The effects of central metals on the photophysical and nonlinear optical properties of reduced graphene oxide–metal(ii) phthalocyanine hybrids

Reduced graphene oxide–metal(II) phthalocyanine (RGO–MPc, M = Cu, Zn and Pb) hybrid materials have been prepared by the covalent functionalization method. The resultant RGO–MPc hybrids are characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, ultraviolet-visible absorption and fluorescence spectroscopy. The RGO–MPc hybrids exhibit strong fluorescence quenching by means of the photo-induced electron transfer or the energy transfer (PET/ET) process between the RGO and MPc moieties. The PET/ET process particularly depends on the fluorescence quantum yield of MPc molecules with different central metals. The nonlinear optical (NLO) properties of the RGO–MPc hybrids are investigated by using the Z-scan technique at 532 nm with 4 ns laser pulses. The results show that the NLO properties of MPc molecules increase in the order of Zn < Pb < Cu, but the RGO–MPc hybrids exhibit NLO performance in the inverse sequence of Zn > Pb > Cu, implying that the NLO response arising from the efficient PET/ET process between RGO and MPc may play a more important role in the NLO properties of RGO–MPc hybrids than that originating from the MPc moiety.