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In this study SiO 2 nanoparticles coated with polyaniline (PANI) shell of various thicknesses have been fabricated successfully by in situ polymerization of aniline on the silica surface through the chemical bonding between amino groups of silica surface and aniline. The addition procedure of dodecylbenzenesulfonic acid plays a key role on whether the thick-shell nanoparticles can be prepared successfully or not. The SiO 2 -PANI core–shell nanoparticles and PANI oligomers were reacted with isocyanates to prepare the conductive polyurethane-PANI-silica hybrid films. Under the same PANI content in nanocomposites, the hybrid films containing the nanoparticles with the thicker PANI shell show superior enhancement on electrical conductivities compared to those containing the thinner-PANI-shell nanoparticles. On the 5-wt.% PANI content, the surface resistance of the nanocomposites can reduce to ∼10 6 Ω/sq, lowering two orders, while the nanoparticles with 1.35-wt.% PANI shell are replaced by those with 13.8-wt.% PANI shell in use. According to the general effective media analysis, the percolation threshold (0.0277) is much lower than the critical volume fraction (0.16) for random packing in three dimensions. As a result of the low percolation threshold, we infer that the conducting core–shell nanoparticles form electrical channels due to the surface connection effect, resulting in the momentous enhancements in the electrical conductivity.

In this study polystyrene (PS) spheres were synthesized by emulsifier-free emulsion copolymerization of styrene with methacrylic acid for the fabrication of photonic crystals. A facile method to significantly improve the solvent resistance of photonic crystals was developed through surface modification of PS spheres by poly(vinyl pyrrolidone) (PVP). We used an ethanol soaking test to evaluate the solvent resistance of photonic crystals prepared by pristine, thermal-treatment, and PVP-modification methods. The crystal structure and the absorption band of the photonic crystals before and after the soaking test were investigated. Experimental results revealed that the photonic crystals prepared from the unmodified PS spheres have a very weak resistance to ethanol, resulting in impossibility of carrying out inverse opal photonic crystals. The improvement on solvent resistance by the thermal-treatment method was limited due to the weak bonding or the mergence of PS spheres. We found the photonic crystal prepared from the PVP-modification PS spheres maintains its integrity very well in the ethanol solution after 5-h soaking. Moreover, the photonic crystal and the corresponding inverse opal photonic crystal revealed excellent structure and optical properties.

This kinetic study simulates the characteristics of diazo dye (C.I. Reactive Red 141, RR 141) decolorization using an upflow-packed bed bio-reactor (immobilized cell system, ICS) with indigenous Aeromonas hydrophila entrapped onto the packing matrix, Porites coral. The kinetic theory of bio-reaction in ICS column is found to be the bio-reaction based on Langmuir adsorption isotherm. Our analyses upon two kinds of experimental data reveal that: (1) both ICS data have the first-order and the zero-order asymptotes, two features of reaction with Langmuir adsorption isotherm; (2) all ICS data have a common adsorption equilibrium constant; (3) both the viability of immobilized cells and the ultimate extent of bio-reaction are proportional to the amount of inlet nutrient source; (4) the former is independent of the flow rate of stream; however, the latter is inversely proportional to the flow rate of stream.

In this study, through the extension of an one-dimensional, dissimilarly charged protrusions surface model set up in our previous work, a novel dissimilarly charged protrusion array (DCPA) model immersed in an electrolyte solution, which could simulate realistically both the surface morphology and the surface charged condition profoundly concerned on a biological cell membrane, or on the surface of a micro-scale, modified particle used in biomedical engineering and water treatment, is proposed. Considering the condition of small protrusions, the electrical potential field due to the electrical double layer (EDL) on DCPA model is solved semi-analytically using both the double Fourier series and the perturbation method. The analysis from the numerical result reveals that, a small, dissimilarly charged protrusion can lead to a steep variation in the local EDL configuration, especially compared with that in the condition when the charged surface is taken roughly as a flat surface using a lumped, mean surface charge density.

This kinetic study provided a first-attempt model prediction to elucidate characteristics of azo dye decolorization in immobilized cell systems (ICSs) using indigenous Aeromonas hydrophila as model biocatalysts. Using mass transfer differential equation, this intrinsic kinetic study could uncover theoretical mysteries behind our prior findings of ICS operation. Moreover, the kinetic-rate constant analysis also confirmed the promising feasibility of threshold operation criteria (e.g., maximum allowable treatment concentration), which were previously determined via analysis of a family of constant-slope isoclines for biostimulation. This kinetic modeling coupled with graphical analysis could also provide a plausible evaluation to determine the most economically feasible biostimulation strategy for non-growth associated biodegradation (e.g., dye decolorization) in ICSs for possible industrial applications.

In this study we used a low film-forming temperature to fabricate high-refractive-index polymer/TiO2 hybrid films featuring high TiO2 contents. We incorporated pre-made TiO2 nanoparticles (NPs) into titanium alkoxide and/or epoxy resin at various NP contents and then investigated the effects of the relative proportions of TiO2 NPs, titanium alkoxide, and epoxy resin on the refractive indices. The variation of the refractive index was examined in terms of the morphologies and compositions of the hybrid films. The maximum values of the refractive indices of the hybrid films occurred at high TiO2 NP contents, but not at pure TiO2 NP contents. Microstructural images suggested that this phenomenon occurred because of the presence of spaces existing between the NPs as a result of our use of an ex situ synthesis method. The maximum values of the refractive indices of the hybrid films featuring a matrix comprising both titanium alkoxide and epoxy resins were larger than those obtained when the matrix was either titanium alkoxide or epoxy resin alone; indeed, the refractive index of a titanium alkoxide/epoxy/TiO2 hybrid film reached as high as 1.972—close to that of a pure anatase titania thin film fabricated at high temperature.

In this study, using the iterative finite difference method, the effect of an irregular condition at boundary, the surface undulation, in a charged surface system on the two dimensional electrokinetic flow near the surface is analyzed. The results reveal that, for the electrokinetic flow, the undulation of charged surface may have two major effects: one is that it changes the flow pattern of electrolyte solution, especially in the region close to the undulated surface; the other is that, due to the increase of effective surface area, the magnitude of velocity field may be increased considerably. In addition, when either the amplitude of undulation is increased, or the period of undulation is decreased, both the maximum velocity and the tangential flow rate will be raised to an extent. This is important for applications, for example, the electrophoresis of a biological cell, the electroosmosis of electrolyte solution in a micro-channel, etc.

Adopting a laboratory-scaled electrodialysis (ED) process, we investigate the performance of a monovalent anion exchange permselective membrane in the reduction of the concentration of sulfate ions during the production of mineral source water from deep sea water (DSW). The dependence of the separation efficiency of anions on the operating time and the applied DC voltage is investigated based on a brine having salinity of about 15% prepared from DSW. The experimental results reveal that if the applied DC voltage is high, the change in the liquid volume during ED is dominated by the ions transported and the effect of electroosmosis. In addition, the amount of chloride ions transported correlates roughly linearly with the operating time, and the transport of sulfate ions is found to be blocked by chloride ions, presumably because of that the pore size of the permselective layer is close to the size of sulfate ions. © 2010 American Institute of Chemical Engineers AIChE J, 2011

In this work, a three-points approach for estimating three-parameters diffusivity of mobile phase via desorption process from polymer film is proposed. In comparison with fitting curve by optimization technique, the new approach gives a substitutive method for estimation of parameters in three-parameters diffusivity. Troublesome tasks, such as guessing start point and dealing with irregular function encountered frequently in optimization approach can be avoided by using present approach. In this new approach, based on three key points on desorption curve, diffusivity parameters can be calculated from a database set-up in anticipation. A three-parameters diffusivity, belonging to a Fujita–Doolittle type diffusivity, is used for illustration. Numerical results reveal that accuracy of present approach is high, if diffusivity of mobile phase meets the diffusivity type prescribed completely. For demonstration in applicability, a computer-produced, random-error desorption curve as a simulated experimental desorption curve is also analyzed, and the results show that diffusivity recovered by present approach is satisfactory.

Two types of silanes, including 3-glycidoxypropyltrimethoxysilane (GPTMS) and 3-aminopropyltriethoxysilane (APTES), were grafted onto polystyrene sulfonic acid-co-maleic acid (PSSA_MA) first, followed by the grafting reaction to the silica surface. The modification of PSSA_MA onto silica was confirmed through FTIR (Fourier transform infrared spectrum), NMR (Nuclear magnetic resonance), and TGA (Thermogravimetric analysis). The grafting ratio of PSSA_MA via APTES with 1-ethyl-3-(3- dimethylaminopropyl)-carbodiimide (EDC) activation reached 18.0 %. As for GPTMS case, the grafting ratio reached 14.4 %, which was slightly lower than that of APTES case. The grafting mechanisms for both cases were elucidated. The epoxysilane was found to react with maleic acid groups on PSSA_MA only. On the other hand, the aminosilane not only interacted with sulfonic groups but also activated maleic acid groups via EDC. However, without the use of the coupling agent, the grafting degree of PSSA_MA was only 3 %, which signified the essential role of coupling agents in this organically modified silica. The average particle size of silica was around 200 nm with or without organic modification from transmission electron microscopy (TEM) and Zetasizer analysis. The APTES-modified samples showed the highest improvement in the ion adsorption capacity in all investigated cases.

The concentration dependency of the diffusivity of a solvent in a polymer solution is derived on the basis of a free volume theory. Applying a molecular kinetics approach, the Fujita–Doolittle equation is modified. The result of numerical simulation reveals that the diffusivity of solvent in a polymer solution depends largely on both the polymer chain structure and its concentration. The applicability of the analytical expression derived is justified by fitting the experimental data for n -alkyl acetate-(poly-methyl acrylate) polymer solutions in the literature.

The controlled release of over-loaded drug in a plate-like polymer matrix, the Higuchi's problem, is investigated theoretically. Taking the advantage of Landau transformation, we restore the concentration profile of drug in a polymer matrix, the rate of release of drug from the polymer matrix, and the temporal variation of location of the moving boundary taking the external mass transfer resistance into account. The applicability of the series of moving boundaries, a numerical approach often adopted, is examined. We found that it may become ineffective when the over-loading of drug in a polymer matrix is too small. In contrast, our method has no such limitation. We conclude that assuming the transfer of drug to occur at a pseudo-steady-state condition is inadequate if the degree of over-loading for drug is low or the external mass transfer resistance is significant.

The electroosmotic flow plays an important role in electrokinetic phenomena, in particular, in the flow of an electrolyte solution in a microchannel, where the electrokinetic equations need to be solved. In general, theseequations are coupled, nonlinear partial differential equations, and solving them analytically is nontrivial. In this study the electrokinetic equations are solved analytically for the case of a general electrolyte solution flow through a planar slit comprising two planar, parallel surfaces, which can have different charged conditions, and the influences of the key parameters on the flow behavior are discussed. Several interesting phenomena are observed. For example, the absolute value of the mean fluid velocity may exhibit an undulant behavior as the bulk concentration of counterions varies. Also, if both the valence of coions and the bulk concentration of counterions are fixed, then depending upon the level of the latter the absolute value of the mean fluid velocity may have a local maximum or local minimum as the valence of counterions varies.

Knowledge about the thermodynamic properties of a polymer solution is essential to its applications. These properties are derived on the basis of a statistical mechanics approach by modifying the classic Flory–Huggins theory in this study. The analytical result derived is fitted to the available experimental data such as toluene–polystyrene and benzene–silicone polymer solutions in the literature, and its performance is satisfactory. We show that the inconsistency between the Flory–Huggins theory and experimental observations for many polymer solutions might arise from the negligence of the effects of the free volume fractions of solvent and polymer and the change in the disorientation entropy of polymer molecules.

The electrical interaction between two planar, parallel dissimilar surfaces, which may have different charged conditions arising from different ion-adsorption mechanisms, in an arbitrary electrolytic solution is investigated theoretically. The electrical interaction force and the interaction energy between these surfaces are evaluated, and analytical expressions for various charged conditions under the Debye-Huckel condition are derived. In general, assuming constant surface potential and assuming constant surface charge density lead respectively to the lower and the upper bounds in the electrical interaction energy between two surfaces. We show that assuming a linear relation between surface potential and surface charge density under the Debye-Huckel condition, as is often done in the literature, is appropriate for two planar parallel surfaces only but becomes inadequate for other orientations or nonplanar surfaces. The present approach does not have this limitation.

The electrophoretic behavior of human erythrocyte is investigated theoretically. The present analysis extends previous studies to that the effect of the membrane structure of a cell is taken into account. The result obtained provides a useful tool for the estimation of the surface properties of human erythrocyte through electrophoretic measurements. Fitting the present model to the experimental data of Haydon and Seaman [Arch. Biochem. Biophys. 122 (1967) 126], for example, reveals that the surface charge of erythrocyte arises mainly from the dissociation of three functional groups, which bond to different sites on cell membrane : (a) N -acetylneuraminic acid (sialic acid) with p K HA Naa =2.6, (b) some kind of α-carboxylic acid with p K HA α−ca =3.35, (c) weak amino base functional group with p K BH + =8.5. The distribution of Na + in the protein layer of a cell is found to vary with the pH of the bulk liquid phase, the possible implication of this phenomenon to cell physiology is discussed.

The fabrication of gradient index plastic optical fiber in a closed co-extrusion process is simulated theoretically. The concentration dependency of the diffusivities of monomers in host polymer is taken into account on the basis of a modified free volume theory together with a generalized Flory–Huggins theory for a three-component polymer solution. The applicability of the model derived is justified by fitting it to the experimental data reported in the literature, and its performance is found to be satisfactory. We show that the diffusion of a mobile phase in a polymer solution is dependent upon the structure and the concentration of polymer, and the concentration of the other mobile phase present.

The temperature dependence of the viscosity of a normal nonpolymeric liquid is analyzed theoretically based on a free volume model. We show that the viscosity is mainly a function of the activation energy for molecular collision. The activation energy is closely related to the temperature, and the relation between the two can be derived based on a cell theory. The applicability of the result derived is justified by fitting it to the experimental data for n-paraffins. We show that, in addition to providing a physically more realistic analytical expression than those in the literature, the analytical result derived in our study is capable of improving the performance of the empirical relation proposed by Doolittle [J. Appl. Phys. 22, 1031 (1951)]. The applicability of the present model to predict the basic properties of glass-forming liquids is also illustrated.

The electrophoretic motion of an entity comprised of a rigid, uncharged core covered by a charge-regulated membrane which simulates a biological cell, in a general a:b electrolyte solution is analyzed. The membrane carries a fixed charge which arises from the dissociation of the acidic functional group HA. We show that the higher the concentration of cations in the bulk liquid phase, the lower the absolute Donnan potential, ∣ ϕ D ∣, and the lower the concentration of functional group, N 0 , the lower the ∣ ϕ D ∣. Also, the higher the pH, the higher the absolute electrical potential, and the greater the N 0 , the lower the pH. The absolute mobility of a cell, ∣ μ ∣, increases with pH, but decreases with the increase in the friction coefficient of the membrane phase, γ . For a fixed total number of HA, if γ is large, μ / μ s is less than unity, μ s being the mobility of the corresponding rigid particle, and it decreases with the thickness of membrane d , and the inverse is true if γ is small. For a medium γ , the variation of μ / μ s as a function of d has a local maximum, and depending upon d , it can be either greater or less than unity.

Soft baking, one of the key steps in photoresist processing, is modeled theoretically. The relevant mechanisms involved in this step and the relative significance of each mechanism are discussed, and an analytical expression for the temporal variation of film thickness is derived. The applicability of the model derived is justified by fitting the experimental data for JSR IX150 and Shipley SPR510LA photoresists reported in the literature. We show that the rate of transfer of solvent is controlled by its convective transport near the film-gas interface.

The conjecture of Tuinier (J. Colloid Interface Sci. 258 (2003) 45) for the electrical potentials near a cylindrical surface and near a spherical surface under the conditions of symmetric electrolyte and large scaled radius are derived by solving the corresponding Poisson-Boltzmann equation. The surface charge density-surface potential relations for these surfaces are also derived under the conditions of constant surface potential. We show that the level of surface charge density for planar, cylindrical, and spherical surfaces follows the order spherical surface > cylindrical surface > planar surface.

The electrophoretic mobility of a particle covered by a membrane in an a:b electrolyte solution is modeled theoretically. The membrane, which simulates the surface of a biological cell, is ion-penetrable, and carries homogeneously distributed negative fixed charges. An approximate expression for the electrophoretic mobility is derived. Based on the results of numerical simulation, we conclude the following: (1) The absolute Donnan potential increases with the concentration of the fixed charges C0, but decreases with the ionic strength I. (2) The greater the valence of cation alpha, the lower the absolute potential distribution. (3) The greater the C0, the greater the absolute mobility of a particle, magnitude of mu, and the greater the friction coefficient of the membrane phase gamma, the smaller the magnitude of mu. (4) A large I or a large a leads to a small magnitude of mu. (5) The greater the ratio (permittivity of solution/permittivity of membrane phase), the smaller the magnitude of mu. (6) For a large gamma, magnitude of mu decreases with the thickness of membrane d under the condition of constant amount of fixed charges. However, if gamma is sufficiently small, the variation of magnitude of mu as a function of d exhibits a maximum. The classic result of Smoluchowski for the electrophoretic mobility of a rigid particle can be recovered as a limiting case of the present model.

Fabrication and characterization of YBa2Cu3Oy Josephson junctions with step‐edge, bi‐epitaxial, and sandwich geometries are performed in this study to investigate the effects of microwave irradiation on the I–V characteristics. I–V curves under microwave irradiation reveal Shapiro steps. The width of the constant voltage steps were modulated by the microwave power. The period of the magnetic induction ΔB detected from the V–Φ curves for superconducting quantum interference devices is temperature dependent. Additionally, Tc and Ic of the proximity sandwich junctions are enhanced by the microwave irradiation.

In this work, an elementary, novel dissimilarly charged protrusions (DCP) surface model in an electrolyte solution considering simultaneously the complexity of both surface morphology and surface charged condition, which are concerned frequently on a biological cell membrane, on a modified micro-particle surface, or in a lab-on-a-chip biosensor device, is proposed. Based on Fourier series and the perturbation technique, the configuration of electrical double layer (EDL) near this complicated charged surface model is successfully solved semi-analytically. The numerical calculation reveals that, the methodology suggested in present study could deal with charged surface systems of arbitrary geography and of arbitrary charge distribution. In the analysis, three special subjects are discussed, including an isolated dissimilarly charged protrusion, the effect of protrusions, and the effect of dissimilarly charged condition on protrusions.

A charged layer with undulated surface exists commonly in natural entities (for example the biological membrane layer and the surface of charged colloid) and in artificial fabrications (for example the peripheral surface of ion-exchange membrane pores). When the micro- or nano-scale charged layer systems are concerned, the effect of undulation of charged layer surface on the electrical phenomenon may become great significant. In this work, using the perturbation method, the significance of undulated surface on a charged layer in the electrical phenomenon is investigated. Under assumptions that the undulation amplitude is small and that the Debye-Huckel approximation is applicable, the electrical potential field in three regions is solved simultaneously. Based on the analytical results it is found that, if compared with that in condition of flat surface, the undulation of charged layer surface decreases/increases the magnitude of electrical potential field near the wave crest/trough, due to the curvature of undulated surface. In addition, the surface potential on the undulated surface shows a wavelike distribution. The analytical results also show that, the significance of undulated surface is determined by the physical parameters, including the geometry of undulated surface, the amplitude and the period of undulation, and the fixed charge density in charged layer.

A novel electrical field assisted membrane module consisting of an array of microchannel units, each microchannel unit comprised of a cylindrical pore and a charged ion-selective membrane layer, is analyzed theoretically. The governing equations for the flow and the electrical fields are solved analytically under the Debye-Huckel condition and the influences of the key parameters on the flow behavior of the system under consideration are investigated through numerical simulation. We show that for a fixed microchannel radius, the volumetric flow rate through a microchannel unit has a maximal value as the radius of the cylindrical pore varies. This maximum is independent of both the strength of the applied field and the density of the fixed charges in the membrane layer, but varies with the permittivity of the membrane layer.

The deformation of a non-rigid particle, such as proteins, DNA, and microorganisms, during its electrophoresis can be significant in practice. This effect is simulated by considering the electrophoresis of an ellipsoidal polyelectrolyte (PE) of varying aspect ratios at a fixed volume. We show that both the double-layer polarization and the counterion condensation can be influenced significantly by the shape of an ellipsoidal PE, making its behaviors different both quantitatively and qualitatively from those of a spherical PE. In addition, the electroosmotic retardation flow inside an ellipsoidal PE also plays an important role as its shape varies. The electrophoretic mobility of a PE might have a local maximum as the amount of its fixed charge varies, which is consistent with the experimental observations in the literature. The level of the amount of the fixed charge at which the local maximum in the electrophoretic mobility occurs depends upon the PE shape, which has not been reported in previous theoretical studies. The results gathered in this study provide valuable information for both the interpretation of experimental observation and the design of relevant electrophoresis devices.

The soft baking step of a photolithography process is analyzed theoretically, taking the effect of the temperature dependence of the diffusivity of solvent into account. A coordinates-transform technique is chosen to solve the moving boundary problem under consideration. The temporal variation of the thickness of a film is predicted, and the result obtained justified by fitting experimental data reported in the literature for both poly(methylmethacrylate) film and Shipley UVIII photoresist. We show that, depending upon the types of photoresist film and the operating conditions, the transport of solvent may be controlled by the diffusion of solvent in a film or the convective transport of solvent from the gas–film interface to the bulk gas phase.