Browsing by Author "Marco, Jose F."

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    Functionalization using biocompatible carboxylated cyclodextrins of iron-based nanoMIL-100
    (2021) Carmona, Thais; Marco, Jose F.; Gimenez-Marques, Monica; Canon-Mancisidor, Walter; Gutierrez-Cutino, Marlen; Hermosilla-Ibanez, Patricio; Perez, Edwin G.; Minguez Espallargas, Guillermo; Venegas-Yazigi, Diego
    Here we report the first example of nanoMIL-100 particles modified with monomeric cyclodextrin derivatives of different length by exploiting strong interactions between non-saturated iron trimers at the external surface and carboxylate functionalities located at the end of biocompatible and flexible linkers of cyclodextrins. The main results revealed that, after the functionalization, the cyclodextrins are selectively located at the external surfaces covering the nanoparticles. Z potential measurements show that this functionalization induced changes respect to the bare nanoMIL-100 particles, however, the presence of the cyclodextrins does not modify the size neither porosity of the nanoparticles. The amount of cyclodextrins attached, investigated by thermogravimetry, increases with the length of the linker between CD cavity and nanoparticle surface, reaching up a 9 % wt. Auger spectroscopy suggested a clear predominant sp(3) character after the functionalizations (vs. sp(2) predominance in the unmodified nanoMIL-100). This study supposes the creation of an alternative family of hybrids based on carboxylated monomeric cyclodextrins.
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    Nanostructured Fe-N-C pyrolyzed catalyst for the H2O2 electrochemical sensing
    (2021) Candia-Onfray, Christian; Bollo, Soledad; Yanez, Claudia; Escalona, Nestor; Marco, Jose F.; Menendez, Nieves; Salazar, Ricardo; Recio, F. Javier
    Fe-N-C pyrolyzed materials have been proposed as substitutes of the noble-based catalyst for energy conversion reactions. However, their use as electrochemical sensors has not been deeply explored. In the present work, different Fe-N-C pyrolyzed catalysts were synthesized for the amperometric sensing of the H2O2 reduction in neutral media. The catalysts were characterized by BET, TEM, FESEM, XPS, Mossbauer spectroscopy, and cyclic voltammetry. The catalysts present an N-doped graphitic matrix with a macroporous structure and mesoporous contribution. Different amounts of N-pyridinic, N-pyrrolic, N-graphitic, N-oxides, and FeN4 sites have been detected on the catalysts. Among the different active sites present in the catalysts, the FeN4 structure is proposed as the most catalytic active site for the hydrogen peroxide reduction reaction (HPRR). Under optimal conditions (0.61 V vs. NHE, 0.00 V vs. Ag/AgCl), the materials show a lineal amperometric response in the range of 0.08 and 14 mu M, with a sensitivity of 31.3 mu A mu M-1 cm(-2), and a detection and quantification limits of 0.25 mu M and 0.75 mu M respectively. The amperometric results indicate that the best performance is reached when increasing the amount of FeN4 active sites, and the redox potential of the FeN4 species becomes more positive. The Fe-N-C catalyst stands out for the more positive working potential than other materials proposed in the literature. (C) 2021 Elsevier Ltd. All rights reserved.