Graphene "smart surface" is now adjustable and can be used in the visible spectrum
Researchers from the National Graphene Institute at the University of Manchester have created an optical device with a unique adjustable range that covers visible light Within the entire electromagnetic spectrum.
published a paper in "Nature Photonics" ("Multispectral graphene-based electro-optical surface with reversible wavelength tunability from visible light to microwave") outlined the application range of this "smart surface" technology, from the following From a generation of display devices to the dynamic thermal blanket spectrum adaptive camouflage used for satellites and multi-purpose. The tunability of the
device is achieved through a method called electrical intercalation. In this case, the process involves inserting lithium ions between the sheets of multilayer graphene (MLG) to control the electrical , Thermal and magnetic properties. The
MLG device is laminated and vacuum sealed in a low-density polyethylene bag, which has a light transmittance of over 90% from visible light to microwave radiation .
Picture: University of Manchester)
The charge turns gray to gold
During the process of charging (embedding) or discharging (de-embedding), the electrical and optical properties of MLG have undergone tremendous changes. Due to the high absorptivity (>80%) of the top graphene layer in the visible state, the discharged device appears dark gray. When the device is fully charged (about 3.8V), the graphene layer appears golden. Using optical effects such as thin-film interference , the achievable color space can be enriched, including the range from red to blue.
Professor Coskun Kocabas, the lead author of the study, said: "We have created a new type of multi-spectral optical device by combining graphene and battery technology.The device has a discoloration capability that was previously unachievable.
"The successful demonstration of graphene-based smart optical surfaces has potential for development in many scientific and engineering fields."
For example, dynamic thermal blankets can selectively reflect visible light or infrared light and allow satellites Reflects radiation from the side facing the sun, while emitting radiation from its shadow side. Similarly, when in the shadow of the earth, the blanket protects the satellite from deep-space cooling [see image below]. These actions will regulate the internal temperature more effectively than static thermal coating.
Previous research has used single-layer and multi-layer graphene to inspect the device in the specific wavelength range of microwave, terahertz , infrared and visible light. However, the challenge of extending the coverage to visible light while maintaining optical activity at longer wavelengths requires innovation in the structure of the device, which overcomes the established problem of integrating optical devices with electrochemical cells.
He added: "Here, we use graphene-based lithium-ion batteries as optical devices." "By controlling the electron density of graphene, we are now able to control light from visible light to microwave wavelengths on the same device."
Nobel Prize winner Sir Kostia Novoselov is the co-author of the paper. He said: "There are very few layers of graphene that provide unprecedented control over its optical properties through charging. Such a device can Find its application in many fields: from adaptive optics to thermal management."
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