This article combines passive wireless nanosensor networks deployed over a large area and unmanned aerial vehicles (UAVs). The use of UAVs in nano communication network applications can significantly expand their capabilities. Particularly, the highly mobile UAV-based gateways considered in the paper, enable the collection of data from thousands of nanosensors without the utilization of complicated multi-hop routing between nanodevices. The article considers the unique properties of the THz frequency range for the wireless energy transfer to nanodevices as well as for communication with them. More specifically, the energy harvested from electromagnetic waves which are radiated by the UAV-based gateway provide sufficient power for the functioning of the passive nanosensor and signal transmission to the gateway (reader). Such passive nanosensors do not require any maintenance, have a long service life and low cost. Thus, the considered case can serve as the basis for numerous monitoring scenarios, including control of the soil state in agriculture, environmental pollution monitoring, and the control of linear objects (pipelines, dams, dikes). In the considered scenario, the paper discusses technical aspects of the system design, including installation of nanosensors, data frame structure, medium access control, the energy consumption of nanosensors, and aspects of electromagnetic wave propagation. Finally, we evaluate the performance of the proposed system using a system-level simulator.