Temperature Dependence of Water Absorption in the Biological Windows and Its Impact on the Performance of Ag2S Luminescent Nanothermometers

The application of nanoparticles in the biological context generally requires their dispersion in aqueous media. In this sense, luminescent nanoparticles are an excellent choice for minimally invasive imaging and local temperature sensing (nanothermometry). For these applications, nanoparticles must operate in the physiological temperature range (25–50 °C) but also in the nearinfrared spectral range (750–1800 nm), which comprises the three biological windows of maximal tissue transparency to photons. In this range, water displays several absorption bands that can strongly affect the optical properties of the nanoparticles. Therefore, a full understanding of the temperature dependence of water absorption in biological windows is of paramount importance for applications based on these optical properties. Herein, the absorption spectrum of water in the biological windows over the 25–65 °C temperature range is systematically analyzed, and its temperature dependence considering the coexistence of two states of water is interpreted. Additionally, to illustrate the importance of state-of-the-art applications, the effects of the absorption of water on the emission spectrum of Ag2S nanoparticles, the most sensitive luminescent nanothermometers for in vivo applications to date, are presented. The spectral shape of the nanoparticles’ emission is drastically affected by the water absorption, impacting their thermometric performanceThis work was financed by the Spanish Ministerio de Ciencia e Innovación under project PID2019-106211RB-I00, by the Instituto de Salud Carlos III (PI19/00565), by the Comunidad Autónoma de Madrid (S2017/BMD3867 RENIM-CM) and co-financed by the European structural and investment fund. Additional funding was provided by the European Union Horizon 2020 FETOpen project NanoTBTech (801305), the Fundación para la Investigación Biomédica del Hospital Universitario Ramón y Cajal project IMP21_A4 (2021/0427), and by COST action CA17140. A.B. acknowledges funding support through the TALENTO 2019T1/IND14014 contract (Comunidad Autónoma de Madrid). F.E.M. and L.D.C. acknowledge the financial support received from the project Shape of Water (PTDC/NAN-PRO/3881/2020) through Portuguese fund

Highly Nonstoichiometric YAG Ceramics with Modified Luminescence Properties

Y3Al5O12 (YAG) is a widely used phosphor host. Its optical properties are controlled by chemical substitution at its YO8 or AlO6/AlO4 sublattices, with emission wavelengths defined by rare-earth and transition-metal dopants that have been explored extensively. Nonstoichiometric compositions Y3+xAl5-xO12 (x ≠ 0) may offer a route to new emission wavelengths by distributing dopants over two or more sublattices simultaneously, producing new local coordination environments for the activator ions. However, YAG typically behaves as a line phase, and such compositions are therefore challenging to synthesize. Here, a series of highly nonstoichiometric Y3+xAl5-xO12 with 0 ≤ x ≤ 0.40 is reported, corresponding to ≤20% of the AlO6 sublattice substituted by Y3+, synthesized by advanced melt-quenching techniques. This impacts the up-conversion luminescence of Yb3+/Er3+-doped systems, whose yellow-green emission differs from the red-orange emission of their stoichiometric counterparts. In contrast, the YAG:Ce3+ system has a different structural response to nonstoichiometry and its down-conversion emission is only weakly affected. Analogous highly nonstoichiometric systems should be obtainable for a range of garnet materials, demonstrated here by the synthesis of Gd3.2Al4.8O12 and Gd3.2Ga4.8O12. This opens pathways to property tuning by control of host stoichiometry, and the prospect of improved performance or new applications for garnet-type materials.Financial support was provided by the ANR-18-CE08-0012 PERSIST and ANR-20-CE08-0007 CAPRE projects of the French National Research Agency (ANR) and the CNRS, the I+D+I Grants PID2021-122328OB-100 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. PhD studentships for WC and XF were financed by the Chinese Scholarship Council (project numbers 201808450100 and 202008450026). Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. EXAFS beamtime was provided by the SOLEIL synchrotron (Gif-sur-Yvette, France) under project 99210047. The project benefitted from the microscopy facilities of the Platform MACLE-CVL which was co-funded by the European Union and Centre-Val de Loire Region (FEDER).Peer reviewe

Recherche de nouvelles couleurs et morphologies dans les matériaux à luminescence persistante

Persistant luminescence is the property of some materials to store energy of light (basically UV). This energy is stored as electrons and (or) holes traped by defects. This materials may also be able to give back this energy as visible light or near infrared during some hours. The mecanism involved in this phenomena is still poorly understood. The aim of this PhD project is to clarify this mecanism by studying diferent kinds of persistant luminescence materials and to try this property in a new application field: outdoor applications (sunlight charging) or to able this materials to be excited by non-containing UV lamps (white LEDs). Therefore, it's necessary to learn more about the "charging" process. The PhD student will study to kinds of matrix: i) Transparent ceramics in which nanocristals of persistant luminescence materials will be precipitated. Excitation, trapping and emission phenomena will be studied by optical spectroscopies and EPR after optical excitation. This work will be done at the IRCP in collaboration with Didier Gourier's group (IRCP) and Mathieu Allix (CEMHTI, Orléans). ii) Persistant cristals. Here the student will show and caracterise this phenomena on diferent monocristals in order to get persistant cristals that emit in a wide range of colors. In both cases, the mecanism will be studied from the bulk material to nanoparticles.La luminescence persistante est la propriété qu’ont certains matériaux de stocker une énergie lumineuse incidente (généralement UV) sous forme d’électrons et (ou) de trous électroniques piégés par des défauts, et de restituer cette énergie sous forme de lumière visible ou proche infra-rouge pendant plusieurs heures. Le mécanisme à l’origine de ce phénomène est cependant toujours mal compris. Le projet de cette thèse a pour objectif d’élucider ce mécanisme en étudiant différents types de matériaux à luminescence persistante et de profiter de cette propriété dans un nouveau champ d’activités : les applications extérieures (lors d’une charge par le soleil par exemple), ou le passage aux nouvelles lampes d’éclairage ne contenant plus d’UV (LED blanches). Le doctorant étudiera deux types de matrices : i) Des céramiques transparentes dans lesquelles sont précipitées des nanoparticules de matériaux à luminescence persistante. Il sera ainsi possible d’étudier les phénomènes (excitation, piégeage, émission) en excitant optiquement (sous rayonnement visible) en suivant in situ l’évolution des spectres en spectrométries RPE et optiques. Cette partie du travail de thèse sera effectué à l’IRCP à Paris en collaboration avec le groupe de Didier Gourier (IRCP), et en collaboration avec le CEMHTI d’Orléans (Mathieu Allix). ii) Des cristaux persistants. Dans ce cas il s’agit de mettre en évidence et de caractériser ce phénomène sur différents monocristaux afin de disposer de cristaux persistants dans une large gamme de couleur. Dans les deux cas, le mécanisme sera étudié dans une approche multi-échelle allant du matériau massif aux nanoparticules

Research of new colours and morphologies in persistent luminescence materials

La luminescence persistante est la propriété qu’ont certains matériaux de stocker une énergie lumineuse incidente (généralement UV) sous forme d’électrons et (ou) de trous électroniques piégés par des défauts, et de restituer cette énergie sous forme de lumière visible ou proche infra-rouge pendant plusieurs heures. Le mécanisme à l’origine de ce phénomène est cependant toujours mal compris. Le projet de cette thèse a pour objectif d’élucider ce mécanisme en étudiant différents types de matériaux à luminescence persistante et de profiter de cette propriété dans un nouveau champ d’activités : les applications extérieures (lors d’une charge par le soleil par exemple), ou le passage aux nouvelles lampes d’éclairage ne contenant plus d’UV (LED blanches). Le doctorant étudiera deux types de matrices : i) Des céramiques transparentes dans lesquelles sont précipitées des nanoparticules de matériaux à luminescence persistante. Il sera ainsi possible d’étudier les phénomènes (excitation, piégeage, émission) en excitant optiquement (sous rayonnement visible) en suivant in situ l’évolution des spectres en spectrométries RPE et optiques. Cette partie du travail de thèse sera effectué à l’IRCP à Paris en collaboration avec le groupe de Didier Gourier (IRCP), et en collaboration avec le CEMHTI d’Orléans (Mathieu Allix). ii) Des cristaux persistants. Dans ce cas il s’agit de mettre en évidence et de caractériser ce phénomène sur différents monocristaux afin de disposer de cristaux persistants dans une large gamme de couleur. Dans les deux cas, le mécanisme sera étudié dans une approche multi-échelle allant du matériau massif aux nanoparticules.Persistant luminescence is the property of some materials to store energy of light (basically UV). This energy is stored as electrons and (or) holes traped by defects. This materials may also be able to give back this energy as visible light or near infrared during some hours. The mecanism involved in this phenomena is still poorly understood. The aim of this PhD project is to clarify this mecanism by studying diferent kinds of persistant luminescence materials and to try this property in a new application field: outdoor applications (sunlight charging) or to able this materials to be excited by non-containing UV lamps (white LEDs). Therefore, it's necessary to learn more about the "charging" process. The PhD student will study to kinds of matrix: i) Transparent ceramics in which nanocristals of persistant luminescence materials will be precipitated. Excitation, trapping and emission phenomena will be studied by optical spectroscopies and EPR after optical excitation. This work will be done at the IRCP in collaboration with Didier Gourier's group (IRCP) and Mathieu Allix (CEMHTI, Orléans). ii) Persistant cristals. Here the student will show and caracterise this phenomena on diferent monocristals in order to get persistant cristals that emit in a wide range of colors. In both cases, the mecanism will be studied from the bulk material to nanoparticles

Recherche de nouvelles couleurs et morphologies dans les matériaux à luminescence persistante

Persistant luminescence is the property of some materials to store energy of light (basically UV). This energy is stored as electrons and (or) holes traped by defects. This materials may also be able to give back this energy as visible light or near infrared during some hours. The mecanism involved in this phenomena is still poorly understood. The aim of this PhD project is to clarify this mecanism by studying diferent kinds of persistant luminescence materials and to try this property in a new application field: outdoor applications (sunlight charging) or to able this materials to be excited by non-containing UV lamps (white LEDs). Therefore, it's necessary to learn more about the "charging" process. The PhD student will study to kinds of matrix: i) Transparent ceramics in which nanocristals of persistant luminescence materials will be precipitated. Excitation, trapping and emission phenomena will be studied by optical spectroscopies and EPR after optical excitation. This work will be done at the IRCP in collaboration with Didier Gourier's group (IRCP) and Mathieu Allix (CEMHTI, Orléans). ii) Persistant cristals. Here the student will show and caracterise this phenomena on diferent monocristals in order to get persistant cristals that emit in a wide range of colors. In both cases, the mecanism will be studied from the bulk material to nanoparticles.La luminescence persistante est la propriété qu’ont certains matériaux de stocker une énergie lumineuse incidente (généralement UV) sous forme d’électrons et (ou) de trous électroniques piégés par des défauts, et de restituer cette énergie sous forme de lumière visible ou proche infra-rouge pendant plusieurs heures. Le mécanisme à l’origine de ce phénomène est cependant toujours mal compris. Le projet de cette thèse a pour objectif d’élucider ce mécanisme en étudiant différents types de matériaux à luminescence persistante et de profiter de cette propriété dans un nouveau champ d’activités : les applications extérieures (lors d’une charge par le soleil par exemple), ou le passage aux nouvelles lampes d’éclairage ne contenant plus d’UV (LED blanches). Le doctorant étudiera deux types de matrices : i) Des céramiques transparentes dans lesquelles sont précipitées des nanoparticules de matériaux à luminescence persistante. Il sera ainsi possible d’étudier les phénomènes (excitation, piégeage, émission) en excitant optiquement (sous rayonnement visible) en suivant in situ l’évolution des spectres en spectrométries RPE et optiques. Cette partie du travail de thèse sera effectué à l’IRCP à Paris en collaboration avec le groupe de Didier Gourier (IRCP), et en collaboration avec le CEMHTI d’Orléans (Mathieu Allix). ii) Des cristaux persistants. Dans ce cas il s’agit de mettre en évidence et de caractériser ce phénomène sur différents monocristaux afin de disposer de cristaux persistants dans une large gamme de couleur. Dans les deux cas, le mécanisme sera étudié dans une approche multi-échelle allant du matériau massif aux nanoparticules

Trap depth distribution determines afterglow kinetics: a local model applied to ZnGa2O4:Cr3+ [Dataset]

Persistent luminescence (PersL) materials have applications in diverse fields such as smart signaling, anticounterfeiting, and in vivo imaging. However, the lack of a thorough understanding of the precise mechanisms that govern PersL makes it difficult to develop ways to optimize it. Here we present an accurate model to describe the various processes that determine PersL in ZnGa2O4:Cr3+ (ZGO:Cr), a workhorse material in the field. A set of rate equations has been solved, and a global fit to both charge/discharge and thermoluminescence measurements has been performed. Our results establish a direct link between trap depth distribution and afterglow kinetics and shed light on the main challenges associated with PersL in ZGO:Cr nanoparticles, identifying low trapping probability and optical detrapping as the main factors limiting the performance of ZGO:Cr, with a large margin for improvement. Our results highlight the importance of accurate modeling for the design of future afterglow materials and devices.This project has received funding from the BBVA Foundation Leonardo Grant for Physics Researchers 2023, and from MCIN/AEI/10.13039/501100011033 by European Union NextGeneration EU/PRTR under grant EUR2023-143467.- fig_2_a.txt : PL spectra (normalized to the R line) measured at 80K: Wavelength in nm (column 1), PL for 420 nm excitation (column 2), PL for 330 nm excitation (column 3) - fig_2_b.txt : PersL spectra (normalized to maximum): Wavelength in nm (column 1), PersL (column 2) - fig_2_c.txt : PL decay measured at 80 K: Time in s (column 1), counts for 420 nm excitation (column 2), fit for 420 nm excitation (column 3), residuals for 420 nm excitation (column 4), counts for 330 nm excitation (column 5), fit for 330 nm excitation (column 6), residuals for 330 nm excitation (column 7). - fig_3_a.txt : Charge/discharge curves: Time in s (column 1), measured intensity for maximum,medium and minimum excitation power (columns 2-4), fitted intensity for maximum,medium and minimum excitation power (columns 5-7). - fig_3_b_1.txt : Thermoluminescence charging at RT: Temperature in K (column 1), measured intensity (column 2), fitted intensity (column 3). - fig_3_b_2.txt : Thermoluminescence charging at 15 K: Temperature in K (column 1), measured intensity (column 2), fitted intensity (column 3). - fig_3_c.txt : Trap depth distribution (normalized to maximum): Trap depth in eV (column 1), rho(Et) (column 2). - fig_4_a_1.txt : Normalized charged traps density (columns colunms correspond to trap depth while rows correspond to time after charging). - fig_4_a_2.txt : Time axis of fig_4_a_1.txt in s - fig_4_a_3.txt : Trap depth axis of fig_4_a_1.txt in eV - fig_4_b.txt : PersL as a function of trap depth and time after excitation: Trap depth in eV (column 1), PersL after t1= 0 s, 1 s, 30 s, 60 s, and 300 s (columns 2-6). - fig_5_1.txt : PersL as a function of delta_E1 and delta_Et . Rows correspond to delta_E1 while columns correspond to delta_Et. - fig_5_2.txt : delta_E1 axis of fig_5_1.txt in eV - fig_5_3.txt : delta_Et axis of fig_5_1.txt in eVPeer reviewe

Cathodoluminescence and microstructural analysis of amorphous yttrium-aluminum-borate luminescent powders

International audienc

Quantification of Emission Efficiency in Persistent Luminescent Materials [Dataset]

Accurate quantification of efficiency enables rigorous comparison between different photoluminescent materials, providing an optimization path critical to the development of next-generation light sources. Persistent luminescent materials exhibit delayed and long-lasting luminescence due to the temporary storage of optical energy in engineered structural defects. Although these materials have recently gained attention for their potential in a wide range of applications, from smart lighting to in vivo imaging, standard characterization methods do not provide a universal comparison of phosphor performance, making it difficult to assess the efficiency of the different processes involved in afterglow. In this work we establish a protocol to obtain the emission quantum yield of persistent phosphors. We determine the persistent and total luminescence quantum yields by considering the ratio of photons emitted in the afterglow and during charging to those absorbed. The method is first applied to transparent single crystals of the most common persistent phosphors, such as SrAl2O4:Eu2+,Dy3+ and Y3Al2Ga3O12:Ce3+,Cr3+. The versatility of our methodology is then demonstrated by quantifying the quantum yield of a thin film based on ZnGa2O4:Cr3+ persistent luminescent nanoparticles, which are commonly used for in vivo imaging. We confirm the high efficiency of strontium aluminate and reveal a strong dependence of the obtained values on the illumination conditions, highlighting a trade-off between efficiency and brightness, which opens the door to precise optimization of the charging conditions for each material and application. Our results contribute to the development of standard characterization protocols for the analysis of the mechanisms governing afterglow, as well as the assessment of the overall efficiency of the process. Such achievements enable a rigorous comparison of the performance of different persistent materials, allowing for optimization routes beyond the usual trial-and-error approach.This project has received funding from the BBVA Foundation Leonardo Grant for Physics Researchers 2023, and by Grant EUR2023-143467 funded by MICIU/AEI/ 10.13039/501100011033 and by the European Union NextGenerationEU/PRTR. V.C. acknowledges Junta de Andalucía for financial support (POSTDOC_21_00694).File List: - Fig1b_KineticScansSAOEuDy.txt : Time (s, column 1), normalized intensity kinetic scans of empty sphere at 400 nm used to calculate Abs (column 2), SAO:Eu,Dy at 400 nm used to calculate Abs (column 3) and SAO:Eu,Dy at 524 nm (column 4). - Fig1c_PersLSpectrumSAOEuDy.txt : Wavelength (nm, column 1), normalized PersL intensity of SAO:Eu,Dy (column 2). - Fig1d_LumSpectrumSAOEuDy.txt : Wavelength (nm, column 1), normalized Lum intensity of SAO:Eu,Dy (column 2). - Fig2a_QYSAOEuDyChargingTime.txt : Charging time (s, column 1), LumQY of SAO:Eu,Dy (column 2), error of LumQY of SAO:Eu,Dy (column 3), PersLQY of SAO:Eu,Dy (column 4) and error of PersLQY of SAO:Eu,Dy (column 5). - Fig2b_ChargingKineticSAOEuDy.txt : Wavelength (nm, column 1), normalized Lum intensity of SAO:Eu,Dy (column 2). - Fig3c_SpectraZGOCr.txt : Wavelength (nm, column 1), normalized Lum intensity of ZGO:Cr (column 2), Wavelength (nm, column 3) and normalized PersL intensity of ZGO:Cr (column 4). - Fig3d_KineticScansZGOCr.txt : Time (s, column 1), normalized intensity kinetic scans of empty sphere at 270 nm used to calculate Abs (column 2), ZGO:Cr at 260 nm used to calculate Abs (column 3) and ZGO:Cr at 696 nm (column 4). - Fig3e_PersLESpectrumZGOCr.txt : Wavelength (nm, column 1) and normalized PersLE intensity of ZGO:Cr (column 2). - Fig4a_IntegratedPersLTemperature.txt : Time after excitation (s, column 1), normalized integrated intensity of ZGO:Cr at RT after excitation at 270 nm (column 2), normalized integrated intensity of ZGO:Cr after excitation at 270 nm with heating at 85 ºC (column 3), Time after excitation (s, column 4), normalized integrated intensity of ZGO:Cr at RT after excitation at 330 nm (column 5), normalized integrated intensity of ZGO:Cr after excitation at 330 nm with heating at 85 ºC (column 6), normalized integrated intensity of SAO:Eu,Dy at RT after excitation at 400 nm (column 7), normalized integrated intensity of SAO:Eu,Dy after excitation at 400 nm with heating at 85 ºC (column 8).Peer reviewe

Scattering Spheres Boost Afterglow: A Mie Glass Approach to Go Beyond the Limits Set by Persistent Phosphor Composition

Persistent luminescence phosphor nanoparticles (PersLNPs) offer exciting opportunities for anticounterfeiting, data storage, imaging displays, or AC-driven lighting applications owing to the possibility to process them as shapable thin coatings. However, despite unique delayed and long-lasting luminescence, the relatively low storage capacity of persistent phosphor nanoparticles combined with the difficulty of harvesting photons from transparent thin layers drastically hinder the perceived afterglow. In order to enhance persistent luminescence (PersL) of thin coatings, herein a novel approach is proposed based on resonant optical nanostructures. In particular, it is demonstrated that the integration of TiO2 scattering spheres in films (with thickness comprised between 1 and 10 µm) made of ZnGa2O4:Cr3+ PersLNPs enables a significant increase in afterglow intensity due to the combination of effective charging and enhanced outcoupling. As a result, a ≈3.5-fold enhancement of the PersL is observed in 2 µm-thick films stuffed with scattering centers using low-light illumination conditions. Furthermore, inclusion of scattering centers leads to an unprecedented acceleration of the PersL charging speed. These results constitute the first example of photonic engineering applied to enhance the properties of PersL materials coatings.This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (NANOPHOM, grant agreement no. 715832). Financial support was also received from the Spanish Ministry of Science and Innovation under grant PID2020-116593RB-I00, funded by MCIN/AEI/10.13039/501100011033, and of the Junta de Andalucía under grant P18-RT-2291 (FEDER/UE). V.C. acknowledges Junta de Andalucía for financial support (POSTDOC_21_00694).Peer reviewe