1. XRD pattern (a) and SEM image (b) of bulk FePS₃

2. TEM image (a) of FePS₃ nanosheets (NSs) and hydrodynamic size of FePS₃ nanosheets (NSs) before (b) and after (c) PEGylation with inset showing the picture of FePS₃-PEG dispersed in PBS and in DMEM

3. UV-Vis-NIR diffuse reflectance spectrum of FePS₃ NSs with inset showing the estimated band gap potential

4. UV-Vis absorption spectra of the mixture solution of FePS₃ NSs mixed with DPBF (1,3-diphenylisobenzofuran) (a) and DPBF solution (b) under 660 nm laser irradiation, and ESR spectra of different reaction systems (c)TEMP: a reagent used to detect ¹O₂. DMPO: a reagent used to detect O₂^•- and ∙OH

5. Vis-NIR spectra of FePS₃ NSs with different concentrations (a), photothermal heating curves for different time at different concentrations (b), and different laser power densities (1064 nm laser) (c), and photothermal curve of FePS₃ NSs under 5 cycles of laser “on-off” (d)

6. Thermal images of different concentrations of FePS₃ nanosheets heated by 1064 nm laser irradiation for different time

7. Linear fitting curve between normalized absorption intensity of FePS₃ NSs at λ=1064 nm divided by the characteristic length of the sample at corresponding concentration (A/L) and the corresponding concentration (a), linear relationship between -lnθ and time of cooling process of FePS₃ NSs after 1064 nm laser irradiation (b), heating and cooling curves of FePS₃ NSs under 1064 nm laser irradiation, and linear relationship between -lnθ and time of the cooling process (c) ε, τ_s and η represent extinction coefficient, time constant in cooling stage, and photothermal conversion efficiency, respectively, of FePS₃ NSs under 1064 nm laser irradiation

8. Relative cell viabilities of 4T1 cells after incubation with different concentrations of FePS₃-PEG

9. In vitro photodynamic therapy (a) and photothermal therapy (b) treatment of 4T1 cells after incubation with different concentrations of FePS₃-PEG

10. Confocal laser scanning microscope (CLSM) images of 4T1 cell viabilities (a), reactive oxygen species (ROS) production (b) and changes in mitochondrial membrane potential (c) after different treatments Calcein-AM/PI, DCFH-DA and JC-1 represent methods for detecting cell viability, ROS production, and changes in mitochondrial membrane potential, respectively