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.

► Role of MPA as a linker inCdSe- TiO2 nanocomposites has been studied.
► Study indicates that MPA leads to a better absorption of CdSe on TiO2 nanoparticles.
► This leads to a better charge transfer and optical stability of the nanocomposites.
► Linker makes the nanocomposites an appropriate material for organic photovoltaics.