Spatial Charges Research Articles

Infrastructuring informal urbanism: Negotiation of water, electricity, and natural gas in urban villages in Chengdu, China

Infrastructure such as water, electricity, and natural gas fundamentally underpins informal housing and industrial development in urban villages. Yet how the infrastructure is built, maintained, and governed, and what are the underlying mechanisms, remain peripheral to existing literature and policy agenda. This study addresses this gap by incorporating a socio-technical approach to infrastructure into informal urbanism to understand the negotiation of water, electricity, and natural gas in two neighboring urban villages in Chengdu, China. Four rounds of fieldwork and in-depth interviews with various stakeholders found highly precarious provision of infrastructure in urban villages. Its spatial layout, facilities, charges, quality control, and maintenance rest uneasily on, and then in turn shape, the development of informal renting markets and industries in different urban villages, especially when considering the cross-sectional interactions between different types of infrastructure. These processes are dominated by stakeholders’ commercial logics embedded in informal urbanism, including the urban village and infrastructure providers’ profit-seeking strategies, enterprises and migrants’ cost-saving behaviors, and the governments’ purposive absence in governing infrastructure, which leads to difficulties in meeting urban village residents’ needs for qualified infrastructure. This study unravels the “black box” of infrastructure in urban villages and puts forward inclusive planning strategies to promote infrastructure in urban villages.

An assessment of electroneutrality implementations for accurate electrochemical ion transport models

During the diffusion and migration of ions in electrolytes, the electrodynamic ion-ion interactions prevent charge separation despite different ionic mobilities, ultimately enforcing electroneutrality in the bulk electrolyte. To model ion transport accurately, a method to enforce electroneutrality must be implemented. In this study, four strategies to implement electroneutrality are discussed and evaluated. The ion distributions that result from a transport model with the different electroneutrality implementations are calculated, considering various electrolytes and sets of electrochemical parameters. The meaningfulness and applicability of each implementation are assessed through spatial charge accumulations, transference numbers, and experimental data from the literature. Combining the electrochemical ion transport models with the electroneutrality constraint for all ions is shown to result in an overdetermined system of equations if the driving forces are calculated under neglection of diffusion potentials. The often-reported model simplification of using the electroneutrality constraint to resolve the transport of one specific species explicitly results in non-physically correct mass transport. A practical approach to precisely describe the measured physicochemical ion movements is obtained by equilibrating spatial charges with the ion conduction for every time step in the ion transport model, which is reasonably applicable to multi-ion systems in three-dimensional frameworks. This comprehensive assessment aims to guide readers in selecting an appropriate electroneutrality implementation framework for ion transport models.

Anions mediated electron-rich metalloporphyrin ionic framework as recyclable catalyst for conversion of urea into cyclic carbonates

As CO2 typical derivative, urea has the potential to be uniquely economical and green raw materials in generating cyclic carbonates via alcoholysis. Nonetheless, the existing processes for obtaining cyclic carbonates from urea alcoholysis reaction pose considerable challenges in achieving efficient catalyst recycling. Functional organic heterogeneous compounds are emerging materials for catalysis and enhanced reusability due to their large number of coordination sites, but they still fall short of effectively modulating the charge distribution of metal ions. Herein, drawing inspiration from the capacity of ionic liquids (ILs) to effectively control the distribution and transfer of spatial charges within materials, metalloporphyrin ionic framework catalysts were developed by combining metal ions and ILs for the transformation of urea into cyclic carbonates. This heterogeneous catalyst, featuring an adjustable structure and stable metal coordination sites on its surface, exhibits remarkable stability, resulting in a 2.7-fold reduction in catalyst dosage compared to other reported supported catalysts. Based on detailed experiments and DFT calculations, this tunable performance can be mainly explained by the effect of porphyrin zinc (II) and IL anions via molecular engineering. These atom-economical transformations provide a direct and selective access to valuable compounds from cheap and available urea using an efficient organic heterogeneous catalyst.

Surface Functionalization and Defect Construction of SnO2 with Amine Group for Enhanced Visible‐Light‐Driven Photocatalytic CO2 Reduction

AbstractPhotocatalytic CO2 reduction to hydrocarbon fuels through solar energy provides a feasible channel for reducing CO2 emission and resource depletion. Nevertheless, severe charge recombination and high energy barrier limit the CO2 reduction efficiency. Herein, a surface amine‐functionalized SnO2 with oxygen vacancies (A‐Vo‐SnO2) is fabricated to achieve visible‐light‐driven photocatalytic CO2 reduction. Specifically, amino groups modified onto the surface of the catalyst can provide more active sites to promote the adsorption of CO2. Meanwhile, the synchronously induced oxygen defect level reduces the band‐gap energy and expands the light‐absorption region from UV light to visible light. The oxygen vacancies can modulate the electronic structure and work as the separation centers of spatial charges, thus promoting the interfacial charge transfer efficiency and providing more catalytic sites, as evidenced by experimental observation and theoretical calculation. As expected, this A‐Vo‐SnO2 exhibits a CH4 evolution rate of 17.27 µmol g−1 h−1 without adding sacrificial agent and co‐catalyst, much higher than 5.98 µmol g−1 h−1 of pure SnO2. This work can provide significant inspiration for the design of defect engineering based on visible‐light‐driven photocatalysts towards photocatalytic CO2 conversion.

Numerical Simulation Study on the Mechanism of Plasma Dissociation of Carbon Dioxide in Atmospheric Pressure Packed-Bed Reactors

This article presents a comprehensive study on the streamer propagation and electric field distribution within a two-dimensional fluid model of a packed bed reactor (PBR) filled with carbon dioxide, utilizing the PASSKEy simulation platform. The research delves into the spatiotemporal evolution of electron density, electric fields and key plasma species in the discharge process. The model simulates a PBR with layered dielectric spheres, indicates that the inner sides of the first and second layers of dielectric spheres are not the primary regions for reactions such as CO<sub>2</sub> dissociation; instead, the main regions are along the streamer propagation path and the outer side of the first layer of dielectric spheres. The study by examining the propagation of streamers in the presence of an electric field, highlighting the influence of anode voltage rise and dielectric polarization on local electric field enhancement. This enhancement leads to increased electron density and temperature, facilitating streamer propagation and the formation of filamentary microdischarges and surface ionization waves. The article provides a detailed analysis of the local electric field evolution at specific points within the PBR. The research further investigates the spatiotemporal dynamics of spatial and surface charges, revealing that negative charges concentrate within the streamer and on the dielectric surface, with densities significantly higher than positive charges. The positive charges' distribution is closely related to the streamer's path, and over time, they come to dominate the charge distribution in the discharge space. The study also explores the surface charge deposition on the dielectric spheres, discusses the evolution trends of the distribution. Additionally, the article discusses the temporal and spatial evolution of key plasma species, including ions and radicals, and their contribution to the overall discharge characteristics. The production mechanisms of carbon monoxide particles, carbon dioxide ions, and oxygen ions are analyzed, with a focus on their spatial distribution and correlation with electron density. The study concludes with an examination of the energy deposition within the PBR, integrating the spatial energy deposition of electrons and major positive ions. The results indicate a total energy deposition value of approximately 1.428 mJ/m, with carbon dioxide ions accounting for 8.8% of this value.

Voltammetric analysis of mephenoxalone drug in pharmaceutical and biological samples using novel screen-printed sensor with boron-doped diamond electrode

A novel screen-printed sensor (SPE) with boron-doped diamond electrode (BDDE) for determination of a muscle relaxant and mild anxiolytic mephenoxalone (MNL) was developed. The sensor utilizes the electrochemical oxidation of MNL, which was firstly studied in aqueous solution using oxygen terminated BDDE. MNL provided an irreversible anodic signal at a potential of + 1380 mV (vs. Ag/AgCl/KCl sat.) over a wide pH range. Britton-Robinson buffer (pH 9) was selected as a suitable electrolyte and the square-wave voltammetric method (SWV) was developed. The low detection limit (55 nmol L–1), wide linear dynamic range (0.1–30 µmol L−1), and good recovery in the analysis of model and pharmaceutical samples (RSD < 1.77%) were attained. Subsequently, the new method was successfully transferred to SPE, which can find application in point-of-care testing. These sensors proved excellent sensitivity and reproducibility in the analysis of biological samples (RSD < 4.94%) without pretreatment and no need of electrolyte. Based on gas chromatography with mass spectrometry (GC-MS) analysis of preparative electrolysis products, a mechanism of the electrochemical oxidation of MNL was proposed, describing the oxidative cleavage of the alkoxybenzene ring. These results were supported with HOMO spatial distribution calculations and atomic charges calculations for arising radical cations, and with spectroelectrochemical measurements.

Strongly Localized Moiré Exciton in Twisted Homobilayers.

Artificially molding exciton flux is the cornerstone for developing promising excitonic devices. In the emerging hetero/homobilayers, the spatial separated charges prolong exciton lifetimes and create out-plane dipoles, facilitating electrically control exciton flux on a large scale, and the nanoscale periodic moiré potentials arising from twist-angle or/and lattice mismatch can substantially alter exciton dynamics, which are mainly proved in the heterostructures. However, the spatially indirect excitons dynamics in homobilayers without lattice mismatch remain elusive. Here the nonequilibrium dynamics of indirect exciton in homobilayers are systematically investigated. The homobilayers with slightly twist-angle can induce a deep moiré potential (>50 meV) in the energy landscape of indirect excitons, resulting in a strongly localized moiré excitons insulating the transport dynamics from phonons and disorder. These findings provide insights into the exciton dynamics and many-body physics in moiré superlattices modulated energy landscape, with implications for designing excitonic devices operating at room temperature.

Construction of 0D/1D CdS/g-C3N4 Z-scheme heterojunction for highly selective photocatalytic benzylamine oxidative coupling

The efficient solar-to-chemical energy conversion system is a green and cost-effective approach for producing high-value-added chemicals in chemical industry, which is highly demanded to develop. Photocatalytic C–N coupling of benzylamine into economic N-benzylidenebenzylamine is a great potential method for alternative conventional organic synthesis. In this work, a zero-dimensional/one-dimensional CdS/g-C3N4 Z-scheme heterojunction was constructed via in situ growing CdS quantum dot onto g-C3N4 nanorod surface for enhancing the spatial separation of charge carriers and maintaining the strong redox ability of the photogenerated charges and applied simultaneously in photocatalytic C–N coupling of benzylamine. This enables 20 wt% CdS/g-C3N4 to exhibit a remarkable photocatalytic performance enhancement for the production of C–N coupled product of benzylamine with the optimal yield of 199.79 μmol which is approximately 4.3 folds than those of pristine g-C3N4 under 2 h visible irradiation. Moreover, benzylamine conversion of approximately 90% within 100 h can be obtained in a gram scale-up reaction. By means of controlled photoelectric chemistry and in situ electron spin resonance spectroscopy experiments, possible spatial photogenerated charges separation and benzylamine conversion mechanisms on the Z-scheme junction were investigated in detail. This work paves a promising strategy for constructing zero-dimensional/one-dimensional Z-scheme heterojunction for the photocatalytic synthesis of high-value-added products.

Novel Co3O4@TiO2@CdS@Au double-shelled nanocage for high-efficient photocatalysis removal of U(VI): Roles of spatial charges separation and photothermal effect

Effective spatial separation and utilization of photogenerated charges are critical for photocatalysis process. Herein, novel Co3O4 @TiO2 @CdS@Au double-shelled nanocage (CTCA) with spatially separated redox centers was synthesized by loading Co3O4 and Au NP cocatalysts on the inner and outer surfaces of Z-scheme heterojunction (TiO2 @CdS). The reduction rate constant of U(VI) by CTCA reached 0.218 min−1 under simulated sunlight irradiation, which was 6.6, 3.2 and 36.3 times than that of monolayer CTCA (0.033 min−1), CTC (0.068 min−1) and CT (0.006 min−1). The full-spectrum light-assisted photothermal catalytic performance can enable CTCA to remove 98.8% of U(VI) and degrade nearly 90% of five organic pollutants simultaneously. Detailed characterizations and theory calculations revealed that the photogenerated holes and electrons in CTCA flow inward and outward. More importantly, Co3O4 acts as a “nano heater” to generate the photothermal effect for further enhancing the charge transfer and accelerating the surface reaction kinetics. Meanwhile, the photogenerated electrons and superoxide radicals play a dominant role in reducing the adsorbed U(VI) to insoluble (UO2)O2·2H2O(s). This work provides valuable input toward a novel double-shelled hollow nanocage reactor with excellent photothermal catalysis ability for efficient recovery U(VI) from uranium mine wastewater to address environmental contamination issues.

Chlorine Adsorption on TiO2(110)/Water Interface: Nonadiabatic Molecular Dynamics Simulations for Photocatalytic Water Splitting

Chloride is one of the most abundant ions in sea water, which is more available than fresh water. Due to lack of H2O adsorbate states near the valence band maximum (VBM) edge, the difficulty of water dissociation incidents has been reported on the rutile TiO2 surface as the excitation energy is around the band gap energy of TiO2. It is interesting whether the extra chloride can be a benefit to the water dissociation or not. In this study, the models of chlorine adatoms placed on the rutile TiO2 (110)/water interface are constructed using ab initio methods. The time-dependent spatial charges, bond-lengths of water molecules, and Hirshfeld charges are calculated by real-time time-dependent density functional theory and the Ehrenfest dynamics theory for investigating the excited state nonadiabatic dynamics of water dissociation. This study presents two photoinduced water-splitting pathways related to chlorine and analyzes the photogenerated hole along the reactions. The first step of water dissociation relies on the localized competition of oxygen charges between the dissociated water and the bridge site of TiO2 for transforming the water into hydroxyl and hydrogen by photoinduced driving force.

Interface characteristics of graphene/ZnS hybrid-dimensional heterostructures.

Graphene/ZnS hybrid-dimensional heterostructure is an excellent combination to regulate and improve the conductivity and sensitivity of components, in which the interface effects have crucial impacts on the performance of devices. In this work, we investigate the interface characteristics of Graphene/ZnS 2D/3D heterostructures. X-ray photoelectron spectra show that the ZnS binding energy shifts to lower energy by 0.3 eV after forming heterojunction with graphene. The fluorescence and absorption spectra confirm the luminescence enhancement and blue-shift of the absorbance edge of ZnS caused by graphene. The composition of Graphene/ZnS heterostructure facilitates separation and transfer of spatial charges, resulting in rapid electron transport.

Enhanced spatial charge separation at surface & interface via GO/MoS2/Ag3PO4 ternary Z-scheme heterostructure for nitrogen photo-fixation

Enhancing spatial charge separation is an efficient strategy for the improvement of photocatalytic performance. Herein, an ammonia synthesis approach was proposed with an in-situ grown ternary GO/MoS2/Ag3PO4 Z-scheme heterostructure photocatalytic system to promote spatial charge separation at surface & interface. Owing to the decent electrical and thermal conductivity properties of GO, ternary photocatalyst delivered evidently enlarged surface area, promoted spatial charges separation and significantly enhanced N2 photo-fixation efficiency under irradiation of visible light. Through the synergistic effect of electron transportation on GO and the efficient separation of electron-hole pairs on heterojunction, the transportation and separation of photo-generated charges can be realized on both surface and interface, leading to better harvest and utilization of light illumination. The possible Z-scheme heterostructure mechanism for N2 photo-fixation reaction was explored, which not only offers a new approach for design of heterostructure photocatalysis system but also provides a novel strategy for enhanced spatial charges separation.

Generation of perfect optical vortex arrays by an optical pen.

Recently, perfect optical vortexes (POVs) have attracted substantial attention, because they have an orbital angular momentum (OAM) and the beam diameter is independent of the topological charges. There are numerous innovative results that have been found by modulating the POV optical field. However, methods for controlling the arbitrary parameters of POV are lacking. In this paper, we use the optical pen to overcome this problem. The optical pen is a high-precision optical field modulation method construction based on the relationship between the optical path difference and phase. Based on this method, we have achieved POV arrays with controllable arbitrary parameters in free space, including the spatial position, numbers, topological charges, beam diameter, and amplitude. This work can be applied not only in the fields of optical tweezers, particle manipulation, and super-resolution microscopic imaging, but also will promote the development of optical communication, quantum information coding, and so on.

Voltammetric study of new psychoactive substance 3‐fluorophenmetrazine

AbstractElectrochemical oxidation of the new psychoactive substance 3‐fluorophenmetrazine (FPM) was studied in phosphate buffers by cyclic voltammetry and differential pulse voltammetry (DPV) on a glassy carbon electrode. The redox potential of FPM in buffered solution strongly depends on pH. Cyclic voltammetry behavior shows the partial influence of adsorption on the electrode process not allowing detailed analysis of the individual steps of the reaction scheme, it means the involvement of electron transfer (E) and chemical reaction (C). Nevertheless, the irreversible shape of the cyclic voltammogram is explained by the participation of hydroxylation nucleophilic addition of water (hydroxylation) after two‐electron/two‐proton oxidation of molecule at the tetrahydro‐1,4‐oxazine ring. The suggested mechanism leading to hydroxylated derivative 2‐(3‐fluorophenyl)‐3‐methyl‐5‐hydroxymorfolin is supported by the calculated highest occupied molecular orbital spatial distribution and atomic charges calculations for electrochemically formed radical cation. Infrared spectroelectrochemistry performed during oxidation in acetonitrile/water also supported the formation of this product.The analytical method of FPM determination on glassy carbon electrode was developed using DPV with an attained limit of detection = 4.7 μmol/L in phosphate buffer of pH 9. The linear range of the calibration curve is from 7.0 to 107.00 μmol/L, correlation coefficient (r) = 0.9988.

Multi-Molecule Field-Coupled Nanocomputing for the Implementation of a Neuron

In recent years, several alternatives have been proposed to face CMOS scaling problems. Among these, molecular Field-Coupled Nanocomputing is a paradigm that encodes information in the spatial charges distribution and promises to consume a minimal amount of power. In this technology, circuits have always been designed using the same molecule type, and logic functions are obtained through specific layouts. This work demonstrates that multi-molecule circuits, which use different kinds of molecules in the same layout, enhance the circuit features and set up a new way to conceive molecular Field-Coupled Nanocomputing. In particular, by inserting different molecules with specific characteristics into appropriate layout positions, it is possible to obtain an artificial neuron behavior using the Majority Voter layout.

Low-frequency noise characterization of AlGaN/GaN HEMTs with and without a p-GaN gate layer

In this paper, low-frequency noise characteristics of commercial AlGaN/GaN high electron mobility transistors with different substrates and devices with and without a p-GaN gate layer are measured and discussed. The noise power spectral density (PSD) of various devices are compared and analyzed under linear-region operation. The 1/f noise behavior exhibits carrier number fluctuation as the dominant cause. Devices with p-GaN gate layer fabricated on Si substrate show the highest normalized noise PSD. Results show that not only flicker noise (1/f noise) exists but that it also accompanied by generation–recombination noise (g–r noise) in the device on SiC substrate. The extracted g–r noise related traps show an activation energy of ∼0.37 eV, which is mostly caused by spatial charges trapping/detrapping with the deep acceptor in the GaN buffer layer.

The first study of triazole fungicide difenoconazole oxidation and its voltammetric and flow amperometric detection on boron doped diamond electrode

Triazole pesticides act as sterol synthesis inhibitors and have been considered as redox-inactive with a variety of electrode materials. In this study, electrochemical oxidation of the fungicide difenoconazole (DFC) was studied in aqueous solutions on oxygen terminated boron doped diamond electrode. It provided a pH-independent irreversible anodic peak at a very positive potential of ca +1.75 V (vs. Ag/AgCl) in acidic media, which could be used for its quantitation in batch voltammetry and flow injection analysis with amperometric detection. The attained detection limits for the determination of DFC in 0.1 mol L−1 HNO3 / phosphate buffer pH 2.0 were 0.049 μmol L−1 for differential pulse voltammetry and 1.58 μmol L−1 for FIA-ED. The former method did not suffer from any significant matrix interferences or interferences of other fungicides and yielded acceptable percentage recovery values (ranging from 96% to 107%) for DFC determination in model river water samples. Similar results comparing both methods at a 95% confidence level were obtained for DFC determination in pesticide preparations. Further, an oxidation mechanism leading to hydroxylated derivative of DFC and subsequent formation of a quinone was suggested. Results were supported with HOMO spatial distribution calculations and atomic charges calculations for arising radical cations.

BT-30 Ceramic Electrophysical Properties

A total complex resistance (impedance) method is used to study the electrophysical characteristics of (BeO + TiO2)-ceramics modified with TiO2 micro- and nanoparticles in an amount of 30 wt.% (BT-30). Dispersion of the actual e′ and imaginary e′′ components of the dielectric permittivity component and specific conductivity in the frequency range from 100 Hz to 100 MHz from room temperature to the boiling point of liquid nitrogen are determined. High values of e′ and e′′ in the low-frequency range are typical for structurally inhomogeneous materials due to the accumulation of electric charges at the surface and within microcrystals. Two dielectric relaxation processes associated with electrical conductivity within the body and at the surface of ceramics are detected for the first time. An increase in conductivity with an increase in the microwave field frequency above 1 MHz is explained by the appearance of a current relaxation component. The activation energy of the static resistance of ceramic specimens is determined as a function of the reciprocal temperature that depends little on the weight content of TiO2 nanoparticles and varies in the range of 0.024 – 0.10 eV This also confirms the existence of two independent conduction processes, weakly dependent on the nanoparticle content in the ceramic composition. With placement of ceramic in a high-frequency electric field, spatial charges are formed, the field of which contributes to creation of additional polarization and dielectric losses.

Transparent Bipolar Thin Film Transistors Based on Topological Insulator of Magneto-Resistive Effect.

Thin film transistors using SiOC insulation film generated a very large IDS current with tunneling phenomena due to the occurrence of space charge limit current due to magnetic resistance effect. When SiOC gate insulation barrier transistor characteristics were investigated, transmission characteristics of bi-directional were observed, low current at levels ~10-7 A, but switching characteristics were superior to or greater than 10-10 A. SiOC Thin Film Insulation Characteristics are a good material for observing magnetic resistance effects, SiOC Transistors without channels clearly demonstrate the difference in spatial charges due to electromagnetic phenomena, and even in low-current insulation, nano-current flows at high speed. The current due to magnetic resistance is bi-directional and has an alternating current that flows in both directions at 0 V.

Chiral Hall effect in strained Weyl semimetals

In this paper, the chiral Hall effect of strained Weyl semimetals without any external magnetic field is proposed. Electron-phonon coupling emerges in the low-energy fermionic sector through a pseudogauge potential. We show that, by using chiral kinetic theory, the chiral Hall effect appears as a response to a real time-varying electric field in the presence of structural distortion and it causes spatial chirality and charges separation in a Weyl system. We also show that the coupling of the electrons to acoustic phonons as a gapless excitation leads to emerging an optical absorption peak at $\omega=\omega_{el}$, where $\omega_{el}$ is defined as a characteristic frequency associated with the pseudomagnetic field. We also propose the strain-induced planar Hall effect as another transport signature of the chiral-anomaly equation.