Ratiometric fluorescence detection of mercuric ions by sole intrinsic dual-emitting gold nanoclusters

Ratiometric fluorescence sensing based on intrinsic dual-emitting nanomaterials is very intriguing for their simplicity and efficacy. However, intrinsic dual-emitting gold nanocluster-based fluorescence ratiometry remains unexplored. In this work, a ratiometric fluorescence assay for detection of mercuric ions (Hg2+) has been developed using sole intrinsic dual-emitting gold nanoclusters (DE-AuNCs). The DE-AuNCs, simply synthesized by reducing chloroauric acid with an appropriate amount of glutathione, had two distinct intrinsic emission bands peaked at 610 nm and 810 nm respectively. When exposed to Hg2+, the 610 nm emission of the DE-AuNCs was remarkably quenched serving as a reporter signal, while the 810 nm emission almost kept unchanged serving as a reference signal, and thus giving a ratiometric signal. This ratiometric method showed high sensitivity and selectivity for sensing Hg2+ with low LOD down to 0.19 ppb which is quite lower than the WHO drinking-water guideline for inorganic mercury, and was successfully applied to the detection of Hg2+ in environmental water samples.