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An ion-imprinted fluorescent polymer (referred to as CQD@SiO@IIP) is presented for recognition of lithium ion. The material is based on the use of carbon quantum dots (CQDs) and is prepared by a surface imprinting technique using benzo-15-crown-5 (B15C5) as the complexing agent, methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinker, 2,2-azobisisobutyronitrile (AIBN) as the radical initiator, and lithium ion as the template. After optimization of the detection conditions, the relative fluorescence intensity (F/F), best measured at excitation/emission wavelength of 360 nm/460 nm, varies linearly with the Li concentration in the range between 0.5 and 50 μmol·L, with a limit of detection of 16 μmol·L. Performance was compared to the non-imprinted material, and the imprinting factor is found to be 4.5. The ion-imprinted fluorescence material was applied to the determination of Li in (spiked) water samples and obtained good recoveries ranged from 102 to 111.6%. [ABSTRACT FROM AUTHOR]

Abstract A direct and facile "bottom-up" approach was carried out to prepare nitrogen doped graphene quantum dots (NGQDs) under hydrothermal conditions. The as-synthesized NGQDs exhibited an excellent excitation-independent upconversion and downconversion photoluminescent (PL) behavior. And further, the NGQDs/BiVO 4 composite photocatalysts were also fabricated to investigate enhanced visible-light photocatalytic performance. The addition of NGQDs in the NGQDs/BiVO 4 could improve the photocatalytic performance, and the results indicated 5.0 wt% NGQDs/BiVO 4 composites showed the optimal photocatalytic performance. The quenching of effects of different scavengers demonstrated that superoxide radical played a major role in MB degradation. A possible mechanism that NGQDs could enhance the photocatalytic performance of NGQDs/BiVO 4 composites had been also proposed. It was estimated that the photocatalytic performance of the NGQDs/BiVO 4 composites for the degradation of MB under visible light could be primarily ascribed to upconversion PL character of NGQDs and the efficient separation of photogenerated electrons and holes. [ABSTRACT FROM AUTHOR]