Fig. 3: Electronic interactions and clusterization processes.

a The diagrammatic illustrations of the cluster formation from isolated chromogens to cluster luminogens in molecular and polymeric systems. b The excitation wavelength-dependent CL of sodium alginate powders; photographs taken under the illumination of (from left to right) UV, blue, and green lights, respectively. c The increased through-space electronic interactions among the chromogenic units in the larger clusters lead to more energy-level splittings and smaller energy gaps (ΔE). d The polymer effect in the CL systems: the tethering effect in the low-molecular-weight oligo(ethylene glycol) (OEG) facilitates the cluster formation through the (n,n) TSC between the oxygen atoms in the short oligomer chain, while in the high-molecular-weight poly(ethylene glycol) (PEG), the synergistic entangling effect (between different polymer chains) and tethering effect (along same polymer chain) results in the formation of oxygenic CLgen networks. The photographs of pure diethyl ether (liquid), pure OEG (liquid), a concentrated PEG solution (100 mM in water), and PEG powders were taken under daylight and UV illumination. b is adapted with permission from ref. ⁵² Copyright (2018) American Chemical Society.