19 research outputs found
Copper-based charge transfer multiferroics with a configuration
Multiferroics are materials with a coexistence of magnetic and ferroelectric
order allowing the manipulation of magnetism by applications of an electric
field through magnetoelectric coupling effects. Here we propose an idea to
design a class of multiferroics with a configuration using the magnetic
order in copper-oxygen layers appearing in copper oxide high-temperature
superconductors by inducing ferroelectricity. Copper-based charge transfer
multiferroics SnCuO2 and PbCuO2 having the inversion symmetry breaking
polar space group are predicted to be such materials. The active inner s
electrons in Sn and Pb hybridize with O states leading the buckling in
copper-oxygen layers and thus induces ferroelectricity, which is known as the
lone pair mechanism. As a result of the configuration, SnCuO2 and PbCuO2
are charge transfer insulators with the antiferromagnetic ground state of the
moment on Cu retaining some strongly correlated physical properties of parent
compounds of copper oxide high-temperature superconductors. Our work reveals
the possibility of designing multiferroics based on copper oxide
high-temperature superconductors.Comment: 18 pages, 5 figures, 1 tabl
Elemental topological ferroelectrics and polar metals of few-layer materials
Ferroelectricity can exist in elemental phases as a result of charge
transfers between atoms occupying inequivalent Wyckoff positions. We
investigate the emergence of ferroelectricity in two-dimensional elemental
materials with buckled honeycomb lattices. Various multi-bilayer structures
hosting ferroelectricity are designed by stacking-engineering. Ferroelectric
materials candidates formed by group IV and V elements are predicted
theoretically. Ultrathin Bi films show layer-stacking-dependent physical
properties of ferroelectricity, topology, and metallicity. The two-bilayer Bi
film with a polar stacking sequence is found to be an elemental topological
ferroelectric material. Three and four bilayers Bi films with polar structures
are ferroelectric-like elemental polar metals with topological nontrivial edge
states. For Ge and Sn, trivial elemental polar metals are predicted. Our work
reveals the possibility of design two-dimensional elemental topological
ferroelectrics and polar metals by stacking-engineering.Comment: 18 pages, 6 figure
Detection of metal ions in biological systems: A review
Metal ions are widely present in biological systems and participate in many critical biochemical processes such as material transportation, energy conversion, information transmission and metabolic regulation, making them indispensable substance in our body. They can cause health problems when deficiency or excess occurs. To understand various metabolic processes and facilitate diseases diagnosis, it is very important to measure the content and monitor the distribution of metal ions in individual cells, tissues and whole organisms. Among the various methods for metal ion detection, fluorescent sensors with organic dyes have attracted tremendous attention due to many advantages such as high fluorescence quantum yield, facile modification approaches and biocompatibility in addition to operation ease, high sensitivity, fast detection speed, and real-time detection. This review summarizes the recent progress on the detection and imaging of the metal ions in biological systems including Na+, K+, Ca2+, Mg2+, Fe2+/Fe3+, Zn2+, and Cu2+ provides an opinion on remaining challenges to be addressed in this field