Formation and origin of multicenter photoluminescence in zeolite-based carbogenic nanodots.

Carbogenic nanodots (CNDs) are inspiring intensive research efforts owing to their excellent optical properties; however, their chemical structures and photoluminescent origins are still under study. Herein, CNDs with interesting multicenter photoluminescence (PL) have been successfully prepared by pyrolysis of organo-templated zeolites. The simultaneously observed excitation-dependent blue and excitation-independent green PL emissions as well as an uncommon ultraviolet-excited cyan emission are quite different from those of the known multicenter emissive CNDs. To get a thorough understanding of the formation of these CNDs and their PL origins, structural characterizations coupled with femtosecond transient absorption and fluorescence lifetime spectra analyses have been employed to study such PL behavior. The results show that the as-prepared CNDs consist of three main batches with different polarities, and they are composed of a combination of six small fluorophores with diverse ratios. The multicenter PL is obtained due to competition between the conjugated domain fluorophores and the surface-occupied functional group fluorophores. This study provides a comprehensive insight into the origin of multicenter photoluminescence in zeolite-based CNDs.