1,721,194 research outputs found
Experiencing Borders as Bridges. Philosophical Inquiry and the Dynamics of In-formation.
No full textIl paper esplora – discutendo le prospettive di Vygotskij e Bachtin – il potenziale della comunità di ricerca filosofica nell’educazione interculturale
"Analysis of extended defects in melt grown GaSe single crystals by convergent beam electron diffraction"
No full text
Self-assembly and branching of sucrose stabilized silver nanoparticles by microwave assisted synthesis: from nanoparticles to branched nanowires structures
No full textSilver nanostructures were synthesized under microwave irradiation from a solution of silver nitrate and sucrose, with any other reducing or capping agent. The size and morphology of nanostructures changed continuously during the irradiation time. The obtained nanostructures at the different irradiation time were characterized by X-Ray diffraction, UV–vis spectroscopy, scanning and transmission electron microscopy and selected area diffraction pattern. It was evidenced that initially Ag nanoparticles were formed, which, as reaction time elapsed, self-assembled and fused with each other to yield nanowires and further branched nanowires. The formation of the silver branched nanostructures can be explained as a process of initial reduction–nucleation–adsorption–growth–branching growth
Characterization and Growth Mechanism of Selenium MicrotubesSynthesized by a Vapor Phase Deposition Route
No full textA simple and rapid vapor deposition route has been developed for the growth of trigonal phase selenium
microtubes in a horizontal tubular furnace under argon flow gas. Selenium powder was evaporated by heating at 300 C, and the
vapors were condensed on different quartz substrates located at 70-140 C. It was found that the morphologies of the products
were strongly affected by small variations of the temperatures of the deposition zones. It was observed that the growth of
microtubes was initiated by formation of nearly spherical microparticles with smooth surfaces; the smooth microspheres were
first covered by a rough layer and then they slowly became empty. The additional selenium atoms transported from the heated
part of the furnace or coming from the consumption of the inner core of the rough microparticles continued to adsorb on the
empty microspheres, allowing two possible growth mechanisms. If the additional Se atoms preferentially went to the
circumferential edges of the empty microspheres, crystalline microtubes with no defects were formed; however, Se atoms could
also follow a spiral growth mechanism starting from the empty shells. This second growth mechanism led to the formation of
semiclosed tubular structures with irregular surfaces, which developed into the relatively completed uniform microtubes with
smooth surfaces. The morphology, microstructure, and chemical composition of the microtubes were characterized by various
means (X-ray diffraction, energy-dispersive X-ray spectroscopy, Raman spectroscopy,UV-vis spectroscopy, scanning electron
microscopy, and transmission electron microscopy). The as-grown Se microtubes may find application as rapid response
photosensors and photocells
"Size-dependent lattice contraction in CdS1-xSex nanocrystals embedded in galass observed by Raman scattering"
No full textSynthesis and growth mechanism of dendritic Cu2−xSe microstructures
Full text linkDendritic crystalline copper selenides Cu2-xSe microstructures with various dimensions have been fabricated in large scale through thermal treatment of CuSe powder in argon flow, without any catalyst. The CuSe powder grains were used as both reagents and substrates for the growth of the Cu2-xSe dendrites. The synthesized microstructures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area diffraction pattern and Raman spectroscopy. Each individual dendrite was mainly composed of a long central trunk with secondary lateral branches. The length of the main trunk was in the range 10-30 mu m, the width of the secondary branch lay in the range 1-5 mu m. The trunk was about 1-2 mu m in diameter while the lateral branches were about 0.4-0.8 mu m in diameter. The lateral branches grew in parallel and kept about 60 degrees with respect to the central trunk.
A possible growth mechanism has been also proposed to account the growth of these Cu2-xSe dendritic microstructures
Poly(vinyl alcohol) capped silver nanoparticles as localized surface plasmon resonance-based hydrogen peroxide sensor
No full textA colorimetric hydrogen peroxide sensor based on localized surface plasmon resonance of poly(vinyl
alcohol) capped silver nanoparticles is introduced. The silver nanoparticles are directly synthesized in
the PVA matrix by a one-step method based on the reduction of the inorganic precursor AgNO3 through
thermal treatment in aqueous medium. No other reagent is used. These nanoparticles are characterized
using UV–vis spectroscopy, transmission electron microscopy and X-ray diffraction. Then they are used
for the preparation, characterization and calibration of a highly sensitive, cost-effective and renewable
localized surface plasmon resonance-based hydrogen peroxide sensor. The silver nanoparticles have the
catalytic ability for the decomposition of hydrogen peroxide; then the decomposition of hydrogen peroxide
induces the degradation of silver nanoparticles. Hence, a remarkable change in the localized surface
plasmon resonance absorbance strength could be observed. As a result, the yellow colour of the silver
nanoparticle–polymer solution was gradually changed to transparent colour. Furthermore, when this
transparent solution was subjected to thermal treatment, it became again yellow and the UV–vis spectroscopy
confirmed that nanoparticles were again formed, suggesting the renewability of this sensor.
The determination of reactive oxygen species such as hydrogen peroxide has possibilities for applying to
medical and environmental applications
"Convergent beam electron diffraction analysis of strain in multilayer structures: a kinematical approach"
No full textonvergent beam electron diffraction (CBED) performed
on plan-view samples has been considered in order to analyse strained
superlattices.
The composition modulation along the growth axis of multilayer materials
and the strain modulation at the interfaces give rise to special features in
higher order Laue zone (HOLZ) reflections. A simple model based on the
expansion-contraction of the lattice spacing in each layer along the growth
direction is proposed to simulate rocking curves in the kinematical
approximation. Applications to
superlattices are
discussed
Tunable Plasmon resonance structures:SERS applications in wines identifications
Full text linkA real time and sensitive methodology has been developeded and optimized to detect water soluble molecules
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