White light emitting MgAl₂O₄:Dy³⁺,Eu³⁺ nanophosphor for multifunctional applications

Abstract

Feeble white emission with a low Colour Rendering Index (CRI) has become the principal gridlock for the extensive commercialization of phosphor converted white LEDs (pc-WLEDs). Fusion of red, green and blue emitting rare-earth (RE) ions in a suitable host can overcome these drawbacks but the energy migration between multiple RE ions at single excitation wavelength defines the key standpoint in designing such white light emitting phosphors. Apart from the abovementioned obstacles, recently traditional optical temperature sensors based on RE ions have faced difficulties due to their low relative sensitivity and large detection error. Keeping these points in mind, in this work, a series of MgAl2O4:Dy3+,Eu3+ nanophosphors are synthesized among which 2% Dy3+,0.2% Eu3+ doped MgAl2O4 nanophosphors demonstrate strong white emission with CIE co-ordinates of (0.31, 0.33), and high quantum yield (∼67%), which could be directly utilized for pc-WLED based solid state lighting devices. Detailed investigation of PL properties reveals that Eu3+ ions can be well sensitized by Dy3+ under near-ultraviolet excitation of 351 nm. Dexter's theory & Reisfeld's approximation are employed for an in-depth analysis of the inter-RE energy transfer (ET) mechanism, which signposts that the dipole-quadrupole interaction phenomenon is responsible for the ET process from Dy3+ to Eu3+. Additionally, the validated ET plays a pivotal role in demonstrating the self-referencing ratiometric temperature sensor behaviour supported by a distinct high temperature thermal quenching trend between Dy3+ and Eu3+ ions. Hence the obtained nanophosphors are highly promising for utilizing in WLED based solid state lighting and self-referencing ratiometric temperature sensor applications.

Enhanced Photoluminescence Properties of Low-Dimensional Eu3+-Activated Y4Al2O9 Phosphor Compared to Bulk for Solid-State Lighting Applications and Latent Fingerprint Detection-Based Forensic Applications

“…The curve of the Y (4–0.05) Al 2 O 9 :Eu 0.05 bulk phosphor can be close fitted to a bi-exponential function, which is expressed as follows: where τ 1 and τ 2 are the decay lifetimes of the luminescence, and A 1 and A 2 are the weighting parameters. The average lifetime ( τ av ) for bi-exponential decay can be described by the equation (Panigrahi et al, 2018): The average lifetime of the Y (4–0.05) Al 2 O 9 :Eu 0.05 bulk and nanophosphor is found to be 0.82 and 1.7 ms, respectively. This result approves the suitability of the nanomaterials for use in several applications over the bulk one, as a greater lifetime is chosen for the practical applications.…”

Blue Emitting BaAl2O4:Ce3+ Nanophosphors with High Color Purity and Brightness for White LEDs

“…To confirm the reduction in nonradiative transitions with the increasing concentration of Ce 3+ activator, the photoluminescence decay profiles of 422 nm emission for both 1% Ce 3+ - and 3% Ce 3+ -doped BaAl 2 O 4 nanophosphors have been measured under 350 nm UV excitation shown in Figure 6. The luminescence decay curves of the 5 d 1 → 4 f 1 transition for the as-prepared nanophosphors were fitted well by a biexponential function, which can be represented as follows (Panigrahi et al, 2018):where A 1 and A 2 are the weighting parameters, and τ 1 and τ 2 are the decay components of the lifetimes of luminescence. The average lifetime for the biexponential decay can be expressed as follows:

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Samarium-Activated La2Hf2O7 Nanoparticles as Multifunctional Phosphors

“…6,7 The host-to-dopant energy-transfer process in nanosized phosphors is highly relevant because of their potential to exhibit higher-resolution displays at lower thermal budget relative to their bulk counterparts. 8 Lanthanide ion-doped nanoparticles (NPs) have displayed outstanding photophysical properties such as large Stoke shift, high color purity, higher excited-state lifetime, and substantial quantum efficiency. 7,9 Such unique properties provide obvious advantages for luminescent materials designed toward UV-excited phosphors, X-ray scintillators, and thermographic phosphors (TGPs).…”