Gold Nanoparticles as Absolute Nanothermometers

Nanothermometry is a challenging field that can open the door to intriguing questions ranging from biology and medicine to material sciences. Gold nanorods are excellent candidates to act as nanoprobes because they are reasonably bright emitters upon excitation with a monochromatic source. Gold nanoparticles are commonly used in photothermal therapy as efficient transducers of electromagnetic radiation into heat. In this work we use the spectrum of the anti-Stokes emission from gold nanorods irradiated in resonance to measure the absolute temperature of the nanoparticles and their surrounding medium without the need for a previous calibration. We show a 4 K accuracy in the determination of the temperature of the medium with spectral measurements of 180 s integration time. This procedure can be easily implemented in any microscope capable of acquiring emission spectra, and it is not limited to any specific shape of nanoparticles.