Search results for "Microscopy"
showing 10 items of 3390 documents
Synthesis of Fullerene- and Nanotube-Like SnS2 Nanoparticles and Sn/S/Carbon Nanocomposites
2009
SnS2 nested fullerene-type (IF) nanoparticles, nanotubes, and SnS2/C hybrid nanostructures were obtained by vapor transport starting from elemental tin and CS2. The reaction was carried out in a single-step process by heating elemental tin metal powder in a horizontal tube furnace at 800−1000 °C. TEM analysis allowed proposing a plausible mechanism for the formation of fullerene-like particles of SnS2 as well as tubes and scrolls from nanosheets of SnS2. Pure material could be obtained by optimizing the reaction based on a product analysis using powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) combined with energy-dispersive X-ray spectroscopy (EDX…
A study on the stability of carbon nanoforms–polyimidazolium network hybrids in the conversion of co2 into cyclic carbonates
2021
Three different carbon nanoforms (CNFs), single-walled and multi-walled carbon nanotubes (SWCNTs, MWCNTs) and carbon nanohorns (CNHs), have been used as supports for the direct polymerization of variable amounts of a bis-vinylimidazolium salt. Transmission electron microscopy confirmed that all CNFs act as templates on the growth of the polymeric network, which perfectly covers the nanocarbons forming a cylindrical (SWCNTs, MWCNTs) or spherical (CNHs) coating. The stability of these hybrid materials was investigated in the conversion of CO2 into cyclic carbonate under high temperature and CO2 pressure. Compared with the homopolymerized monomer, nanotube-based materials display an improved c…
Lateral force microscopy of multiwalled carbon nanotubes
2009
Carbon nanotubes are usually imaged with the atomic force microscope (AFM) in non-contact mode. However, in many applications, such as mechanical manipulation or elasticity measurements, contact mode is used. The forces affecting the nanotube are then considerable and not fully understood. In this work lateral forces were measured during contact mode imaging with an AFM across a carbon nanotube. We found that, qualitatively, both magnitude and sign of the lateral forces to the AFM tip were independent of scan direction and can be concluded to arise from the tip slipping on the round edges of the nanotube. The dependence on the normal force applied to the tip and on the ratio between nanotub…
Carbon-doped titania as a precursor for titanate nanotubes
2018
Carbon-doped titania was fabricated via carbothermal treatment in nitrogen–acetylene gas flow and further used as a precursor for multiwalled titanate nanotube (TNT) synthesis via alkaline hydrothermal route. Investigation of the reaction products after hydrothermal treatment of carbon-doped titania using Transmission electron microscopy, X-ray diffraction, and Brunauer–Emmett–Teller method shows the successful formation of TNTs. The presence of carbon was proved although the type of incorporation could not be certified. All samples show approximately the same carbon content before and after hydrothermal treatment. An increasing pretreatment temperature of titania precursor powders yields m…
Effect of Reaction Parameters on Composition and Morphology of Titanate Nanomaterials
2009
International audience; In the present article, we report the synthesis of titanate nanotubes and nanoribbons with controlled morphology, structure, and chemical composition depending on the main parameters of the synthesis. Hydrothermal processing time, grain size of the precursor, type of agitation, and acid treatment were investigated, and the principal controversies mentioned in the literature such as nanotube crystallographic structure, their chemical composition, and acid treatment impact are discussed. These controversies may be due to the heterogeneities present in all the samples and are rarely considered in the literature. These nanostructures were characterized by Raman spectrosc…
Local photo-oxidation of individual single walled carbon nanotubes probed by femtosecond four wave mixing imaging
2014
Photo-oxidation of individual, air-suspended single walled carbon nanotubes (SWCNTs) is studied by femtosecond laser spectroscopy and imaging. Individual SWCNTs are imaged by four wave mixing (FWM) microscopy under an inert gas (Ar or N2) atmosphere. When imaging is performed in an ambient air atmosphere, the decay of the FWM signal takes place. Electron microscopy shows that SWCNTs are not destroyed and the process is attributed to photoinduced oxidation reactions which proceed via a non-linear excitation mechanism, when irradiation is performed with ∼30 fs pulses in the visible spectral region (500-600 nm). Photo-oxidation can be localized in specific regions of SWCNTs within optical reso…
Carbon nanotube bags: catalytic formation, physical properties, two-dimensional alignment and geometric structuring of densely filled carbon tubes.
2001
The catalytic CVD synthesis, using propyne as carbon precursor and Fe(NO3)3 as catalyst precursor inside porous alumina, gives carbon nanotube (CNT) bags in a well-arranged two-dimensional order. The tubes have the morphology of bags or fibers, since they are completely filled with smaller helicoidal CNTs. This morphology has so far not been reported for CNTs. Owing to the dense filling of the outer mother CNTs with small helicoidal CNTs, the resulting CNT fibers appear to be stiff and show no sign of inflation, as sometimes observed with hollow CNTs. The fiber morphology was observed by raster electron microscopy (REM), transmission electron microscopy (TEM), and atomic force microscopy (A…
Chemical Mimicry: Hierarchical 1D TiO2@ZrO2 Core−Shell Structures Reminiscent of Sponge Spicules by the Synergistic Effect of Silicatein-α and Silint…
2011
In nature, mineralization of hard tissues occurs due to the synergistic effect of components present in the organic matrix of these tissues, with templating and catalytic effects. In Suberites domuncula, a well-studied example of the class of demosponges, silica formation is mediated and templated by an axial proteinaceous filament with silicatein-α, one of the main components. But so far, the effect of other organic constituents from the proteinaceous filament on the catalytic effect of silicatein-α has not been studied in detail. Here we describe the synthesis of core-shell TiO(2)@SiO(2) and TiO(2)@ZrO(2) nanofibers via grafting of silicatein-α onto a TiO(2) nanowire backbone followed by …
The effects of precipitates on CdZnTe device performance
2005
A high-intensity X-ray beam collimated down to a 10-micrometer spot size, available at Brookhaven's National Synchrotron Light Source (NSLS), was employed to perform X-ray mapping to measure the correlation between microscopic defects (precipitates) and variations in the collected charges in long-drift CdZnTe (CZT) detectors. First, we use X-ray diffraction topography (XDT) measurements at the high-energy beamline and IR microscopy to identify the defects distribution and strains in the bulk of CZT crystals. Then, we perform X-ray raster scans of the CZT detectors to measure their responses with 10-micrometer spatial resolution. The brightness of the source allows for good statistics in ver…
Gluing the ‘unwettable’: soil-dwelling harvestmen use viscoelastic fluids for capturing springtails
2014
Gluing can be a highly efficient mechanism of prey capture, as it should require less complex sensory–muscular feedback. Whereas it is well known in insects, this mechanism is much less studied in arachnids, except spiders. Soil-dwelling harvestmen (Opiliones, Nemastomatidae) bear drumstick-like glandular hairs (clavate setae) at their pedipalps, which were previously hypothesized to be sticky and used in prey capture. However, clear evidence for this was lacking to date. Using high-speed videography, we found that the harvestman Mitostoma chrysomelas was able to capture fast-moving springtails (Collembola) just by a slight touch of the pedipalp. Adhesion of single clavate setae increased p…