Interaction Of Carriers Research Articles

Defects in Hybrid Perovskites: The Secret of Efficient Charge Transport

AbstractThe interaction of free carriers with defects and some critical defect properties are still unclear in methylammonium lead halide perovskites (MHPs). Here, a multi‐method approach is used to quantify and characterize defects in single crystal MAPbI3, giving a cross‐checked overview of their properties. Time of flight current waveform spectroscopy reveals the interaction of carriers with five shallow and deep defects. Photo‐Hall and thermoelectric effect spectroscopy assess the defect density, cross‐section, and relative (to the valence band) energy. The detailed reconstruction of free carrier relaxation through Monte Carlo simulation allows for quantifying the lifetime, mobility, and diffusion length of holes and electrons separately. Here, it is demonstrated that the dominant part of defects releases free carriers after trapping; this happens without non‐radiative recombination with consequent positive effects on the photoconversion and charge transport properties. On the other hand, shallow traps decrease drift mobility sensibly. The results are the key for the optimization of the charge transport properties and defects in MHP and contribute to the research aiming to improve perovskite stability. This study paves the way for doping and defect control, enhancing the scalability of perovskite devices with large diffusion lengths and lifetimes.

Wood-Derived Bimetallic and Heteroatomic Hierarchically Porous Carbon Aerogel for Rechargeable Flow Zn-Air Batteries.

It is necessary to correctly research and synthesize efficient and inexpensive catalysts to achieve reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which is also a prerequisite for zinc-air batteries (ZABs). However, it is still a huge challenge to manufacture electrocatalysts with durable and high electrocatalytic performance from biomass. Here, a convenient method of delignification was used to transform natural balsa wood into a layered porous carbon material, FeCo alloy supported on a N, S-doped wood-based carbon aerogel (FeCo@NS-CA) as the cathode in rechargeable flow ZAB. The obtained FeCo@NS-CA with the porous lamellar architecture exhibits superior bifunctional electrocatalysis, including excellent electrochemical activities and superior stabilities. For ORR, relative to the reversible hydrogen electrode, the onset potential of FeCo@NS-CA is 0.97 V, and the half-wave potential is 0.85 V, which is consistent with the potential of commercial Pt/C. For OER, FeCo@NS-CA obtained an overpotential of 450 mV, which is very similar to the overpotential of the benchmark RuO2. The superior performance could be owing to the alloy carrier interaction between the FeCo alloy and the wood-based carbon aerogel co-doped with N and S. Moreover, the bifunctional air cathode in a flow ZAB assembled with the FeCo@NS-CA catalyst at a current density of 10 mA cm-2; the power density is 140 mW cm-2, and the specific capacitance is 760 mA h gZn-1, with a remarkable long-term stability of 400 h better than ZAB of benchmark Pt/C + RuO2. This research lays the foundation for transforming abundant biomass resources into high environmental protection materials for energy-related applications.

Classifying Charge Carrier Interaction in Highly Compressed Elements and Silane.

Since the pivotal experimental discovery of near-room-temperature superconductivity (NRTS) in highly compressed sulphur hydride by Drozdov et al. (Nature 2015, 525, 73–76), more than a dozen binary and ternary hydrogen-rich phases exhibiting superconducting transitions above 100 K have been discovered to date. There is a widely accepted theoretical point of view that the primary mechanism governing the emergence of superconductivity in hydrogen-rich phases is the electron–phonon pairing. However, the recent analysis of experimental temperature-dependent resistance, R(T), in H3S, LaHx, PrH9 and BaH12 (Talantsev, Supercond. Sci. Technol. 2021, 34, accepted) showed that these compounds exhibit the dominance of non-electron–phonon charge carrier interactions and, thus, it is unlikely that the electron–phonon pairing is the primary mechanism for the emergence of superconductivity in these materials. Here, we use the same approach to reveal the charge carrier interaction in highly compressed lithium, black phosphorous, sulfur, and silane. We found that all these superconductors exhibit the dominance of non-electron–phonon charge carrier interaction. This explains the failure to demonstrate the high-Tc values that are predicted for these materials by first-principles calculations which utilize the electron–phonon pairing as the mechanism for the emergence of their superconductivity. Our result implies that alternative pairing mechanisms (primarily the electron–electron retraction) should be tested within the first-principles calculations approach as possible mechanisms for the emergence of superconductivity in highly compressed lithium, black phosphorous, sulfur, and silane.

Formulation and Evaluation of Ranitidine Hydrochloride Loaded Floating Microspheres for the Treatment of Gastric Ulcer

The study was aimed to prepare gastro retentive floating microsphere of Ranitidine Hydrochloride by Ionotropic Gelation technique and solvent evaporation technique by using the different carriers’ ratios (Carbopol 934, Chitosan, and sodium alginate). Both natural and synthetic polymers have been used to prepare floating microspheres and evaluated the relevant parameters. There was no drug and carrier interactions assessed from FTIR. Depending upon the ratio, the percentage yield was found between 58.33% to 90.38%. in all formulations. The surface morphology of microspheres was characterized by SEM and it was discrete, spherical in shape with rough outer surface and showed free flowing properties. The mean particle size of microspheres significantly increases with increasing polymer concentration and the range between 99.92±1.221 to 168.23±1.963 µm. Among all the formulations, RF3 showed high drug entrapment efficiency (87.52%). The percentage in-vitro buoyancy of the floating microspheres was in the range of 66.92% to 81.52%. The in-vitro drug release study revealed that RF3, RF6 and RF9 Formulations having 89.97%,92.91%,93.68% drug released at the end of dissolution studies respectively. It could be concluded that the developed floating microsphere of Ranitidine Hydrochloride can be used for prolonged release in stomach. Therefore improving the bioavailability and patient compliance.

Artificial Graphene on Si Substrates: Fabrication and Transport Characteristics.

Artificial graphene (AG) based on a honeycomb lattice of semiconductor quantum dots (QDs) has been of great interest for exploration and applications of massless Dirac Fermions in semiconductors thanks to the tunable interplay between the carrier interactions and the honeycomb topology. Here, an innovative strategy to realize AG on Si substrates is developed by fabricating a honeycomb lattice of Au nanodisks on a Si/GeSi quantum well. The lateral potential modulation induced by the nanoscale Au/Si Schottky junction results in the formation of quantum dots arranged in a honeycomb lattice to form AG. Nonlinear current-voltage curves of the AG reveal conductance phase transitions with switch on/off voltages, a large electric hysteresis loop, and a strong sharp current peak accompanied by a group of differential-conductance peaks and negative differential conductance around the switch-on voltage, which can be modulated by temperature and light. These features are interpreted by a model based on the Coulomb blockade effect, the collective resonant tunneling, and the coupling of holes in the AG. Our results not only demonstrate an approach to the formation but also will greatly stimulate the characterizations and the applications of innovative semiconductor-based AG.

Transient non-Fourier thermoelastic fracture analysis of a cracked orthotropic functionally graded strip

In this work, the fracture problem of an orthotropic functionally graded strip containing an internal crack parallel to its surfaces subjected to thermal shocks is examined. To eliminate the paradox of infinite heat propagation speed and take the microstructural interactions of thermal energy carriers into account, the non-Fourier, dual-phase-lag theory is employed to investigate the transient heat conduction and the associated thermal stresses response. By utilizing Laplace transform and Fourier transform, the thermoelastic problems are finally reduced to the Cauchy-type singular integral equations, which are solved by the Lobatto–Chebyshev technique numerically. The temperature field and thermal stress intensity factors are evaluated by the numerical inversion of Laplace transform to illustrate the effects of two thermal lags and nonhomogeneous parameters. The results show the fracture risks accompanied by the dual-phase-lag heat conduction can be higher than the classical analysis and it would be more conservative to consider non-Fourier effects in designing the orthotropic functionally graded materials.

Ground-state features and spectral properties of large polaron liquids from low to high charge densities

A new variational approach is proposed at zero temperature for a finite density of charge carriers in order to study ground state features of the Frohlich model including electron-electron and electron-phonon interactions. Within the intermediate electron-phonon coupling regime characteristic of large polarons, the approach takes into account on the same footing polaron formation and polaron-polaron correlations which play a relevant role going from low to high charge densities. Including fluctuations on top of the variational approach, the electronic spectral function is calculated from the weak to the intermediate electron-phonon coupling regime finding a peak-dip-hump line shape. The spectra are characterized by a transfer of spectral weight from the incoherent hump to the coherent peak with decreasing the electron-phonon coupling constant or with increasing the particle density. Three different density regimes stem out: the first, at low densities, where the features of a single large polaron with a substantial incoherent spectral weight are not modified by charge carrier interactions; a second one, at intermediate densities, where the polaronic liquid shows a rapid crossover from incoherent to coherent dynamics; the third one, at high densities, where screening effects are so prominent that the system presents a conventional metallic phase. The results obtained in the low to intermediate density regime turn out to be relevant for the interpretation of recent tunneling and photoemission experiments in SrTiO3-based systems.

Selective Excitation of CdSe/CdS Dot‐in‐Rod Nanocrystals and Distinct Roles of Electrons and Holes in Photophysical and Photochemical Interactions with Ambient Air

CdSe/CdS dot‐in‐rod (DiR) nanocrystals are an advantageous heterostructured semiconductor system with a quasi‐type‐II electronic band structure, which enables a rich diversity of optical manipulation of carrier excitations and interactions. Herein, the selective excitation of respective CdSe quantum dots (QDs) and CdS nanorods of the CdSe/CdS DiR nanostructure is reported, which results in the distinct presence of different types of carriers at the nanorod surface. The presence of only electrons at the surface upon CdSe QD excitation leads to photophysical interactions with ambient air, which is manifested as reversible photoluminescence (PL) of the CdSe QDs. The excitation of CdS nanorods produces holes at the surface, which induces photooxidation of the CdS surface and irreversible change in PL intensity and spectral lineshape. Benefitting from unambiguously relating carrier types to photophysical and photochemical interactions, this research also verifies that trap states at the CdS surface do not act as nonradiative recombination centers, which can be removed by photochemical reactions. Herein, distinct roles of electrons and holes in the photophysical and photochemical interactions with ambient air are identified, and a more precise understanding of the interacting mechanisms is achieved.

(Invited) Entropy-Enhanced Ion Transport in Solid Electrolytes

Long-range ion transport is composed of microscopic steps of ion migration, which is governed by local structures and interactions of the charge carriers with their surroundings. Therefore, understanding the local environments of conducting ions and their impact on ion dynamics and transport pathways are critical to design of high-performance solid electrolytes. We have synthesized and studied a variety of Li superionic conductors. Systematic solid-state nuclear magnetic resonance (NMR) investigations, complemented by pair distribution analysis (PDF) and DFT/MD simulations, have revealed that entropies in structures, compositions, and Li-coordination play a key role in determining ion hoping frequencies, jumping distance, transport pathways, and activation barriers. Via maximizing these entropies, “liquid-like” Li-sublattice is produced with a flattened energy landscape yielding extremely low activation barrier for ion transport. A few such examples will be discussed, including glass, ceramic, and glass-ceramic composites.

Modulation of Gastrointestinal Mucus Properties with Ionic Liquids for Drug Delivery.

The mucus barrier lining the gastrointestinal tract poses a significant barrier to the oral delivery of macromolecular drugs. Successful approaches to overcoming this barrier have primarily focused on reducing drug and carrier interactions with mucus or disrupting the mucus layer directly. Choline-based ionic liquids (ILs) such as choline geranate and choline glycolate (CGLY) have recently been shown to be effective in enhancing the intestinal absorption of macromolecules such as insulin and immunoglobulin (IgG), respectively. Herein, the use of choline-based ILs as mucus-modulating agents for safely improving drug penetration through mucus is described. Choline-based ILs significantly increase the diffusion rates of cationic dextrans through mucin solution. Choline-maleic acid (CMLC 2:1) enhances the diffusion of 4 kDa cationic dextran in mucin solution by more than fourfold when compared to phosphate-buffered saline control. Choline-based ILs also reduce mucus viscosity without significantly impacting the native mucus gel structure. In vitro studies in a mucus-secreting coculture model with Caco-2 and HT29MTX-E12 cells further demonstrate the effectiveness of ILs in improving transport of cationic molecules in the presence of secreted mucus. This work demonstrates the potential for choline-based ionic liquids to be used as nondestructive mucus-modulating agents for enabling enhanced oral delivery of macromolecular drugs.

Quantifying the Charge Carrier Interaction in Metallic Twisted Bilayer Graphene Superlattices.

The mechanism of charge carrier interaction in twisted bilayer graphene (TBG) remains an unresolved problem, where some researchers proposed the dominance of the electron–phonon interaction, while the others showed evidence for electron–electron or electron–magnon interactions. Here we propose to resolve this problem by generalizing the Bloch–Grüneisen equation and using it for the analysis of the temperature dependent resistivity in TBG. It is a well-established theoretical result that the Bloch–Grüneisen equation power-law exponent, p, exhibits exact integer values for certain mechanisms. For instance, p = 5 implies the electron–phonon interaction, p = 3 is associated with the electron–magnon interaction and p = 2 applies to the electron–electron interaction. Here we interpret the linear temperature-dependent resistance, widely observed in TBG, as , which implies the quasielastic charge interaction with acoustic phonons. Thus, we fitted TBG resistance curves to the Bloch–Grüneisen equation, where we propose that p is a free-fitting parameter. We found that TBGs have a smoothly varied p-value (ranging from 1.4 to 4.4) depending on the Moiré superlattice constant, λ, or the charge carrier concentration, n. This implies that different mechanisms of the charge carrier interaction in TBG superlattices smoothly transition from one mechanism to another depending on, at least, λ and n. The proposed generalized Bloch–Grüneisen equation is applicable to a wide range of disciplines, including superconductivity and geology.

Amine-Grafted Mesoporous Carbons as Benzocaine-Delivery Platforms.

Smart porous carriers with defined structure and physicochemical properties are required for releasing the therapeutic drug with precise control of delivery time and location in the body. Due to their non-toxicity, ordered structure, and chemical and thermal stability, mesoporous carbons can be considered modern carriers for active pharmaceutical ingredients whose effectiveness needs frequent dosing algorithms. Here, the novel benzocaine delivery systems based on ordered mesoporous carbons of the cubic structure were obtained with the use of a hard template method and functionalization with amine groups at 40 °C for 8 h. It has been shown that amine grafting strongly modifies the surface chemistry and textural parameters of carbons. All samples indicated good sorption ability towards benzocaine, with evident improvement following the functionalization with the amine groups. The sorption capacity and drug release kinetics were strongly affected by the porosity of carbon carriers and the surface functional groups. The smallest amount of benzocaine (~12%) was released from pristine mesoporous carbon, which could be correlated with strong API–carrier interactions. Faster and more efficient release of the drug was observed in the case of triethylenetetramine modified carbon (~62%). All benzocaine delivery platforms based on amine-grafted mesoporous carbons revealed high permeability through the artificial membrane.

Dragon Fruits as a Reservoir of Natural Polyphenolics with Chemopreventive Properties.

Dragon fruits are a valued source of bioactive compounds with high potential to become a functional food. The aim of the study was to evaluate and compare the chemopreventive potential and chemical composition of fruits harvested in Thailand and Israel. The amount of different compounds in water and methanol extracts and antioxidant activity was investigated. Moreover, cytotoxic activity against cancer and normal cells of skin, prostate, and gastrointestinal origin was performed, accompanied by anti-inflammatory assay based on NO production in RAW 264.7 macrophage model. Additionally, the quenching properties of polyphenols from fruits were determined by the interaction of the main drug carrier in blood human serum (HSA). The chemometric analysis was used to reveal the relationships between the determined parameters. Dragon fruits harvested in Israel revealed higher antioxidant properties and total content of polyphenols and betacyanins when compared to those from Thailand. The examined fruits of both origins showed significant cytotoxic activity toward colon and prostate cancer cells, with no toxic effect on normal cells, but also no anti-inflammatory effect. Moreover, a high binding ability to HSA was observed for water extracts of dragon fruits. All these predestine dragon fruits are the candidates for the attractive and chemopreventive elements of daily diet.

Unmasking CSF protein corona: Effect on targeting capacity of nanoparticles

Among biological fluids, cerebrospinal fluid (CSF) not only protects and support brain, but also plays a pivotal role in intracerebral interaction of various nano-drug carriers. However, it is still uncertain how protein corona from CSF affects the targeting capability of functionalized nanoparticles (NPs). So, two types of polystyrene NPs, including PEGylated polystyrene NPs (PN) and transferrin (Tf)-modified PN (PT), were used to obtain protein corona-coated NPs, by incubating with CSF in vivo and in vitro. Strikingly, both the corona-coated NPs recovered in vivo and in vitro completely lost their active targeting characteristics towards bEnd.3 and C6 cells. Charge-, clathrin- and energy-mediated endocytosis contributed to the improved uptake efficiency of PT, whereas this enhancement in uptake of PT was disappeared after the formation of CSF protein corona. Moreover, serum albumin, which were found both in vivo and in vitro CSF corona, could mediate and facilitate the internalization of corona-coated NPs. Overall, these results have distinctly confirmed that the formation of CSF protein corona could cause the loss of active targeting specificity by shielding the targeting groups on the surface of polystyrene NPs and alter their cellular uptake by other non-specific internalization pathways.

Facile preparation of Ru/Ti1-xZrxO2/GE through hydrothermal method and its low-temperature catalytic oxidation properties of CO and C3H8

A series of Ti1-xZrxO2/GE carrier were prepared by hydrothermal method and Ru was supported on this carrier by impregnation method for low-temperature oxidation of CO and C3H8 and the effects of mass ratios of grahene and molar ratios of Ti/Zr on the catalytic activity were investigated. The obtained catalysts were characterized by XRD, BET, TEM, XPS, H2-TPR, O2-TPD. The results show that the highest conversion and sulfur resistance could be obtained on the Ru/T1Z2G catalyst, which achieved 50 % CO and C3H8 conversion at 125 °C and 226 °C respectively resulting from the formation of ZrTiO4 phase in the ZrO2-TiO2 mixed oxides and the better dispersion of Ru oxide on the TxZyG carrier. In addition, graphene promoted the specific surface area and pore diameter of the catalyst, thus enhancing the uniform distribution of active sites and the interaction of Ru and T1Z2G composite oxide carrier, which played key roles in catalytic performance and SO2 tolerance.

Study of coulomb drag with the effect of local field correction and dielectric medium

We present a numerical calculation for the drag resistivity of charge carriers interaction in coupled layer system separated by a barrier. Analytical expressions of non-linear susceptibility function and effective interlayer Coulomb interaction have been shown for non homogeneous dielectric environment at low temperature and low frequency regime. The system is studied within the model of random phase approximation (RPA) and taking into account the static local field correction (LFC). We employ Hubbard approximations (HA) and self consistent STLS approximations based LFC for obtaining the results, where LFC includes the exchange and correlation effects. Exchange and correlation effects enhanced the drag resistivity and the net screening. Another important quantity is the local form factors (LFF), which is the function of the bare inter- and intra-layer potential of the dielectric media. LFF for a multi-layer system is derived from the Poisson equation solution.

Release behaviors and kinetics of coated bead‐on‐string nanofibrous multilayer membranes loaded with drug particles

AbstractA bead‐on‐string structure with special beads at the microscale level could act as an effective carrier for solid drug particles as well as giving a continuous and sustained release profile. Tetracycline hydrochloride (TCH), used as solid model drug particles, was ground to obtain nanoscale and well‐distributed size. Electrospun poly[lactic‐co‐(glycolic acid)] (PLGA) bead‐on‐string nanofibers loaded with TCH of different particle sizes were fabricated for controlled drug delivery. The morphology of TCH particles and bead‐on‐string nanofibers were observed using a particle sizer and scanning electron microscopy. The effects of drug particle size on the release behaviors of nanofibers were further investigated and analyzed using UV–visible spectrophotometry. In vitro release results suggested that bead‐on‐string nanofibers encapsulating ground TCH particles had higher total drug release quantity compared with unground particle‐loaded nanofibers. Coating of the surface of PLGA/TCH nanofibers was investigated for controlled‐release effects and the release mechanism to understand the drug–polymer carrier interaction. The results indicated that coating on both sides of nanofibrous membranes could effectively decrease the initial burst release. Bead‐on‐string nanofibers proved to be promising mats for drug delivery applications. © 2021 Society of Industrial Chemistry.

Determination of the acoustic phonon-hot carriers interaction in n- and p-type modulation-doped GaInNAs/GaAs quantum wells

We report on the power loss mechanisms of hot carries in as-grown and annealed n- and p-type modulation-doped GaAs/Ga0.68In0.32NyAs1-y (y = 0.009, and 0.012) quantum well structures considering acoustic phonon interactions via the deformation potential (non-polar) and piezoelectric (polar) scatterings. By analysis of the applied electric field dependent amplitude of the Shubnikov de Haas oscillations, it has been revealed that incorporation of N atom into Ga0.68In0.32As switches the dominant power loss mechanism from non-polar to polar mechanism. The piezoelectricity of n- and p-type Ga0.68In0.32NyAs1-y alloys is at least three times higher than N-free samples. A comparison between as-grown n- and p-type samples depicts that the p-type sample's piezoelectricity is higher than that of n-type samples. After thermal annealing, there is a slight decrement and increment in piezoelectric stress constant for n-type the sample with 0.9% and 1.2% N, respectively.

Thousand-fold Increase in Plasmonic Light Emission via Combined Electronic and Optical Excitations.

Surface plasmon enhanced processes and hot-carrier dynamics in plasmonic nanostructures are of great fundamental interest to reveal light-matter interactions at the nanoscale. Using plasmonic tunnel junctions as a platform supporting both electrically and optically excited localized surface plasmons, we report a much greater (over 1000× ) plasmonic light emission at upconverted photon energies under combined electro-optical excitation, compared with electrical or optical excitation separately. Two mechanisms compatible with the form of the observed spectra are interactions of plasmon-induced hot carriers and electronic anti-Stokes Raman scattering. Our measurement results are in excellent agreement with a theoretical model combining electro-optical generation of hot carriers through nonradiative plasmon excitation and hot-carrier relaxation. We also discuss the challenge of distinguishing relative contributions of hot carrier emission and the anti-Stokes electronic Raman process. This observed increase in above-threshold emission in plasmonic systems may open avenues in on-chip nanophotonic switching and hot-carrier photocatalysis.

Coexistence of Short- and Long-Range Ferromagnetic Proximity Effects in a Fe/(Cd,Mg)Te/CdTe Quantum Well Hybrid Structure.

In a Fe/(Cd,Mg)Te/CdTe quantum well hybrid structure, short-range and long-range ferromagnetic proximity effects are found to coexist. The former is observed for conduction band electrons, while the latter is observed for holes bound to shallow acceptors in the CdTe quantum well. These effects arise from the interaction of charge carriers confined in the quantum well with different ferromagnets, where electrons interact with the Fe film and holes with an interfacial ferromagnet at the Fe/(Cd,Mg)Te interface. The two proximity effects originate from fundamentally different physical mechanisms. The short-range proximity effect for electrons is determined by the overlap of their wave functions with d-electrons of the Fe film. On the contrary, the long-range effect for holes bound to acceptors is not associated with overlapping wave functions and can be mediated by elliptically polarized phonons. The coexistence of the two ferromagnetic proximity effects reveals the presence of a nontrivial spin texture within the same heterostructure.