Local Charge Research Articles

Dynamically Reconstructed Triple-Copper-Vacancy Associates Confined in Cu Nanowires Enabling High-Rate and Selective CO2 Electroreduction to C2+ Products.

Electrochemically reconstructed Cu-based catalysts always exhibit enhanced CO2 electroreduction performance; however, it still remains ambiguous whether the reconstructed Cu vacancies have a substantial impact on CO2 -to-C2+ reactivity. Herein, Cu vacancies are first constructed through electrochemical reduction of Cu-based nanowires, in which high-angle annular dark-field scanning transmission electron microscopy image manifests the formation of triple-copper-vacancy associates with different concentrations, confirmed by positron annihilation lifetime spectroscopy. In situ attenuated total reflection-surface enhanced infrared absorption spectroscopy discloses the triple-copper-vacancy associates favor *CO adsorption and fast *CO dimerization. Moreover, density-functional-theory calculations unravel the triple-copper-vacancy associates endow the nearby Cu sites with enriched and disparate local charge density, which enhances the *CO adsorption and reduces the CO-CO coupling barrier, affirmed by the decreased *CO dimerization energy barrier by 0.4eV. As a result, the triple-copper-vacancy associates confined in Cu nanowires achieve a high Faradaic efficiency of over 80% for C2+ products in a wide current density range of 400-800mA cm-2 , outperforming most reported Cu-based electrocatalysts.

Methyl-Symmetrically Substituted Poly(3,4-Dimethylthiophene) as Cathode for Aluminum Ion Batteries.

The aggravation of energy problems and the scarcity of lithium resources have forced us to look for new energy storage systems. Aluminum ion batteries, as a promising energy storage system, have the advantages of environmental friendliness and abundant aluminum resources, and have the potential for application in large-scale energy storage and personal portable electronic devices. To solve the stability problem of aluminum ion batteries during cycling for large-scale energy storage needs, we report a polythiophene-based conductive polymer, poly(3,4-dimethylthiophene) (PDMT), as a high performance cathode material for aluminum ion batteries. By introducing two methyl groups on the thiophene ring, we successfully adjust the local charge density of the heterocyclic thiophene, thus changing the electron delocalization characteristics, and improving the electrochemical reaction activity of the polythiophene (PTH) material as a redox electrode material. This also maintains the symmetry and regularity of the polymer structure, giving the material better cycling stability. The discharge specific capacity reaches 110 mAh g-1 at a current density of 200 mA g-1, far exceeding conventional PTH cathodes (~70 mAh g-1), and the capacity retention rate is 92.7 % after 1000 cycles. It also shows excellent rate performance due to the flexible structure of the conductive polymer.

Light-driven nanoscale vectorial currents.

Controlled charge flows are fundamental to many areas of science and technology, serving as carriers of energy and information, as probes of material properties and dynamics1 and as a means of revealing2,3 or even inducing4,5 broken symmetries. Emerging methods for light-based current control5-16 offer particularly promising routes beyond the speed and adaptability limitations of conventional voltage-driven systems. However, optical generation and manipulation of currents at nanometre spatial scales remains a basic challenge and a crucial step towards scalable optoelectronic systems for microelectronics and information science. Here we introduce vectorial optoelectronic metasurfaces in which ultrafast light pulses induce local directional charge flows around symmetry-broken plasmonic nanostructures, with tunable responses and arbitrary patterning down to subdiffractive nanometre scales. Local symmetries and vectorial currents are revealed by polarization-dependent and wavelength-sensitive electrical readout and terahertz (THz) emission, whereas spatially tailored global currents are demonstrated in the direct generation of elusive broadband THz vector beams17. We show that, in graphene, a detailed interplay between electrodynamic, thermodynamic and hydrodynamic degrees of freedom gives rise to rapidly evolving nanoscale driving forces and charge flows under the extremely spatially and temporally localized excitation. These results set the stage for versatile patterning and optical control over nanoscale currents in materials diagnostics, THz spectroscopies, nanomagnetism and ultrafast information processing.

Surface Hydroxyl and Oxygen Vacancies Engineering in ZnSnAl LDH: Synergistic Promotion of Photocatalytic Oxidation of Aromatic VOCs.

Photocatalytic oxidation has gained great interest in environmental remediation, but it is still limited by its low efficiency and catalytic deactivation in the degradation of aromatic VOCs. In this study, we concurrently regulated the surface hydroxyl and oxygen vacancies by introducing Al into ZnSn layered double hydroxide (LDH). The presence of distorted Al species induced local charge redistribution, leading to the remarkable formation of oxygen vacancies. These oxygen vacancies subsequently increased the amount of surface hydroxyl and elongated its bond length. The synergistic effects of surface hydroxyl and oxygen vacancies greatly enhanced reactant adsorption-activation and facilitated charge transfer to generate •OH, •O2-, and 1O2, resulting in highly efficient oxidation and ring-opening of various aromatic VOCs. Compared with commercial TiO2, the optimized ZnSnAl-50 catalyst exhibited about 2-fold activity for the toluene and styrene degradation and 10-fold activity for the chlorobenzene degradation. Moreover, ZnSnAl-50 demonstrated exceptional stability in the photocatalytic oxidation of toluene under a wide humidity range of 0-75%. This work marvelously improves the photocatalytic efficiency, stability, and adaptability through a novel strategy of surface hydroxyl and oxygen vacancies engineering.

Local electroneutrality breakdown for electrolytes within varying-section nanopores

We determine the local charge dynamics of a z-z\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z-z$$\\end{document} electrolyte embedded in a varying-section channel. By means of an expansion based on the length scale separation between the axial and transverse direction of the channel, we derive closed formulas for the local excess charge for both, dielectric and conducting walls, in 2D (planar geometry) as well as in 3D (cylindrical geometry). Our results show that, even at equilibrium, the local charge electroneutrality is broken whenever the section of the channel is not homogeneous for both dielectric and conducting walls as well as for 2D and 3D channels. Interestingly, even within our expansion, the local excess charge in the fluid can be comparable to the net charge on the walls. We critically discuss the onset of such local electroneutrality breakdown in particular with respect to the correction that it induces on the effective free energy profile experienced by tracer ions.Graphical abstract

Evaluation of electric field distortion at the Gaisberg Tower for continuing current measurements in lightning discharges

Upward lightning requires a distinct approach compared to downward (cloud-to-ground) lightning. Some lightning strikes are triggered by objects on the ground itself. The occurrence of such strikes depends on various factors, including the object’s geometric dimensions, structure, relative location within its environment, as well as the distribution and location of electrical charges within the thundercloud. This phenomenon takes place more and more often due to the spread of wind farms and higher buildings. In this article, simulation and calculation is carried out regarding the Gaisberg Tower in Austria which is actively used as a measurement and research site for lightning purposes. A finite element simulation is carried out to assess the electric field characteristics in the geometry. The close electric field measurement instruments are located 170 m away from the tower on an enclosure which must be considered during data analysis. The result of the created model is validated by former measurement data which confirms the arrangement of the model and creates the opportunity to directly transform the values of the electric field from the field mill to the tower during appropriate conditions.

Piezoionic Elastomers by Phase and Interface Engineering for High-Performance Energy-Harvesting Ionotronics.

Piezoionic materials play a pivotal role in energy-harvesting ionotronics. However, a persistent challenge lies in balancing the structural requirements for voltage generation, current conduction, and mechanical adaptability. The conventional approach of employing crystalline heterostructures for stress concentration and localized charge separation, while effective for voltage generation, often compromises the stretchability and long-range charge transport found in homogeneous quasisolid states. Herein, phase and interface engineering strategy is introduced to address this dilemma and a piezoionic elastomer is presented that seamlessly integrates ionic liquids and ionic plastic crystals, forming a finely tuned microphase-separated structure with an intermediate phase. This approach promotes charge separation via stress concentration among hard phases while leveraging the high ionic charge mobility in soft and intermediate phases. Impressively, the elastomer achieves an extraordinary piezoionic coefficient of about 6.0mV kPa-1, a more than threefold improvement over current hydrogels and ionogels. The resulting power density of 1.3 µW cm-3 sets a new benchmark, exceeding that of state-of-the-art piezoionic gels. Notably, this elastomer combines outstanding stretchability, remarkable toughness, and rapid self-healing capability, underscoring its potential for real-world applications. This work may represent a stride toward mechanically robust energy harvesting systems and provide insights into ionotronic systems for human-machine interaction.

Exploring the Optical and Photovoltaic Changeover for Carbazole-Bridge Push-Pull Switches Against Their Local Excitations and Charge Transfers

This research investigates characterization of low lying excitations of newly designed organic dyes for their local excited and charge transfer-related molecular switching attributes such as donor-acceptor relations against the carbazole bridge. The eight new dyes, having 4 symmetrical (Syn-A-D) and 4 antisymmetric (Anti-A-D) arrangements showed how the push-pull effect can operate to create the charge transfer phenomenon. Their absorption energies (E) for Syn dyes ranged from 2.98 eV to 4.07 eV, with corresponding wavelengths (λmax) ranging from 304 nm to 415 nm. While for their Anti arrangements, it ranged from 1.62 eV to 3.99 eV, with corresponding λmax values as 310-617 nm. Syn-C1 with an ionization potential (IP) of 6.59 eV and an electron affinity (EA) of 2.04 eV can be predicted to be more chemically stable compared to Anti-C2 with an IP of 5.16 eV and an EA of 3.86 eV. Syn-C also has the highest Voc (3.24 eV) and Pmax (22.35 W), indicating that it has the potential to be more chemically stable as compared to the other dyes. The findings of this research contributed to a better understanding of the molecular switching attributes of carbazole-based organic dyes, which could have implications for various applications, including optoelectronics and energy conversion devices.

Terahertz dielectric properties of Fe3O4 thin films deposited on Si (100) substrate

Fe3O4 is considered to be a promising material for terahertz spintronic applications as well as for stealth technology. However, the optical properties of Fe3O4 in the thin film form at terahertz frequencies are not reported in literature. In this article, we present the frequency and temperature dependence of dielectric permittivity (ε 1) and optical conductivity (σ 1) of Fe3O4 films deposited on Si substrate. The σ 1 of these films show absorption peaks related to charge localization and shallow impurities. It is also observed that the Fe2O3/Fe3O4 composite films have large σ 1 and ε 1 indicating their potential use for stealth technology applications. The overall optical properties are found to depend strongly on the microstructure and defects, such as, the grain size and the presence of grain boundaries, anti-phase boundaries, strain disorder due to lattice mismatch and/or the Fe+2/Fe+3 ratio.

Unveiling the Role of Electrostatic Forces on Attraction between Opposing Polyelectrolyte Brushes.

Electrostatic interaction and molecular excluded-volume effects are responsible for a plethora of nonintuitive phenomena in soft-matter systems, including local charge inversion and attraction between similar charges. In the current work, we study the surface forces and swelling behavior of opposing polyelectrolyte brushes using a classical density functional theory that accounts for electrostatic and excluded-volume correlations. We observe that the detachment pressure between similarly charged brushes is sensitive to salt concentration in both the osmotic and salted regimes and can be negative in the presence of multivalent counterions. A comparison of the theoretical results with the mean-field predictions unravels the role of correlation effects in determining the surface forces and brush structure. For systems containing multivalent counterions, the detachment pressure attains negative values at an intermediate brush-brush separation, and the attractive region in the pressure vs distance plot is magnified in terms of both the depth and width of attraction with increasing counterion valency. However, the interbrush attraction vanishes when the size-induced correlations are switched off. We also investigated the role of counterion size and polymer chain length on the detachment pressure. It is found that smaller counterions are more effective in neutralizing the polymer charge than bigger counterions, leading to a reduced interbrush repulsion and, in some cases, attraction between like-charged brushes at intermediate distances. Meanwhile, varying the chain length of the grafted polymers only shifts the location of the attraction basin, with little influence on the interaction strength. The theoretical predictions show qualitative agreement with experimental observations and offer valuable insights into the interaction between similarly charged polymer brushes in the presence of multivalent ions.

Toward Highly Efficient Low‐Carbon Footprint Solar Cells: Impact of High‐Temperature Processing on Epitaxially Grown p‐Type Silicon Wafers

Conventional silicon (Si) wafers are produced by energy‐intensive ingot crystallization which is responsible for a major share of a solar cell's carbon footprint. This work explores Si epitaxially grown silicon wafers (EpiWafers) that are produced by direct epitaxial deposition of trichlorosilane on a reusable substrate. This approach requires less energy and material and hence offers a potential for reduced cost and carbon footprint. Solar cells made from EpiWafers usually suffer from efficiency losses due to recombination at structural crystal defects associated with epitaxial growth. The nature of these defects is investigated and defects at the EpiWafer's back surface are critical. Most of these defects are highly recombination‐active, pairwise‐connected misfit dislocations in the <110> direction. They originate from a lattice mismatch between the highly doped substrate and the less‐doped epitaxially grown layer. In this contribution, the detrimental impact of these defects can be mitigated using typical manufacturing processes of high‐efficiency solar cells, such as KOH etching, gettering, and oxidation. Local minority charge carrier lifetimes as high as 2.2 ms after industrially feasible processes are reported. Simulations using efficiency‐limiting bulk recombination analysis implies that the material would allow conversion efficiencies of up to 25.6% considering tunnel oxide‐passivated contact acting as rear emitter solar cell design.

The moral, the political and social licence in digitally‐driven family policy and intervention: Parents negotiating experiential knowledge and ‘other’ families

AbstractThe article provides a conceptually informed empirical critique of the pursuit of social licence as a warrant for data linkage and predictive analytics in the field of family policy intervention. It draws on research focusing on parental views of digitally‐driven family governance in the United Kingdom. We identify the notion of consensus that undergirds the concept of social licence that acts to obscure inequalities and silence conflict, and to reframe digital surveillance and prediction as a moral rather than political issue. Using focus group and individual interview material, we show how parents assert professional or lay experiential knowledges in making judgements about the legitimacy of and trust in operational data technologies, involving struggles between positionings as parents like ‘us’ and ‘other’ parents. We demonstrate how parents have different leverages from these unequal and morally charged social locations. Inevitably, the application of social licence in the domain of digital family policy and intervention is fractured by entrenched social divisions and inequalities.

Comprehensive quantum chemical study of the associative complex of para-aminobenzoic acid and 7-diethylamino 4-methyl coumarin by adsorption and aromatic bridges.

The present study accounts for the quantum chemical and nonlinear optical properties of the combination of para-aminobenzoic acid and 7-diethylamino 4-methyl coumarin. Three different complexes were designed, surface interaction (adsorption) and two by connecting both molecules with π-bridge benzene and biphenyl. The amino and carboxyl groups were observed to behave as strong donor and acceptor sites in all the complexes. The band gap of the adsorbed complex was found more suitable. The absorption wavelength and intensity both were seen to increase with the increase in the number of benzene rings in the π-bridge. The values of first- and second-order hyperpolarizability suggest the improved nonlinear optical responses of the introduced complexes. Additionally, the negative value of second-order hyperpolarizability suggests the possibility of the occurrence of reverse saturable absorption in these combinations. The reported work gives theoretical insights into the nonlinear optical properties of the combination of para-aminobenzoic acid and 7-diethylamino 4-methyl coumarin. The molecular modeling and the quantum chemical studies were performed with Gaussian software packages. The standard B3LYP-6-311++G(d,p) basis functionals were used for energy minimization and other spectral calculations. All the surface analyses reported here are obtained by employing Multiwfn software. The chemical reactivity was established by the global reactivity descriptors. The intramolecular interactions and charge localization were stated using inter-fragment charge transfer analysis.

Nanometer-Resolved Operando Photo-Response of Faceted BiVO4 Semiconductor Nanoparticles.

Photo(electro)catalysis with semiconducting nanoparticles (NPs) is an attractive approach to convert abundant but intermittent renewable electricity into stable chemical fuels. However, our understanding of the microscopic processes governing the performance of the materials has been hampered by the lack of operando characterization techniques with sufficient lateral resolution. Here, we demonstrate that the local surface potentials of NPs of bismuth vanadate (BiVO4) and their response to illumination differ between adjacent facets and depend strongly on the pH of the ambient electrolyte. The isoelectric points of the dominant {010} basal plane and the adjacent {110} side facets differ by 1.5 pH units. Upon illumination, both facets accumulate positive charges and display a maximum surface photoresponse of +55 mV, much stronger than reported in the literature for the surface photo voltage of BiVO4 NPs in air. High resolution images reveal the presence of numerous surface defects ranging from vacancies of a few atoms, to single unit cell steps, to microfacets of variable orientation and degree of disorder. These defects typically carry a highly localized negative surface charge density and display an opposite photoresponse compared to the adjacent facets. Strategies to model and optimize the performance of photocatalyst NPs, therefore, require an understanding of the distribution of surface defects, including the interaction with ambient electrolyte.

Infrared Nanoimaging of Hydrogenated Perovskite Nickelate Memristive Devices.

Solid-state devices made from correlated oxides, such as perovskite nickelates, are promising for neuromorphic computing by mimicking biological synaptic function. However, comprehending dopant action at the nanoscale poses a formidable challenge to understanding the elementary mechanisms involved. Here, we perform operando infrared nanoimaging of hydrogen-doped correlated perovskite, neodymium nickel oxide (H-NdNiO3, H-NNO), devices and reveal how an applied field perturbs dopant distribution at the nanoscale. This perturbation leads to stripe phases of varying conductivity perpendicular to the applied field, which define the macroscale electrical characteristics of the devices. Hyperspectral nano-FTIR imaging in conjunction with density functional theory calculations unveils a real-space map of multiple vibrational states of H-NNO associated with OH stretching modes and their dependence on the dopant concentration. Moreover, the localization of excess charges induces an out-of-plane lattice expansion in NNO which was confirmed by in situ X-ray diffraction and creates a strain that acts as a barrier against further diffusion. Our results and the techniques presented here hold great potential for the rapidly growing field of memristors and neuromorphic devices wherein nanoscale ion motion is fundamentally responsible for function.

Construction of P−N charge-transfer bridge in porous g-C3N4 for highly efficient visible-light-driven photocatalytic N2 fixation

Solar N2 fixation is a green and pollution-free technology to realize solar energy to chemical energy. Here, P doped g-C3N4 nanosheets (PCNx) with porous structure has been fabricated via a one-step calcination process for efficient ammonia generation. The optimal PCN0.6 catalyst provided an improved visible light photo-performance with an ammonia generation rate of 3110 µg L−1h−1g−1, 15 times higher than that for pristine g-C3N4 (CN). And the quantum efficiency at 400 nm monochromatic light reached 3.29%. Characterization results revealed that the implantation of P−N bonds in g-C3N4 resulted in expanded optical response, larger accessible active sites and efficient separation of electron-hole pairs than that of bulk counterpart. Wavefunction contour maps revealed a more localized charge density distribution upon P doping, leading to a favorable electron-rich structure. The calculated N2 adsorption energy and N2-TPD tests showed the strong capacity of nitrogen chem-adsorption by PCN0.6. Charge density differences and Bader charge demonstrated the electrons transfer from the P doping sites of g-C3N4 to adsorbed N2, thus activating N2 molecules for effective NH4+ generation. This work offered significant insights into the heteroatom doping engineering to construct active sites and steer the charge migration pathways in g-C3N4 for efficient photo-reduction of N2.

Charging infrastructure for electric vehicles in New Zealand

The uptake of electric vehicles (EV) is closely interlinked with the availability of charging infrastructure. Fast charging stations (FCS) can facilitate the uptake of EV, but their installation requires significant investments affecting their profitability. An optimal determination of charging locations and capacities based on associated costs can help to provide infrastructure efficiently. As initial FCS affect installations and costs in later years, a strategic infrastructure development plan over multiple years is required to expand the infrastructure to satisfy the charging demand of a growing EV fleet, while pursuing the goal of minimal costs. Based on former work, a model for the investment-optimal allocation and sizing of FCS over multiple years (including costs for grid connection) is developed. For the first time, a multi-periodic capacitated Arc-Cover Path-Cover formulation with an investment-optimal objective is proposed and applied to New Zealand. The results are analysed with respect to the locations and sizes of FCS, the impact on the coverage of traffic flows, and the related trends over time. They indicate that FCS are to be located along highly trafficked corridors in densely populated regions for being applied profitably. The chosen station locations have below-average installation costs and are capable of covering high shares of EV traffic on inter-regional and highly frequented routes.

Promising sensors for pharmaceutical pollutant adsorption using Clar’s goblet-based 2D membranes

This study focuses on the design of new 2D membranes from connected Clar’s Goblet as a potential sensor for pharmaceutical pollutants, specifically the painkiller drugs aspirin, paracetamol, ibuprofen, and diclofenac. The electronic, optical, and interaction properties are investigated using density functional theory calculations. The Clar’s Goblet membranes (CGMs) that were chosen are semiconductors with an energy gap of around 1.5 eV, according to energy gap calculations and density of states. Molecular electrostatic potential (ESP) analysis shows that CGMs have electrophilic and nucleophilic sites, suggesting their suitability for interacting with pharmaceutical pollutants. The adsorption energies confirm the chemical adsorption of pharmaceutical pollutants with diclofenac showing the strongest adsorption. The UV–Vis absorption spectra of CGMs-drug complexes are analyzed, revealing a redshift compared to the absorption spectrum of CGMs alone, confirming the adsorption of these drugs. Further analysis using hole/electron examinations indicates that the type of excitation is local excitation rather than charge transfer excitation. This study quantitatively characterized hole and electron distribution in excited states using various indices. The analysis revealed local excitation transitions and significant charge transfer between the CGMs molecule and pharmaceutical pollutants. Additionally, non-covalent interaction analysis indicates the presence of van der Waals interactions, highlighting the adsorption behavior of the drugs. These results demonstrate the potential of CGMs as a highly sensitive sensor for pharmaceutical pollutants.

Multi-charged moments and symmetry-resolved Rényi entropy of free compact boson for multiple disjoint intervals

We study multi-charged moments and symmetry-resolved Rényi entropy of free compact boson for multiple disjoint intervals. The Rényi entropy evaluation involves computing the partition function of the theory on Riemann surfaces with genus g > 1. This makes Rényi entropy sensitive to the local conformal algebra of the theory. The free compact boson possesses a global U(1) symmetry with respect to which we resolve Rényi entropy. The multi-charged moments are obtained by studying the correlation function of flux-generating vertex operators on the associated Riemann surface. Symmetry-resolved Rényi entropy is then obtained from the Fourier transforms of the charged moments. Rényi entropy is shown to have the familiar equipartition into local charge sectors upto the leading order. The multi-charged moments are also essential in studying the symmetry resolution of mutual information. The multi-charged moments of the self-dual compact boson and massless Dirac fermion are also shown to match for the cases when the associated reduced density moments are known to be the same. Finally, we numerically check our results against the tight-binding model.

Charge-lattice coupling effects in organic isomeric charge transfer crystals

One of the most important features of organic cocrystals is the interaction between electrons and lattices, which brings interesting physical phenomena. In this work, we prepared two isomeric crystals in which the isomeric donors are used to fabricate charge transfer crystals. Isomeric crystals present different electron–lattice coupling strengths to further affect the charge localization, which leads to different dielectric constants and fluorescence lifetimes. Furthermore, external magnetic field and electric field exhibit different tunability on the photoluminescence and dielectric constants of the isomeric cocrystals due to the significant differences in the coupling between the charge and lattice vibration. Overall, through fabricating isomeric organic crystals, neighbor molecular vibration dependence of electron–lattice coupling is studied, which provides a platform to further understand the lattice vibration dependent spin and optics.