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Figure 1. 

(a) SEM images of Zn-PMA. (b) SEM images of Eu-PMA. (c), (d) SEM images of EuZn-PMA at different magnifications. (e), (f) Transmission electron microscopy (TEM) images of EuZn-PMA. (g) scanning transmission electron microscopy (STEM) image of EuZn-PMA and the corresponding elemental mapping of (h) Zn and (i) Eu.

Figure 2. 

(a), (b) XRD patterns of Zn-PMA, Eu-PMA, EuZn-PMA, PMA, and EuZn-PMA@UO₂²⁺. (c) Full XPS survey spectrum of EuZn-PMA. (d) FTIR spectra of PMA, EuZn-PMA, and EuZn-PMA@UO₂²⁺. (e) Raman spectra of EuZn-PMA and EuZn-PMA@UO₂²⁺. (f) Energy-dispersive X-ray spectroscopy (EDS) spectrum of EuZn-PMA and EuZn-PMA@UO₂²⁺. (g), (h) The 77.3 K nitrogen adsorption-desorption isotherms and pore size distribution of EuZn-PMA and EuZn-PMA@UO₂²⁺. (i) Thermogravimetric (TG) and derivative thermogravimetric (DTG) curves of EuZn-PMA.

Figure 3. 

Spectroscopic and interfacial characterization of EuZn-PMA before and after interaction with UO₂²⁺. (a)−(e) High-resolution XPS spectra of C 1s, O 1s, Zn 2p, Eu 3d, and U 4f. (f) Lifetime fluorescence decay curves of EuZn-PMA before and after adding UO₂²⁺. (g) UV–vis absorption spectra. (h) Zeta potential distribution.

Figure 4. 

(a) Fluorescence spectra of Eu-PMA, Zn-PMA, and EuZn-PMA before and after the addition of UO₂²⁺. (b) Fluorescence spectra of EuZn-PMA (0.1 mg/mL) in the presence of different concentrations of UO₂²⁺ (0−60 μM). (c) At UO₂²⁺ concentrations ranging from 0 to 60 μM, the linear relationship between ([F⁵¹³/F₀]/[F⁶¹⁶/F₀]) and different concentrations of UO₂²⁺.

Figure 5. 

Selectivity and anti-interference performance of EuZn-PMA. (a), (c) Fluorescence spectra and the corresponding fluorescence ratio F⁵¹³/F⁵¹³₀ of EuZn-PMA in the presence of UO₂²⁺ and various common interfering ions. (b), (d) Fluorescence spectra and the corresponding fluorescence ratio F⁵¹³/F⁵¹³₀ of EuZn-PMA in mixed solutions containing UO₂²⁺ and threefold excess concentrations of interfering ions.

Figure 6. 

SEM images and corresponding EDS elemental mapping of EuZn-PMA after reacting with UO₂²⁺. (a), (b) SEM morphology of the EuZn-PMA–UO₂²⁺ composite. (c) STEM image of EuZn-PMA@ UO₂²⁺ and the corresponding elemental mapping of (d) Zn, (e) Eu and (f) U.

Figure 7. 

Quantitative detection of UO₂²⁺ by a smartphone-assisted readout platform.