Exploring confined liquids in single wall carbon nanotubes using positron annihilation spectroscopy

Single wall carbon nanotubes (SWCNTs) are excellent confining media to study the physico-chemical properties of liquids under confinement. Positronium (Ps) is an established probe to investigate the phase behaviour of confined liquids. In the present study, we have investigated the Ps formation/annihilation mechanism in well characterized SWCNTs, before and after benzene confinement in SWCNTs. The results show that positrons are preferentially trapped in the inter-tube region of pristine SWCNTs bundles. However, interestingly, it is observed that when organic molecules like benzene is incorporated inside the tubes, positrons are efficiently trapped inside the SWCNTs, and form Ps. The present study confirms that SWCNTs can be used as a confining media to study the phase transformation of the liquids under confinement through positron annihilation spectroscopy. (author)