Ethylenediamine-Assisted Hydrothermal Synthesis of NaCaSiO₃OH: Controlled Morphology, Mechanism, and Luminescence Properties by Doping Eu³⁺/Tb³⁺

This paper demonstrates a facile hydrothermal method using ethylenediamine (EDA) as a “shape modifier” for the controlled synthesis of rod bunch, decanedron, spindle, flakiness, and flowerlike NaCaSiO₃OH microarchitectures. The set of experimental conditions is important to obtain adjustable shape and size of NaCaSiO₃OH particles, as the change in either the amount of EDA/H₂O or reaction time, or the amount of NaOH. Accordingly, the crystal growth mechanism during the synthesis process is proposed, and it is found that the EDA, acting as the chelating agent and shape modifier, plays a crucial role in fine-tuning the NaCaSiO₃OH morphology. Morphology evolution process of flowerlike NaCaSiO₃OH as a function of NaOH is also explained in detail. Eu³⁺/Tb³⁺ doped NaCaSiO₃OH samples exhibit strong red and green emission under ultraviolet excitation, corresponding to the characteristic electronic transitions of Eu³⁺ and Tb³⁺. These results imply that the morphology-tunable NaCaSiO₃OH:Eu³⁺/Tb³⁺ microarchitectures with tunable luminescence properties are expected to have promising applications for micro/nano optical functional devices

Structural Phase Transformation and Luminescent Properties of Ca_2–<i>x</i>Sr_<i>x</i>SiO₄:Ce³⁺ Orthosilicate Phosphors

The orthosilicate phosphors demonstrate great potential in the field of solid-state lighting, and the understanding of the structure–property relationships depending on their versatile polymorphs and chemical compositions is highly desirable. Here we report the structural phase transformation of Ca_2–<i>x</i>Sr_<i>x</i>SiO₄:Ce³⁺ phosphor by Sr²⁺ substituting for Ca²⁺ within 0 ≤ <i>x</i> < 2. The crystal structures of Ca_2–<i>x</i>Sr_<i>x</i>SiO₄:Ce³⁺ are divided into two groups, namely, β phase (0 ≤ <i>x</i> < 0.15) and α′ phase (0.18 ≤ <i>x</i> < 2), and the phase transition (β → α′) mechanism originated from the controlled chemical compositions is revealed. Our findings verified that the phase transition <i>Pnma</i> (α′-phase) ↔ <i>P</i>2₁/<i>n</i> (β-phase) can be ascribed to the second-order type, and Sr²⁺ ions in Ca_2–<i>x</i>Sr_<i>x</i>SiO₄ preferentially occupy the seven-coordinated Ca²⁺ sites rather than the eight-coordinated sites with increasing Sr²⁺ content, which was reflected from the Rietveld refinements and further clarified through the difference of the Ca–O bond length in the two polymorphs of Ca₂SiO₄. The emission peaks of Ce³⁺ shift from 417 to 433 nm in the composition range of 0 ≤ <i>x</i> ≤ 0.8, and the difference in the decay curves can also verify the phase transformation process. Thermal quenching properties of selected Ca_2–<i>x</i>Sr_<i>x</i>SiO₄:Ce³⁺ samples were evaluated, and the results show that the integral emission intensities at 200 °C maintain >90% of that at room temperature suggesting superior properties for the application as white light-emitting diodes (w-LEDs) phosphors

Near-Infrared Luminescence and Color Tunable Chromophores Based on Cr³⁺-Doped Mullite-Type Bi₂(Ga,Al)₄O₉ Solid Solutions

Cr³⁺-activated mullite-type Bi₂Ga_{(4‑<i>x</i>)}­Al_<i>x</i>O₉ (<i>x</i> = 0, 1, 2, 3, and 4) solid solutions were prepared by the solid state reaction, and their spectroscopic properties were investigated in conjunction with the structural evolution. Under excitation at 610 nm, Bi₂[Ga_{(4‑<i>y</i>)}Al_<i>y</i>]_3.97­O₉:0.03Cr³⁺ (<i>y</i> = 0, 1, 2, 3, and 4) phosphors exhibited broad-band near-infrared (NIR) emission peaking at ∼710 nm in the range 650–850 nm, and the optimum Cr³⁺ concentrations and concentration quenching mechanism were determined. Except for the interesting NIR emission, the body color changed from white (at <i>x</i> = 0) to green (at <i>x</i> = 0.08) for Bi₂Ga_4–<i>x</i>­O₉:<i>x</i>Cr³⁺, and from light yellow (at <i>x</i> = 0) to deep brown (at <i>x</i> = 0.08) for Bi₂Al_4–<i>x</i>­O₉:<i>x</i>Cr³⁺, respectively. Moreover, as a result of variable Al/Ga ratio, the observed body color for Bi₂[Ga_{(4‑<i>y</i>)}Al_<i>y</i>]_3.97­O₉:0.03Cr³⁺ (<i>y</i> = 0, 1, 2, 3, and 4) varied from deep brown to green. The relationship between the observed colors and their diffuse reflectance spectra were also studied for the understanding of the different absorption bands. The results indicated that Cr³⁺-doped Bi₂Ga_{(4‑<i>x</i>)}­Al_<i>x</i>O₉ solid solutions appeared as the bifunctional materials with NIR phosphors and color-tunable pigments

Near-Infrared Luminescence and Color Tunable Chromophores Based on Cr³⁺-Doped Mullite-Type Bi₂(Ga,Al)₄O₉ Solid Solutions

Cr³⁺-activated mullite-type Bi₂Ga_{(4‑<i>x</i>)}­Al_<i>x</i>O₉ (<i>x</i> = 0, 1, 2, 3, and 4) solid solutions were prepared by the solid state reaction, and their spectroscopic properties were investigated in conjunction with the structural evolution. Under excitation at 610 nm, Bi₂[Ga_{(4‑<i>y</i>)}Al_<i>y</i>]_3.97­O₉:0.03Cr³⁺ (<i>y</i> = 0, 1, 2, 3, and 4) phosphors exhibited broad-band near-infrared (NIR) emission peaking at ∼710 nm in the range 650–850 nm, and the optimum Cr³⁺ concentrations and concentration quenching mechanism were determined. Except for the interesting NIR emission, the body color changed from white (at <i>x</i> = 0) to green (at <i>x</i> = 0.08) for Bi₂Ga_4–<i>x</i>­O₉:<i>x</i>Cr³⁺, and from light yellow (at <i>x</i> = 0) to deep brown (at <i>x</i> = 0.08) for Bi₂Al_4–<i>x</i>­O₉:<i>x</i>Cr³⁺, respectively. Moreover, as a result of variable Al/Ga ratio, the observed body color for Bi₂[Ga_{(4‑<i>y</i>)}Al_<i>y</i>]_3.97­O₉:0.03Cr³⁺ (<i>y</i> = 0, 1, 2, 3, and 4) varied from deep brown to green. The relationship between the observed colors and their diffuse reflectance spectra were also studied for the understanding of the different absorption bands. The results indicated that Cr³⁺-doped Bi₂Ga_{(4‑<i>x</i>)}­Al_<i>x</i>O₉ solid solutions appeared as the bifunctional materials with NIR phosphors and color-tunable pigments

Tuning of Photoluminescence and Local Structures of Substituted Cations in <i>x</i>Sr₂Ca(PO₄)₂–(1 – <i>x</i>)Ca₁₀Li(PO₄)₇:Eu²⁺ Phosphors

Local structure modification in solid solution is an essential part of photoluminescence tuning of rare earth doped solid state phosphors. Herein we report a new solid solution phosphor of Eu²⁺-doped <i>x</i>Sr₂Ca­(PO₄)₂–(1 – <i>x</i>)­Ca₁₀Li­(PO₄)₇ (0 ≤ <i>x</i> ≤ 1), which share the same β-Ca₃(PO₄)₂ type structure in the full composition range. Depending on the <i>x</i> parameter variation in <i>x</i>Sr₂Ca­(PO₄)₂–(1 – <i>x</i>)­Ca₁₀Li­(PO₄)₇:Eu²⁺, the vacancies generated in the M(4) site enable the nonlinear variation of cell parameters and volume, and this increases the magnitude of M(4)­O₆ polyhedra distortion. The local structure modulation around the Eu²⁺ ions causes different luminescent behaviors of the two-peak emission and induces the photoluminescence tuning. The shift of the emission peaks in the solid solution phosphors with different compositions has been discussed. It remains invariable at <i>x</i> ≤ 0.5, but the red-shift is observed at <i>x</i> > 0.5 which is attributed to combined effect of the crystal field splitting, Stokes shift, and energy transfer between Eu²⁺ ions. The temperature-dependent luminescence measurements are also performed, and it is shown that the photoionization process is responsible for the quenching effect

Effects of Si Codoping on Optical Properties of Ce-Doped Ca₆BaP₄O₁₇: Insights from First-Principles Calculations

It was recently reported that Ce-doped Ca₆BaP₄O₁₇ displayed blue-green emission under excitation in the near-ultraviolet (UV) region and that luminescence intensities can be greatly improved by codoping with Si. Here, a combination of hybrid density functional theory (DFT) and wave function-based CASSCF/CASPT2 calculations at the spin–orbit level has been performed on geometric and electronic structures of the material to gain insights into effects of Si codoping on its optical properties. It is found that the observed luminescence arises from 4f–5d transitions of Ce³⁺ occupying the two crystallograhically distinct Ca1 and Ca2 sites of the host compound with comparable probabilities, with the energy of the lowest 4f → 5d transition of Ce_Ca1 being slightly higher than that of Ce_ca2. The codopant Si prefers to substitute for the nearest-neighbor (NN) P1 atom over the NN P2 atom around Ce³⁺, and this preference induces a blueshift of the lowest-energy 4f → 5d transition, consistent with experimental observations. The blueshift originates from a reduction in 5d crystal field splitting of Ce³⁺ associated mainly with electronic effects of the NN Si_P1 substitution, while the contribution from the change in 5d centroid energy is negligible. On the basis of calculated results, the energy-level diagram for the 4f ground states and the lowest 5d states of all trivalent and divalent lanthanide ions on the Ca²⁺ sites of Ca₆BaP₄O₁₇ is constructed and discussed in connection with experimental findings

In-situ Growth of Scalable Low-Crystalline γ‑FeOOH@Ni(OH)₂ Nanosheet Heterostructured Catalysts for Stable Oxygen Evolution Reaction at Large Current Density

Transition metal hydroxides have the advantage of high activity and low cost in alkaline electrolytes and are considered one of the most promising catalysts for anodic oxygen evolution reaction (OER). However, single nickel or iron hydroxides is unstable during the reaction process and have a tendency to agglomerate and poor electrical conductivity. Therefore, we designed a kinetically controlled liquid-phase method to synthesize scalable low-crystalline γ-FeOOH@Ni(OH)2 nanosheet arrays on nickle foam (NF) in an open environment. By adjusting the alkalinity and reaction time, we systematically investigated the formation process and the potential mechanisms related to the structural evolution of γ-FeOOH@Ni(OH)2 catalysts. γ-FeOOH@Ni(OH)2 was used as an OER catalyst and showed excellent hydrolytic activity and stability, with a stable operation of more than 320 h at a large current density of 500 mA cm–2. Density functional theory calculations show that the synergistic effect of γ-FeOOH and Ni(OH)2 increases the charge accumulation near the Fermi energy level, thus increasing the chance of electron transfer and effectively facilitating the decomposition of water molecules. This work provides a new strategy for the design and exploration of catalysts for achieving large-scale industrialized water decomposition for hydrogen production in an open environment

Probing Eu²⁺ Luminescence from Different Crystallographic Sites in Ca₁₀M(PO₄)₇:Eu²⁺ (M = Li, Na, and K) with β‑Ca₃(PO₄)₂‑Type Structure

Eu²⁺ local environments in various crystallographic sites enable the different distributions of the emission and excitation energies and then realize the photoluminescence tuning of the Eu²⁺ doped solid state phosphors. Herein we report the Eu²⁺-doped Ca₁₀M­(PO₄)₇ (M = Li, Na, and K) phosphors with β-Ca₃(PO₄)₂-type structure, in which there are five cation crystallographic sites, and the phosphors show a color tuning from bluish-violet to blue and yellow with the variation of M ions. The difference in decay rate monitored at selected wavelengths is related to multiple luminescent centers in Ca₁₀M­(PO₄)₇:Eu²⁺, and the occupied rates of Eu²⁺ in Ca(1), Ca(2), Ca(3), Na(4), and Ca(5) sites from Rietveld refinements using synchrotron power diffraction data confirm that Eu²⁺ enters into four cation sites except for Ca(5). Since the average bond lengths <i>d</i>(Ca–O) remain invariable in the Ca₁₀M­(PO₄)₇:Eu²⁺, the drastic changes of bond lengths <i>d</i>(M–O) and Eu²⁺ emission depending on the variation from Li to Na and K can provide insight into the distribution of Eu²⁺ ions. It is found that the emission band at 410 nm is ascribed to the occupation of Eu²⁺ in the Ca(1), Ca(2), and Ca(3) sites with similar local environments, while the long-wavelength band (466 or 511 nm) is attributed to Eu²⁺ at the M(4) site (M = Na and K). We show that the crystal-site engineering approach discussed herein can be applied to probe the luminescence of the dopants and provide a new method for photoluminescence tuning

DataSheet_2_Comprehensive characterization of ERV-K (HML-8) in the chimpanzee genome revealed less genomic activity than humans.xlsx

Endogenous retroviruses (ERVs) originate from ancestral germline infections caused by exogenous retroviruses. Throughout evolution, they have become fixed within the genome of the animals into which they were integrated. As ERV elements coevolve with the host, they are normally epigenetically silenced and can become upregulated in a series of physiological and pathological processes. Generally, a detailed ERV profile in the host genome is critical for understanding the evolutionary history and functional performance of the host genome. We previously characterized and cataloged all the ERV-K subtype HML-8 loci in the human genome; however, this has not been done for the chimpanzee, the nearest living relative of humans. In this study, we aimed to catalog and characterize the integration of HML-8 in the chimpanzee genome and compare it with the integration of HML-8 in the human genome. We analyzed the integration of HML-8 and found that HML-8 pervasively invaded the chimpanzee genome. A total of 76 proviral elements were characterized on 23/24 chromosomes, including detailed elements distribution, structure, phylogeny, integration time, and their potential to regulate adjacent genes. The incomplete structure of HML-8 proviral LTRs will undoubtedly affect their activity. Moreover, the results indicated that HML-8 integration occurred before the divergence between humans and chimpanzees. Furthermore, chimpanzees include more HML-8 proviral elements (76 vs. 40) and fewer solo long terminal repeats (LTR) (0 vs. 5) than humans. These results suggested that chimpanzee genome activity is less than the human genome and that humans may have a better ability to shape and screen integrated proviral elements. Our work is informative in both an evolutionary and a functional context for ERVs.</p