On the nanoscale interface, electronic structure, and optical properties of nanocarbon-reinforced calcium silicate hydrates

Abstract

This study presents results from quantum chemical simulations of the synergetic interaction, electronic structure, and optical properties of calcium-silicate hydrates (C-S-H) reinforced by graphene-nanoribbons and single-walled carbon nanotubes (SWCNT). The calculations show that C-S-H/graphene-nanoribbon and C-S-H/SWCNT composites are stabilized by electrostatic interaction due to the charge transfer from Ca ions at the interface of C-S-H to the nearby C atoms of the graphene-nanoribbon and SWCNT. Removing Ca ions at the interface drastically decreases the strength of interaction into a weak van der Waals type. The Bader charge transfer analysis and electron distribution topology further confirm these results. Generally, the electronic states of the graphene-nanoribbon and SWCNT are shifted to lower energy in the complex. The electronic structure of graphene-nanoribbon and SWCNT is susceptible to the Ca ions-rich C-S-H environment. The composites’ overall absorption spectra can be considered superimposed of the isolated nanocarbon and C-S-H except in the lower energy region due to charge transfer and realignment of energy states. The results presented here reveal the bonding mechanism of the C-S-H with nanocarbon at the fundamental level. This work serves as a reference for the nanoengineering cement-based material with nanocarbon for the next-generation smart infrastructure.

Insights on the Bonding Mechanism, Electronic and Optical Properties of Diamond Nanothread—Polymer and Cement—Boron Nitride Nanotube Composites

“…The electronic band structures of the C-S-H, BNNT, and C-S-H/BNNT complexes are further calculated to reveal the composites' metallicity, as shown in Figure 11. Our results show that the dispersive bands appear near the Fermi energy due to the lone pair of the Ca ions, as discussed here [81]. On the one hand, the BNNT shows insulating properties having a bandgap of 3.77 eV located at the Γ point.…”

“…The interaction strength is quantified by calculating the binding energy per unit cell. The binding energy of the C-S-H/BNNT is -0.89 eV, which is lower in magnitude compared to the binding energy of the C-S-H/SWCNT (-5.0 eV) and C-S-H/graphene-nanoribbon (-3.24 eV) [81]. Furthermore, the calculated binding energy here is much lower than the binding energy of graphene-based material with the monomer of C-S-H [101].…”

“…Charge density distribution (CDD) and electron localization function (ELF) are also obtained for all structures to visualize the electron redistributions. Both provide descriptive insights into the redistribution of the electronic distribution, thus essential in distinguishing the nature of bonds in the complex structure, as demonstrated in our previous works on similar systems [79][80][81]. The CDD and ELF images are visualized using VESTA [82].…”

“…The prototype C-S-H here is adapted to our recent work that describes the interface of graphenenanoribbon and SWCNT with the C-S-H [81]. The isolated C-S-H has Ca-H2O, Ca-O, and Si-O bonds ranging from 2.35-2.43 Å, 2.39-2.70 Å, and 1.62 -1.70 Å, respectively.…”