Heterogeneous or competitive self-assembly at liquid-liquid interfaces

Date

2009-08

Journal Title

Journal ISSN

Volume Title

Publisher

Texas Tech University

Abstract

Self-assembly of nano-sized objects at liquid-liquid interfaces is of tremendous interest for various natural and industrial applications. For example, surfactant interfacial self-assembly is critical in numerous processes such as lubrication, detergency, biological transferring, and polymer processing. On the other hand, self-assembled nanoparticles at liquid-liquid interfaces serve as building blocks for bottom-up assembly of new functional materials with unique physical properties. However, many industrial processes are performed in the presence of both surfactants and nanoparticles. In spite of the importance, interfacial adsorption when a system contains both surfactants and colloidal particles has not been extensively studied. In particular, there is a limited understanding when nanoparticles are involved. In this dissertation, I have performed molecular dynamics simulations and some experimental work to study the heterogeneous or competitive self-assembly of surfactants and nanoparticles at water-trichloroethylene (TCE) interfaces. Interfacial structures, morphology, dynamics properties, and the influences of surfactant and nanoparticle assembly on interfacial properties were studied.

I also included some preliminary study on hybrid organic-inorganic solar cells, in which the self-assembly of polymers and nanoparticles in the bulk solution and at liquid-solid interfaces is considered to be critical in film morphology. Polymer-fullerene bulk heterojunctions (BHJs) are currently the most efficient combination for organic solar cells; however, the efficiency is not good. One of the promising approaches to improve device efficiency is to use semiconductor nanocrystals as electron acceptor or alkyl thiols as co-solvent. Hybrid polymer-inorganic nanocrystal composites offer an attractive means to combine the merits of polymer and inorganic nanocrystals to achieve higher power conversion efficiency. This study focuses on integrating ZnO and CdSe nanocrystals or 1-octadecanethiol (ODT) into P3HT: PCBM BHJs to improve photovoltaic performance under ambient conditions. The preliminary results reveal that both CdSe and ODT under optimum conditions provided significant enhancement on power conversion efficiency compared with pure organic composites; however, ZnO failed to improve the device performance.

Description

Keywords

Liquid-liquid interface, Self-assembly, Nanoparticle

Citation