Optical Probe Thermometry Using Optically Trapped Erbium Oxide Nanoparticles

ABSTRACTA new thermal imaging technique is characterized that uses an optically trapped erbium oxide nanoparticle cluster of approximately 150 nm. This technique can measure absolute temperature and has an imaging spatial resolution of the trapped particle. Scanning optical probe thermometry has been used to thermally image a cluster of gold nanowires that were excited with the trapping laser. Following a deconvolution of the measured thermal profile, a point spread function of the imaging technique has been determined to be a Gaussian with a FWHM of 165 nm. This width is a function of the clustering of Er2O3 nanoparticles used to image the nanowire. Optical probe thermometry has further been used to measure the temperature of nucleation events where a dichotomy of temperature for nucleated water occurs from degassed water and native water. Degassed water has been measured to nucleate at 555K confirming water adjacent to the gold nanoparticle superheats to the spinodal decomposition temperature before nucleating into a water vapor bubble. Following this event, the temperature inside the vapor bubble rises to the melting point of the gold nanoparticle, 1300 K which is followed by temperature stabilization. The rapid and significant temperature increase is attributed to the loss of a thermal dissipation pathway, to the surrounding water, previously available to the gold nanoparticle due to the insulator nature of the growing vapor envelope around the gold nanoparticle.