Increased optical nonlinearities of multi-walled carbon nanotubes covalently functionalized with porphyrin

Multi-walled carbon nanotubes covalently functionalized with tetraphenylporphyrin (MWCNT–TPP) with diameter ranges of <10, 10–30 and 40–60 nm were prepared by the reaction of MWCNTs with in situ generated porphyrin diazonium compounds. The fluorescence quenching data show that the unique direct linkage mode facilitates the effective photoinduced electron transfer between the excited porphyrin moiety and the extended π-system of MWCNT. The MWCNT–TPP hybrids have larger effective nonlinear absorption coefficients than the individual MWCNTs and porphyrin, and a blended sample. Furthermore, large increases in the optical nonlinearities of MWCNT–TPP hybrid materials were obtained as laser pulse width increased from 5.6 to 11.7 ns. By comparing with the nonlinear optical performance of individual MWCNTs and porphyrin, the pulse-width increased optical nonlinearities of these materials could be attributed to the improved efficiency of photoinduced electron transfer between MWCNTs and porphyrin with the increasing of pulse width.