Carbon Materials Prepared from Invading Pelagic Sargassum for Supercapacitors' Electrodes.

Since 2011, substantial amounts of pelagic Sargassum algae have washed up along the Caribbean beaches and the Gulf of Mexico, leading to negative impacts on the economy and the environment of those areas. Hence, it is now crucial to develop strategies to mitigate this problem while valorizing such invasive biomass. This work deals with the successful exploitation of this pelagic Sargassum seaweed for the fabrication of carbon materials that can be used as electrodes for supercapacitors. Pelagic Sargassum precursors were simply pyrolyzed at temperatures varying from 600 to 900 °C. The resultant carbonaceous materials were then extensively characterized using different techniques, such as nitrogen adsorption for textural characterization, as well as X-ray photoelectron (XPS), Fourier transform infrared spectroscopies (FT-IR) and scanning electron microscopy (SEM), to understand their structures and functionalities. The electrochemical properties of the carbon materials were also tested for their performance as supercapacitors using cyclic voltammetry (CV), the galvanostatic method and electrochemical impedance spectroscopy analyses (EIS). We managed to have a large specific surface, i.e., 1664 m2 g-1 for biochar prepared at 800 °C (CS800). Eventually, CS800 turned out to exhibit the highest capacitance (96 F g-1) over the four samples, along with the highest specific surface (1664 m2 g-1), with specific resistance of about 0.07 Ω g -1.

Spectroscopic, Electrochemical, and Biological Assays of Copper-Binding Molecules for Screening of Different Drugs and Plant Extracts against Neurodegenerative Disorders.

Neurodegenerative disorders, caused by prone-to-aggregation proteins, such as Alzheimer disease or Huntington disease, share other traits such as disrupted homeostasis of essential metal ions, like copper. In this context, in an attempt to identify Cu2+ chelating agents, we study several organic compounds (ethylenediaminetetraacetic acid, phenylenediamine, metformin, salicylate, and trehalose) and organic extracts obtained from Bacopa monnieri L., which has been used in Ayurvedic therapies and presented a broad spectrum of biological properties. For this purpose, UV-visible spectroscopy analysis and electrochemical measurements were performed. Further, biological assays were performed in Caenorhabditis elegans models of polyQ toxicity, in an attempt to obtain better insights on neurodegenerative disorders.

Theoretical study on the interactions between chlordecone hydrate and acidic surface groups of activated carbon under basic pH conditions.

A theoretical study of the influence of acidic surface groups (SG) of activated carbon (AC) on chlordecone hydrate (CLDh) adsorption is presented, in order to help understanding the adsorption process under basic pH conditions. A seven rings aromatic system (coronene) with a functional group in the edge was used as a simplified model of AC to evaluate the influence of SG in the course of adsorption from aqueous solution at basic pH conditions. Two SG were modeled in their deprotonated form: carboxyl and hydroxyl (COO- and O-), interacting with CLDh. In order to model the solvation process, all systems under study were calculated with up to three water molecules. Multiple Minima Hypersurface (MMH) methodology was employed to study the interactions of CLDh with SG on AC using PM7 semiempirical Hamiltonian, to explore the potential energy surfaces of the systems and evaluate their thermodynamic association energies. The re-optimization of representative structures obtained from MMH was done using M06-2X Density Functional Theory. The Quantum Theory of Atoms in Molecules (QTAIM) was used to characterize the interaction types. As result, the association of CLDh with acidic SG at basic pH conditions preferentially occurs between the two alcohol groups of CLDh with COO- and O- groups and by dispersive interactions of chlorine atoms of CLDh with the graphitic surface. On the other hand, the presence of covalent interactions between the negatively charged oxygen of SG and one hydrogen atom of CLDh alcohol groups (O-⋯HO interactions) without water molecules, was confirmed by QTAIM study. It can be concluded that the interactions of CLDh with acidic SG of AC under basic pH conditions confirms the physical mechanisms of adsorption process.

Improving of understanding of beta-hexachlorocyclohexane (HCH) adsorption on activated carbons by temperature-programmed desorption studies.

In order to understand the interactions between beta-hexachlorocyclohexane (HCH) and chemical groups at activated carbon (AC) surface, the solid samples were hydrogenated aiming to decrease the amounts of oxygenated groups. Two AC samples designated by BagH2O and BagP1.5 were prepared by water vapor activation and phosphoric acid activation, respectively, of sugarcane bagasse used as an AC precursor. A more simple molecule 1,2,3-trichloropropane (TCP) is used as a model of chlorinated compound. The AC were characterized by infrared, X-ray photoelectron spectroscopy (XPS), Raman resonance spectroscopies, as well as temperature-programmed desorption coupled with mass spectrometry (TPD-MS). BagP1.5 and BagH2O AC surface contained oxygenated groups. Upon hydrogenation, a decrease of most of these group amxounts was observed for both samples, while hydroxyl groups increased. On the basis of temperature-programmed desorption data obtained for AC samples contaminated with TCP or HCH, it was possible to determine the type of hydrogen bond formed between each AC and HCH.

Assessment of the surface area occupied by molecules on activated carbon from liquid phase adsorption data from a combination of the BET and the Freundlich theories.

A new equation is derived from a combination of the BET (Brunauer, Emmett, Teller) and Freundlich isotherms fitted for liquid phase adsorption data on activated carbons. This equation, depending on the Freundlich parameters and the equilibrium adsorption-desorption constant can be used for assessment of the surface area occupied by the solute molecules on a surface in a liquid phase system under some conditions.