Fabrication and characterization of layer-by-layer assembled films

In the first chapter, we describe the fabrication and study of layer-by-layer (LbL) assembled polyoxometalate (POM) films on molecular level. Variation in ionic strength of the dipping solutions proved to be an efficient parameter in obtaining films with varying loading concentrations. The polymer-nanoparticle interaction under various conditions was visualized with thermodynamic arguments and the contact modes between polymer chain and cluster were related with varying loading concentrations. We also demonstrate the use of LbL assembled conducting polymer film when it is used as a stabilizing layer on the top of a nanoparticle films. Such a layer provides a higher conductivity than an insulating layer so that the electrochemical activity of the redox-active layer inside can also be preserved.;The final chapter deals with applications of POMs as electron accepting layers in polymeric photovoltaic devices. Our research shows that the photoluminescence intensity emitted by a multilayer of conjugated polymer can be quenched to desired level by appropriate loading of POMs during the deposition process. Our modeling shows that this quenching is proportional to amount of POMs used. By loading gold nanoparticles in similar fashion, a blue-shift in PL intensity is obtained along with the PL quenching. Finally, a direct immersion of multilayers in POM solutions after the deposition process also yield multilayers with estimated loadings of POMs. In this case, apart from PL quenching, a three-dimensional swelling of PPV films is observed, that increases UV-absorption.;The second chapter deals with the mass-transfer in the layer-by-layer assembled films. We try to model ionic and electronic transport into such POM films using the electrochemical impedance spectroscopy and try to measure important parameters like diffusion (ionic-electronic) and conductivity. We conclude that for LbL films, the charge of the terminating layer and the porosity of the films have a profound effect on ionic diffusion inside the films. The results for diffusion in POM films with varying loading concentrations correlate with the results obtained in part one. This part also deals with a study on oxygen reduction catalysis by POM films with varying porosity. The results indicate that a higher loading of POMs as well as a highly porous film is required to maximize the catalytic efficiency of POM films for oxygen reduction.