M. D. Merchán

Adsorption of quantum dots onto polymer and Gemini surfactant films: a quartz crystal microbalance study.

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 SiO2 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.

Effect of Micelles on the Dynamic Surface Tension of Zwitterionic Surfactants

Abstract The dynamic surface tension of micellar surfactant solutions was measured using the maximum bubble pressure method. The chosen surfactants were carboxy- and sulfo-betaines. At the beginning, surface tension decay curves are consistent with a diffusion-controlled adsorption. However, at long times these curves were analyzed by using the Fainerman model. From these experiments, the rate constants for demicellization were obtained. The micelle dissociation rate constant depends of the surfactant concentration, the concentration dependence is interpreted by Anianssons theory, and the micelle dissociation constant independent of surfactant concentration was calculated. The rate constants found in this work are of the same order of magnitude as those obtained using classical techniques for fast reactions.

Motivating students of chemical engineering through a cooperative work recording educational videos

The work has been carried out with the participation of students from two different degrees of the University of Salamanca, degree in Chemical Engineering and degree in Audiovisual Communication. The work consists of recording educational videos in which the theoretical basis, the experimental procedure, the necessary equipment and data processing for laboratory practice of Chemical Engineering degree are explained. We have recorded four separate, short videos, since some of them can be used in more than one laboratory work. The second part of the work is to use the model of Flipped Classroom in which students will be prepared independently before going to the laboratory by the viewing of videos. The time allotted to experimental subjects will be used for practical work avoiding the theoretical explanation. The record of the videos was made by fourth- degree students of Audiovisual Communication supervised by their professor who oversaw the quality of the final product. The benefits of this project are analyzed in Conclusions section, and the results of the satisfaction survey conducted among students of both degrees are analyzed.

Langmuir‐Blodgett Methodology: A Versatile Technique to Build 2D Material Films

The Langmuir‐Blodgett (LB) methodology is based on the transfer process of a monolay‐ er adsorbed at the water interface, Langmuir film, from the air‐water interface onto solids by vertical dipping of the substrate immersed on the subphase. The technique allows the continuous variation of material density, packing, and arrangement by compressing or expanding the film by using barriers. Consequently, it provides the possibility of preparing films with the control of interparticle distance necessary to exploit the two‐dimensional (2D) materials in technological applications. In this chapter, we present some examples of fabrication of thin films of 2D material using this methodology. We show some methodologies based on this technique to build thin films of graphene oxides, Quan‐ tum Dots (QDs), and silver nanowires.