Nanodiamond hosting temperature-sensing centers constitutes a closed thermodynamic system, with the only window of energy exchange with the environment without direct contacts of a sensor with intracellular substrates, which is in fact the property of an ideal nanosized thermometer. Here, a new design of a nanodiamond thermometer, based on a 500-nm luminescent nanodiamond embedded into the inner channel of a glass submicron pipette is reported. All-optical detection of temperature, based on spectral changes of the emission of "silicon-vacancy" centers with temperature, is used. We demonstrate the applicability of the thermometric tool to the study of temperature distribution near a local heater, placed in an aqueous medium. The calculated and experimental values of temperatures are shown to coincide within the measurement error at gradients up to 20 {\deg}C/{\mu}m. Until now, temperature measurements on the submicron scale at such high gradients have not been performed. The new thermometric tool opens up unique opportunities to answer the urgent paradigm-shifting questions of cell physiology thermodynamics.
@article{arxiv.2102.07461,
title = {A new tool for precise mapping of local temperature fields in submicrometer aqueous volumes},
author = {Alexey M. Romshin and Vadim E. Zeeb and Artem K. Martyanov and Oleg S. Kudryavtsev and Dmitrii G. Pasternak and Vadim S. Sedov and Victor G. Ralchenko and Andrey G. Sinogeikin and Igor I. Vlasov},
journal= {arXiv preprint arXiv:2102.07461},
year = {2021}
}