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A theoretical investigation on electronic states in triangular MoS2 quantum dots of different sizes is performed within density functional theory first‐principles formalism. Herein, the associated interband optical response from real and imaginary parts of the dielectric function is calculated. The study considers both undoped and Al‐, Si‐, and P‐doped systems. Spin‐related magnetic properties are considered through the evaluation of total magnetic moment. It is revealed that small enough structures have a semiconductor character, but evolve to seemingly half‐metallic with increasing dot size. Nonzero magnetic response is attributed to edge effects. Magnetic behavior of doped systems deviates from the linear dependence of the total magnetic moment with size occurring in the undoped case, producing situations with higher total momentum values. It is found that increasing the doping density may have certain influence over total magnetic moment response of the structures, although edge dominance is kept all the way. Optical properties are not as sensitive to incident light polarization, but they actually do with regard to the particular spin orientation. Calculation for the refraction index in the triangular quantum dots shows values still below the accepted in the MoS2 monolayer case, although a correct trend of variation is reported in this sense. [ABSTRACT FROM AUTHOR]

Phosphorene is an emerging 2D-like material with direct energy band. In this work we report the results of a theoretical study on the electronic structure of phosphorene multilayers. A particular emphasis is put on the investigation of the optical absorption and the functionalization of phosphorene layers with organic molecules such as benzene and fullerene. The investigation is carried out employing the density functional theory, and the effect of using different exchange-correlation functionals for the interlayer van der Waals interaction is discussed. Fundamental quantities like lattice constants, interlayer distance and energy band gap are reported in phosphorene monolayers, bilayers and trilayers. The features of the interband optical absorption are studied from the calculated imaginary part of the dielectric function. The results of the numerical simulation of the phenomenon of the small organic molecule physisorption onto phosphorene indicate that the direct band gap is preserved. In the case of the fullerene physisorption, a deformation in the phosphorene monolayer is induced, leading to a shift of the associated band structure. It is shown that such a modification depends on the particular exchange-correlation functional employed. In the case of benzene physisorption, the electronic structure of the phosphorene remains unchanged and is independent of the position of the benzene molecule. This suggests that benzene would be a good candidate for a molecular coating of phosphorene to shield it against oxidation under ambient conditions. [ABSTRACT FROM AUTHOR]

Blue phosphorene is an attractive nanomaterial that exhibits some remarkable optoelectronic properties. Various studies have verified its ability to adsorb gaseous compounds and, in particular, to dissociate O2, forming covalent bonds between phosphorus and oxygen atoms. These covalent bonds could be the reason behind the oxidation reaction that affects the blue phosphorene in normal room conditions. Theoretically, it has been demonstrated that the blue phosphorene oxide (BPO) is just as stable as the blue phosphorene. Given that metallic oxides are widely used as catalyzers and gas sensors, this opens the possibility of the BPO being presented as a gas sensor as well. For all the above, in this work the optoelectronic properties of BPO were studied, along with the generation of the oxygen vacancies. The investigation was performed within the density functional theory (DFT). In the study of the oxygen vacancy, the formation energy was calculated, and the results are similar to the formation energies of oxygen vacancies in other known oxides. It was found that the BPO with a single vacancy has a favorable energetic stability. The characterization of the vacancy is achieved using the electronic structure and the optical response. Additionally, the analysis of the adsorption of a hydrogen atom on the BPO, and the subsequent formation of hydroxide is presented. [ABSTRACT FROM AUTHOR]