Various methods and devices for ultrasensitive infrared photodetection, infrared imaging, and other optoelectronic applications using the plasmon assisted thermoelectric effect in graphene are described. Infrared detection by the photo-thermoelectric uses the generation of a temperature gradient (ΔT) for the efficient collection of the generated hot-carriers. An asymmetric plasmon-induced hot-carrier Seebeck photodetection scheme at room temperature exhibits a remarkable responsivity along with an ultrafast response in the technologically relevant 8-12 μm band. This is achieved by engineering the asymmetric electronic environment of the generated hot carriers on chemical vapor deposition (CVD) grown large area nanopatterned monolayer graphene, which leads to a record ΔT across the device terminals thereby enhancing the photo-thermoelectric voltage beyond the theoretical limit for graphene. The results provide a strategy for uncooled, tunable, multispectral infrared detection.