Dynamic quenching mechanism based optical detection of carcinogenic Cr(vi) in water and on economical paper test strips via a conjugated polymer

Water pollution caused by heavy metal ions and their oxo-anions comprise the biggest threats to living beings and remains a critical environmental issue. Among various water hazards, hexavalent Cr(vi) is one of the widely spread water pollutants that causes cancer. Herein, we report a very sensitive and selective conjugated polymer poly(1,1′-((2-(benzo[c][1,2,5]thiadiazol-4-yl)-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(pyridin-1-ium)dibromide) (PFPy) based sensing platform for highly accessible and quick identification of hexavalent Cr(vi) in water medium as well as on economical portable paper test strips. PFPy displayed a fluorescence “turn-off” signal in the presence of Cr(vi) via a dynamic fluorescence quenching mechanism with a high quenching constant of 2.25 × 10⁵ M and a low limit of detection (LOD) i.e. 6.79 ppb, which is much lower than the safety limit suggested by the World Health Organization (WHO). Additionally, this analytical method was effectively used for the detection of Cr(vi) in real environmental water samples, which is desirable and challenging.