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Electronic Supplementary Information for:
Laser-derived One-Pot Synthesis of Silicon Nanocrystals Terminated with Organic Monolayers
N. Shirahata,*,a M. R. Linford,b S. Furumi,a L. Pei,b Y. Sakka,a R. J. Gates,b M. C. Asplundb a National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
E-mail: SHIRAHATA.naoto@nims.go.jp b Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602
Experimental Details
Synthesis of samples
Synthesis of the organically-terminated silicon nanocrystals: A 2 mL of 1-octene was treated with
sodium sulfate, and was then collected into Schlenk flask. Next, the Schlenk flask was subjected to
freeze-pump-thaw (FPT) cycle on a grease-free vacuum line for at least 30 min by the use of Dewar
flasks filled with liquid nitrogen in order to remove the dissolved oxygen. Finally, the oxygen-free
1-octene was stored under argon atmosphere until before use. These procedures were performed on a
grease-free glass vacuum line at room temperature and atmospheric pressure. A hydrogen-terminated
wafer of silicon was placed in the quartz cell, and purged several times with Ar gas. Next, the quartz
cell was filled with the oxygen-free 1-octene for subsequent laser ablation in liquid environment. In
the cell, the target silicon was ablated for 30 min by Nd:YAG pulsed laser (λ: 532 nm, power
density: 1.0 J/cm2, pulse duration: 4–6 ns, repetition rate: 10 Hz). After 30 min, the solvent was
removed by rotary evaporation.
The synthesized nanocrystals: 1H NMR (300 MHz, CDCl3, 20ºC, TMS): δ 1.25 (s, 12Η), 1.10 (s,
2H), 0.88 (s, 3H). 13C NMR (75 MHz, CDCl3, 20ºC , TMS): δ 31.74, 29.70, 28.84, 22.64, 14.09.
Preparation of octane-terminated polycrystalline silicon particle (d >200 nm): Silicon powder
(YAMAISHIMETAL, Co. Ltd., No. 600) was used as a starting material. A 10 mg of the powder was
treated for 15 min with an aqueous 1% HF solution to generate the Si-H terminated surface. The
H-terminated silicon particle was then washed with methanol, and was then filtrated with a
polyvinylidene fluoride (PVDF) membrane filter (200 nm diameter pore size, Millipore) to collect
only polycrystalline silicon particles larger than 200 nm in physical size. As a result, we removed the
particles less than 200 nm. Prior to the thermal radical reaction, a 5 mL of 1-octene was treated with
sodium sulfate, and was then collected into Schlenk flask. Next, the Schlenk flask was subjected to
FPT cycle on a grease-free vacuum line for at least 30 min by the use of Dewar flasks filled with
liquid nitrogen in order to remove the dissolved oxygen. Finally, the oxygen-free 1-octene was
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2009
stored under argon atmosphere until before use. To perform a thermal radical reaction, the
H-terminated silicon particle was added into a small three-necked flask with the 1-octene. The flask
was fitted with a thermometer, an argon-gas inlet with oxygen and moisture filters, and a reflux
condenser which the other side was connected to a glass-tube with liquid paraffin to avoid undesired
aeration. Shortly thereafter, the bubbling of the solution with argon-gas was performed for at least 30
min. Subsequently, the solution was heated for 5 h at 120ºC under a flow of argon-gas. After the
excess of 1-octene was removed under reduced pressure with heating in a water bath, the brownish
product, i.e., octane-terminated polycrystalline silicon particle, was obtained, and used as a “bulk
silicon”.
Characterization
Raman spectrum was collected using the 514.5 nm line of an Ar ion laser beam in a backscattering
geometry (BeamLok 2060-RS/T64000, Spectro-Physics, Mountain View, CA/Jobin Yvon, Horiba,
France). To acquire the Raman spectrum, polarized light from the laser was focused on the sample
dropped on a gold-coated glass plate at room temperature. The HRTEM and STEM micrographs of
the sample were obtained using a JEM-2100F with a 0.10 nm in resolution at a 200 kV of
acceleration voltage in bright- and dark-field modes. 1H and 13C NMR spectra were collected at 20ºC
on a JEOL FT NMR system, operating at 300 MHz and 75 MHz, respectively. FTIR spectrum was
examined at 1 cm−1 resolution with 256 scans using a Spectrum GX, Perkin-Elmer. For this
measurement, a 30 μL of chloroform containing the sample was coated over the surface of KBr disk.
Optical absorbance spectrum was recorded in dichloromethane for silicon derivatives at room
temperature with a UV-visible spectrophotometer (U2900, Hitachi Co., Japan) with a 1 nm of
resolution. The PL spectrum was obtained with a Fluorescence Spectrophotometer Model F-7000
(Hitachi High-Technologies, Japan), and the spectral resolution was 1 nm The absorption and PL
spectra of the solvent, i.e., dichloromethane, were subtracted from each of the sample’s spectra,
respectively.
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2009
Fig. S1. TEM images with corresponding to FFT analyses or SAED patterns of a sample prepared in 1-octene. In all the
high resolution images, the single-crystalline nanocrystals overlap each other. (a) The lattice fringe spacings of 3.1 Å and
2.0 Å are consistent with those of the (111) and the (220) planes in diamond-structured silicon, respectively. This image
shows an area of overlap between different nanocrystals with (111) and (220) phase. (c) EDX showed that these
nanocrystals’ assemblages are composed of silicon. (d) An SAED pattern of a 5 nm single crystal (see inset) taken from
[001] direction. (e) A typical STEM image in dark field mode of the nanocrystals. (f) A histogram of size distribution of the
nanocrystal’s sample.
3.1Å
2.0Å
5nm
040
220
400
220
040
220
400
220
000
5nm
(a) (b)
(c) (d)
(111)
(220)
10nm
(e) (f)
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2009
CH2― (CH2)4― CH3
CCH
H
H(f)
(d)
(e)
(c) (b) (a)
0.87
(a)
1.26
(b)
2.02
(c)
4.91
(e)
4.97
(d)
5.44
(f)
02468ppm
CH2=CH2-CH2-CH2-CH2-CH2-CH2-CH3(a)
139.
3
(a)
114.
1
(b)
33.8
(c)
31.7
(d)
28.9
(e)28
.8
(f)
22.6
(g) 14.1
(h)
255075100125150175
ppm
(b) (c) (d) (e) (f) (g) (h)
(A)
(B)
Fig. S2. (A) 1H and (B) 13C NMR spectra of 1-octene.
Fig. S3. FTIR spectrum of silicon nanocrystals prepared in neat 1-octene with the
assignment of the absorption peaks.
8001300180023002800330038003800 2800 1800 800Wavelength (cm–1)
Abso
rban
ce (a
rbun
it)
ν(–C–CH3)2952, 2864 ν(–C–CH2–)
2922, 2852
δ(–C–CH2–)1491
δ(–C–CH3)1442, 1367
δ(Si–CH2–)1230
ν(–O–Si–O–)1000–1100
ν(Si–CH2–)1454
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2009
Fig. S4. Optical absorption spectrum of polycrystalline silicon particle (d>200 nm) terminated with
octane monolayers.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
230 250 270 290 310 330 350 370
283 nm274 nm
00.1
0.3
0.5
0.7
Abs
orba
nce
230 270 310 350
Wavelength (nm)
Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2009
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