Study on Optical Nonlinearities of Porphyrin Covalently Functionalized Single-Wall Carbon Nanotubes

We studied nonlinear absorption of three kinds of porphyrin covalently functionalized SWNTs using Z-scan technique with nanosecond pulses at 440 nm, 460 nm, 480 nm, 500 nm, and 532 nm. The large enhancement of nonlinear absorption in porphyrin covalently functionalized SWNTs were found at 532 nm. This nonlinear behavior of SWNTs has been shown to arise from strong nonlinear scattering, and porphyrin exhibits strong reverse saturable absorption at 532 nm. The porphyrins covalently functionalized SWNTs offer superior performance to the individual SWNTs and porphyrins by combination of nonlinear mechanism and the photoinduced electron or energy transfer between porphyrin moiety and SWNTs.