Adsorption of an Mn atom on a ZnO sheet and nanotube: a density functional theory study

Preparation of Biomass Carbon Composites MgO@ZnO@BC and Its Adsorption and Removal of Cu(II) and Pb(II) in Wastewater

The ternary composite MgO@ZnO@BC was synthesized and characterized for the adsorption of Cu2+, Pb2+ heavy metal ions from wastewater. The results show that the addition of the MgO@ZnO@BC composite results in higher adsorption properties for Cu2+ and Pb2+, with a molar ratio of 5% 0.1 g, and maximum adsorption capacity (50.63 mg/g for Cu2+ and 61.46 mg/g for Pb2+). The Langmuir adsorption isotherm of the adsorption complex and the kinetics of adsorption are secondary kinetics. The adsorption of Cu2+ and Pb2+ was mainly chemisorption, accompanied by physical adsorption. This adsorption method fully conforms to the concepts of clean production and efficient waste utilization, providing a reference for the removal of heavy metal ions from wastewater and waste recycling using ternary composite materials.

Comparative Study on ZnO Monolayer Doped with Al, Ga and In Atoms as Transparent Electrodes

Transparent anodes are indispensable components for optoelectronic devices. Two-dimensional (2D) materials are attracting increasing research interest due to their unique properties and promising applications. In order to design novel transparent anodes, we investigated the electronic, optical, and electrical properties of 2D ZnO monolayers doped with Al, Ga, and In using the first-principles calculation in combination with the Boltzmann transport theory. When the doping concentration of Al, Ga, and In is less than 12.5 wt %, we find that the average transmittance reaches up to 99% in the visible and UV regions. Moreover, the electrical conductivity is enhanced for the Al, Ga, and In doped systems compared to that of the pristine ZnO monolayer. In particular, a good electrical conductivity with a significant improvement for the In doped ZnO monolayer is achieved compared to Al and Ga doping at the 6.25 wt % level. These results suggest that the ZnO monolayer based materials, and in particular the In doped ZnO monolayer, are promising transparent anodes for nanoscale electronic and optoelectronic applications.

Transition Metal Adsorbed-Doped ZnO Monolayer: 2D Dilute Magnetic Semiconductor, Magnetic Mechanism, and Beyond 2D

As an improvement over organic or inorganic layered crystals, the synthetic monolayer ZnO(M) inherits semiconductivity and hostability from its bulk, yet it acts as a promising host for dilute magnetic semiconductors. Here, we report the electronic and magnetic properties of ZnO(M) doped with one 3d transition metal ion and simultaneously adsorbed with another 3d transition metal ion. Two sequences are studied, one where the dopant is fixed to Mn and the adsorbate is varied from Sc to Zn and another where the dopant and adsorbate are reversed. First-principles results show that the stable adsorbed-doped systems possess a lower bandgap energy than that of the host. System magnetic moments can be tuned to |5 - x|μ_B, where x refers to the magnetic moment of the individual 3d atom. An interplay between superexchange and direct exchange yields a ferromagnetic system dually adsorbed-doped with Mn. In addition to a novel material design route, the magnetic interaction mechanism is found beyond two dimensions, having been identified for its three-dimensional bulk and zero-dimensional cluster counterparts.

First-Principles Investigation of Phase Stability, Electronic Structure and Optical Properties of MgZnO Monolayer

MgZnO bulk has attracted much attention as candidates for application in optoelectronic devices in the blue and ultraviolet region. However, there has been no reported study regarding two-dimensional MgZnO monolayer in spite of its unique properties due to quantum confinement effect. Here, using density functional theory calculations, we investigated the phase stability, electronic structure and optical properties of Mg_xZn_1-xO monolayer with Mg concentration x range from 0 to 1. Our calculations show that MgZnO monolayer remains the graphene-like structure with various Mg concentrations. The phase segregation occurring in bulk systems has not been observed in the monolayer due to size effect, which is advantageous for application. Moreover, MgZnO monolayer exhibits interesting tuning of electronic structure and optical properties with Mg concentration. The band gap increases with increasing Mg concentration. More interestingly, a direct to indirect band gap transition is observed for MgZnO monolayer when Mg concentration is higher than 75 at %. We also predict that Mg doping leads to a blue shift of the optical absorption peaks. Our results may provide guidance for designing the growth process and potential application of MgZnO monolayer.