Special Issue "Selected Papers from the 16th Conference of the International Association of Colloid and Interface Scientists (IACIS 2018)"

A special issue of Colloids and Interfaces (ISSN 2504-5377).

Deadline for manuscript submissions: closed (30 September 2018)

Special Issue Editors

Guest Editor
Dr. Reinhard Miller

Max Planck Institute of Colloids and Interfaces, D-14424, Golm, Germany
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Phone: +493315679252
Interests: dynamics and mechanics of liquid interfaces; thermodynamics of adsorption of surfactants and proteins; interfacial interactions and 2D rheology; stability of foams and emulsions
Guest Editor
Prof. Dr. To Ngai

Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
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Interests: colloidal particle; interfacial science; polymer and soft materials
Guest Editor
Prof. Dr. Mieke Kleijn

Laboratory of Physical Chemistry and Colloid Science, Wageningen University, P.O. box 8038, 6700EK Wageningen, The Netherlands
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Guest Editor
Prof. Dr. Ger Koper

Department of Chemical Engineering, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
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Special Issue Information

Dear Colleagues,

IACIS 2018 is the 16th Conference of the International Association of Colloid and Interface Scientists (www.IACIS2018.org) and brings together scientists from academia, research institutes, and industry working in the field of colloids and interfaces. This field is strongly interdisciplinary, combining aspects of physics, chemistry, mathematics and biology. Colloidal systems are nowadays also referred to as “soft matter,” indicating that their structure and dynamics are governed by physical interactions, which are generally weak. The continued development of statistical thermodynamics, advances in theories of liquids and phase transitions, together with computer modelling and simulations have created a powerful conceptual framework. In the last few decades, the field has become more and more integrated with applied sciences, such as food, environmental, and biomedical sciences. The conference provides a podium for presenting scientific posters and oral contributions addressing all these aspects.

Participants of IACIS2018 are cordially invited to contribute original research papers to this Special Issue of Colloids and Interfaces.

Dr. Reinhard Miller
Prof. Dr. To Ngai
Prof. Dr. Mieke Kleijn
Prof. Dr. Ger Koper
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Colloids and Interfaces is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Surface forces and thin liquid films
  • Foams and emulsions
  • Surfactants and self-assembly
  • Colloidal dispersions
  • Polymers and gels
  • Catalysis and surface reactions
  • Wetting and interfacial rheology
  • Interfacial electric phenomena
  • Biologically inspired systems
  • Biomembranes and lipid bilayers
  • Applications food, medicine, environmental technology and energy

Published Papers (17 papers)

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Research

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Open AccessArticle Dynamic Measurements with the Bicone Interfacial Shear Rheometer: Numerical Bench-Marking of Flow Field-Based Data Processing
Colloids Interfaces 2018, 2(4), 69; https://doi.org/10.3390/colloids2040069
Received: 7 October 2018 / Revised: 19 November 2018 / Accepted: 3 December 2018 / Published: 7 December 2018
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Abstract
Flow field-based methods are becoming increasingly popular for the analysis of interfacial shear rheology data. Such methods take properly into account the subphase drag by solving the Navier–Stokes equations for the bulk phase flows, together with the Boussinesq–Scriven boundary condition at the fluid–fluid
[...] Read more.
Flow field-based methods are becoming increasingly popular for the analysis of interfacial shear rheology data. Such methods take properly into account the subphase drag by solving the Navier–Stokes equations for the bulk phase flows, together with the Boussinesq–Scriven boundary condition at the fluid–fluid interface and the probe equation of motion. Such methods have been successfully implemented on the double wall-ring (DWR), the magnetic rod (MR), and the bicone interfacial shear rheometers. However, a study of the errors introduced directly by the numerical processing is still lacking. Here, we report on a study of the errors introduced exclusively by the numerical procedure corresponding to the bicone geometry at an air–water interface. In our study, we set an input value of the complex interfacial viscosity, and we numerically obtained the corresponding flow field and the complex amplitude ratio for the probe motion. Then, we used the standard iterative procedure to obtain the calculated complex viscosity value. A detailed comparison of the set and calculated complex viscosity values was made in wide ranges of the three parameters herein used, namely the real and imaginary parts of the complex interfacial viscosity and the frequency. The observed discrepancies yield a detailed landscape of the numerically-introduced errors. Full article
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Open AccessArticle Synthesis of Submicrocontainers with “Green” Biocide and Study of Their Antimicrobial Activity
Colloids Interfaces 2018, 2(4), 67; https://doi.org/10.3390/colloids2040067
Received: 27 September 2018 / Revised: 27 November 2018 / Accepted: 28 November 2018 / Published: 3 December 2018
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Abstract
The synthesis and properties of submicrocontainers with a shell of nanoparticles of silicon dioxide and a core of polymerized 3-(Trimethoxysilyl) propyl methacrylate loaded with 5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) are considered. The resulting containers were characterized by scanning electron microscopy SEM, laser correlation spectroscopy and thermogravimetric
[...] Read more.
The synthesis and properties of submicrocontainers with a shell of nanoparticles of silicon dioxide and a core of polymerized 3-(Trimethoxysilyl) propyl methacrylate loaded with 5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) are considered. The resulting containers were characterized by scanning electron microscopy SEM, laser correlation spectroscopy and thermogravimetric analysis. The obtained submicrocontainers show low polydispersity with a small increase in size in comparison with the initial droplet size of the Pickering emulsion. The Zeta potential of the final containers was sufficiently negative at pH7 to be stable. The maximum release of encapsulated biocide was observed over approximately 24–27 h with a lease of about 78% of the encapsulated biocide during 3.5 h. The effectiveness of the encapsulated biocide by the Pickering emulsion technique was studied by tests on the growth rate of a microfungi colony (Aspergillus niger, Aspergillus awamori) and the growth rate of the bacteria Bacillus cereus. The test shows that the submicrocontainers of DCOIT facilitate a growth inhibition of 70% against 52% for the free biocide after 5 days; this is due to the fact that free biocide loses its activity promptly, while the encapsulated biocide is released gradually, and thus retains its effectivity for a longer time. Full article
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Open AccessArticle Rheology of Water-in-Crude Oil Emulsions: Influence of Concentration and Temperature
Colloids Interfaces 2018, 2(4), 64; https://doi.org/10.3390/colloids2040064
Received: 29 September 2018 / Revised: 22 November 2018 / Accepted: 22 November 2018 / Published: 26 November 2018
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Abstract
The effect of aqueous phase content and temperature North Sea crude oil emulsion viscoelastic behavior has been studied. Heavy crude oil from the North Sea is of high viscosity and is capable of forming stable water-in-crude oil (w/o) emulsions without introducing any synthetic
[...] Read more.
The effect of aqueous phase content and temperature North Sea crude oil emulsion viscoelastic behavior has been studied. Heavy crude oil from the North Sea is of high viscosity and is capable of forming stable water-in-crude oil (w/o) emulsions without introducing any synthetic surfactants. The aqueous phase volume content was varied from 1 to 40%, and the temperature was varied from 0 to 30 °C. The w/o emulsion viscosity increased sharply when the aqueous phase content exceeds 20%, being more pronounced at the lower temperatures. The viscosity flow curves for emulsions containing more than 20% aqueous phase demonstrate non-Newtonian behavior, in contrast to crude oil, which is Newtonian. The coefficients in the master curve describing the viscosity-temperature dependence were determined. Oscillatory rheological tests showed that the loss modulus substantially exceeds the storage modulus which indicates the liquid-like state of the emulsions. Full article
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Open AccessArticle Low Pressure Hysteresis in Materials with Narrow Slit Pores
Colloids Interfaces 2018, 2(4), 62; https://doi.org/10.3390/colloids2040062
Received: 26 September 2018 / Revised: 11 November 2018 / Accepted: 12 November 2018 / Published: 16 November 2018
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Abstract
Humidity-dependent closing and reopening slit pores can produce hysteresis loops in sorption diagrams even at low relative vapor pressure. Pore closing is supported by adhesion of the slit wall surfaces. In a macroscopic model for sorption hysteresis in narrow slits, the adhesion energy
[...] Read more.
Humidity-dependent closing and reopening slit pores can produce hysteresis loops in sorption diagrams even at low relative vapor pressure. Pore closing is supported by adhesion of the slit wall surfaces. In a macroscopic model for sorption hysteresis in narrow slits, the adhesion energy jumps by a finite value when touching slit walls are separated from each other. We consider a more realistic adhesion model by introducing a smoothly-varying adhesion force, which depends on the distance between the slit walls. The range of the attraction between the slit walls is found to have a pronounced influence on the shape of hysteresis loops at low vapor pressure. A large interaction range avoids an extraordinarily small relative vapor pressure necessary for pore closing, which is a precondition for low pressure hysteresis. Our extended model allows us to describe a discontinuity, which can appear in the desorption branch of swelling/shrinkage diagrams for hardened cement paste. Full article
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Open AccessArticle Anomalous Interfacial Structuring of a Non-Halogenated Ionic Liquid: Effect of Substrate and Temperature
Colloids Interfaces 2018, 2(4), 60; https://doi.org/10.3390/colloids2040060
Received: 19 October 2018 / Revised: 6 November 2018 / Accepted: 13 November 2018 / Published: 14 November 2018
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Abstract
We investigate the interfacial properties of the non-halogenated ionic liquid (IL), trihexyl(tetradecyl)phosphonium bis(mandelato)borate, [P6,6,6,14][BMB], in proximity to solid surfaces, by means of surface force measurement. The system consists of sharp atomic force microscopy (AFM) tips interacting with solid surfaces of mica,
[...] Read more.
We investigate the interfacial properties of the non-halogenated ionic liquid (IL), trihexyl(tetradecyl)phosphonium bis(mandelato)borate, [P6,6,6,14][BMB], in proximity to solid surfaces, by means of surface force measurement. The system consists of sharp atomic force microscopy (AFM) tips interacting with solid surfaces of mica, silica, and gold. We find that the force response has a monotonic form, from which a characteristic steric decay length can be extracted. The decay length is comparable with the size of the ions, suggesting that a layer is formed on the surface, but that it is diffuse. The long alkyl chains of the cation, the large size of the anion, as well as crowding of the cations at the surface of negatively charged mica, are all factors which are likely to oppose the interfacial stratification which has, hitherto, been considered a characteristic of ionic liquids. The variation in the decay length also reveals differences in the layer composition at different surfaces, which can be related to their surface charge. This, in turn, allows the conclusion that silica has a low surface charge in this aprotic ionic liquid. Furthermore, the effect of temperature has been investigated. Elevating the temperature to 40 °C causes negligible changes in the interaction. At 80 °C and 120 °C, we observe a layering artefact which precludes further analysis, and we present the underlying instrumental origin of this rather universal artefact. Full article
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Open AccessFeature PaperArticle Effect of Amplitude on the Surface Dilational Visco-Elasticity of Protein Solutions
Colloids Interfaces 2018, 2(4), 57; https://doi.org/10.3390/colloids2040057
Received: 17 October 2018 / Revised: 6 November 2018 / Accepted: 7 November 2018 / Published: 10 November 2018
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Abstract
Harmonic drop surface area oscillations are performed at a fixed frequency (0.1 Hz) to measure the dilational visco-elasticity for three proteins: β-casein (BCS), β-lactoglobulin (BLG), and human serum albumin (HSA). The surface area oscillations were performed with different amplitudes in order to find
[...] Read more.
Harmonic drop surface area oscillations are performed at a fixed frequency (0.1 Hz) to measure the dilational visco-elasticity for three proteins: β-casein (BCS), β-lactoglobulin (BLG), and human serum albumin (HSA). The surface area oscillations were performed with different amplitudes in order to find the origin of non-linearity effects. The analysis of data shows that the non-linearity in the equation of state—i.e., the relation between surface pressure and surface concentration of adsorbed protein molecules—is the main source of the amplitude effects on the apparent visco-elasticity, while perturbations due to non-uniform expansions and compressions of the surface layer, inertia effects leading to deviations of the drop profile from the Laplacian shape, or convective transport in the drop bulk are of less importance. While for the globular proteins, HSA and BLG the amplitude effects on the apparent visco-elasticity are rather large, for the non-globular protein BCS this effect is negligible in the studied range of up to 10% area deformation. Full article
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Open AccessArticle Rubber Surface Change and Static Charging under Periodic Stress
Colloids Interfaces 2018, 2(4), 55; https://doi.org/10.3390/colloids2040055
Received: 28 September 2018 / Revised: 27 October 2018 / Accepted: 2 November 2018 / Published: 6 November 2018
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Abstract
Rubber materials play an important role in robotics, due to their sensing and actuating abilities, that are exploited in soft smart materials endowed with shape-adaptive and electroadhesive properties. The application of an electric field produces non-linear deformation that has been extensively modelled, but
[...] Read more.
Rubber materials play an important role in robotics, due to their sensing and actuating abilities, that are exploited in soft smart materials endowed with shape-adaptive and electroadhesive properties. The application of an electric field produces non-linear deformation that has been extensively modelled, but is not understood at the molecular level. The symmetric effect (the production of an electric field due to rubber deformation) was recently discovered and explained as follows: rubber surface chemical composition and adsorptive properties change during rubber deformation, allowing the surface to exchange charge with the atmosphere. The present work describes the complex surface morphology and microchemistry of tubing made from vulcanized natural rubber, showing that it is rough and made from two domain types: stiffer elevations containing Br or Al (depending on the sample used) and O, that rise above an elastic base that is exempt of elements other than C and H. The surface area fraction occupied by the elastic base is higher in the strained rubber than when it is relaxed. Electrostatic potential on rubber surfaces was measured as a function of the stretching frequency, using Kelvin electrodes and showing frequency-dependent potential variation. This is explained considering charge exchange between the atmosphere and rubber surface, mediated by water vapor adsorbed in the stretched rubber and trapped when it relaxes. Full article
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Open AccessFeature PaperArticle Dynamic Properties of Mixed Cationic/Nonionic Adsorbed Layers at the N-Hexane/Water Interface: Capillary Pressure Experiments Under Low Gravity Conditions
Colloids Interfaces 2018, 2(4), 53; https://doi.org/10.3390/colloids2040053
Received: 4 October 2018 / Revised: 26 October 2018 / Accepted: 29 October 2018 / Published: 2 November 2018
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Abstract
Capillary pressure experiments are performed in microgravity conditions on board the International Space Station to quantify the dynamic interfacial behavior of mixed adsorption layers of TTAB and C13DMPO at the water/hexane interface. While the non-ionic surfactant C13DMPO is soluble
[...] Read more.
Capillary pressure experiments are performed in microgravity conditions on board the International Space Station to quantify the dynamic interfacial behavior of mixed adsorption layers of TTAB and C13DMPO at the water/hexane interface. While the non-ionic surfactant C13DMPO is soluble in both bulk phases, water and hexane, the cationic surfactant TTAB is only soluble in the aqueous phase. The interfacial layer is thus formed by TTAB molecules adsorbing from the aqueous phase while the C13DMPO molecules adsorb from the aqueous phase, and transfer partially into the hexane phase until both the equilibrium of adsorption and the distribution between the two adjacent liquid phases is established. The experimental constrains as well as all possible influencing parameters, such as interfacial and bulk phase compressibility, interfacial curvature, calibration of pressure and absolute geometry size, are discussed in detail. The experimental results in terms of the dilational interfacial viscoelasticity of the mixed adsorption layers in a wide range of oscillation frequencies show that the existing theoretical background had to be extended in order to consider the effect of transfer of the non-ionic surfactant across the interface, and the curvature of the water/hexane interface. A good qualitative agreement between theory and experiment was obtained, however, for a quantitative comparison, additional accurate information on the adsorption isotherms and diffusion coefficients of the two studied surfactants in water and hexane, alone and in a mixed system, are required. Full article
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Open AccessArticle Failure of Debye-Hückel Screening in Low-Charge Colloidal Suspensions
Colloids Interfaces 2018, 2(4), 51; https://doi.org/10.3390/colloids2040051
Received: 30 September 2018 / Revised: 17 October 2018 / Accepted: 18 October 2018 / Published: 22 October 2018
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Abstract
Derjaguin–Landau–Verwey–Overbeek (DLVO) theory remains the cornerstone of colloid stability. Electrostatic interactions dominate van der Waals attractions at large colloid-colloid separations h, unless strongly screened. Under these conditions, the potential U(h) between charged colloids is expected to be exponentially screened,
[...] Read more.
Derjaguin–Landau–Verwey–Overbeek (DLVO) theory remains the cornerstone of colloid stability. Electrostatic interactions dominate van der Waals attractions at large colloid-colloid separations h, unless strongly screened. Under these conditions, the potential U ( h ) between charged colloids is expected to be exponentially screened, U ( h ) exp ( κ h ) / h , with κ 1 = λ D where λ D is the classical Debye-Hückel screening length. By measuring the force between individual charged particles at dilute electrolyte concentrations (<mM) using optical tweezers, we tested experimentally the prediction κ 1 = λ D in a nonpolar solvent. At low salt concentrations, we found close agreement between the directly-measured decay length κ 1 and Debye-Hückel predictions. However, above a critical electrolyte concentration (≈450 μ M), we obtained significant discrepancies between measured and predicted screening lengths, with κ 1 λ D . In marked contrast to expectations, we found that the measured screening length κ 1 appears to grow as the ionic strength of the solution is increased. The origin of this discrepancy is discussed and the importance of considering the surface is highlighted. Full article
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Open AccessArticle Nanoparticle-Lipid Interaction: Job Scattering Plots to Differentiate Vesicle Aggregation from Supported Lipid Bilayer Formation
Colloids Interfaces 2018, 2(4), 50; https://doi.org/10.3390/colloids2040050
Received: 20 September 2018 / Revised: 13 October 2018 / Accepted: 17 October 2018 / Published: 22 October 2018
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Abstract
The impact of nanomaterials on lung fluids, or on the plasma membrane of living cells, has prompted researchers to examine the interactions between nanoparticles and lipid vesicles. Recent studies have shown that nanoparticle-lipid interaction leads to a broad range of structures including supported
[...] Read more.
The impact of nanomaterials on lung fluids, or on the plasma membrane of living cells, has prompted researchers to examine the interactions between nanoparticles and lipid vesicles. Recent studies have shown that nanoparticle-lipid interaction leads to a broad range of structures including supported lipid bilayers (SLB), particles adsorbed at the surface or internalized inside vesicles, and mixed aggregates. Currently, there is a need to have simple protocols that can readily evaluate the structures made from particles and vesicles. Here we apply the method of continuous variation for measuring Job scattering plots and provide analytical expressions for the scattering intensity in various scenarios. The result that emerges from the comparison between experiments and modeling is that electrostatics play a key role in the association, but it is not sufficient to induce the formation of supported lipid bilayers. Full article
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Open AccessArticle Rheological Properties of Alginate–Essential Oil Nanodispersions
Colloids Interfaces 2018, 2(4), 48; https://doi.org/10.3390/colloids2040048
Received: 27 September 2018 / Revised: 13 October 2018 / Accepted: 15 October 2018 / Published: 17 October 2018
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Abstract
Due to its favorable structural properties and biocompatibility, alginate is recognized as a suitable versatile biopolymer for use in a broad range of applications ranging from drug delivery, wound healing, tissue engineering, and food formulations such as nanodispersions. Rheological analysis plays a crucial
[...] Read more.
Due to its favorable structural properties and biocompatibility, alginate is recognized as a suitable versatile biopolymer for use in a broad range of applications ranging from drug delivery, wound healing, tissue engineering, and food formulations such as nanodispersions. Rheological analysis plays a crucial role in the design of suitable nanoemulsion based coatings. Different essential oil and alginate nanodispersion compositions stabilized by Tween 80 were analyzed for rheological and conductometric properties. The results confirmed that the nanoformulations shared a pseudoplastic non-Newtonian behavior that was more evident with higher alginate concentrations (2%). Nanodispersions made of alginate and essential oil exhibited a slight thixotropic behavior, demonstrating the aptitude to instantaneously recover from the applied stress or strain. Oscillatory frequency sweep tests showed a similar fluid-like behavior for 1% and 2% alginate nanodispersions. Finally, it was demonstrated that advantages coming with the use of the essential oil are added to the positive aspects of alginate with no dramatic modification on the flow behavior. Full article
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Open AccessFeature PaperArticle Imparting Photo-responsive Function to Thermo-responsive Iridescent Emulsions
Colloids Interfaces 2018, 2(4), 47; https://doi.org/10.3390/colloids2040047
Received: 29 September 2018 / Revised: 11 October 2018 / Accepted: 11 October 2018 / Published: 13 October 2018
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Abstract
In our previous paper, we reported that thermo-responsive emulsions can be prepared based on a long-chain amidoamine derivative (C18AA) and tetraoctylammonium bromide (TOAB), and that the C18AA + TOAB emulsions developed a characteristic interference color in a narrow temperature range. However, the coloration
[...] Read more.
In our previous paper, we reported that thermo-responsive emulsions can be prepared based on a long-chain amidoamine derivative (C18AA) and tetraoctylammonium bromide (TOAB), and that the C18AA + TOAB emulsions developed a characteristic interference color in a narrow temperature range. However, the coloration of the original C18AA + TOAB at room temperature exhibited poor brightness. In the present study, we show that the addition of NaOH is effective in both lowering the coloration temperature and improving the brightness of C18AA + TOAB emulsion considerably. Furthermore, we demonstrate that photo-response function can be imparted to C18AA + TOAB iridescent emulsions by introducing a photochromic naphthopyran derivative (Pyran) that reversibly changes from white to yellow upon UV irradiation. The C18AA + TOAB emulsions containing Pyran shows a dual stimuli-responsive iridescent property, and the emulsion color is controllable and reversible through both UV irradiation and temperature. Full article
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Open AccessArticle Synthesis of Hollow Silica Nanocubes with Tuneable Size and Shape, Suitable for Light Scattering Studies
Colloids Interfaces 2018, 2(4), 44; https://doi.org/10.3390/colloids2040044
Received: 14 August 2018 / Revised: 25 September 2018 / Accepted: 5 October 2018 / Published: 10 October 2018
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Abstract
We present a preparation method for hollow silica nanocubes with tuneable size and shape in the range required for light scattering studies. Cuprous oxide nanocubes are prepared by a water-assisted polyol method. By adjusting the water content, the size of the nanocubes can
[...] Read more.
We present a preparation method for hollow silica nanocubes with tuneable size and shape in the range required for light scattering studies. Cuprous oxide nanocubes are prepared by a water-assisted polyol method. By adjusting the water content, the size of the nanocubes can be tuned in the range of 40–120 nm. These cubes function as a shape template in the subsequent coating with Stöber silica, resulting in core-shell nanocubes. Dissolving the core with nitric acid results in hollow silica nanocubes with sizes ranging from 80–120 nm and cubicity shape parameters between 3 and 6.5. Full article
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Open AccessArticle Measurements of Dynamic Contributions to Coherent Neutron Scattering
Colloids Interfaces 2018, 2(3), 31; https://doi.org/10.3390/colloids2030031
Received: 13 July 2018 / Revised: 3 August 2018 / Accepted: 3 August 2018 / Published: 7 August 2018
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Abstract
In this manuscript, we are investigating the contribution of dynamic membrane properties of phospholipid membranes to coherent scattering signals under grazing incidence. Spectroscopic measurements under grazing incidence can provide useful insight into the properties of biological membranes; however, they are often impeded by
[...] Read more.
In this manuscript, we are investigating the contribution of dynamic membrane properties of phospholipid membranes to coherent scattering signals under grazing incidence. Spectroscopic measurements under grazing incidence can provide useful insight into the properties of biological membranes; however, they are often impeded by weak signals. By using grazing-incidence small-angle neutron scattering (GISANS) to identify a dynamic scattering contribution, we are able to independently corroborate the existence of a previously found dynamic mode, now measured by grazing-incidence neutron spin echo spectroscopy (GINSES). Additionally, by increasing the speed of measurement compared to GINSES from several days to hours, we were able to explore the temperature behavior of this mode in phospholipid membranes. These dynamic modes of the membranes show a wavelength of around 700 Å in-plane of the membrane and are most pronounced around 37 C and strongly decrease at lower temperatures below 25 C before vanishing at 20 C. We therefore speculate that they may be linked to biologically relevant functions of the membranes themselves. To our knowledge, this is the first report of an investigation of that membrane mode by means of GISANS. Full article
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Open AccessArticle Direct Determination of the Distribution Coefficient of Tridecyl Dimethyl Phosphine Oxide between Water and Hexane
Colloids Interfaces 2018, 2(3), 28; https://doi.org/10.3390/colloids2030028
Received: 8 June 2018 / Revised: 4 July 2018 / Accepted: 11 July 2018 / Published: 15 July 2018
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Abstract
Drop profile analysis tensiometry is applied to determine the distribution coefficient of a nonionic surfactant for a water/hexane system. The basic idea is to measure the interfacial tension isotherm in two configurations: a hexane drop immersed in the surfactant aqueous solutions at different
[...] Read more.
Drop profile analysis tensiometry is applied to determine the distribution coefficient of a nonionic surfactant for a water/hexane system. The basic idea is to measure the interfacial tension isotherm in two configurations: a hexane drop immersed in the surfactant aqueous solutions at different bulk concentrations, and a water drop immersed into a hexane solution of the same surfactant. Both types of experiments lead to an isotherm for the equilibrium interfacial tensions with the same slope but with a concentration shift between them. This shift refers exactly to the value of the distribution coefficient. Full article
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Review

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Open AccessReview Synthesis and Properties of SBA-15 Modified with Non-Noble Metals
Colloids Interfaces 2018, 2(4), 59; https://doi.org/10.3390/colloids2040059
Received: 2 October 2018 / Revised: 5 November 2018 / Accepted: 12 November 2018 / Published: 14 November 2018
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Abstract
Modification of SBA-15 with non-noble metal leads to functional materials, which can be applied as gas sensors, adsorbents, and catalysts of various reactions. The new materials contain up to four various metals, which are deposited consecutively or simultaneously at various concentrations ranging from
[...] Read more.
Modification of SBA-15 with non-noble metal leads to functional materials, which can be applied as gas sensors, adsorbents, and catalysts of various reactions. The new materials contain up to four various metals, which are deposited consecutively or simultaneously at various concentrations ranging from a fraction of 1% to an amount that is comparable with the mass of silica-support. These materials contain metals at various oxidation levels, usually as oxides, which occur in crystalline form (a typical crystallite size of about 10 nm matches the width of the SBA-15 channels), but in a few other materials, crystalline metal compounds have not been detected. Many researchers have provided detailed physico- chemical characteristics of SBA-15 modified with non-noble metals by the means of various microscopic and spectroscopic techniques. Full article
Open AccessReview Sessile Droplets on Deformable Substrates
Colloids Interfaces 2018, 2(4), 56; https://doi.org/10.3390/colloids2040056
Received: 20 September 2018 / Revised: 19 October 2018 / Accepted: 2 November 2018 / Published: 6 November 2018
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Abstract
Wetting of deformable substrates has gained significant interest over the past decade due to a multiplicity of industrial and biological applications. Technological advances in the area of interfacial science have given rise to the ability to capture interfacial behavior between a liquid droplet
[...] Read more.
Wetting of deformable substrates has gained significant interest over the past decade due to a multiplicity of industrial and biological applications. Technological advances in the area of interfacial science have given rise to the ability to capture interfacial behavior between a liquid droplet and an elastic substrate. Researchers have developed several theories to explain the interaction between the two phases and describe the process of wetting of deformable/soft substrates. A summary of the most recent advances on static wetting of deformable substrates is given in this review. It is demonstrated that action of surface forces (disjoining/conjoining pressure) near the apparent three-phase contact line should be considered. Any consideration of equilibrium droplets on deformable (as well as on non-deformable) substrates should be based on consideration of the excess free energy of the system. The equilibrium shapes of both droplet and deformable substrate should correspond to the minimum of the excess free energy of the system. It has never been considered in the literature that the obtained equilibrium profiles must satisfy sufficient Jacobi’s condition. If Jacobi’s condition is not satisfied, it is impossible to claim that the obtained solution really corresponds to equilibrium. In recently published studies, equilibrium of droplets on deformable substrates: (1) provided a solution that corresponds to the minimum of the excess free energy; and (2) the obtained solution satisfies the Jacobi’s condition. Based on consideration of disjoining/conjoining pressure acting in the vicinity of the apparent three-phase contact line, the hysteresis of contact angle of sessile droplets on deformable substrates is considered. It is shown that both advancing and receding contact angles decrease as the elasticity of the substrate is increased and the effect of disjoining/conjoining pressure is discussed. Fluid inside the droplet partially wets the deformable substrate. It is shown that just these forces coupled with the surface elasticity determine the deformation of the deformable substrates. Full article
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