JP3790149B2 - Metal nano-sized particles and manufacturing method thereof - Google Patents
Metal nano-sized particles and manufacturing method thereof Download PDFInfo
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- JP3790149B2 JP3790149B2 JP2001337283A JP2001337283A JP3790149B2 JP 3790149 B2 JP3790149 B2 JP 3790149B2 JP 2001337283 A JP2001337283 A JP 2001337283A JP 2001337283 A JP2001337283 A JP 2001337283A JP 3790149 B2 JP3790149 B2 JP 3790149B2
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- 239000002245 particle Substances 0.000 title claims description 56
- 239000002105 nanoparticle Substances 0.000 title claims description 50
- 229910052751 metal Inorganic materials 0.000 title claims description 48
- 239000002184 metal Substances 0.000 title claims description 48
- 238000004519 manufacturing process Methods 0.000 title claims description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 62
- 239000002904 solvent Substances 0.000 claims description 46
- 239000006185 dispersion Substances 0.000 claims description 41
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 40
- 229910052802 copper Inorganic materials 0.000 claims description 40
- 239000010949 copper Substances 0.000 claims description 40
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 33
- 229910052759 nickel Inorganic materials 0.000 claims description 31
- 229910017052 cobalt Inorganic materials 0.000 claims description 27
- 239000010941 cobalt Substances 0.000 claims description 27
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 27
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 23
- 239000011593 sulfur Substances 0.000 claims description 23
- 229910052717 sulfur Inorganic materials 0.000 claims description 23
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 20
- 150000003839 salts Chemical class 0.000 claims description 14
- 150000001875 compounds Chemical class 0.000 claims description 13
- 239000002798 polar solvent Substances 0.000 claims description 13
- 239000002244 precipitate Substances 0.000 claims description 11
- -1 fluorocarbon compound Chemical class 0.000 claims description 9
- 238000006722 reduction reaction Methods 0.000 claims description 8
- 238000000926 separation method Methods 0.000 claims description 7
- 238000005199 ultracentrifugation Methods 0.000 claims description 6
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 claims description 5
- 125000000524 functional group Chemical group 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 31
- 239000011737 fluorine Substances 0.000 description 31
- 229910052731 fluorine Inorganic materials 0.000 description 31
- 239000003223 protective agent Substances 0.000 description 17
- 238000000034 method Methods 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 229910000033 sodium borohydride Inorganic materials 0.000 description 8
- 239000012279 sodium borohydride Substances 0.000 description 8
- 239000003446 ligand Substances 0.000 description 7
- 239000007788 liquid Substances 0.000 description 7
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- 238000005119 centrifugation Methods 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 5
- 239000003638 chemical reducing agent Substances 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 238000000746 purification Methods 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- OHMHBGPWCHTMQE-UHFFFAOYSA-N 2,2-dichloro-1,1,1-trifluoroethane Chemical compound FC(F)(F)C(Cl)Cl OHMHBGPWCHTMQE-UHFFFAOYSA-N 0.000 description 4
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000012776 electronic material Substances 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 3
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- OPQARKPSCNTWTJ-UHFFFAOYSA-L copper(ii) acetate Chemical compound [Cu+2].CC([O-])=O.CC([O-])=O OPQARKPSCNTWTJ-UHFFFAOYSA-L 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000000696 magnetic material Substances 0.000 description 3
- 239000002923 metal particle Substances 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 229910052709 silver Inorganic materials 0.000 description 3
- 239000004332 silver Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- YIWUKEYIRIRTPP-UHFFFAOYSA-N 2-ethylhexan-1-ol Chemical compound CCCCC(CC)CO YIWUKEYIRIRTPP-UHFFFAOYSA-N 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 150000001356 alkyl thiols Chemical class 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 230000009918 complex formation Effects 0.000 description 2
- VTXVGVNLYGSIAR-UHFFFAOYSA-N decane-1-thiol Chemical compound CCCCCCCCCCS VTXVGVNLYGSIAR-UHFFFAOYSA-N 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- ZQBFAOFFOQMSGJ-UHFFFAOYSA-N hexafluorobenzene Chemical compound FC1=C(F)C(F)=C(F)C(F)=C1F ZQBFAOFFOQMSGJ-UHFFFAOYSA-N 0.000 description 2
- ZSIAUFGUXNUGDI-UHFFFAOYSA-N hexan-1-ol Chemical compound CCCCCCO ZSIAUFGUXNUGDI-UHFFFAOYSA-N 0.000 description 2
- 150000002430 hydrocarbons Chemical group 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000010970 precious metal Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000005871 repellent Substances 0.000 description 2
- 238000000527 sonication Methods 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 238000009210 therapy by ultrasound Methods 0.000 description 2
- 238000002076 thermal analysis method Methods 0.000 description 2
- ZNQVEEAIQZEUHB-UHFFFAOYSA-N 2-ethoxyethanol Chemical compound CCOCCO ZNQVEEAIQZEUHB-UHFFFAOYSA-N 0.000 description 1
- GTPHVVCYEWPQFE-UHFFFAOYSA-N 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctane-1-thiol Chemical compound FC(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)CCS GTPHVVCYEWPQFE-UHFFFAOYSA-N 0.000 description 1
- URJIJZCEKHSLHA-UHFFFAOYSA-N 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecane-1-thiol Chemical compound FC(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)CCS URJIJZCEKHSLHA-UHFFFAOYSA-N 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- NTIZESTWPVYFNL-UHFFFAOYSA-N Methyl isobutyl ketone Chemical compound CC(C)CC(C)=O NTIZESTWPVYFNL-UHFFFAOYSA-N 0.000 description 1
- UIHCLUNTQKBZGK-UHFFFAOYSA-N Methyl isobutyl ketone Natural products CCC(C)C(C)=O UIHCLUNTQKBZGK-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 125000003368 amide group Chemical group 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- BTANRVKWQNVYAZ-UHFFFAOYSA-N butan-2-ol Chemical compound CCC(C)O BTANRVKWQNVYAZ-UHFFFAOYSA-N 0.000 description 1
- 125000000484 butyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 150000007942 carboxylates Chemical group 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- KYKAJFCTULSVSH-UHFFFAOYSA-N chloro(fluoro)methane Chemical compound F[C]Cl KYKAJFCTULSVSH-UHFFFAOYSA-N 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 description 1
- 238000001246 colloidal dispersion Methods 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010908 decantation Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 125000004185 ester group Chemical group 0.000 description 1
- 125000001033 ether group Chemical group 0.000 description 1
- 150000002170 ethers Chemical class 0.000 description 1
- 150000002222 fluorine compounds Chemical class 0.000 description 1
- 125000001153 fluoro group Chemical group F* 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
- 150000003840 hydrochlorides Chemical class 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000002082 metal nanoparticle Substances 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 125000001453 quaternary ammonium group Chemical group 0.000 description 1
- 230000002940 repellent Effects 0.000 description 1
- 238000001338 self-assembly Methods 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 125000001273 sulfonato group Chemical group [O-]S(*)(=O)=O 0.000 description 1
- 125000004434 sulfur atom Chemical group 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- 238000004506 ultrasonic cleaning Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Images
Description
【0001】
【発明の属する技術分野】
本発明は、ナノサイズの金属超微粒子の技術分野に属し、特に、銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子とその製造方法に関する。
【0002】
【従来の技術とその課題】
ナノサイズ、すなわち、直径がナノメーターのオーダーの金属の粒子はその融点がバルクのものと劇的に異なるため、低温度焼成によって使用可能な導電性ペーストなどとしての応用が期待される。これまで、金や銀、パラジウムや白金などの貴金属のナノサイズ粒子は安定に調製され、触媒や導電性材料、着色材料として応用されてきた。貴金属から成る金属のナノサイズ粒子を得るための代表的な方法の一つは、アルカンチオールなどを保護剤として金属超微粒子のコロイド分散体を調製することである。しかしながら、これらの貴金属ナノ粒子は、その素材が高価であり、供給の不安が生じる場合が無いわけではない。
【0003】
これに対し、卑金属(軽遷移金属)である銅、ニッケルまたはコバルトは安価で供給も十分にある。特に、銅は導電性の電子材料として、また、ニッケルやコバルトは磁性材料として機能し得るので、これらの金属の安価で高純度のナノサイズ粒子が得られれば多くの新しい用途が期待される。しかしながら、銅、ニッケルまたはコバルトは容易に酸化されるため、合金ではなく単一金属の状態でナノサイズ粒子の供給は困難であり、上述したアルカンチオールのような保護剤を用いて安定な分散体を調製することはできない。
本発明の目的は、以上のような現況に鑑み、銅、ニッケルまたはコバルトから成る金属の安定なナノサイズ粒子を高純度に製造することのできる技術を提供することにある。
【0004】
【課題を解決するための手段】
本発明者らは、先に、フルオロカーボン鎖により被覆された銀のナノサイズ粒子が特殊な自己集合性を示すことを明らかにし(T. Yonezawa他、Adv. Mater., 2001, 140)、イオウ含有炭化フッ素系化合物によって被覆・保護された銀のナノサイズ粒子がフッ素系溶媒に分散された分散液から成る発色剤(特願2000−155311)や撥水・撥油表面形成剤を案出している(特願2001−069908)。本発明者は、このたび、それらの技術を更に発展させることにより、銅、ニッケルまたはコバルトのような金属であっても酸化されることなく高純度のナノサイズ粒子に調製され得る新しい技術を確立した。
【0005】
かくして、本発明は、以下の各工程を含む、銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子の製造方法を提供するものである。
(i)極性溶媒中で、銅、ニッケルまたはコバルトから成る金属の金属塩と下記の式(I)で表されるイオウ含有炭化フッ素系化合物とを還元反応に供することにより、前記イオウ含有炭化フッ素系化合物により被覆された銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子が前記溶媒中に分散された第一の分散液を調製する工程;
R−(CF2)m−(CH2)n−SH (I)
但し、式(I)中、Rは、CF3または有機官能基を表わし、mは1〜9の整数、nは1から3の整数を表す。
(ii)前記第一の分散液から溶媒を除去した後、得られる固形物をフッ素系溶媒中に分散させて第二の分散液を調製する工程。
(iii)前記第二の分散液に温エタノールまたは温クロロホルムを添加し超音波処理した後、遠心分離に供し、得られた沈殿を回収して再びフッ素系溶媒中に分散させ、この温エタノールまたは温クロロホルムの添加と超音波処理、遠心分離およびフッ素系溶媒中への分散から成る操作を2回以上繰り返す工程。
本発明に従う金属ナノサイズ粒子の製造方法における特に好ましい態様においては、前記の(iii)の工程の後に、超遠心濃縮分離操作を付加する。
【0006】
本発明は、さらに、上記のごとき方法によって製造される銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子であって、上記の式(I)で表されるイオウ含有炭化フッ素系化合物で被覆されている状態、さらには、これがフッ素系溶媒に分散されている状態で保存、供給することのできる金属ナノサイズ粒子を提供する。
【0007】
【発明の実施の形態】
本発明は、本発明者らによって案出された既述の技術に基き、保護剤としてイオウ含有炭化フッ素系化合物によって被覆・保護された銅、ニッケルまたはコバルトの金属ナノサイズ粒子の分散系を調製するとともに、これにとどまらず、その分散系から余剰の保護剤などを可及的に除去することのできる手法を確立することによって、電子材料や磁性材料として使用されるのにも好適な高度に精製された銅、ニッケルまたはコバルトの金属ナノサイズ粒子の取得を可能にしたものである。
【0008】
以下、本発明の方法を構成する各工程に沿って本発明の実施の形態を詳述する。
炭化フッ素で被覆された金属ナノサイズ粒子分散液の調製(工程( ii ))
本発明に従い銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子を製造するには、先ず、式(I)で表されるイオウ含有炭化フッ素系化合物により被覆された銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子が溶媒中に分散された分散液(以下、第一の分散液と呼ぶことがある)を調製する。このために、極性溶媒中で、銅、ニッケルまたはコバルトから成る金属の金属塩と既述の式(I)で表されるイオウ含有炭化フッ素系化合物とを還元反応に供する。
【0009】
この還元操作は、本発明者らによる特願2000−155311や特願2001−069908に記述されたものと基本的には共通している。還元反応は、一般に、還元剤として、水素化ホウ素ナトリウム、水素化ホウ素カリウムなどアルカリ金属水素化ホウ素塩もしくはアンモニウム水素化ホウ酸塩を用いて行う。温度は常温以上の温度で行えるが、水素化ホウ酸塩が比較的激しい還元剤であるため、あまり高温で還元することは望ましくない(通常は常温であるが、50℃程度までは許容できる)。
【0010】
用いる溶媒は、イオウ含有炭化フッ素系化合物と金属塩の双方を溶解し得るもので、例えば、水、エタノール、メタノール、イソプロパノール、s−ブタノール、n−ブタノール、n−ヘキサノール、2−エチルヘキサノール、ブチルセルソルブ、アセトン、メチルエチルケトン、メチルイソブチルケトン、酢酸エチル、テトラヒドロフランなどの極性溶媒である。金属塩としては、酢酸銅、塩化ニッケル、塩化コバルトなどの上記の極性溶媒中に均一に分散する酢酸塩、塩化物、硫酸塩、硝酸塩、塩酸塩などを用いることができる。金属塩とフッ素系配位子(イオウ含有炭化フッ素系化合物)との混合比率は配位子/金属塩(モル/モル)で0.1以上であり、0.3〜5までで十分に粒子が生成することを確認している。
【0011】
保護剤となるイオウ含有炭化フッ素系化合物としては、特願2000−155311や特願2001−069908に記載されているものに類似のものの中で、特に安定にかつ還元時において迅速に粒子表面の保護が可能な式(I)のR−(CF2)m−(CH2)n−SHを用いる。Rとしては、特願2001−069908に開示している撥水・撥油表面作製に用いられるような場合には高い撥水性を持たせるためにCF3であることが不可欠であったが、本発明においては、これに限らず、適当な有機官能基であってもよい。すなわち、このRは用途に応じて合成法によって種々に変えることができ、一般的にはX−(CH2)o−で表わすことができる。好適なXの例としては、メチル基、カルボン酸塩基、スルホン酸塩基、4級アンモニウム基、フェニル基などを挙げることができる。ここで、oは0以上の整数であるが、最終的に得られる金属ナノ粒子の導電性を高めるためには焼成後の有機成分の量は減らしたほうがよいという観点からできるだけ少ない方がよい。したがって、oは一般に0〜3の整数である。なお、合成の都合上、X−(CH2)o−とフッ素鎖と−(CF2)m−との間がアミド基、エステル基またはエーテル基などで接続されていることもある。炭化フッ素鎖は、特段に長いものは不要であり、逆に本発明の銅などの金属ナノサイズ粒子を導電性ペーストなどに用いる観点からはあまり長いものは望ましくなく、したがって、mは1〜9の整数である。炭化水素鎖の長さを定めるnは1〜3の整数であり、この炭化水素鎖は合成の都合上必須である。
【0012】
還元反応は、一般的には、上述したような保護剤(イオウ含有炭化フッ素系化合物)と金属塩とを同一の極性溶媒に溶解させ、よく混合して、フッ素系配位子(イオウ含有炭化フッ素系化合物)と金属塩との間で錯形成させた後、上述したような水素化ホウ素ナトリウムのような還元剤の水溶液を徐々に滴下することによって行い、これによって、イオウ含有炭化フッ素系化合物によりそのイオウ原子を介して被覆された金属のナノサイズ粒子が極性溶媒中に分散された分散液(第一の分散液)が得られる。
【0013】
本発明における還元操作は、このような均一系の反応によるのが一般的であるが、これに限られず、不均一系の反応によることも可能である。すなわち、保護剤が溶解している溶媒(フッ素系溶媒)と金属塩が溶解している溶媒とが分離している状態でも、これらを一緒にすることにより金属塩とフッ素系配位子との間で錯形成を起こし、フッ素系溶媒に金属イオンを相転移させ、そこに水素化ホウ素ナトリウムのような還元剤の水溶液を徐々に滴下して、金属ナノサイズ粒子が溶媒中に分散された分散液(第一の分散液)を得ることもできる。
このようにして得られる本発明に従う分散液中の銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子は、その粒子径が、一般に、1〜数十nmの範囲にあり、特に約2〜10nmの範囲にあることが多い。
【0014】
フッ素系溶媒への分散(工程( ii ))
上記の工程(i)で得られた第一の分散液は、次に、該分散液を構成する溶媒(極性溶媒)を除去した後、得られる固形物をフッ素系溶媒に分散させることにより第二の分散液を調製する。ここで、フッ素溶媒とは、構成元素としてフッ素を含有する化学構造式で表される溶媒であり、ハイドロクロロフルオロカーボン(HCFC)、クロロフルオロカーボン(CFC)、6フッ化ベンゼン、フッ化エーテルなどが例示できる。
【0015】
第一の分散液から、その溶媒を除去するには、分散液全体を加熱し、金属ナノサイズ粒子の凝集体を沈澱させ、沈澱物をデカンテーションまたはろ取によって取り出す。別の方法として、分散液全体を溶媒留去してもよい。
このようにして得られた固形物をフッ素系溶媒中に導入し、攪拌して分散させることにより、イオウ含有炭化フッ素系化合物により被覆された銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子がフッ素系溶媒中に分散された第二の分散液が得られる。この際、フッ素系溶媒とともに水を加えて水溶性成分(未反応還元剤やその反応副生成物)を取り出し、分液してフッ素系溶媒のみを取り出すようにすることが好ましい。
なお、極性溶媒として水と混合しない極性溶媒やフッ素溶媒を用いて第一の分散液を調製した場合には、水部分を取り除いた後、前述のように、加温して沈澱を生じさせて、フッ素系溶媒に分散させるか、または、全体を溶媒留去してフッ素系溶媒を加える。
【0016】
精製工程(工程( iii ))
銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子がイオウ含有炭化フッ素系化合物により被覆・保護されてフッ素系溶媒中に分散された第二の分散液は、次に、本発明の方法における最も特徴的な工程である精製工程に付される。この精製工程は、余剰の保護剤(イオウ含有炭化フッ素系化合物)を可及的に除去することにより、銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子を有用性を高めるためのものである。
この精製工程は、上記のごとき第二の分散液に温エタノールまたは温クロロホルムを添加し超音波処理した後、遠心分離に供し、得られた沈澱を回収して再びフッ素系溶媒中に分散させることから成る。
【0017】
温エタノールまたは温クロロホルムとは、エタノールまたはクロロホルムを45〜55℃(例えば50℃前後)に加温したものであり、大過剰に(一般に第二の分散液に対して3倍量以上)添加する。次に、加温(45〜55℃、例えば50℃前後)したまま、超音波処理(超音波洗浄)を行う。
さらに、大過剰の極性溶媒(エタノールまたはクロロホルム)の投入によって生じる細かな凝集体を遠心分離操作によって濃縮し、沈澱を回収し、再びフッ素系溶媒に溶解させる。遠心分離操作は、通常の遠心分離機を用いて5000rpm以上の速度で行うのが好ましい。本発明に従えば、温エタノールまたは温クロロホルムの添加と超音波処理、遠心分離、およびフッ素系溶媒中への再分散から成る操作を複数回、一般的には5〜6回繰り返す。
【0018】
このような操作により、金属ナノサイズ粒子の被覆・保護に寄与していない余剰のフッ素系配位子(イオウ含有炭化フッ素系化合物)が除去され、その結果、金属ナノサイズ粒子(イオウ含有炭化フッ素系化合物で被覆・保護された銅、ニッケルまたはコバルトのナノサイズ粒子)は、極性溶媒には分散しなくなり、フッ素系溶媒にのみ分散するような高度に精製されたものとなる。
【0019】
更なる精製が必要とされる場合、例えば、導電性が著しく向上した電子材料として銅のナノサイズ粒子を用いるような場合には、超遠心濃縮分離操作を付加することが好ましい。すなわち、上記の工程(iii)で得られた分散液を加温(一般的には45〜55℃、例えば50℃前後)した状態で超音波照射した後、超遠心濃縮分離操作によって濃縮し、沈澱を回収し、さらに溶媒(温エタノールまたは温クロロホルム)にて洗浄し、余剰のフッ素系配位子(イオウ含有炭化フッ素系化合物)を極力除去する。超遠心濃縮分離操作は、90000×g以上の遠心加速度を加えて実施する。
【0020】
金属ナノサイズ粒子
以上のような操作によって得られる銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子は、イオウ含有炭化フッ素系化合物によって被覆・保護されフッ素系溶媒中に分散された状態で酸化されることもなく長期間にわたり安定に保持される。必要に応じて、フッ素溶媒を除去し真空乾燥して粉末にすることもでき、この状態でも長期間安定に保持され得る。
使用に際しては加熱に供することにより保護剤(イオウ含有炭化フッ素系化合物)を外せばよい。一般的には200〜300℃の低温で保護剤は焼失される。その際、余剰の保護剤が予め可及的に除去されているので、フッ素を含むガスの発生は少なく環境上の問題を最少にしながら、高純度の銅、ニッケルまたはコバルトから成るナノサイズ粒子が得られる。
【0021】
【実施例】
以下に、本発明の特徴をさらに具体的に説明するため実施例および参考例を示すが、本発明はこれらの例によって限定されるものではない。
実施例1
エタノールに、1H,1H,2H,2H−パーフルオロオクタンチオール(以下、F8と記すことがある)(1.5mM)と酢酸銅(5mM、30mL)を導入し、丸底フラスコに入れた。得られた混合溶液をしばらくの間ゆっくり攪拌したところ、系内は薄い青色から緑がかった色に変わり、銅とF8との間で錯体が形成されたことが理解された。その後、常時均一になるよう烈しく攪拌し、水素化ホウ素ナトリウム(0.074g)の水溶液(5mL)を、徐々に一定量ずつ滴下する。溶液は、青緑から褐色に変化し、銅のナノ粒子(ナノサイズ粒子)が生成したことが判明した。滴下終了後、約3時間攪拌を続けた。調製直後は沈澱物等は見られず、均一なナノ粒子分散液であり、その平均粒径は2.4nmであった(図1のTEM写真参照)。放置したところ、白色沈澱が生じた場合があり、そのときにはこれをろ過した。このろ物は水に可溶であり、余剰の水素化ホウ素ナトリウム塩であると理解される。ろ液は黄色から褐色のままであって、有色の沈澱は生じず、さらに、この色は数ヵ月変色せず、銅が酸化されイオン化されることなく安定に保持されていることが示唆された。
この溶液(分散液)をそのまま溶媒留去し、フッ素系溶媒としてHCFC−225(旭硝子製)を加えると該フッ素系溶媒は褐色となり、銅のナノ粒子がフッ素系溶媒に移動したことが理解された。また、残存していると考えられる水溶性の塩(余剰の水素化ホウ素ナトリウムおよびその反応副生成物)を除去するために水を添加し分液した。
得られたナノ粒子分散液を50℃近くまで加温すると、褐色の沈澱が得られたので、これをろ取し、HCFCを添加して攪拌したところ、これに分散した。50℃に加温した温エタノールを加え、超音波処理ののち、6000rpmで遠心分離を行い濃縮し洗浄する操作を5回繰り返すことにより、褐色粉末を得ることができた。この粉末はHCFCのみに分散し、エタノールなどの極性溶媒中には分散しなかった。さらに、100000×gで超遠心分離を行った。
加熱試験を行い熱分析したところ、約230℃で顕著な重量変化が認められ、配位子(保護剤)が外れ(図2の熱天秤グラフ参照)、銅になることが確認された。
【0022】
参考例
保護剤として従来より貴金属に用いられているデカンチオールを用い、このデカンチオールのトルエン溶液と酢酸銅水溶液を同一モル濃度(10mM、各15mL)導入し、丸底フラスコに入れた。得られた混合溶液をしばらくの間、ゆっくり攪拌した。これに水素化ホウ素ナトリウム(0.074g)の水溶液(5mL)を、徐々に一定量ずつ滴下した。溶液は青緑から茶色に変化し、ナノ粒子が生成したことを示した。実際、TEM写真でも粒子の生成が確認された。しかしながら、数日放置すると青色の溶液になった。これは銅が2価のイオンにもどったと考えられる。実際、TEM観察すると、調製直後は数十nmの粒径をもつ粒子が観察される(図3)が、数日後、糸状の会合体が見られた(図4)。これは、銅−チオール錯体がエタノール中で会合したものと理解される。このように、アルキルチオール錯体がエタノール中で会合したものと理解される。このように、アルキルチオールを保護剤としては銅のナノ粒子は安定に生成し得ないことが示された。
【0023】
実施例2
メタノールに1H,1H,2H,2H−パーフルオロデカンチオールと塩化ニッケルを同一モル濃度(5mM、15mL)で導入し、丸底フラスコに入れた。最初緩やかに攪拌したのち、常時均一になるよう烈しく攪拌し、水素化ホウ素ナトリウム(0.4M、5mL)の水溶液を徐々に滴下した。放置した後、白色沈澱が生じた場合にはろ過した。滴下後、エバポレータで溶媒留去した後、HCFC−225を加え、よく溶解させた後、水を少量加え、残留する沈澱を溶解させた。分液し、HCFC−225成分を取り出し乾燥した。濃縮後、50℃に加温したエタノールを加え、超音波処理した後、遠心分離により濃縮し、洗浄することを数度繰り返し、HCFC−225にしか分散しない固体を得た。得られた分散液は安定で、長期間変色はせず、安定なニッケルのナノ粒子ができていることが分かる。TEM写真(図5)から平均粒径は6.5nm程度であることが分かった。XPS(X線光電子分子法)から、ニッケルが生成していることが示された(図6)。
【0024】
【発明の効果】
本発明は、銅、ニッケルまたはコバルトのような酸化性の大きい金属について安定なナノサイズ粒子を実現させたものであり、これらの金属のナノサイズ粒子の電子材料や磁性材料などとしての用途の発展に資することができる。
【図面の簡単な説明】
【図1】本発明に従って調製された銅のナノサイズ粒子の構造を示すTEM(透過電子顕微鏡)写真である。
【図2】本発明に従って調製された銅のナノサイズ粒子から保護剤から外れる様子を観察するために行った熱分析における熱天秤グラフである。
【図3】本発明に対する参考例として実施したアルカンチオールを保護剤とする実験における銅のナノサイズ粒子の構造を示すTEM写真で、調製直後に観察したものである。
【図4】本発明に対する参考例として実施したアルカンチオールを保護剤とする実験における銅のナノサイズ粒子の構造を示すTEM写真で、数日後に観察したものである。
【図5】本発明に従って調製されたニッケルのナノサイズ粒子の構造を示すTEM写真である。
【図6】本発明に従って調製されたニッケルのナノサイズ粒子について行ったXPS(X線光電子分光分析)測定のXPSチャートである。[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of nano-sized ultrafine metal particles, and particularly relates to metal nano-sized particles made of copper, nickel or cobalt and a method for producing the same.
[0002]
[Prior art and its problems]
Nano-sized, that is, metal particles having a diameter of the order of nanometers have a melting point that is dramatically different from that of bulk, and therefore, application as a conductive paste that can be used by low-temperature firing is expected. Until now, nano-sized particles of noble metals such as gold, silver, palladium and platinum have been stably prepared and applied as catalysts, conductive materials and coloring materials. One of the typical methods for obtaining metal nano-sized particles made of a noble metal is to prepare a colloidal dispersion of ultrafine metal particles using alkanethiol or the like as a protective agent. However, these precious metal nanoparticles are not expensive because of the high cost of the materials.
[0003]
In contrast, base metals (light transition metals) such as copper, nickel or cobalt are inexpensive and sufficiently supplied. In particular, since copper can function as a conductive electronic material, and nickel and cobalt can function as a magnetic material, many new uses are expected if nano-sized particles of these metals can be obtained at low cost. However, since copper, nickel or cobalt is easily oxidized, it is difficult to supply nano-sized particles in a single metal state rather than an alloy, and a stable dispersion using a protective agent such as alkanethiol described above. Cannot be prepared.
An object of the present invention is to provide a technique capable of producing high-purity metal stable nano-sized particles made of copper, nickel or cobalt in view of the current situation as described above.
[0004]
[Means for Solving the Problems]
The present inventors have previously demonstrated that silver nano-sized particles coated with fluorocarbon chains exhibit a special self-assembly (T. Yonezawa et al., Adv. Mater., 2001, 140) and contain sulfur. A color former (Japanese Patent Application No. 2000-155311) and a water / oil repellent surface forming agent comprising a dispersion in which silver nano-sized particles coated and protected with a fluorine-containing compound are dispersed in a fluorine-based solvent have been devised. (Japanese Patent Application No. 2001-069908). The present inventor has recently established a new technology that can be prepared into high-purity nano-sized particles without being oxidized even by metals such as copper, nickel or cobalt by further developing these technologies. did.
[0005]
Thus, the present invention provides a method for producing metal nano-sized particles comprising copper, nickel or cobalt, including the following steps.
(I) In a polar solvent, by subjecting a metal salt of a metal composed of copper, nickel or cobalt to a sulfur-containing fluorocarbon compound represented by the following formula (I) for a reduction reaction, the sulfur-containing fluorocarbon Preparing a first dispersion in which nano-sized particles of copper, nickel, or cobalt coated with a system compound are dispersed in the solvent;
R- (CF 2) m - ( CH 2) n -SH (I)
In the formula (I), R represents a CF 3 or an organic functional group, m represents an integer of 1-9 integer, n represents 1 to 3.
(Ii) A step of preparing a second dispersion by removing the solvent from the first dispersion and then dispersing the obtained solid in a fluorinated solvent.
(Iii) After adding warm ethanol or warm chloroform to the second dispersion and sonicating it, it is subjected to centrifugation, and the resulting precipitate is recovered and dispersed again in a fluorinated solvent. A step of repeating the operation consisting of addition of warm chloroform and sonication, centrifugation and dispersion in a fluorinated solvent at least twice.
In a particularly preferred embodiment of the method for producing metal nanosize particles according to the present invention, an ultracentrifugation separation operation is added after the step (iii).
[0006]
The present invention further relates to metal nano-sized particles made of copper, nickel or cobalt produced by the method as described above, and coated with the sulfur-containing fluorine-containing compound represented by the above formula (I). In addition, the present invention provides metal nano-sized particles that can be stored and supplied in a dispersed state in a fluorinated solvent.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is based on the above-described technology devised by the present inventors, and prepares a dispersion of copper, nickel or cobalt metal nanosize particles coated and protected with a sulfur-containing fluorocarbon compound as a protective agent. In addition to this, by establishing a method that can remove surplus protective agents as much as possible from the dispersion system, it is highly suitable for use as an electronic material or magnetic material. This makes it possible to obtain purified metal nano-sized particles of copper, nickel or cobalt.
[0008]
Hereinafter, embodiments of the present invention will be described in detail along the respective steps constituting the method of the present invention.
Preparation of metal nanosize particle dispersion coated with fluorine carbide (process ( ii ))
In order to produce metal nano-sized particles comprising copper, nickel or cobalt according to the present invention, first, a metal comprising copper, nickel or cobalt coated with a sulfur-containing fluorocarbon compound represented by formula (I) is used. A dispersion liquid in which nano-sized particles are dispersed in a solvent (hereinafter sometimes referred to as a first dispersion liquid) is prepared. For this purpose, in a polar solvent, a metal salt of a metal composed of copper, nickel or cobalt and a sulfur-containing fluorocarbon compound represented by the formula (I) are subjected to a reduction reaction.
[0009]
This reduction operation is basically the same as that described in Japanese Patent Application Nos. 2000-155311 and 2001-0669908 by the present inventors. The reduction reaction is generally performed using an alkali metal borohydride salt such as sodium borohydride or potassium borohydride or ammonium borohydride as a reducing agent. Although the temperature can be higher than room temperature, it is not desirable to reduce at a very high temperature because borohydride is a relatively intense reducing agent (normally normal temperature, but acceptable up to about 50 ° C) .
[0010]
The solvent used can dissolve both the sulfur-containing fluorocarbon compound and the metal salt. For example, water, ethanol, methanol, isopropanol, s-butanol, n-butanol, n-hexanol, 2-ethylhexanol, butyl It is a polar solvent such as cellosolve, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate and tetrahydrofuran. Examples of metal salts that can be used include acetates, chlorides, sulfates, nitrates, and hydrochlorides that are uniformly dispersed in the above polar solvents such as copper acetate, nickel chloride, and cobalt chloride. The mixing ratio of the metal salt and the fluorine-based ligand (sulfur-containing fluorine-containing fluorine-based compound) is 0.1 or more in terms of the ligand / metal salt (mol / mol). Has been confirmed to generate.
[0011]
As sulfur-containing fluorine-containing fluorocarbon compounds that serve as protective agents, among those similar to those described in Japanese Patent Application No. 2000-155311 and Japanese Patent Application No. 2001-069908, the particle surface can be protected particularly stably and rapidly during reduction. R— (CF 2 ) m — (CH 2 ) n —SH of the formula (I) is used. As R, CF 3 was indispensable in order to have high water repellency when used for the preparation of water- and oil-repellent surfaces disclosed in Japanese Patent Application No. 2001-069908. The invention is not limited to this, and may be an appropriate organic functional group. That is, this R can be variously changed according to the synthesis method depending on the application, and can be generally represented by X— (CH 2 ) o —. Preferable examples of X include a methyl group, a carboxylate group, a sulfonate group, a quaternary ammonium group, and a phenyl group. Here, o is an integer greater than or equal to 0. However, in order to increase the conductivity of the finally obtained metal nanoparticles, it is better to reduce it as much as possible from the viewpoint that the amount of the organic component after firing should be reduced. Therefore, o is generally an integer from 0 to 3. For the convenience of synthesis, X— (CH 2 ) o —, a fluorine chain, and — (CF 2 ) m — may be connected by an amide group, an ester group, an ether group, or the like. The fluorocarbon chain is not particularly required to be particularly long, and conversely, from the viewpoint of using metal nanosize particles such as copper of the present invention for a conductive paste or the like, it is not desirable, and therefore m is 1-9. Is an integer. N which determines the length of the hydrocarbon chain is an integer of 1 to 3, and this hydrocarbon chain is essential for the convenience of synthesis.
[0012]
In the reduction reaction, generally, the protective agent (sulfur-containing fluorine-containing compound) and the metal salt as described above are dissolved in the same polar solvent and mixed well to obtain a fluorine-based ligand (sulfur-containing carbonization). After the complex formation between the fluorine compound) and the metal salt, an aqueous solution of a reducing agent such as sodium borohydride as described above is gradually added dropwise. Thus, a dispersion liquid (first dispersion liquid) in which the metal nano-sized particles coated via the sulfur atoms are dispersed in a polar solvent is obtained.
[0013]
The reduction operation in the present invention is generally performed by such a homogeneous reaction, but is not limited thereto, and can be performed by a heterogeneous reaction. That is, even when the solvent in which the protective agent is dissolved (fluorine-based solvent) and the solvent in which the metal salt is dissolved are separated, the metal salt and the fluorine-based ligand can be combined by combining them. Dispersion in which metal nano-sized particles are dispersed in a solvent by causing a complex formation between them, causing a phase transition of metal ions to a fluorinated solvent, and gradually dropping an aqueous solution of a reducing agent such as sodium borohydride there. A liquid (first dispersion) can also be obtained.
The nano-sized particles of metal consisting of copper, nickel or cobalt in the dispersion according to the invention thus obtained have a particle size generally in the range of 1 to several tens of nm, in particular about 2 to 10 nm. Often in range.
[0014]
Dispersion in fluorinated solvent (process ( ii ))
The first dispersion obtained in the above step (i) is then removed by removing the solvent (polar solvent) constituting the dispersion and then dispersing the obtained solid in a fluorinated solvent. Prepare a second dispersion. Here, the fluorine solvent is a solvent represented by a chemical structural formula containing fluorine as a constituent element, and examples thereof include hydrochlorofluorocarbon (HCFC), chlorofluorocarbon (CFC), hexafluorobenzene, and fluorinated ether. it can.
[0015]
To remove the solvent from the first dispersion, the entire dispersion is heated to precipitate aggregates of metal nanosize particles, and the precipitate is removed by decantation or filtration. Alternatively, the entire dispersion may be evaporated.
By introducing the solid material thus obtained into a fluorine-based solvent and dispersing it by stirring, the metal nano-sized particles made of copper, nickel or cobalt coated with the sulfur-containing fluorine-containing compound are converted into fluorine. A second dispersion dispersed in the system solvent is obtained. At this time, it is preferable to add water together with the fluorinated solvent to take out the water-soluble component (unreacted reducing agent and its reaction by-product) and separate it to take out only the fluorinated solvent.
In addition, when the first dispersion was prepared using a polar solvent or a fluorine solvent that is not mixed with water as a polar solvent, after removing the water portion, it was heated to cause precipitation as described above. , Dispersed in a fluorinated solvent, or the whole is distilled off and a fluorinated solvent is added.
[0016]
Purification step (step ( iii ))
The second dispersion liquid in which nano-sized particles of a metal composed of copper, nickel or cobalt are coated and protected with a sulfur-containing fluorine-containing compound and dispersed in a fluorine-based solvent is the most characteristic feature of the method of the present invention. To the purification step, which is a typical step. This purification process is intended to increase the usefulness of metal nano-sized particles composed of copper, nickel or cobalt by removing as much as possible the excess protective agent (sulfur-containing fluorine-containing compound).
In this purification step, warm ethanol or warm chloroform is added to the second dispersion as described above and subjected to ultrasonic treatment, followed by centrifugation, and the resulting precipitate is recovered and dispersed again in a fluorinated solvent. Consists of.
[0017]
Warm ethanol or warm chloroform is obtained by heating ethanol or chloroform to 45 to 55 ° C. (for example, around 50 ° C.), and is added in large excess (generally 3 times the amount of the second dispersion). . Next, ultrasonic treatment (ultrasonic cleaning) is performed with heating (45 to 55 ° C., for example, around 50 ° C.).
Further, fine aggregates produced by adding a large excess of polar solvent (ethanol or chloroform) are concentrated by centrifugation, and the precipitate is recovered and dissolved again in a fluorinated solvent. The centrifugal operation is preferably performed at a speed of 5000 rpm or higher using a normal centrifugal separator. According to the present invention, the operation consisting of addition of warm ethanol or warm chloroform and sonication, centrifugation, and redispersion in a fluorinated solvent is repeated a plurality of times, generally 5-6 times.
[0018]
By such an operation, the excess fluorine-based ligand (sulfur-containing fluorine-containing compound) that does not contribute to the coating / protection of the metal nano-sized particles is removed, and as a result, the metal nano-sized particles (sulfur-containing fluorine-containing fluorine). Copper, nickel, or cobalt nano-sized particles coated and protected with a series compound are not highly dispersed in a polar solvent, but are highly purified so that they are dispersed only in a fluorinated solvent.
[0019]
When further purification is required, for example, when copper nano-sized particles are used as the electronic material with significantly improved conductivity, it is preferable to add an ultracentrifugation separation operation. That is, the dispersion obtained in the above step (iii) is ultrasonically irradiated in a heated state (generally 45 to 55 ° C., for example, around 50 ° C.), and then concentrated by an ultracentrifugation separation operation. The precipitate is recovered and further washed with a solvent (hot ethanol or hot chloroform) to remove as much as possible the excess fluorine-based ligand (sulfur-containing fluorine-containing compound). The ultracentrifugation separation operation is carried out by applying a centrifugal acceleration of 90000 × g or more.
[0020]
Metal nano-sized particles Metal nano-sized particles made of copper, nickel or cobalt obtained by the above operations are coated and protected with a sulfur-containing fluorine-containing compound and dispersed in a fluorine-containing solvent. It is kept stable for a long time without being oxidized. If necessary, the fluorine solvent can be removed and vacuum dried to form a powder, and even in this state, it can be stably maintained for a long period of time.
In use, the protective agent (sulfur-containing fluorocarbon compound) may be removed by heating. Generally, the protective agent is burned off at a low temperature of 200 to 300 ° C. At that time, since the surplus protective agent is removed in advance as much as possible, the generation of gas containing fluorine is small, and the nano-sized particles made of high-purity copper, nickel or cobalt are produced while minimizing environmental problems. can get.
[0021]
【Example】
In the following, examples and reference examples will be shown to describe the features of the present invention more specifically, but the present invention is not limited to these examples.
Example 1
1H, 1H, 2H, 2H-perfluorooctanethiol (hereinafter sometimes referred to as F8) (1.5 mM) and copper acetate (5 mM, 30 mL) were introduced into ethanol and placed in a round bottom flask. When the obtained mixed solution was slowly stirred for a while, the inside of the system changed from light blue to greenish color, and it was understood that a complex was formed between copper and F8. Thereafter, the mixture is vigorously stirred so as to be always uniform, and an aqueous solution (5 mL) of sodium borohydride (0.074 g) is gradually added dropwise in a constant amount. The solution turned from blue-green to brown, and it was found that copper nanoparticles (nano-sized particles) were produced. After completion of dropping, stirring was continued for about 3 hours. Immediately after the preparation, precipitates and the like were not observed, and the dispersion was a uniform nanoparticle dispersion, and the average particle size was 2.4 nm (see the TEM photograph in FIG. 1). When left to stand, a white precipitate may be formed, which was then filtered. The filtrate is understood to be soluble in water and excess sodium borohydride salt. The filtrate remained yellow to brown, with no colored precipitation, and this color did not change for several months, suggesting that copper remains stable without being oxidized and ionized. .
It was understood that when this solvent (dispersion) was distilled off as it was and HCFC-225 (manufactured by Asahi Glass) was added as a fluorinated solvent, the fluorinated solvent turned brown and the copper nanoparticles moved to the fluorinated solvent. It was. Moreover, water was added and liquid-separated in order to remove the water-soluble salt (excess sodium borohydride and its reaction by-product) considered to remain.
When the obtained nanoparticle dispersion was heated to nearly 50 ° C., a brown precipitate was obtained. This was collected by filtration, added with HCFC and stirred, and dispersed therein. By adding warm ethanol heated to 50 ° C., sonicating, centrifuging at 6000 rpm, concentrating and washing, the brown powder was obtained 5 times. This powder was dispersed only in HCFC and was not dispersed in a polar solvent such as ethanol. Furthermore, ultracentrifugation was performed at 100,000 × g.
When a heat test was performed and thermal analysis was performed, a significant weight change was observed at about 230 ° C., and it was confirmed that the ligand (protective agent) was removed (see the thermobalance graph in FIG. 2) and became copper.
[0022]
Reference example Using decanethiol, which has been used for precious metals, as a protective agent, the toluene solution of decanethiol and the aqueous copper acetate solution were introduced at the same molar concentration (10 mM, 15 mL each) and placed in a round bottom flask. It was. The resulting mixed solution was stirred slowly for a while. An aqueous solution (5 mL) of sodium borohydride (0.074 g) was gradually added dropwise thereto. The solution changed from blue-green to brown, indicating the formation of nanoparticles. Actually, the generation of particles was also confirmed in the TEM photograph. However, after standing for several days, a blue solution was formed. This is considered that copper returned to the divalent ion. Actually, when observed with TEM, particles having a particle size of several tens of nm were observed immediately after preparation (FIG. 3), but after several days, filamentous aggregates were observed (FIG. 4). This is understood as a copper-thiol complex associated in ethanol. Thus, it is understood that the alkyl thiol complex is associated in ethanol. Thus, it was shown that copper nanoparticles cannot be stably produced using alkylthiol as a protective agent.
[0023]
Example 2
1H, 1H, 2H, 2H-perfluorodecanethiol and nickel chloride were introduced into methanol at the same molar concentration (5 mM, 15 mL) and placed in a round bottom flask. After first gently stirring, the mixture was stirred vigorously so that it was always uniform, and an aqueous solution of sodium borohydride (0.4 M, 5 mL) was gradually added dropwise. If a white precipitate formed after standing, it was filtered. After dropping, the solvent was distilled off with an evaporator, HCFC-225 was added and dissolved well, and then a small amount of water was added to dissolve the remaining precipitate. After liquid separation, the HCFC-225 component was taken out and dried. After concentration, ethanol warmed to 50 ° C. was added, sonicated, concentrated by centrifugation, and washed several times to obtain a solid that could only be dispersed in HCFC-225. It can be seen that the obtained dispersion is stable, does not change color for a long time, and has stable nickel nanoparticles. From the TEM photograph (FIG. 5), it was found that the average particle size was about 6.5 nm. XPS (X-ray photoelectron molecular method) showed that nickel was formed (FIG. 6).
[0024]
【The invention's effect】
The present invention realizes stable nano-sized particles for highly oxidizable metals such as copper, nickel or cobalt, and development of applications of these metal nano-sized particles as electronic materials and magnetic materials. Can help.
[Brief description of the drawings]
FIG. 1 is a TEM (Transmission Electron Microscope) photograph showing the structure of copper nano-sized particles prepared according to the present invention.
FIG. 2 is a thermobalance graph in a thermal analysis performed to observe how the copper nanosized particles prepared according to the present invention are detached from the protective agent.
FIG. 3 is a TEM photograph showing the structure of copper nano-sized particles in an experiment using alkanethiol as a protective agent carried out as a reference example for the present invention, which is observed immediately after preparation.
FIG. 4 is a TEM photograph showing the structure of copper nano-sized particles in an experiment using alkanethiol as a protective agent carried out as a reference example for the present invention, which was observed several days later.
FIG. 5 is a TEM photograph showing the structure of nickel nano-sized particles prepared in accordance with the present invention.
FIG. 6 is an XPS chart of XPS (X-ray photoelectron spectroscopy) measurements performed on nickel nano-sized particles prepared according to the present invention.
Claims (4)
R−(CF2)m−(CH2)n−SH (I)
〔式(I)中、Rは、CF3または有機官能基を表わし、mは1〜9の整数、nは1から3の整数を表す。〕
(ii)前記第一の分散液から溶媒を除去した後、得られる固形物をフッ素系溶媒中に分散させて第二の分散液を調製する工程;および
(iii)前記第二の分散液に温エタノールまたは温クロロホルムを添加し超音波処理した後、遠心分離に供し、得られた沈殿を回収して再びフッ素系溶媒中に分散させ、この温エタノールまたは温クロロホルムの添加と超音波処理、遠心分離およびフッ素系溶媒中への分散から成る操作を2回以上繰り返す工程;
を含むことを特徴とする銅、ニッケルまたはコバルトから成る金属のナノサイズ粒子の製造方法。(I) In a polar solvent, by subjecting a metal salt of a metal composed of copper, nickel or cobalt to a sulfur-containing fluorocarbon compound represented by the following formula (I) for a reduction reaction, the sulfur-containing fluorocarbon Preparing a first dispersion in which nano-sized particles of copper, nickel, or cobalt coated with a system compound are dispersed in the solvent;
R- (CF 2) m - ( CH 2) n -SH (I)
[In the formula (I), R represents a CF 3 or an organic functional group, m is an integer from 1 to 9, n represents an integer of from 1 to 3. ]
(Ii) removing the solvent from the first dispersion, and then dispersing the resulting solid in a fluorinated solvent to prepare a second dispersion; and (iii) adding the second dispersion to the second dispersion. Add warm ethanol or warm chloroform and sonicate, then centrifuge. Collect the resulting precipitate and re-disperse in a fluorinated solvent. Add warm ethanol or warm chloroform, sonicate, and centrifuge. Repeating the operation consisting of separation and dispersion in a fluorinated solvent two or more times;
The manufacturing method of the nanosized particle | grains of the metal which consists of copper, nickel, or cobalt characterized by the above-mentioned.
R−(CF2)m−(CH2)n−SH (I)
〔式(I)中、Rは、CF3または有機官能基を表わし、mは1〜9の整数、nは1から3の整数を表す。〕A metal nanosize particle comprising copper, nickel or cobalt, which is coated with a sulfur-containing fluorocarbon compound represented by the following formula (I).
R- (CF 2) m - ( CH 2) n -SH (I)
[In the formula (I), R represents a CF 3 or an organic functional group, m is an integer from 1 to 9, n represents an integer of from 1 to 3. ]
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JP2006089786A (en) * | 2004-09-22 | 2006-04-06 | Mitsuboshi Belting Ltd | Method for producing metallic nano-particle dispersed in polar solvent |
KR100670767B1 (en) * | 2004-09-24 | 2007-01-17 | 학교법인 포항공과대학교 | Process for the growth of amorphous Silicone Oxide nanowires directly from NiO/Si and nanowires made from the process |
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JP4947509B2 (en) * | 2004-12-09 | 2012-06-06 | 三井金属鉱業株式会社 | Nickel slurry, method for producing the same, and nickel paste or nickel ink using the nickel slurry |
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CN109822108A (en) * | 2018-11-27 | 2019-05-31 | 西安航天化学动力有限公司 | A kind of nano copper particle preparation method of the surface with bayonet fittings |
WO2022190859A1 (en) * | 2021-03-09 | 2022-09-15 | 株式会社ダイセル | Metal nanoparticle-containing dispersion composition |
CN114433864A (en) * | 2022-01-17 | 2022-05-06 | 淮安中顺环保科技有限公司 | Preparation method of nano nickel powder |
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