PH3 and AsH3 Adsorption Through Pristine and Stone-Wales Defected Zinc Oxide Nanosheets: A Density Functional Theory Study

The adsorption of the XH3 (X = As or P) molecules were explored onto a pure and Stone-wales defected ZnONS (SW ZnONS) through density functional theory computations. As XH3 approaches the pure ZnONS their adsorption releases -3.7 to -7.6 kcal/mol, indicating a physisorption. Also, the electronic properties of the nanosheet do not change significantly. But when AsH3 approaches SW ZnONS, its adsorption releases -23.3 kcal/mol, and electronic analysis showed that the SW ZnONS HOMO/LUMO gap reduces about ~ -27.1% and the electrical conductivity increases significantly. Therefore, the SW ZnONS can generate electrical signals when the AsH3 molecule approaches, being a hopeful sensor. τ value which calculated for the desorption of AsH3 from the surface of the SW ZnONS is 9.5 s. This indicates that the SW ZnONS has the advantage of having a short τ as a sensor for AsH3 detection.

Thickness-Dependent Piezoelectric Property from Quasi-Two-Dimensional Zinc Oxide Nanosheets with Unit Cell Resolution

A quantitative understanding of the nanoscale piezoelectric property will unlock many application potentials of the electromechanical coupling phenomenon under quantum confinement. In this work, we present an atomic force microscopy- (AFM-) based approach to the quantification of the nanometer-scale piezoelectric property from single-crystalline zinc oxide nanosheets (NSs) with thicknesses ranging from 1 to 4 nm. By identifying the appropriate driving potential, we minimized the influences from electrostatic interactions and tip-sample coupling, and extrapolated the thickness-dependent piezoelectric coefficient (d33). By averaging the measured d33 from NSs with the same number of unit cells in thickness, an intriguing tri-unit-cell relationship was observed. From NSs with 3n unit cell thickness (n=1, 2, 3), a bulk-like d33 at a value of ~9 pm/V was obtained, whereas NSs with other thickness showed a ~30% higher d33 of ~12 pm/V. Quantification of d33 as a function of ZnO unit cell numbers offers a new experimental discovery toward nanoscale piezoelectricity from nonlayered materials that are piezoelectric in bulk.

Micro-Plasma Assisted Synthesis of ZnO Nanosheets for the Efficient Removal of Cr6+ from the Aqueous Solution

Herein, we report a micro-plasma assisted solvothermal synthesis and characterization of zinc oxide nanosheets (ZnO-NSs) and their application for the removal of Cr6+ ion from aqueous solution. The morphological investigations by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the high-density growth of nanosheets with the typical sizes in the range of 145.8–320.25 nm. The typical surface area of the synthesized ZnO-NSs, observed by Brunauer-Emmett-Teller (BET), was found to be 948 m2/g. The synthesized ZnO-NSs were used as efficient absorbent for the removal of Cr6+ ion from aqueous solution. Various parameters such as pH, contact time, amount of adsorbate and adsorbent on the removal efficiency of Cr6+ ion was optimized and presented in this paper. At optimized conditions, the highest value for removal was 87.1% at pH = 2 while the calculated maximum adsorption capacity was ~87.37 mg/g. The adsorption isotherm data were found to be best fitted to Temkin adsorption isotherm and the adsorption process followed the pseudo-first-order kinetics. Furthermore, the toxicity of ZnO-NSs were also examined against fibroblast cells, which show favorable results and proved that it can be used for wastewater treatment.