A STUDY OF THE CHARACTERISTICS AND SELECTION OF DOPED MATERIALS FOR NIO TO OPTIMIZE GAS SENSING

Gas sensing of hazardous has become a great challenge for several decades. Recently, technical and industrial advancements uninterruptedly produce the emission of hazardous and poisonous gases that are detrimental to human life as a consequence gas detecting devices that are extremely sensitive and selective to such gases are in a high demand. Presently, gas sensors based on p-type NiO are attracting more attention, because of its outstanding repeatability, high specific surface areas, strong sensitivity, cheap cost and environmental friendly. Herein, we evaluated the various production techniques on p-type NiO nanostructures and their use as gas sensors. The basic gas sensing process linked to the p-type NiO is briefly described. The impacts of noble metals, transition metals, and transition metal dichalcogenide and phosphors materials on the NiO gas sensing performance are also examined in depth. With various level of doping, heterostructure NiO depicts improved sensing performance for gases like HCHO, NH3, NO2, C2H5OH and H2. The arrangement of different semiconductor metal oxides to create heterostructures which further enhance the selectivity and sensitivity of the sensing parameters is also addressed. Heterostructure NiO has enhanced sensing capability for gases such as HCHO, NH3, NO2, C2H5OH, and H2 with varying levels of doping. There are many literatures on heterostructures linked to NiO based sensor significantly in last decade. The current work will aid researchers in the selection of doped materials for NiO gas sensors in order to enhance sensitivity.

Predicting thermoelectric properties from chemical formula with explicitly identifying dopant effects

Dopants play an important role in synthesizing materials to improve target materials properties or stabilize the materials. In particular, the dopants are essential to improve thermoelectic performances of the materials. However, existing machine learning methods cannot accurately predict the materials properties of doped materials due to severely nonlinear relations with their materials properties. Here, we propose a unified architecture of neural networks, called DopNet, to accurately predict the materials properties of the doped materials. DopNet identifies the effects of the dopants by explicitly and independently embedding the host materials and the dopants. In our evaluations, DopNet outperformed existing machine learning methods in predicting experimentally measured thermoelectric properties, and the error of DopNet in predicting a figure of merit (ZT) was 0.06 in mean absolute error. In particular, DopNet was significantly effective in an extrapolation problem that predicts ZTs of unknown materials, which is a key task to discover novel thermoelectric materials.

Rare Earths Doped Materials

Тhe properties of the Rare Earth Elements allow a wide range of applications in optoelectronics, fiber amplifiers, solid-state lasers, telecommunications, biosensing, and photocatalysis, just to mention a few [...]

Quenching of the Eu3+ Luminescence by Cu2+ Ions in the Nanosized Hydroxyapatite Designed for Future Bio-Detection

The hydroxyapatite nanopowders of the Eu3+-doped, Cu2+-doped, and Eu3+/Cu2+-co-doped Ca10(PO4)6(OH)2 were prepared by a microwave-assisted hydrothermal method. The structural and morphological properties of the products were investigated by X-ray powder diffraction (XRD), transmission electron microscopy techniques (TEM), and infrared spectroscopy (FT-IR). The average crystal size and the unit cell parameters were calculated by a Rietveld refinement tool. The absorption, emission excitation, emission, and luminescence decay time were recorded and studied in detail. The 5D0 → 7F2 transition is the most intense transition. The Eu3+ ions occupied two independent crystallographic sites in these materials exhibited in emission spectra: one Ca(1) site with C3 symmetry and one Ca(2) sites with Cs symmetry. The Eu3+ emission is strongly quenched by Cu2+ ions, and the luminescence decay time is much shorter in the case of Eu3+/Cu2+ co-doped materials than in Eu3+-doped materials. The luminescence quenching mechanism as well as the schematic energy level diagram showing the Eu3+ emission quenching mechanism using Cu2+ ions are proposed. The electron paramagnetic resonance (EPR) technique revealed the existence of at least two different coordination environments for copper(II) ion.