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3 金属材料合成 3-2 B
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陶瓷工艺
Examples of metal particles from chemical
reduction in aqueous solutions
CTAB = cetyltrimethylammoniumbromide (C16H31)(CH3)3NBrSDS = sodium dodecylsulfate
CH3(CH2)11OSO3Na
Templatingmethod (A4)
纳纳
Dendrimer-TemplatedNanoclusterSynthesis
聚酰胺胺
Structure of poly(amidoamine) dendrimer
(PAMAM)
Generation 2 PAMAM Dendrimer
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Sacrificial
hydrogen
protective
strategy
for
the
nanoparticles
with a Pd shell-Pt core structure.
Y. Wang, N. Toshima, J. Phys. Chem. B, 1997, 101, 5301.
Synthesis of FePtalloy nanoparticle
Mechanism: Chemistry versusArt
PtCl2
2OH)2
Pt seeds
PVP ?AgNO3PVPGrowth(CH
Various Stages of Wire Growth
10 min
40 min20 min60 min
Silver Nanowireswith φ
~40 nm
Ex.) Au nanorodssynthesized by seed-mediated
preparation
ofbimetallic
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chemical reduction://doc.xuehai.net/beab61e9ba638eb80bc6829b3.htmlr
chemical reduction
Planar density of atoms of FCC structure
111: 0.907
100: 0.785
110: 0.555
“ Zipping model”:the formation of the bilayerof CnTAB(squiggles) on the
nanorod(black rectangle) surface may assist nanorodformation as more gold ion (black
dots) is introduced.
The preferential bindingis based on sterics-the Au atom spacing on the side faces
is more comparable to the size of the CTA headgroupthan the close-packed 111 face
of gold, which is at the ends of the nanorods.
(CCH note: Could also be due to energy reason.)
chemical reduction
Mechanism of surfactant-directed metal nanorodgrowth:The single crystalline seed
particles have facets that are differentiallyblocked by surfactant (or an initial
halide layer that then electrostaticallyattracts the cationic surfactant).
Subsequent addition of metal
Synthesis
of
gold
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nanopartichttp://doc.xuehai.net/beab61e9ba638eb80bc6829b3.htmlles
of
different
shapes
z
z
zGeneral idea is the same as the growth of gold nanorods (seed-mediated
method)Slightly change the conditions when growing nanorods (concentration of
different reactants)Cubes, hexagon, triangle, tetrapods, branchedExperimental
methods involve: 1) the preparation of Au seed particles; and 2) the subsequent
addition of an appropriate
quantity of the Au seed solution to the aqueous growth solutionscontaining desired
quantities of
cetyltrimethylammonium
bromide (CTAB), HAuCl4, ascorbic acid (AA), and in some cases a small quantity of
AgNO3.
T. K. Sau, C. J. Murphy, J. Am. Chem. Soc.2004, 126, 8648-8649
Synthesis of gold nanoparticles of different shapes§For triangular profile and cubes,
this corresponds to edge lengths; for hexagonal
profile, this corresponds to the distance between opposite sides; and for
tetrapodsand
branched
phttp://doc.xuehai.net/beab61e9ba638eb80bc6829b3.htmlarticles, this corresponds
to center-to-tip distances. For cubes, triangles and hexagons, the dimensions are
averaged over ~120
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particles and are reproducible to within 5% of the given value; for the other shapes,
the dimensions are averaged over ~120 particles and are within ~10% of the given value.
a)6.0x10-5M AgNO3was used.
b)Seed(5) was used here, otherwise results are reported for seed(1).
zThe factors [CTAB], [Au], [Au3 ]and [AA] are interdependent.
Synthesis of gold nanoparticles of different shapes
[AA]Scale bar = 100 nm increases from A to C and seed concentrationincreases from
C to D.
Synthesis of gold nanoparticles of different shapesTEM images showing cubic to
rod-shaped gold particles produced with low AA concentrationin the presence of small
quantity of AgNO3. [CTAB] was increased from 1.6 x 10-2M (A), to 9.5 x 10-2M (B,C,D).
[Au3
]
decreased
from
(C),http://doc.xuehai.net/beab61e9ba638eb80bc6829b3.html
(B)
whereas
to
seed
concentration increased from C to D. Scale bar ) 100 nm.
Synthesis of gold nanoparticles of different shapesTEM images of branched Au
nanoparticles, varying in the dimension and number of branches. prepared under
various combinations of [seed]/[Au3 ] ratio, and the concentrations of CTAB and AA.
Tetrapods(A), star-shape (B), larger tetra-
pods (C), and multi-pods (D and E).
3.2.4 SonochemicalApproaches for NanoscaleParticle Synthesis
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Ultrasonic: > 20kHz
Formation of Highly Reactive Radicals
Depending on the liquid medium, sonicationleads to the
generation of oxidizing and reducing radicals
In aqueous solution??H2? M In solutes like alcohols, sonicationleads to secondary
radicals
???2(H2O)
?ROH
M? M
RO
H
磁场辅助水热法制备 Ni 纳米粒子
NiCl2·6H2O 酒石酸钠
NaH2PO2·H2
O NaOH
常规条件磁场条件
磁场辅助水热法制备 Ni 纳米粒子://doc.xuehai.net/beab61e9ba638eb80bc6829b3.htmlr
NiCl2·6H2O 柠檬酸三钠 NaH2PO2·H2O NaOH
常规条件
磁场条件
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Electrochemical reduction to prepare Au nanorod
(TEM micrographs of Au
nanorodswith different
aspect ratios 2.7 (top) and
6.1 (bottom). Scale bars
represent 50 nm.
Another important factor controlling the aspect
ratioof the Au nanorodsis the presence of a
silver plateinside theelectrolytic solution,
which is gradually immersed behind thePt
electrode. The redoxreaction between gold
ions generatedfrom the anode and silver metal
leads to the formation of silverions. Wang and
co-workers found that the concentrationof
silver ions and their release rate determined the
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length ofthe nanorods.The complete
mechanism, as well as the roleof the silver
ions, is still unknown.
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