title: Luminescence color control and quantum-efficiency enhancement of colloidal Si nanocrystals by pulsed laser irradiation in liquid.
abstract: We demonstrate the emission color change of white-emitting chlorine-terminated silicon nanocrystals (Cl:Si-ncs) to blue-emitting carbon-terminated silicon nanocrystals (C:Si-ncs), together with the enhancement of the luminescence quantum efficiency from 7% to 13%, by post-laser ablation in 1-octene. Such changes of the PL properties are caused by the size reduction of Si-nc and efficient surface passivation by hydrocarbons, resulting from a high reactivity of 1-octene in the laser-ablation and subsequent nanoparticle-formation processes. Furthermore, the second post-laser irradiation of the C:Si-ncs in trichloroethylene reversibly results in the formation of the Cl:Si-ncs. The preparation yield of C:Si-ncs via the post-laser ablation of Cl:Si-ncs is higher than that of C:Si-ncs directly prepared only by the laser ablation of PSi in 1-octene. This high preparation yield is due to the high laser-ablation efficiency in trichloroethylene compared with 1-octene, which is attributed to the low heat loss of the solvent in the laser-ablation process.
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan.
authors.forename: Ze
authors.initials: Z
authors.lastname: Yuan
authors.affiliation: Graduate School of Science and Technology, Gunma University, Kiryu, Gunma 376-8515, Japan. tnakamura@gunma-u.ac.jp.
authors.forename: Toshihiro
authors.identifier: http://orcid.org/0000-0001-9885-3914
authors.initials: T
authors.lastname: Nakamura
authors.affiliation: Graduate School of Science and Technology, Gunma University, Kiryu, Gunma 376-8515, Japan. tnakamura@gunma-u.ac.jp.
authors.forename: Sadao
authors.initials: S
authors.lastname: Adachi
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan.
authors.forename: Kiyoto
authors.initials: K
authors.lastname: Matsuishi