1,721,005 research outputs found
Oxygen-Mediated Surface Photoreactions: Exploring New Pathways for Sustainable Chemistry
No full textThis Concept analyses and reviews recent works that take advantage of oxygen-mediated surface photoreactions for addressing key issues in the fields of sustainable chemistry, circular production of feedstocks and environmental remediation. Examples of metal and polymer recovery and recycling from waste, metal-free oxidation of organic molecules and exploitation of persistent radicals for destroying pollutants and disinfection are discussed, highlighting common aspects, peculiarities, potential and limitations.Oxygen-mediated surface photoreactions are an extremely versatile tool for environmental remediation, recycling of critical raw materials and sustainable production of feedstocks. This Concept reviews recent works on this class of reaction, including examples of metal and polymer recovery and recycling from waste, metal-free oxidation of organic molecules and exploitation of persistent radicals for destroying pollutants and disinfection.imag
Using optical resonances to control heat generation and propagation in silicon nanostructures
No full textIntegrated electronics, photonics and optoelectronics need full control of lattice reconstruction processes in silicon nanostructures at the nanoscale level. However, conventional thermal treatments do not meet the challenging requirements necessary for developing next-generation devices. Light can be a powerful tool to trigger and control opto-thermal effects in resonant nanostructures. Here we propose a new computational approach to light-matter interactions in silicon nanopillars, which simulates heat generation and propagation dynamics occurring in continuous wave laser processing over a wide temporal range (from 1 fs to about 25 hours). We demonstrate that a rational design of the nanostructure aspect ratio, type of substrate, laser irradiation time and wavelength enables amorphous-to-crystalline transformations to take place with a precise, sub-wavelength spatial localization. In particular, we show that visible light can be exploited to selectively crystallize the internal region of the pillars, which is not possible by conventional treatments. A detailed study on lattice crystallization and reconstruction dynamics reveals that local heating drives the formation of secondary antennas embedded into the pillars, highlighting the importance of taking into account the spatial and temporal evolution of the optical properties of the material under irradiation. This approach can be easily extended to many types of nanostructured materials and interfaces, offering a unique computational tool for many applications involving opto-thermal processes (fabrication, data storage, sensing, catalysis, resonant laser printing, opto-thermal therapy, etc...)
4‐Aminothiophenol Photodimerization Without Plasmons
Full text linkThe photodimerization of 4‐aminothiophenol (PATP) into 4,4′‐dimercaptobenzene (DMAB) has been extensively utilized as a paradigm reaction to probe the role of surface plasmons in nanoparticle‐mediated light‐driven processes. Here I report the first observation of the PATP‐to‐DMAB photoreaction in the absence of any plasmonic mediators. The reaction was observed to occur with different kinetics either for PATP adsorbed on non‐plasmonic nanoparticles (TiO(2), ZnO, SiO(2)) or deposited as macroscopic droplets. Confocal microRaman spectroscopy enabled to investigate the reaction progress in different plasmon‐free contexts, either aerobic or anaerobic, suggesting a new interpretation of the photodimerization process, based on direct laser‐induced activation of singlet oxygen species. These results provide new insights in light‐driven redox processes, elucidating the role of sample morphology, light and oxygen
Food-waste enables carboxylated gold nanoparticles to completely abat hexavalent chromium in drinking water
No full textAssessing green methods for pectin extraction from waste orange peels
No full textIn this work, we assess three different methods for the extraction of pectin from waste orange peels, using water as extracting solvent. “Hot-water”, Rapid Solid Liquid Dynamic (RSLD) and microwave-assisted extractions have been compared and evaluated in terms of amount and quality of extracted pectin, as well as embodied energy. This analysis provides useful guidelines for pectin production from food waste according to green procedures, enabling the identification of acidic “hot-water” as the most sustainable extraction route
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The role of morphology in all-dielectric SERS: A comparison between conformal (T-rex) and non conformal TiO2 shells
No full textAll-dielectric optical nanoantennas and resonators are attracting an ever increasing interest for enhanced Raman spectroscopy. These systems can take advantage of many factors that concur to determine their Raman response, including the type of material, refractive index contrast between interfaces, size, shape, roughness and geometrical configuration. However, the relative impact of each one of those terms on the Raman enhancement is still unclear. Here we report the Raman characterization of SiO2@TiO2 semishell microspheres obtained by rf-magnetron sputtering deposition of a TiO2 thin layer on SiO2 cores. The samples were able to significantly amplify Raman scattering in comparison to planar counterparts, however the overall enhancement was very limited with reference to that observed in conformal, smooth and compact TiO2 shell layers obtained by atomic layer deposition. These results demonstrated that geometry is a key factor to maximize the Raman response of these systems and, in general, it is more important than other parameters, such as the surface roughness or even refractive index of the shell layer, which are usually considered crucial for achieving Raman enhancement
Sodium doped lanthanum manganites thin films: Influence of the oxygen content on the structural parameters
No full textWe report the structural characterisation of La1-xNaxMnO3+delta thin films deposited by Rf-magnetron sputtering onto SrTiO3 (100) single crystal substrates. In particular, we focussed our attention on a series of samples annealed at different pO(2), ranging from 1 to 10(-6) atm. XRD and microRaman data show an expansion of the perovskite lattice for samples annealed in reducing conditions. This results agree with general manganite gas-solid equilibrium involving the formation of Mn4+ as the oxygen content increases. For pO(2) <10(-6) atm the structure rearranges because of the increasing the oxygen vacancies and the volume of the unit cell shrinks
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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