| Abstract
| - We present here a synthetic method for fabricating hollow magnetic mesoporous nanocomposites (diameter∼ 400 nm) made up of ferrite nanoparticles incorporated to the mesoporous shell (shell thickness ∼ 50 nm)of carbon capsules. This methodology has been applied to the insertion of different ferrites such as iron oxidespinel (Fe3O4/γ-Fe2O3), CoFe2O4, NiFe2O4, and MnFe2O4. The size of these inorganic nanoparticles (∼9−17nm) can be modulated easily by varying the temperature of synthesis, as demonstrated in the case of the ironoxide spinel phase. An important characteristic of these nanocomposites is that, in spite of the large amountsof inorganic nanoparticles deposited (30 or 50 wt %), they retain a large porosity made up of mesopores(∼2−4 nm). Moreover, the inner core of these nanocomposites remains completely empty because the ferritenanoparticles are deposited exclusively on the porous carbon layer. We have demonstrated the usefulness ofthis kind of nanocomposites for the immobilization of an enzyme (lysozyme). The results obtained suggestthat the enzyme is stored mainly in the hollow core of the magnetic capsules. Moreover, we have proved thatthe nanocomposite loaded with the enzyme can be manipulated easily by means of an external magneticfield.
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