Search results for "Microscopy"

Hockey-Puck micelles from oligo(p-benzamide)-b-PEG rod-coil block copolymers.

2006

Variation of lattice constant and cluster formation in GaAsBi

2013

We investigate the structural properties of GaAsBi layers grown by molecular beam epitaxy on GaAs at substrate temperatures between 220–315 C. Irrespective of the growth temperature, the structures exhibited similar Bi compositions, and good overall crystal quality as deduced from X-Ray diffraction measurements. After thermal annealing at temperatures as low as 500 C, the GaAsBi layers grown at the lowest temperatures exhibited a significant reduction of the lattice constant. The lattice variation was significantly larger for Bi-containing samples than for Bi-free low-temperature GaAs samples grown as a reference. Rutherford backscattering spectrometry gave no evidence of Bi diffusing out o…

Background-Free Second-Harmonic Generation Microscopy of Individual Carbon Nanotubes

2015

We use polarized second-harmonic generation (SHG) microscopy to investigate pristine air-suspended carbon nanotubes (CNT). We show that SHG originates from CNT chirality, allowing also different response for the two circular polarizations of fundamental light.

Atomic force microscopy and Raman investigation on the sintering process of amorphous SiO2 nanoparticles

2010

We report an experimental investigation on the sintering process induced in fumed silica powders by isochronal thermal treatments at T=1270 K. Three types of fumed silica are considered, consisting of amorphous SiO2 (a-SiO2) particles with mean diameters 7, 14, and 40 nm. The study is performed by atomic force microscopy (AFM), to follow the morphological changes, and by Raman scattering, to obtain information on the concomitant structural modifications. The former method indicates that the sintering process proceeds by aggregation of single particles into larger grains, whose sizes increase with the thermal treatment duration. Furthermore, for each fumed silica type considered, the quantit…

Characterization of Maya Blue Pigment in Pre-Classic and Classic Monumental Architecture of the Ancient Pre-Culombian City of Calakmul (Campeche, Mex…

2011

This paper presents the first evidence of the use of Maya Blue pigment in late pre-classic (c.300BC-300AD) architecture in the Maya Lowlands. This was detected combining an innovative technique, the voltammetry of microparticles (VMP), with atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive X-ray microanalysis (SEM/EDX), visible spectrophotometry and Fourier transform infrared spectroscopy (FTIR). The pigment was found on the polychrome facade of substructure IIC of pre-Columbian city of Calakmul (Campeche, Mexico). The identification of Maya Blue in this building may prove to be the earliest known use of this colour on the …

A monoclonal antibody against an adult-specific cuticular protein of Tenebrio molitor (Insecta, Coleoptera)

1989

International audience; To study the sequential expression of the epidermal program in the mealworm Tenebrio molitor, monoclonal antibodies were prepared against the water-soluble proteins from preecdysial adult cuticle. Among the 16 clones obtained, one of them (named K2F6) recognized a 20-kDa antigen, found only in adult extracts but not in the larval or pupal ones, as revealed by immunoblot analysis. Our results strongly suggest an epidermal origin for this protein. The monoclonal antibody K2F6 fails to react with water-soluble proteins from fat body and hemolymph taken during the deposition of the 20-kDa antigen. Electron microscopic immunogold localization of this antigen showed that i…

A comparison of the Raman LAM and electron microscopy in determining crystallite thickness distributions: Polyethylenes with narrow size distributions

1989

Bon accord entre les resultats obtenus pour des polyethylenes cristallises a 118 o C pendant 2 et 20 minutes lorsqu'on prend en compte l'inclinaison de la chaine et pour des polymeres a distribution etroite

Programmable assembly of peptide amphiphile via noncovalent-to-covalent bond conversion

2017

Controlling the number of monomers in a supramolecular polymer has been a great challenge in programmable self-assembly of organic molecules. One approach has been to make use of frustrated growth of the supramolecular assembly by tuning the balance of attractive and repulsive intermolecular forces. We report here on the use of covalent bond formation among monomers, compensating for intermolecular electrostatic repulsion, as a mechanism to control the length of a supramolecular nanofiber formed by self-assembly of peptide amphiphiles. Circular dichroism spectroscopy in combination with dynamic light scattering, size-exclusion chromatography, and transmittance electron microscope analyses r…

A comparative study on the phase behaviour of highly charged colloidal spheres in a confining wedge geometry

2005

We studied the structures formed in aqueous dispersions of charged colloidal spheres under a constant low salt concentration of c = 6 × 10−6 mol l−1. Particles of diameter 2a = 1000 nm were confined to a low angle wedge geometry with plate separation 0<S<50 µm and observed with video microscopy. Irrespective of the initial particle density n we reproducibly observe the particles to migrate to the narrow wedge side on the timescale of a few days. Thereby an interface between a crystalline structure and a near particle free region is formed, which propagates slowly until the dilute region is exhausted of particles. While the origin of this separation is still unclear, the final extension of t…

Highly Homogeneous 2D/3D Heterojunction Diodes by Pulsed Laser Deposition of MoS2 on Ion Implantation Doped 4H-SiC

2022

In this paper, 2D/3D heterojunction diodes have been fabricated by pulsed laser deposition (PLD) of MoS2 on 4H-SiC(0001) surfaces with different doping levels, i.e., n− epitaxial doping (≈1016 cm−3) and n+ ion implantation doping (&gt;1019 cm−3). After assessing the excellent thickness uniformity (≈3L-MoS2) and conformal coverage of the PLD-grown films by Raman mapping and transmission electron microscopy, the current injection across the heterojunctions is investigated by temperature-dependent current–voltage characterization of the diodes and by nanoscale current mapping with conductive atomic force microscopy. A wide tunability of the transport properties is shown by the SiC surface dopi…