The Construction And Nonlinear Optical Properties Of Porphyrin Covalently Linked Carbon Nanotube/graphene Ensembles

Carbon nanoallotropes from 0D to 1D and 2D,examples of which include C60,singleand multiple-walled carbon nanotubes(SWCNTs/ MWCNTs),and graphene,respectively,have been intensively investigated within both the scientific and the industrial communities during the past two decades.The hexagonal lattice of sp2 carbon atoms bestows excellent electrical,mechanical,thermal and optical properties on both SWCNTs and graphene,making them favored candidates for applications in electronic/optical devices,catalysis,and nanomedicine,and as nanoreactors.Surface functionalization of SWCNTs or graphene have been proposed,which might introduce enhanced or novel properties,thereby leading to new applications for certain functional entities.Photo-and redox-active organic dye-porphyrin covalently functionalized SWCNTs/graphene composites can combine the excellent merits of each of them and also can strongly disturb the high aggregating tendency of SWCNTs or graphene.This paper were carried out with the following two parts focusing on the porphyrin covalently linked nonlinear optical(NLO)nanomaterials.In section two,we have designed and synthesized three novel porphyrin/SWCNTs composites(SWCNT–Pr),and studied the substituent effect on their NLO performance.The structural difference of the composites is only lying in the substituent groups attached at the opposite extremity of tert-butyl substituted 5,10,15,20-tetraphenylporphyrins(TPPs)to the SWCNTs.The three selected substituent groups are neutral phenyl,electron-acceptor 4-cyanophenyl and electron-donor 4-N,N-dimethylaminophenyl respectively.Thorough characterization was carried out by ultraviolet-visible(UV–vis)absorption,steady-state fluorescence,Fourier transform infrared,and Raman spectroscopies,field emission scanning electron microscopy(SEM),transmission electron microscopy,and thermogravimetric analysis(TGA),which collectively unambiguously confirmed that the chosen porphyrins were successfully attached to the surface of the SWCNTs by a 1,2,3-triazole-containing π-conjugated covalent bridge rather than by non-covalent means.Nonlinear transmittance tests by the open-aperture Z-scan technique(532 nm,4 ns duration)revealed that both electron-withdrawing 4-cyano(CN)and electron-donating N,N-dimethylamino(DMA)substituents have positive effects in further optimizing the OL performance of the SWCNT–Pr composites,owing to the increased RSA ability of the porphyrin moieties after attaching CN or DMA.In comparison with CN,the DMA group has a more positive influence on the porphyrins’ excited states and thus effectively further enhanced the RSA process and the final NLO performance of the SWCNT–Pr composites.This may provide a useful guide to the design of better NLO materials for device applications in optoelectronics and photonics.In section three,we designed and prepared two novel reduced graphene oxide composites(RGO-TPP1,RGO-TPP2)which were covalently fused with [2,3-bis-amino-5,10,15,20-tetraphenylporphyrinato]Copper(II)(TPP1)and [2,3-bis-amino-5,10,15,20-tetraphenylporphyrinato]Nickel(II)(TPP2)respectively on their edges through new formed pyrazine links,and tested their NLO properties at 800 nm femtosecond laser.In addition,an ordinary graphene composite(RGO-TPP3)which was covalently functionalized with [3-amino-5,10,15,20-tetraphenylporphyrinato]Copper(II)(TPP3)via acylated reaction was prepared as reference.Thorough characterization was carried out by UV–vis and fluorescence,attenuated total reflection infrared and Raman spectroscopies,X-ray powder diffraction,SEM,atomic force microscope and TGA,which collectively unambiguously confirmed that the metal(Cu,Ni)coordination TPPs were successfully fused to the edges of the graphene of RGO-TPP1 and RGO-TPP2 by a pyrazine-containing π-conjugated covalent bridge.Ultrafast nonlinear transmittance tests by the open-aperture Z-scan technique(800 nm,70 fs duration)revealed that all of the three composites have RSA properties,owing to the brilliant two-photon absorption abilities of the TPP moieties and their efficient energy or electron transfer between them.In comparison with RGO-TPP3,the RGO-TPP1 and RGO-TPP2 have a more ultrafastly brilliant RSA performance,RGO-TPP2 the best,further enhanced OL performance of the graphene composites.The two surprisingly novel graphene composites,RGO-TPP1 and RGO-TPP2,not only have potential applications in ultrafast OL device,but also make themselves favored candidates for catalysis,nanomedicine,et al.