Search results for "Raman spectroscopy."
showing 10 items of 790 documents
Optimization of MCM-41 type silica nanoparticles for biological applications: Control of size and absence of aggregation and cell cytotoxicity
2015
Abstract Mesoporous silica nanoparticles were synthesized at high pH using CTAB as a template and TEOS as a silica precursor. It was shown that varying the NaOH concentration between 5 and 27.5 mM allows the size, pore and silica structure of mesoporous nanoparticles to be precisely tuned. In particular, monodisperse nanoparticles with the MCM-41 structure with size ranging from 90 nm to 450 nm were obtained by increasing the NaOH concentration from 12.5 to 22.5 mM. It thus demonstrates that NaOH concentration must range between 12.5 and 15 mM in order to prepare MCM-41 silica nanoparticles with optimal size for nanovectorization. We also found that under usual conditions the aggregation of…
Topography and morphology of multicomponent catalytic materials based on Co, Ce and Pd oxides deposited on metallic structured carriers studied by AF…
2013
A system of interfaced AFM and Raman microscopes was used to study heterogeneity of complex cat- alytic materials providing information on both the topography and the chemical composition of the surface in one measurement. The catalysts surface was examined at various stages of their preparation: precalcination of steel, washcoating, impregnation and doping. It has been shown that the surface of the precalcined steel sheets is covered mostly by -Al 2 O 3 although there are places where -Fe 2 O 3 and Fe 3 O 4 are also present. Washcoating of the precalcined sheets gives only partly uniform grain distribution of CeO 2 . Impregnation with cobalt leads to formation of uniform coverage of Co 3 O…
Raman and nuclear magnetic resonance investigation of alkali metal vapor interaction with alkene-based anti-relaxation coating.
2016
The use of anti-relaxation coatings in alkali vapor cells yields substantial performance improvements by reducing the probability of spin relaxation in wall collisions by several orders of magnitude. Some of the most effective anti-relaxation coating materials are alpha-olefins, which (as in the case of more traditional paraffin coatings) must undergo a curing period after cell manufacturing in order to achieve the desired behavior. Until now, however, it has been unclear what physicochemical processes occur during cell curing, and how they may affect relevant cell properties. We present the results of nondestructive Raman-spectroscopy and magnetic-resonance investigations of the influence …
A quantitative electron microscopic study of the crystalline structure of ethylene copolymers
1986
Etude de sections minces sur des fractions de composition de copolymeres cristallises dans des conditions extremement severes
Making Graphene Luminescent by Direct Laser Writing
2020
Graphene is not intrinsically luminescent, due to a lack of bandgap, and methods for its creation are tricky for device fabrication. In this study, we create luminescent graphene patterns by a simple direct laser writing method. We analyze the graphene using Raman spectroscopy and find that the laser writing leads to generation of line defects after initial formation of point defects. This Raman data enables us to create a model that explains the luminescence by a formation of small domains due to confinement of graphene by line defects, which is conceptually similar to the mechanism of luminescence in graphene quantum dots. peerReviewed
Ultrastable, Uniform, Reproducible, and Highly Sensitive Bimetallic Nanoparticles as Reliable Large Scale SERS Substrates
2015
International audience; A strong interest exists in developing surface-enhanced Raman spectroscopy (SERS) substrates that uniformly enhance Raman signals of chemical and biological molecules over large scales while reaching the detection limit of trace concentrations. Even though the resonant excitation of localized surface plasmons of single or assembled metallic nanoparticles used in SERS substrates can induce large electromagnetic fields, these substrates display a SERS activity which suffers from poor reproducibility, uniformity, and stability, preventing them from being reliable for applications. In this work, we have developed self-supported large scale Ag/Au bimetallic SERS-active su…
Optical Diagnostics with Ultrafast and Strong Field Raman Techniques
2014
In this chapter, we will discuss some coherent techniques, namely Raman Induced Polarization Spectroscopy (RIPS) and femtosecond Coherent Raman Anti-Stokes Spectroscopy (fs-CARS). We will demonstrate their ability to be used as non-invasive optical diagnostic tools for temperature, density, or concentration measurements, as well as a means of testing collision induced energy transfer models (in a low field regime), and studying the so-called inhomogeneous lineshape effects that are particularly enhanced in the case of hydrogen. We will also show how molecular alignment achieved in a strong field regime can provide additional information about collisional relaxation processes. In all cases, …
Hexakis-adducts of [60]fullerene as molecular scaffolds of polynuclear spin-crossover molecules
2021
A family of hexakis-substituted [60]fullerene adducts endowed with the well-known tridentate 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligand for spin-crossover (SCO) systems has been designed and synthesized. It has been experimentally and theoretically demonstrated that these molecular scaffolds are able to form polynuclear SCO complexes in solution. UV-vis and fluorescence spectroscopy studies have allowed monitoring of the formation of up to six Fe(ii)–bpp SCO complexes. In addition, DFT calculations have been performed to model the different complexation environments and simulate their electronic properties. The complexes retain SCO properties in the solid state exhibiting both thermal- and …
ZnO/ZnS heterostructures for hydrogen production by photoelectrochemical water splitting
2016
This work studies the photoelectrochemical behavior of novel ZnO/ZnS heterostructures obtained by means of anodization in water and glycerol/water/NH4F electrolytes with different Na2S additions under controlled hydrodynamic conditions. For this purpose different techniques such as Field Emission Scanning Electronic Microscopy (FE-SEM) with EDX, Raman spectroscopy and photoelectrochemical water splitting tests under standard AM 1.5 conditions have been carried out. The obtained results showed that the hydrodynamic conditions promoted an ordered nanotubular morphology which facilitates electron-hole separation and consequently, the photoelectrochemical activity for water splitting is enhance…
Paper Functionalized with Nanostructured TiO2/AgBr: Photocatalytic Degradation of 2–Propanol under Solar Light Irradiation and Antibacterial Activity
2020
A facile method to produce paper&ndash