2-(N-Hexylcarbazole-3'-yl)-4-pyridinealdehyde: Cyanide Detection via Benzoin Condensation.

In this research, 2-(N-hexylcarbazole-3'-yl)-4-pyridinealdehyde (probe A) with a donor-pi-acceptor (D-π-A) structure was tested as a new fluorescence sensor. The fluorescence sensor properties of probe A were investigated by using UV-Vis and PL spectrophotometers. The absorption spectrum of probe A did not show a significant change against analytes added to the solution. However, when the emission spectrum of probe A was examined, it gave two very low-intensity emissions at 400 nm and 540 nm. Probe A showed superior selectivity only for cyanide ions (CN-) with the limit of detection (LOD) of 1.42 nM in the presence of various competing analytes. This LOD value is the lowest value reported so far. For the first time, CN- sensing proceeds via benzoin condensation reaction. The stoichiometric ratio and detection mechanism between probe A and CN- were confirmed by Job's plot, HRMS, 1H-NMR, and FT-IR analyses. Probe A also worked successfully in the detection of CN-, which is a highly hazardous and toxic substance, including practical applications (three different real-world water samples). Therefore, probe A was introduced to the field as an effective and striking potential sensor candidate in water quality testing and disease diagnosis, etc.