School of Chemistry

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Fiona Meldrum

Professor of Inorganic Chemistry
Member of the Crystallisation and Directed Assembly group

Contact details

Room: 1.04c
Tel: +44 (0)113 3436414
Email: F.Meldrum@leeds.ac.uk

Keywords

Materials Chemistry
Crystallization
Biomineralization
Biomimetic Crystal growth
Calcium Carbonate
Self-Assembly
Templating

Photograph of Fiona Meldrum

Research interests

My research interests fall under the general category of materials chemistry, and are particularly focused on crystal growth. In this context, my group is examining routes to produce inorganic and organic crystals with defined properties including polymorph, size, morphology, organisation and mechanical properties. Within this topic there is considerable emphasis on biological crystallisation processes, and natural systems such as seashells, bones and teeth are used as an inspiration for the development of novel crystal growth strategies. These experiments also enable us to better understand natural crystal growth phenomena. A broad range of projects are carried out, employing analytical techniques including scanning and transmission electron microscopy, Raman microscopy and X-ray diffraction. A number of current projects are described below.

Controlling Crystal Morphologies
Biological crystals frequently display some amazing morphologies, such as the skeletal elements of the sea urchins which display amazing, sponge-like microstructures. These morphologies are all the more amazing when it is considered that they are also single crystals of CaCO3, the synthetic equivalent of which is a regular rhombohedron. We are attempting to understand how biology controls mineral morphologies, with the aim of applying these routes to synthetic crystal growth. A range of methods have been investigated including (i) use of additives such as block copolymers (ii) precipitation within a mould and (iii) precipitation via an amorphous precursor phase. Excellent control over crystal morphologies has been achieved, leading for example to single crystals with identical structures to sea urchin skeletal elements.

Crystals with Composite Structures
A range of strategies are being investigated to generate crystals with composite structures. Crystals of CaCO3 containing ~ 25 vol % of polystyrene particles have been prepared by growing the crystals in a one-step method in the presence of the particles and specific additives. This approach is being extended to investigate its application to a range of crystals and particles. A wide range of materials such as pigments, drugs and oils are being incorporated within CaCO3 crystals for industrial applications. These composite particles are also expected to have interesting mechanical properties.

Mechanical Properties of Biomimetic Materials
Many biominerals, despite being formed from simple minerals such as calcium carbonate and calcium phosphate, exhibit superior mechanical properties to rival many engineering materials. This behaviour is generally considered to derive from organic macromolecules occluded within the crystals, giving them a composite character, and unique structural organisation. We are currently undertaking a range of experiments to generate biomimetic inorganic/organic hybrid materials, and are investigating structure/functional relationships using techniques such as nanoindentation.

Crystallisation in Confined Volumes
How does the environment a crystal grows in affect its structure and properties? While virtually all synthetic crystallisation experiments are conducted in bulk solution, many natural phenomena such as biological crystal growth and weathering occur within small pores. We are using model porous systems to study this phenomenon and are precipitating inorganic and organic crystals within porous media such as controlled-pore glasses to investigate how the pore size and surface chemistry affect factors such as crystal polymorph and orientation.

Useful links

Further details about my research   
Leeds Centre for Crystallization   
   

Selected publications

Hetherington N.B.J, Kulak A.N., Kim Y.Y., Noel E. H., Snoswell D., Butler M. and Meldrum F. C. (2011) Adv. Func. Mater. “Porous Single Crystals of Calcite from Colloidal Crystal Templates: ACC is Not Required for Nanoscale Templating”, DOI: 10.1002/adfm.201001366.

Stephens C.J., Ladden S.F., Meldrum F.C., Christenson H.K. (2010) Adv. Func. Mater. “Amorphous Calcium Carbonate is Stabilised in Confinement” 20, 2108-2115.

Kim, Y. Y., Ribeiro L., Maillot F., Ward O., Eichhorn, S. J., Meldrum F. C. (2010), Adv. Mater. “Bio-Inspired Synthesis and Mechanical Properties of Calcite–Polymer Particle Composites” 22, 4082-4086.

Meldrum F.C. and Cölfen H. (2008) Chem. Revs “Controlling Mineral Morphologies and Structures in Biological and Synthetic Systems” 108, 4332-4432.