Thursday June the 19th at 11am :
Aerodynamics, aeroelasticity and acoustics Department (DAAA). Metrology, Data Assimilation and Flow Physics.
ONERA – the French Aerospace Lab. Meudon. (Paris)
Phosphors, solid materials that exhibit luminescence,[1] have been studied for a long time and have been used in various applications, particularly in lighting technologies. Among the wide variety of phosphors, here we focus on two types of phosphors : persistent luminescence and thermographic.
Firstly, persistent luminescence phosphors possess the ability to emit light continuously for an extended period following excitation cessation. They have been employed for signaling in dark environments and in toy manufacturing, among other applications. Recently, these materials have become important candidates as transducers integrated into biosensors because the autofluorescence of biological samples and the phenomena of absorption and scattering of incident radiation could be avoided, significantly improving the signal-to-noise ratio. Moreover, when these phosphors emit within the biological windows[2], where radiation has deeper tissue penetration, they can be used for in vivo imaging. Nevertheless, these materials should fulfil some basic requirements for their use in nanomedicine such as uniform nanometric particle size, homogeneous morphology, high colloidal stability in biological media and biocompatibility. Most reported persistent phosphors are synthesized via solid state reaction, resulting in powdered of heterogenous phosphors in size and shape. Actually, a significant challenge lies in developing persistent luminescence nanoparticles that meet all nanomedicine requirements while exhibiting both high and prolonged persistent emission.[3] Herein, we achieved uniform nanoparticles of four different systems (Zn2GeO4:Mn2+,[4] ZnGa2O4:Cr3+,[5] Ga2O4:Cr3+, Y3Al2Ga3O12:Ce3+, Cr3+, Nd3+ [6]) that satisfied all the conditions, by using wet chemistry synthesis and some strategies to improve their optical properties and colloidal stability. Besides, we discuss the potential of the developed particles for different nanomedical applications, including the development of a biosensor, the quantification of the cell internalization and the demonstration of optical imaging in a mouse model.
Regarding to thermographic phosphors, they possess temperature-dependent luminescence properties. In that case, following the excitation, the luminescence of the particles is detected, and the temperature measurement is derived using either the spectral intensity ratio or the lifetime. This principle of phosphor thermometry is being used for flow measurement to understand the heat transfer and/or chemical reactions,[7] when the phosphors are seeded in the flow as tracers. Herein, we discuss briefly how to get 2D high resolution thermometry and velocimetry from isolated thermographic particles and how important is the homogeneity of these particles to discriminate variations between them that could potentially conduct to error in temperature measurement.
[1]Hussain, N. et al. 1 - Introduction to phosphors and luminescence. Rare Earth-Activated Phosphors, 2022, 3-41. DOI : 10.1016/B978-0-323-89856-0.00008-0
[2]Smith, A. M. ; Mancini, M. C. ; Nie, S. Second window for in vivo imaging. Nature Nanotechnology 2009, 4 (11), 710-711. DOI : 10.1038/nnano.2009.326
[3]astaing, V. et al. Persistent luminescent nanoparticles : Challenges and opportunities for a shimmering future. J. Appl. Phys., 2021, 130, 080902. DOI : 10.1063/5.0053283
[4]Calderón-Olvera R.M., Arroyo E.* et al. Persistent Luminescence Zn2GeO4:Mn2+ Nanoparticles Functionalized with Polyacrilic Acid : One-pot Synthesis and Biosensing Applications. ACS Applied Materials and Interfaces, 2023, 15-17, 20613-20624. DOI : 10.1021/acsami.2c21735
[5]Arroyo E. et al. Persistent luminescence of transparent ZnGa2O4:Cr3+ thin films from colloidal nanoparticles of tunable size. Journal of Materials Chemistry C, 2021, 9, 4474-4485. DOI : 10.1039/d1tc00258a
[6]Arroyo E. et al. Highly uniform Y3Al2Ga3O12-based nanophosphors for persistent luminescence bioimaging in the visible and NIR regions. Inorganic Chemistry Frontiers, 2022, 9, 2452-2461. DOI : 10.1039/D2QI00480A
[7]Abram C., Fond B., Beyrau F. Temperature measurement techniques for gas and liquid flows using thermographic phosphor tracer particles. Progress in Energy and Combustion Science, 2018, 64, 93-156. DOI : 10.1016/j.pecs.2017.09.001