Fig. 1. X-ray and electron excitation process: (a) Thomson scattering of atoms; (b) Compton scattering; (c) photoelectric absorption process^[18]

Fig. 2. Cu₄I₄ clusters protected by different ligands: (a) Cu₄I₄(PPh₃)₄; (b) Cu₄I₄(py)₄; (c) Cu₄I₄(tbpy)₄; (d) Cu₄I₄(bzpy)₄; (e) Cu₄I₄(Ph₃As)₃; (f) Cu₄I₄(An₃As)₃(EtCN); (g) Cu₄I₄(Ph₃As)₃(PhCN); (h) Cu₄I₄(An₃As)₃(iPrCN); Atomic colors: white, C; red, Cu; indigo, I; purple, P; blue, N; yellow, As; pink, O; H atoms are omitted to simplify the structure (color online)

Fig. 3. (a) Structure of Cu₄I₆ with different ligands; (b) X-ray emission spectra of the two films and BGO; (c) the two films prepared show green and yellow under X-ray excitation; (d) bright field and X-ray excitation images of the copper mesh; (e) bright field and X-ray excitation images of the USB drive^[35] (color online)

Fig. 4. (a) Pyridine-based organic ligands with different structures; (b) X-ray excitation emission spectra of copper iodine clusters using different ligands; (c) chromaticity diagram of emission wavelengths of a series of copper iodine clusters and crystal emission diagram; (d) comparison of the number of X-ray excitation photons; atomic colors: light purple, H; dark purple, C; red, Br; white, N^[34] (color online)

Fig. 5. (a) Radiation detection limit of Cu₄I₄(Ph₃As₃)₄; (b) stability time response of cluster structure; (c) signal time response of cluster structure under step radiation dose;(d) relationship between light intensity and dose rate^[26]

Fig. 6. (a) (CISDM)₄[Cu₄I₈]·2H₂O crystal structure; (b) detection limit comparison with commercial scintillator materials; (c) radiated light yield comparison with commercial materials; (d) thin film X-ray imaging for grid structure; (e) spatial resolution of copper-iodine cluster thin film imaging; (f) spatial resolution comparison with other scintillator materials; atomic color: white, H; gray, C; red, O; blue, N; yellow, Cu; brown, I^[32](color online)

Fig. 7. Schematic diagram of thin film preparation using PVP-assisted growth^[46]

Fig. 8. (a) SEM characterization of nanocrystals prepared in low-temperature solvents; (b) SEM characterization of the thin film structure prepared on ITO glass; (c) flexible film under sunlight and 254 nm excitation; (d) cluster luminescence characteristics under different states; (e) optical transmittance of ITO glass and flexible film; (f) display of flexible film^[30]

Fig. 9. (a) Cluster crystals (left) and unit cell structure (middle) and photos of crystals under sunlight and ultraviolet light (right); (b) cluster crystals that remain yellow after being in water for a long time; (c) XRD diffraction pattern of cluster crystals after long-term immersion; (d) changes in fluorescence intensity of crystals after long-term immersion in water; (e) crystals remain yellow at different pH values; (f) XRD diffraction pattern of cluster crystals at different pH values; (g) changes in fluorescence intensity of cluster crystals at different pH values; (h) prepared yellow flexible film^[31](color online)

Fig. 10. (a) Schematic diagram of crystal structure; (b) SEM characterization of thin films prepared by filtration; (c) SEM characterization of thin films prepared by soft pressing; (d) comparison of AFM film height distribution prepared by filtration and soft pressing; (e) comparison of quantum yield and radiant luminescence intensity of thin films with different halogenated copper clusters and different preparation methods; (f) comparison of stability of thin films with different halogenated copper clusters and different preparation methods; atomic color: pink, P; green, F; blue, N; white, C; orange, Cu; purple, Cl/Br/I^[28](color online)