JP4730618B2 - Method for producing fine particles - Google Patents
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- JP4730618B2 JP4730618B2 JP2007028882A JP2007028882A JP4730618B2 JP 4730618 B2 JP4730618 B2 JP 4730618B2 JP 2007028882 A JP2007028882 A JP 2007028882A JP 2007028882 A JP2007028882 A JP 2007028882A JP 4730618 B2 JP4730618 B2 JP 4730618B2
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- 239000010419 fine particle Substances 0.000 title claims description 145
- 238000004519 manufacturing process Methods 0.000 title claims description 29
- 239000003446 ligand Substances 0.000 claims description 63
- 239000006185 dispersion Substances 0.000 claims description 40
- 239000011241 protective layer Substances 0.000 claims description 38
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 36
- 239000002904 solvent Substances 0.000 claims description 27
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 24
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 23
- 239000002612 dispersion medium Substances 0.000 claims description 23
- 238000001556 precipitation Methods 0.000 claims description 23
- FUZZWVXGSFPDMH-UHFFFAOYSA-N hexanoic acid Chemical compound CCCCCC(O)=O FUZZWVXGSFPDMH-UHFFFAOYSA-N 0.000 claims description 22
- 239000003054 catalyst Substances 0.000 claims description 20
- 238000000034 method Methods 0.000 claims description 19
- WRIDQFICGBMAFQ-UHFFFAOYSA-N (E)-8-Octadecenoic acid Natural products CCCCCCCCCC=CCCCCCCC(O)=O WRIDQFICGBMAFQ-UHFFFAOYSA-N 0.000 claims description 16
- LQJBNNIYVWPHFW-UHFFFAOYSA-N 20:1omega9c fatty acid Natural products CCCCCCCCCCC=CCCCCCCCC(O)=O LQJBNNIYVWPHFW-UHFFFAOYSA-N 0.000 claims description 16
- QSBYPNXLFMSGKH-UHFFFAOYSA-N 9-Heptadecensaeure Natural products CCCCCCCC=CCCCCCCCC(O)=O QSBYPNXLFMSGKH-UHFFFAOYSA-N 0.000 claims description 16
- 239000005642 Oleic acid Substances 0.000 claims description 16
- ZQPPMHVWECSIRJ-UHFFFAOYSA-N Oleic acid Natural products CCCCCCCCC=CCCCCCCCC(O)=O ZQPPMHVWECSIRJ-UHFFFAOYSA-N 0.000 claims description 16
- QXJSBBXBKPUZAA-UHFFFAOYSA-N isooleic acid Natural products CCCCCCCC=CCCCCCCCCC(O)=O QXJSBBXBKPUZAA-UHFFFAOYSA-N 0.000 claims description 16
- ZQPPMHVWECSIRJ-KTKRTIGZSA-N oleic acid Chemical compound CCCCCCCC\C=C/CCCCCCCC(O)=O ZQPPMHVWECSIRJ-KTKRTIGZSA-N 0.000 claims description 16
- 238000003786 synthesis reaction Methods 0.000 claims description 16
- 230000015572 biosynthetic process Effects 0.000 claims description 15
- 238000005119 centrifugation Methods 0.000 claims description 15
- 239000002041 carbon nanotube Substances 0.000 claims description 13
- QGLWBTPVKHMVHM-KTKRTIGZSA-N (z)-octadec-9-en-1-amine Chemical compound CCCCCCCC\C=C/CCCCCCCCN QGLWBTPVKHMVHM-KTKRTIGZSA-N 0.000 claims description 12
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 12
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 9
- BMVXCPBXGZKUPN-UHFFFAOYSA-N 1-hexanamine Chemical compound CCCCCCN BMVXCPBXGZKUPN-UHFFFAOYSA-N 0.000 claims description 7
- FERIUCNNQQJTOY-UHFFFAOYSA-N Butyric acid Chemical compound CCCC(O)=O FERIUCNNQQJTOY-UHFFFAOYSA-N 0.000 claims description 6
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
- 150000001412 amines Chemical class 0.000 claims description 6
- 150000007524 organic acids Chemical class 0.000 claims description 5
- 150000003573 thiols Chemical class 0.000 claims description 5
- HQABUPZFAYXKJW-UHFFFAOYSA-N butan-1-amine Chemical compound CCCCN HQABUPZFAYXKJW-UHFFFAOYSA-N 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 239000011859 microparticle Substances 0.000 claims description 2
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- 230000001376 precipitating effect Effects 0.000 claims 1
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- 229910052751 metal Inorganic materials 0.000 description 23
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- 239000002105 nanoparticle Substances 0.000 description 19
- 239000000126 substance Substances 0.000 description 19
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- 239000000243 solution Substances 0.000 description 14
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- 239000002244 precipitate Substances 0.000 description 11
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- POILWHVDKZOXJZ-ARJAWSKDSA-M (z)-4-oxopent-2-en-2-olate Chemical compound C\C([O-])=C\C(C)=O POILWHVDKZOXJZ-ARJAWSKDSA-M 0.000 description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- 229910021645 metal ion Inorganic materials 0.000 description 7
- 238000004062 sedimentation Methods 0.000 description 7
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- 239000003638 chemical reducing agent Substances 0.000 description 6
- 230000012010 growth Effects 0.000 description 6
- 239000002994 raw material Substances 0.000 description 6
- -1 Organic acid salts Chemical class 0.000 description 5
- 238000004220 aggregation Methods 0.000 description 5
- 230000002776 aggregation Effects 0.000 description 5
- 125000000217 alkyl group Chemical group 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
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- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 238000004090 dissolution Methods 0.000 description 4
- 239000010936 titanium Substances 0.000 description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 3
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 3
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- 239000012298 atmosphere Substances 0.000 description 3
- 125000004429 atom Chemical group 0.000 description 3
- 230000003197 catalytic effect Effects 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 229910021389 graphene Inorganic materials 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 230000005291 magnetic effect Effects 0.000 description 3
- 125000000896 monocarboxylic acid group Chemical group 0.000 description 3
- 230000006911 nucleation Effects 0.000 description 3
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- 238000000746 purification Methods 0.000 description 3
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- NKJOXAZJBOMXID-UHFFFAOYSA-N 1,1'-Oxybisoctane Chemical compound CCCCCCCCOCCCCCCCC NKJOXAZJBOMXID-UHFFFAOYSA-N 0.000 description 2
- BTOOAFQCTJZDRC-UHFFFAOYSA-N 1,2-hexadecanediol Chemical compound CCCCCCCCCCCCCCC(O)CO BTOOAFQCTJZDRC-UHFFFAOYSA-N 0.000 description 2
- XWAMHGPDZOVVND-UHFFFAOYSA-N 1,2-octadecanediol Chemical compound CCCCCCCCCCCCCCCCC(O)CO XWAMHGPDZOVVND-UHFFFAOYSA-N 0.000 description 2
- DWANEFRJKWXRSG-UHFFFAOYSA-N 1,2-tetradecanediol Chemical compound CCCCCCCCCCCCC(O)CO DWANEFRJKWXRSG-UHFFFAOYSA-N 0.000 description 2
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000012296 anti-solvent Substances 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- 239000002872 contrast media Substances 0.000 description 2
- WNAHIZMDSQCWRP-UHFFFAOYSA-N dodecane-1-thiol Chemical compound CCCCCCCCCCCCS WNAHIZMDSQCWRP-UHFFFAOYSA-N 0.000 description 2
- POULHZVOKOAJMA-UHFFFAOYSA-N dodecanoic acid Chemical compound CCCCCCCCCCCC(O)=O POULHZVOKOAJMA-UHFFFAOYSA-N 0.000 description 2
- 239000002657 fibrous material Substances 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000011541 reaction mixture Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- DUFCMRCMPHIFTR-UHFFFAOYSA-N 5-(dimethylsulfamoyl)-2-methylfuran-3-carboxylic acid Chemical compound CN(C)S(=O)(=O)C1=CC(C(O)=O)=C(C)O1 DUFCMRCMPHIFTR-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- 239000005639 Lauric acid Substances 0.000 description 1
- OYHQOLUKZRVURQ-HZJYTTRNSA-N Linoleic acid Chemical compound CCCCC\C=C/C\C=C/CCCCCCCC(O)=O OYHQOLUKZRVURQ-HZJYTTRNSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- MQRWBMAEBQOWAF-UHFFFAOYSA-N acetic acid;nickel Chemical compound [Ni].CC(O)=O.CC(O)=O MQRWBMAEBQOWAF-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 230000003698 anagen phase Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 150000001722 carbon compounds Chemical class 0.000 description 1
- 239000011362 coarse particle Substances 0.000 description 1
- ZUKDFIXDKRLHRB-UHFFFAOYSA-K cobalt(3+);triacetate Chemical compound [Co+3].CC([O-])=O.CC([O-])=O.CC([O-])=O ZUKDFIXDKRLHRB-UHFFFAOYSA-K 0.000 description 1
- QAHREYKOYSIQPH-UHFFFAOYSA-L cobalt(II) acetate Chemical compound [Co+2].CC([O-])=O.CC([O-])=O QAHREYKOYSIQPH-UHFFFAOYSA-L 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 235000014113 dietary fatty acids Nutrition 0.000 description 1
- USIUVYZYUHIAEV-UHFFFAOYSA-N diphenyl ether Chemical compound C=1C=CC=CC=1OC1=CC=CC=C1 USIUVYZYUHIAEV-UHFFFAOYSA-N 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- JRBPAEWTRLWTQC-UHFFFAOYSA-N dodecylamine Chemical compound CCCCCCCCCCCCN JRBPAEWTRLWTQC-UHFFFAOYSA-N 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
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- 229930195729 fatty acid Natural products 0.000 description 1
- 239000000194 fatty acid Substances 0.000 description 1
- 150000004665 fatty acids Chemical class 0.000 description 1
- VEPSWGHMGZQCIN-UHFFFAOYSA-H ferric oxalate Chemical compound [Fe+3].[Fe+3].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O VEPSWGHMGZQCIN-UHFFFAOYSA-H 0.000 description 1
- 230000005294 ferromagnetic effect Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052735 hafnium Inorganic materials 0.000 description 1
- NXKAMHRHVYEHER-UHFFFAOYSA-J hafnium(4+);disulfate Chemical compound [Hf+4].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O NXKAMHRHVYEHER-UHFFFAOYSA-J 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 150000002505 iron Chemical class 0.000 description 1
- OWZIYWAUNZMLRT-UHFFFAOYSA-L iron(2+);oxalate Chemical compound [Fe+2].[O-]C(=O)C([O-])=O OWZIYWAUNZMLRT-UHFFFAOYSA-L 0.000 description 1
- AQBLLJNPHDIAPN-LNTINUHCSA-K iron(3+);(z)-4-oxopent-2-en-2-olate Chemical compound [Fe+3].C\C([O-])=C\C(C)=O.C\C([O-])=C\C(C)=O.C\C([O-])=C\C(C)=O AQBLLJNPHDIAPN-LNTINUHCSA-K 0.000 description 1
- LNOZJRCUHSPCDZ-UHFFFAOYSA-L iron(ii) acetate Chemical compound [Fe+2].CC([O-])=O.CC([O-])=O LNOZJRCUHSPCDZ-UHFFFAOYSA-L 0.000 description 1
- OYHQOLUKZRVURQ-IXWMQOLASA-N linoleic acid Natural products CCCCC\C=C/C\C=C\CCCCCCCC(O)=O OYHQOLUKZRVURQ-IXWMQOLASA-N 0.000 description 1
- 235000020778 linoleic acid Nutrition 0.000 description 1
- 230000005381 magnetic domain Effects 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
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- 239000002088 nanocapsule Substances 0.000 description 1
- 239000002707 nanocrystalline material Substances 0.000 description 1
- 229940078494 nickel acetate Drugs 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- BBJSDUUHGVDNKL-UHFFFAOYSA-J oxalate;titanium(4+) Chemical compound [Ti+4].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O BBJSDUUHGVDNKL-UHFFFAOYSA-J 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- DCKVFVYPWDKYDN-UHFFFAOYSA-L oxygen(2-);titanium(4+);sulfate Chemical compound [O-2].[Ti+4].[O-]S([O-])(=O)=O DCKVFVYPWDKYDN-UHFFFAOYSA-L 0.000 description 1
- RBFRVUKIVGOWND-UHFFFAOYSA-L oxygen(2-);vanadium(4+);sulfate Chemical compound [O-2].[V+4].[O-]S([O-])(=O)=O RBFRVUKIVGOWND-UHFFFAOYSA-L 0.000 description 1
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Images
Description
本発明は、微粒子の製造方法に関し、さらに詳しくは、カーボンナノチューブ合成用触媒、高密度磁気記録媒体、蛍光体、浄化触媒、医療用造影剤などに用いることができる直径及び標準偏差が制御された微粒子の製造方法に関する。 The present invention relates to a method for producing fine particles. More specifically, the diameter and standard deviation that can be used for a carbon nanotube synthesis catalyst, a high-density magnetic recording medium, a phosphor, a purification catalyst, a medical contrast agent, and the like are controlled. The present invention relates to a method for producing fine particles.
ナノメートルオーダーの直径を有する微粒子は、通常のバルク体では考えられない性質を示すことから、様々な応用が期待されている。例えば、高比表面積に起因する高い触媒能は排ガス浄化触媒や有機合成触媒として、強磁性体微粒子における単磁区構造は高密度磁気記録媒体として、量子サイズ効果による発色現象はディスプレイ用蛍光体として、また可視光域に表面プラズモン共鳴吸収を有する微粒子の超格子構造は光デバイスとして、の利用が考えられている。また、最近ではこれらの応用に加わり、極めて優れた物性を有することで様々の分野での利用が期待されているカーボンナノチューブ（ＣＮＴ）の直径を精密に制御するための成長用触媒としての利用も提案されている。
これらの微粒子応用においては、ほぼすべて、粒子径の分布が狭いことが必要とされている。なぜなら、微粒子に特徴的な諸性質はその大きさに強く依存し、粒子同士が超格子構造を形成する際には微粒子の大きさのばらつきが配列の規則性を決定する要因になるからである。また、ＣＮＴ成長用触媒への利用においては、粒子径のばらつきがそのままＣＮＴ径に反映されるからである。そのため、所望の粒径、許容できるサイズ分布の微粒子を作製することは重要な問題である。
上記に示した様々な応用がある中で、本発明ではＣＮＴ成長用触媒としての微粒子を合成しているため、以下、ＣＮＴに関して詳細に説明する。
Fine particles having a diameter on the order of nanometers exhibit properties that cannot be considered in ordinary bulk bodies, and thus are expected to be used in various applications. For example, the high catalytic capacity due to the high specific surface area is used as an exhaust gas purification catalyst or an organic synthesis catalyst, the single magnetic domain structure in the ferromagnetic fine particles is used as a high-density magnetic recording medium, the coloring phenomenon due to the quantum size effect is used as a display phosphor, The superlattice structure of fine particles having surface plasmon resonance absorption in the visible light region is considered to be used as an optical device. Recently, in addition to these applications, it can also be used as a growth catalyst to precisely control the diameter of carbon nanotubes (CNTs) that are expected to be used in various fields due to their excellent physical properties. Proposed.
Nearly all of these fine particle applications require a narrow distribution of particle sizes. This is because various properties characteristic of fine particles strongly depend on the size, and when the particles form a superlattice structure, the variation in the size of the fine particles becomes a factor determining the regularity of the arrangement. . In addition, when used for a CNT growth catalyst, the variation in particle diameter is directly reflected in the CNT diameter. Therefore, it is an important problem to produce fine particles having a desired particle size and an acceptable size distribution.
Among the various applications described above, since the present invention synthesizes fine particles as a catalyst for CNT growth, the CNT will be described in detail below.
カーボンナノチューブは、黒鉛の一層に相当するグラフェンシート（炭素原子が六角網目状に配列したシート）を筒状に丸めた立体構造を持つ。ＣＮＴは、１枚の円筒状グラフェンシートからなる単層ＣＮＴと、複数枚の円筒状グラフェンシートが同心円状に重なった多層ＣＮＴとがある。また、合成された未処理のＣＮＴの先端は、通常、「キャップ」と呼ばれる半球状のグラファイト層で閉じられた構造になっている。 The carbon nanotube has a three-dimensional structure in which a graphene sheet corresponding to one layer of graphite (a sheet in which carbon atoms are arranged in a hexagonal network) is rolled into a cylindrical shape. The CNT includes a single-walled CNT made of one cylindrical graphene sheet and a multi-walled CNT in which a plurality of cylindrical graphene sheets are concentrically overlapped. In addition, the tip of the synthesized unprocessed CNT usually has a structure closed with a hemispherical graphite layer called “cap”.
ＣＮＴは、ｎｍオーダーの直径と、μｍ〜ｃｍオーダーの長さを有しており、アスペクト比が極めて大きく、先端の曲率半径が数ｎｍ〜数十ｎｍと極めて小さいという特徴がある。ＣＮＴは、機械的にも強靱で、化学的・熱的安定性に優れ、円筒部のらせん構造に応じて金属にも半導体にもなるという特徴がある。そのため、ＣＮＴは、発光デバイス用の電子配線材料、放熱材料、繊維材料、電子放出源（面光源）、トランジスタ材料、電子顕微鏡用の電子放出源（点光源）、あるいは、ＳＰＭ用の探針等への応用が期待されている。 CNTs have a diameter on the order of nm and a length on the order of μm to cm, have an extremely large aspect ratio, and have a feature that the radius of curvature of the tip is as small as several nm to several tens of nm. CNT is mechanically tough, has excellent chemical and thermal stability, and is characterized by being both a metal and a semiconductor depending on the helical structure of the cylindrical portion. Therefore, CNT is an electronic wiring material for a light emitting device, a heat dissipation material, a fiber material, an electron emission source (surface light source), a transistor material, an electron emission source for an electron microscope (point light source), a probe for SPM, etc. Application to is expected.
ＣＮＴを合成する方法には、
（１）Ａｒや水素等の気体雰囲気中において炭素棒間でアーク放電を行わせ、陰極上にＣＮＴを堆積させるアーク法、
（２）触媒を混ぜたグラファイトの表面にＹＡＧレーザー等の強いパルス光を当て、これにより発生した炭素の煙を電気炉で加熱し、反応管の側壁にＣＮＴを付着させるレーザー蒸発法、
（３）触媒金属微粒子上で炭素化合物（例えば、メタン、アセチレン、ベンゼンなど）を熱分解させる化学気相成長法、
などが知られている。
To synthesize CNT,
(1) An arc method in which arc discharge is performed between carbon rods in a gas atmosphere such as Ar or hydrogen, and CNTs are deposited on the cathode;
(2) A laser evaporation method in which a strong pulsed light such as a YAG laser is applied to the surface of the graphite mixed with the catalyst, the generated carbon smoke is heated in an electric furnace, and CNTs adhere to the side walls of the reaction tube.
(3) a chemical vapor deposition method in which a carbon compound (for example, methane, acetylene, benzene, etc.) is thermally decomposed on catalytic metal fine particles,
Etc. are known.
（１）及び（２）の合成法により得られるＣＮＴは、いずれも完全にランダムな方向を向いて絡み合った状態になっている。また、多量のカーボンナノカプセルやアモルファス粒子等を含んでいる場合もある。一方、ＣＮＴの持つ究極の異方性を最大限に引き出すためには、多数本のＣＮＴを基材表面に配向させることが望ましい。また、ＣＮＴを電子配線材料、放熱材料、繊維材料等に応用する場合において、高電流密度、高熱伝導性、高強度等を得るためには、ＣＮＴを基板表面に高密度に生成させることが望ましく、（３）の化学気相成長法がこの目的に適する。さらに、ＣＮＴの特性は直径に依存するので、ＣＮＴ合成時にＣＮＴの直径を任意に制御できることが望ましい。そのためには、ＣＮＴ合成用触媒の直径及び標準偏差を高い精度で制御する必要がある。 The CNTs obtained by the synthesis methods (1) and (2) are both in a state of being intertwined in a completely random direction. Moreover, it may contain a large amount of carbon nanocapsules, amorphous particles, and the like. On the other hand, in order to maximize the ultimate anisotropy of CNTs, it is desirable to orient a large number of CNTs on the substrate surface. In addition, when applying CNTs to electronic wiring materials, heat dissipation materials, fiber materials, etc., in order to obtain high current density, high thermal conductivity, high strength, etc., it is desirable to generate CNTs at a high density on the substrate surface. The chemical vapor deposition method (3) is suitable for this purpose. Furthermore, since the characteristics of CNT depend on the diameter, it is desirable that the CNT diameter can be arbitrarily controlled during CNT synthesis. For this purpose, it is necessary to control the diameter and standard deviation of the CNT synthesis catalyst with high accuracy.
そこでこの問題を解決するために、従来から種々の提案がなされている。
例えば、特許文献１には、ＣＮＴ合成用触媒ではないが、
（１） 鉄（III）アセチルアセトナート、１，２−ヘキサデカンジオール、オレイン酸、オレイルアミン及びジオクチルエーテルをガラス容器中で混合し、
（２） ３０分間加熱還流した後、反応混合物を室温まで冷却し、
（３） 反応混合物にエタノールを加えて黒い生成物を遠心分離で分離し、
（４） 黒い生成物をヘキサン中で、オレイン酸とオレイルアミンの存在下で分散させる
Ｆｅ3Ｏ4ナノ結晶材料の製造方法が開示されている。
同文献には、安定剤／鉄塩の比や反応温度を変えることにより、直径１２ｎｍまでの様々なサイズのＦｅ3Ｏ4を作製できる点が記載されている。
In order to solve this problem, various proposals have heretofore been made.
For example, Patent Document 1 is not a CNT synthesis catalyst,
(1) Iron (III) acetylacetonate, 1,2-hexadecanediol, oleic acid, oleylamine and dioctyl ether are mixed in a glass container,
(2) After heating to reflux for 30 minutes, the reaction mixture is cooled to room temperature,
(3) Add ethanol to the reaction mixture and separate the black product by centrifugation;
(4) A method for producing a Fe 3 O 4 nanocrystalline material in which a black product is dispersed in hexane in the presence of oleic acid and oleylamine is disclosed.
This document describes that various sizes of Fe 3 O 4 up to 12 nm in diameter can be produced by changing the stabilizer / iron salt ratio and the reaction temperature.
また、非特許文献１には、ＣＮＴ合成用触媒ではないが、
（１） ＦｅＣｌ3とＦｅＣｌ2の濃度比が２：１である溶液にアンモニアを加えて粒子を生成させ、生成した粒子を蒸留水で数回洗浄し、
（２） 水性の粒子を希薄アンモニア水に再分散させて、これに過剰のオレイン酸を添加して攪拌し、
（３） ｐＨが僅かに酸性となるまで懸濁液にゆっくりと１Ｍ ＨＣｌを添加し、油状の黒い析出物を沈殿させ、
（４） 析出した粒子をヘキサンに分散させ、この溶液にヘキサンとほぼ同量の貧溶媒（アセトン）を加えて混合し、遠心分離により粗大粒子を析出させる
磁性粒子の製造方法が開示されている。
同文献には、１回の貧溶媒の添加及び遠心分離によって６ｎｍのＦｅ3Ｏ4ナノ粒子が得られる点、及び、貧溶媒の添加及び遠心分離を４回繰り返すことによって、２ｎｍのＦｅ3Ｏ4ナノ粒子が得られる点が記載されている。
Moreover, although it is not a catalyst for CNT synthesis in Non-Patent Document 1,
(1) Ammonia is added to a solution in which the concentration ratio of FeCl 3 and FeCl 2 is 2: 1 to generate particles, and the generated particles are washed several times with distilled water,
(2) Aqueous particles are redispersed in dilute aqueous ammonia, and excess oleic acid is added and stirred.
(3) Slowly add 1M HCl to the suspension until the pH is slightly acidic to precipitate an oily black precipitate,
(4) A method for producing magnetic particles is disclosed in which precipitated particles are dispersed in hexane, a poor solvent (acetone) of approximately the same amount as hexane is added to and mixed with this solution, and coarse particles are precipitated by centrifugation. .
In this document, 6 nm Fe 3 O 4 nanoparticles can be obtained by one addition of anti-solvent and centrifugation, and 2 nm of Fe 3 O is obtained by repeating the addition of anti-solvent and centrifugation four times. It describes that 4 nanoparticles can be obtained.
液相法で均一な直径の微粒子を作製するには、粒子の核生成期と成長期を分離することが重要である。すなわち、まず、多数の核を生成させ、次いで、生成した核の成長を同時に開始させることが重要である。しかしながら、実際の粒子合成において核生成を完全に一致させることは不可能であり、結果として合成される粒子にはバラツキが生じる。これは、より小さな粒子を合成する際に大きな問題となる。
すなわち、核生成期の初期と後期で形成された粒子間の粒径差は、その後の成長期の間も保持される。従って、粒径が大きい場合には、平均粒径に対する粒径差（標準偏差に相当）は、相対的に小さくなり、直径はほぼ均一となる。一方、小さな粒子では、粒径に対する粒径差は、相対的に大きくなり、均一なものが得られにくくなる。
In order to produce fine particles with a uniform diameter by the liquid phase method, it is important to separate the nucleation phase and the growth phase of the particles. That is, it is important to first generate a large number of nuclei and then to start the growth of the generated nuclei simultaneously. However, it is impossible to completely match nucleation in actual particle synthesis, resulting in variations in the synthesized particles. This is a major problem when synthesizing smaller particles.
That is, the particle size difference between the particles formed in the early and late nucleation periods is maintained during the subsequent growth period. Therefore, when the particle size is large, the particle size difference (corresponding to the standard deviation) with respect to the average particle size is relatively small, and the diameter is substantially uniform. On the other hand, with small particles, the particle size difference with respect to the particle size becomes relatively large, and it becomes difficult to obtain uniform particles.
この問題を解決するために、非特許文献１に記載されているように、様々な粒径を持つ粒子を合成した後、微粒子を溶媒に分散させて分散液とし、この分散液に貧溶媒を加えて分級する方法が知られている。しかしながら、従来の方法では、より小さな粒子を分級しようとする場合、分級能が低下するという問題がある。 In order to solve this problem, as described in Non-Patent Document 1, after synthesizing particles having various particle sizes, fine particles are dispersed in a solvent to form a dispersion, and a poor solvent is added to the dispersion. In addition, a classification method is known. However, the conventional method has a problem that the classification ability is lowered when trying to classify smaller particles.
本発明が解決しようとする課題は、相対的に粒径が小さく、かつ、粒度分布の狭い微粒子を製造することが可能な微粒子の製造方法を提供することにある。
また、本発明が解決しようとする他の課題は、より小さな粒子を分級しようとする場合であっても分級能が低下しにくい微粒子の製造方法を提供することにある。
The problem to be solved by the present invention is to provide a method for producing fine particles capable of producing fine particles having a relatively small particle size and a narrow particle size distribution.
Another problem to be solved by the present invention is to provide a method for producing fine particles in which the classification ability is not easily lowered even when trying to classify smaller particles.
上記課題を解決するために本発明に係る微粒子の製造方法は、
第１の配位子からなる第１の保護層で被覆された微粒子を第１の分散媒に分散させた第１の分散液を得る分散工程と、
前記第１の分散液中において、前記微粒子の周囲を被覆する前記第１の保護層を、前記第１の配位子より長さの短い第２の配位子からなる第２の保護層に交換する配位子交換工程と、
配位子交換された前記微粒子を第２の分散媒中に再分散させた第２の分散液を得る再分散工程と、
前記第２の分散液に第１の貧溶媒を添加し、前記第２の保護層で被覆された前記微粒子を分別沈殿させる分別沈殿工程と
を備えていることを要旨とする。
In order to solve the above problems, the method for producing fine particles according to the present invention comprises:
A dispersion step of obtaining a first dispersion in which fine particles coated with a first protective layer comprising a first ligand are dispersed in a first dispersion medium;
In the first dispersion, the first protective layer covering the periphery of the fine particles is replaced with a second protective layer made of a second ligand having a shorter length than the first ligand. A ligand exchange step to exchange;
A redispersion step of obtaining a second dispersion in which the ligand-exchanged fine particles are redispersed in a second dispersion medium;
And a fractional precipitation step in which a first poor solvent is added to the second dispersion, and the fine particles covered with the second protective layer are fractionally precipitated.
一般に、ナノメートルサイズの微粒子を合成する際には、合成中又は合成後における微粒子の凝集を防ぐために、オレイン酸やオレイルアミン又はドデカンチオールなどの長鎖のアルキル基を持つ有機物（第１の配位子）が保護層として用いられる。オレイン酸やオレイルアミンは、微粒子の表面に配位していると考えられているので、微粒子の見かけの半径は、微粒子の真の半径に保護層の厚さを加えたものとなる。一方、液中における微粒子の沈降速度は、微粒子の見かけの半径の２乗に比例する。そのため、微粒子の真の半径が小さくなる程、微粒子間の見かけの半径の相対的な大きさの違いは真の半径差に比べて小さくなり、分級能が低下する。
これに対し、相対的に長さの長い有機物（第１の配位子）で保護された微粒子を合成した後、保護層を第１の配位子より長さの短い有機物（第２の配位子）に配位子交換すると、微粒子の真の半径が相対的に小さい場合であっても、微粒子の見かけの半径の相対的な大きさの違いを大きくすることができる。そのため、平均粒径の小さい微粒子を分級する場合であっても微粒子の分級能が向上し、より粒度分布の狭い微粒子を効率よく得ることができる。
In general, when synthesizing nanometer-sized fine particles, an organic substance having a long-chain alkyl group such as oleic acid, oleylamine, or dodecanethiol (first coordination) is used to prevent aggregation of fine particles during or after synthesis. Child) is used as a protective layer. Since oleic acid and oleylamine are thought to be coordinated on the surface of the fine particles, the apparent radius of the fine particles is the true radius of the fine particles plus the thickness of the protective layer. On the other hand, the sedimentation rate of the fine particles in the liquid is proportional to the square of the apparent radius of the fine particles. Therefore, the smaller the true radius of the fine particles, the smaller the relative difference in the apparent radius between the fine particles, compared with the true radius difference, and the classification ability decreases.
On the other hand, after synthesizing fine particles protected with a relatively long organic substance (first ligand), the protective layer is formed with an organic substance (second alignment) having a shorter length than the first ligand. When the ligand is exchanged with a ligand, the difference in the relative size of the apparent radius of the fine particles can be increased even when the true radius of the fine particles is relatively small. Therefore, even when fine particles having a small average particle diameter are classified, the ability to classify the fine particles can be improved, and fine particles having a narrower particle size distribution can be obtained efficiently.
以下に、本発明の一実施の形態について詳細に説明する。
初めに、第１の配位子からなる第１の保護層で被覆された微粒子の製造方法について説明する。
保護層で被覆された微粒子の製造方法には、微粒子合成後に微粒子の周囲に第１の配位子を配位させる方法と、第１の配位子が共存する条件下で微粒子を合成する方法とがある。後者の方法は、特に、直径が１５ｎｍ以下である微粒子の製造方法として好適である。以下に、後者の方法について詳細に説明する。
Hereinafter, an embodiment of the present invention will be described in detail.
First, a method for producing fine particles covered with the first protective layer made of the first ligand will be described.
The method for producing the fine particles coated with the protective layer includes a method of coordinating the first ligand around the fine particles after the fine particles are synthesized, and a method of synthesizing the fine particles under the condition that the first ligand coexists. There is. The latter method is particularly suitable as a method for producing fine particles having a diameter of 15 nm or less. Hereinafter, the latter method will be described in detail.
［１． 溶解・混合工程］
まず、金属源と、アルコールと、有機物（第１の配位子）とを有機溶媒中で溶解・混合する（溶解・混合工程）。
金属源には、微粒子を構成する少なくとも１つの金属元素を含み、有機溶媒に可溶な化合物を用いる。微粒子が２種以上の金属元素を含む場合、金属源には、２種以上の化合物を用いても良い。
金属源としては、具体的には、
（１） 金属元素（Ｍ）のイオン又はＭＯイオンに有機物が配位した有機錯体、
（２） 金属元素の有機酸塩
などがある。
[1. Dissolution / mixing process]
First, a metal source, an alcohol, and an organic substance (first ligand) are dissolved and mixed in an organic solvent (dissolution / mixing step).
As the metal source, a compound that contains at least one metal element constituting the fine particles and is soluble in an organic solvent is used. When the fine particles contain two or more kinds of metal elements, two or more kinds of compounds may be used as the metal source.
Specifically, as a metal source,
(1) An organic complex in which an organic substance is coordinated to an ion of a metal element (M) or an MO ion,
(2) Organic acid salts of metal elements.
金属源には、合成しようとする微粒子の用途、組成、要求特性等に応じて、最適なものを選択する。
例えば、微粒子をＣＮＴ合成用触媒として用いる場合、金属源には、Ｆｅ、Ｃｏ及びＮｉから選ばれる１以上の第１元素を含む１種又は２種以上の原料を用いるのが好ましい。さらに、４Ａ族元素（Ｔｉ、Ｚｒ、Ｈｆ）及び５Ａ族元素（Ｖ、Ｎｂ、Ｔａ）から選ばれる１以上の第２元素を加えることで触媒の活性度をより向上させることができる。
第１元素を含む有機錯体としては、具体的には、Ｆｅ(III)アセチルアセトナート、Ｆｅ(II)アセチルアセトナート、Ｃｏ(II)アセチルアセトナート、Ｃｏ(III)アセチルアセトナート、Ｎｉ(II)アセチルアセトナートなどがある。
第１元素を含む有機酸塩としては、具体的には、酢酸鉄(II)、シュウ酸鉄(II)、シュウ酸鉄(III)、酢酸コバルト(II)、酢酸コバルト(III)、酢酸ニッケル(II)などがある。
第２元素を含む有機錯体としては、具体的には、ＶＯアセチルアセトナート、ＴｉＯアセチルアセトナート、Ｚｒトリフルオロアセチルアセトナート、Ｈｆトリフルオロアセチルアセトナート、Ｔｉジイソプロポオキサイドビステトラメチルヘプタンジオネートなどがある。
第２元素を含む有機酸塩としては、具体的には、シュウ酸チタン、硫酸チタン、酸化硫酸バナジウム、硫酸バナジウム、酢酸ジルコニウム、硫酸ハフニウムなどがある。
As the metal source, an optimal metal source is selected according to the application, composition, required characteristics, etc. of the fine particles to be synthesized.
For example, when the fine particles are used as a catalyst for CNT synthesis, it is preferable to use one or more raw materials containing one or more first elements selected from Fe, Co, and Ni as the metal source. Furthermore, the activity of the catalyst can be further improved by adding one or more second elements selected from Group 4A elements (Ti, Zr, Hf) and Group 5A elements (V, Nb, Ta).
Specific examples of the organic complex containing the first element include Fe (III) acetylacetonate, Fe (II) acetylacetonate, Co (II) acetylacetonate, Co (III) acetylacetonate, Ni (II ) Acetylacetonate.
Specific examples of the organic acid salt containing the first element include iron (II) acetate, iron (II) oxalate, iron (III) oxalate, cobalt (II) acetate, cobalt (III) acetate, nickel acetate. (II).
Specific examples of the organic complex containing the second element include VO acetylacetonate, TiO acetylacetonate, Zr trifluoroacetylacetonate, Hf trifluoroacetylacetonate, Ti diisopropoxide bistetramethylheptanedionate. and so on.
Specific examples of the organic acid salt containing the second element include titanium oxalate, titanium sulfate, vanadium oxide sulfate, vanadium sulfate, zirconium acetate, and hafnium sulfate.
金属源として２種以上の化合物を用いる場合、金属源の配合比は、合成しようとする微粒子の用途、組成、要求特性等に応じて最適なものを選択する。
例えば、第１元素と第２元素とを含むＣＮＴ合成用触媒を合成する場合において、微粒子中に複数の第１元素が含まれるときには、それらの比率は任意に選択することができる。同様に、微粒子中に複数の第２元素が含まれるときには、それらの比率は任意に選択することができる。
When two or more kinds of compounds are used as the metal source, the optimum mixing ratio of the metal source is selected according to the application, composition, required characteristics, etc. of the fine particles to be synthesized.
For example, in the case of synthesizing a CNT synthesis catalyst containing a first element and a second element, when a plurality of first elements are contained in the fine particles, their ratio can be arbitrarily selected. Similarly, when a plurality of second elements are contained in the fine particles, their ratio can be arbitrarily selected.
一方、微粒子中に含まれる第１元素と第２元素の比率は、触媒活性度に影響を与える。Ｆｅ等の８〜１０族元素に４Ａ族元素又は５Ａ族元素を添加することによって触媒活性が向上するのは、Ｔｉ等の４Ａ族元素及びＶ等の５Ａ族元素は、いずれも炭素との親和力が強く、炭化物が形成される際に熱を発生するためと考えられる。このような効果を得るためには、第２元素の含有量（＝第２元素の原子数×１００／（第１元素の原子数＋第２元素の原子数））は、２ａｔ％以上が好ましい。
一方、第２元素の含有量が過剰になると、触媒活性度はかえって低下する。従って、第２元素の含有量は、５０ａｔ％以下が好ましい。
なお、触媒活性度を向上させる効果に加えて、４Ａ族元素（特に、Ｔｉ）にはＣＮＴの成長速度を増大させる効果があり、５Ａ族元素（特に、Ｖ）には合成されたＣＮＴの直径制御性を向上させる効果がある。
On the other hand, the ratio of the first element and the second element contained in the fine particles affects the catalyst activity. The catalytic activity is improved by adding a group 4A element or a group 5A element to a group 8-10 element such as Fe or the like. Both the group 4A element such as Ti and the group 5A element such as V have an affinity for carbon. This is considered to be because heat is generated when carbide is formed. In order to obtain such an effect, the content of the second element (= number of atoms of the second element × 100 / (number of atoms of the first element + number of atoms of the second element)) is preferably 2 at% or more. .
On the other hand, when the content of the second element is excessive, the catalyst activity is lowered. Accordingly, the content of the second element is preferably 50 at% or less.
In addition to the effect of improving the catalyst activity, the group 4A element (especially Ti) has the effect of increasing the growth rate of CNT, and the group 5A element (particularly V) has a diameter of the synthesized CNT. There is an effect of improving controllability.
アルコールは、金属源を還元し、有機溶媒中において金属イオン又はＭＯイオンを非イオンの状態にするための還元剤である。還元剤には、１種類のアルコールを用いても良く、あるいは、２種以上を組み合わせて用いても良い。
還元剤として使用可能なアルコールとしては、具体的には、１，２−ヘキサデカンジオール、１，２−オクタデカンジオール、１，２−テトラデカンジオールなどがある。
Alcohol is a reducing agent for reducing a metal source and bringing a metal ion or MO ion into a nonionic state in an organic solvent. As the reducing agent, one kind of alcohol may be used, or two or more kinds may be used in combination.
Specific examples of the alcohol that can be used as the reducing agent include 1,2-hexadecanediol, 1,2-octadecanediol, and 1,2-tetradecanediol.
「有機物（第１の配位子）」は、有機酸、有機アミン、及び／又はチオールからなる。有機物には、１種類の有機酸、有機アミン又はチオールを用いても良く、あるいは、２種以上を組み合わせて用いても良い。有機物は、生成した粒子の表面に配位し、第１の保護層となる。
保護層は、主として、微粒子を合成する際に微粒子の凝集を抑制し、粒子径を均一にする作用、及び、後述する分散液中に分散させる際に微粒子の凝集を抑制する作用を有する。このような効果を得るためには、有機物は、相対的に長さ（分子長）の長いものが好ましい。また、保護層は、１種類の有機物からなるものでも良く、あるいは、２種以上の有機物からなるものでも良い。特に、２種以上の有機物を保護層として用いると、微粒子の粒子径が安定化し、均一化するという利点がある。
The “organic substance (first ligand)” includes an organic acid, an organic amine, and / or a thiol. One kind of organic acid, organic amine or thiol may be used for the organic substance, or two or more kinds may be used in combination. The organic matter is coordinated on the surface of the generated particles and becomes the first protective layer.
The protective layer mainly has an action of suppressing the aggregation of the fine particles when synthesizing the fine particles, making the particle diameter uniform, and an action of suppressing the aggregation of the fine particles when dispersed in a dispersion described later. In order to obtain such an effect, the organic substance preferably has a relatively long length (molecular length). Further, the protective layer may be composed of one kind of organic substance, or may be composed of two or more kinds of organic substance. In particular, when two or more organic substances are used as the protective layer, there is an advantage that the particle diameter of the fine particles is stabilized and uniformized.
有機酸としては、具体的には、ＲＣＯＯＨ、ＲＳＯＨ、ＲＰＯＨなどの脂肪酸（Ｒは、アルキル鎖（ＣＨ3(ＣＨ2)x−）を表す）がある。
有機アミンとしては、具体的には、ＲＮＨ2、Ｒ2ＮＨ、Ｒ3Ｎなどの脂肪アミン（Ｒは、アルキル鎖（ＣＨ3(ＣＨ2)x−）を表す）などがある。
チオールとしては、具体的には、Ｒ−ＳＨ（Ｒは、アルキル鎖（ＣＨ3(ＣＨ2)x−）を表す）などがある。
合成時に使用する有機酸としては、特に、オレイン酸、カプロン酸、ラウリン酸、酪酸、リノール酸などが好適である。
また、合成時に使用する有機アミンとしては、特に、オレイルアミン、ヘキシルアミン、ラウリルアミンなどが好適である。
微粒子の粒子径を安定化させるためには、有機物には、オレイン酸とオレイルアミンを組み合わせて用いるのが好ましい。また、粒子によっては（金の場合）、チオールが使われる場合もある。
Specific examples of the organic acid include fatty acids such as RCOOH, RSOH, and RPOH (R represents an alkyl chain (CH 3 (CH 2 ) x —)).
Specific examples of the organic amine include fatty amines such as RNH 2 , R 2 NH, and R 3 N (R represents an alkyl chain (CH 3 (CH 2 ) x —)).
Specific examples of the thiol include R—SH (where R represents an alkyl chain (CH 3 (CH 2 ) x —)).
As the organic acid used in the synthesis, oleic acid, caproic acid, lauric acid, butyric acid, linoleic acid and the like are particularly suitable.
Moreover, as an organic amine used at the time of synthesis, oleylamine, hexylamine, laurylamine and the like are particularly suitable.
In order to stabilize the particle diameter of the fine particles, it is preferable to use a combination of oleic acid and oleylamine as the organic substance. Some particles (in the case of gold) use thiols.
有機溶媒は、上述した金属源、アルコール及び有機物（第１の配位子）を溶解可能なものであればよい。また、溶液は、後述するように所定の温度に加熱されるので、沸点が２００℃以上である溶媒を用いるのが好ましい。有機溶媒としては、具体的には、オクチルエーテル、フェニルエーテルなどがある。これらの有機溶媒は、それぞれ単独で用いても良く、あるいは、２種以上を組み合わせて用いても良い。 The organic solvent should just be what can melt | dissolve the metal source mentioned above, alcohol, and organic substance (1st ligand). Further, since the solution is heated to a predetermined temperature as described later, it is preferable to use a solvent having a boiling point of 200 ° C. or higher. Specific examples of the organic solvent include octyl ether and phenyl ether. These organic solvents may be used alone or in combination of two or more.
溶液中における金属源の濃度は、作製しようとする微粒子の直径、標準偏差等に応じて最適な濃度を選択する。一般に、希薄溶液を用いると、粒径のそろった均一な微粒子が得られる。金属源に加える有機溶媒の量は、金属源の種類にもよるが、通常、金属源１ｍｍｏｌに対して、１０〜５０ｍＬ程度である。
アルコール（還元剤）は、上述したように溶液中に含まれる金属イオン又はＭＯイオンに電子を与え、非イオンの状態にするためのものである。金属イオン又はＭＯイオンが還元されると、これらが互いに集まって微粒子を形成する。還元剤の添加量は、金属源及びその他の原料の種類にもよるが、通常、溶液中に含まれる金属イオン又はＭＯイオンのモル数の１〜２０倍程度である。
有機物（第１の配位子）は、溶液中において金属イオン又はＭＯイオンと結合すると考えられている。この溶液中にさらに還元剤が加えられると、金属イオン又はＭＯイオンが還元されて微粒子状に凝集すると同時に、微粒子の周囲が第１の配位子からなる第１の保護層で被覆された状態となる。有機物の添加量は、金属源及びその他の原料の種類にもよるが、通常、溶液中に含まれる金属イオン又はＭＯイオンのモル数の１〜１０倍程度である。
As the concentration of the metal source in the solution, an optimum concentration is selected according to the diameter, standard deviation, etc. of the fine particles to be produced. In general, when a dilute solution is used, uniform fine particles having a uniform particle diameter can be obtained. The amount of the organic solvent added to the metal source is usually about 10 to 50 mL with respect to 1 mmol of the metal source, although it depends on the type of the metal source.
The alcohol (reducing agent) is for giving electrons to the metal ions or MO ions contained in the solution as described above to make them non-ionic. When metal ions or MO ions are reduced, they gather together to form fine particles. The amount of the reducing agent added is usually about 1 to 20 times the number of moles of metal ions or MO ions contained in the solution, although depending on the types of the metal source and other raw materials.
The organic substance (first ligand) is considered to bind to metal ions or MO ions in the solution. When a reducing agent is further added to this solution, metal ions or MO ions are reduced and aggregated into fine particles, and at the same time, the periphery of the fine particles is covered with the first protective layer made of the first ligand. It becomes. The amount of the organic substance added is usually about 1 to 10 times the number of moles of metal ions or MO ions contained in the solution, although depending on the types of the metal source and other raw materials.
［２． 加熱工程］
次に、溶解・混合工程で得られた均一な溶液を、不活性雰囲気下において１８０℃〜３００℃で加熱する（加熱工程）。加熱により溶液中に、第１の保護層で被覆された微粒子が生成する。
溶液の加熱は、溶液中で生成した微粒子の酸化を防ぐために不活性雰囲気下（例えば、窒素雰囲気下、アルゴン雰囲気下など）で行う。
加熱温度は、使用する原料の種類や目的とする直径に応じて、最適な温度を選択する。一般に、加熱温度が低すぎると、原料間の反応が不十分となる。原料間の反応を効率よく進行させるためには加熱温度は、１８０℃以上が好ましい。
一方、加熱温度が高すぎると、微粒子の凝集が進行し、粒子の直径が不均質になる。従って、加熱温度は、３００℃以下が好ましい。
[2. Heating process]
Next, the uniform solution obtained in the dissolution / mixing step is heated at 180 ° C. to 300 ° C. in an inert atmosphere (heating step). By heating, fine particles covered with the first protective layer are generated in the solution.
The solution is heated under an inert atmosphere (for example, under a nitrogen atmosphere or an argon atmosphere) in order to prevent oxidation of fine particles generated in the solution.
As the heating temperature, an optimum temperature is selected according to the type of raw material used and the target diameter. Generally, when the heating temperature is too low, the reaction between the raw materials becomes insufficient. In order to advance the reaction between the raw materials efficiently, the heating temperature is preferably 180 ° C. or higher.
On the other hand, when the heating temperature is too high, the aggregation of the fine particles proceeds, and the diameter of the particles becomes non-uniform. Therefore, the heating temperature is preferably 300 ° C. or lower.
溶解・混合工程及び加熱工程の条件を最適化すると、合成された微粒子の直径及び標準偏差を制御することができる。
後述する方法を用いて、微粒子を効率よく分級するためには、分級前の微粒子の直径（保護層を除いた、微粒子の真の直径（コア直径））は、０．５〜１５ｎｍが好ましく、さらに好ましくは、０．５〜５ｎｍである。
また、分級前の微粒子の直径の標準偏差（微粒子のコア直径の標準偏差）は、１．０ｎｍ以下が好ましく、さらに好ましくは、０．５ｎｍ以下である。
When the conditions of the dissolution / mixing step and the heating step are optimized, the diameter and standard deviation of the synthesized fine particles can be controlled.
In order to efficiently classify the fine particles using the method described later, the diameter of the fine particles before classification (the true diameter of the fine particles (core diameter excluding the protective layer)) is preferably 0.5 to 15 nm. More preferably, it is 0.5-5 nm.
Further, the standard deviation of the diameter of the fine particles before classification (standard deviation of the core diameter of the fine particles) is preferably 1.0 nm or less, and more preferably 0.5 nm or less.
次に、本発明に係る微粒子の製造方法について説明する。本発明に係る微粒子の製造方法は、分散工程と、配位子交換工程と、再分散工程と、分別沈殿工程とを備えている。 Next, the method for producing fine particles according to the present invention will be described. The method for producing fine particles according to the present invention includes a dispersion step, a ligand exchange step, a redispersion step, and a fractional precipitation step.
［１． 分散工程］
分散工程は、第１の配位子からなる第１の保護層で被覆された微粒子を第１の分散媒に分散させた第１の分散液を得る工程である。
第１の分散媒は、微粒子を均一に分散させることが可能なものであればよい。例えば、微粒子が無極性である場合又は極性が低い場合、第１の分散媒には、ヘキサン、トルエン、クロロホルムなどの極性の低い有機溶媒を用いるのが好ましい。これらは、単独で用いても良く、あるいは、２種以上を組み合わせて用いても良い。
第１の分散媒の量は、配位子交換効率が最も高くなるように、微粒子の組成及び大きさ、第１の分散媒の種類等に応じて、最適な量を選択する。一般に、第１の分散媒の量が少なすぎると、微粒子を十分に分散させることができない。一方、第１の分散媒の量が過剰になると、かえって配位子交換効率が低下する。通常、第１の分散媒の量は、微粒子１０ｍｇに対して、１ｍＬ〜１０００ｍＬ程度である。
[1. Dispersion process]
The dispersion step is a step of obtaining a first dispersion liquid in which fine particles coated with the first protective layer made of the first ligand are dispersed in a first dispersion medium.
The first dispersion medium may be any medium that can uniformly disperse the fine particles. For example, when the fine particles are nonpolar or have a low polarity, it is preferable to use an organic solvent having a low polarity such as hexane, toluene, or chloroform as the first dispersion medium. These may be used alone or in combination of two or more.
The amount of the first dispersion medium is selected in accordance with the composition and size of the fine particles, the type of the first dispersion medium, and the like so that the ligand exchange efficiency is the highest. In general, if the amount of the first dispersion medium is too small, the fine particles cannot be sufficiently dispersed. On the other hand, when the amount of the first dispersion medium is excessive, the ligand exchange efficiency is lowered. Usually, the amount of the first dispersion medium is about 1 to 1000 mL with respect to 10 mg of fine particles.
［２． 配位子交換工程］
配位子交換工程は、第１の分散液中において、微粒子の周囲を被覆する第１の保護層を、第１の配位子より長さの短い第２の配位子からなる第２の保護層に交換する工程である。
第２の配位子には、第１の配位子より長さの短いものを用いる。
例えば、第１の配位子がオレイン酸（Ｃ8Ｈ17ＣＨ＝ＣＨ(ＣＨ2)7ＣＯＯＨ）及びオレイルアミン（Ｃ18Ｈ35ＮＨ2）の混合物である場合、第２の配位子には、
（１）カプロン酸（Ｃ5Ｈ11ＣＯＯＨ）及びヘキシルアミン（Ｃ6Ｈ13ＮＨ2）の混合物、
（２）ブタン酸（Ｃ3Ｈ7ＣＯＯＨ）及びブチルアミン（Ｃ4Ｈ9ＮＨ2）の混合物、
などを用いるのが好ましい。
[2. Ligand exchange process]
In the ligand exchange step, in the first dispersion liquid, the first protective layer covering the periphery of the fine particles is formed of a second ligand composed of a second ligand having a shorter length than the first ligand. This is a step of replacing the protective layer.
As the second ligand, one having a shorter length than the first ligand is used.
For example, when the first ligand is a mixture of oleic acid (C 8 H 17 CH═CH (CH 2 ) 7 COOH) and oleylamine (C 18 H 35 NH 2 ), the second ligand includes ,
(1) a mixture of caproic acid (C 5 H 11 COOH) and hexylamine (C 6 H 13 NH 2 );
(2) a mixture of butanoic acid (C 3 H 7 COOH) and butylamine (C 4 H 9 NH 2 ),
Etc. are preferably used.
第１の分散液に第２の配位子を添加し、所定温度で所定時間加熱すると、配位子交換が起こり、第２の配位子からなる第２の保護層で被覆された微粒子が得られる。
第１の分散液への第２の配位子の添加量は、第１の分散液中の第１の配位子よりも大過剰とする。通常、第２の配位子の添加量は、第１の配位子の１０〜１００倍程度である。
また、加熱温度及び加熱時間は、第１の分散媒の種類、第２の配位子の種類及びその添加量等に応じて、最適な条件を選択する。通常、配位子交換は、分散液を室温〜１００℃で０．１〜４８時間程度還流することにより行う。
When the second ligand is added to the first dispersion and heated at a predetermined temperature for a predetermined time, ligand exchange occurs, and the fine particles covered with the second protective layer made of the second ligand are formed. can get.
The amount of the second ligand added to the first dispersion is larger than that of the first ligand in the first dispersion. Usually, the addition amount of the second ligand is about 10 to 100 times that of the first ligand.
In addition, the heating temperature and the heating time are selected optimally according to the type of the first dispersion medium, the type of the second ligand, the amount added, and the like. Usually, ligand exchange is performed by refluxing the dispersion at room temperature to 100 ° C. for about 0.1 to 48 hours.
配位子交換終了後、分散液から微粒子を回収し、微粒子の洗浄を行う。洗浄は、配位子交換により微粒子から分離した第１の配位子、及び、余分な第２の配位子を除去するために行う。微粒子の回収方法及び洗浄方法は、特に限定されるものではないが、配位子交換終了後の第１の分散液に多量の貧溶媒（例えば、エタノール）を加えて、遠心分離を行うのが好ましい。 After completing the ligand exchange, the fine particles are collected from the dispersion and washed. The washing is performed in order to remove the first ligand and excess second ligand separated from the fine particles by ligand exchange. The method for collecting and washing the fine particles is not particularly limited, but a large amount of poor solvent (for example, ethanol) is added to the first dispersion after completion of the ligand exchange, followed by centrifugation. preferable.
［３． 再分散工程］
再分散工程は、配位子交換された微粒子を第２の有機溶媒中に再分散させた第２の分散液を得る工程である。
第２の分散媒は、微粒子を均一に分散させることが可能なものであればよい。例えば、微粒子が無極性である場合又は極性が低い場合、第２の分散媒には、ヘキサン、トルエン、クロロホルムなどの極性の低い有機溶媒を用いるのが好ましい。これらは、単独で用いても良く、あるいは、２種以上を組み合わせて用いても良い。
第２の分散媒の量は、分級効率が最も高くなるように、微粒子の組成及び大きさ、第２の分散媒の種類等に応じて、最適な量を選択する。一般に、第２の分散媒の量が少なすぎると、微粒子を十分に分散させることができない。一方、第２の分散媒の量が過剰になると、かえって分級効率が低下する。通常、第２の分散媒の量は、微粒子１０ｍｇに対して、１ｍＬ〜１０００ｍＬ程度である。
ここで、配位子交換工程における貧溶媒添加、遠心分離、再分散工程を複数回繰り返すことで、分散媒中の第１の配位子及び余分な第２の配位子をより少なくすることができる。
[3. Redispersion process]
The redispersion step is a step of obtaining a second dispersion in which the ligand-exchanged fine particles are redispersed in the second organic solvent.
The second dispersion medium may be any medium that can uniformly disperse the fine particles. For example, when the fine particles are nonpolar or have a low polarity, it is preferable to use an organic solvent having a low polarity such as hexane, toluene, or chloroform as the second dispersion medium. These may be used alone or in combination of two or more.
The amount of the second dispersion medium is selected in accordance with the composition and size of the fine particles, the type of the second dispersion medium, and the like so that the classification efficiency is the highest. In general, if the amount of the second dispersion medium is too small, the fine particles cannot be sufficiently dispersed. On the other hand, when the amount of the second dispersion medium is excessive, the classification efficiency is lowered. Usually, the amount of the second dispersion medium is about 1 to 1000 mL with respect to 10 mg of fine particles.
Here, the first and extra second ligands in the dispersion medium are reduced by repeating the poor solvent addition, centrifugation, and redispersion steps in the ligand exchange step a plurality of times. Can do.
［４． 分別沈殿工程］
分別沈殿工程は、第２の分散液に貧溶媒を添加し、第２の保護層で被覆された微粒子を分別沈殿させる工程である。
貧溶媒は、微粒子を沈殿させることが可能なものであればよい。例えば、微粒子が無極性である場合又は極性が低い場合、貧溶媒には、エタノール、メタノールなどの極性が高い有機溶媒を用いるのが好ましい。これらは、単独で用いても良く、あるいは、２種以上を組み合わせて用いても良い。
第２の分散液に貧溶媒を少量ずつ添加すると、サイズの大きな粒子から順次沈殿する。この時、貧溶媒の添加量が少なすぎると、微粒子の沈殿が得られず、分級効率が低下する。一方、貧溶媒の添加量が過剰になると、相対的に大きな粒子と小さな粒子が同時に沈降し、粒度分布の狭い微粒子が得られない。従って、貧溶媒の添加量は、第２の分散液中に含まれる微粒子の量、第２の分散媒の種類、貧溶媒の種類、要求される粒度分布等に応じて、最適な量を選択する。通常、貧溶媒の添加量は、第２の分散液１０ｍＬに対して、５〜 ３０ｍＬ程度である。
[4. Separation and precipitation process]
The fractional precipitation step is a step in which a poor solvent is added to the second dispersion and the fine particles coated with the second protective layer are fractionated and precipitated.
The poor solvent may be any one that can precipitate fine particles. For example, when the fine particles are nonpolar or have a low polarity, it is preferable to use an organic solvent having a high polarity such as ethanol or methanol as the poor solvent. These may be used alone or in combination of two or more.
When the poor solvent is added little by little to the second dispersion liquid, the particles are precipitated sequentially from large particles. At this time, if the addition amount of the poor solvent is too small, precipitation of fine particles cannot be obtained and the classification efficiency is lowered. On the other hand, when the amount of the poor solvent added is excessive, relatively large particles and small particles settle simultaneously, and fine particles having a narrow particle size distribution cannot be obtained. Therefore, the addition amount of the poor solvent is selected in accordance with the amount of fine particles contained in the second dispersion, the type of the second dispersion medium, the type of the poor solvent, the required particle size distribution, and the like. To do. Usually, the addition amount of a poor solvent is about 5-30 mL with respect to 10 mL of 2nd dispersion liquids.
第２の分散液に貧溶媒を少量ずつ添加すると、やがて第２の分散液が懸濁する。この状態で放置すると、サイズの大きな粒子が自然沈降する。また、第２の分散液が懸濁した後、第２の分散液に対して遠心分離を行い、沈殿を加速させても良い。
自然沈降又は遠心分離により、サイズの大きな粒子が沈殿した後、上澄み液を取り除く。沈殿は、再度、ヘキサン等の分散媒に分散させて、各種の用途に使用する。
一方、回収された上澄み液にさらに貧溶媒を少量添加すると、貧溶媒の添加量に応じて、さらにサイズの小さな粒子が沈殿する。この時、粒子を自然沈降させても良く、あるいは、遠心分離により沈殿を加速させても良い。以下、同様にして、上澄み液への貧溶媒の添加及び粒子の沈殿を繰り返すと、種々のサイズを有する微粒子の混合物から、特定の平均粒径を有する粒度分布の狭い微粒子を回収することができる。
When the poor solvent is added to the second dispersion little by little, the second dispersion eventually suspends. If left in this state, large particles will naturally settle. Further, after the second dispersion is suspended, the second dispersion may be centrifuged to accelerate the precipitation.
After large particles settle by natural sedimentation or centrifugation, the supernatant is removed. The precipitate is again dispersed in a dispersion medium such as hexane and used for various applications.
On the other hand, when a small amount of a poor solvent is further added to the collected supernatant, particles having a smaller size precipitate according to the amount of the poor solvent added. At this time, the particles may be allowed to settle naturally, or the precipitation may be accelerated by centrifugation. In the same manner, when the addition of the poor solvent to the supernatant and the precipitation of the particles are repeated, fine particles having a specific average particle size and a narrow particle size distribution can be recovered from a mixture of fine particles having various sizes. .
次に、本発明に係る微粒子の製造方法の作用について説明する。
粒子の沈降速度Ｖは、（１）式に示すストークスの式により表される。
Ｖ＝(２ｇＲ2)(ρ1−ρ2)／９μ ・・・（１）
但し、ｇは重力加速度、Ｒは粒子の半径、ρ1は粒子の密度、ρ2は溶媒の密度、μは溶媒の粘度である。
（１）式に示すように、沈降速度Ｖは、粒子半径Ｒの２乗に比例し、最も沈降速度に影響する。すなわち、粒子半径Ｒの差が大きくなる程、沈降速度の差も大きくなる。
Next, the operation of the method for producing fine particles according to the present invention will be described.
The sedimentation velocity V of the particles is expressed by the Stokes equation shown in the equation (1).
V = (2gR 2 ) (ρ 1 −ρ 2 ) / 9μ (1)
Where g is the gravitational acceleration, R is the particle radius, ρ 1 is the particle density, ρ 2 is the solvent density, and μ is the solvent viscosity.
As shown in the equation (1), the sedimentation velocity V is proportional to the square of the particle radius R and most affects the sedimentation velocity. That is, as the difference in particle radius R increases, the difference in sedimentation speed also increases.
一般に、ナノメートルサイズの微粒子を合成する際には、合成中又は合成後における微粒子の凝集を防ぐために、オレイン酸やオレイルアミン又はドデカンチオールなどの長鎖のアルキル基を持つ有機物（第１の配位子）が保護層として用いられる。オレイン酸やオレイルアミンは、微粒子の表面に配位していると考えられているので、微粒子の見かけの半径は、微粒子の真の半径（コアの半径）Ｒ1に保護層の厚さＲ2を加えたものとなる。この微粒子の見かけの半径が（１）式における粒子の半径Ｒに相当する。
従って、保護層の厚さＲ2に比べて微粒子の真の半径Ｒ1がはるかに大きい粒子を分級する時には、粒子半径Ｒ≒粒子の真の半径Ｒ1となるので、保護層の存在により分級能が低下することはない。一方、微粒子の真の半径Ｒ1が保護層の厚さＲ2と同等である微粒子では、微粒子間の真の半径Ｒ1の差が真の半径に対し相対的に大きい場合であっても、保護層を含めた粒子半径Ｒに対しその差は小さくなる。これは、保護層の存在によりサイズ分級能が低下することを意味する。
In general, when synthesizing nanometer-sized fine particles, an organic substance having a long-chain alkyl group such as oleic acid, oleylamine, or dodecanethiol (first coordination) is used to prevent aggregation of fine particles during or after synthesis. Child) is used as a protective layer. Since oleic acid and oleylamine are thought to be coordinated on the surface of the fine particles, the apparent radius of the fine particles is the true radius of the fine particles (core radius) R 1 and the thickness R 2 of the protective layer. It will be added. The apparent radius of the fine particles corresponds to the particle radius R in the equation (1).
Therefore, when classifying particles whose true radius R 1 of the fine particles is much larger than the thickness R 2 of the protective layer, since the particle radius R≈the true radius R 1 of the particles, classification is performed due to the presence of the protective layer. There is no decline in performance. On the other hand, in the fine particles in which the true radius R 1 of the fine particles is equal to the thickness R 2 of the protective layer, even if the difference in the true radius R 1 between the fine particles is relatively large with respect to the true radius, The difference is small with respect to the particle radius R including the protective layer. This means that the size classification ability decreases due to the presence of the protective layer.
例えば、真の直径（２Ｒ1）が３ｎｍと２ｎｍである二つの微粒子の直径差は、５０％（小さい粒子を基準とした場合）となる。これらの粒子が厚さ（Ｒ2）１．３ｎｍの保護層で被覆されていると、大きい粒子の全体の大きさは、３＋１．３＋１．３＝５．６ｎｍとなり、小さい粒子の全体の大きさは、２＋１．３＋１．３＝４．６ｎｍとなる。その結果、二つの微粒子の直径差は、２２％（小さい粒子を基準とした場合）となる。
なお、保護層とコアの密度に違いがあることから、保護層の厚さが変わると（１）式中の（ρ1−ρ2）項も変化し、沈降速度Ｖに影響するが、Ｒ2の影響が最も大きい。
For example, the difference in diameter between two fine particles having a true diameter (2R 1 ) of 3 nm and 2 nm is 50% (when small particles are used as a reference). When these particles are covered with a protective layer having a thickness (R 2 ) of 1.3 nm, the overall size of the large particles is 3 + 1.3 + 1.3 = 5.6 nm, and the overall size of the small particles Is 2 + 1.3 + 1.3 = 4.6 nm. As a result, the difference in diameter between the two fine particles is 22% (based on small particles).
In addition, since there is a difference in the density of the protective layer and the core, if the thickness of the protective layer changes, the (ρ 1 −ρ 2 ) term in the equation (1) also changes and affects the sedimentation velocity V. 2 has the greatest impact.
これに対し、相対的に長さの長い有機物（第１の配位子）で保護された微粒子を合成した後、保護層を第１の配位子より長さの短い有機物（第２の配位子）に配位子交換すると、保護層の厚さＲ2が薄くなるので、粒子半径Ｒの差が、コア半径Ｒ1の差に近づく。すなわち、微粒子の真の半径Ｒ1が相対的に小さい微粒子を分級する場合であっても、微粒子の見かけの半径Ｒの差を相対的に大きくすることができる。そのため、平均粒径の小さい微粒子を分級する場合であっても微粒子の分級能が向上し、より粒度分布の狭い微粒子を効率よく得ることができる。 On the other hand, after synthesizing fine particles protected with a relatively long organic substance (first ligand), the protective layer is formed with an organic substance (second alignment) having a shorter length than the first ligand. When the ligand is exchanged for the ligand, the thickness R 2 of the protective layer becomes thin, and therefore the difference in the particle radius R approaches the difference in the core radius R 1 . That is, even when fine particles having a relatively small true radius R 1 are classified, the difference in the apparent radius R of the fine particles can be made relatively large. Therefore, even when fine particles having a small average particle diameter are classified, the ability to classify the fine particles can be improved, and fine particles having a narrower particle size distribution can be obtained efficiently.
（実施例１、比較例１）
［１． 微粒子の分級］
液相法を用いて、オレイン酸及びオレイルアミンで保護されたナノ粒子（平均コア直径２．９ｎｍ、標準偏差０．７０ｎｍ）を合成した。次いで、このナノ粒子をヘキサン（５０ｍＬ）に分散させた。この分散液にカプロン酸及びヘキシルアミンのモル比１：１の混合液（１０ｇ）を溶かし、６０℃で１時間程度還流する加熱処理を行った（配位子交換）。処理後、分散液にエタノール（２００ｍＬ）を加えて遠心分離を行う操作を２回繰り返すことにより、微粒子を洗浄した。洗浄後、微粒子をヘキサン（５ｍＬ）に再分散させた。
(Example 1, Comparative Example 1)
[1. Fine particle classification]
Using the liquid phase method, nanoparticles protected with oleic acid and oleylamine (average core diameter 2.9 nm, standard deviation 0.70 nm) were synthesized. The nanoparticles were then dispersed in hexane (50 mL). A mixed solution (10 g) of caproic acid and hexylamine in a molar ratio of 1: 1 was dissolved in this dispersion, and heat treatment was performed by refluxing at 60 ° C. for about 1 hour (ligand exchange). After the treatment, the operation of adding ethanol (200 mL) to the dispersion and centrifuging was repeated twice to wash the fine particles. After washing, the microparticles were redispersed in hexane (5 mL).
次に、カプロン酸・ヘキシルアミン保護ナノ粒子のヘキサン分散液を遠心分離用の遠沈管に移し、これにエタノールを１ｍＬずつ加えていった。およそ５ｍＬのエタノールを加えると、分散液が懸濁し始めた。ここで遠心分離を行った。遠心分離終了後、上澄み液を取り除いて沈殿物を回収し、沈殿物をヘキサンに再分散させた。
一方、回収された上澄み液（およそ１０ｍＬ）を別の遠沈管に移し、これにさらに少量（１ｍＬ）のエタノールを加え、再度遠心分離を行った。遠心分離後、上澄み液を取り除いて沈殿物を回収し、沈殿物をヘキサンに再分散させた。以下、同様にして、上澄み液へのエタノールの添加及び遠心分離を複数回繰り返し、分別沈殿によるサイズ分級を行った（実施例１）。
また、配位子交換を行わなかった以外は、実施例１と同様の手順に従い、オレイン酸・オレイルアミン保護ナノ粒子の分別沈殿によるサイズ分級を行った。
Next, the hexane dispersion of caproic acid / hexylamine-protected nanoparticles was transferred to a centrifuge tube for centrifugation, and 1 mL of ethanol was added thereto. When approximately 5 mL of ethanol was added, the dispersion began to suspend. Centrifugation was performed here. After completion of the centrifugation, the supernatant was removed to collect the precipitate, and the precipitate was redispersed in hexane.
On the other hand, the collected supernatant (approximately 10 mL) was transferred to another centrifuge tube, and a small amount (1 mL) of ethanol was added thereto, followed by centrifugation again. After centrifugation, the supernatant was removed to collect the precipitate, and the precipitate was redispersed in hexane. Hereinafter, in the same manner, addition of ethanol to the supernatant and centrifugation were repeated a plurality of times, and size classification was performed by fractional precipitation (Example 1).
Further, size classification by fractional precipitation of oleic acid / oleylamine-protected nanoparticles was performed according to the same procedure as in Example 1 except that ligand exchange was not performed.
［２． 評価］
図１（ａ）及び図１（ｂ）に、それぞれ、カプロン酸及びヘキシルアミンを加えて加熱処理する前のナノ粒子、及び、加熱処理後洗浄したナノ粒子のＴＥＭ写真を示す。図１より、加熱処理によって粒子間隔が減少していることがわかる。これは、合成直後のオレイン酸・オレイルアミン保護ナノ粒子にカプロン酸及びヘキシルアミンを加えて加熱処理することにより配位子交換が行われ、保護層の厚さが薄いカプロン酸・ヘキシルアミン保護ナノ粒子が生成したためである。
[2. Evaluation]
FIG. 1A and FIG. 1B show TEM photographs of nanoparticles before heat treatment by adding caproic acid and hexylamine, and nanoparticles washed after heat treatment, respectively. As can be seen from FIG. 1, the particle spacing is reduced by the heat treatment. This is because caproic acid and hexylamine are added to the oleic acid / oleylamine-protected nanoparticles immediately after synthesis and heat-treated to exchange ligands, and the protective layer has a thin caproic acid / hexylamine-protected nanoparticle. This is because
図２（ａ）に、分別沈殿前のナノ粒子のＴＥＭ写真（左図）及び粒子径のヒストグラム（右図）を示す。また、図２（ｂ）に、５回目の分別沈殿後の沈殿物に含まれるオレイン酸・オレイルアミン保護ナノ粒子（比較例１）のＴＥＭ写真（左図）及びその粒子径のヒストグラム（右図）を示す。さらに、図２（ｃ）に、８回目の分別沈殿後の沈殿物に含まれるカプロン酸・ヘキシルアミン保護ナノ粒子（実施例１）のＴＥＭ写真（左図）及びその粒子径のヒストグラム（右図）を示す。
配位子交換を行わなかった比較例１の場合、平均コア直径２．８ｎｍ、直径標準偏差０．４４ｎｍであった。一方、配位子交換を行った実施例１の場合、平均コア直径２．６ｎｍ、直径標準偏差０．３０ｎｍであった。
図２より、分別沈殿を繰り返すことによりナノ粒子がサイズ分級されていることを確認した。また、配位子交換は、分級能の向上に極めて有効であることがわかった。
FIG. 2A shows a TEM photograph (left figure) and a particle diameter histogram (right figure) of nanoparticles before fractional precipitation. Moreover, in FIG.2 (b), the TEM photograph (left figure) of the oleic acid and oleylamine protection nanoparticle (comparative example 1) contained in the deposit after the 5th fractional precipitation, and the histogram of the particle diameter (right figure) Indicates. Further, FIG. 2 (c) shows a TEM photograph (left figure) of a caproic acid / hexylamine-protected nanoparticle (Example 1) contained in the precipitate after the eighth fractional precipitation and a histogram of the particle diameter (right figure). ).
In the case of Comparative Example 1 in which ligand exchange was not performed, the average core diameter was 2.8 nm and the diameter standard deviation was 0.44 nm. On the other hand, in the case of Example 1 in which ligand exchange was performed, the average core diameter was 2.6 nm, and the diameter standard deviation was 0.30 nm.
From FIG. 2, it was confirmed that the nanoparticles were classified by repeating the fractional precipitation. It was also found that ligand exchange is extremely effective in improving classification ability.
以上、本発明の実施の形態について詳細に説明したが、本発明は上記実施の形態に何ら限定されるものではなく、本発明の要旨を逸脱しない範囲で種々の改変が可能である。 Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.
本発明に係る微粒子の製造方法は、カーボンナノチューブ合成用触媒、高密度磁気記録媒体、蛍光体、浄化触媒、医療用造影剤などに用いられる微粒子の製造方法として用いることができる。 The method for producing fine particles according to the present invention can be used as a method for producing fine particles used for a catalyst for carbon nanotube synthesis, a high-density magnetic recording medium, a phosphor, a purification catalyst, a medical contrast agent, and the like.
Claims (13)
前記第１の分散液中において、前記微粒子の周囲を被覆する前記第１の保護層を、前記第１の配位子より長さの短い第２の配位子からなる第２の保護層に交換する配位子交換工程と、
配位子交換された前記微粒子を第２の分散媒中に再分散させた第２の分散液を得る再分散工程と、
前記第２の分散液に貧溶媒を添加し、前記第２の保護層で被覆された前記微粒子を分別沈殿させる分別沈殿工程と
を備えた微粒子の製造方法。 A dispersion step of obtaining a first dispersion in which fine particles coated with a first protective layer comprising a first ligand are dispersed in a first dispersion medium;
In the first dispersion, the first protective layer covering the periphery of the fine particles is replaced with a second protective layer made of a second ligand having a shorter length than the first ligand. A ligand exchange step to exchange;
A redispersion step of obtaining a second dispersion in which the ligand-exchanged fine particles are redispersed in a second dispersion medium;
A method for producing fine particles, comprising a fractional precipitation step of adding a poor solvent to the second dispersion and fractionally precipitating the fine particles coated with the second protective layer.
請求項１に記載の微粒子の製造方法。 The method for producing fine particles according to claim 1, wherein the fractional precipitation step is to precipitate the fine particles by centrifugation after adding the poor solvent to the second dispersion.
前記第２の配位子は、カプロン酸及びヘキシルアミン、又は、ブタン酸及びブチルアミンからなる請求項１から４までのいずれかに記載の微粒子の製造方法。 The first ligand consists of oleic acid and oleylamine,
The method for producing fine particles according to any one of claims 1 to 4, wherein the second ligand comprises caproic acid and hexylamine, or butanoic acid and butylamine.
The method for producing fine particles according to any one of claims 1 to 12, wherein the fine particles are used as a catalyst for carbon nanotube synthesis.
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