Nanophosphors Research Articles

Influence of carbon dots as modifier and SiO2 shell coating as a protecting layer in YAlO3:Cr3+ phosphors for multimodal applications

This study focuses on the synthesis of SiO2-coated carbon dots (CDs) grafted onto YAlO3:Cr3+ (YAP:Cr3+) nanophosphors (NPs) through a combustion method. The CDs enhance the absorption cross-section of Cr3+ ions, significantly boosting the luminescence of YAP:Cr3+ by 19.29-fold. Further improvement is achieved with a SiO2 coating, leading to a 48.73-fold increase in photoluminescence intensity. The NCs are colour tunable, with emissions ranging from pinkish-red to blue, depending on the concentration of CDs and the excitation wavelength. These properties make them suitable for diverse applications, such as ratio metric fluorescence sensors for detecting Fe3+ ions within the 0–350 µM range, with high sensitivity (0.2 µM) and a low detection limit (4.93 μM). Additionally, they serve as material for white light-emitting diodes (W-LEDs), achieving CIE coordinates of (0.31, 0.30) and a rendering index of 94. The NCs also function as an optical thermometer with a sensitivity of 0.31 % K−1 at 320 K, making them ideal for temperature sensing applications. Moreover, their stability and dual-emissive nature make them highly effective in latent fingerprints (LFPs) detection, enabling high-resolution, level III fingerprint analysis. The dual emission properties of CDs and Cr3+ ions position these NCs as multifunctional materials, suitable for optical sensing, lighting, and security applications.

A novel red emitting Eu3+ doped CaSiO3 nanophosphor derived from agro-wastes for advanced forensic applications

The modified sol–gel approach was utilised to synthesise Eu3+ (1–5 mol%) doped CaSiO3 nanophosphors (NPs) using eggshell (ES) and rice husk ash (RHA) as precursors for SiO2 and CaO, respectively. Powder X-ray diffraction (PXRD) peaks confirm the monoclinic structure of the powdered samples. The photoluminescence (PL) emission spectra display distinct emission peaks corresponding to Eu3+ ions. After optimizing the Eu3+ ion concentration, the highest intensity (CaSiO3:3Eu3+) was achieved at 3 mol%. As the concentration increased beyond this point, the emission intensity decreased due to concentration quenching (CQ). Temperature-dependent photoluminescence (TDPL) was investigated in the range of 303 to 443 K. The results demonstrated that emissions at elevated temperatures are significantly stronger than those at ambient temperature. TDPL studies revealed excellent thermal stability, with emission intensity remaining at 87.5 % even at 423 K. Additionally, the phosphor’s absolute sensitivity of 0.003 K−1 and relative sensitivity of 1.44 % K−1 highlight its strong potential for temperature sensing applications. The suitability of the phosphor for the powder dusting method in fingerprint (FP) detection on various surfaces was also assessed. Under 365 nm UV light, the CaSiO3:3Eu3+ phosphor clearly reveals the level 1–3 structure of LFPs.

Highly efficient Dy3+ activated Sr9Al6O18 nanophosphors for W-LEDs, optical thermometry and deep learning-based intelligent system for personal identification applications

A novel single-phase Dy3+ activated Sr9Al6O18 nanophosphors (NPs) was synthesized using a solution combustion method with urea as the fuel. When phosphors are excited at 350 nm, their photoluminescence (PL) spectra exhibit strong emissions at 484 and 574 nm, which are associated with the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions. These emissions are attributed to magnetic and electric dipole allowed transitions, correspondingly. It is found that dipole–dipole interactions are the main source of concentration quenching and energy transfer among the activator ions. The prepared NPs show thermal stability up to 480 K having an activation energy (Ea) of 0.2437 eV, as determined by temperature-dependent photoluminescence (TDPL). With a remarkable internal quantum efficiency (IQE) of 66.14 %, the optimized phosphor achieves notable relative sensitivity (Sr) and absolute sensitivity (Sa), estimated to be 2.65 % K−1 and 1.38×10−3 K−1 at 300 K, respectively. Thus, Sr9Al6O18:Dy3+ is a promising material for non-contact optical thermometry applications. Latent fingerprints (LFPs) and latent lip prints (LLPs) can be efficiently produced on a variety of surfaces by using the optimized NPs with the simple powder dusting technique. The prints are made visible under UV light with a 365 nm wavelength. The You Only Look Once version 8 (YOLOv8x) approach analyzes the overall morphological correlations of different minutiae to identify essential minutiae that indicate the identities of people from FPs. Splitting and matching multi-scale fingerprints (FPs) features improves the validity of the authenticating findings. The results show that the recommended method, which improves the entire FP authentication process, offers exceptional accuracy, resilience and speed. The findings provide strong support for the implementation of the optimized NPs in photonic devices, optical thermometers, and advanced forensic applications.

SBL-LCGL: sparse Bayesian learning based on Laplace distribution for robust cone-beam x-ray luminescence computed tomography

Objective. To address the quality and accuracy issues in the distribution of nanophosphors (NPs) using Cone-beam x-ray luminescence computed tomography (CB-XLCT) by proposing a novel reconstruction strategy.Approach. This paper introduces a sparse Bayesian learning reconstruction method termed SBL-LCGL, which is grounded in the Lipschitz continuous gradient condition and the Laplace prior to overcome the ill-posed inverse problem inherent in CB-XLCT.Main results. The SBL-LCGL method has demonstrated its effectiveness in capturing the sparse features of NPs and mitigating the computational complexity associated with matrix inversion. Both numerical simulation andin vivoexperiments confirm that the method yields satisfactory imaging results regarding the position and shape of the targets.Significance. The advancements presented in this work are expected to enhance the clinical applicability of CB-XLCT, contributing to its broader adoption in medical imaging and diagnostics.

Electrochemical and photoluminescence properties of Ce3+ doped copper aluminate nanoparticles

In this communication, for the first of its kind, CuAl2O4 doped with Ce3+ (1-9 mol %) are syn- thesized by solution combustion method using Aloe Vera gel as a reducing agent. The as-formed sample was calcined at 500° C for 3 hours, followed by characterization. The addition of dopants to the copper aluminate matrix didn't alter the crystal structure of the host matrix. Bragg reflec- tions confirm the formation of the cubic phase and also absence of other impurities. The surface morphology consists of nanorods arranged one above the other. The estimated crystallite size was found to decrease from 12 to 9 nm whereas, the direct energy band gap increases from 2.84 to 3.02 eV with an increase in dopant concentration. Under λex = 305 nm excitation, photoluminescence (PL) emission spectra have a high intense peak at 553 nm along with a less intense peak at 472 nm. The peak at 553 nm can be attributed to the existence of oxygen vacancies which arise due to the transition of an electron from the 2D3/2→2F7/2 of Ce3+, however, the peak observed at 472 nm results from the transition of ionized oxygen vacancies (VO) to the valence band caused by the 2D3/2→2F5/2 transition. The CIE coordinates lie well within the green region with 5758 K aver- age CCT. Further, Cyclic voltammetry analysis was conducted to investigate oxidation and redox peaks, while electrochemical impedance spectroscopy provided insights into ion transport kinetics. Specific capacitance values ranging from 29 to 59 F/g were obtained for CuAl2O4:Ce(1-9 mol %) NPs. These findings suggest potential applications for the synthesized material in areas such as display technology as a green nano phosphor and energy storage materials.

Exploring γ and UV irradiation responses on thermoluminescence and optical thermometry studies on Y4Al2O9:Ho3+ nanophosphor

A series of green emitting Ho3+ (1–9 mol%) doped Y4Al2O9 nanophosphors (NPs) are synthesized via solution combustion technique. Photoluminescence (PL) studies shows emission peaks recorded at ∼ 522 nm (5F3→5I8), 545 (5F4, 5S2→5I8), 659 (5F5→5I8) and 730 (5F4→5I7) upon excited at 460 nm wavelength. With a tremendous potential for application in white light-emitting diodes (w-LEDs), the phosphors show a bright green emission under 460 nm excitation. They also have a notable activation energy (0.31 eV), high color purity (98.2 %), and a remarkable quantum yield (87.1 %). Most astonishingly, even at temperatures as high as 420 K, YAO:5Ho3+nanoparticles retain 88.9 % of their initial fluorescence intensity. Using the fluorescence intensity ratio (FIR) method, the temperature sensing potential is also investigated. Thermoluminescence (TL) glow curves of γ (1 kGy) and UV (1 h) irradiated YAO:Ho3+(1–9 mol%) NPs exhibit two glow curves and highest intensity is recorded for YAO:5Ho3+NPs. TL characteristics of 5 mol% Ho3+ doped YAO NPs are subjected to γ (1 Gy-5 kGy) and UV (0.25–6 h) irradiation. Two glow curves recorded at 475 K (major peak) and 567 K (shouldered peak) for γ irradiation. However, for UV irradiation two glow curves at 478 K (major peak) and 575 K (shouldered peak) are recorded utilizing a 5 °C per minute heating rate. TL intensity varies with γ and UV exposure is recorded for optimized NPs and major glow peaks showcase linear response for both γ and UV irradiations, indicating that the prepared phosphor can be used in TL personal dosimetry. Furthermore, compared to γ-irradiated phosphor, UV-irradiated phosphor shows greater fading. The overall results clearly demonstrate that the optimized phosphor has proven to be an outstanding candidate for multifunctional applications.

Modulating trap properties by Cr3+-doping in Zn2SiO4: Mn2+ nano phosphor for optical information storage

Photo-stimulated luminescent materials are one of the most attractive alternatives for next-generation optical information storage technologies. However, there are still some challenges in regulating appropriate energy levels of traps in luminescent materials for optical information storage. Herein, a green emission nanophosphor Zn2SiO4: Mn2+, Cr3+ with the trap depth of 1.05 eV, fulfilling the requirements for optical information storage, was fabricated for the first time through the solution combustion method and subsequent heat treatment at 1000 °C for 2 h. The crystal structure, micromorphology, photoluminescence (PL), photoluminescence excitation (PLE), and afterglow properties of Zn2SiO4: Mn2+, Cr3+ were studied systematically. By applying the strategy of trap depth engineering, high trap density with proper trap depth was observed when Cr3+ ions were introduced into Zn2SiO4: Mn2+. Thermoluminescence (TL) glow-curve analysis through the initial rise (IR) method was conducted to gain some insights into the information of traps. As proof of application, optical information storage was experimentally achieved by choosing 275 nm illumination for “information writing” and 980 nm NIR excitation for “information reading”. The results indicate that Zn2SiO4: Mn2+, Cr3+ phosphor holds promise for potential applications in the field of optical information storage.

Alkali Silicates Codoped with NIR-Emitting RE (Nd3+ and Yb3+) Ions for Thermometry Applications.

In the present study, the synthesis of BaSrSiO4 co-doped Yb3+ and Nd3+ nanophosphors (NPs) was successfully achieved through the conventional sol-gel method, as confirmed by X-ray diffraction and SEM analysis, verifying the formation of pure NPs. The FTIR and Raman spectra analysis confirm the formation of silicates, as different modes and vibrations of Si-O and Si-O-Si were seen at 800-1000cm-1. The energy transfer (ET) mechanism between Nd3+ and Yb3+ ions was seen as the emission spectra showed a rise in intensity of one over another. PLE emission spectra showed transitions at 2F7/2-2F5/2 for Yb3+ and from 4F3/2 to (4I9/2, 4I11/2, and 4I13/2) for Nd3+ when excited at 785nm. All the samples record low activation energy, which shows that the rate of reaction will be higher in all the samples, and it will be highest for 1mol% Nd3+ and 1mol% Yb3+. An increasing value of τ was seen with increasing Yb3+ concentration, which confirms the increase in the population of trap centers. The positron annihilation lifetime (PAL) curve showed that 1mol% Yb3+ and 2mol Nd3+ have single vacancies or shallower positron traps, whereas 3mol% Yb3+ and 2mol% Nd3+ have larger defects like surface oxygen vacancy clusters. The other two samples have balance vacancies, which makes them best for thermometry applications. The fluorescence intensity ratio (FIR) was calculated to get sensitivity for thermometry application. 2.13% K-1 sensitivity achieved at 303-333K temperature.

Low-temperature Co-precipitation Synthesis of ZnAl2O4 Nanophosphors Probing its Luminescent, Antibacterial and Anticancer Potentials.

Metal nanoparticles and their binary oxides are well-known for their interactions with biomolecules and their applications in the biomedical field. However, the potential of ternary oxide nanophosphors remains underexplored in these fields due to challenges associated with high-temperature synthesis procedures and the use of toxic chemicals. ZnAl2O4, a ternary oxide matrix, being recognized for its adjustable wide bandgap, impressive surface properties, mechanical strength, thermal stability, and high quantum yield, is chosen for the present work. This study aims to comprehensively investigate the structural, morphological, optical, and cytotoxic properties of zinc aluminate nano phosphors synthesized through a co-precipitation method followed by low-temperature calcination. Analysis using X-ray diffraction spectroscopy (XRD) and Fourier-transform infrared spectroscopy (FTIR) revealed that the formation of the ZnAl2O4 spinel phase initiates at 300°C and completes at 750°C.SEM-EDAX measurements provided further confirmation of the compositional integrity of the synthesized sample. The average crystallite size, determined to be 11.47nm through a W-H plot, along with a higher bandgap value of 4.49eV compared to bulk ZnAl2O4 from the diffuse reflectance spectra (DRS), attests to the success of the nanophosphor synthesis. The self-activated blue luminescent centers of ZnAl2O4 can be fine-tuned to emit light in the green and red regions of the electromagnetic spectrum through appropriate rare earth (RE) doping, utilizing Tb3+ and Eu3+ respectively. Furthermore, the particles underwent short-term in-vitro cytotoxicity testing using Dalton's Lymphoma Ascites cells (DLA) and normal cells, demonstrating high activity against DLA cells while maintaining compatibility with normal cells.

A Spectroscopic Correlative Analysis of Eu3+‐Substituted Zn1‐xSnO3 Nano Phosphors for Anticounterfeiting Applications

AbstractA series of orange–red phosphors Zn1‐xSnO3:xEu3+ synthesized using a sol–gel combustion process is used to study the modified local crystal structure by site‐selective substitution of Eu3+ ions. XRD with the Rietveld refinement analysis reveals an orthorhombic ZnSnO3 structure with a space group 61. SEM and TEM with EDAX analyses confirm the flower‐like morphology of Zn1‐xSnO3:xEu3+ nanorods. Photoluminescence (PL) spectroscopy gives substantial confirmation for the inclusion of Eu3+ ions into the ZnSnO3 host. Judd‐Ofelt analysis confirms the substitution of Eu3+ ion in an asymmetric environment in ZnSnO3, which is responsible for orange–red emission at 615 nm. UV–vis–DRS analysis shows that the addition of Eu3+ ions (1% to 17% in phases of 4%) results in the formation of confined energy states with an increased band gap from 2.78 to 3.29 eV. The ability of ZnSnO3 to host Eu3+ ions signifies that it can be used as an effective luminescent material. Cyclic voltammetry analysis reveals the enhanced charge separation in Zn1‐xSnO3:xEu3+(13%) nanophosphor. The optimized Zn1‐xSnO3:xEu3+(13%) nano phosphor mixed with silicone investigated for the generation of anti‐counterfeiting patterns indicates its potential to generate high‐resolution image patterns on various surfaces under monochromatic UV or visible‐LASER LED illumination.

Europium‐Activated Perovskite Cubical SrZrO3 Red Phosphor: Synthesis, Characterization, and Sustainable Applications in PC‐LEDs and Environmental Forensic Analysis

AbstractA series of SrZrO3 : Eu3+ nano phosphors synthesized by a modified high‐temperature solid‐state reaction method. The structural, functional vibration groups, optical, morphological, luminescence and quantum yield studies were characterized through XRD, FTIR, UV, ‘SEM & HR‐TEM’ and PL analyses respectively. The SrZrO3 : Eu3+ phosphor has a perovskite orthorhombic structure and emits intense red emission around 612 nm when it is excited under 465 nm and covers NUV light range. The calculated average lifetime indicates the nature of the allowed emission transition in Eu3+ (2.44 μs). The calculated colour purity and Commission International del’ Eclairagethe (CIE) chromaticity coordinates are 97.9 % and (0.5894, 0.4031) respectively. The observed quantum yield and thermal stability for the SrZrO3 : Eu3+ (9 mol %) phosphor are 22 % and 87 % at 423 K, respectively. These obtained results suggest that SrZrO3 : Eu3+ (9 mol %) phosphor would meliorate for red‐emitting phosphor in profound RGB‐based pc‐WLED applications.

Eu3+ doped SrMoO4: A promising nanophosphor for enhanced fingerprint detection and cheiloscopy

Developing a single material with diverse applications like fingerprint detection, cheiloscopy, and anti-counterfeiting is truly innovative and has the potential to revolutionize various fields. Here, we synthesized nano phosphors powders of SrMoO4 nanoparticles, doped with spherical-shaped Eu3+ ions via co-precipitation method. X-ray diffraction (XRD) analysis confirmed the formation of the SrMoO4 phase with Eu3+ successfully incorporated into the lattice. Field emission scanning electron microscopy (FESEM) images revealed the nanoparticles to be spherical and monodispersed with a narrow size distribution. Energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Sr, Mo, Eu3+, and O elements, indicating a homogeneous elemental composition. Fourier transform infrared (FTIR) spectroscopy showed characteristic bands for MoO bonds and hydroxyl groups. Diffuse reflectance spectroscopy (DRS) analysis revealed a decrease in band gap with increasing Eu3+ concentration, suggesting that Eu3+ doping potentially modifying the optical properties of SrMoO4, and introducing new functionalities. Their red photoluminescence property, making them suitable for various optical applications. The nanoparticles showed potential applications in fingerprint detection, cheiloscopy (lip print analysis), and anti-counterfeiting due to their red luminescence, small size, and biocompatibility. The developed fingerprints showed excellent contrast, high sensitivity and selectivity on various substrates. In vitro cytotoxicity studies indicated that the nanoparticles were non-toxic to normal kidney epithelial cells at the tested concentrations. Thess versatilities demonstrate the potential of engineered materials for criminal identification in forensic applications. Therefore, they play a crucial role in solving crimes and bringing justice to victims.

Automated Restarting Fast Proximal Gradient Descent Method for Single-View Cone-Beam X-ray Luminescence Computed Tomography Based on Depth Compensation.

Single-view cone-beam X-ray luminescence computed tomography (CB-XLCT) has recently gained attention as a highly promising imaging technique that allows for the efficient and rapid three-dimensional visualization of nanophosphor (NP) distributions in small animals. However, the reconstruction performance is hindered by the ill-posed nature of the inverse problem and the effects of depth variation as only a single view is acquired. To tackle this issue, we present a methodology that integrates an automated restarting strategy with depth compensation to achieve reconstruction. The present study employs a fast proximal gradient descent (FPGD) method, incorporating L0 norm regularization, to achieve efficient reconstruction with accelerated convergence. The proposed approach offers the benefit of retrieving neighboring multitarget distributions without the need for CT priors. Additionally, the automated restarting strategy ensures reliable reconstructions without the need for manual intervention. Numerical simulations and physical phantom experiments were conducted using a custom CB-XLCT system to demonstrate the accuracy of the proposed method in resolving adjacent NPs. The results showed that this method had the lowest relative error compared to other few-view techniques. This study signifies a significant progression in the development of practical single-view CB-XLCT for high-resolution 3-D biomedical imaging.

Defect Induced high-color-rendering white light emissions from Ag-doped ZnO

It is crucial to find high-quality white-light phosphors that are simple to synthesize in order to create efficient lighting. In this pursuit, the focus has been on achieving the emission of white light in ZnO and Ag-doped ZnO emerging as a promising phosphor candidate. The optimized ZnO nano phosphors demonstrated visible-light emission with ideal Commission international de I E “Eclairage frequently abbreviated as coordinates (x = 0.33, y = 0.33 ) and a correlated color temperature of 6200 K, and a color rendering index of 100 for equivalent to day white light. Furthermore, under certain ideal processing conditions, neutral white-light emission (x = 0.33, y = 0.33 at λex = 280 and 370 nm) with a Color correlated temperature (CCT) of 5500 K(approx.) was achieved. The Color Rendering Index (CRI) of the ZnO and Ag:ZnO nanoparticles exceeded 90, with high values approaching 96%, which is necessary for accurately portraying object colors in comparison to natural sunshine. The research findings revealed a decrease in the FS emission intensity with all the UV excitation when Ag doped in ZnO, which aligns well with the principles of Stern-Volmer quenching. A reduction in intensity was observed which may be due to the Ag dopant interacting with the luminescent nanoparticles and causing a reduction in their emitted light. The study successfully develops and optimizes ZnO-based nano phosphors with tailored white-light emission characteristics, presenting a promising solution for achieving energy-efficient and high-quality white-light sources for various lighting applications.

Enhancing thermometric precision: modulating the temperature of maximum sensitivity via erbium dopant addition in Ba2GdV3O11:Tm3+/Yb3+ nano phosphors

Enhancing thermometric precision: modulating the temperature of maximum sensitivity via erbium dopant addition in Ba2GdV3O11 nano phosphors: Tm3+/Yb3+.

Biocompatible luminescent Ce3+sensitized SrF2:Tb3+ anticounterfeiting and forensic fingerprint detection

Rare-earth doped alkaline fluoride nano phosphors have various applications in solid-state luminescence, displays, sensors, dental applications, biological labeling, and security ink. However, their emission intensity is generally weak, and it...

Green color emitting pure cubic zirconia nano phosphor synthesized by solution combustion technique

Green color emitting pure cubic zirconia nano phosphor synthesized by solution combustion technique

Photoluminescence upgradation of La2MgTiO6:2%Dy3+ perovskite with monovalent (Li+), divalent (Ba2+, Sr2+) and trivalent (Bi3+, Sm3+) cation sensitization

Nano phosphors of 2 % Dy3+ (wt%) doped La2MgTiO6 and monovalent/divalent/trivalent co-doped La1.98Dy0.02MgTiO6:x%Ay+ (Ay+: Li+, Ba2+, Sr2+, Bi3+, and Sm3+; 0 ≤ x ≤ 2 wt%) were synthesized by combustion method. From the XRD data, it is deduced that an increase in the valency of co-dopant increases the crystallinity of the double perovskite orthorhombic nanocrystal structure. With an increase in co-dopant size, an elevation in optical bandgap is visible with the highest bandgap of 3.835 eV for Bi3+. The photo-absorption is monotonically broadened for Sr2+, Sm3+, and Li+ around 200–450 nm. Under 351 nm, Dy3+ triggered lattice shows major characteristic emission peaks at 480 nm (4F9/2 → 6H15/2), 574 nm (4F9/2 → 6H13/2), and 670 nm (4F9/2 → 6H11/2), leading to near white light emission with CIE coordinates (0.341, 0.376). Upon co-doping, the PL intensity is significantly increased with maximum emission for trivalent Sm3+, followed by divalent Sr2+ and monovalent Li + respectively. With increasing excitation wavelength, Sr2+ shows a dominated output and it is found that divalent Sr2+ is a potential co-dopant that could enhance luminescence intensity up to 6 times with a Sr2+ → Dy3+ energy transfer efficiency of 86 %. It is specified that the CIE coordinates of Li+ co-doped samples show ideal white emission with color coordinates (0.333, 0.336). The concluding outcomes signify the noblest rare earth Sm3+ co-doping and thus Sm3+ → Dy3+ energy transfer mechanism is discussed in detail.

Investigating the influence of mono-, di-, and trivalent co-dopants (Li+, Na+, K+, Ca2+, Bi3+) on the photoluminescent properties and their prospective role in data security applications for SrAl2O4:Tb3+ nanophosphors synthesized via an eco-friendly combustion method

Nanostructured SrAl2O4:Tb3+/M (M = Li+, Na+, K+, Ca2+, Bi3+) green nanophosphors (NPs) were synthesized through an environmentally friendly combustion process, employing Areca nut (A.N) as a sustainable fuel source. Alkali metal co-dopants were introduced to optimize luminescent intensity and assess their suitability for data security applications. Photoluminescence (PL) intensity increased with rising Tb3+ concentrations (1–5 mol %) until reaching a maximum at 3 mol %, after which quenching occurred. The phenomenon of Tb3+ concentration quenching at 3 mol % was explained using the Van Uitert equation, which accounts for dipole–dipole interactions. To enhance luminescence efficiency, various metal ions, including Li+, Na+, K+, Ca2+, and Bi3+, were explored. Notably, SrAl2O4:Tb3+ (SAO:Tb3+) co-doped with Li+ ions exhibited the highest PL intensity, surpassing that of Tb3+ by a factor of 41. The estimated CIE value for green emission are x = 0.3541 and y = 0.5562. It is observed that the CIE coordinates of Tb3+ activated SAO NPs are situated in the green region. The CCT value of SAO:Tb3+/Li+ was found to be 5117 K, which is useful for cool LEDs. The Li+ doped samples proved exceptionally effective in latent fingerprints (LFPs) detection, revealing level I-III ridge features crucial for personal identification. Under NUV light, the PDMS wrapping of the SAO:Tb3+/Li+ NPs accomplished a green glow. Based on the results, SAO:Tb3+/Li+ green-emitting phosphors is a promising material for white LEDs, optical temperature sensors, and flexible display applications. This comprehensive study underscores the outstanding multifunctional potential of Li+ co-dopants among the various ions considered.

UV/ visible/ NIR sensitized enhanced green luminescence of a newly synthesized salicylic acid coated Tb3+ and Yb3+ ions doped Y2O3 nano-composite phosphor: Prospect as luminescence solar collector material

The present work describes the enhancement of green luminescence of Tb3+ ion in a newly synthesized composite material that contains Tb3+ and Yb3+ ions in Y2O3 nano-phosphor (TYY) coated with salicylic acid (SA) doped polyvinyl alcohol (PVA) polymer matrix (TYY: SA/PVA). XRD results reflect nearly 50 nm size of crystallite in TYY phosphor. On coating, the same with SA-doped PVA polymer visualizes the actual particulate size in microns due to aggregation of nano-crystallites of TYY and indicates the formation of organic/inorganic composite material. In down-conversion of UV radiation, both singlet and triplet states of excited state intra-molecular proton transfer species of SA in TYY: SA/PVA composite material transfer their UV (200 nm–370 nm) excitation energy through Fӧrster and Dexter mechanism to 5D4 state of Tb3+ ions, which enhances green luminescence of Tb3+ ions [5D4 →7F5] by nineteen-fold and decrease in the NIR luminescence intensity of Yb3+ ion [2F5/2 → 2F7/2] in TYY/SA/PVA as compared to the TYY sample indicates coating of SA/PVA polymer on the nano phosphor blocks the quantum cutting process from 4f75 d1 excited state of Tb3+ ions to 2F5/2 state of Yb3+ ions. In contrast, TYY: SA/PVA and TYY material exhibit intense green luminescent emission of Tb3+ ions by up-conversion of NIR radiation through a cooperative energy transfer between two Yb3+ ions [2F5/2 → 5D4 excitation]. A thin layer coating of composite phosphor material shows enhancement in the external quantum efficiency of the solar cell by increasing the efficiency of ∼3–5 % in the 400 nm–1000 nm range compared to the bare solar cell. I–V characteristics of the composite show that simultaneous excitation of this composite material with UV/Visible/NIR radiation increases the photon density in blue, green, and NIR regions for reabsorption by the photovoltaic cell. This preliminary study signifies the scope for developing brighter, high photon flux luminescent composite luminescent solar collecter material with low cost.