Luminescent Silicon Nanoparticles: An improved inverse micelle synthesis and oxide-dependent photoluminescence studies

Huld, Frederik (2015) Luminescent Silicon Nanoparticles: An improved inverse micelle synthesis and oxide-dependent photoluminescence studies. Masters thesis, University of East Anglia.

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Abstract

The luminescence of silicon nanoparticles has been an active area of study for a
number of years. These nanoparticles luminesce when excited by ultraviolet (UV) light
in the ~340 nm region, displaying either a blueish or a reddish colour. The control and
origin of these colours has been debated, with researchers such as Veinot, Kauzlarich and
Tilley claiming that the luminescence can be controlled with the use of nitrogen. In this
thesis, a new synthetic procedure is presented that improves upon the established inversemicelle
technique by replacing the methanol or ethanol quenching agent with copper
chloride. It is found that this new technique lowers the level of surface oxide present in
the form of alcohols on the surface of the nanoparticles, giving blue luminescent particles
with improved surfaces for further chemistry.
Photoluminescence studies are also performed on samples of silicon nanoparticles
synthesised by electrochemical etching, using a variety of oxygen-containing compounds
to probe the behaviour of the photoluminescence spectrum. It is found that there are typically
five Gaussian peaks present in a typical spectrum; occurring at 405 nm, 430 nm,
460 nm 485-90 nm, 500 nm, and 640 nm, subsequently labelled a, b, g, e, and z . It is
also found that molecular oxygen increases the b peak and suppresses the z peak, and
that water has the opposite effect on these two peaks. It is shown that the peaks a, b,
and z are all due to a single site on the surface of the silicon nanoparticle, corresponding
to the cases when the site is oxide-free, occupied by molecular oxygen, and water,
respectively. It is also hypothesised that the luminescence can be controlled via the use
of compounds of different sizes and polarities, with electron-withdrawing molecules increasing
the blue luminescence, and electron-donating molecules increasing the red. g
and e are used as normalising peaks to compare between samples, and are not affected
by oxygen.

Item Type: Thesis (Masters)
Faculty \ School: Faculty of Science > School of Chemical Sciences and Pharmacy
Depositing User: Vailele Chittock
Date Deposited: 29 Jan 2016 11:06
Last Modified: 29 Jan 2016 11:06
URI: https://ueaeprints.uea.ac.uk/id/eprint/56868
DOI:

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