MARÍA DOLORES MERCHÁN MORENO - Academia.edu (original) (raw)

Papers by MARÍA DOLORES MERCHÁN MORENO

Journal of Science: Advanced Materials and Devices, 2021

ACS Applied Materials & Interfaces, 2020

We address here the role of oxidation impurities on the structure of graphene oxide films at the ... more We address here the role of oxidation impurities on the structure of graphene oxide films at the air−water interface by specular neutron reflectivity (SNR). We study films of purified graphene oxide (PGO) and nonpurified graphene oxide in the close-packed state. Nonpurified graphene oxide is constituted by graphene oxide (GO) layers with oxidation impurities adsorbed on the basal plane, while in PGO sheets, impurities are eliminated. SNR measurements show that GO films are formed by welldefined bilayers constituted by 2−3 layers of GO stacked in contact with air and a second layer of impurities submerged in the aqueous subphase. In contrast, PGO films are formed by a single layer in contact with air. We show for the first time that impurities constitute a layer submerged in the aqueous subphase, decrease the elasticity, and favor the collapse of graphene oxide films. Our results allow designing the surface properties of GO trapped at fluid interfaces.

Journal of Luminescence, 2019

Carbon nanoparticles (CNPs) have aroused a great interest due to its strong blue fluorescence emi... more Carbon nanoparticles (CNPs) have aroused a great interest due to its strong blue fluorescence emission. However, the blue fluorescence limits its applications in several cases; therefore, the synthesis of CNPs with multicolor emissions becomes mandatory. A widely used strategy of modulation of CNP photoluminescence is doping the carbon network with nitrogen atoms. Despite the great number of works carried out with N-doped CNPs, some contradictory experimental observations have been reported. These contradictions seem to be due to structural differences resulting of the different synthesis routes. Therefore, it is difficult to correlate the Photoluminescence properties with the nanoparticle structure. To address this issue, we study the Photoluminescence properties of CNPs with different chemical composition and sizes. Nanoparticles were synthesized by an acidic treatment for cutting carbonaceous materials previously reported and five different precursors. Using this methodology, we obtained five different materials which allow correlating the Photoluminescence spectrum with chemical composition and nanoparticle sizes.

ACS Sustainable Chemistry & Engineering, 2019

New nanocomposites based on graphene oxide with polyaniline (PANI) or Fe 3 O 4 nanoparticles (MG)... more New nanocomposites based on graphene oxide with polyaniline (PANI) or Fe 3 O 4 nanoparticles (MG) were synthesized for CO 2 capture. To study the effect of graphene oxide structure on the CO 2 retention capacity, CO 2 /N 2 selectivity, adsorbent regeneration, and adsorption kinetics, two different graphene oxides were synthesized by oxidation of graphite flakes (GO) and commercial carbon nanofibers (NSGO). CO 2 adsorption isotherms at 300 K were evaluated by gravimetric experiments. The results described the CO 2 adsorption as reversible physisorption mechanism, where the CO 2 adsorption capacity increases linearly with the micropore volume. Results also demonstrate the good CO 2 /N 2 selectivity, recyclability, and fast adsorption kinetics of the materials tested. Differences concerning the adsorption properties of nanocomposites are related to the chemical composition and the size of graphene oxide sheets.

Langmuir, 2014

We used quartz crystal microbalance with dissipation to study the mechanical properties, the kine... more We used quartz crystal microbalance with dissipation to study the mechanical properties, the kinetics of adsorption, and the amount of CdSe quantum dots (QDs) adsorbed onto a SiO 2 sensor, referred as bare sensor, onto the sensor modified with a film of the polymer poly(maleic anhydride-alt-1-octadecene), PMAO, or with a film of the Gemini surfactant ethyl-bis(dimethyl octadecyl ammonium bromide), abbreviated as 18-2-18. Results showed that when the sensor is coated with polymer or surfactant molecules, the coverage increases compared with that obtained for the bare sensor. On the other hand, rheological properties and kinetics of adsorption of QDs are driven by QD nanoparticles. Thus, the QD films present elastic behavior, and the elasticity values are independent of the molecule used as coating and similar to the elasticity value obtained for QDs films on the bare sensor. The QD adsorption is a two-step mechanism in which the fastest process is attributed to the QD adsorption onto the solid substrate and the slowest one is ascribed to rearrangement movements of the nanoparticles adsorbed at the surface.

The Journal of Physical Chemistry B, 2008

We have studied the effect of the addition of sodium poly(styrene sulfonate) polymers on the prop... more We have studied the effect of the addition of sodium poly(styrene sulfonate) polymers on the properties of monolayers formed by the adsorption of two carboxybetaines with different number of separation methylenes between their charged groups. Fluorescence and surface tension measurements indicate that above the critical aggregation concentration a surfactant-polymer complex of electrostatic origin is formed in bulk. The complexes have a negative charge that is repelled by the negative charge of the surfactant adsorbed at the interface; consequently, the monolayer seems to be exclusively formed by surfactant carboxybetaines. The high-frequency surface viscoelasticity of the monolayers was studied by surface dynamic light-scattering measurements. The behavior of the dilational elasticity and viscosity is explained by relaxation involving molecular reorientation within the adsorbed layer.

Reaction Kinetics & Catalysis Letters, 1994

... 216 Page 7. SALVADOR, MERCHAN: SUPPORTED CATALYSTS gies depend on coverage. It would then be ... more ... 216 Page 7. SALVADOR, MERCHAN: SUPPORTED CATALYSTS gies depend on coverage. It would then be necessary to obtain a fourth thermogram. ... Catal., i_~7, 103 (1967). 2. A. Brenner, A. Hucul: J. Catal., 56, 134 (1979). 3. JL Falconer, JA Schwartz: Catal. Rev.-Sci. ...

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006

In order to study the effect of charge on the adsorption of surfactants at the air-water interfac... more In order to study the effect of charge on the adsorption of surfactants at the air-water interface, two carboxybetaines have been synthesized with different number of separation methylenes between their charged groups. After purification and structure confirmation, the equilibrium and dynamic surface tensions were measured as a function of surfactant concentration for both the cationic and neutral forms of the surfactant molecules. The effect of ionic strength on the adsorption process was also studied. The equilibrium surface tension values were interpreted according to the Langmuir model and the dynamic surface tension data, converted to surface concentration by the Langmuir parameters, are consistent with the assumption of diffusion control over the range of surfactant concentrations studied. The diffusion coefficients show a progressive decrease in the rate of adsorption when the number of methylene units between the betaine charged groups increase.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004

Dynamic surface tension of aqueous alkaline solutions of 1-N-l-tryptophan-glycerol-ether surfacta... more Dynamic surface tension of aqueous alkaline solutions of 1-N-l-tryptophan-glycerol-ether surfactants, C n-TEG, below its critical micelle concentration has been measured as a function of the surfactant concentration and over a temperature range of 19.7-31.5 • C. The static tension of the alkyl tryptophan-glycerol-ether surfactants with n = 9-11 is analyzed in terms of the combined Frumkin-Davies isotherm. By using this state equation the adsorption kinetics of these surfactants can be interpreted as a diffusion-controlled process.

Advances in Colloid and Interface Science, 2020

Graphene oxide is a derivate of graphene obtained by oxidation of graphite and other carbonaceous... more Graphene oxide is a derivate of graphene obtained by oxidation of graphite and other carbonaceous materials. The more accepted structure consists in carbonyl and carboxyl groups located at the edge of the graphene network and hydroxyl and epoxy groups attached to the basal plane. The percentage of O-groups depends on the synthesis route and the material used as carbon source. In addition, highly oxidized fragments, called oxidative debris, OD, are produced during the oxidation process. These fragments are adsorbed onto the graphene oxide network and can be removed by alkaline washing. The purified material has lower O/C ratio than graphene oxide and its properties are also quite different. Due to its structure, graphene oxide can be adsorbed at the air-water interface of the aqueous solution by diffusion, Gibbs monolayers, or by spreading on a clean water subphase resulting in a Langmuir film. This review is intended to provide information on the importance of controlling the chemical composition, structure, size, and oxidative debris, on the manufacture of graphene oxide films. To this end the review shows the influence of the synthesis route and the starting material on the structure of graphene oxide and analyzes several examples of the behavior and properties of films prepared with different types of graphene oxides. The great variability of behaviors of graphene oxide films caused by the different structure of this material provides a great opportunity to fine-tune the properties of films according to the needs of different applications.

Coloides e interfases, 2005, ISBN 84-7800-524-2, págs. 159-166, 2005

Aulas innovadoras en la formación de los futuros educadores de Educación Secundaria: modelos y experiencias en el Máster en Profesor de Educación Secundaria Obligatoria y Bachillerato, Formación Profesional y Enseñanzas de Idiomas, 2020, ISBN 978-84-1311-323-4, págs. 135-155, 2020

Elaboración de material didáctico utilizando TIC's como herramienta para motivar a los estudiante... more Elaboración de material didáctico utilizando TIC's como herramienta para motivar a los estudiantes que repiten matrícula para Grados en Ciencias

Se describe la construccion y puesta a punto de un equipo que por primera vez permite la realizac... more Se describe la construccion y puesta a punto de un equipo que por primera vez permite la realizacion de experimentos de desorcion termica programada en disolucion. Dicho equipo es utilizado para llevar a cabo un estudio completo de desorcion de varios fenoles desde un carbon activo. El trabajo permite afirmar que es posible extender la desorcion termica programada a procesos en disolucion.

Innovar en las aulas: modelos y experiencias de innovación educativa en el Máster de Profesorado de Educación Secundaria, Bachillerato, Formación Profesional y Enseñanza de Idioma, 2018, ISBN 978-84-9012-888-6, págs. 37-50, 2018

Memoria ID-0112. Ayudas de la Universidad de Salamanca para la innovacion docente, curso 2009-2010.

Memoria ID-018. Ayudas de la Universidad de Salamanca para la innovacion docente, curso 2013-2014.