Search

Alkali‐metal‐based yttrium fluoride host (AY1‒xF4:xEu3+; A: Li/Na/K) nanophosphors were developed using co‐precipitation method. Phase analysis and emission spectral behavior were established for the said nanophosphors. The highest emission observed for NaYF4 doped with Eu3+ was then optimized to achieve maximum photoluminescence (PL) emission for varied dopant amount. The downconversion and upconversion PL studies revealed pure red emission under n‐ultraviolet and infrared excitations. The CIE coordinates are observed to be lie in the red hue of the CIE diagram. The PL decay curves reported to study lifetime of the emitting state and to identify quantum efficiency using Auzel's model for the said nanophosphor. Thermal stability was also evaluated from temperature‐sensitive luminescent spectra. The studies conducted on AYF4:.05Eu3+ (A: Li/Na/K) nanophosphors contemplates that NaYF4 nanophosphors doped with Eu3+ ions are best suited for biophotonic applications as the later one show relatively high emission. [ABSTRACT FROM AUTHOR]

The lithium bismuth alumino borosilicate (LiBiAlBSi) glasses incorporated with different concentrations (0.1 to 2 mol%) of Er3+ ions were formed through the melt quench technique. Studies on optical absorption, photoluminescence, and decay profiles were performed. Detailed analysis of absorption and emission spectra was done by applying Judd- Ofelt (JO) theory. Under an excitation wavelength of 378 nm, the samples show intense green and NIR emission corresponding to transitions 4S3/2 → 4I15/2 (547 nm) and 4I13/2 → 4I15/2 (1538 nm), respectively. Dexter theory was applied to the NIR emission spectra to confirm the dipole–dipole nature of interaction among the Er3+ ions. CIE coordinates for the visible spectra lie in the green region. Various parameters such as stimulated emission cross-section, optical gain, and gain bandwidth for the as-prepared glasses show that these glasses exhibit good luminescence behavior and that the optimized LiBiAlBSiEr10 glass is ideal for laser applications in visible and NIR regions. [ABSTRACT FROM AUTHOR]

Y2SiO5 (YSO) phosphors doped with holmium ions were prepared by the well-established sol–gel method. The structural and functional groups were studied by X-ray diffraction (XRD) and Fourier-transformed infrared (FTIR) spectroscopy, respectively. The observed XRD peaks were matched to the X1 and X2 phase of YSO and the average crystalline size is found to be 26.5 nm. The band gap was calculated using Kubelka–Munk analysis of the diffuse reflectance data. Photoluminescence tests were carried out on the prepared phosphors. At an excitation wavelength of 447 nm, two sharp and closely spaced peaks are observed in the green region around 538 nm and 551 nm. The concentration quenching is observed beyond 0.03 mol Ho3+ ions in YSO and the energy transfer mechanisms are discussed in detail. Dexter’s analysis shows that the interaction between Ho3+ ions is dipole–dipole. The Judd–Ofelt intensity parameters and radiative properties of certain emission transitions of Ho3+ ions were also investigated for an optimized phosphor (Y2SiO5:0.03Ho3+) sample. The estimated J–O parameters (Ωλ (λ = 2, 4 & 6)), are Ω2 = 0.77 × 10–20 cm2, Ω4 = 0.40 × 10–20 cm2 and Ω6 = 2.12 × 10–20 cm2. The magnitude of Ω2 is smaller for YSO than that of other hosts indicating a less asymmetric environment around the Ho–O bond. Branching ratio and stimulated emission for the 5F4 + 5S2 → 5I8 transition are 87.8% and 2.61 × 10–21 cm2, respectively, for Y2SiO5:0.03Ho3+ phosphor. Furthermore, colorimetric analysis shows that the optimized Y2SiO5:0.03Ho3+ phosphor has the highest color purity. Our results confirm that these phosphors can be proposed for utilization as green components in solid-state lighting applications. [ABSTRACT FROM AUTHOR]

In this research work, Dy3+ doped alkali zinc alumino borosilicate (AZABS) glasses have been prepared via melt quenching technique. A series of AZABS glasses of varying concentrations of dysprosium (Dy3+) (0.1–2.5 mol%) was prepared. It was found that under UV excitation, 0.5 mol% Dy3+ doped glass exhibited maximum luminescence intensity. Subsequent photoluminescence studies like emission/excitation spectra, temperature-dependent photoluminescence and decay kinetics were also performed. The value of direct bandgap as calculated from Tauc Plot for 0.5 mol% of Dy3+ ions doped AZABS glass is 2.85 eV. Yellow to blue ratio and colorimetry analysis have showed that the as-prepared glasses are capable of producing cool white light. Application of Dexter theory showed that the energy transfer mechanism between the dopant ions in the glass matrix was of dipole–dipole nature. It is proposed that these Dy3+ doped AZABS glasses can be used as prospective materials in optoelectronic device applications such as solid-state lighting and w-LEDs. [ABSTRACT FROM AUTHOR]

Aim: To study sex-related differences in acute coronary syndrome (ACS) presentation, management and in-hospital outcomes. Materials & methods: We studied 621 ACS patients (150 women, 471 men) of low socio-economic status from South India from February 2015 to January 2016. Multivariable logistic regression methods were used to assess sex differences in the in-hospital outcomes. Adjudicated major adverse cardiovascular events (MACE) included in-hospital cardiac arrest, cardiogenic shock, heart failure, re-infarction, stroke, major bleeding and mortality. Results & conclusion: Mean age in women was 60.97 ± 11.23 years versus 54.5 ± 10.87 years in men (p < 0.001). Women had higher prevalence of hypertension and diabetes and presented with more non-ST elevation ACS. There were no differences in the use of antiplatelets, statins and other pharmacotherapy except for the higher use of nitrates in women. There were no differences in MACE rates between women and men (15.3 vs 9.6%; adjusted odds ratio: 1.43; CI: 0.76-2.69). [ABSTRACT FROM AUTHOR]

Trivalent gadolinium (Gd3+) activated CaY2Al4SiO12 garnet compounds with a variable concentration of Gd3+ ions were synthesized by a sol–gel method. The synthesized garnet compounds were characterized for their structural, morphological, luminescent, and magnetic properties. The x-ray diffraction data of Gd3+ activated CaY2Al4SiO12 garnet compound reveal the cubic structure with Ia3d space group. The scanning electron microscope images represent the morphology of the particles. The photoluminescence properties were analyzed from the excitation and emission spectra. The emission spectra of the CaY2Al4SiO12:Gd3+ garnet compound under 273 nm excitation exhibit two emission peaks at (308 nm and 314 nm) nm and are attributed to 6P5/2 → 8S7/2 and 6P7/2 → 8S7/2 transitions, respectively. The emission peak observed at 314 nm is more intense than the peak observed at 308 nm. The high-intensity peak at 314 nm is used to cure various skin disorders, and hence is beneficial in phototherapy. The intensity of the emission peaks increases up to 0.09 mol of Gd3+ ion concentration in the CaY2Al4SiO12 garnet compound, and beyond, then decreases, showing concentration quenching. The electron paramagnetic resonance of Gd3+ ions in the prepared garnet compound exhibits resonance signals with effective g values at g ≈ 6.5, 5.0, 2.6, 2.2, 2.0, and 1.6 of the U-spectrum, due to cubic, octahedral, or tetrahedral distorted sites. [ABSTRACT FROM AUTHOR]

Trivalent gadolinium (Gd3+) activated strontium silicate (Sr2SiO4:xGd3+; 0.01 ≤ x ≤ 0.11) systems have been synthesized via sol-gel technique. The structural, morphological, luminescent, and magnetic properties have been investigated using X-ray diffraction patterns, scanning electron microscopy (SEM), photoluminescence (PL), and electron paramagnetic resonance (EPR) technique, respectively. The synthesized strontium silicate samples exhibit a mixed phase of α′ and β-Sr2SiO4. The SEM images show irregular morphologies with a random distribution of particles. The PL spectra confirm the ultraviolet emission from the synthesized samples and the optimum concentration of Gd3+ ions is observed at 0.05 mol. With low dopant concentrations, Sr2SiO4:Gd3+ sample displays EPR lines, mainly in the low field region with effective g-values 5.8, 4.5, 3.1, and 2.7. As dopant concentration increases, a broad line appears with geff ~ 2.1 along with the low field lines. A relatively strong crystal field is experienced by Gd3+ ion due to distortions in the immediate environment of the ion, which lead to low field EPR lines. These studies allow the use of gadolinium-activated strontium silicate in phototherapy lamps. [ABSTRACT FROM AUTHOR]

Vertically stacked, layered van der Waals (vdW) heterostructures offer the possibility to design materials, within a range of chemistries and structures, to possess tailored properties. Inspired by the naturally occurring mineral merelaniite, this paper studies a vdW heterostructure composed of a MoS2 monolayer and a PbS bilayer, using density functional theory. A commensurate 2D heterostructure film and the corresponding 3D periodic bulk structure are compared. The results find such a heterostructure to be stable and possess p-type semiconducting characteristics. Due to the heterostructure's weak interlayer bonding, its carrier mobility is essentially governed by the constituent layers; the hole mobility is governed by the PbS bilayer, whereas the electron mobility is governed by the MoS2 monolayer. Furthermore, we estimate the hole mobility to be relatively high (~106 cm2V−1s−1), which can be useful for ultra-fast devices at the nanoscale. [ABSTRACT FROM AUTHOR]

Chromium-doped calcium aluminozincate phosphor with a distinct amount of chromium was prepared via the sol-gel technique. The phase analysis and morphological study along with optical properties were conducted on the prepared material. The room temperature luminescent traits of the sample were studied in detail under 540 nm excitation wavelength. The deep red emission was confirmed from the CIE coordinates calculated using emission data. The decay curves were recorded to calculate the lifetime values for the aforementioned powder samples. The temperature-dependent luminescent characteristics were also investigated to identify the activation energy and thermal stability. The quantum yield was also calculated using luminescence spectra and found to be relatively good for the present phosphor. All of the investigated studies specified above signify that the synthesized phosphor is well suited as a red emitter in lighting and display devices., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)