Scientists from the Center for Functional Nanomaterials (CFN) -- a U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory -- have dramatically improved the response of graphene to light through self-assembling wire-like nanostructures that conduct electricity. The improvement could pave the way for the development of graphene-based detectors that can quickly sense light at very low levels, such as those found in medical imaging, radiation detection, and surveillance applications.

Graphene is a two-dimensional (2-D) nanomaterial with unusual and useful mechanical, optical, and electronic properties. It is both extremely thin and incredibly strong, detects light of almost any color, and conducts heat and electricity well. However, because graphene is made of sheets of carbon only one atom thick, it can only absorb a very small amount of incoming light (about two percent).

One approach to overcoming this problem is to combine graphene with strong light-absorbing materials, such as organic compounds that conduct electricity. Scientists recently demonstrated an improved photoresponse by placing thin films (a few tens of nanometers) of one such conductive polymer, poly(3-hexylthiophene), or P3HT, on top of a single layer of graphene.

Now, the CFN scientists have improved the photoresponse by an additional 600 percent by changing the morphology (structure) of the polymer. Instead of thin films, they used a mesh of nanowires -- nanostructures that are many times longer than they are wide -- made of the same polymer and similar thickness. The research is described in an article published online on Oct. 12 in ACS Photonics, a journal of the American Chemical Society (ACS).

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