A first-principles investigation of Cr adsorption on C8 and B4N4 nanocages in aqueous mediums

Ab Initio Study of the Graphyne-like γ-SiC Nanoflake for Toxic Gas-Sensing Applications

This study focuses on the geometrical, electronic, and optical properties of the γ-graphyne-like novel γ-SiC nanoflake of the γ-silicon carbide (SiC) monolayer using density functional theory calculations. γ-SiC was revealed to be a stable semiconducting nanoflake confirmed by a negative cohesive energy, real vibrational frequencies, and a 1.749 eV energy gap. The adsorption of COCl2, HCN, PH3, AsH3, CNCl, and C2N2 toxic gases on the γ-SiC nanoflake is also studied, which revealed an attractive gas-nanoflake interaction with the adsorption energy ranging from -0.21 to -0.38 eV. The adsorption results in a significant charge transfer between gas-adsorbent complexes. A significant variation in the energy gap and electrical conductivity was observed due to gas adsorption. γ-SiC showed maximum sensitivity at room temperature for CNCl gas. The entire process of adsorption is exothermic and thermodynamically stable. γ-SiC showed a high absorption coefficient over 104 orders with a significant variation in the absorption peak intensity and blue peak shifting. According to the quantum theory and reduced density gradient analysis, all of the gases are physisorbed on the γ-SiC nanoflake due to van der Waals interactions. The obtained results signify the usability of γ-SiC as a potential toxic gas sensor.

Phosphorus-doped T-graphene nanocapsule toward O3 and SO2 gas sensing: a DFT and QTAIM analysis

Tetragonal graphene nano-capsule (TGC), a novel stable carbon allotrope of sp2 hybridization is designed and doped with phosphorus (P) to study the O3 and SO2 gas sensitivity via density functional theory calculation. Real frequencies verified the natural existence of both TGC and P-doped TGC (PTGC). Both TGC and PTGC suffer structural deformations due to interaction with O3 and SO2 gases. The amount of charge transfer from the adsorbent to the gas molecule is significantly greater for O3 adsorption than SO2 adsorption. The adsorption energies for TGC + O3 and PTGC + O3 complexes are - 3.46 and - 4.34 eV respectively, whereas for TGC + SO2 and PTGC + SO2 complexes the value decreased to - 0.29 and - 0.30 eV respectively. The dissociation of O3 is observed via interaction with PTGC. A significant variation in electronic energy gap and conductivity results from gas adsorption which can provide efficient electrical responses via gas adsorption. The blue/red shift in the optical response proved to be a way of detecting the types of adsorbed gases. The adsorption of O3 is exothermic and spontaneous whereas the adsorption of SO2 is endothermic and non-spontaneous. The negative change in entropy verifies the thermodynamic stability of all the complexes. QTAIM analysis reveals strong covalent or partial covalent interactions between absorbent and adsorbate. The significant variation in electrical and optical response with optimal adsorbent-gas interaction strength makes both TGC and PTGC promising candidates for O3 and SO2 sensing.