Publication

Abstract : Porphyrins are versatile chromophores with a variety of desirable features such as a large extinction coefficient in the visible light region, high stability, and prospective photochemical electron-transfer ability and have been widely studied for various photo harvesting and photo electronic devices. Carbon nanotubes (CNTs) have been investigated extensively because of their unique materials properties.1 Covalent and non covalent functionalization of organic molecules with carbon nano materials have primarily focused on dispersion or dissolution properties. Incorporation of photo excited electron donors, such as porphyrins or metalloporphyrins through a covalent linkage with the extended ツ electrons of a carbon nanotube would constitute an ideal candidate for molecular electronic and photovoltaic devices.2 Here, 5,10,15,20 mesotetra (4-aminophenyl) porphyrin (TAP) was used to functionalize single-wall carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs). The SWCNT-TAP and MWCNT-TAP hybrids were characterized by Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy (UV-Vis) and Transmission electron microscopy (TEM). A comparative study on the photophysical properties of TAP, GO-TAP, SWCNT-TAP and MWCNT-TAP hybrids are reported. TAP was functionalized with the as-prepared carboxyl modified SWCNTs and MWCNTs. First the carboxyl modified CNTs were treated with SOCl2 at 70 oC to convert the ♠COOH to ♠COCl groups. Finally the desired functionalized CNTs were achieved by reacting TAP and CNTs-COCl samples in N,N-dimethylformamide under argon. Figure 1 shows UV-visible spectra and PL-spectra of Tap, GO-TAP, MWCNT-TAP, SWCNT-TAP in DMF. The SWCNT-TAP hybrid shows significantly improved solubility compared to MWCNT-TAP and GO-TAP hybrids. SWCNT-TAP, MWCNT-TAP hybrids shows enhanced fluorescent quenching compared to porphyrin than GO-TAP hybrid, indicating excellent electron and/or energy transfer to SWCNT and MWCNT from TAP. We thus report the successful synthesis and characterization of SWCNT-TAP and MWCNT-TAP hybrids, which holds great promise for nonlinear optical and electronics applications.