Effective Charge Distribution Research Articles

0D/2D Bi2WO6:Yb3+,Tm3+/Bi12O17Cl2 S-scheme heterojunction photocatalyst with enhanced full spectrum light activity by upconversion luminescence

To effectively utilize near-infrared light in the solar spectrum, expanding the spectral response range of photocatalysts is one of the main issues at present. Herein, a novel 0D/2D Bi2WO6:Yb3+, Tm3+/Bi12O17Cl2 S-scheme heterostructure with full spectral response is successfully synthesized through a hydrothermal method. The optimized Bi2WO6:Yb3+,Tm3+/Bi12O17Cl2 (1:1) photocatalyst degraded 68.2% and 59.1% of methylene blue (MB) and Rhodamine B (RhB) at 980 nm NIR light irradiation for 240 min, and the degradation of MB and RhB was 96.1% and 92.3% under visible light irradiation for 40 min, respectively. The enhanced photocatalytic activity could be attributed to these synergistic effects including the unique 0D/2D contact interface, the expanded photoresponse range, enhanced upconversion luminescence, as well as efficient energy transfer process between Yb3+/Tm3+ and Bi2WO6. Based on characterization and photocatalytic experiments, the introduction of Bi2WO6:Yb3+, Tm3+ can construct S-scheme heterojunctions with Bi12O17Cl2 and produce a full-spectrum response to sunlight. The result, the Bi2WO6:Yb3+, Tm3+/Bi12O17Cl2 photocatalysts possessed effective charge distribution and migration and maintained the excellent redox capacity of semiconductor materials. The hydroxyl radicals (·OH), superoxide radicals (·O2), and holes (h+) as active species played crucial roles in the degradation process. This work describes a potential method to construct S-scheme photocatalyst with great upconversion activity that possesses full spectral response for water pollution control.

Quantifying the Molecular Polarization Response of Liquid Water Interfaces at Heterogeneously Charged Surfaces.

The hydration shells of proteins mediate interactions, such as small molecule binding, that are vital to their biological function or in some cases their dysfunction. However, even when the structure of a protein is known, the properties of its hydration environment cannot be easily predicted due to the complex interplay between protein surface heterogeneity and the collective structure of water's hydrogen bonding network. This manuscript presents a theoretical study of the influence of surface charge heterogeneity on the polarization response of the liquid water interface. We focus our attention on classical point charge models of water, where the polarization response is limited to molecular reorientation. We introduce a new computational method for analyzing simulation data that is capable of quantifying water's collective polarization response and determining the effective surface charge distribution of hydrated surfaces over atomistic length scales. To illustrate the utility of this method, we present the results of molecular dynamics simulations of liquid water in contact with a heterogeneous model surface and the CheY protein.

A novel double S-scheme photocatalyst Bi7O9I3/Cd0.5Zn0.5S QDs/WO3−x with efficient full-spectrum-induced phenol photodegradation

In this work, Bi7O9I3/Cd0.5Zn0.5S QDs/WO3−x ternary heterojunction with full spectrum response was prepared and applied in the photodegradation of phenol. The results of photocatalytic experiments showed that the prepared Bi7O9I3/Cd0.5Zn0.5S QDs/WO3−x heterojunction had the highest performance under full spectrum, visible and near-infrared light irradiation, and the reaction rates were 4.02, 3.75 and 5.71 times that of pure Bi7O9I3, respectively. This performance improvement results from the construction of double S-scheme heterojunction and the full-spectrum response, which had effective charge distribution and migration as well as an excellent response to sunlight. In addition,·OH and·O2- took the lead role in the process of photodegradation. Combined with the free radical-trapping experiment, ESR experiment and DFT theoretical calculation, the photocatalytic mechanism of double S-scheme system was proposed. This work is contributory to designing novel photocatalytic materials with dual S-scheme heterojunction and the efficient purification of wastewater in environmental remediation.

Determination of the Mechanism of Nucleophilic Reaction of Fenitrothion Using Substituted Phenoxide Nucleophiles in Aqueous Media

The mechanism of the nucleophilic displacement reaction at the phosphorus centre of organophosphates was determined. Phenoxide nucleophiles were reacted with fenitrothion (O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate) in water at 25oC and pseudo-first order rate constant measurements taken. Second-order rate constant (kNuc) was determined for the different concentrations of nucleophiles while the second-order rate constant (klg) for the investigation of 2,4-dichlorophenoxide ion with and series of aryl phosphorothioate esters was also determined. Linear free energy relationship was further determined using the Brϕnsted-type plot. The plots are linear over a range of pKaNuc of 7.15-11.10 that straddles the pKa of the leaving 3-methyl-4-nitrophenoxide ion (pKa = 7.20) with statistically acceptable linear correlations (R2 = 0.987) and (R2 = 0.980). The linearity in the traditional Brϕnsted-type plots shows the sensitivity of the nucleophilic displacement to the basicity of the nucleophiles and hence is consistent with a single transition-state mechanism whose barrier to decomposition is low hence concerted. Analysis of the values of βNuc, βLg and βeq (0.734) with the effective charge distribution in the transition state shows that it has no positive character. The Leffler index presents bond formation being slightly ahead of bond rupture.

The analisis of interaction of monosaccharides with aminoacids in food raw by quantum-chemical methods

The object of research is the products of hydrolysis of the polysaccharide inulin (glucose, fructose) of plant raw materials used for the production of food products for health-improving and prophylactic purposes. The search for optimal conditions for the transformation of polysaccharides in the processes of hydrolytic cleavage into fructose-oligosaccharide products requires a thorough study of both the chemical composition of the raw material and the interaction between the components. This affects both the stability of the initial, intermediate and final products of the hydrolysis of the polysaccharide, and its release from plant materials and the further course of its fragmentation. Literature data indicate that the chemical composition of carbohydrate-containing plant materials, in particular the content of mineral components, has not yet been fully studied and requires additional research and refinement. After all, macro- and microelements in its composition are not only important nutrients, but can also take an active part in the transformation of organic components through complexation at intermediate stages of these processes. In addition, the question of the possible interaction of organic compounds in the composition of food raw materials, in particular biopolymers, which make up a significant part of the mass – carbohydrates and protein compounds, also requires attention. Such interaction under normal conditions has practically not been studied, but it can affect the course of technological processes of processing. The study of intermolecular interactions occurring in complex natural systems is often complicated either by the absence of direct (selective) physical and physicochemical research methods, or by the multicomponent chemical composition of the system, or by the complexity of the objects (substances) of the study themselves. This is especially true for natural substances of a polymeric nature – proteins, peptides, poly- and oligosaccharides. Therefore, the work paid special attention to the study of the interaction of these components. The spatial structure of inulin molecules, oligosaccharides and elementary units of these polymers has been investigated using quantum chemical modeling. The distribution of effective charges on carbohydrate atoms is calculated; it directly affects their reactivity. And also quantum-chemical models of the interaction of protein substances of plant materials with carbohydrates in vacuum and in aqueous solutions are created, depending on their dilution.

Screened Coulomb interactions of general macroions with nonzero particle volume

The author shows that rigid colloidal particles of various shapes can be mapped to an effective point, line, or surface charge distributions. This allows closed-form integral expressions for the electrostatic potential and effective pair potential for particles of possibly arbitrary shape and particle configuration.

Unraveling the effect of charge distribution in a polyelectrolyte multilayer nanofiltration membrane on its ion transport properties

Polyelectrolyte (PE) multilayer nanofiltration membranes are composite membranes obtained by layer-by-layer (LbL) adsorption/advection of oppositely charged polyelectrolytes. The mass transport properties of such polyelectrolyte multilayer membranes (PEMMs) strongly depend on membrane structural parameters related to the synthetic preparation conditions as well as on the operating conditions. Understanding the relationship between such structural features and transport properties remains a difficult question to answer. We propose a one-dimensional numerical simulation framework solving the Nernst-Planck-Poisson equations for the transport of ions through n electrolyte layers En and n polyelectrolyte layers PEn - coining this pressure (p) driven transport model as pEnPEn. We utilize different EnPEn-architectures of this model to interpret experimental data of new LbL-membranes. The proposed model framework systematically evaluates the impact of the effect of polycation/polyanion architecture with respect to the rejection of symmetric and asymmetric salts. pEnPEn can be tuned to reveal and explain the influence of the ionic crosslinking, charge compensation, and overcompensation. The model enables to formulate an effective charge distribution for different polyelectrolyte multilayer (PEM) structures. As such, the model framework gives insightful details on ion rejection phenomena, yet it will be a prerequisite and will become even more valuable when combined with neural network modeling based on a hybrid data set combining pEnPEn simulations with experimental input parameter.

Proposed interaction mechanism between medicine and the diseased cell in diluted homoeopathic medicine

Background: High-diluted homoeopathic medicines practically contain no medicinal molecules. The disease-curing mechanism of homoeopathic medicines has not yet been adequately understood. Acceptable knowledge of this mechanism is essential for further development of homoeopathic science. Objectives: The purpose of this article is to provide a phenomenological model to understand the interaction mechanism between homoeopathic medicines and the diseased cell (DC), which cure diseases with a view to build a conceptual framework that would facilitate subsequent clinical and theoretical investigations. Methods: We have proposed the formation of hydrogen bonded nano and micro clusters (NAM) during the preparation (succession) of homoeopathic medicines. NAM are composed of effective ionic charge (such as O+, H + and other ions) distribution patterns (CDPs). During the electrostatic interaction between CDP around NAM and that around DC, H + ion (proton) or other ion tunnelling takes place, which normalises the highly disordered (higher entropy) state of the CDP around DC to bring it to the normal state. Results: NAM is DC dependent. The entropy change around the DDP leads to information change, which is transmitted to the brain through neurotransmitters to complete the disease remediation process. Proton or ion tunnelling from NAM to DC is quantum mechanical in nature. Conclusion: A novel phenomenological model demonstrating the interaction between DC and homoeopathic medicines (NAM) has been proposed that cures the disease. Ion tunnelling, entropy and related information change (cells signalling) taking place during the healing process appeared to be associated with biological phenomena, yet to be fully developed.

ACTAR TPC performance with GET electronics

The ACTAR TPC detector has been designed as a state-of-art detector for the tracking of ions in nuclear physics experiments. We performed various sets of test measurements with an alpha source, using a reduced size demonstrator of this device, in order to estimate the performances that can be expected from the tracks analysis. The parameters from the detector, from the electronics and from the analysis have been studied, with their influence on the energy resolution and the tracking precision. An effective full 3D charge distribution reconstruction method is also presented in order to analyze particle trajectories in any direction.

Charge calculation studies done on an end-functionalized double-walled carbon nanotube using MOPAC

Carbon nanotubes functionalized with the appropriate group are important from the point of view of applications of these nanotubes in drug delivery. In this work, we study the charge configuration on the surface of a double-walled carbon nanotube (DWCNT) when it is functionalized with the amidogen group using MOPAC, i.e., molecular orbital package. This kind of a study is performed for a DWCNT for the first time. Taking their electrical properties into consideration, we have functionalized this DWCNT with the amidogen functional group. As nitrogen atom in the amidogen group carries a lone pair of electron, amidogen being electron-releasing group, the addition of this causes the variation in the charge values on the carbon atoms of the DWCNT. Thus, net atomic charge is distributed over the DWCNT system. The effective charge variation is observed close to the carbon atom to which the amidogen group is attached. This charge distribution is then compared with the bare DWCNT case where no external group is attached. The effective charge distribution on the DWCNT surface is observed to be dependent on the mutual length of the constituent walls in DWCNT. Analyzing the charge distribution, the current due to a potential difference applied to the outer CNT would generate sufficient torque to overcome the static and dynamic frictional forces that exist between the inner and outer walls, thereby causing the inner tube to rotate. Application of the charge calculation studies for the nanomotor application of the nanotubes is also discussed.

From Intramolecular (Circular) in an Isolated Molecule to Intermolecular Hole Delocalization in a Two‐Dimensional Solid‐State Assembly: The Case of Pillarene

AbstractTo achieve long‐range charge transport/separation and, in turn, bolster the efficiency of modern photovoltaic devices, new molecular scaffolds are needed that can self‐assemble in two‐dimensional (2D) arrays while maintaining both intra‐ and intermolecular electronic coupling. In an isolated molecule of pillarene, a single hole delocalizes intramolecularly via hopping amongst the circularly arrayed hydroquinone ether rings. The crystallization of pillarene cation radical produces a 2D self‐assembly with three intermolecular dimeric (sandwich‐like) contacts. Surprisingly, each pillarene in the crystal lattice bears a fractional formal charge of +1.5. This unusual stoichiometry of oxidized pillarene in crystals arises from effective charge distribution within the 2D array via an interplay of intra‐ and intermolecular electronic couplings. This important finding is expected to help advance the rational design of efficient solid‐state materials for long‐range charge transfer.

From Intramolecular (Circular) in an Isolated Molecule to Intermolecular Hole Delocalization in a Two-Dimensional Solid-State Assembly: The Case of Pillarene.

To achieve long-range charge transport/separation and, in turn, bolster the efficiency of modern photovoltaic devices, new molecular scaffolds are needed that can self-assemble in two-dimensional (2D) arrays while maintaining both intra- and intermolecular electronic coupling. In an isolated molecule of pillarene, a single hole delocalizes intramolecularly via hopping amongst the circularly arrayed hydroquinone ether rings. The crystallization of pillarene cation radical produces a 2D self-assembly with three intermolecular dimeric (sandwich-like) contacts. Surprisingly, each pillarene in the crystal lattice bears a fractional formal charge of +1.5. This unusual stoichiometry of oxidized pillarene in crystals arises from effective charge distribution within the 2D array via an interplay of intra- and intermolecular electronic couplings. This important finding is expected to help advance the rational design of efficient solid-state materials for long-range charge transfer.

Comparative characteristics of a tryptophan molecule in the gas phase and water

The L and D isomers of the tryptophan (Trp) molecule and the (Trp)+ cation in the gas phase and water are calculated at the DFT level to reveal the effect of water considered in the dielectric continuum approximation on the electronic characteristics of the molecule. The distribution of effective atomic charges and bond lengths enables the prediction of the most probable parts of the chemical bond cleavage during the fragmentation of the molecule under the ionizing particle flux. These data are supplemented with a calculation of fragmentation energies. Zwitterionic structures characterized by the appearance of considerable dipole moments and a change in their orientation with respect to the ground state are distinguished among the possible isomeric forms in water.

Charge Renormalization and Charge Oscillation in Asymmetric Primitive Model of Electrolytes

The Debye charging method is generalized to study the linear response properties of the asymmetric primitive model for electrolytes. Analytic results are obtained for the effective charge distributions of constituent ions inside the electrolyte, from which all static linear response properties of system follow. It is found that, as the ion density increases, both the screening length and the dielectric constant receive substantial renormalization due to ionic correlations. Furthermore, the valence of larger ion is substantially renormalized upwards by ionic correlations, whilst that of smaller ions remains approximately the same. For sufficiently high density, the system exhibit charge oscillations. The threshold ion density for charge oscillation is much lower than the corresponding value for symmetric electrolytes. Our results agree well with large scale Monte Carlo simulations.

Particles inside electrolytes with ion-specific interactions, their effective charge distributions, and effective interactions**Project supported by the National Natural Science Foundation of China (Grant Nos. 11174196 and 91130012).

In this work, we explore the statistical physics of colloidal particles that interact with electrolytes via ion-specific interactions. Firstly we study particles interacting weakly with electrolyte using linear response theory. We find that the mean potential around a particle is linearly determined by the effective charge distribution of the particle, which depends both on the bare charge distribution and on ion-specific interactions. We also discuss the effective interaction between two such particles and show that, in the far field regime, it is bilinear in the effective charge distributions of two particles. We subsequently generalize the above results to the more complicated case where particles interact strongly with the electrolyte. Our results indicate that in order to understand the statistical physics of non-dilute electrolytes, both ion-specific interactions and ionic correlations have to be addressed in a single unified and consistent framework.

ChemInform Abstract: Mechanisms of Fibrinogen Adsorption at Solid Substrates

AbstractReview: 100 refs.

Transferable ab Initio Dipole Moment for Water: Three Applications to Bulk Water.

We recently reported a second-generation, ab initio dipole moment surface (DMS) for water and applied it successfully to the IR spectrum of liquid water at 300 K. Here the transferability of this DMS is demonstrated in three applications. One is the distribution of monomer dipole moments, considering two definitions, and effective atomic charges of liquid water at 300 K and also for a model of ice Ih at 0 K. The second one is a calculation of the dielectric constant of liquid water at 280, 300, 320, 340, 360 K, and the third one is correcting the intensities of the IR spectrum of liquid water at 300 K, obtained using the q-TIP4P/F potential, bringing them into much improved agreement with experiment. For the purpose of obtaining statistical ensembles we use molecular dynamics simulations with the TIP4P+E3B water model developed by Skinner and co-workers. The average monomer dipole moments for 300 K water and 0 K ice Ih are 2.94 and 3.54 D, respectively, in good agreement with literature values. Effective monomer charge distributions are derived from the monomer dipoles and give average values of -1.02 e for O and 0.51e for H in liquid water, which are also in agreement with values reported from experiment. The calculated dielectric constant of liquid water at the above five temperatures is compared to experiment and is roughly 10-15% lower than experiment.

SU‐E‐I‐99: Estimation of Effective Charge Distribution by Dual‐Energy CT Reconstruction

Purpose:Computed Tomography (CT) is a method to produce slice image of specific volume from the scanned x‐ray projection images. The contrast of CT image is correlated with the attenuation coefficients of the x‐ray in the object. The attenuation coefficient is strongly dependent on the x‐ray energy and the effective charge of the material. The purpose of this presentation is to show the effective charge distribution predicted by CT images reconstructed with kilovoltage(kV) and megavoltage(MV) x‐ray energy.Methods:The attenuation coefficients of x‐ray can be characterized by cross section of photoionization and Compton scattering for the specific xray energy. In particular, the photoionization cross section is strongly correlated with the effective charge of the object. Hence we can calculate effective charge by solving the coupled equation between the attenuation coefficient and the theoretical cross section. For this study, we use the megavoltage (MV) and kilovoltage (kV) x‐rays of Elekta Synergy as the dual source x‐ray, and CT image of the Phantom Laboratory CatPhan is reconstructed by the filtered back projection (FBP) and iterative algorithm for cone‐beam CT (CBCT).Results:We report attenuation coefficients of each component of the CatPhan specified by each x‐ray source. Also the effective charge distribution is evaluated by the MV and kV dual x‐ray sources. The predicted effective charges are comparable with the nominal ones.Conclusion:We developed the MV and kV dual‐source CBCT reconstruction to yield the effective charge distribution. For more accuracy, it is critical to remove an effect of the scattering photon in the CBCT reconstruction algorithm. The finding will be fine reference of the effective charge of tissue and lead to the more realistic absorbed‐dose calculation.This work was partly supported by the JSPS Core‐to‐Core Program(No. 23003), and this work was partly supported by JSPS KAKENHI 24234567.

Mechanisms of Fibrinogen Adsorption at Solid Substrates

The aim of this work was to critically review recent results pertinent to fibrinogen adsorption at solid/electrolyte interfaces with the emphasis focused on a quantitative analysis of these processes in terms of the electrostatic interactions. Accordingly, in the first part, the primary chemical structure of fibrinogen is analyzed. Physicochemical data pertinent to the bulk properties derived from hydrodynamic, dynamic light scattering and micro-electrophoretic measurements aided by theoretical modeling are discussed. Possible conformations and the effective charge distribution over the fibrinogen molecule for various pH an ionic strength are defined, especially the semi-collapsed conformation prevailing at physiological conditions. Adsorption kinetics of fibrinogen at hydrophilic and hydrophobic (polymer modified) substrates determined by various techniques is described. Adsorption at polymeric carrier particles, pertinent to immunological assays, studied in terms of electrokinetic and concentration depletion methods, are also considered. The reversibility of adsorption, fibrinogen molecule orientations and maximum coverages are thoroughly discussed. The stability of fibrinogen monolayers formed at these carrier particles in respect to pH and ionic strength cyclic changes is also discussed. In the final section interactions and deposition of model colloid particles on fibrinogen monolayers are analyzed which allows one to derive valuable information about molecule orientations. Based on the physicochemical data, adsorption kinetics and colloid particle deposition measurements, probable adsorption mechanisms of fibrinogen on solid/electrolyte interfaces are defined.

Modeling of cylindrical surrounding gate MOSFETs including the fringing field effects

A physically based analytical model for surface potential and threshold voltage including the fringing gate capacitances in cylindrical surround gate (CSG) MOSFETs has been developed. Based on this a subthreshold drain current model has also been derived. This model first computes the charge induced in the drain/source region due to the fringing capacitances and considers an effective charge distribution in the cylindrically extended source/drain region for the development of a simple and compact model. The fringing gate capacitances taken into account are outer fringe capacitance, inner fringe capacitance, overlap capacitance, and sidewall capacitance. The model has been verified with the data extracted from 3D TCAD simulations of CSG MOSFETs and was found to be working satisfactorily.