Nanoscale thermal sensing using hybrid diamond sensors – THESEUS

These ambitious objectives will be fulfilled thanks to the cumulative expertise and collaborative work between 3 academic partners (L2C – UMR5221, Montpellier; Institut Fresnel – IF – UMR7249, Marseille and CUHK, Hong Kong). The partners have expertise in electron spin decoherence in NV centers (L2C and CUHK), diamond-based magnetometry at nanoscale (L2C and CUHK), thermoplasmonics (Institut Fresnel), quantum sensing in biological media (CUHK) and biophotonics (IF and L2C), both on theoretical aspects (CUHK, Institut Fresnel) and on the experimental side (all partners).
The hybrid sensors will be fabricated by coating ferrimagnetic layers (partner L2C) or attaching ferromagnetic particles (partner CUHK) on the diamond probes. In a first stage, their response will be assessed by simply heating in a controlled manner the sensors. Optimization of sensors geometries and of the measurement protocols (partners CUHK – L2C) will be supported by advanced theoretical modelling (partner CUHK). Their spatial resolution and sensitivity at nanoscale will be quantified by imaging temperature gradients produced by thermoplasmonic micro- and nano-structures (partner IF). Correlation between the induced temperature gradient and single gold nanostructures geometry will be provided (partner CUHK). The relevance of such hybrid sensors for biologic imaging will also be investigated, by first identifying all possible artefacts when operated in single cells (partners CUHK – IF) and then by applying the sensor to temperature probing in heat-shock proteins in response to exposure to thermal stress (partners L2C – IF).

Different geometries of hybrid sensors have been considered : sensors built in a diamond bulk substrate, sensors built within a thin diamond membrane bonded on high thermal conductivity substrate, sensors based on nanodiamonds and sensors based on diamond tips. Numerical simulations and experiments, carried by the L2C and Institut Fresnel partners, led to exclude the bulk or membrane-based geometries (due to the high thermal conductivity of diamond). The optimized geometry revealed to be nanodiamonds, or, to some extent, diamond tips.
CUHK developped a first generation of hybrid sensors based on nanodiamonds grafted to ferromagnetic particles operated close to their Curie temperature. By using a single NV centre in a diamond nanopillar coupled with a single magnetic nanoparticle of copper-nickel alloy, the CUHK partner has demonstrated a temperature sensitivity of 76 µK.Hz-1/2?. This hybrid design enables detection of 2 millikelvin temperature changes with temporal resolution of 5 milliseconds.
L2C has also monitored the internalization of luminescent nanodiamonds in live cells and demonstrated a novel methodology for simultaneous visualization of the nanodiamond probes and the cell nucleus utilizing confocal photoluminescence/Raman imaging. Using this technique, the L2C partner could demonstrate the colocalization of the nanodiamonds with the cell nucleus within the diffraction-limited volume of the confocal microscope. At the same time, CUHK has developed methods for simultaneously motion tracking and magnetometry measurement of nanodiamond sensors in live cells, paving the way for evaluating the probe’s temperature sensitivity in complex medium such as a live cell.

The perspectives include :
o the optimization of hybrid sensors coated with ferrimagnetic materials.
o the optimization of the measurement protocols, including dynamical decoupling protocols and an optimization of the hybrid sensor’s architecture.
o the imaging of the temperature distribution above a current constriction line
o the imaging of temperature gradient around single plasmonic particles, including correlation between the particles composition/geometry measured by TEM and the observed thermal distribution measured by Magnetic Resonance Spectroscopy.
o the assessment of the probe’s sensitivity lower bound in single live cells under exogeneous heating, including a thorough analysis of all possible artifacts induced by strain, viscosity, pH, radicals, etc
o the measurement of the temperature evolution during heat-shock protein expression, by monitoring the temperature variation induced by external sources during the heat shock protein delivery.

Publications :
R. Tanos et al., Optimal architecture for wide-field thermal imaging based on NV defects in diamond, AIP Advances 10, 025027 (2020)
A. Finco et al., Imaging non-collinear antiferromagnetic textures via single spin relaxometry, Nat. Commun. 12, 767 (2021)
C.-F. Liu et al., Ultra-sensitive hybrid diamond nanothermometer, National Science Review, nwaa194 (2020)
M. Gulka et al., Simultaneous label-free live imaging of cell nucleus and luminescent nanodiamonds, Scientific report 10, 9791 (2020)

Patent
Pending patent on “all-diamond probes for nanoscale thermal sensing”, CNRS – Montpellier University - QNAMI

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.