Structural and Electronic Properties of Oxidized and Amorphous Nanodiamond Surfaces with Covalently Grafted Polypyrrole

Abstract

Diamond nanoparticles denoted as nanodiamonds (NDs) possess numerous beneficial material properties and are envisioned for a wide range of applications. In this work, complexes of polypyrrole (PPy) organic dye covalently grafted to ND surfaces are investigated by atomic scale density functional theory (DFT) computations with a view to their structural and electronic properties. NDs terminated with oxygen, hydroxyl, carboxyl, anhydride, as well as amorphous carbon (a‐C:H, a‐C:O) have been considered. Thereby the theoretical model is brought close to real nanodiamonds. Spatially separated highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) and a favorable energetic level alignment at the ND–PPy interface are observed for the majority of the oxidized NDs. This feature is also retained for NDs with amorphous surface layer. Excited states are computed by time‐dependent DFT to analyze how the electronic configuration can promote dissociation of excitons, for instance in photovoltaic applications.

Size Effects on Surface Chemistry and Raman Spectra of Sub-5 nm Oxidized High-Pressure High-Temperature and Detonation Nanodiamonds

“…Thus, both HPHT O-NDs and SR O-DNDs seem to undergo a change in surface chemistry with reducing size. This assertion is supported by the fact that specific combinations of oxygen-related groups are needed to fit on the nanodiamond surfaces as shown in several computational studies. , …”

“…This assertion is supported by the fact that specific combinations of oxygen-related groups are needed to fit on the nanodiamond surfaces as shown in several computational studies. 66,67 Size-Dependent Raman Spectra of Nanodiamonds. Successful isolation of sub-5 nm NDs of both DND and HPHT origin provides us a unique opportunity to elucidate some persisting issues, namely, the effects of size, crystallinity (level of lattice and structural defects), and surface on the Raman spectra of NDs.…”

Absolute energy levels in nanodiamonds of different origins and surface chemistries

“…Here, by means of density functional theory (DFT) calculations, the energy diagrams for sub-1 nm NDs of different surface chemistries were constructed. 35 However, the direct applicability of the data obtained for such small NDs is questionable due to the inherent quantum connement at this scale. 36 This work presents the comprehensive opto-electronicchemical study of the as-received, fully hydrogenated (reduced) and fully oxidized NDs.…”