Page 6 - Periodic Issue 02

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In situ X-ray diffraction is an important technique for providing insight
into the chemical reactions of solids. Dr Saul Moorhouse, a recent DPhil
graduate from Professor O’Hare’s group in the Inorganic Chemistry

Laboratory, tells us about a unique piece of equipment he has constructed
to facilitate the study of reactions of inorganic solids using X-ray
diffraction.

Improving our understanding of
the kinetics and mechanisms of
solid-state reactions is becoming
increasingly important as we strive
to ‘design’ new materials with
interesting and useful properties.
Probing reactions as they occur
– or “in situ” – has, for a long
time, been crucial in developing
our appreciation of chemical
processes allowing us to tune the
syntheses of academically and
industrially relevant compounds as
well as assisting in the discovery
of new ones.

The technique of X-ray diffraction Schematic of the ODISC furnace alongside a photograph of the internal furnace set-up. [citation: Rev.
is used to obtain important Sci. Instrum. 83, 084101 (2012)]
information about the structure of interaction of a high-energy synchrotron X-ray beam with
solids. X-rays become “diffracted” by atoms in crystalline crystalline materials undergoing various reactions. By
materials in a way that is characteristic of their individual passing an X-ray beam through samples as they form or
structures. Collecting and processing information react, the interaction of starting materials, the presence
from diffracted X-rays provides us with information about of any important intermediate phases, and the kinetics of
the arrangement of atoms in the structure of the solids product formation can all be accurately probed.
being studied.
A LAYERED FAMILY
DIAMOND DISCOVERIES A particular area of chemistry that I recently spent
My DPhil was partly funded by Diamond Light Source, time working on involves a family of materials called
the UK’s national synchrotron, which is located a short “layered double hydroxides”. These inorganic solids
distance south of Oxford. At synchrotron facilities like have a structure comprising positively charged layers,
Diamond, electrons are accelerated around a ring (often with negatively charged anions residing between the
several hundred metres in circumference) to release layers. Because of the wide variety of industrially relevant
energy in the form of radiation, which is harnessed by anions that can be substituted between the layers,
beamlines positioned around the ring. I undertook my these compounds have a vast range of applications
work at Diamond on the recently commissioned Beamline in the modern day – anything from drug delivery to
I12, also called the Joint Engineering Environment and controlled release of herbicides, from selective uptake
Processing beamline (JEEP). The high energy X-rays of waste anions in water to use as surface catalysts in
harnessed by this beamline have the ideal properties for polymerisation reactions.
penetrating the large sample volumes and thick-walled
sample containers that I used for my reactions. One particular advantage of these materials from my
perspective is that during a reaction, as the anion between
The aim of my DPhil was to study how a variety of solid- the layers is exchanged for one of a different size and
state chemical processes proceed by monitoring the

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Periodic The Magazine of the Department of Chemistry