SLS Growth of Ternary Cu-In-Se Semiconductor Nanowires
A R T I C L E S
NaOEt [Fluka, g95(T)%], C
6
H
5
SeH [Strem, 97%], BiCl
3
[Acros,
slightly as a result of the exothermic reaction. After complete
addition of the Grignard reagent, the reaction slowly cooled to room
temperature and was allowed to stir inside the drybox for 18 h.
The cloudy mixture was then filtered through a fine glass frit, and
a clear and cloudless solution was obtained. All volatile materials
were removed in vacuo, yielding a viscous liquid that contained a
white precipitate. Anhydrous pentane was then added to this viscous
liquid and filtered once more through a fine glass frit, whereby a
clear colorless solution containing the product was isolated. All
volatile materials were removed in vacuo, yielding 2.06 g of a clear
9
9.999%], and n-BuMgCl [Aldrich, 2.0 M solution in diethyl ether]
were all used without additional purification. HPLC grade acetone,
toluene, hexanes, and chloroform were all purchased from Aldrich
and used without additional purification. Anhydrous solvents,
methanol [Aldrich, 99.8%], 1,2-dichlorobezene [Aldrich, 99%],
diphenyl ether [Acros, 99%], diethyl ether [Aldrich, g99.7%],
trioctylphosphine oxide (TOPO) [Acros, 99%], trioctylamine (TOA)
[
Aldrich, 98%] and n-octadecylphosphonic acid [Alfa Aesar,
crystalline solid] were also used without further purification.
Trioctylphosphine (TOP) [Strem, 90%] was prepurified by heating
the solvent to 200 °C under vacuum for 2 h. Then, 1.0 M solutions
of trioctylphosphine selenium (TOPSe) were prepared in advance
of use by stirring overnight appropriate amounts of purified TOP
and selenium pellets [Aldrich, ∼2 mm, 99.999%] inside the drybox
at room temperature. Postpreparative handling and spectroscopy
were conducted under ambient conditions.
3
viscous liquid (90% yield based on BiCl ). A 1.0 M stock solution
was then prepared by dissolving 2.06 g of the product in 6.0 mL
of solvent (4.8 mL of toluene and 1.2 mL of diphenyl ether) and
stored inside the drybox freezer and used directly.
Synthesis of (Gold)Bismuth (Core)Shell Catalyst
Nanoparticles. The (Au)Bi catalyst particles were synthesized
28,29
according to procedures reported by Kuno et al.
Typically, the
Synthesis of Gold Nanoparticles (Au101(PPh
3
)
21Cl
5
,
procedure was carried out as follows: a mixture of phenyl ether
(4.00 mL, 25.2 mmol), TOP (0.600 mL, 1.34 mmol), and 2.5 mL
(0.75 µmol) of the 0.3 mM Au-NP stock solution prepared above
was added to a three-neck flask. This mixture was then heated to
100 °C under vacuum to dry and degas the reagents, after which
Au-NPs). The Au-NPs were synthesized according to the procedure
26
reported by Hutchison et al., which was modified slightly. Briefly,
the procedure was carried out as follows: HAuCl (0.5 g, 1.25
4
mmol) and tetraoctylammonium bromide (0.80 g, 1.47 mmol) were
dissolved in a water/toluene (50 mL:65 mL) mixture inside a
Schlenk flask under nitrogen flow. This mixture was then degassed
under vacuum for ∼5 min at room temperature. Under nitrogen
flow, the solution was stirred vigorously at room temperature until
the golden color had transferred into the organic phase. Triph-
enylphosphine (1.16 g, 4.43 mmol) was then added, and the solution
was stirred vigorously for an additional 15-30 min, until the organic
phase turned white and cloudy. The cloudy solution was then cooled
to 0 °C using an ice bath. An aqueous solution of sodium
borohydride was prepared immediately prior to use, by dissolving
time (∼20 min) the reaction flask was backfilled with N . In a
2
glovebox, an injection solution containing phenyl ether (4.00 mL,
25.2 mmol), TOP (0.600 mL, 1.34 mmol), and Bi(n-Bu) (0.615
3
mmol, 0.615 mL of a 1.0 M stock solution) was prepared. Toluene
(3.0 mL) was combined with the 5.215 mL injection solution to
aid solubility of Bi(n-Bu) , and this mixture was then delivered to
3
the Au-NP solution with a syringe pump at a nominal rate of 7
mL/h. Upon addition of the Bi(n-Bu) mixture, the reaction solution
3
turned progressively darker, with no observed plating of bismuth.
After ∼1.7 h of slow syringe pump addition, the reaction mixture
was allowed to cool to room temperature, and the resulting (Au)Bi
NPs were precipitated by gradual addition of 17.5 mL of acetoni-
trile. Care was taken to prevent adding an excess of acetonitrile as
this leads to a phase separation, which complicates recovery of the
(Au)Bi-NPs. The suspension was then centrifuged at 4300 rpm for
10 min to obtain the (Au)Bi-NP precipitate, which was redissolved
in 2.0 mL of toluene along with a few drops of oleic acid (0.03
mL). The concentration of the (Au)Bi NP catalyst solution was
normalized to an absorbance value of A ) 0.1235 at 500 nm,
(
0.705 g, 18.65 mmol) this reagent in 10 mL of deionized water,
and rapidly added to the cooled cloudy solution (this addition results
in vigorous bubbling and should be performed cautiously). The
reaction mixture was stirred at 0 °C for an additional 5 min before
the ice bath was removed. Gradually warming to room temperature,
the organic phase progressively turned dark purple after which time
it was stirred for an additional 3 h under nitrogen flow. The toluene
layer was then separated and washed twice with 100 mL of
deionized water. All volatiles were removed in vacuo to yield a
dark-purplish solid.
28
yielding an estimated NP stock concentration of ∼0.38 mM. This
solution was stored in a glovebox freezer where it remained stable
for several months. It should be noted that a freshly prepared catalyst
produces the most consistent results in terms of NW quality. If
stored for lengthy periods of time (several months), storage as a
dilute solution results in particle aggregation, evident in absorption
as a clear plasmon peak compared to that of the fresh catalyst which
is small and barely observable (Figure S1 in the Supporting
Information), as well as reduced SLS activity. For lengthy storage
periods, concentrated solutions are preferred.
Additional Purification Procedure for the Au-NPs. The
resulting dark-purplish solid was washed with a series of solvents
(
hexanes, saturated aqueous sodium nitrite, and a 2:3 methanol/
water mixture) to remove the phase transfer catalyst, byproducts,
and unreacted starting materials. This additional washing procedure
was followed exactly according to the published procedure by
2
6
Hutchison et al. After the additional washing steps, the dark-
purplish solid was dissolved in chloroform and the solution was
filtered through a medium frit to remove any insoluble materials.
The deep purple solution was reduced in volume to ∼50 mL under
vacuum. After warming the solution to room temperature, pentane
Synthesis
[(PPh Cu(µ-SePh)
SePh) In(SePh)
version of the procedure reported by Hepp et al. Typically, the
procedure was carried out as follows: C SeNa was prepared by
adding NaOEt (0.477 g, 7.00 mmol) in anhydrous MeOH (7.0 mL) to
SeH (0.675 mL, 1.00 g, 6.37 mmol), which was already dissolved
of
the
Single-Source
Precursor
(
3
)
2
2
In(SePh)
2
]). The
[(PPh Cu(µ-
3 2
)
(
120 mL, HPLC grade) was added slowly to precipitate the product,
2
2
] precursor was synthesized according to a modified
yielding 0.5 g of purified Au-NPs. The Au-NPs (0.5 g, 0.0195
mmol) were dissolved in 65 mL of toluene to generate a 0.0003 M
30
6 5
H
(
0.3 mM) stock solution.
Synthesis of Tributylbismuth (Bi(n-Bu) ). The Bi(n-Bu)
3 3
6 5
C H
precursor was synthesized according to a modified version of the
in 6.0 mL of anhydrous MeOH, followed by stirring of this clear yellow
solution at room temperature for 20 h inside the drybox. A three-neck
flask was then charged with the C H SeNa solution, and InCl (0.352
6 5 3
2
7
procedure previously reported by Mitzi. A three-neck flask was
charged with BiCl (1.89 g, 6.0 mmol) and dissolved in 100 mL of
anhydrous diethyl ether, followed by slow addition of n-BuMgCl
9 mL, 18.0 mmol, 2.0 M solution in diethyl ether) to the reaction
3
g, 1.592 mmol) dissolved in 7.0 mL of anhydrous MeOH was rapidly
(
flask inside the drybox. Upon addition of n-BuMgCl, a white
precipitate immediately formed and the solvent began to bubble
(28) Grebinski, J. W.; Hull, K. L.; Zhang, J.; Kosel, T. H.; Kuno, M. Chem.
Mater. 2004, 16, 5260–5272.
(
29) Grebinski, J. W.; Richter, K. L.; Zhang, J.; Kosel, T. H.; Kuno, M. J.
Phys. Chem. B 2004, 108, 9745–9751.
(
(
26) Weare, W. W.; Reed, S. M.; Warner, M. G.; Hutchison, J. E. J. Am.
Chem. Soc. 2000, 122, 12890–12891.
27) Mitzi, D. B. Inorg. Chem. 1996, 35, 7614–7619.
(30) Banger, K. K.; Jin, M. H. C.; Harris, J. D.; Fanwick, P. E.; Hepp,
A. F. Inorg. Chem. 2003, 42, 7713–7715.
J. AM. CHEM. SOC. 9 VOL. 131, NO. 44, 2009 16179