Weina Song

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.

The effect of peripheral substituents attached to phthalocyanines on the third order nonlinear optical properties of graphene oxide–zinc( ii )phthalocyanine hybrids

Two kinds of graphene oxide–zinc phthalocyanine (GO–ZnPc) hybrid materials have been prepared by the covalent functionalization method. The morphologies and structures of the two kinds of GO–ZnPc hybrids are characterized by a series of methods, such as scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, ultraviolet-visible absorption and fluorescence spectroscopies. From the fluorescence spectra, the two kinds of GO–ZnPc hybrids display strong fluorescence quenching by the photo-induced electron transfer (PET) process from ZnPc moieties to the GO. Energy diagrams show that a PET process from ZnPc molecules to GO nanosheets exists. The third order nonlinear optical (NLO) properties of GO–ZnPc hybrids are investigated by the Z-scan technique at 532 nm with 4 ns laser pulses. The nonlinear absorption coefficient β value of GO–ZnPc(DG)4 is larger than that of GO–ZnPc(TD)4 because GO–ZnPc(DG)4 possesses peripheral substituents with a stronger electron-donating effect compared to GO–ZnPc(TD)4.

Third-order nonlinear optical properties of self-assembled thin films containing tetracarboxylic copper phthalocyanine

Films with alternating layers containing anionic tetracarboxylic copper phthalocyanine [CuPc(COONa)4] and cationic polydiallydimethylammonium chloride (PDDA) were fabricated by electrostatic self-assembled layer-by-layer (LBL) technique. The delicate structure of the film was characterized by a series of techniques. The third-order nonlinear optical properties of the film were measured by the Z-scan technique with laser duration of 4 ns and 21 ps at the wavelength of 532 nm. The film exhibited excellent nonlinear absorption and self-focusing effect. The second-order molecular hyperpolarizability γ value of the film was much larger than that of CuPc(COONa)4 aqueous solution under the irradiation of whether ns or ps pulses. A series of damage experiments of the film for the intense laser pulses were conducted to prove the reliability of the experimental results under the conditions.

Enhanced reverse saturable absorption of electrostatic self-assembled layer by layer films containing (8-quinolineoxy-5-sulfonic acid)phthalocyanine cobalt and graphene oxide

Multilayer films containing α-CoPc(QnSO3Na)4 (CoPc), polydiallydimethyldiallylammonium chloride (PDDA) and graphene oxide (GO) were fabricated through electrostatic self-assembled layer by layer (LBL) technique. UV-Vis spectroscopy was used to characterize the assembly process. Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were utilized to explore the microstructure of the film. The third-order nonlinear properties of the film were studied by Z-scan measurements at 532 nm with 4 ns pulses. When excited by laser with the input intensity of 1.16 μJ, the 25 bilayer CoPc/GO film exhibits strong reverse saturable absorption (RSA) effect. The nonlinear absorption coefficient β value is 1.6 × 10−5 m W−1, which is 5 and 3 orders larger than that of CoPc solution sample and grapheme oxide solution sample, and 1.5 times larger than that of the 35 bilayer CoPc/PDDA film. And also, combination of UV-Vis spectroscopy with Raman spectroscopy was adopted to analyze the enhancement mechanism of nonlinear optical absorption of the film.

The role of sp2/sp3 hybrid carbon regulation in the nonlinear optical properties of graphene oxide materials

Rational regulation of localized sp2/sp3 hybrid carbon structure in graphene oxide systems plays a very important role in developing advanced carbon-based hybrid materials. Here, we report a simple ethanol solvothermal method toward precise control of the growth of the sp2 hybrid carbon configurations/clusters in the sp3 carbon matrix so as to regulate the structure of electronic energy bands in the graphene oxide system. The results of morphology observation, XPS, solid-state 13C MAS NMR, FT-IR and Raman spectroscopy proved that controllable generation of the sp2 hybrid carbon configurations/clusters can be achieved based on an executive oxidation/reduction strategy. Upon excitation by a 532 nm laser with 4 ns pulses, the obtained reduced graphene oxide (160-rGO-6) with a large number of sp2 hybrid carbon configurations displays greater nonlinear reverse saturable absorption response and a higher nonlinear absorption coefficient β of 560 cm GW−1 than graphene oxide with different oxidation degree (GO-X, X = 6, 8, 10 and 12), and reduced graphene oxide with relatively few sp2 hybrid carbon configuration ratios (Y-rGO-6, Y = 80, 100, 120, 140 and 180). The significantly enhanced nonlinear reverse saturable absorption of 160-rGO-6 is attributed to the two photon absorption and excited state absorption originating from the sp2 hybrid carbon configuration system.