Molecular-level enhanced clusterization-triggered emission of nonconventional luminophores in dilute aqueous solution

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Nonconjugated and nonaromatic luminophores based on clustering-triggered emission derived from through-space conjugation have drawn emerging attention in recent years. The reported nonconventional luminophores are emissive in concentrated solution and/or in the solid state, but they tend to be nonluminescent in dilute solution, which greatly limits their sensing and imaging applications. Herein unique clusteroluminogens were designed through modification of cyclodextrin (CD) with amino acids to enable the intermolecular and intramolecular clusterization of chromophores in CD-based confined space. The resulted through-space interactions along with conformation rigidification originated from hydrogen bond interaction and complexation interaction generate blue to cyan fluorescence even in the dilute solution (0.035 wt.%, quantum yield of 40.70%). Moreover, the prepared histidine-modified CD (CDHis) is demonstrated for fluorescent detection of chlortetracycline with high sensitivity and selectivity. This work provides a new and universal strategy to synthesize nonconventional luminophores with bright fluorescence in dilute aqueous solution through molecular-level enhanced clusterization-triggered emission.

This is a pioneer report of nonconventional luminophores with strong luminescence in dilute solution through modification of cyclodextrin with amino acids. As shown in Fig. 1, partially-oxidized β-cyclodextrin aldehyde (CDA) with sodium periodate is firstly obtained, which exhibits high aqueous solubility and reactivity with functional amino groups. The oxidation of CD leads to the cleavage of C2–C3 bond and the collapse of CD skeleton, softening the initial rigid β-CD molecule. Then, 12 amino acids including nonaromatic amino acids and aromatic amino acids are grafted to the flexible CDA molecule. Taking histidine (His) as example, the amino acid-modified CD (CDAA) presents unique clusteroluminescence even in dilute solution (as low as 0.035 wt.%).

Li, Q., Wang, X., Huang, Q. et al. Molecular-level enhanced clusterization-triggered emission of nonconventional luminophores in dilute aqueous solution. Nat Commun 14, 409 (2023).

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