Explore the vast range of titles available.

Doping of semiconductors, i.e., accurately modulating the charge carrier type and concentration in a controllable manner, is a key technology foundation for modern electronics and optoelectronics. However, the conventional doping technologies widely utilized in silicon industry, such as ion implantation and thermal diffusion, always fail when applied to two-dimensional (2D) materials with atomically-thin nature. Surface charge transfer doping (SCTD) is emerging as an effective and non-destructive doping technique to provide reliable doping capability for 2D materials, in particular 2D semiconductors. Herein, we summarize the recent advances and developments on the SCTD of 2D semiconductors and its application in electronic and optoelectronic devices. The underlying mechanism of STCD processes on 2D semiconductors is briefly introduced. Its impact on tuning the fundamental properties of various 2D systems is highlighted. We particularly emphasize on the SCTD-enabled high-performance 2D functional devices. Finally, the challenges and opportunities for the future development of SCTD are discussed.

Traditionally, the surface charge number (SCN) of permanently charged soils/clay minerals is believed to be unaffected by environmental pH. However, recent studies have revealed the occurrence of polarization-induced covalent bonding between H + and the surface O atoms of permanently charged clay minerals. This discovery challenges the traditional notions of “permanently charged soil” and “permanently charged clay mineral”. The purpose of this study is to confirm that there are no true “permanently charged clay” or “permanently charged soil”. In this study, the SCNs of two permanently charged clay minerals, two variably charged clay minerals, five permanently charged soils (temperate soils), and four variably charged soils (tropical or subtropical soils) were measured at different pH values using the universal determination method of SCN. The results showed that: (1) The SCNs of the permanently/variably charged soils and clay minerals decreased significantly with decreasing pH; (2) the SCN of montmorillonite decreased less with decreasing pH than the SCNs of variably charged minerals, whereas the SCN of illite decreased to nearly the same extent, indicating strong polarization-induced covalent bonding between H + and the surface O atoms of illite; (3) the SCNs of permanently charged soils decreased to a similar extent as those of variably charged soils with decreasing pH. This study demonstrated that the concepts, “permanently charged clay mineral” or “permanently charged soil”, are questionable because of the polarization-induced covalent bonding between H + and the surface O atoms of clay minerals.

The PNP nanotransistor, consisting of emitter, base, and collector regions, exhibits distinct behavior based on surface charge densities and various electrolyte concentrations. In this study, we investigated the impact of surface charge density on ion transport behavior within PNP nanotransistors at different electrolyte concentrations and applied voltages. We employed a finite-element method to obtain steady-state solutions for the Poisson–Nernst-Planck and Navier–Stokes equations. The ions form a depletion region, influencing the ionic current, and we analyze the influence of surface charge density on the depth of this depletion region. Our findings demonstrate that an increase in surface charge density results in a deeper depletion zone, leading to a reduction in ionic current. However, at very low electrolyte concentrations, an optimal surface charge density causes the ion current to reach its lowest value, subsequently increasing with further increments in surface charge density. As such, at V app = + 1 V and C 0 = 1 mM , the ionic current increases by 25% when the surface charge density rises from 5 to 20  mC . m - 2 , whereas at C 0 = 10 mM , the ionic current decreases by 65% with the same increase in surface charge density. This study provides valuable insights into the behavior of PNP nanotransistors and their potential applications in nanoelectronic devices.

This research delved into the influence of mesoporous silica’s surface charge density on the adsorption of Cu 2+ . The synthesis of mesoporous silica employed the hydrothermal method, with pore size controlled by varying the length of trimethylammonium bromide (C n TAB, n = 12, 14, 16) chains. Gas adsorption techniques and transmission electron microscopy characterized the mesoporous silica structure. Surface charge densities of the mesoporous silica were determined through potentiometric titration, while surface hydroxyl densities were assessed using the thermogravimetric method. Subsequently, batch adsorption experiments were conducted to study the adsorption of Cu 2+ in mesoporous silica, and the process was comprehensively analyzed using Atomic absorption spectrometry (AAS), Fourier transform infrared (FTIR), and L3 edge X-ray absorption near edge structure (XANES). The research findings suggest a positive correlation between the pore size of mesoporous silica, its surface charge density, and the adsorption capacity for Cu 2+ . More specifically, as the pore size increases within the 3–4.1 nm range, the surface charge density and the adsorption capacity for Cu 2+ also increase. Our findings provide valuable insights into the relationship between the physicochemical properties of mesoporous silica and the adsorption behavior of Cu 2+ , offering potential applications in areas such as environmental remediation and catalysis.

Triboelectric nanogenerators (TENGs), a type of promising micro/nano energy source, have been arousing tremendous research interest since their inception and have been the subject of many striking developments, including defining the fundamental physical mechanisms, expanding applications in mechanical to electric power conversion and self-powered sensors, etc. TENGs with a superior surface charge density at the interfaces of the electrodes and dielectrics are found to be crucial to the enhancement of the performance of the devices. Here, an overview of recent advances, including material optimization, circuit design, and strategy conjunction, in developing TENGs through surface charge enhancement is presented. In these topics, different strategies are retrospected in terms of charge transport and trapping mechanisms, technical merits, and limitations. Additionally, the current challenges in high-performance TENG research and the perspectives in this field are discussed. Tactics for modulating the surface charge density of TENGs by material optimization are summarized. Strategies for manufacturing ultra-high electrode charge density TENGs utilizing advanced circuit designs are demonstrated. The synergistic effects of material optimization and advanced circuit design are presented. Current challenges in the field of TENGs are discussed.

A triboelectric nanogenerator (TENG) with an organic nanocomposite electret thin film as the triboelectric layer for mechanical energy harvesting was investigated systematically. In combination with corona charging, a TENG was fabricated by using embedded-nanocapacitor-structure polytetrafluoroethylene (PTFE) impregnated with gold nanoparticles (Au-NPs). The output performances, stability, and durability of the TENGs with Au-PTFE nanocomposite films were characterized after being washed in water. It was found that the output current increases by 70% and the equivalent surface charge density (ESCD) reaches 85 μC/m 2 in comparison to the virgin PTFE film. Such outstanding performance is likely due to the equivalent nanocapacitors between the Au-NPs and PTFE molecules, which serve as nano charge traps in the nanocomposite electret film under negative high-voltage corona charging. This work not only expands the practical applications of TENGs, but also opens up new possibilities for the development of high performance triboelectric materials.

We describe a novel method to measure the surface charge densities on optical fibers placed in the vicinity of a trapped ion, where the ion itself acts as the probe. Surface charges distort the trapping potential, and when the fibers are displaced, the ion's equilibrium position and secular motional frequencies are altered. We measure the latter quantities for different positions of the fibers and compare these measurements to simulations in which unknown charge densities on the fibers are adjustable parameters. Values ranging from −10 to +50 e µm−2 were determined. Our results will benefit the design and simulation of miniaturized experimental systems combining ion traps and integrated optics, for example, in the fields of quantum computation, communication and metrology. Furthermore, our method can be applied to any setup in which a dielectric element can be displaced relative to a trapped charge-sensitive particle.

Gas-insulated power transmission lines (GILs) can replace cables and overhead transmission lines, playing an important role in DC transmission systems. However, the influence of surface charge accumulation on insulation reliability cannot be ignored as the operational voltage of the DC GIL increases. In this paper, the measurement methods for the insulator surface potential are summarized, including, dust maps, the Pockels effect method, and the electrostatic probe method. Then, a typical surface charge inversion algorithm is introduced. The main influencing factors of surface charge accumulation are analyzed, such as the applied voltage, insulation gas, insulator shape, and temperature. The charge accumulation pathway is revealed. Furthermore, methods for inhibiting the accumulation of surface charges and promoting the dissipation of accumulated charges are introduced to reduce the surface charges on insulators. Finally, the development direction of DC GIL insulators is predicted. We anticipate that the online monitoring of surface charge distribution, clarifying the percentage of charge accumulation pathways, and optimizing the insulator casting process will be the research directions for the insulator surface charge topic in the future. This article provides a comprehensive understanding of the surface charges of GIL insulators and a reference for the insulation design of DC GILs.

Surface flashover of spacers is a key factor limiting the application of HVDC GIS/GIL, while the charge accumulation on the surface of the spacer could have a potential adverse effect on the surface flashover voltage. This paper discusses the laws regarding distribution patterns of surface charges and the related mechanisms. The field-dependent property is discussed in detail to comprehensively illustrate the charge transport mechanism and explain the research differences regarding different surface charge patterns obtained by previous researchers. In addition, the main surface charge control methods for epoxy resin are summarized and discussed. The potential research directions of charge control methods and key points in manufacturing of spacers used in HVDC GIS/GIL are also explored.

From molecules and particles to macroscopic surfaces immersed in fluids, chemical reactions often endow interfaces with electrical charge which in turn governs surface interactions and interfacial phenomena. The ability to measure the electrical properties of a material immersed in any solvent, as well as to monitor the spatial heterogeneity and temporal variation thereof, has been a long-standing challenge. Here, we describe an optical microscopy-based approach to probe the surface charge distribution of a range of materials, including inorganic oxide, polymer, and polyelectrolyte films, in contact with a fluid. The method relies on optical visualization of the electrical repulsion between diffusing charged probe molecules and the unknown surface to be characterized. Rapid image-based measurements enable us to further determine isoelectric points of the material as well as properties of its ionizable chemical groups. We further demonstrate the ability to optically monitor chemically triggered surface charge changes with millisecond time resolution. Finally, we present a scanning-surface probe technique capable of diffraction-limited imaging of spatial heterogeneities in chemical composition and charge over large areas. This technique will enable facile characterization of the solid—liquid interface with wide-ranging relevance across application areas from biology to engineering.