|M.Sc Student||Milyutin Yana|
|Subject||Fluorescence Resonance Energy Transfer (FRET) between|
Adsorbed Molecules as a Means to Study Surface
Contact Lines in Composite Particles
|Department||Department of Chemical Engineering||Supervisor||PROF. Yaron Paz|
|Full Thesis text|
Catalysts that are made of composite particles may comprise of several compounds, where each compound utilizes its own specific properties. On case of multi-step catalysis each domain catalyzes a specific different reaction and the products of these specific reactions react at the interface between the domains to give the final product. For such catalysts, it is highly important not only the interfacial surface areas, but rather the length of the surface contact line (SCL) between the domains of the various constituents. Measuring the length of the SCL is very difficult, and currently may involve microscopic means such as SEM or AFM that are relatively expensive and may require well-trained personnel.
In this work, it was proposed that fluorescence methods, and in particular Fluorescence Resonance Energy Transfer (FRET) may serve to measure SCL length. FRET is a distance-dependent physical process, by which energy is transferred non-radiatively from a donor to an acceptor by means of intramolecular or intermolecular long-range dipole-dipole coupling.
The principle of the method, developed in this thesis, is to selectively adsorb the donor on one type of a domain while selectively adsorbing the acceptor on a second type of domain. The requirement for short distance between the acceptor and the donor is then translated into a linear dependence between the emission intensity and the contour line length. This facilitates, upon using calibrated standards, to easily calculate the length of the contour between the domains.
Large part of the thesis described the optimization of the FRET parameters and the investigation of the selective adsorption of the donor and the acceptor. The adsorption of a variety of donor and acceptor dyes on the surfaces of alumina, silica, gold, and titania was studied. Based on these studies an appropriate model system was chosen, consisting of titania and H3PO4-coated titania as substrates and Fluorescein 5-isothiocyanate (5-FITC) and Tetramethylrodamin B isothiocyanate (TRITC) as donor and acceptor dyes, respectively. A set of well define domains with controlled SCL was prepared. The FRET intensity was measured as a function of SCL length and was found to be linearly dependent on the SCL length.
This novel method provides average properties of the interphase length without requiring highly trained personnel, long measuring time or expensive apparatus. The method described in this research is quite generic, and can be easily modified to ease its implementation.