Fig. 2. In vitro characterization of HSN.

a Absorption spectra of HSN and HSN₀ in 1 × PBS ([pTBCB] = 3 µg mL⁻¹). b DLS profiles of HSN and HSN₀ in 1 × PBS. Inset: TEM images of HSN₀ and HSN. Scale bar: 200 nm. c Zeta potential profiles of HSN and HSN₀. d STEM-EDX element mapping of HSN. Scale bar: 20 nm. e Photothermal heating-cooling cycles of HSN and HSN₀ ([pTBCB] = 12 µg mL⁻¹) under 1064 nm photoirradiation (1 W cm⁻²). f Linear fits of PA amplitudes of HSN (R² = 0.96809) and HSN₀ (R² = 0.97314) as a function of concentration at 1064 nm, respectively. g ·OH generation of HSN under different pH conditions (pH = 7.4, 6.8, 5.5) with or without 1064 nm photoirradiation (1 W cm⁻²). ·OH generation was quantified by the decrease of absorbance of MB at 664 nm. [pTBCB] = 23 µg mL⁻¹, [H₂O₂] = 0.5 mM, [MB] = 1 mM. h ·OH generation by HSN₀ at pH 6.8 with or without 1064 nm photoirradiation (1 W cm⁻²). i Scheme of NIR-II photoirradiation enhanced self-degradation of HSN to HSNS in the presence of H₂O₂. Error bars indicated standard deviations of three independent measurements.