Magnetic and Electronic Properties of Sr Doped Infinite-Layer NdNiO2 Supercell: A Screened Hybrid Density Functional Study.

To understand the influence of doping Sr atoms on the structural, magnetic, and electronic properties of the infinite-layer NdSrNiO2, we carried out the screened hybrid density functional study on the Nd9-nSrnNi9O18 (n = 0-2) unit cells. Geometries, substitution energies, magnetic moments, spin densities, atom- and lm-projected partial density of states (PDOS), spin-polarized band structures, and the average Bader charges were studied. It showed that the total magnetic moments of the Nd9Ni9O18 and Nd8SrNi9O18 unit cells are 37.4 and 24.9 emu g-1, respectively. They are decreased to 12.6 and 4.2 emu g-1 for the Nd7Sr2Ni9O18-Dia and Nd7Sr2Ni9O18-Par unit cells. The spin density distributions demonstrated that magnetic disordering of the Ni atoms results in the magnetism decrease. The spin-polarized band structures indicated that the symmetry of the spin-up and spin-down energy bands around the Fermi levels also influence the total magnetic moments. Atom- and lm-projected PDOS as well as the band structures revealed that Ni(dx2-y2) is the main orbital intersecting the Fermi level. As a whole, electrons of Sr atoms tend to locate locally and hybridize weakly with the O atoms. They primarily help to build the infinite-layer structures, and influence the electronic structure near the Fermi level indirectly.

A simple paper-based sensor fabricated by selective wet etching of silanized filter paper using a paper mask.

We developed a novel strategy for fabrication of microfluidic paper-based analytical devices (µPADs) by selective wet etching of hydrophobic filter paper using a paper mask having a specific design. The fabrication process consists of two steps. First, the hydrophilic filter paper was patterned hydrophobic by using trimethoxyoctadecylsilane (TMOS) solution as the patterning agent. Next, a paper mask penetrated with NaOH solution (containing 30% glycerol) was aligned onto the hydrophobic filter paper, allowing the etching of the silanized filter paper by the etching reagent. The masked region turned highly hydrophilic whereas the unmasked region remains highly hydrophobic. Thus, hydrophilic channels, reservoirs, and detection zones were generated and delimited by the hydrophobic barriers. The effects of some factors including TMOS concentration, etching temperature, etching time, and NaOH concentration on fabrication of µPAD were studied. Being free of any expensive equipment, metal mask and expensive reagents, this rapid, simple, and cost-effective method could be used to fabricate µPAD by untrained personnel with minimum cost. A flower-shaped µPAD fabricated by this presented method was applied to the glucose assay in artificial urine samples with good performance, indicating its feasibility as a quantitative analysis device. We believe that this method would be very attractive to the development of simple microfluidic devices for point-of-care applications in clinical diagnostics, food safety, and environmental protection.