Estudio del sistema RE3+: YAG por medio de imagen de fluorescencia: Dispositivos microestructurados y carga térmica

Tesis doctoral inédita, leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de Materiales. Fecha de lectura: 15-10-201

Quo vadis, nanoparticle-enabled in vivo fluorescence imaging?

The exciting advancements that we are currently witnessing in terms of novel materials and synthesis approaches are leading to the development of colloidal nanoparticles (NPs) with increasingly greater tunable properties. We have now reached a point where it is possible to synthesize colloidal NPs with functionalities tailored to specific societal demands. The impact of this new wave of colloidal NPs has been especially important in the field of biomedicine. In that vein, luminescent NPs with improved brightness and near-infrared working capabilities have turned out to be optimal optical probes that are capable of fast and high-resolution in vivo imaging. However, luminescent NPs have thus far only reached a limited portion of their potential. Although we believe that the best is yet to come, the future might not be as bright as some of us think (and have hoped!). In particular, translation of NP-based fluorescence imaging from preclinical studies to clinics is not straightforward. In this Perspective, we provide a critical assessment and highlight promising research avenues based on the latest advances in the fields of luminescent NPs and imaging technologies. The disillusioned outlook we proffer herein might sound pessimistic at first, but we consider it necessary to avoid pursuing "pipe dreams"and redirect the efforts toward achievable - yet ambitious - goalsThis work has been cofinanced by European Structural and Investment Fund and by the European Union’s Horizon 2020 FET Open program under grant agreement no. 801305 (NanoTBTech). E.X. is grateful for a Juan de la Cierva Formacion scholarship (FJC2018-036734-I). A.B. acknowl- ́ edges funding from Comunidad de Madrid through TALENTO grant ref. 2019-T1/IND-14014. D.

Microfaunal soil food webs in Mediterranean semi-arid agroecosystems. Does organic management improve soil health?

Soil food webs, which are responsible for relevant ecological functions in agroecosystems such as nutrient cycling and pest and disease suppression, represent a crucial aspect of agricultural sustainability. We studied soil properties and microfaunal food web diversity and functioning in six paired organic and conventional fields located in Central Spain to assess the effects of organic farming on soil diversity and functioning in semi-arid conditions. We hypothesized that organic farming may enhance functioning of soil food webs. Our results showed larger differences between crop types, namely olive groves and vineyards, than between farming scheme, i.e. organic and conventional fields, and few benefits of organic farming in terms of soil fertility. Soil properties (total N, C, and P, available P and K, electrical conductivity, NH4+, NO3−, soil moisture, pH) tended to present higher values in vineyards than in olive groves and in conventional than in organic fields. Some plant-parasitic nematodes were associated to organic fields, especially in vineyards, and all soils fell within a degraded soil food web condition, with low Structure and Enrichment Index values. Nematode metabolic footprints showed relevant seasonal dynamics, with the more intensive herbivore activity in spring. We conclude that the lack of conventional pesticides and mineral fertilizers is probably not enough to improve soil conservation in semi-arid Mediterranean agroecosystems, and thus active soil conservation practices, as reduced tillage or cover cropping, are required to increase agroecosystem sustainability.Fundación Internacional para la Restauración de EcosistemasMinisterio de Economía y Competitivida

Nanoprobes for biomedical imaging with tunable near-infrared optical properties obtained via green synthesis

Ideally, any material used should be nontoxic and produced with safe, inexpensive, and energy-effective processes. In the case of optically active nanoparticles, this is often not the case, as they are frequently composed of hazardous heavy metals and/or produced with methods far from being environmentally friendly. Herein, the preparation of Ag2S-based nanoparticles via a simple green synthesis route is explored. Aqueous extracts of roasted coffee are used as sources of coordinating molecules. Optimization of the reaction conditions yields dimeric Ag Ag2S nanoparticles, whose near-infrared photoluminescence can be switched on via H2O2-mediated oxidation. This oxidation transforms suitable photoacoustic contrast agents into fluorescence imaging probes. Theoretical calculations further clarify the role of metallic silver in determining the optical properties of Ag2S. Overall, it is demonstrated that nanomaterials with tangible applicative potential can be prepared via cost- and energy-effective synthesis strategies that entail benign, renewable chemical

Soil chemical properties in abandoned Mediterranean cropland after succession and oak reforestation.

Large extents of cropland have been abandoned in recent decades and more may be abandoned in the near future. These may undergo secondary succession or reforestation. We experimentally tested the response of soil chemical properties to secondary succession (old field) and to Quercus ilex plantation (reforested cropland) in a Mediterranean cropland that was abandoned 13 years ago. We also evaluated the relevance of previous reforestation management (four combinations of presence and absence of irrigation and shading) in addition to current environmental conditions (herbaceous community and cover of oak canopy) on soil chemistry in the reforested cropland. Carbon and NH4+–N concentrations and availability of mineral N were higher in the reforested cropland than in the old field. However, soil pH, total N, P, K and NO3−–N concentrations, mineralization rates, and available PO43−–P were similar in the reforested cropland as well as in the old field. Previous reforestation management practices, particularly irrigation, and current environmental conditions, mostly biomass and composition of the herbaceous community, affected soil chemistry. Irrigation increased K and P concentrations and NH4+–N availability. This study highlights the overall slow dynamics of soil chemistry in Mediterranean ecosystems, which has resulted in little variation of soil properties in reforested cropland after more than a decade. Reforestation can accelerate the recovery of some soil properties of abandoned cropland in comparison with secondary succession, but these effects will be more noticeable in longer time periods.Ministerio de Ciencia y Educación, EspañaComunidad de MadridMinisterio de Economía y Competitividad, Españ

Woody species diversity in temperate Andean forests: the need for new conservation strategies

Chile has more than half of the temperate forests in the southern hemisphere. These have been included among the most threatened eco-regions in the world, because of the high degree of endemism and presence of monotypic genera. In this study, we develop empirical models to investigate present and future spatial patterns of woody species richness in temperate forests in south-central Chile. Our aims are both to increase understanding of species richness patterns in such forests and to develop recommendations for forest conservation strategies. Our data were obtained at multiple spatial scales, including field sampling, climate, elevation and topography data, and land-cover and spectrally derived variables from satellite sensor imagery. Climatic and land-cover variables most effectively accounted for tree species richness variability, while only weak relationships were found between explanatory variables and shrub species richness. The best models were used to obtain prediction maps of tree species richness for 2050, using data from the Hadley Centre's HadCM3 model. Current protected areas are located far from the areas of highest tree conservation value and our models suggest this trend will continue. We therefore suggest that current conservation strategies are insufficient, a trend likely to be repeated across many other areas. We propose the current network of protected areas should be increased, prioritizing sites of both current and future importance to increase the effectiveness of the national protected areas system. In this way, target sites for conservation can also be chosen to bring other benefits, such as improved water supply to populated areas.Universidad de ChileMinisterio de Planificación y Política Económic

Copper Indium Sulfide Quantum Dots as Nanomanometers: Influence of Size and Composition

Mechanical forces control the function of organisms and mediate theinteraction between biological systems and their environments. Knowledge ofthese forces will increase the understanding of biological processes and cansupport the development of novel diagnostic and therapeutic procedures.Although techniques like atomic force microscopy and droplet insertionmethod allow measuring forces over a broad range of values, they are invasiveand lack versatility. A promising way to overcome these hurdles isluminescent nanomanometry. Quantum dots (QDs) specifically have opticalproperties that depend on their size because of the quantum confinement,which makes them responsive to applied forces. Yet, a fine understanding ofhow fundamental parameters affect the response to applied stress is requiredbefore a QD family can be credibly proposed as luminescentnanomanometers. Here, a thorough study is conducted on how size andstoichiometry affect the nanomanometry performance of CuInS2QDs. Thestudied QDs feature pressure-dependent photoluminescence in thered/near-infrared range, which can enable the measurement of mechanicalforces in the range of physiological relevance in a remote and minimallyinvasive way. It is shown that tuning size and stoichiometry cansimultaneously enhance the CuInS2QDs’ brightness and response to appliedpressure, thus providing guidelines for better luminescent nanomanometers

Luminescence thermometry for brain activity monitoring: A perspective

Minimally invasive monitoring of brain activity is essential not only to gain understanding on the working principles of the brain, but also for the development of new diagnostic tools. In this perspective we describe how brain thermometry could be an alternative to conventional methods (e.g., magnetic resonance or nuclear medicine) for the acquisition of thermal images of the brain with enough spatial and temperature resolution to track brain activity in minimally perturbed animals. We focus on the latest advances in transcranial luminescence thermometry introducing a critical discussion on its advantages and shortcomings. We also anticipate the main challenges that the application of luminescent nanoparticles for brain thermometry will face in next years. With this work we aim to promote the development of near infrared luminescence for brain activity monitoring, which could also benefit other research areas dealing with the brain and its illnessesThis work was financed by the Spanish Ministerio de Innovación y Ciencias under project NANONERV PID 2019-106211RB-I00. BD acknowledges support from the Australian Research Council (DE200100985), RMIT University (Vice-Chancellor’s Fellowship Programme) and the Australian Academy of Sciences (JG Russell Award). PR-S is grateful for a Juan de la Cierva—Incorporación scholarship (IJC2019-041915-I). AB acknowledges funding from Comunidad de Madrid through TALENTO grant ref. 2019-T1/IND-14014. EX is grateful for a Juan de la Cierva - Incorporación scholarship (IJC2020-045229-I

Femtosecond-laser-written, stress-induced Nd:YVO4 waveguides preserving fluorescence and Raman gain

We report the formation of optical waveguides in the self-Raman Nd:YVO4 laser crystal by femtosecond laser inscription. The confocal fluorescence and Raman images have revealed that the waveguide is constituted by a locally compressed area in which the original fluorescence and Raman gains of the Nd:YVO4 system are preserved. Thus the obtained structures emerge as promising candidates for highly efficient self- Raman integrated laser sources

Upconverting nanoparticles as primary thermometers and power sensors

Luminescence thermometry is a spectroscopic technique for remote temperature detection based on the thermal dependence of the luminescence of phosphors, presenting numerous applications ranging from biosciences to engineering. In this work, we use the Er3+ emission of the NaGdF4/NaGdF4:Yb3+,Er3+/NaGdF4 upconverting nanoparticles upon 980 nm laser excitation to determine simultaneously the absolute temperature and the excitation power density. The Er3+ 2H11/2→4 I15/2 and 4 S3/2→4 I15/2 emission bands, which are commonly used for thermometric purposes, overlap with the 2 H9/2 →4 I13/2 emission band, which can lead to erroneous temperature readout. Applying the concept of luminescent primary thermometry to resolve the overlapping Er3+ transitions, a dual nanosensor synchronously measuring the temperature and the delivered laser pump power is successfully realized holding promising applications in laser-supported thermal therapies.publishe