THESEUS

THESEUS aims at implementing an atomic-scale thermometer surpassing the performances of present nanoscale temperature probes, by combining unprecedentedly high sensitivity and nanoscale spatial resolution with operation over a broad range of temperature and in various environments (including liquids and biological media). At the same time, the applicability of such sensors will be demonstrated in two fields of applications: thermoplasmonics and biothermics under exogenous heating. The sensor will be based on a novel design of hybrid architecture, building on a transduction of temperature changes on magnetic changes probed by single electronic spins in a diamond. Ultimate performances will be achieved by capitalizing in an innovative manner on (i) the unique sensitivity of diamond NV centers electronic spins on magnetic field and (ii) the efficient transduction of thermal gradient onto magnetic field using temperature-sensitive magnetic materials. Two novel parallel avenues will be pursued: (i) coating nanodiamonds with ferrimagnetic layers and (ii) attaching ferromagnetic nanoparticles to nanodiamonds or diamond nanopillars. Combined to optimized decoupling dynamical protocols enhancing the spin coherence, this mediated detection of temperature via the magnetic field will afford for beyond-state-of-the-art capabilities with sensitivities down to sub-mK/Hz1/2. By relying on single spins, high spatial resolution down to a few tens of nanometers will be achieved. Moreover, such hybrid sensors shall enable unprecedented operation over a broad range of temperature and in various environments including biological media. The sensor's utmost performance will be evidenced by mapping the temperature gradients in the vicinity of gold particles and arrays producing shape controlled temperature profiles, in strong connection with thermoplasmonics issues and applications. The possibility to extend such a mapping to biological objects at a single cell level will be explored, by providing a lower bound of the probe’s sensitivity in a medium as complex as a cell under exogenous heating and by tracking temperature during heat-shock protein expression subjected to thermal stress. The THESEUS program represents a unique opportunity to form a strong union between recognized French experts in nanomagnetometry, bioimaging, and thermoplasmonics from the Laboratoire Charles Coulomb (L2C) and the Institut Fresnel (IF), together with the world-reputed expertise on quantum metrology, nanofabrication, nano-bio interface from the department of Physics of the Chinese University of Hong Kong (CUHK). Such synergy of cross-disciplinary strengths is a prerequisite for attacking major challenges in nanoscale thermodynamics, ranging from quantum physics, material science and engineering, cellular biology, to nanoscience and nanotechnologies. THESEUS promises significant progress in the rapidly-growing field of nanoscale thermal sensing while opening up new prospects still out-of-reach in nanoscale thermodynamics.