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Wednesday, 28 March 2012

Graphene oxide efficiently quenches quantum dots via FRET

Team including ICN researchers reports in Carbon that compared to other carbon-based materials, graphene oxide absorbs a far greater fraction of photons from quantum dots by Förster resonance energy transfer (FRET).

“Simple Förster resonance energy transfer evidence for the ultrahigh quantum dot quenching efficiency by graphene oxide compared to other carbon structures” (Morales-Narvaéz E et al., Carbon, 2012, doi:10.1016/j.carbon.2012.02.081)

Writing in the journal Carbon, a team including Dr Arben Merkoci, ICREA Research Professor, Professor at UAB and leader of ICN's Nanobioelectronics and Biosensors Group, has just described testing of various carbon-based materials for their capacity to absorb photons from quantum dots made of cadmium selenide@zinc sulphide (CdSe@ZnS). They found that graphene oxide far out-performed graphite, carbon nanotubes and carbon nanofibres, offering quenching efficiencies of 91 to 97%: from 1.5 to 5.5 times higher than that obtained with the other materials.

Just as thermal energy (heat) from a warm coffee cup travels to a cold hand, light energy (photons) can travel from a material whose electrons are highly excited (a donor) to a nearby one whose electrons are less excited (an acceptor). One mechanism by which photon transfer occurs is Förster resonance energy transfer (FRET).

Due to their unique set of optical properties, quantum dots are excellent FRET donors. Understanding which materials make the best FRET donors or acceptors should enable exceptional control for engineering devices that operate on photon transfer, such as optical sensors.

Merkoci and his co-workers assessed graphene oxide, graphite, carbon nanotubes and carbon nanofibres for their potential as FRET acceptors. By measuring the fluorescence emission of samples of each material before and after incubation with the CdSe@ZnS quantum dots, the researchers were able to calculate relative quenching efficiencies for each material.

The team analysed these results based on several parameters, including the distance between the quantum dots (donor) and the carbon material (acceptor), the concentration of each component, and the surface area and geometry (atomic or molecular) of each carbon material.

The authors of the study suggest that the impressive quenching efficiency of graphene oxide could be exploited in diverse areas; for example, to develop new quantum dot-based devices in which graphene oxide serves as a transducer platform.

The article can be accessed here.