PTM radicals are often highly coloured and exhibit fluorescence in the red region of the visible spectrum, colour and fluorescence always have the potential to be exploited in optical electronics devices. Just as importantly, PTM radicals are also electroactive. This means they can be easily and reversibly reduced (or oxidized) to their positively or negatively charged (cationic or anionic) species. The different oxidised and reduced forms of PTM are different colours but neither oxidized nor reduced form is magnetic or fluorescent.
Mas-Torrent explained the relevance of this clutch of changeable properties for her self-assembled monolayers (SAMs). "The preparation of SAMs functionalised with PTM radicals on substrates results in multifunctional surfaces which are electrochemically, optically and magnetically active," she said, "We have demonstrated that these SAMs can be used as chemical and electrochemical redox switches with optical and magnetic responses."
Mas-Torrent and her colleagues did not stop with standalone SAMs. They have now added long hydrocarbon side-chains to their PTMs and found that these can also self-assemble on a graphite surface. They then studied behaviour at the interface between the graphite surface and a liquid and found that the self-assembly process is hierarchical and can give rise to complex three-dimensional ordered nanostructures that form double rows composed by a magnetic core of radicals surrounded by the side-chains.
By modifying a surface with molecules that can switch between two states - bistable compounds - the team hopes to open up the possibility of using these systems in memory devices. Surfaces functional
|Contact: Dr. Angela Michiko Hama|
European Science Foundation