Gas Adsorption-sensitive Electrical Conductivity of Defective Single Wall Carbon Nanohorns

We show here electrical responses of the structurally controlled defective single wall carbon nanohorns (SWCNHs) by oxidation or compression treatment on CO2 and O2 adsorption. The morphological and porosity changes of defective SWCNHs were measured by high resolution-transmission electron microscopy (HR-TEM), N2 adsorption at 77 K and Raman spectroscopy. The SWCNH and ox-SWCNH induced a semiconducting behavior and exhibited nand p-type like conductivity responses on adsorption of CO2 and O2 at 303 K, respectively. Similarly, n-type response of SWCNH was transformed into p-type one with the compression treatment. The dramatic changes of electrical responses from n-ytpe to ptype nature of SWCNH by compression treatment were ascribed to both an effect of the annihilation of pentagons of a quasifree electron and reconstruction of individual horn structures.