We used here a scanning electron microscopy approach that detected backscattered electrons (BSEs) and X-rays (from ionization processes) along a large-field (LF) scan, applied on a Cretaceous fossil of a shrimp (area ∼280 mm(2)) from the Araripe Sedimentary Basin. High-definition LF images from BSEs and X-rays were essentially generated by assembling thousands of magnified images that covered the whole area of the fossil, thus unveiling morphological and compositional aspects at length scales from micrometers to centimeters. Morphological features of the shrimp such as pleopods, pereopods, and antennae located at near-surface layers (undetected by photography techniques) were unveiled in detail by LF BSE images and in calcium and phosphorus elemental maps (mineralized as hydroxyapatite). LF elemental maps for zinc and sulfur indicated a rare fossilization event observed for the first time in fossils from the Araripe Sedimentary Basin: the mineralization of zinc sulfide interfacing to hydroxyapatite in the fossil. Finally, a dimensional analysis of the phosphorus map led to an important finding: the existence of a fractal characteristic (D = 1.63) for the hydroxyapatite-matrix interface, a result of physical-geological events occurring with spatial scale invariance on the specimen, over millions of years.

We have imaged the particles of Brazilian soils at multiple length scales, from a few microns to millimeters, and soil particle size distributions were calculated with unmatched precision. The analysis included the Amazonian soil "Terra Mulata de Índio" (TMI), an anthropogenic soil (Anthrosol) with sustained fertility and a large amount of stabilized organic matter. Firstly, the soils were imaged ex situ, without any chemical processing, with sequential electron scanning of the pelletized soil samples, covering a total area of 8 × 8 mm. Secondly, it was performed a computational analysis of the large-field X-ray images assembled from hundreds of adjacent elemental maps, thus resulting in high-definition images (4800 × 4800 pixels). This analytical approach provides a large sampling with the identification of > 10,000 particles over the scanned area. The particles identified consisted of Al, C, Ca, Cr, F, Fe, Mg, Mn, Na, O, P, S, Si and Ti. A significantly larger concentration of C-, Ca-and P-based particles, of up to 100 μm 2 of cross-section area, was found in TMI samples in comparison with oxisol and ultisol soils. While the mean distance between neighboring C, Ca and P particles in TMI was of 40-70 μm, the value was of hundreds of microns in oxisol and ultisol. Furthermore, mapping of micrometric carbon particles by Raman spectroscopy indicated that they have a graphitic structure with a large amount of defects, partially associated with particle oxidation, although a well-preserved sp 2 graphitic structure is also present. From a technological perspective, improved soil amendments, such as biochar, can be rationally designed from the "fingerprint" described here for soil particles of Amazonian Anthrosols (i.e., morphological and structural characteristics), which can result in an increase in fertility and the optimization of carbon sequestration in the future.

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Water-repellent and anticorrosive superhydrophobic cotton fabrics were produced via an eco-friendly water-based coating with core–shell fluorescent silica nanoparticles (SiPs) and subsequent immersion in a mixture of two fluorine-free organosilanes (3-(aminopropyl)­trimethoxysilane and trimethoxy­(octadecyl)­silane). Transmission electron microscopy confirmed the spherical and core–shell structure of SiPs, and Fourier-transform infrared spectroscopy characterized their chemical composition. Scanning electron microscopy with energy-dispersive X-ray spectroscopy confirmed the high coating coverage even after realistic laundering cycles. In confocal laser scanning microscopy, the fluorescent core–shell SiPs were used as probes to characterize the coating coverage on the surface of the cotton fibers. The high fluorescent signal provided by the fluorescent core–shell SiP cores enabled their visualization over large surface areas of the modified cotton fibers, before and after several washing cycles. The hydrophobic property of the cotton fiber treatments was evaluated considering the type of particle coating (monolayer or hierarchization), covalent bond with silanes, and a final curing process. Monolayer coating with fluorescent core–shell SiPs and further silanization yielded cotton fibers with high hydrophobicity and excellent durability (tested up to 10 washing processes), maintaining water contact angle (WCA) values above 150°, repellency grade 3, and lower water uptake (165%) compared to pristine (600%) or silanized cotton fibers (340%). Principal component analysis showed that the silanization process increased the SiP-coated cotton fiber resistance to laundering sustaining nonwetting properties up to 10 washing cycles, which was not observed for SiP-coated fibers subjected to no silanization process. Additionally, the silanized and noncured SiP-coated fibers were tested against solvents and corrosive aqueous media, for which high resistance to toluene, chloroform, and strong acid was observed, with the maintenance of static and dynamic WCAs. Thus, this systematic study allowed us to verify the main factors associated with superior hydrophobicity and durability and achieve an optimized and less toxic approach that combines the deposition of fluorescent core–shell SiPs and binary silanization.

BACKGROUND Sugar cane bagasse (SB) is a by‐product of the sugar cane industry, and is obtained on a large scale. In this paper, SB was used as a source of carbon for preparing a magnetic carbon nanocomposite (MCN‐SB) through one‐step hydrothermal carbonisation (HTC), in the presence of iron (III) nitrate. By way of comparison, SB was replaced by glucose in HTC (MCN‐GLU), and a thermal treatment of this material was then performed under an N2 atmosphere (MCN‐GLU‐HT). The physical and chemical properties of the nanocomposites were assessed, and the magnetic samples were applied as adsorbents. RESULTS MCN‐SB and MCN‐GLU are composed of iron oxide nanoparticles embedded in carbonaceous matrix which also contain oxygenated groups. The MCN‐SB sample was already magnetic after HTC, showing a magnetization saturation (Ms) of 5.0 emu g−1, due to the presence of magnetite, whereas MCN‐GLU consisted of hematite and required additional thermal treatment (HT) to acquire magnetic properties, with MCN‐GLU‐HT showing an Ms of 30.5 emu g−1. In turn, the mesoporous structure and higher specific surface area (SSA) of MCN‐GLU‐HT (SSA 90 m2 g−1) than MCN‐SB (SSA 53 m2 g−1) was a causative factor for its higher capacity of hexavalent chromium [Cr (VI)] removal (939 μg g−1), when compared to MCN‐SB (768 μg g−1), which has a nonporous structure. CONCLUSION The results suggest that SB can be reused, by means of HTC, for the preparation of a magnetically recoverable adsorbent, showing good adsorption properties. © 2022 Society of Chemical Industry (SCI).

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.

Fossilization results from several physical-chemical-geological processes. Original labile and non-bioclastic structures rarely survive throughout this process. In particular, the Crato Formation (Araripe Basin) is one of the most significant Cretaceous Konservat-Lagerstätten due to its well-preserved invertebrates, mainly three-dimensional insects. In general, Crato insects exhibit brown-orange color, constituted by goethite or hematite replacements. In this context, we used the scanning electron microscopy coupled to energy dispersive spectrometer and Raman spectroscopy to analyze Araripeblatta dornellesae, a 115 million-years-old fossil from Crato Formation, Araripe Basin. Our results show that a dark-color material rather than the brown-orange pattern preserve this specimen. The carbon is restricted to the fossil imprint, indicating some retention of the original organic remains. In addition, the presence of original organic components allowed to approach the biochemical aspects further than simple morphology, as well as to elucidate the taphonomical complexity involved in this preservation style.

In this study, we used fluorescent silica particles (SiPs) as probes to characterize the chemical stability of natural rubber (NR)-based coatings in situ without extensive sample preparation. By tuning the size, concentration, and surface charge of the SiPs and the type of solvent, we obtained two distinct NR-SiPs coatings: (1) irregular honeycomb patterns and (2) flat surfaces. Raman spectral mapping was used to investigate the chemical structure and to illustrate the spatial heterogeneity of the multiple components of the NR-SiPs coatings. The stability of the NR-SiPs coatings was assessed under fluid shear force stress and at high ionic strength conditions (NaCl, 0.85% w/v) using a perfusion chamber coupled with a confocal laser scanning microscope. By evaluating the fluorescent signal of the SiPs, we determined their distribution in the NR-based coatings and monitored their chemical stability via in situ confocal imaging. Using the fluorescent SiPs as probes, we could infer the high chemical stability of the coatings at high ionic strength and under shear stress conditions, opening new horizons for the application of NR coatings in medicine, microelectronics, and the automobile industry.