Planar graphitic ZnS, buckling ZnS monolayers and rolled-up nanotubes as nonlinear optical materials: first-principles simulation

Prediction of electronic properties of novel ZnS-ZnO-recycled expanded polystyrene nanocomposites by DFT

DFT calculations using Material Studio (2019) were used to ascertain the changes in electronic properties of recycled expanded polystyrene (rEPS) after modification with nanoparticles of ZnS and ZnO. The nanocomposites were obtained using rEPS and suitable metal salt precursors via a solvothermal method. The XRD analysis was conducted to obtain the crystallography data of the new rEPS-based nanocomposites. Using Material Studio simulation software, the potential photocatalytic properties of the new prepared material was predicted and information on the electronic band structure was extracted. The calculated band gap values for rEPS and ZnS-ZnO-rEPS nanocomposite were 4.217 eV and 2.698 eV, respectively. Furthermore, our results showed that the nanocomposite is a p-type semiconductor. From the electronic structure and the band gap narrowing, these nanocomposites obtained from a waste material may have some potential in photocatalytic applications.

Band alignment engineering: ultrabroadband photodetection with SnX2 (X = S, Se)/ZnS heterostructures

Ultrabroadband mid-frequency infrared photodetectors have important applications in surveillance, medical diagnosis, bioimaging and navigation aids. Thus, researchers hope to detect mid-infrared radiation with larger wavelength. However, due to the limitation of room temperature, it is difficult for these detectors to detect mid-infrared with 4 µm or larger wavelength. Therefore, at room temperature, how to realize mid-infrared detection in a wide range has become an urgent problem to be solved. In this paper, the band structure of SnX₂ (X  =  S,Se)/ZnS and SnS_2(1-ŋ)Se_2ŋ /ZnS was studied by the density functional theory based first-principles methods. Under the specific stacking procedure, changing the [Formula: see text] of SnS_2(1-ŋ)Se_2ŋ , the band gap of heterojunctions can be continuously tuned from 0 to 0.97 eV. Amazingly, the band structure maintains the characteristics of a type-II heterojunction. The photodetection in our work is estimated for wavelengths from 1.2 µm to 10 µm, covering a wide wavelength range of mid-infrared. Such a wide range is considerable in current research. The characteristics of type-II band structure and the wide detection range imply that SnX₂ /ZnS has great potential in mid-frequency infrared detection. Our work may provide some breakthroughs for the research of multiband photodetectors at room temperature.