1,721,024 research outputs found
Synthesis 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
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
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
Synthesis and characterisation of starch-stabilized Ag nanostructures for sensors applications
No full textSilver nanostructures were successfully synthesized through a simple and ‘green’ route using starch as a capping agent. High resolution electron microscopy (HREM), X-ray diffraction (XRD), UV–Vis absorption suggested that Ag nanocrystals, having a size lower than 10 nm, were obtained, in addition a self-assembly into ribbon-like structures was been also observed. The silver nanostructures were electrodeposited onto suitable substrates with gold interdigital electrodes realizing amperometric sensors that showed a high sensitivity to hydrogen peroxide
Characteristics of molybdenum trioxide nanobelts prepared by thermal evaporation technique
No full textSingle-crystalline nanobelts of molybdenum trioxides (MoO(3)) were grown by a thermal evaporation method of molybdenum metal pellets at ambient pressure in a flow of O(2). The chemical composition, crystalline structure and optical properties of the nanobelts were investigated by various characterization techniques such as scanning electron microscopy, transmission electron microscopy, Raman-scattering, energy dispersive X-ray spectroscopy and UV-vis-NIR spectroscopy. The samples were nanobelts with a width up to 50 mu m, about 85 nm in thickness and from tens to several hundred micrometers in length. The analysis indicated that as-synthesized samples were orthorhombic structured MoO(3) grown with [0 0 1] preferred orientation. The fundamental optical absorption edge corresponds to direct allowed transitions with an energy gap located at about 3.01 eV
Green synthesis of Silver nanoparticles with sucrose and maltose: morphological and structural charcaterization
No full textWe present a totally green approach toward the rapid synthesis and stabilization of metal nanoparticles
through the treatment of aqueous solutions of silver nitrate with two commonly available sugars, i.e.,
maltose and sucrose as reducing agents. The average size, size distribution, morphology and internal
crystalline structure of the nanoparticles are studied through high resolution transmission electron
microscopy, selected-area diffraction pattern and UV–Vis spectroscopic technique and are seen to be critically
dependent on the used sugar. The great majority of sucrose-assisted synthesized nanoparticles is
distributed in a size range less than 6.0 nm, with an arithmetic media of 5.2 nm and a statistical standard
deviation of 1.3 nm. For the maltose synthesized sample, the size distribution plot reveals that nanoparticles
are greater (with a mean size of 62.4 nm and a standard deviation of 9.5 nm) and exhibit a more
anisotropic morphology
Green synthesis of sucralose-capped silver nanoparticles for fast colorimetric triethylamine detection
No full textIn this study, a fast colorimetric triethylamine sensor based on localized surface plasmon resonance of silver nanoparticles is presented. The nanoparticles were synthesized by chemical reduction from silver nitrate using glucose as reducing agent and sucralose as capping agent
Controlled synthesis and chain-like self-assembly of silver nanoparticles through tertiary amine
Full text linkIn this study, monodispersed silver nanoparticles with diameter in the range 4-10 nm were first synthesized by chemical reduction from silver nitrate using glucose as reducing agent and sucralose as capping agent, through microwave assisted method. Then, a strong enhancement of the yield of the synthesized nanoparticles and their self-assembly could be achieved through the injection into the colloidal solution, at room temperature, of a tertiary amine (triethylamine, TEA), which acted both as promoter and as directing agent for silver nanoparticles. The yield of the synthesized nanoparticles and the length of the chains could be tuned by facile adjustment of the TEA concentration and reaction time. The interaction between amine and silver nanoparticles made the non-uniform spatial distribution of stabilizers at nanoparticles surfaces and led to the 1D assembly. Transmission electron microscopy (TEM) and UV-Vis spectroscopy have been employed for monitoring the nanochains formation. This mechanism evidenced that sucralose capped silver nanoparticles could also be useful for the real-time naked-eye detection of amine
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