(a) Transmission electron microscopy (TEM) image of OA-capped MnFe2O4 NPs. (b) UV-vis spectrum of OVA-PEG-MnFe2O4 NPs and R837-OVA-PEG-MnFe2O4 NPs (the circle refers to R837 characteristic peaks). (c) FTIR spectrum of OA-capped MnFe2O4 NPs, PEG-MnFe2O4 NPs, and OVA-PEG-MnFe2O4 NPs, respectively. (d) TGA of PEG-MnFe2O4 NPs and OVA-PEG-MnFe2O4 NPs. (e) Zeta potential of PEG-MnFe2O4 NPs, OVA-PEG-MnFe2O4 NPs, and R837-OVA-PEG-MnFe2O4 NPs, respectively. (f) Temperature of water and R837-OVA-PEG-MnFe2O4 NPs dispersed in water at different concentrations under irradiation with an 805 nm laser (1.2 W/cm2).