Charge Shielding Effect Research Articles

Charge shielding effects of PEG bound to NH2-terminated PAMAM dendrimers - an experimental approach.

Cationic poly(amido amine) (PAMAM) dendrimers exhibit great potential for use in drug delivery, but their high charge density leads to an inherent cytotoxicity. To increase biocompatibility, many studies have attached poly(ethylene glycol) (PEG) chains to the dendrimer surface. It is unclear how these tethered PEG chains influence the physicochemical properties of the dendrimer. Here, we develop a fluorescence-based assay utilizing anionic biological tissue to quantify the electrostatic binding affinity of a library of PEG-PAMAM conjugates with various PEG chain lengths and grafting densities. We find that covalently bound PEG chains reduce the electrostatic binding affinity more significantly than what can be achieved through covalent bonds only. Contrary to previous thought, this reduction is not explained by the steric hindrance effects of PEG chains, suggesting that other, non-covalent interactions between PEG and PAMAM are present. Using acetylated PAMAM conjugates, we convert electrostatic binding affinity to the number of charged amines accessible to the physiological environment. These data, coupled with 1H-NMR, allows us to study more closely the non-covalent interactions between PEG and PAMAM. We find that increasing PEG chain length increases the number of non-covalent interactions. Additionally, at low grafting densities, increasing the number of PEG chains on the PAMAM surface also increases the non-covalent interactions. At higher grafting densities, however, PEG chains sterically repel one another, forcing chains to elongate away from the surface and reducing the number of interactions between PAMAM and individual PEG chains. The data presented here provides a framework for a more precise mechanistic understanding of how the length and density of tethered PEG chains on PAMAM dendrimers influence drug delivery properties.

Laser-assisted in-flight muon-catalyzed deuteron-triton fusion

We investigate the deuteron-triton (DT) fusion in a three-body collision system of $\mathrm{T}\ensuremath{\mu}$ (i.e, a muon bound to a triton) impacted by a deuteron in the presence of intense laser fields with a semiclassical (SC) method. In this model, the initial positions and momenta of triton and muon are sampled from microcanonical distribution, and the dynamical process of a deuteron with a given incident kinetic energy colliding with the $\mathrm{T}\ensuremath{\mu}$ atom is simulated by tracing the classical trajectories in the combined Coulomb potentials and laser fields. At the minimum distance between the deuteron and triton, quantum tunneling through the Coulomb barrier emerges, and the penetrability can be estimated with the Wentzel-Kramers-Brillouin formula. DT nuclear fusion occurs after this quantum tunneling, and the total fusion cross section takes the Gamow form. Within the framework of the SC model, we investigate the charge shielding effect, demonstrating that this effect emerges in the low energy regime, where the impact velocity of the deuteron is smaller than the average velocity of muons in the bound state. Furthermore, the tunneling penetrability is considerably enhanced because the deuteron closely approaches the triton due to the quiver motions of charged nuclei driven by intense laser fields. As a result, the fusion cross section in this in-flight muon catalyzed fusion system can be enhanced by up to six orders of magnitude. Moreover, we calculated the DT fusion sections for a wide range of laser parameters and obtained phase diagrams demonstrating the enhanced DT fusion. Finally, important implications in achieving a large number of fusion reactions catalyzed by muons assisted by laser fields are discussed.

Water-Lubricated Aluminum Vanadate for Enhanced Rechargeable Magnesium Ion Storage.

Magnesium ion batteries (MIBs) have attracted much attention due to their low cost and high safety properties. However, the intense charge repulsion effect and sluggish diffusion dynamics of Mg2+ ions result in unsatisfactory electrochemical performance of conventional cathode materials in MIBs. This work reports water-lubricated aluminum vanadate (HAlVO) as high-performance cathode material for Mg2+ ions storage and investigates the capacity fade mechanism of water-free aluminum vanadate (AlVO). The charge density difference based on density functional theory calculation is performed to analyze the charge transfer process of water-lubricated/free aluminum vanadates (HAlVO/AlVO). The different charge transfer phenomena of two materials and the charge shielding effect of water molecule in HAlVO are revealed. Moreover, the single-phase structural evolution process and the Mg2+ ions storage mechanism of HAlVO are further investigated deeply by different in situ and ex situ characterization methods. This work proves that HAlVO is a potential candidate cathode material to satisfy the high-performance reversible Mg2+ ions storage, and the water-lubricated method is an effective strategy to improve the electrochemical performance of vanadium oxides cathode.

Melanin Nanoparticle-Actuated Redox-State Perturbation and Temporally Photoactivated Thermal Stress for Synergistic Tumor Therapy.

The elevation of antioxidant defense systems by adaptation response to localized reactive oxygen species (ROS) accumulation may confer resistance to excessive oxidative stress and cause therapeutic lethality. Herein, a highly effective tumor therapy is developed through perturbation in cellular redox homeostasis. Specifically, metal-ion-assisted oxidation polymerization of the melanin precursor (l-DOPA) whose carboxyl groups exert a charge-shielding effect leads to the formation of catechol-rich but quinone-deficient nanoparticles (NPs). These NPs possess appreciable ROS-scavenging ability, and particularly the raised quinone group levels in oxidized products can then trigger subsequent depletion of antioxidative species (GSH) and, in turn, the redox-cycle consumption of catechol/quinone groups. After incubating with cells, varying degrees of redox-state and energy metabolism fluctuations with time (∼6 h) are observed, where ROS/GSH levels rebound to a maximum peak (up to ∼280%) higher than the normal redox state after hitting the bottom within a short time (1 h). Notably, systematically triggered redox stress response can sensitize cells to an extremely endangered metastable state. The synergy of temporally photoactivated thermal stress can produce overwhelming oxidative stress, thus leading to significant inhibition of cancer cells. This work established a new paradigm of redox perturbator-based programed and combined cancer therapy.

Proton-assisted mixed-valence vanadium oxides cathode with long-term stability for rechargeable aqueous zinc ion batteries

In this work, we developed a rGO assisted vanadium oxide xerogel (abbreviate as VOHG) as cathode material for rechargeable aqueous zinc ion batteries (RA-ZIBs). The VOHG cathode exhibits an ultra-high specific capacity of 625 mA h g−1 at current density of 0.1 A g−1, superior reversibility and a long cycle life with a coulombic efficiency of 100.0% after 10,000 cycles. The VOHG material has mixed valent vanadium ions V4+/V5+and a layer structure with interlayer water. The interlayer water acts as soft support for the VO6 octahedron, forming a large space in the layers for H+/Zn2+ intercalation, which improves the migration rate of Zn2+ due to its charge shielding effect. Protons can move quickly through the interlayer water network by Grotthuss proton transport mechanism. The application of the unique structure of VOHG makes zinc ions battery will be a promising candidate of energy storage device with high-capacity and long cycle stability.

Determining the mobility of polystyrene nano-plastic in saturated quartz Sand-Limestone porous media

To investigate the transport of microplastics in mixed porous media, column experiments are conducted to investigate polystyrene nanoparticles (PSNPs) transport in saturated quartz sand (QS)-limestone (LT) porous media under different physicochemical conditions. The two-dimensional (2D) surface of DLVO interaction energy is calculated to quantify the continuous change of the DLVO energy barrier with ionic strength and predict the critical ionic strengths (CIS). Experimental results suggest the mobility of PSNPs is inhibited as the mass fraction of LT and grain size of PSNPs increases. However, PSNPs mobility is enhanced with initial concentration and flow velocity. Compared with monovalent cation (Na+), divalent cation (Ca2+) has a stronger charge shielding effect. Significantly, there is a significant correlation between the transport kinetic parameters of PSNPs and the DLVO energy barrier, which suggests 2D surface of DLVO interaction energy has a great applied potential in the prediction of nano-plastics behaviors in the natural subsurface environment.

Investigation on Viscosity Behavior of Anionic Polyacrylamide Copolymer in Brine Solutions for Slickwater Fluids Applications at High Salinity and Hardness Conditions

Abstract Slickwater fluids, used to undertake fracturing in low-permeability reservoirs, may be derived from produced water consisting of a range of dissolved salts. The fluids are pumped downhole at high flowrates, and hence friction reducers, e.g., anionic polyacrylamides (APAMs) are added, which also impart viscosity to the fluid resulting in better proppant transport. The present work investigates the effect of an APAM copolymer on the viscosity of slickwater fluids; specifically, at high salinity and hardness conditions. The experimental part of this study demonstrated the impact of the parameters—APAM concentration and salt type/concentration—on slickwater fluid viscosity. In a freshwater–APAM fluid, as monovalent salt (salinity) is added incrementally, fluid viscosity decreased initially owing to the charge-shielding effect; and, then viscosity values were leveled off beyond a certain salinity level. However, a very peculiar behavior was observed for the addition of divalent salts (hardness) to fluid systems. Initially, as hardness increased up to 50k ppm (parts per million), as expected, fluid viscosity showed a significant decrease; on the contrary, as the hardness was raised beyond 50k ppm, the solution viscosity showed a distinctive increase up to 250k ppm. This phenomenon may be explained on the basis of the reverse charge-shielding effect, i.e., excessive divalent ionicity inducing repulsion between polymer charge sites. To model the above experimentally observed non-monotonous viscosity behavior, various machine learning models were employed; support vector regression (SVR)based models predicted the slickwater fluid viscosity with maximum accuracy. Sensitivity analysis was carried out to determine the prominence of the studied input parameters. The modeling work would assist in minimizing trial-and-error in designing/optimizing a slickwater fluid system.

Replacing PEG-surfactants in self-emulsifying drug delivery systems: Surfactants with polyhydroxy head groups for advanced cytosolic drug delivery

AimEvaluation of different polyhydroxy surfaces in SEDDS to overcome the limitations associated with conventional polyethylene glycol (PEG)-based SEDDS surfaces for intracellular drug delivery. MethodsAnionic, cationic and non-ionic polyglycerol- (PG-) and alkylpolyglucoside- (APG-) surfactant based SEDDS were developed and compared to conventional PEG-SEDDS. Particular emphasis was placed on the impact of SEDDS surface decoration on size and zeta potential, drug loading and protective effect, mucus diffusion, SEDDS-cell interaction and intracellular delivery of the model drug curcumin. ResultsAfter self-emulsification, SEDDS droplets sizes were within the range of 35–190 nm. SEDDS formulated with high amounts of long PEG-chain surfactants (>10 monomers) a charge-shielding effect was observed. Replacing PEG-surfactants with PG- and an APG-surfactant did not detrimentally affect SEDDS self-emulsification, payloads or the protection of incorporated curcumin towards oxidation. PG- and APG-SEDDS bearing multiple hydroxy functions on the surface demonstrated mucus permeation comparable to PEG-SEDDS. Steric hinderance and charge-shielding of PEG-SEDDS surface substantially reduced cellular uptake up to 50-fold and impeded endosomal escape, yielding in a 20-fold higher association of PEG-SEDDS with lysosomes. In contrast, polyhydroxy-surfaces on SEDDS promoted pronounced cellular internalisation and no lysosomal co-localisation was observed. This improved uptake resulted in an over 3-fold higher inhibition of tumor cell proliferation after cytosolic curcumin delivery. ConclusionThe replacement of PEG-surfactants by surfactants with polyhydroxy head groups in SEDDS is a promising approach to overcome the limitations for intracellular drug delivery associated with conventional PEGylated SEDDS surfaces.

Nontoxic Metal-Free Visible Light-Responsive Carbon Nitride Quantum Dots Cause Oxidative Stress and Cancer-Specific Membrane Damage.

Graphitic carbon nitride (also known as g-CN or g-C3N4) has the intrinsic ability to generate electron-hole pairs under visible light illumination, resulting in the generation of reactive oxygen species (ROS). We report g-CN quantum dots (g-CNQDs) as a standalone photodynamic transducer for imparting significant oxidative stress in glioma cells, manifested by the loss of mitochondrial membrane potential. With an optimized treatment time, visible light source, and exposure window, the photodynamic treatment with g-CNQDs could achieve ∼90% cancer cell death via apoptosis. The g-CNQDs, otherwise biocompatible with normal cells up to 5 mg/mL, showed ∼20% necrotic cancer cell death in the absence of light due to membrane damage induced by a charge shielding effect at the acidic pH prevailing in the tumor environment. Acute toxicity analysis in C57BL/6 mice with intravenously injected g-CNQDs at a 20 mg/kg dose showed no signs of inflammatory response or organ damage.

Enhanced pseudo-capacitance and rate performance of amorphous MnO2 for supercapacitor by high Na doping and structural water content

Owing to the advantages of high theoretical capacitance, low cost, and environmental friendliness, MnO2 shows a great potential as the electrode material for supercapacitors. However, its low conductivity and sluggish ion migration lead to the unsatisfied electrochemical performance especially at high rates. In this work, amorphous MnO2 with both high Na doping and structural water content (nw-MnO2) is synthesized via a simple redox reaction in the saturated sodium chloride solution. On the one hand, high Na doping can effectively improve the conductivity of MnO2; on the other hand, the charge shielding effect enabled by structural water facilitates the rapid ion migration in MnO2 lattice. In addition, the amorphous feature also provides more active sites and decreases the ion diffusion length. Benefitting from the above merits, the prepared nw-MnO2 electrode delivers superior rate performance (324.7 F g−1 at 0.5 A g−1 and 182.6 F g−1 even at an ultrahigh rate of 50 A g−1) and excellent cycle stability with 91% of capacitance retention over 10,000 cycles. Moreover, the assembled nw-MnO2//activated carbon asymmetric supercapacitor delivers a high energy density of 81.1 Wh kg−1 and superior capacity retention of 101% after 7000 cycles.

Investigating the role of structural water on the electrochemical properties of α-V2O5 through density functional theory.

The α polymorph of V2O5 is one of the few known cathodes capable of reversibly intercalating multivalent ions such as Mg, Ca, Zn and Al, but suffers from sluggish diffusion kinetics. The role of H2O within the electrolyte and between the layers of the structure in the form of a xerogel/aerogel structure, though, has been shown to lower diffusion barriers and lead to other improved electrochemical properties. This density functional theory study systematically investigates how and why the presence of structural H2O within α-V2O5 changes the resulting structure, voltage, and diffusion kinetics for the intercalation of Li, Na, Mg, Ca, Zn, and Al. We found that the coordination of H2O molecules with the ion leads to an improvement in voltage and energy density for all ions. This voltage increase was attributed to the extra host sites for electrons present with H2O, thus leading to a stronger ionization of the ion and a higher voltage. We also found that the increase in interlayer distance and a potential "charge shielding" effect drastically changes the electrostatic environment and the resulting diffusion kinetics. For Mg and Ca, this resulted in a decrease in diffusion barrier from 1.3 eV and 2.0 eV to 0.89 eV and 0.4 eV, respectively. We hope that our study motivates similar research regarding the role of water in both V2O5 xerogels/aerogels and other layered transition metal oxides.

A Versatile Cation Additive Enabled Highly Reversible Zinc Metal Anode

AbstractAqueous zinc metal batteries are receiving broad attention owing to their promising characteristics of low cost, high safety, and environmental benignity. However, severe side reactions over zinc metal anodes (i.e., dendrite growth and by‐product formation) dramatically limit their further development. Herein, the key problems are tackled by introducing a dual‐function electrolyte additive (ammonium cation‐based salts) to achieve long‐term and highly reversible zinc plating/stripping. Specifically, the cation can homogenize the zinc deposition via the charge shielding effect and inhibit by‐product formation by participating in the constitution of contact ion pairs. In such a way, the Zn||Zn symmetric cell stably cycles over 2145 h at a current density of 1 mA cm−2 with the overpotential of merely 25 mV. In addition, the reversibility of energy storage devices based on manganese dioxide and an activated carbon cathode is effectively enhanced. This strategy provides a promising approach for the future development of advanced aqueous metal batteries.

Interlayer‐Expanded MoS2 Containing Structural Water with Enhanced Magnesium Diffusion Kinetics and Durability

AbstractOne obstacle that hinders the development of rechargeable magnesium batteries (RMBs) is the limited selection of cathode materials with decent Mg diffusion kinetics due to the highly polarizing nature of divalent Mg2+. To promote Mg2+ diffusion kinetics, water molecules (H2O) are incorporated into the gaps of MoS2 with enlarged interlayer spacing through an electrochemically assisted method. Owing to the charge shielding effect of crystal H2O, the electrostatic interaction between Mg2+ and host frameworks is weakened, thus hydrous MoS2 (H−MoS2) delivers a Mg diffusion rate three times faster than that of MoS2 before hydration. The facilitated Mg diffusion kinetics in H−MoS2 ensure a high capacity of 190.3 mAh g−1 at 20 mA g−1, accompanied by excellent rate performance (75.1 mAh g−1 retains at 500 mA g−1). Additionally, crystal H2O plays the role of pillars, endowing that the layered structure of H−MoS2 retains stable during repetitive Mg intercalation, thus 91.2 % of initial capacity is retained after 300 cycles.

K-preintercalated MnO2 nanosheets as cathode for high-performance Zn-ion batteries

Manganese oxides are regarded as promising cathode materials for aqueous zinc ion batteries (ZIBs) due to their low cost and high theoretical capacity. However, their practical application is seriously hindered because of the inferior electronic conductivity, sluggish diffusion kinetics and structural instability. Herein, we develop a new K-preintercalated MnO 2 (K 0.19 MnO 2 ·0.56H 2 O, KMO) nanosheet by a facile hydrothermal method. Preintercalation of K + ions into the MnO 2 crystal layers with structural reconstruction can activate more active sites, strengthen the crystal structural stability and facilitate the insertion/extraction of Zn 2+ ions. The charge shielding effect of crystal water promotes the diffusion kinetics of Zn 2+ ions. The obtained KMO electrode delivers high specific capacity (107 mAh g −1 ) and good cycling stability (~87.5% capacity retention after 2000 cycles), revealing its potential application for aqueous ZIBs.

Effect of surface charge density of bacterial cellulose nanofibrils on the rheology property of O/W Pickering emulsions

In this study, the effect of surface charge density of bacterial cellulose nanofibrils (BCNF) on the rheological characteristics of O/W Pickering emulsions was investigated by regulating the fibril charge density. BCNFs with different carboxylate group contents (0.66, 0.90 and 1.16 mmol/g dry cellulose, representing as TOBC-a, -b, and -c) were obtained by 2,2,6,6-tetramethylpiperidine-nitrogen-oxide (TEMPO) oxidation. These oxidized products were used as Pickering stabilizers to prepare O/W Pickering emulsions. Diffusing wave spectroscopy (DWS)-based microrheology was utilized to reflect the rheological features of emulsions. TOBC-a stabilized emulsion had a lower macroscopic viscosity, lower elasticity, and better fluidity. It was because a weaker fiber network was formed in the continuous phase during the ultrasonication emulsification. The influences of pH and ionic strength on the rheological properties of high-charged TOBC-c stabilized emulsions were also investigated. The emulsion prepared at pH 3.0 exhibited the highest viscosity. It was probably because the inter-fibrils electrostatic repulsion was weakened by the addition of HCl, and the hydrogen bonding interaction became dominant due to the protonation of carbohydrate group. At pH 11, the emulsion viscosity was lowest, which was resulted from the destruction of the intra-fibrils hydrogen bonds. With the NaCl concentration increased, the emulsion viscosity and elasticity increased. It was induced by the fact that the charge shielding effect of NaCl facilitated the formation of a tighter fibrils network in the continuous phase. These results have the potential to provide a guide for developing emulsion-based products with appropriate fluidity to broaden the practical application of emulsion.

The effect of piezo-photocatalysis on enhancing the charge carrier separation in BaTiO3/KNbO3 heterostructure photocatalyst

In order to reduce the secondary recombination of photogenic charge carriers caused by the structural defects at the interface of traditional heterostructure photocatlysts, and the charge shielding effect of static condition on the built-in electric field in ferroelectric/piezoelectric photocatalyst, two typical piezoelectric photocatalysts, BaTiO3 and KNbO3, were successfully compounded into a series of BaTiO3/KNbO3 heterostructure photocatalysts for the first time. BaTiO3 nanoparticles with good crystallinity are uniformly distributed on the surface of KNbO3 prism to form the BaTiO3/KNbO3 heterostructure. The piezo-response force microscopy (PFM) results and piezo-photocatalytic degradation experiments stimulated by ultrasonic vibration and light irradiation show that the separation efficiency of photogenic charge carriers and degradation performance are enhanced by the synergistic effect of piezocatalysis and photocatalysis. The piezo-photocatalytic degradation efficiency of BaTiO3/KNbO3 over direct lake blue 5B dye can reach up to 93.3%. The reaction rate constant of 0.3BaTiO3/0.7KNbO3 over the target dye is 4.44 and 8.57 times higher than that of BaTiO3 and KNbO3. This work will provide a promising paradigm to degrade organic pollutants by using synergetic effect of piezocatalysis and photocatalysis, which perhaps facilitates the practical applications of piezo-photocatalytic technology in the environmental field.

Maximized crystal water content and charge-shielding effect in layered vanadate render superior aqueous zinc-ion battery

Emerging as a promising candidate for grid-scale energy storage, aqueous zinc-ion batteries are challenged by both sluggish Zn2+ migration kinetics and poor cyclic stability of cathode materials. Herein, a maximized crystal water content of 14.8 wt% is reported for layered Na5V12O32·11.9H2O as the new cathode material. Such a content has enlarged the lattice space up to 12.75 Å providing spacious channels for rapid Zn2+ migration. The charge-shielding effect of crystal water alleviates the electrostatic interactions between Zn2+ and the cathode framework, enhancing ionic conductivity. The density functional theory calculation reveals that the high crystal water content facilitates the electrical conductivity. These should promote the Zn2+ migration kinetics and cyclic stability. Through characterizations by ex situ X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure analysis, the high crystal water content is found to associate with two-electron redox reactions during Zn2+ (de)intercalation. As a result, the Na5V12O32·11.9H2O cathode presents a reversible capacity of 430.52 mA h/g at 0.1 A/g with 103.7% retention of initial capacity over 3,862 cycles at 1 A/g.

Protein-protein interactions at high concentrations: Effects of ArgHCl and NaCl on the stability, viscosity and aggregation mechanisms of protein solution

The aim of this work was to use the diffusion coefficient ration (Dm/Dline) as a parameter to characterize the stability of protein at high concentration, to compare the effects of ArgHCl and NaCl on the interaction of highly concentrated proteins under different pH conditions, and to explore the correlation with protein stability. For this purpose, a high-concentration bovine serum albumin solution (BSA) was selected as the model system, and the diffusion coefficient, aggregation degree, conformational stability, and solution viscosity of the protein were studied by dynamic light scattering (DLS) and spectral detection techniques. The result showed that there was a significant correlation between the Dm/Dline and the protein aggregation. The Dm/Dline of the protein was minimum at pH 7.4, which corresponded to the maximum degree of aggregation and the highest solution viscosity. At pH 7.4, the hydrophobic interactions and the increased conformational stability of ArgHCl maximized the stability of the protein and reduced the viscosity of the solution by 69.3%. At pH 3.0, the strong charge shielding effect of ArgHCl and NaCl and the decreased conformational stability induced protein aggregation and the gel formation. These findings provided valuable insights into the mechanism of protein aggregation and the diffusion coefficient ration (Dm/Dline) could be a potential tool for the pre-formulation studies.

Bioinspired zwitterionic polyphosphoester modified porous silicon nanoparticles for efficient oral insulin delivery.

The intestinal epithelial and mucus barriers on the gastrointestinal tract limit the bioavailability of oral protein or peptide drugs. Therefore, efficient mucus permeability and cellular internalization are required properties for oral delivery systems. To overcome these two obstacles, porous silicon nanoparticles were modified with poly (pyridyl disulfide ethylene phosphate/sulfobetaine) polymers to make P(PyEP-g-SBm)n-AmPSiNPs (m = 0.1, 0.2, 0.3 and n = 10, 20, 30) nanoparticles (NPs). The insulin-loaded P(PyEP-g-SB)-AmPSiNPs showed favorable stability and good biocompatibility in vitro. The zwitterionic dodecyl sulfobetaine (SB) coated nanoparticles improved the mucus permeability. P(PyEP-g-SBm)20 with the optimal conjugated ratio (m = 0.3) of SB units was determined by evaluating the mucus diffusion rate of NPs. The cellular uptake of P(PyEP-g-SB0.3)n-AmPSiNPs (n = 10, 20, 30) was much higher than AmPSiNPs in the presence of inhibitors (N-acetylcysteine solution and sodium chlorate) (p < 0.01) due to the enhanced charge shielding effect of P(PyEP-g-SB) modification. The P(PyEP-g-SB0.3)20-AmPSiNPs showed about 1.4-1.7 fold increase in the apparent permeability of insulin across Caco-2/HT-29-MTX cell monolayers, compared to AmPSiNPs (p < 0.01). Finally, the in vivo study showed that insulin-loaded P(PyEP-g-SB0.3)20-AmPSiNPs generated 20% reduction of the blood glucose level with an 2-fold increase in oral bioavailability. These suggested that zwitterionic polyphosphoester modified porous silicon nanoparticles, which were of enhanced mucus permeability and cellular internalization, represent a promising carrier for oral delivery of peptide and protein.

Improved the C–V Curve Shift, Trap State Responsiveness, and Dynamic R ON of SBDs by the Composite 2-D–3-D Channel Heterostructure Under the OFF-State Stress

In this article, the C-V curve shift, trap densities responsiveness,and dynamic R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> of AlGaN/GaN/GaN:C (SH:C) and AlGaN/GaN/graded-AlGaN:Si/GaN:C (DH:Si/C) heterostructure Schottky barrier diodes (SBDs) have been systematically analyzed. Due to additional 3-D electrons in graded-AlGaN:Si layer, the composite 2-D-3-D channel of DH:Si/C has a higher carrier concentration. Reducing the OFF-state electric field strength through AlGaN:Si insert layer, a smaller positive shift of C-V curve is achieved under OFF-state stress. Due to the charge shielding effect of AlGaN:Si insert layer, trapping/detrapping effects in GaN:C buffer under the OFF-state stress are well suppressed. Compared with SH:C heterostructure, the trap density responsiveness of DH:Si/C heterostructure under OFF-state stress is significantly reduced. At the same time, trap density responsiveness of the upper channel is immune to OFF-state electric stress time. In addition, the proposed SBDs show lower ON-resistance with on reverse bias stress and better dynamic performance with on reverse stress time.