Luminescence tunability of europium functionalized graphene oxide sheets

Abstract

Luminescence tunable graphene oxide-europium (GO-Eu) composites were obtained by adopting a fresh composite preparation procedure. Unique GO-Eu precursor compositions maintained in acidic pH range and subjected to ultrasonic treatment were found to exhibit fine tuned emission bands ∼600 nm. FT-IR, XPS and SEM studies evidence the uptake of Eu ions in composite sheets and denote their nature of bonding with various functional groups at multiple sites of GO. Initial interaction of Eu ions with GO involves both adsorption as well as bonding processes while, introduction of acidity and ultrasonic treatments hinder the instant aggregation of composite sheets and facilitate the complexation of Eu ions at most reactive sites of GO. Changes in heterogeneous electronic structure of composite sheets alter the relative intensities of radiative transitions from localized states associated with and cause the observed fine tuning of luminescence from composites. These inferences were assessed by examining the emission features of aged GO-Eu composites exposed to different pH and ultrasonic treatment conditions. Distinctive windows of parameters were proposed to achieve relatively narrow and fine tuned emission bands in the wavelength range of 550–750 nm using fresh and aged GO composite dispersions.