Tunable photoluminescence and energy transfer of Eu3+,Ho3+-doped Ca0.05Y1.93-xO2 nanophosphors for warm white LEDs applications

Surfactant-Free Synthesis of Melon Seed-Like CeO2 and Ho@CeO2 Nanostructures with Enriched Oxygen Vacancies: Characterization and Their Enhanced Antibacterial Properties

To overcome the poor antibacterial performance of cerium oxide (CeO2) nanoparticles at low concentrations, melon seed-shaped CeO2 (MS-CeO2) and holmium (Ho)-doped CeO2 (Ho@MS-CeO2) nanoparticles were synthesized using a simple precipitation method without the addition of any surfactants. The surface morphology, phase structure, crystallinity, Ce3+ and Ce4+ valence, lattice defects, and reactive oxygen species (ROS) production of both synthesized nanostructures were examined using different techniques, i.e., scanning electron microscopy (SEM), energydispersive X-ray (EDX), resolution transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), Raman spectroscopy, ultraviolet (UV) spectra, fluorescence spectra, and zeta potential (ζ). The results show that under certain stirring and aging temperatures, CeO2 and Ho-doped CeO2 nanoparticles with a melon seed-like morphology can be prepared in a short period. Both nanoparticles were tested as antiseptic agents against G+ and G - bacteria (E. coli and S. aureus), and the results confirmed that the Ho@MS-CeO2 nanostructures exhibited remarkable antimicrobial activity at a low concentration (0.5 mg/L) compared with the control group, which is attributed to the reversible conversion of Ce3+ and Ce4+ in the ceria crystal lattice, enriched oxygen vacancy, ROS species production, and positive surface charge.

Structural, photoluminescence and energy transfer investigations of novel Dy3+ → Sm3+ co-doped NaCaPO4 phosphors for white-light-emitting diode applications

In this study, Dy3+-doped and Dy3+/Sm3+ co-doped NaCaPO4 white-emitting polycrystalline phosphor samples were synthesized using a solid-state reaction method. The samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field-emission scanning electron microscopy (FE-SEM), and Photoluminescence (PL) analysis. The phase purity characterization and crystal structural analysis were done using the Rietveld refinement-based FullProf Suite software. The Rietveld refinement result confirms single-phase formation for both Sm3+ and Dy3+/Sm3+ co-doped NaCaPO4 samples with an orthorhombic structure and with a monotonic change in lattice parameters with doping. The PL studies of the Dy3+-doped samples revealed two emission bands. However, at 352 nm, the Dy3+/Sm3+-co-doped samples revealed distinctive emission bands for both ions. The emission peaks at 480 nm (blue) and 573 nm (yellow) are related to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions; however, the emission peaks at 600 nm and 647 nm are attributed to the 4G5/2 → 6H7/2 and 4G5/2 → 6H7/2 transitions of Sm3+ ions. The intensity of the Dy3+ emissions decreased as the Sm3+ levels increased but the emission intensity of the Sm3+ ions increased. The co-doping of Sm3+ ions in Dy3+-doped phosphors results in unique characteristics due to the energy transfer (ET) from Dy3+ → Sm3+ ions. The effectiveness of this ET from Dy3+ → Sm3+ ions is positively correlated with the dopant amounts of the Sm3+ ions. The interaction mechanisms have been identified as dipole-dipole based on Dexter's energy transfer and Readfield's approaches. All decay curves can be adequately fitted via bi-exponential functions, suggesting the movement of energy between Dy3+ → Sm3+ ions. Temperature-dependent PL measurements and CIE color coordinate analysis reveal excellent luminescent properties, making these Dy3+/Sm3+ co-doped phosphors advantageous for white light-emitting diode (WLED) technologies.

Modulating Electron Density of Boron-Oxygen Groups in Borate via Metal Electronegativity for Propane Oxidative Dehydrogenation

The robust electronegativity of the [BO3]3- structure enables the extraction of electrons from adjacent metals, offering a strategy for modulating oxygen activation in propane oxidative dehydrogenation. Metals (Ni 1.91, Al 1.5, and Ca 1.0) with varying electronegativities were employed to engineer borate catalysts. Metals in borate lacked intrinsic catalytic activity for propane conversion; instead, they modulated [BO3]3- group reactivity through adjustments in electron density. Moderate metal electronegativity favored propane oxidative dehydrogenation to propylene, whereas excessively low electronegativity led to propane overoxidation to carbon dioxide. Aluminum, with moderate electronegativity, demonstrated optimal performance. Catalyst AlBOx-1000 achieved a propane conversion of 47.5%, with the highest propylene yield of 30.89% at 550 °C, and a total olefin yield of 51.51% with a 58.92% propane conversion at 575 °C. Furthermore, the stable borate structure prevents boron element loss in harsh conditions and holds promise for industrial-scale catalysis.

Multicolor tunable emission through energy transfer in Dy3+/Ho3+ co-doped CaTiO3 phosphors with high thermal stability for solid state lighting applications

The exploration of multicolor emitting phosphors with single phase is extremely important for n-UV chip excited LED/WLED's and multicolor display devices. In this paper, Dy3+, Ho3+ singly doped and Dy3+/Ho3+ co-doped CaTiO3 phosphor materials have been synthesized by solid state reaction method at 1473 K. The synthesized materials were characterized by XRD, FE-SEM, EDX, FTIR, PL and lifetime measurements. The PL emission spectra of Dy3+ doped CaTiO3 phosphors give intense blue and yellow emissions under UV excitation, while the PL emission spectra of Ho3+ doped CaTiO3 phosphor show intense green emission under UV/blue excitations. Further, to get the multicolor emission including white light, Dy3+ and Ho3+ were co-doped simultaneously in CaTiO3 host. It is found that alongwith colored and white light emissions, it also shows energy transfer from Dy3+ to Ho3+ with 367 nm and from Ho3+ to Dy3+ under 362 nm excitations. The energy transfer efficiency is found to be 67.76% and 69.39% for CaTiO3:4Dy3+/3Ho3+ and CaTiO3:3Ho3+/5Dy3+ phosphors, respectively. The CIE color coordinates, CCT and color purity of the phosphors have been calculated, which show color tunability from whitish to deep green via greenish yellow color. The lifetime of 4F9/2 level of Dy3+ ion and 5S2 level of Ho3+ ion is decreased in presence of Ho3+ and Dy3+ ions, respectively. This is due to energy transfer from Dy3+ to Ho3+ ions and vice versa. A temperature dependent photoluminescence studied of CaTiO3:4Dy3+/2Ho3+ phosphor show a high thermal stability (82% at 423 K of initial temperature 303 K) in the temperature range 303-483 K with activation energy 0.17 eV. The PLQY are 30%, 33% and 35% for CaTiO3:4Dy3+, CaTiO3:4Dy3+/2Ho3+ and CaTiO3:3Ho3+ phosphors, respectively. Hence, Dy3+, Ho3+ singly doped and Dy3+/Ho3+ co-doped CaTiO3 phosphor materials can be used in the field of single matrix perovskite color tunable phosphors which may be used in multicolor display devices, n-UV chip excited LED/WLED's and photodynamic therapy for the cancer treatment.

A Eu3+doped functional core-shell nanophosphor as fluorescent biosensor for highly selective and sensitive detection of dsDNA

Lanthanide-doped core-shell nanomaterials have illustrated budding potential as luminescent materials, but their biological applications have still been very limited due to their aqueous solubility and biocompatibility. Here, we report a simple and cost-effective approach to construct a water-stable chitosan-functionalized lanthanoid-based core shell (Ca-Eu:Y2O3@SiO2) nanophosphor. The as-synthesized Ca-Eu:Y2O3@SiO2-chitosan (CEY@SiO2-CH) nanophosphor has been characterized for its structural, morphological, and optical properties, by employing different analytical tools. This sensing platform is suitable for dsDNA probing by tracing the "turn on" fluorescence signal generated by CEY@SiO2-CH nanophosphor with the addition of dsDNA. The ratio of fluorescence intensity enhancement is proportional to the concentration of dsDNA in the range 0.1-90 nM, with the limit of detection at ⁓16.1 pM under optimal experimental conditions. The enhancement in fluorescence response of functionalized core-shell phosphor with dsDNA is due to the antenna effect. Additionally, response of probe has been studied for the real samples displaying percent recovery in between 101 and 105, maximum RSD% upto 5.23 (n = 3). This outcome can be applied to the selective sensing of dsDNA through optical response. These findings establish the CEY@SiO2-CH a simple, portable, and potential candidate as a sensor for rapid and analytical detection of dsDNA.

Enhance photoluminescence properties of Ca-Eu:Y2O3@SiO2 core-shell nanomaterial for the advanced forensic and LEDs applications

The divalent (Ca²⁺)-doped Eu:Y₂O₃@SiO₂ core-shell luminescent nanophosphors have been synthesised by a cost-effective combustion technique. Various characterizations were carried out to confirm the successful formation of the core-shell structure. The TEM micrograph reveals the thickness of the SiO₂ coating over Ca-Eu:Y₂O₃ as ∼25 nm. The optimal value of silica coating over the phosphor has been obtained as 10 vol%(TEOS) of SiO₂, with this value increasing fluorescence intensity by 34 %. Phosphor exhibits CIE coordinates as x = 0.425, y = 0.569 and a CCT value as ∼2115 K with color purity and the respective CRI of 80 % and 98 %, respectively, which make the core-shell nanophosphor suitable for warm LEDs, and other optoelectronic applications. Further, the core-shell nanophosphor has been investigated for the visualisation of latent finger prints and as security ink. The findings point towards the prospective future application of nanophosphor materials for anti-counterfeiting purposes and latent finger prints for forensic purposes.

Unclonable fluorescence of MgO-ZrO2 :Tb3+ nanocomposite for versatile applications in data security, dermatoglyphics

Latent fingerprints (LFPs) are one among the most important types of evidences at crime scenes because of the distinctiveness and tenacity of the friction ridges in fingerprints (FPs). Therefore, it is essential in forensic science to develop a reliable method to detect LFPs. Traditional detection methods still face a number of difficulties, such as limited sensitivity, low contrast, strong background, and complex processing stages. In this study, MgO-ZrO₂ :Tb³⁺ (1-5 mol%) (MZ:Tb) nanocomposites (NCs) were prepared via a simple solution combustion (SC) method at low temperature. The photoluminescence (PL) investigation demonstrates that when excited at 379 nm, the produced NCs emits distinctive emission peaks of terbium ions (Tb³⁺ ). According to the photometric results, the NCs can be employed as warm light NCs and emit light in the green portion of the colour spectrum. The estimated optical band gap from diffuse reflectance spectra is found to be in the range 4.84-4.97 eV. Regardless of the type of surface being used, the optimized MgO-ZrO₂ :Tb³⁺ (4 mol%) (MZ:4Tb) NCs has a strong ability to minimize background fluorescence interference. With high contrast LFP and I-V type of cheiloscopy, these NCs present a flexible fluorescent mark for the identification of levels 1-3 details in forensic investigation.

The effect of ion radius on luminescence for alkali ions doping in Y2O3: Yb3+/Ho3+ thin film

In this paper, alkali ion (Li⁺ Na⁺ K⁺ and Rb⁺)-doped Y₂O₃:Yb³⁺/Ho³⁺ up conversion films were prepared using the sol-gel method. The structures of the films were studied by using X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. A series of high-quality thin films with good crystallization were prepared. For all samples, two emission bands were observed: green emission at 539 (550) nm and red emission at 664 nm, which can be attributed to ⁵F₄ (⁵S₂)→⁵I₇ and ⁵F₅→⁵I₈, respectively. The green emission is dominant, and the red emission is extremely weak. The effect of each alkali-ion dopant on the emission and color adjustment of samples was investigated. The green emission intensity is increased by a factor of 6.33 (Li), 2.03 (Na), 4.82 (K) and 1.92 (Rb) with increasing alkali-ion doping concentration, and red emission is increased by a factor of 7.80 (Li), 1.92 (Na), 4.78 (K) and 1.90 (Rb). The extreme value appears earlier with increasing ion radius. Li⁺ doping boosts luminescence in three ways, and the other alkali ions affect the light emission in two ways. Li⁺ doping and K⁺ doping can be used to adjust the color coordinates towards the 539 nm and 550 nm directions, respectively. Na⁺ and Rb⁺ doping can enhance emission with a stable color. This means that each alkali ion is a suitable choice as a color-regulating ion and can play a role in the regulation of luminescence.