Theoretical study of the non-covalent functionalization of carbon nanotubes for NO and CO detection

Sensing CO and NO gases at room temperature (RT) is of great significance for various industrial and environmental sectors including, pollution monitoring, commercial safety, and medical services, among others. Nanomaterials such as single-walled carbon nanotubes (SWNTs) have emerged as promising candidates for RT gas-sensing applications due to their unique intrinsic properties. Herein, we reported a theoretical study of semiconductor-SWNTs (8,0) as sensitive layer for CO and NO detection. To improve their sensing performance, semiconductor-SWNTs (8,0) were non-covalently functionalized with a series of metalloporphyrins and metallophthalocyanines molecules such as cobalt(II)-phthalocyanine (Pht-Co), cobalt(II)-porphyrin (Por-Co) and iron(II)-porphyrin (Por-Fe). A charge transfer between the functionalizing molecules and SWNTs induces n-type doping of SWNTs. The functionalized SWNTs exhibited superior sensitivity and attachment capacity toward NO and CO compared to pristine SWNTs. By analyzing the interaction between gases and different functionalized SWNTs molecules, the results showed that NO acts as an electron acceptor with all systems. However, CO reacts as an electron donor with Por-Co and Pht-Co functionalized SWNTs and as an electron acceptor with SWNT (8,0) + Por-Fe. From the set of tested molecules, Por-Co is the best candidate for selective detection of both CO and NO with different signals depending on the gas nature.