The possibility of optical excitations at the smallest gap of Cu-delafossite nanocrystals

Even though the quantum size effect on the electronic gap of nano-structures is well-understood, its implication on the optical absorption near band gap energies is still a challenging question, especially for metal-oxides. A unique class of highly stable, self-saturated and self-charge-compensated delafossite nanocrystals has been identified in this paper. The structural and electronic properties of these nanocrystalline Cu-based delafossites have been studied using density functional theory (DFT). To better estimate the electronic excitation energies, and consequently the optical gap, a time-dependent DFT has also been employed. The goal here is to study whether a nano-phase can enhance the optical absorption of near band gap energies of delafossite nano-structures compared to their bulk state to enable their application as a photocatalyst. (paper)