Wetting Properties at Nanometer Scale

The proposed chapter reviews a series of experimental techniques which enable the accurate quantitative study of wetting properties. The introductive part presents some of the many phenomena and processes influenced by wetting, underlining the importance of understanding the fundamental science involved. A few historical considerations about the quantitative study of wetting and related phenomena are given. Next, some of the “classical” techniques employed for studies at the macroscopic scale are presented. The importance of studies of such phenomena at micro- and nanometer level is underlined, as a consequence of the enormous influence that micro- and nanodevices play in our day to day activities, and examples of quantitative studies, involving various measurement techniques, are given from literature. A description of the basic phenomena related to polarization forces in Scanning Polarization Force Microscopy (SPFM) technique is given, followed by experimental details concerning the actual implementation of the technique. Examples of applications of SPFM are given from literature (from the spreading of liquid crystals on solid substrates to studies of corrosion at nanometer level). Particularly, it is emphasized how this versatile technique was successfully used for direct measurements of contact angles for liquid micro- and nano-droplets, enabling the calculation of the dependence of surface potential energy between the surfaces, the spreading coefficient and the disjoining pressure for micro- and nano-droplets

High-Quality Carbon Nanomaterials Synthesized by Excimer Laser Ablation

Due to their special physical and chemical properties and potential applications from hydrogen storage to medical implantation, the carbon-based nanomaterials are in the frame of attention for many research groups all over the world. As synthesis techniques, we highlight arc discharge, chemical vapor deposition (CVD) and laser ablation. Even an expensive technique, laser ablation is suitable for single-wall carbon nanotubes (SWCNTs) synthesis, providing the highest yield of over 70%, while arc discharge yield is about 30% and CVD is about 42%. The most common investigation methods for carbon nanomaterials are micro-Raman spectroscopy, thermo-gravimetric analysis (TGA) and morphological and topographic studies done by atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HR-TEM). We also emphasize in this work that by involving a home-designed reactor, we successfully synthesized SWCNTs, carbon nano-onions (CNOs) as well as graphene in the same reactor. Tuning the experimental parameters, we switch the end type of nanomaterials. We have done comprehensive studies regarding the carbon nanomaterials synthesis

Activated carbons with extremely high surface area produced from cones, bark and wood using the same procedure

Activated carbons have been previously produced from a huge variety of biomaterials often reporting advantages of using certain precursors. Here we used pine cones, spruce cones, larch cones and a pine bark/wood chip mixture to produce activated carbons in order to verify the influence of the precursor on properties of the final materials. The biochars were converted into activated carbons with extremely high BET surface area up to similar to 3500 m(2) g(-1) (among the highest reported) using identical carbonization and KOH activation procedures. The activated carbons produced from all precursors demonstrated similar specific surface area (SSA), pore size distribution and performance to electrodes in supercapacitors. Activated carbons produced from wood waste appeared to be also very similar to "activated graphene" prepared by the same KOH procedure. Hydrogen sorption of AC follows expected uptake vs. SSA trends and energy storage parameters of supercapacitor electrodes prepared from AC are very similar for all tested precursors. It can be concluded that the type of precursor (biomaterial or reduced graphene oxide) has smaller importance for producing high surface area activated carbons compared to details of carbonization and activation. Nearly all kinds of wood waste provided by the forest industry can possibly be converted into high quality AC suitable for preparation of electrode materials

Noble Metal Dispersed on Reduced Graphene Oxide and Its Application in PEM Fuel Cells

Metal-dispersed nanoparticles on reduced graphene oxide as catalyst for oxygen reduction reaction (ORR) demonstrate promising applications in the energy sector. The catalyst activity enhancement and stability improvement investigated in this study are mandatory steps in obtaining feasible electrodes for PEMFC. The chapter deals with the synthesis of noble metal catalysts including platinum and gold nanoparticles dispersed on reduced graphene oxide (PtNPs/rGO and AuNPs/rGrO). The understanding of the correlations between the electrochemical activity on one side and the structure, composition and synthesis method on the other side are provided. Facile routes in order to prepare the well dispersed PtNPs/rGO and AuNPs/rGrO are included. The structure and morphology were characterized by different techniques, namely X-ray diffraction (XRD), Scanning Transmission Electron Microscopy (STEM), specific surface area measurements. In this context we report a hybrid derived electrocatalyst with increased electrochemical active area and enhanced mass-transport properties. The electrochemical performances of PtNPs/rGO and AuNPs/rGrO were tested and compared with a standard PEMFC configuration. The performed electrochemical characterization recommends the prepared materials as ORR electrocatalysts for the further fabrication of cathodes for PEM fuel cells. The research directions as well as perspectives on the subsequent development of more active and less expensive electrocatalysts are established

Hydrogen Chemical Configuration and Thermal Stability in Tungsten Disulfide Nanoparticles Exposed to Hydrogen Plasma

Producción CientíficaThe chemical configuration and interaction mechanism of hydrogen adsorbed in inorganic nanoparticles of WS2 are investigated. Our recent approaches of using hydrogen activated by either microwave or radiofrequency plasma dramatically increased the efficiency of its adsorption on the nanoparticle surface. In the current work we put an emphasis on elucidation of the chemical configuration of the adsorbed hydrogen. This configuration is of primary importance as it affects its adsorption stability and possibility of release. To get insight on the chemical configuration, we combined the experimental analysis methods with theoretical modeling based on the density functional theory (DFT). Micro-Raman spectroscopy was used as a primary tool to elucidate chemical bonding of hydrogen and to distinguish between chemi- and physisorption. Hydrogen adsorbed in molecular form (H2) was clearly identified in all plasma-hydrogenated WS2 nanoparticles samples. It was shown that the adsorbed hydrogen is generally stable under high vacuum conditions at room temperature, which implies its stability at the ambient atmosphere. A DFT model was developed to simulate the adsorption of hydrogen in the WS2 nanoparticles. This model considers various adsorption sites and identifies the preferential locations of the adsorbed hydrogen in several WS2 structures, demonstrating good concordance between theory and experiment and providing tools for optimizing hydrogen exposure conditions and the type of substrate materials.2018-08-08Ministerio de Economía, Industria y Competitividad (Project MAT2014- 54378-R)Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA050U14

Uncovering Cortical Modularity by Nanotechnology

Cortical modularity and nanotechnology might look like a strange pair of concepts taken together, but nevertheless they seem very much suited for each other. Indeed, cortical modularity is a fundamental microanatomic feature of the brain while nanotechnology with its nanometric precision provides nanoscale structures, namely nanowires and carbon nanotubes capable of interacting with the brain at the genetic, molecular, and microcircuit level. Research in neuroscience is essentially a combination of many interdisciplinary sciences where nanoscience and nanotechnology plays a pivotal role. In this chapter we examine carbon nanotubes (CNTs) and nanowires (NWs), and their potential to uncover the function of cortical microcircuits, as well as novel applications for diagnosis and treatment of brain diseases. For example, the simultaneous recording from cortical minicolumns with multi-electrode arrays (MEAs) consisting of CNTs or NWs is emerging for developing cognitive prostheses for a broad range of neurological and psychiatric dysfunctions