Preparation and Sensing Properties of Covalent-linked Europium Complex Monodisperse Polystyrene Microspheres†

doi:10.7503/cjcu20180383

Abstract

Abstract:

Covalent-linked Eu-complex monodisperse polystyrene microspheres were prepared by a simple environment-friendly one-step soap-free emulsion polymerization. Styrene(St), Eu-complex monomer[Eu(AA)₃Phen] and methacrylic acid(MAA) were separately selected as matric monomer, fluorescent monomer, and water-soluble monomer. Meanwhile, Eu-complex monomer was also acted as cross-linked monomer. The chemical composition and morphology of the copolymer microspheres were characterized by ¹³C CP/MAS NMR, Fourier transform infrared spectrophotometer(FTIR), X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM), transmission electron microscope(TEM), particle size analysis and zeta potential analysis. With the increase of Eu-complex content, the stability of the emulsion decreased, and the particle size and its distribution of the polystyrene microspheres increased; meanwhile, the thermal stability of the polystyrene microspheres was also decreased. Through regulating Eu-complex monomer content(0.25%—2.5%, mass fraction), the polystyrene microspheres feature a stable spherical morphology with a narrow size distribution. Excited by ultraviolet light, the polystyrene microspheres can emit the characteristic red light of europium ion. The luminescence of the polystyrene microspheres originates mainly from the sensitization of ligands to europium ions, that is, the energy transfer from ligands to europium ions. Due to the strong binding ability of Fe³⁺ to N and O atoms, the coordination structure of Eu-complex has changed after adding iron ions. As a result, the luminescence of the polystyrene microspheres can be quenched by Fe³⁺, and the common anions and other metal ions have little interference. The quenching efficiency are linearly related to the concentration of Fe³⁺ ranged from 0 to 300 μmol/L. With the increase of the content of the europium complex monomer, the fluorescence intensity of the polystyrene microspheres is enhanced, and the fluorescence detection K_SV of Fe³⁺ is increased, while limit of determent(LOD) is decreased. Regulating the content of the europium complex, the monodisperse copolymer fluorescent microspheres exhibit excellent thermal stability, strong red light emission, and high selectivity for Fe³⁺ fluorescence detection, which have high application value in biological detection and environmental protection.

Key words: Polymer microsphere, Europium complexe, Fluorescence sensor, Iron ion

CLC Number:

TrendMD:

ZHANG Chunyan,LUO Jianxin,LI Wenjun,OU Lijuan,YU Guipeng,PAN Chunyue. Preparation and Sensing Properties of Covalent-linked Europium Complex Monodisperse Polystyrene Microspheres^†[J]. Chem. J. Chinese Universities, 2019, 40(1): 153.

Figures/Tables 8

Scheme 6 Preparation of the Eu-containing polystyrene microspheres

Table 1 Composition, yield, stability and particle size of the Eu-containing polystyrene microspheres

Microsphere	Mass fraction of Eu-complex(%)		$C COOH c$ (%)	Stability	Yeild(%)	d^d/nm	PDI^d	ζ^d/mV
Microsphere	Theoretical^a	Actual^b	$C COOH c$ (%)	Stability	Yeild(%)	d^d/nm	PDI^d	ζ^d/mV
n-PSEu-0	0	0	37	Stable	91	208	0.055	-26.9
n-PSEu-1	0.25	0.24	35	Stable	86	287	0.057	-26.5
n-PSEu-2	0.63	0.60	33	Stable	84	342	0.064	-25.8
n-PSEu-3	1.25	1.19	32	Stable	81	384	0.069	-25.7
n-PSEu-4	2.50	2.38	31	Stable	78	451	0.081	-23.9
n-PSEu-5	3.75	3.59	24	Unstable	69	526	0.232	-17.6

Table 1 Composition, yield, stability and particle size of the Eu-containing polystyrene microspheres

Microsphere	Mass fraction of Eu-complex(%)		$C COOH c$ (%)	Stability	Yeild(%)	d^d/nm	PDI^d	ζ^d/mV
Microsphere	Theoretical^a	Actual^b	$C COOH c$ (%)	Stability	Yeild(%)	d^d/nm	PDI^d	ζ^d/mV
n-PSEu-0	0	0	37	Stable	91	208	0.055	-26.9
n-PSEu-1	0.25	0.24	35	Stable	86	287	0.057	-26.5
n-PSEu-2	0.63	0.60	33	Stable	84	342	0.064	-25.8
n-PSEu-3	1.25	1.19	32	Stable	81	384	0.069	-25.7
n-PSEu-4	2.50	2.38	31	Stable	78	451	0.081	-23.9
n-PSEu-5	3.75	3.59	24	Unstable	69	526	0.232	-17.6

Fig.1 SEM(A, B) and TEM(C, D) images of n-PSEu-0(A, C) and n-PSEu-4(B, D)

Fig.2 13C CP/MAS NMR spectra(A), FTIR spectra(B), XPS scan survey(C), Eu3d(D) and N1s(E) XPS spectra of the Eu-containing polystyrene microspheres Inset: chemical structural formula of the Eu-containing polystyrene microspheres. a. n-PSEu-0; b. n-PSEu-4; c. Eu(AA)3Phen.

Table 2 Thermal, luminescence and sensing properties of the Eu-containing polystyrene microspheres

Microsphere	$T g a$ /℃	$T d b$ /℃	$T p c$ /℃	I^d/a.u.	10^-3 $K SV e$ /(mol·L^-1)	LOD^f(μmol·L^-1)
n-PSEu-0	103	351	446	——	——	——
n-PSEu-1	106	360	442	14	5.93	5.1
n-PSEu-2	110	352	439	45	6.21	3.9
n-PSEu-3	114	351	436	85	7.45	3.2
n-PSEu-4	117	333	424	115	8.37	2.6
n-PSEu-5	——	249	416	119	8.71	2.7

Table 2 Thermal, luminescence and sensing properties of the Eu-containing polystyrene microspheres

Microsphere	$T g a$ /℃	$T d b$ /℃	$T p c$ /℃	I^d/a.u.	10^-3 $K SV e$ /(mol·L^-1)	LOD^f(μmol·L^-1)
n-PSEu-0	103	351	446	——	——	——
n-PSEu-1	106	360	442	14	5.93	5.1
n-PSEu-2	110	352	439	45	6.21	3.9
n-PSEu-3	114	351	436	85	7.45	3.2
n-PSEu-4	117	333	424	115	8.37	2.6
n-PSEu-5	——	249	416	119	8.71	2.7

Fig.3 PL excitation(A) and emission(B) spectra of the water-dispersed Eu-containing polystyrene microspheres λem=616 nm; λex=300 nm. Inset of(B): the fluorescence photographs of the water-dispersed Eu-containing polystyrene microspheres(0.5 mg/mL) under UV-light irradiation. (A) a. n-PSEu-0; b. n-PSEu-1; c. n-PSEu-2; d. n-PSEu-3; e. n-PSEu-4; f. n-PSEu-5. (B) a. n-PSEu-1; b. n-PSEu-2; c. n-PSEu-3; d. n-PSEu-4; e. n-PSEu-5.

Fig.4 Fluorescence response profiles of n-PSEu-4 in aqueous solutions(0.5 mg/mL) upon addition of different metal ions(A), ferric salts(B) and the mixture of Fe3+ and different other metal ions(C)All of the added ion concentrations are 1500 μmol/L. (A)a. K(Ⅰ); b. Ca(Ⅱ); c. Mg(Ⅱ); d. Fe(Ⅲ); e. Co(Ⅱ); f. Ni(Ⅱ); g. Cu(Ⅱ); h. Sn(Ⅱ); i. Hg(Ⅱ); j. Pb(Ⅱ); k. Mn(Ⅱ); l. Ag(Ⅰ). (B) a. Cl-; b. SO42-; c. NO3-; d. CH3COO-. (C) a. None; b. K(Ⅰ); c. Ca(Ⅱ); d. Mg(Ⅱ); e. Co(Ⅱ); f. Ni(Ⅱ); g. Cu(Ⅱ); h. Sn(Ⅱ); i. Hg(Ⅱ); j. Pb(Ⅱ); k. Mn(Ⅱ); l. Ag(Ⅰ).

Fig.5 Fluorescence response of n-PSEu-4 in aqueous solutions(0.5 mg/mL) upon addition of Fe3+Inset of the graph illustrates Stern-Volmer graph of n-PSEu-4.

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