Disclosing Early Excited State Relaxation Events in Prototypical Linear Carbon Chains

Abstract

One-dimensional (1D) linear nanostructures comprising sp-hybridized carbon atoms, as derivatives of the prototypical allotrope known as carbyne, are predicted to possess outstanding mechanical, thermal, and electronic properties. Despite recent advances in the synthesis, their chemical and physical properties are still poorly understood. Here, we investigate the photophysics of a prototypical polyyne (i.e., 1D chain with alternating single and triple carbon bonds), as the simplest model of finite carbon wire and as a prototype of sp-carbon-based chains. We perform transient absorption experiments with high temporal resolution (<30 fs) on monodispersed hydrogen-capped hexayne H$-$(C$\equiv$C)${}_6-$H synthesized by laser ablation in liquid. With the support of detailed computational studies based on ground state density functional theory (DFT) and excited state time-dependent (TD)-DFT calculations, we provide a comprehensive description of the excited state relaxation processes at early times following photoexcitation. We show that the internal conversion from a bright high-energy singlet excited state to a low-lying singlet dark state is ultrafast and takes place with a 200-fs time constant, followed by thermalization on the picosecond timescale and decay of the low-energy singlet state with hundreds of picoseconds time constant. We also show that the timescale of these processes does not depend on the end groups capping the sp-carbon chain. The understanding of the primary photo-induced events in polyynes is of key importance both for fundamental knowledge and for potential optoelectronic and light-harvesting applications of low dimensional nanostructured carbon-based materials.

arXiv comment24 pages, 6 figures

References in corpus (8)

• Confined linear carbon chains: A route to bulk carbyne
• Mechanically induced metal-insulator transition in carbyne
• Carbon nanotube chirality determines properties of encapsulated linear carbon chain
• Semiconductor-to-metal transition in carbon-atom wires driven by sp2 conjugated endgroups
• Raman Scattering Cross Section of Confined Carbyne
• Stable and Solution-Processable Cumulenic sp-Carbon Wires: A New Paradigm for Organic Electronics
• Solvent-dependent termination, size and stability in polyynes synthesis by laser ablation in liquids
• Electronic structure of confined carbyne from joint wavelength-dependent resonant Raman spectroscopy and density functional theory investigations

Cited by in corpus (1)

• Halogen-Terminated Carbon Atomic Wires by Laser Ablation in Halogenated Organic Solvents: Synthesis and Characterization