Surface Defect Engineering via Polyaromatic Cluster Evolution for Efficient Microwave-Driven Carbothermal Shock Synthesis of Nanoparticles

Microwave-driven carbothermal shock (CTS) synthesis has attracted considerable attention as an ultrafast route for nanomaterial production. However, controlling nanoparticle nucleation and growth during the extremely short microwave irradiation period remains challenging. Although defect-rich carbon materials have frequently been employed in microwave-driven CTS synthesis, the influence of a separately introduced defect-containing surface layer on nanoparticle formation remains insufficiently understood. In this study, carbon cloth (CC) was coated with a polyacrylonitrile (PAN) solution and thermally oxidized at 200-400 °C to modify the surface carbon structure through the evolution of PAN-derived polyaromatic clusters prior to microwave irradiation. Raman spectroscopy and X-ray photoelectron spectroscopy indicated that increasing the oxidation temperature promoted the formation of larger and more ordered polyaromatic domains, accompanied by changes in the surface defect characteristics. These structural variations were associated with distinct Cu nanoparticle sizes and distributions following CTS synthesis. Among the investigated oxidation temperatures, the PAN-coated CC treated at 300 °C produced the smallest and most uniformly dispersed Cu nanoparticles, with an average diameter of 58 ± 25 nm. These findings suggest that controlling the structural evolution of PAN-derived surface carbon layers can provide a practical approach for regulating nanoparticle size and dispersion during microwave-driven CTS synthesis.