Titanium nitride nanoparticles as plasmonic nanothermometers

The capability of measuring the temperature at nanometer length scales is highly desirable and useful in numerous fields such as plasmonics, biomedicine, and nanochemistry. Precise and easy-to-implement temperature measurements at these scales would enable the investigation of fundamental processes that occur, for instance, during the synthesis of nanomaterials, or the conversion of electromagnetic energy into thermal one (photothermal conversion). Here, we demonstrate that titanium nitride nanoparticles are effective nanothermometers whose temperature can be measured optically in a reliable and reproducible manner. We leverage the Raman signal from these nanomaterials to measure their temperature, and we do so in two different ways: using the phononic signature induced by the presence of native oxide and using the electronic anti-stoke Raman signal induced by the free electrons in the material. Our findings confirm that titanium nitride nanoparticles, which are already an earth-abundant, low-cost alternative to gold nanoparticles, are also a versatile tool for nanothermometry.