Journal of Colloid And Interface Science (v.363, #2)
The effects of aspect ratio of inorganic fillers on the structure and property of composite ion-exchange membranes
by Chalida Klaysom; Seung-Hyeon Moon; Bradley P. Ladewig; G.Q. Max Lu; Lianzhou Wang (pp. 431-439).
A new type of nanocomposite ion-exchange membranes containing sulfonated polyethersulfone polymers and sulfonated mesoporous silica was prepared. Characterizations revealed that the addition of silica with different shapes had a significant influence on the membrane structure and performance. The newly developed composite membranes showed excellent desalination performance in electrodialysis with high current efficiency of 95%, and lower energy consumption compared to the benchmark commercial membrane, FKE.Display Omitted► Sulfonated mesoporous silica (SS) with different shapes was used as inorganic fillers. ► The composite ion-exchange membranes containing SS and sulfonated polyethersulfone were prepared. ► Aspect ratio of the fillers had significant influence on composite structures and properties. ► The composites showed very promising desalination performance in electrodialysis.A new type of nanocomposite ion-exchange membranes containing sulfonated polyethersulfone (sPES) polymer matrix and sulfonated surface-functionalized mesoporous silica (SS) inorganic fillers was prepared. Various characterizations revealed that the addition of inorganic fillers with different shapes had a significant influence on the membrane structure. The mesoporous inorganic fillers not only created extra pore and water channels, assisting the ionic migration and improving conductivity of the composites, but also provided additional fixed charge groups upon surface modification. This allows the Donnan exclusion to work effectively and thus improve the selectivity of membranes. It was proved that the incorporation of appropriate amount of SS additive could significantly improve the conductivity (up to 20 folds) and permselectivity (about 14%) of the sPES membranes. The performance of these newly developed membranes in desalination by electrodialysis was comparable with that of a commercial membrane (FKE).
Keywords: Composite ion-exchange membrane; Mesoporous silica; Aspect ratio; Electrodialysis; Desalination
Effect of the graft chain length and density on the morphology of radiation-modified polysilane monolayers at the air/water interface
by Hidenori Tanaka; Yuichiro Kunai; Nobuhiro Sato; Tomochika Matsuyama (pp. 440-445).
AFM observation reveals that PMPrS- g-PDEF monolayers have an inhomogeneous structure containing string-like microstructures. In contrast, PMPrS- g-MAH forms uniform monolayers with a smooth surface.Display Omitted► The Langmuir monolayers of two radiation-modified polysilanes are examined. ► Graft density determines the morphology of monolayers. ► Sparsely-grafted polysilane forms inhomogeneous monolayers on the water surface. ► Densely-grafted polysilane forms uniform monolayers with a smooth surface.The variation in the morphology of monolayers at the air/water interface is investigated for two kinds of radiation-modified polysilanes with different structures: poly(diethyl fumarate)-grafted poly(methyl- n-propylsilane) (PMPrS- g-PDEF) and maleic anhydride-grafted PMPrS (PMPrS- g-MAH). PMPrS- g-PDEF has long but sparsely-attached PDEF graft chains, while PMPrS- g-MAH has short but densely-attached MAH graft units. Surface pressure-area measurements indicate that PMPrS- g-PDEF monolayers extensively spread at the air/water interface though PMPrS homopolymer hardly spreads. AFM observation reveals that PMPrS- g-PDEF monolayers have an inhomogeneous structure containing string-like microstructures. This result suggests that PMPrS main chains are detached from the water surface to aggregate together and only PDEF chains spread over the water surface. In contrast, PMPrS- g-MAH forms uniform monolayers with a smooth surface. PMPrS main chains of PMPrS- g-MAH are anchored to the water surface by densely grafted MAH units. It is also demonstrated that only the PMPrS- g-MAH monolayers are successfully deposited layer-by-layer on a solid substrate by the Y-type deposition.
Keywords: Polysilanes; Graft copolymers; γ-Rays; Radiation modification; Monolayers; LB films
Fabrication of 2D photonic crystals using block copolymer patterns on as grown LEDs
by Md. Mahbub Alam; Jin-Yeol Kim; Woo-Gwang Jung (pp. 446-449).
The pattern of PS-b-PMMA block copolymer was transferred to the surface p-GaN of as grown LEDs by the photo-enhanced chemical (PEC) etching. The samples were kept in 0.04M KOH solution in DI water and exposed to UV irradiation at wavelength 254nm for 15min. The patterned LED shows the significant improvement in light extraction and gives much higher intensity in PL and EL data plots.Display Omitted► Deposition of LED structure. ► Fabrication of polymer patterns on topmost layer of as grown LED using PS-b-PMMA diblock copolymer. ► Transfer of polymer pattern to p-GaN of LED by RIE or PEC etching. ► Data plot of PL and EL in patterned LED.Di-block copolymer polystyrene-block-polymethyl methacrylate (PS-b-PMMA) was used to make patterns over a large area of as grown LEDs. The polymer patterns on LEDs surface could be transferred to the underlying p-GaN, the topmost layer of as grown LEDs by both reactive ion etching (RIE) and photo-enhanced chemical (PEC) etching. Removal of remaining polymer chains results in patterned LEDs which shows higher light extraction efficiency. In our experiment, much higher intensity for patterned LEDs in both photoluminescence (PL) and electroluminescence (EL) data plot were found. Similar improvements were found in I– V and L– I curves for patterned LEDs.
Keywords: Block copolymer; Nanopattern; Light emitting diode; Reactive ion etching; Photo enhanced chemical etching; Photoluminescence; Electroluminescence
Nanostructure of polysaccharide complexes
by Sílvia Coelho; Susana Moreno-Flores; José L. Toca-Herrera; Manuel A.N. Coelho; M. Carmo Pereira; Sandra Rocha (pp. 450-455).
Nanoparticles made of gum arabic and chitosan (degree of acetylation 5) at weight ratio of 1 (scale bar=200nm).Display Omitted► Gum arabic–chitosan nanostructures. ► Chitosan degree of acetylation (DA) determines the structure of the complexes. ► Gum arabic and chitosan with high charge density (DA 5%) form nanoparticles of 200nm. ► Using chitosan with higher DA (25%), soluble complexes are obtained. ► Soluble complexes are flat when adsorbed on mica surfaces (height⩽10nm).The interaction of gum arabic (GA) with chitosan (Ch) of different degree of deacetylation was studied by turbidity measurements, dynamic light scattering and atomic force microscopy. The structure of the complexes was found to be directly related to the charge density of chitosan molecules. Gum arabic and chitosan with a degree of deacetylation of 75% form soluble complexes with a loosely globular structure of about 250nm, at weight ratios up to 1.2, if the concentrations are kept low (total biopolymer concentration up to 0.06%). If chitosan has a higher charge density (degree of deacetylation of 93%), colloidal particles are formed, independently of the polymer concentration or ratio. At low concentrations and GA/Ch ratios of 1 or 1.2, the particles have diameters of 200–250nm. The formation of soluble complexes is attributed to a chitosan lower charge density and the presence of non-charged monomers, which prevent the efficient self-assembly of the macromolecules.
Keywords: Degree of deacetylation; Nanoparticles; Soluble complexes; Coacervation; Chitosan; Gum arabic
Synthesis and luminescence properties of Eu(III)-doped nanoporous silica spheres
by Motohiro Tagaya; Toshiyuki Ikoma; Tomohiko Yoshioka; Satoshi Motozuka; Zhefeng Xu; Fujio Minami; Junzo Tanaka (pp. 456-464).
Display Omitted► Luminescent Eu3+-doped nanoporous silica spheres were synthesized. ► Ordered nanopores were preserved with the doping to show the efficient luminescence. ► O−Si−O and Si−OH skeletons in the framework were rearranged with the doping. ► Eu3+ ions were located in a low symmetry of the structures. ► Structural O atoms prevent the aggregation among Eu3+ ions.Europium (III) (Eu3+)-doped nanoporous silica spheres were synthesized, and the states of Eu3+ ions in the silica framework structure were investigated. The ordered nanopores were preserved with the doping at the Eu3+ molar concentration to Si up to 10mol%, and the O−Si−O and Si−OH groups in the structures were clearly rearranged with the doping, indicating the interaction of Eu3+ with the O atoms. The significant morphological changes in the spheres were observed with the doping. The photoluminescence spectral shapes due to the transitions of5D0–7F1 and5D0–7F2 were indicative of the presence of the Eu3+ in an environment of a low symmetry. It was found that the Eu3+ was located inside the silica framework to electrostatically interact with the environmental O atoms, which would prevent the aggregation among Eu3+ ions to show the efficient luminescence. Therefore, the interactions between the Eu3+ ions and silica framework structures in the spheres were successfully clarified.
Keywords: Nanoparticles; Nanoporous silica spheres; Europium; Photoluminescence; Bio-imaging
Benzalkonium chloride and sulfamethoxazole adsorption onto natural clinoptilolite: Effect of time, ionic strength, pH and temperature
by Tania Farías; Louis Charles de Ménorval; Jerzy Zajac; Aramis Rivera (pp. 465-475).
The carefully optimized host systems containing a nontoxic cationic surfactant adsorbed on the external surface of a clinoptilolite natural zeolite may be considered as effective deliverers for partially water soluble drugs such as sulfamethoxazole.Display Omitted► Development of zeolite–surfactant–drug composites for their use as drug deliverers. ► Influence of different physical factors on the adsorption of surfactant and drug onto a natural clinoptilolite. ► Characterization of the prepared composites. ► Drug release experiments.The influence of different physical factors on the adsorption of the cationic surfactant benzalkonium chloride (BC) and the model drug sulfamethoxazole by a purified natural clinoptilolite (NZ) has been studied in order to employ zeolite–surfactant–drug composites as drug deliverer. It has been demonstrated that the adsorption of BC and sulfamethoxazole onto NZ depends of the time, the temperature, the ionic strength and the pH of the aqueous medium. The optimal conditions for the preparation of the zeolite–surfactant and zeolite–surfactant–drug composite materials are established. The results of the composite characterization support the presence of BC and sulfamethoxazole, as well as the structural stability of NZ during the treatments performed. The release experiments in acid medium demonstrate that the adsorption of sulfamethoxazole is reversible. It is also confirmed that the drug release profile corresponds to a diffusion or zero-order mechanism as a function of the compression pressure.
Keywords: Zeolitic support; Clinoptilolite; Cationic surfactant; Drug adsolubilization; Drug release
Study of the bioeffects of CdTe quantum dots on Escherichia coli cells
by Qisui Wang; Tingting Fang; Peng Liu; Xinmin Min; Xi Li (pp. 476-480).
CdTe quantum dots exhibit a dose-dependent inhibitory effect Escherichia coli cells growth using microcalorimetric technique.Display Omitted► CdTe QDs have toxic effect on E. coli cells using microcalorimetric technique. ► The cytotoxicity of QDs was studied by ATR–FTIR spectra, FL polarization, and SEM. ► This effect might attribute to the damaged structure of the cell out membrane.Quantum dots (QDs) hold great potential for applications in nanomedicine, however, only a few studies investigate their toxic- and bio-effects. Using Escherichia coli ( E. coli) cells as model, we found that CdTe QDs exhibited a dose-dependent inhibitory effect on cell growth by microcalorimetric technique and optical density (OD600). The growth rate constants ( k) were determined, which showed that they were related to the concentration of QDs. The mechanism of cytotoxicity of QDs was also studied through the attenuated total reflection–fourier transform infrared (ATR–FTIR) spectra, fluorescence (FL) polarization, and scanning electron microscopy (SEM). It was clear that the cell out membrane was changed or damaged by the addition of QDs. Taken together, the results indicated that CdTe QDs have cytotoxic effects on E. coli cells, and this effects might attribute to the damaged structure of the cell out membrane, thus QDs and by-products (free radicals, reactive oxygen species (ROS), and free Cd2+) which might enter the cells.
Keywords: Quantum dots; Bioeffects; Escherichia coli; Mechanism; Cell out membrane
Effect of pH on the single-step synthesis of gold nanoparticles using PEO–PPO–PEO triblock copolymers in aqueous media
by Qinghui Shou; Chen Guo; Liangrong Yang; Lianwei Jia; Chunzhao Liu; Huizhou Liu (pp. 481-489).
Morphology and stability of gold nanoparticles highly depend on the initial pH of the Pluronic aqueous solution. Gold nanoparticles with core-shell structures were obtained under basic conditions.Display Omitted► The formation of gold nanoparticles can be controlled by varying pH. ► Gold nanoparticles with surrounding Pluronic corona are produced in alkaline media. ► Gold nanoparticles are highly stable under various physicochemical conditions.The influence of pH value on gold nanoparticle production in the presence of Pluronic stabilizers is systematically investigated. The reactions are studied as a function of pH and at fixed concentrations of the two reactants, HAuCl4 and P123 block copolymer. Results indicate that the reaction pathway during the nanoparticle formation can be controlled by varying pH. The nanoparticles synthesized at pH=11.12 have an average diameter of 9.6nm with a narrow size distribution, and the Pluronics are adsorbed on individual gold particle surfaces to form core–shell structures via hydrophobic interactions. The present work provides an economic way to improve the dispersion and stabilization of gold nanoparticles and throws further light on the understanding of gold nanoparticle production using block copolymers.
Keywords: Gold; Nanoparticles; Pluronic; Block copolymers; pH value
Separation and recycling of nanoparticles using cloud point extraction with non-ionic surfactant mixtures
by Muhammad Faizan Nazar; Syed Sakhawat Shah; Julian Eastoe; Asad Muhammad Khan; Afzal Shah (pp. 490-496).
Nanoparticles can be easily separated, recovered and recycled by cloud point extraction.Display Omitted► Inorganic nanoparticles (NPs) can be recovered from non-ionic micellar media by cloud point extraction (CPE). ► A cost-effective purification route for processing NPs requiring relatively cheap and commercially available surfactants. ► Mixing two non-ionic surfactants allows for temperature tunability and optimization of the NP–CPE recovery process. ► The NP–CPE process can be repeated demonstrating reproducibility and recyclability.A viable cost-effective approach employing mixtures of non-ionic surfactants Triton X-114/Triton X-100 (TX-114/TX-100), and subsequent cloud point extraction (CPE), has been utilized to concentrate and recycle inorganic nanoparticles (NPs) in aqueous media. Gold Au- and palladium Pd-NPs have been pre-synthesized in aqueous phases and stabilized by sodium 2-mercaptoethanesulfonate (MES) ligands, then dispersed in aqueous non-ionic surfactant mixtures. Heating the NP-micellar systems induced cloud point phase separations, resulting in concentration of the NPs in lower phases after the transition. For the Au-NPs UV/vis absorption has been used to quantify the recovery and recycle efficiency after five repeated CPE cycles. Transmission electron microscopy (TEM) was used to investigate NP size, shape, and stability. The results showed that NPs are preserved after the recovery processes, but highlight a potential limitation, in that further particle growth can occur in the condensed phases.
Keywords: Non-ionic surfactants; Nanoparticles; Liquid–liquid phase separation; Cloud point extraction
Microwave synthesis of BiPO4 nanostructures and their morphology-dependent photocatalytic performances
by Guangfang Li; Yao Ding; Yafang Zhang; Zhong Lu; Hongzhe Sun; Rong Chen (pp. 497-503).
BiPO4 nanostructures with different morphologies synthesized by a facile microwave irradiation method exhibited different optical properties and photocatalytic activities.Display Omitted► BiPO4 nanomaterials were prepared by a facile microwave irradiation method. ► Various BiPO4 nanostructures were fabricated in different solvents. ► Different BiPO4 nanostructures exhibited different photocatalytic activities. ► A possible formation mechanism of BiPO4 was discussed.A facile and rapid microwave irradiation method was explored for the synthesis of bismuth phosphate (BiPO4) nanostructures with various morphologies and phases in different solvents. The BiPO4 products were characterized by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), UV–vis diffuse reflection spectroscopy (DRS). The effect of the solvents on the formation of the BiPO4 nanostructures was discussed on the basis of experimental results. The different BiPO4 nanostructures exhibited different optical properties, BET surface areas and photocatalytic activities on the degradation of methyl orange (MO) under UV and visible light irradiation. The experimental results suggested that the photocatalytic activity was closely relative with the crystalline phase and band gap of BiPO4. Hexagonal BiPO4 nanoparticles with narrow band gap showed the highest photocatalytic performance.
Keywords: BiPO; 4; Nanostructures; Microwave; Photocatalytic; Morphology-dependent
Length-controlled synthesis of oriented single-crystal rutile TiO2 nanowire arrays
by Yong Liu; Hai Wang; Haibo Li; Wenxia Zhao; Chaolun Liang; Hong Huang; Youjun Deng; Hui Shen (pp. 504-510).
Figures show the optical image, SEM and HRTEM of oriented single-crystal rutile TiO2 nanowire arrays. It is seen that the free-standing nanowire film was continuous and large area (up to 4cm in diameter). The longest length can reach up to 80μm. It can also be concluded that anisotropic crystal growth of the nanowire arrays were along  direction throughout their length.Display Omitted► Large area, length-controlled single-crystal TiO2 nanowire arrays were synthesized. ► The length of single-crystal nanowire array films can be tuned from 10μm to 80μm. ► The single-crystal TiO2 nanowire arrays show excellent photocatalytic activities.A free-standing, large area, oriented single-crystal rutile TiO2 nanowire arrays with a controlled length in the range of 10–80μm are prepared via a facile one-step synthesis. The growth process is studied systematically in an appropriate amount of H2O2 and HCl solution under hydrothermal conditions. The length of the nanowires can be easily tuned by varying the experimental parameters, including reaction temperature and reaction time. High-resolution transmission electron microscopy demonstrated that the nanowires have single-crystal structure. Furthermore, the photoluminescence characteristics and photocatalytic properties of oriented single-crystal rutile TiO2 nanowires was discussed in this paper, respectively. It is found that the increased reaction temperature is helpful to photocatalytic reactivity and photoluminescence properties.
Keywords: Single-crystal; TiO; 2; nanowire arrays; Photocatalysis; Photoluminescence
Hierarchically structured meso-macroporous aluminosilicates with high tetrahedral aluminium content in acid catalysed esterification of fatty acids
by Arnaud Lemaire; Quan-Yi Wang; Yingxu Wei; Zhongmin Liu; Bao-Lian Su (pp. 511-520).
Hierarchically structured spongy or spherical voids assembled meso-macroporous aluminosilicates with high tetrahedral aluminium content have been designed on the basis of the aqueous polymerisation of new stabilized alkoxy-bridged single molecular precursors. After ion exchange, obtained materials show their higher catalytic activity in the esterification reaction of high free fatty acid oils.Display Omitted► Hierarchically meso-macroporous aluminosilicates. ► High tetrahedral aluminium content. ► Alkoxy-bridged single molecular precursors. ► Higher catalytic activity. ► Esterification reaction of high free fatty acid oils.A simple synthesis pathway has been developed for the design of hierarchically structured spongy or spherical voids assembled meso-macroporous aluminosilicates with high tetrahedral aluminium content on the basis of the aqueous polymerisation of new stabilized alkoxy-bridged single molecular precursors. The intimate mixing of an aluminosilicate ester ( sec-BuO)2–Al–O–Si(OEt)3 and a silica co-reactant (tetramethoxysilane, TMOS) with variable ratios and the use of alkaline solutions (pH 13.0 and 13.5) improve significantly the heterocondensation rates between the highly reactive aluminium alkoxide part of the single precursor and added silica co-reactant, leading to aluminosilicate materials with high intra-framework aluminium content and low Si/Al ratios. The spherically-shaped meso-macroporosity was spontaneously generated by the release of high amount of liquid by-products (water/alcohol molecules) produced during the rapid hydrolysis and condensation processes of this double alkoxide and the TMOS co-reactant. It has been observed that both pH value and Al–Si/TMOS molar ratio can strongly affect the macroporous structure formation. Increasing pH value, even slightly from 13 to 13.5, can significantly favour the incorporation of Al atoms in tetrahedral position of the framework. After the total ionic exchange of Na+ compensating cations, catalytic tests of obtained materials were realised in the esterification reaction of high free fatty acid (FFA) oils, showing their higher catalytic activity compared to commercial Bentonite clay, and their potential applications as catalyst supports in acid catalysed reactions.
Keywords: Aluminosilicate; Hierarchical multiporous; Porous self-generation phenomenon; Low Si/Al ratios; Ionic exchange; Esterification reaction; Catalytic test
Large-scale synthesis of ZnO balls made of fluffy thin nanosheets by simple solution process: Structural, optical and photocatalytic properties
by Ahmad Umar; M.S. Chauhan; S. Chauhan; R. Kumar; G. Kumar; S.A. Al-Sayari; S.W. Hwang; A. Al-Hajry (pp. 521-528).
This paper reports a large-scale synthesis of ZnO balls made of fluffy thin ZnO nanosheets by simple solution process at low-temperature of 65±2°C. The synthesized ZnO structures were characterized in detail in terms of their morphological, structural, optical and photocatalytic properties. The as-synthesized ZnO balls were utilized as an efficient photocatalysts for the photocatalytic degradation of methylene blue (MB) dye which exhibits almost complete degradation of MB within 70min under UV-light irradiation. The photocatalytic performances of as-synthesized ZnO balls are found to be better than the commercially available TiO2–UV-100.Display Omitted► Simply synthesized ZnO balls made of fluffy thin nanosheets were utilized for the photocatalytic degradation of methylene blue (MB) dye. ► Almost complete degradation of MB was observed within 70min under UV-light irradiation. ► The synthesized ZnO exhibits superior photocatalytic performance as compared to commercially available TiO2-UV-100 photocatalyst.This paper reports a large-scale synthesis of ZnO balls made of fluffy thin ZnO nanosheets by simple solution process at low-temperature of 65±2°C. The synthesized ZnO structures were characterized in detail in terms of their morphological, structural, optical and photocatalytic properties. The detailed morphological characterizations, done by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), confirmed that the synthesized products are ZnO balls which are made by accumulation of hundreds of thin ZnO nanosheets. Interestingly, it is seen that the nanosheets are arranged in such a special fashion that they made ball-like morphologies. Detailed structural examinations revealed that of as-synthesized ZnO products are well-crystalline and possessing wurtzite hexagonal phase. The optical property, measured by UV–Visible spectroscopy, substantiated good optical properties for as-synthesized ZnO balls. The as-synthesized ZnO balls were utilized as an efficient photocatalysts for the photocatalytic degradation of methylene blue (MB) dye. Almost complete degradation of MB was observed in presence of ZnO balls composed of nanosheets within 70min under UV-light irradiation. By comparing the photocatalytic performance with commercially available TiO2–UV-100, it was observed that the synthesized ZnO balls exhibited superior photocatalytic performance as compared to TiO2–UV-100 photocatalyst.
Keywords: ZnO balls; Fluffy thin nanosheets; Structural, optical and photocatalytic properties
Spectroscopic probing of location and dynamics of an environment-sensitive intramolecular charge transfer probe within liposome membranes
by Bijan Kumar Paul; Nikhil Guchhait (pp. 529-539).
Interaction of a simple ICT probe with liposomes has been studied. The extrinsic probe is shown to penetrate deep into the hydrophobic tail part of the bilayer. The observation of REES underscores an important but yet sporadically discussed issue in membrane biochemistry, that of whether or not water penetration occurs in the inner hydrophobic region of the lipid bilayers.Display Omitted► A prospective molecular reporter for microheterogeneous environments of lipids. ► Modulation of environment-sensitive ICT photophysics and dynamics within lipids. ► Probable location of the probe in hydrocarbon interior of the lipids. ► Slower rate of rotational-relaxation of the probe in both the lipids. ► Red-edge excitation shift study reveals slower solvent-relaxation within the lipids.The present work demonstrates the interaction of an intramolecular charge transfer (ICT) probe 5-(4-dimethylamino-phenyl)-penta-2,4-dienoic acid methyl ester (DPDAME) with liposome membranes of dimyristoyl-l-α-phosphatidylcholine (DMPC) and dimyristoyl-l-α-phosphatidylglycerol (DMPG) studied by steady-state absorption, emission and time-resolved emission techniques. A huge hypsochromic shift together with remarkable enhancement of fluorescence quantum yield of the polarity sensitive ICT emission of DPDAME upon interaction with the lipids has been rationalized in terms of incorporation of the probe into hydrophobic interior of the lipids. Compelling evidences for penetration of the probe into the hydrocarbon interior of the lipids have been deduced from intertwining different experimental results e.g., micropolarity in the immediate vicinity of the probe in lipid environments, steady-state anisotropy, red-edge excitation shift (REES), fluorescence quenching experiments and time-resolved measurements. The rotational relaxation dynamics study of the membrane-bound probe unveils the impartation of high degree of motional rigidity. Wavelength-selective emission behaviour paves way for monitoring of solvent-relaxation in the membranes. Overall, the ICT probe DPDAME displays its commendable sensitivity in deciphering the microheterogeneous environments of liposomal membranes of DMPC and DMPG and promises a new membrane-polarity sensitizing probe.
Keywords: Intramolecular charge transfer; Liposome; Emission spectroscopy; Rotational relaxation dynamics; REES; Solvent-relaxation
Effect of nanoparticle aggregation at low concentrations of TiO2 on the hydrophilicity, morphology, and fouling resistance of PES–TiO2 membranes
by Arcadio Sotto; Arman Boromand; Ruixin Zhang; Patricia Luis; Jesús M. Arsuaga; Jeonghwan Kim; Bart Van der Bruggen (pp. 540-550).
Display Omitted► The observed effects as result of EtOH addition and increase of TiO2 concentration were similar. ► Clusters size is affected by reduction of the dielectric constant of solution and by the depletion of the suspension field. ► Strong correlations are observed between the hydrophilicity and the permeability of manufactured membranes. ► EtOH addition is a suitable procedure for the membrane performance improvement.This paper reports the fabrication and characterization of polyethersulfone–TiO2 (PES–TiO2) nanoparticle composite membranes made from synthesis casting solution consisting of various compositions of polymer solvents (DMF and EtOH) and TiO2 additive. The results also revealed that the membrane permeation and rejection rates, pore size, and porosity were dependent on the TiO2 and EtOH concentrations. Nanoparticles were characterized by zeta potential measurements, TEM observations, and measurement of particle size distributions. Zeta potential measurements in aqueous solution demonstrated that the TiO2 particles size is dominated by electric double layer interactions. Addition of EtOH promotes the increase of the clusters size as consequence of a double effect: reduction of the dielectric constant of solution and the depletion of the suspension field determined by the action of the polymer chains. The observed effects as result of EtOH addition and increase of TiO2 concentration were similar: both procedures provoked an increase of macrovoid dimensions. The modified membranes by TiO2 incorporation showed a structural change from a sponge-like to a finger-like structure. Strong correlations were observed between the hydrophilicity and the permeability of manufactured membranes. The formation mechanism of TiO2-blended membranes was altered, in a similar way, as result of EtOH at different contents of nanoparticles. Fouling resistance of modified membranes was significantly improved showing that EtOH addition is a suitable procedure for the membrane performance improvement. The rejection potential of membranes is hardly affected by the nanoparticles and EtOH incorporation into the polymeric solution.
Keywords: Nanoparticle aggregation; Membrane fouling; Double layer interaction; PES–TiO; 2
Iron–dextran complex: Geometrical structure and magneto-optical features
by Bartłomiej Graczykowski; Andrzej Dobek (pp. 551-556).
Cross section of the iron–dextran complex, Sigma–Aldrich, as obtained from magneto-optical measurements.Display Omitted► The Cotton–Mouton effect in iron–dextran complex solution is studied. ► A modified method of measurement allows the estimation of magnetic dipole moment. ► Anisotropy of the linear magneto-optical polarizability is also calculated. ► Molecular mass of the complex is estimated on the basis of light scattering measurements. ► Mean linear optical polarizability and its anisotropy are obtained.Molecular mass of the iron–dextran complex (M w=1133kDa), diameter of its particles (∼8.3nm) and the content of iron ions in the complex core ( NFe=6360) were determined by static light scattering, measurements of refractive index increment and the Cotton–Mouton effect in solution. The known number of iron ions permitted the calculation of the permanent magnetic dipole moment value to be μFe=3.17×10−18ergOe−1 and the determination of anisotropy of linear magneto-optical polarizabilities components asΔχ=9.2×10-21cm3. Knowing both values and the value of the mean linear optical polarizability α=7.3×10−20cm3, it was possible to show that the total measured CM effect was due to the reorientation of the permanent and the induced magnetic dipole moments of the complex. Analysis of the measured magneto-optical birefringence indicated very small optical anisotropy of linear optical polarizability components,κ α, which suggested a homogeneous structure of particles of spherical symmetry.
Keywords: Iron–dextran complex; Cotton–Mouton effect; Light refractive index; Light scattering; Optical polarizability; Magnetic dipole moment; Magneto-optical polarizability
Rheological behaviour and spectroscopic investigations of cerium-modified AlO(OH) colloidal suspensions
by Rudina Bleta; Olivier Jaubert; Marie Gressier; Marie-Joëlle Menu (pp. 557-565).
The adsorption of [Ce(NO3)4(H2O) x]− complex ions onto the boehmite surface induces a strong thixotropic behaviour.Display Omitted► Cerium salts have a strong ability to complex with nitrate ions stabilising boehmite particles. ► Such complexation induces a strong thixotropic behaviour. ► The degree of thixotropy is different according to the type of Ce-salt used.The rheological behaviour of aqueous suspensions of boehmite (AlO(OH)) modified with different Ce-salts (Ce(NO3)3, CeCl3, Ce(CH3COO)3 and Ce2(SO4)3) was investigated at a fixed Ce/Al molar ratio (0.05). Freshly prepared boehmite suspensions were near-Newtonian and time-independent. A shear-sensitive thixotropic network developed when Ce-salts with monovalent anions were introduced in the nanoparticle sols. The extent of particle aggregation dramatically increased with ageing for Ce(NO3)3 and CeCl3 whereas an equilibrium value was reached with Ce(CH3COO)3. The addition of Ce2(SO4)3 with divalent anions involved no thixotropy but rather a sudden phase separation.The combined data set of IRTF and DRIFT spectra indicated that freeNO3- anions of peptized boehmite adsorb on the nanoparticle surface by H-bond. The introduction of Ce-salts in the boehmite sol led to the coordination between Ce3+ ions andNO3- anions adsorbed on boehmite i.e. to [Ce(NO3)4(H2O) x]− complex. Such coordination led to a thixotropic behaviour which was lower with Ce(NO3)3 compared to CeCl3 and Ce(CH3COO)3. In contrast, Ce2(SO4)3 formed insoluble complexes with dissolved aluminium species. The formation of H-bonded surface nitrate complexes was found to play a decisive role on the particle–particle interactions and consequently on the rheological behaviour of the sols.
Keywords: Colloid; Boehmite; Thixotropy; Cerium; Vibrational spectroscopies
Addition of silica nanoparticles to tailor the mechanical properties of nanofibrillated cellulose thin films
by Mohamed Eita; Hans Arwin; Hjalmar Granberg; Lars Wågberg (pp. 566-572).
Addition of SiO2 nanoparticles into a thin film of PVAm-NFC results in doubling the Young’s modulus of the film.Display Omitted► Fabrication of functional thin films based on renewable resources (NFC). ► The thin films were characterized by QCM-D, ellipsometry and AFM. ► Young’s modulus of NFC/PVAm film was doubled upon incorporation of SiO2. ► These thin films maintain a relatively high transmission of visible light.Over the last decade, the use of nanocellulose in advanced technological applications has been promoted both due the excellent properties of this material in combination with its renewability. In this study, multilayered thin films composed of nanofibrillated cellulose (NFC), polyvinyl amine (PVAm) and silica nanoparticles were fabricated on polydimethylsiloxane (PDMS) using a layer-by-layer adsorption technique. The multilayer build-up was followed in situ by quartz crystal microbalance with dissipation, which indicated that the PVAm–SiO2–PVAm–NFC system adsorbs twice as much wet mass material compared to the PVAm–NFC system for the same number of bilayers. This is accompanied with a higher viscoelasticity for the PVAm–SiO2–PVAm–NFC system. Ellipsometry indicated a dry-state thickness of 2.2 and 3.4nm per bilayer for the PVAm–NFC system and the PVAm–SiO2–PVAm–NFC system, respectively. Atomic force microscopy height images indicate that in both systems, a porous network structure is achieved. Young’s modulus of these thin films was determined by the Strain-Induced Elastic Buckling Instability for Mechanical Measurements (SIEBIMM) technique. The Young’s modulus of the PVAm/NFC films was doubled, from 1 to 2GPa, upon incorporation of silica nanoparticles in the films. The introduction of the silica nanoparticles lowered the refractive index of the films, most probably due to an increased porosity of the films.
Keywords: Buckling; Cellulose; Light transmission; Porous; Strain; Thin film
Aggregation of nanoparticles in a block copolymer bilayer
by Houyang Chen; Eli Ruckenstein (pp. 573-578).
The dissipative particle dynamics (DPD) simulation is employed to examine the aggregation of nanoparticles in a block copolymer bilayer.Display Omitted► Aggregation of particles in bilayers can be controlled by grafting with polymers. ► Small aggregates are located at the interfaces of the membrane. ► Large aggregates are located in the hydrophilic domains. ► Size of aggregates decreases with increasing length of the grafting polymers.In this paper, we examine, by dissipative particle dynamics (DPD) simulation, the interactions between nanoparticles and block copolymer bilayer membranes. The bilayer has a hydrophobic core and hydrophilic head groups on both sides of the core. Nanoparticles without or with a grafted homopolymer are considered. For the conditions investigated, the single nanoparticles and small aggregates are located at the interfaces of the membrane, namely the interfaces between the hydrophilic domains of the membrane and the solvent as well as at the interface between the hydrophobic and hydrophilic domains of the membrane. The large aggregates are located in the hydrophilic domains. By increasing the length of the homopolymer grafted on the nanoparticles, the size of the aggregates in the membrane decreases. At relatively short DPD step times, the particles aggregate in the solvent. As the time increases, the single particles and aggregates penetrate into the membrane.
Keywords: Dissipative particle dynamics; Block copolymer bilayer; Particle aggregate
Equilibrium clusters in concentrated lysozyme protein solutions
by P. Kowalczyk; A. Ciach; P.A. Gauden; A.P. Terzyk (pp. 579-584).
Equilibrium clusters of lysozyme at 293K and pH 7.8 and volume fraction of 0.12, 0.033, and 0.12.Display Omitted► The studied lysozyme solutions are dominated by monomers only forϕ⩽0.012. ► For the strong dilution 70% of proteins are in a form of monomers. ► For ϕ=0.033 only 20% of proteins do not belong to a cluster. ► For ϕ=0.12 almost no individual particles exits, and branched, irregular clusters of large extent appear.We have studied the structure of salt-free lysozyme at 293K and pH 7.8 using molecular simulations and experimental SAXS effective potentials between proteins at three volume fractions, ϕ=0.012, 0.033, and 0.12. We found that the structure of lysozyme near physiological conditions strongly depends on the volume fraction of proteins. The studied lysozyme solutions are dominated by monomers only forϕ⩽0.012; for the strong dilution 70% of proteins are in a form of monomers. For ϕ=0.033 only 20% of proteins do not belong to a cluster. The clusters are mainly elongated. For ϕ=0.12 almost no individual particles exits, and branched, irregular clusters of large extent appear. Our simulation study provides new insight into the formation of equilibrium clusters in charged protein solutions near physiological conditions.
Keywords: Equilibrium clusters; Salt-free lysozyme solutions; Short-range attraction and weak long-range repulsion effective potential; Scattering experiments
Positive cooperative mechanistic binding of proteins at low concentrations: A comparison of poly (sodium N-undecanoyl sulfate) and sodium dodecyl sulfate
by Susmita Das; Monica R. Sylvain; Vivian E. Fernand; Jack N. Losso; Bilal El-Zahab; Isiah M. Warner (pp. 585-594).
Surfactant binding with BSA is positive cooperative for pSUS while negative cooperative for SDS.Display Omitted► We present a study of the interactions of SDS compared with a novel molecular micelle pSUS with four acidic proteins. ► pSUS binding follows a positive co-operative mechanistic binding to all the four proteins in the low concentration region. ► SDS binding is primarily negative cooperative. ► Protein surfactant interactions interactions are primarily hydrophobic and hence greater for pSUS. ► Protein separation in PAGE is achieved at concentrations 25times less for pSUS, as compared to SDS.The interactions of the negatively charged achiral molecular micelle, poly (sodium N-undecanoyl sulfate) (poly-SUS), with four different proteins using intrinsic and extrinsic fluorescence spectroscopic probes, are studied. A comparison of poly-SUS with the conventional surfactant, sodium dodecyl sulfate (SDS), and the monomeric species, SUS, is also reported. In this work, we observed that poly-SUS preferentially binds to acidic proteins, exhibiting positive cooperativity at concentrations less than 1mM for all proteins studied. Moreover, it appears that the hydrophobic microdomain formed through polymerization of the terminal vinyl group of the monomer, SUS, is largely responsible for the superior binding capacity of poly-SUS. From these results, we conclude that the interactions of poly-SUS with the acidic proteins are predominantly hydrophobic and postulate that poly-SUS would produce superior interactions relative to SDS at low concentrations in polyacrylamide gel electrophoresis (PAGE). As predicted, use of poly-SUS allowed separation of the His-tagged tumor suppressor protein, p53, at sample buffer concentrations as low as 0.08% w/v (2.9mM), which is 24 times lower than required for SDS in the standard reducing PAGE protocol. This work highlights the use of poly-SUS as an effective surfactant in 1D biochemical analysis.
Keywords: Intrinsic fluorescence; Poly-SUS; SDS; Molecular micelle; Protein–surfactant interaction; Cooperative binding; SDS–PAGE
Effects of electrolyte concentration and counterion valence on the microstructural flow regimes in dilute cetyltrimethylammonium tosylate micellar solutions
by N. Tepale; E.R. Macías; F. Bautista; J.E. Puig; O. Manero; M. Gradzielski; J.I. Escalante (pp. 595-600).
Generalized flow diagram that allows identifying the mechanisms that control the shear thickening transition.Display Omitted► Behavior of dilute micellar solutions depends strongly on ionic strength. ► A critical deformation is required in order to develop shear thickening. ► Macroscopic behavior is controlled by electrostatic screening and chemical equilibrium. ► Rheological behavior of such systems can be summarized in a generalized flow diagram.The shear thickening behavior and the transition to shear thinning are examined in dilute cetyltrimethylammonium tosylate (CTAT) micellar solutions as a function of surfactant concentration and ionic strength using electrolytes with different counterion valence. Newtonian behavior at low shear rates, followed by shear thickening and shear thinning at higher shear rates, are observed at low and intermediate surfactant and electrolyte concentrations. Shear thickening diminishes with increasing surfactant concentration and ionic strength. At higher surfactant or electrolyte concentration, only a Newtonian region followed by shear thinning is detected. A generalized flow diagram indicates two controlling regimes: one in which electrostatic screening dominates and induces micellar growth, and another, at higher electrolyte and surfactant concentrations, where chemical equilibrium among electrolyte and surfactant counterions controls the rheological behavior by modifying micellar breaking and reforming. Analysis of the shear thickening behavior reveals that not only a critical shear rate is required for shear thickening, but also a critical deformation, which appears to be unique for all systems examined, within experimental error. Moreover, a superposition of the critical shear rate for shear thickening with surfactant and electrolyte concentration is reported.
Keywords: Generalized dynamic diagram; Ionic strength; Micellar solutions; Shear-induced structures; Shear thickening
Removal of methyl orange from aqueous solution using bentonite-supported nanoscale zero-valent iron
by Zheng-xian Chen; Xiao-ying Jin; Zuliang Chen; Mallavarapu Megharaj; Ravendra Naidu (pp. 601-607).
UV–vis spectral (a) MO(20mg/L) before reaction; (b) MO(20mg/L) after reaction.Display Omitted► Synthesis of bentonite-supported zero-valent iron nanoparticles (B-nZVI). ► Degradation of methyl orange from aqueous solution. ► Characterization of B-nZVI. ► The mechanism of degradation of methyl orange by B-nZVI.Zero-valent iron (ZVI) nanoparticles tend to agglomerate, resulting in a significant loss in reactivity. To address this issue, synthesized bentonite-supported nanoscale zero-valent iron (B-nZVI) was used to remove azo dye methyl orange (MO) in aqueous solution. Batch experiments show that various parameters, such as pH, initial concentration of MO, dosage, and temperature, were affected by the removal of MO. Scanning electron microscopy (SEM) confirmed that B-nZVI increased their reactivity and a decrease occurred in the aggregation of iron nanoparticles for the presence of bentonite (B). Using B-nZVI, 79.46% of MO was removed, whereas only 40.03% when using nZVI after reacting for 10min with an initial MO concentration of 100mg/L (pH=6.5). Furthermore, after B-nZVI reacted to MO, XRD indicated that iron oxides were formed. FTIR showed that no new bands appeared, and UV–vis demonstrated that the absorption peak of MO was degraded. Kinetics studies showed that the degradation of MO fitted well to the pseudo first-order model. A degradation mechanism is proposed, including the following: oxidation of iron, adsorption of MO to B-nZVI, formation of Fe(II)–dye complex, and cleavage of azo bond. Finally, the removal rate of MO from actual wastewater was 99.75% when utilizing B-nZVI.
Keywords: Nanoscale; Zero-valent iron; Bentonite; Methyl orange; Degradation
Adsorption–desorption mechanism of phosphate by immobilized nano-sized magnetite layer: Interface and bulk interactions
by Adva Zach-Maor; Raphael Semiat; Hilla Shemer (pp. 608-614).
Interface and bulk adsorption and desorption mechanisms of phosphate by a homogenous porous layer of nano-sized magnetite particles immobilized onto granular activated carbon is presented.Display Omitted► Phosphate was initially bonded onto the Fe3O4 surface via bidentate complexation then diffused into the interior layer. ► Phosphate desorption, by alkaline eluent, was predominantly a surface reaction. ► Five successive fix-bed adsorption/regeneration cycles were successfully applied. ► Innovative correlation of adsorption–desorption performance with diffusion mechanism is presented.Phosphate adsorption mechanism by a homogenous porous layer of nano-sized magnetite particles immobilized onto granular activated carbon (nFe-GAC) was studied for both interface and bulk structures. X-ray Photoelectron Spectroscopy (XPS) analysis revealed phosphate bonding to the nFe-GAC predominantly through bidentate surface complexes. It was established that phosphate was adsorbed to the magnetite surface mainly via ligand exchange mechanism. Initially, phosphate was adsorbed by the active sites on the magnetite surface, after which it diffused into the interior of the nano-magnetite layer, as indicated by intraparticle diffusion model. This diffusion process continues regardless of interface interactions, revealing some of the outer magnetite binding sites for further phosphate uptake. Desorption, using NaOH solution, was found to be predominantly a surface reaction, at which hydroxyl ions replace the adsorbed phosphate ions only at the surface outer biding sites. Five successive fix-bed adsorption/regeneration cycles were successfully applied, without significant reduction in the nFe-GAC adsorption capacity and at high regeneration efficiency.
Keywords: Iron oxide; Fixed-bed; XPS; Composite adsorbent; Saturation
Aniline as a dispersing and stabilizing agent for reduced graphene oxide and its subsequent decoration with Ag nanoparticles for enzymeless hydrogen peroxide detection
by Sen Liu; Lei Wang; Jingqi Tian; Yonglan Luo; Xinxin Zhang; Xuping Sun (pp. 615-619).
An aqueous dispersion of reduced graphene oxide has been successfully prepared via chemical reduction of graphene oxide by hydrazine hydrate in the presence of aniline for the first time. We further demonstrated the subsequent decoration of rGO with Ag nanoparticles by in situ chemical reduction of silver salts, and the resultant AgNP/rGO nanocomposites exhibit good catalytic activity toward the reduction of hydrogen peroxide.Display Omitted► Stable dispersions of rGO were prepared using aniline as stabilizing agent. ► rGO was decorated by Ag nanoparticle via in situ reduction of Ag salt by aniline. ► The resulting AgNP/rGO exhibits notable catalytic activity toward reduction of H2O2.An aqueous dispersion of reduced graphene oxide (rGO) has been successfully prepared via chemical reduction of graphene oxide (GO) by hydrazine hydrate in the presence of aniline for the first time. The noncovalent functionalization of rGO by aniline leads to a rGO dispersion that can be very stable for several months without the observation of any floating or precipitated particles. Several analytical techniques including Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) have been used to characterize the resulting rGO. Taking advantages of the fact reducing ability of aniline toward AgNO3, we further demonstrated the subsequent decoration of rGO with Ag nanoparticles (AgNPs) by in situ chemical reduction of silver salts. It was found that such AgNP/rGO nanocomposites exhibit good catalytic activity toward the reduction of hydrogen peroxide (H2O2), leading to an enzymeless sensor with a fast amperometric response time of less than 2s. The linear detection range is estimated to be from 100μM to 80mM ( r=0 .9991), and the detection limit is estimated to be 7.1μM at a signal-to-noise ratio of 3.
Keywords: Aniline; Graphene oxide; Ag nanoparticle; Hydrogen peroxide detection
Kinetic properties of pancreatic and intestinal sPLA2 from chicken and mammals using the monomolecular film technique
by Aida Karray; Zied Zarai; Youssef Gargouri; Robert Verger; Sofiane Bezzine (pp. 620-625).
The ability of Chicken PLA2 group IIA to hydrolyse pure 1,2 DDPC contrary to the human one.Display Omitted► The interfacial kinetic and binding data for the pancreatic and intestinal sPLA2 from bird and mammals. ► PC, in contrast to PE and PG, were resistant to the hydrolysis by hPLA2-IIA. ► ChPLA2-IIA was found to be able to hydrolyse all phospholipids. ► The binding of sPLA2 at the lipid–water interface is governed by the electrostatic and hydrophobic forces.The interfacial kinetic and binding data for the pancreatic and intestinal sPLA2 from bird and mammals show that these enzymes have dramatically different ability to bind and hydrolyse phospholipids. The main conclusions from our experimental data indicate that phosphatidylcholine monolayers (PC), in contrast to phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), were resistant to the hydrolysis by human intestinal sPLA2. Conversely, chicken intestinal sPLA2 was found to be able to hydrolyse all the phospholipids tested, including PC. The experiments show also that the interfacial penetrating ability of chicken sPLA2 (from intestine and pancreas) was higher than their mammalian’s orthologs. This observation is confirmed by the activity of pancreatic chicken PLA2 measured on PC film showing that the interfacial pressure window that permits sPLA2 activity was very large, between 5 and 20dynescm−1, compared with the porcine pancreatic sPLA2-IB which was inactive at pressure above 15dynescm−1.In trying to establish a structure–function relationship, we examined the surface electrostatic potentials of the various sPLA2 from chicken and mammals. We reported in this study that the binding, orientation and persistence of sPLA2 at the lipid–water interface is probably governed by the electrostatic and hydrophobic forces operative at this surface. These variations argue strongly that these enzymes are not isoforms and that they are expected to have functions other than the release of lipid mediators for the biosynthesis of the eicosanoids.
Keywords: Abbreviations; sPLA2; secreted phospholipase A2; ChPLA2-IB; chicken pancreatic sPLA2; ChPLA2-IIA; chicken intestinal sPLA2; pPLA2-IB; porcine pancreatic sPLA2; hPLA2-IIA; human intestinal sPLA2; β-CD; β-cyclodextrin; 1,2 DDPC; l-2 didodecanoyl-sn-glycero-3-phosphatidylcholin; 1,2 POPG; 1 palmitoyl-2-oleoyl-sn-3-phosphatidyl-glycerol; 1,2 DDPE; 1,2 didodecanoyl-sn-3-phosphatidy-ethanolaminePhospholipase A2; Lipid monolayer; Intestinal sPLA2-IIA; Pancreatic sPLA2-IB; Penetration capacity; Binding surface
Adsorption of BTX (benzene, toluene, o-xylene, and p-xylene) from aqueous solutions by modified periodic mesoporous organosilica
by Cícero P. Moura; Carla B. Vidal; Allen L. Barros; Luelc S. Costa; Luiz C.G. Vasconcellos; Francisco S. Dias; Ronaldo F. Nascimento (pp. 626-634).
TG and DTG curves of PMO with deconvolution and enlargement (left), region between 550°C and 850°C (right).Display Omitted► A PMO was synthesized by combining a silica source and a surfactant. ► XRD, BET, TG, NMR, as well as GC–MS analyses were performed. ► The PMO had hexagonally ordered mesopores, resistant to heating up to 340°C. ► The adsorption of BTX onto the PMO in aqueous medium was evaluated. ► Both kinetic and isotherm models were tested.The capacity of a periodic mesoporous organosilica (PMO) to adsorb the aromatic compounds benzene, toluene, o-, and p-xylenes (BTX), which are usually present in produced waters, was investigated under both column and batch processes. The PMO was synthesized by condensation of 1,4 bis(triethoxisilyl)benzene (BTEB) under acidic conditions by using structure-directing agent (SDA) Pluronic P123 in the presence of KCl. Thermogravimetric analysis showed that the presence of the surfactant decreases the thermal stability of the PMO. The small-angle X-ray diffraction pattern, as well as the nitrogen adsorption/desorption isotherm measurements, revealed that the synthesized material has a crystalline structure, with hexagonally-ordered cylindrical mesopores. The adsorption kinetics study indicated an adsorption equilibrium time of 50min and also showed that the data best fitted the pseudo-first order kinetic model. The intraparticle diffusion model was also tested and pointed to the occurrence of such process in all cases. Both Langmuir and Temkin models best represented the adsorption isotherms of toluene; Langmuir and Redlich–Peterson models best represented the data obtained for the other compounds. Adsorption capacity decreases in the order benzene>o-xylene>p-xylene>toluene. Satisfactory results were observed in the application of the synthesized PMO for the removal of BTX from aqueous solution.
Keywords: Periodic mesoporous organosilica; Adsorption; BTX
Gelation of ionic liquid with exfoliated montmorillonite nanoplatelets and its application for quasi-solid-state dye-sensitized solar cells
by Chia-Hsin Lee; Ken-Yen Liu; Shun-Hsiang Chang; Keng-Jen Lin; Jiang-Jen Lin; Kuo-Chuan Ho; King-Fu Lin (pp. 635-639).
The exfoliated montmorillonite nanoplatelets incorporating in the PMII-based electrolyte system for DSSC not only perform like a gelator but also enhance the photovoltaic performance of DSSC.Display Omitted► The exfoliated montmorillonite (exMMT) is a two-dimensional electrolyte with negative charge. ► The exMMT was able to gel the PMII-based electrolyte system for DSSC. ► The PCE of DSSC was increased from 6.58% to 7.77% at full sun after gelled by exMMT.The exfoliated montmorillonite (exMMT) nanoplatelets that carry negative charges are capable of adsorbing 1-methyl-3-propyl-imidazolium cations to form a gel-type ionic liquid-based electrolyte system for dye-sensitized solar cell (DSSC). Interestingly, it also increases the power conversion efficiency of DSSC from 6.58% to 7.77% at full sun. The increased efficiency is attributed to the decreased resistance of gel electrolyte system and enhanced reduction reaction rate at the counter electrode, both of which are related to the two-dimensional electrolyte nature of exMMTs that repel theI-/I3- redox couples toward their major conduction pathway.
Keywords: Dye-sensitized solar cell; Ionic liquid; Gel type; Nanoclay; Electrolytes
Effect of submicron particles on electrowetting on dielectrics (EWOD) of sessile droplets
by Debapriya Chakraborty; Gogineni Sai Sudha; Suman Chakraborty; Sunando DasGupta (pp. 640-645).
Electrowetting on dielectric with droplet containing submicron particles.Display Omitted► Effects of submicron-sized particles on EWOD of sessile droplets. ► Theoretical description using an energy minimization approach. ► Experimental investigation of the system. ► Beads act as suspended dielectrics mimicking a system of two capacitors in series. ► Reduction in contact angle saturation.The present study elucidates the effects of included submicron-sized particles on the wetting behavior of sessile droplets under the influence of applied electric field in an electro-wetting-on-dielectric (EWOD) configuration. A thermodynamic description using an energy minimization approach is used to analyze the experimental results related to the effects of the included particles on the EWOD phenomenon, considering the effects of line tension as well. The effects of particle size and concentration on interfacial areas are included in the model to analyze the wetting characteristics. Experiments are also conducted with submicron-sizes latex beads, in an effort to elucidate the related phenomena. It is further postulated that these beads act as suspended dielectrics in the droplet, thereby mimicking a system of two capacitors in series. An effective electrical permittivity of the composite medium is used to study the experimental results related to contact angle changes at different concentrations and diameters of submicron particles in the droplet.
Keywords: EWOD; Submicron particles; Contact angles; Contact angle saturation; Droplet
The effect of contact angle hysteresis on droplet coalescence and mixing
by Michael A. Nilsson; Jonathan P. Rothstein (pp. 646-654).
Two droplets coalescing on a superhydrophobic surface. Increasing contact angle hysteresis is shown to reduce the droplet deformation, the frequency of droplet oscillation and the rate of mixing.Display Omitted► Teflon surface, consistent advancing contact angle, varied contact angle hysteresis. ► Droplet coalescence on minimal hysteresis mimic air-based droplet coalescence. ► Droplet coalescence falls into three distinct regimes. ► Increased hysteresis dampens droplet coalescence dynamics. ► Droplet mixing is enhanced on low hysteresis surfaces.In this work, droplet coalescence and the subsequent mixing in superhydrophobic surfaces is studied over a range of impact velocities and impact angles. Sanded Teflon surfaces are used as a novel two-dimensional microfluidics platform. These superhydrophobic surfaces exhibit a constant advancing contact angle ofθ A=150° over a broad range of contact angle hysteresis. As a result, the effect of contact angle hysteresis on droplet coalescence and mixing can be studied. Based on the observed characteristics of coalescence, three different regimes of coalescence are identified as a function of both Weber number and impact angle. These regimes include oscillation dominated, rotation dominated, and mixed dynamics. It is shown that within Weber number ranges achievable in this experiment, hysteresis greatly reduces the deformation of the droplet coalescence process and the subsequent mixing. In head-on collisions, higher hysteresis is found to decrease the frequency at which the resulting dr oscillates. In the case of glancing collisions, where the resulting droplet is found to rotate, higher hysteresis increases the rate of rotation although the overall angular momentum is found to be independent of contact angle hysteresis.
Keywords: Contact angle hysteresis; Wetting; Coalescence; Mixing; Drop dynamics; Superhydrophobic
Effect of deposition parameters on the wettability and microstructure of superhydrophobic films with hierarchical micro–nano structures
by Bharathibai J. Basu; J. Manasa (pp. 655-662).
Surface morphology of superhydrophobic films deposited from cobalt chloride solution in the presence of cetyl trimethyl ammonium bromide displaying needle-like structures.Display Omitted► Fabrication of superhydrophobic films with a simple solution immersion method. ► A unique flower-like surface morphology with hierarchical micro-nano structure. ► Discussion of the mechanism of film formation. ► Correlation of surface roughness and wettability using theoretical interpretations.Superhydrophobic films with hierarchical micro–nano structures were deposited on glass substrates by solution immersion method from a solution containing cobalt chloride, urea and cetyl trimethyl ammonium bromide (CTAB). Subsequently the films were hydrophobized with a low surface energy material like octadecanoic acid under ambient conditions resulting in superhydrophobic surfaces with water contact angle (WCA) of about 168° and contact angle hysteresis of 1°. The effect of deposition parameters such as solution composition, temperature, deposition time and alkanoic acid treatment on surface morphology and wettability of the films was studied. Mechanism of formation of cobalt chloride carbonate hydroxide film is discussed. Addition of CTAB to the solution resulted in a change in the surface morphology of the deposited films with flower-like structures. The wettability of films obtained under different process conditions was correlated to surface roughness using Wenzel and Cassie models.
Keywords: Superhydrophobic; Solution immersion; Water contact angle (WCA); Sliding angle; Surface morphology
Wetting films on chemically patterned surfaces
by Stoyan I. Karakashev; Klaus W. Stöckelhuber; Roumen Tsekov (pp. 663-667).
Self organization of the water on patterned and unpatterned (hydrophobic) glass surface after film rupture; from left to right: meshes 200, 300 and 400 (with the corresponding surface grids bellow) and the unpatterned hydrophobic surface.Display Omitted► Drainage of wetting films on chemically patterned surfaces. ► Self-assembling of liquid after film rupturing. ► Zigzag three-phase contact line (TPCL) in contact with grid of droplets.The behavior of thin wetting films on chemically patterned surfaces was investigated. The patterning was performed by means of imprinting of micro-grid on methylated glass surface with UV-light ( λ=184.8nm). Thus imprinted image of the grid contained hydrophilic cells and hydrophobic bars on the glass surface. For this aim three different patterns of grids were utilized with small, medium and large size of cells. The experiment showed that the drainage of the wetting aqueous films was not affected by the type of surface patterning. However, after film rupturing in the cases of small and medium cells of the patterned grid the liquid from the wetting film underwent fast self-organization in form of regularly ordered droplets covering completely the cells of the grid. The droplets reduced significantly their size upon time due to evaporation. In the cases of the largest cell grid, a wet spot on the place of the imprinted grid was formed after film rupturing. This wet spot disassembled slowly in time. In addition, formation of a periodical zigzag three-phase contact line (TPCL) was observed. This is a first study from the planned series of studies on this topic.
Keywords: Patterned surfaces; Wetting films; Capillary phenomena; Hydrophobic; Hydrophilic
Ultra lightweight PMMA-based composite plates with robust super-hydrophobic surfaces
by Paola Pareo; Gian Luca De Gregorio; Michele Manca; Maria Savina Pianesi; Luisa De Marco; Francesco Cavallaro; Margherita Mari; Silvio Pappadà; Giuseppe Ciccarella; Giuseppe Gigli (pp. 668-675).
Schematic illustration of the composite plates coated with an ad hoc synthesized alkoxysilane-functionalized fluoromethacrylic polymer. The picture shows the superhydrophobicity of the functionalized surface.Display Omitted► Extremely lightweight plates made of an engineered PMMA-based composite material. ► Synthesis of functional coatings for easy-to-clean application. ► Durable superhydrophobic surfaces of an engineered composite material.Extremely lightweight plates made of an engineered PMMA-based composite material loaded with hollow glass micro-sized spheres, nano-sized silica particles and aluminum hydroxide prismatic micro-flakes were realized by cast molding. Their interesting bulk mechanical properties were combined to properly tailored surface topography compatible with the achievement of a superhydrophobic behavior after the deposition of a specifically designed hydrophobic coating. With this aim, we synthesized two different species of fluoromethacrylic polymers functionalized with methoxysilane anchoring groups to be covalently grafted onto the surface protruding inorganic fillers. By modulating the feed composition of the reacting monomers, it was possible to combine the hydrophobic character of the polymer with an high adhesion strength to the substrate and hence to maximize both the water contact angle (up to 157°) and the durability of the easy-to-clean effect (up to 2000h long outdoor exposure).
Keywords: Composite materials; Fluoroacrylic polymers; Superhydrophobic surfaces; Easy-to-clean effect
Fabrication of superhydrophilic poly(styrene-alt-maleic anhydride)/silica hybrid surfaces on poly(vinylidene fluoride) membranes
by Jian-Hua Wang; Li-Ping Zhu; Bao-Ku Zhu; You-Yi Xu (pp. 676-681).
There are many uniform smooth spheres of SMA on PVDF/SMA blend membrane surface. After modified by APTS, a surface with micro-nano hierarchical structure was generated and which was superhydrophilicity.Display Omitted► PVDF/poly(styrene-alt-maleic anhydride) (SMA) blend membrane was prepared. ► Superhydrophilicity hybrid surface was gained on the membrane at room temperature. ► The hybrid surface was gained by reacting SMA and aminopropyltriethoxysilane. ► The hybrid surface possessed micro-nano hierarchically structure. ► The choice of aminopropyltriethoxysilane solvent is important.Superhydrophilic organic/inorganic hybrid surfaces have been fabricated on blend membranes of poly(vinylidene fluoride) (PVDF) and poly(styrene-alt-maleic anhydride) (SMA). The blend membranes were prepared from PVDF/SMA mixed solution with N,N-dimethylacetamide (DMAc) as solvent by immersion–precipitation phase inversion process. The gained blend membranes were immersed into γ-aminopropyltriethoxysilane (APTS) solution to generate SMA/silica hybrid surfaces by the reaction between anhydrides and APTS. The hybrid surfaces chemical compositions, morphologies and hydrophilicity were investigated in detail. It demonstrates that the hybrid surfaces possess micro-nano hierarchical structure and display superhydrophilicity property and good stability. Finally, the reaction and formation mechanism of the superhydrophilicity hybrid surface was discussed.
Keywords: Poly(vinylidene fluoride); Poly(styrene-alt-maleic anhydride); Membrane; Superhydrophilicity; Silica; Hybrid
Metal-ion retention properties of water-soluble amphiphilic block copolymer in double emulsion systems ( w/ o/ w) stabilized by non-ionic surfactants
by Manuel Palencia; Bernabé L. Rivas (pp. 682-689).
Metal-ion retention properties of water-soluble amphiphilic polymers in presence of reverse double emulsion (REGs) were studied. According to our results, metal-ion retention is mainly the result of polymer-metal interaction. Interaction between PSMA and REGs is strongly controlled by amount of metal-ions added. As metal-ion concentration was increased, a negative effect on PSMA retention capacity and flocculation of REGs were produced.Display Omitted► Amphiphilic polymers in double emulsion systems (DES) were studied by diafiltration. ► Non-controlled transport processes of DESs produce a negligible retention. ► Interaction between PSMA and REGs is strongly controlled by pH. ► Interaction between PSMA and REGs is strongly controlled by metal ions added. ► Negative effect on PSMA retention capacity and flocculation phenomena are produced.Metal-ion retention properties of water-soluble amphiphilic polymers in presence of double emulsion were studied by diafiltration. Double emulsion systems, water-in-oil-in-water, with a pH gradient between external and internal aqueous phases were prepared. A poly(styrene- co-maleic anhydride) (PSAM) solution at pH 6.0 was added to the external aqueous phase of double emulsion and by application of pressure a divalent metal-ion stream was continuously added. Metal-ions used were Cu2+ and Cd2+ at the same pH of polymer solution. According to our results, metal-ion retention is mainly the result of polymer–metal interaction. Interaction between PSMA and reverse emulsion globules is strongly controlled by amount of metal-ions added in the external aqueous phase. In addition, as metal-ion concentration was increased, a negative effect on polymer retention capacity and promotion of flocculation phenomena were produced.
Keywords: Double emulsion; Amphiphilic block copolymer; Retention properties; Reverse emulsion; Diafiltration
Primary charge effects on prolate spheroids with moderate aspect ratios
by Florian Keller; Hermann Nirschl; Willy Dörfler (pp. 690-702).
Counter ion distribution on the surface of a spheroid in a shear flow and influence of the double layer thickness on the rotary resistance functionYH.Display Omitted► We study the influence of the electric double layer on spheroids with moderate aspect ratios. ► An efficient semi-implicit method based on a splitting of the Stokes equation is proposed. ► There exists a linear relation between the force/torque and the ambient flow field. ► The linear relation can be described by the resistance functions. ► In the low zeta potential regime, approximate formulas can be given.In this article, we investigate the behavior of charged spheroidal colloids with moderate aspect ratios in linear flow fields. We use direct numerical simulation with body-fitted grids for the solution of the Stokes–Poisson–Nernst–Planck system to include all non-linear effects. Therefore, we propose an efficient semi-implicit time discretization based on a splitting of the Stokes equation. We will study the effects of the electric double layer on the forces, torques and on the motion of spheroidal particles. For low Reynolds numbers, we find approximating linear expressions between the ambient fluid flow and the force and torque on the particle. The description of this linear behavior is based on the resistance functions, whose dependencies on the Debye length and the zeta potential are investigated. It is recovered that the resistance functions obey a quadratic dependence on the zeta potential in the small zeta potential regime. For low values of the zeta potential, approximate formulas for the resistance functions are given. The approximation properties are carefully studied by comparing the approximate results with direct numerical simulations. For the case of a shear flow, the approximate formulas can be used to avoid time-consuming direct numerical simulations.
Keywords: Primary charge effects; Charged prolate spheroid; Electric double layer; Linear flow field; Direct numerical simulation
In situ ligand exchange of thiol-capped CuInS2/ZnS quantum dots at growth stage without affecting luminescent characteristics
by Hyunki Kim; Minwon Suh; Byung-Hwa Kwon; Dong Seon Jang; Sung Wook Kim; Duk Young Jeon (pp. 703-706).
An aliphatic-thiol ligand of CuInS2/ZnS core/shell quantum dots is replaced with a hydroxyl-functionalized thiol ligand during the growth stage. After the ligand-exchange, negligible changes were observed in their luminescence characteristics.Display Omitted► An aliphatic-thiol ligands of CuInS2/ZnS core/shell quantum dots are exchanged during growth stage. ► Ligand-exchanged quantum dots show excellent dispersibility on polar solvents. ► Negligible changes were observed in their luminescence characteristics. ► A 70% of initial ligands are exchanged to hydroxyl-functionalized ligands.An aliphatic thiol ligand of CuInS2/ZnS core/shell quantum dots is replaced with a hydroxyl-terminated thiol ligand by utilizing ‘on–off state’ of ligands during growth stage of the quantum dots. After the ligand-exchange, negligible differences were observed on both photoluminescence spectrum and luminescent quantum efficiency. The reason for the high retention of luminescent efficiency comes from no local agglomeration and no surface deterioration of QDs. It is also observed that 70% of initial ligands are exchanged by the replacing ligand, determined by FT-IR and1H NMR. The proposed method provides the quantum dots with an excellent dispersibility in polar solvents, supported by identical luminescence decay characteristics of the QDs.
Keywords: Quantum dots; Surfactant; Luminescence; Ternary structured semiconductor; Ligand exchange
Drastic difference in porous structure of calcium alginate microspheres prepared with fresh or hydrolyzed sodium alginate
by Kazuki Akamatsu; Kaho Maruyama; Wei Chen; Aiko Nakao; Shin-ichi Nakao (pp. 707-710).
By utilizing the slight difference in fresh or hydrolyzed sodium alginate as starting materials, the porous structures of the calcium alginate microspheres were successfully controlled by employing the SPG membrane emulsification technique.Display Omitted► Calcium alginate microspheres were prepared by the SPG membrane emulsification technique. ► Nonporous and spherical microspheres were prepared with fresh sodium alginate polymers. ► Porous and spherical microspheres were prepared with 82-day-hydrolyzed sodium alginate polymers. ► The BET surface area of the microspheres prepared with 82-day-hydrolyzed sodium alginate was 6.5 times larger.Fresh or hydrolyzed sodium alginate was used as a material for preparing calcium alginate microspheres, and a drastic difference in porous structure was observed between them, even though the other materials and the preparation method except for the sodium alginate were exactly the same. When fresh sodium alginate was used, nonporous microspheres were obtained. In contrast, when 82-day-hydrolyzed sodium alginate, whose molecular weight became 7% of the molecular weight of the fresh sodium alginate, was used, porous microspheres with 6.5 times larger BET surface area were obtained. XPS studies indicated that the atomic ratio of Ca, the crosslinker of the alginic acid polymer, was almost the same in both cases. Therefore, the difference in porous structure was not attributed to the amount of crosslinking points, but to the low-molecular-weight compounds formed by hydrolysis, and they would work as pore-generating agents.
Keywords: Alginate; Membrane emulsification; Microsphere; Porous structure; SPG membrane; Hydrolysis
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