Reductive Inner-Sphere Electrosynthesis of Ammonia via a Nonelectrocatalytic Outer-Sphere Redox.

Electrochemistry of outer-sphere redox molecules involves an essentially intact primary coordination sphere with minimal secondary sphere adjustments, resulting in very fast electron transfer events even without a noble metal-based electrocatalyst. Departing from conventional electrocatalytic paradigms, we incorporate these minimal reaction coordinate adjustments of outer-sphere species to stimulate the electrocatalysis of energetically challenging inner-sphere substrates. Through this approach, we are able to show an intricate 8e- and 9H+ transfer inner-sphere reductive electrocatalysis at almost half the energy input of a conventional inner-sphere electron donor. This methodology of employing outer-sphere redox species has the potential to notably improve the cost and energy benefits in electrochemical transformations involving fundamental substrates such as water, CO2, N2, and many more.

Synergistic effects of the substrate-ligand interaction in metal-organic complexes on the de-electronation kinetics of a vitamin C fuel cell.

The rising demand for portable energy conversion devices has spurred the advancement of direct liquid fuel cells (DLFCs) employing fuels such as alcohol, ammonia, hydrazine, and vitamin C. In these devices, various precious metal platforms have been explored to increase the de-electronation kinetics and reduce catalyst poisoning, but with substantial cost implications. We demonstrate the crucial role of ligands in non-precious organometallic complexes in influencing the de-electronation kinetics of fuel molecules through a unique substrate-ligand synergistic interaction. This unique chemistry imparts electron deficiency at the catalytic metal center while simultaneously populating the ligand with an extensive proton charge assembly. This distinct substrate-ligand interaction enhances the DLFC performance by coulombically dragging the substrate with a distinct amplification in its de-electronation kinetics. By integrating this approach with a ferricyanide/ferrocyanide half-cell reaction, a precious metal-free vitamin C fuel cell is developed, which is capable of generating an open circuit voltage of ∼950 mV, a peak power density of ∼97 mW cm-2 at a peak current density of ∼215 mA cm-2 with the performance metrics nearly 1.7 times higher than a precious metal based DLFC. This highlights the potential of the substrate-ligand synergy in the design of efficient molecular catalysts for energy conversion applications.

Spin Inertia and Auto-Oscillations in Ferromagnets.

Recent experimental confirmation of spin inertia in ferromagnets positions this well-developed material class as a prime candidate for THz frequency applications. Spin-torque driven critical spin dynamics, such as auto-oscillations, play the central role in many spin-based technologies. Yet, the pressing question on spin inertia's effect on spin-torque driven dynamics in ferromagnets has remained unexplored. Here, we develop the theoretical framework of precessional auto-oscillations for ferromagnets with spin inertia. We discover and introduce the concept of nutational auto-oscillations and demonstrate that they can become pivotal for future ultrahigh frequency technologies. We conclude by revealing parallels between spin dynamics in ferrimagnets and inertial ferromagnets and derive an isomorphism that establishes a foundation for synergistic knowledge transfer between these research fields.

A Spontaneous Heavy Hydrogen Generator via a Protium Redox.

The extreme significance of heavy hydrogen (D2) in medicinal, nuclear, and chemical sectors, despite its scarce natural abundance, underscores the vital imperative for inventing novel chemistries for its production. We showcase a spontaneous heavy hydrogen generator during commensurate electrical energy production by decoupling the direct chemistry of OD-/D+ dual ions via a protium redox. This exergonic electrochemistry yields ∼357 mL of D2 in nearly 85 h of continuous operation, with a commensurate electrical energy output of 122 kJ/per mole of D2. This laboratory-level demonstration of spontaneous heavy hydrogen production presents a novel chemistry for the scalable manufacture of nonprimordial D2.

Theory of tensorial Gilbert damping in antiferromagnets.

Although the magnetic Gilbert damping was considered as a scalar quantity in micromagnetic and atomistic spin simulations, recent investigations show that the Gilbert damping parameter is a tensor. Here, we investigate the effect of anisotropic and chiral damping in one-sublattice ferromagnets and two-sublattice antiferromagnets. We employ linear response theory to calculate the susceptibility with the damping tensor and determine the ferromagnetic and antiferromagnetic resonance frequencies together with the effective damping. Our results show that apart from the scalar Gilbert damping, the antisymmetric chiral damping has a significant contribution to the spin dynamics that it breaks the antiparallel alignment of two sublattices in antiferromagnets even in the absence of an applied field. To this end, we also compare the tensorial damping and cross-sublattice scalar damping in antiferromagnets.

Electrostatically driven unidirectional molecular flux for high performance alkaline flow batteries.

To mitigate the mismatch between energy availability and energy demand due to day/night shifts and seasonal variations, intensive efforts have been dedicated to storing renewable energy in various energy storage modules. Redox flow batteries have an upper hand over conventional batteries as energy storage modules due to their capability of decoupling energy and power. However, interfacial events, such as mass transport and electron transfer, play pivotal roles in flow batteries' energy storage and conversion mechanisms. We show that by activating electrostatic forces at the interface, unidirectional molecular flux can be achieved to and from the driving electrode surface, thereby generating a parallel or antiparallel electrostatic current along with a diffusion current. This approach of triggering electrostatic forces in flow batteries enhances their volumetric energy density and amplifies the energy efficiency to values as high as ∼92% without altering the solubility limit of the redox active species.

Aqueous OH-/H+ dual-ion gradient assisted electricity effective electro-organic synthesis of 2,5-furandicarboxylic acid paired with hydrogen fuel generation.

The OH-/H+ dual-ion gradient has a hidden electromotive force of 0.82 V under standard conditions; however, its non-redox nature completely prevents its direct interconversion as electrical driving force. We show by using organic molecules whose heterogeneous electron transfer is pH dependent, OH-/H+ dual-ion energy can be directly harvested as electrical driving force for performing simultaneous electro-organic synthesis and hydrogen fuel production in an electricity effective manner. To demonstrate this dual-ion gradient assisted electro-organic synthesis, 5-hydroxymethylfurfural (HMF) is chosen as the model molecule because of the immense techno commercial applications of its oxidized products. This dual-ion assisted device only required âˆ¼1 V to provide a current density of 50 mA/cm2 and for achieving the same rate; the traditional state-of-the-art electrolytic cell required a doubling of the applied potential. The dual-ion gradient assisted device can convert biomass-derived HMF to economically important FDCA with âˆ¼90 % yield and âˆ¼87 % Faradaic efficiency with simultaneous H2 fuel production at a potential as low as 1 V.

Aqueous OH- /H+ Dual-Ion Zn-Based Batteries.

Aqueous Zn-based batteries hold multiple advantages of eco-friendliness, easy accessibility, high safety, easy fabrication, and fast kinetics, while their widespread applications have been greatly limited by the relatively narrow thermodynamically stable potential windows (i. e., 1.23 V) of water and the mismatched pH conditions between cathode and anode, which presents challenges regarding how to maximize the output voltage and the energy density. Recently, aqueous OH- /H+ dual-ion Zn-based batteries (OH- /H+ -DIZBs), where the Zn anode reacts with hydroxide ions (OH- ) in alkaline electrolyte while hydrogen ions (H+ ) are involved in the cathode reaction in the acidic electrolyte, have been reported to be capable of broadening the working voltage and improving the energy density, which offers practical feasibility toward overcoming the above limitations. This Review thus takes this chance to investigate the recent progress on aqueous OH- /H+ -DIZBs. First, the concept and the history of such OH- /H+ -DIZBs are introduced, and then special emphasis is put on the working mechanisms, the progress of the development of new batteries, and how the electrolytes improve their performance. Finally, the challenges and opportunities in this field are discussed.

Theroy of magnetic inertial dynamics in two-sublattice ferromagnets.

The magnetic inertial dynamics have previously been investigated for one sublattice ferromagnets. Here, we develop the magnetization dynamics in two-sublattice ferromagnets including the intra- and inter-sublattice inertial dynamics. First, we derive the magnetic susceptibility of such a ferromagnet. Next, by finding the poles of the susceptibility, we calculate the precession and nutation resonance frequencies. Our results suggest that while the resonance frequencies show decreasing behavior with the increasing intra-sublattice relaxation time, the effect of inter-sublattice inertial dynamics has an opposite effect.

Dynamics of the relativistic electron spin in an electromagnetic field.

A relativistic spin operator cannot be uniquely defined within relativistic quantum mechanics. Previously, different proper relativistic spin operators have been proposed, such as spin operators of the Foldy-Wouthuysen and Pryce type, that both commute with the free-particle Dirac Hamiltonian and represent constants of motion. Here we consider the dynamics of a relativistic electron spin in an external electromagnetic field. We use two different Hamiltonians to derive the corresponding spin dynamics. These two are: (a) the Dirac Hamiltonian in the presence of an external field, and (b) the semirelativistic expansion of the same. Considering the Foldy-Wouthuysen and Pryce spin operators we show that these lead to different spin dynamics in an external electromagnetic field, which offers possibilities to distinguish their action. We find that the dynamics of both spin operators involve spin-dependent and spin-independent terms, however, the Foldy-Wouthuysen spin dynamics additionally accounts for the relativistic particle-antiparticle coupling. We conclude that the Pryce spin operator provides a suitable description of the relativistic spin dynamics in a weak-to-intermediate external field, whereas the Foldy-Wouthuysen spin operator is more suitable in the strong field regime.

Generalisation of Gilbert damping and magnetic inertia parameter as a series of higher-order relativistic terms.

The phenomenological Landau-Lifshitz-Gilbert (LLG) equation of motion remains as the cornerstone of contemporary magnetisation dynamics studies, wherein the Gilbert damping parameter has been attributed to first-order relativistic effects. To include magnetic inertial effects the LLG equation has previously been extended with a supplemental inertia term; the arising inertial dynamics has been related to second-order relativistic effects. Here we start from the relativistic Dirac equation and, performing a Foldy-Wouthuysen transformation, derive a generalised Pauli spin Hamiltonian that contains relativistic correction terms to any higher order. Using the Heisenberg equation of spin motion we derive general relativistic expressions for the tensorial Gilbert damping and magnetic inertia parameters, and show that these tensors can be expressed as series of higher-order relativistic correction terms. We further show that, in the case of a harmonic external driving field, these series can be summed and we provide closed analytical expressions for the Gilbert and inertial parameters that are functions of the frequency of the driving field.

Signatures of relativistic spin-light coupling in magneto-optical pump-probe experiments.

Femtosecond magneto-optical pump-probe measurements of ultrafast demagnetization show an intriguing difference in the first 100 fs of the magneto-optical Kerr response depending on whether the polarization of the pump and probe beams are in parallel or perpendicular configuration (Bigot et al 2009 Nat. Phys. 5 515). Starting from a most general relativistic Hamiltonian we focus on the ultra-relativistic light-spin interaction and show that this coupling term leads to different light-induced opto-magnetic fields when pump and probe polarization are parallel and perpendicular to each other, providing thus an explanation for the measurements. We also analyze other pump-probe configurations where the pump laser is circularly polarized and the employed probe contains only linearly polarized light and show that similar opto-magnetic effects can be anticipated.

Ab Initio Theory of Coherent Laser-Induced Magnetization in Metals.

We present the first materials specific ab initio theory of the magnetization induced by circularly polarized laser light in metals. Our calculations are based on nonlinear density matrix theory and include the effect of absorption. We show that the induced magnetization, commonly referred to as inverse Faraday effect, is strongly materials and frequency dependent, and demonstrate the existence of both spin and orbital induced magnetizations which exhibit a surprisingly different behavior. We show that for nonmagnetic metals (such as Cu, Au, Pd, Pt) and antiferromagnetic metals the induced magnetization is antisymmetric in the light's helicity, whereas for ferromagnetic metals (Fe, Co, Ni, FePt) the imparted magnetization is only asymmetric in the helicity. We compute effective optomagnetic fields that correspond to the induced magnetizations and provide guidelines for achieving all-optical helicity-dependent switching.

Landmark-based geometric morphometric analysis of wing shape among certain species of Aedes mosquitoes in District Dehradun (Uttarakhand), India.

BACKGROUND & OBJECTIVES: Insect wing morphology has been used in many studies to describe variations among species and populations using traditional morphometrics, and more recently geometric morphometrics. A landmark-based geometric morphometric analysis of the wings of three species of Aedes (Diptera: Culicidae), viz. Ae. aegypti, Ae. albopictus and Ae. pseudotaeniatus, at District Dehradun was conducted belling on the fact that it can provide insight into the population structure, ecology and taxonomic identification. METHODS: Adult Aedes mosquito specimens were randomly collected using aerial nets and morphologically examined and identified. The landmarks were identified on the basis of landmark based geometric morphometric analysis thin-plate spline (mainly the software tps-Util 1.28; tps-Dig 1.40; tps-Relw 1.53; and tps-Spline 1.20) and integrated morphometrics programme (mainly twogroup win8 and PCA win8) were utilized. RESULTS: In relative warp (RW) analysis, the first two RW of Ae. aegypti accounted for the highest value (95.82%), followed by Ae. pseudotaeniatus (90.89%), while the lowest (90.12%) being recorded for Ae. albopictus. The bending energies of Ae. aegypti and Ae. pseudotaeniatus were quite identical being 0.1882 and 0.1858 respectively, while Ae. albopictus recorded the highest value of 0.9774. The mean difference values of the distances among Aedes species performing Hotelling's T 2 test were significantly high, predicting major differences among the taxa. In PCA analysis, the horizontal and vertical axis summarized 52.41 and 23.30% of variances respectively. The centroid size exhibited significant differences among populations (non-parametric Kruskal-Wallis test, H = 10.56, p < 0.01). INTERPRETATION & CONCLUSION: It has been marked out that the geometric morphometrics utilizes powerful and comprehensive statistical procedures to analyze the shape differences of a morphological feature, assuming that the studied mosquitoes may represent different genotypes and probably come from one diverse gene pool.