Preparation And Nonlinear Properties Of Long-chain Hydroxyphthalocyanine/graphene Oxide Composites

As the laser is widely used in various fields,the nonlinear optical materials have been investigated by researchers.Now,carbon-based materials such as graphene oxide are paid more attention on account of the exhibit excellent nonlinear optical(NLO)properties.But,the poor solubility of GO comes as the first obstacle for their optical applications.The formation of covalent bonds with soluble molecules to modify graphene materials in water or organic solvents become an advanced research emphasis.1,8,15,22-tetra-[2-(2-hydroxy)ethyloxy]phthalocyanine MPc(EG)4(M = Cu?Zn?Ni?In?Pb),1,8,15,22-tetra-[2-(2-hydroxy)ethyloxy] ethyloxy phthalocyanine Zinc ZnPc(DG)4,and 1,8,15,22-tetra-(5-hydroxypentyloxy)phthalocyanine Zinc ZnPc(TD)4were synthesized.These phthalocyanines were characterized by Uv-Vis,FT-IR and MOLDI-TOF mass spectra.The third-order nonlinear optical properties of phthalocyanines were investigated by Z-scan method.Then,the second-order hyperpolarizability ? value were calculated from Z-scan curves.The fluorescence lifetime and fluorescence quantum yield were obtained by fluorescence spectra.And the triplet lifetime and triplet quantum yield were acquired by transient absorption spectra.Based on these optical parameters,the crossing rate between the singlet state and the triplet state are obtained.The relations between the central metal or the peripheral substituents with the the nonliear optical properties of Pcs are discussed.ZnPc(DG)4and ZnPc(TD)4 were selected because they possess better nonlinear properties than other phthalocyanines.The phthalocyanines with the better nonlinear absorption were covalently bonded with graphene oxide.Two kinds of graphene oxide–Zinc phthalocyanine(GO–ZnPc)hybrid materials have been prepared with the formation of the ethter groups.The morphologies of hybrid materials are obtained with scanning electron microscope(SEM),and atomic force microscopy(AFM).The structure of hybrid materials are analyzed by Fourier transform infrared(FT-IR)spectra,X-ray photoelectron spectroscopy(XPS)and Raman spectra.The third optical properties of hybrid materials are studied with Z-scan.And the energy level of ZnPc/GO hybrid materials are calculated by the Ultraviolet-visible(UV-vis)spectra and the fluorescence spectra,indicating that the photo-induced charge transfer(PET)from ZnPc to GO exists.The relations between the photo-induced charge transfer(PET)and the nonlinear optical properties of ZnPc/GO hybrid materials can be investigated by comparing the electron-donating groups of ZnPc(DG)4/GO and ZnPc(TD)4/GO.The nonlinear optical coefficient ? value of ZnPc(DG)4/GO is larger than that of ZnPc(TD)4/GO because the peripheral substituents of ZnPc(DG)4 possess stronger electron-donating ability.The PET process from ZnPc to GO existed calculated by the ?GPET value.