PMo11V@N-CNT electrochemical properties and its application as electrochemical sensor for determination of acetaminophen

A polyoxometalate-nanocarbon composite, PMo11V@N-CNT, was prepared by a simple procedure which consisted of the immobilization of phosphovanadomolybdate (PMo11V) onto N-doped carbon nanotubes (N-CNT). The FTIR and XPS characterizations confirmed its successful synthesis. The cyclic voltammograms of glassy carbon electrode (GCE) modified with PMo11V and PMo11V@N-CNT showed four Mo-centred redox processes (MoVI/V) and a vanadium redox process (VV/IV). All were surface-confined redox processes. Additionally, PMo11V@N-CNT/GCE showed good stability and well-resolved redox peaks with high current intensities. The electrocatalytic sensing properties of PMo11V@N-CNT/GCE towards acetaminophen (AC) in the presence of tryptophan (TRP) were evaluated by square wave voltammetry. Under the conditions used, the peak current increased linearly with AC concentration in the presence of TRP, with a linear range from 1.5 × 10−6 to 3.9 × 10−4 mol dm−3 and a detection limit of 1.0 × 10−6 mol dm−3.info:eu-repo/semantics/publishedVersio

Selectividad química y diastereomérica en reacciones de hidrogenación sobre catalizadores metálicos soportados

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Física Aplicada. Fecha de lectura: 26-11-199

Exploring the insertion of ethylenediamine and bis(3-aminopropyl)amine into graphite oxide

© 2014 The Author(s). Published by Taylor & Francis.The influence of ethylenediamine and bis(3-aminopropyl)amine insertion into graphite oxide using toluene and ethanol–water media was studied by elemental analysis, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetry, temperature-programmed desorption and diffuse reflectance infrared Fourier transform spectroscopy. In every case, amine was incorporated between the basal planes and on the edges of the material through different interactions with epoxy, hydroxyl, carboxyl and carbonyl groups resulting in new-layered materials. Results show that incorporation was homogeneous for ethylenediamine irrespective of the solvent and that the higher level of intercalation in non-polar media was probably a consequence of the inhibition of competitive reactions with the solvent. For bis(3-aminopropyl)amine, the higher reaction times required to obtain satisfactory degrees of intercalation in the non-polar solvent suggests that with this solvent the process is kinetically controlled for longer chain amines.The authors acknowledge the MICINN of Spain (Projects CTQ-2011-29272-C04-01 and -03) for financial support.Peer Reviewe

Structural properties of alumina- and silica-supported Iridium catalysts and their behavior in the enantioselective hydrogenation of ethyl pyruvate

Iridium catalysts were prepared using alumina or silica as supports and two preparation methods, incipient wetness impregnation and flame spray pyrolysis. These catalysts were characterized, after reduction in hydrogen, by transmission electron microscopy, infrared spectroscopy of adsorbed CO and microcalorimetry of CO chemisorption. Aliquots of these catalysts were tested in the ethyl pyruvate hydrogenation using cinchonidine as a chiral modifier. Different enantioselectivities to (R)-ethyl lactate were obtained depending on the support material and the preparation method. Based on the structural characterization it is proposed that the different enantioselectivities are mainly due to different surface structure of the iridium nanoparticles caused by the support interaction.Authors acknowledge the MICINN of Spain (Projects CTQ-2011-29272-C04-01 and -03) for financial support.Peer Reviewe

Desde el ácido grafítico al óxido de grafeno: propiedades y aplicaciones derivadas de su química superficial

Trabajo presentado en la XXXIV Reunión Bienal de la Real Sociedad Española de Química, celebrada en Santander (España) del 15 al 18 de septiembre de 2013.La concesión del premio Nobel de Física en 2010 a los investigadores A. Geim y K. Novoselov por sus trabajos sobre el grafeno, ha despertado un enorme interés en los materiales laminares derivados del grafito. El número de publicaciones científicas realizadas sobre óxido gráfitico ha pasado desde una media de menos de 20, hasta 2004, a más de 130 en 2012; mientras que los artículos que contienen el término óxido de grafeno, han sido más de 3000 en 2012 (y hasta 2007 no se usaba este término). De hecho lo que hace pocos años llamábamos ácido u óxido grafítico ha pasado a designarse como óxido de grafeno. Los campos donde son aplicados los óxidos de grafito o de grafeno (OGs) también han aumentado exponencialmente, pasando de ser aplicados como adsorbentes de contaminantes de aguas (grafitos expandidos) a ser mencionados como refuerzo de polímeros, como material para producir baterías de Li, como componentes de sensores de gases, para fabricar semiconductores o ultracondensadores o electrodos, etc. Aparte estarían las aplicaciones catalíticas de las que cabe destacar las fotocatalíticas (con TiO2). Cabe resaltar que los OGs son materiales muy versátiles, y que permiten combinarse con otros sólidos para conseguir muy diversos ¿materiales compuestos¿. Además los OGs pueden ser la base para producir grafeno. Igualmente las propiedades de superficie de los OGs son interesantes ya que permiten anclar en sus superficies compuestos moleculares que, por ejemplo, pueden tener propiedades catalíticas. En esta comunicación se van a presentar algunos resultados recientes de nuestro grupo de investigación, en los que tras inmovilizar el complejo Ru-BINAP en los OGs lo aplicamos como catalizador enantioselectivo en la hidrogenación de metilacetoacetato; o cuando comprobamos una mayor estabilidad como catalizador en hidrogenación de cinamaldehido del complejo Ru(PPh3)3Cl2 enlazado covalentemente sobre OGs funcionalizados usando [3-(2-Aminoetilamino)propil]trimetoxisilano. Asimismo hemos introducido funciones básicas, al realizar el proceso de exfoliación de OGs en atmósfera de amoniaco, y las aplicamos como catalizadores en la deshidrogenación de bioetanol.Peer Reviewe

MnFe2O4@CNT-N as novel electrochemical nanosensor for determination of caffeine, acetaminophen and ascorbic acid

For the first time, a glassy carbon electrode (GCE) modified with novel N-doped carbon nanotubes (CNT-N) functionalized with MnFe2O4 nanoparticles (MnFe2O4@CNT-N) has been prepared and applied for the electrochemical determination of caffeine (CF), acetaminophen (AC) and ascorbic acid (AA). The electrochemical behaviour of CF, AC and AA on the bare GCE, CNT-N/GCE and MnFe2O4@CNT-N/GCE were carefully investigated using cyclic voltammetry (CV) and square-wave voltammetry (SWV). Compared to bare GCE and CNT-N modified electrode, the MnFe2O4@CNT-N modified electrode can remarkably improve the electrocatalytic activity towards the oxidation of CF, AC and AA with an increase in the anodic peak currents of 52%, 50% and 55%, respectively. Also, the SWV anodic peaks of these molecules could be distinguished from each other at the MnFe2O4@CNT-N modified electrode with enhanced oxidation currents. The linear response ranges for the square wave voltammetric determination of CF, AC and AA were 1.0 × 10−6 to 1.1 × 10−3 mol dm−3, 1.0 × 10−6 to 1.0 × 10−3 mol dm−3 and 2.0 × 10−6 to 1.0 × 10−4 mol dm−3 with detection limit (S/N = 3) of 0.83 × 10−6, 0.83 × 10−6 and 1.8 × 10−6 mol dm−3, respectively. The sensitivity values at the MnFe2O4@CNT-N/GCE for the individual determination of AC, AA and CF and in the presence of the other molecules showed that the quantification of AA and CF show no interferences from the other molecules; however, AA and CF interfered in the determination of AC, with the latter molecule showing the strongest interference. Nevertheless, the obtained results show that MnFe2O4@CNT-N composite material acted as an efficient electrochemical sensor towards the selected biomolecules