Nanomaterials for electrochemical detection of pollutants in water: A review

The survival of living beings, including humanity, depends on a continuous supply of clean water. However, due to the development of industry, agriculture, and population growth, an increasing number of wastewaters is discarded, and the negative effects of such actions are clear. The first step in solving this situation is the collection and monitoring of pollutants in water bodies to subsequently facilitate their treatment. Nonetheless, traditional sensing techniques are typically laboratory-based, leading to potential diminishment in analysis quality. In this paper, the most recent developments in micro- and nano-electrochemical devices for pollutant detection in wastewater are reviewed. The devices reviewed are based on a variety of electrodes and the sensing of three different categories of pollutants: nutrients and phenolic compounds, heavy metals, and organic matter. From these electrodes, Cu, Co, and Bi showed promise as versatile materials to detect a grand variety of contaminants. Also, the most commonly used material is glassy carbon, present in the detection of all reviewed analytes.     

Catalytic Nitrene Transfer by an FeIV-Imido Complex Generated by a Comproportionation Process

Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from Fe^II and Fe^III precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV-visible, Mössbauer), ESI-MS and DFT studies, an Fe^IV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the Fe^II precursor was expected by a two-electron oxidative addition, its formation from an Fe^III precursor was unprecedented. Thanks to a combination of spectroscopic (UV-visible, EPR, Hyscore and Mössbauer), ESI-MS and DFT studies, we found that, when starting from the Fe^III precursor, an Fe^III tosyliodinane adduct was formed and decomposed into an Fe^V tosylimido species which generated the catalytically active Fe^IV tosylimide through a comproportionation process with the Fe^III precursor.     

A control-theoretic perspective on optimal high-order optimization

Mathematical Programming - We provide a control-theoretic perspective on optimal tensor algorithms for minimizing a convex function in a finite-dimensional Euclidean space. Given a function...     

A Stable Porphyrin Functionalized Graphite Electrode Used at the Oxygen Evolution Reaction Potential

Many researches have been devoted to rechargeable power generators that can store (but also release) energy. This availability is ensured through (e. g.) the oxygen evolution reaction (OER). However, (i) large values of the overpotentials and (ii) a progressive detriment of the anode (graphite) electrode limit the ultimate device. In view of enhancing the electrode performances, graphite was protected by following different strategies, which oblige to follow precise preparation protocols. Here, we prove that a thin layer of free-base porphyrin molecules is able to protect the underneath graphite electrode from detriment even if many (about 100) electrochemical cycles are performed.     

Recent advances and challenges in the recovery and purification of cellular exosomes

Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed.     

Tips and Tricks for the Surface Engineering of Well-Ordered Morphologically Driven Silver-Based Nanomaterials

Particularly-shaped silver nanostructures are successfully applied in many scientific fields, such as nanotechnology, catalysis, (nano)engineering, optoelectronics, and sensing. In recent years, the production of shape-controlled silver-based nanostructures and the knowledge around this topic has grown significantly. Hence, on the basis of the most recent results reported in the literature, a critical analysis around the driving forces behind the synthesis of such nanostructures are proposed herein, pointing out the important role of surface-regulating agents in driving crystalline growth by favoring (or opposing) development along specific directions. Additionally, growth mechanisms of the different morphologies considered here are discussed in depth, and critical points highlighted.     

Auger electron emission in proton-induced interactions in living matter: A TILDA-V Monte Carlo tracking

The present work focuses on studying the contribution of the Auger electron emission in proton-induced interactions in biological matter. The Monte Carlo track-structure code, TILDA-V, was then used for modeling the protons beams of 10 keV to 100 MeV in biological matter, namely, water vapor and hydrated DNA. The main ionizing processes are described by means of an extensive set of ab initio differential and total cross sections computed within a quantum-mechanical CDW-EIS approximation.     

A Continuous-Time Random Walk Extension of the Gillis Model

We consider a continuous-time random walk which is the generalization, by means of the introduction of waiting periods on sites, of the one-dimensional non-homogeneous random walk with a position-dependent drift known in the mathematical literature as Gillis random walk. This modified stochastic process allows to significantly change local, non-local and transport properties in the presence of heavy-tailed waiting-time distributions lacking the first moment: we provide here exact results concerning hitting times, first-time events, survival probabilities, occupation times, the moments spectrum and the statistics of records. Specifically, normal diffusion gives way to subdiffusion and we are witnessing the breaking of ergodicity. Furthermore we also test our theoretical predictions with numerical simulations.     

A Comparative Study of the Semiconductor Behavior of Organic Thin Films: TCNQ-Doped Cobalt Phthalocyanine and Cobalt Octaethylporphyrin

The structure formed by cobalt phthalocyanine (CoPc) and cobalt octaethylporphyrin (CoOEP) with electron-acceptor tetracyano-π-quinodimethane (TCNQ), was studied by Density Functional Theory (DFT) methods. According to theoretical calculations, both cobalt systems can establish dispersion forces related to TCNQ and also in both cases the link between them is built by means of hydrogen bonds. Based on the results of these DFT calculations, we developed experimental work: the organic semiconductors were doped, and the thermal evaporation technique was used to prepare semiconductor thin films of such compounds. The structure of the films was studied by FTIR and Raman spectroscopy. The optical properties of the CoPc-TCNQ and CoOEP-TCNQ films were investigated by means of UV-Vis measurements. The results obtained were used to estimate the type of transitions and the optical bandgap. The results were compared to the previously calculated theoretical bandgap. The CoOEP-TCNQ film presented the smallest theoretical and experimental bandgap. Finally, the electrical properties of the organic semiconductors were evaluated from a PET (polyethylene terephthalate)/indium tin oxide (ITO)/cobalt macrocycle-TCNQ/silver (Ag) device we prepared. The CoOEP-TCNQ-based device showed an ohmic behavior. The device manufactured from CoPc-TCNQ also showed an ohmic behavior at low voltages, but significantly changed to SCLC (space-charge limited conductivity) at high voltage values.