5 research outputs found
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Intercalation
of molecules into layered materials is actively researched
in materials science, chemistry, and nanotechnology, holding promise
for the synthesis of van der Waals heterostructures and encapsulated
nanoreactors. However, the intercalation of organic molecules that
exhibit physical or chemical functionality remains a key challenge
to date. In this work, we present the synthesis of heterostructures
consisting of porphines sandwiched between a Cu(111) substrate and
an insulating hexagonal boron nitride (<i>h</i>-BN) monolayer.
We investigated the energetics of the intercalation, as well as the
influence of the capping <i>h</i>-BN layer on the behavior
of the intercalated molecules using scanning probe microscopy and
density functional theory calculations. While the self-assembly of
the molecules is altered upon intercalation, we show that the intrinsic
functionalities, such as switching between different porphine tautomers,
are preserved. Such insulator/molecule/metal structures provide opportunities
to protect organic materials from deleterious effects of atmospheric
environment, can be used to control chemical reactions through spatial
confinement, and give access to layered materials based on the ample
availability of synthesis protocols provided by organic chemistry
Layered Insulator/Molecule/Metal Heterostructures with Molecular Functionality through Porphyrin Intercalation
Intercalation
of molecules into layered materials is actively researched
in materials science, chemistry, and nanotechnology, holding promise
for the synthesis of van der Waals heterostructures and encapsulated
nanoreactors. However, the intercalation of organic molecules that
exhibit physical or chemical functionality remains a key challenge
to date. In this work, we present the synthesis of heterostructures
consisting of porphines sandwiched between a Cu(111) substrate and
an insulating hexagonal boron nitride (<i>h</i>-BN) monolayer.
We investigated the energetics of the intercalation, as well as the
influence of the capping <i>h</i>-BN layer on the behavior
of the intercalated molecules using scanning probe microscopy and
density functional theory calculations. While the self-assembly of
the molecules is altered upon intercalation, we show that the intrinsic
functionalities, such as switching between different porphine tautomers,
are preserved. Such insulator/molecule/metal structures provide opportunities
to protect organic materials from deleterious effects of atmospheric
environment, can be used to control chemical reactions through spatial
confinement, and give access to layered materials based on the ample
availability of synthesis protocols provided by organic chemistry
Probing the Site-Dependent Kondo Response of Nanostructured Graphene with Organic Molecules
TCNQ
molecules are used as a sensitive probe for the Kondo response
of the electron gas of a nanostructured graphene grown on Ru(0001)
presenting a moiré pattern. All adsorbed molecules acquired
an extra electron by charge transfer from the substrate, but only
those adsorbed in the FCC-Top areas of the moiré show magnetic
moment and Kondo resonance in the STS spectra. DFT calculations trace
back this behavior to the existence of a surface resonance in the
low areas of the graphene moiré, whose density distribution
strongly depends on the stacking sequence of the moiré area
and effectively quenches the magnetic moment for HCP-Top sites
Adsorption Conformation and Lateral Registry of Cobalt Porphine on Cu(111)
The tetrapyrrole
macrocycle of porphine is the common core of all
porphyrin molecules, an interesting class of π-conjugated molecules
with relevance in natural and artificial systems. The functionality
of porphines on a solid surface can be tailored by the central metal
atom and its interaction with the substrate. In this study, we present
a local adsorption geometry determination for cobalt porphine on Cu(111)
by means of complementary scanning tunneling microscopy, high-resolution
X-ray photoelectron spectroscopy, X-ray standing wave measurements,
and density functional theory calculations. Specifically, the Co center
was determined to be at an adsorption height of 2.25 ± 0.04 Å
occupying a bridge site. The macrocycle adopts a moderate asymmetric
saddle-shape conformation, with the two pyrrole groups that are aligned
perpendicular to the densely packed direction of the Cu(111) surface
tilted away from the surface plane
Corrugation in the Weakly Interacting Hexagonal-BN/Cu(111) System: Structure Determination by Combining Noncontact Atomic Force Microscopy and X‑ray Standing Waves
Atomically
thin hexagonal boron nitride (<i>h</i>-BN)
layers on metallic supports represent a promising platform for the
selective adsorption of atoms, clusters, and molecular nanostructures.
Specifically, scanning tunneling microscopy (STM) studies revealed
an electronic corrugation of <i>h</i>-BN/Cu(111), guiding
the self-assembly of molecules and their energy level alignment. A
detailed characterization of the <i>h</i>-BN/Cu(111) interface
including the spacing between the <i>h</i>-BN sheet and
its supportelusive to STM measurementsis crucial to
rationalize the interfacial interactions within these systems. To
this end, we employ complementary techniques including high-resolution
noncontact atomic force microscopy, STM, low-energy electron diffraction,
X-ray photoelectron spectroscopy, the X-ray standing wave method,
and density functional theory. Our multimethod study yields a comprehensive,
quantitative structure determination including the adsorption height
and the corrugation of the sp<sup>2</sup> bonded <i>h</i>-BN layer on Cu(111). Based on the atomic contrast in atomic force
microscopy measurements, we derive a measurable–hitherto unrecognized–geometric
corrugation of the <i>h-</i>BN monolayer. This experimental
approach allows us to spatially resolve minute height variations in
low-dimensional nanostructures, thus providing a benchmark for theoretical
modeling. Regarding potential applications, <i>e.g.</i>,
as a template or catalytically active support, the recognition of <i>h</i>-BN on Cu(111) as a weakly bonded and moderately corrugated
overlayer is highly relevant