1,720,969 research outputs found
Inorganic nanosized UV filters for cosmetic applications
No full textL’attività di ricerca di questo lavoro di tesi riguarda lo studio di filtri inorganici con un ampio range di schermatura UV e ridotta attività fotocatalitica da applicare in cosmetica per la protezione della pelle contro gli effetti dei raggi UV. Sono stati sintetizzati campioni a base di TiO2 in nanoparticelle di silice mesoporosa (MSN), dimostrando però un'elevata attività fotocatalitica. Al fine di evitare il contatto diretto tra il fotocatalizzatore e l'ambiente circostante, i filtri sintetizzati sono stati rivestiti con una shell di silice non porosa, portando ad un abbattimento dell'attività fotocatalitica, senza pregiudicare le proprietà UV. Infine, sono stati sviluppati nanomateriali autosigillanti a base di BixTiyOz in MSN. Il doppio ruolo degli ioni Bi3+ nell'aumento delle proprietà UV e nell'abbattimento della fotocatalisi fa sì che il materiale proposto sia un perfetto candidato per lo sviluppo di filtri UV di prossima generazione. Inoltre, le interessanti proprietà emerse possono essere ampiamente sfruttate nell'ambito dei filtri solari con l'obbiettivo di abbattere il fotodegrado delle matrici organiche presenti nella formulazione
Sistema multianalitico integrato per la valutazione degli effetti dell’alta marea sui paramenti lapidei veneziani
No full textThe (Building) Stones of Venice under Threat: A Study about Their Deterioration between Climate Change and Land Subsidence
Full text linkCultural heritage assets face significant threats from climate change and land subsidence, leading to extensive social, economic, and environmental losses, and damage to artistic and monumental heritage in Italian coastal cities. In particular, addressing these challenges in the Venetian context necessitates the development of an adaptation plan for the lagoon area and the identificat on of targeted intervention strategies to preserve cultural and territorial heritage. To address these objectives, a systematic study was conducted to investigate the deterioration patterns exhibited by the most representative lithologies used in Venetian buildings. Thirty samples of five carbonate stone varieties subjected to natural aging were monitored in six different areas of Venice’s historic center and on Torcello Island, selected based on altimetry relative to tidal zero and exposure to environmental forces. An integrated multi-analytical approach was employed to identify and map macro- and micro-morphologies of stone surfaces related to chemical weathering and physical decay.
Stones underwent evaluation during nine monitoring periods using various tests (ultrasound P-wave velocity and colorimetric measures) and analyses (μX-Ray Fluorescence, X-ray powder diffraction, stereomicroscope observations, and recognition of biological patinas). Data processing aimed to elucidate how microclimate and intrinsic stone features influence the occurrence and progression of deterioration phenomena. From the experimental findings, a Stone Deterioration Index and Intervention Procedures (SDIi) were proposed to estimate deterioration rates and assess the need for targeted intervention through conservative actions
Temperature Matters: An Infrared Spectroscopic Investigation on the Photocatalytic Efficiency of Titania Coatings
No full textTitania is one of the most studied photocatalytic materials for self-cleaning applications. To maximize the photocatalytic
efficiency, different strategies are currently under investigation, such as control of the nano- or microstructure,
optimization of the crystalline phase and addition of doping agents. A parameter too often neglected
is temperature, which dramatically affects the self-cleaning processes in thin titanium dioxide (TiO2) films. In this
study, we prepared a titania coating using the sol–gel route. Stearic acid and a triblock copolymer (Pluronic
F127) were used as model pollutants. A dedicated heating cell was used to precisely control the temperature.
The infrared spectroscopy was used to follow the amount of residual pollutant agents within 60 minutes every
10 C. The photocatalytic reaction rate was calculated for the stearic acid in the 25–60 C range
Evaluating two nanosilica dimensional range for the consolidation of degraded silicate stones
No full textThe application of silica nanoparticles strengthening agents in conservation of monumental and architectural heritage field is currently a challenge of particular interest. Some commercial products are already on the market and several studies highlighted the related strength and weakness. In order to contribute to the knowledge of the interaction between nanoparticles and stone materials as well as to provide key elements to improve the approach to conservative treatments, two silica nanoparticles products for the consolidation of silicate stones were developed in the laboratory. Bianco Sardo granite, Firenzuola and Muggia sandstones were selected as substrates for the experimentation after a laboratory investigation of their open porosity. Silica nanoparticles having two different particles size, both compatible with the porosimetric features of the selected stones, were synthesized and dispersed in an ethanol-water solution. The carrier was specifically studied for avoiding the agglomeration of silica nanoparticles and facilitating the penetration of the products in the stone substrates. Sound and artificially aged specimens were impregnated by capillary absorption method and the effectiveness of the treatment was evaluated through morphological and physical analyses. Microscopic observations, colorimetric analyses, sponge tests, ultrasound velocity determinations and porosimetric measurements showed positive results, which encourage, on one hand, the use of silica nanoparticles for consolidating silicate stones, on the other hand, further researches aimed to improve the synthesized products by reaching a deeper penetration and the reduction of water absorption
Climate change and land subsidence in the frame of "Venezia 2021" project : the deterioration of architectural stone materials
No full textThe overflowing of the canals and the flooding of the pedestrian walkways are the consequences of the well-known periodic large water inflow into the Venetian lagoon (high water or acqua alta). These phenomena lead the strong degradation of the stone buildings over time. With the aim to better understand the effects of high water and support the best actions and practices for preserving the cultural heritage of Venice by Municipality and Superintendences, thirty samples of five varieties of carbonate lithotypes were exposed to natural weathering in different Venetian areas and on Torcello island. The specimens were periodically monitored and compared with samples made of the same lithologies subjected to accelerated artificial aging tests. The results concerning the main deterioration morphologies observed on all the samples after three years of exposure are here presented and commented
Bi2SiO5@g-SiO2 upconverting nanoparticles: a bismuth-driven core-shell self-assembly mechanism
No full textCore-shell systems have attracted increasing interest among the research community in recent years due to their unique properties and structural features, and the development of new synthetic strategies is still a challenge. In this work, we have investigated lanthanide-doped Bi2SiO5 nanocrystal formation inside mesoporous silica nanoparticles (MSNs). The role of both synthesis temperature and concentration of the bismuth precursor impregnated into the MSNs is discussed, showing an unprecedented strategy for the simultaneous stabilization of a crystalline core and a glassy shell. Temperature dependent synchrotron radiation X-ray powder diffraction (SR-XRPD) and high resolution transmission electron microscopy (HR-TEM) analyses allow one to follow the crystalline core growth. A mechanism for the formation of a Bi2SiO5@g-SiO2 core-shell nanosystem is proposed. In addition, the easy tunability of the color output of the upconverting system is demonstrated by means of suitable doping lanthanide ions with potential applications in several fields
Photo-degradation of Methylene Blue by TiO2 containing ordered mesoporous silica nanoparticles with large pores and spherical morphology
No full text
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
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