JP2020131328A - Nanoparticle and method for producing the same - Google Patents
Nanoparticle and method for producing the same Download PDFInfo
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- JP2020131328A JP2020131328A JP2019026145A JP2019026145A JP2020131328A JP 2020131328 A JP2020131328 A JP 2020131328A JP 2019026145 A JP2019026145 A JP 2019026145A JP 2019026145 A JP2019026145 A JP 2019026145A JP 2020131328 A JP2020131328 A JP 2020131328A
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- Prior art keywords
- metal oxide
- nanoparticles
- phase
- seed particles
- metal
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- Granted
Links
- 239000002105 nanoparticle Substances 0.000 title claims abstract description 128
- 238000004519 manufacturing process Methods 0.000 title claims description 29
- 239000002245 particle Substances 0.000 claims abstract description 206
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 80
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 80
- 239000012702 metal oxide precursor Substances 0.000 claims abstract description 54
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 40
- 239000003607 modifier Substances 0.000 claims abstract description 29
- 238000010335 hydrothermal treatment Methods 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 23
- 230000001376 precipitating effect Effects 0.000 claims abstract description 6
- 230000006911 nucleation Effects 0.000 claims description 56
- 238000010899 nucleation Methods 0.000 claims description 56
- 239000013078 crystal Substances 0.000 claims description 30
- 239000000126 substance Substances 0.000 claims description 23
- 239000000243 solution Substances 0.000 claims description 19
- 238000001556 precipitation Methods 0.000 claims description 14
- 229910052751 metal Inorganic materials 0.000 claims description 8
- 239000002184 metal Substances 0.000 claims description 8
- 229910000000 metal hydroxide Inorganic materials 0.000 claims description 8
- 150000004692 metal hydroxides Chemical class 0.000 claims description 8
- 150000002736 metal compounds Chemical class 0.000 claims description 5
- 150000004696 coordination complex Chemical class 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 4
- 150000003839 salts Chemical class 0.000 claims description 4
- 239000003637 basic solution Substances 0.000 claims description 3
- 239000012071 phase Substances 0.000 description 90
- 238000006243 chemical reaction Methods 0.000 description 31
- 238000012360 testing method Methods 0.000 description 27
- 239000000463 material Substances 0.000 description 21
- 238000009826 distribution Methods 0.000 description 18
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical group O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 14
- 230000015572 biosynthetic process Effects 0.000 description 13
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical group [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 description 13
- 229910010413 TiO 2 Inorganic materials 0.000 description 11
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical class O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 11
- 239000010936 titanium Substances 0.000 description 11
- 239000011258 core-shell material Substances 0.000 description 10
- 239000010408 film Substances 0.000 description 10
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 description 10
- 230000000704 physical effect Effects 0.000 description 10
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 9
- 238000003917 TEM image Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 9
- 239000002243 precursor Substances 0.000 description 9
- 230000004913 activation Effects 0.000 description 8
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 8
- 239000007864 aqueous solution Substances 0.000 description 7
- 239000003125 aqueous solvent Substances 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- 238000002441 X-ray diffraction Methods 0.000 description 6
- 230000002378 acidificating effect Effects 0.000 description 6
- JZQOJFLIJNRDHK-CMDGGOBGSA-N alpha-irone Chemical compound CC1CC=C(C)C(\C=C\C(C)=O)C1(C)C JZQOJFLIJNRDHK-CMDGGOBGSA-N 0.000 description 6
- 150000002430 hydrocarbons Chemical class 0.000 description 6
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 6
- 239000007791 liquid phase Substances 0.000 description 6
- 238000010998 test method Methods 0.000 description 6
- 229910000859 α-Fe Inorganic materials 0.000 description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 5
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 229930195733 hydrocarbon Natural products 0.000 description 5
- 229910001566 austenite Inorganic materials 0.000 description 4
- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 description 4
- 229910002113 barium titanate Inorganic materials 0.000 description 4
- 239000012620 biological material Substances 0.000 description 4
- 125000004432 carbon atom Chemical group C* 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 4
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 4
- 239000003153 chemical reaction reagent Substances 0.000 description 4
- MWKFXSUHUHTGQN-UHFFFAOYSA-N decan-1-ol Chemical compound CCCCCCCCCCO MWKFXSUHUHTGQN-UHFFFAOYSA-N 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- 239000011257 shell material Substances 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 235000010215 titanium dioxide Nutrition 0.000 description 4
- GYSCBCSGKXNZRH-UHFFFAOYSA-N 1-benzothiophene-2-carboxamide Chemical compound C1=CC=C2SC(C(=O)N)=CC2=C1 GYSCBCSGKXNZRH-UHFFFAOYSA-N 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 3
- WWZKQHOCKIZLMA-UHFFFAOYSA-N Caprylic acid Natural products CCCCCCCC(O)=O WWZKQHOCKIZLMA-UHFFFAOYSA-N 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 3
- GHVNFZFCNZKVNT-UHFFFAOYSA-N Decanoic acid Natural products CCCCCCCCCC(O)=O GHVNFZFCNZKVNT-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 235000010724 Wisteria floribunda Nutrition 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 3
- 230000007062 hydrolysis Effects 0.000 description 3
- 238000006460 hydrolysis reaction Methods 0.000 description 3
- 239000000693 micelle Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 125000001424 substituent group Chemical group 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 3
- PMBXCGGQNSVESQ-UHFFFAOYSA-N 1-Hexanethiol Chemical compound CCCCCCS PMBXCGGQNSVESQ-UHFFFAOYSA-N 0.000 description 2
- KBPLFHHGFOOTCA-UHFFFAOYSA-N 1-Octanol Chemical compound CCCCCCCCO KBPLFHHGFOOTCA-UHFFFAOYSA-N 0.000 description 2
- BBMCTIGTTCKYKF-UHFFFAOYSA-N 1-heptanol Chemical compound CCCCCCCO BBMCTIGTTCKYKF-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 2
- AMQJEAYHLZJPGS-UHFFFAOYSA-N N-Pentanol Chemical compound CCCCCO AMQJEAYHLZJPGS-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- ZUDYPQRUOYEARG-UHFFFAOYSA-L barium(2+);dihydroxide;octahydrate Chemical compound O.O.O.O.O.O.O.O.[OH-].[OH-].[Ba+2] ZUDYPQRUOYEARG-UHFFFAOYSA-L 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000004108 freeze drying Methods 0.000 description 2
- 229910000856 hastalloy Inorganic materials 0.000 description 2
- 229910052595 hematite Inorganic materials 0.000 description 2
- 239000011019 hematite Substances 0.000 description 2
- FXHGMKSSBGDXIY-UHFFFAOYSA-N heptanal Chemical compound CCCCCCC=O FXHGMKSSBGDXIY-UHFFFAOYSA-N 0.000 description 2
- ZSIAUFGUXNUGDI-UHFFFAOYSA-N hexan-1-ol Chemical compound CCCCCCO ZSIAUFGUXNUGDI-UHFFFAOYSA-N 0.000 description 2
- JARKCYVAAOWBJS-UHFFFAOYSA-N hexanal Chemical compound CCCCCC=O JARKCYVAAOWBJS-UHFFFAOYSA-N 0.000 description 2
- 238000001027 hydrothermal synthesis Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 229910010272 inorganic material Inorganic materials 0.000 description 2
- 239000011147 inorganic material Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 235000014413 iron hydroxide Nutrition 0.000 description 2
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 2
- 238000012933 kinetic analysis Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000000178 monomer Substances 0.000 description 2
- NUJGJRNETVAIRJ-UHFFFAOYSA-N octanal Chemical compound CCCCCCCC=O NUJGJRNETVAIRJ-UHFFFAOYSA-N 0.000 description 2
- HGBOYTHUEUWSSQ-UHFFFAOYSA-N pentanal Chemical compound CCCCC=O HGBOYTHUEUWSSQ-UHFFFAOYSA-N 0.000 description 2
- -1 phosgens Chemical class 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000008213 purified water Substances 0.000 description 2
- 238000010079 rubber tapping Methods 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- 238000010189 synthetic method Methods 0.000 description 2
- 238000002411 thermogravimetry Methods 0.000 description 2
- NQPDZGIKBAWPEJ-UHFFFAOYSA-N valeric acid Chemical compound CCCCC(O)=O NQPDZGIKBAWPEJ-UHFFFAOYSA-N 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- QNRATNLHPGXHMA-XZHTYLCXSA-N (r)-(6-ethoxyquinolin-4-yl)-[(2s,4s,5r)-5-ethyl-1-azabicyclo[2.2.2]octan-2-yl]methanol;hydrochloride Chemical compound Cl.C([C@H]([C@H](C1)CC)C2)CN1[C@@H]2[C@H](O)C1=CC=NC2=CC=C(OCC)C=C21 QNRATNLHPGXHMA-XZHTYLCXSA-N 0.000 description 1
- ZRKMQKLGEQPLNS-UHFFFAOYSA-N 1-Pentanethiol Chemical compound CCCCCS ZRKMQKLGEQPLNS-UHFFFAOYSA-N 0.000 description 1
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 1
- VPIAKHNXCOTPAY-UHFFFAOYSA-N Heptane-1-thiol Chemical compound CCCCCCCS VPIAKHNXCOTPAY-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 150000001299 aldehydes Chemical class 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- OBETXYAYXDNJHR-UHFFFAOYSA-N alpha-ethylcaproic acid Natural products CCCCC(CC)C(O)=O OBETXYAYXDNJHR-UHFFFAOYSA-N 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 125000003368 amide group Chemical group 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 150000001413 amino acids Chemical class 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 125000003710 aryl alkyl group Chemical group 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- RQPZNWPYLFFXCP-UHFFFAOYSA-L barium dihydroxide Chemical compound [OH-].[OH-].[Ba+2] RQPZNWPYLFFXCP-UHFFFAOYSA-L 0.000 description 1
- 229910001863 barium hydroxide Inorganic materials 0.000 description 1
- GONOPSZTUGRENK-UHFFFAOYSA-N benzyl(trichloro)silane Chemical compound Cl[Si](Cl)(Cl)CC1=CC=CC=C1 GONOPSZTUGRENK-UHFFFAOYSA-N 0.000 description 1
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical class [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 1
- 150000001720 carbohydrates Chemical class 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- ITZXULOAYIAYNU-UHFFFAOYSA-N cerium(4+) Chemical compound [Ce+4] ITZXULOAYIAYNU-UHFFFAOYSA-N 0.000 description 1
- 239000007771 core particle Substances 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 125000004093 cyano group Chemical group *C#N 0.000 description 1
- 125000006165 cyclic alkyl group Chemical group 0.000 description 1
- 125000000753 cycloalkyl group Chemical group 0.000 description 1
- 238000013500 data storage Methods 0.000 description 1
- VTXVGVNLYGSIAR-UHFFFAOYSA-N decane-1-thiol Chemical compound CCCCCCCCCCS VTXVGVNLYGSIAR-UHFFFAOYSA-N 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000012377 drug delivery Methods 0.000 description 1
- 150000002081 enamines Chemical class 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 125000004185 ester group Chemical group 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- RTZKZFJDLAIYFH-UHFFFAOYSA-N ether Substances CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 1
- 125000001033 ether group Chemical group 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 125000002485 formyl group Chemical group [H]C(*)=O 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- AEDIXYWIVPYNBI-UHFFFAOYSA-N heptanamide Chemical compound CCCCCCC(N)=O AEDIXYWIVPYNBI-UHFFFAOYSA-N 0.000 description 1
- MNWFXJYAOYHMED-UHFFFAOYSA-N heptanoic acid Chemical compound CCCCCCC(O)=O MNWFXJYAOYHMED-UHFFFAOYSA-N 0.000 description 1
- 125000000623 heterocyclic group Chemical group 0.000 description 1
- ALBYIUDWACNRRB-UHFFFAOYSA-N hexanamide Chemical compound CCCCCC(N)=O ALBYIUDWACNRRB-UHFFFAOYSA-N 0.000 description 1
- 238000000024 high-resolution transmission electron micrograph Methods 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 125000000468 ketone group Chemical group 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000013081 microcrystal Substances 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000004660 morphological change Effects 0.000 description 1
- FUZZWVXGSFPDMH-UHFFFAOYSA-N n-hexanoic acid Natural products CCCCCC(O)=O FUZZWVXGSFPDMH-UHFFFAOYSA-N 0.000 description 1
- 239000002159 nanocrystal Substances 0.000 description 1
- 229940031182 nanoparticles iron oxide Drugs 0.000 description 1
- 125000000449 nitro group Chemical group [O-][N+](*)=O 0.000 description 1
- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
- KZCOBXFFBQJQHH-UHFFFAOYSA-N octane-1-thiol Chemical compound CCCCCCCCS KZCOBXFFBQJQHH-UHFFFAOYSA-N 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 150000002923 oximes Chemical class 0.000 description 1
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- IPWFJLQDVFKJDU-UHFFFAOYSA-N pentanamide Chemical compound CCCCC(N)=O IPWFJLQDVFKJDU-UHFFFAOYSA-N 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 102000004196 processed proteins & peptides Human genes 0.000 description 1
- 108090000765 processed proteins & peptides Proteins 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
- 150000003384 small molecules Chemical class 0.000 description 1
- 239000000344 soap Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 125000000472 sulfonyl group Chemical group *S(*)(=O)=O 0.000 description 1
- 125000004434 sulfur atom Chemical group 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 150000003573 thiols Chemical class 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- 238000004627 transmission electron microscopy Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
- B82B1/00—Nanostructures formed by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
- B82B3/00—Manufacture or treatment of nanostructures by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/10—Preparation or treatment, e.g. separation or purification
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/02—Oxides; Hydroxides
- C01G49/06—Ferric oxide (Fe2O3)
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
Abstract
Description
本発明は、ナノ粒子及びその製造方法に関する。 The present invention relates to nanoparticles and a method for producing the same.
近年、材料・情報・バイオ等広範な産業の基盤にかかわるものとしてナノテクノロジーが注目されている。ナノとは基礎となる単位の１０−９倍の量であることを示す接頭辞であり、１メートルの１０９分の１が１ナノメートルである。ナノテクノロジーとはこのように微小な世界を扱う科学技術である。このナノテクノロジーと材料科学の融合より生まれた、ナノメートルオーダーの粒径を持つ粒子は「ナノ粒子」と呼ばれている。ナノ粒子は量子サイズ効果や大きな比表面積を有することから、バルクや小さな分子とは異なりサイズに依存した光学特性、電磁気特性等を示すことが知られている（非特許文献１及び２）。そのため、物理学、電子工学、情報工学、触媒化学、バイオサイエンス等幅広い分野でのナノ粒子の応用が進んでいる。また、材料も金属や金属酸化物、有機物等多岐に渡る（非特許文献３及び４）。 In recent years, nanotechnology has been attracting attention as being involved in the foundation of a wide range of industries such as materials, information, and biotechnology. Nano and is a prefix indicating the amount of 10 -9 times the underlying units, 1 10 9 minutes of 1 meter is 1 nanometer. Nanotechnology is a science and technology that deals with such a minute world. Particles with a particle size on the order of nanometers, born from this fusion of nanotechnology and materials science, are called "nanoparticles". Since nanoparticles have a quantum size effect and a large specific surface area, they are known to exhibit size-dependent optical properties, electromagnetic properties, and the like, unlike bulk and small molecules (Non-Patent Documents 1 and 2). Therefore, the application of nanoparticles in a wide range of fields such as physics, electronic engineering, information engineering, catalytic chemistry, and bioscience is advancing. In addition, there are a wide variety of materials such as metals, metal oxides, and organic substances (Non-Patent Documents 3 and 4).
ナノ粒子の合成法としては、熱プラズマ法（気相）、噴霧熱分解法（気相）、逆ミセル法（液相）、ホットソープ法（液相）、ソルボサーマル法（液相、超臨界相）、水熱合成法（液相、超臨界相）等、様々な工業的合成法が知られている。いずれの方法も、合成される粒子は、その温度、圧力、溶媒密度下において、安定相が得られる。 As a method for synthesizing nanoparticles, a thermal plasma method (gas phase), a spray thermal decomposition method (gas phase), an inverse micelle method (liquid phase), a hot soap method (liquid phase), and a sorbothermal method (liquid phase, supercritical) Various industrial synthesis methods such as phase) and hydrothermal synthesis (liquid phase, supercritical phase) are known. In either method, the particles to be synthesized have a stable phase under their temperature, pressure and solvent density.
ところで、多くの金属酸化物には、異なる結晶構造、異なる結晶形がある。金属酸化物をナノ粒子化する場合、例えば、対象の金属酸化物が酸化鉄（ＩＩＩ）であると、比較的低温ではα酸化鉄（ＩＩＩ）のナノ粒子が得られる。 By the way, many metal oxides have different crystal structures and different crystal forms. When the metal oxide is made into nanoparticles, for example, if the metal oxide of interest is iron (III) oxide, nanoparticles of α-iron oxide (III) can be obtained at a relatively low temperature.
一方、ナノ粒子の平均粒子径が数ｎｍ以下のオーダーになると、表面効果、ナノサイズ効果により、平均粒子径が数十ｎｍ以上のオーダーである場合に比べて金属酸化物の相状態が不安定相の状態へとシフトする場合があることが知られている。 On the other hand, when the average particle size of the nanoparticles is on the order of several nm or less, the phase state of the metal oxide is unstable compared to the case where the average particle size is on the order of several tens of nm or more due to the surface effect and the nanosize effect. It is known that it may shift to a phase state.
しかしながら、ナノ粒子の平均粒子径を数ｎｍ以下のオーダーにしたとしても、生成されるナノ粒子の主な生成相は、安定相となる。例えば、金属酸化物が酸化鉄（ＩＩＩ）である場合に不安定相であるγ相の酸化鉄（ＩＩＩ）のナノ粒子を合成することは極めて難しいとされる。加えて、金属酸化物が酸化チタン（ＩＶ）である場合に不安定相であるアモルファス相のナノ粒子を合成することは、不可能とされる。 However, even if the average particle size of the nanoparticles is on the order of several nm or less, the main production phase of the produced nanoparticles is a stable phase. For example, when the metal oxide is iron (III) oxide, it is extremely difficult to synthesize nanoparticles of γ-phase iron (III) oxide, which is an unstable phase. In addition, it is not possible to synthesize nanoparticles in an amorphous phase, which is an unstable phase when the metal oxide is titanium (IV) oxide.
本発明は、このような問題に鑑みてなされたものであり、不安定相を形成したい金属酸化物の種類によらず、また、ナノ粒子の平均粒子径の大きさによらずに、不安定相（準安定相を含む）の金属酸化物ナノ粒子を簡便かつ安定して供給可能な技術を提供することを目的とする。 The present invention has been made in view of such a problem, and is unstable regardless of the type of metal oxide in which the unstable phase is to be formed and regardless of the size of the average particle size of the nanoparticles. It is an object of the present invention to provide a technique capable of supplying metal oxide nanoparticles of a phase (including a metastable phase) easily and stably.
本発明者らは、上記の課題を達成するために鋭意研究を重ねた結果、ナノサイズの金属粒子を種粒子とし、当該種粒子の存在下で金属酸化物前駆体を臨界水条件で水熱処理することで、不安定相を形成したい金属酸化物の種類によらず、また、種粒子の平均粒子径の大きさによらずに、種粒子の表面に準安定相の金属酸化物を析出できることを見出し、本発明を完成するに至った。具体的に、本発明では、以下のようなものを提供する。 As a result of intensive studies to achieve the above problems, the present inventors have made nano-sized metal particles into seed particles, and hydrothermally heat-treated the metal oxide precursor in the presence of the seed particles under critical water conditions. By doing so, a metastable phase metal oxide can be precipitated on the surface of the seed particles regardless of the type of metal oxide for which the unstable phase is to be formed and regardless of the size of the average particle size of the seed particles. The present invention has been completed. Specifically, the present invention provides the following.
第１の特徴に係る発明は、表面に準安定相の金属酸化物が析出されたナノ粒子を提供する。 The invention according to the first feature provides nanoparticles in which a metastable phase metal oxide is precipitated on the surface.
第２の特徴に係る発明は、準安定相の金属酸化物が析出された析出層を有し、前記析出層は、エピタキシャル層、多結晶層又はアモルファス層を含む、ナノ粒子を提供する。 The invention according to the second feature has a precipitation layer in which a metal oxide of a metastable phase is precipitated, and the precipitation layer provides nanoparticles including an epitaxial layer, a polycrystalline layer or an amorphous layer.
第１及び第２の特徴に係る発明によると、これまで実現不可能とされていた準安定相の金属酸化物ナノ粒子を、不安定相を形成したい金属酸化物の種類によらず、また、平均粒子径の大きさによらずに利用することが可能となる。 According to the inventions relating to the first and second features, the metastable phase metal oxide nanoparticles, which have been considered unrealizable until now, can be treated regardless of the type of metal oxide in which the unstable phase is desired to be formed. It can be used regardless of the size of the average particle size.
そして、ナノ粒子の表面に準安定相の金属酸化物が析出されるため、半導体材料、触媒材料、生体材料、磁気データ記憶、バイオセンシング、ドラッグデリバリー等、幅広い用途に応用することが可能である。 Since the metastable phase metal oxide is deposited on the surface of the nanoparticles, it can be applied to a wide range of applications such as semiconductor materials, catalyst materials, biomaterials, magnetic data storage, biosensing, and drug delivery. ..
第３の特徴に係る発明は、第１又は第２の特徴に係る発明において、平均粒子径の標準偏差を前記平均粒子径で除した変動係数が０．１５以下であるナノ粒子を提供する。 The invention according to the third feature provides nanoparticles having a coefficient of variation of 0.15 or less obtained by dividing the standard deviation of the average particle size by the average particle size in the invention according to the first or second feature.
ナノ粒子は、そのサイズに依存したバルク材料とは異なる物性を持つ。第３の特徴に係る発明によると、ナノ粒子の粒子径分布が狭く、粒子径が厳密に制御されているため、準安定相の金属酸化物ナノ粒子に特有な物性を効果的に発揮させることができる。 Nanoparticles have different physical properties than bulk materials that depend on their size. According to the invention relating to the third feature, since the particle size distribution of the nanoparticles is narrow and the particle size is strictly controlled, the physical properties peculiar to the metastable phase metal oxide nanoparticles can be effectively exhibited. Can be done.
第４の特徴に係る発明は、金属酸化物によるナノサイズの粒子を種粒子とし、前記種粒子の存在下で金属酸化物前駆体を亜臨界水条件又は超臨界水条件で水熱処理することで、前記種粒子の表面に準安定相の金属酸化物を析出する工程を含む、ナノ粒子の製造方法である。 The invention according to the fourth feature is that nano-sized particles of metal oxide are used as seed particles, and the metal oxide precursor is hydrothermally treated under subcritical water conditions or supercritical water conditions in the presence of the seed particles. , A method for producing nanoparticles, which comprises a step of precipitating a metastable phase metal oxide on the surface of the seed particles.
第４の特徴に係る発明によると、種粒子の存在下で金属酸化物前駆体を水熱処理したことから、温度により過飽和度・反応速度を効率よく制御できる。そして、結果として、これまで実現不可能とされていた準安定相の金属酸化物ナノ粒子を、不安定相を形成したい金属酸化物の種類によらず、また、平均粒子径の大きさによらずに供給することができる。 According to the invention according to the fourth feature, since the metal oxide precursor is hydroheat-treated in the presence of seed particles, the degree of supersaturation and the reaction rate can be efficiently controlled by the temperature. As a result, the metastable phase metal oxide nanoparticles, which have been considered unrealizable until now, depend on the type of metal oxide in which the unstable phase is desired to be formed, and on the size of the average particle diameter. Can be supplied without.
ところで、ナノ粒子は、そのサイズに依存したバルク材料とは異なる物性を持つ。その物性を制御するためには、粒子径、形状の制御が重要である。しかしながら、これらの核発生、成長機構に基づく合成法では、均一な粒子径を得ることは原理的にも極めて困難である。 By the way, nanoparticles have different physical properties from bulk materials depending on their size. In order to control the physical properties, it is important to control the particle size and shape. However, it is extremely difficult in principle to obtain a uniform particle size by a synthetic method based on these nucleation and growth mechanisms.
第４の特徴に係る発明によると、種粒子に粒子前駆体を導入して種粒子を成長させていることから、種粒子の成長前に比べ、ナノ粒子の粒子径分布の範囲を狭くすることができる。例えば、５ｎｍから１０ｎｍと２倍の平均粒子径の範囲で粒子径分布をもつ種粒子の粒子群が平均５ｎｍ成長することで、成長後の粒子の平均粒子径は、１０〜１５ｎｍとなり、平均粒子径の範囲を２倍から１．５倍に狭くすることができる。 According to the invention relating to the fourth feature, since the particle precursor is introduced into the seed particle to grow the seed particle, the range of the particle size distribution of the nanoparticles is narrowed as compared with that before the growth of the seed particle. Can be done. For example, when a group of seed particles having a particle size distribution in the range of 5 nm to 10 nm, which is twice the average particle size, grows by an average of 5 nm, the average particle size of the grown particles becomes 10 to 15 nm, and the average particles. The diameter range can be narrowed from 2 to 1.5 times.
なお、金属酸化物前駆体を水熱処理に付したとしても、種粒子の非存在下では、金属酸化物前駆体は、安定相の金属酸化物に変化する。 Even if the metal oxide precursor is subjected to hydrothermal treatment, the metal oxide precursor changes to a stable phase metal oxide in the absence of seed particles.
第５の特徴に係る発明は、第４の特徴に係る発明において、前記種粒子が準安定相の金属酸化物である、製造方法である。 The invention according to the fifth feature is the production method in which the seed particle is a metal oxide in a metastable phase in the invention according to the fourth feature.
第６の特徴に係る発明は、第４又は第５の特徴に係る発明において、前記種粒子を構成する金属酸化物の格子定数が、前記種粒子を構成する金属酸化物と同一の化学式である安定相の金属化合物の格子定数とは異なる、製造方法である。 In the invention according to the sixth feature, in the invention according to the fourth or fifth feature, the lattice constant of the metal oxide constituting the seed particle is the same chemical formula as the metal oxide constituting the seed particle. This is a production method different from the lattice constant of the stable phase metal compound.
第７の特徴に係る発明は、第４から第６のいずれかの特徴に係る発明において、前記種粒子を構成する金属酸化物の結晶構造が、前記種粒子を構成する金属酸化物と同一の化学式である安定相の金属化合物の結晶構造とは異なる、製造方法である。 In the invention according to the seventh feature, in the invention according to any one of the fourth to sixth features, the crystal structure of the metal oxide constituting the seed particle is the same as that of the metal oxide constituting the seed particle. This is a production method different from the crystal structure of a stable phase metal compound having a chemical formula.
第５から第７の特徴に係る発明によると、種粒子が準安定相の金属酸化物であり、格子定数あるいは結晶構造が安定相のものとは異なる。そのため、種粒子が安定相の金属酸化物である場合に比べて、種粒子を構成する相と同質の準安定相の金属酸化物を種粒子表面に効率よく析出させることができる。 According to the inventions according to the fifth to seventh features, the seed particles are metastable metal oxides, and the lattice constant or crystal structure is different from that of the stable phase. Therefore, as compared with the case where the seed particle is a stable phase metal oxide, a metastable metal oxide having the same quality as the phase constituting the seed particle can be efficiently precipitated on the seed particle surface.
第８の特徴に係る発明は、第４から第７のいずれかの特徴に係る発明において、前記水熱条件下での溶液に含まれる前記ナノ粒子の含有量が０．０１ｍｏｌ／ｌ以上である、製造方法である。 The invention according to the eighth feature is the invention according to any one of the fourth to seventh features, wherein the content of the nanoparticles contained in the solution under hydrothermal conditions is 0.01 mol / l or more. , The manufacturing method.
第８の特徴に係る発明によると、反応器に供給された種粒子の合計表面積を一定以上確保することができ、金属酸化物前駆体を種粒子表面への被膜形成に供する際、余剰の金属酸化物前駆体が残り、該余剰の金属酸化物前駆体から安定相の金属酸化物が生成されるのを抑えることができる。 According to the invention according to the eighth feature, the total surface area of the seed particles supplied to the reactor can be secured above a certain level, and when the metal oxide precursor is used for forming a film on the surface of the seed particles, a surplus metal is used. The oxide precursor remains, and it is possible to suppress the formation of a stable phase metal oxide from the surplus metal oxide precursor.
第９の特徴に係る発明は、第３又は第４の特徴に係る発明において、前記水熱処理を行う際の溶液に含まれる前記金属酸化物前駆体の濃度が１ｍｏｌ／ｌ以下である、製造方法である。 The invention according to the ninth feature is the production method according to the third or fourth feature, wherein the concentration of the metal oxide precursor contained in the solution at the time of performing the hydrothermal treatment is 1 mol / l or less. Is.
ナノ粒子を液相にて合成する場合、オストワルトライプニングと呼ばれる、再溶解・析出法を併用することが知られている。この手法を用いると、比較的小さなナノ粒子が再溶解し、再溶解されたナノ粒子成分が比較的大きなナノ粒子上に析出するため、粒子径分布の幅をよりいっそう狭めることができる。 When synthesizing nanoparticles in the liquid phase, it is known to use a redissolution / precipitation method called Ostwald tripping in combination. When this method is used, the width of the particle size distribution can be further narrowed because the relatively small nanoparticles are redissolved and the redissolved nanoparticles are deposited on the relatively large nanoparticles.
第９の特徴に係る発明によると、水熱処理を行う際の溶液に含まれる金属酸化物前駆体の濃度に上限が設けられているため、再溶解・析出法の原理を応用しているにも関わらず、溶液中で金属水酸化物が過飽和状態になり、金属酸化物前駆体の均一核生成が起こり、かえって粒子径分布が広くなるのを防ぐことができる。 According to the invention relating to the ninth feature, since the concentration of the metal oxide precursor contained in the solution during hydrothermal treatment is set to an upper limit, the principle of the redissolution / precipitation method is also applied. Nevertheless, it is possible to prevent the metal hydroxide from becoming supersaturated in the solution, causing uniform nucleation of the metal oxide precursor, and rather widening the particle size distribution.
また、一般的に知られているオストワルトライプニングによる結晶成長は、数時間から数日という長い時間を要するが、第９の特徴に係る発明ではそれほど長い時間を要しない。また、一般的に知られているオストワルトライプニングによる結晶成長で生成する相は、安定相であるが、第９の特徴に係る発明では、種粒子の表面に準安定相の金属酸化物を析出させることができる点で画期的である。 Further, the generally known crystal growth by Ostwald tripping takes a long time of several hours to several days, but the invention according to the ninth feature does not require so long time. Further, the phase formed by crystal growth by generally known Ostwar tripping is a stable phase, but in the invention according to the ninth feature, a metal oxide of a metastable phase is precipitated on the surface of seed particles. It is epoch-making in that it can be made to do.
第１０の特徴に係る発明は、第４から第９のいずれかの特徴に係る発明において、前記水熱処理の温度が、前記金属酸化物前駆体が均一核生成する速度よりも前記金属酸化物前駆体が不均一核生成する速度の方が大きい温度である、製造方法である。 The invention according to the tenth feature is the invention according to any one of the fourth to ninth features, wherein the temperature of the hydrothermal treatment is higher than the rate at which the metal oxide precursor forms uniform nuclei. It is a manufacturing method in which the rate at which the body forms heterogeneous nuclei is higher.
第１０の特徴に係る発明によると、主として金属酸化物前駆体の不均一核生成が進行するため、表面に析出される金属酸化物において、準安定相の割合をよりいっそう高めることができる。 According to the invention according to the tenth feature, since heterogeneous nucleation of the metal oxide precursor mainly proceeds, the proportion of the metastable phase in the metal oxide precipitated on the surface can be further increased.
第１１の特徴に係る発明は、第４から第１０のいずれかの特徴に係る発明において、前記金属酸化物前駆体は、金属塩、金属錯体、金属水酸化物から選択される１種以上である、製造方法である。 The invention according to the eleventh feature is the invention according to any one of the fourth to tenth features, wherein the metal oxide precursor is one or more selected from a metal salt, a metal complex, and a metal hydroxide. There is a manufacturing method.
第１１の特徴に係る発明によると、金属酸化物前駆体が水系溶媒に好適に溶解されるため、水熱処理を効率よく進めることができる。 According to the invention according to the eleventh feature, since the metal oxide precursor is suitably dissolved in an aqueous solvent, hydrothermal treatment can be efficiently carried out.
第１２の特徴に係る発明は、第４から第１１のいずれかの特徴に係る発明において、前記金属酸化物前駆体が塩基性溶液に溶解されている、製造方法である。 The invention according to the twelfth feature is the production method in which the metal oxide precursor is dissolved in a basic solution in the invention according to any one of the fourth to eleventh features.
第１２の特徴に係る発明によると、酸性条件下に比べて金属酸化物前駆体の溶解度が高く、水熱処理の反応場での金属水酸化物の過飽和度を小さく抑えることができ、結果として、種粒子表面における不均一核生成を支配的に進めることができる。 According to the invention according to the twelfth feature, the solubility of the metal oxide precursor is higher than that under acidic conditions, and the supersaturation degree of the metal hydroxide in the reaction field of the hydrothermal treatment can be suppressed to a small value, and as a result, Non-uniform nucleation on the surface of seed particles can be predominantly promoted.
第１３の特徴に係る発明は、第４から第１２のいずれかの特徴に係る発明において、前記水熱処理が有機修飾剤の存在下で行われる。 In the invention according to the thirteenth feature, in the invention according to any one of the fourth to twelfth features, the hydrothermal treatment is performed in the presence of an organic modifier.
通常、水系溶媒と有機修飾剤とは相分離する。しかしながら、亜臨界水条件又は超臨界水条件では、有機修飾剤が水と均一相を形成する。 Usually, the aqueous solvent and the organic modifier are phase-separated. However, under subcritical or supercritical water conditions, the organic modifier forms a homogeneous phase with water.
第１３の特徴に係る発明によると、ナノ粒子の表面に有機修飾剤がキャッピングし、ナノ粒子の表面エネルギーを低くし、ミセル形成することができる。そして、有機修飾剤の存在により、酸化物モノマーと錯体を形成し、それがイオンよりも安定であるために、有機修飾剤の亜臨界水又は超臨界水への溶解度がいっそう高まり、それにより、さらに高速にオストワルトライプニングを進めることが可能である。そして、種粒子の粒子径よりも小さな径の準安定相金属酸化物のナノ粒子を、種粒子の総重量よりも大量に合成することができる。加えて、オストワルトライプニングの効果により、粒子径分布の幅をよりいっそう狭めることができる。 According to the invention according to the thirteenth feature, an organic modifier is capped on the surface of the nanoparticles, the surface energy of the nanoparticles is lowered, and micelles can be formed. The presence of the organic modifier forms a complex with the oxide monomer, which is more stable than the ion, which further increases the solubility of the organic modifier in subcritical or supercritical water, thereby. It is possible to proceed with Ostwar tripping at even higher speeds. Then, nanoparticles of the metastable phase metal oxide having a diameter smaller than the particle diameter of the seed particles can be synthesized in a larger amount than the total weight of the seed particles. In addition, due to the effect of Ostwald tapping, the width of the particle size distribution can be further narrowed.
第１４の特徴に係る発明は、第４から第１３のいずれかの特徴に係る発明において、前記工程を経た後の前記ナノ粒子の平均粒子径の標準偏差を前記平均粒子径で除した変動係数が、前記工程を経る前の前記種粒子の前記変動係数よりも小さい。 The invention according to the fourteenth feature is the coefficient of variation in the invention according to any one of the fourth to thirteenth features, which is obtained by dividing the standard deviation of the average particle size of the nanoparticles after the step by the average particle size. However, it is smaller than the coefficient of variation of the seed particle before going through the step.
ナノ粒子は、そのサイズに依存したバルク材料とは異なる物性を持つ。第１４の特徴に係る発明によると、ナノ粒子の粒子径分布が狭く、粒子径が厳密に制御されているため、準安定相の金属酸化物ナノ粒子に特有な物性を効果的に発揮させることができる。 Nanoparticles have different physical properties than bulk materials that depend on their size. According to the invention relating to the fourteenth feature, since the particle size distribution of the nanoparticles is narrow and the particle size is strictly controlled, the physical properties peculiar to the metastable phase metal oxide nanoparticles can be effectively exhibited. Can be done.
本発明によると、不安定相を形成したい金属酸化物の種類によらず、また、ナノ粒子の平均粒子径の大きさによらずに、不安定相（準安定相を含む）の金属酸化物ナノ粒子を簡便かつ安定して供給可能な技術を提供することができる。 According to the present invention, the metal oxide of the unstable phase (including the metastable phase) does not depend on the type of the metal oxide for which the unstable phase is formed and the size of the average particle size of the nanoparticles. It is possible to provide a technique capable of supplying nanoparticles easily and stably.
以下、本発明の具体的な実施形態について、詳細に説明するが、本発明は、以下の実施形態に何ら限定されるものではなく、本発明の目的の範囲内において、適宜変更を加えて実施することができる。 Hereinafter, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and the present invention is carried out with appropriate modifications within the scope of the object of the present invention. can do.
＜ナノ粒子＞
本実施形態におけるナノ粒子は、表面に準安定相の金属酸化物が析出されたナノ粒子である。
<Nanoparticles>
The nanoparticles in this embodiment are nanoparticles in which a metal oxide having a metastable phase is precipitated on the surface.
金属酸化物は、安定相及び準安定相を形成可能であれば、特に限定されない。本実施形態において、安定相とは、ある温度および圧力下において自由エネルギーが最も低くなる相をいい、真の安定状態に相当する。準安定相とは、真の安定状態ではなく、熱平衡状態では存在しないが、所定の条件が充足されることによって暫定的に存在し得る相をいい、外部から大きな乱れが与えられない限り安定に存在できるような状態に相当する。準安定相は、小さな乱れに対しては安定であるが、外部から大きな乱れが与えられると不安定になり、準安定相から安定相に変化する。 The metal oxide is not particularly limited as long as it can form a stable phase and a metastable phase. In the present embodiment, the stable phase means the phase in which the free energy is the lowest under a certain temperature and pressure, and corresponds to a true stable state. A metastable phase is a phase that is not in a true stable state and does not exist in a thermal equilibrium state, but can temporarily exist when certain conditions are satisfied, and is stable unless a large disturbance is given from the outside. It corresponds to a state in which it can exist. The metastable phase is stable to small turbulences, but becomes unstable when a large turbulence is applied from the outside, and changes from a metastable phase to a stable phase.
安定相及び準安定相を形成可能な金属酸化物の例として、酸化鉄（ＩＩＩ）、酸化チタン（ＩＶ）、酸化セリウム（ＩＶ）、チタン酸バリウム等が挙げられる。 Examples of metal oxides capable of forming a stable phase and a metastable phase include iron (III) oxide, titanium (IV) oxide, cerium (IV) oxide, barium titanate and the like.
酸化鉄（ＩＩＩ）は、化学式Ｆｅ２Ｏ３で表され、酸化第二鉄、ヘマタイト、赤色酸化鉄、合成磁赤鉄鉱、弁柄、三酸化二鉄とも称される。酸化鉄（ＩＩＩ）は、安定相であるα相と、準安定相であるβ相、γ相及びε相とを形成可能である。 Iron (III) oxide is represented by the chemical formula Fe 2 O 3 , and is also referred to as ferric oxide, hematite, red iron oxide, synthetic hematite, valve stem, and ferric trioxide. Iron (III) oxide can form a stable α phase and a metastable β phase, γ phase, and ε phase.
酸化チタン（ＩＶ）は、化学式ＴｉＯ２で表され、二酸化チタン、単に酸化チタン、チタニアとも称される。酸化チタン（ＩＶ）は、安定相であるルチル型（正方晶）と、準安定相であるアナターゼ型（正方晶）及びブルッカイト型（斜方晶）とを形成可能である。 Titanium oxide (IV) is represented by the chemical formula TiO 2 , and is also referred to as titanium dioxide, simply titanium oxide, or titania. Titanium oxide (IV) can form a stable phase, rutile type (tetragonal crystal), and a metastable phase, anatase type (tetragonal crystal) and brookite type (orthorhombic crystal).
酸化セリウム（ＩＶ）は、化学式ＣｅＯ２で表され、セリアとも称される。酸化セリウム（ＩＶ）は、安定相である蛍石構造の結晶形態と、準安定相である立方晶の結晶形態とを形成可能である。 Cerium (IV) oxide is represented by the chemical formula CeO 2 and is also referred to as ceria. Cerium (IV) oxide can form a crystal form of a fluorite structure, which is a stable phase, and a cubic crystal form, which is a metastable phase.
チタン酸バリウムは、化学式ＢａＴｉＯ３で表され、ペロブスカイト構造をもつ人工鉱物である。チタン酸バリウムは、安定相である立方晶の結晶状態と、準安定相である菱面体晶、斜方晶、及び正方晶の結晶状態とを形成可能である。 Barium titanate is an artificial mineral represented by the chemical formula BaTIO 3 and having a perovskite structure. Barium titanate can form a cubic crystal state as a stable phase and a rhombic crystal, orthorhombic crystal, and tetragonal crystal states as metastable phases.
本実施形態に係るナノ粒子において、準安定相の金属酸化物が析出された析出層の例として、エピタキシャル層、多結晶層、及びアモルファス層等が例示される。 Examples of the precipitated layer in which the metal oxide of the metastable phase is precipitated in the nanoparticles according to the present embodiment include an epitaxial layer, a polycrystalline layer, and an amorphous layer.
本実施形態において、エピタキシャル層とは、エピタキシャル成長によって成膜された層をいい、エピタキシャル成長とは、薄膜結晶成長技術のひとつであり、基材ナノ粒子の表面で結晶成長を行い、基材ナノ粒子の結晶面にそろえて配列する成長の様式をいう。 In the present embodiment, the epitaxial layer means a layer formed by epitaxial growth, and epitaxial growth is one of the thin film crystal growth techniques, in which crystal growth is performed on the surface of the substrate nanoparticles to obtain the substrate nanoparticles. A mode of growth that is aligned with the crystal plane.
本実施形態では、エピタキシャルの状態は、基材ナノ粒子を構成する物質とエピタキシャル層を構成する物質とが同じホモエピタキシャルであってもよいし、これらの物質が異なる物質であるヘテロエピタキシャルであってもよい。 In the present embodiment, the epitaxial state may be a homoepitaxial in which the substance constituting the substrate nanoparticles and the substance constituting the epitaxial layer are the same homoepitaxial, or heteroepitaxial in which these substances are different substances. May be good.
一般に、エピタキシャル成長が起こるには、基材ナノ粒子を構成する物質とエピタキシャル層を構成する物質との格子定数がほぼ等しく、これらの物質の温度による膨張係数が近いことが好ましいとされている。一例として、本実施形態に記載のナノ粒子は、γ−酸化鉄（ＩＩＩ）ナノ粒子の表面に、γ−酸化鉄（ＩＩＩ）結晶にてエピタキシャル成長されたエピタキシャル層が形成された態様を当然に包含する。 In general, in order for epitaxial growth to occur, it is preferable that the lattice constants of the substances constituting the substrate nanoparticles and the substances constituting the epitaxial layer are substantially equal, and the expansion coefficients of these substances with respect to temperature are close to each other. As an example, the nanoparticles according to the present embodiment naturally include an embodiment in which an epitaxial layer epitaxially grown with γ-iron (III) crystals is formed on the surface of γ-iron (III) oxide nanoparticles. To do.
本実施形態において、多結晶層とは、ＴＥＭ（透過型電子顕微鏡）の顕微鏡像において、結晶方位の異なる２つ以上の結晶粒・微結晶から形成された層をいう。 In the present embodiment, the polycrystalline layer means a layer formed of two or more crystal grains / microcrystals having different crystal orientations in a microscope image of a TEM (transmission electron microscope).
本実施形態において、アモルファス層とは、アモルファス状態、すなわち非晶質状態には至っていないがアモルファスに近い状態となっている層をいい、一部に結晶構造を有していてもよい。 In the present embodiment, the amorphous layer means an amorphous layer, that is, a layer that has not reached the amorphous state but is in a state close to amorphous, and may have a crystal structure in a part thereof.
ナノ粒子の平均粒子径の下限は特に限定されない。種粒子の表面にエピタキシャル層を形成するに際しての製造安定性を確保する等の観点から、ナノ粒子の平均粒子径の下限は、２ｎｍ以上であることが好ましく、５ｎｍ以上であることがより好ましい。加えて、これまで準安定相の状態で金属酸化物ナノ粒子を供給するのが難しかったという観点から、ナノ粒子の平均粒子径の下限は、１０ｎｍ以上であることが特に好ましい。 The lower limit of the average particle size of nanoparticles is not particularly limited. From the viewpoint of ensuring production stability when forming the epitaxial layer on the surface of the seed particles, the lower limit of the average particle size of the nanoparticles is preferably 2 nm or more, and more preferably 5 nm or more. In addition, the lower limit of the average particle size of the nanoparticles is particularly preferably 10 nm or more from the viewpoint that it has been difficult to supply the metal oxide nanoparticles in the metastable phase state.
ナノ粒子の平均粒子径の上限も特に限定されないが、半導体材料、触媒材料、生体材料等多くの分野に応用するに際しての暴露表面積（接触可能性）の最大化、種粒子の表面にエピタキシャル層を形成するに際し、種粒子の表面に十分なエピタキシャル層を形成できるだけの表面積を確保する等の観点から、ナノ粒子の平均粒子径の上限は、１μｍ以下であることが好ましく、５００ｎｍ以下であることがより好ましく、１００ｎｍ以下であることがさらに好ましく、５０ｎｍ以下であることが特に好ましい。 The upper limit of the average particle size of nanoparticles is not particularly limited, but the exposed surface area (contactability) is maximized when applied to many fields such as semiconductor materials, catalyst materials, and biological materials, and an epitaxial layer is provided on the surface of seed particles. From the viewpoint of securing a surface area sufficient to form a sufficient epitaxial layer on the surface of the seed particles during formation, the upper limit of the average particle size of the nanoparticles is preferably 1 μm or less, and preferably 500 nm or less. It is more preferably 100 nm or less, and particularly preferably 50 nm or less.
析出層の厚さの下限は特に限定されないが、半導体材料、触媒材料、生体材料等多くの分野に応用するに際し、表面に準安定相の金属酸化物が形成されていることの機能を十分に発揮させる等の観点から、析出層の厚さの下限は、０．１ｎｍ以上であることが好ましく、０．３ｎｍ以上であることがより好ましく、０．５ｎｍ以上であることが特に好ましい。 The lower limit of the thickness of the precipitation layer is not particularly limited, but when applied to many fields such as semiconductor materials, catalyst materials, and biological materials, the function of forming a metastable phase metal oxide on the surface is sufficient. From the viewpoint of exerting the effect, the lower limit of the thickness of the precipitation layer is preferably 0.1 nm or more, more preferably 0.3 nm or more, and particularly preferably 0.5 nm or more.
析出層の厚さの上限も特に限定されないが、種粒子の表面に析出層を形成するに際し、析出層を構成する金属酸化物の前駆体が残存し、残存した金属酸化物前駆体から安定相の金属酸化物が生成されるのを防ぐため、析出層の厚さの下限は、２０ｎｍ以下であることが好ましく、１５ｎｍ以下であることがより好ましく、１０ｎｍ以下であることが特に好ましい。 The upper limit of the thickness of the precipitation layer is not particularly limited, but when the precipitation layer is formed on the surface of the seed particles, the metal oxide precursor constituting the precipitation layer remains, and the remaining metal oxide precursor is used as a stable phase. In order to prevent the formation of the metal oxide of the above, the lower limit of the thickness of the precipitation layer is preferably 20 nm or less, more preferably 15 nm or less, and particularly preferably 10 nm or less.
また、粒子径分布の幅の狭さを示す指標として、平均粒子径の標準偏差を平均粒子径で除した変動係数を用いることができる。ナノ粒子は、そのサイズに依存したバルク材料とは異なる物性を持つ。準安定相の金属酸化物ナノ粒子に特有な物性を効果的に発揮させる観点から、変動係数は、小さいほうが好ましい。変動係数は、０．１５以下であることが好ましく、０．１３以下であることがより好ましく、０．１０以下であることがさらに好ましい。 Further, as an index indicating the narrowness of the particle size distribution, the coefficient of variation obtained by dividing the standard deviation of the average particle size by the average particle size can be used. Nanoparticles have different physical properties than bulk materials that depend on their size. From the viewpoint of effectively exhibiting the physical properties peculiar to the metal oxide nanoparticles of the metastable phase, the coefficient of variation is preferably small. The coefficient of variation is preferably 0.15 or less, more preferably 0.13 or less, and even more preferably 0.10 or less.
本実施形態において、種々の粒子の平均粒子径及び層厚は、ＴＥＭ（透過型電子顕微鏡）により粒子の画像を撮像し、そのＴＥＭ像を画像解析・画像計測ソフトウェアにより解析して求めた値であるものとする。 In the present embodiment, the average particle diameter and layer thickness of various particles are values obtained by imaging an image of the particles with a TEM (transmission electron microscope) and analyzing the TEM image with image analysis / image measurement software. Suppose there is.
＜ナノ粒子の製造方法＞
続いて、本実施形態に係るナノ粒子の製造方法を説明する。本製造方法は、金属酸化物によるナノサイズの粒子を種粒子とし、該種粒子の存在下で金属酸化物前駆体を亜臨界水条件又は超臨界水条件で水熱処理する工程を含む。この工程を経ることで、種粒子の表面に準安定相の金属酸化物を析出させることができる。
<Manufacturing method of nanoparticles>
Subsequently, a method for producing nanoparticles according to the present embodiment will be described. The present production method includes a step of using nano-sized particles of metal oxide as seed particles and hydrothermally treating the metal oxide precursor under subcritical water conditions or supercritical water conditions in the presence of the seed particles. By going through this step, a metal oxide having a metastable phase can be precipitated on the surface of the seed particles.
種粒子の存在下で金属酸化物前駆体を水熱処理することで、温度により過飽和度・反応速度を効率よく制御できる。そして、結果として、これまで実現不可能とされていた準安定相の金属酸化物ナノ粒子を、不安定相を形成したい金属酸化物の種類によらず、また、平均粒子径の大きさによらずに供給することができる。 By hydrothermally treating the metal oxide precursor in the presence of seed particles, the degree of supersaturation and reaction rate can be efficiently controlled by the temperature. As a result, the metastable phase metal oxide nanoparticles, which have been considered unrealizable until now, depend on the type of metal oxide in which the unstable phase is desired to be formed, and on the size of the average particle diameter. Can be supplied without.
ところで、ナノ粒子は、そのサイズに依存したバルク材料とは異なる物性を持つ。その物性を制御するためには、粒子径、形状の制御が重要である。しかしながら、これらの核発生、成長機構に基づく合成法では、均一な粒子径を得ることは原理的にも極めて困難である。 By the way, nanoparticles have different physical properties from bulk materials depending on their size. In order to control the physical properties, it is important to control the particle size and shape. However, it is extremely difficult in principle to obtain a uniform particle size by a synthetic method based on these nucleation and growth mechanisms.
本製造方法によると、種粒子に粒子前駆体を導入して種粒子を成長させていることから、種粒子の成長前に比べ、ナノ粒子の粒子径分布の範囲を狭くすることができる。言うなれば、上記工程を経た後のナノ粒子の平均粒子径の標準偏差を平均粒子径で除した変動係数が、工程を経る前の種粒子の変動係数よりも小さくすることができる。例えば、５ｎｍから１０ｎｍと２倍の平均粒子径の範囲で粒子径分布をもつ種粒子の粒子群が平均５ｎｍ成長することで、成長後の粒子の平均粒子径は、１０〜１５ｎｍとなり、平均粒子径の範囲を２倍から１．５倍に狭くすることができる。 According to this production method, since the particle precursor is introduced into the seed particles to grow the seed particles, the range of the particle size distribution of the nanoparticles can be narrowed as compared with before the seed particles are grown. In other words, the coefficient of variation obtained by dividing the standard deviation of the average particle size of the nanoparticles after the above step by the average particle size can be made smaller than the coefficient of variation of the seed particles before the step. For example, when a group of seed particles having a particle size distribution in the range of 5 nm to 10 nm, which is twice the average particle size, grows by an average of 5 nm, the average particle size of the grown particles becomes 10 to 15 nm, and the average particles. The diameter range can be narrowed from 2 to 1.5 times.
なお、金属酸化物前駆体を水熱処理に付したとしても、種粒子の非存在下では、金属酸化物前駆体は、安定相の金属酸化物に変化する。 Even if the metal oxide precursor is subjected to hydrothermal treatment, the metal oxide precursor changes to a stable phase metal oxide in the absence of seed particles.
〔水熱処理〕
本実施形態において、水熱処理とは、原料を加圧した熱水中で溶解、析出させることで、原料から金属酸化物を得る処理をいう。原料の加水分解により水酸化物が生成し、その水酸化物が脱水縮合することで金属酸化物を生じる。
ＭＡｘ＋ｘＨ２Ｏ→Ｍ（ＯＨ）ｘ＋ｘＨＡ
Ｍ（ＯＨ）Ｘ→ＭＯｘ／２＋（ｘ／２）Ｈ２Ｏ
[Hydraulic heat treatment]
In the present embodiment, the hydrothermal treatment refers to a process of obtaining a metal oxide from a raw material by dissolving and precipitating the raw material in pressurized hot water. Hydroxide is produced by hydrolysis of the raw material, and the hydroxide is dehydrated and condensed to produce a metal oxide.
MA x + xH 2 O → M (OH) x + xHA
M (OH) X → MO x / 2 + (x / 2) H 2 O
水熱処理は、亜臨界水条件又は超臨界水条件で行われる。本実施形態において、亜臨界水条件とは、水の状態図における臨界点（３７４℃，２１８気圧（２２．１ＭＰａ））に近い温度、圧力の熱水状態をいう。また、超臨界水条件とは、臨界点を超える温度及び圧力の熱水状態をいう。亜臨界水条件あるいは超臨界水条件では、水溶液が低粘度化することによって、優れた浸透力と激しい加水分解作用を発揮することができる。 Hydrothermal treatment is performed under subcritical water conditions or supercritical water conditions. In the present embodiment, the sub-critical water condition refers to a hot water state having a temperature and pressure close to the critical point (374 ° C., 218 atm (22.1 MPa)) in the water phase diagram. The supercritical water condition refers to a hot water state having a temperature and pressure exceeding the critical point. Under subcritical water conditions or supercritical water conditions, the viscosity of the aqueous solution is reduced, so that excellent penetrating power and vigorous hydrolysis action can be exhibited.
水熱処理の温度は、亜臨界水条件又は超臨界水条件にあれば、特に限定されないが、金属酸化物前駆体が均一核生成する速度よりも、金属酸化物前駆体が不均一核生成する速度の方が大きい温度であることが好ましい。そのような温度条件にあることで、主として金属酸化物前駆体の不均一核生成が進行するため、表面に析出される金属酸化物において、準安定相の割合をよりいっそう高めることができる。 The temperature of the hydrothermal treatment is not particularly limited as long as it is under subcritical water conditions or supercritical water conditions, but the rate of heterogeneous nucleation of the metal oxide precursor is higher than the rate of uniform nucleation of the metal oxide precursor. Is preferably a higher temperature. Under such temperature conditions, heterogeneous nucleation of the metal oxide precursor mainly proceeds, so that the proportion of the metastable phase in the metal oxide precipitated on the surface can be further increased.
具体的に、水熱処理の温度は、４５０℃以下であることが好ましく、４００℃以下であることがより好ましく３００℃以下であることがさらに好ましい。 Specifically, the temperature of the hydrothermal treatment is preferably 450 ° C. or lower, more preferably 400 ° C. or lower, and even more preferably 300 ° C. or lower.
〔種粒子〕
種粒子は、金属酸化物によるナノサイズの粒子であれば、特に限定されないが、種粒子の表面に準安定相の金属酸化物を効率よく析出させるには、種粒子を構成する物質もまた準安定相であることが好ましい。そのため、種粒子は、準安定相の金属酸化物であり、種粒子を構成する金属酸化物の格子定数及び結晶構造は、当該種粒子を構成する金属酸化物と同一の化学式である安定相の金属化合物の格子定数及び結晶構造とは異なることが好ましい。例えば、種粒子の表面に準安定相であるγ相の酸化鉄（ＩＩＩ）を析出させたい場合、種粒子としてγ相の酸化鉄（ＩＩＩ）を用いることが好ましい。
[Seed particle]
The seed particle is not particularly limited as long as it is a nano-sized particle made of a metal oxide, but in order to efficiently deposit a metastable phase metal oxide on the surface of the seed particle, the substance constituting the seed particle is also quasi. It is preferably a stable phase. Therefore, the seed particles are metastable metal oxides, and the lattice constant and crystal structure of the metal oxides constituting the seed particles are of the stable phase having the same chemical formula as the metal oxides constituting the seed particles. It is preferable that the lattice constant and crystal structure of the metal compound are different. For example, when it is desired to precipitate γ-phase iron (III) oxide which is a metastable phase on the surface of seed particles, it is preferable to use γ-phase iron (III) oxide as seed particles.
種粒子の平均粒子径の下限は特に限定されない。種粒子の表面に準安定相の金属酸化物を析出させるに際しての製造安定性を確保する等の観点から、種粒子の平均粒子径の下限は、２ｎｍ以上であることが好ましく、５ｎｍ以上であることがより好ましい。加えて、これまで準安定相の状態で金属酸化物ナノ粒子を供給するのが難しかったという観点から、種粒子の平均粒子径の下限は、１０ｎｍ以上であることが特に好ましい。 The lower limit of the average particle size of the seed particles is not particularly limited. From the viewpoint of ensuring production stability when depositing a metastable phase metal oxide on the surface of seed particles, the lower limit of the average particle size of seed particles is preferably 2 nm or more, preferably 5 nm or more. Is more preferable. In addition, from the viewpoint that it has been difficult to supply metal oxide nanoparticles in a metastable phase, the lower limit of the average particle size of the seed particles is particularly preferably 10 nm or more.
種粒子の平均粒子径の上限も特に限定されないが、半導体材料、触媒材料、生体材料等多くの分野に応用するに際しての暴露表面積（接触可能性）の最大化、種粒子の表面に準安定相の金属酸化物を十分に析出できるだけの表面積を確保する等の観点から、種粒子の平均粒子径の上限は、１μｍ以下であることが好ましく、５００ｎｍ以下であることがより好ましく、１００ｎｍ以下であることがさらに好ましく、５０ｎｍ以下であることが特に好ましい。 The upper limit of the average particle size of the seed particles is not particularly limited, but the exposed surface area (contactability) is maximized when applied to many fields such as semiconductor materials, catalyst materials, and biological materials, and the metastable phase on the surface of the seed particles. The upper limit of the average particle size of the seed particles is preferably 1 μm or less, more preferably 500 nm or less, and more preferably 100 nm or less, from the viewpoint of securing a surface area sufficient for precipitating the metal oxide of the above. It is more preferable, and it is particularly preferable that it is 50 nm or less.
水熱処理を行う際の亜臨界水又は超臨界水（以下、「超臨界水等」とも称する。）に含まれる種粒子の濃度の下限は、特に限定されない。反応器に供給された種粒子の合計表面積を一定以上確保する観点から、種粒子の濃度の下限は、０．０１ｍｏｌ／ｌ以上であることが好ましく、０．０５ｍｏｌ／ｌ以上であることがより好ましく、０．１ｍｏｌ／ｌ以上であることがさらに好ましい。種粒子の合計表面積を一定以上確保することで、金属酸化物前駆体を種粒子表面への被膜形成に供する際、余剰の金属酸化物前駆体が残り、該余剰の金属酸化物前駆体から安定相の金属酸化物が生成されるのを抑えることができる。 The lower limit of the concentration of seed particles contained in subcritical water or supercritical water (hereinafter, also referred to as "supercritical water") when performing hydrothermal treatment is not particularly limited. From the viewpoint of securing the total surface area of the seed particles supplied to the reactor to a certain level or more, the lower limit of the concentration of the seed particles is preferably 0.01 mol / l or more, and more preferably 0.05 mol / l or more. It is preferably 0.1 mol / l or more, and more preferably 0.1 mol / l or more. By securing the total surface area of the seed particles to a certain level or more, when the metal oxide precursor is used to form a film on the surface of the seed particles, a surplus metal oxide precursor remains and is stable from the surplus metal oxide precursor. The formation of phase metal oxides can be suppressed.
種粒子の濃度の上限も特に限定されないが、種粒子及び金属酸化物前駆体の量のバランスを考慮すると、１ｍｏｌ／ｌ以下であることが好ましく、０．５ｍｏｌ／ｌ以下であることがより好ましい。 The upper limit of the concentration of the seed particles is not particularly limited, but considering the balance between the amounts of the seed particles and the metal oxide precursor, it is preferably 1 mol / l or less, and more preferably 0.5 mol / l or less. ..
〔金属酸化物前駆体〕
本実施形態において、金属酸化物前駆体とは、準安定相を形成したい金属酸化物を構成する各原料成分を水系溶媒中に混合して得た中間原料であって、未だ準安定相の金属酸化物になっていないものをいう。
[Metal oxide precursor]
In the present embodiment, the metal oxide precursor is an intermediate raw material obtained by mixing each raw material component constituting the metal oxide for which a metastable phase is to be formed in an aqueous solvent, and is still a metal having a metastable phase. It is not an oxide.
金属酸化物前駆体の種類は、種粒子に表面に準安定相の金属酸化物を析出可能な材料であれば、特に限定されない。具体的に、金属酸化物前駆体は、金属塩、金属錯体、金属水酸化物から選択される１種以上が挙げられる。これらの材料であることで、金属酸化物前駆体を水系溶媒に好適に溶解させることができる。 The type of the metal oxide precursor is not particularly limited as long as it is a material capable of precipitating a metastable phase metal oxide on the surface of the seed particles. Specifically, the metal oxide precursor may be one or more selected from metal salts, metal complexes, and metal hydroxides. With these materials, the metal oxide precursor can be suitably dissolved in an aqueous solvent.
例えば、表面にγ相の酸化鉄（ＩＩＩ）を析出させる場合、金属酸化物前駆体は、硝酸鉄水溶液である。また、表面に正方晶のチタン酸バリウムを析出させる場合、金属酸化物前駆体は、チタン酸塩と、水酸化バリウムと、水酸化カリウムとを水系溶媒中で混合した混合溶液である。 For example, when γ-phase iron (III) oxide is precipitated on the surface, the metal oxide precursor is an aqueous iron nitrate solution. When rectangular barium titanate is precipitated on the surface, the metal oxide precursor is a mixed solution of titanate, barium hydroxide, and potassium hydroxide mixed in an aqueous solvent.
中でも、金属酸化物前駆体は、金属錯体であることが好ましい。金属錯体は、金属塩に比べて水系溶媒の中で安定であるため、金属酸化物前駆体を水熱処理するに際し、溶液中で金属水酸化物が過飽和状態になるのを防ぐことができ、結果として、金属酸化物前駆体が均一核生成するのを抑えることができる。 Above all, the metal oxide precursor is preferably a metal complex. Since the metal complex is more stable in an aqueous solvent than the metal salt, it is possible to prevent the metal hydroxide from becoming oversaturated in the solution when the metal oxide precursor is hydrothermally treated, resulting in this. As a result, it is possible to suppress the formation of uniform nuclei of the metal oxide precursor.
また、金属酸化物前駆体は、塩基性溶液に溶解されていることが好ましい。この場合、酸性条件下に比べて金属酸化物前駆体の溶解度が高く、水熱処理の反応場での金属水酸化物の過飽和度を小さく抑えることができ、結果として、種粒子表面における不均一核生成を支配的に進めることができる。 Further, the metal oxide precursor is preferably dissolved in a basic solution. In this case, the solubility of the metal oxide precursor is higher than that under acidic conditions, and the degree of supersaturation of the metal hydroxide in the reaction field of the hydrothermal treatment can be suppressed to a small value, resulting in heterogeneous nuclei on the surface of the seed particles. The generation can proceed predominantly.
水熱処理を行う際の超臨界水等に含まれる金属酸化物前駆体の濃度の下限は特に限定されないが、種粒子及び金属酸化物前駆体の量のバランスを考慮すると、０．０１ｍｏｌ／ｌ以上であることが好ましく、０．０５ｍｏｌ／ｌ以上であることがより好ましい。 The lower limit of the concentration of the metal oxide precursor contained in supercritical water or the like during hydrothermal treatment is not particularly limited, but considering the balance of the amounts of seed particles and the metal oxide precursor, 0.01 mol / l or more. It is preferably 0.05 mol / l or more, and more preferably 0.05 mol / l or more.
金属酸化物前駆体の濃度の上限も、特に限定されない。ここで、ナノ粒子を液相にて合成する場合、オストワルトライプニングと呼ばれる、再溶解・析出法を併用することが知られている。この手法を用いると、比較的小さなナノ粒子が再溶解し、再溶解されたナノ粒子成分が比較的大きなナノ粒子上に析出するため、粒子径分布の幅をよりいっそう狭めることができる。 The upper limit of the concentration of the metal oxide precursor is also not particularly limited. Here, when the nanoparticles are synthesized in the liquid phase, it is known that a redissolution / precipitation method called Ostwald tripping is used in combination. When this method is used, the width of the particle size distribution can be further narrowed because the relatively small nanoparticles are redissolved and the redissolved nanoparticles are deposited on the relatively large nanoparticles.
水熱処理を行う際の溶液に含まれる金属酸化物前駆体の濃度を所定の閾値以下にすると、再溶解・析出法の原理を応用しているにも関わらず、溶液中で金属水酸化物が過飽和状態になり、金属酸化物前駆体の均一核生成が起こり、かえって粒子径分布が広くなるのを防ぐことができる。 When the concentration of the metal oxide precursor contained in the solution during hydrothermal treatment is set to a predetermined threshold or less, the metal hydroxide is generated in the solution even though the principle of the redissolution / precipitation method is applied. It is possible to prevent a supersaturated state, uniform nucleation of the metal oxide precursor, and rather widening of the particle size distribution.
水熱処理後のナノ粒子の粒子径分布の幅をよりいっそう狭める観点から、金属酸化物前駆体の濃度の上限は、１ｍｏｌ／ｌ以下であることが好ましく、０．５ｍｏｌ／ｌ以下であることがより好ましく、０．１ｍｏｌ／ｌ以下であることがさらに好ましい。 From the viewpoint of further narrowing the width of the particle size distribution of the nanoparticles after the hydrothermal treatment, the upper limit of the concentration of the metal oxide precursor is preferably 1 mol / l or less, and preferably 0.5 mol / l or less. More preferably, it is 0.1 mol / l or less.
〔有機修飾剤〕
必須ではないが、水熱処理は、有機修飾剤の存在下で行われることが好ましい。
[Organic modifier]
Although not essential, the hydrothermal treatment is preferably carried out in the presence of an organic modifier.
通常、水系溶媒と有機修飾剤とは相分離する。しかしながら、亜臨界水条件又は超臨界水条件では、有機修飾剤が水と均一相を形成する。 Usually, the aqueous solvent and the organic modifier are phase-separated. However, under subcritical or supercritical water conditions, the organic modifier forms a homogeneous phase with water.
本実施形態では、ナノ粒子の表面に有機修飾剤がキャッピングし、ナノ粒子の表面エネルギーを低くし、ミセル形成することができる。そして、有機修飾剤の存在により、酸化物モノマーと錯体を形成し、それがイオンよりも安定であるために、有機修飾剤の亜臨界水又は超臨界水への溶解度がいっそう高まり、それにより、さらに高速にオストワルトライプニングを進めることが可能である。そして、種粒子の粒子径よりも小さな径の準安定相金属酸化物のナノ粒子を、種粒子の総重量よりも大量に合成することができる。加えて、オストワルトライプニングの効果により、粒子径分布の幅をよりいっそう狭めることができる。 In the present embodiment, an organic modifier is capped on the surface of the nanoparticles, the surface energy of the nanoparticles is lowered, and micelles can be formed. The presence of the organic modifier forms a complex with the oxide monomer, which is more stable than the ion, which further increases the solubility of the organic modifier in subcritical or supercritical water, thereby. It is possible to proceed with Ostwar tripping at even higher speeds. Then, nanoparticles of the metastable phase metal oxide having a diameter smaller than the particle diameter of the seed particles can be synthesized in a larger amount than the total weight of the seed particles. In addition, due to the effect of Ostwald tapping, the width of the particle size distribution can be further narrowed.
有機修飾剤としては、微粒子の表面に炭化水素を強結合せしめることのできるものであれば特には限定されず、有機化学の分野、無機材料分野、高分子化学の分野を含めてナノ粒子の応用が期待されている分野で広く知られている有機物質から選択することができる。 The organic modifier is not particularly limited as long as it can strongly bond hydrocarbons to the surface of fine particles, and applications of nanoparticles include the fields of organic chemistry, inorganic materials, and polymer chemistry. Can be selected from widely known organic substances in the field in which they are expected.
有機修飾剤としては、例えば、エーテル結合、エステル結合、Ｎ原子を介した結合、Ｓ原子を介した結合、金属−Ｃ−の結合、金属−Ｃ＝の結合及び金属−（Ｃ＝Ｏ）−の結合等の強結合を形成することを許容するものが挙げられる。該炭化水素としては、その炭素数は特に限定されず、炭素数１や２のものであってもよいが、炭素数３あるいはそれ以上の鎖を有する長鎖炭化水素であるものが好ましく、例えば、炭素数３〜２０の直鎖又は分岐鎖、あるいは環状の炭化水素等が挙げられる。 Examples of the organic modifier include ether bond, ester bond, bond via N atom, bond via S atom, bond of metal-C-, bond of metal-C = and metal- (C = O)-. Those that allow the formation of strong bonds such as the bonds of The hydrocarbon has no particular limitation on the number of carbon atoms and may have 1 or 2 carbon atoms, but a long-chain hydrocarbon having a chain having 3 or more carbon atoms is preferable, for example. , Linear or branched hydrocarbons having 3 to 20 carbon atoms, cyclic hydrocarbons, and the like.
炭化水素は、置換されていてもよいし、非置換のものであってもよい。該置換基としては、有機化学の分野、無機材料分野、高分子化学の分野等で広く知られた官能基の中から選択されたものであってよく、該置換基は１又はそれ以上が存在していてもよいし、複数の場合互いは同じでも異なっていてもよい。 The hydrocarbon may be substituted or unsubstituted. The substituent may be selected from functional groups widely known in the fields of organic chemistry, inorganic materials, polymer chemistry, etc., and one or more of the substituents are present. It may be the same or different from each other in the case of a plurality.
有機修飾剤としては、例えば、アルコール類、アルデヒド類、ケトン類、カルボン酸類、エステル類、アミン類、チオール類、アミド類、オキシム類、ホスゲン、エナミン類、アミノ酸類、ペプチド類、糖類等が挙げられる。 Examples of the organic modifier include alcohols, aldehydes, ketones, carboxylic acids, esters, amines, thiols, amides, oximes, phosgens, enamines, amino acids, peptides, saccharides and the like. Be done.
代表的な修飾剤としては、例えば、ペンタノール、ペンタナール、ペンタン酸、ペンタンアミド、ペンタンチオール、ヘキサノール、ヘキサナール、ヘキサン酸、ヘキサンアミド、ヘキサンチオール、ヘプタノール、ヘプタナール、ヘプタン酸、ヘプタンアミド、ヘプタンチオール、オクタノール、オクタナール、オクタン酸、オクタンアミド、オクタンチオール、デカノール、デカナール、デカン酸、デカンアミド、デカンチオール等が挙げられる。 Typical modifiers include, for example, pentanol, pentanal, pentanoic acid, pentanamide, pentanthiol, hexanol, hexanal, hexanoic acid, hexaneamide, hexanethiol, heptanol, heptanal, heptanic acid, heptanamide, heptanthiol, Examples thereof include octanol, octanal, octanoic acid, octaneamide, octanethiol, decanol, decanol, decanoic acid, decaneamide and decanethiol.
上記炭化水素基としては、置換されていてもよい直鎖又は分岐鎖のアルキル基、置換されていてもよい環式アルキル基、置換されていてもよいアリール基、置換されていてもよいアラルキル基、置換されていてもよい飽和又は不飽和の複素環式基等が挙げられる。置換基としては、例えば、カルボキシ基、シアノ基，ニトロ基、ハロゲン、エステル基、アミド基、ケトン基、ホルミル基、エーテル基、水酸基、アミノ基、スルホニル基、−Ｏ−、−ＮＨ−、−Ｓ−等が挙げられる。 Examples of the hydrocarbon group include a linear or branched alkyl group which may be substituted, a cyclic alkyl group which may be substituted, an aryl group which may be substituted, and an aralkyl group which may be substituted. , Saturated or unsaturated heterocyclic groups which may be substituted, and the like. Examples of the substituent include a carboxy group, a cyano group, a nitro group, a halogen, an ester group, an amide group, a ketone group, a formyl group, an ether group, a hydroxyl group, an amino group, a sulfonyl group, -O-, -NH-, and-. Examples include S-.
以下、本実施形態での試験例により本発明を具体的に説明するが、本発明はこれらに限定されるものではない。 Hereinafter, the present invention will be specifically described with reference to the test examples in the present embodiment, but the present invention is not limited thereto.
＜試験例１＞ 水熱処理による酸化鉄（ＩＩＩ）粒子の成長結晶相制御
〔試験方法〕
γ−酸化鉄ナノ粒子（平均粒径：３．７ｎｍ）５０ｍｇを種粒子として２．２ｍＬの硝酸鉄水溶液（０．０５６ｍｏｌ／ｌ，０．１１ｍｏｌ／ｌの２種類）に加えた（ｐＨ１〜２）。溶液を回分式反応器（容積５ｍＬ）に封入し、２００℃において１０分間水熱処理した。
<Test Example 1> Control of growth crystal phase of iron (III) oxide particles by hydrothermal treatment [Test method]
50 mg of γ-iron oxide nanoparticles (average particle size: 3.7 nm) was added as seed particles to 2.2 mL of an iron nitrate aqueous solution (2 types of 0.056 mol / l and 0.11 mol / l) (pH 1-2). ). The solution was sealed in a batch reactor (volume 5 mL) and hydrothermally treated at 200 ° C. for 10 minutes.
また、１ｍｏｌ／ｌのＮａＯＨ水溶液を用いて溶液のｐＨを１１〜１２に調整して同様の試験を行った。比較のため、各ｐＨにおいて種粒子を加えず硝酸鉄水溶液（０．０５６ｍｏｌ／ｌ）を水熱処理した．得られた粒子はＸ線回折（ＸＲＤ）及び透過型電子顕微鏡（ＴＥＭ）により分析した。 Further, the pH of the solution was adjusted to 11 to 12 using a 1 mol / l NaOH aqueous solution, and the same test was conducted. For comparison, an aqueous iron nitrate solution (0.056 mol / l) was hydrothermally treated at each pH without adding seed particles. The resulting particles were analyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM).
〔結果〕
まず、各条件において種粒子自体が溶解・変性してしまう可能性を考え、種粒子のみの溶液を各ｐＨにおいて水熱処理したが、粒子の溶解は起こらなかった．
〔result〕
First, considering the possibility that the seed particles themselves would dissolve and denature under each condition, the solution of only the seed particles was hydrothermally treated at each pH, but the particles did not dissolve.
図１に硝酸鉄水溶液の水熱処理により得られた粒子のＸＲＤパターンを示す。種粒子を加えずに硝酸鉄溶液を水熱処理した試料では、酸性条件において、α-酸化鉄のピークのみが得られた。また、塩基性条件では、α-酸化鉄のピーク及びＦｅＯ（ＯＨ）のピークが得られた。この結果は、反応場において図２（Ａ）に示すような均一核生成が起き、α−酸化鉄が生成したものと考えられる。 FIG. 1 shows an XRD pattern of particles obtained by hydrothermal treatment of an aqueous iron nitrate solution. In the sample obtained by hydrothermally treating the iron nitrate solution without adding seed particles, only the peak of α-iron oxide was obtained under acidic conditions. Further, under basic conditions, a peak of α-iron oxide and a peak of FeO (OH) were obtained. As a result, it is considered that uniform nucleation as shown in FIG. 2 (A) occurred in the reaction field and α-iron oxide was produced.
酸性条件において，硝酸鉄濃度が０．０５６ｍｏｌ／ｌである条件では、γ−酸化鉄のピークのみが得られたが、０．１１ｍｏｌ／ｌである条件では、α−酸化鉄のピークが出現した。硝酸鉄濃度０．０５６ｍｏｌ／ｌの条件では，種粒子を添加したことにより不均一核生成が起こり、種粒子表面にγ−酸化鉄が析出し、図２（Ｂ）のような核成長が起こったと考えられる。しかしながら、硝酸鉄が高濃度になると、反応場において過飽和度が大きくなり、不均一核生成よりも均一核生成が支配的に起こったと考えられる。 Under acidic conditions, only the peak of γ-iron oxide was obtained under the condition that the iron nitrate concentration was 0.056 mol / l, but the peak of α-iron oxide appeared under the condition of 0.11 mol / l. .. Under the condition of iron nitrate concentration of 0.056 mol / l, heterogeneous nucleation occurs due to the addition of seed particles, γ-iron oxide is precipitated on the surface of the seed particles, and nucleation as shown in FIG. 2 (B) occurs. It is thought that it was. However, when the concentration of iron nitrate becomes high, the degree of supersaturation increases in the reaction field, and it is considered that uniform nucleation predominates over heterogeneous nucleation.
一方、塩基性条件では、硝酸鉄濃度が０．０５６ｍｏｌ／ｌ及び０．１１ｍｏｌ／ｌである条件において共にγ−酸化鉄のピークのみが得られた。酸性条件では高濃度においてα−酸化鉄のピークが得られているため、塩基性条件の方が粒子表面での不均一核生成に適している条件であることが示唆された。水酸化鉄の溶解度は高温になるにつれ、酸性条件では減少し、塩基性条件では増大する。塩基性条件では、反応温度での溶解度が高いため、反応場での水酸化鉄の過飽和度が小さくなり、高濃度でも粒子表面における不均一核生成が支配的に起こったと考えられる。 On the other hand, under the basic conditions, only the peak of γ-iron oxide was obtained under the conditions where the iron nitrate concentration was 0.056 mol / l and 0.11 mol / l. Since the peak of α-iron oxide was obtained at high concentration under acidic conditions, it was suggested that basic conditions are more suitable for heterogeneous nucleation on the particle surface. The solubility of iron hydroxide decreases under acidic conditions and increases under basic conditions as the temperature rises. Under basic conditions, the solubility at the reaction temperature is high, so that the degree of supersaturation of iron hydroxide in the reaction field is small, and it is considered that heterogeneous nucleation on the particle surface predominantly occurred even at high concentrations.
＜試験例２＞ 反応温度の影響
水溶性Ｔｉ錯体を用いて合成したＮｉ／ＢａＴｉＯ３コアシェルナノ粒子をモデルに、反応温度の影響について検討する。
<Test Example 2> Effect of reaction temperature The effect of reaction temperature will be examined using Ni / BaTiO 3- core-shell nanoparticles synthesized using a water-soluble Ti complex as a model.
〔試験方法〕
［試薬］
試験には、以下の試薬を用いた。
・Ｎｉナノ粒子（平均粒径：８０ｎｍ）
・チタンペルオキソクエン酸アンモニウム水溶液（Ｔｉ＝５ｗｔ％）
（（ＮＨ４）４［Ｔｉ２（Ｃ６Ｈ４Ｏ７）２（Ｏ２）２］・４Ｈ２Ｏ，フルウチ化学株式会社）
・水酸化バリウム８水和物
（Ｂａ（ＯＨ）２・８Ｈ２Ｏ，富士フィルム和光純薬株式会社，純度９８．０％）
・水酸化カリウム(ＫＯＨ，富士フィルム和光純薬株式会社，純度８５．０％）
〔Test method〕
[reagent]
The following reagents were used in the test.
-Ni nanoparticles (average particle size: 80 nm)
・ Titanium peroxocitrate ammonium aqueous solution (Ti = 5 wt%)
((NH 4 ) 4 [Ti 2 (C 6 H 4 O 7 ) 2 (O 2 ) 2 ] ・ 4H 2 O, Furuuchi Chemical Co., Ltd.)
· Barium hydroxide octahydrate (Ba (OH) 2 · 8H 2 O, Fuji Film Wako Pure Chemical Co., 98.0% purity)
・ Potassium hydroxide (KOH, Fuji Film Wako Pure Chemical Industries, Ltd., purity 85.0%)
［試験装置］
以下の装置を用いて実験を行った。
・回分式反応器（５ｍＬ），材質：ハステロイ、ＡＫＩＣＯ
・振盪式リアクター加熱攪拌装置，ＡＫＩＣＯ，ＳＡＨ−Ｒ１６−５００
[Test equipment]
Experiments were conducted using the following equipment.
・ Batch reactor (5 mL), material: Hastelloy, AKICO
・ Shaking reactor heating and stirring device, AKICO, SAH-R16-500
［試験方法］
チタンペルオキソクエン酸アンモニウム水溶液、水酸化バリウム8水和物、クエン酸を精製水に加え攪拌後ｐＨを調整し塩基性にすることで、透明な水溶性ＢａＴｉＯ３前駆体を得た。この前駆体溶液にＮｉナノ粒子を加え超音波により分散させた。その後５ｍＬ回分式反応器に封入し、リアクターを用いて反応を行った。その後、水により反応器を冷却させ反応を終了させた。反応器から生成物を回収し、遠心洗浄・凍結乾燥を行うことで乾燥粒子を得た。いずれの場合もＢａ／Ｔｉモル比は約１で、反応時間は６０分であった。
[Test method]
A transparent aqueous solution of ammonium peroxocitrate, barium hydroxide octahydrate, and citric acid were added to purified water, and the pH was adjusted to make the pH basic after stirring to obtain a transparent water-soluble BaTIO 3 precursor. Ni nanoparticles were added to this precursor solution and dispersed by ultrasonic waves. Then, it was sealed in a 5 mL batch reactor and the reaction was carried out using a reactor. Then, the reactor was cooled with water to terminate the reaction. The product was recovered from the reactor and subjected to centrifugal washing and freeze-drying to obtain dried particles. In each case, the Ba / Ti molar ratio was about 1 and the reaction time was 60 minutes.
〔結果〕
［生成粒子の評価］
まず、生成粒子の評価を行った。第１の試験条件を図３に示す。また、Ｎｉナノ粒子の濃度を４．３４ｗｔ％、０．５１ｗｔ％と変化させて合成した粒子のＴＥＭ像を図４に示す。図４（Ａ）は、Ｎｉナノ粒子の濃度が４．３４ｗｔ％である場合の生成粒子のＴＥＭ像であり、図４（Ｂ）は、Ｎｉナノ粒子の濃度が０．５１ｗｔ％である場合の生成粒子のＴＥＭ像である。
〔result〕
[Evaluation of generated particles]
First, the produced particles were evaluated. The first test condition is shown in FIG. Further, FIG. 4 shows a TEM image of the particles synthesized by changing the concentration of Ni nanoparticles to 4.34 wt% and 0.51 wt%. FIG. 4 (A) is a TEM image of the produced particles when the concentration of Ni nanoparticles is 4.34 wt%, and FIG. 4 (B) is a case where the concentration of Ni nanoparticles is 0.51 wt%. It is a TEM image of the generated particles.
いずれの場合においても、Ｎｉナノ粒子表面上への均一な被膜形成が確認された。またＮｉナノ粒子添加量を少なくするほどシェルの厚さは厚くなることが確認できた。Ｎｉナノ粒子表面にすべて均一にＢａＴｉＯ３が被膜した場合、Ｎｉナノ粒子４．３４ｗｔ％添加時では被膜厚さが約４ｎｍ、０．５１ｗｔ％添加時では被膜厚さが約２０ｎｍとなると予測される。Ｎｉナノ粒子４．８ｗｔ％添加時はおおよそ予測通りの被膜厚さであるが、Ｎｉナノ粒子０．５１ｗｔ％添加時では予測される被膜厚さよりも薄かった。この理由として、Ｎｉナノ粒子０．５１ｗｔ％添加時ではＢａＴｉＯ３原料が被膜形成にすべて消費されず未反応のものが残っているためであると考えられる。 In each case, uniform film formation on the surface of Ni nanoparticles was confirmed. It was also confirmed that the thickness of the shell became thicker as the amount of Ni nanoparticles added was reduced. When BaTIO 3 is uniformly coated on the surface of all Ni nanoparticles, it is predicted that the film thickness will be about 4 nm when 4.34 wt% of Ni nanoparticles are added and about 20 nm when 0.51 wt% is added. .. When 4.8 wt% of Ni nanoparticles were added, the film thickness was approximately as expected, but when 0.51 wt% of Ni nanoparticles were added, the film thickness was thinner than expected. It is considered that the reason for this is that when 0.51 wt% of Ni nanoparticles are added, all the BaTiO 3 raw materials are not consumed for film formation and unreacted ones remain.
図５は、Ｎｉナノ粒子と生成粒子のＸＲＤパターンである。いずれの粒子もＮｉ以外のピークは確認されず、シェル構造は結晶化しておらずアモルファスであることがわかった。 FIG. 5 is an XRD pattern of Ni nanoparticles and produced particles. No peaks other than Ni were confirmed in any of the particles, and it was found that the shell structure was not crystallized and was amorphous.
［反応温度・ｐＨの影響］
続いて、コアシェル構造形成における反応温度の影響を調べた。第２の試験条件を図６に示す。またＮｉを添加した場合と添加しなかった場合の各反応温度における生成粒子を図７に示す。１００℃においてＮｉナノ粒子を加えずＢａＴｉＯ３前駆体のみで合成した場合では粒子は生成しておらず均一核生成が起こらない条件であることがわかった。一方、Ｎｉナノ粒子を添加した場合では、Ｎｉナノ粒子表面に均一にＢａＴｉＯ３が被膜していた。このことから、１００℃では核生成は起こらず成長のみが起こる条件であることが分かる。また、２００℃で合成した場合、ＢａＴｉＯ３前駆体のみでも粒子が生成していたため、均一核生成が起こる条件であることが分かる。Ｎｉナノ粒子を添加した場合においても、コアシェル構造は形成していたものの、シェル構造はやや粗く、均一核生成も併発していた。
以上より、均一なコアシェル構造の形成は低温の方が望ましいことが確認された。
[Effects of reaction temperature and pH]
Subsequently, the effect of the reaction temperature on the formation of the core-shell structure was investigated. The second test condition is shown in FIG. Further, FIG. 7 shows the generated particles at each reaction temperature when Ni was added and when Ni was not added. It was found that when the mixture was synthesized only with the BaTIO 3 precursor at 100 ° C. without adding Ni nanoparticles, no particles were formed and uniform nucleation did not occur. On the other hand, when Ni nanoparticles were added, BaTIO 3 was uniformly coated on the surface of the Ni nanoparticles. From this, it can be seen that at 100 ° C., nucleation does not occur and only growth occurs. Further, when synthesized at 200 ° C., particles were generated only with the BaTiO 3 precursor, so that it can be seen that the conditions are such that uniform nucleation occurs. Even when Ni nanoparticles were added, the core-shell structure was formed, but the shell structure was slightly coarse, and uniform nucleation also occurred.
From the above, it was confirmed that the formation of a uniform core-shell structure is desirable at a low temperature.
＜試験例３＞ 核生成・核成長の制御
水溶性Ｔｉ錯体を用いて合成したＮｉ／ＢａＴｉＯ３コアシェルナノ粒子をモデルに、速度論解析から核生成・核成長がそれぞれ支配的となる条件に関する検討を行った。
<Test Example 3> Control of nucleation and nucleation Using a model of Ni / BaTIO 3 core-shell nanoparticles synthesized using a water-soluble Ti complex, a study on the conditions under which nucleation and nucleation are dominant from kinetic analysis. Was done.
〔試験方法〕
［試薬］
試験には、以下の試薬を用いた。
・Ｎｉナノ粒子（平均粒径：８０ｎｍ）
・チタンペルオキソクエン酸アンモニウム水溶液（Ｔｉ＝５ｗｔ％）
（（ＮＨ４）４［Ｔｉ２（Ｃ６Ｈ４Ｏ７）２（Ｏ２）２］・４Ｈ２Ｏ，フルウチ化学株式会社）
・６ｍｏｌ／ｌの塩酸（ＨＣｌ，富士フィルム和光純薬株式会社）
〔Test method〕
[reagent]
The following reagents were used in the test.
-Ni nanoparticles (average particle size: 80 nm)
・ Titanium peroxocitrate ammonium aqueous solution (Ti = 5 wt%)
((NH 4 ) 4 [Ti 2 (C 6 H 4 O 7 ) 2 (O 2 ) 2 ] ・ 4H 2 O, Furuuchi Chemical Co., Ltd.)
・ 6 mol / l hydrochloric acid (HCl, Fuji Film Wako Pure Chemical Industries, Ltd.)
［試験装置］
以下の装置を用いて実験を行った。
・回分式反応器（５ｍＬ），材質：ハステロイ、ＡＫＩＣＯ
・振盪式リアクター加熱攪拌装置，ＡＫＩＣＯ，ＳＡＨ−Ｒ１６−５００
[Test equipment]
Experiments were conducted using the following equipment.
・ Batch reactor (5 mL), material: Hastelloy, AKICO
・ Shaking reactor heating and stirring device, AKICO, SAH-R16-500
［試験方法］
チタンペルオキソクエン酸アンモニウム水溶液を精製水に加え攪拌後、加水分解速度を抑えるために塩酸でｐＨを酸性にすることで水溶性Ｔｉ前駆体を得た。この前駆体溶液にＮｉナノ粒子を加え超音波により分散させた。その後５ｍＬ回分式反応器に封入し、反応を行った。反応圧力は飽和水蒸気圧以上となるように反応器への投入量を調整した。反応後、水により反応器を冷却させ反応を終了させた。反応器から生成物を回収し、遠心洗浄・凍結乾燥を行うことで乾燥粒子を得た。
[Test method]
A water-soluble Ti precursor was obtained by adding an aqueous solution of titanium peroxocitrate to purified water and stirring the mixture, and then acidifying the pH with hydrochloric acid to suppress the hydrolysis rate. Ni nanoparticles were added to this precursor solution and dispersed by ultrasonic waves. Then, it was sealed in a 5 mL batch reactor and the reaction was carried out. The amount charged into the reactor was adjusted so that the reaction pressure was equal to or higher than the saturated steam pressure. After the reaction, the reactor was cooled with water to terminate the reaction. The product was recovered from the reactor and subjected to centrifugal washing and freeze-drying to obtain dried particles.
［分析装置］
分析は以下の装置を用いて行った。
・Ｘ線回折装置（ＸＲＤ）、ＲＩＧＡＫＵ、ＳｍａｒｔＬａｂ ９ＭＴＰ
[Analysis equipment]
The analysis was performed using the following equipment.
-X-ray diffractometer (XRD), RIGAKU, SmartLab 9MTP
結晶子サイズはＨａｌｄｅｒ−Ｗａｇｎｅｒ法を用いて求めた。その式を以下に示す。 The crystallite size was determined using the Hander-Wagner method. The formula is shown below.
上記式において、βは積分幅、θはＢｒａｇｇ角、ＫはＳｃｈｅｒｒｅｒ定数、λはＸ線の波長、Ｄは結晶子サイズ、εは不均一格子歪みである。 In the above equation, β is the integration width, θ is the Bragg angle, K is the Scherrer constant, λ is the wavelength of the X-ray, D is the crystallite size, and ε is the non-uniform lattice strain.
・透過型電子顕微鏡（ＴＥＭ）、ＨＩＴＡＣＨＩ、Ｈ−７６５０
・超高分解能収差補正型分析電子顕微鏡（ＳＴＥＭ・／ＥＤＳ），ＦＥＩ−Ｃｏｍｐａｎｙ、Ｔｉｔａｎ３ＴＭ ６０−３００
・誘導結合プラズマ発光分光分析装置（ＩＣＰ−ＯＥＳ）、ＴｈｅｒｍｏＦｉｓｈｅｒ、ｉＣＡＰ６５００
-Transmission electron microscope (TEM), HITACHI, H-7650
・ Ultra-high resolution aberration correction type analytical electron microscope (STEM // EDS), FEI-Company, Titan 3TM 60-300
Inductively coupled plasma emission spectrophotometer (ICP-OES), Thermo Fisher, iCAP6500
〔結果〕
速度論解析から核生成・核成長がそれぞれ支配的となる条件に関する検討を行った。図８に均一核生成とＮｉナノ粒子表面でのＴｉＯ２の不均一核生成、そしてＮｉナノ粒子表面で不均一核生成したＴｉＯ２の成長反応のアレニウスプロットを示す。ここで、ＴｉＯ２の不均一核生成、成長反応の速度定数はそれぞれＮｉナノ粒子添加時の反応初期、後期の速度定数と均一核生成の速度定数との差をとったものである。この直線の傾きから活性化エネルギーを求めると、均一核生成の活性化エネルギーは約７３ｋＪ／ｍｏｌ、Ｎｉナノ粒子表面での不均一核生成反応の活性化エネルギーは約４６ｋＪ／ｍｏｌ、ＴｉＯ２の成長反応の活性化エネルギーは約５５ｋＪ／ｍｏｌであった。原料にＴｉＯ２ゲルを用いた場合のＴｉＯ２粒子の水熱合成の活性化エネルギーは８９．１ｋＪ／ｍｏｌであるとの報告があり（内田聡ら，色材，７２（１９９９）６８０−６８９）、今回得られた均一核生成の活性化エネルギーと比較的近い値であるため、今回の結果が妥当であることが示された。若干ズレがあるのは、出発原料の違いや測定誤差に起因するものと考えられる。また、均一核生成に比べ不均一核生成の方が容易に起こるため、活性化エネルギーが小さくなると考えられる。また、異種物質での不均一核生成であるＮｉナノ粒子表面でのＴｉＯ２の不均一核生成よりも、同物質上への反応であるＴｉＯ２が成長する反応の方が起こりやすいために、活性化エネルギーは大きく変化していないが、全体的に反応速度が大きくなり、直線が速度定数が大きい方向へシフトしたものと考える。また、均一核生成とＮｉナノ粒子表面上での不均一核生成の直線は温度が約２７２℃で交差することがわかる。この点より高温では、均一核生成の速度が不均一核生成の速度を上回る。そのため、均一核生成が優先的に起こると考える。一方、この点より低温では、不均一核生成の速度の方が大きくなるために、不均一核生成が優先的に起こると考える。図９及び図１０にこの交点近傍の温度条件で合成した粒子のＴＥＭ像を示す。交点よりも高温である３００℃で合成した粒子は均一核生成がほとんどであり、コアシェル構造は形成していないことがわかる。一方、交点より低温である２００℃で合成した粒子は均一核生成が起こっているものの不均一核生成・成長が起こり、コアシェル構造が形成していることを確認できた。
〔result〕
From kinetic analysis, we examined the conditions under which nucleation and nucleation dominate. Shows the Arrhenius plot of the homogeneous nucleation and Ni heterogeneous nucleation of TiO 2 in the nanoparticle surface, and heterogeneous nucleation the TiO 2 of the growth reaction with Ni nanoparticle surface in FIG. Here, the rate constants of the heterogeneous nucleation and growth reaction of TiO 2 are the differences between the rate constants of the early and late reactions when Ni nanoparticles are added and the rate constants of uniform nucleation. When the activation energy is obtained from the slope of this straight line, the activation energy for uniform nucleation is about 73 kJ / mol, the activation energy for the heterogeneous nucleation reaction on the surface of Ni nanoparticles is about 46 kJ / mol, and the growth of TiO 2 The activation energy of the reaction was about 55 kJ / mol. It has been reported that the activation energy of hydrothermal synthesis of TiO 2 particles when TiO 2 gel is used as a raw material is 89.1 kJ / mol (Satoshi Uchida et al., Color material, 72 (1999) 680-689). Since the value is relatively close to the activation energy for uniform nucleation obtained this time, it was shown that this result is appropriate. The slight deviation is considered to be due to the difference in starting materials and measurement error. Moreover, since heterogeneous nucleation occurs more easily than uniform nucleation, it is considered that the activation energy becomes smaller. In addition, the reaction in which TiO 2 grows, which is a reaction on the same substance, is more likely to occur than the non-uniform nucleation of TiO 2 on the surface of Ni nanoparticles, which is non-uniform nucleation in a different substance. Although the activation energy has not changed significantly, it is considered that the reaction rate has increased overall and the straight line has shifted toward a larger rate constant. It can also be seen that the straight lines of uniform nucleation and non-uniform nucleation on the surface of Ni nanoparticles intersect at a temperature of about 272 ° C. At higher temperatures than this point, the rate of uniform nucleation exceeds the rate of heterogeneous nucleation. Therefore, it is considered that uniform nucleation occurs preferentially. On the other hand, at lower temperatures than this point, the rate of heterogeneous nucleation is higher, so it is considered that heterogeneous nucleation occurs preferentially. 9 and 10 show TEM images of particles synthesized under temperature conditions near this intersection. It can be seen that most of the particles synthesized at 300 ° C., which is higher than the intersection, generate uniform nuclei and do not form a core-shell structure. On the other hand, it was confirmed that the particles synthesized at 200 ° C., which is lower than the intersection, had uniform nucleation but heterogeneous nucleation and growth, and a core-shell structure was formed.
以上より、コアシェル構造の形成には、均一核生成とコアシェル構造形成の初期段階であるコア粒子表面上でのシェル材料の不均一核生成の反応速度の制御が非常に重要であり、その反応速度を解析することによりコアシェル構造の形成条件を推算可能であることが示された。 From the above, it is very important to control the reaction rate of uniform nucleation and heterogeneous nucleation of shell material on the surface of core particles, which is the initial stage of core-shell structure formation, for the formation of core-shell structure. It was shown that the formation conditions of the core-shell structure can be estimated by analyzing.
＜試験例４＞ 有機修飾剤を用いた結晶成長の制御
有機修飾剤としてデカン酸を用いた超臨界水熱処理による酸化セリウム（ＩＶ）ナノ粒子の形態変化をモデルに、有機修飾剤を用いた結晶成長の制御について検討する。
<Test Example 4> Control of crystal growth using an organic modifier Crystals using an organic modifier, modeled on the morphological change of cerium (IV) nanoparticles due to supercritical water heat treatment using decanoic acid as an organic modifier. Consider control of growth.
〔試験方法〕
デカン酸で修飾したセリア粉末（ＩＴＥＣ社製）１０．３ｍｇ（０．０２ｍｏｌ／ｌ）を５ｍＬのバッチ式反応器に移した。 次いで、２．５ｍＬのＨ２Ｏ、０．０３６ｍＬ（０．０６ｍｏｌ／ｌ）、０．０７２ｍＬ（０．１２ｍｏｌ／ｌ）又は０．１４４ｍＬ（０．２４ｍｏｌ／ｌ）のデカン酸を撹拌せずに加えた。反応器を４００℃で１０分間加熱し、次いで水浴（２０℃）中で急冷した。沈殿物をヘキサンで分散させ、エタノールを加えて１回遠心分離した。 得られたナノ結晶をシクロヘキサンに溶解した。試料を高分解能透過型電子顕微鏡（ＨＲＴＥＭ）、フーリエ変換赤外分光計（ＦＴ−ＩＲ）及び熱重量分析（ＴＧＡ）によって分析した。
〔Test method〕
10.3 mg (0.02 mol / l) of decanoic acid-modified ceria powder (manufactured by ITEC) was transferred to a 5 mL batch reactor. Then 2.5 mL of H 2 O, 0.036 mL (0.06 mol / l), 0.072 mL (0.12 mol / l) or 0.144 mL (0.24 mol / l) of decanoic acid without agitation. added. The reactor was heated at 400 ° C. for 10 minutes and then quenched in a water bath (20 ° C.). The precipitate was dispersed with hexane, ethanol was added, and the mixture was centrifuged once. The obtained nanocrystals were dissolved in cyclohexane. Samples were analyzed by high resolution transmission electron microscope (HRTEM), Fourier transform infrared spectrometer (FT-IR) and thermogravimetric analysis (TGA).
〔結果〕
図１１は、修飾ナノ粒子の形状およびサイズが超臨界水熱処理後に変化したことを示す。有機修飾剤の濃度が増加するにつれて、ナノ粒子の形態は球形から立方体に変化した。これは、修飾セリアナノ粒子が超臨界水中で再溶解および成長し得ることを証明している。さらに、粒子の表面上の改質剤および水熱中の改質剤は成長プロセスを制御する。
〔result〕
FIG. 11 shows that the shape and size of the modified nanoparticles changed after supercritical water heat treatment. As the concentration of the organic modifier increased, the morphology of the nanoparticles changed from spherical to cubic. This demonstrates that modified ceria nanoparticles can be redissolved and grown in supercritical water. In addition, modifiers on the surface of the particles and modifiers in water heat control the growth process.
図１２から、低改質剤濃度条件で処理された試料の粒度分布は、広範囲の粒度分布、大きい粒子の成長および小さい粒子の溶解を示している。結果はオストワルド成長によるものと推察される。しかしながら、高改質剤濃度サンプルの結果は狭い粒度分布を示し、４ｎｍ未満のナノ粒子がなくなったことは、配向凝集に起因する可能性がある。
From FIG. 12, the particle size distribution of the sample treated under the low modifier concentration condition shows a wide range of particle size distribution, large particle growth and small particle dissolution. The result is presumed to be due to Ostwald's growth. However, the results of the high modifier concentration sample showed a narrow particle size distribution, and the absence of nanoparticles smaller than 4 nm may be due to orientation aggregation.
Claims (14)
前記析出層は、エピタキシャル層、多結晶層又はアモルファス層を含む、ナノ粒子。 It has a precipitation layer in which a metal oxide of a metastable phase is precipitated,
The precipitation layer is nanoparticles including an epitaxial layer, a polycrystalline layer or an amorphous layer.
Claims 4 to 13 that the coefficient of variation obtained by dividing the standard deviation of the average particle size of the nanoparticles after the process by the average particle size is smaller than the coefficient of variation of the seed particles before the process. The manufacturing method according to any one of.
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