Molecularly imprinted polymers with Mn-doped ZnS quantum dots were prepared using dibutyl phthalate as the template molecule, 3-aminopropyltriethoxysilane as the functional monomer and the tetraethoxysilane as the cross-linker.

An eco-friendly fluorescence polymer nanoparticle based on carbon quantum dots and poly(methyl methacrylate) nanoparticles is successfully fabricated to detect sulfadiazine. By making use of the abundant functional group of carbon quantum dots and poly(methyl methacrylate) nanoparticles, without any extra modification, the synthetic process of the fluorescence nanoparticles is reduced and the unnecessary chemical molecules are avoided being brought into the reaction system. The investigation of the fluorescence property of carbon quantum dots shows that the prepared carbon quantum dots are the excitation independent. In addition, the morphology of the synthesized fluorescence polymer nanoparticle is tested by the scanning electron microscope and shows that the fluorescence sensor possesses a good spherical core–shell structure. Moreover, under the optimized condition, the prepared fluorescence polymer nanoparticle possesses a good selectivity in the detection of sulfadiazine under a mixture solution. Moreover, the limit of detection is 4 μmol.l−1 within the detective range from 10 μmol.l−1 to 60 μmol.l−1. Meanwhile, the fluorescence quenching mechanism is considered with the photoinduced electron transfer mechanism. Finally, the practical research on the detection of sulfadiazine in tap water shows that the recovery range and relative standard deviation are 97.5% − 105.1% and 2.1%–4.5%, respectively.

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The fluorescence mechanism of dual-emission carbon quantum dots (DCQDs) is investigated by the improved intercept method, of which the DCQDs with high quantum yield are synthesized by hydrothermal method by using the precursor of sulfadiazine. The research of the morphology, chemical properties and fluorescence properties on DCQDs, shows that DCQDs have graphene-like structure and well-resolved lattice fringes, and that DCQDs fluorescence emission as well intensity has reversibility between acid and alkaline. Based on the ultraviolet absorption spectrum (UV–vis) of the DCQDs, the band gap of DCQDs is estimated by the improved intercept method. Then, the change law of DCQDs emission wavelength at different excitation wavelengths is studied by using the estimated band gap. It is found that the improved intercept method is well consisted with the emission change law of DCQDs at different excitation wavelengths. In addition, the influence of different concentration of Fe3+ on the estimated band gap of DCQDs shows that the Fe3+ has big influence on the band gap of 3.99 eV and 3.06 eV but almost no effect on band gap of 4.93 eV and 3.67 eV. It indicates that the quenching of Fe3+ to DCQDs may be due to the band gap caused by surface defect is changed by Fe3+. Also, DCQDs are used as probe to detect Fe3+ and used as spray ink. Thereby, the improved intercept method may provide a new direction for researching the fluorescence mechanism of carbon quantum dots.