Fig. 4. (a) Illustration of the synthesis of block copolymers by the “one-prepolymer” approach. (b) Low-magnification TEM image of Fe₃O₄–CsPbBr₃ block copolymers. For each copolymer chain, the Fe₃O₄ and CsPbBr₃ segments were highlighted in red and yellow, respectively. Inset shows a fluorescence image of Fe₃O₄–CsPbBr₃ block copolymers under UV irradiation. (c) Distribution of the species resulting from copolymerization. About 500 chains were counted for statistical analysis. Others refer to multiblock chains. (d) Magnified TEM image of a single Fe₃O₄–CsPbBr₃ diblock chain. (e) HAADF-STEM image and the corresponding elemental mapping of another diblock chain. (f) Extinction and PL (dashed) spectra of Fe₃O₄–CsPbBr₃ block copolymers and CsPbBr₃ nanocubes. (g) Photograph showing the attraction of Fe₃O₄–CsPbBr₃ block copolymers by a magnet. (h) Photograph of the dried Fe₃O₄–CsPbBr₃ block copolymers under UV irradiation. (i and j) HAADF-STEM images of di- and triblock copolymers of Fe₃O₄–Ag, respectively. (k) TEM image of Fe₃O₄–Au block copolymers.