Mike Lazell's Homepage

Research Interests

I am a postdoctoral research associate with the Prof. Paul O'Brien group at Imperial College of Science, Technology and
Medicine,Dept. of Chemistry, in the Barton lab.  I am current working on quantum dots of semiconductor materials and
Chemical Vapour Deposition (CVD) of these materials.

Some of the posters I have presented recently Nanoparticles - Does Size Really Matter
                                                                               CVD - The Search for New Precursors

and some leaflets which detail some of the work that I have been doing here at ICSTM.

Nanoparticles - An Introduction

Research into small particles can be traced back to Faraday’s work on gold colloids in 1857. Ostwald’s
publication of “The World Of Neglected Dimensions” drew attention to this then new field of chemistry
suggested the size of colloidal particles and the idea of a gradual transition between molecular and colloidal
states. These particles are often less than 20 nm in diameter and are now often referred to as quantum dots,
Q-particles, artificial atoms (because of their hydrogen like electronic structure) and microelectrodes (due to
the similarity in reactions of colloidal particles and compact electrodes) are of interest to scientists in a wide
range of disciplines. The synthesis of stable robust colloidal particles is a considerable challenge to chemists
and material scientists. Even the most advanced methods of atomic manipulation (scanning tunnelling
microscope) cannot produce devices smaller than 10 nm, therefore chemical methods need to be employed to
produce materials exhibiting quantum behaviour.Physical chemists and physicists have investigated the novel
properties of small particles which can often be attributed the large surface area or the restriction of electronic
entities within the nanocrystal core.

The synthesis of nanocrystalline materials has developed in the fields of colloid and organometallic chemistry,
where the growth of small particles has been achieved by restricting growth using either kinetics or surface
species to passivate particles. Nanocrystals are particles in the 1-20 nm size range and although small, most
retain a certain degree of crystallinity. It is for particles this small, that the properties are in a transitionary state
between molecules and bulk material. Such small particles interact with light predominantly by absorption, not
by scattering, allowing powerful optical methods to be used for analysis of the properties, for example, kinetic
studies for the detection of short lived intermediates. The study of small particles includes quantum dots of
semiconductors which have unusual properties.

The properties of a bulk semiconductor are not dictated by single atoms, but are a result of a periodic array of
a large number of molecules or atoms in a crystal lattice. A transition from bulk semiconductor behaviour to
molecular properties is observed as smaller particles are investigated. In this transitionary range, catalytic,
electronic and optical properties change drastically. Non linear optical properties have been reported in
quantum dots due to the presence of charge carriers trapped in surface defects. The optical non linearity of a
polymer matrix containing 50 Å CdS or PbS nanoparticles was found to be controlled by surface treatment with

Catalytic properties of metal quantum dots have also been investigated. A 10-4 M dispersion of 7 nm diameter
Ag colloids in an organic solute yields free radicals when exposed to UV light. Each radical transfers an electron
to a colloidal particle which can store a large number of electrons. Under static conditions, a number of
electrons can reside on a particle producing a negative potential high enough for hydrogen evolution.

2(CH3)2COH  +  AgnX-® 2(CH3)2CO  +  2H+  +  Agn(X+2)-
Agn(X+2)-  +  2H+ ® AgnX-   + H      (n = agglomeration number)

2(CH3)2COH ®  2(CH3)2CO  +  H2

Quantum size effects in semiconductors nanoparticles are probably of the most interest. The synthesis of
semiconductor nanoparticles started in the 1980’s, with the aim of splitting water, reducing it to hydrogen by
photo-induced electrons and oxidising it to oxygen by photo-induced holes but was unsuccessful.

General route to Nanoparticles - Schematic

ã M. Lazell and Paul O'Brien

Ph.D Research

I studied at Queen Mary and Westfield College, Dept. of Chemistry, with Dr. Alice C. Sullivan.  The thesis was entitled

Metallasiloxanes; synthesis, characterisation and their applications.


Various molecular metallasiloxane compounds containing the M-O-Si unit have been reviewed.  These compounds have been
prepared using suitable metal reagents and the dilithium disiloxanediolate or the dilithium silanediolate.  The catalytic activity
for ring-opening polymerisation of cyclic siloxanes and their potential use as novel single source precursors for lithium metal
oxides is investigated.

Chapter 1 describes the metallasiloxane compounds derived from dilithium silanediolate and various metal chlorides.  The X-ray
crystal structures of the compounds [Cr(OSiPh2OSiPh2O)2]-m-[Li(py)2]2 and [Co((OSiPh2)2O)((OSiPh2)3O)]-m- [Li(py)2]2 are
presented.  In addition the results of attempts to elucidate the factors which might affect the formation of ring expanded products
are discussed.

Chapter 2 describes the literature dealing with anionic polymerisation of cyclic siloxanes.  The synthesis and structural
characterisation of [{O(Ph2SiONa)2}4].NaOH.H2O.8pyridine.(toluene) and [K{O(Ph2SiO)2SiPh2OH}]2 is described.  The inactivity
of the potassium compound towards ring-opening polymerisation of cyclic siloxanes is discussed in the context of currently accepted mechanistic features of this process.

Chapter 3 describes the use of lithium bridged metallasiloxanes, for example ‘[LiM{O(SiPh2O)2}3].4LiCl.4THF’, M = Nb or Ta,
as novel single source precursors for lithium metal oxides.  The thermal decomposition of these precursors was performed under
vacuum and in air and the results showed that atmosphere is important in determining the purity of the lithium metal oxide.  Also
the solvent which the compound is prepared in is important as this changes the purity of the oxides produced;  the presence of
pyridine has an adverse effect.  The deposition of these oxides onto silicon wafers is carried out with very promising results for
LiMO3, M = Nb or Ta.

One of the crystals structures in my thesis


Presentations and Posters

A copy of my most recent Curriculum Vitae


I have a Suzuki GSXR-750 which is my third bike.  My previous bikes were an Aprilia RS125 and a Honda RVF 400R, see some piccy's below.

I have the gold/silver/black one above (not me riding it).

  Some Interesting Links

Garbage Homepage
Prodigy Homepage
James D. Mathew's NC35 Homepage
Star Trek Homepage
Star Wars Homepage
Dr. WHO Homepage
South Park Homepage


  Some Chemistry Links

Lancaster chemicals
British Library
RSC Homepage
New Scientist
Science jobs

  Some Computer Links

Watford Electronics
Simply Computers
Hewlett Packard

Audio Links

Garbage: Push It
Prodigy: Breathe, Firestarter

  Sports Links

Cricket (Lords)
Tennis (Wimbledon)

E-mail me at m.r.lazell@ic.ac.uk

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This page last updated on 24/03/99