A sensitive AIEE probe for amphiphilic compounds

Abstract

α-Cyanostilbene substituted with dimethylaniline and hydroxyl groups exhibits profound intensity enhanced bathochromic shifts in an aqueous medium as compared to organic solvents. These conspicuous emission changes are attributed to aggregation as a consequence of restricted intramolecular rotation. This observation is commonly termed as aggregation induced enhanced emission (AIEE). Single crystal X-ray crystallographic data suggest a zigzag molecular packing arrangement with intermolecular hydrogen bonding between –CN and –OH moieties. This unique observation is exploited as a diagnostic tool to probe amphiphilic compounds in aqueous media. Fluorescence investigations reveal that at lower surfactant concentrations emission due to aggregation is preserved, while at higher surfactant concentrations the aggregated emission is lost with concomitant changes to the micelle structure. Dynamic light scattering (DLS) and Scanning Electron Microscopy (SEM) experiments were used to examine the effect of surfactants on the particle size and morphology, respectively. This sensitive AIEE fluorescence response can also be visually observed by using a hand-held UV lamp.