Flux measurements of carbon dioxide and water vapor above tropical rain forests are often difficult to interpret because the terrain is usually complex. This complexity induces heterogeneity in the surface but also affects lateral movement of carbon dioxide (CO2) not readily detected by the eddy covariance systems. This study describes such variability using measurements of CO2 along vertical profiles and along a toposequence in a tropical rain forest near Manaus, Brazil. Seasonal and diurnal variation was recorded, with atmospheric CO2 concentration maxima around dawn, generally higher CO2 build-up in the dry season and stronger daytime CO2 drawdown in the wet season. This variation was reflected all along the toposequence, but the slope and valley bottom accumulated clearly more CO2 than the plateaus, depending on atmospheric stability. Particularly during stable nights, accumulation was along lines of equal altitude, suggesting that large amounts of CO2 are stored in the valleys of the landscape. Flushing of this store only occurs during mid-morning, when stored CO2 may well be partly transported back to the plateaus. It is clear that, for proper interpretation of tower fluxes in such complex and actively respiring terrain, the horizontal variability of storage needs to be taken into account not only during the night but also during the mornings.

a Studies involving water splitting to form hydrogen and oxygen have attracted attention because H2is considered the fuel of the future. Photoelectrocatalysts have been widely used for this application, and several metal oxides can be applied as catalysts. Among them, we highlight zinc oxide nanorods (ZnONRs) and titanate nanotubes (TiNTs); however, their individual nanostructures exhibit disadvantages. For example, ZnONR shows rapid recombination of the photogenerated charges, and TiNT gives rise to randomly orientated films; these disadvantages limit their application as photoanodes. In this study, for the first time, we present a new class of multihierarchical electrodes based on TiNT-decorated ZnONR films that exhibited superior results to the individual species. The TiNTs are homogenously dispersed over the surface of the rods without forming agglomerates, giving rise to a heterojunction that exhibits lower recombination rates. It was found that the results are better when the contents of TiNT in the electrode are higher; thus, glycine was successfully used as a bridge to link both of the structures, increasing the amount of TiNT decorating the rods. As a result, the photocurrent generated with these multihierarchical electrodes is higher than that obtained for pure ZnONR electrodes (0.9 mA and 0.45 mA, respectively), and the electrode potentials for O2 evolution is lower than that observed for pure TiNT electrodes (0 V and 0.8 V vs. ERHE, respectively). The IPCE values are also higher for the multihierarchical electrodes.

Cell-penetrating peptides (CPPs) are a topical subject potentially exploitable for creating nanotherapeutics for the delivery of bioactive loads. These compounds are often classified into three major categories according to their physicochemical characteristics: cationic, amphiphilic, and hydrophobic. Among them, the group of hydrophobic CPPs has received increasing attention in recent years due to toxicity concerns posed by highly cationic CPPs. The hexapeptide PFVYLI (P, proline; F, phenylalanine; V, valine; Y, tyrosine; L, leucine; and I, isoleucine), a fragment derived from the C-terminal portion of α1-antitrypsin, is a prototypal example of hydrophobic CPP. This sequence shows reduced cytotoxicity and a capacity of nuclear localization, and its small size readily hints at its suitability as a building block to construct nanostructured materials. In this study, we examine the self-assembling properties of PFVYLI and investigate its ability to form noncovalent complexes with nucleic acids. By using a combination of biophysical tools including synchrotron small-angle X-ray scattering and atomic force microscopy-based infrared spectroscopy, we discovered that this CPP self-assembles into discrete nanofibrils with remarkable amyloidogenic features. Over the course of days, these fibrils coalesce into rodlike crystals that easily reach the micrometer range. Despite lacking cationic residues in the composition, PFVYLI forms noncovalent complexes with nucleic acids that retain β-sheet pairing found in amyloid aggregates. In vitro vectorization experiments performed with double-stranded DNA fragments indicate that complexes promote the internalization of nucleic acids, revealing that tropism toward cell membranes is preserved upon complexation. On the other hand, transfection assays with splice-correction oligonucleotides (SCOs) for luciferase expression show limited bioactivity across a narrow concentration window, suggesting that the propensity to form amyloidogenic aggregates may trigger endosomal entrapment. We anticipate that the findings presented here open perspectives for using this archetypical hydrophobic CPP in the fabrication of nanostructured scaffolds, which potentially integrate properties of amyloids and translocation capabilities of CPPs.

Bismuth vanadate has been widely used in photocatalysis and photoelectrocatalysis due to its physical and chemical properties; for these applications, the control of the crystalline structure and morphology is essential. The development of methodologies to improve the control of these parameters is usually very time and energy-consuming, and further studies require several experiments. In this context, the use of microwave irradiation as a heating source is desirable, since it drastically reduces the reaction time. However, the unique interaction of the microwave with the reactional species makes the development of microwave-assisted synthesis protocols a big challenge. Here, we report a study on how the solvent (water, water/ethanol 1:1, ethanol, and ethylene glycol), pH (1–14), the use of hexadecyltrimethylammonium bromide (CTAB), and solvothermal vs reflux conditions affect the crystalline structure and morphology of BiVO4 nanomaterials prepared by microwave-assisted methods. We found that monoclinic and tetragonal BiVO4 are obtained in acidic media. Also, the use of water and water/ethanol as solvents results in 2D nanomaterials, whereas nanoparticles are observed by using ethanol and ethylene glycol. Finally, the use of CTAB and hydrothermal conditions leads to smaller and denser particles.

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Polymer nanocomposites based on poly(vinyl alcohol) (PVA) and ZnO hold a privileged position in the development of organic/inorganic hybrid multifunctional materials for applications ranging from food packing to biotechnological platforms. However, a remarkable drawback is that most of the currently available synthetic routes are based on approaches that are both time-and energy-consuming and often lead to heterogeneous polymer films that require compatibilizers to disperse inorganic nanoparticles into the organic matrix. In this work, we present a route for synthesizing ZnO_PVA nanocomposite films through a sol−gel strategy that uses microwaves as a heat source and PVA as a reactant. We show that nanocomposites produced using this approach exhibit enhanced mechanical properties, UV shielding capabilities, and antimicrobial activity and potentialize their application in the production of antibacterial films against Gram-positive and Gram-negative strains. We show that these properties are easily modulated by controlling the synthesis parameters, such as the irradiation time and power, and the use of PVA excludes the need for compatibilizers since it simultaneously behaves as the polymer matrix and a mediator for in situ synthesis of nanostructured ZnO clusters. The method presented here is straightforward, inexpensive, and applied to other polyols to enhance the functionalities of materials based on these compounds.