The invention relates to the field of ionizing radiation dosimetry, in particular to ionizing radiation dosimeters intended for measuring the dose of ionizing radiation absorbed in a nanovolume. The scope of the invention is high dose gradient dosimetry and radiobiology. The present invention proposes to manufacture a sensitive element of a dosimeter from nanoparticles sensitive to ionizing radiation, uniformly distributed on a substrate insensitive to ionizing radiation or embedded in a matrix insensitive to ionizing radiation, the nanoparticles being made of solid material with a band gap and located in a layer less than 100 nm thick. To read the dose of ionizing radiation absorbed by the nanoparticles, it is proposed to measure thermally stimulated exoelectron emission from the nanoparticles. In this case, the total number of emitted exoelectrons will be proportional to the dose of ionizing radiation absorbed by the nanoparticles.