Origin of the High Upconversion Green Luminescence Efficiency in β-NaYF4:2%Er3+,20%Yb3+

Site-selective spectroscopy in hexagonal β-NaYF4:Er 3+,Yb3+ has revealed different environments for Er 3+ ions (multisite formation). The low-temperature 4S 3/2 → 4I15/2 Er3+green emission depends on the excitation wavelength associated with the 4F 7/2 Er3+ level. We have studied the effect of hydrostatic pressure on the green, red, and blue Er3+ emission upon NIR excitation at ∼980 nm, in order to establish the role played by energy resonance conditions and the multiple Er3+ sites due to the disordered structure for the upconversion (UC) process (energy tuning). The variation of photoluminescence spectra and lifetimes as a function of pressure and temperature reveals that the origin of the high green UC efficiency of the β-NaYF4:Er3+,Yb3+ compound is mainly due to the multisite distribution, and the low phonon energy of the host lattice. © 2011 American Chemical Society.This work was financially supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) (under Project No. MAT2008-06873-C02-01) and by the MALTA-CONSOLIDER INGENIO 2010 Project (Ref. No. CSD2007-00045). The author also thanks the Spanish MICINN for a FPI research grant (Ref. No. BES-2009-013434).Peer Reviewe

Self-assembly of ultra-thin lanthanide oxide nanowires via surfactant-mediated imperfect oriented attachment of nanoparticles

We report a simple synthesis of ultra-thin lanthanide oxide nanowires and ribbons via the autoclave-based decomposition of lanthanide oleates within passivating surfactants. Electron microscopy reveals the formation of linear self assemblies of lanthanide oxide nanoparticles that subsequently recrystallize into high aspect ratio materials via an “imperfect oriented attachment” mechanism

Origin of the high upconversion green luminescence efficiency in -NaYF4:2% Er3+,20% Yb3+

Site-selective spectroscopy in hexagonal beta-NaYF4:Er3+,Yb3+ has revealed different environments for Er3+ ions (multisite formation). The low-temperature S-4(3/2) -> (I15/2Er3+)-I-4 green emission depends on the excitation wavelength associated with the F-4(7/2) Er3+ level. We have studied the effect of hydrostatic pressure on the green, red, and blue Er3+ emission upon NIR excitation at similar to 980 nm, in order to establish the role played by energy resonance conditions and the multiple Er3+ sites due to the disordered structure for the upconversion (UC) process (energy tuning). The variation of photoluminescence spectra and lifetimes as a function of pressure and temperature reveals that the origin of the high green UC efficiency of the beta-NaYF4:Er3+,Yb3+ compound is mainly due to the multisite distribution, and the low phonon energy of the host lattice

Nano-ZnO leads to tubulin macrotube assembly and actin bundling triggering cytoskeletal catastrophe and cell necrosis

Zinc is a crucial element in biology that plays chief catalytic, structural and protein regulatory roles. Excess cytoplasmic Zinc is toxic to the cells so there are cell-entry and intracellular buffering mechanisms that control intracellular Zinc disponibility. Tubulin and actin are two Zinc-scavenging proteins that are essential components of the cellular cytoskeleton implicated in cell division, migration and cellular architecture maintenance. Here we demonstrate how exposure to different ZnO nanostructures, namely ZnO commercial nanoparticles and custom-made ZnO nanowires, produce acute cytotoxic effects in human keratinocytes (HaCat) and epithelial cells (HeLa) triggering a dose-dependent cell retraction and collapse. We show how engulfed ZnO nanoparticles dissolve intracellularly, triggering actin filament bundling and structural changes in microtubules, transforming these highly dynamic 24nm diameter polymers into rigid macrotubes of tubulin, severely affecting cell proliferation and survival. Our results demostrate that nano-ZnO causes an acute cytoskeletal collapse that triggers necrosis, followed by a late reactive oxygen species (ROS)-dependent apoptotic process.This work has been supported by the Spanish ISCIII-MINECO under Projects ref. PI13/01074, AES 2013; FONDOS FEDER; MAT2012-38664-C02-01. We especially thank the IDIVAL for their support to LGH and the IDIVAL-Microscopy Unit for all the microscopy imaging

Free-labeled nanoclay intracellular uptake tracking by confocal Raman imaging

Laponite is a nanoplatform that has been successfully used as a new biomaterial for drug delivery, tissue engineering and bioimaging at the nanoscale. In general, a deep knowledge of the mechanism interaction of the nanomaterial with biological components in a physiological environment is highly desirable for properly characterizing its therapeutic efficacy and toxicology. Up to know, the use of fluorescent dyes labelling both, the nanomaterial and cell components, has been a requirement to characterize the cell uptake and to visualize the entrance of the nanomaterial into the cytosol and the cell nucleus. The used of fluorophores usually perturb the physiological medium and can interfere in the nanomaterial cell interaction. A new Raman imaging methodology to track the uptake and internalization of Laponite nanoparticles into J774 macrophages line cells is presented in this work. The combination of Raman spectroscopy and confocal microscopy provides direct information about the localization of the nanoparticle into the cell, through its unique vibrational fingerprint without labelling or adding dyes, and taking advantage of the fact that Laponite and biological molecules bands can be clearly differentiated.We would like to thank IDIVAL for financial support, Projects N°NVAL16/17, INNVAL19/18 and NVAL18/07. CRL thanks the MINECO for the Juan de la Cierva Formación grant (ref. FJCI-2015-25306). This work has been supported by the Spanish MINECO, Instituto de Salud Carlos III, the European Union FEDER funds under Projects ref. PI16/00496 (AES 2016), PI19/00349 and DTS19/00033 (AES 2019). The authors are grateful to Dr F Madrazo and the Laser Microscopy Unit of the IDIVAL Institute for the use of the Confocal Raman Imaging Microscope