A simple AIE-active fluorogen for relay recognition of Cu2+ and pyrophosphate through aggregation-switching strategy

A simple benzothizole-based derivative 2-(benzo [d]thiazol-2-yl)phenyl)picolinamide (BTPPA) with aggregation-induced emission (AIE) character has been developed. BTPPA is non-emissive in DMF, but displays strong fluorescence emission in DMF/H2O (1:9, v/v, Tris-HCl 10 mM, pH = 7.1) solution due to its aggregation. The BTPPA aggregates exhibit highly selective recognition toward Cu2+ ions through formation of BTPPA-Cu2+ complex with a 1:1 binding stoichiometry, leading to disaggregation and complete fluorescence quenching. The in situ generated BTPPA-Cu2+ complex can further act as a chemosensing ensemble for highly selective recognition of pyrophosphate (PPi) via Cu2+ displacement approach, which results in re-aggregation of BTPPA and fluorescence recovery. Thus relay recognition of Cu2+ and PPi has been achieved with 'on-off-on' emission changes through aggregation-switching strategy. The limits of detection for Cu2+ and PPi were estimated to be 5.06 x 10(-7) M and 4.73 x 10(-6) M. In addition, detection of Cu2+ and PPi in real samples such as tea, fish, crab meat, toothpaste and detergent were also achieved with good recoveries and small relative standard deviations, demonstrating the potential practicability of BTPPA and BTPPA-Cu2+ for Cu2+ and PPi detection in real samples.