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Graphene Membranes Enable a Novel Approach to Ubiquitous Photodetectors

Posted By Dexter Johnson, IEEE Spectrum, Monday, March 12, 2018

Image: University of Manchester

Back in January, scientists in Andre Geim’s research team at the University of Manchester reported that light could be used to enhance proton transport through graphene.  What this means is the possibility of an entirely new class of photodetectors, which are used in just about everything from high-speed optical communication networks to the remote control for your TV.

Needless to say, an entirely new class of photodetectors—based on proton transport as opposed to all current photodetectors today that are based on electron transport—is a pretty significant development. You add on to this the fact that the photodetectors made from graphene are 100,000 times more responsive than silicon and you have the basis of a transformative technology.

What regular readers of The Graphene Council may have missed earlier this month in an Executive Q&A with Jeffrey Draa, CEO of Grolltex, was that we got some indications in that interview that the technology being developed in Geim’s lab is ramping up for commercial applications.

Draa said in the interview: “…we’re also starting to get some inquiries for an application that actually Dr. Andre Geim at the University of Manchester, who, of course, was the discoverer of graphene was very passionate about. This is one of the very first applications that he thought futuristically would really make the world a better place, and that third application that we're starting to see on the horizon is graphene as a proton exchange membrane in a hydrogen fuel cell.”

Draa in this interview points to the initial applications that were discussed almost four years ago for this graphene-based proton exchange membrane. At the time, Geim had discovered that contrary to the prevailing wisdom that graphene was impermeable to all gas and liquids  it could, in fact, allow protons to pass through. This made scientists immediately conjure up the proton exchange membranes that are central to the functioning of fuel cells.

While there’s no reason to think that these graphene membranes won’t someday make for excellent proton exchange membranes for fuel cells, the problem is that fuel cells are not exactly ubiquitous. However, photodetectors certainly are ubiquitous, making for a much larger potential market for these graphene membranes.

Of course, it’s a pretty big step to make these graphene membranes go from being used for fuel cells to being used in photodetectors. So how did this application switch occur?

The University of Manchester scientists started with monolayer graphene decorated with platinum (Pt) nanoparticles. In operation, photons (light) strike the membrane and excite the electrons in the graphene around the Pt nanoparticles. This makes the electrons in the graphene become highly reactive to protons. This, in turn, induces the electrons to recombine with protons to form hydrogen molecules at the Pt nanoparticles. This process mimics the way in silicon-based photodetectors operate based on electron-hole recombination.

While there are similarities between the semiconductor approach to electron-hole recombination, the photon-proton effect used in this graphene membrane would represent a big departure from the previous approach and nobody is quite sure what the implications might be.

However, it is clear that this graphene membrane that Grolltex is working on with the scientists at Manchester may have a new set of applications that extends far beyond just typical membrane-based technologies.

Tags:  Andre Geim  fuel cells  membranes  photodetectors  University of Manchester 

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