Probing the compositional, structural and morphological aspects of CdSe-TiO2 nanocomposites by surface-sensitive techniques

In this work, a colloidal suspension of trioctyl phosphine oxide/trioctyl phosphine (TOPO/TOP)-capped CdSe QD's of size ∼5 nm was prepared by chemical route and these QD's were anchored on the surface of sol-gel prepared nanoporous TiO₂ layers in THF-ethanol solvent either by direct adsorption or with the aid of bi-functional linker molecule mercaptoacetic acid (MPA). The particle size estimation of both TiO₂ and CdSe nanoparticles by X-ray diffraction (XRD) and transmission electron microscopic (TEM) measurements concur well with each other. Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) studies elucidate the signatures of TiO₂, CdSe nanoparticles and linker which is also supported by the presence of contrasting images in TEM studies respectively. XPS depth-profiling measurements have been used as a probe to determine the chemical composition and structure of CdSe nanocrystals and CdSe-TiO₂ nanocomposites respectively. The CdSe nanoparticles and CdSe-TiO₂ nanocomposites formed by different routes are modeled, based on the observations of several complimentary techniques.