Facile organic solvent-free synthesis of size-controlled hierarchically structured magnetic hollow spheres and potential application in adsorption for bovine serum album

► Organic solvent-free synthesis of size-controlled magnetic hollow spheres(MHS). ► Polystyrene template curvature - effect on the morphology of MHS. ► MHS sphere wall is composed of primary nanoparticles with varied morphologies and stacking modes. ► MHS with nanorodlike primary particles vertically stacked wall shows the maximum BSA adsorption.