Aqueous Afterglow Dispersion Enabling On-Site Ratiometric Sensing of Mercury Ions

Pollution caused by heavy metal ions has become a global issue owing to their severe threat to our ecological environment and human health. However, it remains a considerable challenge to sensitive sensing of heavy metal ions in an efficient, selective and high signal-to-noise ratio way. Herein, we present a portable and sensitive method to probe mercury ions (Hg2+) by using an ultralong afterglow dispersion. The in-situ encapsulation of phosphorescent carbon dots (CDs) within rigid hydrogen-bonded organic frameworks (HOFs) leads to ultralong room temperature phosphorescence (RTP) in water with a maximum lifetime of up to 974.86 ms. Moreover, the resultant CDs@HOFs composite material exhibits robust and long-term RTP emission with enhanced performance under strongly acidic or alkaline conditions, which contributes to the practical detection of Hg2+ in polluted water. As such, an efficient and sensitive afterglow probe is facilely fabricated by integrating CDs@HOFs with a Hg2+ probe Rhodamine B derivative (RhBTh), demonstrating selective sensing of Hg2+ with greatly improved signal-to-noise ratios based on the Förster resonance energy transfer system (TS-FRET). This work not only provides a reliable and versatile method for realizing robust RTP emission in water, but also expands the applications of afterglow materials in the field of optical sensing of toxic analytes.