Graphene Quantum Dot Embedded Hydrogel for Dissolved Iron Sensing

A robust and accurate chemical sensor for dissolved iron has been developed, based on highly fluorescent graphene quantum dots (GQDs). This work describes the construction of a GQD embedded hydrogel that displays strong fluorescence emission from the bulk structure. The hydrogel is made from poly(2-hydroxyethyl methacrylate) (pHEMA) and crosslinked by ethylene glycol dimethacrylate to form a water permeable, flexible and transparent material. Polymerisation in the presence of the GQDs physically entraps the fluorescent nano-particles within the hydrogel. The fluorescence properties of the GQD-pHEMA hydrogels have been thoroughly characterised, including by confocal microscopy in the first reported use of this technique for a GQD composite material. Sensing of dissolved Fe(III) by the GQD-pHEMA hydrogels has been demonstrated, whereby the Fe(III) quenches the GQDs fluorescence emission. The GQD-pHEMA hydrogels were selective to Fe(III) and showed a linear response for concentrations in the range of 10-200 mu M.