Electromagnetic properties of Carbon-Graphene Xerogel, Graphite and Ni-Zn Ferrite composites in polystyrene matrix in the X-Band (8.2 – 12.4 GHz)

The electromagnetic properties of Carbon-Graphene Xerogel (CGX), Flaky graphite (GR) and Nickel-Zinc ferrite (FeNiZn) composites in polystyrene (PS) matrix were studied in the X-Band range (8.2 – 12.4 GHz). In this work the Expanded Polystyrene (EPS) waste material was processed into polystyrene through the recycling of EPS. The polystyrene obtained was utilized as dielectric matrix, mainly because PS is a wellknown organic polymer that presents low dielectric loss and light weight, which contribute to applications in composites for the aerospace field. In order to produce the final composite specimens, the CGX additive was previously synthesized through a sustainable method that employed the use of waste from the paper and pulp industry (black liquor). Afterwards, the morphological and structural analysis were made through Scanning Electron Microscope (SEM) and Raman Spectrometer, respectively. On the other hand, the magnetic ferrite material, FeNiZn, was obtained for the composite production through calcination, whereas the GR utilized was commercially obtained. It was observed that the increase of CGX and GR influenced on the increase of the Complex Permittivity, and that 10 wt% CGX + 50wt% FeNiZn composite sample demonstrated an absorption peak at 10.5 GHz. The results are relevant concerning the recycling of EPS waste through its use as dielectric matrix, thus developing greener and low-weight composite materials to be used in microwave applications.Keywords: Carbon-Graphene. Composite. Recycling. Polystyrene. Microwave.

Structural and spectroscopic characterization of epiisopiloturine-metal complexes, and anthelmintic activity <i>vs</i>. <i>S. mansoni</i>

<p>Epiisopiloturine (EPI), extracted from leaves of <i>Pilocarpus microphyllus</i>, a plant originally from the Amazon and Savanna regions in Brazil, was described as a potential drug against Schistosomiasis, a neglected severe disease. Herein, EPI was complexed with copper(II) or zinc(II) salts and the isolated species, [Cu(epi)₄](ClO₄)₂ (<b>1</b>) and [Zn(epi)₂Cl₂] (<b>2</b>), were structurally and spectroscopically characterized. By using X-ray diffraction, the crystal structures of both metal complexes were determined, indicating a square pyramidal geometry for copper for <b>1</b> and a tetrahedral environment around zinc for <b>2</b>. EPR spectra of <b>1</b> show a typical tetragonal environment around the central metal ion with some tetrahedral distortion, both in the solid state and in frozen acetonitrile solution, in accordance with crystallographic data. For <b>2</b>, NMR spectra have bands consistent with a tetrahedral species in solid state or in DMSO-d₆ solution. These spectroscopic characterization data were further supported by Density Functional Theory calculations, showing that these metal complexes are also stable in solution. Those metal complexes were tested against adult worms of <i>Schistosoma mansoni</i>, in comparison to the free alkaloid as anthelmintic agent. Coordination with copper(II) improved the alkaloid schistosomicidal properties, while binding to zinc(II) decreased its activity.</p