Alberto Bolaños

Preparation of Fe3O4 Nanoparticles and Removal of Methylene Blue through Adsorption

In this work, we studied the catalytic activity, structural properties, and behavior of a Fe3O4 magnetic system. The Fe3O4 nanoparticles were prepared by the thermal decomposition method. X-ray diffraction confirmed the presence of a structural Fe3O4 phase, where acicular shape of the grains is shown. Transmission Mossbauer spectroscopy showed a wide distribution of particle sizes at room temperature, some of these present superparamagnetic behavior and are responsible of paramagnetic sites. The hysteresis loops obtained by the use of a vibrating sample magnetometer showed that these nanoparticles exhibit superparamagnetic behavior. However, the cycles present a significant contribution from a ferrimagnetic component at 2 K, which agrees with Mossbauer results. Through scanning electron microscopy, a tendency to the agglomeration of nanoparticles was observed. Nanoparticle activity in the degradation of methylene blue (MB) was studied through fluorescence spectroscopy, finding dye adsorption properties.

CARACTERIZACION ESPECTROSCOPICA Y ANALISIS TERMICO DE LOS COMPLEJOS TRIFENILFOSFINA-RUTENIO(II) CONTENIENDO EL LIGANDO 2,6-DIMETILPIRAZINA Y OTROS N-HETEROCICLICOS

Los complejos sintetizados [RuCl2(2,6-dmpz)2(PPh3)2] y [RuCl2(CO)(N-het)(PPh3)2], (donde N-het son 2,6-dimetilpirazina (2,6-dmpz), Imidazol (Imz) y pirazina (pz)) PPh3 = trifenilfosfina, se sintetizaron a partir de RuCl2(PPh3)3 y un ligando N-heterociclico. Estos complejos se caracterizaron por tecnicas espectroscopicas. Para el complejo [RuCl2(2,6-dmpz)2(PPh3)2] el espectro Ir indica que los cloros se encuentran en posicion cis. El espectro electronico de los complejos presenta intensas bandas de transferencia de carga, asignadas a las transiciones de los orbitales dp llenos del rutenio a los orbitales pp * vacios de los anillos N-heterociclicos. Los estudios termicos de DSC y TGA para los complejos del tipo diclorocarbonil(N-heterociclico)bis(trifenilfosfina)rutenio(II), donde los N-heterociclicos son 2,6-dmpz, Imz y pz, indican que la estabilidad termica de los complejos depende de la nucleofilidad del ligando nitrogenado.