Ultrasensitive Ratiometric Nanothermometer with Large Dynamic Range and Photostability

Abstract

Thermally responsive fluorescent nanoparticles can be constructed to allow robust, rapid, and noninvasive temperature measurements. Furthermore, due to their tiny size, they can be used to detect temperature changes at the nanoscale. In this way, such sensors are ideally suited to emerging applications including intracellular temperature sensing and microelectronics failure diagnostics. Despite their potential, current nanothermometers still suffer from limited sensitivity, dynamic range, and stability. By introducing thermal enhanced anti-Stokes emission from a pair of lanthanide ions, ytterbium and neodymium, we show an increase of more than 1 order of magnitude in both the sensitivity and the dynamic range when compared to conventional ytterbium and erbium-codoped nanothermometers. Here, we report heterogeneous temperature-responsive nanoparticles with a new record of sensitivity (9.6%/K at room temperature and above 2.3%/K at elevated temperatures up to 413 K) that can be used for ratiometric thermometry. The heterogeneous nanostructure design shows that the thermal responses can be fine-tuned by the controlled growth of nanoparticles. The stability of the ultrasensitive nanothermometers has enabled long-term noncontact monitoring of local heat dissipation of a microelectronic device.

Making Nd3+ a Sensitive Luminescent Thermometer for Physiological Temperatures—An Account of Pitfalls in Boltzmann Thermometry

“…In particular, it is higher than 1% K −1 for the full physiological temperature regime (30 • C-75 • C), which is practically difficult to achieve around room temperature with any single ion Boltzmann thermometer, especially in the NIR regime [49][50][51]57]. Typically, energy transfer-based thermometers are used in those cases [30,43,54,55] for which the underlying thermometric mechanisms are often not well established. The present results show promising potential of Nd 3+ for physiological temperature sensing by means of luminescence thermometry, if the boundary conditions for the validity of a Boltzmann equilibrium are met which requires low Nd 3+ concentrations.…”

“…As an alternative, the lanthanide ion Nd 3+ (4f 3 ) has become a promising candidate for in vivo nanothermometry [30,[38][39][40][41][42][43]. This is related to the fact that its most intense radiative transitions all lie within BW I and BW II.…”

“…One way to overcome this problem and achieve an order of magnitude higher relative sensitivities has already been demonstrated by a phonon-assisted energy transfer between Nd 3+ and Yb 3+ [30,54,55] or recently, also Nd 3+ and Er 3+ [43]. However, the underlying temperature calibration model for the temperature-dependent LIR based on energy transfer is far from trivial and, strictly stated, Boltzmann's law does not apply for those situations [53].…”

A Theoretical Framework for Ratiometric Single Ion Luminescent Thermometers—Thermodynamic and Kinetic Guidelines for Optimized Performance

“…[ 31,35,37,87–91 ] The shielded nature of the 4f orbitals and the resulting 4f n → 4f n ‐based narrow emission peaks at well‐defined wavelengths allow to accurately measure LIRs without substantial spectral overlap. [ 87–91 ] If doped into thermally stable inorganic nano‐ or microcrystalline hosts, lanthanides thus found many promising applications such as Pr 3+ , [ 19,92–95 ] Nd 3+ (often sensitized with Yb 3+ ) [ 33,96–121 ] or Tm 3+[ 122–124 ] in the field of room temperature sensing and thermal bioimaging. Er 3+ and Yb 3+ is the traditional lanthanide couple for upconversion‐based in vivo imaging, [ 125–133 ] or in situ temperature monitoring of catalytic reactions or flow reactions in microfluidic devices.…”

Surface Plasmon Enhanced Fluorescence Temperature Mapping of Aluminum Nanoparticle Heated by Laser

“…Thermometry at sub-micron length scales has found application in microelectronics [ 11 , 12 , 13 ], microfluidics [ 14 , 15 , 16 ], and nanomedicine [ 17 , 18 , 19 ]. Enhancing the spatiotemporal resolution of temperature sensing techniques further advances the application of a fundamental heat transfer mechanism for small and rapidly heated particles.…”