Rosana F. Gonçalves

Functional Nanomaterials for Applications in Energy Storage and Conversion

In addition to economical concerns, the energy production based on fossil fuels provokes serious environmental problems as a consequence of pollutant emissions. Hydrocarbons and oxides of nitrogen, carbon, and sulfur have demonstrated to be leading factors in the occurrence of phenomena with a high impact in the environment such as photochemical smog, global warming, acid rain, and so on. These environmental problems have led to new technologies in the fields of energy production and storage for a sustainable development in order to a reduction of pollutant emissions from fossil fuel combustion.

Novel Gd(OH)3, GdOOH and Gd2O3 Nanorods: Microwave-Assisted Hydrothermal Synthesis and Optical Properties

We present a study of the controlled synthesis and optical properties of single-crystals Gd(OH)3, GdOOH and Gd2O3 nanorods. In this work, Gd(OH)3 nanorods were synthesized by a simple and fast microwave-assisted hydrothermal method. This process combined with the thermal decomposition oxidation of Gd(OH)3 nanorods as precursors enabled the preparation of single-crystalline GdOOH and Gd2O3 structures with well-defined morphology at low temperatures. The crystal structure dependence on the optical properties was investigated. We observed a green shift effect on the photoluminescence (PL) emission spectra from Gd(OH)3 to Gd2O3 nanorods, which can be attributed to different types of surface defects, as well as intrinsic properties that contribute significantly to the modified PL behavior.

Structure, Morphology, and Optical Properties of (Cal(1-3x)Eu(2x)) WO4 Microcrystals

In this letter, we report the efficient, surfactant-free, microwave-hydrothermal method of synthesizing calcium europium tungstate [(Ca1−3xEu2x)WO4, x = 0, 0.05, 0.01, 0.02, and 0.04] microcrystals. The structure and morphology were investigated using X-ray diffraction (XRD), Fourier-transform Raman (FT-Raman) spectroscopy, and field emission scanning electron microscopy (FE-SEM). XRD patterns and FT-Raman spectra indicated that all (Ca1−3xEu2x)WO4 microcrystals has a scheelite-type tetragonal structure. FE-SEM images revealed that the Eu3+ ions systematically affect the crystal shape and that there are two different types of superstructures: rice- and dumbbell-like microcrystals. The photoluminescence emission of the doped microcrystals changed relative to that of pure CaWO4 owing to the presence of defects and new energy levels associated with the Eu3+ content, which promotes the appearance of intermediate electronic levels in the band gap.