Materials Science Forum Vol. 1121

Abstract: This study provides accounts of the bonding character, electronic structure, and optical properties of the cellulose–polyaniline hybrid complex using principles of quantum mechanics. The calculations revealed cellulose and polyaniline binding energy per unit ranged from -0.52 eV to -0.68 eV. The electron localization function of the complex revealed that there was no value at the interface but deformed basins, indicating a physisorption type of interaction. The highest occupied molecular orbitals and lowest molecular orbitals are mainly dominated by the polyaniline, with minor hybridization of the orbitals of the cellulose in all configurations. These results indicate that the bonding between cellulose and polyaniline is characterized as an unshared electron interaction. Generally, the density of states of the cellulose and polyaniline complex can be considered a superposition of the states of isolated subsystems—the bandgap of the complex ranges from 2.30 eV to 2.87 eV. The lowest bandgap is observed when the prototype polyaniline is placed near the cellulose hydroxy and hydroxymethyl group. Further, the optical absorption spectra are calculated using time-dependent density functional theory. The results indicate that the prominent peak of the prototype polyaniline at 3.59 eV (345.36 nm) is suppressed at the complex. Meanwhile, in the higher energy region, the optical absorption spectra can be considered a superposition of the absorption spectra of the isolated constituents. The results presented here provide new information on the cellulose–polyaniline complex's bonding mechanism and give the resulting electronic–optical properties. The results will be helpful in the development of innovative biomaterials, fibers, and multifunctional composites based on cellulose and polyaniline.

Abstract: Chemical inertness of pristine carbon nanotubes (CNTs) poses challenges on their biocompatibility. In this paper, surface modification of pristine (5, 5) single-walled carbon nanotube (SWCNT) was explored through substitutional Boron (B) and Nitrogen (N) doping forming a C₃₈NB isomer. The electronic topology and binding mechanism of acetic acid adsorption on the isomer was then examined in the context of first-principles Density Functional Theory (DFT). Accordingly, high abundance of localized electrons between the substitutional doping sites indicates chemical binding of the substitutional atoms with the SWCNT. These are further supported by the calculated bond angles. When the acid was adsorbed on the C₃₈NB isomer, spontaneous charge redistributions were observed which are attributed to the oxidation caused by the O atoms and the charge acceptance of the C atoms. Topological analyses revealed that the net charge transfers for all considered configurations were towards the acid. In addition, the Lowest Unoccupied Molecular Orbital (LUMO) and Highest Occupied Molecular Orbital (HOMO) revealed the nonuniform distribution of electronic charges near the Fermi level. Finally, calculations of the electron localization function (ELF) showed that there was no orbital hybridization between the acid and the isomer. Further, the absence of localized electrons between their interaction points implied a physical binding mechanism. The results of the study could be used for future opto-electronic experiments and electrochemical biosensing applications of CNTs.

Abstract: The utilization of the Miedema semi-empirical model has proven to be an effective approach for the estimation of Gibbs free energy in solid solutions within binary and ternary systems. Research findings indicate that in systems such as FeAl, FeMn, FeB, FeV, FeGa, AlMn, AlGa, and AlV, the Gibbs free energy exhibits highly negative values. Conversely, systems FeSn, AlB, and AlSn demonstrate positive Gibbs free energy values, with the most negative observing at a molar fraction of 50% for Fe. These results have been corroborated through studies involving the mechanosynthesis of binary and ternary FeAl based alloys. It is thus inferred that the Miedema model can be reliably employed for predictive purposes, facilitating the estimation of Gibbs free energy and the exploration of potential multicomponent system formations.