文摘
A systematic study of the interaction between 蟺-extended porphyrins and single-walled carbon nanotubes (SWNTs) is reported here. Zinc porphyrins with 1-pyrenyl groups in the 5,15-meso positions, 1, as well as compounds where one or both of the pyrene groups have been fused at the meso and 尾 positions of the porphyrin core, 2 and 3, respectively, have been examined. The strongest binding to SWNTs is observed for porphyrin 3, leading to debundling of the nanotubes and formation of stable suspensions of 3鈥揝WNT hybrids in a range of common organic solvents. Absorption spectra of 3鈥揝WNT suspensions are broad and continuous (位 = 400鈥?400 nm), and the Q-band of 3 displays a significant bathochromic shift of 33 nm. The surface coverage of the SWNTs in the nanohybrids was estimated by spectroscopic and analytical methods and found to reach 64% for (7,6) nanotubes. The size and shape of 蟺-conjugated porphyrins were found to be important factors in determining the strength of the 蟺鈥撓€ interactions, as the linear anti-3 isomer displays more than 90% binding selectivity compared to the bent syn-3 isomer. Steady-state photoluminescence measurements show quenching of porphyrin emission from the nanohybrids. Femtosecond transient absorption spectroscopy reveals that this quenching results from ultrafast electron transfer from the photoexcited porphyrin to the SWNT (1/kCT = 260 fs) followed by rapid charge recombination on a picosecond time scale. Overall, our data demonstrate that direct 蟺鈥撓€ interaction between fused porphyrins and SWNTs leads to electronically coupled stable nanohybrids.
Keywords:
蟺-extended porphyrins; noncovalent 蟺鈭捪€ interaction; single-walled carbon nanotubes; nanohybrids; isomer selectivity; femtosecond transient absorption; ultrafast electron transfer
