Tunable luminescence of graphene oxide-polyaniline nano-composite: Effect of an anionic surfactant

Abstract

Luminescence of the graphene oxide-polyaniline (GO-PANI) nano-composite has been found to be tuned in the presence of an anionic surfactant (sodium dodecyl sulphate, SDS). In acidic medium (pH~2.5), graphene oxide (GO), grafted by polyemeraldine salt form of polyaniline (PANI), interacts with SDS having concentration above 2 mM and there by hemispherical surface micelles on GO sheets are formed by replacing of some of the PANI chains from GO surfaces. This leads to a non-polar environment around the fluorophoric moiety of the GO-PANI nano-composite. In consequence, relative contribution of the slightly blue shifted luminescence due to charge transfer species in GO-PANI decreases. In addition to this, intercalation of SDS between the GO layers weakens the stacking interaction among the basal planes of GO and as a result of it, two emission bands at 300–310 nm and 330–345 nm, originating due to the functional groups attached with GO sheets sp2 conjugated carbon atom in GO, are markedly appeared. In alkaline medium (pH~10.5), polyemeraldine base of PANI remains non interacting with GO and so the effect of SDS on the luminescence is similar with that of alkaline dispersion of GO, in presence of SDS, where SDS intercalated largely separated layers of GO moiety shows two characteristics luminescence bands of GO.