Professor Fiona Meldrum

Profile

Fiona Meldrum holds a chair in Inorganic Chemistry at the University of Leeds, where her research centres on bio-inspired materials chemistry, and in particular on inorganic crystallisation. She obtained her undergraduate degree in Natural Sciences from the University of Cambridge in 1989, and her doctorate in mineralisation in biological and bio-inspired systems from the University of Bath in 1992. Following a postdoctoral position at the University of Syracuse, USA in which she studied nanoparticle assembly, she was then awarded a Humboldt Research Fellowship to investigate organic matrix directed crystallisation using surface plasmon spectroscopy at the Max Planck Institute for Polymer Research, Mainz. Fiona then joined the Australian National University in Canberra where she developed a renewed interest in biomineralisation processes, before finally returning to the UK to take up a lectureship at Queen Mary, University of London in 1998. In 2003, Fiona moved to the University of Bristol where she remained until she joined the University of Leeds in 2009.

Fiona and her group are fascinated by crystallisation processes, and use a wide range of techniques including imaging-based methods, spectroscopy and microfluidics to better understand the mechanisms that govern crystal nucleation and growth from solution. They also have significant interests in controlling the structures and properties of crystals, and have taken inspiration from biomineralisation processes to develop new strategies for generating single crystals with complex morphologies and mechanical properties to rival those of their biogenic counterparts. Current interests include polymorph control, the formation of crystals with composite structures, using microfluidic systems to study crystallisation processes, and the use of physical environments – namely confinement and surface topography – to control crystallisation. We have also recently started a new project on “MoSS: Molecular Solid Solutions: From Concept to Applications” in whcih we are creating solid solutions of small organic molecules in order to create crystals with tunable properties.

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.

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.

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.

Studying Crystallisation Using Microfluidic Systems

Crystallisation processes are typically studied in bulk solution where they can be affected by impurities, the inhomogeneities that occur in solutions during mixing, the vessel surface and convection effects. It can therefore be difficult to achieve reproducible results, or to study rapid reactions. With their ability to create both static arrays of droplets, continuously flowing droplets, and defined reaction chambers, microfluidic devices provide an attractive solution to this problem. We are using microfluidic systems to study and control crystallisation processes. Droplet-based systems are being used to study crystallisation mechanisms, where the ability to inject solution into flowing droplets allows us to perform multi-step reactions. These devices can also be used for in situ analysis, including synchrotron powder X-ray diffraction.

Molecular Organic Solid Solutions (MoSS)

The doping of crystals with impurities is well-established as a powerful method for enhancing the properties of inorganic, metallic and semiconductor materials. This is termed the creation of a solid solution. However, little is known about the doping of crystals of small organic molecules (molecular solid solutions, MoSS). Existig data on MoSS suggest that this stratgey has enormous potential for controlling the structures and properties of the product crystals. The introduction of dopant molecules can potentially change the polymorph of the product crystals and stabilise different polymorphs, produce different morphologies and sizes and change the rate of formation and growth of crystals. Importantly, it can als change properyies such as solubility and resistance to fracture, which are critical to many appications.

We are part of an EPSRC Programme gant, led by Prof Aurora Cruz-Cabeza at Durham University, in which we combine crystal engineering, high throughout crystallisation, atomic-scale characterisation and modelling of crystal structure and growth, data handling and AI methods to understand the design rules underlying the foration of MoSS and their structure-property relationships. This will ultimately allow us to use this strategy to tune the structures and properties of mol;ecular crystals in a predicatble way.

Biomorphs

Soluble additives are widely used to control crystal morphologies. Typically, additives interact with specific crystal faces, leading to the formation of crystals whose morphologies reflect the underlying symmetry of the crystal lattice. Sometime, however, additives can generate crystalline materials with complex morphologies and curved surfaces, whose forms resemble those of biological structures such as bacteria. These have been termed “biomorphs”. While it is well known that simple polyelectrolytes can generate biomorphs from sparingly-soluble compounds such as calcium carbonate and barium sulfate, the mechanisms underlying these processes is currently not known. We are investigating the formation of biomorphs using a wide range of analytical techniques, and have identified a new underlying mechanism.

Primary investigator (PI)

• Crystallisation in the Real World: Delivering Control through Theory and Experiment
• DYNAMIN: Dynamic Control of Mineralisation
• Flow-Xl: A New UK Facility for Analysis of Crystallisation in Flow Systems
• New strategies for controlling crystallisation

Qualifications

• MA (Cantab)
• PhD

Professional memberships

• Royal Society of Chemistry
• Materials Research Society

Research groups and institutes

• Crystallisation and Directed Assembly

Current postgraduate researchers

• Thomas Dunn