Extended Data Fig. 10: Multimodal imaging of tumours in a living mouse using NaYF₄:3%Er@NaGdF₄-(¹⁸F) probe.

a, HAADF-STEM image of NaYF₄:3%Er@NaGdF₄ nanoparticles. b, Element mapping of NaYF₄:3%Er@NaGdF₄ nanoparticles. c, Relaxation rate R₁ (1/T₁) versus various Gd³⁺ concentrations of NaYF₄:3%Er@NaGdF₄ nanoparticles (0.03, 0.06, 0.12, and 0.24 mM) at room temperature. d, PL, MR and PET imaging of the tumour on a living mouse after intratumoural injection of NaYF₄:3%Er@NaGdF₄-(¹⁸F) probe. Scale bar: 1 cm. This is the first investigation of combined PET, MRI and NIR-II PL signals into single nanoparticles for multimodal in vivo imaging of tumours. In comparison, conventional PL materials are mainly large crystals, which are grown at extremely high temperatures (> 1000 °C) and lack nanostructured modulation and designability, thus hampering advanced multimodal bioimaging and biosensing. Because the signals of PET and MRI are affected by ¹⁸F and Gd³⁺, respectively, similar performance to reported ¹⁸F-labeled NaGdF₄-based probes can be obtained using our NaYF₄:3%Er@NaGdF₄-(¹⁸F) PLNPs. The longitudinal proton relaxation rate (R₁) as a function of Gd³⁺ concentration in our NaYF₄:3%Er@NaGdF₄ led to a R₁ relaxivity of 18.7 mM⁻¹·s⁻¹, which is lower than that of NaGdF₄-based probes (28.39 mM⁻¹·s⁻¹)⁵¹ but is 5.4-fold higher than that of clinically used Gd-DTPA (3.45 mM⁻¹·s⁻¹)⁵².