RESUMEN
Achieving highly transparent and emissive films based on perovskite quantum dots (PQDs) is a challenging task since their photoluminescence quantum yield (PLQY) typically drops abruptly when they are used as building blocks to make a solid. In this work, we obtain highly transparent films containing FAPbBr3 quantum dots that display a narrow green emission (λ = 530 nm, full width at half-maximum (FWHM) = 23 nm) with a PLQY as high as 86%. The method employed makes use of porous matrices that act as arrays of nanoreactors to synthesize the targeted quantum dots within their void space, providing both a means to keep them dispersed and a protective environment. Further infiltration with poly(methyl methacrylate) (PMMA) increases the mechanical and chemical stability of the ensemble and serves to passivate surface defects, boosting the emission of the embedded PQD and significantly reducing the width of the emission peak, which fulfills the requirements established by the Commission Internationale de l'Éclairage (CIE) to be considered an ultrapure green emitter. The versatility of this approach is demonstrated by fabricating a color-converting layer that can be easily transferred onto a light-emitting device surface to modify the spectral properties of the outgoing radiation.
RESUMEN
Lanthanide-activated fluoride-based nanostructures are extremely interesting multifunctional tools for many modern applications in nanomedicine, e.g., bioimaging, sensing, drug delivery, and photodynamic therapy. Importantly, environmental-friendly preparations using a green chemistry approach, as hydrothermal synthesis route, are nowadays highly desirable to obtain colloidal nanoparticles, directly dispersible in hydrophilic media, as physiological solution. The nanomaterials under investigation are new KY3F10-based citrate-capped core@shell nanostructures activated with several lanthanide ions, namely, Er3+, Yb3+, Nd3+, and Gd3+, prepared as colloidal water dispersions. A new facile microwave-assisted synthesis has been exploited for their preparation, with significant reduction of the reaction times and a fine control of the nanoparticle size. These core@shell multifunctional architectures have been investigated for use as biocompatible and efficient contrast agents for optical, magnetic resonance imaging (MRI) and computerized tomography (CT) techniques. These multifunctional nanostructures are also efficient noninvasive optical nanothermometers. In fact, the lanthanide emission intensities have shown a relevant relative variation as a function of the temperature, in the visible and near-infrared optical ranges, efficiently exploiting ratiometric intensity methods for optical thermometry. Importantly, in contrast with other fluoride hosts, chemical dissolution of KY3F10 citrate-capped nanocrystals in aqueous environment is very limited, of paramount importance for applications in biological fluids. Furthermore, due to the strong paramagnetic properties of lanthanides (e.g., Gd3+), and X-ray absorption of both yttrium and lanthanides, the nanostructures under investigation are extremely useful for MRI and CT imaging. Biocompatibility studies of the nanomaterials have revealed very low cytotoxicity in dfferent human cell lines. All these features point to a successful use of these fluoride-based core@shell nanoarchitectures for simultaneous diagnostics and temperature sensing, ensuring an excellent biocompatibility.