Fig. 2. Characterization of NaGdF₄@PEG@bevacizumab–Cy5.5 nanoparticles (NPBCNs). (a) Transmission electron microscopy (TEM) images of NaGdF₄ nanoparticles and NPBCNs. (b) X-ray diffraction (XRD) pattern of NHS–PEG–cholesterol, NPBCNs, NaGdF₄@PEG–NHS–Cy5.5 nanoparticles (NPCNs) and NaGdF₄ nanoparticles. (c) Fourier transformation infrared (FTIR) spectra of NaGdF₄ nanoparticles, NPCNs, NPBCNs. (d) T₁-Weighted MR imaging of NPBCNs at different concentrations of Gd and the T₁ relaxivity NPBCNs.