Luminescence nanothermometry has emerged over the past decade as an exciting field of research due to its potential applications where conventional methods have demonstrated to be ineffective. Preclinical research has been one of the areas that have benefited the most from the innovations proposed in the field. Nevertheless, certain questions concerning the reliability of the technique under in vivo conditions have been continuously overlooked by most of the scientific community. In this proof-of-concept, hyperspectral in vivo imaging is used to explain how unverified assumptions about the thermal dependence of the optical transmittance of biological tissues in the so-called biological windows can lead to erroneous measurements of temperature. Furthermore, the natural steps that should be taken in the future for a reliable in vivo luminescence nanothermometry are discussed together with a perspective view of the field after the findings here reported.

nanoheaters with multiparameter sensing for reliable thermal feedback during in vivo tumor therapy.

Optical probes operating in the second near-infrared window (NIR-II, 1,000-1,700 nm), where tissues are highly transparent, have expanded the applicability of fluorescence in the biomedical field. NIR-II fluorescence enables deep-tissue imaging with micrometric resolution in animal models, but is limited by the low brightness of NIR-II probes, which prevents imaging at low excitation intensities and fluorophore concentrations. Here, we present a new generation of probes (Ag 2 S superdots) derived from chemically synthesized Ag 2 S dots, on which a protective shell is grown by femtosecond laser irradiation. This shell reduces the structural defects, causing an 80-fold enhancement of the quantum yield. PEGylated Ag 2 S superdots enable deep-tissue in vivo imaging at low excitation intensities (<10 mW cm −2) and doses (<0.5 mg kg −1), emerging as unrivaled contrast agents for NIR-II preclinical bioimaging. These results establish an approach for developing superbright NIR-II contrast agents based on the synergy between chemical synthesis and ultrafast laser processing.

Methylammonium lead halide perovskite has emerged as a new class of low-temperature-processed high-performance semiconductors for optoelectronics, but with photoresponse limited to the UV-visible region and low environmental stability. Herein, we report a flexible planar photodetector based on MAPbI microarrays integrated with NaYF:Yb/Er upconversion nanoparticles (UCns) that offers promise for future high performance and long-term environmental stability. The promise derives from the confluence of several factors, including significantly enhanced photons absorption in the visible spectrum, efficient energy transition in the near-infrared (NIR) region, and inhibition of water attack by the hydrophobic UCns capping layer. The UCns layer aided in remarkably enhanced photodetection capability in the visible spectrum with detectivity (D*) reaching 5.9 × 10 Jones, among the highest reported values, due to the increased photocarrier lifetime and decreased reflectivity. Excellent NIR photoresponse with spectral responsivity (R) and D* as high as 0.27 A W and 0.76 × 10 Jones were obtained at 980 nm, respectively, superior to the reported values of state-of-the-art organic-perovskite NIR photodetectors. Moreover, the hydrophobic UCns capping layer serving as a moisture inhibitor allowed significantly enhanced long-term environmental stability, e.g., 70% vs 27% performance retained after 1000 h exposure in 30-40% RH humidity air without encapsulation for the bilayer and the neat MAPbI devices, respectively. These results suggest that the composite based on perovskite and UCns is promising for constructing high-performance broadband optoelectronic devices with long-term stability.

A critical analysis of the synthesis routes, properties and optical features of Ag2S nanoparticles is presented. The future perspectives of this material for advanced bioimaging are discussed.