Functional polymer microspheres as “turn-off” chemosensors for detection of copper cations

Functional polymer microspheres with fluorescent carbazole unit and various functional groups, such as amide, pyridyl, and imidazole, were prepared by distillation precipitation copolymerization of divinylbenzene (DVB) as a crosslinker, N-vinylcarbazole (NVCz), together with acrylamide (AAm), 4-vinylpyridine (VPy), and 1-vinylimidazole ((VIM) as functional monomers in acetonitrile in the absence of any stabilizer. The resultant polymer microspheres were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy, photoluminescent spectroscopy, inductively coupled plasma (ICP), and X-ray photoelectron microscopy (XPS). The functional polymer microspheres acted as a “turn-off” chemical sensor with excellent stability for determination of copper cation (Cu 2+ ) in methanol via the quenching effect of fluorescence after adsorption of Cu 2+ from the solution through the capture ability of functional groups, such as pyridyl, imidazole, and amide on the surface of polymer microspheres. A good linear relationship was set up between the photoluminescence intensity at the emission peak of 352 nm and the Cu 2+ concentrations ranging from 0 to 1.0 μM with the presence of pyridyl group as a ligand. The effects of the functional groups were investigated on the fluorescent response for the microspheres as chemical sensors.