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

Fig. 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

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

Fig. 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

Fig. 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)

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

Fig. 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, τs and η represent extinction coefficient, time constant in cooling stage, and photothermal conversion efficiency, respectively, of FePS3 NSs under 1064 nm laser irradiation

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

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

Fig. 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