Study of Molecular Sensitization Processes of Nanostructured Metal Oxides

Functional hybrids are nano-composite materials lying at the interface of organic and inorganic realms, combining properties and advantages of both materials, and possibly minimizing their disadvantages. Nanostructured titanium dioxide is one of the most investigated material for hybrid systems, as its application areas range from photovoltaics and photocatalysis to photo-/electrochromics, optoelectronics and sensors. Among organic molecules, metal-phthalocyanines (MPcs) are of particular interest due their great versatility and high thermal and chemical stability. A critical and very challenging issue in hybrid system engineering is the contemporary achievement of the metal oxide nano-crystals and the molecular sensitization process. As the high crystalline quality of TiO2 is commonly obtained through thermal treatments, its organic decoration is usually carried out in successive separate steps. Supersonic beams techniques (SuMBD) offer to overcome this challenge, thanks to the possibility of working with both organic molecules and inorganic aggregates, and to the ability to achieve physical and chemical processes at surfaces. The final aim of this thesis work is the study of the molecular sensitization processes, induced by supersonic beams approaches, occurring at the titanium dioxide/copper phthalocyanine interface. A preliminary extensive analysis of the nanostructured TiO2 thin films grown by PMCS is performed, in order to test the material peculiarities resulting from the non conventionality of the deposition technique. At the Parma IMEM-CNR Laboratories, the as-grown TiO2 thin films were investigated by means of several electron microscopy techniques. The morphological and luminescence properties have been evaluated by Scanning Electron Microscopy and Cathodoluminescence, while Transmission Electron Microscopy analyses provided the structural information. These studies have been integrated by surface photoelectron spectroscopies (XPS and UPS), that the candidate performed at the Trento IMEM-CNR Laboratories in order to study the material electronic properties. Moreover, the effects of annealing treatments on the observed properties have been investigated and discussed. Photoelectron emission experiments on both copper and free-base phthalocyanine, grown by SuMBD. These experiments have been carried out at synchrotron ELETTRA (Trieste). The aim of this study was to understand the real influence of the metal core on the molecule electronic properties. Taking advantages of the high resolution of the synchrotron facility, it was possible to determine well suitable fit models for both molecules. In particular, the deconvolution model related to the CuPc was decisive in the last part of this thesis work, to analyze the reactivity processes at the inorganic/organic interface. After achieving a comprehensive knowledge of the electronic properties of both the organic and the inorganic counterparts, we focused our attention to the chemical reactivity phenomena occurring at their interface, which is the final aim of this thesis work. In the Trento IMEM-CNR Laboratories, we got two hybrid systems with the same configuration (CuPc/TiO2) in a combined PMCS/SuMBD approach. In both cases the nanocrystalline metal oxide has been synthesized by PMCS, at room temperature without the need of any thermal treatment. In order to understand the role of the kinetic energy during the sensitization process, the CuPc deposition has been performed by molecular seeded beams at high (experiment A) and low (experiment B) kinetic energies. For both hybrid systems, a complete characterization of core levels and valence band states have been performed at increasing organic coverages, in order to better emphasize the dynamic of the chemical bonds formation at the interface, induced by different kinetic energies.Combinando materiali organici ed inorganici è possibile ottenere materiali funzionali ibridi con proprietà fisico-chimiche modulate al tipo di applicazione desiderata. Un sistema ibrido particolarmente promettente per l’energetica e la sensoristica è quello costituito da biossido di titanio nanostrutturato e metalloftalocianine. Una delle sfide più attuali nell’ingegnerizzazione di sistemi ibridi è la realizzazione contemporanea dell’ossido metallico nanostrutturato e della sensitizzazione molecolare. Infatti i comuni metodi di crescita del TiO2 si servono di processi termici al fine di attivarne la cristallizzazione; affinchè ciò non vada a danneggiare le molecole organiche funzionalizzanti, i processi di sensitizzazione molecolare vengono solitamente effettuati in una fase successiva. Le tecniche di deposizione basate su fasci supersonici possono superare questo ostacolo, grazie alla possibilità di lavorare con materiali sia organici (SuMBD) che inorganici (PMCS), e alla capacità di attivare processi chimici e fisici alle interfacce. Lo scopo di questo lavoro di tesi è appunto lo studio dei processi di sensitizzazione molecolare indotti da fasci supersonici, realizzato sull’interfaccia biossido di titanio/rameftalocianina (n-TiO2/CuPc). Studi preliminari sono stati effettuati separatamente sia sul materiale inorganico che sulle molecole organiche, al fine di analizzarne le peculiarità risultanti dalla non convenzionalità della tecnica di crescita. I film sottili di TiO2 as-grown sono stati analizzati presso I laboratori del IMEM-CNR di Parma, mediante diverse tecniche di microscopia elettronica. Le proprietà morfologiche e di luminescenza sono stati osservate mediante Microscopio Elettronico a Scansione e Catodoluminescenza, mentre le informazioni strutturali sono state ottenute da misure di Microscopia Elettronica in Trasmissione. Tali studi sono stati integrati da Spettroscopie di superficie (XPS and UPS) effettuate presso I laboratori IMEM-CNR di Trento, al fine di analizzare le proprietà elettroniche del materiale. Inoltre, sono stati analizzati gli effetti dei trattamenti termici sulle proprietà appena descritte. Ulteriori esperimenti di Spettroscopie da fotoelettroni sono state effettuati su film di ftalocianina-rame (CuPc) e free-base (H2Pc), al fine di individuare l’influenza del centro metallico sulle proprietà elettroniche della molecola. Tali analisi sono state effettuate presso il sincrotrone ELETTRA (Trieste). Dopo aver studiato le proprietà elettroniche di entrambi I materiali, sono stati analizzati i fenomeni di reattività alle loro interfacce. Presso i laboratori IMEM-CNR di Trento abbiamo ottenuto due sistemi ibridi con la stessa configurazione CuPc/TiO2. In entrambi i casi l’ossido metallico nanostrutturato è stato sintetizzato a temperatura ambiente con la sorgente PMCS, senza ulteriori post-processing termici. Al fine di studiare il ruolo dell’energia cinetica durante il processo di sensitizzazione, la deposizione della CuPc è stata effettuata mediante fasci molecolari supersonici sia ad alta (esperimento A) che a bassa (esperimento B) energia cinetica. Entrambi I sistemi ibridi sono stati analizzati acquisendo i core levels e gli stati della banda di valenza durante le varie fasi della deposizione. In questo modo è stato possible osservare la dinamica della formazione di legami chimici indotti dalla diversa energia cinetic

The effects of claw regeneration on territory ownership and mating success in the fiddler crab Uca mjoebergi

Underlying male quality is often reflected in the condition of sexually selected traits. In fiddler crabs, male success in both intra- and interspecific interactions is highly dependent on the size of the major claw. However, males are often forced to autotomize their major claw. Claw regeneration significantly altered the structure of a males' major claw in Uca mjoebergi. We found, however, that claw regeneration did not affect signal quality. Both males and females were unable to visually distinguish a regenerated claw from an original claw. Although regenerated males were inferior fighters, males were able to compensate for this fighting disadvantage by avoiding fights with other males. Regenerated males were, however, less likely to acquire and defend high-quality territories and consequently suffered a decrease in mating success

Calibrating Tropical Forest Coexistence in Ecosystem Demography Models Using Multi-Objective Optimization Through Population-Based Parallel Surrogate Search

Tropical forest diversity governs forest structures, compositions, and influences the ecosystem response to environmental changes. Better representation of forest diversity in ecosystem demography (ED) models within Earth system models is thus necessary to accurately capture and predict how tropical forests affect Earth system dynamics subject to climate changes. However, achieving forest coexistence in ED models is challenging due to their computational expense and limited understanding of the mechanisms governing forest functional diversity. This study applies the advanced Multi-Objective Population-based Parallel Local Surrogate-assisted search (MOPLS) optimization algorithm to simultaneously calibrate ecosystem fluxes and coexistence of two physiologically distinct tropical forest species in a size- and age-structured ED model with realistic representation of wood harvest. MOPLS exhibits satisfactory model performance, capturing hydrological and biogeochemical dynamics observed in Barro Colorado Island, Panama, and robustly achieving coexistence for the two representative forest species. This demonstrates its effectiveness in calibrating tropical forest coexistence. The optimal solution is applied to investigate the recovery trajectories of forest biomass after various intensities of clear-cut deforestation. We find that a 20% selective logging can take approximately 40 years for aboveground biomass to return to the initial level. This is due to the slow recovery rate of late successional trees, which only increases by 4% over the 40-year period. This study lays the foundation to calibrate coexistence in ED models. MOPLS can be an effective tool to help better represent tropical forest diversity in Earth system models and inform forest management practices.publishedVersio

Tree mortality and Extreme Rainfall in the Amazon

Mesoscale Convective Systems (MCS) are responsible for severe rainfall in the Amazon and can produce strong descending winds that can uprooting or break trees the most dominant mode of tree mortality in the Amazon. Our results show that severe rainfall help to explain the observed residence time of woody biomass and tree mortality in the Amazon

\u201cArchivi intermediali: il valzer nella testualit\ue0 byroniana\u201d

Tratto ricorrente del discorso letterario fin dall\u2019antichit\ue0, l\u2019interazione fra testo e danza fa della letteratura una delle possibili chiavi d\u2019accesso alla ricostruzione storica dei fenomeni legati alla danza, ovvero un particolare archivio del corpo. Caso specifico di \uabletteralizzazione della danza\ubb \ue8 l\u2019incontro intermediale fra la testualit\ue0 byroniana e il valzer. Introdotto ufficialmente a Londra nel 1812, il valzer venne salutato come un ballo sconveniente, che riscosse comunque il favore della migliore societ\ue0, incluso quello del Principe Reggente. Nel 1813 Byron si un\uec al coro censorio con il poemetto \u201cWaltz\u201d, pubblicato in forma anonima, che sviluppava il tema della promiscuit\ue0 del nuovo ballo. L\u2019apparente moralismo di Byron viene qui letto nel contesto della Reggenza come reazione a una pratica sociale con specifiche connotazioni di genere e classe, rintracciando la presenza ricorrente del valzer a livello figurale nella produzione byroniana

Global biosphere-climate interaction : a causal appraisal of observations and models over multiple temporal scales

Improving the skill of Earth system models (ESMs) in representing climate-vegetation interactions is crucial to enhance our predictions of future climate and ecosystem functioning. Therefore, ESMs need to correctly simulate the impact of climate on vegetation, but likewise feedbacks of vegetation on climate must be adequately represented. However, model predictions at large spatial scales remain subjected to large uncertainties, mostly due to the lack of observational patterns to benchmark them. Here, the bidirectional nature of climate-vegetation interactions is explored across multiple temporal scales by adopting a spectral Granger causality framework that allows identification of potentially co-dependent variables. Results based on global and multi-decadal records of remotely sensed leaf area index (LAI) and observed atmospheric data show that the climate control on vegetation variability increases with longer temporal scales, being higher at inter-annual than multi-month scales. Globally, precipitation is the most dominant driver of vegetation at monthly scales, particularly in (semi-)arid regions. The seasonal LAI variability in energy-driven latitudes is mainly controlled by radiation, while air temperature controls vegetation growth and decay in high northern latitudes at inter-annual scales. These observational results are used as a benchmark to evaluate four ESM simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Findings indicate a tendency of ESMs to over-represent the climate control on LAI dynamics and a particular overestimation of the dominance of precipitation in arid and semi-arid regions at inter-annual scales. Analogously, CMIP5 models overestimate the control of air temperature on seasonal vege-tation variability, especially in forested regions. Overall, climate impacts on LAI are found to be stronger than the feedbacks of LAI on climate in both observations and models; in other words, local climate variability leaves a larger imprint on temporal LAI dynamics than vice versa. Note however that while vegetation reacts directly to its local climate conditions, the spatially collocated character of the analysis does not allow for the identification of remote feedbacks, which might result in an underestimation of the biophysical effects of vegetation on climate. Nonetheless, the widespread effect of LAI variability on radiation, as observed over the northern latitudes due to albedo changes, is overestimated by the CMIP5 models. Overall, our experiments emphasise the potential of benchmarking the representation of particular interactions in online ESMs using causal statistics in combination with observational data, as opposed to the more conventional evaluation of the magnitude and dynamics of individual variables

Multi-scale sensible heat fluxes in the urban environment from large aperture scintillometry and eddy covariance

Sensible heat fluxes (QH) are determined using scintillometry and eddy covariance over a suburban area. Two large aperture scintillometers provide spatially integrated fluxes across path lengths of 2.8 km and 5.5 km over Swindon, UK. The shorter scintillometer path spans newly built residential areas and has an approximate source area of 2-4 km2, whilst the long path extends from the rural outskirts to the town centre and has a source area of around 5-10 km2. These large-scale heat fluxes are compared with local-scale eddy covariance measurements. Clear seasonal trends are revealed by the long duration of this dataset and variability in monthly QH is related to the meteorological conditions. At shorter time scales the response of QH to solar radiation often gives rise to close agreement between the measurements, but during times of rapidly changing cloud cover spatial differences in the net radiation (Q*) coincide with greater differences between heat fluxes. For clear days QH lags Q*, thus the ratio of QH to Q* increases throughout the day. In summer the observed energy partitioning is related to the vegetation fraction through use of a footprint model. The results demonstrate the value of scintillometry for integrating surface heterogeneity and offer improved understanding of the influence of anthropogenic materials on surface-atmosphere interactions