Enhancing photothermal conversion of Cu_2-xS nanosphere and CNT nanocomposite using low-frequency phonon resonance

Solar energy utilization is advanced by integrating plasmonic copper chalcogenide (Cu_2-xS) nanospheres with CNTs, leveraging the complementary optical and thermal properties. Cu_2-xS nanocrystals, recognized for the wide plasmonic absorption in near-infrared region, are combined with CNTs, which exhibit excellent phonon transport due to the well-ordered lattice structure. The resulting nanocomposite demonstrates improved light absorption and enhanced interfacial thermal transport. Finite-difference time-domain simulations reveal significant enhancements in absorption cross-section and local electric field intensity, attributed to the localized surface plasmon resonance effects and resonance interactions among Cu_2-xS nanospheres. Additionally, molecular dynamics simulations demonstrate that low-frequency phonon resonance at Cu_2-xS/CNT interface increases the phonon density of states, thus promoting thermal conduction. Raman spectroscopy further confirms the influence of Cu_2-xS on the phonon vibration modes within Cu_2-xS/CNT nanocomposites. The enhanced photothermal conversion mechanism arises from the combined effects of localized surface plasmon resonances and low-frequency phonon resonances. This study reveals the mechanisms of nanoscale photothermal conversion enhancement and promotes the development of photothermal materials for efficient solar energy utilization. © 2025 Elsevier B.V.