Tanta Spataru

Sustainable one-pot integration of ZnO nanoparticles into carbon spheres: manipulation of the morphological, optical and electrochemical properties.

ZnO-carbon composite spheres were synthesized via starch hydrothermal carbonization (HTC) in the presence of a soluble zinc salt (acetate), followed by thermal processing under an argon atmosphere. Besides sustainability, the one-pot procedure represents a scalable synthesis of tailored carbon-metal oxide spheres with a structurally-ordered carbon matrix obtained at a relatively low temperature (700 °C). The ability of zinc cations to develop different linkages with starchs hydrophilic functional groups and to act as external nucleators determines an increase in HTC yield; the effect is obvious even in the presence of small concentrations of zinc in the reaction medium (0.005 M), thus providing a way to improve the carbonization process efficiency. It is also shown that zinc content is the control vector of the spherical composites properties: a variation from 0.3 to 4.8 at% not only induces a variation in their size (200 nm-10 μm), interconnectivity (from disperse spheres to necklace-like aggregations), surface area and connected porosity (from micro- to mesoporosity), but also of their electrochemical and white light adsorption and emission features. Since the variation in zinc content is made by a simple adjustment of the raw material concentrations, the functionality of these carbon-based materials can be modulated in a straightforward manner.

1-Picryl-2-phenyl-2-(4-picrylamidophenyl) diazenium betaine and its radical-anion: synthesis and physical properties

The betainic title compound represents a structure with interesting physicochemical properties. These were studied by cyclic voltammetry (CV), electron paramagnetic resonance (EPR) spectroscopy, magnetic and spectral measurements. CV investigations show that the process in acetonitrile corresponds to chemically reversible one-electron reduction leading to the formation of a radical-anion. Chemical reduction of the betaine in dichloromethane with powdered sodium ascorbate in the presence of 15-crown-5 ether yielded a radical-anion (with an EPR spectrum similar to that of 2,2-diphenyl-1-picrylhydrazyl, DPPH). Linnett’s theory explains the similarity of EPR spectra for DPPH and the radical-anion. The title betaine is diamagnetic in solid state. In solution, it shows a weak hypsochromic effect.Graphical abstract