Fig. 1.

Analytical strategy and fluorescent property of PBI-CB. a Schematic representation of the two-step judgment strategy for differentiation and identification of illicit drugs via scent sniffing. b Chemical structures of PBI-CB and PBI-PE. c Fluorescent images of PBI-CB and PBI-PE in solid state under UV light (365 nm). d UV-vis absorption spectra and fluorescence emission spectra of PBI-CB recorded in different solvents at a concentration of 5.0 × 10⁻⁶ mol L⁻¹ and at room temperature (λ_ex = 480 nm). Inset: fluorescent pictures of the four solutions under UV light (365 nm)