AbstractThe authors describe an “off-on” colorimetric and fluorometric assay for the determination of Cu(II). It is based on the use of upconversion nanoparticles (UCNPs) of type NaYF4:Yb(III),Er(III) that were functionalized with branched polyethylenimine (BPEI). A color change from colorless to blue occurs within 2 s after addition of Cu(II) to a solution of the modified UCNPs. The color change can be visually detected at Cu(II) concentrations down to 80 μM. The upconversion fluorescence of the modified UCNPs, measured at excitation wavelength of 980 nm, is reduced due to the predominant inner filter effect caused by the formation of the BPEI-Cu(II) complex. Normalized fluorescence intensity drops linearly in the 50 nM to 10 μM Cu(II) concentration range, and the fluorometric detection limit is 45 nM. Both the color and the fluorescence are recovered on addition of EDTA. Excellent selectivity over other metal ions and anions is achieved. Graphical abstractUpconversion nanoparticles of type NaYF4:Yb,Er were functionalized with branched polyethylenimine (UCNP/BPEI) and used in an “off-on” colorimetric and fluorometric assay for Cu(II). The upconversion fluorescence is selectively quenched on addition of Cu(II), and this is accompanied by a rapid colorless-to-blue color switch. The colorimetric changes and quenched fluorescence can be reversed by adding EDTA.

中文翻译：

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基于使用支化聚乙烯亚胺功能化的 NaYF4:Yb(III),Er(III) 上转换纳米粒子对 Cu(II) 进行“关断”比色和荧光测定

摘要作者描述了一种用于测定 Cu(II) 的“关断式”比色和荧光分析。它基于使用带有支化聚乙烯亚胺 (BPEI) 功能化的 NaYF4:Yb(III)、Er(III) 类型的上转换纳米粒子 (UCNP)。将 Cu(II) 添加到修饰的 UCNPs 溶液后 2 秒内颜色会从无色变为蓝色。颜色变化可以在 Cu(II) 浓度低至 80 μM 时进行视觉检测。由于 BPEI-Cu(II) 复合物的形成导致主要的内部过滤效应，在 980 nm 激发波长下测量的改性 UCNP 的上转换荧光降低。归一化荧光强度在 50 nM 至 10 μM C​​u(II) 浓度范围内线性下降，荧光检测限为 45 nM。加入 EDTA 后颜色和荧光均恢复。实现了优于其他金属离子和阴离子的选择性。图形摘要 NaYF4:Yb,Er 类型的上转换纳米粒子用支化聚乙烯亚胺 (UCNP/BPEI) 功能化，并用于 Cu(II) 的“关断”比色和荧光测定。添加 Cu(II) 后，上转换荧光被选择性淬灭，并且伴随着快速的无色到蓝色的颜色转换。添加 EDTA 可以逆转比色变化和淬灭的荧光。添加 Cu(II) 后，上转换荧光被选择性淬灭，并且伴随着快速的无色到蓝色的颜色转换。添加 EDTA 可以逆转比色变化和淬灭的荧光。添加 Cu(II) 后，上转换荧光被选择性淬灭，并且伴随着快速的无色到蓝色的颜色转换。添加 EDTA 可以逆转比色变化和淬灭的荧光。