Bartolomeu C. Viana

Spectroscopic analysis and X-ray diffraction of trunk fossils from the Parnaíba Basin, Northeast Brazil.

The Parnaiba Sedimentary Basin is of the Paleozoic age and is located in Northeast Brazil, covering the states of Piauí, Maranhão and Tocantins and a small part of Ceará and Pará. In this work we applied several chemical analytical techniques to characterize trunk fossils found in the Parnaíba Sedimentary Basin, collected from four different sites, and discuss their fossilization process. We performed a study of the trunk fossils through X-ray diffraction, energy dispersive spectroscopy, infrared and Raman spectroscopy. The analysis allow us to identify the different compositions which are present in the trunk fossils: kaolinite (Al2Si2O5(OH)4), hematite (Fe2O3) and quartz (SiO2). Based in these results we were able to identify that the main fossilization mechanism of the trunk fossil was silicification. Furthermore, through Raman spectroscopy, we have observed the presence of carbonaceous materials in the Permian fossils, as evidenced by the D and G Raman bands. The relative intensities and bandwidths of the D and G bands indicated that the carbon has a low crystallinity. Thus, most of trunk fossils analyzed were permineralized and not petrified, because there is the presence of carbon that characterizes the partial decomposition of the organic matter in some trunks.

Photoluminescence Enhancement of Titanate Nanotubes by Insertion of Rare Earth Ions in Their Interlayer Spaces

The optical properties of titanate nanotubes (TiNts) intercalated with rare earths (RE) ions were intensively investigated in this study. To prepare the nanomaterials, sodium titanate nanotubes (Na-TiNts) were submitted to ion exchange reactions with different rare earth elements (RE: Pr3+, Er3+, Nd3+, and Yb3+). To the best of our knowledge, it is the first time that these RE-TiNts were synthesized. All samples were characterized by Raman spectroscopy, X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). Furthermore, the optical properties were examined using photoluminescence spectroscopy (PL) and UV-Vis-NIR absorption spectroscopy. The PL intensity (visible range) of the RE-TiNt samples showed a strong dependence when the temperature was decreased down to 20źK. This PL enhancement probably was promoted by electronic modifications in titanate layer band gap and/or interface charge transfers due to RE ions intercalation.

Understanding the impact of crosslinked PCL/PEG/GelMA electrospun nanofibers on bactericidal activity

Herein, we report the design of electrospun ultrathin fibers based on polycaprolactone (PCL), polyethylene glycol (PEG), and gelatin methacryloyl (GelMA), and their potential bactericidal activity against three different bacteria Staphylococcus aureus, Pseudomonas aeruginosa, and Methicillin-resistant Staphylococcus aureus (MRSA). We evaluated the morphology, chemical structure and wettability before and after UV photocrosslinking of the produced scaffolds. Results showed that the developed scaffolds presented hydrophilic properties after PEG and GelMA incorporation. Our developed scaffolds were thus able to significantly reduce gram-positive, negative, and MRSA bacteria. Furthermore, we performed a series of study for better mechanistic understanding of the scaffolds bactericidal activity through protein adsorption study and analysis of the reactive oxygen species (ROS) levels. In summary, we have demonstrated the design and generation of electrospun fibers with improved hydrophilicity and efficient bactericidal activity without the association of any antibiotics.

Characterization of the inclusion complex of the essential oil of Lantana camara L. and β-cyclodextrin by vibrational spectroscopy, GC–MS, and X-ray diffraction

AbstractThe genus Lantana is widely used in folk medicine because its essential oil has antibacterial, antifungal and repellent activity. However, its thermal instability and low solubility in water reduce its technological application. In this work, an inclusion complex was prepared consisting of the essential oil of Latana camara L. (LCEO) and β-cyclodextrin (β-CD). The complex was characterizated by vibrational spectroscopy (Raman and FTIR spectroscopy), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The optimization of the ratio of the LCEO and β-CD in the inclusion complex was determined by gas chromatography coupled to mass spectrometry (GC–MS); it was inferred that the ratio of guest–host = 6:94 (m:m) was the optimal ratio. Shifts in some peak positions of the vibrations modes in Raman spectra of L. camara and β-CD provided clearer and better evidence of inclusion complex formation than infrared spectroscopy did. Results of DSC and XRD characterization of inclusion complex are in good agreement with Raman results.Graphical AbstractFormation of the inclusion complex between β-CD and LCEO as well as its characterization by different analytical techniques such as infrared spectroscopy and Raman spectroscopy, DSC, XRD and GC–MS.

Phonon confinement model to measure the average sizes of anatase nanoparticles synthesized by a solvothermal method using H2O2

Universidade Federal do Piaui Centro de Ciencias da Natureza Departamento de Quimica Departamento de Fisica LIMAV