The influence of Fe doping on the structural, magnetic and optical properties of nanocrystalline ZnO particles

We report the results of an investigation of Fe-doped nanocrystalline ZnO particles synthesized using the co-precipitation method with doping concentrations from 5 up to 31 at%. To understand how the dopant influenced the structural, magnetic and optical properties of nanocrystalline ZnO particles, X-ray diffraction, energy dispersive X-ray spectroscopy, infrared absorption spectroscopy, UV-vis spectroscopy, electron spin resonance spectroscopy (ESR) and vibrating sample magnetometer were employed. From the analysis of X-ray diffraction, our Fe-doped nanocrystalline ZnO particles are identified as having the wurtzite crystal structure and the unit cell volume increases with increasing doping concentrations. However, impurity phases are observed for Fe contents higher than 21 at%. Sample structures were further studied by infrared spectra, from which a broad and strong absorption band in the range of 400-700 cm⁻¹ and -OH stretching vibrational mode at approximately 3400 cm⁻¹ were observed. Ultraviolet-visible measurements showed a decrease in the energy gap with increasing Fe content, probably due to an increase in the lattice parameters. Magnetic measurements showed a ferromagnetic behavior for all samples. ESR results indicate the presence of Fe in both valence states Fe²⁺ and Fe³⁺.     

Accessing π-expanded heterocyclics beyond dibenzothiophene: Syntheses and properties of phenanthrothiophenes

A series of phenanthrothiophenes are designed and synthesized from polyarylthiophenes through regioselective Scholl reactions in one step using iron chloride as catalyst. The molecular structures of these heteroarenes displayed multiple twisted fjords, which perturb the shapes of the polycyclic frameworks to pack in slipped to near-perfect face-to-face styles in parallel or antiparallel packings. Field-effect transistor devices using single crystals of 6,12-difluorodiphenanthro[9, 10-b:9′, 10′]thiophene gave a hole mobility of 0.22 cm² V⁻¹ s⁻¹.