Nanodiamond particles (NDs) have recently risen in popularity owing to their unique and perspective properties. Merging NDs with organic molecules, such as polypyrrole (PPy), into hybrid organic-semiconductor functional systems gives rise to potential applications in photovoltaics (PV), which is supported by prior experimentally observed charge transfer between bulk diamond and PPy. This work focuses on the most relevant (111) and (100) O-terminated ND facets with different coverage of surface terminating oxygens in ether, epoxide, ketone, and peroxide positions. We use density functional theory (D FT) computations employing B3LYP functional and 6-31G(d) basis set. Energetically the most favorable oxidized ND facets were further optimized with PPy in physisorbed configurations. Analysis of geometry, binding energy, HOMO-LUMO gap, and charge transfer was done on the relaxed PPy-ND structures. Multiple hydrogen bonds are formed between PPy amino groups and O atoms on ND surface. PPy on 1 × 1 reconstructions is energetically favorable with exothermic binding energy (2.7 eV) and high charge transfer (up to 0.26 e-) in the dark. The HOMO-LUMO at the PPy-ND interface becomes spatially separated and significantly closer in energy (down to about 1 eV). These features may be beneficial for photovoltaic applications of nanodiamond.Keywords: DiamondDiamond, nanoparticles, polypyrrole, density functional theory, charge transfer
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