nanodiamond formation (dia.formation) compared to amorphous crystal disorder. 5 e - nm 2 10, which is 130 times larger than 7 e - nm 2 It required that.

[0105] Figure 9B shows plots of normalized particle number and diameter against reaction progress in studies using adamantane as a precursor. The plots for gray diamonds are shown under conditions of 200 keV / 296 K, white diamonds under 80 keV / 296 K, gray circles under 200 keV / 100 K, and white circles under 80 keV / 100 K. The horizontal axis in Figure 9B represents the conversion rate.

[0106] Figure 10 shows the relative standard distribution of particle size against the normalized reaction progress in a study using adamantane as a precursor. The horizontal axis of Figure 10 represents the conversion rate.

[0107] Figure 11A shows the temperature dependence of the rate constant in the adamantane polymerization reaction under 200 keV conditions, and Figure 11B shows the temperature dependence under 80 keV conditions. The vertical axis in Figures 11A and B shows the conversion rates in Ada.

[0108] As shown in Figure 12, analysis using the Arrhenius plot revealed that under 200 keV and 80 keV conditions, the Arrhenius activity energy was Ea = 0.40 and 1.68 kJ / mol, and the frequency factor A (PEF = -17.3, -17.1, A = 3.1, 3.7 × 10) was -8 nm 2 / e - ) was.

[0109] Figure 13 A and B contain adamantane (H 16 ) and Adamantane-D16(D 16 An analysis was conducted on the temperature dependence of the rate constant in the polymerization reaction of ) under 200 keV and 80 keV conditions. The lower conversion rate of adamantane-D16 indicates a kinetic isotope effect. Furthermore, a comparison of the polymerization reactions of adamantane and adamantane-D16 suggests that carbon-hydrogen covalent bonds remain on the surface of the nanodiamonds. In other words, nanodiamonds derived from adamantane-based compounds have carbon-hydrogen covalent bonds on their surface, and it is determined that the surface of the nanodiamonds is composed of hydrogen.

[0110] Figure 14 shows the estimated sequential reaction mechanism in the polymerization reaction of adamantane.

[0111] Electrons ionize the adamantane molecule, generating adamantane radical cations and electrons. Subsequently, these radical cations and electrons cause the rate-determining CH bond to break, generating adamantyl radical and a hydrogen radical. After that, it is thought that adamantane dimer and hydrogen gas are produced.

[0112] Adamantane molecules bond together, much like LEGO® blocks, to form defect-free nanodiamonds (NDs). Given that adamantane is readily obtainable from the thermal decomposition of petroleum and natural gas, this mild and rational approach to nanodiamonds is expected to contribute to accelerating nanodiamond research, which has already attracted considerable attention in many basic and applied studies. [Industrial applicability]

[0113] This disclosure provides a novel method for producing nanodiamonds, which can be widely used in a wide range of industrial fields, including electronics, optics, and biomedical applications.

Claims

1. A method for producing nanodiamonds, comprising irradiating a cyclic aliphatic hydrocarbon compound with an electron beam to generate nanodiamonds from the cyclic aliphatic hydrocarbon compound, The aforementioned cyclic aliphatic hydrocarbon compound is sp ３ A method for producing nanodiamonds, which are cyclic aliphatic hydrocarbon compounds containing carbon.

2. The aforementioned cyclic aliphatic hydrocarbon compound, sp ３ It has a three-dimensional structure containing carbon and a six-membered ring, or three or more six-membered rings are sp ３ A method for producing nanodiamonds according to claim 1, wherein the compound has a polycyclic hydrocarbon skeleton formed by condensation through carbon linkage.

3. A method for producing nanodiamonds according to claim 1, comprising generating nanodiamonds from a cyclic aliphatic hydrocarbon compound by irradiating it with an electron beam in an energy range of 1 eV to 500 keV.

4. The current density of the electron beam is 10 －3 A / cm ２ ~10 ５ A / cm ２ The method for producing nanodiamonds according to claim 1.

5. The total electron dose (TED) of the irradiated electron beam is 10 ２ ~10 １０ e － nm －２ The method for producing nanodiamond according to claim 1, wherein the total electron dose (TED) of the irradiated electron beam is 10

6. The method for producing nanodiamonds according to claim 1, wherein the cyclic aliphatic hydrocarbon compound is an adamantane-based compound.

7. The adamantane compound is selected from the group consisting of adamantane, diamantane, triamantane, and their derivatives, as well as combinations thereof. The derivative is selected from a derivative in which at least one carbon atom and hydrogen atom of the adamantane compound is substituted with a heteroatom, and a derivative having substituents. The heteroatom is selected from nitrogen, phosphorus, silicon, sulfur, oxygen, and boron. The substituent is selected from an aryl group, a hydroxycarbonyl group, an amino group, and a halogen atom. The method for producing nanodiamonds according to claim 6, wherein the aryl group and the amino group may or may not have further substituents.

8. A method for producing nanodiamonds according to any one of claims 1 to 7, wherein the cyclic aliphatic hydrocarbon compound is irradiated with the electron beam under temperature conditions of 200°C or less.

9. 10 －８ Pa-10 －２ A method for producing nanodiamonds according to any one of claims 1 to 7, comprising irradiating with the electron beam for 1 second to 1 hour under a vacuum of Pa.

10. A method for producing nanodiamonds according to any one of claims 1 to 7, wherein the acceleration voltage of the electron beam is 10V to 300kV.

11. The process includes coating the substrate with the cyclic aliphatic hydrocarbon compound before irradiation with the electron beam, A method for producing nanodiamonds according to any one of claims 1 to 7, comprising irradiating the substrate with the electron beam to form a nanodiamond thin film containing at least one of the solitary nanodiamond particles or aggregates of the solitary particles.

12. The method for producing nanodiamonds according to claim 11, wherein the grain size of the nanodiamonds contained in the nanodiamond thin film is 1 nm or more and less than 1,000 nm, and the crystallinity of the nanodiamond thin film is 60% to 100%.

13. The method for producing nanodiamonds according to claim 11, wherein the surface roughness of the nanodiamond thin film is 0.1 nm to 100.0 nm.

14. The method for producing nanodiamonds according to claim 11, wherein the thickness of the nanodiamond thin film is 1 nm to 1 μm.

15. A method for producing nanodiamonds according to claim 11, comprising the step of doping the nanodiamonds by using an additive or by post-modification.

16. Nanodiamonds are formed by the polymerization of structural units made of adamantane compounds.

17. The nanodiamond according to claim 16, wherein the particle shape is spherical and the roundness is in the range of 70 to 100%.

18. The nanodiamond according to claim 16, wherein the conversion rate of the adamantane-based compound to the nanodiamond is 90% or more.

19. The nanodiamond according to claim 16, wherein the surface of the nanodiamond has a carbon-hydrogen covalent bond.

20. A nanodiamond thin film comprising the nanodiamond described in any one of claims 16 to 19, The aforementioned isolated nanodiamond particles, or aggregates thereof, The crystal grain size of the nanodiamond thin film is from 1 nm to 1000 nm. The crystallinity of the nanodiamond thin film is 60% to 100%. A nanodiamond thin film having a surface roughness of 0.1 nm to 100 nm.

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