Browsing all articles tagged with adsorption Archives | nanotechnologies.qc.ca
Dec
28

Nanopatterning with dendrimers

Author Rémi Longtin    Category Nanopatterning     Tags , ,

Presentation

The following section is a short introduction to my most recent research (2007 to 2009) at the University of Geneva in the laboratory for colloids and surface chemistry.

G10 PAMAM dendrimer on silicaThe adsorption of macromolecules at the solid-liquid interface is a very common yet complicated phenomenon. One has simply to think of what happens when a drop of blood falls on a surface. Blood is a complex colloidal system. The fluid contains several macromolecules (proteins, biopolymers) as well as ions (Fe, K, Cl, Na etc.) and other cells all interacting with each other and with the surface. Preventing or promoting the adsorption of blood (or its specific constituents) to a surface may be critical in some biomedical applications. This example illustrates how macromolecular adsorption is ubiquitous, yet can be of great importance for both industry and fundamental science.

In terms of nano-technological applications, charged macromolecules from solutions can be used to pattern mineral surfaces. Typically, an interface will acquire a charge when immersed in a solution, water in this case. Similarly, the macromolecule’s ionizable functional groups can take or release protons, thus have a pH-dependent charge. When the charges of both molecule and surface have opposite signs and are of sufficient magnitude, adsorption via electrostatic interactions occurs.
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Jul
16

Hydrogen storage

Introduction

The automobile fleet is contributing significantly to air quality degradation in large cities. The use of hydrogen as a fuel is interesting since combustion delivers a lot of energy without polluting. However, some obstacles, like the efficient storage of this gas, remain before it can be implemented in the transportation industry.

Figure 1: Hydrogen powered car built by BMW

Figure 1: Hydrogen powered car built by BMW

Hydrogen storage solutions

The United States Department of energy (DOE) has fixed two targets for hydrogen storage solutions applied to automotive transportation. The first target requires a ratio of hydrogen weight / tank weight that is superior to 0,065 (6,5% weight). This target limits the weight of the tank. The second target requires a hydrogen volumetric density higher than 62 kg/m in order to limit the volume of the tank.

Four main solutions were proposed to solve this problem:

  • Compression or liquefaction of hydrogen
  • Metal hydrides
  • Chemical tanks
  • Adsorbent materials

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Feb
15

Hydrogen storage – literature

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Reference books

R. Saito, G. Dresselhaus and M. S. Dresselhaus, Physical Properties of carbon nanotubes, Imperial College Press, Londres, 1998

G. Gao, T. Cagin and W. A. Goddard III, Energetics, Structure, Mechanical and Vibrational Properties of Single Walled Carbon Nanotubes (SWNT), Foresight Institute, 1997 (pdf©)

D. Frenkel and B. Smit, Understanding molecular simulation: from algorithms to applications, Academic Press, San Diego, 1996

C. Ngô and H. Ngô, Physique statistique, Masson, Paris, 1995

R. A. Oriani, The physical and metallurgical aspects of hydrogen in metals, Fourth International Conference on Cold Fusion, 1993 (pdf)

Nanotube fabrication methods

S. Iijima, Helical microtubules of graphitic carbon, Nature 354 (1991), 56-58 (pdf©)

S. Iijima and T. Ichihashi, Single-shell carbon nanotubes of 1-nm diameter, Nature 363 (1993), 603-605 (pdf©)

A. Thess, R. Lee, P. Nikolaev, H. Dai, P. Petit, J. Robert, C. Xu, Y. H. Lee, S. G. Kim, A. G. Rinzler, D. T. Colbert, G. E. Scuseria, D. Tománek, J. E. Fischer and R. E. Smalley, Crystalline Ropes of Metallic Carbon Nanotubes, Science 273 (1996), 483-487 (pdf©)
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