Synthesis of single-crystalline hollow

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Synthesis of single-crystalline hollow ß-FeOOH
nanorods via a controlled imcomplete-reaction
coure
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Abstract

• Single-crystalline ß-FeOOH hollow nanorods have
  been synthesized though a two-step route. The
  formation process of hollow space is from inside
  to outside.

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• Recently, much effort has been devoted to
  synthesis of hollow inorganic materials because
  of their low density and high surface area
  compared with bulk materials. These materials may
  be find a wide range of potential applications in
  many areas, such as catalysts, potential drug
  carriers, coatings, low-density materials and
  nano-reactor.Many hollow inorganic materials
  including metals, non-oxides and metal oxides
  have been synthesized.

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• The general approach for synthesizing such
  materials is based on the use of hard-template or
  soft-template such as polystyrene beads, colloid
  particles, emulsions, vesicles and droplets.
  Moreover, most of products are polycrystalline
  submicrometer spheres aggregated of
  nanoparticles. To my best knowledge,only several
  non-sphere and single-crystalline hollow
  structures have been prepared.

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• In this paper, we present a novel selftemplate
  route for fabricating single-crystalline ß-FeOOH
  hollow nanorods with length in the range of
  70-110 nm and width in the range of 20-30 nm.
  Hollow cavitys will be gained by controlling the
  degree of the phase transition from Fe(OH)3 to
  ß-FeOOH and the Ostwald ripening process
  happening at the interior of nanorods.

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Ostwald ripening process

• Many small crystals form in a system initially
  but slowly disappear except for a few that grow
  larger, at the expense of the small crystals. The
  smaller crystals act as "nutrients" for the
  bigger crystals. As the larger crystals grow, the
  area around them is depleted of smaller crystals

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Explanation for the occurrence of Ostwald
ripening

• Larger crystals are more energetically favored
  than smaller crystals. While the formation of
  many small crystals is kinetically favored, (i.e.
  they nucleate more easily) large crystals are
  thermodynamically favored. Small crystals have a
  larger surface area to volume ratio than large
  crystals. Molecules on the surface are
  energetically less stable than the ones already
  well ordered and packed in the interior. Large
  crystals, with their greater volume to surface
  area ratio, represent a lower energy state. Thus,
  many small crystals will attain a lower energy
  state if transformed into large crystals and this
  is what we see in Ostwald ripening.

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Pictorial example of crystal ripening from a
precipitate
 Day 6. A single crystal has appeared in the
precipitate. The precipitate feeds the growth of
the crystal and a zone of depletion appears
around the crystal as it grows. This depletion
zone looks like a halo around the crystal.
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Day 10
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Day 13
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Day 16
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??CS??(????????)
????
2mLCS??15mL0.3mol/L FeCl3??15mL???0.408g??82?2h
???????
???????
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??????????????

• (1)XRDRigaku D/max-?A200,CuKa,
• (2)TEM JEM-100CXII, ????80kV
• (3)HRTEM Technai F30, ????300kV
• (4)FT-IR Bio-Rad model FTS-165 IR ?????
• (5)TGA Mettler Toledo SDTA851e, N2, ????20?/min

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• 82???20min???????Fe(OH)3

?????????,???Fe(OH)3????????-?????????ß-FeOOH???
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• ?????180???2h?,??????Fe(OH)3???,????????????

Ostwald????,??????????????????????
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???????

• ??????????ß-FeOOH????????????????????,??????????,?
  ?????????
• ??????????????????????????????????????????????????
  ?,????????a-Fe2O3

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Templates for Synthesizing Nanoparticles
????????
19
??????

• ????????(AAO),
• ??????,???
• ?????????????????
• ??????
• ???

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???-????
Carbon Nanotube
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???-???????
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???-????????

• ???????????????SDS????????SDBSAOT
• ??????????????????CTAB
• ????????Triton-X t-octyl-(OCH2CH2)xOH,

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??????????

• ???????????????????????????????

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??????????

• ????????-??????-?

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Redox synthesis by NiSO4 and NaH2PO2 in
cyclohexane-water-polyglycol emulsion system
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?Fe3?Fe2?????????????SDS??,??????????????????,??
??????????,??????????????????????????,?????????,??
?FeOOH,???????Fe2O3?
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??????
FeOOH
???
Fe2O3
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????????

• Shape control and associated magnetic properties
  of spinel cobalt ferrite nanocrystals
• JACS 2004, 102, 126, 6164-6168

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??????

• ??????????????,?????????????,?????????5nm??CoFe2O4
  ??????,?????????????????

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????

• 2mmol Co(acac)2,40mL???,20mmol 1,2-??????,10mL??,1
  8mL?????????140?,?????4mmol Fe(acac)3?30mL????????
  ???????260?,????30min???,?????,????,????,??5nm???
  ??

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????

• ?100mg????????,??1mmol Co(acac)2?2mmol
  Fe(acac)3?10mmol 1-????5mL???5mL????????????,??10
  15?/min?????260????30min????,???????????,?????8nm?
  ?CoFe2O4?

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????????????????????????????190???????????,??????
??????????????????????????????????????,?????CoFe
2O4?????????????????????????????????????????????
????
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???????,??????????,????????,?????????????,????????
????,???????
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????????

• Unidirectionally Aligned Copper Hydroxide
  Crystalline Nanorods from
• Two-Dimensional Copper Hydroxy Nitrate

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????

• ?????????????1D Cu(OH)2???????????????Mg(OH)2?????
  ??,???????OH-?NO3-?????2D???Cu2(OH)3NO3?NaOH??????
  ???,????1D???Cu(OH)2?

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???????
R. Xu, H. C. Zeng, Chem. Mater., 2003, 15,
2040-2048
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????????
?????
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????

• ?2.5g????Cu2(OH)3NO3???????,????2mol/L?NaOH??,????
  ,???,????????48h,???????,??????????????,35?????,??
  ???

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??????????????????????????Cu(OH)2??,?JCPDS??13-420
???
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• FTIR???????Cu2(OH)3NO3?????Cu(OH)2??b?,700cm-1????
  ????Cu-O??,?3303?3567cm-1?????OH-??????,?a??NO3-??
  ???1340cm-1???????b???,??NO3-???OH-???

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????????

• ?????-??????Eu2O3??? JACS 2004,126,5976-5977

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??????

• ?????????????0.01mol/L??,??????????????,??Eu/??1/
  20???????????,????????????80???72h?????,??????,???
  150???1??,????700???10???

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????????Philips Xpert PRO ??????,???????Eu2O3,???
?a1.085nm,?JCPDS???86-2476??? ??????????????,????
???,Eu?O??????????23?
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The function of the Al2O3 template
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???Eu2O3?????????,???????????,??????????,???5080n
m,???????????????????,???????????Eu2O3????TEM?????
?????70nm,???5nm?
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TEM???????????????,????????????????Eu2O3??,??(222)
??????,???????????????????????HRTEM????b