This paper reports a simple, rapid and sensitive fluorescence sensor for the parallel determination of iron (III) (Fe 3+ ), terbium (III) (Tb 3+ ) and europium (III) (Eu 3+ ) ions using Carbon Dot (CD) serving as a fluorescence probe. The Carbon Dot (CD), which was synthesized via an acid-cutting method using anthracite coal as the carbon source, was found to have rich carboxyl and hydroxyl groups on its surface. The fluorescence of the as-prepared CD can be selectively quenched by the Fe 3+ ion via non-radiative electron-transfer, and furthermore, the as-prepared CD can also sensitize the luminescence of both Tb 3+ and Eu 3+ ions through the antenna effect and enhance the fluorescence of Tb 3+ and Eu 3+ by more than several orders of magnitude. Therefore, the as-prepared CD was applied as a fluorescence probe towards the parallel determination of Fe 3+ , Tb 3+ and Eu 3+ and exhibited detection limits in 0.019, 0.10 and 0.79 μM, respectively. The fluorescence quenching mechanism and energy transfer mechanism were also studied in details.
The Fenton system (Fe2+/H2O2) generates ·OH with a high oxidation potential. However, as reactants themselves, H2O2 and Fe2+ can act as ·OH initiators as well as ·OH scavengers, leading to the need for a high dosage of reactants and increased costs. As a mixing-sensitive reaction, the ·OH-related reaction kinetics (·OH with Fe2+, H2O2, and RhB) was determined from the reaction rates (which were a constant in this work) and stoichiometry, in which the latter could be regulated by an addition strategy of Fenton reagents. This suggests that ·OH competitive reactions could be controlled by applying a macrolevel addition strategy. Herein, the effects of different addition approaches of Fe2+ and H2O2 on ·OH competitive reactions were quantitatively and systematically studied by analyzing the removal of the model pollutant RhB. We found that without stirring, and compared with a one-time addition, once H2O2 or Fe2+ was added in a step-wise pattern (e.g., one drop by one drop, 2 times, or 4 times), a high concentration of H2O2 or Fe2+ existed in a localized place for a longer period, resulting in a lower proportion of ·OH reacting with RhB, which we ascribed to an enhanced reaction between Fe2+, H2O2, and ·OH. However, when H2O2 and Fe2+ were added from two close points without stirring, a larger proportion of ·OH was scavenged by H2O2 and Fe2+; while under stirring, even a one-time addition of H2O2 or Fe2+ could cause severe scavenging of ·OH. The results also revealed a linear relationship between the RhB removal percentage and wavelength blue-shifts. This study showed that microlevel ·OH competitive reactions could be controlled by applying a macrolevel addition strategy of Fenton reagents without the addition of external chemicals. The results suggest this methodology can also offer an approach to lower ·OH invalid consumption by regulating the addition strategy in bigger reactors.
Lin Xiang,Xianju Zhou,Yongjie Wang,Li Li,Sha Jiang,Guotao Xiang,Chuan Jing,Jingfang Li,Lu Yao
Near infrared (NIR) light emitting phosphors have attracted more and more attention with the development of science and technology . Herein, we report a series of environmentally-friendly low-cost Fe 3+ -activated ZnGa 2 O 4 phosphors which exhibit intense broadband NIR light emitting. According to density functional theory (DFT) calculations, ZnGa 2 O 4 host possesses an indirect wide bandgap. The emission of the Fe 3+ -doped phosphors demonstrates a wide band spanning from 650 to 850 nm, with the maximum at 720 nm and a full width at half maxima (FWHM) of 70 nm, showing a large overlap with the absorption of phytochromes (PR and PFR). The luminescence intensity remains at 71% when the temperature is raised to 423 K. The phosphors are fabricated into light emitting diodes (LEDs) which produces strong NIR emission with CIE color coordinates of (0.65, 0.31). All these results suggest that ZnGa 2 O 4 :Fe 3+ is a promising NIR luminescent material , which is expected to be a candidate for indoor plant culture LEDs.
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