A Ratiometric Fluorescence Method Based on PCN-224-DABA for the Detection of Se(IV) and Fe(III)

Abstract

In this study, 3,4-diaminobenzoic acid (DABA) was introduced into the porphyrin metal-organic framework (PCN-224) for the first time to prepare a ratiometric fluorescent probe (PCN-224-DABA) to quantitatively detect ferric iron (Fe(III)) and selenium (IV) (Se(IV)). The fluorescence attributed to the DABA of PCN-224-DABA at 345 nm can be selectively quenched by Fe(III) and Se(IV), but the fluorescence emission peak attributed to tetrakis (4-carboxyphenyl) porphyrin (TCPP) at 475 nm will not be disturbed. Therefore, the ratio of I_345nm/I_475nm with an excitation wavelength of 270 nm can be designed to determine Fe(III) and Se(IV). After the experimental parameters were systematically optimized, the developed method shows good selectivity and interference resistance for Fe(III) and Se(IV) detection, and has good linearity in the ranges of 0.01-4 μM and 0.01-15 μM for Fe(III) and Se(IV) with a limit of detection of 0.045 μM and 0.804 μM, respectively. Furthermore, the quenching pattern was investigated through the Stern-Volmer equation, and the results suggest that both Se(IV) and Fe(III) quenched on PCN-224-DABA can be attributed to the dynamic quenching. Finally, the constructed ratiometric fluorescent probe was applied in the spiked detection of lake water samples, which shows good applicability in real sample analysis. Moreover, the Fe(III) and Se(IV) contents in spinach and selenium-enriched rice were determined, respectively.

Keywords: ferric iron; porphyrin metal–organic framework; quenching; ratiometric fluorescence; selenium.

Figure 1

Schematic of the preparation of PCN-224-DABA and its applications in the determination of Se(IV) and Fe(III).

Figure 2

(A,B) SEM and (C) TEM images, and (D) the element mapping of PCN-224-DABA; (E) FT-IR spectra of (a) DABA, (b) TCPP, (c) PCN-224, and (d) PCN-224-DABA; XPS spectra of (F) PCN-224-DABA, (G) C 1s, (H) O 1s, (I) N 1s, and (J) Zr 3d.

Figure 3

Fluorescence emission spectra of different systems at (A,B) pH = 1 and (C,D) pH = 2.

Figure 4

Stern–Volmer diagram of (A) PCN-224-DABA + Se(IV) and (B) PCN-224-DABA + Fe(III); emission spectrum of PCN-224-DABA with different concentrations of (C) Se(IV) and (D) Fe(III).

Figure 5

SEM images of PCN-224-DABA with (A) Tris-HCl (pH = 1), (B) Se(IV), (F) Tris-HCl (pH = 2.0), and (G) Fe(III); TEM images of PCN-224-DABA with (C–E) Se(IV) and (H,I) with Fe(III).

Figure 6

(A) FT-IR and (B) XPS spectra of PCN-224-DABA (a), PCN-224-DABA + Se(IV) (b), and PCN-224-DABA + Fe(III) (c); XPS spectra of (C) N 1s, (D) C 1s, (E) O 1s, and (F) Zr 3d of PCN-224-DABA (a), PCN-224-DABA + Se(IV) (b), and PCN-224-DABA + Fe(III) (c); XPS spectra of (G) Se 3d and (H) Fe 2p.

Figure 7

The effects of (A) pH, (B) temperature, and (C) reaction time on the detection of Se(IV); (D) fluorescence spectra of the reaction system with different concentrations of Se(IV) and (E,F) corresponding scatter plots.

Figure 8

The effects of (A) pH, (B) temperature, and (C) reaction time on the detection of Fe(III); (D) fluorescence spectra of the reaction system with different concentrations of Fe(III) and (E,F) corresponding scatter plots.

Figure 9

Selectivity and interference study of the ratiometric fluorescence method based on PCN-224-DABA for (A,B) Se(IV) and (C–E) Fe(III) detection.