We report the synthesis and theoretical study of two new colorimetric chemosensors with special selectivity and sensitivity to Ni2+ and Cu2+ ions over other metal cations in the CH3CN/H2O solution. Compounds (E)-4-((2-nitrophenyl)diazenyl)-N,N-bis(pyridin-2-ylmethyl)aniline (A) and (E)-4-((3-nitrophenyl)diazenyl)-N,N-bis(pyridin-2-ylmethyl)aniline (B) exhibited a drastic color change from yellow to colorless, which allows the detection of the mentioned metal cations through different techniques.
The interaction of sensors with these metal ions induced a new absorption band with a hypsochromic shift to the characteristic signal of the free sensors. A theoretical study via time-dependent density functional theory (TD-DFT) was performed. This method has enabled us to reproduce the hypsochromic shift in the maximum UV–vis absorption band and explain the selective sensing of the ions. For all of the systems studied, the absorption band is characterized by a π → π* transition centered in the ligand. Instead of Ni2+ and Cu2+ ions, the transition is set toward the σ* molecular orbital with a strong contribution of the 3dx2-y2 transition (π → 3dx2-y2). These absorptions imply a ligand-to-metal charge transfer (LMCT) mechanism that results in the hypsochromic shift in the absorption band of these systems.
Oxides for new-generation electronics
New Sensitive and Selective Chemical Sensors for Ni2+ and Cu2+ Ions: Insights into the Sensing Mechanism through DFT Methods
Manuel A. Treto-Suárez, Jorge Tapia, Yoan Hidalgo-Rosa, Dayan Páez-Hernández, Elies Molins, Ximena Zarate*, and Eduardo Schott*
When illuminating a non-centrosymmetric material with light of energy higher than the bandgap, a net current appears because the electrons do not see the same electronic environment in one direction and the opposite direction, thus they hold a net momentum. This is the bulk photovoltaic effect (BPE), which depends on the light polarization.
Spin-charge conversion requires materials with a large spin-orbit coupling, which is typically obtained in heavy metal (Pt, etc.) ions. Here we demonstrate spin pumping across interfaces between metallic SrVO3, where V is a 3d1 ion, epitaxial thin films and ferromagnetic Ni80Fe20.
Building on recent developments in electronic-structure methods, we define and calculate the flexoelectric response of two-dimensional (2D) materials fully from first principles. In particular, we show that the open-circuit voltage response to a flexural deformation is a fundamental linear-response property of the crystal that can be calculated within the primitive unit cell of the flat configuration.
We present a complete structural study of the successive phase transitions observed in the YBaMn2O6 compound with the layered ordering of cations on the perovskite A-site. We have combined synchrotron radiation X-ray powder diffraction and symmetry-adapted mode analysis to describe the distorted structures as pseudosymmetric with respect to the parent tetragonal structure.
The development of new synthetic methodologies of perovskite oxynitrides is challenging but necessary for the search of new compounds and the investigation of new properties. Here, we report a new method of preparation of the perovskite LaTaON2 that has been investigated as a pigment and photocatalyst for water splitting.