High-sensitivity lanthanide ratiometric nanothermometer in the second biological window through bidirectional thermal response engineering

Abstract

In recent years, lanthanide-doped nanothermometers have made significant progress as non-contact temperature sensing tools in a variety of biological fields. However, limited sucesses has been met in high-sensitivity nanothermometers operating in the second near-infrared (NIR-II) biological window, which can enable sub-centermiter tissue penetration at micrometer-level imaging resolutions. Here, we adopted a core-shell struture to develop a high-sensitivity lanthanide ratiometetric nanothermormeter through bidirectional thermal response of two emissions peak in the NIR-II window. We show that, under 808 nm exciation, the emission intensity at 1330 nm from neodymium ions exhibits a quenching effect, while the one at 1565 nm from erbium ions shows an enhancement at elevated temperatures. This contrasted temeparture dependency endows the nanothermometer to have a high relative sensitivity above 2.3 %°C⁻¹ , with a mxium of 2.5% °C⁻¹, throughout the entire physiological temperature range (30-45 °C). This high-sensitivity nanothermometer enables reliable differenatiaon of temperature differences in both normal and inflamed mice, highlighting its promising uses for in vivo appliations.