Journal of Colloid And Interface Science (v.362, #1)
Multi-lamellar vesicle formation in a long-chain nonionic surfactant: C16E4/D2O system
by Luigi Gentile; Kell Mortensen; Cesare Oliviero Rossi; Ulf Olsson; Giuseppe A. Ranieri (pp. 1-4).
Transient viscosity obtained under constant shear rate of 0.5s−1 for 40wt.% of C16E4 in D2O at 55°C and relative SANS patterns. The typical transient viscosity of Multi-lamellar vesicle (MLV) formation is observed.Display Omitted► Shear-induced structures: Shear-induced lamellar-to-MLV transition in 40wt.% C16E4/D2O system. ► Rheo-SANS, rheo-NMR and rheology elucidate the shear-induced transition. ► NMR size determination of shear-induced multilamellar vesicles. ► Temperature effect on the MLV formation.The temperature dependent rheological and structural behavior of a long-chain C16E4 (tetraethylene glycol monohexadecyl ether) surfactant in D2O has been studied within the regime of low shear range. In the absence of shear flow, the system forms a lamellar liquid crystalline phase at relatively high temperatures. The present paper reports on the shear-induced multi-lamellar vesicle (MLV) formation in C16E4/D2O at 40wt.% of surfactant in the temperature range of 40–55°C. The transition from planar lamellar structure to multi-lamellar vesicles has been investigated by time-resolved experiments combining rheology and nuclear magnetic resonance (rheo-NMR), rheo small-angle neutron scattering (rheo-SANS) and rheometry. The typical transient viscosity behavior of MLV formation has been discovered at low shear rate value of 0.5s−1.
Keywords: C; n; E; m; Rheology; Rheo-SANS; Rheo-NMR; MLV formation
Ionic liquid-based stable nanofluids containing gold nanoparticles
by Baogang Wang; Xiaobo Wang; Wenjing Lou; Jingcheng Hao (pp. 5-14).
Proposed heat transport mechanism for the ionic liquid-based nanofluids containing gold nanoparticles.Display Omitted► The stable ionic liquid-based nanofluids containing gold nanoparticles (Au NPs) were prepared. ► Brownian motion should be one key effect factor in the heat transport processes of ionic liquid-based gold nanofluids. ► The results may shed lights on comprehensive understanding of heat transport mechanisms in nanofluids.A one-phase and/or two-phase method were used to prepare the stable ionic liquid-based nanofluids containing same volume fraction but different sizes or surface states of gold nanoparticles (Au NPs) and their thermal conductivities were investigated in more detail. Five significant experiment parameters, i.e. temperature, dispersion condition, particle size and surface state, and viscosity of base liquid, were evaluated to supply experimental explanations for heat transport mechanisms. The conspicuously temperature-dependent and greatly enhanced thermal conductivity under high temperatures verify that Brownian motion should be one key effect factor in the heat transport processes of ionic liquid-based gold nanofluids. While the positive influences of proper aggregation and the optimized particle size on their thermal conductivity enhancements under some specific conditions demonstrate that clustering may be another critical effect factor in heat transport processes. Moreover, the remarkable difference of the thermal conductivity enhancements of the nanofluids containing Au NPs with different surface states could be attributed to the surface state which has a strong correlation with not only Brownian motion but also clustering. Whilst the close relationship between their thermal conductivity enhancements and the viscosity of base liquid further indicate Brownian motion must occupy the leading position among various influencing factors. Finally, a promisingly synergistic effect of Brownian motion and clustering based on experimental clues and theoretical analyses was first proposed, justifying different mechanisms are sure related. The results may shed lights on comprehensive understanding of heat transport mechanisms in nanofluids.
Keywords: Ionic liquids; Nanofluids; Gold nanoparticles; Thermal conductivity
A facile method of synthesis of asymmetric hollow silica spheres
by Junjie Yuan; Zhengqi Wang (pp. 15-20).
Asymmetric hollow silica spheres was synthesized by sol–gel processs.Display Omitted► A facile method for preparing asymmetric hollow silica spheres was developed. ► The morpholology of asymmetric hollow silica spheres can be precisely controlled via changing the ratio of ethanol to water. ► The formation mechanism of asymmetric hollow silica spheres was described.This paper presents a “one-step” method to synthesize asymmetric hollow silica spheres. In this method, when positively charged polystyrene particles were blended with mercaptopropyltriethoxysilane and stirred at 50°C in alkaline ethanol/water medium for a period of time, Janus or lobed asymmetric hollow silica spheres could be directly obtained, just changing the ratio of ethanol to water in the reaction medium. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterize the morphology and topography of the asymmetric hollow silica spheres. The formation mechanism was described in detail.
Keywords: Asymmetric hollow silica spheres; Synthesis; Sol–gel process
Solid-state synthesis of embedded single-crystal metal oxide and phosphate nanoparticles and in situ crystallization
by C. Díaz; M.L. Valenzuela; D. Bravo; C. Dickinson; C. O’Dwyer (pp. 21-32).
A new solid state organometallic route to embedded nanoparticle-containing inorganic materials is shown that allows the formation of embedded individual single-crystal nanoparticles of SiP2O7, TiO2, P4O7, WP2O7 and SiO2. In situ recrystallization formation of nanocrystals of WP2O7 and SiP2O7 is also possible due to electron beam induced reactions allowing nanoparticles to be written into host materials. The method and can be extended to nearly any metal capable of successful coordination as an organometallic to allow embedded nanoparticle layers and features to be written on surfaces for application as high mobility pyrophosphate lithium–ion cathode materials, catalysis and nanocrystal embedded dielectric layers.Display Omitted► First derivatives of cyclic phosphazenes containing two metals in non-geminal positions. ► Electron beam writing of nanoparticles within an amorphous host and embedded nanoparticle formation in the solid state. ► Growth mechanism of twinned nanocrystals of WP2O7. ► Stabilizing role of P4O7 during crystallization of embedded nanoparticles in oxide host. ► Model of sintering-based recrystallization to explain embedded nanoparticle formation.A new solid state organometallic route to embedded nanoparticle-containing inorganic materials is shown, through pyrolysis of metal-containing derivatives of cyclotriphosphazenes. Pyrolysis in air and at 800°C of new molecular precursors gives individual single-crystal nanoparticles of SiP2O7, TiO2, P4O7, WP2O7 and SiO2, depending on the precursor used. High resolution transmission electron microscopy investigations reveal, in most cases, perfect single crystals of metal oxides and the first nanostructures of negative thermal expansion metal phosphates with diameters in the range 2–6nm for all products. While all nanoparticles are new by this method, WP2O7 and SiP2O7 nanoparticles are reported for the first time. In situ recrystallization formation of nanocrystals of SiP2O7 was also observed due to electron beam induced reactions during measurements of the nanoparticulate pyrolytic products SiO2 and P4O7. The possible mechanism for the formation of the nanoparticles at much lower temperatures than their bulk counterparts in both cases is discussed. Degrees of stabilization from the formation of P4O7 affects the nanocrystalline products: nanoparticles are observed for WP2O7, with coalescing crystallization occurring for the amorphous host in which SiP2O7 crystals form as a solid within a solid. The approach allows the simple formation of multimetallic, monometallic, metal-oxide and metal phosphate nanocrystals embedded in an amorphous dielectric. The method and can be extended to nearly any metal capable of successful coordination as an organometallic to allow embedded nanoparticle layers and features to be deposited or written on surfaces for application as high mobility pyrophosphate lithium–ion cathode materials, catalysis and nanocrystal embedded dielectric layers.
Keywords: Embedded nanoparticles; Electron microscopy; Organometallics; Nanomaterials; Colloids; Synthesis; Metal oxide; Phosphates; Crystallization
Effect of Triton X-100 on the stability of aqueous dispersions of copper phthalocyanine pigment nanoparticles
by Jiannan Dong; Shuang Chen; David S. Corti; Elias I. Franses; Yan Zhao; Hou T. Ng; Eric Hanson (pp. 33-41).
Postulated conformations of Triton X-100 on CuPc-U (left) and CuPc-S (right) at their maximum densities studied.Display Omitted► The adsorption density of Triton X-100 is higher on the hydrophobic than on the hydrophilic CuPc particles. ► Some adsorbed surfactant remains irreversibly adsorbed after the solution is diluted. ► The stabilization mechanism for the hydrophobic CuPc particles is primarily steric. ► The stabilization mechanism for the hydrophilic CuPc particles is primarily electrostatic. ► For dispersions in water the zeta potential is not a good predictor of dispersion stability.The effect of Triton X-100 on the colloidal dispersion stability of CuPc-U (unsulfonated and hydrophobic) and CuPc-S (surface sulfonated and hydrophilic) particles in aqueous solutions (water and NaNO3) was investigated at 25°C. Its adsorption density was determined from surfactant concentrations analyzed by an HPLC method with a UV detector. The experimental dispersion stability ratios of the particles were determined from dynamic light scattering (DLS) data, with the Rayleigh-Debye-Gans (RDG) light scattering theory.The adsorption densities of Triton X-100 on both the CuPc-U and CuPc-S increase with increasing concentration of surfactant up to the critical micelle concentration (cmc), and then reach a plateau. The maximum adsorption densityΓ m is higher for the CuPc-U (d h=160nm) than that for the CuPc-S (d h=90nm). The hydrophobic chains are inferred to be adsorbed onto the surfaces, and the hydrophilic ethylene oxide chains are in a coil conformation. The Wapp-values for the CuPc-U dispersions are affected mainly by the surfactant fractional surface coverage θ. Adding NaNO3 has no significant effect on the dispersion stability. The stabilization mechanism for the CuPc-U is inferred to be primarily steric, as expected. The stability ratios for the CuPc-S in solutions with NaNO3 are higher than those for CuPc-U, and decrease with increasing concentration of NaNO3, indicating that the stabilization is affected by the screening of electrostatic repulsive forces. The zeta potential is not a good predictor of the electrostatic stabilization, pointing to the need for new and improved theories.
Keywords: Copper phthalocyanine pigment; Triton X-100; Nonionic surfactant adsorption; Dispersion stability; Steric effects; Electrostatic effects; Electrosteric effects
Preparation of MCM-41 incorporated with lacunary Keggin polyoxometalate and its catalytic performance in esterification
by Baoshan Li; Wei Ma; Jianjun Liu; Shengli Zuo; Xianfen Li (pp. 42-49).
The mesoporous MCM-41 materials were incorporated with lacunary polyoxometalate by the direct synthesis method and the impregnation method, respectively. A is 25%LPOM-DS, and B is 25%LPOM-IM.Display Omitted► Lacunary polyoxometalate (LPOM) was encapsulated into MCM-41 via an original direct synthesized method. ► LPOM-DS samples showed better performance than LPOM-IM materials on the esterification of n-butanol with acetic acid. ► The conversion rate of n-butanol was up to 89.7%, and the selectivity of butyl acetate was nearly 100%. ► The strong interactions of LPOM with the support ensured little loss of LPOM from the composites in liquid phase reactions.The ordered mesoporous MCM-41 materials incorporated with lacunary polyoxometalate were prepared via an original direct synthesis method. As the control, the samples with similar lacunary polyoxometalate loadings were also prepared by impregnation of MCM-41. The prepared samples were characterized by XRF, XRD, FT-IR, Raman spectra, HRTEM, SEM, N2 adsorption isotherm, TG–DTA, and NH3–TPD technology. The results show that the lacunary polyoxometalate is better dispersed in the direct synthesized samples than in the impregnated samples, and its structure remains intact after formation of the materials. The catalytic performance of the materials was tested using the esterification of n-butanol with acetic acid. The direct synthesized samples display excellent catalytic performance and reusability, which is superior to the impregnated samples. Under the optimized conditions, the conversion of n-butanol is 89.7%, and the selectivity of butyl acetate is nearly 100%.
Keywords: Polyoxometalate; Mesoporous molecular sieve MCM-41; Mesoporous material; Catalyst; Esterification
In situ photoexcitation of silver-doped titania nanopowders for activity against bacteria and yeasts
by Katarzyna Kowal; Katarzyna Wysocka-Król; Marta Kopaczyńska; Ewa Dworniczek; Roman Franiczek; Magdalena Wawrzyńska; Melinda Vargová; Miroslav Zahoran; Erik Rakovský; Peter Kuš; Gustav Plesch; Andrej Plecenik; Fathima Laffir; Syed A.M. Tofail; Halina Podbielska (pp. 50-57).
SEM microphotographs of prepared nanopowders at magnification (a) as-prepared sample – Ti-1, (b) sample annealed at 400°C – Ti-2, (c) Ag-doped as-prepared sample – Ti-3, (d) sample annealed at 400°C which was doped by Ag–Ti-4.Display Omitted► We synthesize four nanomaterials based on titanium dioxide. ► We obtain materials in different crystalline form. ► We examine antimicrobial activity with respect to UV-A irradiation. ► Photoexcitation of titanium dioxide based nanomaterials increases activity against microbes.Photocatalytic and in situ microbial activityofthe amorphous and annealed states of Ag-doped and un-doped titania were examined. Studiesontheir structure, morphology, composition, and the photo-absorption characteristics of these materials were performed. Theseresultswere correlated with the photocatalytic and microbial activity against methicillin resistant Staphylococcus aureus K324 (MRSA), methicillin susceptible S. aureus ATCC 25923 (MSSA), Escherichia coli PA 170, and yeasts Candida albicans ATCC 90028. The annealed powders containing anatase form of titania exhibited relatively higher photocatalytic activity,correspondingto activity against MRSA,when exposed to UV-A radiation. In comparison, amorphous powders exhibited low photoactivity and showed poor antibacterial performance against MRSA under UV-A exposure. Doping of amorphous titania with Ag resulted in an anti-MRSA effectwithoutexposure to UV radiation. In the Ag-doped crystalline anatase samples, the size of Ag primary nanocrystallites increased, which led tothedecrease in the surface concentration of Aganddetrimentanti-MRSA activity.
Keywords: Titania nanopowders; Anatase; Silver; Antimicrobial activity; Photocatalytic activity; MRSA
Dynamics of Pseudomonas aeruginosa association with anionic hydrogel surfaces in the presence of aqueous divalent-cation salts
by Victoria B. Tran; Ye Suel Sung; Suzanne M.J. Fleiszig; David J. Evans; C.J. Radke (pp. 58-66).
PAK bacteria exhibit an accumulation burst on an anionic hydrogel surface when immersed in: (a) aqueous MgCl2 and (b) aqueous CaCl2.Display Omitted► PAK strain of Pseudomonas aeruginosa exhibits burst association on anionic hydrogel membranes. ► Bursting arises from reversible aqueous divalent-cation bridging. ► Divalent cations collapse the anionic gel and destroy surface binding sites for the bacteria. ► The few strongly bound bacteria on the gel are likely due to increased hydrophilicity of the anionic gel surface. ► This study emphasizes a delicate balance of physical and chemical forces between bacteria and substrate surfaces.Binding of bacteria to solid surfaces is complex with many aspects incompletely understood. We investigate Pseudomonas aeruginosa uptake kinetics onto hydrogel surfaces representative of soft-contact lenses made of nonionic poly(2-hydroxyethylmethacrylate) (p-HEMA), anionic poly(methacrylic acid) (p-MAA), and anionic poly(acrylic acid) (p-AA). Using a parallel-plate flow cell under phase-contrast microscopy, we document a kinetic “burst” at the anionic hydrogel surface: dilute aqueous P. aeruginosa first rapidly accumulates and then rapidly depletes. Upon continuing flow, divalent cations in the suspending solution sorb into the hydrogel network causing the previously surface-accumulated bacteria to desorb. The number of bacteria eventually bound to the surface is low compared to the nonionic p-HEMA hydrogel. We propose that the kinetic burst is due to reversible divalent-cation bridging between the anionic bacteria and the negatively charged hydrogel surface. The number of surface bridging sites diminishes as divalent cations impregnate into and collapse the gel. P. aeruginosa association with the surface then falls. Low eventual binding of P. aeruginosa to the anionic hydrogel is ascribed to increased surface hydrophilicity compared to the counterpart nonionic p-HEMA hydrogel.
Keywords: Pseudomonas aeruginosa; Soft-contact lenses; Nonionic and anionic hydrogels; Aqueous divalent cations
Structure and surface coverage of water-based stearate coatings on calcium carbonate nanoparticles
by Xuetao Shi; Imre Bertóti; Béla Pukánszky; Roberto Rosa; Andrea Lazzeri (pp. 67-73).
Effect of thermal treatment on the arrangement of stearate molecules on the surface of PCC coated with stearin in aqueous medium.Display Omitted► We coated PCC particles coated with stearin in aqueous medium. ► The coating shows an incomplete monolayer and a few physically adsorbed layers. ► We proposed a model based on a micelle adsorption mechanism. ► We also proposed that during drying the physisorbed layers rearrange. ► The model predicts that the aliphatic tails point out of the particles.In a preceding paper it was found that, during coating with solutions of a stearin salt in water, whatever the concentration used, a considerable part of the PCC surface remains free, indicating the development of an incomplete monolayer. This was explained by assuming a micelle adsorption mechanism as the dominating process in water, resulting in the formation of a multilayer structure composed of an inner incomplete chemisorbed monolayer and one or more physically adsorbed layers. This model predicted a physisorbed layer in which polar groups are oriented outwards of the particles, resulting in a hydrophilic surface, and contrary to experimental evidence. In this paper we propose that during the drying stage the physisorbed calcium stearate layers undergo a complex rearrangement leading to a hydrophobic coating with the aliphatic tails oriented outwards of the particles. The results of XRD measurements proved that the physisorbed stearate layer is crystalline, while DSC model experiments indicated that the layer goes through phase transitions during heat treatment. The proposed model matched with IGC measurements, showing a clear dependence of the specific component of surface energy on the amount of absorbed stearin. The agreement with values obtained for solvent and dry-coated particles support the proposed rearrangement of alkanoate molecules in the coating.
Keywords: Precipitated calcium carbonate; Monolayer coverage; Micelle adsorption mechanism; Surface energy; Stearin; Water coating
Chelating template-induced encapsulation of NiO cluster in mesoporous silica via anionic surfactant-templated route
by Kui Niu; Dongjian Shi; Weifu Dong; Mingqing Chen; Zhongbin Ni (pp. 74-80).
Schematic illustration of HED3A-assisted introduction of nickel-(II) and the formation of NiO clusters in mesopores during the synthesis of mesoporous composites.Display Omitted► We use triprotic surfactant as template for fabricating mesoporous silica. ► All nickel ions can be introduced into mesopores by means of chelating template. ► The derived composites exhibit fundamental mesoporous characteristics. ► The composition of composites can be adjusted by altering Ni2+/HED3A in initial template. ► Variety of metal oxides/silica mesoporous composites can be prepared via this route.In this study, we develop a novel one-step method for synthesis of nickel oxide/silicon dioxide (NiO/SiO2) mesoporous composites by using N-hexadecyl ethylenediamine triacetate (HED3A) as structure-directing agent. Besides playing a role in directing the mesophase formation, the anionic surfactant also functions as a chelating agent that binds nickel ions. Ultraviolet–visible (UV–vis) and Fourier transform infrared (FTIR) spectroscopic analyses were undertaken to determine the chelating ability between HED3A and nickel ions. By adjusting the molar ratio of Ni2+/HED3A in the template solution, a series of mesoporous composites with various NiO contents were obtained after calcination. These composites were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and nitrogen adsorption/desorption. The results showed that the generated NiO nanoparticles were aggregated into clusters with the size less than 20nm, and the composites retained mesoporous characteristics even with high NiO contents. HRTEM images also revealed the migration and aggregation for NiO nanoparticles during the sintering process. Moreover, the energy-dispersive X-ray spectrum (EDX) results showed a close linear relationship between Ni/Si in the composites and Ni2+/HED3A in the templates. This chelating surfactant-assistant encapsulation route has the potential to synthesize diversiform metal oxide/silica mesoporous composites with designated compositions.
Keywords: Chelating surfactant; Nickel oxide; Mesoporous composites; Structure-directing agent; Linear relationship
Synthesis and assembly of gold nanoparticle-doped polymer solid foam films at the liquid/liquid interface and their catalytic properties
by Lan-Jun Chen; Huihui Ma; Kuangcai Chen; Hyeong-Rae Cha; Yong-Ill Lee; Dong-Jin Qian; Jingcheng Hao; Hong-Guo Liu (pp. 81-88).
Foam films of P2VP doped with Au nanoparticles were fabricated at the liquid/liquid interface. The composite films exhibit effective catalytic activity.Display Omitted► Gold nanoparticle-doped foam-like P2VP film formed at the liquid/liquid interface. ► UV-light treatment led to further reduction ofAuCl4- and cross-linking of P2VP. ► The self-assembly of P2VP-AuCl4- complexes resulted in the formation of the film. ► The composite films exhibited effective catalytic activity. ► Durable catalytic activity was achieved after the third cycle.Gold nanoparticle-doped poly(2-vinylpyridine) (P2VP) microcapsules and foam films were synthesized and assembled at the P2VP chloroform solution/HAuCl4 aqueous solution interface at 25°C. It was found that Au nanoparticles with the average diameter of 2.1nm were homogeneously embedded in and adsorbed on the walls of the capsules and foams, the nanoparticles were composed of Au(0) and Au(III) with the molar ratio of about 75/25, and the mass percent of Au elements was measured to be 19.65%. The formation of the nanostructures was attributed to the self-assembly of P2VP at the liquid/liquid interface, the simultaneous reduction ofAuCl4- ions by a small amount of ethanol in the chloroform and adsorption ofAuCl4- ions. After irradiated by UV-light for 1h, the average diameter of the nanoparticles was found to be 2.2nm, and theAuCl4- ions were transformed to Au(0) completely. The catalytic performance of these composite nanostructures were evaluated by using the reduction of 4-nitrophenol (4-NP) by potassium borohydride in aqueous solutions. The catalytic activity was very high in the first cycle, decreased rapidly and slightly in the second and third cycles, respectively, due to the aggregation of some nanoparticles, and stabilized after the third cycle.
Keywords: Gold nanoparticles; Liquid/liquid interface; Polymer; Composite films; Catalysis
Large pore volume mesoporous copper particles and scaffold microporous carbon material obtained from an inorganic–organic nanohybrid material, copper-succinate-layered hydroxide
by Mohammad Yeganeh Ghotbi; Narjes Bagheri; S.K. Sadrnezhaad (pp. 89-93).
Surface morphologies of scaffold microporous carbon (a) and mesoporous copper particles (b).Display Omitted► A new nanohybrid, copper-succinate-layered material was synthesized. ► Heat-treating processes of the nanohybrid produced two type materials. ► Scaffold microporous carbon material at 500°C. ► Large pore volume mesoporous metallic copper at 600°C.Copper-succinate-layered hydroxide (CSLH), a new nanohybrid material, was synthesized as an inorganic–organic nanohybrid, in which organic moiety was intercalated between the layers of a single cation layered material, copper hydroxide nitrate. Microporous scaffold carbon material was obtained by thermal decomposition of the nanohybrid at 500°C under argon atmosphere followed by acid washing process. Furthermore, the heat-treated product of the nanohybrid at 600°C was ultrafine mesoporous metallic copper particles. The results of this study confirmed the great potential of CSLH to produce the carbon material with large surface area (580m2/g) and high pore volume copper powder (2.04cm3/g).
Keywords: Layered structures; Nanohybrid; Microporous carbon; Mesoporous copper
Syntheses of silsesquioxane (POSS)-based inorganic/organic hybrid and the application in reinforcement for an epoxy resin
by Caihua Ni; Guifeng Ni; Liping Zhang; Jiaquan Mi; Bolong Yao; Changping Zhu (pp. 94-99).
Epoxy resin network reinforced by caged silsesquioxane with functional groups of epoxy and 1,4-butanediol diglycidyl ether.Display Omitted► We have prepared a novel inorganic/organic hybrid material containing silsesquioxane and functional groups of epoxy. ► The hybrid material shows great reinforcement for crosslinked epoxy resin when mixed with the resin. ► The reinforcement is ascribed to nano-scale effect of the POSS structure and the anchor structure. ► Kinetics revealed that two kinds of curing reactions occurred in different temperature ranges.A new inorganic/organic hybrid material containing silsesquioxane was prepared by the reaction of caged octa (aminopropyl silsesquioxane) (POSS-NH2) with n-butyl glycidyl ether ( nBGE) and 1,4-butanediol diglycidyl ether (BDGE). The copolymers of POSS, nBGE, and BDGE could be obtained with varied feed ratio of POSS-NH2, nBGE, and BDGE in the preparation. The hybrid material was added into an epoxy resin (E51) for enhancing the toughening and thermal properties of the epoxy resin. The results showed that the toughening and the thermal properties of the cured epoxy resin were greatly improved by the addition of the hybrid. The enhancement was ascribed to nano-scale effect of the POSS structure and the formation of anchor structure in the cured network. The investigation of kinetics for the curing process of the hybrid-modified epoxy resin revealed that two kinds of curing reactions occurred in different temperature ranges. They were attributed to the reactions between amino groups of the curing agent with epoxy groups of E51 and with residue epoxy groups in the hybrid. The reacting activation energies were calculated based on Kissinger’s and Flynn–Wall–Ozawa’s methods, respectively.
Keywords: Silsesquioxane; Hybrid material; Epoxy resin; Enhancement
Cooperative antimicrobial activity of CdTe quantum dots with rocephin and fluorescence monitoring for Escherichia coli
by Zhihui Luo; Qingsheng Wu; Meng Zhang; Ping Li; Yaping Ding (pp. 100-106).
CdTe QDs are used to increase the efficacy of rocephin, and they collaborate to realize “1+1>2” cooperative antimicrobial effects against Escherichia coli. Fluorescent enhancement effect of CdTe QDs with E. coli is firstly adopted to synchronously monitor the concentration changes in E. coli.Display Omitted► CdTe QDs are used to greatly enhance efficacy of rocephin for the first time. ► Rocephin with CdTe QDs can achieve cooperative antimicrobial effects to Escherichia coli. ► CdTe QDs are inventively adopted to monitor the concentration changes in E. coli synchronously.In this study, the cooperative antibacterial efficiency of CdTe quantum dots (QDs) and rocephin against Escherichia coli ( E. coli) was investigated. Colony-forming capability assay and diameter of inhibition zone (DIZ) measurement showed the antibiotic action of CdTe QDs-rocephin complex was better than the superposition of pure CdTe QDs and rocephin. The fractional inhibitory concentration index (FICI) indicated that CdTe QDs-rocephin complex could achieve great cooperative antimicrobial effects. The infrared ray (IR) spectrum, photoluminescence (PL) spectrophotometry, and detection of reactive oxygen species (ROS) indicated that CdTe QDs and rocephin formed a stable antimicrobial group through electrostatic attraction and hydrogen bonds and then killed the E. coli together. Meanwhile, the fluorescence intensity of CdTe QDs and the optical density (OD) value of E. coli showed a good linear relationship. Thus, dynamic monitoring to total bacterial concentration in the antibacterial process was realized by the CdTe QDs.
Keywords: Quantum dots; Antibiotics; Cooperative antimicrobial effects; Synchronous monitoring
Modifying the surface of Fe3O4/SiO2 magnetic nanoparticles with C18/NH2 mixed group to get an efficient sorbent for anionic organic pollutants
by Xiaole Zhang; Hongyun Niu; Yuanyuan Pan; Yali Shi; Yaqi Cai (pp. 107-112).
Synthesis strategy of Fe3O4/SiO2/C18+NH2 MNPs.Display Omitted► The mixed groups both contribute to the adsorption of targets which brings about high extraction ability of the sorbent. ► The silica coat can provide more bonding sites for functional groups and enhance the stability of the sorbent. ► The Fe3O4 core endues the sorbent with magnetic separation ability which simplifies the extraction greatly.In this article, C18/NH2 mixed group modified Fe3O4/SiO2 magnetic nanoparticles (Fe3O4/SiO2/C18+NH2 MNPs) were successfully synthesized and used for the extraction of perfluorinated compounds (PFCs) from large volume of water solution. The Fe3O4/SiO2/C18+NH2 MNPs, about 25nm in diameter, possess high extraction ability to the anionic organic pollutants due to the dual function of hydrophobic octadecyl group and cationic aminopropyl groups at low pH. More than 90% of the targets can be extracted from 500mL of water solution with 0.1g of the MNP sorbent at pH 3. Twenty min is sufficient to reach adsorption equilibrium, and the targets can be desorbed from the sorbent readily with 12mL of alkalized methanol after magnetic separation. Simplified extraction procedure could be achieved because of the superparamagnetism and high saturation magnetization of the sorbent (44emug−1). Therefore, preconcentration of trace level of PFCs from water solution can be performed by using this Fe3O4/SiO2/C18+NH2 MNP sorbent which are stable for multiple reuses.
Keywords: Fe; 3; O; 4; /SiO; 2; /C; 18; +; NH; 2; MNPs; Mixed functionalized; Extraction; Perfluorinated compounds
Two-component supramolecular organogels formed by maleic N-monoalkylamides and aliphatic amines
by Xuzhong Luo; Zhixing Chen; Wei Xiao; Zengfu Li; Qiong Wang; Jinlian Zhong (pp. 113-117).
The complexes of maleic N-monoalkylamides and aliphatic amines gelatinize a number of organic solvents via acid–base interactions and intermolecular hydrogen bonding.Display Omitted► Two-component gelators are comprised of maleic N-monoalkylamides and aliphatic amines. ► Two-component gelators form sheet-like and fiber-shaped aggregates in diverse organic solvents. ► The local microstructure of aggregates in the organogels has been obtained.The complexes of maleic N-monoalkylamides and aliphatic amines lead to the formation of sheet-like and fiber-shaped aggregates in diverse organic solvents. Their morphologies and microstructures were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), as well as small angle X-ray diffraction (SA-XRD). The results reveal that the alkyl chain lengths of 8–12 carbons for maleic N-monoalkylamides, and 12–18 carbons for aliphatic amines, are suitable for obtaining highly efficient two-component gelators.
Keywords: Two-component organogel; Maleic N-monoalkylamides; Aliphatic amines; Hydrogen bonding; Acid–base interaction
Fibrinogen stability under surfactant interaction
by Natalia Hassan; Leandro R.S. Barbosa; Rosangela Itri; Juan M. Ruso (pp. 118-126).
The SAXS curves are compatible to the scattering of paired-dimers, arrangement of two fibrinogen dimmers, in this studied concentration range.Display Omitted► Fluorination plays two opposite roles in fibrinogen stability. ► C8HONa and C8FONa monomers interact with fibrinogen paired-dimer without promoting dissociation. ► C12HONa and the protein promote the surfactant self-assembling (pearl necklace model).Differential scanning calorimetry (DSC), circular dichroism (CD), difference spectroscopy (UV–vis), Raman spectroscopy, and small-angle X-ray scattering (SAXS) measurements have been performed in the present work to provide a quantitatively comprehensive physicochemical description of the complexation between bovine fibrinogen and the sodium perfluorooctanoate, sodium octanoate, and sodium dodecanoate in glycine buffer (pH 8.5). It has been found that sodium octanoate and dodecanoate act as fibrinogen destabilizer. Meanwhile, sodium perfluorooctanoate acts as a structure stabilizer at low molar concentration and as a destabilizer at high molar concentration. Fibrinogen’s secondary structure is affected by all three studied surfactants (decrease in α-helix and an increase in β-sheet content) to a different extent. DSC and UV–vis revealed the existence of intermediate states in the thermal unfolding process of fibrinogen. In addition, SAXS data analysis showed that pure fibrinogen adopts a paired-dimer structure in solution. Such a structure is unaltered by sodium octanoate and perfluoroctanoate. However, interaction of sodium dodecanoate with the fibrinogen affects the protein conformation leading to a complex formation. Taken together, all results evidence that both surfactant hydrophobicity and tail length mediate the fibrinogen stability upon interaction.
Keywords: Fibrinogen; Fluorinated; Hydrogenated; DSC; SAXS
Amination of surfaces via self-assembly of dopamine
by Ying Liu; Bo Yu; Jingcheng Hao; Feng Zhou (pp. 127-134).
Self-oxidation polymerization of dopamine was prevented in an oxygen free acidic solution, allowing for surface amination of a variety of substrates after self-assembly of dopamine.Display Omitted► Surface amination was realized by self-assembly of dopamine on a variety of substrates including silicon, gold, and mica. ► Self-oxidation polymerization of dopamine was prevented in an oxygen free acidic solution. ► The amino group of dopamine monolayer can be used for secondary derivation reaction.Catechols can strongly bind to a variety of substrates so as to functionalize the target surfaces by forming self-assembled monolayer. However, catecholic amine might self-oxidize and polymerize at high pH since the amine is susceptible to nucleophilic addition reaction that results in polymerized oligomers on surfaces. Therefore, the availability of amines for further derivation reaction would be restricted to a large extent. Herein, by controlling pH values to avoid self-oxidative polymerization, dopamine (DA) forms thin and surface-adherent monolayers onto a wide range of inorganic and organic materials, including mica, silica, and Au surface, allowing amination of the surfaces that resemble commercially used aminosilanization. The self-assembly process was traced by surface topography and elemental composition analysis using atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), and electrochemical characterization (electrochemical impedance spectroscopy and cyclic voltammetry measurements). Then, the aminated surfaces were used for secondary derivation reactions to create a variety of ad-layers, including patterned streptavidin through specific binding interaction with biotin and ferrocene surface via amidation reaction. The surface and interface properties of the obtained surfaces were tested by electrochemical measurements.
Keywords: Dopamine; Self-assembled monolayer; Amination; AFM
Molecular dynamics simulations of surfactants at the silica–water interface: Anionic vs nonionic headgroups
by Naga Rajesh Tummala; Liu Shi; Alberto Striolo (pp. 135-143).
The heterogeneous charge distribution on the substrate affects the orientation of adsorbed non-ionic surfactant headgroups. Coiling of headgroups is observed when random positive and negative charges are present on the substrate.Display Omitted► Molecular dynamics of ionic SDS and non-ionic C12E6 on silica substrates were studied. ► Competitive adsorption between water and surfactants is observed. ► Competitive adsorption limits the sodium dodecyl sulfate on the silica surfaces. ► Coulombic interactions between the substrate and C12E6 headgroups dictate the surfactant behavior. ► These interactions define the adsorbed aggregate morphology of the adsorbed surface aggregate.Understanding surfactant adsorption on surfaces at the molecular level will provide us with the ability to design specific surfactants for surface modification. We conducted molecular dynamics simulations for sodium dodecyl sulfate (SDS) and hexaethylene glycol monododecyl ether (C12E6) adsorbed on silica substrates with varying degree of hydroxylation. Our results shed light on the effects of hydroxylation on the surfactant aggregate morphology. The discrete charge distribution on the substrate surface appears to dictate both surfactant adsorption and aggregate morphology. The differences in aggregate morphology observed for anionic SDS and non-ionic C12E6 on silica substrates are discussed quantitatively and compared to available experimental data.
Keywords: Surface aggregates; Amphiphilic molecules; Surfactants on oxide surfaces; SDS; C; 12; E; 6; Electrostatic interactions
Sorption behaviour of nanocrystalline MOR type zeolite for Th(IV) and Eu(III) removal from aqueous waste by batch treatment
by Pankaj Sharma; Radha Tomar (pp. 144-156).
The results of this work indicate that synthetic analogue MOR4 shows better sorption affinity for Eu(III).Display Omitted► The BET studies demonstrate the mesoporous character of MOR type materials. ► Sorption of Th(IV) and Eu(III) on analogues of MOR is a favourable and physisorption process. ► Nanocrystalline MOR4 is proved to be good sorbent for both Th(IV) and Eu(III). ► The sorbed metal ions cannot get desorbed by groundwater.The nanocrystalline mordenite (MOR) type zeolite materials with initial chemical composition Na2O:Al2O3:10SiO2:48H2O have been synthesized under hydrothermal conditions. MOR1 and MOR2 are spherically shaped nanocrystals, whereas MOR3 and MOR4 have rod-like morphology. This paper reports the sorption characteristics of MOR analogues for Th(IV) and Eu(III) removal from aqueous nuclear waste. Sorption of Th(IV) and Eu(III) on MOR1, MOR2, MOR3 and MOR4 in a single component system with varying initial metal ion concentration, solution pH, contact times, sorbent dose and temperatures has also been investigated. Further, the Langmuir and Freundlich sorption models have been applied to describe equilibrium isotherms at different temperatures. The adsorption capacity increases largely with increasing solution pH and temperature of the system. Specific surface area and pore volume have been investigated by Brunauer–Emmett–Teller (BET) method. The N2 adsorption isotherm presents a type IV isotherm with narrow hysteresis loop which indicates the presence of mesopores related to inter-particle voids. Thermodynamic results indicate that the sorption follows an endothermic physisorption process. It has been found that these exchangers have good sorption capacity and out of which MOR4 has highest sorption capacity. Thus, nanocrystalline MOR4 is proved to be good sorbent for both Th(IV) and Eu(III).
Keywords: Mordenite; Zeolite; Sorption; Nanosize; Radionuclides; Isotherm
Periodic mesoporous organosilicas with bis(8-quinolinolato) dioxomolybdenum(VI) inside the channel walls
by Ying Yang; Ying Zhang; Shijie Hao; Qiubin Kan (pp. 157-163).
Novel periodic mesostructured organometallic silicas of MCM-41 type bearing homogeneously distributed bis(8-quinolinolato)dioxomolybdenum(VI) inside the channel walls are synthesized via a convenient one-pot method..Display Omitted► One-pot synthesized organomolybdenum(VI) functionalized PMOs are highly ordered. ► Organomolybdenum(VI) species distribute homogeneously in the framework of materials. ► Catalytic performances relate to the textual and morphological properties.Novel periodic mesostructured organometallic silicas of MCM-41 type bearing homogeneously distributed bis(8-quinolinolato)dioxomolybdenum(VI) inside the channel walls (denoted as MoO2Q2@PMO-x) are synthesized via a convenient one-pot method and examined as catalysts in the epoxidation of cyclooctene. The ordered mesoporous structures as well as the organometallic groups incorporated into the framework are fully determined by comprehensive characterization techniques such as XRD, TEM, N2 adsorption/desorption, SEM, FT-IR, UV–vis spectroscopy, solid-state NMR, ICP-AES, XPS and TG/DSC. MoO2Q2@PMO-6% catalyst exhibits higher activity for the epoxidation of cyclooctene with tert-butyl hydroperoxide than other MoO2Q2@PMO materials and its homogeneous or randomly grafted analogue.
Keywords: Molybdenum; 8-Quinolinol; Periodic mesoporous organosilicas (PMOs); Cyclooctene epoxidation
Adsorption of cetyltrimethylammonium bromide and/or cetyldimethylbenzylammonium chloride on partly covered hanging mercury drop electrode
by Argyri Koniari; Antonis Avranas (pp. 164-171).
Capacitance time curves at various potential jumps show arrangement of surfactant molecules with reorientation and interaction.Display Omitted► Adsorbed surfactants on mercury are used as templates. ► The second adsorbed surfactant does not remove away the first one. Films and synergy effects are observed. ► The already adsorbed CTAB on mercury does not permit the desorption–reorientation peaks of CDBACl. ► Shifts of the capacitance peaks are attributed to a slow change in the organization of the monolayer. ► The ordering and arrangement of molecules could be controlled by appropriate selection of templates.Adsorbed cetyldimethylbenzylammonium chloride (CDBACl) or cetyltrimethylammonium bromide (CTAB) on mercury is used as template for the adsorption of CTAB, CDBACl, or their equimolar mixture at 20°C. Adsorptive stripping voltammetry with the two step procedure is used. The results are compared with previously published results on the adsorption of CTAB and CDBACl on mercury and then transferred in base electrolyte. A surfactant is preadsorbed. The adsorption of the second does not remove away from the mercury the first one, as evidenced by the capacitance measurements and the repeated scans. The surfactants were maintained close to each other and in the vicinity of the electrode by the applied electric field. In all cases studied, there was a decrease in the capacitance in the potential range −0.8 to −1V to very low capacitance values forming condensed film. Mixed films and synergy effects were observed. The already adsorbed CTAB on mercury did not permit the desorption–reorientation peaks of CDBACl. Shifts of the capacitance peaks were observed to more positive potentials and were attributed to the occurrence of a slow change in the organization of the monolayer. The electrical state of the preadsorbed surfactant would be of critical importance in the formation of the various structures. The results suggested that the ordering and arrangement of molecules could be controlled by appropriate selection of templates.
Keywords: Cetyltrimethylammonium bromide; Cetyldimethylbenzylammonium chloride; Adsorptive stripping voltammetry; Differential capacitance; Condensed film; Template
Interaction of supramolecular centers of silica surface with aromatic amino acids
by N.V. Roik; L.A. Belyakova (pp. 172-179).
Adsorption of aromatic amino acids onto the surface of silica with chemically attached β-cyclodextrin moieties.Display Omitted► β-Cyclodextrin-containing silica preparation under mild conditions. ► Aromatic amino acids adsorption on b-cyclodextrin-containing silica. ► Kinetic adsorption process is described by pseudo-second order kinetic model.Surface grafting of β-cyclodextrin onto aminopropylsilica has been carried out under mild conditions using 1,1′-carbonyldiimidazole as an activator. The obtained β-cyclodextrin-silica has been characterized by means of chemical and IRspectral analysis. Adsorption of para-aminobenzoic and para-aminosalicylic acids onto the surface of hydroxylated silica, aminopropylsilica, and silica with chemically attached β-cyclodextrin moieties has been studied in relation to duration of contact, equilibrium concentration, and solution pH. Chemical immobilization of β-cyclodextrin onto silica surface improves adsorption parameters for aromatic amino acids. The well-known mathematical models for the kinetic and equilibrium adsorption processes have been used, and the main adsorption parameters have been calculated. Kinetic curves of aromatic amino acids adsorption correspond to the model of pseudo-second order reaction. The major contribution to the equilibrium adsorption of para-aminobenzoic and para-aminosalicylic acids onto β-cyclodextrin-containing silica is due to the formation of surface inclusion complexes between grafted oligosaccharide molecules and aromatic amino acids.
Keywords: Silica; β-Cyclodextrin; Aromatic amino acid; Adsorption; IR spectroscopy; UV spectroscopy
QCM study of the adsorption of polyelectrolyte covered mesoporous TiO2 nanocontainers on SAM modified Au surfaces
by Agata Pomorska; Kirsi Yliniemi; Benjamin P. Wilson; Dmitry Shchukin; Diethelm Johannsmann; Guido Grundmeier (pp. 180-187).
The adsorption kinetics of polyelectrolyte covered TiO2 nanocontainers on chemically modified gold surfaces could be measured by means of QCM as a function of ionic strength and pH.Display Omitted► Surface layer, ionic strength and pH have strong effect on NCs deposition process. ► Surface charges enable adsorption at acidic pH regardless ionic strength. ► Deposition at higher pH strongly depends on salt concentration. ► The Debye length becomes thinner at the high ionic strength. ► The particle can approach the surface close enough that deposition can take place.Mesoporous TiO2 nanocontainers (NCs) covered with polyelectrolyte multilayers were adsorbed on self-assembled monolayer (SAM) modified gold substrates at different values of pH and ionic strength. The adsorption process was followed in situ by means of a quartz crystal microbalance (QCM) and the morphology of the adsorbate was investigated by means of FE-SEM images taken of the substrates after each adsorption process. Deposition could be achieved if either the particles and the surface had opposite charge, or if the salt concentration was sufficiently high, reducing the repulsion between the spheres and the surface. In the latter case the adsorption kinetics could be explained in the context of the DLVO-theory. Using conditions of like charges, one has a means to control the speed of deposition by means of ionic strength. However, interparticle aggregation and cluster deposition on the surface were observed at high ionic strength. Such conditions have to be avoided to obtain a uniform deposition of separated nanocontainers on the surface.
Keywords: Abbreviations; AUT; 11-amino-1-undecanthiol; HBHW; Half Band Half Width; MUA; 15-mercaptopentadecanoic acid; NCs; nanocontainers; SAM; self-assembled monolayersNanocontainer; TiO; 2; QCM; DLVO; Adsorption process; SAM
Photochromism-based detection of volatile organic compounds by W-doped TiO2 nanofibers
by Ming Jin; Xintong Zhang; Hongting Pu; Shunsuke Nishimoto; Taketoshi Murakami; Akira Fujishima (pp. 188-193).
W-doped TiO2 nanofibers mats provides a good way in detection of pollutants in indoor air, especially for the volatile organic compounds (VOCs).Display Omitted► W-doped TiO2 nanofibers were prepared by electrospinning techniques. ► The fibers formed a mat after calculation with diameters of 0.2–0.4μm. ► Nanofibers showed good photocatalytic activities toward VOCs. ► Photochromism provides a good way in detection of pollutants in indoor air.W-doped TiO2 nanofibers with various compositions (W/Ti: 2–8%) were fabricated by the electrospinning method from respective precursor solutions containing tungsten(V) pentaethoxide, titanium tetraisopropoxide (TTIP), and polyvinylpyrrolidone (PVP), followed with calcination at 550°C. Morphological and structural characteristics of these nanofibers were studied with SEM, XRD and XPS. W-doping inhibited the crystal growth and anatase-to-rutile transformation of TiO2 nanofibers. W-doped TiO2 nanofiber mats showed good photocatalytic oxidation abilities for acetone. Obvious color change from white to blue of mats during the photocatalysis process can be detected by naked eyes, which provides a good way in detection of pollutants in indoor air, especially for the volatile organic compounds (VOCs).
Keywords: Photocatalyst; Photocatalytic oxidation; Photochromism; Volatile organic compounds; TiO; 2; nanofiber
Impedimetric biosensor based on self-assembled hybrid cystein-gold nanoparticles and CramoLL lectin for bacterial lipopolysaccharide recognition
by Maria D.L. Oliveira; Cesar A.S. Andrade; Maria T.S. Correia; Luana C.B.B. Coelho; Pankaj R. Singh; Xiangqun Zeng (pp. 194-201).
Effect of different concentrations of LPS from E. coli, S. enterica, S. marcescens and K. pneumoniae on Δ RCT during the interaction of the lectin-modified electrode with glycoconjugates.Display Omitted► A new strategy to construct an electrochemical biosensor for bacterial LPS has been described. ► AFM images showed that LPS was specifically recognized. ► A sensor for selective discrimination of LPS types with high sensitivity has been achieved. ► The biosensor provides an appropriate biomimetic interface for specific recognition of LPS.We report the development of a new selective and specific electrochemical biosensor for bacterial lipolysaccharide (LPS). An electrode interface was constructed using al-cysteine-gold nanoparticle (AuNpCys) composite to be immobilized by electrostatic interaction in the network of a poly(vinyl chloride-vinyl acetate maleic acid) (PVM) layer on a gold bare electrode. The impedimetric biosensor is fabricated by self-assembled CramoLL lectin on the PVM–AuNpCys–modified gold electrode through electrostatic interaction. CramoLL is used as the recognition interface. AFM images showed that LPS was specifically recognized on the PVM–AuNpCys–CramoLL system surface. The measurements of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) showed that the electrochemical response of a redox probe system (K4[Fe(CN)6]4−/K3[Fe(CN)6]3−) were blocked, due to the procedures of modified electrode with PVM–AuNpCys–CramoLL. In the majority of the experiments the lectin retained its activity as observed through its interaction with LPS from Escherichia coli, Serratia marcescens, Salmonella enterica and Klebsiella pneumoniae. The results are expressed in terms of the charge transfer resistance and current peak anodic using the EIS and CV techniques for the development of a biosensor for contamination by endotoxins. A new type of sensor for selective discrimination of LPS types with a high sensitivity has been obtained.
Keywords: Impedance spectroscopy; Cyclic voltammetry; Bacterial lipopolysaccharide; Endotoxins; Cratylia mollis; Nanoparticles
On modeling incipient crystallization of sparingly soluble salts in frontal membrane filtration
by M. Kostoglou; A.J. Karabelas (pp. 202-214).
Incipient crystallization on semi-permeable membranes: Schematic diagram of the proposed model structure.Display Omitted► Framework for modeling the incipient scaling on desalination membranes. ► An approximate size-scale separation modeling procedure is proposed. ► The contributions to scaling by bulk and surface nucleation are analyzed. ► Overlapping of particle and membrane concentration polarization layers treated.Modeling incipient crystallization (“scaling”) in desalination membrane modules is a very difficult task due to several complications arising from the interplay of physico-chemical solution conditions (leading to supersaturation) with the flow field and related transport processes, including solid phase generation phenomena and membrane surface geometrical changes caused by the developing discrete particles. Although eventually all these aspects must be included in a comprehensive process model, it is fruitful to isolate and tackle them separately, thereby improving our understanding and developing techniques which will facilitate the ensuing synthesis of an integrated modeling framework. The focus in this work is on solid phase generation phenomena accounting for the membrane surface geometrical changes. A mean field model is developed that includes bulk and surface particle nucleation and growth processes. The relative importance of the two types of processes is analyzed. It is shown that, if thick concentration boundary layers exist around surface particles, the mean field theory—although not strictly valid—can be approximately used to estimate the transport coefficients, in conjunction with a unit cell problem for transport processes around a single surface particle. The unit cell problem is formulated and typical results for the flow and concentration field therein are presented as well as the corresponding mass transfer coefficients.
Keywords: Incipient scaling; Semi-permeable membranes; Desalination; Salt precipitation; Population balances; Transport coefficients; Multi-scale modeling
Finite-amplitude dynamics of coupled cylindrical menisci
by B.L. Cox; P.H. Steen (pp. 215-220).
The cylindrical meniscus is a liquid/gas interface of circular-cap cross-section constrained along its axis and bounded by end-planes (see figure). The inviscid motions of coupled cylindrical menisci are studied here. Motions result from the competition between inertia and surface tension forces. Restriction to shapes that are of circular-cap cross-section leads to an ordinary differential equation (ode) model, with the advantage that finite-amplitude stability can be examined. The second-order nonlinear ode model has a Hamiltonian structure, showing dynamical behavior like the Duffing-oscillator. The energy landscape has either a single- or double-welled potential depending on the extent of volume overfill. Total liquid volume is a bifurcation parameter. Unlike the spherical-cap problem, however, axial disturbances can also destabilize, depending on overfill. For large volumes, previously known axial stability results are applied to find the limit at which axial symmetry is lost and comparison is made to the Plateau-Rayleigh limit.Display Omitted► Inviscid motion of coupled menisci exhibits Duffing-like behavior. ► Total liquid volume is the appropriate bifurcation parameter. ► Large-volume equilibrium states are analogous to constrained full-cylinder. ► Constraint results in stabilization beyond Plateau–Rayleigh limit.The cylindrical meniscus is a liquid/gas interface of circular-cap cross-section constrained along its axis and bounded by end-planes. The inviscid motions of coupled cylindrical menisci are studied here. Motions result from the competition between inertia and surface tension forces. Restriction to shapes that are of circular-cap cross-section leads to an ordinary differential equation (ode) model, with the advantage that finite-amplitude stability can be examined. The second-order nonlinear ode model has a Hamiltonian structure, showing dynamical behavior like the Duffing-oscillator. The energy landscape has either a single- or double-welled potential depending on the extent of volume overfill. Total liquid volume is a bifurcation parameter, as in the corresponding problem for coupled spherical-cap droplets . Unlike the spherical-cap problem, however, axial disturbances can also destabilize, depending on overfill. For large volumes, previously known axial stability results are applied to find the limit at which axial symmetry is lost and comparison is made to the Plateau–Rayleigh limit.
Keywords: Capillarity; Finite-amplitude motion; Fluid oscillations; Surface tension; Plateau–Rayleigh instability
Does macroscopic flow geometry influence wetting dynamic?
by Qi Min; Yuan-Yuan Duan; Xiao-Dong Wang; Zhan-Peng Liang; Chao Si (pp. 221-227).
The dynamic contact angle (θ D) versus moving velocity of contact line ( U) for non-Newtonian fluids wetting on glass (the hollow symbols stand for the sessile drop method while the solid symbols are for the Wilhelmy plate method).Display Omitted► Fluids’ dynamic wetting behavior was studied by sessile drop and Wilhelmy plate methods. ► Macroscopic flow geometry does not influence the wetting behavior of Newtonian fluids. ► Macroscopic flow geometry does influence the dynamic wetting behavior of non-Newtonian fluids. ► The mechanism is the macroscopic flow geometry only influence the viscosity distribution of non-Newtonian fluids.The macroscopic flow geometry has long been assumed to have little impact on dynamic wetting behavior of liquids on solid surfaces. This study experimentally studied both spontaneous spreading and forced wetting of several kinds of Newtonian and non-Newtonian fluids to study the effect of the macroscopic flow geometry on dynamic wetting. The relationship between the dynamic contact angle,θ D, and the velocity of the moving contact line, U, indicates that the macroscopic flow geometry does not influence the advancing dynamic wetting behavior of Newtonian fluids, but does influence the advancing dynamic wetting behavior of non-Newtonian fluids, which had not been discovered before.
Keywords: Dynamic wetting; Dynamic contact angle; Macroscopic flow geometry; Sessile drop method; Wilhelmy plate method
Block copolymer micellization induced microphase mass transfer: Partition of Pd(II), Pt(IV) and Rh(III) in three-liquid-phase systems of S201–EOPO–Na2SO4–H2O
by Pinhua Yu; Kun Huang; Chao Zhang; Keng Xie; Xiuqiong He; Junmei Zhao; Fuli Deng; Huizhou Liu (pp. 228-234).
A mass transfer model describes the anionic exchange process between platinum metal ion complexes and the phase-forming salt anions across the microphase interfaces of copolymer micelles.Display Omitted► The appearance of three liquid phases permits one-step separation of Pd, Pt and Rh. ► The phase behavior has a correlation with three-phase partitioning of Pd, Pt and Rh. ► Microphase interfacial structure is an important factor in mass transfer of metals.Three-liquid-phase partitioning of Pd(II), Pt(IV) and Rh(III) in systems of S201(diisoamyl sulfide)/nonane–EOPO(polyethylene oxide–polypropylene oxide random block copolymer)–Na2SO4–H2O was investigated. Experimental results indicated that the selective enrichment of Pd(II), Pt(IV) and Rh(III) respectively into the S201 organic top phase, EOPO-based middle phase and Na2SO4 bottom phase was achieved by control over the phase behavior of the three-liquid-phase systems (TLPS). The microphase mass transfer behavior of Pt(IV), Pd(II) and Rh(III) was closely related to the micellization of EOPO molecules. A suggested micro-mechanism model and a mass transfer model describe the micellization of EOPO molecules and the effect on mass transfer of platinum ions across the microphase interfaces. The salting-out induced continuous dehydration and ordered arrangement of the hydrophilic PEO segments in amphiphilic EOPO micelle, and these are the main driving forces for mass transfer of platinum metal ions onto the exposed activity sites of the dehydrated PEO segments. The differences in microphase interfacial structure of EOPO micelles are crucial for the efficient separation between Pt(IV), Pd(II) and Rh(III).
Keywords: Three-liquid-phase system; Platinum metals; Microphase; Micellization; Mass transfer
Coalescence of particle-laden drops with a planar oil–water interface
by David Harbottle; Pablo Bueno; Rebecka Isaksson; Ilona Kretzschmar (pp. 235-241).
A particle-laden drop initially at rest at a planar oil–water interface undergoing partial coalescence. Approximate time scale for coalescence event ≈30ms.Display Omitted► Colloidal particles affect the mechanism for drop coalescence. ► Complete coalescence is observed at the onset of non-Newtonian flow. ► Viscous and elastic components dampen the propagating capillary wave. ► Elasticity of the particle network resists the inward pull of interfacial tension.The coalescence mechanism of a particle-laden drop resting at an oil–water interface has been studied. Two mechanisms for drop coalescence are observed; (i) complete coalescence, in which the drop experiences total coalescence in one event, and (ii) partial coalescence, where a drop is observed to separate during coalescence, producing a smaller secondary drop that rebounds and comes to rest at the planar oil–water interface. For particle-laden drops of approximately 4mm in diameter, we show the critical condition for partial to complete coalescence to be dependent on the particle concentration, and the interparticle interaction energy. Colloidal silica spheres dispersed in 10−4M KNO3 electrolyte solution are highly charged and remain dispersed in the drop. By increasing the solids concentration, we measure the transition from partial to complete coalescence at 20wt.%. However, this critical condition can be reduced by increasing the interparticle interaction energy. In 1M KNO3 electrolyte solution, the particle surface charge is sufficiently screened such that particle clusters readily form in the water drop. With particle clustering, transition from partial to complete coalescence is measured at 8wt.% solids.
Keywords: Coalescence; Particle-laden; Drop; Colloid; Silica particles