Narrow Results

According to the first-principle method for the density functional theory (DFT), combined with the hybrid functional (HSE06), the electronic structure and effective mass of Mg-doped GaN and Mg–Fe co-doped GaN systems are calculated, and the stability of the co-doped structure is analyzed from the perspective of formation energy and phonon dispersion. The results showed that the introduction of Fe improved the characteristics of GaN:Mg system: the GaN material doped with Mg merely would cause the material’s valence band maximum to exceed the Fermi level, presenting a $p$-type conduction; the addition of Fe increased the energy band density of the system, and the insulation of the material was enhanced due to the higher energy level of the introduced impurity. Furthermore, the influence of Mg doping on the magnetic properties of GaN-based diluted magnetic semiconductor (DMS) was considered as well, with the magnetic moment obtained from co-doping Mg–Fe slightly reduced by a comparison of that of GaN:Fe measured by our research group. The results showed that the difference in the effective mass of GaN:Mg:Fe system in different directions was smaller than that of GaN:Mg system, indicating that the anisotropy of the system was reduced by doping Fe.

To explore the excellent sensor for detecting the pollution gas $S{O}_2$, the adsorptions of $S{O}_2$ molecule on the surfaces of Fe/Co-doped carbon nanotubes (CNTs) and single vacancy defected (8, 0) CNTs were investigated by using density functional theory (DFT). In addition, the adsorption energies, geometries, energy gaps and electronic structures were analyzed. The results showed that Fe/Co-doping and single-vacancy-defected can improve the adsorption and sensitiveness of CNTs toward $S{O}_2$. Considering the changes of energy gap before and after the $S{O}_2$ molecule adsorbed on each modified CNTs and its adsorption strength, Fe-doped CNTs (Fe-CNTs) and Co-doped site-2 single-vacancy-defected CNTs performed better for detecting $S{O}_2$ molecule. With the decreasing number of electrons of the doped atom (Fe, Co, Ni), the adsorption became more stable. The results of this paper are profound and meaningful for designing $S{O}_2$ sensing devices.

Nd/Pr co-doped ${\mathrm{\text{Bi}}}_2{\mathrm{\text{WO}}}_6$ photocatalytic materials were prepared via a simple one-step hydrothermal method. The physicochemical properties of the prepared samples were characterized by XRD, Raman, UV-Vis DRS, PL, SEM, BET analysis and photocatalytic tests. The results showed the co-dopants of Nd and Pr ions with the concentration of 1% Nd and 1% Pr exhibited the highest photocatalytic activity. Rhodamine B (RhB) was almost completely degraded within only 10 min. The increased photocatalytic activity on the co-doped ${\mathrm{\text{Bi}}}_2{\mathrm{\text{WO}}}_6$ is attributed to the increasing specific surface area, the inhibited recombination of photogenerated carriers and the reduced band gap energy. This study provides a helpful strategy for developing effective photocatalysts.