Photo-driven electron transfer from FAPbBr 3 perovskites nanocrystals to photodeactivatable 4-(phenylazo) benzoic acid

Formamidinium lead bromide (FAPbBr 3 ) perovskite nanocrystals (NCs) are promising materials due to their narrow band emission and high photoluminescence (PL) quantum yield. In the present work, oleyl amine functionalized FAPbBr 3 NCs were synthesized. These NCs were then attached to 4-(phenylazo)benzoic acid (PABA) to form a fluorescent photodeactivatable FAPbBr 3 NCs-PABA dyad. Ultraviolet (UV) irradiation caused trans–cis isomerization of PABA that reverted to the trans -isomer upon storage in the dark after 40 min. Upon UV irradiation of the FAPbBr 3 NCs-PABA dyad, PABA was converted from the trans isomer to the cis isomer. Strong PL quenching of FAPbBr 3 NCs was observed due to photoexcited charge transfer from the conduction band of NCs to the LUMO of the cis -isomer of PABA. The decrease in the PL intensity of NCs also manifested as a decrease in the PL lifetime. The positions of band edges, estimated by cyclic voltammetry, suggested that the electron transfer from photoexcited FAPbBr 3 NCs to the cis -isomer of PABA was responsible for the PL quenching of FAPbBr 3 NCs. The photoinduced reversible trans–cis isomerization of PABA accompanied by the strong PL quenching of FAPbBr 3 NCs in the FAPbBr 3 NCs-PABA dyad, due to photoexcited electron transfer from NCs to PABA in the dyad, could help in the design of photo-driven fluorescent probes with high-contrast due to the narrow emission band of FAPbBr 3 NCs.