On the Prediction of Well-Ordered Porous Anodic Alumina Films
JOURNAL OF PHYSICAL CHEMISTRY C
Authors: Heinschke, Silvio; Schneider, Joerg J.
Abstract
Porous hexagonal ordered anodic alumina (PAOX) is a long-known porous oxide material. Despite its straightforward experimental approach, a precise understanding of the microscopic processes that lead to the formation of the material and the hexagonal arrangement is only possible with the help of various theoretical models. To the best of our knowledge, there is no model that establishes a theoretical connection between the long-range order of the PAOX system and its physicochemical properties. Therefore, we present in this paper the derivation of a known key figure ("porosity number"), which makes a statement about the pore arrangement with the highest symmetry. By combining this key figure with the abstract concept of entropy production, we enable the microscopic approach to be combined with macroscopic bulk parameters. The theory is based on the most realistic assumption, that the pore habitus can be described based on the inner and outer pore volume of the PAOX cells. Herein, the former is characterized by an ion flow toward the anode and the latter by a flow toward the electrolyte bulk. In addition, the parameters required to describe PAOX growth are reduced to a minimum by showing that within our theoretical model, the growth is only controlled by migration-dependent parameters and that convection and diffusion terms are negligible.
Physicochemical profile of Os (III) complexes with pyrazine derivatives: From solution behavior to DNA binding studies and biological assay
JOURNAL OF MOLECULAR LIQUIDS
Authors: Biedulska, Malgorzata; Krolicka, Aleksandra; Lipinska, Andrea D.; Krychowiak-Masnicka, Marta; Pieranski, Michal; Grabowska, Kinga; Nidzworski, Dawid
Abstract
New series of osmium(III) complexes with pyrazinamide (PZA) and its analogues (PTA, PAOX) were synthesized. The physicochemical features in the solid phase have been identified and confirmed using elemental analysis, mass spectrometry, spectroscopic techniques (FT-IR, H-1 NMR) and thermogravimetric analysis. Based on the studies we confirmed bidentate nature of selected pyrazine derivatives and proven involvement azomethine and amine nitrogen atoms in coordination of metal ion. In particular, complex (2) is more stable than (1) and (3), retaining thermal stability up to 120 degrees C. After one stage dehydration process, the simultaneous destruction of Os(III) complexes architecture was observed with immediate decomposition and elimination of pyrazine derivatives. The acid-base equilibria studies of newly synthesized Os(III) complexes were carried out by combined pH-metric-spectrophotometric and potentiometric titrations in the aqueous solution. Os(III) complexes exhibited rich redox chemistry as demonstrated by cyclic voltammetry. The cyclic voltammograms revealed a well-defined redox couples which correspond to reversible, single-electron Os-III -> Os-II reduction within -1.152 to -1.374 V vs Ag/AgCl and Os-III -> Os-IV oxidation within 0.460-0.831 V vs Ag/AgCl.The binding ability of bioactive ligand and their Os( III) complexes with Calf Thymus DNA (CT-DNA) were investigated by spectrophotometric titration. The observed hypsochromic and bat hodromic shifts with simultaneous hyperchromic effect confirmed mixed mode of interaction with biological target Biological activity of Os(III) complexes, i.e. antimicrobial, cytotoxic, haemolytic and photodynamic potential were studied. (C) 2020 Elsevier B.V. All rights reserved.