Charge Layer Research Articles

Low-temperature regulated interfacial polymerization of nanofiltration membrane for efficient Li+/Mg2+ separation

Selectively removing Mg2+ and enriching Li+ from salt lakes using positively charged polyamide nanofiltration (NF) membranes based on Donnan exclusion theory and size sieving effect is expected to address the issue of lithium resource scarcity. However, simultaneously achieving high selectivity and permeability remains a challenge for the currently reported membranes. In this study, we developed a novel positively charged NF membrane by the strategy of low-temperature-induced interfacial polymerization (IP). Low-temperature conditions during the IP reaction regulated the diffusion of amine monomers, resulting in changes in the morphology, chemical composition, and surface properties of the polyamide (PA) layer. Consequently, the obtained membrane features a positively charged PA layer with a relatively loose structure, owing to the low temperature slowing down both the amine monomer diffusion and the IP reaction, which finally reduces the crosslinking degree. The optimal NF membrane prepared in this study with a lower N/O ratio of 0.75 exhibited high water permeance (10.2 L m−2 h−1 bar−1) compared to the pristine membrane prepared at room temperature, high Li+/Mg2+ separation selectivity (29.9), excellent stability, and the purity of Li+ reached 60.0 %. Moreover, after two-stage filtration of the simulated brine using the prepared NF membrane, the Mg2+/Li+ mass ratio dropped significantly from the initial 40 in the initial feed solution to 0.22 in the final permeate solution, demonstrating its considerable potential for practical application in Li+ and Mg2+ separation. Since the high positive charge of the membrane also causes certain lithium rejection, future research should focus on optimizing the membrane charge for more efficient lithium extraction with high recovery.

Preparation of hybrid nanofiltration membranes based on Schiff base reaction for hard water softening

To obtain positively charged layer and achieve high divalent cation rejection, a novel nanofiltration (NF) membrane was successfully fabricated by utilizing polyethyleneimine (PEI), newly fabricated polyacrolein (PA) and amine silane coupling agent γ-aminopropyl triethoxysilane (APTES). The PA was synthesized via radical polymerization to avoid the migration and volatilization of small molecule in the typical coating process, making NF membranes even with great stability. On the one hand, the PEI crosslinked with PA through Schiff base reaction; on the other hand, the in-situ hydrolysis self-polycondensation of APTES generated loose networks with Si-O-Si bonds which provided the permeation channel for water and accordingly boosted the water permeance. The water permeance of the optimal PEI/PA/APTES membrane could reach 16.9 L·m-2·h-1·bar-1 and the Mg2+ and Ca2+ rejections were 98.8% and 97.3%, respectively, better than those of commercial NF membranes, breaking up the “trade off” effect. This study prepared a high-performance PEI/PA/APTES hybrid NF membrane oriented for hard water softening in tap water and brackish water via the non-interfacial macromolecule crosslinking coating method.

Enhancement effects of Ga-Gd Co-doping on the structure, conductivity, and interfacial polarization of CeO2-based electrolytes

Gd0.1Ce0.9-xGaxO2-δ (x = 0, 0.04,0.07, 0.12) are synthesized via the citric acid-EDTA combustion method as an electrolyte material for intermediate-temperature solid oxide fuel cells. XRD and Rietveld refinement revealed that the material exhibits a single-phase cubic fluorite structure. SEM and EDS analyses demonstrated that the incorporation of Ga ions improved the sample's density, increased the grain size, and provided better element dispersion. XPS analysis confirms that Ga-Gd co-doping leads to increased oxygen vacancy concentration and modifies the oxidation states of Ce. Impedance spectroscopy results indicated that Ga-Gd co-doped ceria has higher ionic conductivity and lower activation energy compared to Gd single-doped ceria. In comparison to Gd0.1Ce0.9O1.95, the best-performing Gd0.1Ce0.83Ga0.07O2-δ achieved nearly a 26-fold increase in ionic conductivity and a 66 % reduction in activation energy. The clearance coefficient of Gd0.1Ce0.83Ga0.07O2-δ reached 100.95, while the blocking factor decreased by nearly 73 % compared to Gd0.1Ce0.9O1.95. The incorporation of Ga ions led to a nearly one order of magnitude reduction in the dissipation of oxygen vacancy concentration in the space charge layer, with the potential decreasing from 0.3971V (Gd0.1Ce0.9O1.95) to 0.3117V (Gd0.1Ce0.83Ga0.07O2-δ). Dielectric studies clarified the contribution of the Gd-Ga synergistic effect on interfacial polarization. In terms of single-cell performance, the NiO-GDC| Gd0.1Ce0.83Ga0.07O2-δ|LSCF cell exhibited higher power density and current density, particularly showing a 42.9 % performance improvement at 650 °C compared to NiO-GDC|Gd0.1Ce0.9O1.95|LSCF. Density functional theory calculations indicated that the incorporation of Ga ions effectively suppresses the electronic conductivity of CeO2 and significantly reduces the formation energy, binding energy, and migration barrier of oxygen vacancies. Therefore, Ga-Gd co-doping can be regarded as an effective strategy for enhancing the performance of ceria-based electrolytes in IT-SOFCs.

New approaches to enhancing the performance of ceria-based electrolytes: A study on the microstructure, ionic conductivity, and mechanical properties of Cu-Gd Co-doping

This study addresses the performance limitations of traditional SOFC electrolytes at intermediate temperatures by synthesizing Cu-Gd co-doped ceria-based electrolytes, Gd0.1Ce0.9-xCuxO2-δ (x=0.04, 0.07, 0.10), using the citric acid-EDTA combustion method. This aims to enhance the ionic conductivity and mechanical stability of solid oxide fuel cells (SOFC) at intermediate to high temperatures. XRD and Rietveld refinement indicate that the introduction of Cu ions has not disrupted the original single-phase cubic fluorite structure of Gd0.1Ce0.9O1.95. SEM and EDS analyses indicate that Cu incorporation increased grain size and improved elemental distribution. XPS analysis confirmed that Cu-Gd co-doping increased the concentration of oxygen vacancies and hindered the reduction of Ce4+. Density functional theory calculations suggest that Cu addition effectively suppressed electronic conductivity in the Gd0.1Ce0.9O1.95 system and significantly lowered the formation, binding, and migration energy barriers of oxygen vacancies. EIS analysis revealed that the sample with x=0.07 had a 20 % reduction in ionic conduction activation energy and exhibited the highest ionic conductivity of 0.013 S/cm at 750°C, two orders of magnitude higher than that of singly doped Gd0.1Ce0.9O1.95. This enhancement is attributed to a certain extent to the scavenging rate of Gd0.1Ce0.83Cu0.07O2-δ reaching 22.30, while the blockage factor has decreased by nearly 60 % compared to Gd0.1Ce0.9O1.95. Additionally, Cu incorporation resulted in a nearly tenfold decrease in the extent of oxygen vacancy concentration loss in the space charge layer, reducing the potential from 0.41 V (Gd0.1Ce0.9O1.95) to 0.34 V (Gd0.1Ce0.83Cu0.07O2-δ), which benefits the concentration of oxygen vacancies in the space charge layer. Moreover, in terms of mechanical properties, compared to singly doped samples, co-doped samples exhibited increases of approximately 20.2 % in Vickers hardness, 78.3 % in fracture toughness, and 54.8 % in flexural strength. Thus, Cu-Gd co-doping can be considered an effective strategy for enhancing the performance of ceria-based electrolytes in IT-SOFCs.

Bound Charge Layering Near a Spherical Ion: Moving Beyond Born Theory.

The response of aqueous solvent to a dissolved ion is analyzed in terms of the bound charge, the net charge of the solvent in the vicinity of the solute. The total amount of bound charge is , where Qion is the charge of the ion and ϵ is the solvent dielectric constant, in both continuum and molecular theory. Aqueous solvation involves an inner layer of bound charge way over this value, followed by another layer that almost or over compensates the first layer, and so on. We demonstrate how layering of charge explains the strong solvation response of aqueous solvent. Born theory, in which the ion resides in a cavity within a dielectric continuum, places all the bound charge on the cavity surface. Without accounting for bound charge layering, it cannot describe the strong aqueous solvation response. The only adjustable parameter in Born theory is the cavity radius, and unphysically small values of the radius are required to match the Born prediction to the actual solvation free energy. We propose a simple analytical model for aqueous solvation of a spherical ion that incorporates bound charge layering. We point out which parameters are expected to be solvent-specific and transferable between different solutes, while other parameters should depend upon ion and solvent size. The solvation energy from finite, periodically replicated simulations must be corrected to describe an ion at infinitely dilution. We present a very simple correction, and demonstrate its accuracy.

Effect of Layer Charge Density and Charge Location on the Swelling of Smectite: Implications for Geological Storage of CO2 and High-Level Nuclear Wastes

Effect of Layer Charge Density and Charge Location on the Swelling of Smectite: Implications for Geological Storage of CO2 and High-Level Nuclear Wastes

The charge layer structure of dispersed liquid droplets of extra-heavy oil and its correlation with the oil–water interface properties in the system

To address the charge layer structure in dispersed heavy oil droplets and its correlation with oil–water interfacial properties, this study investigates the influence of asphaltenes on the oil–water interfacial characteristics and emulsion stability of heavy oils. Techniques such as dynamic light scattering, and interfacial tension measurement were employed to conduct this research. It highlighted how the molecular structure and dispersibility of asphaltenes influence the interfacial tension and stability of oil emulsions. The research demonstrated that the interfacial activity and size of asphaltenes affect their aggregation and adsorption at the oil–water interface. Furthermore, it examined how aromatics enhance the dispersibility of asphaltenes and reduce the average droplet size in oil emulsions, thereby improving the stability of heavy oil systems. These findings enhance understanding of the complex interactions at the oil–water interface, especially involving asphaltenes in extra-heavy oils.

Tailor-Made Heterocharged Covalent Organic Framework Membrane for Efficient Ion Separation.

Pore size sieving, Donnan exclusion, and their combined effects seriously affect ion separation of membrane processes. However, traditional polymer-based membranes face some challenges in precisely controlling both charge distribution and pore size on the membrane surface, which hinders the ion separation performance, such as heavy metal ion removal. Herein, the heterocharged covalent organic framework (COF) membrane is reported by assembling two kinds of ionic COF nanosheets with opposite charges and different pore sizes. By manipulating the stacking quantity and sequence of two kinds of nanosheets, the impact of membrane surface charge and pore size on the separation performance of monovalent and multivalent ions is investigated. For the separation of anions, the effect of pore size sieving is dominant, while for the separation of cations, the effect of Donnan exclusion is dominant. The heterocharged TpEBr/TpPa-SO3H membrane with a positively charged upper layer and a negatively charged bottom layer exhibits excellent rejection of multivalent anions and cations (Ni2+, Cd2+, Cr2+, CrO4 2-, SeO3 2-, etc). The strategy provides not only high-performance COF membranes for ion separation but also an inspiration for the engineering of heterocharged membranes.

Crystalline Covalent organic framework membrane with tailored chargeability for efficient pharmaceutical rejection by in-situ functionalization of polyethylene-imine

The nanofiltration (NF) membrane with better hydrophilicity, uniform pore size distribution, and dually charged properties is highly desirable to improve the pharmaceutical rejection, especially for the neutral and positively charged pharmaceuticals. Herein, a TpPa membrane was first in-situ crystallized via PTSA-mediated interfacial catalytic polymerization (ICP) strategy using 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa), followed by post-functionalization with PEI to narrow pore size, improve hydrophilicity, and tailor membrane charges to enhance pharmaceutical rejection. PTSA was used as a catalyst to enhance the crystallinity of the TpPa membrane. The PEI introduction narrowed the pore radius from 0.382 nm to 0.272 nm, improved surface hydrophilicity from 74.8°to 37.0°, and shifted surface charge from -19.25 mV to 11.15 mV. This PEI-functionalized TpPa (TpPa-PEI) layers exhibited heterogeneous charges on both sides with a positively charged top and negatively charged bottom. MgCl2 rejection increased from 13.67% to 83.0% without sacrificing water permeance. Additionally, pharmaceutical rejection and the water permeance of the optimal TpPa-PEI membrane exceeded those of the TpPaIP-PEI membrane fabricated without PTSA by about 3.3 and 1.3 times, respectively. Furthermore, compared to the pristine TpPa membranes, the substantially enhanced electropositivity of the optimal TpPa-PEI membrane led to 3-5 times increase in positively charged pharmaceutical rejection (94.1% for propranolol, 97.2% for sulpiride, and 71.2% for metformin). The synergy of negatively charged bottom TpPa-PEI layers and reduced pore size maintained sulfadiazine rejection of 62.1%. Mechanistic study confirmed that PEI penetrated 100 nm into the TpPa layer and cross-linked with the aldehyde groups, leading to tailored chargeability, improved hydrophilicity, and reduced pore size. Via a PEI cross-linking strategy, sub-nanometer channels of crystalline COF layers can be rationally designed, featuring precisely tailored chargeability and hydrophilicity, promising functionalization of the membrane pores and remarkably robust for water reuse.

Detection of Layer Charge Density in Layered Double Hydroxides and Studies on Host‐Guest Interactions

AbstractThe layer charge density of layered double hydroxides (LDHs) significantly affects interlayer spacing, the arrangement of interlayer anions and water molecules, thermal stability, as well as adsorption performance. However, traditional methods for evaluating the layer charge density of LDHs are complex, prone to large errors, and impacted by numerous factors, rendering these methods unable to facilitate direct comparisons of layer charge density across different LDH compositions. Consequently, this study proposes a novel approach based on the host‐guest supramolecular interactions in LDHs to investigate the layer charge density by analyzing changes in the position of the infrared absorption peaks of interlayer guest species. The shifts in infrared absorption peak positions are employed to assess the layer charge density of MgAl‐LDHs with varying molar ratios (M2+/M3+=2, 2.5, 3, 3.5, 4). The validity of using infrared peak position shifts is corroborated through a combination of techniques, including Raman spectroscopy, TG‐DTG, XRD, Zeta potential, and adsorption analyses. Furthermore, the layer charge density of NiAl, CoAl, MgFe, and NiFe‐LDHs are evaluated, confirming the universality of the infrared method. By ranking layer charge density of LDHs with different compositions and ratios, this study resolves the challenge of comparing LDHs with diverse layer compositions.

Solid-phase electrochemiluminescence immunosensing platform based on bipolar nanochannel array film for sensitive detection of carbohydrate antigen 125.

Development of simple solid-phase electrochemiluminescence (ECL) immunosensor with convenient fabrication for high-performance detection of tumor biomarkers is crucial. Herein, a solid-phase ECL immunoassay was constructed based on a bipolar silica nanochannel film (bp-SNA) modified electrode for highly sensitive detection of carbohydrate antigen 125 (CA 125). Inexpensive and readily available indium tin oxide (ITO) electrode was used as the supporting electrode for the growth of bp-SNA. bp-SNA consists of a bilayer SNA film with different functional groups and charge properties, including negatively charged inner layer SNA (n-SNA) and positively charged outer layer SNA (p-SNA). The nanochannels of bp-SNA were used for the immobilization of ECL emitter tris(bipyridine)ruthenium(II), while the outer surface was utilized for constructing the immunorecognition interface. Due to the dual electrostatic interaction composed of electrostatic attraction from n-SNA and electrostatic repulsion from p-SNA, ECL emitter could be stably confined within bp-SNA, providing stable and high ECL signals to the modified electrode. After amino groups on the outer surface of bp-SNA were derivatized with aldehyde groups, recognition antibodies could be covalently immobilized, and an immunosensor was obtained after blocking nonspecific sites. When CA 125 binds to the antibodies on the recognition interface, the formed complex reduces the diffusion of the co-reactant tripropylamine (TPrA) to the supporting electrode, decreasing the ECL signal. Based on this mechanism, the constructed immunosensor can achieve sensitive ECL detection of CA 125. The linear detection range is from 0.01 to 100U/mL, with a detection limit of 4.7mU/mL. CA 125 detection in serum is also achieved. The construction immunosensor has advantages including simple and convenient fabrication, high stability of the immobilized emitter, and high selectivity, making it suitable for CA 125 detection.

Biofilm Microenvironment-Sensitive Anti-Virulent and Immunomodulatory Nano-on-Nanodroplets to Combat Refractory Biofilm Infection Through Toxin Neutralization and Phagocytosis.

Biofilm-associated wound infection is principally perceived as the bacterial defense mechanism that hinders antibiotic penetration, causes toxin impairment, and suppresses the immunological responses of the host immune system. Several antibiofilm agents have been developed, but the least of these agents can simultaneously cornerstone on the biofilm-associated immunosuppression and bacterial toxin-induced cellular dysfunction. Inspired by the fusogenic property of nanodroplets and immunomodulatory functions of metal nanoparticles, biofilm targeted anti-virulent immunomodulatory cationic nanoparticle shelled nanodroplets (C-AgND) is fabricated to completely disintegrate and eradicate the Staphylococcus aureus (S. aureus) biofilm. The specific binding of C-AgND neutralizes the negatively charged EPS layer, causing their destabilization followed by penetration of the nanoformulation into the biofilm matrix, killing the persister cells. Consequently, C-AgND eliminates the virulence property of the S. aureus biofilm through α-hemolysin neutralization. C-AgND promotes a strong immunomodulatory effect by polarizing macrophages into their M1 phenotype to induce phagocytosis of the disintegrated biofilm-released residual cells, rejuvenating the host's innate immune responses for the complete eradication of the biofilm. Moreover, the ex vivo skin wound infection model illustrates an excellent biofilm eradication efficacy of C-AgND in comparison to the commercial ones, rendering them to be a promising replacement of existing antibiofilm agents in clinical application.

CFD Modeling of HBI/scrap Melting in Industrial EAF and the Impact of Charge Layering on Melting Performance.

The melting of scrap and hot briquetted iron (HBI) in an AC electric arc furnace (EAF) is simulated by an advanced 3D computational fluid dynamics (CFD) model that captures the arc heating, the scrap/HBI melting process, and the solid collapse mechanisms. The CFD model is used to simulate a scenario where charge layering and EAF power profiles are provided by a real EAF operation. CFD simulation of the EAF operation shows proper prediction of the charge melting when compared with standard industry practice. Namely, the CFD model predicts a 32.5%/67.5% ratio of solid/liquid steel at the beginning of refining, which approaches the 30%/70% ratio used in standard practice. Based on this prediction, the melting rate in the CFD results differs by 8.3% from actual EAF operation. The impact of charge layering on melting is also investigated. CFD results show that distributing charge material into a greater number of layers in the first bucket (10 layers as compared to 4) enhances the melting rate by 12%. However, including dense material at the bottom of the furnace deteriorates melting performance, reducing the impact of the number of layers of the charge. The CFD platform can be used to optimize the use of HBI/scrap in real EAF operations and to determine best recipe practices.

Direct observation of space-charge-induced electric fields at oxide grain boundaries.

Space charge layers (SCLs) formed at grain boundaries (GBs) are considered to critically influence the properties of polycrystalline materials such as ion conductivities. Despite the extensive researches on this issue, the presence of GB SCLs and their relationship with GB orientations, atomic-scale structures and impurity/solute segregation behaviors remain controversial, primarily due to the difficulties in directly observing charge distribution at GBs. In this study, we directly observe electric field distribution across the well-defined yttria-stabilized zirconia (YSZ) GBs by tilt-scan averaged differential phase contrast scanning transmission electron microscopy. Our observation clearly reveals the existence of SCLs across the YSZ GBs with nanometer precision, which are significantly varied depending on the GB orientations and the resultant core atomic structures. Moreover, the magnitude of SCLs show a strong correlation with yttrium segregation amounts. This study provides critical insights into the complex interplay between SCLs, orientations, atomic structures and segregation of GBs in ionic crystals.

Role of ex-situ HfO2 passivation to improve device performance and suppress X-ray-induced degradation characteristics of in-situ Si3N4/AlN/GaN MIS-HEMTs

The role of ex-situ HfO2 passivation in in-situ Si3N4/AlN/GaN-based metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) to improve the device performance and protect the device from severe degradation under high-energy X-ray irradiation has been investigated. Here, the root cause and mechanism for the degradation have been studied utilizing different material/device characterizations. X-ray photoelectron spectroscopy results suggest that several Si-N bonds in stoichiometric Si3N4 and Hf-O bonds in HfO2 passivation film can be broken under X-ray irradiation, where numerous charges might be trapped easily and deteriorate the interface quality. Furthermore, due to the generation of chemical vacancies under X-ray, a band tail near the edge of valence band maximum in Si3N4 and HfO2 films can be created. The obtained results suggest that MIS-HEMT fabricated with an atomic layer deposited (ALD)-HfO2 (MIS-HEMT B) has relatively greater performance compared to MIS-HEMT fabricated without ex-situ HfO2 (MIS-HEMT A) according to the higher maximum drain current (Idmax), peak transconductance (gmmax) and lower current collapse, denoting the effectiveness of ALD-HfO2 to passivate the surface traps. It is noticed that X-ray irradiation induces numerous negative charges in the dielectric layers and degrades the device performance. Interestingly, after X-ray irradiation, the degradation rates in Idmax, gmmax, and current collapse are significantly lower in MIS-HEMT B compared to MIS-HEMT A, suggesting the potential irradiation hardening mechanism of ALD-HfO2 to protect the MIS-HEMTs from unexpected degradations during X-ray irradiation. Finally, these results emphasize the importance of high-quality dielectric films in MIS-HEMTs to enhance the device performance and safeguard the device under high-energy irradiation, especially in the space environment.

Characterization of the Lithium/Solid Electrolyte Interface in the Presence of Nanometer-thin TiOx Layers for All-Solid-State Batteries.

It is still unclear which role space charge layers (SCLs) play within an all-solid-state battery during operation with high current densities, as well as to which extent they form. Herein, we use a solid electrolyte with a known SCL formation and investigate it in a symmetric cell under non-blocking conditions with Li metal electrodes. Since the used LICGC™ electrolyte is known for its instability against lithium, it is protected from rapid degradation by nanometer-thin layers of TiOx deployed by atomic layer deposition. Close attention is given to the interfacial properties, as now additional Li+ can traverse through the interface depending on the applied bias potential. The interlayer's impedance response shows efficient lithium-ion conduction for low bias potentials and a diffusion-limiting effect towards high positive and negative potentials. SCLs grow up to a thickness of 5.1 μm. Additionally, estimating the apparent rate constant of the charge transfer across the interface indicates that the potentials where kinetics are hindered coincide with the widest SCLs. In conclusion, the investigation under higher steady-state currents was only possible because of the improved stability due to the interlayer. No chemo-physical failure could be observed after 800+ hours of cycling. However, an ex-situ SEM study shows a new phase at the interface, which grows into the electrolyte.

Embedding Reverse Electron Transfer Between Stably Bare Cu Nanoparticles and Cation-Vacancy CuWO4.

Cu nanoparticles (NPs) have attracted widespread attention in electronics, energy, and catalysis. However, conventionally synthesized Cu NPs face some challenges such as surface passivation and agglomeration in applications, which impairs their functionalities in the physicochemical properties. Here, the issues above by engineering an embedded interface of stably bare Cu NPs on the cation-vacancy CuWO4 support is addressed, which induces the strong metal-support interactions and reverse electron transfer. Various atomic-scale analyses directly demonstrate the unique electronic structure of the embedded Cu NPs with negative charge and anion oxygen protective layer, which mitigates the typical degradation pathways such as oxidation in ambient air, high-temperature agglomeration, and CO poisoning adsorption. Kinetics and in situ spectroscopic studies unveil that the embedded electron-enriched Cu NPs follow the typical Eley-Rideal mechanism in CO oxidation, contrasting the Langmuir-Hinshelwood mechanism on the traditional Cu NPs. This mechanistic shift is driven by the Coulombic repulsion in anion oxygen layer, enabling its direct reaction with gaseous CO to form the easily desorbed monodentate carbonate.

Unraveling Asymmetric Electrochemical Kinetics in Low-Mass-Loading LiNi1/3Mn1/3Co1/3O2 (NMC111) Li-Metal All-Solid-State Batteries

In this study, we fabricated a Li-metal all-solid-state battery (ASSB) with a low mass loading of NMC111 cathode electrode, enabling a sensitive evaluation of interfacial electrochemical reactions and their impact on battery performance, using Li1.3Al0.3Ti1.7(PO4)3 (LATP) as the solid electrolyte. The electrochemical behavior of the battery was analyzed to understand how the solid electrolyte influences charge storage mechanisms and Li-ion transport at the electrolyte/electrode interface. Cyclic voltammetry (CV) measurements revealed the b-values of 0.76 and 0.58, indicating asymmetry in the charge storage process. A diffusion coefficient of 1.5 × 10−9 cm2⋅s−1 (oxidation) was significantly lower compared to Li-NMC111 batteries with liquid electrolytes, 1.6 × 10−8cm2⋅s−1 (oxidation), suggesting that the asymmetric charge storage mechanisms are closely linked to reduced ionic transport and increased interfacial resistance in the solid electrolyte. This reduced Li-ion diffusivity, along with the formation of space charge layers at the electrode/electrolyte interface, contributes to the observed asymmetry in charge and discharge processes and limits the rate capability of the solid-state battery, particularly at high charging rates, compared to its liquid electrolyte counterpart.

Blue energy conversion utilizing smart ionic nanotransistors

The use of concentration gradients across nanofluidic membranes for energy generation presents a novel and sustainable approach to power production. This study investigates the impact of ion nanotransistor configurations on ion transport and energy generation. Two types of cylindrical symmetrical nanotransistors, PNP and NPN, were tested. Using the finite element method, the Poisson-Nernst-Planck and Navier-Stokes equations were solved to evaluate how the configuration of soft layers, concentration ratios, and charge density influence energy output. Results show that the NPN configuration consistently outperforms the PNP setup in energy production, with energy generation ranging from 40pW to 56pW, compared to 35pW to 43pW for the PNP structure, when soft layer charge density increase from 25mol/m3 to 100mol/m3. The superior performance of the NPN arrangement is attributed to its higher electrostatic potential and enhanced ion mobility. These findings underscore the potential of NPN nanotransistor configurations for optimizing energy generation as well as water desalination in nanofluidic systems.

Double modulation of the electric field in InGaAs/Si APD by groove rings for the achievement of THz gain-bandwidth product

Abstract Avalanche photodiode (APD) is commonly used as a receiver in optical communication and light detection and ranging (LIDAR), offering highly sensitive photodetection capabilities. A key strategy for improving the gain-bandwidth product (GBP) of the APD involves the optimization of the electric field distribution using the charge layer. However, traditional modulation methods to adjust the carrier transport and avalanche process using the charge layer often face challenges (inefficiency and non-uniformity). An InGaAs/Si APD based on the wafer bonding method with a GBP up to 1.03 terahertz (THz) is reported theoretically in this work. The charge layer and groove rings are inserted at the InGaAs/Si bonded interface to modulate the electric field in the APD effectively, demonstrating low dark current and reduced avalanche bias of the device. This approach induces a dramatic and rapid variation of the electric field at the interface while reducing the gradient of the electric field in the multiplication layer. Additionally, the indirect impact of the groove ring on mitigating the adverse effects of the lattice mismatch is pointed out, and the optimal doping concentration range of the charge layer is identified to enhance the modulation effect of the electric field for stronger impact ionization. These findings provide valuable insights for the next-generation InGaAs/Si APDs with high GBP for high-speed data transmission.