Journal of Colloid And Interface Science (v.366, #1)
Cover 1 (OFC).
Optoelectrowettability conversion on superhydrophobic CdS QDs sensitized TiO2 nanotubes by Xia Fan; Xian Li; Dongliang Tian; Jin Zhai; Lei Jiang (1-7).
The optoelectrically cooperative wettability conversion occurred on CdS QDs sensitized TiO2 nanotube surface at critical voltage of 12 V, which was decreased by 18 V comparing with only using electrical stimulus. The patterned wetting is instantly obtained with masking light through ITO.Display Omitted► Superhydrophobic CdS QDs sensitized TiO2 nanotubes were prepared for optoelectrically cooperative wettability conversion. ► CdS QDs were used as the stable and effective sensitize layer. ► The critical voltage was highly decreased comparing with only using electric stimulus. ► Stable and controllable surface of TiO2 nanotubes exhibited better resolution of patterned wettable region. ► Improved setup with ITO top electrode could be used for any nanostructures on different substrates.This work demonstrates the process of building optoelectrically cooperative surface wetting in smart and precise way. The superhydrophobic photosensitive film is constructed with TiO2 nanotube arrays. Compared with conventional organic dyes, CdS quantum dots (QDs) as sensitizer layer are modified on TiO2 nanotubes surface to improve photosensitivity of the composited surface in visible light region, which offer the benefit for designing and fabricating solid state hetero-junction devices. ITO glass is introduced as top electrode to apply electrical and optical stimuli and the patterned wetting is instantly obtained with masking light through ITO. The optoelectrically cooperative wettability conversion occurred on superhydrophobic TiO2 nanotube surface at critical voltage of 12 V, which was decreased by 18 V comparing with only using electric stimulus. This study provides potential applications for TiO2 nanotube arrays to the associated research of liquid reprography, location-controlled microfluidic device and lab-on-chip.
Keywords: TiO2 nanotube; CdS QDs; Optoelectrowettability conversion; Patterned wetting;
Stabilization of intrinsic defects at high temperatures in ZnO nanoparticles by Ag modification by Ranjan K. Sahu; K. Ganguly; T. Mishra; M. Mishra; R.S. Ningthoujam; S.K. Roy; L.C. Pathak (8-15).
Display Omitted► An easy route to introduce plenty of defects in ZnO. ► Evidences for silver is an efficient stabilizer of intrinsic defects in ZnO at high temperatures. ► Defect controlled electronic properties of unmodified and Ag modified ZnO.The stabilization of defects in ZnO at high temperatures has been investigated. The properties of unmodified and modified ZnO nanoparticles (NPs) with 2 at.% of Ag prepared by microwave assisted combustion method, have been systematically studied using X-ray diffraction (XRD), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) and photocatalytic activity measurements. Though the XRD data shows a marginal shift in the ZnO peak position upon Ag addition, the amount of shift does not change with annealing temperatures. The PL data reveals that the defect mediated visible emission intensity of unmodified ZnO NPs increases with increase in the annealing temperature, whereas it remains almost unchanged in Ag–ZnO. This study clearly establishes that silver is an efficient stabilizer of intrinsic defects in ZnO at high temperatures. This is further supported by the core and valence band XPS spectra.
Keywords: Ag modification; ZnO nanoparticles (NPs); Thermal stabilization of defects; Annealing effect;
Preparation of aqueous core/silica shell microcapsules by Keith Bean; Camilla F. Black; Norman Govan; Paul Reynolds; Mark R. Sambrook (16-22).
Display Omitted► Preparation of aqueous core/silica shell microcapsules. ► Correlation of synthesis conditions to particle products formed. ► Elucidation of mechanism of formation of silica shell walls.Water core/silica shell microcapsules are prepared via the hydrolysis and subsequent polycondensation of tetraethoxysilane in a surfactant stabilised water-in-oil emulsion. The relationship between preparative conditions, including pH and silane concentration, has been related to final particle structure. Furthermore, the nature of the catalyst has been found to affect the mechanism by which the shells are formed, with an interfacial polymerisation proposed for ammonium hydroxide catalysed synthesis in agreement with previous reports and a new colloidosome assembly process for sodium hydroxide catalysis. In both cases shell aging processes are observed to continue beyond initial shell formation suggesting that trans-shell diffusion of reactants may be feasible, or that rapid hydrolysis is required in order to load high concentrations of the reactants into the internal phase before significant shell formation.
Keywords: Microencapsulation; Core/shell particles; Aqueous core; Interfacial polymerisation;
A facile strategy for obtaining fresh Ag as SERS active substrates by Zibao Gan; Aiwu Zhao; Maofeng Zhang; Dapeng Wang; Wenyu Tao; Hongyan Guo; Da Li; Ming Li; Qian Gao (23-27).
Display Omitted► A facile strategy was reported to obtain on-line fresh Ag as SERS substrates. ► The laser-driven generation of Ag/AgCl composites from AgCl precursors was surveyed. ► Fresh Ag surfaces with defects have a significant SERS sensitivity to probe molecules. ► Raman intensity is dependent on the extent of defect and the proportion of fresh Ag. ► The strategy is simple, efficient and feasible.A facile strategy has been reported to obtain on-line fresh Ag as surface-enhanced Raman scattering (SERS) active substrates by making AgCl nanoparticles exposed to the laser beam of Raman spectrometer. The composition and morphology of AgCl nanoparticles were characterized by X-ray diffraction (XRD), UV–visible (UV–vis) spectroscopy and scanning electron microscopy (SEM). The laser-driven evolvement and possible formation mechanism of cubic AgCl nanoparticles to Ag/AgCl composites were also investigated by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and high-resolution transmission electron microscopy (HRTEM). Raman measurements demonstrate that the fresh Ag nanoparticles with a few defects have a prominent SERS sensitivity to probe molecules, such as the 4-mercaptopyridine (4-Mpy) and 4-aminothiophenol (PATP) molecules. The SERS intensity of 4-Mpy and PATP increases up to the maximum when the laser irradiation time is prolonged to 50 s, which corresponds to the defect extent and the proportion of fresh Ag in the Ag/AgCl composites. This work provides a simple, efficient and feasible approach for obtaining on-line fresh Ag as SERS substrates.
Keywords: SERS; Fresh Ag; Irradiation time; 4-Mercaptopyridine;
Concomitant synthesis of highly crystalline Zn–Al layered double hydroxide and ZnO: Phase interconversion and enhanced photocatalytic activity by Kingshuk Dutta; Somnath Das; Amitava Pramanik (28-36).
Display Omitted► A facile hydrothermal method for concurrent synthesis of crystalline LDH phase and ZnO. ► Phase transitions from pure LDH to pure ZnO. ► Self-limiting growth of plate LDH turned to non-self-limiting in presence of Al salt. ► Formation of Al-doped ZnO and sequential increase in crystallinity of substrate LDH phase. ► Both Al-doped ZnO and nano LDH substrate samples showed superior photocatalytic activity.Metal oxide/hydroxide with hierarchical nanostructures has emerged as one of the most promising materials for their unique, attractive properties and feasibility of applications in various fields. In this report, a concomitant synthesis of crystalline zinc aluminum layered double hydroxide (ZnAl-LDH) nanostructure and ZnO is presented using Al substrate as template. Studies on interconversion of ZnO to LDH phase in bulk solution under hydrothermal conditions produced Al-doped ZnO (AZO) in one case, and in other, it improves the crystallinity of LDH film templated on Al substrate. In presence of Al salt, the self-limiting growth nature of plate LDH turned to non-self-limiting. Materials obtained during phase transition, AZO in bulk solution and crystalline porous ZnAl-LDH on substrate, have been demonstrated as effective photocatalysts for decomposition of congo red in aqueous medium.
Keywords: ZnAl–NO3 LDH; Al-doped ZnO; Phase interconversion; Photocatalysis;
Effect of sulfate on Cu(II) sorption to polymer-supported nano-iron oxides: Behavior and XPS study by Hui Qiu; Shujuan Zhang; Bingcai Pan; Weiming Zhang; Lu Lv (37-43).
Display Omitted► Sulfate plays a significant role in Cu(II) uptake by polymer-based nano-hydrated ferric oxide. ► Effect of sulfate on copper uptake varied with the host surface chemistry and the co-ions type. ► Formation of ternary complexes may be responsible for the effect of sulfate on copper uptake. ► Besides co-ions, more attention should be paid to the effect of counter ions on heavy metals removal.Iron oxides tend to be immobilized within nanoporous supports to improve their feasibility for practical environmental remediation including arsenic and heavy metal removal. Contrary to the co-ions, little is known concerning the effect of counter ions on the performance of the resultant composites. In this study, two hybrid sorbents (denoted as HFO–PS− and HFO–PS0, respectively) were prepared by loading hydrous ferric oxide (HFO) nanoparticles onto two polystyrene beads: PS−, negatively charged with sulfonic acid groups, and PS0, covalently bonded with neutral chloromethyl groups. Effects of sulfate on their sorption toward Cu ions were investigated. Consistent with the case in bulky HFO particles, the amount of Cu adsorbed on HFO–PS0 was markedly promoted by introducing sulfate. As for HFO–PS−, with monovalent cation as background (Na+), it exhibited an apparent decrease in Cu sorption as a result of the competing effect of Na ions and the Cu–SO4 complexation in solution. Contrarily, the adsorbed Cu was increased by introducing sulfate in the divalent cation background (Ca), because sulfate ions were allowed to access to the loaded HFO nanoparticles due to the screening of the sulfonic acid groups caused by Ca ions. XPS spectroscopy further demonstrated that besides the electrostatic effects, the formation of Cu–SO4 ternary complexes also accounted for the enhanced Cu sorption on both bulky HFO and hybrid HFO sorbents in the presence of sulfate. These results indicated that the effect of counter-ion ligands on metal adsorption to hybrid iron oxides was largely dependent on the surface properties of the host materials.
Keywords: Hydrated ferric oxide; Heavy metals; Removal; XPS; Nanocomposite;
Molecular level dispersion of graphene in polymer matrices using colloidal polymer and graphene by Mohsen Moazzami Gudarzi; Farhad Sharif (44-50).
Display Omitted► Stable dispersion of graphene-polymer by using latex technology is achieved. ► Interparticle interaction plays a key role on assembly of colloidal particles. ► Graphene was successfully stabilized using polymers particles with hydrophilic shell. ► Fine dispersion of graphene in the polymer matrix assure during the colloid drying.A novel and environmentally friendly method based on mixing of colloidal polymer particles and graphene sheets has been developed. It is found that colloidal polymers can be employed to stabilize graphene oxide (GO) sheets during reduction to graphene. Adsorption of polymer particles at the surface of graphene layers seems to be underlying mechanism of stabilization of graphene sheets. Surface polarity of the polymer particles is crucial for the successful stabilization of graphene layers. Presence of colloidal particles at the surface of graphene prohibits restacking and agglomeration of nanolayers, resulting in fine dispersion of graphene throughout the polymeric matrix. Formation of strong bond between polar segments of the polymer chain and oxygen groups of graphene sheets generates a strong interface improving final properties of the composites. Inclusion of merely 2 wt% of graphene into an acrylic resin resulted in an increase of 522% and 242% in modulus and hardness, respectively.
Keywords: Colloidal polymer; Graphene; Polymer adsorption; Stabilizer;
Extraordinarily water permeable sol–gel formed nanocomposite nanofibrous membranes by Seyed Shahin Homaeigohar; Hossein Mahdavi; Mady Elbahri (51-56).
Display Omitted► An electrospun nanofibrous membrane was mechanically stabilized using titania nanofillers. ► Wettability of the membrane was also significantly enhanced. ► Water permeability improved considerably owing to these two achievements. ► This extraordinary permeability implies a very low energy consuming water filtration.Electrospun nanofibrous membranes (ENMs) are considered as a state of the art in water filtration technology mainly owing to their high interconnected porosity and tunable pore size assumed to offer a very high permeability also selectivity. However, the extremely high surface area makes the ENMs prone to mechanical breakdown and lack of wettability lowering the filtration efficiency. Hence, any attempt to enhance both the mechanical properties and hydrophilicity of the ENMs is highly recommended.In the current study, the structural and transport properties of polyethersulfone (PES) ENMs were modified through incorporation of titania (TiO2) nanoparticles via a sol–gel approach. Presence of titania precursor increased the conductivity of the electrospun solution thereby optimized the structural features of the electrospun mat in terms of formation of very thin beadless nanofibers, a higher porosity and smaller pore size. Moreover, a significant rise in mechanical properties, thermal stability and switching from a highly hydrophobic membrane to a superhydrophilic one occur simultaneously. The combination of a more optimum porosity, very high mechanical properties and hydrophilicity leads to a significantly higher water permeability in the TiO2/PES ENMs encouraging us to propose it as a water filtration membrane with longer life span and lower energy consumption.
Keywords: Electrospinning; Membrane; Composite nanofiber; Titania nanoparticle; Sol–gel;
Phospholipids as an alternative to direct covalent coupling: Surface functionalization of nanoporous alumina for protein recognition and purification by Thomas D. Lazzara; Daniela Behn; Torben-Tobias Kliesch; Andreas Janshoff; Claudia Steinem (57-63).
Display Omitted► Vesicles larger than the pore size of AAO can be used for surface functionalization. ► The vesicle’s lipid composition determines that of the monolayer. ► Receptor lipids are laterally mobile and their density can be readily adjusted. ► Optical transparency of AAO allows label-free in situ analysis of protein binding. ► Functionalized and large surface area allows protein purification from cell lysates.Anodic aluminum oxide (AAO) substrates with aligned, cylindrical, non-intersecting pores with diameters of 75 nm and depths of 3.5 or 10 μm were functionalized with lipid monolayers harboring different receptor lipids. AAO was first functionalized with dodecyl-trichlorosilane, followed by fusion of small unilamellar vesicles (SUVs) forming a lipid monolayer. The SUVs’ lipid composition was transferred onto the AAO surface, allowing us to control the surface receptor density. Owing to the optical transparency of the AAO, the overall vesicle spreading process and subsequent protein binding to the receptor-doped lipid monolayers could be investigated in situ by optical waveguide spectroscopy (OWS). SUV spreading occurred at the pore-rim interface, followed by lateral diffusion of lipids within the pore-interior surface until homogeneous coverage was achieved with a lipid monolayer. The functionality of the system was demonstrated through streptavidin binding onto a biotin–DOPE containing POPC membrane, showing maximum protein coverage at 10 mol% of biotin–DOPE. The system enabled us to monitor in real-time the selective extraction of two histidine-tagged proteins, PIGEA14 (14 kDa) and ezrin (70 kDa), directly from cell lysate solutions using a DOGS-NTA(Ni)/DOPC (1:9) membrane. The purification process including protein binding and elution was monitored by OWS and confirmed by SDS–PAGE.
Keywords: Affinity chromatography; Anodic aluminum oxide; Confocal fluorescence microscopy; Hybrid solid supported membrane; Lipid monolayer; Multi-functional surface; Nanoporous substrate; Optical biosensor; Optical waveguide spectroscopy; Protein adsorption;
Silver-perfluorodecanethiolate complexes having superhydrophobic, antifouling, antibacterial properties by Jae-Seung Chung; Byoung Gak Kim; Soojin Shim; Seong-Eun Kim; Eun-Ho Sohn; Jeyong Yoon; Jong-Chan Lee (64-69).
Silver-perfluorodecanethiolate complexes having superhydrophobic, antifouling, antibacterial properties were prepared and their surface properties were systematically studied.Display Omitted► It is the first report about silver-perfluorodecanethiolate complexes (AgSF). ► We verifying the interesting characters of these materials using various techniques. ► AgSF having hierarchical micro-/nano-sized wire-shaped structure were obtained. ► AgSF shows excellent superhydrophobic and antifouling properties. ► Ag-nanoparticles were generated via UV, and exhibited antibacterial properties.Silver-perfluorodecanethiolate complexes having superhydrophobic, antifouling, antibacterial properties were prepared by a reaction of silver nitrate with perfluorodecanethiol. When the silver nitrate to perfluorodecanethiol molar ratio was 1/2, silver-perfluorodecanethiolate complexes having hierarchical micro-/nano-sized wire shapes were obtained, and they showed superhydrophobic and antifouling properties. After UV irradiation, silver nanoparticles were generated on the wires and exhibited antibacterial properties.
Keywords: Silver-thiolate complex; Superhydrophobicity; Antifouling; Antibacterial;
Synthesis, characterization and examination of Gd[DO3A-hexylamine]-functionalized silica nanoparticles as contrast agent for MRI-applications by Verena Feldmann; Jörn Engelmann; Sven Gottschalk; Hermann A. Mayer (70-79).
Display Omitted► Nanoparticulate contrast agents for magnetic resonance imaging. ► Silica nanoparticles were covalently functionalized with Gd(III) chelate complexes. ► Detailed quantification of the surface functionalization is reported. ► High local relaxivities per nanoparticle were obtained.Spherical, nonporous and monodisperse silica nanoparticles (NPs) with a diameter of about 100 nm were synthesized and covalently functionalized with lanthanoid(III) (Ln = Gd or Y) chelate complexes, which serve as contrast agents (CAs) for magnetic resonance imaging (MRI). The materials were fully characterized after each synthetic step by different analytical methods, such as dynamic light scattering, scanning electron microscopy, DRIFT and NMR spectroscopy, thermogravimetry and elemental analysis, as well as zetapotential measurements. High surface concentrations of Gd(III) complexes (up to 50 μmol g−1) were determined by ICP-AES and T 1-measurements, respectively. MRI experiments show the typical concentration-dependent increase of the longitudinal relaxation rate. T 1-weighted images of samples with more than 25 μg NPs per 100 μL agar display a clear contrast enhancement in the agar layer. The transverse relaxivities r 2 of the materials are significantly higher than r 2 of the corresponding free Gd(III) complexes in water and medium, whereas the longitudinal relaxivities r 1 are slightly increased. Due to the high loading of Gd(III) complexes, the relaxivities per particle are remarkably high (up to 2.78 × 105 mM−1 s−1 for r 1). Thus, new hybrid materials, based on nonporous silica NPs with high local relaxivity values were synthesized, which can serve as very effective CAs for MRI.
Keywords: Silica nanoparticles; Contrast agents; Magnetic resonance imaging;
Control over the crystal phase, crystallinity, morphology of AgVO3 via protein inducing process by Tao Chen; Mingwang Shao; Hongyan Xu; Chunye Wen; Shuit-Tong Lee (80-87).
Display Omitted► Pure and crystalline metastable α-AgVO3 is obtained using bio-inspired way. ► Three proteins were used as model agents. ► The amounts and surface charges of proteins played a key role over α-AgVO3.A facile and bio-inspired route for the preparation of pure and highly crystalline metastable α-AgVO3 is presented. Three kinds of proteins (bovine hemoglobin, bovine serum albumin, and lysozyme) were employed as inducer, which had substantial effects on the nucleation and growth of α-AgVO3. Moreover, the amount of proteins also played a key role over the morphology and crystalline of products. The VO 3 - /protein complex acted as a driver to induce the formation of metastable phase, which was confirmed by resonance Rayleigh scattering and UV–vis absorption spectra. The results indicated that tailoring an interaction between protein and inorganic molecules was the key in bio-inspired selective synthesis of metastable phase, which may find applications in the design of other new functional inorganic materials.
Keywords: Metastable phase; AgVO3; Polymorphs; Proteins;
Competitive adsorption of polymer and surfactant at a liquid droplet interface and its effect on flocculation of emulsion by J.S. Nambam; John Philip (88-95).
At low surfactant concentrations the monomers and micelles associate with polymer coils, leading to stretching of the tail regions. At surfactant concentration ≫CAC, the surfactant molecules preferentially adsorb at the droplet interface by desorbing the polymers and at very high surfactant concentration, the polymer–surfactant complexes binds several drops together forming flocs.Display Omitted► Studies on competitive adsorption of polymer and surfactant at oil–water interface show some interesting results. ► Our results indicate that surfactant has a tendency to preferentially adsorb at the oil–water interface. ► Polymer–surfactant association can lead to a synergistic enhancement of emulsion stability or bridging flocculation. ► Our results are useful for preparing oil-in-water formulations with long term stability.We investigate the competitive adsorption of polymer and surfactant at oil–water interface by measuring the hydrodynamic diameter, zeta potential, microstructure and rheology. The polymer used in our experiment is a statistical copolymer of polyvinyl alcohol and vinyl acetate copolymer (PVA–Vac) and the emulsion is oil-in-water system with an average droplet diameter of 200 nm. At low surfactant concentrations, the hydrodynamic diameter remains unchanged but above a critical aggregation concentration, it increases dramatically. The phase contrast optical microscopic images of emulsion droplets preadsorbed with polymers of higher molecular weight show a systematic increase in the floc size on increasing surfactant concentration due to biding of polymer–surfactant complexes on several droplets. The dramatic increase in zeta potential of the droplets on increasing ionic surfactant concentration clearly indicates a preferential adsorption of surfactant at the oil–water interface. The enhanced viscosity upon addition of ionic surfactant into polymers confirms the strong interaction between them. Our studies show that lower molecular weight polymers with suitable ionic surfactants can synergistically enhance the stability of formulations, while longer chain polymers induce bridging flocculation. Our results are useful for preparing oil-in-water formulations with long term stability.
Keywords: Polymer; Surfactant; Emulsions; Hydrodynamic diameter; Zeta potential;
Influence of the nature of the polycation on the adsorption kinetics and on exchange processes in polyelectrolyte multilayer films by Vincent Ball; Abdelghani Laachachi; Valérie Toniazzo; David Ruch (96-104).
Display Omitted► Dynamics of polyelectrolyte multilayer films. ► Deposition kinetics. ► Polyelectrolyte exchange processes. ► Film erosion.The deposition of polyelectrolyte multilayer films (PEMs) appears more and more as a versatile tool to functionalize a broad range of materials with coatings having controlled thicknesses and properties. To increase the control over the properties of such coatings, a good knowledge of their deposition mechanism is required. Since Cohen Stuart et al. (Langmuir 18 (2002) 5607–5612) showed that the adsorption of one polyelectrolyte could induce desorption of polyelectrolyte complexes instead of regular deposition, more and more findings highlight peculiarities in the deposition of such films. Herein we demonstrate that the association of sodium polyphosphate (PSP) as the polyanion and either poly(-L-lysine hydrobromide) (PLL) or poly(allylamine chloride) (PAH) as the polycations may lead to non-monotonous film deposition as a function of time. Complementary, films containing PSP and PLL can be obtained from a (PLL–HA) n template films after the exchange of HA (hyaluronic acid) from the sacrificial template by PSP from the solution. This exchange is accompanied by pronounced film erosion. However, when starting from a (PAH–HA) n template, the film erosion and exchange due to the contact with PSP is by far less pronounced, nevertheless the film morphology changes. These findings show that the nature of the polycation used to deposit the PEM film may have a profound influence of the film’s response to a competing polyanion.
Keywords: Polyelectrolyte multilayer films; Exchange processes; Deposition kinetics;
Ionic strength effect in HSA adsorption on mica determined by streaming potential measurements by Maria Dąbkowska; Zbigniew Adamczyk (105-113).
Mechanism of HSA adsorption at mica, pH = 3.5.Display Omitted► Revealing mechanism of human serum albumin (HSA) adsorption on mica. ► Determining the coverage of HSA on mica as a function of ionic strength. ► Developing a theoretical model of HSA adsorption on mica.Adsorption and desorption of human serum albumin (HSA) from aqueous solutions on mica were studied using AFM and in situ streaming potential measurements. A quantitative interpretation of these experiments was achieved in terms of the theoretical model postulating a 3D adsorption of HSA molecules as discrete particles. These measurements, performed for various ionic strength, allowed one to determine the coverage of HSA as a function of the zeta potential of mica. This allowed one to determine the amount of irreversibly bound HSA as a function of the ionic strength. It was found that the coverage of irreversibly adsorbed HSA increased from 0.52 mg m−2 for I = 1.3 × 10−3 M to 1.6 mg m−2 for I = 0.15 M (pH = 3.5). The significant role of ionic strength was attributed to the lateral electrostatic repulsion among adsorbed HSA molecules, positively charged at this pH value. This was quantitatively interpreted in terms of the effective hard particle concept previously used for colloid particles. The experimental results confirmed that monolayers of irreversibly bound HSA of a well-controlled coverage can be produced by adjusting the ionic strength of the suspension.
Keywords: Human serum albumin adsorption on mica; Irreversibly bound HSA; HSA molecule adsorbed on mica; Model 3D adsorption of HSA molecules; Monolayers of HSA molecules; Streaming potential of HSA of covered surfaces; Zeta potential of HSA-covered mica;
Preparation of mesoporous ferrisilicate with high content of framework iron by pH-modification method and its catalytic performance by Baoshan Li; Junqing Xu; Jianjun Liu; Shengli Zuo; Zhiyun Pan; Ziyu Wu (114-119).
The mesoporous ferrisilicates (MFS) with high iron content were synthesized by internal pH-modification method, and the Fe K-edge XAFS results indicate Fe3+ ions incorporate into the silicate framework with a tetrahedral coordination structure.Display Omitted► Mesoporous ferrisilicates with high content of iron were prepared via pH-modification method. ► The optimum limit of iron in the silicate framework could be up to 10.5 wt.% (Si/Fe = 8). ► The color of high iron content mesoporous ferrisilicate is white.The mesoporous ferrisilicates (MFS) with high iron content were synthesized by pH-modification method, and the iron content could be up to 10.5 wt.% (Si/Fe = 8). The pH was kept less than 2 at pre-hydrothermal synthesis step and was adjusted to 11 during hydrothermal step. The samples were characterized by XRD, HRTEM, N2-sorption, XRF, FTIR, DRUV–vis, Fe K-edge EXAFS, EPR, and DSC. The results suggested that the MFS materials were ordered 2D hexagonal mesophase of MCM-41, and the iron atoms were tetrahedral coordinated in the silica framework. This material could efficiently catalyze the hydroxylation of phenol in water medium using H2O2 as an oxidant, and the phenol conversion could be up to 52% under the optimal experimental conditions.
Keywords: High content heteroatom molecular sieves; Mesoporous ferrisilicates; pH-Modification method; Phenol hydroxylation;
Adsorption of CH4 and CO2 on Zr-metal organic frameworks by Hussein Rasool Abid; Gia Hung Pham; Ha-Ming Ang; Moses O. Tade; Shaobin Wang (120-124).
Zr-metal organic frameworks (Zr-MOF) exhibit high CH4 and CO2 adsorption and additive of ammonium hydroxide produces Zr-MOF with higher selectivity of CO2/CH4.Display Omitted► Zr-MOFs were prepared with addition of ammonia as additive. ► Ammonia additive affects textural structure of Zr-MOF. ► Nanosize Zr-MOF presents high adsorption of CH4 and CO2. ► Ammonia modified Zr-MOF exhibits high selectivity of CO2/CH4.Zirconium-metal organic frameworks (Zr-MOFs) were synthesized with or without ammonium hydroxide as an additive in the synthesis process. It was found that addition of ammonium hydroxide would change the textural structure of Zr-MOF. The BET surface area, pore volume, and crystal size of Zr-MOF were reduced after addition of ammonium hydroxide. However, the crystalline structure and thermal stability were maintained and no functional groups were formed. Adsorption tests showed that Zr-MOF presented much higher CO2 adsorption than CH4. Zr-MOF exhibited CO2 and CH4 adsorption of 8.1 and 3.6 mmol/g, respectively, at 273 K, 988 kPa. The addition of ammonium hydroxide resulted in the Zr-MOF with a slight lower adsorption of CO2 and CH4, however, the selectivity of CO2/CH4 is significantly enhanced.
Keywords: Zr-MOF; Ammonium hydroxide; Adsorption; Carbon dioxide; Methane;
Influence of MgO template on carbon dioxide adsorption of cation exchange resin-based nanoporous carbon by Long-Yue Meng; Soo-Jin Park (125-129).
The porous carbons were directly prepared from a weak acid cation exchange resin by the carbonization of a mixture with Mg acetate.Display Omitted► The nanoporous carbons were directly prepared from a cation exchange resin and Mg acetate. ► The microstructure of the obtained porous carbons was significantly affected by the Mg acetate-to-resin ratio. ► By dissolving the MgO template, the nanoporous carbons exhibited high specific surface areas and pore volume. ► The CO2 adsorption capacities of the nanoporous carbons were enhanced by increasing the Mg acetate-to-resin ratio.In this work, porous carbons with well-developed pore structures were directly prepared from a weak acid cation exchange resin (CER) by the carbonization of a mixture with Mg acetate in different ratios. The effect of the Mg acetate-to-CER ratio on the pore structure and CO2 adsorption capacities of the obtained porous carbons was studied. The textural properties and morphologies of the porous carbons were analyzed via N2/77 K adsorption/desorption isotherms, SEM, and TEM, respectively. The CO2 adsorption capacities of the prepared porous carbons were measured at 298 K and 1 bar and 30 bar. By dissolving the MgO template, the porous carbons exhibited high specific surface areas (326–1276 m2/g) and high pore volumes (0.258–0.687 cm3/g). The CO2 adsorption capacities of the porous carbons were enhanced to 164.4 mg/g at 1 bar and 1045 mg/g at 30 bar by increasing the Mg acetate-to-CER ratio. This result indicates that CER was one of the carbon precursors to producing the porous structure, as well as for improving the CO2 adsorption capacities of the carbon species.
Keywords: CO2 adsorption; Acryl-based cation exchange resin; MgO;
Electrochemical biosensor based on CdS nanostructure surfaces by Jiqing Qian; Shancheng Yan; Zhongdang Xiao (130-134).
We have demonstrated a novel glucose sensor based on the highly efficient immobilization of GOD with chitosan on a Au nanoparticles modified ITO–CdS nanorods surface.Display Omitted► The CdS is able to efficiently increase the electron transfer reactivity of GOD. ► The Au nanoparticles are deposited to enhance the electron transfer process. ► In addition, chitosan is an efficient redox mediator.Well-defined hexangularly faced CdS nanorod arrays have been grown directly on a conductive ITO glass via a facile one-step and non-template hydrothermal approach. Gold nanoparticles were decorated onto the nanorods to enhance the electron transfer process of electrode. Glucose oxidase (GOD) was then immobilized on the CdS through crosslinking with chitosan (CS), which resulted in a glucose biosensor with high enzyme loading and excellent sensitivity. Such a chitosan-encapsulated GOD-based biosensor revealed a relatively rapid response time of less than 50 s, and an approximate linear detection range of glucose concentration, from 50 to 500 μmol L−1 with a detection limit of 38 μmol L−1 and an electrode sensitivity of 5.9 μA mM−1.
Keywords: Glucose biosensor; CdS nanorod arrays; Electron transfer; Bioelectronics;
Photodegradation of hazardous dye quinoline yellow catalyzed by TiO2 by Vinod Kumar Gupta; Rajeev Jain; Shilpi Agarwal; Arunima Nayak; Meenakshi Shrivastava (135-140).
Variation of the rate constant with different concentrations of TiO2.Display Omitted► Nonbiodegradable quinoline yellow is removed. ► Process is much faster in basic solutions than neutral or acidic. ► The rate decreases with the increase in dye concentration. ► Complete mineralization of dye can be achieved.The photocatalytic degradation of hazardous dye quinoline yellow, employing a heterogeneous photocatalytic process using TiO2 photocatalyst irradiated with 6 W UV light source tungsten lamp, has been studied. The effect of various operational parameters, i.e., dye concentration, photocatalyst concentration, pH of the solution, substrate concentration, and electron acceptor such as hydrogen peroxide on the degradation rate of aqueous solutions of quinoline yellow has been examined. The disappearance of the dye follows a pseudo first order kinetics according to the Langmuir Hinshelwood model. Results show that the use of an efficient photocatalyst and the selection of optimal operational parameters may lead to complete decolorization and to sustainable decrease in the chemical oxygen demand (COD) of the dye waste water.
Keywords: Decolorization; Quinoline yellow dye; Anatase TiO2; Kinetics; COD;
Arsenate uptake and arsenite simultaneous sorption and oxidation by Fe–Mn binary oxides: Influence of Mn/Fe ratio, pH, Ca2+, and humic acid by Gaosheng Zhang; Huijuan Liu; Jiuhui Qu; William Jefferson (141-146).
As(V) retention, As(III) oxidation and sorption were obviously affected by Mn/Fe molar ratio, and the Fe–Mn binary oxide has much higher sorption capacity toward As(III) than that of As(V) at each Mn/Fe molar ratio.Display Omitted► Arsenic uptake was obviously affected by Mn/Fe molar ratio of the binary oxide. ► The Fe–Mn binary oxides were more effective for As(III) removal than As(V). ► The MnO2 content in the Fe–Mn binary oxides can effectively oxidize As(III) to As(V). ► The presence of calcium ions enhanced arsenic sorption. ► The coexisting humic acids slightly decreased arsenic sorption.Arsenate retention, arsenite sorption and oxidation on the surfaces of Fe–Mn binary oxides may play an important role in the mobilization and transformation of arsenic, due to the common occurrence of these oxides in the environment. However, no sufficient information on the sorption behaviors of arsenic on Fe–Mn binary oxides is available. This study investigated the influences of Mn/Fe molar ratio, solution pH, coexisting calcium ions, and humic acids have on arsenic sorption by Fe–Mn binary oxides. To create Fe–Mn binary oxides, simultaneous oxidation and co-precipitation methods were employed. The Fe–Mn binary oxides exhibited a porous crystalline structure similar to 2-line ferrihydrite at Mn/Fe ratios 1:3 and below, whereas exhibited similar structures to δ-MnO2 at higher ratios. The As(V) sorption maximum was observed at a Mn/Fe ratio of 1:6, but As(III) uptake maximum was at Mn/Fe ratio 1:3. However, As(III) adsorption capacity was much higher than that of As(V) at each Mn/Fe ratio. As(V) sorption was found to decrease with increasing pH, while As(III) sorption edge was different, depending on the content of MnO2 in the binary oxides. The presence of Ca2+ enhanced the As(V) uptake under alkaline pH, but did not significantly influence the As(III) sorption by 1:9 Fe–Mn binary oxide; whereas the presence of humic acid slightly reduced both As(V) and As(III) uptake. These results indicate that As(III) is more easily immobilized than As(V) in the environment, where Fe–Mn binary oxides are available as sorbents and they represent attractive adsorbents for both As(V) and As(III) removal from water and groundwater.
Keywords: Fe–Mn binary oxides; Arsenic; Sorption; Oxidation;
CO2 adsorption by activated templated carbons by Marta Sevilla; Antonio B. Fuertes (147-154).
Display Omitted► Templated mesoporous carbons are chemically activated with KOH. ► Large number of micropores are generated by activation. ► Activated carbons exhibit high CO2 adsorption uptakes and they can easily be regenerated.Highly porous carbons have been prepared by the chemical activation of two mesoporous carbons obtained by using hexagonal- (SBA-15) and cubic (KIT-6)-ordered mesostructured silica as hard templates. These materials were investigated as sorbents for CO2 capture. The activation process was carried out with KOH at different temperatures in the 600–800 °C range. Textural characterization of these activated carbons shows that they have a dual porosity made up of mesopores derived from the templated carbons and micropores generated during the chemical activation step. As a result of the activation process, there is an increase in the surface area and pore volume from 1020 m2 g−1 and 0.91 cm3 g−1 for the CMK-8 carbon to a maximum of 2660 m2 g−1 and 1.38 cm3 g−1 for a sample activated at 800 °C (KOH/CMK-8 mass ratio of 4). Irrespective of the type of templated carbon used as precursor or the operational conditions used for the synthesis, the activated samples exhibit similar CO2 uptake capacities, of around 3.2 mmol CO2 g−1 at 25 °C. The CO2 capture capacity seems to depend on the presence of narrow micropores (<1 nm) rather than on the surface area or pore volume of activated carbons. Furthermore, it was found that these porous carbons exhibit a high CO2 adsorption rate, a good selectivity for CO2–N2 separation and they can be easily regenerated.
Keywords: Carbon dioxide adsorption; Chemical activation; Templated carbon;
Adsorption and protein-induced metal release from chromium metal and stainless steel by M. Lundin; Y. Hedberg; T. Jiang; G. Herting; X. Wang; E. Thormann; E. Blomberg; I. Odnevall Wallinder (155-164).
Display Omitted► Metal release from chromium and stainless steel surfaces in contact with proteins. ► Albumin, mucin, and lysozyme showed high affinities for the metal surfaces. ► More metal species are released in protein solutions than protein-free solutions. ► This is significant both for chromium metal and different stainless steel grades. ► The grades investigated include different microstructures and compositions.A research effort is undertaken to understand the mechanism of metal release from, e.g., inhaled metal particles or metal implants in the presence of proteins. The effect of protein adsorption on the metal release process from oxidized chromium metal surfaces and stainless steel surfaces was therefore examined by quartz crystal microbalance with energy dissipation monitoring (QCM-D) and graphite furnace atomic absorption spectroscopy (GFAAS). Differently charged and sized proteins, relevant for the inhalation and dermal exposure route were chosen including human and bovine serum albumin (HSA, BSA), mucin (BSM), and lysozyme (LYS). The results show that all proteins have high affinities for chromium and stainless steel (AISI 316) when deposited from solutions at pH 4 and at pH 7.4 where the protein adsorbed amount was very similar. Adsorption of albumin and mucin was substantially higher at pH 4 compared to pH 7.4 with approximately monolayer coverage at pH 7.4, whereas lysozyme adsorbed in multilayers at both investigated pH. The protein–surface interaction was strong since proteins were irreversibly adsorbed with respect to rinsing. Due to the passive nature of chromium and stainless steel (AISI 316) surfaces, very low metal release concentrations from the QCM metal surfaces in the presence of proteins were obtained on the time scale of the adsorption experiment. Therefore, metal release studies from massive metal sheets in contact with protein solutions were carried out in parallel. The presence of proteins increased the extent of metals released for chromium metal and stainless steel grades of different microstructure and alloy content, all with passive chromium(III)-rich surface oxides, such as QCM (AISI 316), ferritic (AISI 430), austentic (AISI 304, 316L), and duplex (LDX 2205).
Keywords: Chromium; Protein adsorption; Metal release; Stainless steel; Lysozyme; Albumin; Mucin;
Selective adsorption of uranium(VI) from aqueous solutions using the ion-imprinted magnetic chitosan resins by Limin Zhou; Chao Shang; Zhirong Liu; Guolin Huang; Adesoji A. Adesina (165-172).
Display Omitted► The ion-imprinted magnetic chitosan resins (IMCR) have small diameters, magnetic proprieties, and fast kinetic. ► The ion-imprinting process increases UO 2 2 + adsorption capacity and selectivity. ► Equilibrium data fitted well with the Langmuir and D–R isotherm models. ► UO 2 2 + adsorption is an exothermic spontaneous process that kinetically followed the second-order model.The ion-imprinted magnetic chitosan resins (IMCR) prepared using U(VI) as a template and glutaraldehyde as a cross-linker showed higher adsorption capacity and selectivity for the U(VI) ions compared with the non-imprinted magnetic chitosan resins (NIMCR) without a template. The results showed that the adsorption of U(VI) on the magnetic chitosan resins was affected by the initial pH value, the initial U(VI) concentration, as well as the temperature. Both kinetics and thermodynamic parameters of the adsorption process were estimated. These data indicated an exothermic spontaneous adsorption process that kinetically followed the second-order adsorption process. Equilibrium experiments were fitted in Langmuir, Freundlich, and Dubinin–Radushkevich adsorption isotherm models to show very good fits with the Langmuir isotherm equation for the monolayer adsorption process. The monolayer adsorption capacity values of 187.26 mg/g for IMCR and 160.77 mg/g for NIMCR were very close to the maximum capacity values obtained at pH 5.0, temperature 298 K, adsorbent dose 50 mg, and contact time 3 h. The selectivity coefficient of uranyl ions and other metal ions on IMCR indicated an overall preference for uranyl ions. Furthermore, the IMCR could be regenerated through the desorption of the U(VI) ions using 0.5 M HNO3 solution and could be reused to adsorb again.
Keywords: Ion-imprinted; Chitosan; Magnetic resins; Adsorption; U(VI) ions;
Behavior of stabilized multiwalled carbon nanotubes in a FeCl3 coagulation system and the structure characteristics of the produced flocs by Mengchang He; Ruijing Zhou; Xuejun Guo (173-178).
Display Omitted► Humic acid-stabilized multiwalled carbon nanotubes (HA-MWNTs) were effectively removed during the coagulation. ► HA-MWNTs did not change the phase feature of the low-crystalline ferrihydrite. ► It was suggested that HA-MWNTs increased the degree of polymerization of the produced flocs. ► MWNTs might be used as a potential coagulant aid in water treatment for the enhanced removal of organic chemicals.The understanding of the fate and the transport of carbon nanotubes (CNTs) in the water treatment process will provide important information for assessing the environmental risks of CNTs. To fill the knowledge gap, this study investigated the removability of multiwalled carbon nanotubes (MWNTs) stabilized by humic acid (HA) during the coagulation–flocculation–sedimentation (CFS) process. The structure characteristics of the produced flocs were systematically investigated using a variety of characterization approaches. The configuration resembling a root–soil system is shown in the images of scanning and transmission electron microscopy (SEM and TEM). With the incorporation of HA-MWNTs into the produced flocs, the X-ray diffraction (XRD) patterns of MWNTs completely disappeared. Fourier transform infrared spectra (FT-IR) and Mössbauer spectra suggested that the intervention of HA-hinged MWNTs increased the degree of polymerization and the particle size of the produced hydrous ferric oxide (HFO). Finally, both the effective sequestration of MWNTs by CFS demonstrated here and the high sorption capacity of MWNTs for phenanthrene implied that MWNTs might be used as a potential coagulant aid in water processing for the enhanced removal of hydrophobic organic chemicals.
Keywords: Multi-wall carbon nanotubes (MWNTs); Removal; Coagulation; Flocs; Mössbauer spectra;
Surface-immobilized PAMAM-dendrimers modified with cationic or anionic terminal functions: Physicochemical surface properties and conformational changes after application of liquid interface stress by Verena Katzur; Mirjam Eichler; Erika Deigele; Christiane Stage; Peter Karageorgiev; Jürgen Geis-Gerstorfer; Gottfried Schmalz; Stefan Ruhl; Frank Rupp; Rainer Müller (179-190).
Flexibility of polyamidoamine (PAMAM) dendrimer structure was retained after covalent immobilization to silicon model surfaces as proven by zeta potential and dynamic contact angle analysis.Display Omitted► Surface free energy is higher for dendrimer coatings than for corresponding monolayers. ► Surfaces modified with NH2-dendrimers turn hydrophobic during wetting with water. ► Surfaces modified with COOH-dendrimers turn hydrophilic during wetting with water. ► Surface charge formation is influenced by conformational changes of dendrimer branches. ► High flexibility of dendrimer branches is maintained after surface immobilization.Functionalization of surfaces with highly branched dendrimer molecules has gained attractiveness for various applications because the number of functional groups exceeds those of surfaces functionalized with self-assembled monolayers. So far, little is known about the physicochemical properties of dendrimer functionalized surfaces, especially if the flexibility of dendrimer structure remains after covalent immobilization. Therefore, the purpose of this study was to covalently immobilize polyamidoamine (PAMAM) dendrimer molecules exhibiting terminal amine and carboxyl groups to silicon model surfaces and to explore their properties and structure at the solid–air and solid–liquid interface. Our results show that the surface free energy is higher for PAMAM coatings than for analogously terminated SAMs and also higher for carboxyl than amine functionalized coatings. Furthermore, several findings suggest that conformational freedom of the dendrimers was preserved after surface immobilization. Wet compared to dry PAMAM―NH2 surfaces show reduced hydrophilicity and increased contact angle hysteresis, whereas PAMAM―COOH surfaces become more hydrophilic and showed decreased hysteresis. Streaming current measurements showed an unexpected behavior for PAMAM―COOH surfaces in that they reveal a net positive surface charge over a wide pH range in spite of the carboxylated periphery. All of these results indicate a certain degree of masking, burrowing, back-folding and unfolding of functional groups upon environmental changes.
Keywords: Polyamidoamine dendrimer; Self-assembled monolayer; Streaming potential; Dynamic contact angle; Surface free energy; Sum frequency spectroscopy;
Rapid and reversible switching between superoleophobicity and superoleophilicity in response to counterion exchange by Jin Yang; Zhaozhu Zhang; Xuehu Men; Xianghui Xu; Xiaotao Zhu; Xiaoyan Zhou; Qunji Xue (191-195).
Display Omitted► We use layer-by-layer assembly technology to fabricate superoleophobic surfaces. ► The surface is produced by the etching and boiling water treatment of the aluminum. ► The number of polyelectrolyte deposition cycles has a great effect on oleophobicity. ► Surface oleophobicity can be rapidly and reversibly switched by counterion exchange.We use a simple layer-by-layer (LbL) assembly and counterion exchange technology to rapidly and reversibly manipulate the oleophobicity of the textured aluminum surfaces. Such textured surfaces can be produced by the HCl etching and boiling water treatment of the flat aluminum plates. The LbL deposition of polyelectrolytes is performed on these surfaces to generate the polyelectrolyte multilayer films. The films are able to coordinate with perfluorooctanoate anions, leading to the surfaces with different oleophobicity. The resulting surface produced by 1.5 cycles of polyelectrolyte deposition exhibits superoleophobicity by displaying contact angles greater than 150° with low surface tension liquids. Counterion exchange in this polyelectrolyte multilayer emerged easily to control the surface composition, which leads to tunable wettability that can be rapidly and reversibly switched between superoleophobicity and superoleophilicity.
Keywords: Superoleophobic; Switchable; Rapid; Layer-by-layer; Counterion exchange;
Stable water and glycerol marbles immersed in organic liquids: From liquid marbles to Pickering-like emulsions by Edward Bormashenko; Roman Pogreb; Albina Musin (196-199).
Display Omitted► Marbles gave rise to water-in-oil and glycerol-in-oil Pickering-like emulsions. ► Non-polar liquids supported the formation of emulsions. ► Polar liquids did not support the formation of emulsions. ► Immersed marbles did not trap air. ► Direct contact of the liquid filling the marble and the surrounding liquid was demonstrated.Water and glycerol marbles coated with various powders and immersed in organic liquids gave rise to water-in-oil and glycerol-in-oil Pickering-like emulsions. Non-polar oils such as polydimethylsiloxane, toluene, xylenes and chlorinated solvents supported the formation of emulsions, whereas polar liquids such as dimethylsulfoxide, N,N,-dimethylformamide, acetone and ethanol did not. It is demonstrated that there is a direct contact between a liquid filling the immersed marble and the surrounding liquid. A phenomenological theory of the marbles’ sinking into emulsion is proposed.
Keywords: Liquid marbles; Surface tension; Organic liquids; Hydrophobic particles; Pickering emulsions;
Influence of substrate rigidity on primary nucleation of cell adhesion: A thermal fluctuation model by Jianyong Huang; Xiaoling Peng; Chunyang Xiong; Jing Fang (200-208).
Display Omitted► The mechanism of cell-substrate interfacial adhesion nucleation was investigated. ► Energy potential wells were used to describe conformational changes in integrins. ► A concept of nucleation domain was proposed to describe cell adhesion formation. ► The dependence of cell adhesion nucleation on substrate rigidities was elucidated.Experimental investigations have demonstrated that cells can actively sense and respond to physical aspects of their environments, such as substrate stiffness of biomaterials, via integrin receptors with the help of stochastic thermal undulations of cell membranes. This paper develops a physical model for the mechanism of integrin-dependent cell-substrate adhesion nucleation in order to investigate the influence of substrate stiffness on primary adhesion formation. In this model, a series of so-called energy potential wells are established to quantitatively describe force-driven conformational changes of integrins on elastic substrates with different rigidities. A concept of nucleation domain is proposed to characterize the necessary condition of integrin-mediated cell-substrate primary adhesion formation. In the framework of classical statistical mechanics, the competitive relationship is investigated between the local thermal undulations of plasma membranes and the conformational conversions of substrate-binding integrins. The quantitative dependence of integrin-mediated adhesion nucleation on substrate rigidities is systematically explored, which shows a reasonable agreement with existing experimental results.
Keywords: Integrin-dependent cell-substrate adhesion; Substrate stiffness; Thermal undulation; Energy potential well; Nucleation domain;
Investigation into the potential ability of Pickering emulsions (food-grade particles) to enhance the oxidative stability of oil-in-water emulsions by Maryam Kargar; Khorshid Fayazmanesh; Mina Alavi; Fotios Spyropoulos; Ian T. Norton (209-215).
Lipid oxidation was monitored by measuring the concentration of primary lipid oxidation product, using the peroxide value method. Increasing the Microcrystalline cellulose (MCC) concentration from 0.5% to 2.5% results in a decrease in the hydroperoxide formation due to their ability to scavenge free radicals through their negative charge and build a thick interface around droplets.Display Omitted► Oil-in-water emulsions stabilised by food grade particles. ► Physical and oxidative stability of samples were monitored over extended time. ► Increasing the particle concentration was found to decrease droplet size. ► MCC particles significantly reduced the lipid oxidation rate.In this study the potential ability of food-grade particles (at the droplet interface) to enhance the oxidative stability was investigated. Sunflower oil-in-water emulsions (20%), stabilised solely by food-grade particles (Microcrystalline cellulose (MCC) and modified starch (MS)), were produced under different processing conditions and their physicochemical properties were studied over time. Data on droplet size, surface charge, creaming index and oxidative stability were obtained. Increasing the food-grade particle concentration from 0.1% to 2.5% was found to decrease droplet size, enhance the physical stability of emulsions and reduce the lipid oxidation rate due to the formation of a thicker interfacial layer around the oil droplets. It was further shown that, MCC particles were able to reduce the lipid oxidation rate more effectively than MS particles. This was attributed to their ability to scavenge free radicals, through their negative charge, and form thicker interfacial layers around oil droplets due to the particles size differences. The present study demonstrates that the manipulation of emulsions’ interfacial microstructure, based on the formation of a thick interface around the oil droplets by food-grade particles (Pickering emulsions), is an effective approach to slow down lipid oxidation.
Keywords: Pickering emulsions; Lipid oxidation; Food-grade particles; Interfacial microstructure;
Application of kinetic Monte Carlo method to equilibrium systems: Vapour–liquid equilibria by E.A. Ustinov; D.D. Do (216-223).
Display Omitted► Novel application of Kinetic Monte Carlo (kMC) to describe equilibrium systems. ► An advantage of the kMC is the absence of discarded trial moves of molecules. ► kMC is more effective than traditional MC for analysis of inhomogeneous systems. ► The chemical potential is determined directly within the framework of kMC.Kinetic Monte Carlo (kMC) simulations were carried out to describe the vapour–liquid equilibria of argon at various temperatures. This paper aims to demonstrate the potential of the kMC technique in the analysis of equilibrium systems and its advantages over the traditional Monte Carlo method, which is based on the Metropolis algorithm. The key feature of the kMC is the absence of discarded trial moves of molecules, which ensures larger number of configurations that are collected for time averaging. Consequently, the kMC technique results in significantly fewer errors for the same number of Monte Carlo steps, especially when the fluid is rarefied. An additional advantage of the kMC is that the relative displacement probability of molecules is significantly larger in rarefied regions, which results in a more efficient sampling. This provides a more reliable determination of the vapour phase pressure and density in case of non-uniform density distributions, such as the vapour–liquid interface or a fluid adsorbed on an open surface. We performed kMC simulations in a canonical ensemble, with a liquid slab in the middle of the simulation box to model two vapour–liquid interfaces. A number of thermodynamic properties such as the pressure, density, heat of evaporation and the surface tension were reliably determined as time averages.
Keywords: Kinetic Monte Carlo; Vapour–liquid interface; Surface tension; Heat of evaporation;
Hydroxyapatite-coated carboxymethyl chitosan scaffolds for promoting osteoblast and stem cell differentiation by Rusdianto Budiraharjo; Koon Gee Neoh; En Tang Kang (224-232).
Display Omitted► CMCS scaffolds were coated with HAP of different morphology and coverage. ► High HAP coverage on scaffold enhances osteoblast attachment and proliferation. ► HAP coatings enhance osteoblastic differentiation of the osteoblasts and stem cells. ► Minimal effect of HAP morphology on enhancement of osteoblastic differentiation.The behavior of MC3T3 osteoblasts and human bone marrow stem cells on non-coated and hydroxyapatite (HAP)-coated carboxymethyl chitosan (CMCS) scaffolds was investigated in this study. Four HAP-coated scaffolds with different coating morphology and coverage were prepared by mineralization for 1 week in four different mineralizing solutions. Viability, attachment, proliferation, and differentiation of the osteoblasts on these scaffolds were evaluated, and an osteogenic gene expression analysis was carried out to investigate the osteoblastic differentiation of the stem cells. No cytotoxic effects were observed with both the non-coated and coated scaffolds. The non-coated CMCS scaffold supports attachment, proliferation, and differentiation of the osteoblasts and directs stem cell differentiation to osteoblast. Coating the scaffold with HAP substantially enhances these effects on the osteoblasts and stem cells. The main improvement was in the late stage of osteoblast differentiation since osteoblastic differentiation of the osteoblasts and stem cells in this stage was significantly enhanced by the coatings regardless of the variation in morphology and coverage. On the other hand, high HAP coverage was beneficial in stimulating osteoblast attachment and proliferation. This study demonstrates the good potential of HAP-coated CMCS scaffolds as osteogenic scaffolds to stimulate bone healing.
Keywords: Carboxymethyl chitosan; Hydroxyapatite; Scaffold; Osteoblast; Stem cell;
Electric-field-induced fabrication of covalently linked second-order nonlinear optical multilayer films on nonconductive substrates by Shiwei Wang; Lisha Zhao; Zhanchen Cui (233-235).
Display Omitted► NLO film was prepared on nonconductor by electric-field-induced assembly method. ► NLO film was assembled on the cladding layer directly. ► NLO films obtained here have excellent environmental and thermal stability.A highly stable second-order nonlinear optical multilayer film was constructed on insulating substrates using the electric-field-induced layer-by-layer assembly technique. The substrates used in this method could be arbitrary. In another, the substrates could be modified with polyanion solution by spin coating as cladding layer. Then, the nonlinear optical multilayer films were assembled on the cladding layer directly by the electric-field-induced layer-by-layer assembly technique. The resulting cross-linked multilayer films fabricated by this method displayed high optical transparency, good thermal stability, and excellent nonlinear optical properties which can be made into waveguide devices directly.
Keywords: Nonlinear optical; Electric-field-induced; Layer-by-layer assembly; Nonconductive substrates;