Tuning the structural and electronic properties and chemical activities of stanene monolayers by embedding 4d Pd: a DFT study.

We have thoroughly investigated the interaction of some gas molecules (CO, NO, N2O and NH3) with Pd-decorated stanene nanosheets using density functional theory calculations. In this regard, we have considered three patterns for embedding Pd into the stanene monolayer, and then placed gas molecules on the Pd-decorated systems. Initially, we have optimized the structure of the Pd-decorated stanene to obtain its electronic properties. The charge density difference plot of the Pd-decorated system represents the accumulation of charge density on the adsorbed Pd atom. The adsorption energies, density of states, charge density differences and electronic band structures were analyzed in detail to fully exploit the gas sensing performance of Pd-decorated stanene systems. All the studied gas molecules form covalent bonds with the embedded Pd atom, which indicates the strong interaction between gas molecules and Pd-decorated stanene. The adsorption of gas molecules on pattern-III Pd-embedded stanene monolayers is more energetically favorable than that on the pattern-I and pattern-II ones. Besides, band structure calculations indicate changes in the electronic structure of the studied systems upon gas adsorption. Based on Mulliken charge analysis, the positive charge transfer occurred from the gas molecules to the Pd-decorated stanene systems. The results of this paper could provide a useful basis for materials scientists to design and modify novel sensing materials based on Pd-decorated stanene monolayers.

The Interaction of Acrolein with Pristine and N-doped TiO2 Anatase Nanoparticles: A DFT Study.

Density functional theory calculations were carried out in order to study the effects of the adsorption of acrolein molecule on the structural and electronic properties of TiO2 anatase nanoparticles. The ability of pristine and N-doped TiO2 anatase nanoparticles to recognize toxic acrolein (C3H4O) molecule was surveyed in detail. It was concluded that acrolein molecule chemisorbs on the N-doped anatase nanoparticles with large adsorption energy and small distance with respect to the nanoparticle. The results indicate that the adsorption of acrolein on the N-doped TiO2 is energetically more favorable than the adsorption on the pristine one, suggesting that the N doping can energetically facilitate the adsorption of acrolein on the N-doped nanoparticle. It means that the N-doped TiO2 nanoparticle can react with acrolein molecule more efficiently. The interaction between acrolein molecule and N-doped TiO2 can induce substantial variations in the HOMO/LUMO molecular orbitals of the nanoparticle, changing its electrical conductivity which is helpful for developing novel sensor devices for the removal of harmful acrolein molecule. The large overlaps in the projected density of states spectra reveal the formation of chemical bond between two interacting atoms. Charge analysis based on Mulliken charges indicates that charge is transferred from the acrolein molecule to the TiO2 nanoparticle.