Thiophene Molecules Research Articles

Solution-grown unidirectionally oriented crystalline thin films of a U-shaped thienoacene-based semiconductor for high-performance organic field-effect transistors

Strategically dialkylated bis(benzo[4,5]thieno)[2,3-b:3′,2′-d]thiophene molecules having an overall U-shaped configuration can self-organize into bilayer lamellar structures, demonstrating high charge-transport properties in thin-film organic transistors.

Chemical interactions of thiophene with ZnO and Al-doped ZnO thin films

In this study, ZnO and Al-doped ZnO films have been synthesized by five different deposition methods. Electrochemical measurements performed on films immersed in S-containing isooctane indicate that the texture and polarity of the surface of the films are key features affecting the adsorption of thiophene molecules. Specifically, ZnO films possessing a large amount of Zn-terminated (002) wurtzite surfaces are observed to be the most sensitive to the concentration of thiophene in isooctane.

Adsorptive desulfurization of diesel oil using nickel nanoparticle-doped activated carbon beads with/without carbon nanofibers: Effects of adsorbate size and adsorbent texture

Nickel (Ni)-doped activated carbon beads (ACBs) with/without carbon nanofibers (CNFs) were synthesized for the efficient desulfurization of diesel oil by adsorption. The materials were characterized for their physico-chemical properties, using the BET, SEM, XRD, and TPD analysis. The in-situ dispersed Ni nanoparticles in the ACBs served the dual role of catalyzing the growth of the CNFs (average thickness c.a. 70nm) across the ACB surface and the removal of S-containing compounds from the liquids. The adsorption capacity of Ni/ACBs (without CNF-containing adsorbents) was approximately 3.5 times higher than that of Ni-CNF/ACBs for the large sized dibenzothiophene molecules, because of the higher BET surface area and pore volume of the former adsorbent. On the contrary, the adsorption capacity of Ni-CNF/ACBs was higher than that of Ni/ACBs for the small sized thiophene molecules, despite the BET surface area and pore volume being smaller in the CNF-containing adsorbent, indicating that the π-complexion interactions were dominant over physisorption in the graphitic CNFs. The comparative adsorption data indicate that the adsorption capacities of the prepared Ni-containing adsorbents with/without CNFs in this study were greater than most of the adsorbents discussed in the literature. This study assumes significance from the perspective of selecting suitable adsorbents for the different sized-S-compounds in diesel oil.

Vibrational properties of noncovalently oligothiophene-functionalized graphene nanomaterials

In this paper, the non resonant Raman spectra of hybrid nanostructures obtained by confinement of oligothiophene derivatives in two sheets of graphene are calculated in the framework of spectral moments method, together with a bond-polarizability model. Minimum energy calculations are performed, using a convenient Lennard-Jones expression of the van der Waals intermolecular potential, to derive the optimum configurations of oligothiophene with graphene. Parallel configuration of thiophene molecules with respect to the graphene plane was considered.

Effect of anchoring atom and electrostatic gating on the electronic transport properties in single molecular electronic devices

The effect of anchoring atom and electrostatic gate on the electron transport through gated thiophene single molecular device is studied by utilizing non-equilibrium Green’s function coupled with self-consistent extended Huckel theory. Gated gold–molecule–gold junctions are built using thiophene (Tp) molecule as functional component and sulphur (S) and selenium (Se) as anchoring atoms in field effect transistor (FET) configuration. The electron transport analysis of the gated thiophene single molecular device is investigated through the current–voltage and the electron transmission spectra. The results show that the anchoring atoms modulate the transport nature of these devices in a controlled manner. We find that the S–Tp–S device produces larger current than Se–Tp–Se device. Also we studied the effect of electrostatic gating on S–Tp–S and Se–Tp–Se device. We find that, positive bias or negative bias for Vg, will correspondingly, raise or lower the transmission coefficients T(E) in relation to the Fermi level (EF) for both the devices. Our results show that magnitude of Isd current varies more than one order for same Vsd over different Vg bias for S–Tp–S device, whereas for Se–Tp–Se device Isd current varies more than five times for same Vsd over different Vg bias. Se–Tp–Se device shows gate controlled NDR behavior. Finally, we demonstrated the application of using thiophene based single molecular FET to realize five basic logic gates very low Vsd bias. The key feature of the suggested design is the opportunity of demonstrating various logic gates with just one molecular unit transistor and demonstrated at very low Vsd bias.

Investigation of metal-exchanged mesoporous Y zeolites for the adsorptive desulfurization of liquid fuels

Removal of sulfur from transportation fuels using zeolites as sorbents is an attractive desulfurization method, because of its low energy and cost requirements. However, diffusion limitations within the micropore structure of zeolites can reduce their adsorption capacity, especially when refractory sulfur compounds are present in fuels. Moreover, the selective adsorption of sulfur compounds from a mixture of hydrocarbons can be very challenging. The objective of this study was to address the aforementioned challenges of adsorptive desulfurization of fuels using metal-exchanged mesoporous Y zeolites. Mesoporosity was introduced in the Y zeolites by two top-down methods (desilication and surfactant-assisted). Metals, Ce and Cu, were introduced via ion-exchange. The prepared metal-exchanged mesoporous zeolites were characterized and tested in terms of their sulfur adsorption capacity using a fixed-bed column and model fuels. The strength of adsorption was determined using isosteric heat of adsorption calculations. Our results demonstrated that mesoporous Y reduced diffusion limitations and were very effective sorbents for removing sulfur compounds with high kinetic diameter, such as dibenzothiophene (DBT). Metals highly increased the selectivity toward sulfur compounds. According to experimental results, the tendency of thiophenic molecules to adsorb on the zeolites increase in the order of thiophene (TP)<benzothiophene (BT)<DBT. The results of this study revealed that metal-exchanged mesoporous Y zeolites have the potential to display remarkable sulfur removal properties since the mesopores allow access to zeolite active sites while the metal cations improve the selectivity and/or capacity for sulfur compounds.

Electronic structures of spinterface for thiophene molecule adsorbed at Co, Fe, and Ni electrode: First principles calculations

First principles calculations are adopted to study the spin polarization properties of thiophene molecule which adsorbed at the Co, Fe, and Ni electrode surfaces. The density of states, spin-polarized density distributions as well as the differential charge density distributions are obtained. It is found that the p orbital of the thiophene molecule will interact with the d orbital of the ferromagnetic electrodes, which will generate new spin coupling states and lead to obvious spin polarization in the thiophene molecule. Different electrodes induce different spin polarization properties, and in which the Fe electrode will bring the biggest spin polarization of the thiophene molecule. People can selectively and efficiently inject spin polarized electrons into molecules by choosing suitable ferromagnetic electrodes in organic spintronic devices.

LINEAR ACENES LINKED THIOPHENE, ELECTRONIC AND CHEMICAL PROPERTIES: PROSPECTS FOR MOLECULAR ORGANIC ELECTRONIC MATERIAL

We report a theoretical study of linear acene (n=1 to 7) linked thiophene properties functionality. The total ground state and band gap energies, Coulomb potential and nuclear repulsion energy are calculated by DFT, MP2 at B3LYP exchange level of the theory and 6-311G* basis set. The results are in good agreement with the experimental and theoretical values. It is found that the total ground state energy of the system and band gap energy decreases with an increasing number of electrons in the rings. The addition of thiophene molecules tends to improve the electronic and chemical properties of the linear acenes, the material exhibit potential application in the organic molecular electronic material.

Fabrication and performance of electrochemically grafted thiophene silicon nanoparticle anodes for Li-ion batteries

In this work, we developed thiophene-grafted Si nanoparticle anodes for Li-ion batteries. The surface of Si nanoparticles was chemically modified with thiophene molecules via an electrochemical grafting process. This study is an overture for future endeavours where the thiophene layer on the modified Si- nanoparticles will function as an anchor point when co-polymerised with conducting polymers to produce a chemically bonded Si/conducting polymer anode composite. This in principle should mitigate the loss of electrical connection with Si due to any structural breakdown that may occur during cell cycling. Furthermore, the effect of the thiophene layer on the capacity and the cyclability of the Si electrode was apparent where the new material retained ~39% of the starting capacity after 60 cycles, compared to the unmodified Si electrodes, that merely lasted for 10 cycles with only 4% capacity retention. This is due to the thiophene layers which create an artificial solid electrolyte interphase around the Si nanoparticles protecting them from degradation. Additionally, the viability of using conducting polymers as anode composites under charging/discharging conditions was investigated via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) to conclude whether or not n-doping of the conducting polymer is required in such applications.

Monte Carlo simulations of phase equilibria and microstructure of thiophene/[Bmim][PF6]/CO2

Monte Carlo simulations were carried out to calculate the phase behavior of thiophene in the binary and ternary mixtures of 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) and carbon dioxide using a united atom model. The calculated pure ionic liquid densities and structural properties of [Bmim][PF6] as well as the vapor pressure of thiophene in the ionic liquid were compared with the available experimental data in the literatures, and a good agreement was obtained. Based on the radial distribution functions (RDFs) and spatial distribution functions (SDFs) results, thiophene molecules prefer to organize around the C10 atom of the butyl chain connected with the imidazolium ring. The concept of local composition in solutions was used to better understand the solution structure. It is shown that thiophene molecules can strongly associate with the cation. For the ternary system of CO2/thiophene/IL, CO2 can affect the solubility of thiophene in ionic liquid when the pressure is changed. CO2 molecules interact with the anion stronger than thiophene molecules. This implies that CO2 can be used as a potential recovery desorbent of thiophenic compounds in the ionic liquid by tuning the pressure.

A molecular understanding of the phase-behavior of thiophene in the ionic liquid [C4mim]+[BF4]− for extraction from petroleum streams

Sulfur compounds are an important contaminant in the combustion process and are responsible for many environmental and human health problems. In response, world-wide environmental regulations on sulfur limits are increasing significantly and efforts to find new efficient extraction solvents has become a top priority. Following this trend, molecular dynamics simulations were carried out to study the desulfurization process in n-dodecane (a diesel fuel model) using the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate and the model sulfur compound thiophene. The main goal of this work was to identify/clarify the mechanism involved in the extraction of thiophene from diesel fuel using an IL. The radial distribution function (RDF) shows that thiophene interacts preferentially with the cation ring. This interaction was identified as a strong pi–pi interaction using spatial distribution function (SDF) analysis and confirmed using a QTAIM approach. In general, the presence of thiophene molecules does not alter the IL structure. The equilibrium solubility of thiophene predicted in the IL was 45 times greater than in n-dodecane. Moreover, the solvation process of thiophene in the IL relative to n-dodecane is enthalpically driven due to the strong cation–thiophene pi–pi interaction as suggested by the SDF analysis. Overall, our results indicate that the mechanism of the desulfurization process of thiophene in the IL is attributed mainly to pi–pi interactions between the cation ring and thiophene, and is not due to interactions with the cation alkyl chain as previously suggested in the literature.

Photocatalytic oxidation of thiophene on RuO2/SO42−-TiO2: Insights for cocatalyst and solid-acid

Thiophene is one of the main sulfur-containing compounds present in gasoline and difficult to be oxidized with the conventional oxidative processes. Photocatalytic oxidation is believed to be a promising way to remove the sulfur-containing compounds from gasoline. Here we studied the photocatalytic oxidation of thiophene on RuO2/SO42−-TiO2 photocatalyst. We found that high activity can be achieved on 0.045wt.% RuO2/1M SO42−-TiO2 using molecular oxygen as oxidant. The sulfur in thiophene is oxidized to SO3 finally. SEM and XRD measurements show that the crystallinity of TiO2 is greatly improved by sulfation process. IR spectra of pyridine adsorption measurements gives the evidence for that the surface acidity property of TiO2 is also greatly improved. We can conclude that the synergistic effect of RuO2 acting as an oxidation cocatalyst and SO42−-TiO2 acting as a Lewis acid which capture superoxide species/activate thiophene molecules is responsible for the activity enchancement of thiophene photocatalytic oxidation. The synergistic effect between oxidation catalysis and acid catalysis is crucial for developing highly active photocatalysts for environmental protection.

Computational Chemistry Analysis of Hydrodesulfurization Reactions Catalyzed by Molybdenum Disulfide Nanoparticles

Molybdenum disulfide, MoS2, is a very versatile material used in several applications of science and engineering. In particular, when supported on alumina, it is a widely used catalyst for hydrotreating processes in petroleum refineries. Stringent environmental norms and uncertainty in import of low sulfur crude oil put pressure on refiners worldwide to develop more efficient catalysts to meet the demand of clean fuel. The hydrodesulfurization of thiophene and dibenzothiophene on both unpromoted and nickel-promoted MoS2 catalyst is analyzed using a multiscale approach including classical molecular dynamics (MD) and density functional theory (DFT). MD simulations are performed on a hydrocarbon mixture containing sulfur compounds to determine relative positions of thiophene and dibenzothiophene molecules with respect to the MoS2 catalytic surface previous to possible reactions that are then studied with DFT. The sample box contains a total of 57 515 atoms and is able to represent a realistic size of the nanocatalyst process. Under typical hydrodesulfurization conditions, vacancies are needed for adsorption of sulfur compounds and therefore activation of hydrogen becomes an important step. In addition, complexes of MoS2 with graphene and boron nitride, BN, surfaces are also analyzed. MoS2–graphene complexes show improvement in the efficiency of adsorption of thiophene on the catalyst edge. Both hydrogenation and direct desulfurization pathways are presented on pristine MoS2 clusters as well as under typical hydrodesulfurization conditions.

PBE–DFT theoretical study of organic photovoltaic materials based on thiophene with 1D and 2D periodic boundary conditions

Conjugated organic systems such as thiophene are interesting topics in the field of organic solar cells. We theoretically investigate π-conjugated polymers constituted by n units (n = 1–11) based on the thiophene (Tn) molecule. The computations of the geometries and electronic structures of these compounds are performed using the density functional theory (DFT) at the 6–31 G(d, p) level of theory and the Perdew–Burke–Eenzerhof (PBE) formulation of the generalized gradient approximation with periodic boundary conditions (PBCs) in one (1D) and two (2D) dimensions. Moreover, the electronic properties (HOCO, LUCO, Egap, Voc, and Vbi) are determined from 1D and 2D PBC to understand the effect of the number of rings in polythiophene. The absorption properties—excitation energies (Eex), the maximal absorption wavelength (λmax), oscillator strengths, and light harvesting—efficiency are studied using the time-dependent DFT method. Our studies show that changing the number of thiophene units can effectively modulate the electronic and optical properties. On the other hand, our work demonstrates the efficiency of theoretical calculation in the PBCs.

Exploiting the locality of periodic subsystem density-functional theory: efficient sampling of the Brillouin zone

In order to approximately satisfy the Bloch theorem, simulations of complex materials involving periodic systems are made times more complex by the need to sample the first Brillouin zone at points. By combining ideas from Kohn–Sham density-functional theory (DFT) and orbital-free DFT, for which no sampling is needed due to the absence of waves, subsystem DFT offers an interesting middle ground capable of sizable theoretical speedups against Kohn–Sham DFT. By splitting the supersystem into interacting subsystems, and mapping their quantum problem onto separate auxiliary Kohn–Sham systems, subsystem DFT allows an optimal topical sampling of the Brillouin zone. We elucidate this concept with two proof of principle simulations: a water bilayer on Pt[1 1 1]; and a complex system relevant to catalysis—a thiophene molecule physisorbed on a molybdenum sulfide monolayer deposited on top of an α-alumina support. For the latter system, a speedup of 300% is achieved against the subsystem DTF reference by using an optimized Brillouin zone sampling (600% against KS-DFT).

Molecular dynamics of photodissociation: towards more complex systems

SynopsisWe present a combined experimental and theoretical study of the photodissociation of thiophene mole-cule using energy-resolved electron-ion-ion coincidence technique and self-consistent charge density functional tight-binding theory combined with a statistical approach. The observed complex molecular dynamics with many internal-energy-dependent fragmentation pathways is successfully described by the theoretical simulations.

Structural Properties and Dynamics of Thiophene in Sub/Supercritical Carbon Dioxide from Car-Parrinello Molecular Dynamics Simulations.

Structrual and dynamic properties of thiophene (C4H4S) in supercritical carbon dioxide were studied using Car-Parrinello molecular dynamics simulations. The geometries and energies optimized for the thiophene-CO2 complex show a stable C-H···O hydrogen bond interactions both in gas phase and in supercritical CO2. The radial distribution functions of CO2 around thiophene in the supercritical phase state show a correlation suggesting C-H···O hydrogen bond and S···C interaction. Local structural properties of the mixtures were investigated by angular-radial distributions and spatial distribution functions. The results show a mutually parallel arrangement between the thiophene plane and CO2 molecules at short distances and a high probability of the thiophene being located in the radial directions of the CO2 molecules. The decay of orientational correlations at 318.15 K shows slower relaxation compared to those of 298.15 K for first and second rank correlations. The vibrations of CO2 and thiophene molecules have been examined through an analysis of the velocity autocorrelation functions of the atoms. The C-H stretching modes of thiophene in the isolated configuration are less red-shifted and have a much narrower frequency range than that in the mixtures.

Pore Size Dependence of Adsorption and Separation of Thiophene/Benzene Mixtures in Zeolites

Grand canonical ensemble Monte Carlo simulations were applied to study the adsorption and separation of thiophene from binary and ternary mixtures of benzene and n-alkanes in nine types of zeolites. Adsorption of thiophene is important for removing sulfur from gasoline. The computed pure component adsorption isotherms are in good agreement with experimental results for FAU zeolites. The calculated Qst for thiophene in FAU were found to be 33–46 kJ/mol depending on uptake, in good agreement with the experimental data. The adsorption heats as a function of zeolite pore diameter suggest high thiophene affinity when the pore diameter is between 4.6 and 5 A. Binary mixture simulations at two different compositions show that FER is very selective toward thiophene over benzene at 373 K. The thiophene selectivity shows a significant dependence on pore size in binary mixtures, and the smaller thiophene molecule can replace benzene at elevated pressures due to size entropy effects for some zeolites. For ternary mix...

Electrooxidative Desulfurization of a Thiophene-Containing Model Fuel Using a Square Wave Potentiometry Technique

A dynamic electrochemical technique was used for desulfurization of thiophene-containing solutions. First, adsorption of thiophene from an aqueous solution onto a platinum electrode surface and electrooxidative behavior of thiophene were studied using a cyclic voltammetry technique, and then, a square wave potentiometry method was utilized to electrochemically desulfurize the aqueous thiophene solution and a thiophene-containing model fuel. Results indicated that, for thiophene molecules, the best adsorption potential is 0.2 V and the maximum electrooxidation rate occurs at 1.1 V. Also, the optimal square wave frequency was found as 50 Hz. Ion chromatographic measurement of sulfate ion concentration revealed that reaction conversion was 100% in the electrooxidative desulfurization of aqueous thiophene solution. The high desulfurization efficiency can be attributed to excellent electrocatalytic activity of the platinum electrode and performing experiments at the best operating conditions. On the basis of g...

High Yield Ultrafast Intramolecular Singlet Exciton Fission in a Quinoidal Bithiophene.

We report the process of singlet exciton fission with high-yield upon photoexcitation of a quinoidal thiophene molecule. Efficient ultrafast triplet photogeneration and its yield are determined by photoinduced triplet-triplet absorption, flash photolysis triplet lifetime measurements, as well as by femtosecond time-resolved transient absorption and fluorescence methods. These experiments show that optically excited quinoidal bithiophene molecule undergoes ultrafast formation of the triplet-like state with the lifetime ∼57 μs. CASPT2 and RAS-SF calculations have been performed to support the experimental findings. To date, high singlet fission rates have been reported for crystalline and polycrystalline materials, whereas for covalently linked dimers and small oligomers it was found to be relatively small. In this contribution, we show an unprecedented quantum yield of intramolecular singlet exciton fission of ∼180% for a quinoidal bithiophene system.