Strontium Aluminate Phosphors Research Articles

Visible characteristics and durability assessment of methyl methacrylate-based luminescent road marking using unencapsulated SrAl2O4: Eu2+, Dy3+ under coupling service conditions

Luminescent road markings (LRMs) have attracted growing attention due to the enhanced road visibility in low-light conditions and energy-saving benefits. However, high-performance strontium aluminate phosphors (SrAl2O4: Eu2+, Dy3+) are prone to hydrolyze while the conventional encapsulation methods of phosphors produces luminance loss. This paper presented a novel perspective using methyl methacrylate (MMA)-based two-component resins with unencapsulated phosphor (UP) to prepare LRMs with balanced luminescent properties road durability. Luminescent properties, skid resistance, impact resistance, and abrasion rate were evaluated as the response value to optimize the formulations through design of experimental (DOE) methods. The results show that LRMs exhibit outstanding water resistance and abrasion resistance after soaking for 120 hours coupling with wet-wheel abrasion for 20 minutes due to effective bonding between the carboxylic acid-based resin and phosphors. The luminance loss is less than 5 % after undergoing three-wheel abrasion following 480 hours of ultraviolet aging. Furthermore, the macroscopic performance was integrated with microscopic properties through morphological, elemental, and functional group analysis. The results demonstrated that the addition of plasticizer balanced the relationship among the mechanical properties by transforming the curing structure of the coating from resin-encapsulated granular protrusions into layer-like structures.

Mechanoluminescence and Optically Stimulated Anti-Stokes Luminescence of Composites Based on Epoxy Resin and Strontium Aluminate Phosphors SrAl2O4:Eu2+, Dy3+ and Sr4Al14O25:Eu2+, Dy3+

Mechanoluminescence and Optically Stimulated Anti-Stokes Luminescence of Composites Based on Epoxy Resin and Strontium Aluminate Phosphors SrAl2O4:Eu2+, Dy3+ and Sr4Al14O25:Eu2+, Dy3+

Improving flow dynamics and storage longevity of a low-cost phosphorescent fingerprint powder.

An inexpensive, commercially available doped strontium aluminate phosphor with long-lived afterglow was prepared as a luminescent fingerprint dusting powder suited for challenging, highly patterned substrates; however, prolonged exposure to humidity was found to reduce that powder's affinity for fingermarks. Here, an enhanced preparation for synthesizing that fingerprint dusting powder is presented that prevents powder aggregation and loss of function upon exposure to humid environments. This was achieved by introducing a flow regulator during synthesis: hydrophobic silica SIPERNAT® D10 or SIPERNAT® D17. Increasing the hydrophobicity of the powder prevents aggregation by inhibiting the uptake of water, thereby improving the material's flow dynamics and transfer behavior from brush to fingermark. The angle of repose and flow characteristics made by the modified powders were quantified, with excellent affinity for fingermarks observed, even after being stored under 85% (±5%) humidity for 4 weeks. A preliminary comparison of the performance of the modified hydrophobic powders relative to the unmodified precursor revealed that more of the SIPERNAT® treated powder typically adhered to fingermarks while simultaneously imparting less background development. In addition, fewer clumps of particulate were observed in the developed fingermarks after addition of a hydrophobic flow regulator. This technical report outlines the updated method for synthesizing the fingerprint powder, with summarized flow performance results, and a demonstration of the modified powder's affinity for simulated fingermark evidence.

Impact of Dy3+ and Ce3+ ion doping on the photoluminescence, thermoluminescence, and electrochemical properties of strontium aluminate (SrAl2O4) and barium aluminate (BaAl2O4) phosphors

Impact of Dy3+ and Ce3+ ion doping on the photoluminescence, thermoluminescence, and electrochemical properties of strontium aluminate (SrAl2O4) and barium aluminate (BaAl2O4) phosphors

Photoluminescent polypropylene nanofiber-supported polyethylene terephthalate integrated with strontium aluminate phosphor

In order to develop photochromic materials with persistent afterglow emission, such as concrete and smart windows, electrospun polypropylene nanofibers (PPNF) were incorporated into polyethylene terephthalate (PET) for reinforcement. Nanoparticles of lanthanide-activated strontium aluminum oxide (NLSA) were physically embedded into polyethylene terephthalate films to produce transparent PPNF@PET smart membranes. Electrospinning was utilized to create PPNF, which were subsequently included as a roughening agent into PET membranes. The green coloration detected upon exposing the PPNF@PET film to ultraviolet light was verified by CIE Lab coordinates and photoluminescence analysis. The PPNF@PET hybrids with low quantities of NLSA were found to immediately reverse this emission activity after removing the ultraviolet source, which suggest fluorescence emission. Afterglow photoluminescence was detected at higher phosphor concentrations in PPNF@PET by slow reversibility of the light emission, which suggests glow in the dark emission. After 365 nm of excitation, a 517 nm emission band could be monitored from the PPNF@PET hybrids. The chemical structure and morphology of LSA nanoparticles and PPNF were studied, showing diameters of 80–120 nm and 75–180 nm, respectively. Different analysis methods were employed to examine the morphologies of PPNF@PET membranes. As compared to a NLSA-free polyethylene terephthalate control sample, the PPNF@PET smart membranes demonstrated improved scratch resistance. The hydrophobicity and UV resistance of the PPNF@PET smart membranes were improved with an increase in the concentration of NLSA.

Preparation of photoresponsive lanthanide aluminate-immobilized nanofibers from recycled bioplastic via solution blowing spinning for optical authentication labeling

Photochromism is an intriguing technology to enhance the authentication of various commercial materials. In order to produce a transparent authentication film, it is also significant to improve the engineering process of anti-counterfeiting materials. In contrast to electrospinning, the solution blowing spinning (SBS) technique has been recently developed to produce nanofibers at low-cost and high yield with no need to apply high voltage. It has been essential to reduce the toxic pollution caused by plastic waste. Herein, we develop a photoluminescent nanofibrous membrane from recycled polylactic acid (PLA) waste and nanoparticles of strontium aluminate (NSA) by using the simple SBS technique. We investigated the potential use of the NSA@PLA composite nanofibers for photochromic anti-counterfeiting driven by ultraviolet light. Encapsulating the nanoparticle form of the strontium aluminate phosphor into polylactic acid nanofibers is necessary to ensure the transparent characteristic of the nanofibrous film. The film transparency can be further improved by the efficient dispersion of NSA without aggregation in the polylactic acid solution. Nanofibrous membranes with varying emission characteristics were produced by varying the NSA ratio. Both of X-ray diffraction (XRD) and Transmission electron microscopy (TEM) demonstrated the morphology of NSA to show diameters of 5–12 nm. The morphologies of the nanofibrous membranes were examined using various analytical methods, including energy-dispersive X-ray spectroscopy (EDX), X-ray fluorescence spectroscopy (XRF) and scanning electron microscopy (SEM). The mechanical characteristics and optical luminescence were also examined. SEM analysis of the NSA@PLA nanofibers showed diameters of 100–220 nm. The NSA@PLA nanofibrous membranes exhibited an emission peak at 518 nm upon excitation at 365 nm. The contact angles of the NSA@PLA nanofibrous membranes increased from 138.2° to 144.5° as the NSA concentration was increased, indicating an improved superhydrophobicity. Exposure to ultraviolet light caused the transparent nanofibers to undergo a rapid and strongly reversible photochromism to greenish emission. The present study can be reported as an easy and efficient approach to create anti-counterfeiting materials that offer a perfect market with social and financial profits.

Mechano-luminescence of Eu2+, Dy3+ co-doped strontium aluminate phosphors with the substitution of calcium ions

Mechano-luminescent material can emit light under various external mechanical forces such as pressure, friction, impact and ultrasound. Elastic-luminescent materials have the property that the light signal increases linearly with the increase in stress and has been widely applied. A series of strontium aluminate/strontium calcium samples doped together with europium and dysprosium have been prepared by a high-temperature solid-state method. The effect of strontium/calcium ratio on the crystal structure and luminescence property of the samples have been systematically studied. With the increase of Ca substitution, the crystal field environment around divalent europium ions varies which leads to the changes of the emission peaks. The color presented from samples was tuned from green to blue which offers the possibility of color regulation of mechano-luminescence. Among these samples, the elastic-luminescence of the sample Sr0.8Ca0.2Al2O4: Eu2+, Dy3+ shows an excellent performance as the signal increases linearly with the applied pressure, so it has the potential to be used as a pressure sensor.

Reviewing the Bio-Applications of SrAl2O4:Eu2+, Dy3+ Phosphor

Strontium aluminate (SrAl2O4) phosphor nanoparticles with Eu2+, and Dy3+ co-doping exhibit high brightness and long afterglow properties, storing light energy and glowing slowly under different conditions. It has been widely studied that SrAl2O4:Eu2+, Dy3+ (SAO) phosphor nanoparticles with a green visible emission can penetrate deep into the tissue, show low self-fluorescence, cause minimal light damage, and are biocompatible. SAO phosphor nanoparticle synthesis and modification mechanisms are outlined in this review. Biological therapies, in addition to the detection of substances in organisms, are provided by these excellent priorities. Despite the existing research, it has been demonstrated that nanostructures of SAO luminescence particles have great potential to be applied to tissue engineering and drug delivery systems. The current scientific achievements can provide a reference for research in the areas mentioned above, as well as stimulate biomedical disciplines to pay attention to SAO luminescence nanoparticles.

Brighten strontium aluminate long-persistence materials via optimizing defect energy level distribution

Afterglow brightness of inorganic persistent luminescent (PersL) materials upon ceasing light excitation represents an important parameter for various glow-in-the-dark applications. Although the emission wavelength of PersL materials is developed to cover over the whole spectral range from ultraviolet to near infrared light, and light emission is sufficiently long-lasting with a fractional number of rare-earth doped PersL materials commercially available, PersL materials with high initial afterglow brightness at room-temperature condition remain rarely reported. Employing trap-controlled temperature dependency of persistent luminescence mechanism, defect energy level distribution, and microwave-assisted solid-state reaction, here a highly bright green-emitting strontium aluminate phosphor is reported. Higher initial afterglow brightness (a photometric luminance of 99.8 cd/m2, enhanced 1.7 times than that of the commercial one) is achieved due to the massive aggregation of charge carriers at shallow-trap energy levels. The relation between initial afterglow brightness and trap energy level distribution is investigated. The glowing-in-the-dark composite panel composed of Sr4Al14O25:Eu2+, Dy3+ and Polydimethylsiloxane can light up the safety sign and the map of fire evacuation route. These findings may provide a major step forward to developing high-brightness PersL materials and are expected to further benefit a wide range of PersL material systems for practical glow-in-the-dark applications.

Snap-through Crack Propagation in Architected Bonded Interfaces Analyzed Using a Mechanoluminescent SAO/E Coating.

We investigate the mechanics of crack propagation in architected adhesive joints whose adherends are inspired to the base plate of the barnacle Amphibalanus (=Balanus) amphitrite, and feature an array of buried hollow cylindrical channels located perpendicularly to the direction of crack growth. Selective laser sintering is used to obtain the adherends that are subsequently bonded in the double cantilever beam configuration to ascertain the mechanics of crack growth. Finite element (FE) simulations are deployed to determine the strain energy release rate (ERR) and to elucidate the salient features of the fracture process. It is shown that the channels induce a modulation of the ERR and enable a crack tip shielding mechanism. Besides, FE simulations based on a cohesive zone approach indicate the occurrence of crack pinning/depinning cycles that are validated via experiments. A highlight of the present study is the use of a mechanoluminescent (ML) coating to unravel the evolution of the transient stress field in the crack tip region. The coating comprises an optical epoxy resin loaded with doped strontium aluminate phosphors (SrAl2O4/Eu2+) and converts mechanical energy into light emission with intensity proportional to the magnitude of mechanical stress. By combining the ML emission patterns with the stress distribution obtained from FEA, we unveil interesting details of snap-through cracking in architected bio-inspired adhesive joints.

Tunable luminescence and electrical properties of cerium doped strontium aluminate (SrAl2O4:Ce3+) phosphors for white LED applications

In new research growth long after glow material is a potential candidate due to its physical properties, chemical stability and wide application in modern solid-state lightning (LED), display devices, dosimetry and sensors. A cerium doped strontium aluminate phosphor (SrAl2O4:Ce3+) was synthesized by conventional solid-state reaction method. The crystal structure and morphology of phosphors, while doping rare earth metal and lithium metal ion was investigated by using X-ray diffraction, Raman spectroscopy and field emission scanning electron microscopy. Fourier transformed infrared spectrum results of the synthesized phosphor composition conforms the characteristic vibration bands of synthesized phosphor. Surface composition analysis of the prepared samples was examined using X-ray photoelectron spectroscopy. Photoluminescence emission band observed at ∼420 nm, ∼490 nm and ∼610 nm region under the excitation wavelength of 256 nm. Wight light emission was confirmed using the Commission Internationale de L'Eclairage (CIE) chromatic coordinate graph. The correlated colour temperature (CCT) value of 0.5% Ce3+ doped SAO of phosphors was calculated is in the range of 1543 K, which is indicated the synthesized phosphors performance as warm white light source. The obtained phosphor has a high dielectric constant and low loss tangent which is useful to optoelectronic devices.

Preparation of a low-cost fingerprint powder that harnesses white light to emit long-lived phosphorescence

An inexpensive, commercially available doped strontium aluminate phosphor with long-lived afterglow has been prepared and assessed in the role of a luminescent fingerprint dusting powder. Blue, green, and aqua phosphorescence persisting for ca. 30 s was obtainable from treated fingermarks after charging the powders with the white light (400–700 nm) setting of a forensic light source. Imaging the phosphorescent afterglow enabled the elimination of background emissions encountered during latent fingermark examination. This was demonstrated by visualising fingermarks on substrates that possess inbuilt fluorescent security features and highly patterned substrate backgrounds, without any need for bespoke scientific equipment.

Immobilization of Strontium Aluminate into Recycled Polycarbonate Plastics towards an Afterglow and Photochromic Smart Window.

A transparent smart window made of recycled polycarbonate plastic (PCP) waste was prepared and immobilized with strontium aluminate phosphor nanoparticles (SAPN). It has afterglow emission, super-hydrophobicity, durability, photostability, good mechanical properties, ultraviolet protection, and high optical transmittance. To create an afterglow emission polycarbonate smart window (SAPN@PCP), recycled polycarbonate waste was integrated with various concentrations of SAPN (15-52 nm). SAP micro-scale powder was made using the solid-state high temperature method. The SAP nanoparticles were produced using the top-down method. To create a colorless plastic bulk, recycled polycarbonate waste was inserted into a hot bath. This colorless plastic was thoroughly combined with SAPN and cast to create an afterglow luminous smart window. To investigate its photoluminescence properties, spectrum profiles of excitation and emission were measured. According to the luminescence parameters, the phosphorescent colorless polycarbonate plates displayed a change in color to strong green under UV illumination and greenish-yellow in a dark box. The afterglow polycarbonate smart window displayed two emission peaks at 496 and 526 nm, and an absorption wavelength of 373 nm. Upon increasing the SAPN ratio, the hydrophobic activity, hardness, photostability, and UV protection were improved. Luminescent polycarbonate substrates with lower SAPN ratio demonstrated rapid and reversible fluorescence under UV light, while the higher SAPN content in the luminous polycarbonate substrates showed afterglow.

Investigation of Atomic Layer Deposition Post-Coating Properties of Phosphorescent SrAl2O4: Eu2+, Dy3+ Fibers Produced By Electrospinning

In this research, phosphorescent SrAl2O4:Eu2+, Dy3+ fibers were produced by electrospinning and coated with atomic layer deposition (ALD) technique to enhance the photoluminescence (PL) properties, and water & thermal resistance. Particle form of Eu2+-activated strontium aluminate phosphors possess many remarkable features that have been reported over and over, for example, nontoxic, stable, efficient. PL enhancement and stability in water of these particles were provided by nano encapsulation process by ALD that has just been published in our previous paper. In this study, for the first time, SrAl2O4 based long persistence phosphor fibers were coated with the ALD method to both improve their PL and provide water & thermal resistance property. In this successfully carried out study, luminescence, optic, chemical and structural properties of phosphor in fiber form were investigated in detail. These improved submicron afterglow fibers which are SrAl2O4:Eu2+, Dy3+ based are promising materials for applications such as solar cells, luminescent labels for bioimaging, mechanoluminescence sensor, etc.

Preparation of flame-retardant, hydrophobic, ultraviolet protective, and luminescent transparent wood.

Transparent wood with multifunctional properties has recently attracted more attention as an efficient building product. Here, we describe the development of transparent wood with long-persistent phosphorescence, tough surface, high durability, photostability, and reversibility without fatigue, and with ultraviolet shielding, superhydrophobicity, and flame-retardant activity. This long-persistent phosphorescent, or glow-in-the-dark, smart wood exhibited an ability to continue emitting light for prolonged periods of time. The photoluminescent translucent wooden substrate was prepared by immobilizing lignin-modulated wooden bulk with an admixture of methylmethacrylate (MMA), ammonium polyphosphate (APP), and lanthanide-doped strontium aluminate (LSA; SrAl2 O4 :Eu2+ ,Dy3+ ) phosphor nanoparticles. The photoluminescent transparent wood displayed a colour switch from colourless to bright white beneath ultraviolet (UV) light and greenish-yellow in the dark as reported by Commission Internationale de l'Éclairage laboratory colorimetric space coordinates. The generated phosphorescent wooden substrates demonstrated an absorbance band at 365 nm and an emission band at 516 nm. The phosphorescent transparent wood was improved flame-retardant properties, ultraviolet shielding, and superhydrophobic properties, as well as a reversible long-persistent phosphorescent responsiveness to UV light without fatigue. The current approach demonstrated a potential large-scale production strategy for multifunctional transparent wooden substrates for a range of applications such as smart windows, gentle indoor and outdoor lighting, and safety directional signs in buildings.

Photocatalytic Reaction Properties of TiO₂-Supported on the Long Lasting Phosphor: Sr₄Al14O25:Eu2+,Dy3.

The TiO₂/Sr4Al14O25:Eu2+,Dy3+ photocatalytic composite was prepared by depositing the nano-crystalline titanium dioxide layer on the long-lasting phosphor substrate of strontium aluminate, using a low-pressure chemical vapor deposition (LP-CVD). The photocatalysis characteristic was studied by examining the photodegradation of benzene (C6H6) gas under UV, visible light illumination, and in the darkness. The photocatalytic composite of TiO₂-deposited Sr₄Al14O25:Eu2+,Dy3+ showed an active photocatalytic reactivity under UV-light as well as visible-light illumination. The mechanism of the photocatalysis reaction for the TiO₂-deposited strontium aluminate phosphor composite was interpreted in point of the energy band structure and phosphorescent emission. The coupling of nanocrystalline TiO₂ with the strontium aluminate phosphor might result in an energy band bending at the interface of TiO₂/Sr₄Al14O25:Eu2+,Dy3+, making the titanium dioxide at the junction to be photo-reactive even in a visible wavelength region. In addition, the depth profile of Auger electron spectroscopy (AES) confirmed a possible formation of oxygen vacancies at the interface between TiO₂ and Sr₄Al14O25:Eu2+,Dy3+. Then, oxygen defects create extra electrons which may excited subsequently to the conduction band and participate in a photocatalytic reaction, resulting in an enhancement of the photodecomposition of benzene. The LP-CVD TiO₂-strontium aluminate phosphor was also photoactive in the darkness because of light emission from the long lasting phosphor. Also, the TiO₂-deposited Sr₄Al14O25:Eu2+,Dy3+ long lasting phosphor was analyzed by a XRD (X-ray diffraction), TEM (transmission electron microscopy), UV/visible spectroscopy and AES.

Bright yellow-emitting long persistent luminescence from Mn2+-activated strontium aluminate phosphor

We developed bright yellow-emitting long persistent luminescence (LPL) materials Sr4Al14O25:Mn2+ and Sr4Al14O25:Mn2+,N (N = Zr4+, Ho3+, Er3+) by high temperature solid–state reaction. The addition of Zr4+, Ho3+ and Er3+ can regulate trap distributions and improve energy storage ability of the materials. The LPL performance of SAO:Mn2+,Ho3+ is optimal, considering LPL intensity and duration time. Bright LPL of SAO:Mn2+,Ho3+ can be observed for 3 h by naked eyes in dark after removing the excitation source. Profiles of LPL spectra are different from those of PL, because the two types of Mn2+ centers do not play equal parts in LPL and photoluminescence (PL). Trap depths of TL peaks centered at 354 K (peak 1) and 455 K (peak 2) are 0.60 and 0.72 eV, respectively. And peak 1 at 354 K is the effective TL peak responsible for LPL. In SAO:Mn2+,Ho3+,Mn2+ ions doped in Al3+ sites serve as emitting centers, and positively charged HoSr· defects are the main effective trap centers. Finally, a feasible LPL mechanism of SAO:Mn2+,Ho3+ was proposed to clarify the generation process of LPL.

Application of Green Solvents for Rare Earth Element Recovery from Aluminate Phosphors

Two processes applying green solvents for recovering rare earth elements (REEs) from different types of aluminate phosphors are demonstrated in this report. For magnesium aluminate-type phosphors, a pretreatment with peroxide calcination was implemented first, and then followed by a supercritical fluid extraction (SFE) process. Supercritical carbon dioxide (sc-CO2) provides an effective and green medium for extracting REEs from dry materials. With the addition of a complex agent, tri-n-butyl phosphate-nitric acid complex, highly efficient and selective extraction of REEs using supercritical carbon dioxide can be achieved. The highest extraction efficiency was 92% for europium from the europium doped barium magnesium aluminate phosphor (BAM), whereas the highest extraction selectivity was more than 99% for the REEs combined from the trichromatic phosphor. On the other hand, for strontium aluminate type phosphors, a direct acid leaching process is suggested. It was found out that acetic acid, which is considerably green, could have high recovery rate for dysprosium (>99%) and europium (~83%) from this strontium aluminate phosphor materials. Nevertheless, both green processes showed promising results and could have high potential for industrial applications.

Mechanoluminescence behaviour on Eu2+/Dy3+ activated SrAl2O4 phosphor

Synthesis of Eu/Dy rare earth doped strontium aluminate phosphor or material with varying concentration of co-dopant (Dy3+) and fixed concentration of dopant (Eu2+) is reported inside the manuscript. Phosphor are prepared and synthesized by using the technique of solid-state reaction in reducing atmosphere and activated charcoal was used to create the atmosphere. Mechanoluminescence pattern were recorded for variable concentration of doping / co-doping ions and it is found with the increment in the concentration of co-dopant up-to 1 mol%, the ML intensity increases and after that the ML intensity decrement occurs due to the phenomenon of concentration quenching. Similarly, for the optimized concentration the ML pattern obtained for gamma – irradiated phosphor and it shows linear response with dose so our study supports the ML dosimeter application to detect the radiation via mechanoluminescence study. The suitable models are compared herein, which are already reported by so many authors.

MN and DY doped strontium aluminate’soptical properties- a comparative study

Through sol gel method Mn and Dy doped Strontium aluminate phosphors prepared. The prepared phosphors has been characterized by Powder X-ray diffraction, Scanning electron microscope. Optical properties were carried out by photoluminescence analysis. Photoluminescence studies of the prepared phosphors showed prominent IR emission, green emission and UV emission. To investigate the reaction that took place in the process of sample preparation, simultaneous TG–DSC testing was conducted from room temperature to 1000˚C.