Silicon Nanoparticles Produced by Femtosecond Laser Ablation in Ethanol: Size Control, Structural Characterization, and Optical Properties

Abstract

Spherical silicon nanoparticles were prepared by laser ablation of a single crystal Si wafer immersed in 95% ethanol with a pulse duration shorter than the time of electron−phonon relaxation (from 35 to 900 fs). The size distribution depends on the pulse duration as well as the width of the size distribution, which increases with the increase of the laser pulse duration. High resolution transmission electron microscopy performed on 20−40 nm particles showed polycrystalline particles made up mainly of silicon (α-Si) crystallites with the diamond structure and in some cases cubic silicon carbide (SiC) inclusions. Electron energy loss spectroscopy data on the large particles are very similar to bulk Si. Raman analysis extended to small frequencies showed a downshift and an asymmetrical broadening of the first-order Si optical peak with respect to bulk Si in good agreement with a spatial confinement in 5−10 nm crystallites. The photoluminescence spectra present a maximum of emission band at about 640 nm.

Luminescent silicon nanocrystals produced by near-infrared nanosecond pulsed laser ablation in water

“…Si-NCs are identified by the Raman line at 518 cm −1 , Fig. 2(a); its redshift ( = −2.2 ± 0.2 cm −1 ) and broadening respect to the lineshape related to a bulk Si crystal agree with the phonon confinement effect [18]. The dependence of the peak shift on the Si-NC size (d in nm) is given by the following phenomenological law [19]:…”

The Surface of Nanoparticle Silicon as Studied by Solid-State NMR

“…The chemical and physical information that is currently available on the various elemental silicon systems has been obtained primarily through two significantly disparate approaches: (1) The study of ultra-low surface-area materials (~10 −4 m 2 g −1 ), using ultra-high vacuum (UHV) instrumentation and the techniques of “surface science”, that is, infra-red (IR) spectroscopy [24], scanning tunneling microscopy (STM) [25], atomic force microscopy (ATM) [26], transmission electron microscopy (TEM) [4,27], high-resolution electron energy loss spectroscopy (HREELS) [28] or X-ray photoelectron spectroscopy (XPS) [27], etc. , and (2) the study of high-surface-area materials (~10 2 m 2 g −1 ) by solid-state nuclear magnetic resonance (NMR) [13,14,15,16,17,18,19].…”

Magnetic colloid by PLA: Optical, magnetic and thermal transport properties

“…Since the thermal conductivity of the ethanol (0.17 W/mK at 25 • C) is much smaller than that of the water (0.60 W/mK at 25 • C), ethanol solution can get easily vaporized to such an enhanced condition and decomposes into CH 4 , C 2 H, 4 CH 3 CHO and CH 3 gases at very high localized temperature and pressure [18]. It is reported earlier that during laser ablation in ethanol free carbon also generated due to decomposition of ethanol [19,20]. It might be possible that these compounds restrict the oxidation of ablated Co by attaching around it hence a layer of carbon around the cobalt protects the oxidation of Co. Chen et al [21] also reported the synthesis of pure Co NPs in ethanol by liquid phase pulse laser ablation.…”