Fluorescence-based detection of mercury ions using carbon dots: role of synthesis route

This work demonstrates the significance of the synthesis routes, namely microwave and hydrothermal methods, of green-emitting carbon dots prepared from the same precursors in the selective detection of Hg2+ ions. Aside from providing the advantage of a shorter time scale for the synthesis of C-dots (5 min) compared to the hydrothermal route (8 h) at a synthesis temperature of 180°C, the C-dots prepared via the microwave synthesis route exhibit higher absolute quantum yield (1.8 times) while retaining similar pH and concentration-dependent emission properties. Due to the difference in surface nitrogen content, the microwave synthesized C-dot fluorescence emission exhibit a linear behavior from 8 nM to 64 nM of Hg2+ ions and provides a limit of detection of 3.09 nM whereas hydrothermally synthesized particles exhibit linear variation from 0.5 µM to 4 µM with a detection limit of 0.22 µM        .