4 research outputs found
A Minimal Cluster Model of Valence Electrons in Adatom-Assisted Adsorbed Molecules: NCH<sub>3</sub>/Cu(110) and OCH<sub>3</sub>/Cu(110)
In
this study, we found that the local density of states and ionization
energy spectrum of the valence electrons of methylnitrene (NCH<sub>3</sub>) adsorbed on Cu(110) can be calculated from molecular orbital
calculations of a simple artificial isolated NCH<sub>3</sub>–Cu<sub>2</sub> molecular cluster in which the two Cu atoms form bonds to
the N atom. Such a NCH<sub>3</sub>–Cu<sub>2</sub> cluster represents
the basic structural unit of a NCH<sub>3</sub> molecule adsorbing
on a Cu double-added-row structure. This finite NCH<sub>3</sub>–Cu<sub>2</sub> cluster structure is not optimized as a single system but
is extracted directly from an optimized surface structure obtained
by density functional theory with periodic boundary conditions. With
this approach, we obtained excellent agreement between the measured
ultraviolet photoemission spectra (UPS) and the theoretical calculation
results. To further examine this minimal cluster concept, we analyzed
methoxy (OCH<sub>3</sub>) adsorption on Cu(110) and found a OCH<sub>3</sub>–Cu<sub>3</sub> cluster structure. On the basis of
this structure, we calculated UPS and also obtained substantial agreement
with the experimental UPS. These results may indicate that, when substrate
adatoms bridge the adsorption of a molecule and a surface, a small
cluster consisting of the adsorbate and the neighboring bonding substrate
adatoms suffices to describe the electronic structure of the valence
electrons of the adsorbates
Scanning Tunneling Microscopy and Density Functional Theory Studies of Adatom-Involved Adsorption of Methylnitrene on Copper(110) Surface
In this study, we used scanning tunneling
microscopy (STM) and
density functional theory (DFT) to examine the bonding structure of
CH<sub>3</sub>N adsorbed on the Cu(110) surface. A previous study
[<i>Chin. J. Phys.</i> <b>2005</b>, <i>43</i>, 212–218] shows the adsorbed CH<sub>3</sub>N aggregate to
form a zigzag structure with a <i>p</i>(2 × 3) unit
cell, without considering the possibility of adsorbate-induced surface
reconstruction. Here, we propose a revised adsorption structure, with
the key feature of bonding each CH<sub>3</sub>N with two Cu adatoms
in a tetrahedral manner. Three structure models (double-row, dimer,
and alternative-dimer) are examined by ab initio calculations. We
find that the most energetically favorable model is the double-row
model with CH<sub>3</sub>N bonding alternatingly along either side
of double added rows from Cu adatoms
β‑SnWO<sub>4</sub> Photocatalyst with Controlled Morphological Transition of Cubes to Spikecubes
A distinct morphology of β-SnWO<sub>4</sub> with hierarchically
multiarmed architecture and overall hexahedral symmetry – entitled
as spikecube – is fabricated for the first time via a polyol-mediated
synthesis. The growth of the β-SnWO<sub>4</sub> spikecubes is
investigated and attributed to thermodynamic and kinetic control.
In a sequential reaction, crystalline cubes of β-SnWO<sub>4</sub> enclosed by {100} facets grow in a first Ostwald ripening-based
step. A kinetically controlled growth process to spikecubes follows
under formation of multiarmed spikes on the facets of the cubic seeds.
Such a growth process differs significantly from the literature concerning
highly branched crystals. The synergistic effect of morphological
modification (i.e., introducing more surface reaction sites) and textural
alteration (i.e., incorporation of the <i>p</i>-block Sn<sup>2+</sup> into simple tungsten oxide to reframe its band structure)
leads to an enhanced photocatalytic activity of the β-SnWO<sub>4</sub> spikecubes being 150% higher in comparison to benchmark WO<sub>3</sub> photocatalysts
β‑SnWO<sub>4</sub> Photocatalyst with Controlled Morphological Transition of Cubes to Spikecubes
A distinct morphology of β-SnWO<sub>4</sub> with hierarchically
multiarmed architecture and overall hexahedral symmetry – entitled
as spikecube – is fabricated for the first time via a polyol-mediated
synthesis. The growth of the β-SnWO<sub>4</sub> spikecubes is
investigated and attributed to thermodynamic and kinetic control.
In a sequential reaction, crystalline cubes of β-SnWO<sub>4</sub> enclosed by {100} facets grow in a first Ostwald ripening-based
step. A kinetically controlled growth process to spikecubes follows
under formation of multiarmed spikes on the facets of the cubic seeds.
Such a growth process differs significantly from the literature concerning
highly branched crystals. The synergistic effect of morphological
modification (i.e., introducing more surface reaction sites) and textural
alteration (i.e., incorporation of the <i>p</i>-block Sn<sup>2+</sup> into simple tungsten oxide to reframe its band structure)
leads to an enhanced photocatalytic activity of the β-SnWO<sub>4</sub> spikecubes being 150% higher in comparison to benchmark WO<sub>3</sub> photocatalysts