BUSCADOR RECOLECTA

Nanophosphor integration in an optical cavity allows unprecedented
control over both the chromaticity and the directionality of the
emitted light, without modifying the chemical composition of the
emitters or compromising their efficiency. Our approach opens a
route towards the development of nanoscale photonics based solid
state lighting., Peer Reviewed

The development of smart illumination sources represents a central challenge for current technology. In this context, the quest for novel materials that enable efficient light generation is essential. Metal halide compounds with perovskite crystalline structure (ABX3) have gained tremendous interest in the last five years since they come as easy-to-prepare high performance semiconductors. Perovskite absorbers are driving the power-conversion-efficiencies of thin film photovoltaics to unprecedented values. Nowadays, mixed-cation, mixed-halide lead perovskite solar cells reach efficiencies consistently over 20% and promise to get close to 30% in multijunction devices when combined with silicon cells at no surcharge. Nonetheless, perovskites¿ fame extends further since extensive research on these novel semiconductors has also revealed their brightest side. Soon after their irruption in the photovoltaic scenario, demonstration of efficient color tunable¿with high color purity¿perovskite emitters has opened new avenues for light generation applications that are timely to discuss herein., Peer Reviewed

Rare-earth-based phosphors are the materials on
which current solid-state lighting technology is built. However,
their large crystal size impedes the tuning, optimization, or
manipulation of emitted light that can be achieved by their
integration in nanophotonic architectures. Herein we demonstrate
a hybrid plasmonic−photonic architecture capable of both
channeling in a specific direction and enhancing by eight times
the emission radiated by a macroscopically wide layer of
nanophosphors. In order to do so, a slab of rare-earth-based
nanocrystals is inserted between a dielectric multilayer and a
metal film, following a rational design that optimizes the
coupling of nanophosphor emission to collective modes
sustained by the metal−dielectric system. Our approach is
advantageous for the optimization of solid-state lighting systems., Peer reviewed

A one-pot simple procedure for the synthesis of uniform, ellipsoidal Eu3+-doped sodium lanthanum tungstate and molybdate (NaLa(XO4)2, X  = W, Mo) nanophosphors, functionalized with carboxylate groups, is described. The method is based on a homogeneous precipitation process at 120 °C from appropriate Na+, Ln3+ and tungstate or molybdate precursors dissolved in ethylene glycol/water mixtures containing polyacrylic acid. A comparative study of the luminescent properties of both luminescent materials as a function of the Eu3+ doping level has been performed to find the optimum nanophosphor, whose efficiency as X-ray computed tomography contrast agent is also evaluated and compared with that of a commercial probe. Finally, the cell viability and colloidal stability in physiological pH medium of the optimum samples have also been studied to assess their suitability for biomedical applications., This work has been supported by the Spanish Ministry of Science, Innovation and Universities, Spain (RTI2018-094426-B-I00), the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (NANOPHOM, grant agreement no. 715832), DGA and Fondos Feder, Aragón, Spain (Bionanosurf E15_17R) and CSIC, Spain (PIC2016FR1). This work was also supported in part by Siemens Healthcare S.L.U., Spain MM thanks MINECO, Spain for Juan de la Cierva Fellowship., Peer reviewed

Herein, we analyze the temporal evolution of the electroluminescence of light-emitting electrochemicalcells (LECs), a thin-film light-emitting device, in order to maximize the luminous power radiated bythese devices. A careful analysis of the spectral and angular distribution of the emission of LECsfabricated under the same experimental conditions allows describing the dynamics of the spatial regionfrom which LECs emit,i.e.the generation zone, as bias is applied. This effect is mediated by dipolereorientation within such an emissive region and its optical environment, since its spatial drift yields adifferent interplay between the intrinsic emission of the emitters and the local density of optical states ofthe system. Our results demonstrate that engineering the optical environment in thin-film light-emittingdevices is key to maximize their brightness, 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), and the Spanish Ministry of Economy and Competitiveness via the Unidad de Excelencia María de Maeztu MDM-2015-0538 and under grants, MAT2017-88821-R, and MAT2017-88584-R., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)., Peer reviewed

Mesoporous silica features open and accessible
pores that can intake substances from the outside. The
combination of mesoporous silica with plasmonic nanostructures
represents an interesting platform for an optical sensor based on
the dependence of plasmonic modes on the refractive index of the
medium in which metallic nanoparticles are embedded. However,
so far only a limited number of plasmonic nanostructures are
combined with mesoporous silica, including random dispersion of
metallic nanoparticles and flat metallic thin films. In this study, we
make a mesoporous silica layer on an aluminum nanocylinder
array. Such plasmonic arrangements support both localized surface
plasmon resonances (LSPRs) and extended modes which are the
result of the hybridization of LSPRs and photonic modes
extending into the mesoporous layer. We investigate in situ optical reflectance of this system under controlled pressure of
isopropanol vapor. Upon exposure, the capillary condensation in the mesopores results in a gradual spectral shift of the reflectance.
Our analysis demonstrates that such shifts depend largely on the nature of the modes; that is, the extended modes show larger shifts
compared to localized ones. Our materials represent a useful platform for the field of environmental sensing, Peer reviewed

The combination of light‐emitting diodes (LEDs) and rare earth (RE) phosphors as color‐converting layers comprises the basis of solid‐state lighting. Indeed, most LED lamps include a photoluminescent coating made of phosphor material, i.e., crystalline matrix suitably doped with RE elements, to produce white light from a blue or ultraviolet LED chip. Transparent phosphor‐based films constitute starting materials for new refined emitters that allow different photonic designs to be implemented. Among the different photonic strategies typically employed to tune or enhance emission, surface texturing has proved its versatility and feasibility in a wide range of materials and devices. However, most of the nanofabrication techniques cannot be applied to RE phosphors directly because of their chemical stability or because of their cost. The first monolithic patterned structure of down‐shifting nanophosphors with square arrays of nanoholes with different lattice parameters is reported in this study. It is shown that a low‐cost soft‐nanolithography procedure can be applied to red‐emitting nanophosphors (GdVO4:Eu3+ nanocrystals) to tune their emission properties, attaining a twofold directional enhancement of the emitted light at predesigned emission wavelengths in specific directions., This project received funding from the Spanish Ministry of Economy and Competitiveness under grant MAT2017‐88584‐R (AEI/FEDER, UE) and PID2019‐106860GB‐I00 (AEI/FEDER, UE), the excellence program SEV‐2015‐0496, and the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (NANOPHOM, grant agreement no. 715832 and ENLIGHTMENT, grant no. 637116). P.M acknowledges financial support from an FPI contract (2017) of the MICINN (Spain) cofounded by the ESF and the UAB. E.C.O. acknowledges the Spanish Ministry of Universities for the funding through an FPU program (FPU19/00346)., Peer reviewed

We report on the fabrication of ZnGa2O4:Cr3+ transparent thin films and the evaluation, for the first time in literature, of their persistent red to NIR emission. For this purpose, we have used a simple and economic global strategy based on wet processing methods from colloidal nanospheres with uniform size. A microwave-assisted hydrothermal method was first developed for the synthesis of the precursor particles, which allows size tuning from 300 nm to 30 nm through simple modification of the Zn precursor and the Cr content of the starting solutions. ZnGa2O4:Cr3+ transparent thin films over quartz substrates were then easily fabricated by spin coating, and their structural and optical characteristics were analyzed in detail after annealing at high temperature to elucidate the effect of processing temperature and particle size on films properties. Indeed, our results indicate that high temperature annealing does not compromise the transparency of the films while improves their photoluminescence. In addition, the analysis reveals that persistence luminescence in our films is rather independent of the size of the precursor nanoparticles. Due to their transparency and persistent emission properties, films fabricated from colloidal suspensions of ZnGa2O4:Cr3+ nanoparticles show great potential for applications in the fields of chemical sensing, information storage, labelling, and anti-counterfeiting technology., Peer reviewed

Fluoride-based compounds doped with rare-earth cations are the preferred choice of materials to achieve efficient upconversion, of interest for a plethora of applications ranging from bioimaging to energy harvesting. Herein, we demonstrate a simple route to fabricate bright upconverting films that are transparent, self-standing, flexible, and emit different colors. Starting from the solvothermal synthesis of uniform and colloidally stable yttrium fluoride nanoparticles doped with Yb3+ and Er3+, Ho3+, or Tm3+, we find the experimental conditions to process the nanophosphors as optical quality films of controlled thickness between few hundreds of nanometers and several micrometers. A thorough analysis of both structural and photophysical properties of films annealed at different temperatures reveals a tradeoff between the oxidation of the matrix, which transitions through an oxyfluoride crystal phase, and the efficiency of the upconversion photoluminescence process. It represents a significant step forward in the understanding of the fundamental properties of upconverting materials and can be leveraged for the optimization of upconversion systems in general. We prove bright multicolor upconversion photoluminescence in oxyfluoride-based phosphor transparent films upon excitation with a 980 nm laser for both rigid and flexible versions of the layers, being possible to use the latter to coat surfaces of arbitrary shape. Our results pave the way toward the development of upconverting coatings that can be conveniently integrated in applications that demand a large degree of versatility., Peer reviewed

Persistent phosphors are luminescent sources based on crystalline materials doped with rare-earth or transition metal cations able to produce light after the excitation source vanishes. Although known for centuries, these materials gained renewed interest after the discovery of Eu2+,RE3+ co-doped aluminates and silicates in the late 1990s due to their unprecedented afterglow properties. In contrast, persistent nanophosphors have emerged only recently as a nanoscale alternative to their bulk counterparts, offering exciting opportunities of particular relevance for in vivo imaging, optical data storage, or unconventional light generation. However, taking advantage of the avenues opened by nanoscience demands developing new synthetic strategies that allow precise control of the morphology, surface, and defect chemistry of the nanomaterials, along with a profound understanding of the physical mechanisms occurring in the nanoscale. Besides, advanced physicochemical characterization is required to assess persistent luminescence in a quantitative manner, which allows strict comparison among different persistent nanophosphors, aiming to propel their applicability. Herein, we revisit the main phenomena that determine the emission properties of persistent nanoparticles, discuss the most promising preparation and characterization protocols, highlight recent achievements, and elaborate on the challenges ahead, Peer reviewed

Photonic nanostructures have proven useful to enhance the performance of a wide variety of materials and devices for sensing, catalysis,
light harvesting, or light conversion. Herein, we discuss the role of nanophotonics in current and next-generation designs of white lightemitting
diodes (LEDs). We discuss recent developments on luminescent materials designed as alternatives to rare earth-doped inorganic
microcrystals, i.e., phosphors, for color conversion in LEDs, which has opened the door to the integration of resonant photonic architectures.
Nanophotonics enables the devised light–matter interaction with luminescent materials in the nanoscale, which allows providing
emitting devices with both enhanced performance and novel functionalities to tackle technological challenges ahead, Peer reviewed

Owing to their unique non-linear optical character, lanthanide-based up-converting materials are potentially interesting for a wide variety of fields ranging from biomedicine to light harvesting. However, their poor luminescent efficiency challenges the development of technological applications. In this context, localized surface plasmon resonances (LSPRs) have been demonstrated as a valuable strategy to improve light conversion. Herein, we utilize LSPR induced by gold nanoparticles (NPs) to enhance up-conversion photoluminescence (UCPL) in transparent, i.e. scattering-free, films made of nanophosphors formed by fluoride–oxyfluoride host matrix that feature high thermal stability. Transparency allows excitation by an external source without extinction losses caused by unwanted diffuse reflection. We provide a simple method to embed gold NPs in films made of YF/YOF:Yb3+,Er3+ UC nanophosphors, via preparation of a viscous paste composed of both UC nanophosphors and colloidal gold NPs, reducing complexity in sample fabrication. The dimensions of gold NPs are such that their associated LSPR matches spectrally with the green emission band of the Er3+ doped nanophosphors. In order to demonstrate the benefits of plasmonic nanoparticles for UCPL in nanophosphor films, we provide a careful analysis of the structural properties of the composite thin films along with precise characterization of the impact of the gold NPs on the photophysical properties of UC nanophosphors., This project is financially supported by the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (NANOPHOM, grant agreement no. 715832). T. T. N. is thankful to MCIN/AEI/10.13039/501100011033 and European Union Next GenerationEU/PRTR for funding her Juan de la Cierva Formación contract.

Afterglow properties of persistent phosphors are attracting a great deal of attention in the fields of bioimaging, sensing, labeling, safety, or security. Complex garnet oxides, especially those doped with Ce3+ and Cr3+, are particularly relevant to this end since their persistent luminescence can be tuned through matrix composition and activated by visible light, in contrast to the vast majority of persistent phosphors that require UV excitation. Most extended preparation routes yield micrometer-sized phosphors that display strong light scattering, which limits their versatility and applicability. Herein, nanostructured garnet oxide-based thin films that are transparent and feature persistent luminescence properties are demonstrated. Following a sol–gel route and after high temperature annealing, few hundred nanometre-thick Y3Al2Ga3O12:Ce3+,Cr3+ transparent films showing efficient green emission and afterglow are attained. Gd3Al2Ga3O12:Ce3+,Cr3+ transparent thin films displaying yellow afterglow with distinct persistent kinetics are demonstrated, to prove the generality of the approach herein proposed. Its versatility is further demonstrated by developing layered phosphors with time-dependent chromaticity due to the unique persistent emission color – upon blue light excitation – and kinetics of each layer forming the stack. The results pave an avenue toward nanodevices and multifunctional coatings in which afterglow offers hitherto unexplored properties., 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). V.C. thanks Junta de Andalucía for financial support (POSTDOC_21_00694).

Transparent coatings made of rare-earth doped nanocrystals, also known as nanophosphors, feature efficient photoluminescence and excellent thermal and optical stability. Herein, we demonstrate that the optical antennas prepared by colloidal lithography render thin nanophosphor films with a brighter emission. In particular, we fabricate gold nanostructures in the proximity of GdVO4:Eu3+ nanophosphors by metal evaporation using a mask made of a monolayer of polymer beads arranged in a triangular lattice. Optical modes supported by the antennas can be controlled by tuning the diameter of the polymer spheres in the colloidal mask, which determines the shape of the gold nanostructure, as confirmed by numerical simulations. Confocal microscopy reveals that metallic antennas induce brighter photoluminescence at specific spatial regions of the nanophosphor film at targeted frequencies as a result of the coupling between gold nanostructures and nanophosphors. Patterning of nanophosphor thin layers with arrays of metallic antennas offers an inexpensive nanophotonic solution to develop bright emitting coatings of interest for color conversion, labeling, or anti-counterfeiting., 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). M.R. thanks CSIC for funding through a JAE Intro ICU scholarship (JAEICU-21-ICMS-21)., Peer reviewed

Herein, we demonstrate that rapid thermal annealing allows achieving close-to-one photoluminescence quantum yield while preserving the transparency of rare-earth nanocrystal films, which further enables their integration with nanophotonics. The combination with periodic arrays of aluminum nanodisks that support collective plasmonic resonances leads to enhanced directional emission., 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). E.C.O. acknowledges the grant FPU19/00346 funded by MCIN/AEI/10.13039/501100011033 and ESF Investing in your Future. S. M. and K.T. thanks support from MEXT, Japan (Kakenhi 21H04619, 22H01776) and the
Futaba foundation., Peer reviewed

Herein, we demonstrate that rapid thermal annealing allows achieving close-to-one photoluminescence quantum yield while preserving the
transparency of rare-earth nanocrystal films, which further enables their integration with nanophotonics. The combination with periodic arrays of
aluminum nanodisks that support collective plasmonic resonances leads to enhanced directional emission., 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). E.C.O. acknowledges the grant FPU19/00346 funded by MCIN/AEI/10.13039/501100011033 and ESF Investing in your Future. S. M. and K.T. thanks support from MEXT, Japan (Kakenhi 21H04619, 22H01776) and the Futaba foundation., Peer reviewed

This paper is part of the Special Topic on Emerging Materials and Devices for Efficient Light Generation., S.M. acknowledges financial support from the Futaba electronics Memorial Foundation. R.J.H. acknowledges support from the University of Minnesota College of Science and Engineering and Ronald L. and Janet A. Christenson. M.A. acknowledges support by the Royal Academy of Engineering under the Research Fellowship programme and by the Leverhulme Early Career Fellowship (Grant Agreement No. ECF-2019-224) funded by the Leverhulme Trust and the Isaac Newton Trust. G.L. acknowledges financial support from the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (NANOPHOM, Grant Agreement No. 715832)., Peer reviewed

Herein a versatile and scalable method to prepare periodically corrugated nanophosphor surface patterns
displaying strongly polarized and directional visible light emission is demonstrated. A combination of inkjet printing and
soft lithography techniques is employed to obtain arbitrarily shaped light emitting motifs. Such predesigned luminescent
drawings, in which the polarization and angular properties of the emitted light are determined and finely tuned through the
surface relief, can be used as anti-counterfeiting labels, as these two specific optical features provide additional means to
identify any unauthorized or forged copy of the protected item. The potential of this approach is exemplified by processing
a self-standing photoluminescent quick response (QR) code whose emission is both polarized and directionally beamed.
Physical insight of the mechanism behind the directional out-coupled photoluminescence observed is provided by finitedifference time-domain calculations., 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) and 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). E. C. O. acknowledges the grant FPU19/00346 funded by
MCIN/AEI/10.13039/501100011033 and ESF Investing in your Future. M. R. thanks CSIC for funding through a JAE Intro ICU scholarship (JAEICU-21-ICMS-21). This work has been partially supported by the European Union and the State of Upper Austria within the strategic program Innovative Upper Austria 2020 and #upperVision2030, project: WI2020-578813/4 “DigiManu (Extended 2021), Peer reviewed

In this work, we theoretically and experimentally study the influence of the optical environment on the radiative decay rate of luminescent nanoparticles forming a thin film. We use electric dipole sources in finite-difference time-domain simulations to analyze the effect of modifying the effective refractive index of transparent layers made of phosphor nanocrystals doped with rare earth cations, and propose a significant correction to previously reported analytical models for calculating the radiative decay rate.
Our predictions are tested against an experimental realization of such films, in which we manage to vary the effective refractive index in a gradual and controllable manner.
Our model accurately accounts for the measurements attained, allows us discriminating the radiative and non-radiative contributions to the time-resolved photoluminescence, and provides a way to rationally tune the spontaneous decay rate and hence the photoluminescence quantum yield of an ensemble of nanoparticles., 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), 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 TED2021-129679B-C22., Peer reviewed

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 to the difficulty to harvest photons from transparent thin layers drastically hinder the perceived afterglow. In order to enhance persistent luminescence (PersL) of thin coatings, herein we propose a novel approach based on resonant optical nanostructures. In particular, we demonstrate 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, we observe a ~ 3.5-fold enhancement of the PersL in 2 μm-thick films stuffed with scattering centres using low-light illumination conditions. Furthermore, inclusion of scattering centres leads to an unprecedented acceleration of the PersL charging speed. Our 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)., - Figure1f_XRD.txt : 2 theta (º, column 1), normalized XRD reflection intensity of reference sample (column 2) and 5 V% sample (column 3). - Figure2b_NormLumEmission.txt : Wavelength (nm, column 1), normalized Lum intensity of reference sample (column 2) and 5 V% sample (column 3). - Figure2c_NormLumExcitation.txt : Wavelength (nm, column 1), normalized Lum excitation intensity of reference sample (column 2) and 5 V% sample (column 3). - Figure2d_NormPersLDecays.txt : Time (s, column 1), normalized PersL decay intensity of reference sample (column 2) and 5 V% sample (column 3). - Figure2e_NormPersLEmission.txt : Wavelength (nm, column 1), normalized PersL intensity of reference sample (column 2) and 5 V% sample (column 3). - Figure3a_AbsTransm.txt : Wavelength (nm, column 1), transmittance of reference sample (%, column 2), 5 V% sample (%, column 3), absorptance of reference sample (%, column 4), 5 V% sample (%, column 5). - Figure3b_MieEfficiency.txt : Wavelength (nm, column 1), calculated scattering efficiency of TiSi spheres in a medium with an effective refractive index of 1.4 (arb. units, column 2). - Figure3c_FDTD_Field420nmXZ_ref.txt : X (nm, column 1), Z (nm, row 1), electric field intensity in reference sample at 420 nm wavelength (column to to end). - Figure3d_FDTD_Field696nmXZ_ref.txt : X (nm, column 1), Z (nm, row 1), electric field intensity in reference sample at 696 nm wavelength (column to to end). - Figure3e_FDTD_Field420nmXZ_5V%.txt : X (nm, column 1), Z (nm, row 1), electric field intensity in 5 V% sample at 420 nm wavelength (column to to end). - Figure3f_FDTD_Field696nmXZ_5V%.txt : X (nm, column 1), Z (nm, row 1), electric field intensity in 5 V% sample at 696 nm wavelength (column to to end). - Figure3g_FDTD_Field420nmXY_5V%.txt : X (nm, column 1), Y (nm, row 1), electric field intensity in 5 V% sample at 420 nm wavelength (column to to end). - Figure3h_FDTD_Field696nmXY_5V%.txt : X (nm, column 1), Y (nm, row 1), electric field intensity in 5 V% sample at 696 nm wavelength (column to to end). - Figure4a_Lum-PersLEnhancement_Wavelength.txt : Sample (column 1), Lum enhancement with 420 nm wavelength excitation (column 2), Lum enhancement with 560 nm wavelength excitation (column 3), PersL enhancement with 420 nm wavelength excitation (column 4), PersL enhancement with 560 nm wavelength excitation (column 5). - Figure4b_ChargingKinetics.txt : Charging time (s, column 1), normalized integrated PersL intensity of reference sample (column 2), measured error of integrated PersL intensity of reference sample (column 3), normalized integrated PersL intensity of 5 V% sample (column 4), measured error of integrated PersL intensity of 5 V% sample (column 5). - Figure4c_PersLEnhancementChargingTime.txt : Charging time (s, column 1), PersL ehancement (column 2). - Figure5b_PersLCharging_wLED.txt : Charging time (min, column 1), normalized integrated PersL intensity of reference sample (column 2), normalized integrated PersL intensity of 5 V% sample (column 3). - Figure5e_PersLDecay_UV.txt : Time (min, column 1), normalized PersL intensity of reference sample (column 2), normalized PersL intensity of 5 V% sample (column 3)., Peer reviewed

In this work, we theoretically and experimentally study the influence of the optical environment on the radiative decay rate of rare-earth transitions in luminescent nanoparticles forming a thin film. We use electric dipole sources in finite-difference time-domain simulations to analyze the effect of modifying the effective refractive index of transparent layers made of phosphor nanocrystals doped with rare earth cations, and propose a correction to previously reported analytical models for calculating the radiative decay rate. Our predictions are tested against an experimental realization of such luminescent films, in which we manage to vary the effective refractive index in a gradual and controllable manner. Our model accurately accounts for the measurements attained, allows us to discriminate the radiative and non-radiative contributions to the time-resolved photoluminescence, and provides a way to rationally tune the spontaneous decay rate and hence the photoluminescence quantum yield in an ensemble of luminescent nanoparticles., 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), 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 TED2021-129679B-C22., Peer reviewed

Herein a versatile and scalable method to prepare periodically corrugatednanophosphor surface patterns displaying strongly polarized and directionalvisible light emission is demonstrated. A combination of inkjet printing andsoft lithography techniques is employed to obtain arbitrarily shaped lightemitting motifs. Such predesigned luminescent drawings, in which thepolarization and angular properties of the emitted light are determined andfinely tuned through the surface relief, can be used as anti-counterfeitinglabels, as these two specific optical features provide additional means toidentify any unauthorized or forged copy of the protected item. The potentialof this approach is exemplified by processing a self-standingphotoluminescent quick response code whose emission is both polarized anddirectionally beamed. Physical insight of the mechanism behind thedirectional out-coupled photoluminescence observed is provided byfinite-difference time-domain calculations., 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) and 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). E. C. O. acknowledges the grant FPU19/00346 funded by MCIN/AEI/10.13039/501100011033 and ESF Investing in your Future. M. R. thanks CSIC for funding through a JAE Intro ICU scholarship (JAEICU-21-ICMS-21). This work has been partially supported by the European Union and the State of Upper Austria within the strategic program Innovative Upper Austria 2020 and #upperVision2030, project: WI-2020-578813/4 “DigiManu (Extended 2021)”., Peer reviewed

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 reviewed

Lanthanide-doped upconversion nanoparticles (UCNPs), as multifunctional light sources, are finding utility in diverse applications ranging from biotechnology to light harvesting. However, the main challenge in realizing their full potential lies in achieving bright and efficient photon upconversion (UC). In this study, we present a novel approach to fabricate an array of gold nanoantennas arranged in a hexagonal lattice using a simple and inexpensive colloidal lithography technique, and demonstrate a significant enhancement of UC photoluminescence (UCPL) by up to 35-fold through plasmon-enhanced photoexcitation and emission. To elucidate the underlying physical mechanisms responsible for the observed UCPL enhancement, we provide a comprehensive theoretical and experimental characterization, including a detailed photophysical description and numerical simulations of the spatial electric field distribution. Our results shed light on the fundamental principles governing the enhanced UCNPs and pave the way for their potential applications in photonic devices., This project is financially supported by the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (NANOPHOM, grant agreement no. 715832). T.T.N. is thankful to grant FJC2020-046006-I funded by MCIN/AEI /10.13039/501100011033 and by the European Union Next Generation EU/PRTR. M.R. acknowledges CSIC for the funding through a JAE Intro ICU program
(JAEIntro-2021-ICMS-01)., Peer reviewed

Lanthanide-doped upconversion nanoparticles (UCNPs), as multifunctional light sources, are finding utility in diverse applications ranging from biotechnology to light harvesting. However, the main challenge in realizing their full potential lies in achieving bright and efficient photon upconversion (UC). In this study, we present a novel approach to fabricate an array of gold nanoantennas arranged in a hexagonal lattice using a simple and inexpensive colloidal lithography technique, and demonstrate a significant enhancement of UC photoluminescence (UCPL) by up to 35-fold through plasmon-enhanced photoexcitation and emission. To elucidate the underlying physical mechanisms responsible for the observed UCPL enhancement, we provide a comprehensive theoretical and experimental characterization, including a detailed photophysical description and numerical simulations of the spatial electric field distribution. Our results shed light on the fundamental principles governing the enhanced UCNPs and pave the way for their potential applications in photonic devices., Upconversion luminescence, Plasmon, Nanostructure Financial support: European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (NANOPHOM, grant agreement no. 715832), grant FJC2020-046006-I funded by MCIN/AEI /10.13039/501100011033 and by the European Union Next Generation EU/PRTR, JAE Intro ICU program (JAEIntro-2021-ICMS-01)., Figure_1 Fig 1b.txt : AFM height map from -10 to 140 nm. 516x516 pixels, 2000x2000 nm (388 nm/pixel) Figure_2 Fig 2a.txt Fig_2b.txt : Wavelength in nm (column 1) and calculated IIE (column 2) Fig_2c_1.txt: Simulated electric field at 980nm intensity in a YZ plane. The first column correspond to the Y coordinates and the first row correspond to the X coordinates. Fig_2c_2.txt: Simulated electric field intensity at 980nm in a XY plane. The first column correspond to the X coordinates and the first row correspond to the Y coordinates. Figure_3 Fig 3a.txt Fig 3b.txt Fig 3c.txt Fig 3d.txt, Peer reviewed

In this manuscript, we demonstrate a new approach to develop highly transparent thin films with effective refractive index close to unity that can be easily generalized to create highly performing photonic materials. Central to the procedure herein proposed is the used of sacrificial polymer nanosphere thin films that can be coated by chemical vapor deposition with thin interconnected shells of metal oxides, which gives rise to ultralow refractive index slabs upon removal of the organic template. The method herein presented is compatible with the processing techniques employed for other nanomaterials, which allows us to over-come the challenge of integrating ultralow refractive index materials into more complex photonic architectures. As proofs-of-principle of their potential significance in the field of photonics, we show how to obtain (i) a very thin film acting as a highly diffusive random optical medium, which results from the high refractive index contrast between the air-like refractive index film and spherical scatterers dispersed in it, and (ii) a film loaded with nanophosphors displaying enhanced photoluminescence out-coupling, as a result of the reduced light guiding losses achieved by the low dielectric contrast between the host of the emitters and the surrounding environment., This project received funding from the Spanish Ministry of Science and Innovation under grant PID2020-116593RB-I00, funded by MCIN/AEI/10.13039/501100011033, the Junta de Andalucía under grant P18-RT-2291 (FEDER/UE), and the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (NANO-PHOM, grant agreement no. 715832)., Figure 2: - Data_2d_RT_exp_1cy.txt - Data_2d_RT_exp_2cy.txt - Data_2d_RT_exp_3cy.txt - Data_2d_RT_the_1cy.txt - Data_2d_RT_the_2cy.txt - Data_2d_RT_the_3cy.txt - Data_2e_nk_1cy.txt - Data_2e_nk_2cy.txt - Data_2e_nk_3cy.txt - Data_2f_1cy.txt - Data_2f_2cy.txt - Data_2f_3cy.txt - Data_2f_glass.txt Figure 3: - Data_3d_r_146nm.txt - Data_3d_r_188nm.txt - Data_3d_r_225nm.txt - Data_3d_r_250nm.txt - Data_3e_r_146nm.txt - Data_3e_r_146nm_air.txt - Data_3e_r_188nm.txt - Data_3e_r_188nm_air.txt - Data_3e_r_225nm.txt - Data_3e_r_225nm_air.txt - Data_3e_r_250nm.txt - Data_3e_r_250nm_air.txt Figure 4: - Data_4c_corrected_PL.txt - Data_4d_theoretical_outcouplig_versus_refractive_index.txt, Peer reviewed