A novel ratiometric fluorescent nanosensor for visual sensing of Fe3+ has been developed by integrating yellow-emissive rhodamine derivatives (RhB) onto the surface of silica nanospheres embedded with red CdTe QDs. Such a nanohybrid fluorescent sensor RhB-CdTe@SiO2 QDs displays two distinct emission peaks 556 nm and 651 nm under a single excitation wavelength in the presence of Fe3+. The yellow fluorescence of RhB could be selectively increased by Fe3+ due to the strong chelating ability of RhB to Fe3+, while the red fluorescence of CdTe QDs is almost constant, resulting in a distinct fluorescence color transformation from red to yellow, which can be applied for the visual detection of Fe3+. This approach shows high sensitivity and selectivity toward Fe3+, and the detection limit is determined to be 20.5 nM, which is lower than the maximum level (0.3 mg/L, equivalent to 5.4 μM) of Fe3+ ions permitted in drinking water by U.S. Environmental Protection Agency (EPA). For practical application, we dope the mixture of RhB-CdTe@SiO2 QDs and PVA onto the filter paper and fabricate test strips to directly visual inspection of Fe3+ in water. The paper based sensor has a visual detection limit of 1 μM by naked eyes, showing its promising application for onsite visual quantification of ferric ion without the need for elaborate equipment.

中文翻译：

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基于高选择性和灵敏度比率荧光纳米传感器的可视测定水溶液中的铁离子

通过将黄色发光的若丹明衍生物（RhB）集成到嵌有红色CdTe QD的二氧化硅纳米球表面上，已经开发出了一种新型的比率式荧光纳米传感器，用于视觉感知Fe3 +。这种纳米混合荧光传感器RhB-CdTe @ SiO2 QDs在存在Fe3 +的情况下，在单个激发波长下显示两个不同的发射峰556 nm和651 nm。由于RhB对Fe3 +具有很强的螯合能力，RhB的黄色荧光可以被Fe3 +选择性地增加，而CdTe QD的红色荧光几乎恒定，从而导致从红色到黄色的明显荧光颜色转换，可用于视觉检测Fe3 +。这种方法显示出对Fe3 +的高灵敏度和选择性，并且检测极限被确定为20.5 nM，低于美国环境保护署（EPA）在饮用水中允许的最大Fe3 +离子含量（0.3 mg / L，相当于5.4μM）。对于实际应用，我们将RhB-CdTe @ SiO2 QDs和PVA的混合物掺杂到滤纸上，并制作测试条以直接目视检查水中的Fe3 +。纸基传感器的肉眼可见检测极限为1μM，这表明它在无需复杂设备的情况下可用于现场视觉定量三价铁离子。