Title

Micro and nano scale organization and its photoelectronic applications

Date of Completion

January 2006

Keywords

Chemistry, Polymer

Degree

Ph.D.

Abstract

First, Amorphous Al(Meq)3, a potential substitute which crystallizes more slowly than Alq3 but possesses excellent thermal stability as compared to Alq3, was used to study the long-term stability of organic LEDs. Blends of Al(Meq)3 and Alq3 show even greater morphological stability improvement of the amorphous phase over Al(Meq) 3 films. Polyurea (poly(1,4-phenylene-2,6-pyridylurea) ligand, a potential OLEDs precursor, has shown well controlled photo-assisted hydrolysis to cleanly decompose into amines. The controllability and cleanness of final products of the photo hydrolysis could make it a prospective material for photo-resist application or possible controlled metal cation release system. ^ Secondly, a kinetic surface ligand exchange step in the beginning of the process is proposed to explain the contradictory phenomenon of immediately photoluminescence quenching followed by gradual recovery of PL intensity in the case of primary amines. Different quenching and recovering speed and extent of various amines indicated that the surface packing ability and diffusion rate of amines play an important role in the exchange process. Chemical etching of CdSe NCs by amines is proposed to explain the characteristic bottleneck behavior of the observed blue shift of UV/Vis absorption and PL emission spectra during exposure of CdSe NCs to 3-amino-1-propanol at high temperature. Water and oxygen are found to play an important role in the etching process. ^ Finally, the DNA-assisted assembly of microspheres into close-packed 2D opaline arrays is successfully conducted. After the first monolayer was immobilized using the non-covalent hybridization of DNA, by passing these 2D opaline arrays through an air/liquid interface, multilayers were selectively removed leaving behind the DNA-bound monolayer, without losing its original long-range order. DNA hybridization was found to play an important role in immobilizing the first monolayer of 2D opaline arrays onto the substrate, with an approximate strength three times higher than that of non-specific interactions. ^