Selective chemiluminescence method for the determination of trinitrotoluene based on molecularly imprinted polymer-capped ZnO quantum dots

Developing a selective and sensitive tool for recognizing 2,4,6-trinitrotoluene (TNT) is of great importance from both security and contamination viewpoints. Here, a novel molecularly imprinted polymer (MIP) based chemiluminescence (CL) assay is described for the determination of TNT in environmental samples. ZnO quantum dots (QDs) were synthesized using a simple and economical process and applied as efficient supports for the MIP layer. The MIP layer was produced using (3-aminopropyl)triethoxysilane (APTES) as a monomer and tetraethoxysilane (TEOS) as a cross-linker, in the presence of TNT as the template. The MIP-labeled ZnO QD composite (MIP@QDs) was characterized using photoluminescence emission, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The prepared composite showed a remarkable promoting effect on the weak chemiluminescence emission of an alkaline permanganate-rhodamine B (RB) system. This effect was described based on the catalytic activity of the composite. Moreover, in the presence of TNT, its molecules were adsorbed onto specific sites of the MIP and placed near the QDs, resulting in a noticeable decrease in the CL intensity of the KMnO₄-RB-MIP@QDs system. Based on this effect, a selective and highly sensitive CL assay was introduced for the TNT determination. Under the optimal conditions, a linear relationship was obtained between the decreased CL intensity and TNT concentration in the ranges 0.02-50 and 50-200 ng mL^-1 with a detection limit (3σ) of 6.8 pg mL^-1. This method had good selectivity towards TNT but not towards similar species such as 2-nitrotoluene, 2,4-dinitrotoluene, etc.