On-surface synthesis of a polyynic carbon chain with ~40 alkyne units

Abstract

Carbyne, an elusive sp-hybridized linear carbon allotrope, has fascinated chemists and physicists for decades. Due to its high chemical reactivity and extreme instability, carbyne was much less explored in contrast to the sp2-hybridized carbon allotropes such as graphene. Herein, we report the on-surface synthesis of a polyynic carbon chain with ~40 alkyne units (80 carbon atoms), exhibiting the longest polyyne synthesized and characterized to date as a model for carbyne. The polyynic structure of carbon chains with alternating triple and single bonds is unambiguously revealed by bond-resolved atomic force microscopy, and the decoupled polyynic carbon chain exhibits a band gap of 3.67 eV measured by scanning tunneling spectroscopy. Our results provide a feasible route for the synthesis of long and stable polyynic carbon chains, leading a way to the final preparation of carbyne.