Efficient dual-phase visual detection of pesticides in real samples with electron-rich emitters carrying multiple twists

Abstract

Precise monitoring of pesticides in daily consumable items and the environment is crucial to save society. By considering numerous challenges, such as the cost, operational difficulties, and portability of existing pesticide detection strategies, we herein introduce simple, low-cost triphenylamine (TPA)-enriched structurally diverse π-conjugates as potential dual-state emitters for rapid and visual detection of pesticides, mainly trifluralin (TN; highly toxic to aquatic animals and affects fertile soil) and fenitrothion (FN; an organophosphorus insecticide, lethal to humans on high exposure). Other pesticides, i.e., glyphosate (GP) and imidacloprid (IM), also poorly responded. The newly designed small molecules displayed intense, visually detectable emission in both solution and solid states due to the extensive π-conjugations and multiple twisted sites in the molecular structures. An increment of the TPA units increases the energy of the LUMO of the probes, and thus, the emission profiles alter in solution and solid states. However, these probes are capable of detecting TN and FN selectively through photo-induced electron transfer (PET) and inner-filter effect (IFE) mechanisms, and can be recognised through the naked eye. Among the three probes, AIEEgen TT1 showed the maximum efficiency with a detection limit up to 180 nM due to favorable PET/IFE and its crystalline nature that would facilitate capturing the analytes in the void space. All the findings are well elucidated with experimental and theoretical support. Thus, a handy paper-based platform is presented to visually recognize TN and FN pesticide residues present in soil, fruits, and vegetables. Such an inexpensive protocol would help common people to test household items before handling them.