Array of electrodeposited Ru-decorated TiO<Subscript>2</Subscript> nanotubes with enhanced photoresponse

Although TiO₂ anatase phase has been widely chosen as the main photocatalyst, it presents high electron/hole recombination rate. However, today, what is sought is a semiconductor material with enhanced photocatalytic activity with higher photon to electron conversion efficiency by introduction of electrons trap dopants. In this paper, TiO₂ nanotubes arrays obtained by anodization of Ti substrates were decorated with Ru via electrodeposition, and their photo-response was investigated. First, voltammetric experiments were performed to elucidate the route of Ru reduction on the TiO₂ surface and to select the range of potentials for Ru deposition. The reduction potentials were used for controlling the amount of Ru distributed all over the surface. Although Ru was electrodeposited at potentials over the range from ??0.025 to ??0.188 V vs. Ag/AgCl, the deposition of 3.7 mC cm^?2 at ??0.100 V for 30 min resulted in a tenfold greater photocurrent when compared to the recorded photocurrent for the undecorated TiO₂ nanotubes array. Next, Ru-decorated TiO₂ nanotubes with a length of 323?±?18 nm and inner and outer diameters of 91 and 104 nm, respectively, were characterized using SEM-WDS, SEM-FEG, XRD, and XPS. UV-Vis-NIR diffuse reflectance spectroscopy and photoluminescence (PL) measurements, which revealed a maximum PL emission at 445 nm, showed that for the array of Ru-decorated TiO₂ nanotubes, the electron-hole recombination may be effectively inhibited by the presence of ruthenium electrodeposited, which can make this photocatalyst even more attractive for environmental applications. The performances of the TiO₂ and Ru-decorated TiO₂ catalysts were compared in heterogeneous photocatalysis experiments for color removal of an azo-dye, which presented a pseudo-first-order rate constant more than twofold greater for the Ru-decorated TiO₂ catalysts.     

Regio- and diastereoselective synthesis of anticancer spirooxindoles derived from tryptophan and histidine via three-component 1,3-dipolar cycloadditions in an ionic liquid

A small library of novel hybrid spiroheterocycles containing spirooxindole, pyrrolidine and indole/imidazole moieties were synthesized with complete regio- and diastereoselectively in good to excellent yields from a three-component process starting from a series of variously substituted (E)-(2-nitrovinyl)benzenes, indoline-2,3-dione derivatives and l-tryptophan or l-histidine in an ionic liquid. The key step of this transformation is a 1,3-dipolar cycloaddition reaction involving a rare class of in situ-generated azomethine ylides derived from aromatic amino acids. The compounds thus synthesized were evaluated for their anticancer activity and were shown to inhibit the proliferation of FaDu cells, a human epithelial cell line isolated from a squamous cell carcinoma of the hypopharynx, via apoptotic cell death.     

NH4I-catalyzed chalcogen(S/Se)-functionalization of 5-membered N-heteroaryls under metal-free conditions

Herein, we described the NH₄I-catalyzed CH bond chalcogenation of N-heteroaryls in the presence of a minimum amount of DMSO/H₂O/acetic acid as additives (2.5/2.5/1?M equiv., respectively), under metal-free conditions. Under optimized conditions, a wide variety of sulfenyl/selenyl imidazo[1,2-α]pyridines were prepared in very good yields. Moreover, the present approach was also highly efficient for the chalcogenation of different 5-membered N-heteroaryls, e.g., indole, imidazothiazole, indazole and imidazopyrimidine derivatives.     

Enhancement of antibacterial efficiency at silver electrodeposited on coconut shell activated carbon by modulating pulse frequency

The natural antibacterial activity of silver represents an alternative to deal with the ever increasing pathogenic breakouts related with contaminated water resources. In this study, silver was deposited on the surface of activated carbon (AC) particles via pulsed electrodeposition (PED) employing an electrochemical reactor operating at fixed and fluidized bed regimes. Silver-coated activated carbon (Ag/AC) particles were prepared at different current pulse frequency values. Antimicrobial properties of the produced material were tested against two well-known foodborne pathogens, i.e., Escherichia coli O157:H7 and Salmonella typhimurium. The results demonstrate a strong influence of the applied current pulse frequency on both the bactericidal efficiency and the specific surface of silver deposited on the activated carbon. Antibacterial results demonstrate up to eight orders of magnitude decrease in the CFU cm^?3 (colony-forming units per cm³) against both microorganisms in just 20 min contact time. Additional chronoamperometry transient data were fitted to the Scharifker-Hills nucleation model for the electrodeposition of silver at a rotating disk electrode, revealing an instantaneous nucleation growth processes. The Ag/AC particles were characterized by field emission scanning electron microscopy (FE-SEM), specific surface area (S_BET), Raman spectroscopy, energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD), demonstrating the existence of crystalline phase formation of a preferential (200) plane growth with silver and silver oxide being present.

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Local well-posedness for higher order nonlinear dispersive systems

We study nonlinear dispersive systems of the form

On The Homotopy Type of

We consider the homotopy type of classifying spaces , where is a finite -group, and we study the question whether or not the mod cohomology of , as an algebra over the Steenrod algebra together with the associated Bockstein spectral sequence, determine the homotopy type of . This article is devoted to producing some families of finite 2-groups where cohomological information determines the homotopy type of .

     

Microstructure and Optical Bandgap of Cobalt Selenide Nanofilms

Semiconductors - The purpose of this research is to explore the properties of CoSe nanostructured thin films on glass substrates prepared by a chemical solution deposition method. Special attention...     

A low complexity mechanism for congestion notification in rural IPSec‐enabled heterogeneous backhaul networks

Management in wireless backhaul networks is a challenging task, especially in rural and isolated environments. In these scenarios, the backhaul network usually consists of a set of heterogeneous wireless links that provide limited and variable bandwidth to the access networks, often 3G/4G small cells. Because of the highly constrained nature of this type of backhaul network, intelligent and joint management in both the backhaul network and the access network is crucial in order to avoid performance degradation caused by traffic congestion. In order to avoid the saturation in the backhaul network, access networks should consider the backhaul state when taking decisions in the admission control and scheduling procedures. However, no standardized mechanisms currently exist for sharing management information between both networks. In this work, we propose to use the Explicit Congestion Notification (ECN) bit in the outer IP headers present in the Iuh 3GPP IPSec‐enabled interfaces in order to notify the backhaul congestion state to the access network. We analyze for the referred scenario, compatibility and security details, validating our approach by running numerically simulations and implementing the notification mechanism. Our low complexity approach offers 2% accuracy and backhaul update latency lower than 10 ms during 80% of the time, which makes the solution appropriate for admission control and scheduling intervals in small cells.     

Long‐Term Electrical and Mechanical Function Monitoring of a Human‐on‐a‐Chip System

The goal of human‐on‐a‐chip systems is to capture multiorgan complexity and predict the human response to compounds within physiologically relevant platforms. The generation and characterization of such systems is currently a focal point of research given the long‐standing inadequacies of conventional techniques for predicting human outcome. Functional systems can measure and quantify key cellular mechanisms that correlate with the physiological status of a tissue, and can be used to evaluate therapeutic challenges utilizing many of the same endpoints used in animal experiments or clinical trials. Culturing multiple organ compartments in a platform creates a more physiologic environment (organ–organ communication). Here is reported a human 4‐organ system composed of heart, liver, skeletal muscle, and nervous system modules that maintains cellular viability and function over 28 days in serum‐free conditions using a pumpless system. The integration of noninvasive electrical evaluation of neurons and cardiac cells and mechanical determination of cardiac and skeletal muscle contraction allows the monitoring of cellular function, especially for chronic toxicity studies in vitro. The 28‐day period is the minimum timeframe for animal studies to evaluate repeat dose toxicity. This technology can be a relevant alternative to animal testing by monitoring multiorgan function upon long‐term chemical exposure.     

Self‐Assembly of Atomically Thin Chiral Copper Heterostructures Templated by Black Phosphorus

The fabrication of 2D systems for electronic devices is not straightforward, with top‐down low‐yield methods often employed leading to irregular nanostructures and lower quality devices. Here, a simple and reproducible method to trigger self‐assembly of arrays of high aspect‐ratio chiral copper heterostructures templated by the structural anisotropy in black phosphorus (BP) nanosheets is presented. Using quantitative atomic resolution aberration‐corrected scanning transmission electron microscopy imaging, in situ heating transmission electron microscopy and electron energy‐loss spectroscopy arrays of heterostructures forming at speeds exceeding 100 nm s^?1 and displaying long‐range order over micrometers are observed. The controlled instigation of the self‐assembly of the Cu heterostructures embedded in BP is achieved using conventional electron beam lithography combined with site specific placement of Cu nanoparticles. Density functional theory calculations are used to investigate the atomic structure and suggest a metallic nature of the Cu heterostructures grown in BP. The findings of this new hybrid material with unique dimensionality, chirality, and metallic nature and its triggered self‐assembly open new and exciting opportunities for next generation, self‐assembling devices.