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Mn²⁺ Luminescence in Ca₉Zn_1-xMn_xNa(PO₄)₇ Solid Solution, 0 ≤ x ≤ 1.

ABSTRACT: The solid solution Ca₉Zn_1-xMn_xNa(PO₄)₇ (0 ≤ x ≤ 1.0) was obtained by solid-phase reactions under the control of a reducing atmosphere. It was demonstrated that Mn²⁺-doped phosphors can be obtained using activated carbon in a closed chamber, which is a simple and robust method. The crystal structure of Ca₉Zn_1-xMn_xNa(PO₄)₇ corresponds to the non-centrosymmetric β-Ca₃(PO₄)₂ type (space group R3c), as confirmed by powder X-ray diffraction (PXRD) and optical second-harmonic generation methods. The luminescence spectra in visible area consist of a broad red emission peak centered at 650 nm under 406 nm of excitation. This band is attributed to the ⁴T₁ → ⁶A₁ electron transition of Mn²⁺ ions in the β-Ca₃(PO₄)₂-type host. The absence of transitions corresponding to Mn⁴⁺ ions confirms the success of the reduction synthesis. The intensity of the Mn²⁺ emission band in Ca₉Zn_1-xMn_xNa(PO₄)₇ rising linearly with increasing of x at 0.05 ≤ x ≤ 0.5. However, a negative deviation of the luminescence intensity was observed at x = 0.7. This trend is associated with the beginning of a concentration quenching. At higher x values, the intensity of luminescence continues to increase but at a slower rate. PXRD analysis of the samples with x = 0.2 and x = 0.5 showed that Mn²⁺ and Zn²⁺ ions replace calcium in the M5 (octahedral) sites in the β-Ca₃(PO₄)₂ crystal structure. According to Rietveld refinement, Mn²⁺ and Zn²⁺ ions jointly occupy the M5 site, which remains the only one for all manganese atoms within the range of 0.05 ≤ x ≤ 0.5. The deviation of the mean interatomic distance (∆l) was calculated and the strongest bond length asymmetry, ∆l = 0.393 Å, corresponds to x = 1.0. The large average interatomic distances between Mn²⁺ ions in the neighboring M5 sites are responsible for the lack of concentration quenching of luminescence below x = 0.5.

SUBMITTER: Gallyamov EM

PROVIDER: S-EPMC10301442 | biostudies-literature | 2023 Jun

REPOSITORIES: biostudies-literature

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Publications

Mn2+ Luminescence in Ca9Zn1-xMnxNa(PO4)7 Solid Solution, 0 ≤ x ≤ 1.

Gallyamov Eldar M EM Titkov Vladimir V VV Lebedev Vladimir N VN Stefanovich Sergey Y SY Lazoryak Bogdan I BI Deyneko Dina V DV

Materials (Basel, Switzerland) 20230614 12

The solid solution Ca9Zn1-xMnxNa(PO4)7 (0 ≤ x ≤ 1.0) was obtained by solid-phase reactions under the control of a reducing atmosphere. It was demonstrated that Mn2+-doped phosphors can be obtained using activated carbon in a closed chamber, which is a simple and robust method. The crystal structure of Ca9Zn1-xMnxNa(PO4)7 corresponds to the no ...[more]

PMID: 37374575

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Project description:Zinc germanate doped with Mn2+ (Zn2GeO4:Mn2+) is known to be a persistent luminescence green phosphor with potential applications in biosensing and bioimaging. Such applications demand nanoparticulated phosphors with a uniform shape and size, good dispersibility in aqueous media, high chemical stability, and surface-functionalization. These characteristics could be major bottlenecks and hence limit their practical applications. This work describes a one-pot, microwave-assisted hydrothermal method to synthesize highly uniform Zn2GeO4:Mn2+ nanoparticles (NPs) using polyacrylic acid (PAA) as an additive. A thorough characterization of the NPs showed that the PAA molecules were essential to realizing uniform NPs as they were responsible for the ordered aggregation of their building blocks. In addition, PAA remained attached to the NPs surface, which conferred high colloidal stability to the NPs through electrostatic and steric interactions, and provided carboxylate groups that can act as anchor sites for the eventual conjugation of biomolecules to the surface. In addition, it was demonstrated that the as-synthesized NPs were chemically stable for, at least, 1 week in phosphate buffer saline (pH range = 6.0-7.4). The luminescence properties of Zn2GeO4 NPs doped with different contents of Mn2+ (0.25-3.00 mol %) were evaluated to find the optimum doping level for the highest photoluminescence (2.50% Mn) and the longest persistent luminescence (0.50% Mn). The NPs with the best persistent luminescence properties were photostable for at least 1 week. Finally, taking advantage of such properties and the presence of surface carboxylate groups, the Zn2GeO4:0.50%Mn2+ sample was successfully used to develop a persistent luminescence-based sandwich immunoassay for the autofluorescence-free detection of interleukin-6 in undiluted human serum and undiluted human plasma samples. This study demonstrates that our persistent Mn-doped Zn2GeO4 nanophosphors are ideal candidates for biosensing applications.

Dataset Information

Mn²⁺ Luminescence in Ca₉Zn_1-xMn_xNa(PO₄)₇ Solid Solution, 0 ≤ x ≤ 1.

Publications

Mn<sup>2+</sup> Luminescence in Ca<sub>9</sub>Zn<sub>1-<i>x</i></sub>Mn<i><sub>x</sub></i>Na(PO<sub>4</sub>)<sub>7</sub> Solid Solution, 0 ≤ <i>x</i> ≤ 1.

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