Five–seven-ring carbon ribbon conducts like a metal

A University of Science and Technology of China-led team reports narrow carbon pentaheptite nanoribbons in Nature. Unlike graphene’s familiar six-membered rings, the ribbons contain a central chain of seven-membered rings flanked by chains of five-membered rings. The team first made polycyclooctadiene chains, transformed them through on-surface reactions and fused them laterally into two atomically precise structures. Measurements and calculations show metal-like electron transport and conductance, suggesting a route toward fully covalent, atomically narrow carbon 'quantum wires.' The result matters because theory had long predicted conductive five–seven-ring carbon allotropes, while precise synthesis and structural verification remained difficult. These are still nanoscale samples made on surfaces under ultrahigh vacuum, not manufacturable wires. Room-temperature contacts, current capacity, defect tolerance, longer lengths, substrate transfer and environmental stability all remain to be demonstrated.