Nanocrystalline lanthanide-doped Lu3Ga5O12 garnets: interesting materials for light-emitting devices

Performance analysis of three distinct NixV2Oy single-phase nano self-assemblies for asymmetric supercapacitor fabrication and effective detection of low-concentration hazardous herbicide

Single-phase inorganic nanostructures with multiple applications are required for cost-effective, sustainable applications to save the environment from toxic activities. Nickel vanadate (NixV2Oy), possessing three phases, such as NiV2O6, Ni2V2O7, and Ni3V2O8, acts as an effective electrode material and potential electrochemical sensors. Nickel vanadate phases (NiV2O6, Ni2V2O7, and Ni3V2O8) were synthesized through the gel-matrix technique, and their phase purity, crystallinity, morphology, optical properties, etc., were evaluated and studied. Electrochemical studies infer that NiV2O6 exhibits the highest specific capacity of 251 C g-1 (69.7 mA h g-1) at 1 A g-1 compared to the other nickel vanadate phases and provides better cyclic stability of 80.19% for 5000 cycles. The asymmetric supercapacitor device fabricated from NiV2O6 results in a specific capacity of 189 C g-1 (52.5 mA h g-1), energy density of 59.06 W h kg-1, and a power density of 1125 W kg-1 with a capacitive retention rate of 74.91% and coulombic efficiency of 99.61% for 10 000 cycles. The electrochemical detection potential of NixV2Oy in bifenox herbicide has been studied with all the synthesized nanostructures. Among them, NiV2O6-based sensor probes demonstrated excellent characteristics, including high sensing current and low detection limits of 0.6 nM with a linear range of 1-57 nM. The real-time herbicide detection of NiV2O6 in live samples was checked with freshly harvested potatoes. This advancement further enhances the utilization of NixV2Oy materials for electrochemical applications.

Polycrystalline Er-doped Y3Ga5O12 nanofilms fabricated by atomic layer deposition on silicon at a low temperature and the exploration on electroluminescence performance

Polycrystalline erbium-doped Y₃Ga₅O₁₂ garnet (YGG) nanofilms are deposited by atomic layer deposition on Si substrates after annealing down to 800 °C, based on which ∼1.53 μm electroluminescence (EL) devices are fabricated. The optimal EL performance depends on the adjustment of Y/Ga ratio and Ga₂O₃ interlayer thickness within the nanolaminates, which exert no prominent impact on the crystallization and film morphology of YGG nanofilms. EL spectra reveal that the crystalline structure after annealing impacts the surrounding environment of Er³⁺ ions, leading to different emission peaks. These silicon-based devices present a low turn-on voltage of ∼25 V, while the external quantum efficiency and maximum optical power density reach 2.51% and 10.03 mW cm^-2, respectively. The EL is ascribed to the impact-excitation of doped Er³⁺ ions in polycrystalline YGG nanofilms by energetic electrons, the conduction mechanism of which is confirmed to be the Poole-Frenkel mode. These prototype devices possess excellent stability and can operate for up to 49 hours under continuous current injection, verifying the improvement of device performance by the utilization of gallium in the fabrication of garnet nanofilms. The Si-based YGG:Er EL devices are of promising potential for integrated optoelectronic applications.

Stokes and upconverted luminescence in Er3+/Yb3+-doped Y3Ga5O12 nano-garnets

The green, red, near-infrared and near-infrared-to-visible upconverted luminescence properties of Er3+/Yb3+ codoped Y3Ga5O12 nanocrystalline powders have been studied using laser spectroscopy. A diffuse reflectance and luminescence spectra confirm that Er3+ and Yb3+ ions occupy the Y3+ sites of the single-phase cubic nano-garnet. Very bright green and red luminescence of the Er3+ ions are detected by the naked eyes, even for a laser power as low as 15 mW, when the Yb3+ ions are excited at 970 nm. The red upconverted emission is more intense than that under direct excitation of the Er3+ ions. The power dependence and the dynamics of the near-infrared-to-green and near-infrared-to-red upconverted emissions show the existence of different two-photon energy transfer upconversion processes. The results here presented indicate that Er3+/Yb3+ codoped Y3Ga5O12 can be a good candidate as an optical nanoheater and nanothermometer in biomedicine applications in the first biological window.

Stokes and anti-Stokes luminescence in Tm3+/Yb3+-doped Lu3Ga5O12 nano-garnets: a study of multipolar interactions and energy transfer dynamics

Nanocrystalline Lu₃Ga₅O₁₂ garnets doped with Tm³⁺/Yb³⁺ ions have been synthesized and characterized for their structural, Stokes and anti-Stokes luminescence properties. Multipolar interactions among active ions, energy transfer and diffusion parameters have been estimated in the nano-garnets.

Efficient Nd3+ sensitized Yb3+ emission and infrared-to-visible energy conversion in gallium nano-garnets

We studied the structural and luminescence properties of nanocrystalline RE₃Ga₅O₁₂ (RE = Gd, Y and Lu) garnets co-doped with 1 mol% of Nd³⁺ and 10 mol% of Yb³⁺ ions. The Nd³⁺ sensitized Yb³⁺ emission at 1025 nm is observed due to efficient Nd³⁺ to Yb³⁺ energy transfer.

Infrared-to-Visible Light Conversion in Er(3+) -Yb(3+) :Lu3 Ga5 O12 Nanogarnets

Er(3+) -Yb(3+) co-doped Lu3 Ga5 O12 nanogarnets were prepared and characterized; their structural and luminescence properties were determined as a function of the Yb(3+) concentration. The morphology of the nanogarnets was studied by HRTEM. Under 488 nm excitation, the nanogarnets emit green, red, and near-infrared light. The decay curves for the ((4) S3/2 , (2) H11/2 ) and (4) F9/2 levels of the Er(3+) ions exhibit a non-exponential nature under resonant laser excitation and their effective lifetimes are found to decrease with an increase in the Yb(3+) concentration from 1.0 to 10.0 mol %. The non-exponential decay curves are well fitted to the Inokuti-Hirayama model for S=8, indicating that the mechanism of interaction for energy transfer between the optically active ions is of dipole-quadrupole type. Upon 976 nm laser excitation, an intense green upconverted emission is clearly observed by the naked eyes. A significant enhancement of the red-to-green intensity ratio of Er(3+) ions was observed with an increase in Yb(3+) concentration. The power dependence and the dynamics of the upconverted emission confirm the existence of two-photon upconversion processes for the green and red emissions.

Structural, elastic and vibrational properties of nanocrystalline lutetium gallium garnet under high pressure

An ab initio study of the structural, elastic and vibrational properties of the lutetium gallium garnet (Lu₃Ga₅O₁₂) under pressure has been performed in the framework of the density functional theory, up to 95 GPa.

Near-infrared upconversion nanoparticles for bio-applications

Upconversion nanoparticles (UCNs) attract intensive attentions in biomedical applications. They have shown great potential in bioimaging, biomolecule detection, drug delivery, photodynamic therapy and cellular molecules interactions. Due to the anti-Stokes optical property and NIR excitation, UCNs overcome the drawbacks encountered in conventional luminescent biomarkers. High signal to noise ratio, low cytotoxicity and stable high throughput results are obtained using UCNs as luminescent labels or light triggers in biomedical applications. In this review article, the reason for choosing UCNs as biomedical agents, the progress of the UCNs development and case studies of their biomedical applications will be discussed.

Intense up-conversion luminescence in Er3+/Yb3+ co-doped CeO2 powders

The Er(3+) and Er(3+)/Yb(3+) co-doped CeO2 powders have been prepared by a urea combustion route. The structural, morphological, compositional and vibrational analysis of the Er(3+):CeO2 and Er(3+)/Yb(3+):CeO2 powders have been studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and Fourier transform infrared spectroscopy. The optical and luminescence properties of Er(3+):CeO2 and Er(3+)/Yb(3+):CeO2 powders have been studied by using laser excited spectroscopy. The effects of Yb(3+) doping on up-conversion luminescence of Er(3+) co-doped CeO2 powders were studied. The ratio of red to green intensity is decreased in Er(3+):CeO2 whereas the ratio is increased in Er(3+)/Yb(3+):CeO2 powders with increase of power. The effect of co-doping with the Yb(3+) ions on the visible luminescence of Er(3+) and the energy transfer mechanism responsible for the variation in the green and red intensity are discussed. The results indicate that these materials may be suitable for display and light emitting devices.

Lanthanide-based luminescent NanoGUMBOS

Lanthanide photochemistry has been frequently studied for its high luminescence intensity, narrow emission band, and stable luminescent lifetime decay. In the work presented here, nanoparticles prepared using an aerosolization process were derived from europium-based GUMBOS (Group of Uniform Material Based on Organic Salts). These nanoparticles were characterized using electron microscopy, X-ray photoelectron spectroscopy (XPS), absorbance, and photoluminescence spectroscopy. An average diameter of 39.5 ± 8.4 nm for our nanoparticles was estimated by use of electron microscopy. Absorbance, luminescence, and luminescence lifetime decay measurements indicate intense and steady luminescence, which suggests a multitude of possible applications for lanthanide-based GUMBOS, especially in sensory devices, OLEDs, and photovoltaic devices.