Study on the preparation of multi-walled carbon nanotube/phthalocyanine composites and their optical limiting effects

In this article, multi-walled carbon nanotubes were noncovalently functionalized with different metal phthalocyanines by π–π stacking method. Multi-walled carbon nanotubes were dispersed by sonication into the phthalocyanines solution in chloroform or N, N-dimethyl formamide before refined purification by centrifugation. It could be observed that the metal phthalocyanine molecules adhered to the surface of multi-walled carbon nanotubes in the transmission electron microscopy images. These composites were characterized by thermo gravimetric analysis and UV/Vis absorption spectrum. The optical limiting responses of these composites in N, N-dimethyl formamide solution were studied by Q-switched Nd:YAG laser instrument with nanosecond pulse of 1064 nm and repetition rate of 10 Hz. It was noted that the optical limiting ability of these composites solution was stronger than that of multi-walled carbon nanotubes or phthalocyanine alone. In addition, carbon nanotube was commonly purified in concentrated nitric acid, which usually introduced carboxylic groups on the carbon nanotubes. Herein, the effect of introduced carboxylic groups in the nitric acid treatment on the π–π stacking was also studied based on thermogravimetric analysis of composite multi-walled carbon nanotube/copper phthlaocyanine.