Diamond is among the best solid-state dosimeters for measuring ionising radiation. Diamond nanoparticles (DNPs) could be used to estimate doses at nanovolumes, which is desirable for determining ionising radiation absorption by a single structural nanounit of DNA. However, there is no research aimed at verifying the possibility of exploiting DNP for nanodosimetry. To measure a DNP response to radiation, weak electron emission spectroscopy could be applied. This article is based on understanding diamond nanoparticles’ electron emission behaviour. First, it’s necessary to understand their electron emission without any type of radiation, then compare the results to the nanoparticles with the radiation treatment. For the photoemission (PE) technique, diamond nanoparticles are irradiated by UV photons to promote photoelectron emission, which has an energy of 4.0–6.0 eV, showing a proportional response of the emitted electrons to the increasing amount of radiation. It was found out that the PE signals reach an energy maximum between 5.2 eV and 5.9 eV; furthermore, the photothermalstimulated emission (PTSE) highlights that the diamond nanoparticles reach their energy maximum value around a temperature of 530 to 570 °C. Concluding with a comparison between the PE and PTSE data and the electron-radiated diamond nanoparticles with a dose of 20 Gy, 40 Gy, 60 Gy, 80 Gy and 100 Gy, used for clinical purposes, it was found out that the diamond nanoparticles have similar signals to the PE and PTSE, which suggests that the diamond nanoparticles could have the potential to be used as a nano-dosimeter.