Light-trapping hybrid gels
doi:10.1038/nindia.2011.30 Published online 28 February 2011
Researchers have designed highly fluorescent novel hybrid hydrogels by mixing clay materials with fluorescent dye molecules. Using a layered silicate material such as clay provides a scaffold for sequestering dye molecules, allowing them to self-assemble into highly fluorescent hybrid hydrogels.
Hydrogels with fluorescent molecules have potential applications as biosensors and for drug delivery. However, designing highly fluorescent gels with optimal optical properties has so far been a challenge. The researchers took layered magnesium organosilicate and modified it with amino groups to produce 'aminoclay' (AC). They then modified the aminoclay with coronene salt (CS) and perylene salt (PS) — potassium tetracarboxylates of coronene and perylene, which are highly fluorescent dye molecules.
The researchers prepared various hybrid states using AC, CS and PS. In hybrid states, the negatively charged carboxylate groups of the dyes interacted electrostatically with the positively charged aminoclay in water, resulting in the formation of non-covalent hybrid materials. They then excited the hybrid states with ultraviolet and visible light.
CS–AC and PS–AC hybrid hydrogels showed weak blue and greenish–yellow fluorescence, respectively. In mixed CS–PS–clay hybrids in aqueous solution, an energy transfer between CS and PS with strong green emission was observed. The researchers produced xerogels from hybrid hydrogels and then made films from the resulting xerogels. The films showed similar fluorescence properties to the hybrid hydrogels.
Such self-assembly may allow a variety of molecules that can trigger fluorescence changes to be incorporated into the hydrogels, giving great promise for applications such as stimuli-responsive supramolecular systems and sensors, say the researchers.
Rao, V. K. et al. Light-harvesting hybrid hydrogels: energy-transfer-induced amplified fluorescence in noncovalently assembled chromophore–organoclay composites. Angew. Chem. Int. Ed. 50, 1179-1184 (2011) | Article |