Dummy Molecularly Imprinted Polymers-Capped CdTe Quantum\nDots for the Fluorescent Sensing of 2,4,6-Trinitrotoluene

Abstract

Molecularly imprinted polymers (MIPs)\nwith trinitrophenol (TNP)\nas a dummy template molecule capped with CdTe quantum dots (QDs) were\nprepared using 3-aminopropyltriethoxy silane (APTES) as the functional\nmonomer and tetraethoxysilane (TEOS) as the cross linker through a\nseed-growth method via a sol–gel process (i.e., DMIP@QDs) for\nthe sensing of 2,4,6-trinitrotoluene (TNT) on the basis of electron-transfer-induced\nfluorescence quenching. With the presence and increase of TNT in sample\nsolutions, a Meisenheimer complex was formed between TNT and the primary\namino groups on the surface of the QDs. The energy of the QDs was\ntransferred to the complex, resulting in the quenching of the QDs\nand thus decreasing the fluorescence intensity, which allowed the\nTNT to be sensed optically. DMIP@QDs generated a significantly reduced\nfluorescent intensity within less than 10 min upon binding TNT. The\nfluorescence-quenching fractions of the sensor presented a satisfactory\nlinearity with TNT concentrations in the range of 0.8–30 μM,\nand its limit of detection could reach 0.28 μM. The sensor exhibited\ndistinguished selectivity and a high binding affinity to TNT over\nits possibly competing molecules of 2,4-dinitrophenol (DNP), 4-nitrophenol\n(4-NP), phenol, and dinitrotoluene (DNT) because there are more nitro\ngroups in TNT and therefore a stronger electron-withdrawing ability\nand because it has a high similarity in shape and volume to TNP. The\nsensor was successfully applied to determine the amount of TNT in\nsoil samples, and the average recoveries of TNT at three spiking levels\nranged from 90.3 to 97.8% with relative standard deviations below\n5.12%. The results provided an effective way to develop sensors for\nthe rapid recognition and determination of hazardous materials from\ncomplex matrices.