Computational study of physisorption and chemisorption of polypyrrole on H‐terminated (111) and (100) nanodiamond facets

Abstract

Interaction of diamond with molecules is important for various applications. For instance, experimentally observed charge transfer between bulk diamond and polypyrrole (PPy) is promising for photovoltaics. Here we explore the interactions of PPy with surfaces of nanodiamonds (NDs) by density functional theory (DFT) calculations at the B3LYP/6-31G(d) level of theory. The most probable H-terminated 1 Â 1 (111) and 2 Â 1 (100) diamond surface facets are considered. Geometrical arrangement, binding energy (E b ), interaction energy (E int ), charge transfer (Dq), and HOMO-LUMO gap are calculated on geometrically relaxed structures of PPy on the ND facets in physisorbed or chemisorbed configuration. Energetically, the most favorable is physisorption of PPy on NDs. For chemisorption, one-bond contact is more favorable than two-bond contact, with the most probable binding on (100) facet. Charge transfer of electrons (up to Dq ¼ À0.11 e À ) from PPy to diamond is observed for all the configurations in the dark. In some cases, the calculations reveal spatial separation of the HOMO and LUMO, which may be useful for photovoltaic applications. Truncated octahedral ND (left), (111) facets are in blue, (100) facets are in red. (111)-(100)-(111) corner of ND (bottom), and (111) facet with chemisorbed PPy (top). C atoms are in gray, H atoms are in white, N atoms are in blue.

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

“…Overall, significant values of charge transfer are obtained for most of the structures, including the nanodiamonds with an amorphous surface layer, which are included in Table S10, Supporting Information. The charge transfer values for the a‐C:H structures are consistent with the values obtained for the reconstructed hydrogenated NDs . Moreover, higher charge transfer is obtained for the a‐C:O structures than for the a‐C:H structures.…”

“…Consistently with the hydrogenated NDs [23] the C-C bond lengths between PPy and ND are mostly shorter for the two-bond contacts than for the one-bond contacts. This is owing to the less www.advancedsciencenews.com www.pss-b.com steric repulsion from the removal of the two surface functional groups instead of one for the former case, especially for the carboxylated and hydroxylated NDs.…”

“…The charge transfer values for the a-C: H structures are consistent with the values obtained for the reconstructed hydrogenated NDs. [23] Moreover, higher charge transfer is obtained for the a-C:O structures than for the a-C:H structures. This is the same trend as for the reconstructed diamond surfaces.…”

“…More details on the computational setup are provided in our prior work. [23] To study the contact formation, different non-equivalent positions of one-bond and two-bond covalent contacts of PPy (represented by six Py units) on the relaxed ND slabs were optimized. During this optimization, the outermost C atoms, and terminating O and H atoms were allowed to relax, while the rest of the particle was kept fixed.…”

“…This work builds upon prior theoretical works investigating electronic and energetic characteristics of the most simplified PPy-ND system where all surface dangling bonds, and internal surfaces of ND were passivated merely by hydrogen [22,23] and system of PPy merely physisorbed on oxidized NDs. [24] Here, we concentrate on the system of PPy chemisorbed (covalently bonded) on oxidized NDs.…”