Search results for "nanoparticle"
showing 10 items of 2198 documents
Non-conventional Fe3C-based nanostructures
2011
Novel Fe3C-based nanostructures with an inner layered structure have been synthesized by a simple medium-temperature (T = 700 °C) process based on carbothermal reduction. In this process, the iron precursor reacts with a selected nitrogen rich carbon source (namely, 4,5-dicyanoimidazole) to form wrapped nano-sheets of Fe3C@C(N). The nanosheets are composed of 5 nm crystalline Fe3C nanoparticles, which are integrated into a nitrogen-doped carbon phase giving rise to the wrapped morphology. By variation of reaction parameters (such as initial concentration, temperature, reaction time), the typical accompanying side products of iron carbide such as metallic iron and amorphous carbon can be kep…
Quantitative analysis of localized surface plasmons based on molecular probing
2010
International audience; We report on the quantitative characterization of the plasmonic optical near-field of a single silver nanoparticle. Our approach relies on nanoscale molecular molding of the confined electromagnetic field by photoactivated molecules. We were able to directly image the dipolar profile of the near-field distribution with a resolution better than 10 nm and to quantify the near-field depth and its enhancement factor. A single nanoparticle spectral signature was also assessed. This quantitative characterization constitutes a prerequisite for developing nanophotonic applications.
Surface plasmon subwavelength optics.
2003
International audience; Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons- in particular their interaction with light-can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio-photonics.
Nanosensors and other techniques for detecting nanoparticles in the environment
2014
Abstract: Detecting nanomaterials in the environment is a demanding task, not only because of the extremely small size of the particles and their potential sequestration and agglomeration, but also because of their unique physical and chemical characteristics. The aim of this review is to recommend a way forward on tackling the challenge of engineered nanomaterial detection in the environment. An overview will be presented of the available analytical techniques used for the detection and characterization of nanoparticles in environmental matrices including particle-size analysis, particle-fraction concentration counts, surface-area analysis, morphology, and particle chemical composition ana…
In Situ Heating TEM Study of Onion-like WS2 and MoS2 Nanostructures Obtained via MOCVD
2007
We report on the in situ heating transmission electron microscopy (TEM) study of WS2 and MoS2 nanoparticles obtained from metal–organic chemical vapor deposition (MOCVD). The general behavior of MoS2 and WS2 is similar: Round, amorphous particles in the pristine sample transform to hollow, onion-like particles upon annealing. A second type of particle with straight layers exhibits only minor changes. A significant difference between both compounds could be demonstrated in their crystallization behavior. The results of the in situ heating experiments are compared to those obtained from an ex situ annealing process under Ar.
Tuning of an Optical Dimer Nanoantenna by Electrically Controlling Its Load Impedance
2009
International audience; Optical antennas are elementary units used to direct optical radiation to the nanoscale. Here we demonstrate an active control over individual antenna performances by an external electrical trigger. We find that by an in-plane command of an anisotropic load medium, the electromagnetic interaction between individual elements constituting an optical antenna can be controlled, resulting in a strong polarization and tuning response. An active command of the antenna is a prerequisite for directing light wave through the utilization of such a device.
Nanomaterials and phase sensitive based signal enhancment in surface plasmon resonance
2018
Measurement of small molecules in extremely dilute concentrations of analyte play an important role in different issues ranging from food industry to biological, pharmaceutical and therapeutical applications. Surface plasmon resonance (SPR) sensors can be a suitable choice for detection of small molecules based on interactions with biomolecules. However, sensitivity of the system for detection of these molecules is very low. Improving sensitivity has been a challenge for years. Therefore, different methods have been used to enhance SPR signals. The SPR signal enhancement using numerous nanomaterials has provided exciting results. Among various nanomaterials, metal nanoparticles (for instanc…
Modelling nanoparticles formation in the plasma plume induced by nanosecond pulsed lasers
2012
International audience; Nanoparticles formation in a laser-induced plasma plume in the ambient air has been investigated by using numerical simulations and physical models. For high irradiances, or for ultrashort laser pulses, nanoparticles are formed by condensation, as fine powders, in the expanding plasma for very high pairs of temperature and pressure. At lower irradiances, or nanosecond laser pulses, another thermodynamic paths are possible, which cross the liquid-gas transition curve while laser is still heating the target and the induced plasma. In this work, we explore the growth of nanoparticles in the plasma plume induced by nanosecond pulsed lasers as a function of the laser irra…
Mechanical, degradation and drug-release behavior of nano-grained Fe-Ag composites for biomedical applications.
2018
Abstract An original fabrication route of high-strength bulk Fe-5Ag and Fe-10Ag nanocomposites with enhanced degradation rate is reported. Near fully dense materials with fine nanostructures and uniform distribution of Ag nanoparticles were obtained employing high energy attrition milling of Fe-Ag2O powder blends followed by cold sintering – high pressure consolidation at ambient temperature that allowed the retention of the nanoscale structure. Annealing in hydrogen flow at 550 °C resulted in enhanced ductility without coarsening the nanostructure. The strength in compression of Fe5Ag and Fe10Ag nanocomposites was several-fold higher than the values reported for similar composites with mic…