Thermometry at the nanoscale

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 Ln 3+ 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 Ln 3+ -based up-converting NPs and b-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.

Nanoscale thermal imaging of dissipation in quantum systems

“…Despite its vital importance the microscopic behavior of a system is usually not formulated in terms of dissipation because the latter is not a readily measureable quantity on the microscale. Although nanoscale thermometry is gaining much recent interest [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] , the existing thermal imaging methods lack the necessary sensitivity and are unsuitable for low temperature operation required for study of quantum systems. Here we report a superconducting quantum interference nano-thermometer device with sub 50 nm diameter that resides at the apex of a sharp pipette and provides scanning cryogenic thermal sensing with four orders of magnitude improved thermal sensitivity of below 1 µK/Hz 1/2 .…”

“…Such signals are several orders of magnitude below the best sensitivity of several mK Hz 1 2 ⁄ ⁄ of any of the existing imaging techniques [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] (Fig. 1a) including radiation-based thermometry utilizing infra-red 6 , fluorescence in nanodiamonds 4,7,8 , Raman 9 , or transmission electron beam 5 , and atomic force microscopy (AFM) outfitted with thermocouple or resistive thermometers [10][11][12][13][14][15] . Moreover, none of the existing imaging techniques was demonstrated to operate at sufficiently low temperatures that are essential for study of quantum systems.…”

LaF3 core/shell nanoparticles for subcutaneous heating and thermal sensing in the second biological-window

“…11 Despite the continuously growing list of systems that could operate as simultaneous NHs and nanothermometers (NThs), including polymeric NPs, quantum dots, nanodiamonds, metallic NPs, and rare earth-doped NPs, only a few of them show real potential of working subcutaneously. [12][13][14] This is so because most of them operate in the visible spectrum domain, where optical penetration into tissues is minimal. To avoid this limitation, it is necessary to shift their operation spectral range from the visible to the spectral infrared ranges where tissues become partially transparent (due to simultaneous attenuation in both tissue absorption and scattering), lying in the so-called biological windows (BWs).…”

Assessing Single Upconverting Nanoparticle Luminescence by Optical Tweezers

“…This is the case, for instance, of intracellular thermal sensing experiments, in which the cell´s temperature is obtained from the spectral analysis of the Er 3+ ion emission of Er/Yb codoped UCNPs incorporated in living cells. [14][15][16] Thus, the spectral shape of Er 3+ ion emission must be carefully investigated. In the past, optical characterization of UCNPs has been mainly limited to ensemble-averaged measurements performed either on stable colloidal suspensions or in powder samples.…”