A naked-eye colorimetric sensor for chloroform

A phenoxazine based molecule termed SP has been synthesized and used as selective sensor for halogenated solvents. This molecule shows selective fast response towards halogenated solvent via naked-eye detectable chromism. SP shows colorless solution when dissolved in most solvents initially but changes to blue color in chloroform under UV irradiation (λ=365 nm) within 5 s. The luminescence spectra of SP in halogenated solvent show a large bathochromic shift (> 100 nm) with 60-fold enhanced emission intensity compared to that in halogen-free solvents. It is also worth mentioning that the photoinduced reaction between SP molecule and the halogenated solvents occurred. Based on the detailed NMR, fluorescence and mass spectra, the possible radical reaction mechanism was proposed. Different from the majority of solvatochromic sensors that based on the polarity of solvents for detection of halogenated solvents, our sensor system worked in a special fashion.