Spintronics is receiving considerable attention due to its promise of new technological advancements. Spintronic devices are made with ferromagentic materials, use the electron spin to carry information, and are used in modern computers, and are anticipated to play a leading role the future of computer deisgn.

 

Commonly used ferromagnetic materials (Fe, Co, Ni and alloys thereof) have spin polarizations of 45-55%, far from the ideal 100%. Heusler compounds have a composition M₂M´Z, (M,M´ are typically 3d transition metals, and Z is a main group element). Many Co₂M´Z Heuslers are predicted to have 100% SP at the Fermi level. Such materials, said to be half-metallic, are ideal candidates for spintronic devices, and are actively widely studied as bulk and thin film materials.

 

Our goals are to synthesise and characterize Co₂M'Z (M´=Cr,Mn,Fe;Z=Al,Si,Ge) nanostructures. Short term goals are: i) the preparation of ternary Co₂M'Zand quaternary [Co₂M'xM''1xZ and Co₂M'ZxZ'1-x] nanoparticles, ii) preparation of Co₂M'Z nanowires. Long term goals are to integrate these materials in spintronic devices, specifically granular magnetoresistance devices and racetrack memory. As Co₂M'Z free-standing nanostructures are virtually unstudied, this work will make a strong impact in this emerging field. An important accomplishment of this work will be establishing whether the high SP character is present in Co₂M’Z nanostructures, as well as facilitate the study of their magnetic and electronic properties in the vicinity of surfaces. This knowledge is a prerequisite for the preparation of devices based on these materials.

There is currently a great interest in producing nanoparticles that are (1) biocompatible, (2) magnetic, and (3) photoluminescent. Such nanoparticles can be used in a variety of in-vivo clinical tasks as magnetic resonance imaging (MRI) contrast agents, labelling, and drug delivery agents. However, given there is no single material that simultaneously possess these three desired properties, composite nanostructures such as core-shell nanoparticles are currently being studied as candidate materials.

Our goal is to design new nanostructures exhibiting magnetism and luminescence, where the latter property is imparted through the use of lanthanide ions.A particular emphasis will be put on the synthesis of water-soluble nanoparticles, that can be used in both in-vitro and in-vivo applications.

 

In addition to the synthesis of doped metal oxide nanocrystals, students will extensively use electron microscopy, SQUID magnetometry, UV-vis absorption spectroscopy, photoluminescence, and x-ray absorption spectroscopy (XANES, EXAFS, and XMCD) to probe the electronic properties of these materials. Methods such as magnetic resonance imaging (MRI) will be used to assess the capabilities of the new materials for clinical use.

It has recently been found that ferromagnetism can be activated in thin films and nanocrystals of the coinage metals (Au, Ag, Cu), which are non-magnetic in the bulk. This ferromagnetism was thought to only occur when strong charge-transfer occurs at the metal/molecule interface in capped nanocrystals, for example when capped with an alkane thiol.

 

The goals of this project are to:

 

• Identify the threshold chemical modification that leads to the onset of ferromagnetism.

• Understand the effect various capping ligands have on: the magnetic moment carried by surface gold

atoms, the charge transfer occurring, and the magnetic anisotropy at the surface

• In the case of nanocrystals, study the magnetic properties as function of size.

• Besides coinage metals, this behaviour has been observed in Pd and Pt nanocrystals.

Work will aim to verify whether this magnetism can be generally instilled in any nanocrystalline metals. This

would radically change the magnetic periodic table.

 

We are also exploring how magnetism can be imparted to naked nanoparticles and thin films.

 

In addition to the synthesis of metallic nanocrystals, students will extensively use electron microscopy, SQUID magnetometry, UV-vis absorption spectroscopy, and x-ray absorption spectroscopy (XANES, EXAFS, and XMCD) to probe the electronic properties of these materials.

To meet the increasing energy demands, renewable energy sources (e.g. solar & wind) will become ever more important. However, these energy sources are intermittent; as such we need to find a way to store this energy when it is plentiful, to use it in periods of need. We look to nature to accomplish this. Plants use photosynthesis to store solar energy in the form of chemical bonds. Our approach is similar, whereas we aim to store reneweable energy in the chemical of hydrogen gas, using water as a feedstock. We are interested in designing new photoelecatalysts to help negotiate the multiple electron transfers and bond breaking/making steps in the splitting of water into hydrogen and oxygen gas.

 

Our research uses facile hydrothermal synthesis to form Earth-abundant water-splitting catalysts, in the form of MOx/graphene (G) nanocomposites, for the generation of solar fuels (H₂ and O₂). We demonstrated the formation of high surface-area nanocrystalline hematite (α-Fe₂O₃) electrodes (without G), and we are confident the same advantageous nanostructured architecture will be retained once graphene is included.

 

In addition to gaining experience in hydrothermal synthesis, students extensively use electron microscopy, SQUID UV-vis absorption spectroscopy, and x-ray photoelectron spectroscopy, and electrochemistry to probe the electronic, structural, and electrocatalytic properties of these materials.