We attach mixed films of TiO 2 and Fe 2 O 3 to SiO 2 microparticles by simply adjusting the ratio of TiO 2 and Fe 2 O 3 nanoparticles initially added during the bulk heteroaggregation step. Incorporating magnetic functionality into micro-and nanoscale devices and catalysts is desirable due to the ease of their recovery after use. We thus incorporate a small quantity of Fe 2 O 3 nanoparticles (9:1 TiO 2 :Fe 2 O 3 added), and find both species present on the SiO 2 support (see Figure , EDS mapping).