Figure 3. Sub-micron thermometry using nanodiamonds.

a, Frequency scan of a single nanodiamond containing approximately 500 NV centers. The four red points indicate the measurement frequencies used to extract the temperature as detailed in Methods. b, Two-dimensional confocal scan of nanodiamonds (circles) and Au NPs (cross) spin-coated onto a glass coverslip. The color bar represents fluorescence given in counts per second (cps). c, Temperature of a single nanodiamond as a function of laser power for two different laser-focus locations. The red data points depict the dramatic heating of a nanodiamond as a result of laser illumination on a nearby Au NP. The blue data points depict the same measurement with the laser focus displaced by 0.8 μm from the Au NP location; this results in the negligible heating of the nanodiamond as a function of laser power. The inset shows the measured temperature change of a nanodiamond, when the surrounding temperature is controlled by a Peltier element. d, Temperature changes measured (red points) at the six nanodiamond locations in (b) as a function of distance from the illuminated Au NP (cross). The blue curve represents the theoretical temperature profile based upon a steady-state solution of the heat equation. All data in this figure are obtained on a glass coverslip, and all error bars correspond to one standard deviation.