ABSTRACT
We conduct ab-initio electronic structure calculations to explore a novel category of magnetic Heusler compounds, comprising solely 3d transition metal atoms and characterized by high spin magnetic moments. Specifically, we focus on Co2YZ Heusler compounds, where Y and Z represent transition metal atoms such that the order of the valence is Co > Y > Z. We show that these compounds exhibit a distinctive region of very low density of minority-spin states at the Fermi level when crystallizing in the L21 lattice structure. The existence of this pseudogap leads most of the studied compounds to a Slater-Pauling-type behavior of their total spin magnetic moment. Co2FeMn is the compound that presents the largest total spin magnetic moment in the unit cell reaching a very large value of 9 µB. Our findings suggest that these compounds are exceptionally promising materials for applications in the realms of spintronics and magnetoelectronics.
ABSTRACT
We report, for the first time, the influence of oxygen vacancies on band structure and local electronic structure of [Formula: see text] (SZO) nanophosphors by combined first principle calculations based on density functional theory and full multiple scattering theory, correlated with experimental results obtained from X-ray absorption and photoluminescence spectroscopies. The band structure analysis from density functional theory revealed the formation of new energy states in the forbidden gap due to introduction of oxygen vacancies in the system, thereby causing disruption in intrinsic symmetry and altering bond lengths in SZO system. These defect states are anticipated as origin of observed photoluminescence in SZO nanophosphors. The experimental X-ray absorption near edge structure (XANES) at Zn and Sr K-edges were successfully imitated by simulated XANES obtained after removing oxygen atoms around Zn and Sr cores, which affirmed the presence and signature of oxygen vacancies on near edge structure.
ABSTRACT
Zinc(ii) phthalocyanine (TEMPO-ZnPc), peripherally functionalized with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) radicals is synthesized and its magneto structural and electrochemical behaviors are investigated. TEMPO-ZnPc shows multi-electron ring based reduction reactions and a TEMPO based oxidation reaction. Spectroelectrochemical measurements support these peak assignments. TEMPO-ZnPc is tested as a homogeneous and heterogeneous ascorbic acid (AA) sensor. Disappearance of TEMPO-ZnPc based reduction processes and the observation of new waves at around 0 and 1.20 V with respect to increasing AA concentration indicate the interaction of TEMPO-ZnPc with AA and usability of the complex as an electrochemical AA sensor. For practical usage as heterogeneous electrocatalysts for AA sensing, a glassy carbon electrode (GCE) is coated with TEMPO-ZnPc (GCE/TEMPO-ZnPc) and this modified electrode is tested as a heterogeneous AA sensor. The redox peak of GCE/TEMPO-ZnPc at 0.81 V decreases the peak current while a new wave is observed at 0.65 V during the titration of the electrolyte with AA. GCE/TEMPO-ZnPc sense AA with 1.75 × 10(-6) mol dm(-3) LOD with a sensitivity of 1.89 × 10(3) A cm mol(-1).
