Fig. 1

(a) Schematic illustration of synthesis and preparation of TPSe NPs. (b) TEM image of TPSe NPs. (c) Dynamic light scattering of TPSe NPs. (d) Absorption spectral and NIR-II fluorescence of TPSe NPs (DI water). (e) Changes in photothermal temperature of water and TPSe aqueous solutions of varied concentrations. (f) Infrared images of TPSe NPs solutions in the sixth minute upon laser illumination. (g) Photothermal heating curves of TPSe aqueous solutions (40 µg mL^− 1) upon laser irradiation with various powers of 808 nm light. (h) Temperature profiles of TPSe NPs and ICG irradiated at 1 W cm^− 2 by 808 nm light for 10 laser on/off cycles. (i) Temperature profile of TPSe NPs (40 µg mL^− 1) under 808 nm laser irradiation for 10 min at 1 W cm^− 2 with subsequent natural cooling process after turning off the laser (yellow curve) and the linear time data versus -Ln (θ) obtained from the cooling process (red curve). (j) Stability test of TPSe NPs kept at 4 °C for 28 days