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This study employs the kinetics framework of Marcus-Hush-Chidsey (MHC) to investigate the charge transfer at the interface of lithium electrode and electrolyte in lithium(ion)-batteries. The charge-transfer rate constant is evaluated for different facets of lithium, namely (1 0 0), (1 1 0), (1 0 1), and (1 1 1) as a function of surface charge density with the aid of DFT calculations. The results highlight and quantify the sensitivity of the rate of lithium plating and stripping to the surface orientation, surface charge density, and charge-transfer over-potential. An intrinsic kinetics competition among the different surface orientations is identified together with an asymmetry between the lithium plating and stripping and showcased to influence the deposit morphology and surface protrusions and indentations. This work was supported by the European Union’s Horizon 2020 Research and Innovation Program for the Solidify Project (875557)

Biosensor is a device used to detect the presence and function of bio-molecules in different biological fluid. In the field of biosensor development gold nanoparticle attracts great attention due to unique properties and surface charges. Different gold nanoparticle (gnp) based biosensors are now in use for clinical application. Gold nanoparticles can be conjugated with the fluorescence chemicals easily and can be used for detection of different charged biological tissues. Negatively charged gold nanoparticles were prepared and conjugated with fluorescence dye methylene blue. Surface charge, fluorescence characteristics and size of the methylene blue gold nanoparticles and the conjugates were studied. The shifting peak of absorption of gold nanoparticles in the UV–Vis spectroscopic study indicated the possibility of the gold nanoparticles methylene blue conjugate formation. The conjugate can be used for identification of excitable cells from excitable and non-excitable cells containing tissues.

Recent advances in nanotechnology have witnessed tremendous progress concerning nanofiber synthesis and practical applications. Electrospinning is a simple, versatile, and cost-effective technology that relies on electrostatic repulsions between surface charges to continuously fabricate various scalable assemblies from a wide range of raw materials (polymers, ceramics, nanoparticles, carbon nanomaterials, gels, etc.) with diameters down to macro-nano scale. Nanofibers prepared by electrospinning possess remarkable large and specific surface area to volume ratio, interconnected and tunable structures, diverse morphologies, physio-chemical and mechanical properties. In this paper, Polyvinylidene fluoride (PVDF) nanofibers with different concentrations and under constant electrospinning conditions have been prepared and characterized. The increase of the PVDF polymeric concentration improved the morphological structure of the PVDF nanofibers due to the enhanced molecular chain entanglement which allows the stretching and elongation of the fibers during the electrospinning process. At higher PVDF concentration, the fiber diameters become thinner and beadless nanofiber mats are obtained. Finally, the potential practical applications of electrospun PVDF nanofibers are addressed in this paper.

Catalytic reactions always accompany steric and electronic effects. Due to the modulated structure and functionality, the surface charge of porous coordination cage can be tuned under the same topology. This provides a straightforward way to investigate the steric and electronic effects by using cage catalysts. Herein, we prepared two cages with 24- negative surface charge and zero surface charge and applied them in guest encapsulation and Knoevenagel condensation. The high anionic cage shows considerably higher adsorption kinetic for positive guests and much-improved reactivity in the catalytic reaction when comparing to the neutral counterpart. The negative charge was proved to be the dominant factor for the much-improved catalytic reactivity, rather than the cage structure. This finding provides new thoughts for design a suitable platform to investigate the individual impact factors for the catalytic reactions.

Although nanochannels in tortuous shape exhibit unusual transportational characteristics, the traditional theoretical analysis of nanofluidics in such kinds of systems remains challenging, partly due to their complicated boundary description. In this paper, by developing a curvilinear coordinate system for such tortuous nanochannels, we solve the electrostatic Poisson–Boltzmann equation analytically for a two-dimensional nanochannel, with its effectiveness confirmed through numerical calculation. The influences of the geometric profile on the distribution of electric potential, ionic concentration, and surface charge on channel walls are quantitatively evaluated in a facilitated way in terms of the curvilinear coordinates introduced. Such a technique can be widely applied to many nanofluidic systems in curved channels.

Amorphous iron phosphate, FePO4.2H2O, was synthesized at ambient temperature using an inorganic sol-gel method coupled with a microwave route. The experimental conditions for the gelling of the Fe (III)-H3PO4 system are defined. Potentiometric Time Titration (PTT) and Potentiometric Mass Titration (PMT) methods were used to investigate the acid-base surface chemistry of obtained phosphate. Variations of surface charge with the contact time, Q = f(t), are examined for time contact ranged from 0 to 72 hours. The concentrations suspensions used for this purpose were 0.75, 1.25, and 2.5 g/L. The point of zero charges (PZC) and isoelectric point (IEP) were defined using the derivative method examining the variations , at lower contact time. A value of 5.4 was obtained for both PZC and IEP. Q in the function of the t method is performed for synthesized FePO4. 2H2O in NaCl and KCl electrolytes. The optimal surface charge of 40 C corresponding to insertion of 4.2x10-4 M of Na+ or K+, is achieved in explored conditions. The results suggest that the synthesized iron phosphate is amorphous.

The sluggish kinetics for water oxidation is recognized as one of the major problems for the unsatisfied photoelectrochemical (PEC) performance. Herein, we developed a feasible strategy based on in-situ selective surface cation exchange, for activating surface water oxidation reactivity toward boosted PEC water oxidation of BiVO4 photoanodes with fundamentally improved surface charge transfer. The as-constructed Co/BiVO4 photoanodes exhibit 2.6 times increase in photocurrent density with superior stability, in comparison to those of pristine counterpart. Moreover, the faradaic efficiency of as-fabricated photoanode can be up to ∼95% at 1.23 V (vs. RHE). The unique selective replacement of Bi by Co on the surface could modify the electronic structure of BiVO4 with reduced energy barrier of the deprotonation of OH* to O, thus favoring the overall excellent PEC performance of Co/BiVO4 photoanode.

Understanding the hydrogenation of organic compounds in the aqueous phase has always been fundamentally important for improving carbon neutral pathways to fuels and value-added chemicals. In this study, we investigated both thermodynamic and kinetic profiles of benzaldehyde hydrogenation over the Pd(111) and Pt(111) metal surfaces using density functional theory (DFT) and ab initio molecular dynamic (AIMD) simulations. The adsorption of H2 shows the mixed preference of H adsorption sites on the Pt(111), while the fcc adsorption site is dominant for H on the Pd(111). When benzaldehyde is added to the systems, we observe a strong reduction of benzaldehyde on charged Pd (111) surface compared with that on neutral surface. In contrast, charged state of the Pt(111) surface does not change their interaction. Subsequent hydrogenation reaction of benzaldehyde over Pd(111), proceeding via Langmuir-Hinshelwood mechanism, is affected by two major factors: the presence of H2O solvent and surface charge. The presence of H2O solvent greatly reduces the activation energy of C H and O H bond formation during the hydrogenation process. Furthermore, the hydrogenation step via C H bond formation is preferred thermodynamically and kinetically over O H bond formation during thermocatalytic hydrogenation, while the opposite trend holds true during electrocatalytic hydrogenation.

CQDs-doped TiO2 (C-TiO2) has drawn increased attention in recent because of its excellent catalytic performance. Understanding the transport of C-TiO2 in porous media is necessary for evaluating the environmental process of this new nanomaterial. Column experiments were used in this study to investigate ionic strength (IS), dissolved organic matter (DOM) and sand grain size on the transport of C-TiO2. The mobility of C-TiO2 was inhibited by the increased IS and decreased sand grain size, but was promoted by the increased DOM concentration. The promotion efficiency of DOM ranked as humic acid (HA) > alginate (Alg) > bovine serum albumin (BSA), which was in the same order as their ability to change surface charges. The micromodels of pore network were prepared via 3D printing to further reveal the deposition mechanisms and spatial/temporal distribution of C-TiO2 in porous space. C-TiO2 mainly attached to the upstream region of collectors because of interception. The collector ripening was observed after long-time deposition. The existence of DOM caused visible decrease of C-TiO2 deposition in the pore network. HA caused the most remarkable reduce of deposition in the three types of DOM, which was consistent with the column experiment results. This research is helpful to predict the transport of C-TiO2 in natural porous media.

Native bone is piezoelectric in nature and generates abundant surface charges under mechanical compression, which regulate osteoblast proliferation, differentiation, adhesion, and so on. Poly (vinylidene fluoride) (PVDF) is becoming one of the most popular piezoelectric polymers because of its easy processability and good biocompatibility. Unfortunately, because only the β and γ crystal phases of PVDF have piezoelectricity, post-treatments, for example, polarizing at high temperature, are required to enhance the piezoelectricity of PVDF scaffolds after fabrication. In this study, we reported a phase-separation-hydration method to fabricate a calcium phosphate silicate (CPS)-doped PVDF scaffold. Our method fabricated a better piezoelectric scaffold than native bone without further processing (∼ 3 pC/N vs. 0.7 pC/N). In addition, the scaffold was mechanically compatible (∼ 7 MPa) with the cancellous bone with sufficient porosity (∼ 45%) to facilitate osteoblast infiltration and bone ingrowth. The in vitro biocompatibility analyses proved that the prepared CPS-PVDF scaffold was biocompatible with osteoblast cells and encouraged osteoblast redifferentiation. In conclusion, our results suggest that this CPS-PVDF scaffold is a promising candidate for bone tissue engineering applications.

Specific interactions of yttrium and lanthanum ions with a fatty acid Langmuir monolayer were investigated using vibrational sum frequency spectroscopy. The trivalent ions were shown to interact with the charged form of the carboxylic acid group from nanomolar concentrations (

Zn-doped nickel ferrite nanoparticles (ZnxNi(1-x)Fe2O4) were synthesized using the co-precipitation technique. The structural and compositional studies of the ZnxNi(1-x)Fe2O4 nanoparticles revealed their face-centred cubic spinel structure and an appropriate amount of Zn doping in nickel ferrite nanoparticles, respectively. The morphological analysis had been carried out to obtain the particle size of the synthesized nanoparticles. The magnetic studies revealed the superparamagnetic nature of the ZnxNi(1-x)Fe2O4 nanoparticles, and the maximum magnetization of 30 emu/g for the Zn0.2N0.8Fe2O4 sample. The M − H curves were fitted with the Langevin function to obtain the magnetic particle diameter of ZnxNi(1-x)Fe2O4 nanoparticles. The electrical conduction in ZnxNi(1-x)Fe2O4 nanoparticles was explained through the Verway hopping mechanism. The Zn0.2N0.8Fe2O4 nanoparticle exhibited a higher electrical conductivity of 42 μS/cm and surface charge of −29/7 mV due to the enhanced hopping of Fe3+ ions in the octahedral sites. Owing to this nature, they were identified as the suitable candidates in the applications such as thermoelectrics, hyperthermia, magnetic coating and for the preparation of conducting ferrofluids.

Despite the broad range of interest and applications, controls on the electric surface charge and the zeta potential of silica in contact with aqueous solutions saturated with dissolved CO2 at conditions relevant to natural systems, remains unreported. There have been no published zeta potential measurements conducted in such systems at equilibrium, hence the effect of composition, pH, temperature and pressure remains unknown. We describe a novel methodology developed for the streaming potential measurements under these conditions, and report zeta potential values for the first time obtained with Fontainebleau sandstone core sample saturated with carbonated NaCl, Na2SO4, CaCl2 and MgCl2 solutions under equilibrium conditions at pressures up to 10 MPa and temperatures up to 40 °C. The results demonstrate that pH of solutions is the only control on the zeta potential, while temperature, CO2 pressure and salt type affect pH values. We report three empirical relationships that describe the pH dependence of the zeta potential for: i) dead (partial CO2 pressure of 10-3.44 atm) NaCl/Na2SO4, ii) dead CaCl2/MgCl2 solutions, and iii) for all live (fully saturated with dissolved CO2) solutions. The proposed new relationships provide essential insights into interfacial electrochemical properties of silica-water systems at conditions relevant to CO2 geological storage.

By surface modification with APTMS, spontaneous coagulation casting (SCC) of fused silica based on Isobam was achieved and the possible coagulation and molding mechanism is proposed. Through the interaction between the polar groups on the Isobam molecular chain and the incorporated –NH2 groups on the surface of the silica particles, Isobam molecular chains were adsorbed on the surface of particles, which initiate the formation of flocs and the solidification of the suspension. The addition of dispersant TMAH results in the hydrolyzation of Isobam, forming more –COO–, which effectively improves the fluidity and stability of the suspension. Then the zeta potential, rheological properties and coagulation behavior of the suspension were systematically investigated and the fused silica suspension with high solid content (up to 52 vol%), low viscosity and good coagulation properties were prepared at 1.8 wt% TMAH and 0.5 wt% Isobam dosage. After sintering at 1260 °C for 4 hours, the fused silica ceramics (50 vol% solid content) shows a high bending strength of 61.59 MPa, the lowest dielectric loss tanδ of 8.46 × 10-4 and the dielectric constant of 3.72. Thus, this work provides a simple and effective method for preparing fused silica and other ceramics with negative surface charge by Isobam SCC.

Heavy metal-containing wastes pose long-term environmental threats. In the present work, cementitious binders in the presence of halloysite nanotubes (HNTs) at 1 wt%, 3 wt%, and 5 wt% by mass were used to immobilize lead (Pb(II)). Semi-dynamic leaching tests were used to quantify the Pb(II) leaching up to 64 days. The results showed that the addition of 1 wt%, 3 wt%, and 5 wt% HNTs particles strongly reduced the Pb(II) release. The optimal dosage of HNTs was 3 wt%, which decreased the cumulative release of Pb(II) by around 40.5% after 64 days. Isothermal calorimetry, X-ray diffractometry (XRD), thermogravimetry (TG), mercury intrusion porosimetry (MIP) and compression tests were then used to investigate better immobilization effect with HNTs addition. The results showed that HNTs particles promoted cement hydration, refined the pore structure of the hardened cementitious binders, decreased permeability, and enhanced mechanical strength. Zeta potential measurements indicated that the negative surface charge of the HNTs particles could adsorb Ca2+ ions from the pore solution of cement hydration, then facilitating adsorption of Pb(OH)3−.

Most studies combine high-capacity silicon (Si) with high-conductivity carbon materials to overcome the poor electrical connectivity of Si, but the pathway for the Li+ rapid transmission to Si is often ignored. Lithium titanate (LixTiyOz) as a protective additive to improve the transmission speed of Si-based anodes has attracted extensive scientific interest. However, highly reactive titanium precursor imparts great difficulties in precisely controlling the growth of LixTiyOz on the Si surface, resulting in poor secondary particle formation, and severely weakening the advantage of LixTiyOz at the Si-based electrode level. Herein, we propose a confined interfacial assembly method to combine the controlled Li2Ti3O7 building blocks and the Si nanoparticles through the electrostatic interaction and Ostwald-ripening. This facile and reproducible method relies on the surface charge change effect of CTAB, the solvent-confinement effect of glycerol and the crystalline dimension control of ammonia. The Li2Ti3O7 building blocks has a height-adjustable shape (2D-layered, 3D-spherical), size, and controlled coating surface. As a result, the selected hierarchical microcluster has the advantages of rapid 3D interpenetrating electron/Li+ pathways, buffer space and electrolyte barrier, which achieves superior rate capability (1261 mAh g−1 at 5 A g−1) and high stable cycle performance (1080 mAh g−1 after 1000 cycles at 2 A g−1).

Prompt recombination of photo-generated charges in semiconducting material strictly restrict photocatalytic process efficiency. Herein, coupling of CuxP nanoparticles and PbTiO3 nanoplates through inert atmosphere calcination process for outstanding H2 production has been reported. Uniform edging distribution of CuxP nanoparticles over PbTiO3 nanoplates; witnessed from TEM analysis revealed an intimate material contact for charge transportation to the active reaction sites of catalyst surface. Besides, junction interface between CuxP and PbTiO3 component; confirmed from XPS and Mott-Schottky analysis yield an amplified photo/electro-chemical and catalytic performance. A stronger photocurrent density via., H2O2 electron scavenger and larger photovoltage in junction material compared with PbTiO3 counterpart; follows higher surface charge transfer efficiency and slower potential decay with longer charge carriers lifetime simultaneously. The PbTiO3 nanoplates with an optimum amount of CuxP have achieved maximum H2 production attaining conversion efficiency of 9.72%. Consequently, a type-II energy band alignment mechanism has been proposed for enhanced H2 production.

The effect of the surface conductivity on the electrical and mechanical characteristics of the surface dielectric barrier discharge actuator has been numerically investigated in this study. Two typical AC-surface dielectric barrier discharge actuators, wire-to-plate and plate-to-plate have been considered to control airflow alongside a flat dielectric plate. A sinusoidal high voltage of varied frequencies and amplitudes is supplied to the active electrode, and the passive electrode, which is grounded, is encapsulated inside a dielectric plate. Two-species ion transport model, involving generic positive and negative ions, coupled to the electrostatics model is assumed. The electrostatic field is affected by both the space and the surface charges. The surface charge is accumulated due to ion deposition, but its distribution varies due to the surface ohmic conduction. The Navier-Stokes equations for the flow simulation, which include the time-averaged electrohydrodynamic body force determined from the discharge model, are solved to analyze the flow field and the boundary layer morphology. The numerical algorithm has been implemented in the COMSOL commercial package. The significance of the dielectric surface conductivity on the discharge behavior and the flow field has been shown. The dielectric surface conductivity behaves non-monotonically and affects the flow field by altering the EHD force strength, direction and distribution.

Rational tuning the surface charge state for catalysts is an attractive strategy to promote their catalytic activity toward catalyzing diverse chemical and electrochemical reactions. In this work, we modified the surface of a pure tungsten carbide (WC) material with an ultra-thin nitrogen doped carbon (NC) layer (WC@NC) for catalyzing alkaline hydrogen evolution reaction (HER). The XPS studies revealed an increased electron density on WC when the NC layer was introduced on its surface. Thus, a significant decrease of 282 mV in overpotential at 10 mA cm−2 was observed on WC@NC electrode in comparison with the pristine WC electrode. The higher electrochemical active surface area, lower activation energy barrier, and excellent durability were identified by various electrochemical measurements. The three-dimensional charge density difference was also calculated and the results indicated that an electron-transfer process occurred from the NC layer (donor) to the WC layer (acceptor) through the interface of WC@NC composite material. The analysis explained the underlying mechanism for the promotion of the HER activity. Such a comprehensive study is expected to provide useful guidance for promoting the catalytic performance of diverse catalysts toward different reactions.

Tight ceramic ultrafiltration membranes have been proven to exhibit good rejection performance for reactive dye wastewater at high temperatures because of their high thermal and chemical resistance. However, the application of ceramic membranes for the treatment of cationic dye wastewater is challenging because of their surface charge. In this study, a ceramic membrane is modified by grafting aminosilane (KH-551) to enhance the positive charge of the membrane surface. The rejection performance of the charged modified ceramic membrane toward the methylene blue solution is significantly improved. The modification substance is bonded to the ceramic membrane surface via covalent bonding, which imparts good thermal stability. The modified ceramic membrane exhibits stable separation performance toward the methylene blue solution. Overall, this study provides valuable guidance for the adjustment of the ceramic membrane surface charge for treating industrial cationic dye wastewater.

Explore the photo-piezoelectric synergistic micro-mechanism by density functional theory (DFT) calculations at the electronic and atomic level is important. In this work, to understand the synergistic mechanism, atomic and electronic properties of typical piezoelectric and photocatalytic material BaTiO3 were initially investigated with different strains. Subsequently, the adsorption of volatile organic compounds (VOCs) on the BaTiO3 (001) surface was determined during the piezoelectric process. In addition, the relationship between deformation ratio, the electronic structure and adsorption energy was understood in the deformation ratio range of 7%-12% for the optimal catalytic effect. The results of charge density differences and Born effective charge reveal the synergistic mechanism of piezoelectric photocatalysis. The built-in electric field formed by polarization results in the enhanced separation of charges, which makes the surface charges aggregation, enhancing the adsorption of VOCs, and benefiting the subsequent photocatalytic degradation. This work can provide significant theoretical guidance for the piezoelectric photocatalytic degradation of pollutants with the optimal strain range.

When blood comes in contact with dialyzer membranes, the interfacial bioactivation reactions occurring at blood/membrane boundaries detect the gross mechanism of thrombogenicity. In the presence of biocompatible polymers, the adhesion and subsequent interactions of platelets, as well as other serum components (e.g., proteins), are altered. It delays thrombus formation. In this study, the hemocompatibility of polyvinylpyrrolidone (PVP) modified polyethersulphone (PES) hemodialysis membrane fabricated using UV-assisted photochemical synthesis was investigated. To obtain varying degrees of PVP modification on each membrane, each coated surface was aged within the viscous polymer suspension for a predetermined duration. The correlation between the membrane induced hemocompatibility with membrane roughness, chemical composition, and surface charge at different aging duration of coating. In our study, we performed a comprehensive investigations on membrane morphology, hydrophilicity and its chemical composition using Atomic Force Microscopy (AFM), Fourier Transform Infra-Red (FTIR) Spectroscopy, Nuclear Magnetic Resonance (NMR), Zeta potential, and Scanning Electron Microscopy (SEM). The coated samples were analyzed using Luminex assays for the inflammatory biomarkers of Serpin/Antithrombin-III, C5a, 1L-1α, 1L-1β, IL6, and C5b-9. Modified membranes showed significant resistance against fibrinogen adsorption compared to their bare membrane counterpart. This inherent antifouling activity against fibrinogen adsorption was observed more on modified membranes that aged longer within the PVP suspension during synthesis. A longer ageing period contributed to the enhanced PVP modification, hence, more stable polymeric hydration layers. In addition, both bare and coated membranes triggered both complement system activation and inflammatory responses, but to a mild degree in the latter case. Coated membranes at longer coating duration, around ∼4 minutes, had smoother surfaces and lower magnitudes of surface charge and consequently exhibited reduced release of all biomarkers (except IL-1α), indicating enhanced biocompatibility. Higher levels of C5a were observed in membranes coated at 1 and 2 minutes, promoting modest reduction toward the release of other components.

Acid modification of sheep wool changed the surface charge from a negative to a positive one as demonstrated by means of zero-charge point determination. The positive surface facilitated the adsorption of nitrate (NO3 −) anions. The amount of nitrates in solution within 20–100 mg/dm3 was determined applying a home-developed ultraviolet spectrometry method. A little more effective modifier was 0.01 M hydrochloric acid (HCl) than the 0.1 M one. In the case of citric acid concentration, the effect was opposite. Wool modified with hydrochloric acid showed higher nitrate adsorption (up to 5 mg/g) compared with the sample modified with citric acid, (up to 1.7 mg/g of nitrate and 3, respectively). Testing eight adsorption isotherm models indicated inhomogeneity of the adsorbed layer from chemical as well as physical aspects. The Freundlich, Temkin and Halsey models fitted best. The study demonstrated that biopolymer modified using a suitable acid has the potential to remove nitrates from an aquatic environment.

Background Climate change, population growth, water pollution, and mismanagement of water resources all contribute to freshwater depletion. To cleanse dirty water, efficient and long-lasting technology is required. Membrane technologies are being developed to provide a cost- effective and efficient water treatment option to meet the ever-increasing demand for high quality- water. Methods A facile method was performed to develop outstanding hydrophilicity, fouling resistance, high rejection rate and water flux ultrafiltration (UF) membrane. The membranes were made using a non-solvent induced phase separation (NIPS) approach by combination of sulfonated polyethersulfone (SPES) and Titania nanotubes (TNTs) modified with sulfopropyl methacrylate (TNTs-g-PSPA) as a nanofiller. The fouling resistance of the fabricated membranes was explored using various foulants, comprising humic acid (HA), sodium alginate (SA), bovine serum albumin (BSA), and natural organic matter (NOM) solution. Significant findings The results revealed that the membranes surface charge concentration, porosity, and textural properties were improved. The hybrid membrane's pure water flux containing 5 wt% TNTs-g-PSPA hybrid was 402 L m−2 h−1, around 2-fold that of the pristine membrane. The fashioned membrane with 4 wt% TNTs-g-PSPA removed greater than 98% of NOM, without a rejection rate loss.

The stability of dispersions containing charged particles may obviously be regulated by salt. In some systems, the effective charge, as measured by the potential some small distance away from the particles, can have a sign opposite to the bare surface charge. If charge reversal takes place, there is typically a salt concentration regime within which colloidal stability increases with added salt. These experimental findings on dispersions have been corroborated by atomic force microscopy investigations, where an attraction is found at short separations. This attraction is stronger than expected from standard DLVO theory, and there has been considerable debate concerning its origin. In this work, we use simple coarse-grained models of these systems, where the bare surfaces carry a uniform charge density, and ion-specific adsorption is absent. Our hypothesis is that these experimental observations can be explained by such a simplistic pure Coulomb based model. Our approach entails grand canonical Metropolis Monte Carlo (MC) simulations as well as correlation-corrected Poisson-Boltzmann (cPB) calculations. In the former case, all ions have a common size, while the cPB utilizes a point-like model. We devote significant attention on apparent surface charge densities and interactions between large flat model surfaces immersed in either a 2:1 salt or a 3:1 salt. In contrast to most of the previous theoretical efforts in this area, we mainly focus on the weak long-ranged repulsion and its connection to an effective surface charge. We find a charge reversal and a concomitant development of a free energy barrier for both salts. The experimentally observed nonmonotonic dependence of colloidal stability on the salt concentration is reproduced using MC simulations as well as cPB calculations. A strong attraction is observed at short range for all investigated cases. We argue that in our model, all non-DLVO aspects can be traced to ion–ion correlations.

Due to the compact two-dimensional interlayer pore space and the high density of interlayer molecular adsorption sites, clay minerals are competitive adsorption materials for carbon dioxide capture. We demonstrate that with a decreasing interlayer surface charge in a clay mineral, the adsorption capacity for CO2 increases, while the pressure threshold for adsorption and swelling in response to CO2 decreases. Synthetic nickel-exchanged fluorohectorite was investigated with three different layer charges varying from 0.3 to 0.7 per formula unit of Si4O10F2. We associate the mechanism for the higher CO2 adsorption with more accessible space and adsorption sites for CO2 within the interlayers. The low onset pressure for the lower-charge clay is attributed to weaker cohesion due to the attractive electrostatic forces between the layers. The excess adsorption capacity of the clay is measured to be 8.6, 6.5, and 4.5 wt % for the lowest, intermediate, and highest layer charges, respectively. Upon release of CO2, the highest-layer charge clay retains significantly more CO2. This pressure hysteresis is related to the same cohesion mechanism, where CO2 is first released from the edges of the particles thereby closing exit paths and trapping the molecules in the center of the clay particles.

One approach to the improvement of implant-tissue interface is the creation of a bioactive surface. Here, bioactive glass-zirconia core-shell spherical nanoparticles were synthesized using a combination of sol-gel and sonochemical methods. The results revealed that the nanoparticles possess a ∼ 16 ± 4 nm rough tetragonal zirconia shell that surrounded the bioactive glass core. The optimized structure was coated on Ti6Al4V substrate through electrophoretic deposition technique. In order to obtain a stable suspension of nanoparticles in ethanol, dopamine was used as a surface treatment agent and cathodic electrophoretic deposition was successfully achieved on Ti6Al4V substrate. Also, the utilization of polyethyleneimine improved the adhesion between the coating and substrate. Due to the differences in surface charge of zirconia and bioactive glass nanoparticles, a high voltage and surfactant concentration are necessary for the simultaneous deposition of the particles. However, in the presence of core-shell nanoparticles, this issue was overcome. Microscopic examination of the coatings confirmed the elimination of cracks in core-shell constituted coatings. The adhesion between the coating and substrate increased significantly due to the rough surface of the core-shell nanoparticles. The Ca–P deposit formation on the surface of the bioactive glass and core-shell coatings were confirmed by scanning electron microscopy and energy-dispersive X-ray spectroscopy.

Hypothesis: The properties of the oxidized surface for common materials, such as silicon and titanium, are known to be markedly different from the reduced surface. We hypothesize that surface-oxidized aluminum gallium nitride ((oxidized-AlGaN)/GaN) surface charge behavior is different to unoxidized AlGaN (with ultrathin native oxide only), which can be validated via surfactant adsorption. Understanding these differences will explain why (oxidized-AlGaN)/GaN-based sensors are better performing than AlGaN ones, which has been previously demonstrated but not understood. Experiments: The surface of an AlGaN/GaN structure was oxidized with hot piranha solution and oxygen plasma. AFM force measurements and imaging were performed to probe the charge properties of the surface in aqueous solutions of varying pH containing only an acid or base, or with an added ionic surfactant: cationic cetyltrimethylammonium bromide (CTAB) or anionic sodium dodecylsulfate (SDS). Findings: The (oxidized-AlGaN)/GaN surface is positively charged at pH 4 and pH 5.5, although pH 5.5 should be close to the isoelectric point of the surface. The surface is negatively charged at pH 10 and pH 12, and sufficiently charged to attract cooperative adsorption of CTAB aggregates at pH 12. At pH 2, the evidence is inconclusive, but the surface is most likely positively charged. Compared to unoxidized AlGaN, the (oxidized-AlGaN)/GaN surface shows a wider range of surface charge magnitude over pH values between 2 and 12. This suggests that the (oxidized-AlGaN)/GaN surface has a higher surface hydroxyl group density than unoxidized AlGaN, which explains the higher sensitivity for pH sensors based on (oxidized-AlGaN)/GaN structures.

Sodium lignosulfonate (SLS) as sacrificial agent (SA) was investigated on the effectiveness in reducing Cetyl Trimethyl Ammonium (CTAB) cationic surfactant adsorption. X-Ray diffractometer (XRD), X-Ray fluorescent (XRF), Scanning electron microscopy (SEM), electron dispersive X-Ray (EDX) and Brunauer-Emmet-Teller (BET) were used to characterize the mineralogy, elemental composition and surface area of kaolinite. Fourier transform infrared-attenuated total reflectance (FTIR-ATR) was used to characterized kaolinite and SLS. The adsorption was done by depletion method using Ultraviolet–visible spectroscopy (UV–Vis). Effectiveness as sacrificial agent in mixture and pre-treatment were studied. The underlying mechanism that responsible for the effectiveness of SA were interpreted and examined. Positive outcome shows that SLS as SA manages to reduce CTAB adsorption. The SLS as SA successfully in reducing CTAB adsorption by using pre-treatment method. Effective underlying mechanism involved is SLS as SA adsorbed readily with the cation bridging assistance from the divalent salt and reversed the surface charge by creating a second layer. As high as 50% CTAB reduction had been seen in the experimental work. This study shows that SLS as SA effectively reducing the CTAB adsorption in pre-treatment.

The antigen binding fragment (Fab) is pepsin-digested product from egg yolk immunoglobulin (IgY), which shows lower immunogenicity and higher antibacterial activity. However, it limited the application of Fab due to the spontaneous adsorption and aggregation at the air-liquid interface. The present work is to investigate the effect of surfactants polysorbate 20 (PS20), poloxamer 188 (P188), and polyethylene glycol (PEG) on the aggregation stability of Fab of IgY. The results confirmed the positive role of surfactants in improving Fab stability. PS20 could effectively prevent the generation of Fab aggregates (DLS and light-obscuration analysis). It could also distinctly increase the internal hydrophobicity level, fortify the surface charge by altering the molecular conformational characteristics of Fab. The results of CLSM and surface tension demonstrated that P188 and PEG were co-adsorbed with Fab at the air-liquid interface and inhibited the formation of aggregation. PS20 competitively adsorbed in the gap between Fab molecules to inhibit the formation of aggregates. These findings would give an in-depth understanding of protein aggregation behavior influenced by surfactants and provide a theoretical basis for the development of functional food based on Fab active fragments.

High-entropy alloys (HEAs), as a special heterostructure, possesses many exclusive advantages, including the inherited merits from each component and the synergistic regulation of electronic properties, which has a great potential for catalyzing complicated redox conversions. Herein, we reveal that the synthesized nano-HEA plays a unique role in the multi-electron and multiphase conversions of lithium polysulfides (LiPSs) in lithium-sulfur batteries (Li-S). Owing to the strong affinity with LiPSs, nano-HEA enriches the activity of LiPSs around the electrode more than 17 times higher than that of the control sample (without nano-HEA addition), significantly reducing the concentration polarization. In addition, the activation polarization was greatly suppressed by the nano-HEA catalyst, which is demonstrated by the lower Tafel slope, higher exchange current density, and the larger current response from the scanning electrochemical microscopy (SECM). Besides, the smooth and continuous redistribution of surface charge is further revealed by DFT calculation, benefiting the multi-electron reactions of LiPSs. As a result, Li-S batteries assembled with nano-HEA modified separators delivered outstanding capacity retention rates of 83.3% (2 C after 500 cycles in coin cell) and 82% (0.1 C 150 cycles in pouch cell), respectively.

Molecular separation is critical to mitigating the issues of water contamination and shortage and currently focuses on the use of framework materials fabricated by special building blocks. However, developing a simple and tunable synthesis methodology for materials with alternative permeation and selectivity remains challenging. Here, we fabricate a series of nanochannel membranes composed of uniform spherical covalent organic frameworks (COFs). Diversified spherical COFs have diameters ranging from ∼150 to ∼800 nm, therefore demonstrating a programmable surface charge distribution from −24 to −63 mV. COF membranes with tailor-made surface charge enable different surface energy levels and allow increasing water permeation of 15.5 to 34.5 L m−2 h−1 bar−1. Furthermore, COFs can also act as filters, achieving up to 99.7% rejection and separation of the opposite charged dyes. We expect these COFs with tunable surface charge to be applicable to variety of fields, including sieving, batteries, and water treatments.

Enzymatic dehairing, as a crucial part of cleaner leather processing, has reached processive advancement with potentially replacing the traditional hair removal due to increasing pressure from environmental demand. However, this cleaner technology based on proteases has a problem that the hide grain (collagen-rich structure) is susceptible to be hydrolyzed, decreasing the quality of finished leather. From the perspective of improving the stability of collagen fibers and their resistance to proteolysis, a method for protecting the hide grain during the enzymatic dehairing process was developed. The results showed that calcium ions had a swelling effect on collagen fibers under near-neutral conditions (pH 6.0–10.0), decreasing the thermal stability of collagen and the proteolysis resistance of collagen significantly. The alkaline environment (pH 10.0–12.0) will promote the dissociation of carboxyl groups in hide collagen, promoting the combination of calcium ions and carboxyl groups. This strategy can change the surface charge of collagen fibers and strengthen the connection between collagen fibers, thus improving protease resistance and the thermal stability of collagen. However, collagen fibers could swell violently once the alkalinity of the solution environment was extreme. Despite the above situation, calcium ion was still conducive to maintain the structural stability of collagen fibers. At pH 10.0–12.0, pretreating animal hide with a solution containing calcium ions can improve the protease resistance of hide grain, making the hide grain well-protected. This method provided an effective way to establish a safer enzymatic unhairing technology based on substrate protection. • A collagen protection method for hair removal of animal hide was developed. • This method applied calcium ions to collagen at alkaline conditions (pH 10.0–12.0). • Pretreatment results of calcium ions at different pH values on animal hide were compared.

Plasma-initiated free radical polymerization was used to engineer carbon nanoparticles (CNPs) with tailored chemical and physical properties. Following surface modification, CNPs were loaded with a highly effective anti-infection agent called metal-free Russian propolis ethanol extract (MFRPEE), thus, creating nano-based drug delivery systems (NBDDSs). The loading of MFRPEE onto grafted CNPs occurred naturally through both electrostatic interactions and hydrogen bonding. When constructed under optimal experimental conditions, the NBDDSs were stable under physiologic conditions, and demonstrated enhanced anti-biofilm activity when compared with free MFRPEE. Mechanistic studies revealed that the enhanced anti-infectious activity of the NBDDSs was attributed to the modified surface chemistry of grafted CNPs. More specifically, the overall positive surface charge on grafted CNPs, which stems from quaternary ammonium polymer brushes covalently bound to the CNPs, provides NBDDSs with the ability to specifically target negatively charged components of biofilms. When studying the release profile of MFRPEE from the modified CNPs, acidic components produced by a biofilm triggered the release of MFRPEE bound to the NBDDS. Once in its free form, the anti-infectious properties of MFRPEE became activated and damaged the extracellular polymeric matrix (EPM) of the biofilm. Once the architecture of the biofilm became compromised, the EPM was no longer capable of protecting the bacteria encapsulated within the biofilm from the anti-infectious agent. Consequently, exposure of bacteria to MFRPEE led to bacterial cell death and biofilm inactivation. The results obtained from this study begin to examine the potential application of NBDDSs for the treatment of healthcare-associated infections (HCAIs).

Surface charge transfer doping has been widely utilized to tune the electronic and optical properties of semiconductor photodetectors based on low-dimensional materials. Although many studies have been conducted on the performance (response time, responsivity, etc.) of doped photodetectors and their mechanisms, they merely examined a specific thickness and did not systematically explore the dependence of doping effects on the number of layers. This work performs a series of investigations on ReS2 photodetectors with different numbers of layers and demonstrates that the p-dopant tetrafluorotetracyanoquinodimethane (F4-TCNQ) converts the deep trap states into recombination centers for few-layer ReS2 and induces a vertical p-n junction for thicker ReS2. A response time of 200 ms is observed in the decorated 2-layer ReS2 photodetector, more than two orders of magnitude faster than the response of the pristine photodetector, due to the disappearance of deep trap states. A current rectification ratio of 30 in the F4-TCNQ-decorated sandwiched ReS2 device demonstrates the formation of a vertical p-n junction in a thicker ReS2 device. The responsivity is as high as 2,000 A/W owing to the strong carrier separation of the p-n junction. Different thicknesses of ReS2 enable switching of the prominent operating mechanism between transforming deep trap states into recombination centers and forming a vertical p-n junction. The thickness-dependent doping effect of a two-dimensional material serves as a new mechanism and provides a scheme toward improving the performance of other semiconductor devices, especially optical and electronic devices based on low-dimensional materials.

Malachite green (MG) is one of synthetic dyes used as a biological stain, antifungal, and antiprotozoal material in fish farming industry, even though the growing concern of its health hazards. For the first time TiO2/ZnS nanocomposites with boost adsorption properties for MG removal were synthesized through the simple successive ionic layer adsorption and reaction (SILAR) method. TiO2 with 80/20 heterogeneous anatase/rutile phase was prepared afterwards various contents of ZnS were deposited over TiO2 via SILAR. The samples were analyzed using XRD, FTIR, FESEM, EDX, HRTEM, DRS, zeta potential, and nitrogen adsorption/desorption measurements. The impact of adsorption parameters; initial dye concentration, adsorbent dose, and contact time on the MG elimination were investigated. The adsorption studies confirmed that the nanocomposite is characterized with low adsorbent dose 0.125 g/L, high dye removal 95.2%, and fast adsorption equilibrium time 10 min. Various adsorption kinetic models; Weber-Morris intraparticle diffusion, pseudo-first order, Elovich, pseudo-second order, were studied. The Dubinin–Radushkevich showed better conventionality than Langmuir and Freundlich isother model. High adsorption capacity (1118.6 mg/g) of mesoporous TZS2 is attributed to the synergistic effect of large surface area (350 m2/g) and highly negative surface charge (− 33.7 mV).

The X-ray irradiation of gold salt aqueous solutions in the synthesis of gold nanoparticles (AuNPs) in the absence of any reducing agent or stabilizer is presented. The size, dispersion, number of particles, yield and morphology evolution during the radiolytic formation of AuNPs were followed simultaneously using in situ small-angle X-ray scattering. This study provides an insight into the overall kinetics and formation mechanisms at the initial stage of AuNP synthesis without reductants and stabilizers. The pH-dependent speciation of aqueous HAuCl4 and its influence on the synthesis, structure and properties of AuNPs were observed. The result sheds light on the key parameters required to obtain stable monomodal particles and the influence of the surface charge and reactivity of the chemical solution on the final particle size and shape.

A basic logic gate based on conventional silicon transistors needs the combination of at least two transistors in series or parallel. Two-dimensional (2D) materials with atomic thickness and flexib...

Graphdiyne(GDY) has the unique feature in the topological ordered arranged sp- and sp2-hybridized carbon atoms, thus deriving a series of 2D allotropes. Due to inhomogeneous π-bonding and carbon orbital overlap between different hybrid carbon atoms, GDY possesses a natural band gap with a Dirac cones structure. And GDY exhibits semiconductor property with a conductivity of 2.516×l0−4 S/m at room temperature. The topological distribution of alkyne and benzene bonds of GDY makes its surface charge distribution extremely uneven, which produces high intrinsic activity for further modification. Its unique molecular structure endows the specific interaction with various species, such as ions, atoms, molecules and nanoparticles, showing excellent charge transport capability and unique advantages in mass transfer and energy conversion. From the view of the interaction principle between GDY and different compositions, we summarized the application of GDY-based materials in the fields of catalysis, energy conversion and storage, biological detection and so on.

Two-dimensional (2D) transition-metal dichalcogenide (TMDC)-based semiconducting van der Waals (vdW) heterostructures are considered as potential candidates for next-generation nanoelectronics due to their unique and tunable properties. Controlling the carrier type and band alignment in 2D TMDCs and their vdW heterostructures is critical for realizing heterojunctions with the desired performances and functionalities. In this report, controlling the carrier type and band alignment in a vertical MoTe2/MoS2 heterojunction is presented via thickness engineering and surface charge transfer doping. A highly rectifying p-n diode and a nonrectifying n-n junction are obtained with different MoTe2 thicknesses due to their different doping conditions. A vertical tunnel diode is subsequently achieved with a controlled oxygen plasma treatment, which selectively induces degenerate p-type doping to MoTe2, whereas the intrinsic n-type characteristic of MoS2 is maintained during the treatment. These techniques to realize multifunctional diodes are universal and applicable to emerging nanoelectronics based on 2D materials.

Polyelectrolyte multilayers are promising drug carriers with potential applications in the delivery of poorly soluble drugs. Furthermore, the polyelectrolyte multilayer contributes towards electrostatic interactions, which enhances the physical and chemical stability of colloids when compared to those prepared by other approaches. The aim of this work was to generate a polyelectrolyte multilayer on well characterised nanoparticles of the poorly water-soluble drug, griseofulvin. Griseofulvin (GF) nanoparticles (300 nm) were produced by wet bead milling, bearing a negative surface charge due to the use of poly(sodium 4-styrenesulfonate) (PSS) as a stabiliser. Six further layers of alternating chitosan and PSS polyelectrolyte multilayer were successfully generated at the particle surface either via use of: (1) the conventional method of adding excess coating polymer followed by centrifugation, or (2) the continuous in situ approach of adding sufficient amount of coating polymer. The continuous in situ method was designed de novo by the consecutive addition of polymers under high shear rate mixing. In comparison to the continuous in situ method, the conventional method yielded nanoparticles of smaller size (282 ±9 nm vs. 497 ±34 nm) and higher stability by maintaining its size for 6 months. In conclusion, the parent griseofulvin nanosuspension proved to be a suitable candidate for the polyelectrolyte multilayer fabrication providing an avenue for a bespoke formulation with versatile and potentially enhanced drug delivery properties.

Structural unsteadiness and limited electrochemical kinetics upon cycling seriously impede further applications of birnessite cathodes for rechargeable aqueous zinc‑ion batteries (ZIBs), even though they have high voltage platforms and distinctively layered structures for preferable (de)intercalation of zinc ions. Herein, yolk-shell structured K-birnessite (K0.48Mn2O4·0.49H2O)@mesoporous carbon nanospheres (KMOH@C) with rich oxygen vacancies are synthesized for the first time with a two-step diffusion-driven strategy of hydrothermal synthesis followed by etching with KOH. The transport of reaction ions is regulated by surface charge and pore structure of the carbon shells, thus K-birnessite is preciously transferred into the hollow mesoporous carbon (HMC) nanospheres. Furthermore, the etching effect of KOH and the confinement effect of HMC nanospheres generate intercalated K+ and abundant oxygen vacancies into KMOH, leading to an excellent electrochemical kinetics. Meanwhile, HMC nanospheres also endow rapid electron/ion transport and stabilize the crystal structure of K-birnessite. Therefore, KMOH@C exhibits superior electrochemical performances with high reversible capacities of 412.7 and 122.2 mA h g‒1 at 0.5 and 10.0 A g‒1 than reported cathodes, respectively. Moreover, an exceptional cyclability of 129.6 mA h g‒1 even after 6000 cycles at 3.0 A g‒1 is achieved, making the KMOH@C cathode highly competitive for eco-friendly aqueous ZIBs.

The superconducting magnet, as a main component of the international thermonuclear experimental reactor (ITER), is critical to the ITER's long-term stability. Polyimide (PI) not only has excellent electrical properties at cryogenic temperature, but also has strong irradiation resistance, which has become the common choice of insulating materials for the superconducting magnet. Due to the pulsed power supply used in the ITER, PI is facing the dual challenges of cryogenic temperature and pulsed voltage. The surface charge characteristics of irradiated PI film by different doses of electron beam were studied in this paper. The surface charging is completed under the pulse voltage with 40% relative humidity. The partial discharge initial voltage (PDIV) and breakdown voltage in liquid nitrogen (LN2) were measured by electrostatic voltmeter. The findings indicate that proper irradiation can help to minimize charge accumulation and decrease the trap level. At the same time, the PDIV and breakdown voltage can be increased by irradiation. However, too much irradiation can weaken this influence.

Hypothesis The absorption capacity and kinetics of nanocellulose foams are controlled by the surface charge of the fibers, which affects swelling and determine the porosity and structure of the network. Experiments Absorption kinetics were quantified at time scales ranging from fractions of a second to minutes. The mass absorption rate as well as the area profile for the liquid stains were simultaneously measured. Findings The absorption profile followed a three-stage mechanism: wicking, transition and fiber swelling. Absorption of fluids differing in ionic strength revealed the critical role played by electrostatic forces. Nanocellulose foam absorption capacity is 25% higher for water than for 0.9 wt% NaCl solution. The absorption kinetics of nanocellulose foam are also tuneable by modulating the surface charge. High surface charge nanocellulose foams have slower absorption in water than their low surface charged analogues. This behaviour is driven by the lower pore sizes developed in high surface charge foams, as determined by X-ray CT. Small Angle X-ray Scattering revealed structural homogeneity of high surface charge foams upon absorption of water due to high fibrillation and fiber swelling.

Hypothesis: Stimuli-responsive Pickering emulsions have attracted considerable interest due to their widespread potential applications. Especially pH-responsive behavior could be easily implemented. In this work, we reported a pH-responsive Pickering emulsion based on amphiphilic graphene quantum dots at a low concentration which shows a great potential from the environmental and economic perspective. The stimuli responsive properties would make the smart Pickering emulsifiers recyclable and reusable. Experiments: The amphiphilic-adaptable graphene quantum dots functionalized by alkyl groups (C-GQDs) were synthesized by a facile one-step pyrolysis method. The pH-responsive emulsion performances were investigated, and the mechanism of pH-responsive of C-GQDs was studied by dynamic light scattering. Findings: The amphiphilicity of C-GQDs could be acquired controllably and effectively by this facile one-step pyrolysis method, which are able to stabilize Pickering emulsion at a very low concentration (0.001%). The amphiphilicity of C-GQDs are capable of changing in response to environmental stimuli. When the pH value of aqueous solution adjusts to 2, these C-GQDs aggregate in contrast to their stability in neutral condition due to the alternation of surface charges. The pH-responsive aggregation/ dispersion behavior of C-GQDs allows us to tune the interactions between oil-in-water emulsion droplets without introduction of destabilization agents. This will provide huge economic benefits in industrial applications in the future.

This paper presents a solution for the regulation of electric field along the post insulator of 1 MV DC GIL for ITER neutral beam injector (NBI). To regulate the electric field distribution, a simulation model of the post insulator with surface nonlinear conductivity is developed. The actual working conditions of NBI GIL including a square wave voltage, a radiation environment as well as surface charge accumulation are considered. The results show that radiation will lead to a significant increase in the conductivity of SF6 gas, which makes the heteropolar charges from the SF6 gas domain dominate the surface charge. The tangential electric field on the insulator surface is seriously distorted by heteropolar charges. The post insulator with the design of surface nonlinear conductivity can effectively dissipate the surface charge and the tangential electric field along the insulator surface can be reduced by up to 46.5%. This paper aims to propose research methods and feasible means for the reasonable insulation design of NTER GIL to ensure the safe and stable operation of ITER.

In the flotation of finely disseminated iron ores, fine hematite and gangue minerals (mainly quartz) always co-exist in the pulp, their higher interface energies would cause complex interfacial interactions and aggregations. Thus, particle aggregation characteristics in hematite-quartz systems with sodium oleate (NaOL) were studied in this research. The focused beam reflectance measurement (FBRM) and Zeta potential distribution analyses revealed that quartz and hematite particles formed hetero-aggregates at pH 5.0–7.0, while NaOL would weaken the hetero-aggregation by inducing the aggregate formation of hematite particles. The adsorption and contact angle tests indicated that hetero-aggregation inhibition could be attributed to oleate ion (OL−) adsorption onto hematite surfaces, which changed the surface charge and hydrophobic characteristics. Theoretical calculations demonstrated that the hydrophobic interactions among hematite particles, rendered hydrophobic by NaOL, were the main cause of hematite particles forming large aggregates.

In this work, we developed the voltage-transient method to characterize the properties of traps in AlGaN/GaN high-electron-mobility transistors (HEMTs) in the OFF-state. By monitoring the drain voltage transients of the HEMTs at various temperatures, three types of trapping mechanism were identified: 1) buffer charge trapping, which occurred on a timescale of approximately 1 ms; 2) charge trapping in the AlGaN layer at the gate–drain edge with the energy level ( ${E}_{a}$ ) of approximately 0.54 eV; and 3) surface charge trapping with ${E}_{a}$ of approximately 0.28 eV. In particular, we extracted accurate amplitudes for the first two trapping behaviors and studied the dependence of the trapping effect on the filling bias conditions. The results showed that the buffer charge trapping was primarily affected by the drain voltage, whereas the charge trapping on the drain side of the gate was affected by both the drain and gate voltages; these results were verified by drift-diffusion simulations. In addition, we observed the third trapping behavior, which was apparent in the measurement window beyond 308 K, thus demonstrating the advantages of our method for correctly and effectively monitoring the changes in the peaks in the time constant spectrum.

Iron oxide nanoparticles (IONPs) are increasingly being employed for in vivo biomedical nanotheranostic applications. The development of novel IONPs should be accompanied by careful scrutiny of their biocompatibility. Herein, we studied the effect of administration of three formulations of IONPs, based on their starting materials along with synthesizing methods, IONPs-chloride, IONPs-lactate, and IONPs-nitrate, on biochemical and ultrastructural aspects. Different techniques were utilized to assess the effect of different starting materials on the physical, morphological, chemical, surface area, magnetic, and particle size distribution accompanied with their surface charge properties. Their nanoscale sizes were below 40 nm and demonstrated surface up to 69m2/g, and increased magnetization of 71.273 emu/g. Moreover, we investigated the effects of an oral IONP administration (100 mg/kg/day) in rat for 14 days. The liver enzymatic functions were investigated. Liver and brain tissues were analyzed for oxidative stress. Finally, a transmission electron microscope (TEM) and inductively coupled plasma optical emission spectrometer (ICP-OES) were employed to investigate the ultrastructural alterations and to estimate content of iron in the selected tissues of IONP-exposed rats. This study showed that magnetite IONPs-chloride exhibited the safest toxicological profile and thus could be regarded as a promising nanotherapeutic candidate for brain or liver disorders.