4 research outputs found
Phenyl Functionalization of Atomically Precise Graphene Nanoribbons for Engineering Inter-ribbon Interactions and Graphene Nanopores
Graphene
nanoribbons (GNRs) attract much attention from researchers
due to their tunable physical properties and potential for becoming
nanoscale building blocks of electronic devices. GNRs can be synthesized
with atomic precision by on-surface approaches from specially designed
molecular precursors. While a considerable number of ribbons with
very diverse structures and properties have been demonstrated in recent
years, there have been only limited examples of on-surface synthesized
GNRs modified with functional groups. In this study, we designed a
nanoribbon, in which the chevron GNR backbone is decorated with phenyl
functionalities, and demonstrate the on-surface synthesis of these
GNRs on Au(111). We show that the phenyl modification affects the
assembly of the GNR polymer precursors through π–π
interactions. Scanning tunneling spectroscopy of the modified GNRs
on Au(111) revealed that they have a band gap of 2.50 ± 0.02
eV, which is comparable to that of the parent chevron GNR. The phenyl
functionalization leads to a shift of the band edges to lower energies,
suggesting that it could be a useful tool for the GNR band structure
engineering. We also investigated lateral fusion of the phenyl-modified
GNRs and demonstrate that it could be used to engineer different kinds
of atomically precise graphene nanopores. A similar functionalization
approach could be potentially applied to other GNRs to affect their
on-surface assembly, modify their electronic properties, and realize
graphene nanopores with a variety of structures
Interfacial Self-Assembly of Atomically Precise Graphene Nanoribbons into Uniform Thin Films for Electronics Applications
Because of their
intriguing electronic and optical properties, atomically precise graphene
nanoribbons (GNRs) are considered to be promising materials for electronics
and photovoltaics. However, significant aggregation and low solubility
of GNRs in conventional solvents result in their poor processability
for materials characterization and device studies. In this paper,
we demonstrate a new fabrication approach for large-scale uniform
thin films of nonfunctionalized atomically precise chevron-type GNRs.
The method is based on (1) the exceptional solubility of graphitic
materials in chlorosulfonic acid and (2) the original interfacial
self-assembly approach by which uniform films that are single-GNR
(∼2 nm) thick can be routinely prepared. These films can be
transferred to various substrates including Si/SiO<sub>2</sub> and
used for the streamlined fabrication of arrays of GNR-based devices.
The described self-assembly approach should be applicable to other
types of solution-synthesized atomically precise GNRs as well as large
polyaromatic hydrocarbon (PAH) molecules and therefore should facilitate
and streamline their device characterization
Pristine Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene Enables Flexible and Transparent Electrochemical Sensors
In
the era of the internet of things, there exists a pressing need
for technologies that meet the stringent demands of wearable, self-powered,
and seamlessly integrated devices. Current approaches to developing
MXene-based electrochemical sensors involve either rigid or opaque
components, limiting their use in niche applications. This study investigates
the potential of pristine Ti3C2Tx electrodes for flexible and transparent electrochemical
sensing, achieved through an exploration of how material characteristics
(flake size, flake orientation, film geometry, and uniformity) impact
the electrochemical activity of the outer sphere redox probe ruthenium
hexamine using cyclic voltammetry. The optimized electrode made of
stacked large Ti3C2Tx flakes demonstrated excellent reproducibility and resistance to
bending conditions, suggesting their use for reliable, robust, and
flexible sensors. Reducing electrode thickness resulted in an amplified
faradaic-to-capacitance signal, which is advantageous for this application.
This led to the deposition of transparent thin Ti3C2Tx films, which maintained their
best performance up to 73% transparency. These findings underscore
its promise for high-performance, tailored sensors, marking a significant
stride in advancing MXene utilization in next-generation electrochemical
sensing technologies. The results encourage the analytical electrochemistry
field to take advantage of the unique properties that pristine Ti3C2Tx electrodes can
provide in sensing through more parametric studies
Nitrogen-Doping Induced Self-Assembly of Graphene Nanoribbon-Based Two-Dimensional and Three-Dimensional Metamaterials
Narrow
graphene
nanoribbons (GNRs) constructed by atomically precise bottom-up synthesis
from molecular precursors have attracted significant interest as promising
materials for nanoelectronics. But there has been little awareness
of the potential of GNRs to serve as nanoscale building blocks of
novel materials. Here we show that the substitutional doping with
nitrogen atoms can trigger the hierarchical self-assembly of GNRs
into ordered metamaterials. We use GNRs doped with eight N atoms per
unit cell and their undoped analogues, synthesized using both surface-assisted
and solution approaches, to study this self-assembly on a support
and in an unrestricted three-dimensional (3D) solution environment.
On a surface, N-doping mediates the formation of hydrogen-bonded GNR
sheets. In solution, sheets of side-by-side coordinated GNRs can in
turn assemble via van der Waals and π-stacking interactions
into 3D stacks, a process that ultimately produces macroscopic crystalline
structures. The optoelectronic properties of these semiconducting
GNR crystals are determined entirely by those of the individual nanoscale
constituents, which are tunable by varying their width, edge orientation,
termination, and so forth. The atomically precise bottom-up synthesis
of bulk quantities of basic nanoribbon units and their subsequent
self-assembly into crystalline structures suggests that the rapidly
developing toolset of organic and polymer chemistry can be harnessed
to realize families of novel carbon-based materials with engineered
properties