Highly Efficient Photothermal Effect by Atomic-Thickness Confinement in Two-Dimensional ZrNCl Nanosheets

We report a giant photothermal effect arising from quantum confinement in two-dimensional nanomaterials. ZrNCl ultrathin nanosheets with less than four monolayers of graphene-like nanomaterial successfully generated synergetic effects of larger relaxation energy of photon-generated electrons and intensified vibration of surface bonds, offering predominantly an enhancement of the electronphonon interaction to a maximized extent. As a result, they could generate heat flow reaching an ultrahigh value of 5.25 W/g under UV illumination with conversion efficiency up to 72%. We anticipate that enhanced electronphonon coupling in a quantum confinement system will be a powerful tool for optimizing photothermal conversion of inorganic semiconductors.