Carbon 41 (2003) 2141–2148
F ormation of hydrogen-capped polyynes by laser ablation of
C particles suspended in solution
a,b,c, b b a,b
Masaharu Tsuji , Shingo Kuboyama , Toshinori Matsuzaki , Takeshi Tsuji
Institute for Materials Chemistry and Engineering
Department of Applied Science for Electronics and Materials
Graduate School of Engineering Sciences
Japanese Science and Technology
Received 10 May 2003; accepted 26 May 2003
Laser ablation of C particles suspended in hexane or methanol solution has been studied using a Nd:YAG laser (266,
355, 532, and 1064 nm). Insoluble product analysis by Raman spectroscopy showed that C particles transformed to
graphite-like ones. On the other hand, soluble product analysis by HPLC coupled with UV absorption spectroscopy and
GC/MS demonstrated that linear hydrogen-capped polyynes (C H : n58, 10, 12) were formed. The dominant C H
n 2 n 2
polyyne was C H in all cases. The relative abundance of polyynes decreased with increasing wavelength of the Nd:YAG
laser, except for 266-nm irradiation in hexane, where the relative abundance of polyynes at 355 nm was greater than that at
266 nm. It was therefore concluded that photochemical processes are more important than thermal ones for the formation of
polyynes. The relative abundance of polyynes in hexane was greater than that in methanol. The dependence of relative
abundance of polyynes on the particles concentration, laser irradiation time, and laser power was measured in order to obtain
information on formation mechanism of polyynes. These results and reported laser photochemical processes of C
molecules in the gas phase suggested that C radicals produced from C are polymerized and hydrogenated to form C H
and much smaller amounts of C H and C H .
10 2 12 2
2003 Elsevier Ltd. All rights reserved.
A. Carbyne; Fullerene; B. Laser irradiation; C. Chromatography; Raman spectroscopy
1 . Introduction visible absorption spectrometer and GC/MS. It was found
that the degree of polymerization of polyynes depended on
One-pot synthesis of linear polyynes (carbyne) has the solvent. The relative abundance of polyynes increased
recently received considerable attention because they are with increasing particle concentration from 0.5 to 4 mg/
promising one-dimensional conducting materials and im- ml, then decreased above that until 10 mg/ml was reached.
portant interstellar species [1,2]. We have recently found The relative abundance of polyynes decreased with in-
that hydrogen-capped polyynes (C H : n58–16, even creasing wavelength of the Nd:YAG laser, 355.532.
numbers) are formed directly by laser ablation of graphite 1064 nm.
particles suspended in benzene, toluene, or hexane solution In order to extend this study, we investigate here the
. An unfocused Nd:YAG laser (355, 532, and 1064 nm) formation of polyynes by laser photodissociation of C
was used as an irradiation source. Resolved products in resolved in toluene solution or laser ablation of C
solutions were analyzed using HPLC coupled with UV and particles suspended in hexane or methanol solution. Poly-
ynes are produced only from the latter suspension of C
particles. The relative abundance of polyynes produced is
Corresponding author. Present address: Institute for Materials
measured as a function of particle concentration, laser
Chemistry and Engineering, Kyushu University, Kasugakoen 6-1,
irradiation time, and laser power at 355-nm irradiation in
Kasuga, Fukuoka 816-8580, Japan. Tel.: 181-92-583-7815; fax:
order to obtain information on the formation mechanism of
firstname.lastname@example.org (M. Tsuji).
polyynes from suspension of C particles. The decompo-
0008-6223/03/$ – see front matter 2003 Elsevier Ltd. All rights reserved.