Journal of Colloid And Interface Science (v.365, #1)

Cover 1 (OFC).

Microfluidic circuit analysis I: Ion current relationships for thin slits and pipes by Dalton J.E. Harvie; Christian J.C. Biscombe; Malcolm R. Davidson (1-15).
Motivated by the requirements of volume and ion conservation in electrokinetic circuits, analytical and numerical methods for calculating the flowrate and ion currents in two dimensional microfluidic channels are developed.Display Omitted► Conservation of ion charge is required in electrokinetic circuits. ► Ion concentration is well represented by a local geometric mean in binary systems. ► This mean is uniform within a single channel when the flow is fully developed. ► The Boltzmann distribution is valid irrespective of double layer overlap. ► Ion current (and flowrate) expressions are derived for thin slits and pipes.Existing microfluidic circuit theories consider conservation of volume and conservation of total charge at each channel intersection (node) that exists within a circuit. However, in a strict sense conservation of number (or charge) for each ion species that is present should also be applied. To be able to perform such a conservation the currents due to the movement of each ion species (electrokinetic ion currents) that occur within each channel need to be known. Hence, we here present analytical and numerical methods for calculating these ion currents (and fluid flowrates) in Newtonian binary electrolyte solutions flowing within two-dimensional thin slits and pipes. Analytical results are derived in the limits of low potential, high potential, and thin double layers. We show that irrespective of double layer overlap, the Boltzmann distribution is valid provided that a local geometric mean is used for the reference ion concentration. While the real significance of the work lies in its application to multi-channel microfluidic circuit theory (see the accompanying paper of Biscombe et al. ), the present results show that even in single channels, ion current behaviour can be surprisingly complex.
Keywords: Electrokinetic; Microfluidic; Circuit; Electro-osmosis; Electroviscous;

Microfluidic circuit analysis II: Implications of ion conservation for microchannels connected in series by Christian J.C. Biscombe; Malcolm R. Davidson; Dalton J.E. Harvie (16-27).
When co-ions move against the flow in a microchannel network, different fully developed, steady-state flow solutions may arise even if the flow rate and total current are fixed.Display Omitted► Each channel within a circuit may have a different reference ion concentration. ► These concentrations are related by conservation of volume and ion currents. ► A single channel may have two flow solutions for a set flow rate and pair of ion currents. ► A complex circuit may have many flow solutions for the same inlet/outlet conditions.A mathematical framework for analysing electrokinetic flow in microchannel networks is outlined. The model is based on conservation of volume and total charge at network junctions, but in contrast to earlier theories also incorporates conservation of ion charge there. The model is applied to mixed pressure-driven/electro-osmotic flows of binary electrolytes through homogeneous microchannels as well as a 4:1:4 contraction–expansion series network. Under conditions of specified volumetric flow rate and ion currents, non-linear steady-state phenomena may arise: when the direction of the net co-ion flux is opposite to the direction of the net volumetric flow, two different fully developed, steady-state flow solutions may be obtained. Model predictions are compared with two-dimensional computational fluid dynamics (CFD) simulations. For systems where two steady states are realisable, the ultimate steady behaviour is shown to depend in part upon the initial state of the system.
Keywords: Electrokinetic; Microfluidic; Circuit; Electro-osmosis; Electroviscous;

Superhydrophobic polyaniline hollow bars: Constructed with nanorod-arrays based on self-removing metal-monomeric template by Wenbin Zhong; Yuntao Li; Yujie Wang; Xiaohua Chen; Yongxin Wang; Wantai Yang (28-32).
Display Omitted► Superhydrophobic hollow polyaniline bars are constructed with arrays of nanorods. ► Aniline and cadmium acetate can form self-removing metal-monomeric “template”. ► The molecular formula of “template” is Cd(aniline)0.7(OH)1.1(Ac)0.9. ► The “template” is decomposed during the polymerization of aniline. ► Polyaniline multidimensional architectures can be prepared without the “template”.Superhydrophobic hollow polyaniline (PANI) bars assembled from nanorod-arrays were prepared in the presence of metal-monomeric template. Toward preparing these PANI bars, self-assembling and “template” methods were simultaneously applied. The self-removing metal-monomeric “template” was probably formed when a high concentration of aniline (0.5 M) was added into the cadmium acetate solution, and then decomposed gradually during the oxidative polymerization of aniline. In addition, a superhydrophobic flower-like PANI hierarchical structure was also prepared without the “template” (cadmium acetate aqueous solution containing a low concentration of aniline (0.05 M)). The formation mechanism of the hollow PANI bars was discussed.
Keywords: Polyaniline; Array; Superhydrophobicity; Template; Self-assembly;

Mitoxantrone-loaded zeolite beta nanoparticles: Preparation, physico-chemical characterization and biological evaluation by Stefan Grund; Tristan Doussineau; Dagmar Fischer; Gerhard J. Mohr (33-40).
A new host–guest system consisting of zeolite beta nanoparticles as host and mitoxantrone as guest shows interesting features in terms of optical properties as well as in terms of cytotoxicity when applied to cancer cells. The described functional host–guest nanosystem appears highly promising towards the development of new theranostic nanodevices.Display Omitted► 100 nm-sized mitoxantrone-loaded spherical zeolite beta nanoparticles. ► Mitoxantrone loading of 6.8 μmol/g. ► Low toxicity of bare zeolite beta. ► Efficient cytotoxicity of mitoxantrone-loaded zeolite beta toward cancer cells. ► NIR optical properties.This article describes the preparation and the physico-chemical characterization of a new host–guest system consisting of zeolite beta nanoparticles as host and mitoxantrone as guest. The resulting host–guest system mitoxantrone@beta is characterized in terms of morphology (transmission electron microscopy, dynamic light scattering), structure (powder wide-angle X-ray diffraction, nitrogen sorption), surface charge (ξ-potential measurements), and optical properties (UV–visible absorption, steady-state fluorescence). Mitoxantrone@beta particles are monodisperse in size with a mean diameter centered around 100 nm. Mitoxantrone guest molecules are adsorbed at the micropore entrances of zeolite host. Resulting nanoparticles retrieve the interesting optical properties of guest molecules with a fluorescence emission band in the near-infrared region. Mitoxantrone loading is comparatively evaluated by three different means (elemental analysis, direct and indirect UV–visible absorption studies) showing a loading level of 6.8 μmol/g. Mitoxantrone@beta nanoparticles also show a noticeable cytotoxic effect when applied to cancer cells.
Keywords: Zeolites; Mitoxantrone; Nanoparticles; Host–guest system; Cytostatics; Cancer;

An in situ, one-pot surface functionalization has been used to synthesize bright luminescence, colloidal stable silica coated CdSe/ZnS nanocomposite.Display Omitted► Developing an in situ, one-pot preparation procedure for functionalized nanocomposites. ► Minimizing nanoparticles aggregation by introducing an optimum amount of active functional groups. ► Single or multiple nanoparticles has been coated with silica shell. ► Sequence of addition of TEOS and organosilanes has important effect on properties of final product. ► Suggesting the mechanism of producing bright luminescence or colloidal stable nanoparticles.In this article, a systematic study of the design and development of surface-modification schemes for silica coated nanocomposite via an in situ, one-pot way is presented. Silica coated CdSe/ZnS nanoparticles were prepared in a water-in-oil microemulsion and subsequently surface modified via addition of various organosilane reagents to the microemulsion system. The resulting functionalized composite nanoparticles were characterized by different techniques like Transmission Electron Microscopy (TEM), photoluminescence spectroscopy and zeta-potential measurements. The results demonstrate that depending on the sequence of addition of silica precursors and organosilanes the product can show bright luminescence or considerable colloidal stability. The organosilanes molecules which are used here, act both as a stabilizer of the microemulsion system (regarding the charge compensation) and as a functional group the final product on top of silica shell.Using these surface-modification process, silica coated nanoparticles can be more readily conjugated with biomolecules and used as highly luminescent, sensitive, and reproducible labels in bioanalytical applications. Most importantly such surface functionalization could pave the way for controlled multi-mixed nanoparticles encapsulation (for example magnetic and QD nanoparticles).
Keywords: Nanocomposite; Microemulsion; Silica shell; Zeta-potential; Surface functionalization; Photoluminescence;

A novel photoanode architecture of dye-sensitized solar cells based on TiO2 hollow sphere/nanorod array double-layer film by Guotian Dai; Li Zhao; Jing Li; Li Wan; Fan Hu; Zuxun Xu; Binghai Dong; Hongbing Lu; Shimin Wang; Jiaguo Yu (46-52).
The novel photoanode based on TiO2 hollow sphere/nanorod double-layer film has the highest η, which was due to its relatively large surface area, enhanced light-harvesting capability, small dark current, low transport resistance and long electron lifetime.Display Omitted► Double-layer film photoanode was fabricated based on TiO2 nanorod arrays and hollow spheres. ► TiO2 hollow sphere overlayer had large surface area for effective adsorption of dye molecules. ► TiO2 nanorod array underlayer could improve electron transport rate and light harvesting efficiency. ► DSSCs based on TiO2 double-layer film had the maximum conversion efficiency. ► Our work opened up a new avenue for the development of DSSCs with high efficiency.A novel TiO2 double-layer (DL) film consisting of TiO2 hollow spheres (HSs) as overlayer and single-crystalline TiO2 nanorod arrays (RAs) as underlayer was designed as the photoanode of dye-sensitized solar cells (DSSCs). This new-typed TiO2 HS/RA DL film could significantly improve the efficiency of DSSCs owing to its synergic effects, i.e. the relatively large specific surface area of TiO2 HSs for effective dye adsorption, enhanced light harvesting capability originated from TiO2 RA film, and rapid interfacial electron transport in one-dimensional TiO2 nanorod arrays. The overall energy-conversion efficiency of 4.57% was achieved by the formation of TiO2 DL film, which is 16% higher than that formed by TiO2 HS film and far larger than that formed by TiO2 RA film (η  = 0.99%). The light absorption and interfacial electron transport, which play important roles in the efficiency of DSSCs, were investigated by UV–vis absorption spectra and electrochemical impedance spectra.
Keywords: Dye-sensitized solar cells; Titanium dioxide; Hollow sphere; Nanorod array; Double-layer film;

Interfacial and self-assembly properties of bolaamphiphilic compounds derived from a multifunctional oil by Tanya Hutter; Charles Linder; Eliahu Heldman; Sarina Grinberg (53-62).
Self assembly characteristics, critical aggregation concentration and effect of molecular structure of cationic bolaamphiphiles derived from vernonia oil in aqueous solutions.Display Omitted► CAC and interfacial characteristics of novel cationic bolaamphiphiles were studied. ► Configuration at air/water interface vs. bola structure and interfacial parameters. ► Molecular structure vs. self-aggregate geometry is discussed. ► Monolayered membrane vesicles and fibers are among the formed aggregate structures. ► Amides instead esters at the hydrophobic domain increase CAC value significantly.The self-assembly characteristics in aqueous solutions of cationic bolaamphiphiles with systematic changes in their chemical structure is described with respect to their interfacial properties within water and at the air/water interface. Six cationic bolaamphiphiles were synthesized from multifunctional vernonia oil with the following variations: (a) two different alkyl chain lengths connecting the head groups, (b) polar ester or hydrogen bonding amide groups within the hydrophobic domain, and (c) an acetylcholine cationic head group with different conjugation sites to the alkyl chain. Surface tension measurements were used for determining critical aggregation concentration (CAC) values and air/water interfacial parameters such as ‘effectiveness’, surface excess concentration and area occupied by one molecule in the air/water interface. Fluorescent studies with pyrene were used to characterize CAC properties within the aqueous volume and transmission electron microscopy (TEM) for determining the aggregate structure’s size, homogeneity and morphology. A bolaamphiphile molecular structure vs. interfacial property relationship was derived from this data which could be used to determine the molecular structure properties needed to generate interfacial forces to form either spherical vesicles or fibrous networks. The effects of the aliphatic chain length, head group orientation and functional groups within the hydrophobic domain on CAC, surface tension properties and self-aggregate morphology are described. Most bolaamphiphiles studied had CAC values in the 10–190 μM range, while two out of the six were found to assemble into MLM spherical vesicles with diameters ranging up to 120 nm suitable for drug delivery applications. Others formed a gelatinous network of fibers or multi-lamellar vesicles.
Keywords: Critical aggregation concentration; Bolaamphiphiles; Self-assembly; Vesicles; Interfacial properties;

Click-chemistry for surface modification of monodisperse-macroporous particles by Aslıhan Bayraktar; Berna Saraçoğlu; Çiğdem Gölgelioğlu; Ali Tuncel (63-71).
Display Omitted► The hydrophilicity of monodisperse-macroporous particles was adjusted via click-chemistry. ► The hydrophilic/hydrophobic molecular brushes on the particles were generated. ► Protein adsorption behavior was efficiently regulated by the surface modification.In this study, click chemistry was proposed as a tool for tuning the surface hydrophilicity of monodisperse-macroporous particles in micron-size range. The monodisperse-porous particles carrying hydrophobic or hydrophilic molecular brushes on their surfaces were obtained by the proposed modification. Hydrophilic poly(glycidyl methacrylate-co-ethylene dimethacrylate), poly(GMA-co-EDM) particles were hydrophobized by the covalent attachment of poly(octadecyl acrylate-co-propargyl acrylate), poly(ODA-co-PA) copolymer onto the particle surface via triazole formation by click chemistry. In the second part, Hydrophobic poly(4-chloromethylstyrene-co-divinylbenzene), poly(CMS-co-DVB) particles were hydrophilized by the covalent attachment of poly(vinyl alcohol), PVA onto their surface also via triazole formation by click chemistry. The presence of PVA and poly(ODA-co-PA) copolymer on the corresponding particles was shown by FTIR-DRS. After click-coupling reactions applied for both hydrophobic poly(CMS-co-DVB) and hydrophilic poly(GMA-co-EDM) particles, the marked changes in surface polarity were shown by contact angle measurements. Protein adsorption characteristics of plain and modified particles were investigated for both materials. In the isoelectric point of albumin, the non-specific albumin adsorption decreased from 225 to 80 mg/g by grafting PVA onto the poly(CMS-co-DVB) beads. On the other hand, the non-specific albumin adsorption onto the plain poly(GMA-co-EDM) beads increased from 50 to 400 mg/g by the covalent attachment of poly(ODA-co-PA) copolymer onto the bead-surface via click chemistry. The protein adsorption behavior was efficiently regulated by the covalent attachment of appropriate molecular brushes onto the surfaces of selected particles. The results indicated that “click chemistry” was an efficient tool for controlling the polarity of monodisperse-macroporous particles.
Keywords: Click-chemistry; Surface modification; Monodisperse-porous particles; Chromatographic packing; High performance liquid chromatography;

Colloidal probe atomic force microscopy was used to measure the force profile between weakly-charged probe particle and substrate in a solution of highly-charged, adsorbing nanoparticles.Display Omitted► Interaction force between weakly-charged microparticle and plate measured using AFM. ► Solution contained highly-charged nanoparticles that adsorb to particle and plate. ► At low nanoparticle concentrations, strong electrostatic repulsion develops. ► At higher nanoparticle, concentrations depletion and structural forces develop. ► Behavior is fundamentally different from nonadsorbing nanparticle systems.We have measured the force between a weakly charged micron-sized colloidal particle and flat substrate in the presence of highly charged nanoparticles of the same sign under solution conditions such that the nanoparticles physically adsorb to the colloidal particle and substrate. The objective was to investigate the net effect on the force profile between the microparticle and flat substrate arising from both nanoparticle adsorption and nanoparticles in solution. The experiments used colloidal probe atomic force microscopy (CP-AFM) to measure the force profile between a relatively large (5 μm) colloidal probe glass particle and a planar glass substrate in aqueous solutions at varying concentrations of spherical nanoparticles. At very low nanoparticle concentrations, the primary effect was an increase in the electrostatic repulsion between the surfaces due to adsorption of the more highly charged nanoparticles. As the nanoparticle concentration is increased, a depletion attraction formed, followed by longer-range structural forces at the highest nanoparticle concentrations studied. These results suggest that, depending on their concentration, such nanoparticles can either stabilize a dispersion of weakly-charged colloidal particles or induce flocculation. This behavior is qualitatively different from that in nonadsorbing systems, where the initial effect is the development of an attractive depletion force.
Keywords: Depletion forces; Colloidal probe atomic force microscopy; Binary colloidal systems; Interparticle forces; Colloidal forces;

Mechanism of structural networking in hydrogels based on silicon and titanium glycerolates by Tat’yana G. Khonina; Alexander P. Safronov; Elena V. Shadrina; Maria V. Ivanenko; Anna I. Suvorova; Oleg N. Chupakhin (81-89).
Different mechanisms of networking in hydrogels based on silicon tetraglycerolate (STG), titanium tetraglycerolate (TTG), and combined silicon tetraglycerolate–titanium tetraglycerolate (STG/TTG) precursors.Display Omitted► The gelation of silicon– and titanium–glycerol precursors was investigated. ► The gelation time depends on pH or electrolyte addition in an opposite way. ► Silicon–glycerol hydrogel is a polymeric single-phase system. ► Titanium–glycerol hydrogels are colloid or polymeric systems.Formation of organic/inorganic hydrogels based on silicon– and titanium–glycerol precursors synthesized by transesterification of alkoxy derivatives in excess of glycerol was investigated. The precursors in excess of glycerol and obtained gels were studied by chemical and physical methods including gelation kinetics, IR spectroscopy, XRD, dynamic and electrophoretic light scattering, mechanical deformation, which disclosed the basic difference in the gelation mechanism and structure of network in the hydrogels. Due to this difference, the gelation time of silicon– and titanium–glycerol precursors depended on pH or electrolyte addition in an opposite way. In the wide pH range, silicon–glycerol hydrogel was a polymeric single-phase system formed by the polymeric network homogeneously swollen in liquid water/glycerol medium. Flory–Rehner theory applied to the elastic modulus of these gels gave 40–180 monomer base units in the subchains of the network depending on water content in the gel. The mechanism of networking was three-dimensional polycondensation promoted by the electrically charged functional groups attached to the flexible polymeric chains. Electrolyte solutions provided the gelation according to Hofmeister series. Titanium–glycerol hydrogels were heterogeneous colloid systems at pH > 1.5 and single-phase polymeric gels at lower pH. Electrolyte solutions provided the gelation according to Schultze–Hardy rule.
Keywords: Sol–gel; Silicon–glycerol precursor; Titanium–glycerol precursor; Silicon tetraglycerolate; Titanium tetraglycerolate; Hydrogel; Colloidal gelation; Polymeric gelation; Network structure;

Ultrathin and nanostructured ZnO-based films for fluorescence biosensing applications by Cristina Satriano; Maria Elena Fragalà; Yana Aleeva (90-96).
Display Omitted► Ultrathin ZnO–SiO2 films deposited by integrated colloidal lithography and MOCVD. ► Thicknesses, morphologies and surface chemical compositions studied by XPS and SEM. ► Optical properties investigated by LSM and FRAP experiments. ► The emission of the ZnO-based films is significantly enhanced by protein adsorption. ► Fluorescence sensing tunable by chemical/topographical patterning of ZnO–SiO2 films.The fluorescence-based sensing capability of ultrathin ZnO–SiO2 nanoplatforms, deposited by an integrated approach of colloidal lithography and metal organic chemical vapor deposition, has been investigated upon adsorption of fluorescein-labeled albumin, used as model analyte biomolecule. The protein immobilization process after spontaneous adsorption/desorption significantly enhances the green emission of the different ZnO-based films, as evidenced by scanning confocal microscopy, corresponding to a comparable protein coverage detected by X-ray photoelectron spectroscopy. Moreover, experiments of fluorescence recovery after photobleaching evidence that the protein lateral diffusion at the biointerface is affected by the chemical and/or topographical patterning of hybrid ZnO–SiO2 surfaces. The used approach is very promising for biomolecular detection applications of these ZnO–SiO2 nanoplatforms, by simple sizing of the 2D vs. 3D patterning design, which in turn is accomplished by the fine tuning of the integrated colloidal lithography–chemical vapor deposition processes.
Keywords: ZnO thin film; MOCVD–colloidal lithography; Biosensing; Protein adsorption; Fluorescence recovery after photobleaching;

Single-step fabrication of patterned gold film array by an engineered multi-functional peptide by Marketa Hnilova; Dmitriy Khatayevich; Alisa Carlson; Ersin Emre Oren; Carolyn Gresswell; Sam Zheng; Fumio Ohuchi; Mehmet Sarikaya; Candan Tamerler (97-102).
Display Omitted► Combinatorially selected inorganic-binding peptides are versatile molecular linkers. ► Peptides control assembly and in situ synthesis of nanometallic particles on surface. ► Tested peptides can functionalize surfaces at ambient conditions. ► Bio-enabled fabrication route offers modularity, flexibility, biocompatibility.This study constitutes a demonstration of the biological route to controlled nano-fabrication via modular multi-functional inorganic-binding peptides. Specifically, we use gold- and silica-binding peptide sequences, fused into a single molecule via a structural peptide spacer, to assemble pre-synthesized gold nanoparticles on silica surface, as well as to synthesize nanometallic particles in situ on the peptide-patterned regions. The resulting film-like gold nanoparticle arrays with controlled spatial organization are characterized by various microscopy and spectroscopy techniques. The described bio-enabled, single-step synthetic process offers many advantages over conventional approaches for surface modifications, self-assembly and device fabrication due to the peptides’ modularity, inherent biocompatibility, material specificity and catalytic activity in aqueous environments. Our results showcase the potential of artificially-derived peptides to play a key role in simplifying the assembly and synthesis of multi-material nano-systems in environmentally benign processes.
Keywords: Gold-nanoparticle arrays; Inorganic-binding peptides; Micro-contact printing; Peptide-mediated nucleation;

Copper nanoparticles incorporated with conducting polymer: Effects of copper concentration and surfactants on the stability and conductivity by Long Quoc Pham; Jong Hwa Sohn; Chang Woo Kim; Ji Hyun Park; Hyun Suk Kang; Byung Cheol Lee; Young Soo Kang (103-109).
Display Omitted► Copper nanoparticle was synthesized with CTAB and PVP. ► Conducting ink prepared with synthesized Cu nanoparticles and PEDOT/PSS shows an improvement in conductivity. ► SDBS was used to protect the conductive ink from oxidation in ambient air.Copper nanoparticles are prepared in aqueous solution by reducing copper ions with hydrazine hydrate in the presence of cetyl trimethylammonium bromide (CTAB) and polyvinylpyrrolydone (PVP) as stabilizers. With only CTAB was used as stabilizer, copper nanoparticles are aggregated and partially oxidized to Cu2O. When both PVP and CTAB were used, dispersed copper nanoparticles with 56 nm diameter were obtained. Copper nanoparticles are simply mixed with poly (3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) in aqueous solution to form conducting composite. The effect of copper weight percent and surfactants on the conductivity and stability of the composite has been investigated.
Keywords: Copper nanoparticles; Conducting polymer; Conducting ink;

Mechanism of interaction of hydrocalumites (Ca/Al-LDH) with methyl orange and acidic scarlet GR by Ping Zhang; Guangren Qian; Huisheng Shi; Xiuxiu Ruan; Jing Yang; Ray L. Frost (110-116).
Methyl orange and acidic scarlet GR have different routes reacted with Ca/Al-LDH-Cl. Methyl orange is through intercalation into Ca/Al-LDH-Cl, while acidic scarlet GR is only adsorbed on with Ca/Al-LDH-Cl.Display Omitted► Hydrocalumites (Ca/Al-LDH) were synthesized and characterized. ► Methyl orange and acidic scarlet GR modified the Ca/Al-LDH-Cl. ► This work has shown that methyl orange was intercalated with Ca/Al-LDH-Cl. ► Acidic scarlet GR was adsorbed onto Ca/Al-LDH-Cl surfaces.The development of new materials for water purification is of universal importance. Among these types of materials are layered double hydroxides (LDHs). Non-ionic materials pose a significant problem as pollutants. The interaction of methyl orange (MO) and acidic scarlet GR (GR) adsorption on hydrocalumite (Ca/Al-LDH-Cl) was studied by X-ray diffraction (XRD), infrared spectroscopy (MIR), scanning electron microscope (SEM), and near-infrared spectroscopy (NIR). The XRD results revealed that the basal spacing of Ca/Al-LDH-MO was expanded to 2.45 nm, and the MO molecules were intercalated with a interpenetrating bilayer model in the gallery of LDH, with 49° tilting angle. Yet, Ca/Al-LDH-GR was kept the same d-value as Ca/Al-LDH-Cl. The NIR spectrum for Ca/Al-LDH-MO showed a prominent band around 5994 cm−1, assigned to the combination result of the N―H stretching vibrations, which was considered as a mark to assess MO ion intercalation into Ca/Al-LDH-Cl interlayers. From SEM images, the particle morphology of Ca/Al-LDH-MO mainly changed to irregular platelets, with a “honey-comb” like structure. Yet, the Ca/Al-LDH-GR maintained regular hexagon platelets, which was similar to that of Ca/Al-LDH-Cl. All results indicated that MO ion was intercalated into Ca/Al-LDH-Cl interlayers, and acidic scarlet GR was only adsorbed upon Ca/Al-LDH-Cl surfaces.
Keywords: Hydrocalumites; Methyl orange (MO); Acidic scarlet GR (GR); Intercalation; Adsorption; Near-infrared spectroscopy (NIR);

Growth Kinetics of uncapped platinum nanocrystals follows a diffusion-limited Ostwald ripening whereas an additional contribution from surface reaction is needed in the presence of a capping agent.Display Omitted► Growth kinetics of platinum nanocrystals was studied by SAXS. ► Observed Ostwald ripening as the growth mechanism in the absence of any capping agent. ► Deviation from Ostwald ripening when PVP was used as the capping agent. ► Role of the surface becomes important in presence of a capping agent.In order to examine the applicability of the diffusion-limited Ostwald ripening model to the growth kinetics of nanocrystals, platinum nanocrystals prepared by two different methods have been investigated by a combined use of small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). One of the methods of synthesis involved the reduction of chloroplatinic acid by sodium citrate while in the other method reduction was carried out in the presence of polyvinylpyrrolidone (PVP) as a capping agent. The growth of platinum nanocrystals prepared by citrate reduction in the absence of any capping agent follows a Ostwald ripening growth with a D 3 dependence. In the presence of PVP, the growth of platinum nanocrystals does not completely follow the Ostwald ripening model, making it necessary to include a surface reaction term in the growth equation. Thus, the growth of platinum nanocrystals in the presence of PVP has contributions both from diffusion and surface reaction, exhibiting a D 3  +  D 2 type behavior.
Keywords: Platinum nanocrystals; Diffusion-limited growth; Surface reaction-limited growth; Small angle X-ray scattering; Transmission electron microscopy;

Synthesis of a β-cyclodextrin-modified Ag film by the galvanic displacement on copper foil for SERS detection of PCBs by Jingpeng Yuan; Yongchao Lai; Junling Duan; Quanqin Zhao; Jinhua Zhan (122-126).
β-Cyclodextrin-modified Ag film (β-CD-Ag) was synthesized through one-pot step and used as SERS-active substrate, which exhibited effective sensitivity for PCBs detection at low concentration.Display Omitted► The SERS-active substrate was synthesized with the assistance of β-cyclodextrin. ► The characterization confirmed β-cyclodextrin was immobilized on the substrate. ► The substrate effectively enriched low concentration polychlorinated biphenyls. ► The SERS substrates have high enhancement factor for detecting PCBs.A mono-6-thio-β-cyclodextrin-modified silver film was synthesized via galvanic displacement on copper foil. The prepared silver films could enrich non-polar polychlorinated biphenyls (PCBs) molecules from hydrophilic phase using thiolate β-cyclodextrins (SH-β-CDs) as receptors. The components of as-prepared Ag-coated-Cu (Ag–Cu) film were confirmed by powder X-ray diffraction (XRD). Both surface-enhanced Raman spectroscopy (SERS) and energy dispersive X-ray spectroscopy (EDS) measurements gave strong evidences that the thiolated β-cyclodextrins (SH-β-CDs) had been immobilized on the surface of silver film. Compared to the substrates prepared in the absence of SH-β-CD, the surface morphology of the CD-modified Ag films was obviously changed. The interfacial enrichment and the capability of substrates to form inclusion complexes with PCBs molecules were tested by using PCB-15 (4,4′-dichlorobiphenyl) as the probe molecules via SERS technique. The measured SERS spectra could distinguish the PCB-15 molecules at micro-molar level according to the most intense CCC bending in-plane mode of PCBs. The enhancement factor (EF) of the SERS substrates for PCB-15 was 1.2 × 105, which was comparable with a number of previous reports.
Keywords: Polychlorinated biphenyls (PCBs); Detection; Surface-enhanced Raman spectroscopy (SERS); Cyclodextrins (CDs); Silver films;

LAPONITE® assisted dispersion of carbon nanotubes in water by Maksym Loginov; Nikolai Lebovka; Eugene Vorobiev (127-136).
Display Omitted► LAPONITE®-assisted dispersion of MWCNT results in formation of stable suspension. ► LAPONITE® forms the hydrophilic shells on the surface of hydrophobic MWCNTs. ► Efficient dispersability requires critical LAPONITE®/MWCNT ratio X  ≈ 0.25 wt/wt. ► Critical ratio X corresponds to complete coverage of MWCNTs by LAPONITE®. ► Stabilized MWCNTs form percolation networks above 0.058 wt%.The ability of LAPONITE® to stabilize aqueous suspensions of multiwalled carbon nanotubes (MWCNTs) was investigated with the help of analytical centrifugation, microscopic image analysis, and measurements of electrical conductivity of hybrid LAPONITE® + MWCNT suspensions. The impact of nanotube concentration Cn (0.0025–0.5 wt%) and LAPONITE®/MWCNTs ratio X (varied within 0–1 wt/wt) on the properties of LAPONITE® + MWCNT hybrid suspensions was discussed. It was observed that sonication of MWCNTs at critical minimal concentration of LAPONITE® Xc  ≈ 0.25 ± 0.05 resulted in efficient dispersion and formation of stabilized suspensions of individual nanotubes. The stabilization of nanotubes in the presence of LAPONITE® was explained by adsorption of LAPONITE® particles and formation of a hydrophilic charged shell on the surface of nanotubes. Increase of MWCNT concentration above the critical value resulted in percolation and formation of spatially extended electrically conductive networks of particles.
Keywords: LAPONITE®; Multiwalled carbon nanotubes (MWCNTs); Aqueous suspensions; Ultrasonication; Stabilization; Analytical centrifugation; Electrical conductivity; Percolation;

Display Omitted► Ultra-large-pore FDU-12 (ULP-FDU-12) silica with Fm3m symmetry was synthesized. ► Ethylbenzene was identified as excellent swelling agent for synthesis of ULP-FDU-12. ► Unit-cell size of as-synthesized and calcined FDU-12 reached 55 and 52 nm. ► FDU-12 with pore diameter up to 36 nm was obtained. ► Closed-pore FDU-12 was obtained through thermally-induced pore closure at 400–450 °C.Ultra-large-pore FDU-12 (ULP-FDU-12) silica with face-centered cubic structure (Fm3m type) of spherical mesopores was synthesized using Pluronic F127 triblock copolymer (EO106PO70EO106) and ethylbenzene as a new micelle expander at initial temperature of 14 °C. Ethylbenzene was identified on the basis of its reported extent of solubilization in poly(ethylene oxide)–poly(propylene oxide)-type surfactant micelles, which was similar to that of xylene, the latter having been shown earlier to afford ULP-FDU-12. The unit-cell parameter of as-synthesized ULP-FDU-12 was 55 nm, which is similar to the highest value reported when xylenes (mixture of isomers) were used and larger than that achieved with trimethylbenzene. The unit-cell parameter of calcined ULP-FDU-12 reached 52 nm. For the obtained materials, the nominal pore cage diameter calculated from nitrogen adsorption reached 32 nm, whereas the actual pore cage diameter calculated using the geometrical relation was 36 nm. The pore entrance size was below 5 nm before the acid treatment, but was greatly enlarged as a result of the treatment. The sample prepared without hydrothermal treatment was converted to ordered closed-pore silica at as low as 400–450 °C. Our study confirms the ability to select micelle expanders on the basis of data on solubilization of compounds in micelle solutions.
Keywords: Ordered mesoporous silica; FDU-12; Cage-like mesopore; Micelle expander; Closed-pore silica;

Targeted therapy of SMMC-7721 liver cancer in vitro and in vivo with carbon nanotubes based drug delivery system by Zongfei Ji; Gaofeng Lin; Qinghua Lu; Lingjie Meng; Xizhong Shen; Ling Dong; Chuanlong Fu; Xiaoke Zhang (143-149).
A highly effective targeted DDS based on chitosan and folic acid modified single walled carbon nanotubes for controllable loading/release of anti-cancer agent doxorubicin was constructed. The obtained DDS not only effectively killed the HCC SMMC-7721 cell lines and depressed the growth of liver cancer, but also displayed much less in vivo toxicity than free doxorubicin..Display Omitted► We construct FA/CHI/SWNTs as tumor targeting delivery vehicles for doxorubicin. ► DOX/FA/CHI/SWNTs can effectively kill the SMMC-7721 liver cancer cell and depress the growth of liver cancer on nude mice rather than DOX. ► DOX/FA/CHI/SWNTs have less in vivo toxicity than DOX.A new type of drug delivery system (DDS) involved chitosan (CHI) modified single walled carbon nanotubes (SWNTs) for controllable loading/release of anti-cancer doxorubicin (DOX) was constructed. CHI was non-covalently wrapped around SWNTs, imparting water-solubility and biocompatibility to the nanotubes. Folic acid (FA) was also bounded to the outer CHI layer to realize selective killing of tumor cells. The targeting DDS could effectively kill the HCC SMMC-7721 cell lines and depress the growth of liver cancer in nude mice, showing superior pharmaceutical efficiency to free DOX. The results of the blood routine and serum biochemical parameters, combined with the histological examinations of vital organs, demonstrating that the targeting DDS had negligible in vivo toxicity. Thus, this DDS is promising for high treatment efficacy and low side effects for future cancer therapy.
Keywords: Carbon nanotubes; Chitosan; Folic acid; Drug delivery system; Liver cancer;

Display Omitted► Quadruplex (G4 DNA)/monolayer interactions at the air–water interface were studied. ► G4 DNA shifted πA isotherm of the cationic film to lower molecular areas. ► The cationic monolayer induced formation of multistranded assemblies of G-4 DNA. ► Potassium or sodium quadruplexes slowed down formation of multi-stranded assemblies.We report on the interactions between a 21-mer quadruplex-forming oligonucleotide bearing human telomere sequence of dG3(T2AG3)3 (G4 DNA) and a positively charged dioctadecyldimethylammonium bromide (DODAB) monolayer at the air–aqueous interface, studied by surface film balance measurements. In the presence of G4 DNA, the πA isotherm of the cationic Langmuir film shifted to lower molecular areas when compared with the reference isotherm recorded on the subphase containing only 50 mM triethylamine–acetate (TEAA) buffer. The presence of quadruplex-stabilizing metal cations (K+ or Na+) further affected profiles of πA isotherms. Further insight into processes related to the G4 DNA – monolayer interactions was provided by recording time profiles of the surface pressure of monolayer at a constant mean molecular area. In these experiments G4 DNA and/or metal ions were sequentially injected under the monolayer surface. Results indicated that multistranded assemblies of G4 DNA were formed at the monolayer interface even in the absence of metal ions, which suggested that the charged cationic surface of Langmuir monolayer induced aggregation of guanine-rich DNA strands. The presence of sodium and potassium ions inhibited formation of multi-stranded assemblies through the competitive G-quadruplex formation but to different extent that might be related to the differences in stability and topology of both quadruplexes.
Keywords: Air–aqueous interface; G-quadruplex; Guanine-gel; Human telomere DNA; Langmuir monolayer;

Design and characterization of Ni2+ and Co2+ decorated Porous Magnetic Silica spheres synthesized by hydrothermal-assisted modified-Stöber method for His-tagged proteins separation by M. Benelmekki; E. Xuriguera; C. Caparros; E. Rodríguez-Carmona; R. Mendoza; J.L. Corchero; S. Lanceros-Mendez; Ll.M. Martinez (156-162).
Display Omitted► Synthesis of Porous Magnetic Silica (PMS) by one-step cost-effective process. ► Decoration of the PMS spheres by Co2+ and Ni2+. ► Evaluation of the binding capacity of the PMS spheres to the H6-tagged GFP protein. ► Binding capacity depends strongly on the amount of cations adsorbed by the PMS spheres.The complete elimination of enzymes from the reaction mixture and the possibility of its recycling for several rounds result in great benefits, allowing the reduction of the enzyme consumption and their usability in continuous processes. In this work, it is evaluated the capture of a H6-tagged green fluorescence protein (GFP-H6) on porous magnetic spheres using the Co2+ and Ni2+ affinity adsorption as a possible cost-effective and up-scaled alternative way for the immobilization of His-tagged proteins. For this purpose, Porous Magnetic Silica (PMS) spheres were synthesized by one-step hydrothermal-assisted modified-Stöber method. The obtained spheres have a homogenous size distribution of 400 nm diameter. The γ-Fe2O3 nanoparticles are homogenously distributed in the silica matrix. The obtained PMS spheres have a saturation magnetization of about 10 emu/g. Magnetophoresis measurements show a total separation time of 16 min at 60 T/m. The obtained PMS spheres were successfully and homogenously decorated with Co2+ and Ni2+ and then evaluated for the capture of a GFP-H6 protein. The results were compared with the performance of the commercial beads Dynabeads® His-Tag Isolation & Pulldown.
Keywords: Magnetophoresis; Magnetic particles; His-Tag proteins; Metal affinity; Surfactant;

Homogeneous functional Ni–P/ceramic nanocomposite coatings via stable dispersions in electroless nickel electrolytes by Yoram de Hazan; Franziska Knies; Dariusz Burnat; Thomas Graule; Yoko Yamada-Pittini; Christos Aneziris; Maren Kraak (163-171).
Display Omitted► Co-deposition of functional Ni–P/ceramic nanocomposite coatings is studied. ► Nanoparticle stability in plating electrolyte is studied at high temperature. ► Comb-polyelectrolyte surfactants provide steric stability up to 60–75 °C. ► The CFT of dispersions in electrolyte is increased by 2 °C per 1% propylene glycol. ► Homogeneous Ni–P nanocomposite coatings with 22 vol.% TiO2 are demonstrated.Stable nanoparticle dispersions in concentrated electrolytes are prerequisite for a variety of advanced nanocomposites prepared by deposition techniques. In this work we investigate the synthesis of electroless Ni–P/functional ceramic coatings from concentrated electrolytes containing functional nanoparticles such as TiO2, α-Fe2O3, ITO, and CeO2. Stable nanoparticle dispersions in both low and high phosphorus electrolytes are achieved at plating temperatures (80–90 °C) by a generalized scheme employing comb-polyelectrolyte and antifreeze additives. Dispersion stability at room temperature is achieved in both low and high phosphorus EN media using anionic comb-polyelectrolyte surfactants with polyether side chain of 1100 g/mol. The optimal surfactant concentration is determined by zeta-potential and thermo-gravimetric analysis. Without additives the dispersions flocculate and sediment between 65 and 80 °C. Such phenomenon is believed to be associated with a critical flocculation temperature (CFT). The CFT is also weekly dependent on the particle type and the high ionic strength media. Addition of antifreeze additives such as propylene glycol and urea to the dispersions restores stability and increase the CFT for all particles. We estimate an average increase of the CFT by 1.5–2 °C per 1% additive for all particles and electrolytes. While the particle stabilization scheme is generalized in this work, the composite EN plating proved highly dependent on particle type. Baths containing ITO nanoparticles showed no plating reactions and those containing α-Fe2O3 no nanoparticle co-deposition. In contrast, homogeneous Ni–P/TiO2 and Ni–P/CeO2 nanocomposites with up to 22 vol.% nanoparticles are produced. The possible application of the stabilization principles developed here for other functional nanocomposite systems is discussed.
Keywords: Nanoparticle; Dispersion; Comb polyelectrolyte; Ionic strength; CFT; Ni–P; Composite; TiO2;

Display Omitted► Three PDI dimers linked with conjugated chains have been prepared. ► A short linkage induced strong intramolecular interactions between the PDI units. ► A long linkage favored intermolecular aggregation in solution and in the solid states.Three perylenetetracarboxylic diimide (PDI) dimers linked with a conjugated chain of different lengths have been designed and prepared. The UV–Vis absorption and fluorescence spectra of these three dimers revealed different photophysical properties owing to the different length of the linkage. The intermolecular ππ interactions were found to be enhanced significantly with the increase in the length of the linkage and therefore induced different aggregation behaviors of these molecules. The structure of the molecular aggregates was investigated by X-ray diffraction (XRD), and the morphology of the aggregates was examined by atomic force microscopy (AFM). One-dimensional fibers were observed for the aggregates of compounds 2 and 3, and thin solid films were observed for the aggregates of compound 1.
Keywords: Perylenetetracarboxylic diimide; Dimer; Aggregation; Fluorescence spectrum; Absorption spectrum;

A general method based on the stimuli-responsiveness of polymers has been developed to measure the ionization constants of polymer thin films using ellipsometry, dynamic contact angle titration, and surface plasmon resonance imaging.Display Omitted► A versatile approach to fabricate robust polymer thin films. ► A general method to measure ionization constants of polymer films. ► The pK a of P4VP films measured by ellipsometry, dynamic contact angle, and SPRi.A general method has been developed to determine the ionization constants of polymer thin films based on the stimuli-responsiveness of the polymer. Robust polymer films were fabricated on silicon wafers and gold slides using perfluorophenyl azide (PFPA) as the coupling agent. The ionization constants were measured by a number of techniques including ellipsometry, dynamic contact angle goniometry, and surface plasmon resonance imaging (SPRi). Using poly(4-vinylpyridine) (P4VP) as the model system, P4VP thin films were fabricated and the ionization constants of the films were measured taking advantage of the pH responsive property of the polymer. The pK a determined by ellipsometry, ∼4.0, reflects the swelling of the polymer film in response to pH. The pK a value calculated from the dynamic contact angle measurements, ∼5.0, relies on the change in hydrophilicity/hydrophobicity of the films as the polymer undergoes protonation/deprotonation. The pK a value measured by SPRi, ∼4.9, monitors in situ the change of refractive index of the polymer thin film as it swells upon protonation. This was the first example where SPRi was used to measure the ionization constants of polymers.
Keywords: Polymer thin films; Covalent immobilization; Ionization constant; Poly(4-vinylpyridine); Contact angle titration; Surface plasmon resonance imaging;

Comparison between non-doped and DP-Cyt doped liposomes on the DNA condensation ability. The higher amount of DNA is absorbable on Lx-Cyt system, notwithstanding the lower cationic lipid content with respect to Lx, owing to the occurrence of hydrophobic forces between the nucleobase and the DNA.Display Omitted► Nucleolipid liposomes/DNA association is driven by electrostatic and specific interactions. ► The nucleolipid DP-Cyt enhances the DNA binding capacity of liposomes. ► The new lipoplexes represent an alternative to the existing systems for DNA delivery.The interactions between cationic liposomes doped with the anionic nucleolipid 1,2-dipalmitoyl-sn-glycero-3-cytidine diphosphate (DP-Cyt) and deoxyribonucleic acid (DNA) were investigated. Toward this goal, new liposomal and lipoplex formulations characterized by the presence of the anionic amphiphile DP-Cyt were proposed. The effects of incorporation of the cytosine functionalized lipid DP-Cyt into the cationic bilayers were analyzed by means of electrophoretic mobility, dynamic light scattering (DLS) and fluorescence spectroscopy techniques. These approaches allowed us to follow the DNA condensation process and to identify specific electrokinetic characteristics of liposome and DNA–liposome complexes formation. Specifically, DP-Cyt liposomes and DNA were shown to form electrically stable or unstable complexes depending on the charge ratio between the phosphate group of DNA and the cationic lipid. Remarkably, a prominent role for DP-Cyt in enhancing the DNA binding capacity on liposomes was demonstrated. Zeta potential experiments performed on systems with different liposomes/DNA ratio showed that the value of the charge neutralization point is a function of the content of the incorporated DP-Cyt. As a whole, our data demonstrate that the association of cationic DP-Cyt doped liposomes with DNA is driven by both electrostatic interaction and additional specific interactions at the polar head level based on the cytidine nucleobase.
Keywords: Lipoplexes; Nucleolipids; Molecular interaction; Nucleic acids; Self-assembly; Zeta potential;

Kinetic study of the phase-transfer catalytic epoxidation of 1,4-bis(allyloxy)butane by Elżbieta Kaczmarczyk; Ewa Janus; Eugeniusz Milchert; Krzysztof Karakulski (191-197).
Kinetic data of the 1,4-bis(allyloxy)butane (DiBan) epoxidation were presented. The effect of agitation speed, the nature of solvent, the type of PT catalyst and molar ratio of H2O2:DiBan, DiBan:Na2WO4:H3PO4 on the course of this reaction was described.Display Omitted► Kinetic data of 1,4-bis(allyloxy)butane epoxidation under aqueous–organic system. ► Hydrogen peroxide as an oxidant. Na2WO4·2H2O, H3PO4 and ammonium salt generate the active form of catalyst. Agitation speed, solvent and molar ratio of reagents are important to high reaction rate.The epoxidation of 1,4-bis(allyloxy)butane (DiBan) with hydrogen peroxide as an oxidant in the presence of o-phosphoric acid and sodium tungstate as an epoxidation catalyst was carried out in an organic solvent/aqueous solution two-phase medium. A few different phase-transfer catalysts were used in the process. The effect of the stirring speed, nature of solvent, the type of PT catalyst and molar ratio of H2O2:DiBan, DiBan:Na2WO4:H3PO4 on the DiBan conversion as the function of time was studied.Based on the experimental results, a pseudo-first-order expression for the reaction rate was applied and most efficient conditions epoxidation were developed.
Keywords: Epoxidation; Phase-transfer catalysis; Kinetics; Allyl ethers;

(TH)3PW12 was prepared via facile direct precipitation method and exhibited photocatalytic activity for degradation of rhodamine B (RhB) under visible light irradiation.Display Omitted► The (TH)3PW12 was prepared via direct precipitation method. ► The (TH)3PW12 showed photocatalytic activity for degradation of RhB under visible light. ► The (TH)3PW12 can be separated from the photocatalytic system easily for reuse.(TH)3PW12 (TH = thionine, PW 12 = PW 12 O 40 3 - ) composite was prepared by direct precipitation of TH and PW12. The (TH)3PW12 was characterized via UV–vis spectrum, FT-IR, SEM, and BET surface area. PW12 was intact during the precipitation process. The composite has a bar-like shape and relatively large surface area (Langmuir surface of (TH)3PW12 was 31.59 m2  g−1, BET surface was 20.26 m2  g−1). Using the material as the photocatalyst, rhodamine B (RhB) was efficiently bleached and mineralized under visible light irradiation (λ  > 420 nm). The kinetics of the photodecomposition follow the first-order reaction. The (TH)3PW12 catalyst can be easily separated from the reaction system and has good stability for reuse.
Keywords: Polyoxometalate; Direct precipitation method; Photocatalysis; Visible light;

Surface mercapto engineered magnetic Fe3O4 nanoadsorbent for the removal of mercury from aqueous solutions by Shengdong Pan; Haoyu Shen; Qihong Xu; Jian Luo; Meiqin Hu (204-212).
Display Omitted► SH-Fe3O4-NMPs have been synthesized in an environmentally friendly method. ► The uptake of Hg(II) by SH-Fe3O4-NMPs was much higher than those of other adsorbents. ► Effects of pH value and conjugate anions were intensively studied. ► Role of surface SH on adsorption mechanism of Hg(II) ions was investigated. ► SH-Fe3O4-NMPs can be separated easily after adsorption by an external magnet.In this study, mercapto-functionalized nano-Fe3O4 magnetic polymers (SH-Fe3O4-NMPs) have been prepared and characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), thermogravimetry and differential thermogravimetry analyses (TG–DTA), as well as Fourier-transformed infrared spectroscopy (FTIR). The adsorptive characteristics of the SH-Fe3O4-NMPs intended for removal of mercury (II) were deeply studied. The results showed that the adsorption efficiency increased with pH increasing and reached a plateau at pH above 3.0. The adsorption data obtained at the optimized condition, i.e., 308 K and pH of 3.0, were well fitted with the Freundlich isotherm. The adsorption of Hg(II) reached equilibrium within 60 min. Thermodynamic parameters such as ΔHθ , ΔSθ and ΔGθ suggested that the adsorption processes of Hg(II) onto the SH-Fe3O4-NMPs were endothermic and entropy favored in nature, with ΔHθ at 30.31 kJ mol−1, ΔSθ at 111.41 J mol−1  K−1. The effects of mercury salts, i.e., Hg(NO3)2, HgSO4, and different acids, were also deeply investigated and showed that the adsorption capacity of Hg(II) onto the SH-Fe3O4-NMPs decreased when Cl existed.
Keywords: Mercapto-functionalized nano-Fe3O4 magnetic polymers (SH-Fe3O4-NMPs); Surface mercapto engineered; Adsorption; Hg(II); Freundlich isotherm; pH effect; Cl effect;

Adsorption of arsenite and selenite using an inorganic ion exchanger based on Fe–Mn hydrous oxide by Małgorzata Szlachta; Vasyl Gerda; Natalia Chubar (213-221).
Display Omitted► Inorganic mixed adsorbent is based on Fe(III)–Mn(III) hydrous oxides and MnCO3. ► Material was synthesised using a hydrothermal precipitation approach. ► Adsorbent had a high selectivity and adsorptive capacity towards As(III) and Se(IV).The adsorption behaviour and mechanism of As(III) and Se(IV) oxyanion uptake using a mixed inorganic adsorbent were studied. The novel adsorbent, based on Fe(III)–Mn(III) hydrous oxides and manganese(II) carbonate, was synthesised using a hydrothermal precipitation approach in the presence of urea. The inorganic ion exchanger exhibited a high selectivity and adsorptive capacity towards As(III) (up to 47.6 mg/g) and Se(IV) (up to 29.0 mg/g), even at low equilibrium concentration. Although pH effects were typical for anionic species (i.e., the adsorption decreased upon pH increase), Se(IV) was more sensitive to pH changes than As(III). The rates of adsorption of both oxyanions were high. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) studies showed that the ion exchange adsorption of both anions took place via OH groups, mainly from Fe(III) but also Mn(III) hydrous oxides. MnCO3 did not contribute directly to As(III) and Se(IV) removal. A higher adsorptive capacity of the developed material towards As(III) was partly due to partial As(III) oxidation during adsorption.
Keywords: Adsorption; Arsenite; Fe–Mn hydrous oxide; Inorganic ion exchanger; Selenite;

Short timescale inkjet ink component diffusion: An active part of the absorption mechanism into inkjet coatings by T.T. Lamminmäki; J.P. Kettle; P.J.T. Puukko; C.J. Ridgway; P.A.C. Gane (222-235).
The polar liquid (water) diffuses into the polymer network of hydrophilic binder polymer (polyvinyl alcohol, PVOH) and partially fixes there acting as a swelling agent. The water molecule diffusion opens the PVOH polymer network and the colourant of inkjet ink follows into the PVOH polymer matrix. In the case of styrene acrylate latex, the hydrophobic nature of latex prevents the diffusion of the polar liquid into the polymer network of the binder and there exists only a surface diffusion. The colourant of inkjet ink remains on the top of binder.Display Omitted► The polar liquid diffuses into the PVOH causing swelling and causing closure of some pores. ► The swelling of PVOH reduces pore diameters and pore volume of coating layer. ► At the beginning of liquid uptake, the small pores dominate the inkjet ink vehicle imbibition. ► The hydrophobic nature of latex prevents the diffusion of the polar liquid into the polymer. ► The polar liquid diffusion on the styrene acrylic latex is a surface diffusion.The structures of inkjet coatings commonly contain a high concentration of fine diameter pores together with a large pore volume capacity. To clarify the interactive role of the porous structure and the coincidentally occurring swelling of binder during inkjet ink vehicle imbibition, coating structures were studied in respect to their absorption behaviour for polar and non-polar liquid. The absorption measurement was performed using compressed pigment tablets, based on a range of pigment types and surface charge polarity, containing either polyvinyl alcohol (PVOH) or styrene acrylic latex (SA) as the binder, by recording the liquid uptake with a microbalance. The results indicate that, at the beginning of liquid uptake, at times less than 2 s, the small pores play the dominant role with respect to the inkjet ink vehicle imbibition. Simultaneously, water molecules diffuse into and within the hydrophilic PVOH binder causing binder swelling, which diminishes the number of active small pores and reduces the diameter of remaining pores, thus slowing the capillary flow as a function of time. The SA latex does not absorb the vehicle, and therefore the dominating phenomenon is then capillary absorption. However, the diffusion coefficient of the water vapour across separately prepared PVOH and SA latex films seems to be quite similar. In the PVOH, the polar liquid diffuses into the polymer network, whereas in the SA latex the hydrophobic nature prevents the diffusion into the polymer matrix and there exists surface diffusion. At longer timescale, permeation flow into the porous coating dominates as the resistive term controlling the capillary driven liquid imbibition rate.
Keywords: Diffusion; Absorption; Porosity; Permeability; Ink dye adsorption; Inkjet printing; Coating;

(a) An example of the adhesive force maps measured over a charged SiN x film using force–distance curve (FDC), (b) the induced adhesive force and surface potential increases with the charging electric field; the induced adhesive force decays with time due to (c) charge build in the dielectric film, and (d) charge relaxation.Display Omitted► Novel characterization techniques to study dielectric charging in MEMS. ► Techniques use force–distance curve (FDC) measurements performed by an AFM. ► Measured the surface potential and adhesive force induced over charged dielectrics. ► FDC measures meniscus force and larger levels of surface potential on the nanoscale. ► We correlate between results from proposed techniques and other methods (C/DCT, KPFM).The work presents a comprehensive package of novel nanoscale characterization techniques to study dielectric charging in electrostatic nano- and microelectromechanical systems (NEMS and MEMS). The proposed assessment methodologies are based on the force–distance curve (FDC) measurements performed using an atomic force microscope (AFM) to measure, for the first time, the induced surface potential and adhesive force over charged dielectric films. They were employed to study plasma enhanced chemical vapor deposition (PECVD) silicon nitride films for application in electrostatic capacitive RF MEMS switches. Three different techniques were introduced including the application of FDC measurements to study charging in bare SiN x films, metal–insulator–metal (MIM) capacitors, and MEMS switches. The results from the three methods were correlated and compared with the published data from other characterization techniques, mainly charge/discharge current transient (C/DCT) and Kelvin probe force microscopy (KPFM). The unique advantages of the proposed FDC-based characterization techniques are twofold. First, they can measure the multiphysics coupling between the dielectric charging phenomenon and tribological issues at the interface between the switch bridge and the dielectric surface. Second, the FDC-based techniques can measure larger levels of induced surface potential over charged dielectric films which results from the high electric field normally used to actuate MEMS switches. Based on the proposed FDC techniques, the influence of several parameters on dielectric charging/discharging processes was investigated: the dielectric film thickness, deposition conditions, substrate, and electrical stress conditions.
Keywords: Nanotribology; Force–distance curve; Adhesive force; Dielectric charging; Silicon nitride; Electrostatic NEMS/MEMS; RF MEMS switch; Reliability; Nanoscale characterization;

Both CCR and CCA mode observed in experiments were theoretically analyzed and the theoretical solution of contact angle in the CCR stage was derived.Display Omitted► CCR, CCA and mixed modes were found in evaporation experiments of water droplet sessile on PDMS and Teflon surfaces. ► Theoretical solution of contact angle during CCR stage with any value of initial contact angle was derived. ► Time of CCR stage depends on variation of contact angles and proportional to D(c 0  −  c )/ρ and the square of contact radius. ► Variation rate of liquid-vapor area was on the order of D(c 0  −  c )/ρ, and the total evaporation time can be estimated.Experiments of sessile water droplet evaporation on both polydimethylsiloxane (PDMS) and Teflon surfaces were conducted. All experiments begin with constant contact area mode (the initial contact angle is greater than 90°), switch to constant contact angle mode and end with mixed mode. Based on the assumptions of spherical droplet and uniform concentration gradient, theoretical analyses for both constant contact area and constant contact angle modes are made and theoretical solutions are derived accordingly, especially a theoretical solution of contact angle is presented first for CCR stage with any value of the initial contact angle. Moreover, comparisons between the theoretical solutions and experimental data of contact angle in CCR stage demonstrate the validity of the theoretical solution and it would help for a better understanding and application of water droplet on solid surfaces, which is quite often encountered in lab-on-a-chip, polymerase chain reaction (PCR) and other micro-fluidics devices.
Keywords: Droplet; Evaporation; Contact angle; Constant contact radius; Hydrophobic surfaces;

Enhanced surface segregation of poly(methyl methacrylate) end-capped with 2-perfluorooctylethyl methacrylate by introduction of a second block by Huagang Ni; Jie Gao; Xuehua Li; Yanyan Hu; Donghuan Yan; XiuYun Ye; Xinping Wang (260-267).
The segregation of the fluorinated moieties in end-capped poly(methyl methacrylate)-b-poly(n-octadecyl methacrylate) was greatly enhanced by the crystallinity of poly(n-octadecyl methacrylate) block.Display Omitted► New fluorinated diblock copolymers were synthesized. ► Thin films made of these polymers exhibit robust surface segregation. ► Fluorine enrichment factor increase linearly with increasing PODMA fusion enthalpy. ► Self-assembly process imparts synergistically a higher degree of PODMA crystallinity.New fluorinated copolymers of poly(methyl methacrylate)-b-poly(butyl methacrylate) or poly(n-octadecyl methacrylate) end-capped with 2-perfluorooctylethyl methacrylate (PMMA x -b-PBMA y -ec-PFMA z or PMMA x -b-PODMA y -ec-PFMA z ) were synthesized by living atom transfer radical polymerization. Thin films made of PMMA230-b-PODMA y -ec-PFMA1 were characterized by differential scanning calorimetry, angle-resolved X-ray photoelectron spectroscopy and X-ray diffraction. These films were found to exhibit robust surface segregation of the end groups. Furthermore, the fluorine enrichment factor at the film surface was found to increase linearly with increasing degree of polymerization of poly(n-octadecyl methacrylate) and its increasing fusion enthalpy in the second block, which enhances the segregation of the fluorinated moieties.
Keywords: End-capped polymer; Fluorinated copolymer; Diblock copolymer; Surface segregation; Chain structure;

Display Omitted► Effects of sulfate on U(VI)-carbonato surface species on ferrihydrite were examined. ►pH dependent U(VI) sorption in ferrihydrite was not largely affected by sulfate. ► In air, sulfate and carbonate ligands competitively react with U(VI) surface species. ► At 2% pCO2, no contribution of sulfate ligands on the U(VI) ternary surface species.Understanding uranium (U) sorption processes in permeable reactive barriers (PRB) are critical in modeling reactive transport for evaluating PRB performance at the Fry Canyon demonstration site in Utah, USA. To gain insight into the U sequestration mechanism in the amorphous ferric oxyhydroxide (AFO)-coated gravel PRB, U(VI) sorption processes on ferrihydrite surfaces were studied in 0.01 M Na2SO4 solutions to simulate the major chemical composition of U-contaminated groundwater (i.e., [ SO 4 2 - ] ∼13 mM L−1) at the site. Uranyl sorption was greater at pH 7.5 than that at pH 4 in both air- and 2% pCO2-equilibrated systems. While there were negligible effects of sulfate ligands on the pH-dependent U(VI) sorption (<24 h) in both systems, X-ray absorption spectroscopy (XAS) analysis showed sulfate ligand associated U(VI) surface species at the ferrihydrite–water interface. In air-equilibrated systems, binary and mono-sulfate U(VI) ternary surface species co-existed at pH 5.43. At pH 6.55–7.83, a mixture of mono-sulfate and bis-carbonato U(VI) ternary surface species became more important. At 2% pCO2, there was no contribution of sulfate ligands on the U(VI) ternary surface species. Instead, a mixture of bis-carbonato inner-sphere (38%) and tris-carbonato outer-sphere U(VI) ternary surface species (62%) was found at pH 7.62. The study suggests that the competitive ligand (bicarbonate and sulfate) coordination on U(VI) surface species might be important in evaluating the U solid-state speciation in the AFO PRB at the study site where pCO2 fluctuates between 1 and 2 pCO2%.
Keywords: Uranium; Sorption; XAS; Ternary; Sulfate; Ternary complexes;

Nearly vanishing oil/water interfacial tensions induced by amphiphilic diblock copolymers drive interfacial instabilities and lead to dispersal of block copolymer micelles in water.Display Omitted► Micropipette tensiometry to characterize interfacial behavior of amphiphilic copolymers within evaporating emulsion droplets. ► Instabilities coincident with an approach of interfacial tension nearly to zero. ► Interfacial tension and instabilities depend on solvent type and polymer composition.Evaporating droplets of volatile organic solvent containing amphiphilic block copolymers may undergo hydrodynamic instabilities that lead to dispersal of copolymer micelles into the surrounding aqueous phase. As for related phenomena in reactive polymer blends and oil/water/surfactant systems, this process has been ascribed to a nearly vanishing or transiently negative interfacial tension between the water and solvent phases induced by adsorption of copolymer to the interface. In this report, we investigate the influence of the choice of organic solvent and polymer composition for a series of polystyrene-b-poly(ethylene oxide) (PS–PEO) diblock copolymers, by in situ micropipette tensiometry on evaporating emulsion drops. These measurements suggest that the sensitivity to the organic solvent chosen reflects both differences in the bare solvent/water interfacial tension as well as the propensity of the copolymer to aggregate within the organic phase. While instabilities coincident with an approach of the interfacial tension nearly to zero were observed only for copolymers with PEO content greater than 15 wt.%, beyond this point the interfacial behavior and critical concentration needed to trigger surface instability were found to depend only weakly on copolymer composition.
Keywords: Emulsion droplets; Block copolymer; Interfacial instabilities; Interfacial tension; Micropipette tensiometry; Self-assembly;

Pure short-chain glycerol fatty acid esters and glycerylic cyclocarbonic fatty acid esters as surface active and antimicrobial coagels protecting surfaces by promoting superhydrophilicity by Romain Valentin; Marion Alignan; Géraldine Giacinti; François N.R. Renaud; Bernard Raymond; Zéphirin Mouloungui (280-288).
Display Omitted► Superhydrophilic surfaces coated by fatty acid esters. ► Fatty acid esters behave like solvo-surfactants. ► Structure, texture and solvo-surfactive properties induce superhydrophilicity. ► Fatty acid esters present anti microbial activity.Pure glycerol fatty acid esters and glycerylic cyclocarbonic fatty acid esters have an amphiphilic structure, giving these biomolecules a broad range of physico-chemical and biological properties. Physico-chemical properties depend on chain lengths, odd or even carbon numbers on the chain, and glyceryl or cyclocarbonic polar heads. The spectrum of melting-point values for these molecules is large. Surface-activity is very important and through determination of the critical aggregation concentration (CAC), some fatty-acid esters are considered as solvo-surfactant biomolecules. Coupling these self-aggregation and crystallization properties, superhydrophilic surfaces were obtained. An efficient durable water repellent coating of various metallic and polymeric surfaces was allowed. Moreover, these fatty acid esters promoting superhydrophilicity showed biological activity against Gram positive, Gram negative, and yeast-like micro-organisms. Such surfaces coated by self-assembled fatty acid esters in a stable coagel state present a novel solution to surface-contamination risks from pathogen proliferation.
Keywords: Pure monoglycerides; Pure glycerol carbonate esters; Superhydrophilicity; Solvo-surfactants; Critical aggregation concentration; Coagels; Self-aggregation; Biological molecules;

Display Omitted► Surface characterization using various technologies. ► Radical-induced graft polymerization of TMSPMA on COC surface for bonding PDMS. ► Integration of PDMS valve to a COC microdevice via established bonding protocol. ► Demonstration of valve-enabled on-chip fluidic handling.Thermoplastics have been increasingly used for fabricating microfluidic devices because of their low cost, mechanical/biocompatible attributes, and well-established manufacturing processes. However, there is sometimes a need to integrate such a device with components made from other materials such as polydimethylsiloxane (PDMS). Bonding thermoplastics with PDMS to produce hybrid devices is not straightforward. We have reported our method to modify the surface property of a cyclic olefin copolymer (COC) substrate by using corona discharge and grafting polymerization of 3-(trimethoxysilyl)propyl methacrylate; the modified surface enabled strong bonding of COC with PDMS. In this paper, we report our studies on the surface modification mechanism using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurement. Using this bonding method, we fabricated a three-layer (COC/PDMS/COC) hybrid device consisting of elastomer-based valve arrays. The microvalve operation was confirmed through the displacement of a dye solution in a fluidic channel when the elastomer membrane was pneumatically actuated. Valve-enabled microfluidic handling was demonstrated.
Keywords: Surface modification; Microfluidic valves; Thermoplastics; Elastomer;

Interactions of salicylic acid derivatives with calcite crystals by Marko Ukrainczyk; Matija Gredičak; Ivanka Jerić; Damir Kralj (296-307).
Model of interaction of N-salicyloil-l-aspartic acid with calcium ion at the step position of calcite {1 0 4} crystal faceDisplay Omitted► The crystal growth kinetic of calcite at low supersaturation was studied. ► Salicylic acid (SA) and its amino acid derivatives were used as additives. ► The electrokinetic, spectroscopic and adsorption measurements were performed too. ► The aspartic acid-based moieties are proposed as effective binding agents for drugs.Investigation of basic interactions between the active pharmaceutical compounds and calcium carbonates is of great importance because of the possibility to use the carbonates as a mineral carrier in drug delivery systems. In this study the mode and extent of interactions of salicylic acid and its amino acid derivates, chosen as pharmaceutically relevant model compounds, with calcite crystals are described. Therefore, the crystal growth kinetics of well defined rhombohedral calcite seed crystals in the systems containing salicylic acid (SA), 5-amino salicylic acid (5-ASA), N-salicyloil-l-aspartic acid (N-Sal-Asp) or N-salicyloil-l-glutamic acid (N-Sal-Glu), were investigated. The precipitation systems were of relatively low initial supersaturation and of apparently neutral pH. The data on the crystal growth rate reductions in the presence of the applied salicylate molecules were analyzed by means of Cabrera & Vermileya’s, and Kubota & Mullin’s models of interactions of the dissolved additives and crystal surfaces. The crystal growth kinetic experiments were additionally supported with the appropriate electrokinetic, spectroscopic and adsorption measurements. The Langmuir adsorption constants were determined and they were found to be in a good correlation with values obtained from crystal growth kinetic analyses. The results indicated that salicylate molecules preferentially adsorb along the steps on the growing calcite surfaces. The values of average spacing between the adjacent salicylate adsorption active sites and the average distance between the neighboring adsorbed salicylate molecules were also estimated.
Keywords: Calcium carbonate; Calcite; Salicylic acid derivatives; Crystal growth kinetics; Adsorption; Drug delivery;

Self-organized TiO2 nanorod arrays on glass substrate for self-cleaning antireflection coatings by Qinghui Mu; Yaogang Li; Hongzhi Wang; Qinghong Zhang (308-313).
TiO2 nanorod arrays with different morphologies and structures were successfully synthesized on glass substrate by a facile solvothermal process.Display Omitted► A sample method was used to fabricate TiO2 nanorod arrays on glass substrate. ► Nanorod arrays with different morphology and structure were obtained. ► Hydrophobic and photocatalytic properties resulted in self-cleaning performance.Herein we report the direct fabrication of TiO2 subwavelength structures with 1-dimensional TiO2 nanorods on glass substrate through solvothermal process to form self-cleaning antireflection coatings. TiO2 precursor solutions with different solvent constituents create TiO2 nanorods with much different morphologies grown on glass substrates. Apiculate TiO2 nanorods with vertical orientation are grown on the glass substrate which is solvothermally treated in the precursor solution containing ethylene glycol. This glass substrate exhibit the highest transmittance of 70–85% in the range of 520–800 nm and negligible absorption in visible light region (400–800 nm). Furthermore, the TiO2 nanorod arrays show high hydrophobicity and photocatalytic degradation ability which offer the glass substrate self-cleaning properties for both hydrophilic and oily contaminants.
Keywords: Nanorod arrays; Antireflection; Self cleaning; Hydrophobicity; Photocatalysis;

Surface tension drawing of liquid from microplate capillary wells by Willem Schwalb; Tuck Wah Ng; Jonathan Kok Keung Lye; Oi Wah Liew; Brandon Huey-Ping Cheong (314-319).
Display Omitted► The pulling action on a droplet from a capillary creates controllable flow via surface tension effects. ► The flow characteristics are dependent on liquid bridge sustaining features and the rod diameter used. ► It is also possible to produce mixing together with liquid extraction when the liquid bridge ruptures. ► This approach promises important uses in biochemical analysis, particularly in the field.Pressure differentials are routinely used to actuate flow in capillaries. We advance here an alternative means of flow generation that capitalizes on the extension of a liquid bridge achieved by the drawing of a rod through the action of surface tension. This meets the exigencies of creating controllable flow using simpler and more compact means. We found the ability to generate controllable flow to be strongly affected by the liquid bridge sustaining features, and that the use of rod diameters larger than the capillary was more conducive. The extensional flow resulting from the rupture of the liquid bridge was also found to have a strong circulation component which facilitated mixing. The approach here is highly amenable for use in capillary well microplates which have significant advantages over standard microplates. The features of this approach offer usage possibilities in biochemical applications in the field, such as in the leukocyte cell adhesion and hemagglutination tests of blood samples.
Keywords: Capillary; Microplate; Liquid bridge; Flow; Mixing;

Patterning of Gd2(WO4)3:Ln3+ (Ln = Eu, Tb) luminescent films by microcontact printing route by Dong Wang; Piaoping Yang; Ziyong Cheng; Wenxin Wang; Zhiyao Hou; Yunlu Dai; Chunxia Li; Jun Lin (320-325).
Fluorescence microscope images of the patterned films for Gd2(WO4)3:Eu3+ (a) and Gd2(WO4)3:Tb3+ (b) under 254 nm UV irradiation.Display Omitted► The patterned luminescent Gd2(WO4)3:Ln3+ (Ln = Eu, Tb) films were prepared via microcontact printing. ► The Pechini-type sol–gel method was combined with softlithography. ► They show luminescence under ultraviolet and low-voltage electron beams excitation. ► This technique has potential for field emission displays (FEDs) applications.Gd2(WO4)3 doped with Eu3+ or Tb3+ thin phosphor films with dot patterns have been prepared by a combinational method of sol–gel process and microcontact printing. This process utilizes a PDMS elastomeric mold as the stamp to create heterogeneous pattern on quartz substrates firstly and then combined with a Pechini-type sol–gel process to selectively deposit the luminescent phosphors on hydrophilic regions, in which a Gd2(WO4)3:Ln3+ (Ln = Eu, Tb) precursor solutions were employed as ink. X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectra, as well as low voltage cathodoluminescence (CL) spectra were carried out to characterize the obtained samples. Under ultraviolet excitation and low-voltage electron beams excitation, the Gd2(WO4)3:Eu3+ samples exhibit a strong red emission arising from Eu3+ 5D0,1,27F1,2 transitions, while the Gd2(WO4)3:Tb3+ samples show the green emission coming from the characteristic emission of Tb3+ corresponding to 5D47F6,5,4,3 transitions. The results show that the patterning of rare earth-doped phosphors through combining microcontact printing with a Pechini-type sol–gel route has potential for field emission displays (FEDs) applications.
Keywords: Sol–gel; Microcontact printing; Patterning; Gd2(WO4)3;

Tuning the zeta potential of a dielectric surface in contact with an aqueous solution by a floating gate field effect transistor is analyzed for the first time.Display Omitted► Surface charge property can be tuned by a floating gate field effect transistor (FGFET). ► FGFET is superior to the conventional FET to tune the surface charge property. ► FGFET has great potential to control ions, fluids, and particle electrokinetic transport.Tuning surface charge property by a floating gate field effect transistor (FGFET) is proposed and analyzed for the first time. The FGFET has an additional floating gate electrode embedded inside the dielectric channel wall and is superior to the conventional FET to tune the surface charge property of a dielectric material in contact with an aqueous solution.
Keywords: Microfluidics; Nanofluidics; Electrokinetics; Field effect control; Field effect transistor (FET); Floating gate field effect transistor (FGFET);