The Raman spectra were obtained using a Bruker SENTERRA spectrometer, solid state laser excitation operating at a wavelength of 785 nm and a CCD detector. The measurements were made with resolution of 3–5 cm−1, aperture of 25 × 1000 μm and over a spectral range of 1780 to 390 cm−1. The laser power at the exit of the laser was 50 mW and 10 accumulations were made with an acquisition time of 50 s each. These parameters were previously adjusted to obtain the best signal-to-noise ratio without altering the physical and chemical integrity of the samples. The spectra obtained were treated with OPUS 7.0 and Origin 8 software from Bruker and a baseline correction was applied.
SEM measurements were performed in a scanning electron microscope combined with an Energy dispersive X-ray spectroscopy (EDS) Hitachi model TM 3000 compact instrument, with a smoothing magnification of 15x up to 30,000x (digital zoom: 2x and 4x), which allows topographic images to be obtained with a large depth of focus. No sample preparation was required for the analyses, and each one of the samples were fixed in a specific metallic sampler from the SEM equipment.
SEM measurements were performed in a scanning electron microscope combined with an Energy dispersive X-ray spectroscopy (EDS) Hitachi model TM 3000 compact instrument, with a smoothing magnification of 15x up to 30,000x (digital zoom: 2x and 4x), which allows topographic images to be obtained with a large depth of focus. No sample preparation was required for the analyses, and each one of the samples were fixed in a specific metallic sampler from the SEM equipment.