WLED Applications Research Articles

Unveiling the mechanism for excellent thermal stability in Bi3+-doped Y2O3 phosphors for NUV-pumped WLED applications

In recent years, there has been a growing interest in novel cyan-emitting phosphors to address the cyan gap in the emission spectra of commercial WLEDs. Herein, the cyan-emitting Bi3+-doped Y2O3 (Y2O3:Bi3+) powder was synthesized by a facile solid-state reaction method. XRD analysis confirmed the substitution of Y3+ ions by Bi3+ ions in both C2 and S6 sites within the Y2O3 lattice. The high-purity Y2O3:Bi3+ phosphors under the excitation of NUV light exhibited a prominent cyan emission band centered at 492 nm and a faint violet emission shoulder at 410 nm, attributed to the 3P1 (3A)→1S0 and 3P1 (3Eu) → 1S0 transitions of the Bi3+ ions in the C2 and S6 sites, respectively. The highest PL intensity was achieved with 2%Bi3+ doping and annealing at 1300°C for 5 hours in air. For the first time, it is reported that the PL intensity of Y2O3:Bi3+ phosphor measured at 423 K (150°C) remains at 82% of its intensity at 298 K (25°C), indicating its excellent thermal stability. A mechanism proposing energy transfer from the 3B level of the C2 to 3Eu level of the S6 site in the Y2O3 lattice contributes to the phosphor's thermal stability. It is suggested that the relative PL intensity between 3B and 3Eu levels significantly influences the thermal stability of the Y2O3:Bi3+ phosphors. A cyan LED device was successfully fabricated by coating the Y2O3:Bi3+ phosphor layer onto the top surface of a 310 nm NUV-LED chip. The internal quantum efficiency (IQE) of the Y2O3:2%Bi3+ phosphors was estimated to be approximately 73.85%. These findings indicate that the synthesized Y2O3:Bi3+ phosphor is a promising candidate for use as a cyan-emitting component in NUV-pumped WLED applications.

Development of highly thermal-stable blue emitting Y4Al2O9:Bi3+ phosphors for w-LEDs, fingerprint and data security applications

A new blue-emitting Y4Al2O9:Bi3+ (YAO:Bi3+) phosphor is synthesized using the solution combustion method with mushroom extract as a binder. Its structural properties, concentration effects, temperature-dependent luminescence, and performance in LED devices are thoroughly investigated. Upon excitation at 367 nm, a strong blue light emission at 423 nm is observed, attributed to the 3P1→1S0 transition of Bi3+. The quantum efficiency reached approximately 63.5 %. The CIE diagram shows that the emission colour falls within the intense blue region, achieving a colour purity (CP) of 94 %. YAO:Bi3+ exhibits strong absorption in the near-ultraviolet range (330–400 nm), making it suitable for LEDs powered by near-ultraviolet chips. A thermal quenching experiment revealed an activation energy (Ea) of 0.323 eV, indicating that this YAO:Bi3+ phosphor possesses good thermal stability. This study showcases the use of YAO:Bi3+ phosphor in encapsulated LED devices. The device’s Commission Internationale de l’Éclairage (CIE) coordinates are (0.325, 0.310), with a high colour rendering index (CRI) of 94.70 and a low correlated colour temperature (CCT) of 5915 K at a current of 120 mA. These properties indicate that this phosphor is suitable for developing white LED devices powered by near-ultraviolet chips. The optimized YAO:Bi3+ phosphor is employed to enhance the detection of Level I-III fingerprint (FP) details with high resolution and contrast, showing effective visualization of latent fingerprints (LFPs) on various substrates. Furthermore, it is used as a model for developing fluorescent ink, which is applied to different media. The results suggest that YAO:Bi3+ phosphor has significant potential for applications in w-LEDs, advanced forensics, and anti-counterfeiting ink technologies.

Synergistic enhancement of photoluminescence and advanced deep learning model through YOLOv8x in combined effects of carbon dots and Sr₉Al₆O₁₈:Sm³⁺ phosphors

A series of orange-red-emitting Sr₉Al₆O₁₈:Sm³⁺ (1–11 mol %) phosphors are synthesized using the combustion method, while carbon dots (CDs) are produced from urea and citric acid. The incorporation of CDs into the Sr₉Al₆O₁₈:Sm³⁺ (SAO:Sm3+) matrix reduced both negative and positive defects, enhancing the crystallinity of the phosphor. A significant spectral overlap is observed between the emission of CDs and the absorption of SAO:Sm³⁺. An 11.9-folds enhancement in luminescence intensity is detected from the 5 wt% CDs@SAO:Sm³⁺ composite, along with an extended fluorescence lifetime. The energy transfer between CDs and Sm³⁺ is demonstrated, with the increased PL intensity attributed to the Förster Resonance Energy Transfer (FRET) mechanism. The CDs@SAO:Sm³⁺ composites demonstrated excellent selectivity and high contrast when developing latent fingerprints (LFPs). Level I–III structural characteristics of LFPs are easily recognized under ulta violet (UV) light. Furthermore, YOLOv8x, an effective deep learning model, has been modified for the important forensic science task of LFPs recognition. YOLOv8x is able to precisely locate LFPs in complex backgrounds by employing the real-time object detection capabilities of the architecture. With this adjusting, detection speed and accuracy are much increased, making it an effective tool for forensic analysis and law enforcement applications. The optimized orange-red-emitting CDs@SAO:Sm³⁺ composites is synthesized with soluble polyvinyl alcohol (PVA) to produce a transparent anti-counterfeiting ink. The resulting film exhibited excellent flexibility, foldability, and superior thermal and optical properties. In summary, the highly efficient CDs@SAO:Sm³⁺ composite is a versatile luminescent material with multifunctional capabilities, making it ideal for flexible films, LFPs detection, and white light-emitting diodes (w-LEDs) applications.

Structural, optical, and surface analysis of Dy³⁺ doped Ba₂Mg(BO₃)₂ phosphor for w-LED applications

The present study reports on the phase formation, spectral, surface, and luminescence properties of the yellowish-white emitting Ba2Mg(BO3)2:Dy3+ phosphors synthesized by the solid-state reaction method. The XRD and Rietveld refinement results confirm the trigonal phase of BaMg(BO3)2:Dy3+ with space group R-3m. The scanning electron microscopy image shows the needle-like morphology of the synthesized particles. The band structure of the Ba2Mg(BO3)2 host has been investigated in the framework of the density functional theory (DFT) by evaluating the band structure and density of states (DOS). Under 350 nm excitation, all the phosphors emit yellowish-white light with CIE color coordinates of (x = 0.39, y = 0.39). The optimum PL concentration of Dy3+ doped Ba2Mg(BO3)2 host was obtained to be 2.5 mol % with a critical distance of 21 Å and a CCT value of 4240 K. The X-ray photoelectron study reveals the presence of all the elements on the surface of the phosphor. The result shows that Ba2Mg (BO3)2:Dy3+ phosphors can be considered as a yellowish-white light emitter in w-LEDs.

Comparative investigation on carbon dots and chloride fluxes modified ZnAl2O4:Cr3+ nanophosphors for temperature sensing, cutting-edge forensic, anti-counterfeiting and w-LEDs applications

A novel Cr3+ doped ZnAl2O4 is synthesized by grafting carbon dots (CDs) and chloride fluxes (NaCl, KCl, NH4Cl) through the solid-state reaction method. Upon excitation at 530 nm wavelength, the Cr3+ ions in the ZAO NPs emit red light due to the influence of a strong crystal field. This red emission arises from the electric dipole 2Eg→4A2g of the Cr3+ ions. Among the chloride fluxes examined, NH4Cl had a significant impact on the PL intensity. Notably, when CDs are incorporated into the ZAO:7Cr3+/NH4Cl NPs, a remarkable increase of 17.25-folds in photoluminescence (PL) intensity is observed. This enhancement is substantially higher than that of CDs alone (11.23-folds) and NH4Cl alone (3.82-folds). The increased PL intensity is attributed to the Förster resonance energy transfer (FRET) mechanism. Furthermore, the addition of CDs (5 wt.%) enhanced the colour purity (CP) of ZAO:7Cr3+/NH4Cl NCs to 99.8%, achieving a high Internal quantum efficiency (IQE) of 93.4 %. Notably, the CDs (5 wt.%)@ZAO:7Cr3+/NH4Cl NCs maintained 92.43 % of their emission intensity even at 420 K, demonstrating exceptional thermal stability compared to ZAO:7Cr3+ NPs. Moreover, the NPs holds promise for optical thermometry, boasting a high relative sensitivity (Sr) of 6.74 × 10–2 %K-1 across a temperature range spanning from 300 to 480 K. Moreover, the latent fingerprints (LFPs) developed using CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs demonstrate remarkable selectivity and high contrast. Under UV irradiation, the structural features of LFPs at levels I–III are clearly visible. In addition, the strong red fluorescence emitted by CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs makes them suitable for applications in AC. CDs(5 wt.%)@ZAO:7Cr3+ NCs exhibit significant potential for w-LED fabrication, achieving a correlated colour temperature (CCT) of 5517 K, a CIE coordinate of (0.332, 0.331), and a high colour rendering index (CRI) of Ra = 94, outperforming ZAO:7Cr3+/NH4Cl NPs. Overall results clearly demonstrates that, CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs are effective for applications in optical thermometry, dactyloscopy, w-LEDs, and AC.

Structural determination, energy transfer and color-tunable photoluminescence of stable LiYSiO4: Ce/Tb/Sm Phosphors toward nUV pumped wLEDs application

Study on photon emission of Ce3+-doped phosphors is essential for advanced optoelectronic application. However, it remains quite difficult to design near-ultraviolet excitable Ce3+-activated silicate blue/cyan-emitting phosphors because of the combined influence of iconicity of Ce3+, crystal field strength, and nephelauxetic effect. Herein, Ce3+ incorporated into a proper host LiYSiO4 (LYS) phosphor is mechanistically investigated and shown efficient blue/cyan photoluminescence (PL) owing to Ce3+ 5d1 electronic state experiencing appropriate crystal field splitting. The comprehensive analysis based on structural refinement, dynamic/static spectra, and density functional theory calculations indicates that Ce3+ ions are energetically favored in octahedral Y site as compared with Li site in the host, resulting in attractive PL properties. According to the principle of color superposition and via cascading energy transfer (ET) from Ce3+ → Tb3+ → Sm3+, systematic PL tuning in a large color gamut is realized by further codoping with the green- and red-emissions of Tb3+ and Sm3+ in the phosphor LYS: Ce3+/Tb3+/Sm3+. The direct ET from Ce3+ → Sm3+ is difficult to occur due to the metal-metal charge transfer effect. Of note, the PL thermal-quenching of Ce3+ is mainly associated with multiphonon relaxation, while the quenching of Tb3+/ Sm3+ is primarily due to the cross relaxation (CR) process via dipole-dipole (d-d) interaction. The appropriate distance between the two nearest adjacent Y sites in the host together with the ET are conducive to weaken the CR process of Tb3+/Sm3+, leading to high PL efficiency. Finally, a prototype pc-wLED assembled via a remote ‘capping’ packaging strategy and by using only the stably composition-optimized white-emitting LYS: Ce3+/Tb3+/Sm3+ demonstrates that the phosphor is promising for high-quality of light.

Multimode Luminescence Tailoring in PMA4Na(In,Sb)Cl8 Organic–inorganic Hybrid Metal Halide via Rigid Benzene Ring Induced Local Lattice Distortion

AbstractLow dimensional organic‐inorganic hybrid metal halide materials have attracted extensive attention due to their superior optoelectronic properties. However, low photoluminescence quantum yields (PLQYs) caused by parity‐forbidden transition hinder their further application in optoelectronic devices. Herein, a novel yellow‐emitting PMA4Na(In,Sb)Cl8 (C7H10N+, PMA+) low‐dimensional OIMHs single crystal with a PLQY as high as 88 % was successfully designed and synthesized, originating from the fact that the doping of Sb3+ effectively relaxes the parity‐forbidden transition by strong spin‐orbit (SO) coupling and Jahn‐Teller (JT) interaction. The as‐prepared crystal shows an efficient dual emission peaking 495 and 560 nm at low temperature, which are ascribed to different levels of 3P1→1S0 transitions of Sb3+ in [SbCl6]3− octahedral caused by JT deformation. Moreover, wide‐range luminescence tailoring from cyan to orange can be achieved through adjusting excitation energy and temperature because of flexible [SbCl6]3− octahedral in the PNIC lattice. Based on a relative stiff lattice environment, the 560 nm yellow emission under 350 nm light excitation exhibits abnormal anti‐thermal quenching from 8 to 400 K owing to the suppression of non‐radiative transition. The multimode luminescence regulation enriches PMA4Na(In,Sb)Cl8 great potential in the field of optoelectronics such as temperature sensing, low temperature anti‐counterfeiting and WLED applications.

Exploring the viability of thermally robust β-BaB2O4: Dy3+ through FIR based polynomial approach for advanced temperature sensing and WLED applications

In this present work, we have explored the optical, structural, and thermal sensing properties of novel β-BaB2O4: xDy3+ (x = 1, 2, 3, 4, and 5 mol%) phosphors prepared using the solid-state reaction method. The optimization of the phosphors was achieved by using the characteristic emission spectra of Dy³⁺ ions. A thorough investigation was conducted into the various mechanisms contributing to concentration quenching, including cross-relaxation pathways, multipole-multipole interactions, and non-radiative energy transfer processes. Using the diffused reflectance spectra, significant parameters including optical band gap, nephelauxetic ratio, bonding parameter, and refractive index were evaluated. Temperature-dependent optical properties revealed a very high quenching temperature of 492.7 K. Using the florescent intensity ratio (FIR) with polynomial fit from 2nd to 5th order, the highest absolute sensitivity was obtained as 0.0472 K−1 at 483 K, and the highest relative sensitivity of 0.3922 % K−1 at 303 . Finally, the optimized phosphor exhibited exceptional thermal stability up to 500˚C with nearly 1 wt% of loss.

Combustion synthesis and photoluminescence of Ca2SrWO6:Dy3+ double perovskite: An approach for white light emission

Luminescent Ca2SrWO6:Dy3+ double perovskites are synthesized via the combustion route of material synthesis, wherein urea is taken as fuel. The as-prepared phosphor series comprehensively characterized for their structural and photoluminescence (PL) properties. The Rietveld refinement of XRD data revealed monoclinic crystallized microcrystals with mixed particles of the size of less than 1 µm, studied via SEM. Ca2SrWO6:Dy3+ displayed standard Dy3+ transitions 4F9/2–6H15/2 (blue emission) and 4F9/2–6H13/2 (yellow emission) collectively resulted in white light emission, confirmed via CIE study. Under 278 and 388 excitations, 2 mol% doping of Dy3+ found to be optimum concentration, beyond which concentration quenching is observed due to dipole–dipole interaction. The Y/B ratio ∼1 shows potential to produce white light and make phosphor suitable for WLED applications. The Ca2SrWO6:Dy3+ phosphor displayed notably high thermal stability with PL intensity persisted 77.6 % at LED burning temperature (150 °C) when compared to PL intensity attained at room-temperature, which is basically due to the rigid perovskite structure. In addition, the PL decay lifetime of 4F9/2 state was calculated by utilizing decay curves. Subsequently, the PL quantum efficiency and non-radiative relaxation rate are determined. The theoretical model of Auzel’s fit function is used to calculate to quantum efficiency and was found to be 93.27 % for Ca2SrWO6:2 % Dy3+ phosphor. Moreover, the photometric results reveals that the CIE points are lies in white region of CIE diagram with comparable CCT. The collective results indicated the utility of the phosphor for potential WLED applications.

Synthesis and investigation of the optical characteristics of RE3+ activated Ca2Li2Si2O7 (Rare earth = Eu, Tb) phosphor for W-LED application

Novel Eu3+ and Tb3+ ions-doped Ca2Li2Si2O7 luminescent materials were prepared by a low-temperature solid-state reaction technique for LED application. The electronic transitions of 5D0 → 7F2 (Eu3+) and 5D4 → 7F5 (Tb3+) have caused the luminescent material to exhibit strong luminosity in 613 nm (red) and 545 nm (green), respectively. Fourier transform infrared (FT-IR) spectra were applied for the identification of functional groups, and powder X-ray diffraction (XRD) was used for structural analysis. Morphological data was gathered using scanning electron microscopy (SEM). Its color was also determined by calculating the CIE coordinates. The excitation, PL properties, and luminescence decay time of the emission transitions of Eu3+ (5D0 → 7F2) and Tb3+ (5D4 → 7F5) were measured in order to analyze luminosity spectra.

Synthesis and Characterizations of Novel bi-ligand TbEu(cpioa)phen Phosphors with High Quantum Efficiency for WLED Applications.

The hydrothermal method was employed to synthesize a novel bi-ligands LnMOF: Ln(cpioa)phen. The secondary ligand 1, 10-phen serves as a bridging agent to further facilitate energy transfer between Ln ions and the primary ligand H3cpioa. A comparison between Ln(cpioa) MOFs (Ln: Tb3+, Eu3+) and Ln(cpioa)phen MOFs (Ln: Tb3+, Eu3+) reveals that addition of the secondary ligand significantly improves the emission intensity by as high as almost 34 times. After detailed structural study, it is found that different Ln ions have the similar coordination in the Ln(cpioa)phen MOF. In addition, the chromaticity of Ln(cpioa)phen MOFs can be easily tuned by the amounts of doping Ln ions. La0.974Tb0.0255Eu0.0005(cpioa)phen MOF has a white emission with a CIE coordinate of (0.323, 0.343). Characterizations of corresponding LED devices show that device based on Ln(cpioa)phen MOF has better photoluminescence performances, which indicates that Ln(cpioa)phen MOF has great potential of for WLED applications.

Robust structure, spectral adjustability of single-component silicate oxyapatite Sr2La8(SiO4)6O2: Ce/Tb/Sm toward phosphor-converted wLEDs application

The lack of photons in electromagnetic spectrum region of 400–450 nm, termed cyan gap among other photoluminescence (PL) coverage issues, confines the full-visible- spectrum white light's overall capability for color rendering in part of previously studied single-component phosphors. Herein, we have mechanistically investigated that a Ce3+ incorporated silicate oxyapatite Sr2La8(SiO4)6O2 (SLS) phosphor, via a facile sol-combustion synthesis under low temperature, shows efficient cyan PL with broad full width at half maxima (fwhm, ∼90 nm) and high quantum yield (QY, ∼46.3 %) as a result of tendentious dual-site occupations and parity-allowed 4f1 ↔ 5d transitions of Ce3+, based on a combination of steady/transient-state spectroscopy and theoretical calculations. According to the principle of color superposition, the color-tunable PL, including the white emission with low coordinated color temperature (CCT) and high color rendering index (CRI), is realized by further codoping the characteristic green/red line emissions from Tb3+ and Sm3+ ions in the SLS: Ce. The low PL QY (∼32.7 %) from the monodoped Tb or Sm, due to its forbidden 4f-4f transitions, is cleverly alleviated via cascade-connected energy transfer (ET) from Ce → Tb → Sm. The direct ET from Ce → Sm is hardly occurred because of the metal-mental charge transfer (MMCT) effect. Finally, a prototype pc-wLED assembled via a remote ‘capping’ packaging strategy and using only the stably composition-optimized white-emitting SLS: Ce/Tb/Sm demonstrates attractive performance of the designed device (CCT 4243 K, CRI (Ra) 87, CIE (0.365, 0.381), and LE 76 lm⋅W−1 under 120 mA) and the phosphor is promising for high-quality of light.

A red-emitting Sm3+-activated BaLaMgNbO6 phosphor for WLED applications obtained by using an isotopic doping strategy (Y → La)

BaLa1-x-yMgNbO6: xSm3+, yY3+ phosphors were successfully synthesized via high-temperature solid-state reaction method. The crystal structure of representative samples was determined using X-ray diffraction and Rietveld refinement, confirming high phase purity of the prepared phosphors. In the singly doped BaLa1-xMgNbO6: 0.05 S m3+ sample, red emission was observed under 406 nm excitation with an internal quantum efficiency of 27.8 %. The thermal stability at 599 nm (483 K) retained 72.39 % of the emission intensity. To further enhance the luminescent properties, co-doping strategy was employed by substituting Y3+ for La3+ ions. This adjustment significantly improved the brightness of the phosphors. For instance, in BaLa0.93MgNbO6: 0.05 S m3+, 0.02Y3+, the emission intensity at 599 nm was enhanced by 3.27 times compared to BaLa0.95MgNbO6: 0.05 S m3+, with an internal quantum efficiency increased from 27.8 % to 60.2 %. Moreover, the color purity of BaLa1-x-yMgNbO6: xSm3+, yY3+ phosphors reached 99 %. Warm white LED devices fabricated using BaLa0.93MgNbO6: 0.05 S m3+, 0.02Y3+ exhibited a color rendering index (Ra) of 95.7 and a color temperature of 4938K, indicating broad application potential. Experimental results demonstrate that BaLa0.93MgNbO6: 0.05 S m3+, 0.02Y3+ phosphors with double perovskite structure are a novel and high-performance material for warm white LED phosphors.

Insight into Tendentious Multisite Colonization, Site Environment Modulation, and Energy Transfer of Steady Ba2CaB2Si4O14: Ce/Tb/Sm/Sr/Na toward nUV-Pumped wLED Application

Insight into Tendentious Multisite Colonization, Site Environment Modulation, and Energy Transfer of Steady Ba₂CaB₂Si₄O₁₄: Ce/Tb/Sm/Sr/Na toward nUV-Pumped wLED Application

Highly saturated red-emitting novel europium doped yttrium calcium borate (Eu3+: Y2CaB10O19) phosphor materials for eco-friendly solid-state lighting applications

Optical parameters like low correlated color temperature (CCT), color rendering index (CRI), color purity, thermal stability and etc. are crucial parameters for the practical applications of white light emitting diode applications. High color purity around 100 % red emitting novel europium doped yttrium calcium borate (Eu3+: Y2CaB10O19) phosphors were harvested by conventional solid-state synthesis technique. The novel host material possesses monoclinic crystal structure with no observable shift in the diffraction lines with varying dopant concentrations. FTIR studies revealed the presence of BO3 and BO4 networks in the host lattice responsible for structural rigidity and good thermal stability. The phosphor materials synthesized xEu3+: Y2CaB10O19 (x = 0.01, 0.03, 0.05, 0.07 and 0.09), are sensitive to both 250 nm (UV) and 393 nm (Near UV/blue LED) for excitation that can produce deep orange (594 nm) emission along with red emission (612 nm). The optimum Eu3+ ion concentration was fixed at 5 mol% of dopant ions to prevent the concentration quenching. As prepared optimal phosphor material possesses high color purity around 100 %, CCT of 1214 K defines its applicability in WLED applications. The synthesized phosphor materials pertain excellent switching response, thermal stability and the fabricated P-i-G possesses desired photometric parameters for its practical applications.

Novel White Phosphor Bi3+ co-doped SrCeO3: 2 wt% Sm3+ Synthesized via Fuel Excess Gel Combustion Synthesis for wLED Applications.

Co-doping strategy is done if the emission from the activator is relatively low with existing excitation energy. Thus, to enrich the emission from an activator, the sensitizer like Bi3+ is co-doped onto the host and this intermediator transfers its emission energy to the activator. Prior to the study, no investigations had been conducted, marking the foundational exploration of the sensitizer effect within the rare earth-doped SrCeO3 matrix aimed at enhancing luminescence properties. The current study focuses on the innovation of single-phase robust white phosphors, SrCeO3: 2wt% Sm3+: xBi3+ (x = 0 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%) to coat near UV LED chips for high CRI wLED applications. The novel perovskites were synthesized using a low-temperature fuel excess gel combustion method, utilizing citric acid as the fuel and ammonium nitrate as an extra oxidizer. Upon co-doping SrCeO3: 2wt% Sm3+ with bismuth, the impact of changing sensitizer concentration on both the development of crystalline phases, morphology, elemental composition, band gap energy, and the luminescent properties of ceramic powders were explored through X-ray diffraction, FE-SEM, Energy dispersive spectra, UV-visible absorption spectra, and photoluminescence characterization methods. The experimental results revealed the orthorhombic single-phase formation of SrCeO3: 2wt% Sm3+: xBi3+perovskites yielding high crystallinity and luminescence maximum at critical sensitizer concentration 1 wt% Bi3+. Also, the bright white light emission of all the perovskites was confirmed using the CIE color diagram. Thus, nano-perovskite SrCe0.97Sm0.02O3: 1wt% Bi3+ acts as an inevitable direct phosphor coating the near UV chip in LEDs, which can be a great revolution in energy savings applications.

Influence of carbon dots integrated in Pr3+ doped gahnite nanophosphor for thermal sensing, data fortification and fingerprint visualization analysis through YOLOv8x deep learning embedded model

The remarkable optical properties of carbon dots (CDs) render them highly promising as a versatile group of carbon-based nanomaterials. Integrating hydrothermally synthesized CDs into zinc aluminate doped with Pr3+ ions (ZnAl2O4:Pr3+) nanophosphors (ZAO:Pr3+ NPs) fabricated via the solution combustion (SC) technique holds great potential. The aim of synthesizing these nanocrystals (NCs) is to explore their potential uses in optical thermometry and anti-counterfeiting (AC) measures. The synthesized nanoparticles (NPs) and nanocomposites (NCs) underwent characterization using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra to verify their phase, morphology, particle size, oxidation state, and chemical composition. When excited at 447 nm, the Pr3+ doped ZAO: NPs exhibited an orange-red emission band at 614 nm. A remarkable enhancement in PL intensity, by a factor of 39.02 folds, is noted upon embedding CDs into the ZAO:Pr3+ NPs (CDs@ ZAO:Pr3+). The enhanced PL intensity can be ascribed to the Förster resonance energy transfer (FRET) mechanism. Even at a temperature of 423 K, the NPs retains 95.4% of its emission intensity compared to that at room temperature, showcasing exceptional thermal stability. The 5 wt% CDs@ZAO:1Pr3+ NCs demonstrate a high colour purity (CP) of 98.3%. Moreover, these NCs hold promise for optical thermometry applications across a broad temperature range spanning from 303 to 463 K. Utilizing the exceptional ZAO:1Pr3+ NPs and 5 wt% CDs@ZAO:1Pr3+ NCs, two representative white light emitting diodes (w-LEDs) have been successfully developed, boasting satisfactory luminous efficacy and colour-rendering index (CRI). This underscores their potential for high-performance w-LED applications. Simultaneously, a highly sensitive, non-contact optical thermometer has been engineered, featuring maximum relative sensitivities of approximately 44.51×10−4K−1 and 75.48×10−4K−1 at the emission intensities corresponding to 673, 693, 712 and 735 nm, respectively. We have developed a simple brush mode technique for creating a variety of patterns using the manufactured AC security ink. The latent fingerprints (LFPs) visualized using 5 wt% CDs@ZAO:1Pr3+ NCs exhibit excellent resolution and contrast, enabling the easy identification of fingerprint characteristics from levels I-III. Employing deep learning utilizing the YOLOv8x algorithm, fluorescence images of the revealed LFPs demonstrate remarkable alignment with standard controls, suggesting a high degree of similarity. In addition, the fabricated white light emitting diode (w-LED) boasts a favorable colour rendering index (Ra=87) alongside Commission International de L′Eclairage (CIE) coordinates (0.617, 0.376). Consequently, the inclusion of 5wt% CDs@ZAO:1Pr3+NPs showcases remarkable luminescent attributes and holds promising prospects across various applications.

Energy transfer of Eu3+/Dy3+ ions co-doped BaCO3 elaborated by auto-combustion process

Samples of undoped and (Eu3+, Dy3+) ions co-doped BaCO3, were synthesized by autocombustion method. The samples nanostructures were characterized by various techniques such as X-ray diffraction, scanning electron microscopy (SEM), Photoluminescence (PL) spectroscopy and electron paramagnetic resonance (EPR). Based on XRD analysis, the undoped and (Eu3+, Dy3+) co-doped BaCO3 kept its orthorhombic structure. The calculated crystallite sizes for undoped and (Eu3+, Dy3+) co-doped BaCO3 samples are 70 and 49 nm, respectively. The FTIR spectra allowed the determination of the vibration modes of BaCO3. Morphological analysis showed that the synthesized powders consist of spherical and agglomerated particles. The EPR measurements exhibited a narrow response for BaCO3, along with an increased intensity in the case of the Eu3+ doped and (Eu3+, Dy3+) co-doped samples, indicating the incorporation of Eu3+ and Dy3+ ions into the matrix. The effect of Dy3+ (0.5 %) on the luminescence properties of BaCO3:Eu3+were studied. The results indicated that the lifetimes of the state 5D0 of Eu3+ increase from 1.15 to 1.31 ms in the presence of Dy3+, proving an energy transfer from Dy3+ to Eu3+ ions. This transfer was verified also by photoluminescence spectra, quantum efficiency of the 5D0 → 7F2 emission (80 %) and the emission cross section (39×10−22 cm2). The CCT (4239 K) and CRI (87) were calculated. Therefore, Eu3+, Dy3+ co-doped BaCO3 material could be used in the fields of w-LED applications.

Substitutional effects of the anionic group systems [BO33−], [PO43− ], and [SO42−] on the down-conversion photoluminescence properties of Y2O3:Er3+ nanophosphors

A series of Y2O3, Y2O3: Er3+ (1 %) and Y2O3-AG: Er3+ (1 %) (where AG = BO33−, PO43−, and SO42−) nanophosphors were prepared via a chemical combustion technique. The primary X-ray powder diffraction results showed that the Y2O3:Er3+ phosphor materials crystallized into a cubic standard structure, while the Y2O3-AG: Er3+ phosphor materials transformed to hexagonal and tetragonal structures for the [PO43−] and [BO33−]-based phosphors, respectively. However, no changes were observed for the [SO42−]-based phosphor materials. The scanning electron microscope micrographs revealed that the particles were formed in the nanometre range with different sizes and shapes. The fourier-transformed infrared spectra showed the presence of various structural groups in the pure Y2O3 and Y2O3-AG: Er3+ phosphors. In addition to that, the optical bandgap energy values were obtained using the diffuse reflection spectra (DRS) spectra and Kubelka-Munk function theory. Under UV-379 nm excitation for the Y2O3-AG: Er3+ phosphors, the Y2O3–SO4: Er3+ emitted the most intense green light at 563 nm wavelength. The Commission Internationale de l'Elcairage colour coordinates and correlated color temperature values indicated that the Y2O3:Er3+, Y2O3-PO4:Er3+, and Y2O3–SO4:Er3+ phosphor materials are potential candidates for producing enhanced green color components in white light-emitting diode (w-LED) applications.

Investigation of ZnO nanoparticles co-doped with dual transition elements showing swift photocatalytic performance and viable for WLED application

Investigation of ZnO nanoparticles co-doped with dual transition elements showing swift photocatalytic performance and viable for WLED application