State Energy Research Articles

Sonoinduced Tumor Therapy and Metastasis Inhibition by a Ruthenium Complex with Dual Action: Superoxide Anion Sensitization and Ligand Fracture.

Photoresponsive ruthenium(II) complexes have recently emerged as a promising tool for synergistic photodynamic therapy and chemotherapy in oncology, as well as for antimicrobial applications. However, the limited penetration power of photons prevents the treatment of deep-seated lesions. In this study, we introduce a sonoresponsive ruthenium complex capable of generating superoxide anion (O2•-) via type I process and initiating a ligand fracture process upon ultrasound triggering. Attaching hydroxyflavone (HF) as an "electron reservoir" to the octahedral-polypyridyl-ruthenium complex resulted in decreased highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps and triplet-state metal to ligand charge transfer (3MLCT) state energy (0.89 eV). This modification enhanced the generation of O2•- under therapeutic ultrasound irradiation at a frequency of 1 MHz. The produced O2•- rapidly induced an intramolecular cascade reaction and HF ligand fracture. As a proof-of-concept, we engineered the Ru complex into a metallopolymer platform (PolyRuHF), which could be activated by low-power ultrasound (1.5 W cm-2, 1.0 MHz, 50% duty cycle) within a centimeter range of tissue. This activation led to O2•- generation and the release of cytotoxic ruthenium complexes. Consequently, PolyRuHF induced cellular apoptosis and ferroptosis by causing mitochondrial dysfunction and excessive toxic lipid peroxidation. Furthermore, PolyRuHF effectively inhibited subcutaneous and orthotopic breast tumors and prevented lung metastasis by downregulating metastasis-related proteins in mice. This study introduces the first sonoresponsive ruthenium complex for sonodynamic therapy/sonoactivated chemotherapy, offering new avenues for deep tumor treatment.

Experimental study on rotational energy transfer in LiH (X1Σ+ v) + Ar collisions

Abstract Using high-resolution transient laser spectroscopy, the rotational energy transfer between LiH (12, 8) and Ar through collisions was studied. LiH (12, 8) was generated via degenerate stimulated hyper-Raman (DSHR) scattering. The population of LiH (12, J″ ≠ 8) generated during collisions were obtained using transient laser-induced fluorescence (LIF). According to the rate equation, the rate coefficients for the transfer from (12, 8) to (12, J″) states are between 7.1×10-12 and 3.5×10-13 cm3 molecule-1 s-1 within 2 μs of the collision occurring. Above 2 μs, the rate coefficient is no longer constant. Meanwhile, no vibrational relaxation occurs before 10 μs. The rotational energy Erot is the sum of the rotational energies of rotational states (12, J″). Within the period of 0-10 μs, the value of Erot decreases from 541 cm-1 to 390 cm-1. The distribution of translational energy Etrans at different moments of LiH (12, 8) is obtained by measuring the Doppler broadened line widths. It increases from 707 cm-1 at 0 μs to 852 cm-1 at 10 μs. Therefore, when rotational relaxation occurs, the decrease in rotational energy is approximately equal to the increase in translational energy.

Rigorous Holographic Bound on AdS Scale Separation

We give an elementary proof of the following property of unitary, interacting four-dimensional N=2 superconformal field theories: At large central charge c, there exist at least c single-trace, scalar superconformal primary operators with dimensions Δ≲c (suppressing multiplicative logarithmic corrections). This follows from a stronger, more refined bound on the spectral density in terms of the asymptotic growth rate of the central charge. The proof employs known results on the structure of Coulomb branch operators. Interpreted holographically, this bounds the possible degree of scale separation in semiclassical AdS5 half-maximal supergravity. In particular, the bulk must contain an infinite tower of charged scalar states of energies parametrically below the large black hole threshold EBH∼c. We address the extreme case of AdS5 pure supergravity, ruling it out as the asymptotic limit of certain sequences in theory space, though the general question remains open. Published by the American Physical Society 2024

Room-Temperature Persistent Phosphorescence of Aggregated Gold Nanoclusters under Molecular Crystal Confinements.

We report color-tunable and solvent-processable persistent fluorescence to phosphorescence switching at room temperature by doping gold nanoclusters (AuNCs) inside molecular crystals. This provides a significant insight into the tunability of the photoluminescence property of the dopant depending on the crystal environment and compactness of confinement, with the possibility of energy transfer from crystal to aggregated AuNCs. For test cases, we have doped histidine-stabilized AuNCs (HIS-AuNCs) inside histidine (HIS-AuNCs-HIS) and isophthalic acid (HIS-AuNCs-IPA) crystals, respectively, and glutathione-stabilized AuNCs (GSH-AuNCs) inside histidine crystals (GSH-AuNCs-HIS). The maximal phosphorescence decay time recorded for crystal doped aggregated AuNCs was 9.38 ms, and the photoluminescence quantum yield value was measured as 25%. The possible energy states and potential interactions between aggregated NCs and host crystals were accounted for through density functional theory calculations and docking techniques, respectively. This finding opens new possibilities for designing and producing color-tunable persistent AuNC-based luminous crystals for multilayer information encryption, display, and biological applications.

Computational studies on the catalytic potential of the double active site for enzyme engineering

Proteins possessing double active sites have the potential to revolutionise enzyme design strategies. This study extensively explored an enzyme that contains both a natural active site (NAS) and an engineered active site (EAS), focusing on understanding its structural and functional properties. Metadynamics simulations were employed to investigate how substrates interacted with their respective active sites. The results revealed that both the NAS and EAS exhibited similar minimum energy states, indicating comparable binding affinities. However, it became apparent that the EAS had a weaker binding site for the substrate due to its smaller pocket and constrained conformation. Interestingly, the EAS also displayed dynamic behaviour, with the substrate observed to move outside the pocket, suggesting the possibility of substrate translocation. To gain further insights, steered molecular dynamics (SMD) simulations were conducted to study the conformational changes of the substrate and its interactions with catalytic residues. Notably, the substrate adopted distinct conformations, including near-attack conformations, in both the EAS and NAS. Nevertheless, the NAS demonstrated superior binding minima for the substrate compared to the EAS, reinforcing the observation that the engineered active site was less favourable for substrate binding due to its limitations. The QM/MM (Quantum mechanics and molecular mechanics) analyses highlight the energy disparity between NAS and EAS. Specifically, EAS exhibited elevated energy levels due to its engineered active site being located on the surface. This positioning exposes the substrate to solvents and water molecules, adding to the energy challenge. Consequently, the engineered enzyme did not provide a significant advantage in substrate binding over the single active site protein. Further, the investigation of internal channels and tunnels within the protein shed light on the pathways facilitating transport between the two active sites. By unravelling the complex dynamics and functional characteristics of this double-active site protein, this study offers valuable insights into novel strategies of enzyme engineering. These findings establish a solid foundation for future research endeavours aimed at harnessing the potential of double-active site proteins in diverse biotechnological applications.

Madelung mechanics and superoscillations

In single-particle Madelung mechanics, the single-particle quantum state Ψ(x→,t)=R(x→,t)eiS(x→,t)/ℏ is interpreted as comprising an entire conserved fluid of classical point particles, with local density R(x→,t)2 and local momentum ∇→S(x→,t) (where R and S are real). The Schrödinger equation gives rise to the continuity equation for the fluid, and the Hamilton–Jacobi equation for particles of the fluid, which includes an additional density-dependent quantum potential energy term Q(x→,t)=−ℏ22m∇→R(x→,t)R(x→,t) , which is all that makes the fluid behavior nonclassical. In particular, the quantum potential can become negative and create a nonclassical boost in the kinetic energy. This boost is related to superoscillations in the wavefunction, where the local frequency of Ψ exceeds its global band limit. Berry showed that for states of definite energy E, the regions of superoscillation are exactly the regions where Q(x→,t)<0 . For energy superposition states with band-limit E+ , the situation is slightly more complicated, and the bound is no longer Q(x→,t)<0 . However, the fluid model provides a definite local energy for each fluid particle which allows us to define a local band limit for superoscillation, and with this definition, all regions of superoscillation are again regions where Q(x→,t)<0 for general superpositions. An alternative interpretation of these quantities involving a reduced quantum potential is reviewed and advanced, and a parallel discussion of superoscillation in this picture is given. Detailed examples are given which illustrate the role of the quantum potential and superoscillations in a range of scenarios.

Repetitive shock waves generated by a single long pulse underwater arc discharge

The electrohydraulic effect induced by underwater arc discharge is an efficient way to generate controllable, high-intensity shock waves. However, the development process of underwater arc discharge involves the complex coupling of plasma arc, gas bubble, and liquid medium, of which the evolution mechanism is not well understood. In this paper, the underwater arc discharge process at a millisecond pulse (&amp;gt;50 ms) was investigated by high-speed shadow imaging and colorimetric temperature measurement, and a simulation model of bubble pulsation was proposed to quantitatively estimate the state variation and energy transfer of the gas bubble. The results indicate that the whole arc discharge process can be categorized into three successive stages: short-period oscillation, long-period oscillation, and quasi-steady state. The vapor inside the bubble can reach a supercritical state (827 K and 140 MPa) at the minimum bubble radius. The simulation shows that the light radiation absorption and the heat conduct loss through metal electrodes are the two dominant factors influencing the pulsation of the bubble, and further analysis indicates that the dynamic evolution of the arc determines the bubble pulsation mode. Our findings demonstrate why and how repetitive electrohydraulic shock waves can be generated by a single long pulse underwater arc discharge, providing a low-cost way of shock wave generator based on an AC/DC high-voltage power source.

Li/La and Cu modified ZnO semiconductor: Highly boosted of dielectric and sunlight-treatment of thiamethoxam and brilliant green contaminants

Solving the global environmental problem which related to the dissolved organic pollutants into water systems is an essential issue for human-health and aquatic life. This study represents the simple synthesis of new Li/La and Cu modified ZnO compositions as active photocatalysts and proper dielectric materials for electrical energy storage devices. The synthesized powders have one phase nature with hexagonal lattice indexed to ZnO structure. The field emission scanning electron microscopy (FESEM) clearly showed that (Li, La) modified ZnO powder consist of a mixture of particles having open hexagonal tube and spherical shapes. The FESEM picture of (Li, Cu, La) modified ZnO powder revealed lumps like cabbage shape mainly composed of pieces like sheets or papers. The purity and elemental composition were also verified by energy dispersive spectroscopy (EDS) analysis. The addition of (Li, La) and (Li, Cu, La) ions to ZnO semiconductor extremely improved the dielectric constant which is a benefit for application in solid state energy storage systems. (Li, Cu, La) modified ZnO sample is a suitable catalyst for removal of organic waste owing to its high response to visible light spectrum with measured band gap energy of 2.76 eV. The synergistic effect of Li+, Cu2+ and La3+ dopants induced high visible light photodegradation activities against thiamethoxam pesticide and brilliant green dye with measured efficiencies of 92 and 96 % after reaction time of 50 min, respectively. The high stability and mineralization properties of (Li, Cu, La) modified ZnO catalyst leads to the conclusion that this composition has a potential use in wastewater treatment.

Phonon-assisted leakage current of InGaN light emitting diode

Abstract We report on the leakage current mechanism in a blue GaN-based light-emitting diode (LED). The device structure was grown by the MOCVD technique on a sapphire substrate. The LED was characterized through various measurements including current-voltage, electroluminescence, and secondary ion mass spectroscopy (SIMS). Capacitance-voltage measurements were employed to calculate the depletion layer thickness at different bias voltages and analyze the doping profile in the active layer. The reverse temperature-dependent current-voltage measurements were carried out to study the leakage mechanism. The leakage current was explained by phonon-assisted tunneling of charge carriers through deep trap states. The trap energy and density of states were extracted from the application of the introduced model. Cathodoluminescence measurements were performed to evaluate the density of dislocations, which were then compared to X-ray diffraction measurements. The determined value was close to the density of states obtained from the tunneling model.

Approximate solutions for diatomic molecules under combined potentials in a global monopole and Aharonov–Bohm flux field

AbstractBound state energy eigensolutions of nine different diatomic molecules, specifically, , TiH, , CO, NO, ScH, CrH, HCl and LiH, placed in a point‐like global monopole, have been calculated by solving the time‐independent Schrödinger equation (SE). The molecules are confined by the Aharonov–Bohm (AB) flux field and the interaction potential among the charged particles is governed by the combined screened modified Kratzer potential (SMKP) plus Hulthén potential model. Three other special cases of the interaction potential have also been discussed here. Asymptotic iteration method has been used for the mathematical calculations. It is difficult to solve the SE exactly for any non‐zero values of the azimuthal quantum number due to the presence of the centrifugal barrier term. The well‐known Pekeris approximation technique for the terms and has taken into consideration for the purpose of performing numerical computations connected to an arbitrary state. The outcomes of this study are in reasonable agreement with the results of previous research on SMKP, Kratzer‐Fues potential, and modified Kratzer potential in the Minkowski space. It is observed that the energy spectra of the diatomic molecules suffer considerable change due to the effects of the background AB‐flux field and topological defect parameter.

Light elements adsorption modulates the electronic structure of h-BC2N / g-C6N6 nanoribbons

Abstract The electronic properties of h-BC2N / g-C6N6 nanoribbons were calculated using the first principles method. Three states of ferromagnetic, antiferromagnetic, and paramagnetic coupling were set. The energy of the ferromagnetic coupling state was found to be the lowest, indicating that the final stable state was the ferromagnetic coupling state. The thermodynamic stability was also verified in the ferromagnetic coupling state. The h-BC2N / g-C6N6 nanoribbons itself is magnetic with a magnetic moment of 2μB and is a direct narrow band gap semiconductor material. In order to change the electronic properties, six different atoms (B, C, N, Al, Si, P) were adsorbed in the h-BC2N / g-C6N6 nanoribbon, and their band structure and charge density were studied. The results show that the adsorption of different atoms in h-BC2N / g-C6N6 nanoribbons will produce different results. Among them, the adsorption of N and P atoms changes its properties from a semiconductor to a half-metal, which can generate a 100% polarized current in the Fermi surface. This provides more development directions for spintronics devices.&amp;#xD;

Non-Hermitian linear-response theory for spin diffusion in quantum systems

Spin transport theory of non-Hermitian quantum systems, where the non-Hermiticity led to a series of exotic phenomena when the system experiences dissipation to an environment is proposed. The goal is a better understanding of the spin diffusion in the one-dimensional non-Hermitian XXZ model which allows the transport coefficients be computed analytically. Moreover, we analyzed the electric transport in the one-dimensional non-Hermitian Hubbard model which is a very important model of electrons strongly correlated, where we have investigated the effect of non-Hermitian parameters like the imaginary hopping on AC and DC conductivities of the system. We analyzed the large U limit of this model, where such non-Hermiticity contributes with a minus sign in the virtual exchange of quasiparticles and the behavior of the ground state energy and low-lying excitations is reversed.

Electronic Structure Methods for Simulating Flavin's Spectroscopy and Photophysics: Comparison of Multi-reference, TD-DFT, and Single-Reference Wave Function Methods.

The use of flavins and flavoproteins in photocatalytic, sensing, and biotechnological applications has led to a growing interest in computationally modeling the excited-state electronic structure and photophysics of flavin. However, there is limited consensus regarding which computational methods are appropriate for modeling flavin's photophysics. We compare the energies of low-lying excited states of flavin computed with time-dependent density functional theory (TD-DFT), equation-of-motion coupled cluster (EOM-EE-CCSD), scaled opposite-spin configuration interaction [SOS-CIS(D)], multiconfiguration pair-density functional theory (MC-PDFT), and several multireference perturbation theory (MR-PT2) methods. In the first part, we focus on excitation energies of the first singlet excited state (S1) of five different redox and protonation states of flavin, with the goal of finding a suitable active space for MR-PT2 calculations. In the second part, we construct two sets of one-dimensional potential energy surfaces connecting the S0 and S1 equilibrium geometries (S0-S1 path) and the S1 (π,π*) and S2 (n,π*) equilibrium geometries (S1-S2 path). The first path therefore follows a Franck-Condon active mode of flavin while the second path maps crossings points between low-lying singlet and triplet states in flavin. We discuss the similarities and differences in the TD-DFT, EOM-EE-CCSD, SOS-CIS(D), MC-PDFT and MR-PT2 energy profiles along these paths. We find that (TD-)DFT methods are suitable for applications such as simulating the spectra of flavins but are inconsistent with several other methods when used for some geometry optimizations and when describing the energetics of dark (n,π*) states. MR-PT2 methods show promise for the simulation of flavin's low-lying excited states, but the selection of orbitals for the active space and the number of roots used for state averaging must be done carefully to avoid artifacts. Some properties, such as the intersystem crossing geometry and energy between the S1 (π,π*) and T2 (n,π*) states, may require additional benchmarking before they can be determined quantitatively.

Color Polymorphism and Room Temperature Phosphorescence of 4-Bromo-2,7-Di-Tert-Butyl- 9-Methoxypyrene.

Color polymorphism combined with crystal packing-dependent luminescence properties of polymorphs reflects differences in intermolecular interactions in different molecular arrangements. The title compound has two polymorphic crystal structures having strikingly different absorption and luminescence spectra that result from different packing motifs in the crystal lattice. The polymorph with brick wall-like packing of molecules is white and shows very weak violet fluorescence whereas the second polymorph, where molecules are arranged in columnar stacks, is bright yellow and displays intense green fluorescence with maximum at 487 nm (20530 cm-1). In the white polymorph, where the distance between neighboring chromophores is increased, absorption and fluorescence spectra are similar to those of monomer in solution, and intersystem crossing to triplet manifold is the dominant pathway of relaxation. In the yellow polymorph, molecules within the columnar stacks are rotated which mitigates the steric hindrance and leads to closer π-stacking of the pyrene cores. That increases the ππ overlap and strengthens intermolecular interactions decreasing energy of the excited states. This affects emission spectra and photophysical processes-fluorescence yield grows whereas triplet formation yield decreases when S1 is lowered below higher triplet states and conditions for effective vibronic spin-orbit coupling are not favorable. The effect is not observed for other similar pyrene derivatives, testifying the uniqueness of the phenomenon.

Synthesis, biological properties, drug-likeness, In silico ADME studies and theoretical studies on 1,3,2λ5-diazaphosphinane derivatives: A DFT investigation

Under various reaction conditions, Tetraphosphorus decasulphide P4S10 and Lawesson's reagent LR interacted with 2-cyano-N-[(2-hydroxyphenyl) methylidene] acetohydrazide (1) to synthesize a new 1,3,2λ5-diazaphosphinane derivatives 2–4. The three novel compounds 2−4 have been synthesized and characterized by elemental and spectral analyses (UV–Vis, FT-IR, MS, and 1H–NMR) throughout the current inquiry. The ground state energies, harmonic vibrational wavenumbers, and ground state geometries of the investigated compounds 2−4 were optimized by applying the density functional theory (DFT) at the B3LYP level, utilizing 6–311++G (d, p) basis sets. The first principal study has been investigated for the electronic properties, molecular electrostatic potentials, and quantum chemical identities. There was a noticeable shift in intramolecular charge from the occupied to the empty molecular orbitals. Time-dependent density functional theory (TD-DFT) and the CAM-B3LYP/6–311++G (d, p) function was used to conduct the UV–Vis analysis. A few bacterial and fungal strains were used to test the antimicrobial activities. The stability of the molecule resulting from hyper conjugative interactions that cause its nonlinear optical activity and charge delocalization was investigated using a natural bond orbital approach. The Mullikan atomic charge and molecular electrostatic potential are also anticipated. The value of the HOMO-LUMO energy gap indicates the possibility of charge transfer within the molecule. Compound 4 is the most reactive, with an energy difference between the border orbital of ΔEgap = 2.97 eV, according to analysis of the global descriptors. In addition, compared to the other 2 and 3 compounds under study, compound 4 is the softest, least stable, and has the largest electronic exchange capacity. Examined the structure-activity relationship using DFT calculations (SAR) and compared the findings with real-world antimicrobial outcomes for compounds 2–4. Also, Drug-likeness and In silico ADME studies were performed.

Multi-peak soliton dynamics and decoherence via the attenuation effects and trapping potential based on a fractional nonlinear Schrödinger cubic quintic equation in an optical fiber

Fiber optic research continues to develop due to the need for fast information technology. The input signal in an optical fiber is in the form of a soliton wave that propagates in the fiber with a balanced index of refraction, dispersion, and diffraction. Fiber optics may lose some of the signal over time if they solely use a nonlinear refractive index. This study aims to examine into the dynamics and decoherence of multi-peak solitons caused by electromagnetic signal attenuation and potential trap in the propagation via optical fibers. The methods used start with the stationary solution of the nonlinear Schrödinger Cubic Quintic equation, the Newton-Raphson method, and the fourth-order Runge-Kutta. In stationary solutions, the p (state energy) and ρ (Lèvy index) values affect the number, pulse width, and height of soliton peaks. Increased p and ρ values lead to increased instability, causing the data transmitted into the optical fiber to collapse and become unreadable by the receiver. In the excited state (p > 0), the decoherence phenomenon occurs and causes wave instability and destruction. In term of energy intensity, a stable form of transmission in the ground state has a pattern of continuously weakening, decreasing, and smoothing, while in the excited state there is a spike in the intensity of the electromagnetic wave. Based on this study, multi-peak solitons can only be applied for propagation distances, which tend to be short due to their dynamics and decoherence.

Deciphering the doublet luminescence mechanism in neutral organic radicals: spin-exchange coupling, reversed-quartet mechanism, excited-state dynamics.

Neutral organic radical molecules have recently attracted considerable attention as promising luminescent and quantum-information materials. However, the presence of a radical often shortens their excited-state lifetime and results in fluorescence quenching due to enhanced intersystem crossing (EISC). Recently, an experimental report introduced an efficient luminescent radical molecule, tris(2,4,6-trichlorophenyl)methyl-carbazole-anthracene (TTM-1Cz-An). In this study, we systematically performed quantum theoretical calculations combined with the path integral approach to quantitatively calculate the excited-state dynamics processes and spectral characteristics. Our theoretical findings suggest that the sing-doublet D1 state, originating from the anthracene excited singlet state, is quickly converted to the doublet (trip-doublet) state via EISC, facilitated by a significant nonequivalence exchange interaction, with ΔJ ST = 0.174 cm-1. The formation of the quartet state (Q1, trip-quartet) was predominantly dependent on the exchange coupling 3/2J TR = 0.086 cm-1 between the triplet spin electrons of anthracene and the TTM-1Cz radical. Direct spin-orbit coupling ISC to the Q1 state was minimal due to the nearly identical spatial wavefunctions of the and Q1 levels. The effective occurrence of reverse intersystem crossing (RISC) from the Q1 to D1 state is a critical step in controlling the luminescence of TTM-1Cz-An. The calculated RISC rate k RISC, including the Herzberg-Teller effect, was 3.64 × 105 s-1 at 298 K, significantly exceeding the phosphorescence and nonradiative rates of the Q1 state, thus enabling the D1 repopulation. Subsequently, a strong electronic coupling of 37.4 meV was observed between the D1 and D2 states, along with a dense manifold of doublet states near the D1 state energy, resulting in a larger reverse internal conversion rate k RIC of 9.26 × 1010 s-1. Distributed to the D2 state, the obtained emission rate of k f = 2.98-3.18 × 107 s-1 was in quite good agreement with the experimental value of 1.28 × 107 s-1, and its temperature effect was not remarkable. Our study not only provides strong support for the experimental findings but also offers valuable insights for the molecular design of high-efficiency radical emitters.

Regulating coordination environment around transition metal (Fe, Co) single atom catalysts for efficient Hg0 adsorption

Elemental mercury (Hg0) is one of the main pollutants released during coal combustion, which is difficult to remove due to its hydrophobicity and volatility, resulting in serious environmental pollution. Therefore, it is urgent to develop a low-cost and high-performance catalyst to remove Hg0. In this work, using first-principles study, the effect of nonmetal (NM = B, C and O) coordination environment on the charge distribution of graphene-supported transition metal single atom catalysts (TM-N4-SAC) has been investigated. It is found that regulating the TM-N4-SAC with NM coordination atoms with fewer valence electrons than N atom can cause TM atoms to lose more electrons, and the charge distribution in the active center to be locally deviated. Moreover, in-depth analysis of the adsorption configuration, charge density difference, charge transfer, adsorption energy and density of state of Hg0 adsorption on NM modified TM-N4-SAC confirmed that the adsorption of Hg0 can be effectively enhanced only when TM atoms lose more electrons. Thus, Fe-N3B- and Co-N3B-SAC have the strongest ability to adsorb Hg0 because they have the most negative adsorption energy of −1.13 and −0.49 eV. This work provides theoretical guidance for the design of SAC for efficient adsorption of Hg0.

Frequency-Dependent Vibronic Effects in Steady State Energy Transport.

The interplay between electronic and intramolecular high-frequency vibrational degrees of freedom is ubiquitous in natural light-harvesting systems. Recent studies have indicated that an intramolecular vibrational donor-acceptor frequency difference can enhance energy transport. Here, we analyze the extent to which different intramolecular donor-acceptor vibrational frequencies affect excitation energy transport in the natural nonequilibrium steady state configuration. Comments are included on the less physical equilibrium case for comparison with the literature. It is found that for constant Huang-Rhys factors, whereas the acceptor population increases in the equilibrium case when the intramolecular vibrational frequency of the acceptor exceeds that of the donor, this increase is negligible for the nonequilibrium steady state. Therefore, these changes in acceptor population do not significantly enhance energy transport in the nonequilibrium steady state for the natural scenario of incoherent light excitation with biologically relevant parameters of typical photosynthetic complexes. Insight about a potential mechanism to optimize energy transfer in the nonequilibrium steady state based on increasing the harvesting time at the reaction center is analyzed.

Tunnel transport problem for open multilayer nitride nanostructures with an applied constant magnetic field and time-dependent potential: An exact solution

A quantum mechanical theory for description of electronic quasistationary states in two-dimensional (2D) layered semiconductor nanostructure was developed. A constant external magnetic field B was directed along semiconductor layers. The presence of internal electric fields F originated from the potential barriers and wells in semiconductor layers was taken into account. The vector of F was directed perpendicularly to semiconductor layers. The interaction of tunneled electrons with a time-dependent electromagnetic fields was analyzed in detail. An approach to obtain an exact solution to the problem based on a combination of the Lewis-Riesenfeld method for complete Schrödinger equation and scattering theory was developed. Application of the scattering theory in combination with the -matrix and transfer-matrix methods allowed us to calculate the electron quasistationary spectra. Effects of magnetic field on the resonant energy and width of electronic quasistationary states as well as on the electronic conductivity were also discussed. Published by the American Physical Society 2024