laser-derived one-pot synthesis of silicon nanocrystals ... · synthesis of samples synthesis of...

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: [email protected] 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.


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)


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


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)


laser-derived one-pot synthesis of silicon nanocrystals ... · synthesis of samples synthesis of...

Documents