Site-selective CO disproportionation mediated by localized surface plasmon resonance excited by electron beam.

Recent reports of hot-electron-induced dissociation of small molecules, such as hydrogen, demonstrate the potential application of plasmonic nanostructures for harvesting light to initiate catalytic reactions. Theories have assumed that plasmonic catalysis is mediated by the energy transfer from nanoparticles to adsorbed molecules during the dephasing of localized surface plasmon (LSP) modes optically excited on plasmonic nanoparticles. However, LSP-induced chemical processes have not been resolved at a sub-nanoparticle scale to identify the active sites responsible for the energy transfer.

Metastable morphological states of catalytic nanoparticles.

During the catalytic synthesis of graphene, nanotubes, fibers, and other nanostructures, many intriguing phenomena occur, such as phase separation, precipitation, and analogs of capillary action. Here, we demonstrate, using in situ, real-time transmission electron microscope imaging and modeling, that the catalytic nanoparticles display functional, metastable states, reminiscent of some protein ensembles in vivo. As a carbon nanostructure grows, the nanoparticle elongates due to an energetically favorable metal-carbon interaction that overrides the surface energy increase of the metal.

Determination of atomic positions from time resolved high resolution transmission electron microscopy images.

For many reaction processes, such as catalysis, phase transformations, nanomaterial synthesis etc., nanoscale observations at high spatial (sub-nanometer) and temporal (millisecond) resolution are required to characterize and comprehend the underlying factors that favor one reaction over another. The combination of such spatial and temporal resolution (up to 600 µs), while rich in information, produces a large number of snapshots, each of which must be analyzed to obtain the structural (and thereby chemical) information.

Nanocatalyst shape and composition during nucleation of single-walled carbon nanotubes.

The dynamic evolution of nanocatalyst particle shape and carbon composition during the initial stages of single-walled carbon nanotube growth by chemical vapor deposition synthesis is investigated. Classical reactive and molecular dynamics simulations are used, along with environmental transmission electron microscope video imaging analyses. A clear migration of carbon is detected from the nanocatalyst/substrate interface, leading to a carbon gradient showing enrichment of the nanocatalyst layers in the immediate vicinity of the contact layer.

Temperature Calibration for In Situ Environmental Transmission Electron Microscopy Experiments.

In situ environmental transmission electron microscopy (ETEM) experiments require specimen heating holders to study material behavior in gaseous environments at elevated temperatures. In order to extract meaningful kinetic parameters, such as activation energies, it is essential to have a direct and accurate measurement of local sample temperature. This is particularly important if the sample temperature might fluctuate, for example when room temperature gases are introduced to the sample area.

Nucleation of graphene and its conversion to single-walled carbon nanotubes.

We use an environmental transmission electron microscope to record atomic-scale movies showing how carbon atoms assemble together on a catalyst nanoparticle to form a graphene sheet that progressively lifts-off to convert into a nanotube. Time-resolved observations combined with theoretical calculations confirm that some nanoparticle facets act like a vice-grip for graphene, offering anchoring sites, while other facets allow the graphene to lift-off, which is the essential step to convert into a nanotube.

Formation of nanodiamonds at near-ambient conditions via microplasma dissociation of ethanol vapour.

Clusters of diamond-phase carbon, known as nanodiamonds, exhibit novel mechanical, optical and biological properties that have elicited interest for a wide range of technological applications. Although diamond is predicted to be more stable than graphite at the nanoscale, extreme environments are typically used to produce nanodiamonds. Here we show that nanodiamonds can be stably formed in the gas phase at atmospheric pressure and neutral gas temperatures <100 °C by dissociation of ethanol vapour in a novel microplasma process.

Temperature-programmed electrospray-differential mobility analysis for characterization of ligated nanoparticles in complex media.

An electrospray-differential mobility analyzer (ES-DMA) was operated with an aerosol flow-mode, temperature-programmed approach to enhance its ability to characterize the particle size distributions (PSDs) of nanoscale particles (NPs) in the presence of adsorbed and free ligands. Titanium dioxide NPs (TiO2-NPs) stabilized by citric acid (CA) or bovine serum albumin (BSA) were utilized as representative systems. Transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry were used to provide visual information and elemental-based PSDs, respectively.

Centrifugal Shape Sorting of Faceted Gold Nanoparticles Using an Atomic Plane-Selective Surfactant.

Highly refined shape populations of gold nanoparticles (AuNPs) are important for emerging applications in catalysis, plasmonics, and nanomaterials growth. To date, research efforts have focused on achieving monodisperse shape by synthetic control or postsynthetic processing that relies on centrifugal sedimentation-based sorting schemes where differences in the particle mass and aspect ratios (e.g.

Shape-controlled Au particles for InAs nanowire growth.

We present a study of InAs nanowire (NW) growth with shape-controlled Au seed particles. In comparison to more conventional spherical particles, the highly faceted, shaped Au particles are found to enhance the initial growth kinetics of InAs NWs at identical growth conditions. Analysis of the NWs after growth by transmission electron microscopy and energy-dispersive spectroscopy suggests that while In diffuses into the bulk of the shaped Au particles, in accordance with the vapor-liquid-solid (VLS) growth mechanism, the surface faceting is preserved.