Electric Field Dissociation Research Articles

Cooperation of Strong Electric Field and H2O Dissociation on Co3O4-Decorated SiC Rods for Photodriven CO2 Methanation with 100% Selectivity.

Solar-driven methanation of carbon dioxide (CO2) with water (H2O) has emerged as an important strategy for achieving both carbon neutrality and fuel production. The selective methanation of CO2 was often hindered by the sluggish kinetics and the multiple competition of other C1 byproducts. To overcome this bottleneck, we utilized a biomass synthesis method to synthesize SiC rods and then constructed a direct Z-scheme heterojunction Co3O4/SiC catalyst. The substantial difference in work functions between SiC and Co3O4 served as a significant source of the charge driving force, facilitating the conversion of CO2 to CH4. The high-valent cobalt Co(IV) in Co3O4 acts as an active species to promote efficient dissociation of water. This favorable condition greatly enhanced the likelihood of a high concentration of electrons and protons around a single site on the catalyst surface for CO2 methanation. DFT calculation showed that the energy barrier of CO2 hydrogenation was significantly reduced at the Co3O4/SiC heterojunction interface, which changed the reaction pathway and completely converted the product from CO to CH4. The optimum CH4 evolution rate of Co3O4/SiC samples was 21.3 μmol g-1 h-1 with 100% selectivity. This study has an important guiding significance for the selective regulation of CO2 to CH4 products in photocatalysis applications.

Study on physical properties of ethylbenzene under external electric field

External electric field dissociation is an effective means of hazardous substance degradation. As a volatile hazardous substance, there is no corresponding research on ethylbenzene (EB). In this work, calculations of EB were conducted under an external electric field (0 V·mm−1–2570 V·mm−1) and density functional theory (DFT) with 6–31 G+ (d, p) basis set. All results agree closely at that when the electric field increases along a certain direction, energy of EB increases and the barrier of potential energy for dissociation decreases. When the voltage reached a certain level, the barrier of dissociation disappears, indicating that EB is under an extremely unstable state and can be easily degraded. Then, the tunnel ionization was studied to have a more comprehensive view about this research. Above conclusions provide a reference for the study of the characteristics of EB molecules or mixtures containing it under an external electric field.

Electrohydrodynamic conduction pumping of a viscoelastic dielectric fluid with the Onsager–Wien effect

Due to the Onsager–Wien effect (enhanced electric field dissociation), electrohydrodynamic (EHD) conduction pumping problems in the Oldroyd-B viscoelastic dielectric liquid are solved using the finite volume method. Fully coupled nonlinear equations, including the Naiver–Stokes (N–S) equation, the Nernst–Plank equation of the ion conduction mechanism, and the constitutive equation of viscoelastic fluid, are thoroughly implemented. Our numerical model is fully verified with two benchmark cases, and simulations are performed under different conduction numbers C0 (0.01–103), Weissenberg numbers Wi (0.01–50), and viscosity ratios (0.3–0.9). Two limiting operating states of EHD conduction pumping, the Ohmic and the saturation regimes, are discussed in detail. Elastic instability is more likely to occur in the Ohmic regime, and the thickness of the heterocharge layer (called the dissociation layer) remains sensitive to C0 and the elasticity values. Current density and pressure generation show crucial degrees of dependence on the fluid elasticity and viscosity ratio.

Improving the efficiency of the organic solar cell (CuPc/C60) via PEDOT: PSS as a photoconductor layer doped by silver nanoparticles

In this work, the efficiency of organic photovoltaic cells (OPV) based on copper phthalocyanine (CuPc) as donor/fullerene (C60) as an acceptor was improved via Poly(3,4-ethylene dioxythiophene):Polystyrene sulfonate (PEDOT:PSS) as (photoconductor transport layer) embedded by silver nanoparticles. Silver nanoparticles (AgNPs) were prepared using a thermochemical method. The change of the surface plasmonic band position of AgNPs has been explained by the Uv-Vis spectra. Different sizes and shapes of AgNPs have been confirmed from images of a transmission electron microscope (TEM). Thin films of PEDOT: PSS embedded by different sizes and shapes of AgNPs were made on glass/ITO using Spin Coater. The last two layers of CuPc and C60 were precipitated using a vacuum evaporation technique. The study of the prepared junction film using AFM showed a morphological smooth on the surface layers due to the good distribution of AgNPs. Cell efficiency of OPV was improved from 0.663 to 0.925 with increasing the particle sizes of AgNPs from 43 nm to 57 nm. The increase in VOC, ISC, and fill factor with increasing the particle size can be attributed to the increase in scattering light and the built-in electric field that generate due to surface plasmon resonance around AgNPs embedded in PEDOT:PSS. The scattering increases the excitons (e-h) generation and built-in electric field dissociation these excitons to e- and h+ and move to terminal connection and improved the cell efficiency.

Photoresponse in gate-tunable atomically thin lateral MoS2 Schottky junction patterned by electron beam

Among various atomically thin two-dimensional materials, molybdenum disulphide (MoS2) is attracting considerable attention because of its direct energy bandgap in the 2H-semiconducting phase. On the other hand, a 1T-metallic phase, which is very important for unique applications, has been created by various methods. Recently, we demonstrated the creation of in-plane 1T-metal/2H-semiconductor MoS2 lateral Schottky junctions by using electron beam irradiation techniques and revealed their unique electrical properties. Here, we report the optoelectronic measurements proving the formation of this few-layer MoS2 lateral Schottky junction. A large photocurrent is confirmed in the reverse bias voltage regime, while it decreases with increasing distance between an electrode placed on the 2H region and the 2H/1T junction. These results suggest a concentration of high electric field and rapid dissociation of photogenerated excitons at the few-layer lateral Schottky junction, which are beneficial for highly efficient photodetectors.

High Electron Mobility and Its Role in Charge Carrier Generation in Merocyanine/Fullerene Blends

Charge carrier generation and drift dynamics have been investigated in two types of dye:fullerene heterojunctions: vacuum-deposited merocyanine:C60 and solution-processed merocyanine:PC61BM blends by combining electric-field-induced fluorescence quenching and ultrafast time-resolved carrier drift measurements. We demonstrate that interfacial charge transfer (CT) states are strongly heterogeneous with energies dependent on the acceptor material and its domain sizes. Interfacial CT states on large C60 domains have low energies, while CT states on PC61BM domains have larger energies, which are weakly dependent on the domain sizes. We distinguish two interfacial CT state dissociation pathways: (i) ultrafast, weakly dependent on the electric field and (ii) slow field-assisted dissociation during entire CT state lifetime. We attribute process i to low-energy, weakly bound CT states on large fullerene domains and process ii to strongly bound CT states on small domains or single fullerene molecules. The electron mobility in films with 50% of C60 is several times higher than in the films with PC61BM and orders of magnitude higher than the hole mobility. We conclude that efficient carrier generation at low electric fields typical for operating solar cells relies on unperturbed motion of highly mobile electrons; thus, fast motion and extraction of electrons are crucial for efficient solar cells.

Role of Thickness towards the Optical and Electrical Properties of Photoactive Layer MEH-PPV: TiO<sub>2</sub> Nanocomposite Thin Films

In recent years, the research on organic solar cells systems based on nanocomposite containing conjugated polymers has lead to great attention with the aim or replacing conventional inorganic solar cells. This nanocomposite can be processed at lower cost, low weight and ease of synthesis with greater versatility than todays solar cell. In this study, we investigated the dependence of physical, optical and electrical properties on the thickness of MEH-PPV: TiO2 nanocomposite thin films for organic solar cell application. It was found the optical properties of photo-active layer MEH-PPV: TiO2 nanocomposite thin films improved with increasing its thickness however the electrical properties decreased. The absorption coefficients of photoactive layer are high in the visible region (400-600 nm) with optimum absorption region at 500 nm. The shift of absorption edge toward longer wavelength with increased of nanocomposite photoactive layer thickness due to narrowing band gap caused by the effects of electron-electron and electron-impurity scattering. In addition the study of illuminated current-voltage (I-V) characteristics revealed the increment of recombination process with increased of photoactive layer thicknesses. It was found such increased in resistivity from 136x103 to 1600x103 Ω.cm is closely related to the electric field and exciton dissociation which is decreased with increased photoactive thickness.

Field-Enhanced Photocurrent Spectroscopy of Excitonic States in Single-Wall Carbon Nanotubes

Excitonic and free-carrier transitions in single-wall carbon nanotubes are distinguished using field-enhanced photocurrent spectroscopy. Electric field dissociation allows for the detection of bound-exciton states that otherwise would not contribute to the photocurrent. Excitonic states associated with both the ground-state semiconductor and the ground-state metallic nanotube transitions are resolved. The observation of a metallic excitonic state corroborates recent predictions of a symmetry gap existing in metallic nanotubes.

Effect of electric field on spray deposited CdTe thin films

CdTe thin films have been deposited using spray pyrolysis with and without electric field. The improvement in the film properties with the electric field is observed which is mainly due to the reduction of droplet size. The presence of CdTeO 3 peaks in the X-ray diffraction pattern for films deposited without electric field at 350 °C is attributed to the slow dissociation of complexes containing Cd and Te ions on the substrate. The reduction in the droplet size under the influence of electric field and faster dissociation of droplets at high temperature leads to complete pyrolytic reaction for a nearly oxide free CdTe film formation. Energy dispersive X-ray analysis indicates stoichiometric Cd and Te atomic concentrations, with oxygen and chlorine impurities in varying amount for different substrate temperatures, with and without electric field. The presence of chlorine gives rise to an intense photoluminescence peak at 1.40 eV along with a weak peak at 0.84 eV. The intensities of both peaks diminish when the films are prepared with the electric field, due to reduction of chlorine concentration and morphological changes in the films.

Natural Electrophoresis of Norepinephrine and Ascorbic Acid

The electric field produced by cell membranes, extending only a few nanometers, is 1000 times stronger than the electric fields required to produce dissociation of molecular complexes. Using the complex formed by norepinephrine (NE) and ascorbic acid (AA), we have demonstrated the quantitative binding of AA to NE, the use of capillary electrophoresis to measure quantitative binding of nonelectrolyte complexes, the determination of a dissociation constant (Kd) from electric field-dissociation constants (Ke), and a model for natural dissociation of the NE–AA complex due to the electric field generated by a cell membrane. NE–AA dissociation constants show little effect of NE concentration or pH changes. NE-related compounds also bind AA: epinephrine > norepinephrine > tyrosine > histamine > phenylalanine. Serotonin does not bind AA. Phosphorylated AA and glucose also bind NE at 0.05 and 0.08 of the AA binding, respectively. Natural electrophoresis of molecular complexes allows compounds to travel through the body in a protected state and still be available for physiological activity upon reaching a membrane.

Electric field dissociation of H+ 2: close-coupled scattering calculations

Close-coupling scattering calculations have been carried out to predict the magnitude of electric fields required to dissociate specific vibration—rotation levels in H+ 2. Results for electric fields up to 40 kV cm−1, which may dissociate levels up to 25 cm−1 below the dissociation limit, are presented. The results are used to simulate spectra which are compared with experimental spectra. A method for extracting the eigenphase sum from a coupled channel scattering calculation is described in the appendix and used in the calculations.

Electric field dissociation of H+2: close-coupled scattering calculations

Electric field dissociation of H+2: close-coupled scattering calculations

Microwave electronic spectrum of the Ne···Ne+ long-range complex

We have used an ion beam method to observe 276 transitions in the microwave electronic spectrum of the long-range Ne···Ne+ ionic complex, involving levels which lie within 10.2 cm-1 of the lowest dissociation limit. An electric field dissociation technique has been used to access directly levels with binding energies of up to 6.8 cm-1 and we have been able to construct an experimental energy level pattern for at least 17 vibration–rotation progressions in this region of the potential. Microwave–microwave double resonance and Zeeman effect measurements have been crucial in establishing this energy level pattern. The levels are populated by the vertical electron impact ionisation of the neutral neon dimer, produced by means of a nozzle beam, with some population of higher rotational levels of the dimer ion probably resulting from larger cluster fragmentation. A case (c) effective Hamiltonian analysis has been successful in describing the levels in six of the progressions but a full theoretical analysis requires a coupled-states calculation. Analysis of Zeeman splittings for the microwave lines identifies the J values of the levels involved. The observed g-factors provide information about the transition from case (c) to case (e) coupling as both the rotational quantum number increases and the energy levels become more weakly bound.

Microwave Spectroscopy at the Dissociation Limit

An ion beam technique has been developed that combines some of the methods of mass spectrometry and molecular spectroscopy and is designed for the study of molecular ions at energy levels lying very close to the lowest dissociation limit. Microwave radiation is used to drive spectroscopic transitions, and electric field dissociation of the weakly bound levels provides a high degree of state selection for sensitive detection of the spectra. The analysis of the spectra requires unconventional approaches to the description of the long-range levels and their spectroscopic study and provides stringent tests of ab initio theories.

Observation of a microwave spectrum of the long-range He…N + complex

We report the first spectroscopic observation of the HeN + molecular ion. We use a technique in which a mass-selected ion beam is exposed to tunable microwave radiation, and transition involving the weakly bound long-range levels are detected by means of state-selective electric field dissociation, producing N + fragment ions. Three of the observed microwave transitions exhibit 14N hyperfine structure, whilst a fourth transition consists of a single unsplit line. Preliminary observations of Zeeman effects are also described. The results are discussed in terms of molecular energy levels lying close to one or other of the three He( 1S) + N + ( 3P) dissociation asymptotes, which are split by spin-orbit coupling.

Observation of a microwave spectrum of the long-range He … H 2+ complex

We report the first spectroscopic observations of the HeH 2 + molecular ion. We use an ion beam technique in which mass-selected ions are exposed to microwave radiation, and transitions involving weakly bound long-range levels are detected by means of state-selective electric field dissociation. One of the observed transitions exhibits complex proton nuclear hyperfine structure; another shows a simple field-free spectrum but extensive Zeeman structure in the presence of an applied magnetic field. The results are discussed in terms of coupled-channel calculations using a recent ab initio potential surface.

Microwave electronic spectra of the Ar 2+ and Ne 2+ ions: a combined neutral/ion molecular beam technique

We describe a new ion source in which a nozzle beam of neutral molecules is ionised by an electron beam and the resulting molecular ion beam is studied by microwave spectroscopic methods. This ionisation technique results in significant population of the near-dissociation levels of the molecular ion, so that a sensitive state-selective electric field dissociation method can be used to detect the spectra. We have observed the first state-to-state resonant electronic spectra of the Ar 2 + and Ne 2 + ions.

Ion-beam spectroscopy of long-range complexes

Ion-beam techniques provide opportunities for extremely sensitive spectroscopic studies of molecular ions. Transitions involving the energy levels lying close to the dissociation limit may be detected through a range of indirect methods; electric field dissociation has proved to be particularly valuable. This review describes IR and microwave studies of a range of molecular ions, mostly diatomic; we compare the different detection methods and the molecular information each provides. These investigations have revealed the first electronic spectra of the H2+ and D2+ ions, leading to detailed characterisations of the long-range H⋯H+ and D⋯D+ charge–induced-dipole states, and also providing accurate data with which to test ab initio calculations. In the case of the HD+ ion the high spectroscopic resolution achieved enabled the nuclear hyperfine interactions to be measured; these revealed marked asymmetry in the electron distribution as the dissociation asymptote is approached. H3+, the only polyatomic molecule to be investigated in our laboratory so far, exhibits an extraordinarily rich and complex IR predissociation spectrum, which arises from metastable periodic states embedded in a chaotic sea of levels lying above the lowest dissociation limit. Other examples of predissociation spectra involving rotationally quasibound levels are described. In recent work the first 37 bound levels of the long-range He⋯Ar+ complex, counting from the dissociation limit downwards, have been identified and described theoretically. In this very weakly bound region the Born–Oppenheimer approximation collapses because of extremely strong coupling between the electronic and nuclear rotational motions. Finally, we describe new experiments using a combined neutral–ion beam source which has enabled the first state-to-state resonant spectra of the Ar2+ and Ne2+ molecular ions to be observed.

Microwave spectra of the D2+ and HD+ ions near their dissociation limits

We have observed and measured seven microwave transitions in D2+, which are vibration–rotation components of the 2pσu–1sσg electronic band system. We also report two microwave rotational components involving the 1sσ v=21 level of HD+, which lies close to the first dissociation limit. Our experiments use ion beam techniques in which state selection is achieved by electric field dissociation. The techniques and theory of electric field dissociation are discussed, and fragment ion kinetic energy spectra described. Ab initio calculations of the transition frequencies for both D2+ and HD+ are in excellent agreement with experiment, and the hyperfine structure of the rotational transitions in HD+ confirms previous demonstrations of the increasing asymmetry in the electron distribution as the dissociation limit is approached. The electronic transition in D2+ which involves the highest bound level of the ground state shows an unexpected hyperfine splitting, which is interpreted in terms of g/u symmetry breaking by the deuteron Fermi contact interaction.

Microwave electronic spectroscopy, electric field dissociation and photofragmentation of the H + 2 ion

Three Microwave electronic transitions in the H+2 molecular ion have been observed between the 1sσg ground state and the long-range minimum of the first excited 2pσu state. Electric field dissociation is used as an indirect method for detecting the transitions. Calculations of electric field dissociation are presented in which the rotation of the molecule is included, allowing predictions of the strengths of the electric field required to dissociate particular vibration–rotation levels in the 1sσg state. The 2pσu(v= 0, N= 2)–1sσg(v= 19, N= 1) transition was also observed using microwave photodissociation and calculations of the photodissociation cross-sections are given. An unexpected splitting was observed in two of the transitions and is interpreted in terms of g/u symmetry breaking caused by the proton Fermi contact interaction.