By integrating graphene based photothermo-electric detectors with micromachined silicon nitride membranes, we are able to achieve room temperature responsivities on the order of ∼7–9 V/W (at λ = 10.6 μm), with a time constant of ∼23 ms.Of course it's not as simple as a single sheet. The team have not only used graphene for the sensor itself but use thin strips to graphene to hold and thermally isolate the sensor from the main substrate.
Graphene-Based Thermopile for Thermal Imaging Applications
Allen L. Hsu, Patrick K. Herring, Nathaniel M. Gabor, Sungjae Ha, Yong Cheol Shin, Yi Song, Matthew Chin, Madan Dubey, Anantha P. Chandrakasan, Jing Kong, Pablo Jarillo-Herrero, and Tomás Palacios
Nano Letters 2015 15 (11), 7211-7216