150 research outputs found
Tuning the HOMO–LUMO Gap of Pyrene Effectively via Donor–Acceptor Substitution: Positions 4,5 Versus 9,10
Donor and acceptor substituents were introduced at pyrene’s K-regions in order to engineer its optoelectronic properties. A study of the influence of the substitution pattern on the frontier orbitals as well as on the molecular packing is provided. A comparison with the pure donor and acceptor substituted pyrene derivatives highlights the strong impact of the presented donor–acceptor substitution
Molecular Logic with a Saccharide Probe on the Few-Molecules Level
In this Communication we describe a two-component saccharide
probe
with logic capability. The combination of a boronic acid-appended
viologen and perylene diimide was able to perform a complementary
implication/not implication logic function. Fluorescence quenching
and recovery with fructose was analyzed with fluorescence correlation
spectroscopy on the level of a few molecules of the reporting dye
Synthesis of an Acceptor–Donor–Acceptor Multichromophore Consisting of Terrylene and Perylene Diimides for Multistep Energy Transfer Studies
Motivated by the results obtained
from the investigation of singlet–singlet
annihilation in a linear multichromophore comprising terrylene diimides
(TDI) and perylene diimide (PDI) in 2010, we report the detailed process
toward the successful synthesis of a TDI–PDI–TDI dyad.
Ineffective synthetic pathways, which were necessary for the understanding
of the step-by-step construction of the complex multichromophore,
are described, leading toward a universal synthetic plan for multicomponent
systems containing rylene diimides separated by rigid oligophenylene
spacers
Field Effect Transistors Based on Polycyclic Aromatic Hydrocarbons for the Detection and Classification of Volatile Organic Compounds
We show that polycyclic aromatic
hydrocarbon (PAH) based field effect transistor (FET) arrays can serve
as excellent chemical sensors for the detection of volatile organic
compounds (VOCs) under confounding humidity conditions. Using these
sensors, w/o complementary pattern recognition methods, we study the
ability of PAH-FET(s) to: (i) discriminate between aromatic and non-aromatic
VOCs; (ii) distinguish polar and non-polar non-aromatic compounds;
and to (iii) identify specific VOCs within the subgroups (i.e., aromatic
compounds, polar non-aromatic compounds, non-polar non-aromatic compounds).
We further study the effect of water vapor on the sensor array’s
discriminative ability and derive patterns that are stable when exposed
to different constant values of background humidity. Patterns based
on different independent electronic features from an array of PAH-FETs
may bring us one step closer to creating a unique fingerprint for
individual VOCs in real-world applications in atmospheres with varying
levels of humidity
B<sub>2</sub>N<sub>2</sub>‑Dibenzo[<i>a</i>,<i>e</i>]pentalenes: Effect of the BN Orientation Pattern on Antiaromaticity and Optoelectronic Properties
Two BN units were
embedded in dibenzo[<i>a</i>,<i>e</i>]pentalene
with different orientation patterns, which significantly
modulated its antiaromaticity and optoelectronic properties. Importantly,
the vital role of the BN orientation in conjugated molecules with
more than one BN unit was demonstrated for the first time. This work
indicates a large potential of the BN/CC isosterism for the development
of new antiaromatic systems and highlights the importance of precise
control of the BN substitution patterns in conjugated materials
Surface Pretreatment Boosts the Performance of Supramolecular Affinity Materials on Quartz Crystal Microbalances for Sensor Applications
A Teflon-like
coating is the key for the boost in sensitivity of
quartz microbalances for the tracing of airborne analytes. Since the
undesired signals for the interfering compounds are suppressed and
the ones for the targeted compounds (e.g., peroxide explosives) are
enhanced, the PCA output is improved
Role of Sub-Nanometer Dielectric Roughness on Microstructure and Charge Carrier Transport in α<i>,</i>ω‑Dihexylsexithiophene Field-Effect Transistors
The effect of dielectric roughness
on the microstructure evolution
of thermally evaporated α,ω-dihexylsexithiophene (α,ω-DH6T)
thin films from a single molecular layer to tens of monolayers (ML)
is studied. Thereby, the surface roughness of dielectrics is controlled
within a sub-nanometer range. It is found that the grain size of an
α,ω-DH6T ML is affected by dielectric roughness, especially
for 1.5 ML, whereby the transistor performance is barely influenced.
This can be attributed to a domain interconnection in the second layer
over a long-range formed on the rough surface. With deposition of
more layers, both microstructure and charge carrier transport exhibit
a roughness-independent behavior. The structural characterization
of α,ω-DH6T 10 ML by grazing-incidence wide-angle X-ray
scattering reveals that the interlayer distance is slightly decreased
from 3.30 to 3.15 nm due to a higher roughness, while an unchanged
π-stacking distance is in excellent agreement with the roughness-independent
hole mobility. This study excludes the influence of molecular-solvent
interaction and preaggregation taking place during solution deposition,
and provides further evidence that the microstructure of the interfacial
layer of organic semiconductors has only minor impact on the bulk
charge carrier transport in thicker films
Efficient Coupling of Nanoparticles to Electrochemically Exfoliated Graphene
Electrochemically exfoliated graphene
(EEG) is a new generation
of high-quality graphene that holds great promise for the construction
of hybrid materials. However, the assembly of EEG hybrids with well-defined
nanostructures has remained a major challenge. In this study, we demonstrate
a bottom-up approach toward the assembly of EEG sheets with a series
of functional nanoparticles (Si, Fe<sub>3</sub>O<sub>4</sub>, and
Pt NPs) into two-dimensional sandwich-like hybrid nanostructures.
Polyaniline in the emeraldine base form functions as a versatile dopant
to couple NPs onto EEG through either electrostatic interactions or
hydrogen bonding. This protocol enables processing and assembly of
EEG using an economical pathway, for which we further demonstrate
the potential application of EEG-Si hybrids as high-performance anode
material for lithium storage
Synthesis of Stable Nanographenes with OBO-Doped Zigzag Edges Based on Tandem Demethylation-Electrophilic Borylation
A tandem demethylation-aryl
borylation strategy was developed to
synthesize OBO-doped tetrabenzo[<i>a,f,j,o</i>]perylenes
(namely “bistetracenes”) and tetrabenzo[<i>bc,ef,kl,no</i>]coronenes (namely “peritetracenes”). The OBO-doped
bistetracene analogues exhibited excellent stability and strong fluorescence,
in contrast to the unstable all-carbon bistetracene. Single-crystal
X-ray analysis for OBO-doped bistetracene revealed a twisted double
[5]helicene structure, indicating that this synthesis is applicable
to new heterohelicenes. Importantly, cyclodehydrogenation of the bistetracene
analogues successfully produced the unprecedented heteroatom-doped
peritetracenes, which opened up a new avenue to periacene-type nanographenes
with stable zigzag edges
Positive Magneto-LC Effect in Conjugated Spin-Bearing Hexabenzocoronene
The
first neutral spin carrying hexabenzocoronene (HBC) derivative
is described. The conjugated phenyl nitroxide substituted HBC with
five alkyl chains exhibits a positive magneto-LC effect in columnar
hexagonal liquid crystalline phase as probed by differential scanning
calorimetry and electron paramagnetic resonance spectroscopy. Surprisingly,
at 140 K the Δ<i>M</i><sub>S</sub> = 2 transition
can be observed indicating a thermally accessible triplet state between
the neighboring molecules in the columnar arrangements
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