Strong blue absorption of green Zn2SiO4:Mn2+ phosphor by doping heavy Mn2+ concentrations

Bright Yellow Luminescence from Mn2+-Doped Metastable Zinc Silicate Nanophosphor with Facile Preparation and Its Practical Application

Mn2+-doped β-Zn2SiO4, a metastable phase of zinc silicate, is widely acknowledged for the uncertainties linked to its crystal structure and challenging synthesis process along with its distinctive yellowish luminescence. In this study, a vivid yellow luminescence originating from Mn2+-doped metastable zinc silicate (BZSM) nanophosphor is suggested, achieved through a straightforward single-step annealing process. The reliable production of this phosphor necessitates substantial doping, surplus SiO2, a brief annealing duration, and prompt cooling. The verification of the phase is demonstrated based on its optical and crystallographic characteristics. Moreover, the effective utilization of excimer lamps in practical scenarios is effectively demonstrated as a result of the vacuum ultraviolet excitation property of BZSM nanophosphor. This outcome paves the way for additional deployment of metastable zinc silicate in various fields, consequently generating novel prospects for future advancements.

Pressure-Induced Remarkable Spectral Red-Shift in Mn2+ -Activated NaY9 (SiO4 )6 O2 Red-Emitting Phosphors for High-Sensitive Optical Manometry

To settle the low sensitivity of luminescent manometers, the Mn2+ -activated NaY9 (SiO4 )6 O2 red-emitting phosphors with splendid pressure sensing performances are developed. Excited by 408 nm, the resulting products emit bright red emission originating from 4 T1 (4 G) → 6 A1 transition of Mn2+ , in which the optimal concentration of the activator ion is ≈1 mol%. Moreover, the admirable thermal stability of the developed phosphors is studied and confirmed by the temperature-dependent emission spectra, based on which the activation energy is derived to be 0.275 eV. By analyzing the pressure-dependent Raman spectra, the structural stability of the synthesized compounds at extreme conditions is verified. Furthermore, the designed phosphors exhibit remarkable spectral red-shift at elevated pressure. Especially, as pressure increases from 0.75 to 7.16 GPa, the emission band centroid shifts from 617.2 to 663.4 nm, resulting in a high sensitivity (dλ/dP) of 7.00 nm GPa-1 , whereas the full width at half maximum (FWHM) increases from 83.0 to 110.6 nm, leading to the ultra-high sensitivity (dFWHM/dP) of 10.13 nm GPa-1 . These achievements manifest that the designed red-emitting phosphors are appropriate for ultrasensitive optical manometry. More importantly, the developed manometer is a current global leader in sensitivity, when operating in the band-width mode, that is, FWHM.

Precursor recommendation for inorganic synthesis by machine learning materials similarity from scientific literature

Synthesis prediction is a key accelerator for the rapid design of advanced materials. However, determining synthesis variables such as the choice of precursor materials is challenging for inorganic materials because the sequence of reactions during heating is not well understood. In this work, we use a knowledge base of 29,900 solid-state synthesis recipes, text-mined from the scientific literature, to automatically learn which precursors to recommend for the synthesis of a novel target material. The data-driven approach learns chemical similarity of materials and refers the synthesis of a new target to precedent synthesis procedures of similar materials, mimicking human synthesis design. When proposing five precursor sets for each of 2654 unseen test target materials, the recommendation strategy achieves a success rate of at least 82%. Our approach captures decades of heuristic synthesis data in a mathematical form, making it accessible for use in recommendation engines and autonomous laboratories.

Structural designing of Zn2SiO4:Mn nanocrystals by co-doping of alkali metal ions in mesoporous silica channels for enhanced emission efficiency with short decay time

High purity Zn₂SiO₄:Mn crystals were synthesized by impregnating a precursor solution into mesoporous silica followed by sintering process. The effects of doping alkali metal ions (Li⁺, Na⁺, K⁺) on the structural, morphological and photoluminescence properties were investigated. Formation of single phase α-Zn₂SiO₄:Mn crystals was confirmed from X-ray diffraction. The crystal size was significantly decreased from 54 nm to 35 nm with increasing molar concentration of alkali metal ion dopants in Zn₂SiO₄:Mn. Zn₂SiO₄:Mn crystals co-doped with alkali metal ions showed stronger emission and faster decay times compared to the un-doped Zn₂SiO₄:Mn phosphor. The highest emission quantum yields (EQEs) of 68.3% at λ_exc 254 and 3.8% at λ_exc 425 nm were obtained for the K⁺ ion doped samples with Mn²⁺ : K⁺ ratio of ∼1 : 1. With alkali metal ions (Li⁺, Na⁺, K⁺) co-doping, the decay time of Zn₂SiO₄:Mn crystals was shortened to ∼4 ms, whereas the emission intensity was elevated, with respect to un-doped Zn₂SiO₄:Mn crystals. Zn₂SiO₄:Mn crystal growth in silica pores together with selective doping with alkali metal ions paves a way forward to shorten the phosphor response time, without compromising emission efficiency.

Alkali metal ions co-doped Zn₂SiO₄:Mn nanocrystals were synthesized in a mesoporous silica matrix using solution impregnation method. A high PL-QY of 68.3% at λ_exc 254 nm and 3.8% at λ_exc 425 nm with faster decay time of <5 ms is obtained.

A stochastic analysis based on a one-dimensional random walk model of the persistent phosphorescence of Mn2+ ions doped in zinc magnesium phosphate

The persistent phosphorescence of β-Zn₃(PO₄)₂:Mn²⁺ and γ-(Zn²⁺,Mg²⁺)₃(PO₄)₂:Mn²⁺ systems showing long-tailed non-exponential decay is simulated via stochastic analysis using electron hopping between traps.

Research progress of Mn doped phosphors

In this review article, Mn applications have been divided into three parts.

Luminescence enhancement of (Sr1-x Mx )2 SiO4 :Eu2+ phosphors with M (Ca2+ /Zn2+ ) partial substitution for white light-emitting diodes

Eu²⁺ -doped Sr₂ SiO₄ phosphor with Ca²⁺ /Zn²⁺ substitution, (Sr_1-x M_x )₂ SiO₄ :Eu²⁺ (M = Ca, Zn), was prepared using a high-temperature solid-state reaction method. The structure and luminescence properties of Ca²⁺ /Zn²⁺ partially substituted Sr₂ SiO₄ :Eu²⁺ phosphors were investigated in detail. With Ca²⁺ or Zn²⁺ added to the silicate host, the crystal phase could be transformed between the α-form and the β-form of the Sr₂ SiO₄ structure. Under UV excitation at 367 nm, all samples exhibit a broad band emission from 420 to 680 nm due to the 4f⁶ 5d¹  → 4f⁷ transition of Eu²⁺ ions. The broad emission band consists of two peaks at 482 and 547 nm, which correspond to Eu²⁺ ions occupying the ten-fold oxygen-coordinated Sr.(I) site and the nine-fold oxygen-coordinated Sr.(II) site, respectively. The luminescence properties, including the intensity and lifetime of Sr₂ SiO₄ :Eu²⁺ phosphors, improved remarkably on Ca²⁺ /Zn²⁺ addition, and promote its application in white light-emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd.