Photoluminescence characterization of aged and regenerated mesoporous silica

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Blending for student engagement: lessons learned for the MOOCs and beyond

The purpose of this ongoing, three-year action research study is to explore the digital challenges of student engagement in higher education within the experimental platform of blended learning. Research questions examine the role of digital innovation in supporting diverse learners, as well as building meaningful connections with technology for undergraduate teacher education students. Results from qualitative data collected through instructor journals and field notes and student mid-term and exit surveys during year one, indicate blended learning can be effective for modelling how to use technology to shift learners towards more active agency. The immediacy of the localised university classroom delivered a viable research setting for digital experimentation, while providing a significant lived experience for undergraduates to springboard their future technological practices with K–12 students. Four pedagogical opportunities for digital intentionality in virtual spaces emerged during data analysis and are shared as considerations for future innovation: (1) designing digital resources, (2) scaffolding student learning, (3) learner customisation, and (4) promoting the lived experience. Lessons learned could be effective in helping develop higher quality educational experiences for on-campus students, as well as scaffolding greater engagement in online formats involving more global populations (e.g., massive online open courses – MOOCs)

Formation mechanisms and phase stability of solid-state grown cspbi3 perovskites

CsPbI3 inorganic perovskite is synthesized by a solvent-free, solid-state reaction, and its structural and optical properties can be deeply investigated using a multi-technique approach. X-ray Diffraction (XRD) and Raman measurements, optical absorption, steady-time and time-resolved luminescence, as well as High-Resolution Transmission Electron Microscopy (HRTEM) imaging, were exploited to understand phase evolution as a function of synthesis time length. Nanoparticles with multiple, well-defined crystalline domains of different crystalline phases were observed, usually surrounded by a thin, amorphous/out-of-axis shell. By increasing the synthesis time length, in addition to the pure α phase, which was rapidly converted into the δ phase at room temperature, a secondary phase, Cs4PbI6, was observed, together with the 715 nm-emitting γ phase

Insight into the Molecular Model in Carbon Dots through Experimental and Theoretical Analysis of Citrazinic Acid in Aqueous Solution

The molecular emission model is the most accredited one to explain the emission properties of carbon dots (CDs) in a low-temperature bottom-up synthesis approach. In the case of citric acid and urea, the formation of a citrazinic acid (CZA) single monomer and oligomers is expected to affect the optical properties of the CDs. It is therefore mandatory to elucidate the possible role of weak bonding interactions in determining the UV absorption spectrum of some molecular aggregates of CZA. Although this carboxylic acid is largely exploited in the synthesis of luminescent CDs, a full understanding of its role in determining the final emission spectra of the produced CDs is still very far to be achieved. To this aim, by relying on purely first-principles density functional theory calculations combined with experimental optical characterization, we built and checked the stability of some molecular aggregates, which could possibly arise from the formation of oligomers of CZA, mainly dimers, trimers, and some selected tetramers. The computed vibrational fingerprint of the formation of aggregates is confirmed by surface-enhanced Raman spectroscopy. The comparison of experimental data with calculated UV absorption spectra showed a clear impact of the final morphology of the aggregates on the position of the main peaks in the UV spectra, with particular regard to the 340 nm peak associated with n-π∗ transition

High Contrast Imaging in the Visible: First Experimental Results at the Large Binocular Telescope

In February 2014, the SHARK-VIS (System for High contrast And coronography from R to K at VISual bands) Forerunner, a high contrast experimental imager operating at visible wavelengths, was installed at LBT (Large Binocular Telescope). Here we report on the first results obtained by recent on-sky tests. These results show the extremely good performance of the LBT ExAO (Extreme Adaptive Optics) system at visible wavelengths, both in terms of spatial resolution and contrast achieved. Similarly to what was done by (Amara et al. 2012), we used the SHARK-VIS Forerunner data to quantitatively assess the contrast enhancement. This is done by injecting several different synthetic faint objects in the acquired data and applying the ADI (angular differential imaging) technique. A contrast of the order of $5 \times 10^{-5}$ is obtained at 630 nm for angular separations from the star larger than 100 mas. These results are discussed in light of the future development of SHARK-VIS and compared to those obtained by other high contrast imagers operating at similar wavelengths.Comment: Astronomical Journal - Accepted for publicatio

Raman spectra and vibrational analysis of CsPbI3: a fast and reliable technique to identify lead halide perovskite polymorphs

A major issue in the development of Lead halide perovskites is the assessment of the crystal structure of the samples, due to their typically limited time-stability, and the understanding of the role of external factors that can induce a crystal phase transformation (such as humidity, intense light flux, temperature, etc.). In this perspective, it is of utmost importance to have at disposal a fast and reliable experimental tool able to give an immediate indication of the polymorph of the sample with the possibility to integrate in-situ measurements for constant monitoring. In this paper we propose Raman spectroscopy as the ideal technique to solve this problem. The vibrational analysis of CsPbI3 in the α-phase and δ-phase and of the Cs4PbI6 secondary phase is reported and all the vibrational modes are assigned by comparing experimental spectra of the phases to Raman modes calculated within the DFT framework. Finally, the mechanism of laser induced phase degradation was studied using in-situ Raman measurements providing new insights on the secondary phase generated during the process

Transient absorption study on Red Vermilion darkening in presence of chlorine ions and after UV exposure

The application of no destructive techniques in the field of Cultural Heritage is becoming fundamental to understanding degradation phenomena. In this study, Transient Absorption (TA) spectroscopy was exploited to explain the process which causes the darkening of Red Vermilion, a famous pigment known also as cinnabar. The optical properties involved in the process are studied in pure HgS and chlorine doped HgS samples, before and after exposure to UV light (365 nm). The study was carried out with particular attention on the ground state bleaching signals, directly connected to the formation of intra-gap trap levels responsible for the pigment degradation. First derivative reflectance spectra reveal the presence of these defectivities, while the analysis of Tauc plots from Kubelka Munk function confirms the reduction of energy band gap due to UV exposure. With the help of Density Functional calculations, we simulated the role of S vacancies in producing a defective alpha-phase, the consequent reduction of the energy band gap and, finally, the progressive phase transformation to the cubic metacinnabar. Transient Absorption turns out to be an important tool of diagnosis about the conservation state of pigments applied in the field of Cultural Heritage

Demographic Decline, Population Ageing and Modern Financial Approaches to Urban Policy

This article discusses the interaction between demographic aging, population decline, and various aspects of the local development challenges facing public authorities. In particular, this article examines some of the financial issues arising from population aging and decline and the ways in which new approaches to public finance are being used in support of European Union regional and urban policy. In this context, it is argued that a comprehensive portfolio investment approach has the potential to significantly improve policy effectiveness

Life Cycle Assessment (LCA): New poplar clones allow an environmentally sustainable cultivation

In Italy 72 poplar clones ( Populus spp.) are registered for commercialization. They were selected for fast growth, stem shape and disease resistance. The new selections (named MSA) includes genotypes with very high resistance to all the main diseases and to one insect, Phloeomizus passerinii (Sign.). Fast growth and disease resistance allow to produce wood with low environmental and economic costs; for this reason in some Italian Regions the introduction of a percentage of these clones in poplar stand is mandatory to obtain funding for their establishment (Rural Development Plan). To better understand the environmental advantages deriving from the use of these clones, in comparison with the old genotypes (particularly ‘I-214’), a ‘Life Cycle Assessment’ approach was applied considering as impact indicator the CO 2 equivalent emissions; from stoolbed to commercial stand, primary data were collected from an Italian experience. Firstly with the Inventory Analysis all the raw material, energy, wastes and emissions related were collected for each cultivation phase. The Analysis showed a reduction of 9% of CO 2 eq. ha -1 emitted, growing MSA instead of ‘I-214’. Considering the emissions per volume of wood, ‘I-214’ requests 47.5 kg CO 2 eq. per m 3 , compared with MSA that request 36.6 kg CO 2 eq. per m 3

Integrating sol-gel and carbon dots chemistry for the fabrication of fluorescent hybrid organic-inorganic films

Highly fluorescent blue and green-emitting carbon dots have been designed to be integrated into sol-gel processing of hybrid organic-inorganic materials through surface modification with an organosilane, 3-(aminopropyl)triethoxysilane (APTES). The carbon dots have been synthesised using citric acid and urea as precursors; the intense fluorescence exhibited by the nanoparticles, among the highest reported in the scientific literature, has been stabilised against quenching by APTES. When the modification is carried out in an aqueous solution, it leads to the formation of silica around the C-dots and an increase of luminescence, but also to the formation of large clusters which do not allow the deposition of optically transparent films. On the contrary, when the C-dots are modified in ethanol, the APTES improves the stability in the precursor sol even if any passivating thin silica shell does not form. Hybrid films containing APTES-functionalized C-dots are transparent with no traces of C-dots aggregation and show an intense luminescence in the blue and green range