Examinando por Autor "Moreno, Rodrigo"
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Publicación Porous Alkaline‑Earth Doped Multiwall Carbon Nanotubes with Base Catalytic Properties(Springer, 2019-05-04) Barrios‑Bermúdez, N.; Santos‑Granados, J; Calvino‑Casilda, V; Cerpa‑Naranjo, A; Rojas‑Cervantes, M.L.; Moreno, RodrigoAlkaline-earth doped multiwall carbon nanotubes, M-CNT (M=Mg, Ca, Sr, Ba) have been prepared by a combined method of ionic exchange and precipitation. The wide characterization of the solids by nitrogen adsorption, ATR–FTIR, thermal analysis, XRD, scanning electron microscopy, transmission electron microscopy, point of zero charge (PZC), and X-ray photoelectron spectroscopy shows that the incorporation of M to the CNTs has been successfully produced. The doping with the alkaline-earth cations causes a decrease in the SBET value of the raw material, mainly due to the blockage of mesopores by the metal carbonate phase formed in most of cases. This metallic phase also contributes to the destabilization of the nanotubes by promoting their oxidation. According to PZC values, the acid character of oxidized CNTs changes to basic for the M-CNT series, Mg-CNT showing the highest PZC value. The basic properties of the catalysts have been tested in the C–C bond forming reaction of Knoevenagel, by carrying out the condensation of ethyl cyanoacetate with benzaldehyde or 4-methoxybenzaldehyde.Publicación Rheological Properties of Different Graphene Nanomaterials in Biological Media(MDPI, 2022-05-18) Cerpa Naranjo, Arisbel; Pérez Piñeiro, Javier; Navajas Chocarro, Pablo; Lado Touriño, Isabel; Barrios Bermúdez, Niurka; Moreno, Rodrigo; Rojas Cervantes, María LuisaCarbon nanomaterials have received increased attention in the last few years due to their potential applications in several areas. In medicine, for example, these nanomaterials could be used as contrast agents, drug transporters, and tissue regenerators or in gene therapy. This makes it necessary to know the behavior of carbon nanomaterials in biological media to assure good fluidity and the absence of deleterious effects on human health. In this work, the rheological characterization of different graphene nanomaterials in fetal bovine serum and other fluids, such as bovine serum albumin and water, is studied using rotational and microfluidic chip rheometry. Graphene oxide, graphene nanoplatelets, and expanded graphene oxide at concentrations between 1 and 3 mg/mL and temperatures in the 25–40 ◦C range were used. The suspensions were also characterized by transmission and scanning electron microscopy and atomic force microscopy, and the results show a high tendency to aggregation and reveals that there is a protein–nanomaterial interaction. Although rotational rheometry is customarily used, it cannot provide reliable measurements in low viscosity samples, showing an apparent shear thickening, whereas capillary viscometers need transparent samples; therefore, microfluidic technology appears to be a suitable method to measure low viscosity, non-transparent Newtonian fluids, as it is able to determine small variations in viscosity. No significant changes in viscosity are found within the solid concentration range studied but it decreases between 1.1 and 0.6 mPa·s when the temperature raises from 25 to 40 ◦C.