Magnetic circular dichroism of opal crystals infiltrated with iron porphyrin
Synthetic opal crystals composed of silica spheres of diameter ~250 nm were infiltrated with highly concentrated (10 mM) buffered phosphate solution of iron porphyrin (FeTPPS). Magnetic circular dichroism (MCD) in the visible spectral range was investigated on hybrid samples immersed in polar (ethanol) or non-polar (hexane, toluene) solutions and situated in magnetic field. The MCD effect was observed in the spectral region of 550–650 nm in the vicinity of Q-absorption bands of FeTPPS. In 350 mT magnetic field the relative optical transmission change by 2.4⋅10–4 was determined at the Q0-band of 0.3 mm thick infiltrated opal sample. The dispersion-like lineshape of MCD spectra corresponded to the A-type term. An average refraction index and refraction index contrast of composite system was controlled by immersion of infiltrated opal samples into various liquids. As a result, the spectral position of the stop band in opal photonic crystal was tuned with respect to FeTPPS absorption bands. When the Q band of FeTPPS was within the stop band of opal, the optical contrast of photonic crystal was changed by external magnetic field due to the MCD effect.
Keywords: photonic band gap materials, infiltrated opal, magnetooptical effects
PACS: 42.70.Qs, 78.20.Ls