Layer-by-Layer Fabrication of Fullerene-Intercalated Orthogonal Molecular Architectures Enhances Thermoelectric Behavior of Graphene-Based Nanodevices.

Despite the significant potential of molecular-scale devices for miniaturized electronics and energy conversion applications, conventional self-assembled monolayers (SAMs) exhibit limitations in simultaneously optimizing electrical conductivity and thermopower due to constrained electronic pathway modulation. This study demonstrates a molecular engineering strategy employing a discretely arranged conjugated molecular backbone to construct ordered cage-like supramolecular cavities, enabling controlled intercalation of fullerene within bipyridine-based SAMs grown on graphene-substrates. Quartz crystal microbalance and atomic force microscopy measurements confirmed the structural integrity of the fullerene-trapped SAMs.

Investigation impact of (Ni, Cu) co-doping on the electronic, optical, magnetic, and I-V characteristics of GaP nanosheets.

Context: The impact of the combination of transition metals on the electronic, optical, magnetic, and I-V characteristics of GaP nanosheet was carried out by first-principles density functional theory (DFT) with nonequilibrium green's function calculations. The band energy results of the GaP structure showed a semiconductor feature with a direct band gap of 1.29 eV.

The effect of the oxygen dangling on the thermoelectric properties of organic Thienoisoindigo single-molecule junction.

Context: Theoretical investigation for thermoelectric characteristics of organic Thienoisoindigo single-molecule is carried out using the first-principles calculations based on the density functional theory. It reveals that modifying the position or removing oxygen atoms significantly alters the thermoelectric properties. Transmission coefficient calculations show that the lowest unoccupied molecular orbital (LUMO) dominates across all molecular configurations.

Orientational Effects and Molecular-Scale Thermoelectricity Control.

The orientational effect concept in a molecular-scale junction is established for asymmetric junctions, which requires the fulfillment of two conditions: (1) design of an asymmetric molecule with strong distinct terminal end groups and (2) construction of a doubly asymmetric junction by placing an asymmetric molecule in an asymmetric junction to form a multicomponent system such as Au/Zn-TPP+M/Au. Here, we demonstrate that molecular-scale junctions that satisfy the conditions of these effects can manifest Seebeck coefficients whose sign fluctuates depending on the orientation of the molecule within the asymmetric junction in a complete theoretical investigation. Three anthracene-based compounds are investigated in three different scenarios, one of which displays a bithermoelectric behavior due to the presence of strong anchor groups, including and .

Investigating the optical properties and electronic structure of gallium phosphide nanotubes doped with arsenic via implementing first-principles calculations.

Context: This study investigates the impact of arsenic doping on the optical characteristics and electronic structure of zigzag (8, 0) and armchair (4, 4) gallium phosphide nanotubes using first-principles calculations based on the GaPAs system, where x = 0, 0.25, 0.5, 0.

Energy gap and aromatic molecular rings.

The manuscript combines rational density functional theory simulations and experimental data to investigate the electrical properties of eight polycyclic aromatic hydrocarbons (PAHs). The optimized geometries reveal a preference for one-row, two-row and three-row ring distributions. Band structure plots demonstrate an inverse correlation between the number of aromatic rings and band gap size, with a specific order observed across the PAHs.

Quantum Interference and Contact Effects in the Thermoelectric Performance of Anthracene-Based Molecules.

We report on the single-molecule electronic and thermoelectric properties of strategically chosen anthracene-based molecules with anchor groups capable of binding to noble metal substrates, such as gold and platinum. Specifically, we study the effect of different anchor groups, as well as quantum interference, on the electric conductance and the thermopower of gold/single-molecule/gold junctions and generally find good agreement between theory and experiments. All molecular junctions display transport characteristics consistent with coherent transport and a Fermi alignment approximately in the middle of the highest occupied molecular orbital/lowest unoccupied molecular orbital gap.

Signatures of Room-Temperature Quantum Interference in Molecular Junctions.

ConspectusDuring the past decade or so, research groups around the globe have sought to answer the question: "How does electricity flow through single molecules?" In seeking the answer to this question, a series of joint theory and experimental studies have demonstrated that electrons passing through single-molecule junctions exhibit exquisite quantum interference (QI) effects, which have no classical analogues in conventional circuits. These signatures of QI appear even at room temperature and can be described by simple quantum circuit rules and a rather intuitive magic ratio theory. The latter describes the effect of varying the connectivity of electrodes to a molecular core and how electrical conductance can be controlled by the addition of heteroatoms to molecular cores.

Electrostatic Fermi level tuning in large-scale self-assembled monolayers of oligo(phenylene-ethynylene) derivatives.

Understanding and controlling the orbital alignment of molecules placed between electrodes is essential in the design of practically-applicable molecular and nanoscale electronic devices. The orbital alignment is highly determined by the molecule-electrode interface. Dependence of orbital alignment on the molecular anchor group for single molecular junctions has been intensively studied; however, when scaling-up single molecules to large parallel molecular arrays (like self-assembled monolayers (SAMs)), two challenges need to be addressed: 1.

Exploring seebeck-coefficient fluctuations in endohedral-fullerene, single-molecule junctions.

For the purpose of creating single-molecule junctions, which can convert a temperature difference Δ into a voltage Δ the Seebeck effect, it is of interest to screen molecules for their potential to deliver high values of the Seebeck coefficient = -Δ/Δ. Here we demonstrate that insight into molecular-scale thermoelectricity can be obtained by examining the widths and extreme values of Seebeck histograms. Using a combination of experimental scanning-tunnelling-microscopy-based transport measurements and density-functional-theory-based transport calculations, we study the electrical conductance and Seebeck coefficient of three endohedral metallofullerenes (EMFs) ScN@C, ScC@C, and ErN@C, which based on their structures, are selected to exhibit different degrees of charge inhomogeneity and geometrical disorder within a junction.

Optimised power harvesting by controlling the pressure applied to molecular junctions.

A major potential advantage of creating thermoelectric devices using self-assembled molecular layers is their mechanical flexibility. Previous reports have discussed the advantage of this flexibility from the perspective of facile skin attachment and the ability to avoid mechanical deformation. In this work, we demonstrate that the thermoelectric properties of such molecular devices can be controlled by taking advantage of their mechanical flexibility.

Molecular-scale thermoelectricity: as simple as 'ABC'.

If the Seebeck coefficient of single molecules or self-assembled monolayers (SAMs) could be predicted from measurements of their conductance-voltage (-) characteristics alone, then the experimentally more difficult task of creating a set-up to measure their thermoelectric properties could be avoided. This article highlights a novel strategy for predicting an upper bound to the Seebeck coefficient of single molecules or SAMs, from measurements of their - characteristics. The theory begins by making a fit to measured - curves using three fitting parameters, denoted , , .

Thermoelectric Properties of 2,7-Dipyridylfluorene Derivatives in Single-Molecule Junctions.

A series of 2,7-dipyridylfluorene derivatives have been synthesized with different substituents (2H, 2Me, 2OMe, 2CF, and O) at the C(9) position. Experimental measurements on gold|single-molecule|gold junctions, using a modified scanning tunneling microscope-break-junction technique, show that the C(9) substituent has little effect on the conductance, although there is a more significant influence on the thermopower, with the Seebeck coefficient varying by a factor of 1.65 within the series.

Quantum interference and heteroaromaticity of para- and meta-linked bridged biphenyl units in single molecular conductance measurements.

Is there a correlation between the (hetero)aromaticity of the core of a molecule and its conductance in a single molecular junction? To address this question, which is of fundamental interest in molecular electronics, oligo(arylene-ethynylene) (OAE) molecular wires have been synthesized with core units comprising dibenzothiophene, carbazole, dibenzofuran and fluorene. The biphenyl core has been studied for comparison. Two isomeric series have been obtained with 4-ethynylpyridine units linked to the core either at para-para positions (para series 1-5) or meta-meta positions (meta series 6-10).

Discriminating single-molecule sensing by crown-ether-based molecular junctions.

Crown-ether molecules are well known to selectively bind alkali atoms, so by incorporating these within wires, any change in electrical conductance of the wire upon binding leads to discriminating sensing. Using a density functional theory-based approach to quantum transport, we investigate the potential sensing capabilities of single-molecule junctions formed from crown ethers attached to anthraquinone units, which are in turn attached to gold electrodes via alkyl chains. We calculate the change in electrical conductance for binding of three different alkali ions (lithium, sodium, and potassium).