Alan Fernando Yoshiaki Matsushita

In the pursuit of sustainable energy solutions and advancements in energy storage technology, this research focuses on the synthesis, characterization, and electrochemical evaluation of a Keggin-Type polyoxoniobate compound for potential application in sodium-ion batteries (SIBs). While lithium-ion batteries have been the standard, concerns about lithium availability and environmental issues have prompted the exploration of alternative materials for SIBs. Polyoxoniobates, a subclass of polyoxometalates, have unique properties that make them promising candidates for the development of high-performance SIBs. This study delves into the relatively uncharted territory of polyoxoniobates in SIBs. The research investigates the adaptation of polyoxoniobate structures to enhance their electrochemical properties, the understanding of sodium ion storage mechanisms, and comprehensive characterization. A specific Keggin-Type polyoxoniobate compound is synthesized and examined for its potential as an electrode material for SIBs. The structural analysis confirms the successful synthesis of the compound, with X-ray diffraction patterns, Raman spectroscopy, and FTIR spectra demonstrating its purity and integrity. Scanning electron microscopy reveals the unique morphology of the composite material, indicating interactions between graphene oxide (GO) and polyoxoniobates. Elemental analysis further confirms the composition of the composite material, aligning with the expected stoichiometry. Electrochemical characterization using various techniques, including cyclic voltammetry, chronopotentiometry charge/discharge, and electrochemical impedance spectroscopy, provides insights into the electrochemical behavior of the synthesized material. These findings contribute to the understanding of structure-activity relationships in polyoxoniobates and their potential as crucial components in future SIBs.

This paper presents a method for the controlled reduction of silver chloride (AgCl) by D-(+)-Maltose in the presence of poly(sodium 4-styrenesulfonate) (PSS). PSS, acting as a polyelectrolyte, plays a crucial role in the process by accommodating silver ions (Ag+) through electrostatic interactions during synthesis and stabilizing the resulting silver nanoparticles (AgNPs). UV-Vis spectra revealed distinct absorption bands characteristic of AgNPs, with the Ag-PSS ratio affecting the size and distribution of nanoparticles. Dynamic light scattering (DLS) and zeta potential measurements confirmed the relationship between silver concentration and nanoparticle uniformity. Layer-by-Layer (LbL) deposition of Ag-PSS nanohybrids on cotton fabric surfaces, offering a unique approach for fabric modification. Energy-Dispersive X-ray Spectroscopy (EDS) analysis demonstrated a consistent increase in silver content with an increase in bilayers. Scanning Electron Microscopy (SEM) revealed enhanced fiber roughness, indicating effective nanohybrid deposition. Elemental mapping showcased uniform elemental distribution across the fiber surface, underscoring the precision of the LbL technique. In conclusion, this study presents an effective method for achieving uniform surface modification of cotton fibers through LbL deposition of Ag-PSS nanohybrids.

The interaction between polyelectrolytes and metal ions is governed by different types of interactions, leading to the formation of different phases, from liquid state to weak gels, through an appropriate choice of metal ion/polyelectrolyte molar ratio. We have found that lanthanide ions, europium(III) and terbium(III), are able to form polymer composites with poly(sodium acrylate). That interaction enhances the luminescent properties of europium(III) and terbium(III), showing that Eu³⁺/poly(sodium acrylate) (PSA) and Tb³⁺/PSA composites have a highly intense red and green emission, respectively. The effect of cations with different valences on the luminescent properties of the polymer composites is analyzed. The presence of metal ions tends to quench the composite emission intensity and the quenching process depends on the cation, with copper(II) being by far the most efficient quencher. The interaction mechanism between lanthanoid ions and PSA is also discussed. The composites and their interactions with a wide range of cations and anions are fully characterized through stationary and non-stationary fluorescence, high resolution scanning electronic microscopy and X-ray diffraction.

Aromatic hydrocarbons are extensive environmental pollutants occurring in both water and air media, and their removal is a priority effort for a healthy environment. The use of adsorbents is among the several strategies used for the remediation of these compounds. In this paper, we aim the synthesis of an amphiphilic hydrogel with the potential for the simultaneous sorption of a set of monocyclic and polycyclic aromatic hydrocarbons associated with toxicity effects in humans. Thus, we start by the synthesis of a copolymer-based in chitosan and β-cyclodextrin previously functionalized with the maleic anhydride. The presence of β-cyclodextrin will confer the ability to interact with hydrophobic compounds. The resulting material is posteriorly incorporated in a cryogel of poly(vinyl alcohol) matrix. We aim to improve the amphiphilic ability of the hydrogel matrix. The obtained hydrogel was characterized by swelling water kinetics, thermogravimetric analysis, rheological measurements, and scanning electron microscopy. The sorption of aromatic hydrocarbons onto the gel is characterized by pseudo-first-order kinetics and Henry isotherm, suggesting a physisorption mechanism. The results show that the presence of maleic anhydride-β-cyclodextrin and chitosan into hydrogels leads to an increase in the removal efficiency of the aromatic compounds. Additionally, the capacity of this hydrogel for removing these pollutants from a fossil fuel sample has also been tested.