Characterization of nanodiamond samples for intracellular temperature sensing

Nitrogen-Vacancy (NV) center in nanodiamonds offers unique advantages for thermometry applied in biological samples. Small size and biocompatibility make nanodiamonds promising as nanoscale thermometers. The energy level structure of NV centers enables optical initialization and readout of the spin state, particularly in their triplet ground state, where the energy gap (D gs ) between | m s = 0 ⟩ and | m s = ± 1 ⟩ is sensitive to environmental conditions. Variations in temperature, magnetic, or electric fields induce changes in the energy structure of the system, allowing for precise reconstruction of applied field values and facilitating the use of NV centers as sensors. The purpose of this work is to characterize the response of a set of nanodiamonds to a change in temperature: knowing the value of the coefficient that links the change in temperature to a change in D gs makes possible to use nanodiamonds inside cells as thermometers. Moreover, some techniques that can reduce the uncertainty related to the estimation of this coupling constant are investigated.