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As part of the revolution in electrochemical nanoscience,
there
is growing interest in using electrochemistry to create nanostructured
materials and to assess properties at the nanoscale. Herein, we present
a platform that combines scanning electrochemical cell microscopy
with ex situ scanning transmission electron microscopy to allow the
ready creation of an array of nanostructures coupled with atomic-scale
analysis. As an illustrative example, we explore the electrodeposition
of Pt at carbon-coated transmission electron microscopy (TEM) grid
supports, where in a single high-throughput experiment it is shown
that Pt nanoparticle (PtNP) density increases and size polydispersity
decreases with increasing overpotential (i.e., driving force). Furthermore,
the coexistence of a range of nanostructures, from single atoms to
aggregates of crystalline PtNPs, during the early stages of electrochemical
nucleation and growth supports a nonclassical aggregative growth mechanism.
Beyond this exemplary system, the presented correlative electrochemistry–microscopy
approach is generally applicable to solve ubiquitous structure–function
problems in electrochemical science and beyond, positioning it as
a powerful platform for the rational design of functional nanomaterials.
We report an enhancement of up to 85% in the photocurrent generated from a bismuth vanadate photoanode through the prior deposition of mass-selected Ti nanoclusters onto the semiconductor surface. We studied the effect of a variety of cluster sizes, deposited at the same density and with the same energy (1.5 keV per cluster), over the surface of separate BiVO 4 photoanodes in a cluster beam source. Using mass-selected clusters of a narrow size distribution, we were able to reveal that the photocurrent is strongly dependent on the cluster size (in the size regime examined), leading to an increase of up to 85% in the photocurrent for Ti 2000AE54 clusters. Remarkably the quantities of metal used to achieve such an enhancement are on the 2.8 Â 10 À7 g cm À2 level, resulting from the optimum density which is approximately 0.4 monolayers. This work highlights the importance of submonolayer surface treatments, using accurate mass-selected nanoclusters, for the modification of semiconductor surfaces in order to improve the interfacial charge transfer properties. † Electronic supplementary information (ESI) available: Mass spectrum showing no target oxidation; examples of processed STEM images for Ti 2000 and Ti 8000 ; XPS survey for cluster modied BiVO 4 ; J-V curve for Ti 923 modied BiVO 4 ; J-V for Ti 8000 modied BiVO 4 ; stability JV curves for BiVO 4 under white light and blue light illumination; J-V curve for cluster modied FTO control experiment. See
Monolayer-protected (MP) Au clusters present attractive quantum systems with a range of potential applications e.g. in catalysis. Knowledge of the atomic structure is needed to obtain a full understanding of their intriguing physical and chemical properties. Here we employed aberration-corrected scanning transmission electron microscopy (ac-STEM), combined with multislice simulations, to make a round-robin investigation of the atomic structure of chemically synthesised clusters with nominal composition Au(SCHCHPh) provided by two different research groups. The MP Au clusters were "weighed" by the atom counting method, based on their integrated intensities in the high angle annular dark field (HAADF) regime and calibrated exponent of the Z dependence. For atomic structure analysis, we compared experimental images of hundreds of clusters, with atomic resolution, against a variety of structural models. Across the size range 123-151 atoms, only 3% of clusters matched the theoretically predicted Au(SR) structure, while a large proportion of the clusters were amorphous (i.e. did not match any model structure). However, a distinct ring-dot feature, characteristic of local icosahedral symmetry, was observed in about 20% of the clusters.
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