Magnetically activated adhesives: towards on-demand magnetic triggering of selected polymerisation reactions.

On-demand initiation of chemical reactions is becoming increasingly popular in many areas. The use of a magnetic field to trigger reactions is an intriguing concept, with vast potential in both research and industrial settings, though it remains a challenge as yet unsolved. Here we report the first example of on-demand magnetic activation of a polymerisation process using an anaerobic adhesive formulation as an example of this new approach toward triggering polymerisation reactions using an external magnetic field.

The immobilisation of chiral organocatalysts on magnetic nanoparticles: the support particle cannot always be considered inert.

A systematic study concerning the immobilisation onto magnetic nanoparticles of three useful classes of chiral organocatalyst which rely on a confluence of weak, easily perturbed van der Waals and hydrogen bonding interactions to promote enantioselective reactions has been undertaken for the first time. The catalysts were evaluated in three different synthetically useful reaction classes: the kinetic resolution of sec-alcohols, the conjugate addition of dimethyl malonate to a nitroolefin and the desymmetrisation of meso anhydrides. A chiral bifunctional 4-N,N-dialkylaminopyridine derivative could be readily immobilised; the resulting heterogeneous catalyst is highly active and is capable of promoting the kinetic resolution of sec-alcohols with synthetically useful selectivity under process-scale friendly conditions and has been demonstrated to be reusable in a minimum of 32 consecutive cycles.

NMR studies into colloidal stability and magnetic order in fatty acid stabilised aqueous magnetic fluids.

We report the physico-chemical characterisation of fatty acid stabilised aqueous magnetic fluids, which are ideal systems for studying the influence of nanoparticle aggregation on the emergent magnetic resonance properties of the suspensions. Stable colloids of superparamagnetic magnetite, Fe(3)O(4), nanoparticle clusters in the 80 to 100 nm size range were produced by in situ nanoparticle growth and stabilisation, and by suspending pre-formed nanoparticles. NMR relaxation analysis shows that the magnetic resonance properties of the two types of suspension differ substantially and provides new insights into how the relaxation mechanisms are determined by the organisation of the nanoparticles within the clusters.

Biomimetic synthesis of hierarchically porous nanostructured metal oxide microparticles--potential scaffolds for drug delivery and catalysis.

Hierarchically porous hybrid microparticles, strikingly reminiscent in their structure of the silica skeletons of single-cell algae, diatoms, but composed of titanium dioxide, and the chemically bound amphiphilic amino acids or small proteins can be prepared by a simple one-step biomimetic procedure, using hydrolysis of titanium alkoxides modified by these ligands. The growth of the hierarchical structure results from the conditions mimicking the growth of skeletons in real diatoms--the self-assembly of hydrolysis-generated titanium dioxide nanoparticles, templated by the microemulsion, originating from mixing the hydrocarbon solvent and water on action of amino acids as surfactants. The obtained microsize nanoparticle aggregates possess remarkable chemical and thermal stability and are promising substrates for applications in drug delivery and catalysis.

Precursor and solvent effects in the nonhydrolytic synthesis of complex oxide nanoparticles for bioimaging applications by the ether elimination (Bradley) reaction.

Investigation of the solvent and alkoxide precursor effect on the nonhydrolytic sol-gel synthesis of oxide nanoparticles by means of an ether elimination (Bradley) reaction indicates that the best crystallinity of the resulting oxide particles is achieved on application of aprotic ketone solvents, such as acetophenone, and of smallest possible alkoxide groups. The size of the produced primary particles is always about 5 nm caused by intrinsic mechanisms of their formation. The produced particles, possessing the composition of natural highly insoluble minerals, are biocompatible.

The first magnetic nanoparticle-supported chiral DMAP analogue: highly enantioselective acylation and excellent recyclability.

Recyclable organocatalysts: The first chiral DMAP analogue immobilized on magnetic nanoparticles is a highly active catalyst that is capable of the acylation of racemic sec-alcohols under convenient, process-scale friendly conditions (room temperature, 5 mol % loading, with acetic anhydride as the acylating agent) with excellent enantiodiscrimination. The catalyst is easily recovered and possesses unprecedented recyclability-in this study it was demonstrated to retain excellent activity and selectivity over 32 iterative cycles.

Linear assemblies of magnetic nanoparticles as MRI contrast agents.

Using a one-step procedure we have prepared magnetic fluids comprising of polyelectrolyte stabilized magnetite nanoparticles. These nanocomposites are comprised of linear, chain-like assemblies of magnetic nanoparticles, which can be aligned in parallel arrays by an external magnetic field. We have shown the potential use of these materials as contrast agents by measuring their MR response in live rats.