The creation of new carbon forms with different topologies has emerged as an exciting topic in both fundamental chemistry and materials science. Carbyne (linear carbon chain), 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.
On-surface synthesis is emerging as a promising approach for atomically precise fabrication of highly reactive 1D nanostructures with sp-hybridization that could be hardly synthesized via conventional solution synthetic chemistry. Xu's group employed the on-surface synthesis strategy, utilizing C4Br6 as a precursor, to synthesize polyynic carbon chains on the Au(111) surface via dehalogenative polymerization and subsequent demetallization, and the longest chain consists of ~120 carbon atoms. The polyynic structure of carbon chains with alternating single and triple bonds was unambiguously revealed by bond-resolved AFM.
Moreover, to measure the intrinsic electronic property of the carbon chain, a specific C14 polyyne was produced via tip-induced dehalogenation and ring-opening of the decachloroanthracene molecule (C14Cl10) on a bilayer NaCl/Au(111) surface at 4.7 K. The electronic properties were characterized by scanning tunnelling spectroscopy (STS), exhibiting two pronounced peaks at -3.4 V and 2.4 V, corresponding to the positive and negative ion resonances (PIR and NIR), respectively, exhibiting a band gap of 5.8 eV. This work from Prof. Wei Xu'group provides bond-resolved experimental insights into the structure of the polyynic carbon chains and may open an avenue for the synthesis and characterization of long polyynes without endgroups.
Research Report:On-surface synthesis and characterization of polyynic carbon chains
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