Fig. 2

Construction and characterization of SCNGs. The STEM images of SCNGs using different modes and energy dispersive X-ray (EDX) spectroscopy mapping images of the C, P, O and Fe elements (a SE: second electronic, b BF: bright field, c DF: dark field, d, e HAADF: high-angle annular dark field). j The size distribution of MNPs (green line) and SCNGs (orange line) in buffer. k FT-IR spectra of the MNPs (green line) and SCNGs (orange line). l TG test of the MNPs (green line) and SCNGs (orange line). Scale bar in a–e, 100 nm. Scale bar in f–i, 50 nm. Source data are provided as a Source Data file