Fig. 6: Broaden the CL horizon from organic clusters to inorganic, metallic, and hybrid clusters.

a The diagrammatic illustration for the CL from the organic clusters of small molecules and large polymers. b Examples of CL systems from inorganic clusters: the aqueous solutions of PbBr₂ and BaPt(CN)₄ salts are nonemissive as isolated ionic species, but their clusters in the aggregate state are photoluminescent. c Examples of metallic CL systems: the aqueous solutions of the oligo(gold-thiolate) chain (left) and the copper salt (right) do not luminesce upon photoexcitation, whose CLs are turned on when large amounts of ethanol (f_e) are added into the water due to the formation of the gold and copper clusters in the aqueous mixtures. d An example of CL systems from hybrid clusters: the organic-inorganic hybrid complex (TPPGPA) is nonluminescent in the dilute DMF solution as molecular species, but their organic and metallic clusters in the aggregates emit lights of complementary colors of cyan-blue and yellow, respectively, resulting in the white-light emission of the crystalline aggregates. b is adapted with permission from ref. ⁸⁷ Copyright (2021) Wiley-VCH Verlag GmbH & Co. c is adapted with permission from ref. ⁸⁸ Copyright (2012) American Chemical Society and ref. ⁸⁹ Copyright (2016) Wiley-VCH Verlag GmbH & Co. d is adapted with permission from ref. ⁹⁰ Copyright (2021) Chinese Chemical Society.