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Researchers from Singapore and the UK have jointly announced a new benchmark in broadband, non-linear optical-limiting behavior using single-sheet graphene dispersions in a variety of heavy-atom solvents and film matrices.

Single-sheet graphene dispersion when substantially spaced apart in liquid cells or solid film matrices can exhibit novel excited state absorption mechanism that can provide highly effective broadband optical limiting well below the onset of microbubble or microplasma formation.

Graphenes are single sheets of bonded into a hexagonal array. In nature, they tend to stack to give graphite.

In a breakthrough, researchers from the National University of Singapore (NUS), DSO National Laboratories and University of Cambridge have developed a method to prevent the re-stacking of these sheets by attaching alkyl surface chains to them, while retaining the integrity of the nano-graphene pockets on the sheets.

This method in turn produced a material that can be processed in a solution and dispersible into solvents and film matrices. As a consequence, the researchers observed a new phenomenon. They found that the dispersed graphenes exhibit a giant non-linear optical-absorption response to intense nanosecond over a wide spectral range with a threshold that was much lower than that found in carbon black suspensions and carbon nanotubes suspensions. This set a new record in energy limiting onset of 10 mJ/cm2 for a linear of 70%.

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