The design and synthesis of functional nanocomposites are very important since these materials have been widely used in different fields such as catalytic chemical reaction, the fabrication of chemical sensors or biosensor as well as the design of the nanodrug delivery systems. Herein, a new method for preparing the Chitosan/Fe 3 O 4 /SiO 2 magnetic nanocomposites by the reverse microemulsion route was developed. The magnetic fluid, which was consisted of the chitosan and Fe 3 O 4

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... was firstly prepared based on the strong supra-molecules interaction between chitosan and Fe 3 O 4 nanoparticles. Then, due to the better and stronger affinity of the silica to chitosan, the chitosan modified magnetic fluids was successfully doped into the silica nanoparticles while the silica nanoparticles was being formed in the reverse microemulsion system. In this case, the magnetic chitosan/Fe 3 O 4 /SiO 2 nanocomposites was successfully synthesized. Thereafter, the magnetic nanocomposites were characterized by transmission electron microscopy (TEM), magnetization curve, SEM energy spectrum, X-ray diffraction (XRD) and zeta potential of the nanoparticles surface techniques, respectively. Our results showed that the as-prepared Chitosan/Fe 3 O 4 /SiO 2 magnetic nanocomposites were spherical shape with core-shell structure apparently and their size is about 60 nm. More importantly, it was also found that there were lots of nanochannels inside the as-prepared Chitosan/Fe 3 O 4 /SiO 2 magnetic nanocomposites due to the porous hydrogel structural property of the chitosan. At the same time, the nanochannel behavior of the nanocomposites was further investigated by using the Luminol-H 2 O 2 chemiluminescence reaction based on the catalytic effect of magnetic Fe 3 O 4 particles towards the chemiluminescence reaction. The chemiluminescence investigating results showed that the 60 nm Chitosan/Fe 3 O 4 /SiO 2 magnetic nanocomposites offered a lot of nanochannels, which allowed both the luminol and H 2 O 2 to be diffused into the inner part of the nanocomposites to react with Fe 3 O 4 particles in the core part of the nanocomposites and produce the catalytic chemiluminescence signals. This behavior of the as-prepared magnetic nanocomposites may pave way to design the chemiluminescence-based sensor or biosensor.