Sulfur and nitrogen co‐doped graphene quantum dot‐assisted chemiluminescence for sensitive detection of tryptophan and mercury (II)
Yue Li, Jia Wang, Yaqiong Yang, Suqin Han
Abstract
Abstract A simple one‐step thermal treatment to prepare strong fluorescent sulfur and nitrogen co‐doped graphene quantum dots (SN‐GQD) using citric acid and l ‐cysteine as precursors was developed. The ultra‐weak chemiluminescence (CL) from the reaction of hydrogen peroxide (H 2 O 2 ) and periodate (IO 4 − ) was significantly enhanced by SN‐GQD in acidic medium. The enhanced CL was induced by excited‐state SN‐GQD (SN‐GQD*), which was produced from the transfer energy of (O 2 ) 2 * and 1 O 2 to SN‐GQD and recombination of oxidant‐injected holes and electrons in SN‐GQD. In the presence of tryptophan (Trp), the CL intensity of the SN‐GQD–H 2 O 2 –KIO 4 system was greatly diminished. This finding was used to design a novel method for determination of Trp in the linear range 0.6–20.0 μM, with a limit of detection (LOD) of 58.0 nM. Furthermore, Hg 2+ was detectable in the range 0.1–9.0 μM with a LOD of 64.0 nM, based on its marked enhancement of the SN‐GQD–H 2 O 2 –KIO 4 CL system. The proposed method was successfully applied to detect Trp in milk and human plasma samples and Hg 2+ in drinking water samples, with recoveries in the range 95.7–107.0%.