title: Alkyl-functionalized oxide-free silicon nanoparticles: synthesis and optical properties.
abstract: Highly monodisperse silicon nanoparticles (1.57 +/- 0.21 nm) are synthesized with a covalently attached alkyl monolayer on a gram scale. Infrared spectroscopy shows that these silicon nanoparticles contain only a few oxygen atoms per nanoparticle. XPS spectra clearly show the presence of unoxidized Si and attached alkyl chains. Owing to the relatively efficient synthesis (yields approximately 100-fold higher than of those previously reported) the molar extinction coefficient epsilon can be measured: epsilon(max) = 1.7 x 10(-4) M(-1)cm(-1), only a factor of 4 lower than that of CdS and CdSe nanoparticles of that size. The quantum yield of emission ranges from 0.12 (C(10)H(21)-capping) to 0.23 (C(16)H(33)-capping). UV/Vis absorption and emission spectroscopy show clear vibrational progressions (974 +/- 14 cm(-1); up to five vibrational bands visible at room temperature), resembling bulk SiC phonons, which support the monodispersity observed by TEM. This was also confirmed by time-resolved fluorescence anisotropy measurements, which display a strictly monoexponential decay that can only be indicative of monodisperse, ball-shaped nanoparticles.
authors.affiliation: Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, Wageningen, 6703 HB, The Netherlands.
authors.forename: Milena
authors.initials: M
authors.lastname: Rosso-Vasic
authors.forename: Evan
authors.initials: E
authors.lastname: Spruijt
authors.forename: Barend
authors.initials: B
authors.lastname: van Lagen
authors.forename: Luisa
authors.initials: L
authors.lastname: De Cola
authors.forename: Han
authors.initials: H
authors.lastname: Zuilhof