Noncovalent exohedral functionalization of carbon nanotubes with double-decker phthalocyanines

The exohedral functionalization of single-walled carbon nanotubes with yttrium, lanthanum, gadolinium, and terbium double-decker phthalocyanines (or bisphthalocyanines) was achieved via a reflux process in butanol. The noncovalent functionalization with the bisphthalocyanines was confirmed using a combination of spectroscopic and microscopic techniques. Infrared and X-ray photoelectron spectroscopy analyses indicated the absence of new bonds, verifying that the phthalocyanines interact noncovalently with the nanotubes. Scanning and transmission electron microscopy analyses revealed a uniform distribution of the bisphthalocyanines complexes across the nanotube surfaces. Thermogravimetric analysis showed that combustion of the hybrids started at approximately 300 °C and ended between 620 and 650 °C. The incorporation of metal complexes was observed to decrease the thermal stability by roughly 50–100 °C compared to the pristine nanotubes, depending on the metal. Additionally, the weight percentage of double-decker structures in the hybrids varied with the metal, reaching 28.7 % for YPc₂, 26.4 % for LaPc₂, 30.6 % for GdPc₂, and 25.9 % for TbPc₂.