Thiophene Molecules Research Articles

Molecular junction of n-thiophenes sandwiched between two Au (111) electrodes

ABSTRACTIn this work, the electron-transport properties of the molecular junction of oligothiophenes sandwiched between two Au (111) electrodes are studied based on the combination of the density functional theory and non-equilibrium Green’s function (NEGF) approach. From the calculation of electron properties, it is revealed that by increasing the number of thiophenes rings the (highest occupied molecular orbital-lowest unlocked molecular orbital) gap and the total energy decreases. Also, the transmission coefficient at zero voltage and the current–voltage curve for the thiophene molecules is calculated. The results indicate that the electrical conductivity and the value of band gap decrease exponentially with increasing the length of the molecules. Moreover, by simulating this molecular wire, we were able to obtain a current in the range of micro-amperes, which is a good current in the electronic application. However, it is known that the linear-response conductance is overestimated about an order of magnitude or more by the NEGF + DFT approach when semi-local approximate functional like PBE is used.

On the optoelectronic properties of non-covalently functionalized graphene for solar cell application

In this study, we report a simple approach toward the non-covalent functionalization of graphene by anthracene and thiophene molecules in different configurations, depending on the direction of the molecules approach to the surface of graphene. We examined structural, optoelectronic and vibrational properties of graphene before and after interaction with anthracene and thiophene. The density functional theory at B3LYP with 6-311G(d,p), 6-31G(d,p) and 6-31G(d) was employed to choose appropriate basis set that provides a more accurate molecular–properties description. This is important to compare and understand the deep relationship between the chemical structure of these heterostructures and their related properties to be chosen as an active layer in electronic devices. The device-based thiophene–graphene with perpendicular configuration film as an active layer in CdTe/CdS solar cell shows the best performance with a power conversion efficiency of $$9.58\%$$ , an open-circuit voltage of $$0.7\,\hbox {V}$$ , a short-circuit current density of $$24.47\,\hbox {mA}\,\hbox {cm}^{2}$$ and a fill factor of $$55.92\%$$ under simulated AM1.5 conditions at $$1000\,\hbox {W}\,\hbox {m}^{2}$$ .

ADSORPTION OF THIOPHENE ON N-DOPED TiO2/MoS2 NANOCOMPOSITES INVESTIGATED BY VAN DER WAALS CORRECTED DENSITY FUNCTIONAL THEORY

Comparison of structural and electronic properties between pristine and N-doped titanium dioxide-(TiO2)/molybdenum disulfide (MoS2) nanocomposites and their effects on the adsorption of thiophene molecule were performed using density functional theory calculations. To correctly estimate the adsorption energies, the van der Waals interactions were taken into account in the calculations. On the TiO2/MoS2 nanocomposite, thiophene molecule tends to be strongly adsorbed by its sulfur atom. The five-fold coordinated titanium atom of TiO2 was found to be an active binding site for thiophene adsorption. The results suggest that the thiophene molecule has not any mutual interaction with MoS2 nanosheet. The electronic structures of the complex systems are discussed in terms of the density of states and molecular orbitals of the thiophene molecules adsorbed to the TiO2/MoS2 nanocomposites. It was also found that the doping of nitrogen atom is conductive to the interaction of thiophene with nanocomposite. Thus, it can be concluded that the interaction of thiophene with N-doped TiO2/MoS2 nanocomposite is more energetically favorable than the interaction with undoped nanocomposite. The sensing capability of TiO2/MoS2 toward thiophene detection was greatly increased upon nitrogen doping. These processes ultimately lead to the strong adsorption of thiophene on the N-doped TiO2/MoS2 nanocomposites, indicating potential applicability of these nanocomposites as novel gas sensors.

Thiophene/Graphene Interface Peculiarities for Potential Organic Electronic Applications

Interfacial study between thiophene molecule and graphene surface is presented by employing density functional theory methods. To do so, interfacing separation distance is varied from 1.00A to 2.50A. Our reported HOMO-LUMO energy gap values, adsorption energy as well as binding energy show the existence of intermolecular forces accumulated from the attractive van der Waals and Pauli repulsion forces. It is noted subsequently that the growing intermolecular forces are very sensitive even to relatively a small change in the interfacing separation distance between the molecule and surface. In the electronic density of states, dense electrons population of the thiophene/graphene system is found with appearance of spinpolarization at energy Fermi level. Moreover, a slight magnetic behaviour on thiophene molecule, accompanied by a decrease in the magnetization of graphene surface, is observed in the presence of the molecule near to the surface.

Nut-like MOF/hydroxylated graphene hybrid materials for adsorptive desulfurization of thiophene.

Nowadays, sulfur compounds in fuel oils are the main source of environmental pollution and ultra-deep desulfurization of fuel oils has become a top priority. Many porous materials such as activated carbon and metal–organic frameworks (MOFs) have attracted attention in the field of adsorption desulfurization in recent years. A series of novel MOF/hydroxylated graphene hybrid materials were successfully designed and synthesized with different ratios for application in the field of ADS. The hydroxylated graphene (HG) was found dispersed not just on the surface but also inserted in the MOF crystals in what we call a nut-like structure. It was found that the introduction of a small amount (<8%) of HG does not hinder the formation of the Cu-BTC structure. Meanwhile, the adsorption performances of these composites for thiophene from oils were evaluated using batch adsorption tests at room temperature. The synergistic effect between Cu-BTC and HG in the hybrid materials can improve the adsorption capacity for thiophene molecules. The experimental equilibrium curve fitted well with the theoretical Langmuir isotherm model. The maximum sulfur adsorption capacity of 35.6 mg S g−1 for the hybrid materials was calculated using the Langmuir adsorption equation, which increased by 48% compared to parent Cu-BTC. Thus, these hybrid materials have great potential for application in the adsorptive desulfurization process, especially for thiophenic compounds.

Adsorption and Desulfurization Mechanism of Thiophene on Layered FeS(001), (011), and (111) Surfaces: A Dispersion-Corrected Density Functional Theory Study.

Layered transition-metal chalcogenides have emerged as a fascinating new class of materials for catalysis. Here, we present periodic density functional theory (DFT) calculations of the adsorption of thiophene and the direct desulfurization reaction pathways on the (001), (011), and (111) surfaces of layered FeS. The fundamental aspects of the thiophene adsorption, including the initial adsorption geometries, adsorption energies, structural parameters, and electronic properties, are presented. From the calculated adsorption energies, we show that the flat adsorption geometries, wherein the thiophene molecule forms multiple π-bonds with the FeS surfaces, are energetically more favorable than the upright adsorption geometries, with the strength of adsorption decreasing in the order FeS(111) > FeS(011) > FeS(001). The adsorption of the thiophene onto the reactive (011) and (111) surfaces is shown to be characterized by charge transfer from the interacting Fe d-band to the π-system of the thiophene molecule, which causes changes of the intramolecular structure including loss of aromaticity and elongation of the C–S bonds. The thermodynamic and kinetic analysis of the elementary steps involved in the direct desulfurization of thiophene on the reactive FeS surfaces is also presented. Direct desulfurization of thiophene occurs preferentially on the (111) surface, as reflected by the overall exothermic reaction energy calculated for the process (ER = −0.15 eV), with an activation energy of 1.58 eV.

Understanding the grain-growth mechanism of high-performance organic semiconducting diphenyl-dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene molecules

We report here our investigation on the grain-growth mechanism of diphenyl-dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene (DPh-DBTTT), which was recently published as a high-performance organic semiconductor. Atomic force microscopy revealed that unconventional needle-like structures grew on the surface of DPh-DBTTT thin films, and these structures became more dominant as the film thickness increased and the deposited film's surface temperature decreased. In combination with the crystal structure simulations, the grazing-incidence wide-angle x-ray scattering data indicated that the DPh-DBTTT molecules preferred an edge-on orientation near the interface between the substrate and DPh-DBTTT thin film, while the needle-like structures consisted of a face-on arrangement of the molecules. We suggest that this structural change originates from the large step-edge energy barrier of the DPh-DBTTT molecules. Our findings would be highly valuable to the design of new high-performance organic semiconducting materials and optimization of the conditions of thin-film deposition.

High-Performance Single-Electron Transistor Based on Metal–Organic Complex of Thiophene: First Principle Study

The ab initio perspective based on density functional theory and nonequilibrium Green’s function for the modeling of single electron transistors (SETs) based on thiol-ended thiophene and chromium complex of thiol-ended thiophene and their functioning in the Coulomb blockade regime has been discussed. Both thiol-ended thiophene molecule and its chromium complex have been analyzed for the charge stability and conductance dependence on the gate voltage and source–drain bias. The charging energies for the isolated and SET environment for both the islands have been calculated and discussed. Also, the effect of orientation and the dielectric medium has been studied in order to increase the conductance of SET with the combination of a particular orientation and a dielectric medium. The effect of different electrodes on charge stability diagram has also been studied. The analysis shows a remarkably improved conductance for the chromium complex of thiol-ended thiophene molecule in the SET environment than the thiol-ended thiophene molecule in the SET environment resulting in a fast switching metal–organic SET.

Expanding the Scope of Diamond Surface Chemistry: Stille and Sonogashira Cross-Coupling Reactions

Well-defined covalent surface functionalization of diamond is a crucial, yet nontrivial, matter because of diamond’s intrinsic chemical inertness and stability. Herein, we demonstrate a two-step functionalization approach for H-terminated boron-doped diamond thin films, which can lead to significant advances in the field of diamond hybrid photovoltaics. Primary diamond surface functionalization is performed via electrochemical diazonium grafting of in situ diazotized 4-iodoaniline. The freshly grafted iodophenyl functional moieties are then employed to couple a layer of thiophene molecules to the diamond surface via two well-established Pd-catalyzed cross-coupling reactions, i.e., Stille and Sonogashira. X-ray photoelectron spectroscopy analysis indicates a dense coverage and successful cross-coupling in both cases. However, we find that the Stille reaction is generally accompanied by severe surface contamination, in spite of process optimization and thorough rinsing. Sonogashira cross-coupling on the oth...

Deep oxidative desulfurization of gasoline induced by PMoCu@MgCu2O4-PVA composite as a high-performance heterogeneous nanocatalyst

In this paper, a new type of inorganic-organic hybrid nanocatalyst has been prepared by the composition of the potassium salt of Cu-substituted phosphomolybdic acid (K5PMo11CuO39 abbreviated as PMoCu), magnesiocopperite (MgCu2O4) and polyvinyl alcohol (PVA). The assembled PMoCu-MgCu2O4@PVA composite was characterized by FT-IR, XRD, and SEM. The results of characterizations revealed that PMoCu and MgCu2O4 homogeneously dispersed on PVA surface. The PMoCu-MgCu2O4@PVA was exploited as a heterogeneous nanocatalyst for deep oxidative desulfurization (ODS) of gasoline and model oil. High desulfurization efficiency was achieved using hydrogen peroxide/acetic acid (H2O2/AcOH) as an oxidant at 35 °C after 60 min. On the basis of the suggested ODS system, the mercaptan and sulfur content of gasoline could be removed with 97% and 98% yield, respectively. The ODS of thiophene molecules, which are difficult to remove, could be reached to 97%. Also, PMoCu-MgCu2O4@PVA was demonstrated an excellent recyclability performance in the ODS reactions for five times without noticeable decrease in catalytic activity. It is believed that the present PMoCu-MgCu2O4@PVA/H2O2/AcOH system can be a convenient strategy to obtain clean gasoline fuel.

Constructing facilitated transport pathway in hybrid membranes by incorporating MoS2 nanosheets

Constructing facilitated transport pathways using two-dimensional (2D) nanosheets as building blocks is an emerging approach to achieving highly selective passage of small molecules with similar physical properties. Due to high chemical inertness and low structural defects, molybdenum disulfide (MoS2) 2D nanosheets hold great promise in a broad range of molecular separation applications. In this study, MoS2 nanosheets were incorporated in Pebax matrix to remove thiophene from the n-octane-thiophene mixture. The moderate binding energy of thiophene on the basal plane of MoS2 enabled the construction of continuous facilitated transport pathways on the MoS2 nanosheet for rapid diffusion of thiophene molecules. When the content of MoS2 in the hybrid membrane was 4wt%, the membrane displayed an optimum desulfurization performance with a permeation flux of 11.42kg/ (m2h) (22.27% higher than that of Pebax membrane) and an enrichment factor of 9.11 (65.94% higher than that of Pebax membrane) at 60°C with a feed solution containing 1312ppm thiophene. This study is the first attempt of using MoS2 nanosheets in pervaporative separations of small molecules liquid mixture, which may open a novel avenue to constructing facilitated transport pathway within membranes for efficient molecular sieving.

A New Approach to Understand the Adsorption of Thiophene on Different Surfaces: An Atom Probe Investigation of Self-Assembled Monolayers.

Atom probe tomography was used to analyze self-assembled monolayers of thiophene on different surfaces, including tungsten, platinum, and aluminum, where the tungsten was examined in both pristine and oxidized forms. A glovebag with controlled atmospheres was used to alter the level of oxidation for tungsten. It was shown that different substrates lead to substantial changes in the way thiophene adsorbs on the surface. Furthermore, the oxidation of the surface strongly influenced the adsorption behavior of the thiophene molecules, leading to clear differences in the amounts and compositions of field evaporated ions and molecular ions.

Benchmarking semiempirical and DFT methods for the interaction of thiophene and diethyl sulfide molecules with a Ti(OH)4(H2O) cluster.

Semiempirical methods pm6 and pm7 as well as density functional theory functionals exchange LSDA, exchange-correlation PW91 and PBE, hybrid B3LYP1 and PBE0 were compared for energy and geometry of thiophene, diethyl sulfide (DES) molecules and their binding to a frozen Ti(OH)4(H2O) complex having one coordinatively unsaturated Ti5C site representing small fragment of TiO2 anatase (001) surface. PBE0/6-31G(d) with DFT-D3 dispersion correction was the best method for description of thiophene and DES molecules geometries as comparison with experimental data demonstrated. Semiempirical methods pm6 and pm7 resulted in only three of four possible binding configurations of thiophene with the Ti(OH)4(H2O) complex while pm7 described correctly the enthalpy and all configurations of DES binding with the Ti(OH)4(H2O) complex. SBKJC pseudopotential and LSDA with and without dispersion correction produced flawed results for many configurations. PBE0 and PBE with and without dispersion correction and PW91 with 6-31G(d) basis set systematically produced dependable results for thiophene and DES binding to the Ti(OH)4(H2O) complex. PBE0-D3/6-31G(d), B3LYP1-D3/6-31G(d), and PBE-D3/6-31G(d) gave best match of binding energy for thiophene while PBE0/6-31G(d) gave best match of DES binding energy as comparison with CCSD(T) energy demonstrated. On the basis of the superior results obtained with PBE0/6-31G(d), it is the recommended method for modeling of adsorption over TiO2 surfaces. Such a conclusion is in agreement with recent literature.

Competitive adsorption mechanism of thiophene with benzene in FAU zeolite: The role of displacement

To explore the whole process of competitive relationship changing with increasing adsorption amount, the competitive adsorption mechanism of benzene/thiophene in siliceous faujasite (FAU) zeolite from infinite dilution to saturation adsorption was analyzed through grand canonical ensemble Monte Carlo simulations for the first time. Results showed that the competitive adsorption mechanism transferred from “ideal-displacement adsorption” to “insertion-displacement adsorption” with an inflection point of 40molecule/UC, as the total loading amount of benzene and thiophene grew. At “ideal-displacement adsorption” stage, both benzene and thiophene molecules adsorbed ideally on S and W sites. Meanwhile, as the total loading closed to 40molecule/UC, increasing amount of thiophene on favorable S adsorption sites was displaced by benzene and migrated to W sites. Comparatively, at “insertion-displacement adsorption” stage, benzene molecules continued displacing some thiophene adsorbed on S sites when the total loading increased. The displaced thiophene inserted near the center of the supercage. The transformation in this competitive adsorption mechanism was due to the interaction energy. Besides, higher thiophene concentration, adsorption temperatures and ratios of Si/Al to some extent contributed to the increase in the selectivity for thiophene.

Adsorption of thiophene on the surfaces of X12Y12 (X = Al, B, and Y = N,P) nanoclusters; A DFT study

Density functional theory (DFT) calculations are performed to study the response of X12Y12 nanoclusters (Al12N12, Al12P12, B12N12, and B12P12) towards adsorption of thiophene molecule. The interaction energies of thiophene on nanoclusters are evaluated with long range and dispersion corrected (ωB97XD and M06-2X), and conventional non-corrected (B3LYP) methods in order to estimate the dispersion effects. The dispersion corrected (ωB97XD) binding energies of thiophene on Al12N12 and Al12P12 are −60.4 and −45.0kJ·mol−1, respectively. The corresponding non-corrected binding energies calculated at B3LYP method are −43.6 and −30.3 kJ·mol−1, respectively. Thiophene is physisorbed on B-containing surfaces where binding energies are −10.4, −8.3 (ωB97XD) and −6.3 and −4.1 (B3LYP) kJ·mol−1 for B12N12 and B12P12, respectively. Changes in electronic properties such as HOMO-LUMO gap, Fermi level and densities of states are also analyzed to realize the sensing ability of nanoclusters for thiophene molecule. Among all the studied nanoclusters, Al12N12 is the strongest adsorbent for thiophene whereas B12N12 shows the highest change in the electronic structure when a thiophene molecule is adsorbed.

Spin polarization properties at the spinterface of thiophene/Fe(100): First principles calculations

Based on density functional theory (DFT), the spin polarization properties of a thiophene molecule which is adsorbed at Fe (100) surface are discussed. A variety of horizontal and vertical adsorption configurations as well as their influences on the spin density distributions are studied in detail. The spin polarization comes from the [Formula: see text]-[Formula: see text] orbital coupling between the thiophene molecule and the electrode, which leads to the molecules’ energy level shifting and the density of states (DOS) broadening, so the two spin states near the Fermi level are exchange split. It is also found that the interfacial spin polarization is different under different contact configurations, and the biggest one will be obtained when the S atom is directly placed above the Fe atom at the horizontal direction. On the other hand, interface spin inversion can be obtained by adjusting the adsorption position, which will be helpful to build spin sensors.

Negative Differential Resistance, Memory, and Reconfigurable Logic Functions Based on Monolayer Devices Derived from Gold Nanoparticles Functionalized with Electropolymerizable TEDOT Units

We report on hybrid memristive devices made of a network of gold nanoparticles (10 nm diameter) functionalized by tailored 3,4(ethylenedioxy)thiophene (TEDOT) molecules, deposited between two planar electrodes with nanometer and micrometer gaps (100 nm to 10 um apart), and electropolymerized in situ to form a monolayer film of conjugated polymer with embedded gold nanoparticles (AuNPs). Electrical properties of these films exhibit two interesting behaviors: (i) a NDR (negative differential resistance) behavior with a peak/valley ratio up to 17, and (ii) a memory behavior with an ON/OFF current ratio of about 1E3 to 1E4. A careful study of the switching dynamics and programming voltage window is conducted demonstrating a non-volatile memory. The data retention of the ON and OFF states is stable (tested up to 24h), well controlled by the voltage and preserved when repeating the switching cycles (800 in this study). We demonstrate reconfigurable Boolean functions in multiterminal connected NP molecule devices.

Analysis of the second harmonic generation signal from a liquid/air and liquid/liquid interface.

Three different liquid interfaces, water/air, thiophene/air, and water/thiophene, were probed using the second harmonic generation (SHG) technique. Thiophene and water have been chosen because the hyperpolarizability of these molecules has already been measured or calculated and the different values can be found in literature. We have studied the microscopic structure of these interfaces by comparing the components of the second order susceptibility tensor determined from the SHG polarization curve analysis with those determined via a molecular dynamics (MD) simulation of these interfaces. We have indeed computed the structure and orientation of water and thiophene molecules at the liquid/air and liquid/liquid (L/L) interfaces as a function of the distance from the interface. The integrated susceptibility values calculated by MD simulations agree well with SHG results and validate the choice of force fields that should permit to quantify more complex L/L interfaces.

Modeling the thermodynamic properties and phase behaviour of organic sulfur molecules with a group contribution based statistical associating fluid theory approach (GC-SAFT-VR)

Leveraging the demonstrated accuracy of the group contribution statistical associating fluid theory for potentials of variable range (GC-SAFT-VR) equation of state to predict the phase equilibrium and thermodynamic properties of fluids, we use this approach to study organic sulfur molecules and their mixtures. Knowledge of the phase equilibria and thermodynamic properties of sulfur containing compounds, while of interest in a number of fields, is important to the development of petroleum products with lower sulfur content. In this work the CH(thiophene) and –S- functional groups are characterized by fitting to experimental data for pure thiophene and cross interactions determined in order to extend the GC-SAFT-VR equation of state to the study of organic sulfur molecules. Theoretical predictions are compared with experimental results for the phase behavior of 3-methylthiophene, 2-methylthiophene, and benzothiophene, as well as their binary mixtures with alkanes, alkenes, aromatics, carbon dioxide, and alcohols. As far as we are aware, this work is the first SAFT-based study of mixtures containing thiophene molecules with aromatics, alcohols, and hydrocarbon molecules. The GC-SAFT-VR approach is found to accurately predict the phase behavior of the sulfur organic compounds studied, providing a method to determine the phase behavior of these compounds without heavy reliance on experimental data.

Spin polarization properties of thiophene molecule adsorbed to the edge of zigzag graphene nanoribbon

Spin polarization properties of thiophene molecule adsorbed to the edge of zigzag graphene nanoribbon (GNR) are studied based on density functional theory calculations. It is shown that there is charge transfer between the thiophene molecule and the zigzag GNR, which changes the bond lengths of the thiophene molecule. Another consequence of the charge transfer is the spontaneous spin polarization of the thiophene molecule. The mechanism of the spontaneous spin polarization is also discussed based on the analysis of the density of states. It is found that the p orbitals of the carbon atoms and the sulfur atom in thiophene molecule become spin split near the Fermi energy, so preferential fillings of the spin-splitted p orbitals make the thiophene molecule spin polarized. This spontaneous spin polarization of thiophene molecules adsorbed to the zigzag GNR could be a new route to graphene-based organic spintronic devices.