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Atomic Force Microscopy Experiments on Interfaces and Surface Forces

The Atomic Force Microscope (AFM) was employed to study the flow of Newtonian liquids at solid interfaces, by directly measuring the hydrodynamic drainage force acting on a sphere approaching a flat surface. Contrary to the common assumption of no-slip, our force measurements provide clear evidence of boundary slip. We also found that the degree of boundary slip is a function of the liquid viscosity and the shear rate and that current theories of slip do not adequately describe the experimental data. Furthermore, in this Thesis, the structure and the surface properties of a range of systems of interest in interface and surface science are described. In particular, the morphology of soft layers (H* aggregates formed in Langmuir-Blodgett films), adsorbed particles (nanostructured gold surfaces and Ca(OH)2 nanoparticles), and molecular aggregates (micelles of nucleolipids and polymers containing their complementary bases) were investigated.

Mostra/Nascondi contenuto.
Chapter 1 1 CHAPTER 1 INTRODUCTION 1.1 Preamble Developments in the microscopy field, as in control, manipulation and measurement devices on a nanoscopic scale, led to the invention of the Scanning Tunneling Microscope (STM) by Binnig and Rohrer in 1982 [1]. Shortly afterwards, in 1986, Binnig, Quate and Gerber invented the Atomic Force Microscope (AFM) [2]. STM relies on measurement of exponentially decaying tunneling current between a metal tip and a conducting substrate. Since its invention and the recognition for its inventors of the Nobel Prise in 1986, STM has found a wide use in studies of inorganic materials [3,4], organic material [5,6] and dynamic processes [7], including reactions [8]. Not being restricted to conductive materials, AFM is a much more versatile instrument than STM, and more adopted in studies applied to colloidal systems and soft matter. The number of publications related to AFM has increased constantly since its invention, and the instrument is now a fundamental tool in most research laboratories of the world. The Atomic Force Microscope probably earned its initial popularity in virtue of its capability of providing images of samples with atomic resolution [5,9-12] in vacuum, air or liquid environment. The materials being investigated are almost endless: thin and thick film coatings, ceramics, composites, synthetic and biological membranes, biological macromolecules, metals, polymers, and semiconductors. The AFM is being applied in several fields of research, such as materials science and engineering, biochemistry and biology, in studies of the most varied phenomena, such as colloidal stability [13], characterisation of nanostructures and molecules [12,14,15], adhesion and delamination [8,16], surface elasticity [16], corrosion, etching, friction [17,18] and lubrication.

Tesi di Dottorato

Dipartimento: Chimica

Autore: Chiara Neto Contatta »

Composta da 190 pagine.

 

Questa tesi ha raggiunto 776 click dal 20/03/2004.

 

Consultata integralmente 2 volte.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.