Tunable UV Photoexcitation of Carbon Atomic Wires: Investigating the Roles of Chain Length, Termination Groups, and Environment

Carbon atomic wires (CAWs), linear one-dimensional carbon nanostructures, are attracting increasing attention in materials science due to their remarkable electrical, mechanical, optical, and transport properties, which make them promising candidates for being the next generation supercapacitors, batteries, hydrogen storage, organic semiconductors, and active optical elements. However, their intrinsic instability currently hinders their practical implementation. Previous studies have shown that CAWs mainly degrade through crosslinking interactions, exposure to high temperatures, hydrogenation and oxidation. Furthermore, a clear relationship between the wire structure, solvent polarity, and stability has been observed, with longer wires and more polar solvents reducing CAWs stability, while terminal groups strongly influence the degradation processes. Despite this, the photodegradation kinetics has not yet been fully and systematically investigated. Gaining such understanding is of fundamental importance for the rational design of CAWs-based materials for optoelectronic applications where light exposure is inevitable. In this work, we introduce a synchrotron-based approach that enables precise photoexcitation of CAWs with different chemical structures, tuned in resonance with their characteristic absorption vibronic peaks in the UV. This UV resonance Raman approach allows real-time monitoring of photodegradation directly through the time evolution of Raman spectra of each wire. We compare the photostability in different environments (i.e., acetonitrile, water, and aqueous colloidal silver nanoparticle dispersions), focusing on the role of two key structural parameters—sp-carbon chain length and terminal functional groups—in controlling the stabilization of these systems.