Thanks to a temporary storage of optical energy at defects, persistent phosphors, i.e. transition metal- or rare earth- doped materials, feature unique long-lasting luminescence. Apart from their current industrial development as micro sized powders dispersed in polymers for design and night signalization, persistent phosphors rise interest for nanotechnologies as high-security-level labelling. However, their relatively low storage capacity combined to the difficulty to finely tune their properties hurdle their development. In this regard, processing persistent phosphors as low scattering coatings offers tremendous opportunities: in addition to facilitating energy storage, transparency allows playing with devised photonics architectures to unprecedently boost persistent properties.
This Conference Presentation, “Nanophosphor-based photonic architectures for efficient light conversion,” was recorded at Photonics Europe 2022 held in Strasbourg, France.
SrAl2O4: Eu2+, Dy3+ nanoparticles prepared by pulsed laser ablation in liquids (PLAL) could be a green and versatile technique to obtain inorganic nanoparticles with persistent luminescence and different morphologies and sizes. Laser ablation technique could deliver large amounts of energy highly concentrated into one point of a material and has been carried out in vacuum, in air and in liquids. Because of the unique confinement effect from liquid environment, there is many advantages when the laser ablation occurs in liquid. In this paper, we focus on the control of the size through proper laser parameters, choice of the reaction solution. Persistent luminescent SrAl2O4: Eu2+, Dy3+ phosphor was obtained by laser ablation in liquids.
Rare earth doped aluminates, such as SrAl2O4:Eu2+,Dy3+ and CaAl2O4:Eu2+,Nd3+ , are among the best known materials for persistent luminescence or afterglow emission. Their Eu2+ counterparts, which were beforehand finely studied, also exhibit long lasting luminescence properties. It recently appeared that the hexagonal polymorph of SrAl2O4, which is not stable at room temperature, could have promising luminescent properties. A recently efficient way to elaborate the hexagonal Sr1-x/2Al1-xSixO4:Eu2+, with interesting photoluminescence properties, has been developed by full glass crystallization. Still, the persistent luminescence properties of this strontium aluminosilicate compound have never been reported. Here, advanced optical properties such as persistent luminescence emission, persistent luminescence decay and thermoluminescence have been performed in order to report about the persistent luminescence potential of the strontium aluminosilicate hexagonal polymorph.
Persistent luminescence materials present many applications including security lighting and bio-imaging. Many progresses have been made in the elaboration of persistent luminescent nanoparticles suitable for the first NIR partial transparency window (650 - 950 nm). Moving to the second and third near-infrared partial transparency windows (1000 nm - 1800 nm) allows further reducing of scattering, absorption and tissue autofluorescence effects. In this work, we present the synthesis of Co2+ and Ni2+ doped zinc-gallate nanoparticles with broad emission covering the NIR-II range. Site occupancy, energy levels, optical features and persistent phenomena are presented.
ZnGa2O4:Cr3+ is an optical material well known for its deep red persistent luminescence properties which are centered in the first biological window. In this work, Yb3+, Cr3+ co-doped zinc gallate oxide has been prepared in the form of glass-ceramics. The studied samples have been elaborated via conventional melt quenching process leading to nanometer scale phase separated glass which was subsequently crystallized to obtain nanocrystals embedded in a transparent glass matrix. In these as-prepared ZnGa2O4:Cr3+,Yb3+ glass-ceramics, regular Cr3+ emission (at around 695 nm) as well as Yb3+ emission (between 950 and 1100 nm) is observed. Several photoluminescence emission and excitation experiments have been recorded in order clarify (i) the simultaneous emission of these cations in different optical windows and (ii) the energy transfer process between these two emitting centers. Further studies proved that Yb3+ is not only active in photoluminescence but also in persistent luminescence, leading to a material demonstrating persistent luminescence properties in both first and second biological windows (650-950 and 1000-1350 nm respectively). Thermoluminescence experiments have been carried out on these materials in order to gain deeper information about the persistent luminescence process.
Given the increasing demand for optical in vivo bioimaging materials, persistent luminescence in the red/near infrared range is receiving particular attention. Within this work, several elaboration ways of ZnGa2O4:Cr3+, respectively by solid state, by microwave assisted hydrothermal synthesis and by glass crystallization have been carried out. Structural analysis shows that all methods lead to pure spinel structure. Powder micrometric material is obtained by solid state reaction while nanoparticles are obtained by the two other methods. In the case of the glass-ceramics process, the nanocrystals obtained are trapped in a glassy matrix. This kind of elaboration leads to nanoparticles with lower amount of defects, no surface contact with air and an increase signal of the persistent luminescence compared to disperse nanoparticles. These good persistent luminescence properties are well correlated to thermoluminescence glow curves analysis. Moreover, such glass ceramics can be used as a good tool to study more deeply the persistent luminescence process of nanoparticles in a transparent environment and samples are easier to characterize.
The development of materials showing efficient red-emitting persistent luminescence is still an ongoing challenge. As it shows red emission, around 613 nm, Pr3+ remains a good candidate for such application. Indeed, the transition from its 1D2 excited state to its 3H4 ground state is responsible of the red emission. In this paper the effect of Na substitution in NaNbO3:Pr3+ by K or Li cations in term of Metal-to-Metal Charge Transfer (MMCT) band position and its possible effect on persistent luminescence properties were investigated. MMCT energy shows increasing tendency with increasing average distance between A site (A = Li, Na, K, Pr) of perovskite. The most intense (efficient) photoluminescence was observed under MMCT excitation in Li0.03Na0.97NbO3:Pr3+. The relaxation pathways were discussed based on the configurational coordinate model.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.