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The detection and removal of Atrazine (ATZN), a pesticide of environmental concern, requires more efficient methods to facilitate its degradation. The adequate structural morphology, high specific surface area, great photothermal conversion performance, higher amount of oxygenated functional groups, and intense and stable fluorescence signals are considered as favorable properties of the materials used in the in the proposal of physicochemical methods for detection, capture and degradation of nitrogenous herbicides. Herein, the design, preparation, and characterization of MnFe2O4@CDs as a dual-functional material is reported. Due to its optical, photothermal, textural and surface chemistry properties, the material is able to capture, detect, and degrade the herbicide "Atrazine" in synthetic samples. The preparation of the proposed composites, formed by particles of bimetallic oxides (Mn-Fe2O4) and a covering of carbon dots (CDs), was confirmed using various characterization techniques including SEM, TEMHR, RAMAN, FTIR, UV-Visible, Photoluminescence, DRX, N2 adsorption-desorption isotherms, superficial chemistry, and photothermal. The study revealed that the ATZN capture occurs through hydrogen bonding interaction between −COOH and −COH functional groups exposed on CDs surface and amine groups −NH− of the herbicide. Furthermore, the CDs behave as fluorescent markers of single-channel employed to detect ATZN and to monitor the capture-degradation process. The MnFe2O4@CDs composite was integrated as the main thermoactive material into a photothermal reactor on which was incident a NIR laser. The high near-infrared absorption of the Mn-Fe2O4 particles resulting in an efficient photothermal conversion; which in turn, increase the temperature of the surrounding medium. The increase in temperature promotes the activation of persulfate (PS) at the interface of the MnFe2O4@CDs−PS system producing SO4• − radicals as oxidizing agents of atrazine. Our results demonstrate that the process may effectively degrade 99 % of atrazine for a concentration of CATZN [20 mM], when NIR light irradiated by 45 min and the system reaches a temperature of ca. 53 ºC. Additionally, the degradation of ATZN was confirmed by analysis of total organic carbon (TOC). The fluorometric analytical assay by CDs-base fluorescence probes allowed following the FL signal at 520 nm(λexit = 375 nm) for the capture “turn on” and degradation “turn off” of atrazine. Finally, as a comparison, we highlight the significant efficiency shown by the process studied here, compared to other similar atrazine degradation processes previously reported. 

Single-particle electrochemistry has become an important area of research with the potential to determine the rules of electrochemical reactivity at the nanoscale. These techniques involve addressing one entity at the time, as opposed to the conventional electrochemical experiment where a large number of molecules interact with an electrode surface. These experiments have been made feasible  through the utilization of ultramicroelectrode (UMEs), i.e., electrodes with at least one dimension, e.g., diameter of 30 μm or less. This paper provides a theoretical and practical introduction to single entity electrochemistry (SEE), with emphasis on collision experiments between suspended NPs and UMEs to introduce concepts and techniques that are used in several SEE experimental modes. We discuss the intrinsically small currents, below 1 nA, that result from the electroactive area of single entities in the nanometer scale. Individual nanoparticles can be detected using the difference in electrochemical reactivity between a substrate and a nanoparticle (NP). These experiments show steady-state behavior of single NPs that result in discrete current changes or steps. Likewise, the NP can have transient interactions with the substrate electrode that result in current blips. We review the effect of diffusion, the main mass transport process that limits NP/electrode interactions. Also, we pointed out the implications of aggregation and tunneling in the experiments. Finally, we provid a perspective on the possible applications of single-element electrochemistry of electrocatalyst. 

Because of its large electrochemical window, acetonitrile (MeCN) is one of the most widely used solvents in electrochemistry. It is a suitable solvent for nonaqueous electrolytes that allows studies of cathodic and anodic processes, but electrolyte purification remains challenging. As received, the high-performance liquid chromatography (HPLC) grade is unsuitable for most electroanalytical applications. We present an approach to optimize the purification of HPLC-grade acetonitrile to yield a tetrabutylammonium perchlorate (TBAP)/MeCN electrolyte for experiments in nonaqueous media. We used cyclic voltammetry (CV) to show the background due to impurities and to guide the experimental design to a background current acceptable for CVs of a 1 mM typical concentration of a redox-active molecule. We use 3A molecular sieves, followed by distillation over CaH2 with a final treatment with Al2O3. The optimized procedure yields CH3CN with small background currents, increasing the signal-to-noise ratio and minimizing chemical complications over a wide potential window. Our approach includes discriminating between impurities in the solvent and electrolyte salts; for TBAP, we recrystallize from ethyl acetate and 95 % ethanol. The process and theoretical guidelines apply to other nonaqueous electrolytes dealing with electroactive impurities, including organic molecules, oxygen, and water. 

Tungsten has unique physical and chemical properties that make it ideal for high-temperature applications. At room temperature, it is being considered for medical applications due to its protection by an oxide/hydroxide film. However, breakdown of the oxide film and tungsten dissolution can have adverse effects on human health. This study investigates the corrosion of tungsten with and without dispersed oxides of rare-earth elements (ThO2, CeO2, and La2O3) in a 3 wt-% NaCl solution using electrochemical techniques. The results suggest that tungsten dissolution occurs after the formation of an oxide film, likely WO3, on the surface of tungsten and dispersed oxide tungsten. La2O3 and CeO2 may decrease the corrosion rate of tungsten, while WThO2/tungsten has similar corrosion rates to tungsten. The study concludes that CeO2 or La2O3 could replace ThO2 in tungsten due to the radioactive nature of Th.