Diffusion Potential Research Articles

Towards surface diffusion potential mapping on atomic length scale

The surface diffusion potential landscape plays an essential role in a number of physical and chemical processes such as self-assembly and catalysis. Diffusion energy barriers can be calculated theoretically for simple systems, but there is currently no experimental technique to systematically measure them on the relevant atomic length scale. Here, we introduce an atomic force microscopy based method to semiquantitatively map the surface diffusion potential on an atomic length scale. In this proof of concept experiment, we show that the atomic force microscope damping signal at constant frequency-shift can be linked to nonconservative processes associated with the lowering of energy barriers and compared with calculated single-atom diffusion energy barriers.

Bionic Thermoelectric Response with Nanochannels.

Thermosensation, the ability to detect environmental temperature change, is one of most ancient and crucial processes for the survival of all living organisms. Mammals use temperature-sensitive transient receptor potential (thermoTRP) cation channels as thermometers to convert the temperature change into electrical signals that are finally received as action potentials by nerve endings. In this work, we report the bionic thermosensation by solid-state hybrid nanochannels based on the principle of thermally sensitive permselective ion transport. The hybrid nanochannels possess an asymmetric structure, consisting of ultrasmall silica nanochannels (∼2.3 nm in diameter, ∼100 nm in length) supported by large-sized track-etched poly(ethylene terephthalate) conical nanochannels. When the hybrid nanochannels are engineered to separate two electrolyte solutions, the temperature change in one solution can be directly converted into trans-nanochannel diffusion potential, akin to the natural thermosensation process. Two bionic modes, namely, in the absence and presence of a concentration gradient, were studied to imitate the natural thermosensation of thermoTRP ion channels and shark, respectively. In both cases, real-time thermoelectric response was captured with a fast relative response speed (electrical response time versus temperature change time) of higher than 98%, as well as excellent stability and reversibility. Moreover, the nanochannels are highly sensitive to thermal stimulus, showing a sensitivity of 0.71 mV/K comparable to the natural thermosensation. The experimental results coincide well with the theoretical relationship between electrical response and temperature change derived in terms of a quasi-steady-state ion transport model. Finite element simulations based on coupled Poisson-Nernst-Planck (PNP) and Einstein-Stokes equations were also performed, confirming that the sensitive thermoelectric response originates from the highly cationic selectivity of nanochannels.

Investigation of benzodiazepines (BZDs) in a DPPC lipid bilayer: Insights from molecular dynamics simulation and DFT calculations

Toxicity is an essential parameter for drug development process and drug design. In this context, the effects of concentration of two Benzodiazepine drugs (diazepam, clonazepam) on fully hydrated dipalmitoylphosphatidylcholine (DPPC) has been studied at 323 K using molecular dynamics simulations. Various properties of bilayer such as membrane area per lipid, mass density distributions, order parameters, radial distribution functions, lateral diffusion, and electrostatic potential have been examined at three different concentrations of each drug. The location of drugs in the membrane are estimated by free energy profiles and to evaluate the results at a more detailed theoretical level, density functional theory (DFT) calculations have been carried out. It was revealed that penetration into the bilayer for diazepam is more favorable than clonazepam. On the other hand, within the fatty acid tail area both drugs are located in the middle of membrane at ∼0.75–1.5 nm from center of bilayer.

(Invited) Differential Reference Concentration Cell Method for Determination of Thermodynamic Factors in Concentrated Binary Electrolytes

Accurate models of ion transport in isothermal binary solutions require measurements of various properties, including ionic conductivity, salt diffusivity, cation transference number (t0 +), and the thermodynamic Darken factor (χ). In this work a novel method is proposed to quantify composition-dependent values of χ(1-t0 +). Recent studies of highly concentrated “solvent-in-salt” electrolytes suggest a strong variation of transference number with respect to composition. In fact t0 + for electrolyte systems may double in magnitude in the highly concentrated regimes.1 Previous studies have quantified the Darken factor by assuming that t0 + is relatively constant across the concentration range of interest. Furthermore, concentration-cell experiments typically fix arbitrary reference concentrations that may be far from the test concentration across the liquid junction. Such methods employ integral values of t0 +; the accuracy of thermodynamic properties, and thereby numerical models, may be compromised if there are substantial concentration differences and concomitant local changes in t0 +.2 An alternative approach to concentration-cell experiments would apply differential forms of the equations relating potential difference, composition, thermodynamic factor, and cation transference number.3 We propose a novel approach to concentration-cell experiments in which a matrix of liquid-junction potentials banded about a variable reference concentration is employed. Coupled with independent t0 + measurements, this 3-dimensional surface for potential difference can be numerically fitted to reliably and accurately determine differential values of the thermodynamic factor χ across the solubility range of an electrolyte. The feasibility of the method is demonstrated with the electrolyte lithium hexafluorophosphate in propylene carbonate (LiPF6:PC) to determine concentration-cell liquid-junction potential (U) across a wide concentration range (0M-3M). Transference-number measurements via Hittorf-cell experiments are then used to isolate χ from differential measurements of χ(1-t0 +) as a function of electrolyte particle fraction (y). Suo, L., Hu, Y. S., Li, H., Armand, M. & Chen, L. A new class of Solvent-in-Salt electrolyte for high-energy rechargeable metallic lithium batteries. Nat. Commun. 4, 1–9 (2013).Lundgren, H., Scheers, J., Behm, M. & Lindbergh, G. Characterization of the Mass-Transport Phenomena in a Superconcentrated LiTFSI:Acetonitrile Electrolyte. J. Electrochem. Soc. 162, A1334–A1340 (2015).Newman, J. & Thomas-Alyea, K. E. Electrochemical Systems. (John Wiley & Sons, 2004). Figure 1

The Analytical Transport Network Model for Energy Materials Design and Characterization: Extensions for the Modeling of Coupled Flows and Structural Mechanics

The design and characterization of next-generation, heterogeneous materials for application in energy technologies (batteries, fuel cells, etc.) increasingly relies on a fundamental understanding of how the 3-D properties of a material’s microstructure influences its performance. The Analytical Transport Network (ATN) Model was developed to offer a computationally quick and inexpensive means for analytically examining the link between 3-D structure and performance in such materials [1], [2]. In this talk, we present recent extensions of the model to constant-property, coupled, flow phenomena that conform to Onsager reciprocity (e.g., thermoelectric or electrokinetic phenomena). In addition, we discuss the development of a mechanics of materials model written in ATN nomenclature, which makes it possible to characterize a network’s flow and mechanical properties using the same analytical formalism. Finally, we present refinements and extensions to our software for applying the model to 3-D, voxel-based images, which can be artificially generated or obtained by 3-D imaging techniques, such as x-ray tomography. The ATN model is a lumped-element approach for modeling potential flow (and recently structural mechanics) in microstructural networks, e.g., in porous materials, heterogeneous materials, or, generally, in any composite whose components comprise multiple, interwoven networks of channels [1], [2]. The central question that ATN aims to address is: How does the relative arrangement and the individual geometric characteristics of a network’s channels, i.e., their topology and morphology, impact the network’s flow behavior? The question is motivated by the longer-term goal of rationally designing microstructural networks to obtain desired material properties. In [1]and [2], steady-state, diffusive potential flow of a single-entity was considered, e.g., electrical/heat conduction or trace species diffusion. In [2], the model additionally accounted for the loss or gain of flow across channel boundaries, e.g., heat loss due to surface convection or species consumption due to 1storder surface reactions. ATN predictions of effective network resistance and surface exchange were calculated, with minimal additional error, up to 6 orders of magnitude faster than Finite Element Analysis (FEA). Furthermore, because ATN’s fundamental modeling element is a physical channel, as opposed to sub-channel-scale element, graph theory could be used to mathematically examine how the interplay of channel morphology and topology impact network flow. These advantages carry into the model’s extensions presented in this talk. [1] A. P. Cocco, A. Nakajo, and W. K. S. Chiu, “Analytical transport network theory to guide the design of 3-D microstructural networks in energy materials: Part 1. Flow without reactions,” J. Power Sources, vol. 372, 2017. [2] A. P. Cocco and W. K. S. Chiu, “Analytical transport network theory to guide the design of 3-D microstructural networks in energy materials: Part 2. Flow with reactions,” J. Power Sources, 2017.

Lithium ion trapping mechanism of SiO2 in LiCoO2 based memristors

Pt/LiCoO2/SiO2/Si stacks with different SiO2 thicknesses are fabricated and the influence of SiO2 on memristive behavior is investigated. It is demonstrated that SiO2 can serve as Li ion trapping layer benefiting device retention, and the thickness of SiO2 must be controlled to avoid large SET voltage and state instability. Simulation model based on Nernst potential and diffusion potential is postulated for electromotive force in LiCoO2 based memristors. The simulation results show that SiO2 trapping layer decreases the total electromotive field of device and thereby prevents Li ions from migrating back to LiCoO2. This model shows a good agreement with experimental data and reveals the Li ion trapping mechanism of SiO2 in LiCoO2 based memristors.

Control the relaxation properties of the diffuse bistable potential

The purpose of this work is to investigate procedures to control the population dynamics in a bistable potential. We use the solutions of the Fokker–Planck equation for the distribution function corresponding to a bistable potential under action of an external electric field. The control is performed with a piecewise protocol with time independent potentials. This protocol provides to be adequate for this problem, controlling the time necessary to balance of system probabilities. Some trajectories were controlled and the limits of procedure clarified. Nevertheless, with the application of the control protocol we clarify some simple phenomena of the system, associating the application of the external field with the system diffusion coefficient.

A Simplified Method to Assess the Impact of Sediment and Nutrient Inputs on River Water Quality in Two Regions of the Southern Coast of South Africa.

Many rivers in the southern coastal region of the Western Cape Province, South Africa, are known to be in a poor state. Since the 1990s, the river water quality of this coastal region has been affected by increasing populations and by intensifying land use activities. Simplified risk assessment approaches are critical to identify in a timely manner areas where land use activities may impact water quality, particularly for regions with limited data. For this study, a simple assessment approach to estimate the impacts of land use activities on river water quality was improved by incorporating landscape potentials that take into account environmental factors. The methods were applied to two regions experiencing intensive land use along the southern coast. The findings indicate that the incorporation of the landscape potentials, (i) the landscape sediment generation potential and (ii) the diffuse nitrate potential, to estimate the impacts of sediment and nutrient inputs on river water quality need to be considered. Agricultural activities and informal settlements contribute to the increasing sediment and nutrient inputs of the river reaches. Areas with high proportions of river reaches at increasing pollution risk need to be managed on a large scale to ensure that all the potentially affected sub-catchments are included.

Diffusiophoresis of a Highly Charged Porous Particle Induced by Diffusion Potential

Diffusiophoresis, the motion of a colloidal particle in response to the concentration gradient of solutes in the suspending medium, is investigated theoretically on the basis of numerical computations in this study for charged porous particles, especially highly or extremely porous ones, focusing on the electrophoresis component induced by diffusion potential, which is generated spontaneously in a binary electrolyte solution where the diffusivities of the two ionic species are distinct. A benchmark carbonic acid solution of H(aq)+ and HCO3(aq)- is chosen to be the major suspending medium, as its large diffusion potential and remarkable performance in practical applications have been reported recently in the literature. More than 3 orders of magnitude increase in particle diffusiophoretic mobility is predicted under some circumstances, should the permeability of the particle increase 10-fold. Nonlinear effects such as the motion-deterring double-layer polarization effect pertinent to highly charged particles and the counterion condensation or shielding/screening effect pertinent to porous particles are investigated in particular for their impact on the particle motion, among other electrokinetic parameters examined. A visual demonstration of the nonlinear double-layer polarization is provided. Moreover, both the chemiphoresis and the electrophoresis components are explored and analyzed in detail. The results presented here can be applied in biochemical and biomedical fields involving DNAs and proteins, which can be modeled excellently as charged porous particles in their electrokinetic motion.

Modeling Transport Properties in Concentrated Systems Considering Species Association

Species association – including effects such as ion pairing and solvent complexation – can complicate electrochemical transport dynamics. As a liquid electrolyte becomes more concentrated, driving forces for association become stronger and may profoundly impact system performance. Ion pairing has been proposed to explain the extended diffuse double layers observed at ionic-liquid/electrode interfaces [1]. Researchers also have justified the low or negative cation transference numbers observed for many lithium electrolytes by suggesting that ions associate [2]. These discussions motivated our systematic study of species association effects in concentrated electrolytes. The Nernst–Planck theory has been used to study reactive multi-species liquid electrolytes [3], but it ignores solute/solute interactions, limiting applicability to dilute solutions [4]. In concentrated solutions, such interactions can alter transport dynamics substantially, even when species concentrations are relatively low. Monroe has illustrated that interactions between lithium salts and dissolved oxygen can manifest diffusion potentials that change open-circuit voltages of metal-air batteries considerably [5]. Accordingly, even the minor species produced by weak association should not be ignored in concentrated electrolytes. A multi-species concentrated-solution model considering species association will provide a more general and comprehensive interpretation of experimental transport-property data. Monroe and Delacourt derived flux-explicit transport laws from Onsager–Stefan–Maxwell equations, and emphasized the need for thermodynamic rigor in multi-species transport characterization [6]. The present research advances their framework further, by accounting for species association. In systems were species associate, the Onsager–Stefan–Maxwell transport equations are further constrained by local association equilibria and kinetics. Thus some transport properties may be intrinsically correlated. We will present reformed flux-explicit transport equations and clarify how locally equilibrated association affects apparent transport dynamics. Three systems, namely, doped ion-conductive ceramics, ionic liquids, and binary solutions, will be analyzed: we will investigate carrier/carrier interaction in doped solid electrolytes, and illustrate how defects or doped elements induce diffusion polarization; we will model the ionic-liquid double layer in cases where ions can combine to form a neutral pair; and we will discuss how the association of solutes affects transference-number measurements in liquid binary solutions. [1] M.A. Gebbie, et al., PNAS. 110, 9674-9679 (2013) [2] G. Richardson, et al., J. Electrochem. Soc., 165(9), H561-H567 (2018) [3] S. Clark, et al., ChemSusChem,10, 4735 – 4747 (2017) [4] A.M. Bizeray, et al., J. Electrochem. Soc., 163(8), E223-E229 [5] C. W. Monroe, J. Electrochem. Soc., 164(11), E3547-E3551 (2017) [6] C. W. Monroe and C. Delacourt, Electrochimica Acta, 114, 649–657 (2013)

A Micro-agar Salt Bridge Electrode for Analyzing the Proton Turnover Rate of Recombinant Membrane Proteins.

To date, more than 50% of all pharmacological drugs target the transport kinetics of membrane proteins. The electrophysiological characterization of membrane carrier proteins reconstituted in lipid bilayer membranes is a powerful but delicate method for the assessment of their physicochemical and pharmacological properties. The substrate turnover number is a unique parameter that allows the comparison of the activity of different membrane proteins. In an electrogenic transport, the gradient of the translocated substrate creates a membrane potential that directly correlates to the substrate turnover rate of the protein. By using silver chloride electrodes, a diffusion potential, also called liquid junction potential, is induced, which alters electrode potential and significantly disturbs precise membrane potential measurements. Diffusion potential can be minimized by a salt bridge, which balances electrode potential. In this article, a micro-agar salt bridge is designed to improve the electrophysiological set-up, which uses micropipettes for the membrane formation. The salt solution is filled into a microcapillary pipette tip, stabilized by the addition of agarose, and can be easily mounted to a standard electrode. The electrode potential of a micro-salt bridge electrode is more stable compared to a standard electrode. The implementation of this system stabilizes electrode potential and allows more precise measurements of membrane potential generated by a pH gradient. Using this system, the proton turnover rates of the mitochondrial carriers UCP1 and UCP3 are reinvestigated and compared to earlier measurements.

Observation and Simulation of Available Solar Energy at N’Djamena, Chad

The objective of this work is to evaluate the available solar potential at N’Djamena (12°08N, 15°04E) from 2017 to 2018. To achieve this goal, we used various datasets and model including: the in situ shortwave radiation (by pyranometer) measurement and sunshine duration (by Campbell-Stokes heliograph) obtained from N’Djamena station, observations from MODIS (aerosol optical depth (AOD) and precipitable water) satellite sensors, and simulations from Streamer radiative code. The results show the presence of a good available solar potential with an annual global potential of 4.71 kWh/m2/d. At the intra-seasonal time scale, there are two maximums for the global solar potential. The first maximum is registered in the month of March (spring) with value of 5.7 kWh/m2/d and the second in October (autumn) with value of 5.18 kWh/m2/d. However, the minimum of global potential is recorded in winter (from December to February) with values around 3.86 kWh/m2/d. Then, the measured global irradiation allowed validating the Streamer radiative transfer code with a score of more than 98%. Subsequently, this model was used to simulate direct normal and diffuse irradiation for several types of days (clear, dusty and cloudy days). An examination of the dust influence on solar radiation based on selected cases (AOD = 2.05) indicates a mean decrease of 3.33 and 3.17 kWh/m2/d, respectively, for the total and direct normal potential. This corresponds to an increase of the diffuse potential of 0.52 kWh/m2/d. Finally, an increase of 5.82 cm of precipitable water per day tends to decrease the overall potential of 0.73 kWh/m2/d and the direct normal potential of 1.74 kWh/m2/d. For this cloudy day, the potential has increased more than 0.89 kWh/m2/d.

The Investigation of Frequency and Voltage Dependence of Electrical Characteristics in Al/P3HT/p-Si (MPS) Structures

Abstract Metal-polymer-semiconductor (Al/P3HT/p-Si) structures have been fabricated and their electrical characteristics have been investigated using capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements. These measurements were performed in the frequency and voltage range of 3 kHz-1MHz and ±5 V, respectively, at room temperature. The values of diffusion potential (VD), doping concentration of acceptor atoms (NA), Fermi energy level (EF) and barrier height (ФB) were obtained from the reverse bias C−2 vs V plot for each frequency by considering interface states (Nss), series resistance (Rs), and interfacial layer effects. All these parameters were found as strong functions of frequency and voltage. The values of both Nss and Rs decrease with increasing frequency. On the other hand, the value of Nss is prominent in the inversion and depletion regions at low frequency, but Rs and interfacial layer are prominent in the accumulation region at high frequency. Therefore, to see the effect of Rs both the C-V and G/ω-V plots were corrected for high frequencies. The voltage dependent profile of Nss and Rs were also obtained from Hill-Coleman and Nicollian-Brews method, respectively. Obtained results confirm that the values of Nss, Rs and interfacial layer are more effective on the impedance measurements

Oxygen transporter for the hypoxic transplantation site

Cell transplantation is a promising treatment for complementing lost function by replacing new cells with a desired function, e.g. pancreatic islet transplantation for diabetics. To prevent cell obliteration, oxygen supply is critical after transplantation, especially until the graft is sufficiently re-vascularized. To supply oxygen during this period, we developed a chemical-/electrical-free implantable oxygen transporter that delivers oxygen to the hypoxic graft site from ambient air by diffusion potential. This device is simply structured using a biocompatible silicone-based body that holds islets, connected to a tube that opens outside the body. In computational simulations, the oxygen transporter increased the oxygen level to >120 mmHg within grafts; in contrast, a control device that did not transport oxygen showed <6.5 mmHg. In vitro experiments demonstrated similar results. To test the effectiveness of the oxygen transporter in vivo, we transplanted pancreatic islets, which are susceptible to hypoxia, subcutaneously into diabetic rats. Islets transplanted using the oxygen transporter showed improved graft viability and cellular function over the control device. These results indicate that our oxygen transporter, which is safe and easily fabricated, effectively supplies oxygen locally. Such a device would be suitable for multiple clinical applications, including cell transplantations that require changing a hypoxic microenvironment into an oxygen-rich site.

A closer look at the Nernst-Planck model for liquid junctions in galvanic cells and the concept of EMF

It is realized now that what is called the liquid-junction potential is given, in the classical theory of Nernst and Planck, by a line integral, which is path independent only in the case of a single independent concentration. Although previous model studies suggest that this integral is consistent with the potential calculated by the 1D version of Poisson's equation in the limit of long diffusion times, it is shown here, with a simple static model, that this may be true in the 3D space only at an infinitely large cross-section of the junction. At finite cross-sections, supposing that a charge separation exists, the potential difference across it is a function of the area of the cross-section and the distance across it, which is at variance with the properties of the integral. It is argued therefore that this integral cannot be interpreted in terms of electrostatics, but represents a quantity, the EMF, which is conceptually different from the potential.

Characterization of a multidrug-resistant Klebsiella pneumoniae ST607-K25 clone responsible for a nosocomial outbreak in a neonatal intensive care unit.

Multidrug-resistant Klebsiella pneumoniae strains are regularly involved in hospital outbreaks. This study describes an ESBL-producing K. pneumoniae clone (ST607-K25) responsible for a nosocomial outbreak in a neonatal intensive care unit. Fourteen strains isolated from 13 patients were included. Antimicrobial susceptibility testing was performed by the agar diffusion method. A clonal link was first investigated by fingerprinting (ERIC-PCR and REP-PCR) then confirmed by MLST. Characterization was performed by molecular detection and identification of several drug resistance and virulence determinants. All strains expressed the same antibiotype, combining ESBL production, fluoroquinolones and aminoglycoside resistance, except for one which remained susceptible to fluoroquinolones. Fingerprinting methods confirmed the clonal link and MLST identified a ST607 clone. Molecular investigations revealed: (I) genes encoding for two narrow-spectrum beta-lactamases (SHV-1 and TEM-1) and an ESBL (CTX-M-15); (II) absence of any chromosomal mutation in quinolone resistance-determining- regions (QRDR) of gyrA/gyrB and parC/parE genes; (III) genes encoding for three plasmid-mediated quinolone-resistance (PMQR) determinants: oqxAB (14/14), aac(6')-Ib-cr (14/14) and qnrB (13/14); (IV) production of a K25 capsule; and (V) carriage of three genes encoding for virulence factors: mrkD (type 3 fimbriae) (14/14), ybts (yersiniabactin) (12/14) and entB (enterobactin) (14/14). We described a multidrug-resistant Kp ST607 clone responsible for a nosocomial outbreak in vulnerable and premature newborns. Molecular investigations allowed us to identify several resistance factors responsible for ESBL production (CTX-M-15) and quinolone resistance (three PMQR determinants). The detection of a gene (ybtS) belonging to the high-pathogenicity island yersiniabactin could partly explain its high colonization and diffusion potential.

Role of TiO2 Anatase Surface Morphology on Organophosphorus Interfacial Chemistry

Optimization of physicochemical properties of TiO2 anatase for organophosphorus remediation remains challenging. One approach is to use anatase nanofibers, prepared from hydrothermally synthesized titanates. Charge densities and potentials of anatase nanofibers were determined from atomic force microscopy force–curve measurements using the modified Derjaguin, Landau, Verwey, Overbeek theory, which includes roughness and hydration forces, in the pH range 4–9. Calculated values were −0.007 to −0.03 C m–2 and −70 to −150 mV, respectively. In contrast, at neutral pH, the magnitudes of diffuse layer surface charge densities and potentials have a minimum in anatase nanoparticles. These observations and zeta-potential results suggest that nanofiber surfaces are more acidic compared with nanoparticles. This is consistent with nanofibers having ∼3-fold higher adsorption for organophosphorus methyl parathion (pH ≈ 7). The resulting adsorption includes contributions from (1) charge accumulation at local coordination...

GENERATION DEPENDENT TARGETING POTENTIAL OF DONEPEZIL LOADED POLY (PROPYLENEIMINE) DENDRIMER THROUGH GOAT NASAL MUCOSA

Objective: In the domain of nano drug delivery, dendrimers are the most explored bioactive polymeric carrier system. The present work was aimed to study the diffusion potential of different generations of Poly (propyleneimine) (PPI) dendrimers on goat nasal mucosa in an ex vivo study and synthesize a stable dendrimer for olfactory drug delivery.Methods: The generations (3.0G, 4.0G, and 5.0G) of PPI dendrimer were synthesized, and PEGylated by MPEG 5000 and then loaded with donepezil. A comparative study was carried out among all generations in term of their drug loading capacity, stability, sustained release behaviour as well as for targeting efficacy. An ex-vivo study was carried out on Franz Diffusion Cell with goat nasal mucosa.Results: The developed G3, G4, and G5 dendrimerformulations had entrapment efficiency of 24.33±0.56%, 40.12±0.62%, and 60.4±0.6%, respectively. The nasal diffusion study revealed that 5.0G PPI dendrimer increased diffusion of donepezil up to 47% as compared to the pure solution of donepezil while 10% improvement in diffusion was seen as compared to 4.0 G PPI dendrimer. Thus obtained results claimed that the drug loading as well as targeting potential of PPI dendrimers increased with the increase in the number of generation. The investigation outcome indicated promising results of 5.0G PPI dendrimer over the 3.0G and 4.0G PPI dendrimer generations for their drug loading capacity, stability, and sustained release action.Conclusion: The 5.0G PPI dendrimer proved its superior candidature over the other lower generations of PPI dendrimers for drug delivery and drug targeting.

Measuring Inner Layer Capacitance with the Colloidal Probe Technique

The colloidal probe technique was used to measure the inner layer capacitance of an electrical double layer. In particular, the forces were measured between silica surfaces and sulfate latex surfaces in solutions of monovalent salts of different alkali metals. The force profiles were interpreted with Poisson-Boltzmann theory with charge regulation, whereby the diffuse layer potential and the regulation properties of the interface were obtained. While the diffuse layer potential was measured in this fashion in the past, we are able to extract the regulation properties of the inner layer, in particular, its capacitance. We find systematic trends with the type of alkali metal ion and the salt concentration. The observed trends could be caused by difference in ion hydration, variation of the binding capacitance, and changes of the effective dielectric constant within the Stern layer. Our results are in agreement with recent experiments involving the water-silica interface based on a completely independent method using X-ray photoelectron spectroscopy in a liquid microjet. This agreement confirms the validity of our approach, which further provides a means to probe other types of interfaces than silica.

Research on low-carbon diffusion considering the game among enterprises in the complex network context

Considering the game among enterprises, this paper studies low-carbon diffusion problem from the perspective of network characteristics and consumers' environmental awareness. Under the scenario of heterogeneous environmental awareness, the low-carbon diffusion model based on evolutionary game theory and complex network theory is established to describe the game of enterprises' low-carbon strategy adoption in the network and the strategy learning among network neighbors. Simulation analysis in complex networks reveals the roles of network characteristics such as average degree, degree distribution and consumers' environmental awareness played in low-carbon diffusion. The results show that increasing the connections among enterprises in the industry can help the spread of low-carbon strategies. However, the diffusion potential of the network is largely exploited when the average degree exceeds 6, and the low-carbon strategies spread slowly afterwards. A certain percentage of green consumers drives this certain percentage of enterprises to implement low-carbon strategies approximately in equilibrium which indicates that the low-carbon diffusion rate can reach 100% when all consumers become green consumers who are willing and able to pay for low-carbon premium. White customers contribute to the spread of low-carbon strategies, but the promotion effect is not as good as green customers. The small-world (SW) network is more efficiently than the scale-free (SF) network in low-carbon diffusion when consumers' environmental awareness is low. However, when the consumers' environmental awareness is higher than a certain value, the SF network has a higher diffusion rate in equilibrium than the SW network.