Figure 2.

Morphology and characterization. a) STEM and EDS mapping of the PEGylated BPNSs (scale bar, 50 nm). b) AFM image and height profile of BPNSs (left, scale bar, 100 nm) and PEGylated BPNSs (right, scale bar, 1 µm). c) Zeta potentials of BPNSs and PEGylated BPNSs. d) Raman scattering spectra of BPNSs and PEGylated BPNSs. e) UV–vis absorbance spectra of PEGylated BPNSs dispersed in aqueous solution with different concentrations (inset, calibration curve of absorbance versus PEGylated BPNSs concentration). f) Photothermal activities of the PEGylated BPNSs dispersed in aqueous solution at varied concentrations (0, 6.25, 12.5, 25, and 50 µg mL⁻¹) at a power density of 1 W cm⁻². g) Determination of the photothermal‐conversion efficiency at 808 nm. h) Real‐time temperature curves of PEGylated BPNS in aqueous solution for twelve laser ON/OFF cycles. For each cycle, the sample was irradiated by an 808 nm diode laser for 5 min and allow natural cooling for 20 min.