Asymmetric giant hollow carbon tubes enabled by a template-assisted functionalization strategy

Asymmetric chemical environments, in which opposing surfaces exhibit distinct functionalities or reactivities, hold significant promises for a wide range of applications. However, achieving such chemical asymmetry within nanoscale spaces remains a formidable challenge. In this study, we propose a general strategy, based on a template-assisted functionalization, for constructing asymmetric chemical environments within nanoscale spaces. As a proof of concept, giant hollow carbon tubes (gHCTs) are selectively functionalized with positively charged amino groups exclusively on their inner surfaces by exploiting the protective effect of an anodic aluminum oxide template, which shields the outer surface during chemical modification. The resulting gHCTs, bearing a pronounced positive charge on their inner surfaces, are capable of preferentially attracting and confining negatively charged species within their hollow channels. Building on this principle, negatively charged gold nanoparticles are selectively loaded onto the tube inner space. For larger SN-38NPs exhibiting more complex interactions, sustained release is observed specifically for those encapsulated within the positively charged inner cavity, owing to the combined effects of nanoconfinement and electrostatic attraction. These findings highlight the potential of the template-assisted functionalization strategy as a versatile approach for engineering asymmetric nanospaces, opening new opportunities for the selective adsorption of charged nanomaterials and controlled drug loading and release, as well as other advanced applications.