Fluorometric determination of sulfadiazine by using molecularly imprinted poly(methyl methacrylate) nanobeads doped with manganese(II)-doped ZnS quantum dots

The surface of poly(methyl methacrylate) nanospheres (PMMA-NSs) was molecularly imprinted with sulfadiazine by a surface imprinting method. Simultaneously, Mn(II)-doped ZnS quantum dots were incorporated into the imprinted PMMA-NSs. The morphology of the fluorescent nanoprobe was characterized by transmission electron microscopy which revealed good spheroidal core-shell structure and a homogeneous distribution of the QDs. Following binding of sulfadiazine, fluorescence (best measured at excitation/emission maxima of 335/592 nm) is increasingly quenched. The detection range is 5-40 mu mol center dot L-1 of sulfadiazine, and the detection limit is 0.24 mu mol center dot L-1. The fluorescence quenching mechanism is discussed, and a photo-induced electron transfer process is shown to account for quenching. The fluorescent probe was applied to the determination of sulfadiazine in spiked tap water with recoveries and RSDs of 96.6-100.2% and 2.7-3.9%, respectively. The detection of sulfadiazine in spiked lake water exhibited the recoveries and RSDs with 99.3-104.8% and 1.8-4.2%, respectively. Graphical abstract Schematic presentation of synthesis of PMMA-Ns, Mn-doped ZnS QDs, MQPs, and the elution diagram of SD from MQPs, and the relative reagents including: sodium dodecyl benzene sulfonate(SDBS), (3-aminopropyl)triethoxysilane(APTES), 3-mercaptopropionic acid (MPA), tetraethylorthosilicate(TEOS)and sulfadiazine(SD), and nanoparticles including: polymer(methyl methacrylate) nanospheres(PMMANs), MIPs@QDs@PMMANs(MQPs) and carbon quantum dots(CQDs).