Rapid detection of Hg²⁺ in an ON-OFF-ON process using N doped carbon dots

Contamination of ground water with pollutants released from various anthropogenic activities is a major concern due to its adverse effects on the environment and human health. Rapid and efficient detection of such pollutants is the first step toward remediation of the problem. Herein we report a two-point fluorescence turn OFF-ON detection method for Hg²⁺ ions using nitrogen doped carbon dots (NCDs). The NCDs obtained through solvothermal treatment of ammonium citrate tribasic in DMF at 190 °C for four hours exhibited a quantum yield of 9.67%. Hg²⁺ detection is demonstrated in two steps, first the quenching of the fluorescence of NCDs by Hg²⁺ and second the fluorescence recovery upon addition of ascorbic acid from different sources. A rapid filter paper-based detection device is demonstrated based on the principles developed.