JoVE Visualize What is visualize?
Stop Reading. Start Watching.
Advanced Search
Stop Reading. Start Watching.
Regular Search
Find video protocols related to scientific articles indexed in Pubmed.
Production of Water-Soluble Few-Layer Graphene Mesosheets by Dry Milling with Hydrophobic Drug.
Langmuir
PUBLISHED: 11-20-2014
Show Abstract
Hide Abstract
A novel, fast and easy mechano-chemistry-based (dry milling) method has been developed to exfoliate graphene with hydrophobic drugs generating few layer graphene mesosheets (< 10 nm in thickness and ~ 1 µm in width). The electronic properties of the graphitic structure were partially preserved after the milling treatment compared to Graphene Oxide (GO) prepared by Hummers' method. Several characterization techniques such as thermogravimetric analysis (TGA), Raman spectroscopy, atomic force microscopy (AFM), Electron Microscopy (EM) and molecular dynamics simulation were used to characterize this material. The drug-exfoliated mesosheets were pharmacologically inactive offering a new approach for making water-soluble few-layer graphene mesosheets upon dry milling with hydrophobic drugs, mainly used as exfoliating agents.
Related JoVE Video
Size-dependent dissociation of carbon monoxide on cobalt nanoparticles.
J. Am. Chem. Soc.
PUBLISHED: 02-04-2013
Show Abstract
Hide Abstract
In situ soft X-ray absorption spectroscopy (XAS) was employed to study the adsorption and dissociation of carbon monoxide molecules on cobalt nanoparticles with sizes ranging from 4 to 15 nm. The majority of CO molecules adsorb molecularly on the surface of the nanoparticles, but some undergo dissociative adsorption, leading to oxide species on the surface of the nanoparticles. We found that the tendency of CO to undergo dissociation depends critically on the size of the Co nanoparticles. Indeed, CO molecules dissociate much more efficiently on the larger nanoparticles (15 nm) than on the smaller particles (4 nm). We further observed a strong increase in the dissociation rate of adsorbed CO upon exposure to hydrogen, clearly demonstrating that the CO dissociation on cobalt nanoparticles is assisted by hydrogen. Our results suggest that the ability of cobalt nanoparticles to dissociate hydrogen is the main parameter determining the reactivity of cobalt nanoparticles in Fischer-Tropsch synthesis.
Related JoVE Video
A reaction cell with sample laser heating for in situ soft X-ray absorption spectroscopy studies under environmental conditions.
J Synchrotron Radiat
PUBLISHED: 01-23-2013
Show Abstract
Hide Abstract
A miniature (1 ml volume) reaction cell with transparent X-ray windows and laser heating of the sample has been designed to conduct X-ray absorption spectroscopy studies of materials in the presence of gases at atmospheric pressures. Heating by laser solves the problems associated with the presence of reactive gases interacting with hot filaments used in resistive heating methods. It also facilitates collection of a small total electron yield signal by eliminating interference with heating current leakage and ground loops. The excellent operation of the cell is demonstrated with examples of CO and H2 Fischer-Tropsch reactions on Co nanoparticles.
Related JoVE Video
Experimental and theoretical investigation of the electronic structure of Cu2O and CuO thin films on Cu(110) using x-ray photoelectron and absorption spectroscopy.
J Chem Phys
PUBLISHED: 01-17-2013
Show Abstract
Hide Abstract
The electronic structure of Cu(2)O and CuO thin films grown on Cu(110) was characterized by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The various oxidation states, Cu(0), Cu(+), and Cu(2+), were unambiguously identified and characterized from their XPS and XAS spectra. We show that a clean and stoichiometric surface of CuO requires special environmental conditions to prevent loss of oxygen and contamination by background water. First-principles density functional theory XAS simulations of the oxygen K edge provide understanding of the core to valence transitions in Cu(+) and Cu(2+). A novel method to reference x-ray absorption energies based on the energies of isolated atoms is presented.
Related JoVE Video
Revealing correlation of valence state with nanoporous structure in cobalt catalyst nanoparticles by in situ environmental TEM.
ACS Nano
Show Abstract
Hide Abstract
Simultaneously probing the electronic structure and morphology of materials at the nanometer or atomic scale while a chemical reaction proceeds is significant for understanding the underlying reaction mechanisms and optimizing a materials design. This is especially important in the study of nanoparticle catalysts, yet such experiments have rarely been achieved. Utilizing an environmental transmission electron microscope equipped with a differentially pumped gas cell, we are able to conduct nanoscopic imaging and electron energy loss spectroscopy in situ for cobalt catalysts under reaction conditions. Studies reveal quantitative correlation of the cobalt valence states with the particles nanoporous structures. The in situ experiments were performed on nanoporous cobalt particles coated with silica, while a 15 mTorr hydrogen environment was maintained at various temperatures (300-600 °C). When the nanoporous particles were reduced, the valence state changed from cobalt oxide to metallic cobalt and concurrent structural coarsening was observed. In situ mapping of the valence state and the corresponding nanoporous structures allows quantitative analysis necessary for understanding and improving the mass activity and lifetime of cobalt-based catalysts, for example, for Fischer-Tropsch synthesis that converts carbon monoxide and hydrogen into fuels, and uncovering the catalyst optimization mechanisms.
Related JoVE Video

What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

How does it work?

We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.