3D network magnetophotonic crystals fabricated on Morpho butterfly wing templates
A simple synthesis method combining a sol-gel route followed by a reduction step is developed for the fabrication of magnetophotonic crystal (MPC) materials from Morpho butterfly wings. The sol-gel route leads to hematite with a photonic crystal structure (PC-α-Fe2O3) being faithfully replicated from a biotemplate, and the desired magnetophotonic crystal Fe3O4 (MPC-Fe3O4) is obtained by the reduction of the PC-α-Fe2O3 under a H2/Ar atmosphere. The structural replication fidelity of the process is demonstrated on both the macro- and microscale, and even down to the nanoscale, as evidenced by scanning electron microscopy, X-ray diffraction, reflectance measurements, and transmission electron microscopy. It is found that the chemical transformation of PC-α-Fe2O3 to MPC-Fe3O4 changes only the dielectric constant and does not induce structural defects that could affect the photonic-crystal properties of the composite. The photonic band gap of MPC-Fe3O4 can be red-shifted with an increase of the external magnetic field strength, which is further supported by theoretical calculations. The reported biomimetic technique provides an effective approach to produce magnetophotonic crystals from nature with 3D networks, which may open up an avenue for the creation of new magneto-optical devices and theoretical research in this field.