Physicochemical investigation of shrimp fossils from the Romualdo and Ipubi formations (Araripe Basin)

The Ipubi and Romualdo Formations are Cretaceous units of the Araripe Basin (Santana Group). The first and most ancient was deposited in a lake environment, and some fossils were preserved in shales deposited under blackish conditions. The second was deposited in a marine environment, preserving a rich paleontological content in calcareous concretions. Considering that these two environments preserved their fossils under different processes, in this work we investigated the chemical composition of two fossilized specimens, one from each of the studied stratigraphic units, and compared them using vibrational spectroscopy techniques (Raman and IR), X-ray diffraction and large-field energy-dispersive X-ray spectroscopy (EDS) mappings. Calcite was observed as the dominant phase and carbon was observed in the fossils as a byproduct of the decomposition. The preservation of hydroxide calcium phosphate (Ca10(PO4)6(OH)2, hydroxyapatite) was observed in both fossils. In addition, it was observed that there was a smaller amount of pyrite (pyritization) in the Romualdo Formation sample than in the Ipubi one. Large-field EDS measurements showed the major presence of the chemical elements calcium, oxygen, iron, aluminum and fluoride in the Ipubi fossil, indicating a greater influence of inorganic processes in its fossilization. Our results also suggest that the Romualdo Formation fossilization process involved the substitution of the hydroxyl group by fluorine, providing durability to the fossils

Photoelectrodes with titanate nanotubes sensitized by mesoporphyrin derivative from cashew nut shell

Titanate nanotubes (TiNTs) with the chemical composition Na2Ti3O7.nH2O (NaTiNT) were obtained througha hydrothermal method in highly alkaline medium. Protonated titanates nanotubes (H-TiNTs), with the compositionH2Ti3O7.nH2O, were prepared by ion exchange reaction through a suspension of Na2Ti3O7nH2Onanotubes in HCl medium, promoting the exchange of Na+ ions by H+. Both Na2Ti3O7.nH2O andH2Ti3O7.nH2O products, as well the TiO2 used as raw material for the nanotubes processing, were used asstarting material for the solar cells photoelectrodes sensitized using mesoporphyrin extracted from a precursorof cashew nut shell. Exposing the NaTiNT sample to solar radiation of 1258 W/m2, a short-circuit currentdensity (ISC) of 13 A/cm2 and an open-circuit voltage (VOC) of 370 mV were registered and, a current densityof 7.6 A/cm2 and a voltage of 256 mV for the prototype cell based on H-TiNTs. A current density of 1.1A/cm2 and an open-circuit voltage of 1.6 mV were obtained for the cell using TiO2 as electrode.Keywords: Titanate Nanotubes. Ionic exchange. Mesoporphyrin. Dye-sensitized solar cell

Structural and vibrational properties of the titanate nanotubes e nanoribbons

Este trabalho relata o estudo das propriedades estruturais, morfolÃgicas e vibracionais dos nanotubos e das nanofitas de titanato obtidos a partir do tratamento hidrotÃrmico de TiO2 em soluÃÃo aquosa de NaOH. As propriedades fÃsicas destas nanoestruturas, como preparadas e tratadas termicamente, sÃo discutidas e comparadas com seus similares sÃlidos estendidos (Na2Ti3O7 e Na2Ti6O13). Os resultados obtidos por microscopia eletrÃnica de transmissÃo, microscopia eletrÃnica de varredura, espectroscopia de emissÃo atÃmica, espectroscopia de energia dispersiva de raios-X, difraÃÃo de raios-X, espectroscopia de absorÃÃo no infravermelho com transformada de Fourier e espectroscopia Raman permitem concluir que as camadas (paredes ou lamelas) de nanotubos e nanofitas de titanato, como preparados, sÃo isoestrutural ao composto lamelar Na2Ti3O7. Nos nanotubos de titanato as ligaÃÃes quÃmicas sÃo deformadas por causa da curvatura das paredes, enquanto nas nanofitas de titanato as camadas apresentam apenas a desordem estrutural causada pelo efeito do tamanho. O comportamento tÃrmico das nanofitas de titanato à similar ao relatado na literatura para os nanotubos de titanatos, onde mudanÃas estruturais e morfolÃgicas, com o aumento da temperatura, sÃo observadas e indicam que as nanofitas quando submetidas a altas temperaturas mudam sua morfologia para grandes bastÃes (sÃlido estendido) com uma mistura das fases Na2Ti3O7 e Na2Ti6O13. Este resultado à similar ao comportamento do Na2Ti3O7, sÃlido estendido, quando tratado termicamente. Concluimos que os nanotubos e as nanofitas de titanato tÃm a mesma composiÃÃo quÃmica Na{2-x}HxTi3O7.nH2O (0<x<2). Neste trabalho mostramos que a espectroscopia Raman pode ser usada para uma fÃcil e rÃpida identificaÃÃo das mudanÃas morfolÃgicas e estruturais das nanoestruturas de titanato. Estudamos tambÃm a sÃntese, caracterizaÃÃo e aplicaÃÃo dos nanotubos de titanato trocados com Ce4+. As propriedades fÃsico-quÃmicas destes nanotubos sÃo discutidas em comparaÃÃo com os nanotubos de titanato de sÃdio puros. As imagens de microscopia eletrÃnica de transmissÃo mostraram que os nanotubos de titanato trocados com Ce4+ tÃm a mesma morfologia dos nanotubos de titanato de sÃdio e suas paredes externas sÃo decoradas com nanopartÃculas de Ãxido de cÃrio. O mecanismo de formaÃÃo das nanopartÃculas à baseado na precipitaÃÃo do Ãon CÃrio na superfÃcie do nanotubo. NÃs observamos um deslocamento do limiar da banda de absorÃÃo em direÃÃo à regiÃo visÃvel do espectro eletromagnÃtico que foi atribuÃda aos efeitos da adiÃÃo ou intercalaÃÃo do Ce4+ e/ou presenÃa das nanopartÃculas de CeO2 decorando a superfÃcie dos nanotubos. Um deslocamento para o vermelho ("red shift") dos modos vibracionais associados com a interaÃÃo Ãon metÃlico - oxigÃnio foi observado e identificado como sendo devido ao efeito da intercalaÃÃo de Ce4+ à estrutura, como tambÃm devido à ancoragem das nanopartÃculas de CeO2 Ãs paredes dos nanotubos. NÃs mostramos que este sistema hÃbrido à promissor para aplicaÃÃes em fotocatÃlise usando a regiÃo azul do espectro eletromagnÃtico. Essa aplicaÃÃo foi demonstrada para a fotodegradaÃÃo do corante tÃxtil azul reativo 19 usando luz visÃvel.This work reports a study on the structural, morphological and vibrational properties of titanate nanotubes and nanoribbons obtained from hydrothermal treatment of TiO$_2$ in aqueous NaOH solutions. The physical properties of these as-synthesized and heat-treated nanostructures are discussed in comparison with their bulk (Na$_2$Ti$_3$O$_7$ and Na$_2$Ti$_6$O$_{13}$) counterparts. The results obtained from transmission electron microscopy, scanning electron microscopy, atomic emission spectroscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, infrared and Raman spectroscopies allowed us to conclude that the layers of both as-synthesized titanates nanotubes and nanoribbons are isostructural to the Na$_2$Ti$_3$O$_7$ lamellar compound. In the titanate nanotubes the chemical bonds are deformed because of the curvature of walls while in the titanates nanoribbons the layers present structural disorder by size effects. The thermal behavior of titanate nanoribbons is similar to those reported in literature for titanate nanotubes, where structural and morphological changes with increases of temperature are observed and indicated that the nanoribbons, at high temperatures, change to bulk with a phase mixing of Na$_2$Ti$_3$O$_7$ and Na$_2$Ti$_6$O$_{13}$. This is similar to what happens with the bulk Na$_2$Ti$_3$O$_7$ when thermally treated. Thus, we conclude that the chemical composition of both the titanate nanotubes and the titanate nanoribbons is the same, Na$_{2-x}$H$_x$Ti$_3$O$_7$.nH$_2$O (0$leq$x$leq$2). Also, we suggest that Raman spectroscopy can be used for an easy and quick identification of both morphology and structure changes of the nanosized titanates. Furthermore, in this work we report the synthesis, characterization and application of Ce ion-exchanged titanate nanotubes. The physicochemical properties of these nanotubes are discussed in comparison with their pure titanate nanotube counterparts. The transmission electron microscope images showed that the Ce ion-exchanged titanate nanotubes have the same morphology of the pristine nanotubes and their external walls are decorated with cerium oxide nanoparticles. The mechanism of nanoparticle formation is based on the precipitation of Ce ion at the nanotube surface. We observed a shift of the absorption band edge towards the visible region that is attributed to the effects of Ce$^{4+}$ addition (intercalation) and/or the presence of CeO$_2$ nanoparticles decorating the nanotubes surfaces. A red shift of vibrational modes associated with metal ion - oxygen interaction was observed and identified as being due to the effect of Ce addition to the lattice as well as the anchoring of CeO$_2$ nanoparticles to the nanotube wall. We show that this hybrid system is promising for applications in photocatalysis using the blue region of the electromagnetic spectrum and this was demonstrated for photodegradation of reactive blue 19 textile dye using visible light ilumination

Vibrational and structural properties of TiO2 nanocrystals dispersed into porous glass matrix

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoMateriais nanoestruturados sÃo objetos de intensa investigaÃÃo devido as suas notÃveis propriedades fÃsicas e quÃmicas e quando comparados em suas formas âbulk". Os fenÃmenos induzidos pela reduÃÃo do tamanho sÃo interessantes por si prÃprio e abrem oportunidades Ãnicas, nÃo somente para o uso dessas propriedades em vÃrias aplicaÃÃes mÃs tambÃm para o aprimoramento da tecnologia corrente. Os sistemas quÃmicos integrados (SQI) sÃo um conjunto à parte com complexidade prÃpria e diferentes possibilidades de combinaÃÃes de nanosistemas para obtenÃÃo de materiais com uma funcionalidade desejada. Por exemplo, o crescimento de nanocristais nas cavidades de um hospedeiro poroso à um SQI atrativo, pois o ambiente dos poros pode ser usado como nanoreatores. Da mesma forma que o sistema pode ser muito promissor para catÃlise à tambÃm importante no estudo das propriedades induzidas pelo tamanho do material hÃspede. Neste trabalho, estudamos as propriedades estruturais e vibracionais de nanocristais de TiO2 dispersos dentro dos poros do vidro vycor. Foram estudados nanocristais de TiO2 com tamanhos variando de 3-20 nm na fase anatÃsio. O tamanho dos nanocristais foi monitorado atravÃs de microscopia de transmissÃo eletrÃnica e espalhamento Raman. O modo Eg, com freqÃÃncia em torno de 144 cm-1, experimenta um deslocamento e alargamento de seu pico com a diminuiÃÃo do tamanho do nanocristal. Este fenÃmeno à atribuÃdo ao efeito induzido pelo tamanho e analisamos os resultados experimentais com base no modelo de confinamento de fÃnons. Quando o tamanho do nanocristal à pequeno, a regra de seleÃÃo q &#8776; 0 no espalhamento Raman de primeira ordem à relaxada e fÃnons com grandes valores de q contribuem para a intensidade do pico Raman. A freqÃÃncia do pico Raman à medida que o tamanho diminui segue o mesmo comportamento da relaÃÃo de dispersÃo de fÃnons para o TiO2 âbulk".Nanostructured materials are the subject of intense investigation due to their remarkable properties as compared their bulk counterparts. The size-induced phenomena are interesting their own and open unique opportunities not only for using these properties in novel applications but also for improving the current technology. In this scenario integrated chemical systems (ICS) are set apart owing their complexity and the possibility ofcombining diferent nanosystems for getting materials with a designed functionality. For instance, nanocrystal growth in the cavities of a porous host is an attractive ICS because the porous is a restricted environment that can be used as nanoreactors. Besides the such system is very promising for catalysis it also important for studying the size-induced properties of the guest material as well. In this work we report the study of vibrational and structural properties of TiO2 nanocrystals dispersed into a porous vycor glass. We have obtained very small TiO2 nanocrystals in the anatase form. The nanocrystal size is controlled via the mass increment only thus preventing the growth through the coalescence process. The nanocrystal size as monitored through transmission electron microscope and Raman scattering. The Eg lowest frequency mode experiences an upshift and becomes broader as the nanocrystal size decreases. This phenomena is attributed to a size-induced eÂect and we analyzed it based on a phonon conÂnement model. As the nanocrystal size gets smaller the q = 0 selection rule is relaxed and the phonon conÂnement involves large q values contribute to the Raman intensity. The frequency follows the same trend of the phonon dispersion relation for the TiO2 bulk as the nanocrystal size decreases

CARBONIZAÇÃO DE BIOMASSA DE BABAÇU E SUAS POTENCIAIS APLICAÇÕES: UMA PROSPECÇÃO TECNOLÓGICA

Recentemente, agregar valor à biomassa, em geral, tem sido um aspecto importante da pesquisa, pois fornece uma variedade de benefícios sócio-econômicos. O babaçu (Orbignya phalerata) é uma das espécies vegetais nativas comuns no centro-norte do território brasileiro. Este fruto apresenta relevante potencial tecnológico, sobretudo somado a  uma das tecnicas mais promissoras de conversão de biomassa, a carbonização e dessa forma, a biomassa adquire maior valor agregado. O objetivo desse estudo é realizar um rastreamento das pesquisas já desenvolvidas e com resultados patenteados, analisando pesquisas com as palavras-chave: carbonização, carbonização hidrotérmica, babaçu (nome científico: Orbignya phalerata), carvão, biomassa e suas combinações. A prospecção foi realizada no Instituto Nacional de Propriedade Industrial do Brasil (INPI) e Derwent Innovations Index, e para a busca de artigos, na base de periódicos Google Scholar (Google Acadêmico) e Scopus. Os resultados obtidos na prospecção para o INPI, foram insatisfatórios, em relação ao Derwent Innovations Index. Como conclusão, observa-se que ainda são necessárias mais pesquisas que levem a um maior entendimento e descoberta de novas tecnologias de utilização desta biomassa e suas aplicações, principalmente no Brasil.</p

New data on Beurlenia araripensis Martins-Neto & Mezzalira, 1991, a lacustrine shrimp from Crato Formation, and its morphological variations based on the shape and the number of rostral spines.

Fossil freshwater carideans are very rare worldwide. Here, we present new taxonomic remarks about Beurlenia araripensis from the Early Cretaceous laminated limestones of the Crato Formation, Araripe Basin, northeastern Brazil. We analyzed five fossil samples, testing the morphological variations such as, rostrum with 5 to 14 supra-rostral spines and 2 to 3 sub-rostral spines, which appears as serrate for Caridea. This variation demonstrates a morphologic plasticity also seen in extant species of the group, such as those of the genera Macrobrachium and Palaemon

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 20 K. 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 the combination of three different polymers polycaprolactone (PCL), polyethylene glycol (PEG), and gelatin methacryloyl (GelMA), and their potential bactericidal activity against three different bacteria Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. 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. Moreover, they were able to significantly reduce gram-positive, negative, and MRSA bacteria mainly after UV photocrosslinking (PCL:PEG:GelMa-UV). Furthermore, we performed a series of study for gaining a better mechanistic understanding of the scaffolds bactericidal activity through protein adsorption study and analysis of the reactive oxygen species (ROS) levels. Furthermore, the in vivo subcutaneous implantation performed in rats confirmed the biocompatibility of our designed scaffolds