Mercaptosuccinic acid-coated NIR-emitting gold nanoparticles for the sensitive and selective detection of Hg2 +

A sensitive fluorescent detection platform for Hg 2   + was constructed based on mercaptosuccinic acid (MSA) coated near-infrared (NIR)-emitting gold nanoparticles (AuNPs). The thiolated mercaptosuccinic acid was employed as both reducing agent and surface coating ligand in a one-step synthesis of NIR-emitting AuNPs (MSA-AuNPs), which exhibited stable fluorescence with the maximum wavelength at 800   nm and a wide range of excitation (220–650   nm) with the maxima at 413   nm. The MSA coated NIR-emitting AuNPs showed a rapid fluorescence quenching toward Hg 2   + over other metal ions with a limit of detection (LOD, 3δ) as low as 4.8   nM. The sensing mechanism investigation revealed that the AuNPs formed aggregation due to the “recognition” of Hg 2   + from the MSA, and the resultant strong coupling interaction between Hg 2   + and Au (I) to further quench the fluorescence of the AuNPs, which synergistically resulted in a highly sensitive and selective fluorescence response toward Hg 2   + . This proposed strategy was also demonstrated the possibility to be used for Hg 2   + detection in water samples.