Functionalization of silicon carbide nanotube by dichlorocarbene: A density functional theory study

The existence of numerous unsaturated π bonds on surface of nanotubes is hopeful for effective chemical functionalization. Recently, the dichlorocarbene (CCl2)-functionalization has been widely applied to modify the electronic properties of carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs), through a simple one-step formation of the open three-membered-ring (3MR) structure. Here using density functional theory methods, we study the CCl2-functionalization of silicon carbide nanotubes (SiCNTs). Three distinct sequential steps are identified as: (1) 3MR formation, (2) Cl shift from C to Si atom, and (3) C bridging between a Si-C bond. Since the initial 3MR-formation is notably exothermic (2.47 eV), the subsequent steps take place easily, leading to the eventual adjacent C2formation in the alternative C-Si network. Clearly, the adsorption behavior of CCl2on SiCNTs contrasts sharply to that on CNTs and BNNTs, where the open 3MR structure is the eventually stabilized state with the two C-Cl bonds intactness. Such effective C-Cl splitting significantly decreases the band gap of SiCNT by about 50%. The adsorption of more CCl2molecules leads to a transition from semiconducting SiCNT to degenerated p-type semiconducting SiCNT. The present results not only testify the high surface chemical reactivity of SiCNT, but also show a new way of tuning the electronic properties of SiCNT.