Amplified fluorescence detection and adsorption of Au3+ by the fluorescent melamine formaldehyde microspheres incorporated with N and S co-doped carbon dots

Gold is one of the potential toxic heavy metals. In the present study, Au3+ was detected and removed by newly-designed fluorescent microspheres (MF-CDs), i.e. melamine formaldehyde microspheres incorporated with N and S co-doped carbon dots (N,S-CDs). N,S-CDs played the role as sensing unites and melamine formaldehyde microspheres (MF) as carriers. When MF-CDs were attempted as the fluorescence probe, enhanced fluorescence sensing performance towards Au3+ was achieved with wider linear range (0.05–2 μM) and lower limit of detection (31 nM) compared to the N,S-CDs probe. In addition, when MF-CDs were used as the adsorbent, the adsorption capacity towards Au3+ reached up to 1 mmol g−1, about ten times more than that of MF. Moreover, the Au3+ adsorbed on the MF-CDs could be in-situ transferred to gold nanoparticle (AuNP), forming the immobilized nanocatalyst, i.e. MF-CDs-AuNP, which could further assist the reduction of 4-nitrophenol with acceptable reusability. This study paved an avenue to design the multifunctional materials for simultaneous detection, removal and recycling of environmental concerned pollutants.