Synthesis of cadmium selenide quantum dots modified with thiourea type ligands as fluorescent probes for iodide ions

摘要

Highly luminescent and stable CdSe quantum dots(QDs)modified with 4-substituted pyridine type ligands containing thiourea groups:1-(4-nuorobenzoyl)-3-(5-(pyridin-4-yl)-1,3,4-thiadiazol-2-yl)thiourea(PyTU);were prepared through a ligand exchange process,and were characterized by transmission electron microscopy(TEM),fluorescence spectroscopy,UV-vis spectroscopy and FT-IR spectroscopy.The synthesized nanocomposites show higher fluorescence(FL)intensity and are more stable in comparison with original QDs.The PyTU-CdSe QDs allow a highly sensitive determination of iodide via significant FL intensity quenching.Under optimal conditions,the relative FL intensity is decreased linearly with increasing iodide concentration in the range 0-50 mu M with a detection limit of 1.5 X 10~(-9)M,while the FL intensity of PyTU-CdSe QDs to other anions including F~-,Cl~-,Br~-,SCN~-,HCOO~-,CH3COO~-,HSO3~-,and C2O4~(2-)is negligible.It is found that the decreased luminescence intensity of the PyTU-CdSe QDs dependent on the concentration of iodide is best described by a Stern-Volmer equation.The possible mechanism is discussed.