| The scientific work presented in this thesis pertains to the physical chemistry of colloidal/aqueous and air/aqueous interfaces. With the purpose to improve our knowledge of the kinetic and the equilibrium processes occurring at these surfaces, interface selective nonlinear spectroscopic methods of second harmonic and sum frequency generation have been utilized to investigate: (1) transport of ions across liposome bilayer (2) interfacial acid-base chemistry at the polystyrene carboxyl particle surface (3) identification and physical properties of organic ions at the air/aqueous interface and (4) surface polarity of colloidal systems.;Surfaces are everywhere in nature and the scientific endeavor dedicated to the understanding of surfaces is vast. If man's inquisitiveness to know and appreciate the physical nature is not the singular reason to study surfaces, it may then be added that a concrete understanding of the physical and chemical properties of various interfaces has numerous applications in the fields of medical science and technology. With the advent of lasers and thereafter the discovery of 2nd order nonlinear spectroscopy, which provides molecular information specific to the surface, the potential of investigating multitude aspects of interfacial chemistry is at its apex.;Many discoveries have been made in the long history of surface science. The scientific results presented in this thesis represent, in accordance with the words of Sir Isaac Newton, merely some pebbles from the great ocean of truth. Some of the key findings of the experimental work based on second harmonic and sum frequency generation reported here are: the channel vs. carrier based ionophores differ in their rate of ion transport across liposome bilayer (chapter 2), the acidity of carboxyl functional group affixed at the polystyrene particle surface differ from that of expected in the bulk aqueous solution (chapter 3), small aromatic charged compounds adsorb at the air/aqueous interface, with electron rich species exhibiting fluctuation in their average molecular orientation (chapters 4 to 6), and the surface of latex particle is polar than bulk water (chapter 7). |
