Facile Conversion of Toxic Cigarette Butts to N,S-Codoped Carbon Dots and Their Application in Fluorescent Film, Security Ink, Bioimaging, Sensing and Logic Gate Operation.

The present work is emphasized on converting toxic cigarette butts (CBs) into highly fluorescent N,S-codoped carbon dots by a facile hydrothermal approach and exploring their multiple applications. The as-produced carbon dots (CBCDs) exhibited bright and stable fluorescence with a quantum yield of 26% and used as a label-free probe for "on-off-on" sequential detection of Fe and ascorbic acid (AA). The fluorescence of CBCDs can be significantly quenched by Fe ions through static quenching and restored upon the subsequent addition of AA due to the reduction of Fe to Fe by AA.