Sensitive detection of pyrraline with a molecularly imprinted sensor based on metal-organic frameworks and quantum dots

A novel opto-sensor was constructed by anchoring the molecularly imprinted polymers (MIPs) onto the surfaces of metal-organic frameworks (MOFs) and CdSe/ZnS quantum dots (QDs) via one-step reverse micro-emulsion polymerization. It was used for highly selective and sensitive detection of pyrraline (PRL) in milk powders. High selectivity was guaranteed by molecular imprinting, and sensitivity was improved by double signal amplification using the CdSe/ZnS QDs nanocrystals as fluorescent elements and MOFs as an imprinting matrix. The QDs were introduced into the molecularly imprinted sensor as a tentacle to sense bonding interactions between the MIPs and target molecules and to transduce them into fluorescent signals. The opto-sensor had a high fluorescence quantum yield because of the use of hydrophobic CdSe/ZnS QDs and the reverse micro-emulsion. Under optimized conditions, the fluorescence intensity of the opto-sensor was linear with increasing PRL concentration over the range 5 × 10−6–1 × 10−3 mol L−1, with a detection limit of 3.9 × 10−6 mol L−1. Recoveries of 90–110% were achieved in direct selective detection of PRL in milk powders.