Thermometry at the nanoscale

TLDR

Non‑invasive nanoscale thermometers with high spatial resolution have become an active research area, driven by demands from nanotechnology and biomedicine. The review surveys recent luminescent and non‑luminescent nanoscale thermometers and discusses challenges and opportunities for highly sensitive ratiometric thermometers at physiological temperatures with submicron resolution. Luminescent thermometers include organic dyes, quantum dots, and lanthanide ions embedded in polymer or hybrid matrices, while non‑luminescent thermometers employ scanning thermal microscopy, nanolithography, carbon nanotube, and biomaterial approaches. Emphasis has been placed on ratiometric examples achieving spatial resolution below 1 µm, such as intracellular thermometers based on organic dyes, thermoresponsive polymers, mesoporous silica nanoparticles, quantum dots, lanthanide‑based up‑converting nanoparticles, and β‑diketonate complexes.

Abstract

Non-invasive precise thermometers working at the nanoscale with high spatial resolution, where the conventional methods are ineffective, have emerged over the last couple of years as a very active field of research. This has been strongly stimulated by the numerous challenging requests arising from nanotechnology and biomedicine. This critical review offers a general overview of recent examples of luminescent and non-luminescent thermometers working at nanometric scale. Luminescent thermometers encompass organic dyes, QDs and Ln3+ions as thermal probes, as well as more complex thermometric systems formed by polymer and organic–inorganic hybrid matrices encapsulating these emitting centres. Non-luminescent thermometers comprise of scanning thermal microscopy, nanolithography thermometry, carbon nanotube thermometry and biomaterials thermometry. Emphasis has been put on ratiometric examples reporting spatial resolution lower than 1 micron, as, for instance, intracellular thermometers based on organic dyes, thermoresponsive polymers, mesoporous silica NPs, QDs, and Ln3+-based up-converting NPs and β-diketonate complexes. Finally, we discuss the challenges and opportunities in the development for highly sensitive ratiometric thermometers operating at the physiological temperature range with submicron spatial resolution.