Electronic Transition Probabilities Research Articles

Influence of Spin-Orbit Coupling on the Optical and Thermoelectric Properties of Lateral MoSe2-WSe2 Heterostructure

In this letter, the spin-orbit coupling (SOC) effect in lateral MoSe2-WSe2 heterostructure was theoretically investigated. The results demonstrate that the SOC effect induces band splitting, narrows the band gap, and reduces the effective mass of electrons. These alterations indicates the enhanced probability of electron transitions from the valence band to the conduction band. Additionally, the SOC effect leads to red shift in the absorption peaks and the presence of SOC effect has transformed the heterostructure from being originally a p-type thermoelectric material to a n-type thermoelectric material, increasing its thermoelectric figure of merit (ZT). Our work not only contributes to a deeper understanding of its physical mechanisms , but also provides a reference for its potential applications in the field of thermoelectric and optical devices.

Electric Field-Induced Enhanced Raman Spectroscopy Sensor and Photocatalysis with Thermoelectric-Plasmonic Metal Nanocomposites.

Electric field-induced surface-enhanced Raman scattering (E-SERS) substrates have been proven to further enhance the attained Raman intensity. Herein, integrated with plasmonic Ag nanoparticles (Ag NPs), the thermoelectric Bi2Te3 plate as an E-SERS substrate decreased the limit of detection by 2 orders of magnitude and increased the SERS signal by >20 times compared to those without electrical field induction. The thermoelectric potential produced by the Bi2Te3 plate could modulate the electron density and subsequently change the Fermi level of Ag. This increases the resonant electron transition probability using a broad range of molecules. The plasmon-activated catalytic reactions of the interconversion between p-nitrothiophenol and p,p'-dimercaptoazobenzene could be controlled through the E-SERS template. On the basis of the finite element method, explicit theoretical analysis indicated that the Ag NP-Bi2Te3-molecule charge transfer could improve our understanding of the SERS and photocatalytic mechanism.

Characterizing of PVA/CMC/MWCNTs nanocomposite films doped Zn0.9Ni0.1S nanoparticles for comprehensive γ-ray radiation shielding performance

Nanocomposite films were prepared from Carboxymethylcellulose (CMC), Polyvinyl alcohol (PVA) polymers and multi-walled carbon nanotubes (MWCNTs) using the casting technique. The resulting PVA/CMC/MWCNTs nanocomposite films have been incorporated with various concentrations of the Zn0.9Ni0.1S nanoparticles. The γ-ray radiation shielding capabilities of the films were discussed in details for various gamma sources using the Phy-X/PSD software in the energy range (0.015–15 MeV). The linear (LAC) and mass (MAC) attenuation parameters, the half-value layer (HVL), the tenth value layer (TVL), the effective atomic number (Zeff) were determined. The γ-ray buildup factors, were also determined for different penetration depths in the range (0.5–40 MFP). Results showed that, the shielding parameters are greatly affected by the density of the samples and the PVA/CMC/MWCNTs samples have the highest shielding ability in the energy region ranges (0.015–0.2 MeV) and (5–15 Mev). The structural and chemical characteristics of the films and the nanoparticles were examined using X-ray diffraction technique. The films elemental composition and morphology were discussed using energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscope (SEM) techniques, respectively. The linear and nonlinear optical properties, including the extinction coefficient (K), the energy gap (Eg), the refractive index (n), the dielectric parameters, nonlinear susceptibilities(χ(1), χ(3)) and nonlinear refractive index (n2), were discussed by UV–Vis spectroscopy's absorbance and transmittance spectra. A reduction in Eg values from 4.55 eV to 4.5 eV and 4.41 eV for films doped with 1 wt% and 3 wt% of Zn0.9Ni0.1S. The uniform distribution of the added nanoparticles at 5 wt% has been confirmed. The energy dispersion parameters confirmed a higher probability of electronic transitions at low energy due to the intermolecular modifications.

Tailoring Interfacial Electric Field by Gold Nanoparticles Enable Electrocatalytic Lithium Polysulfides Conversion for Lithium-Sulfur Batteries.

Although lithium-sulfur batteries (LSBs) are considered as the promising next rechargeable storage system ascribing to their decent specific capacity of inorganic sulfur, the development is partially impeded by inferior electronic conductivity, severe shuttle effect, and large volume variation. To tackle the issues above, a great deal of effort is made on sulfur-containing polymer (SCP) that shows better electrochemical performance. Nevertheless, sluggish conversion of lithium polysulfides (LiPSs) obstructs battery performance yet. Herein, electrocatalytic LiPSs with full conversion by tailoring the interfacial electric field are discovered based on gold nanoparticles (AuNPs) anchored on sulfurized polyaniline (SPANI). A downhill path of Gibbs free energy from organosulfur polymer to intermediate product means more spontaneously and favorable for full conversion, as the significant enhancement of electron density of state in the vicinity of the HOMO level for the AuNPs increase the electron transition probability rate. This composite delivers satisfactory electrochemical performance, especially increased rate capacity of >300 mAh g-1. Furthermore, catalyst mechanism on molecule level is proposed that AuNPsdominate chemical enhancement and higher electron delocalizablility betweenAuNPs and LiPSs molecules. These results can erect a promising strategy for enhancing lithium polysulfides full conversion.

A first-principles study of the electronic structure and mechanical and optical properties of Mn-doped K2SiF6

The lattice constants, electronic structures, mechanical and optical properties of non-doped and Mn4+-doped K2SiF6 (KSF:Mn4+) were investigated using first-principles calculations. The calculated results show that Mn4+ doping enlarges the lattice constant and cell volume of KSF. Around the Fermi energy level, there is a decrease in the peak of density of states, significantly weakening the electron localization property. Mn4+ doping induces two impurity energy levels, causing a shift in the electronic states of KSF towards to the low-energy, thereby altering in the energy band structure. This alteration results in a narrower forbidden bandwidth, which reduces the photon energy required for electron transitions. Consequently, it increases the probability of electron transitions from the valence band to the conduction band, thereby enhancing the material's photocatalytic ability in the visible and ultraviolet regions. The pressure-volume relations are described using the Birch-Murnaghan's equation of state to calculate the bulk modulus of KSF and KSF:Mn4+, which is associated to the hardness of a material under particular conditions. This study provides a theoretical basis for a better understanding of the effects of Mn4+ doping on the mechanical properties, electronic structure and optical properties of KSF.

Research on electronic and optical properties of pristine and Ag/Au/Cu-doped graphene/MoS2 heterostructures

The Dirac cone in the single-layer graphene limits its application in electronic devices such as Schottky barrier diodes and field-effect transistors. Thus, we make the novel heterostructures based on graphene to solve this problem. The electronic and optical properties of pristine and Ag/Au/Cu-doped graphene/MoS2 heterostructures are investigated by using the density functional theory. For the Ag/Au/Cu-doped MoS2 monolayer, the results show that they are magnetic. Their bands across the Fermi level, which indicates these systems are metallic. For the Ag/Au/Cu-doped graphene/MoS2 heterostructures, they are metallic and nonmagnetic. Especially in the Au-doped graphene/MoS2, the Dirac cone opens about 66 meV. It means that Au-doped graphene/MoS2 has the potential to be a candidate material for high speed electronic devices. Compared with pristine heterostructure, the probability of electron transition in the low energy region is the enhanced in Ag/Au/Cu-doped systems. The optical absorption coefficient of doped heterostructure is enhanced in the range of 0–0.4 eV and 1.7–2.7 eV. This work indicates that these heterostructures have a certain potential in the application of nanodevices.

Peculiarities of Electron Transport through the Contact Regions between Semiconductor Quantum Wires with Different Cross Sections

In present work peculiarities of electron transport with transition from quantum wires with smaller cross sections to quantum wires with larger cross sections are studied. Electron transition probabilities through corresponding contact regions of such quantum wires are calculated as functions of charge carrier kinetic energy and quantum wire cross sections ratio. Peculiarities of electron pass through the defects in quantum wires in the form of rectangular grooves and steps are also studied. Electron transition probabilities through the defect regions are calculated as functions of electron kinetic energy and geometry and size of the defects. Probability density distributions of electron detection in different regions of simulated structures have been calculated.

Quasiparticle approach to collective quantum dielectric response

In current research, we use a generalized quantum multistream model to develop an effective quasiparticle theory for quantum many-body effects. The N-electron Schrödinger–Poisson stream model is reduced to a system of coupled differential equations with new wavefunction representation for collective quantum excitations in the many electron system. The current theory is then applied to the collective quantum statistical behavior of homogenous electron gas. Moreover, the generalized energy dispersion relation, which incorporates the quasiparticle band structure, is used to calculate the linear dielectric response of collective quantum excitations in the electron gas with arbitrary degree of degeneracy beyond many-body theories, limiting assumptions such as the independent electron and the random phase approximations. Important parameters of electron gas such as the dynamic structure factor, the loss function, the static charge screening, optical reflectivity, and the electronic stopping power are investigated as applications of current theory. The quasiparticle theory incorporates effects both due to single-electron excitations as well as the electrostatic interaction among electrons in a single picture. Existence of Van-Hove-like singularity at the plasmon wavenumber leads to distinct features of quasiparticle response to electromagnetic perturbations in the electron gas. It is shown that collective quantum excitations in high density electron gas below a given critical electron temperature are blocked due to existence of a large quasiparticle energy bandgap above the Fermi level. A new equation of states is given for the quasiparticle excitation in the electron gas, based on the transition probability of electrons to the quasiparticle level. It is found that, the screening potential of a static charge in quasiparticle model has an oscillatory Lennard–Jones-type attractive form.

The Linear Optical Properties of Rhodamin110 Organic Dye Doped with Metal Nanoparticles

Background:
 Laser dyes are unsaturated hydrocarbon compounds that have the advantage of having double or triple bonds coupled with carbon atom chains. This system benefits from light absorption in the visible range (200–700 nm) and the transmission spectrum of absorption in the visible range
 Materials and Methods:
 This research has focused on the effect of Adding ethanol solution to rhodamine110 dye with different concentrations, the linear properties (permeability, absorbance) of Rhodamine110 dye were studied as it was dissolved in ethanol to prepare solutions with concentrations (0. 01, 0.03, 0.05) and at room temperature
 Results:
 The absorbance A of Rhodamine110 dye with ethanol was calculated for the above concentrations, respectively, as well as and the transmittance T was calculated for the above concentrations, respectively, to obtain curves and rhodamine110 dyes were mixed with nanomaterials to improve the properties of the dyes
 Conclusion:
 In this study, According to Beer-Lambert's rule, increasing the dye concentration will increase absorbance, which will raise the linear optical coefficients (refractive index and coefficient of absorption) for all produced samples. The probability of electronic transitions will definitely be affected by the type of solvent., and this has an impact on linear optical characteristics, particularly the positions and width of the absorption spectra. And the addition of nanomaterials added better improvements to the dye. The results showed that the highest linear properties appeared when the silver nanomaterials with rhodamine110 dye

Collective quantum approach to resonant photo-plasmonic effect

In this research, we investigate the resonant photo-plasmonic effect in the framework of the dual length-scale driven damped collective quantum excitations of the spill-out electrons at the metal surface. The bulk plasmon and the spill-out electron excitations are modeled using the Hermitian and the damped non-Hermitian effective Schrödinger–Poisson systems, respectively, matched appropriately at the metal–vacuum boundary. It is shown that, when driven by an external field, the system behaves quite analogous to the driven damped mechanical oscillations in the wavenumber domain, causing the spill-out electron collective excitation resonance. However, in the current model, the resonance takes place due to matching of the wavenumber of the driving pseudoforce with that of the spill-out electron excitations, which can be either due to single-electron or collective oscillations. Hence, the RPP effect considered here leads to both conventional resonant photo-electric and the photo-plasmonic effects due to the dual-tone nature of collective quantum oscillations. The current model may be extended to a similar resonance effect in nanometer-sized metal surfaces with a non-planar geometry. A new equation of state for the electron number density of spill-out electrons is obtained, which limits the plasmonic response in high-density and low-temperature regime due to the small transition probability of electrons to the spill-out energy band.

Effect of Organic Molecular Volume on Organic Photodiodes

AbstractThe development of light‐absorbing organic molecules with calculated oscillator strength (f) is widely investigated to improve the performances of organic photoelectric devices such as organic photodiodes (OPDs). The oscillator strength estimates the probability of radiative electronic transition of a single molecule. However, most photoelectric devices are composed of organic thin films rather than a single organic molecule. Herein, the molecular volume is considered the critical parameter for the design of organic molecules. Three novel organic molecules, Et‐H, Me‐Me, and Me‐H, with similar oscillator strengths and different molecular volumes, are designed and synthesized as proof‐of‐concept. Their experimental absorption properties and organic photodiode performances are investigated. Me‐H, which has the smallest molecular volume and highest molecular packing density, shows the highest absorption coefficient in organic thin films and the best OPD performance with the highest external quantum efficiency.

Efficient stabilization of cyanonaphthalene by fast radiative cooling and implications for the resilience of small PAHs in interstellar clouds

After decades of searching, astronomers have recently identified specific Polycyclic Aromatic Hydrocarbons (PAHs) in space. Remarkably, the observed abundance of cyanonaphthalene (CNN, C10H7CN) in the Taurus Molecular Cloud (TMC-1) is six orders of magnitude higher than expected from astrophysical modeling. Here, we report unimolecular dissociation and radiative cooling rate coefficients of the 1-CNN isomer in its cationic form. These results are based on measurements of the time-dependent neutral product emission rate and kinetic energy release distributions produced from an ensemble of internally excited 1-CNN+ studied in an environment similar to that in interstellar clouds. We find that Recurrent Fluorescence – radiative relaxation via thermally populated electronic excited states – efficiently stabilizes 1-CNN+, owing to a large enhancement of the electronic transition probability by vibronic coupling. Our results help explain the anomalous abundance of CNN in TMC-1 and challenge the widely accepted picture of rapid destruction of small PAHs in space.

Influence of K/Na ions on structure and luminescence properties of red phosphors K0.5Na0.5Gd(WO4)2: Eu3+

In this paper, we demonstrated the influence of K/Na alkali ions on the structural and photo-cathodoluminescence properties of novel K0.5Na0.5Gd(WO4)2:Eu3+ red phosphor synthesized by the solid-state method. The purity of phosphors is determined from the X-ray diffraction. Rietveld refinement studies confirms that the compounds both K0.5Na0.5Gd(WO4)2:Eu3+ and NaGd(WO4)2:Eu3+ were crystallized in the tetragonal structure with I41/a space group and KGd(WO4)2:Eu3+ was crystallized in monoclinic structure with C2/c space group. The FTIR results indicate that the presence of characteristic functional groups in synthesized samples. The optical bandgap determined from the UV-Visible reflectance spectra in the order K0.5Na0.5Gd(WO4)2:Eu3+ <KGd(WO4)2:Eu3+<NaGd(WO4)2:Eu3+. The photoluminescence excitation spectrum reveal that all the synthesized phosphors can be efficiently excited near UV and Ultraviolet (UV) indicating suitable for solid state display applications. The PL emission spectra indicate the two characteristic emissions located at 614 nm (5D0→7F1) and 590 nm (5D0→7F1) under the excitation of 395 nm. The Judd-Offelt (JO) intensity parameters are calculated to investigate the luminescence behavior and to determine the local structure around the activator related to the Eu3+ ion. The Ω2 > Ω4 of JO parameters indicates the asymmetric environment around the activator suggesting the co-valency of Eu-O bonds with respect to host matrix. Radiative lifetime, branching ratio, electronic dipole transition probabilities were calculated based on the Judd-Ofelt formalism. Cathodoluminescence studies shows the characteristic emission of the Eu3+ ions for low current and voltage which further confirms the pure red color emission of phosphors. All the synthesized phosphors can emit the red emissions with correlated color temperature range from 1500 to 2000 K. For K0.5Na0.5Gd(WO4)2:Eu3+ sample the chromaticity coordinate (x = 0.667, y = 0.329) are closer to the NTSC trichromatic coordinated (x = 0.67,y = 0.33) than that of Y2O2S:Eu3+ suggesting that K0.5Na0.5Gd(WO4)2:Eu3+ can be a potential red phosphor material for warm white LED's applications.

Electronic Energy Levels and Optical Transitions in Samarium(III) Solvates.

Lanthanide luminescence fascinates with a complicated electronic structure and "forbidden" transitions. By studying the photophysics of lanthanide(III) solvates, a close to ideal average coordination geometry can be used to map both electronic energy levels and transition probabilities. Some lanthanide(III) ions are simpler to study than others, and samarium(III) belongs to the more difficult ones. The 4f5 system has numerous absorption and emission lines in the visible and infrared parts of the spectrum and in this work, the energy levels giving rise to these transitions were mapped, the transition probability between them was calculated, and it was shown that the electronic structures of the samarium(III) solvates in DMSO, MeOH, and water are different.

Theoretical studies, spectroscopic investigation, molecular docking, molecular dynamics and MMGBSA calculations with 2‐hydrazinoquinoline

We report a comprehensive account on the theoretical and spectroscopic study of 2-hydrazinoquinoline. Computational studies have been performed using density functional theory (DFT) via B3LYP functional and 6-311++G (d,p) basis set. The theoretically predicted spectra showed good agreement with the experimentally obtained IR, NMR and UV spectra. TD-DFT provided information regarding the electronic transition probabilities. Calculation of the energy and structures of the FMO helped in understanding the stability, reactivity and other vital molecular properties. The NBO analysis afforded the insights on the various donor–acceptor interactions at the orbital level, that are responsible for stabilizing the molecule. The distribution of electron density across the molecule was studied using molecular electrostatic potential (MEP). The ELF studies were used to identify the electronic localization within the molecule. The pharmaco-kinetic properties along with the drug-likeness was analyzed as a part of understanding the therapeutic potential of the molecule. Molecular docking studies with four macromolecular targets (COVID-19 viral main protease, FABG4 enzyme, Cruzain and RIP2 Kinase) revealed reasonably good binding affinities. The stability of the best two docked-complexes were investigated using 200ns molecular dynamics simulation followed by effective free energy calculation using MMGBSA.

Crystal-amorphous Ni(OH)2 nanocages as SERS substrate with conspicuous defects-induced charge-transfer resonance for ultrasensitive detection of MicroRNA 155

Herein, an innovative Ni(OH)2 nanocages (Ni(OH)2 NCs) with crystal-amorphous structure were fabricated as surface-enhanced Raman scattering (SERS) substrate, which realized excellent SERS enhancement by the significant defects-induced charge transfer resonance and was applied to the construction of SERS biosensor for ultrasensitive microRNA 155 (miRNA 155) detection. The surface oxygen vacancy (Ovs) and defective phases endowed Ni(OH)2 NCs the increased charge carrier density and preponderant energy-level matching with signal molecules methylene blue (MB), thereby inducing the remarkable charge transfer resonance via the augment of electron transition probability for improving the SERS effect of Ni(OH)2 NCs. Impressively, the SERS performance of Ni(OH)2 NCs was stronger than that of amorphous Ni(OH)2 nanocages (a-Ni(OH)2 NCs), ascribing to the abundant Ovs and high degree of charge transfer (ρCT) in Ni(OH)2 NCs. Furthermore, the limited target miRNA 155 was transformed into the plentiful MB molecules by employing the target-related cleavage amplification reaction and hybridization chain reaction (HCR), thus achieving an enhanced SERS intensity for detecting target miRNA 155 based on Ni(OH)2 NCs substrate and obtaining a low detection limit of 30 aM. This strategy developed candidate materials for the practical applications of SERS technology and provided a promising method to disease diagnosis.

Thermoelectric Field-Assisted Raman Scattering and Photocatalysis with GaN-Plasmonic Metal Composites

The combination of metallic nanoparticles (NPs) with semiconductors used as surface-enhanced Raman scattering (SERS) substrates have been widely reported. However, the additional enhancements provided by the semiconductors are impressively small and have little effect on the SERS signal compared with that from the metallic NPs alone. Herein, thermoelectric semiconductor material gallium nitride (GaN) and silver nanoparticles (Ag NPs) are combined to create an electric-field-induced SERS (E-SERS) substrate, which further improves the SERS signal intensity by an order of magnitude compared to that without electric field induction. Based on the chemical enhancement induced by the thermoelectric potential, the presented E-SERS substrate realizes the detection over a broad kind of molecules, even with small Raman scattering cross sections. We show that the thermoelectric potential could regulate the charge exchange between GaN and Ag NPs and then shift the Fermi level of the Ag NPs over a wide-ranging distribution, which could increase the resonant electron transition probabilities with the detected molecules. Furthermore, the E-SERS substrate is also realized to monitor and manipulate the plasmon-activated redox reactions. Based on the finite element calculations, a detailed and comprehensive theoretical analysis is conducted to deepen the understanding of the chemical SERS and plasmon-activated photocatalyst mechanism.

Infrared radiation and thermal cyclic performance of a high-entropy rare-earth hexaaluminate coating prepared by atmospheric plasma spraying

In this study, a high-entropy RMgAl11O19 (HE-RMA, R = La, Pr, Nd, Sm, Gd) and LaMgAl11O19 (LMA) coatings were fabricated by atmospheric plasma spraying. The phase composition, microstructure, thermal stability, infrared emissivity performance and shock resistance were comparatively characterized. The results showed that doping multiple rare-earth cations could be conductive to enhance the infrared emissivity. The as-sprayed HE-RMA coating exhibited the highest infrared emissivity, which reached up to 0.971 at 1000 °C. The reason for the improvement of the infrared emissivity was attributed to introduced impurity energy level resulting from doping cations, which could reduce the forbidden bandwidth and increase probability of electronic transition. Meanwhile, HE-RMA coating exhibited better shock resistance at 1100 °C due to superior fracture toughness (1.84 ± 0.41 MPa·m1/2) during thermal cycling test at 1100 °C. In addition, HE-RMA coating still exhibited high infrared emissivity (0.932 at 1000 °C) at 1100 °C annealing for 100 h with only a slight reduction.

An Application of Interacting Boson Model-2 (IBM-2) Configuration Mixing in Tin Nuclei

Using IBM-2 configuration mixing calculations, the normal and intruder 2p-2h bands in even-even tin isotopes are examined. The states of the normal and intruder bands were computed separately and then mixed using a basic band-mixing Hamiltonian. The experimental data for energy levels and electronic transition probability from current and past investigations are compared.

Emission of electromagnetic radiation due to spin-flip transitions in a ferromagnet

We theoretically analyze the probability of electromagnetic wave emission due to electron transitions between spin subbands in a ferromagnet. Different mechanisms of such spin-flip transitions are considered. One mechanism is electron transitions caused by the magnetic field of the wave. Another mechanism is due to the Rashba spin–orbit interaction. While the two mentioned mechanisms contribute in a homogeneously magnetized ferromagnet, there are two other mechanisms that occur for a non-collinearly magnetized medium. The first mechanism is known and is due to the dependence of the exchange interaction constant on the quasimomentum of the conduction electrons. The second one is due to the minimal coupling. It follows from the connection of spin and spatial degrees of freedom in any non-collinearly magnetized medium. We study these mechanisms in a non-collinear ferromagnet with a helicoidal magnetization distribution. Estimations of the probabilities of electron transitions due to different mechanisms are made for realistic parameters, and we compare the mechanisms. We also estimate the radiation power and the threshold current in a simple model in which spin is injected into the ferromagnet by a spin-polarized electric current through a tunnel barrier.