Oxide and hydrogen capped ultrasmall blue luminescent Si nanoparticles

Abstract

We dispersed electrochemical etched silicon into a colloid of ultrasmall ultrabright Si nanoparticles. Direct imaging using transmission electron microscopy shows particles of ∼1 nm in diameter, and infrared and electron photospectroscopy show that they are passivated with hydrogen. Under 350 nm excitation, the luminescence is dominated by an extremely strong blue band at 390 nm. We replace hydrogen by a high-quality ultrathin surface oxide cap by self-limiting oxidation in H2O2. Upon capping, the excitation efficiency drops, but only by a factor of 2, to an efficiency still two-fold larger than that of fluorescein. Although of slightly lower brightness, capped Si particles have superior biocompatability, an important property for biosensing applications.

Second harmonic generation in microcrystallite films of ultrasmall Si nanoparticles

“…The substrates were ͑100͒ oriented, 1-10 ⍀ cm resistivity, p-type boron doped silicon, laterally anodized in hydrogen peroxide and HF acid 5,6,9 while advancing the wafer in the etchant at a reduced speed of ϳ1 mm per hour. Subsequent immersion in an ultrasound acetone or water bath crumbles the top film into ultrasmall particles.…”

“…Silicon was dispersed into a suspension nanoparticle colloid of ϳ1 nm across. 5,6 The particles were then reconstituted to create large, thick, uniform, and under control layers of microcrystallites on device quality Si substrates. The film is excited by near-infrared femtosecond two photon process at 750-830 nm.…”

Fluorescent silicon clusters and nanoparticles

“…Light emission in the blue spectral range is a known phenomenon for colloidal suspensions of silicon nanoparticles (Kimura, 1999;Belomoin et al, 2000;Valenta et al, 2008) and silicon nanocrystal films (Loni et al, 1995;Canham et al, 1996;de Boer et al, 2010;Ondič et al, 2014). At the present time, there seems to be a consensus that the vast majority of reported fluorescent bands in the blue spectral range are due to localised transitions, rather than being caused by quantum confinement (Dasog et al, 2013(Dasog et al, , 2016).…”

“…further, and to date numerous examples of nanostructured forms of fluorescent silicon have been reported (Takagi et al, 1990;Brus et al, 1995;Hirschman et al, 1996;Borsella et al, 1997;Ehbrecht et al, 1997;Cullis et al, 1997;Huisken et al, 1999;Pavesi et al, 2000;Belomoin et al, 2000Belomoin et al, , 2002Mangolini et al, 2005;Falconieri et al, 2005;Brewer and von Haeften, 2009;Vincent et al, 2010;He et al, 2011;Dasog et al, 2014;Li et al, 2016). Hence, we have a rich set of data available on electronic and structural properties that unpin our understanding of the fluorescence of silicon clusters and nanoparticles.…”

A silicon nanoparticle-based polymeric nano-composite material for glucose sensing

“…USiN were made by electrochemical etching of a (1 0 0)-ori ented p-type (1-10 X cm) silicon wafer in hydrofluoric acid and hydrogen peroxide followed by shaking off the particles from the etched wafer using ultrasound in water or organic solvents such as benzene, isopropyl alcohol and tetrahydrofuran (THF) [10]. This etching technique can be used to prepare 1-nm particles (USiN1) and 2.8-nm particles (USiN2.8), depending on etching conditions.…”