Charge Regulation Research Articles

Reactive Monte Carlo simulations for charge regulation of colloidal particles.

We use a reactive Monte Carlo simulation method and the primitive model of electrolyte to study acid-base equilibrium that controls charge regulation in colloidal systems. The simulations are performed in a semi-grand canonical ensemble in which colloidal suspension is in contact with a reservoir of salt and strong acid. The interior of colloidal particles is modeled as a low dielectric medium, different from the surrounding water. The effective colloidal charge is calculated for different numbers of surface acidic groups, pH, salt concentrations, and types of electrolyte. In the case of potassium chloride, the titration curves are compared with the experimental measurements obtained using potentiometric titration. A good agreement is found between simulations and experiments. In the case of lithium chloride, the specific ionic adsorption is taken into account through the partial dehydration of lithium ion.

Remote Monitoring of Wind Speed and Produced Voltage Measured by Anemometer

Anemometer is a device used to measure wind speed at weather measurement stations. An Anemometer, which is used to measure the wind speed of an area, is widely used in weather stations. With the anemometer, wind speed and weather forecasts of a certain region are made. In this study, the wind speed values of a sample anemometer in a certain region and the voltage produced by the anemometer for wind energy were remotely monitored via the Internet of Things. In the system created, Arduino Uno microcontroller development board for the control of the system, a sample anemometer for measuring wind speed and generating voltage, LCD shield for displaying wind speed and voltage values on the screen, esp8266 wifi module for sending instant data from the anemometer to the thingspeak IoT platform and for feeding the system. solar panel and battery charge regulator are used. In this study, the wind speed in a certain region and the monitoring of voltage produced depending on the wind speed was monitored on an internet basis. The system was operated in a certain region and the wind speed values and the generated voltage were monitored both instantaneously on the LCD screen and graphically on the thingspek an IoT platform as instantaneous, hourly, daily and weekly. With this system created, the thingview application was used for instant tracking on android devices.

Study on CO2 Adsorption and Permeance of Porous Carbon and Nitrogen Membranes Co-regulated by Charge and Strain

In order to capture and separate CO2 effectively, a novel method of controlling gas permeance by charge and strain is proposed, which has the superiority of controlled dynamic. The effects of porous C9N7 nanosheets on CO2 capture and permeability under different charge quantities and strains were analysed by molecular dynamics (MD) simulations and first-principles density function (DFT) calculations. The molecular permeability of CO2 can be as high as 5.9 × 107 GPU (CO2/CH4 separation) through 5 e- charge regulation. In addition, CO2 permeability increased with the increase of tensile strain, and the maximum permeability of 9% stretched C9N7 membrane is 3.6 × 107 GPU. On this basis, the method of combining negative charge and tensile strain was adopted to study the synergic effect. Under the condition of negative charge of 1 e- and tensile strain of 3%, CO2 permeability (CO2/CH4 separation) reached 3.2 × 107 GPU, which was 8 times of CO2 permeability when only 3% strain was added and 9 times of CO2 permeability when only 1 e- was added. Additionally, under the circumstance of negative charge of 5 e-, the CO2 obtained extra electrons -0.0666 e compared with natural C9N7 membrane. These results provide theoretical guidance for the development of highly controllable materials with CO2 capture and separation.

Redox‐mediated proton transport of two‐dimensional polyaniline‐based nanochannels for fast capacitive performance

AbstractTwo‐dimensional (2D) materials are being increasingly exploited for ion transport and storage under nanoconfinement. Here we demonstrate distinct ion transport behavior upon potential‐induced redox reaction in 2D tungstate anion cross‐linked polyaniline (TALP) electrode. It is found that, in the neutral electrolyte, SO42− ion serves as the main charge carrier in 2D polyaniline backbone when the electrical double layer charging dominates. While in an acidic electrolyte, proton transport in TALP turns to be the dominant ion behavior that is associated with the proton‐promoting surface redox processes. Moreover, higher capacitance along with better capacitive retention at a high rate is also demonstrated for TALP electrode in acidic electrolyte compared with that in the neutral environment. The results show that 2D nanoionics can be manipulated by applying redox‐active materials to build the nanochannels that allow the regulation of surface charge and chemistry with potential‐specific redox reactions.

Curvature effects in charge-regulated lipid bilayers.

We formulate a theory of electrostatic interactions in lipid bilayer membranes where both monolayer leaflets contain dissociable moieties that are subject to charge regulation. We specifically investigate the coupling between membrane curvature and charge regulation of a lipid bilayer vesicle using both the linear Debye-Hückel (DH) and the non-linear Poisson-Boltzmann (PB) theory. We find that charge regulation of an otherwise symmetric bilayer membrane can induce charge symmetry breaking, non-linear flexoelectricity and anomalous curvature dependence of free energy. The pH effects investigated go beyond the paradigm of electrostatic renormalization of the mechano-elastic properties of membranes.

Study Optimization of a Hybrid Solar-Wind System from an Individual in Ouagadougou

This work is a contribution to the study of hybrid systems for converting solar and wind energy into electricity in Burkina Faso. The approach consists of evaluating and analyzing the production of a wind turbine and a solar field in order to optimize the production of all the technologies. The results obtained made it possible to evaluate the operating performance of the installation and to show the complementarity between the two energy sources with regard to temporary and seasonal variations in resources. During nighttime periods or periods of low sunlight, the wind turbine is a good alternative to energy storage by batteries, the output of the wind turbine can be up to 853.76 W. It was also a question of proposing solutions for optimizing the hybrid system through the automation of the hybrid charge regulator. A minimum height of 30 m above the ground has been chosen as the optimum height for the wind turbine.

Surface charge modulation enhanced high stability of gold oxidation intermediates for electrochemical glucose sensors.

Rapid and accurate blood glucose detection is significant for diagnosing and treating diabetes. Herein, ultra-low-content gold nanoparticles were loaded on different metal foams and applied to electrochemical enzyme-free glucose sensors via simple displacement reactions. The structures and properties of the produced catalysts were determined by various characterization methods. The performance of the glucose sensor was examined in relation to the interactions between three different metal substrates and gold. The one with the best performance is the sample of gold nanoparticles grown on copper foam (Au300 Cu Foam). It has the advantage of a porous three-dimensional network, a large electroactive surface area, and the high catalytic activity of gold. The combination of Cu and Au increased the valence state of Au, thus favoring the catalytic activity for glucose oxidation. Cyclic voltammetry and chronoamperometry measurements revealed that Au is responsible for the electrocatalytic oxidation of glucose. The sensitivity of Au300 Cu Foam was found to be 10 839 μA mM-1 cm-2 in the linear range of 0.00596-0.0566 mM, with a detection limit (LOD) of 0.223 μM, and 2-3 s response time at 0.4 V vs. Ag/AgCl. The Au300 Cu Foam glucose sensor also offered outstanding stability and anti-interference performance. The prepared Au300 Cu Foam electrode was also successfully applied to detect different levels of glucose in human body fluids, such as saliva. These characteristics make Au300 Cu Foam promising for non-invasive glucose detection.

How pH induced surface charge modification explains the effect of petrophysical and hydrological factors on recovery trends of water drive gas reservoirs

It is generally known that water drive oil reservoirs are more efficient than water drive gas reservoirs. In the petroleum literature, several studies have documented recovery trends based on petrophysical factors other than the wettability factor.Consistent with the high concentration of carbon dioxide in natural gas systems, the pH induced wetting transition reported in petroleum recovery research associated with low salinity water flooding is a potential factor that can impact gas recovery from natural gas systems. In this paper, we have reviewed extensively the fundamental aspects of pH induced wetting transition associated with surface charge regulation in different lithologies. In so doing, we have developed theoretical models that aid explanation of gas recovery trends from different lithologies associated with natural gas systems under aquifer drive. Most importantly, putting our models in the context of fundamental theories associated with pH induced surface charge modification, we have successfully correlated the literature based wetting transition trends of gas recovery to petrophysical properties of absolute permeability and rock type as well as hydrological effect associated with aquifer type.

Ising density functional theory for weak polyelectrolytes with strong coupling of ionization and intrachain correlations.

We report a theoretical framework for weak polyelectrolytes by combining the polymer density functional theory with the Ising model for charge regulation. The so-called Ising density functional theory provides an accurate description of the effects of polymer conformation on the ionization of individual segments and is able to account for both the intra- and interchain correlations due to the excluded-volume effects, chain connectivity, and electrostatic interactions. Theoretical predictions of the titration behavior and microscopic structure of ionizable polymers are found to be in excellent agreement with the experiment.

Equilibrium Conformations and Surface Charge Regulation of Spherical Polymer Brushes in Stretched Regimes

In the present work, we study the equilibrium conformations of linear polyelectrolytes tethered onto a spherical, oppositely charged core in equilibrium with an ionic reservoir of fixed concentration. Particular focus is placed on the situation of stretched chains, where the monomer concentration is known to display an inverse square-law decay far away from the spherical surface, which is then further extrapolated all the way down to the grafting core. While the equilibrium distributions of mobile ions are computed in the framework of a classical Density Functional Theory (cDFT) that incorporates both their size and electrostatic correlations within the grafted polyelectrolyte, the equilibrium configuration of the latter is described by its averaged radius of gyration, which is taken as a variational parameter that guarantees mechanical equilibrium across the polymer-solvent interface. The averaged particle size is then analyzed over a wide range of polymerization degrees, ionic concentrations and functionality of the polymer backbones. Two distinct regimes can be identified: at high ionic strengths, swelling of the grafted polymers is dominated by ionic entropic contribution as well as polymer size effects, whereas at low ionic concentrations a balance between electrostatic and entropic effects is the main driven mechanism for particle stretching. Using Monte Carlo simulations, we then proceed to investigate the effects of charge regulation when the brush core is further decorated with active functional sites randomly distributed over its surface, which act as receptors onto which dissolved acidic ions can be adsorbed.

Local charge regulation by doping Li+ in BaGa2O4:Bi3+ to generate multimode luminescence for advanced optical Morse code

In the field of advanced anti-counterfeiting research, it is a hot issue to develop a multimodal anti-counterfeiting material with adjustable luminescence characteristics. Here, persistent luminescent materials of BaGa2O4:xBi3+ (x = 0-0.02) and BaGa2O4:0.005Bi3+,yLi+ (y = 0.001–0.02) were synthesized by a solid state reaction at high temperature. BaGa2O4: Bi3+ exhibited a broad blue emission at ∼470 nm (transition from [GaO4]) and a sharp NIR emission at ∼710 nm (3P1→1S0 transition of Bi3+), upon UV excitation at 250 nm. Incorporation of Li+ in BGO: 0.005Bi3+ induced the emission color shifting from blue to green. After stoppage of UV excitation, the BGO:0.005Bi3+ exhibited white afterglow with emission peaks at the range of 500–700 nm. However, incorporation of Li+ leaded to a stronger green afterglow and a weaker NIR afterglow. When the afterglow disappeared, the sample outputted afterglow again after heating processing. The prepared samples exhibited time- and temperature-dependent multimode luminescence, so they were used as components, combined with Morse code to realize multi-modal dynamic anti-counterfeiting. The outcomes in this work indicate that the prepared luminescent materials have broad prospects in advanced anti-counterfeit applications.

A novel cationic graphene modified cyclodextrin adsorbent with enhanced removal performance of organic micropollutants and high antibacterial activity

The coexistence of pathogenic microorganisms and refractory organic chemicals in water nurtures certain biological and chemical risks to human beings and the water environment as a whole. For an environmentally friendly utilization of water cleaning and recycling technologies, a bifunctional cationic cyclodextrin material (GD-DTAC) with adsorption and bactericidal function was designed. By a simple crosslinking method, GD-DTAC was prepared with graphene supported citric acid-β-cyclodextrin polymer (GD) and dimethyldodecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DTAC). Following the introduction of rich quaternary ammonium groups by DTAC, GD-DTAC realized a double regulation of surface positive charge and wettability. The maximum adsorption capacities of Roxarsone (ROX), Methyl Orange (MO) and Bisphenol A (BPA) were 153.59 mg/g, 445.60 mg/g and 237.90 mg/g, respectively. Antibacterial activity tests showed the efficiency of DTAC not only for enhanced adhesion resistance, but it also realized the sterilization function. This work displays the potential of the prepared bifunctional materials for the removal of pollutants from wastewater as well as the suppression of micro-pollutants. The successful preparation of GD-DTAC provided a basis for the bifunctional material, which showed a great potential in adsorption and antibiosis.

A Versatile and Simple Approach to Electrochemical Colloidal Probes for Direct Force Measurements.

The colloidal probe technique, which is based on micrometer-sized colloidal particles that are attached to the end of a cantilever, revolutionized direct force measurements by atomic force microscopy (AFM). Its major advantages are a defined interaction geometry and a high force sensitivity. Here, we present a versatile and simple approach for preparing spherical electrodes in the micrometer range on an otherwise insulated AFM cantilever. Thereby, it becomes possible to combine direct force measurements and potentiostatic control of the probe for various types of electrode materials. Two examples for the use of such electrochemical colloidal probes (eCP) are presented: First, on soft, conductive films of poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) the adhesion behavior was studied. The current through the contact area between the probe and film remained constant until the jump-out of contact, indicating a constant geometrical contact area. Second, the long-range forces due to diffuse layer overlap between an eCP and a glass surface have been determined as a function of the externally applied potential. The resulting interaction force profiles are in good agreement with those calculated based on charge regulation and solutions of the full Poisson-Boltzmann equation.

Size and roughness dependent temperature effects on surface charge of silica nanoparticles

Silica nanoparticles (SNP) with different sizes and surface areas are used in numerous micro/nanofluidic applications, while their surface charge properties play a major role in their function. In many of these applications, SNPs also undergo temperature variation. We present that an increase in temperature yields a substantial increase in SNP surface charge depending on nanoparticle size and surface roughness, which cannot be estimated by existing theory. As a continuation of our earlier work characterizing the deviation of SNP surface charging from theoretical predictions due to curvature and EDL overlap effects, this study presents the differentiation from the theory in temperature dependence under various conditions. As we calculate surface chemistry as a function of local ionic conditions (Charge Regulation), temperature variation changed the equilibrium constants of protonation/deprotonation reactions of the SNP surface, in addition to changes occurring in relative permittivity and ionic mobilities. Results show that variation of SNP surface charge by temperature decreases by decreasing particle size and/or increasing roughness size, compare to theoretical flat plate calculations considering similar temperature-dependent properties and charge regulation on the surface. We characterized these deviations by obtaining an “electrokinetic similarity” between different systems of various size and roughness at various ionic conditions based on the non-dimensional groups of λ/D P and λ/D R . Based on these, we devised a phenomenological model as an extension to the flat plate theory to successfully predict the surface charge of SNPs as a function of the particle size, roughness size, and temperature. The current findings are important for the characterization of SNPs through temperature variations and can also be used to adjust the surface charge of SNPs by tuning the temperature. • Nanoparticle surface charge increases with increasing temperature. • Temperature effects on surface charge change with particle size and surface condition. • Temperature dependent ionic diffusion and surface charge regulation were considered. • Temperature dependent solution of PNP with charge regulation is presented. • A model for nanoparticle charging is extended from analytical solution.

Polyelectrolyte-nanoparticle mutual charge regulation and its influence on their complexation

The complexation between a charged nanoparticle and an oppositely charged linear polyelectrolyte is studied using coarse-grained Semi-Grand Canonical Monte Carlo simulations. This is done for systems where one or both of the macromolecules are titratable, i.e. they have a pH-dependent charge. The presence of charge fluctuation is found to have a significant impact on the ionization of both macromolecules, the conformational properties of the adsorbed polyelectrolyte and the charge of the resulting complex. When both macromolecules are titratable, we find that the impact is larger when the absolute difference in the pKa values of the nanoparticle and polyelectrolyte increases. The physicochemical concepts here discussed are found to be in good agreement with previous experimental observations, providing a fundamental basis to rationalize these experiments.

Design of Multifunctional Nanopore Using Polyampholyte Brush with Composition Gradient

Molecular organizations and charge patterns inside biological nanopores are optimized by evolution to enhance ionic and molecular transport. Inspired by the nuclear pore complex that employs asymmetrically arranged disordered proteins for its gating, we here design an artificial nanopore coated by an asymmetric polyampholyte brush as a model system to study the asymmetric mass transport under nanoconfinement. A nonequilibrium steady-state molecular theory is developed to account for the intricate charge regulation effect of the weak polyampholyte and to address the coupling between the polymer conformation and the external electric field. On the basis of this state-of-the-art theoretical method, we present a comprehensive theoretical description of the stimuli-responsive structural behaviors and transport properties inside the nanopore with all molecular details considered. Our model demonstrates that by incorporating a gradient of pH sensitivity into the polymer coatings of the nanopore, a variety of asymmetric charge patterns and functional structures can be achieved, in a pH-responsive manner that allows for multiple functions to be implemented into the designed system. The asymmetric charge pattern inside the nanopore leads to an electrostatic trap for major current carriers, which turns the nanopore into an ionic rectifier with a rectification factor above 1000 at optimized pH and salt concentration. Our theory further predicts that the nanopore design behaves like a double-gated nanofluidic device with pH-triggered opening of the gates, which can serve as an ion pump and pH-responsive molecular filter. These results deepen our understanding of asymmetric transport in nanoconfined systems and provide guidelines for designing polymer-coated smart nanopores.

A House Solar Power Station

Solar energy is one of the main power sources of electricity in the world. It has become widespread as an attractive solution to provide low power consumption to human groups live in remote villages or areas away from the national electric grid, also when the electric power is underproduction such as in our country (Iraq). For this reasons we designed a system of photovoltaic generator with facilities to be built in houses. The system consists of three basic parts of equipment, 3KW peak solar panels, which could be spread easily at the housetop, a storage battery system and the electrical control system. The electrical control system was completely designed and tested using ORCAD simulator, it consists of 4KW battery charge regulator with 300V system, and 220V, 50Hz transformerless three – level square wave inverter.

Surface Charge Regulation of MIL-100(Fe) by Anion Exchange for Demulsifying the Cationic Surfactant-Stabilized O/W Emulsion

Demulsifying ionic surfactant-stabilized emulsions remains an emerging issue due to the stringent electrostatic barriers. In this work, a phosphate-mediated anion exchange strategy was proposed to fabricate a metal-organic framework, MIL-100(Fe), with adjustable surface charge for effective demulsification toward a cationic surfactant-stabilized emulsion. By adjusting the pH of the phosphate precursor solution, the surface charge of MIL-100(Fe) can be fine-tuned. At pH 3.0, the phosphate-exchanged MIL-100(Fe) with the zeta potential decreasing from 21.4 to 6.1 mV exhibited a significant enhancement of the demulsification efficiency (DE) from 35 to 91%. Further elevating the pH to 9.0 results in the zeta potential of the phosphate-exchanged MIL-100(Fe) to be reversed to -2.0 mV, and the DE can be optimized to 96% within 5 min. The demulsification mechanism was systematically explored based on the zeta potential, distribution of the surfactant, viscoelastic modulus evaluation, and morphological characterization of the emulsion in combination with monitoring of the dynamics process of demulsification. It was found that the phosphate-exchanged MIL-100(Fe) captured by the emulsion can lead to the release of the surfactant and heterogenization of the interfacial film, causing the elasticity of the emulsion to decrease and the irreversible deformation of emulsion droplets. Consequently, the destabilized emulsion could be subjected to the effective demulsification either by the fusion pathway mediated by the phosphate-exchanged MIL-100(Fe) or direct rupture. This work emphasized a facile and promising approach to deal with the cationic surfactant-emulsified oily wastewater and disclosed the fundamental demulsification process.

Design of a Photovoltaic Pumping System for Irrigation using Solar Energy in the department of Lambayeque-Peru

Due to the large amount of electrical energy necessary for human life and the fact that its origin is nonrenewable, a deterioration of the various ecosystems has been caused, due to the depletion of natural resources. Therefore, it is necessary to find effective solutions that mitigate ecological problems, based on that, this study seeks to implement a photovoltaic pumping system for irrigation using solar energy in the Department of Lambayeque, to take advantage of this natural resource. The methodology implemented is the applied one, with an experimental design. The instrument used for data collection is the registration form. The results showed that effectively the proposed design allows the pumping of a water flow equivalent to 270.4 m3 / day, capturing an average radiation of 6.55 kW / m2 per day. The use of a charge regulator connected to 4 batteries improved the operation of the photovoltaic pumping system and allows maintaining the durability of the equipment that compose it. It was concluded that the design of the photovoltaic pumping system is effective for the irrigation of crops in Lambayeque

Charge regulation engineering to suppress Jahn-Teller distortion in low crystallinity In-doping MnCo2O4 for high activity pseudocapacitors and hydrogen evolution reaction

Jahn-Teller distortion in the transition metal oxides (TMOs) could cause the poor activity and stability in the potentially promising materials for the supercapacitor and electrocatalyst. Herein, a novel strategy to address this problem by a charge regulation engineering is provided, in which, the Jahn-Teller distortion in the low crystallinity In-doped MnCo2O4 (In/MnCo2O4) in-situ grown on the Nickel foam (NF) (In/MnCo2O4-NF) by a simple laser-assisted method is significantly reduced. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectrum (XANES) analyses show that the strong electronic interaction between the doped In and Mn/Co suppresses Jahn-Teller distortion of Mn3+ and Co3+ cations in the In/MnCo2O4. Moreover, density functional theory (DFT) calculations reveal that the enhanced electrochemical activity and the effects of suppressed Jahn-Teller distortion. As a result, In/MnCo2O4-NF material shows a highly supercapacitive performance with a high specific capacitance of 1436.8F g−1 at a current density of 1 A g−1, a high rate capability of 71.9% of the capacitance retention at 20 A g−1, and a superior cycle stability (90.1% of the specific capacitance retention after 16,000 cycles). When being paired with activated carbon, the quasi-solid-state asymmetric supercapacitor provides a maximum energy density of 61.5 Wh kg−1 at a power density of 963.2 W kg−1 and an ultra-long cycling lifespan (84.6% retention after 120,000 cycles at 10 A g−1). Furthermore, In/MnCo2O4-NF as an electrocatalyst has a high hydrogen evolution reaction (HER) performance with a low overpotential (61.8 mV) and a small Tafel slope (76 mV dec-1).