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Colloids Interfaces, Volume 3, Issue 1 (March 2019)

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Open AccessArticle
Release of Pharmaceutical Peptides in an Aggregated State: Using Fibrillar Polymorphism to Modulate Release Levels
Colloids Interfaces 2019, 3(1), 42; https://doi.org/10.3390/colloids3010042
Received: 8 October 2018 / Revised: 15 March 2019 / Accepted: 15 March 2019 / Published: 26 March 2019
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Abstract
Traditional approaches to achieve sustained delivery of pharmaceutical peptides traditionally use co-excipients (e.g., microspheres and hydrogels). Here, we investigate the release of an amyloidogenic glucagon analogue (3474) from an aggregated state and the influence of surfactants on this process. The formulation of peptide [...] Read more.
Traditional approaches to achieve sustained delivery of pharmaceutical peptides traditionally use co-excipients (e.g., microspheres and hydrogels). Here, we investigate the release of an amyloidogenic glucagon analogue (3474) from an aggregated state and the influence of surfactants on this process. The formulation of peptide 3474 in dodecyl maltoside (DDM), rhamnolipid (RL), and sophorolipid (SL) led to faster fibrillation. When the aggregates were subjected to multiple cycles of release by repeated resuspension in fresh buffer, the kinetics of the release of soluble peptide 3474 from different surfactant aggregates all followed a simple exponential decay fit, with half-lives of 5–18 min and relatively constant levels of release in each cycle. However, different amounts of peptide are released from different aggregates, ranging from 0.015 mg/mL (3475-buffer) up to 0.03 mg/mL (3474-DDM), with 3474-buffer and 3474-RL in between. In addition to higher release levels, 3474-DDM aggregates showed a different amyloid FTIR structure, compared to 3474-RL and 3474-SL aggregates and a faster rate of degradation by proteinase K. This demonstrates that the stability of organized peptide aggregates can be modulated to achieve differences in release of soluble peptides, thus coupling aggregate polymorphism to differential release profiles. We achieved aggregate polymorphism by the addition of different surfactants, but polymorphism may also be reached through other approaches, including different excipients as well as changes in pH and salinity, providing a versatile handle to control release profiles. Full article
(This article belongs to the Special Issue Biosurfactants: Trends and Applications)
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Open AccessArticle
Adsorption of Uranium (VI) from Aqueous Solutions by Amino-functionalized Clay Minerals
Colloids Interfaces 2019, 3(1), 41; https://doi.org/10.3390/colloids3010041
Received: 22 December 2018 / Revised: 20 March 2019 / Accepted: 22 March 2019 / Published: 23 March 2019
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Abstract
Silylation of clay minerals from Cherkasy deposit (Ukraine) montmorillonite (layer silicate) and palygorskite (fibrous silicate) was performed using organosilane (3-aminopropyl)triethoxysilane (APTES). Solvents with different polarity (ethanol, toluene) were used in synthesis. The structure of modified minerals was characterized by complex of methods (X-ray [...] Read more.
Silylation of clay minerals from Cherkasy deposit (Ukraine) montmorillonite (layer silicate) and palygorskite (fibrous silicate) was performed using organosilane (3-aminopropyl)triethoxysilane (APTES). Solvents with different polarity (ethanol, toluene) were used in synthesis. The structure of modified minerals was characterized by complex of methods (X-ray powder diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption-desorption at −196 °C and thermal analysis). Studies of adsorption characteristics of APTES-modified clay minerals were carried out in relation to uranium (VI). The results indicated that modified montmorillonite and palygorskite were effective materials for water purification from UO22+. Full article
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Open AccessArticle
Wetting Properties of Polyetheretherketone Plasma Activated and Biocoated Surfaces
Colloids Interfaces 2019, 3(1), 40; https://doi.org/10.3390/colloids3010040
Received: 29 December 2018 / Revised: 27 February 2019 / Accepted: 12 March 2019 / Published: 16 March 2019
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Abstract
Polyetheretherketone (PEEK) biomaterial is a polymer which has been widely used since the early 90s as a material for human bone implant preparations. Nowadays it is increasingly used due to its high biocompatibility and easily modeling, as well as better mechanical properties and [...] Read more.
Polyetheretherketone (PEEK) biomaterial is a polymer which has been widely used since the early 90s as a material for human bone implant preparations. Nowadays it is increasingly used due to its high biocompatibility and easily modeling, as well as better mechanical properties and price compared to counterparts made of titanium or platinum alloys. In this paper, air low-temperature and pressure plasma was used to enhance PEEK adhesive properties as well as surface sterilization. On the activated polymeric carrier, biologically-active substances have been deposited with the Langmuir-Blodgett technique. Thereafter, the surface was characterized using optical profilometry, and wettability was examined by contact angle measuring. Next, the contact angle hysteresis (CAH) model was used to calculate the surface free energy of the modified surface of PEEK. The variations of wettability and surface free energy were observed depending on the deposited monolayer type and its components. Full article
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Open AccessFeature PaperArticle
Calibration Routine for Quantitative Three-Dimensional Flow Field Measurements in Drying Polymer Solutions Subject to Marangoni Convection
Colloids Interfaces 2019, 3(1), 39; https://doi.org/10.3390/colloids3010039
Received: 22 February 2019 / Revised: 6 March 2019 / Accepted: 12 March 2019 / Published: 15 March 2019
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Abstract
Surface-tension induced flows may have a significant impact on the surface topography of thin films or small printed structures derived from polymer solution processing. Despite a century of research on Marangoni convection, the community lacks quantitative experimental flow field data, especially from within [...] Read more.
Surface-tension induced flows may have a significant impact on the surface topography of thin films or small printed structures derived from polymer solution processing. Despite a century of research on Marangoni convection, the community lacks quantitative experimental flow field data, especially from within drying solutions. We utilize multifocal micro particle tracking velocimetry (µPTV) to obtain these data and show a calibration routine based on point spread function (PSF) simulations as well as experimental data. The results account for a varying sample refractive index, beneficial cover-glass correction collar settings as well as a multifocal lens system. Finally, the calibration procedure is utilized exemplarily to reconstruct a three-dimensional, transient flow field within a poly(vinyl acetate)-methanol solution dried with inhomogeneous boundary conditions. Full article
(This article belongs to the Special Issue Colloids and Interfaces in Printing Technology)
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Open AccessReview
Kinetics of Spreading over Porous Substrates
Colloids Interfaces 2019, 3(1), 38; https://doi.org/10.3390/colloids3010038
Received: 18 January 2019 / Revised: 25 February 2019 / Accepted: 11 March 2019 / Published: 15 March 2019
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Abstract
The spreading of small liquid drops over thin and thick porous layers (dry or saturated with the same liquid) is discussed in the case of both complete wetting (silicone oils of different viscosities over nitrocellulose membranes and blood over a filter paper) and [...] Read more.
The spreading of small liquid drops over thin and thick porous layers (dry or saturated with the same liquid) is discussed in the case of both complete wetting (silicone oils of different viscosities over nitrocellulose membranes and blood over a filter paper) and partial wetting (aqueous SDS (Sodium dodecyl sulfate) solutions of different concentrations and blood over partially wetted substrates). Filter paper and nitrocellulose membranes of different porosity and different average pore size were used as a model of thin porous layers, sponges, glass and metal filters were used as a model of thick porous substrates. Spreading of both Newtonian and non-Newtonian liquid are considered below. In the case of complete wetting, two spreading regimes were found (i) the fast spreading regime, when imbibition is not important and (ii) the second slow regime when imbibition dominates. As a result of these two competing processes, the radius of the drop goes through a maximum value over time. A system of two differential equations was derived in the case of complete wetting for both Newtonian and non-Newtonian liquids to describe the evolution with time of radii of both the drop base and the wetted region inside the porous layer. The deduced system of differential equations does not include any fitting parameter. Experiments were carried out by the spreading of silicone oil drops over various dry microfiltration membranes (permeable in both normal and tangential directions) and blood over dry filter paper. The time evolution of the radii of both the drop base and the wetted region inside the porous layer were monitored. All experimental data fell on two universal curves if appropriate scales are used with a plot of the dimensionless radii of the drop base and of the wetted region inside the porous layer on dimensionless time. The predicted theoretical relationships are two universal curves accounting quite satisfactorily for the experimental data. According to the theory prediction, (i) the dynamic contact angle dependence on the same dimensionless time as before should be a universal function and (ii) the dynamic contact angle should change rapidly over an initial short stage of spreading and should remain a constant value over the duration of the rest of the spreading process. The constancy of the contact angle on this stage has nothing to do with hysteresis of the contact angle: there is no hysteresis in the system under investigation in the case of complete wetting. These conclusions again are in good agreement with experimental observations in the case of complete wetting for both Newtonian and non-Newtonian liquids. Addition of surfactant to aqueous solutions, as expected, improve spreading over porous substrates and, in some cases, results in switching from partial to complete wetting. It was shown that for the spreading of surfactant solutions on thick porous substrates there is a minimum contact angle after which the droplet rapidly absorbs into the substrate. Unfortunately, a theory of spreading/imbibition over thick porous substrates is still to be developed. However, it was shown that the dimensionless time dependences of both contact angle and spreading radius of the droplet on thick porous material fall on to a universal curve in the case of complete wetting. Full article
(This article belongs to the Special Issue Colloids and Interfaces in Printing Technology)
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Open AccessArticle
Scaling Behavior of Pattern Formation in the Flexographic Ink Splitting Process
Colloids Interfaces 2019, 3(1), 37; https://doi.org/10.3390/colloids3010037
Received: 31 January 2019 / Revised: 8 March 2019 / Accepted: 8 March 2019 / Published: 13 March 2019
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Abstract
We considered pattern formation, i.e. viscous fingering, in the ink splitting process between an elastic flexographic printing plate and the substrate. We observed an unexpected scaling behavior of the emerging pattern length scale (i.e., finger width) as a function of printing velocity, fluid [...] Read more.
We considered pattern formation, i.e. viscous fingering, in the ink splitting process between an elastic flexographic printing plate and the substrate. We observed an unexpected scaling behavior of the emerging pattern length scale (i.e., finger width) as a function of printing velocity, fluid viscosity, surface tension, and plate elasticity coefficients. Scaling exponents depended on the ratio of the capillary number of the fluid flow, and the elastocapillary number defined by plate elasticity and surface tension. The exponents significantly differed from rigid printing plates, which depend on the capillary number only. A dynamic model is proposed to predict the scaling exponents. The results indicate that flexo printing corresponded to a self-regulating dynamical equilibrium of viscous, capillary, and elastic forces. We argue that these forces stabilize the process conditions in a flexo printing unit over a wide range of printing velocities, ink viscosities, and mechanical process settings. Full article
(This article belongs to the Special Issue Colloids and Interfaces in Printing Technology)
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Open AccessArticle
Titanium Silicates Precipitated on the Rice Husk Biochar as Adsorbents for the Extraction of Cesium and Strontium Radioisotope Ions
Colloids Interfaces 2019, 3(1), 36; https://doi.org/10.3390/colloids3010036
Received: 27 December 2018 / Revised: 24 February 2019 / Accepted: 1 March 2019 / Published: 12 March 2019
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Abstract
The aim of the work was the development of cheap and effective adsorbents based on titanium silicates deposited on the products of thermochemical processing of rice husk to extract cesium and strontium radioisotopes from aqueous media. Synthesis of adsorbents was carried out using [...] Read more.
The aim of the work was the development of cheap and effective adsorbents based on titanium silicates deposited on the products of thermochemical processing of rice husk to extract cesium and strontium radioisotopes from aqueous media. Synthesis of adsorbents was carried out using the cheapest and widely used titanium water-soluble reagent, titanium sulfate (an intermediate product of white rutile pigment production), as feedstock. After treatment with titanium sulfate and neutralization, hydrothermal treatment was carried out in various ways. The traditional method of processing in an autoclave was used, as well as the blowing at different temperatures by steam. The distribution coefficients and the adsorption capacity for cesium and strontium ions on these sorbents were studied. Along with the chemical composition of adsorbents obtained by those ways, the type and the temperature of hydrothermal treatment also affected the adsorption properties. It was found that the adsorbent obtained by hydrothermal treatment in an autoclave has the highest degree of cesium ions extraction (Kd = 27,500). The highest degree of strontium ions extraction (Kd = 2,095,000) has an adsorbent obtained by hydrothermal treatment with water vapor blowing. Full article
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Open AccessArticle
Sorption Membranes and Filter for Water Purification and Disinfection in Outdoor Conditions
Colloids Interfaces 2019, 3(1), 35; https://doi.org/10.3390/colloids3010035
Received: 27 December 2018 / Revised: 2 March 2019 / Accepted: 4 March 2019 / Published: 11 March 2019
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Abstract
The aim of this article was to develop a simple, cheap, light, highly efficient sorption membrane and filtering device for the purification of naturally polluted water with application in outdoor conditions. Sorption membranes have been prepared from cellulose pulp using paper and pulp [...] Read more.
The aim of this article was to develop a simple, cheap, light, highly efficient sorption membrane and filtering device for the purification of naturally polluted water with application in outdoor conditions. Sorption membranes have been prepared from cellulose pulp using paper and pulp technology. The sorbents were introduced into paper pulp as a filler (as activated carbon) or were chemically grafted to cellulose fibers. The absorption ability of such membranes assembled in a filter device has been investigated. The removal of weighted small mechanical particles, microorganisms, dissolved organic contaminants and colloids, and the undesirable ion impurities by the filter was investigated. Using a 10 × 10 cm filter, purification and disinfection of 18 liters of natural polluted water from a lake was done. Purification of dirty water occurs with gravity from a tank (bucket). Full article
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Open AccessArticle
Thermal Transformation of Caffeic Acid on the Nanoceria Surface Studied by Temperature Programmed Desorption Mass-Spectrometry, Thermogravimetric Analysis and FT–IR Spectroscopy
Colloids Interfaces 2019, 3(1), 34; https://doi.org/10.3390/colloids3010034
Received: 31 December 2018 / Revised: 22 February 2019 / Accepted: 5 March 2019 / Published: 11 March 2019
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Abstract
The studies of pyrolysis of caffeic acid (CA) and its surface complexes is important for the development of technologies of heterogeneous catalytic pyrolysis of plant- and wood- based renewable biomass components. In this work, the structure and thermal transformations of the surface complexes [...] Read more.
The studies of pyrolysis of caffeic acid (CA) and its surface complexes is important for the development of technologies of heterogeneous catalytic pyrolysis of plant- and wood- based renewable biomass components. In this work, the structure and thermal transformations of the surface complexes of CA on the surface of nanoceria were investigated using Fourier transform–infrared (FT–IR) spectroscopy, thermogravimetric analysis (TGA) and temperature-programmed desorption mass spectrometry (TPD MS). It was found that CA on the surface of cerium dioxide forms several types of complexes: bidentate carboxylates, monodentate carboxylates and complexes formed as a result of interaction with phenolic hydroxyl groups. This is due to the ability of nanosized cerium dioxide to generate basic hydroxyl groups that can deprotonate phenolic groups to form phenolates on the surface. The main pyrolysis products were identified. The possible ways of forming 3,4-dihydroxyphenylethylene, acetylene carboxylic acid, pyrocatechol and phenol from surface complexes of CA were suggested. It was established that on the nanoceria surface effectively occur the decarboxylation, decarbonylation, and dehydration reactions of the CA, which are the desirable processes in biomass conversion technologies. Full article
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Open AccessArticle
Development of Cu-Modified PVC and PU for Catalytic Generation of Nitric Oxide
Colloids Interfaces 2019, 3(1), 33; https://doi.org/10.3390/colloids3010033
Received: 22 December 2018 / Revised: 16 February 2019 / Accepted: 4 March 2019 / Published: 9 March 2019
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Abstract
Nitric oxide (NO) generating surfaces are potentially promising for improving haemocompatibility of blood-contacting biomaterials. In the present report, Cu-modified poly(vinyl chloride) (PVC) and polyurethane (PU) were prepared via polydopamine (pDA)-assisted chelation. The copper content on the PVC and PU modified surfaces, assessed by [...] Read more.
Nitric oxide (NO) generating surfaces are potentially promising for improving haemocompatibility of blood-contacting biomaterials. In the present report, Cu-modified poly(vinyl chloride) (PVC) and polyurethane (PU) were prepared via polydopamine (pDA)-assisted chelation. The copper content on the PVC and PU modified surfaces, assessed by inductively coupled plasma - optical emission spectrometry (ICP-OES), were about 3.86 and 6.04 nmol·cm−2, respectively. The Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) data suggest that copper is attached to the polymer surface through complex formation with pDA. The cumulative leaching of copper from modified PVC and PU during the five day incubation in phosphate buffered saline (PBS), measured by inductively coupled plasma mass spectrometry (ICP-MS), was about 50.7 ppb and 48 ppb, respectively which is within its physiological level. Modified polymers were tested for their ability to catalytically generate NO by decomposing of endogenous S-nitrosothiol (GSNO). The obtained data show that Cu-modified PVC and PU exhibited the capacity to generate physiological levels of NO which could be a foundation for developing new biocompatible materials with NO-based therapeutics. Full article
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Open AccessArticle
Comparative Study of Printed Multilayer OLED Fabrication through Slot Die Coating, Gravure and Inkjet Printing, and Their Combination
Colloids Interfaces 2019, 3(1), 32; https://doi.org/10.3390/colloids3010032
Received: 31 January 2019 / Revised: 28 February 2019 / Accepted: 3 March 2019 / Published: 6 March 2019
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Abstract
In this study, multilayer organic light-emitting diodes (OLEDs) consisting of three solution-processed layers are fabricated using slot die coating, gravure printing, and inkjet printing, techniques that are commonly used in the industry. Different technique combinations are investigated to successively deposit a hole injection [...] Read more.
In this study, multilayer organic light-emitting diodes (OLEDs) consisting of three solution-processed layers are fabricated using slot die coating, gravure printing, and inkjet printing, techniques that are commonly used in the industry. Different technique combinations are investigated to successively deposit a hole injection layer (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)), a cross-linkable hole transport layer (N,N′-bis(4-(6-((3-ethyloxetan-3-yl)methoxy)-hexyloxy)phenyl)-N,N′-bis(4-methoxyphenyl)biphenyl-4,4′-diamin (QUPD)), and a green emissive layer (TSG-M) on top of each other. In order to compare the application techniques, the ink formulations have to be adapted to the respective process requirements. First, the influence of the application technique on the layer homogeneity of the different materials is investigated. Large area thickness measurements of the layers based on imaging color reflectometry (ICR) are used to compare the application techniques regarding the layer homogeneity and reproducible film thickness. The total stack thickness of all solution-processed layers of 32 OLEDs could be reproduced homogeneously in a process window of 30 nm for the technique combination of slot die coating and inkjet printing. The best efficiency of 13.3 cd A−1 is reached for a process combination of slot die coating and gravure printing. In order to enable a statistically significant evaluation, in total, 96 OLEDs were analyzed and the corresponding 288 layers were measured successively to determine the influence of layer homogeneity on device performance. Full article
(This article belongs to the Special Issue Colloids and Interfaces in Printing Technology)
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Open AccessArticle
Experimental Investigation of Water Based Colloidal Gas Aphron Fluid Stability
Colloids Interfaces 2019, 3(1), 31; https://doi.org/10.3390/colloids3010031
Received: 12 November 2018 / Revised: 21 February 2019 / Accepted: 25 February 2019 / Published: 3 March 2019
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Abstract
Today, the drilling operators use the Colloidal Gas Aphron (CGA) fluids as a part of drilling fluids in their operations to reduce formation damages in low-pressure, mature or depleted reservoirs. In this paper, a Taguchi design of experiment (DOE) has been designed to [...] Read more.
Today, the drilling operators use the Colloidal Gas Aphron (CGA) fluids as a part of drilling fluids in their operations to reduce formation damages in low-pressure, mature or depleted reservoirs. In this paper, a Taguchi design of experiment (DOE) has been designed to analyse the effect of salinity, polymer and surfactant types and concentration on the stability of CGA fluids. Poly Anionic Cellulose (PacR) and Xanthan Gum (XG) polymers are employed as viscosifier; Hexadecyl Trimethyl Ammonium Bromide (HTAB) and Sodium Dodecyl Benzene Sulphonate (SDBS) have been also utilized as aphronizer. Moreover, bubble size distributions, rheological and filtration properties of aphronized fluids are investigated. According to the results, the polymer type has the highest effect, whereas the surfactant type has the lowest effect on the stability of CGA drilling fluid. It was also observed that increasing salinity in CGA fluid reduces the stability. Finally, it should be noted that the micro-bubbles generated with HTAB surfactant in an electrolyte system, are more stable than SDBS surfactant. Full article
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Open AccessArticle
Removal of Rhodamine B (A Basic Dye) and Acid Yellow 17 (An Acidic Dye) from Aqueous Solutions by Ordered Mesoporous Carbon and Commercial Activated Carbon
Colloids Interfaces 2019, 3(1), 30; https://doi.org/10.3390/colloids3010030
Received: 10 January 2019 / Revised: 15 February 2019 / Accepted: 21 February 2019 / Published: 26 February 2019
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Abstract
In this work, adsorption of rhodamine B (RB) and acid yellow 17 (AY17) was investigated on ordered mesoporous carbon material obtained by soft-templating method with hydrochloric acid (ST-A). For comparison, the adsorption process on commercial activated carbon CWZ-22 was also carried out. The [...] Read more.
In this work, adsorption of rhodamine B (RB) and acid yellow 17 (AY17) was investigated on ordered mesoporous carbon material obtained by soft-templating method with hydrochloric acid (ST-A). For comparison, the adsorption process on commercial activated carbon CWZ-22 was also carried out. The sorbents were characterized by nitrogen adsorption/desorption isotherms and scanning electron microscopy. Langmuir and Freundlich adsorption isotherm models were applied to simulate the equilibrium data of RB and AY17. Adsorption isotherm data could be better described by the Langmuir model than the Freundlich model. The adsorption kinetics of RB and AY17 on studied carbons could be well depicted by using pseudo-second-order kinetic modeling. The adsorption capacity increased with temperature increase in the range of 298–315 K. In the whole diffusion process, the intraparticle diffusion was involved, but not the whole rate-controlling step. The calculated thermodynamic parameters, including Gibbs free energy (∆G), enthalpy (∆H), and entropy (ΔS) suggested that adsorption processes of RB and AY17 on ST-A and CWZ-22 were endothermic and spontaneous. Full article
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Open AccessCommunication
Impact of a Linear Array of Hydrophilic and Superhydrophobic Spheres on a Deep Water Pool
Colloids Interfaces 2019, 3(1), 29; https://doi.org/10.3390/colloids3010029
Received: 23 January 2019 / Revised: 19 February 2019 / Accepted: 20 February 2019 / Published: 22 February 2019
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Abstract
The impact of solid bodies on the free surface of liquid pools is involved in many practical applications—such as bullets and air-to-sea anti-torpedo defense systems, or the water entry of athletes in water sports—aimed at improving the performance through a control of cavity [...] Read more.
The impact of solid bodies on the free surface of liquid pools is involved in many practical applications—such as bullets and air-to-sea anti-torpedo defense systems, or the water entry of athletes in water sports—aimed at improving the performance through a control of cavity dynamics. This work reports an experimental investigation of the impact of a linear array of hydrophilic (H) and superhydrophobic (SH) spheres on a deep water pool. The array consisted of ten magnetic spheres, with different permutations of H and SH spheres. Using high speed shadowgraphy, we captured the underwater kinematics of the array for different permutations of H and SH spheres. In particular, we observed the evolution or absence of an air cavity attached to the array as a function of the position of the H and SH spheres. The position of the first SH sphere from the leading edge of the array (ZSH) emerged as a key parameter that alters the characteristics of cavity evolution. The appearance and pinch-off characteristics of a wake cavity behind the trailing edge were governed by the wetting properties of the leading and trailing surfaces of the array. The position of the first SH surface, as well as the wetting characteristics of the leading and trailing surfaces, are potential control parameters to alter underwater cavity evolution during solid surface impact on deep water pools. Full article
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Open AccessArticle
Surface Complexation Modeling of Biomolecule Adsorptions onto Titania
Colloids Interfaces 2019, 3(1), 28; https://doi.org/10.3390/colloids3010028
Received: 15 December 2018 / Revised: 13 February 2019 / Accepted: 14 February 2019 / Published: 18 February 2019
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Abstract
The adsorption of nucleic acid components on the surface of nanocrystalline titanium dioxide (anatase, pHpzc = 6.5) in NaCl solutions was investigated using potentiometric titrations and multibatch adsorption experiments over a wide range of pH and ionic strengths. The Basic Stern surface [...] Read more.
The adsorption of nucleic acid components on the surface of nanocrystalline titanium dioxide (anatase, pHpzc = 6.5) in NaCl solutions was investigated using potentiometric titrations and multibatch adsorption experiments over a wide range of pH and ionic strengths. The Basic Stern surface complexation model was applied to experimental data to obtain quantitative equilibrium reaction constants. Adsorption results suggest that there is a considerable difference in the binding of nucleobases, nucleosides, and nucleotides with an anatase surface. Full article
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Open AccessArticle
Solid Phase Extraction of Trace Amounts of Praseodymium Using Transcarpathian Clinoptilolite
Colloids Interfaces 2019, 3(1), 27; https://doi.org/10.3390/colloids3010027
Received: 23 December 2018 / Revised: 8 February 2019 / Accepted: 8 February 2019 / Published: 14 February 2019
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Abstract
Sorptive properties of the Transcarpathian clinoptilolite towards Pr(III) were studied under dynamic conditions. The sorption capacity of clinoptilolite under optimal conditions (sorbent grain diameter of 0.20–0.31 mm; pH 9.0, temperature of preliminary precalcination of 350 °C, and flow rate of the Pr(III) salt [...] Read more.
Sorptive properties of the Transcarpathian clinoptilolite towards Pr(III) were studied under dynamic conditions. The sorption capacity of clinoptilolite under optimal conditions (sorbent grain diameter of 0.20–0.31 mm; pH 9.0, temperature of preliminary precalcination of 350 °C, and flow rate of the Pr(III) salt solution with the concentration of 1.0 μg·mL−1 through the sorbent of 5 mL·min−1) was equal to 47.5 mg·g−1. The best desorbent of Pr from the clinoptilolite was the 1 M solution of KCl acidified with HCl to a pH value of 3.0. The method of Pr(III) trace amounts preconcentration in a solid phase extraction mode with further determination of this REE via spectrophotometric technique was developed. The linearity of the proposed method was evaluated in the range of 2–100 ng·mL−1 with detection limit of 0.7 ng·mL−1. Full article
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Open AccessArticle
Anomalously Slow Dewetting of Colloidal Particles at a Liquid/Gas Interface
Colloids Interfaces 2019, 3(1), 26; https://doi.org/10.3390/colloids3010026
Received: 17 December 2018 / Revised: 3 February 2019 / Accepted: 4 February 2019 / Published: 8 February 2019
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Abstract
We consider the anomalously slow dewetting of colloidal particles adsorbed at a liquid/gas interface. The particles move in the vertical direction under the action of a regular capillary force and an irregular force caused by defects (roughness and chemical heterogeneity). The particle diffusion [...] Read more.
We consider the anomalously slow dewetting of colloidal particles adsorbed at a liquid/gas interface. The particles move in the vertical direction under the action of a regular capillary force and an irregular force caused by defects (roughness and chemical heterogeneity). The particle diffusion is modeled by a random walk over a potential minima with jump rates determined by the Arrhenius law. The averaged particle motion is found under the assumption of Gaussian distributions for characteristic properties of spatial heterogeneities. Full article
(This article belongs to the Special Issue Wetting on Micro/Nano-Scale: From Fundamentals to Application)
Open AccessArticle
Colloidal Metal Oxide Nanoparticles Prepared by Laser Ablation Technique and Their Antibacterial Test
Colloids Interfaces 2019, 3(1), 25; https://doi.org/10.3390/colloids3010025
Received: 10 January 2019 / Revised: 29 January 2019 / Accepted: 31 January 2019 / Published: 4 February 2019
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Abstract
In this article we report the production of metal oxide (TiFe2O4, ZnFe2O4) nanoparticles by pulsed laser ablation technique in a liquid environment. We used nanosecond Nd: YAG laser systems working at 532 nm and 1064 [...] Read more.
In this article we report the production of metal oxide (TiFe2O4, ZnFe2O4) nanoparticles by pulsed laser ablation technique in a liquid environment. We used nanosecond Nd: YAG laser systems working at 532 nm and 1064 nm of wavelength and the energy of the laser beam was kept constant at 80 mJ. Absorbance spectra, surface plasmon resonance, optical band-gap, and nanoparticle morphology were investigated using ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Changing the wavelength of the laser for growth, nanoparticles showed shift between the absorbance and surface plasmon resonance peaks in their UV-Vis spectra, which implies that the optical properties of the colloid nanoparticles depend on laser parameters. This was confirmed with the variation of the band gap energy. Furthermore, redshift for the absorbance peak was observed for samples as-grown at 532 nm around 150 nm as a function of time preparation. Conversely, for the samples as-grown at 1064 nm there was no shift in the absorbance spectra, which could be due to agglomeration and formation of larger particles. The characterization results showed appropriate plasmonic photo-catalysts properties of the particles, hence the photoactivation of the nanoparticles was examined on antibacterial effect using colonies of Staphylococcus aureus and Escherichia coli. Full article
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Open AccessArticle
Experimental Investigations of Behaviour of Biosurfactants in Brine Solutions Relevant to Hydrocarbon Reservoirs
Colloids Interfaces 2019, 3(1), 24; https://doi.org/10.3390/colloids3010024
Received: 21 December 2018 / Revised: 29 January 2019 / Accepted: 30 January 2019 / Published: 2 February 2019
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Abstract
In this study, we investigated the behaviour of rhamnolipid and Greenzyme in brine solutions relevant to hydrocarbon reservoir. Prior to this work, several studies only reported the behaviour of the biosurfactants dissolved in sodium chloride solutions of varied salinity. The results of this [...] Read more.
In this study, we investigated the behaviour of rhamnolipid and Greenzyme in brine solutions relevant to hydrocarbon reservoir. Prior to this work, several studies only reported the behaviour of the biosurfactants dissolved in sodium chloride solutions of varied salinity. The results of this study are relevant to the application of the biosurfactants in enhanced oil recovery, during which the compounds are injected into reservoir saturated with formation water, typically of high salinity and complex composition. Surface tension and conductivity methods were used to determine the critical micelle concentrations of the biosurfactants, Gibbs surface excess concentrations and standard free energy at water-air interface. The results show that rhamnolipid and Greenzyme could reduce the surface tension of water from 72.1 ± 0.2 mN/m to 34.7 ± 0.4 mN/m and 47.1 ± 0.1 mN/m respectively. They were also found to be stable in high salinity and high temperature with rhamnolipid being sensitive to brine salinity, composition and pH while Greenzyme showed tolerance for high salinity. Furthermore, the Gibbs standard free energy of micellisation shows that rhamnolipid and Greenzyme have the tendency to spontaneously form micelles with rhamnolipid showing more surface adsorption. However from maximal Gibbs surface excess concentration calculations, Greenzyme monomers tend to favour aggregation more than that of rhamnolipid. Full article
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Open AccessArticle
Practical Formulation Science for Particle-Based Inks
Colloids Interfaces 2019, 3(1), 23; https://doi.org/10.3390/colloids3010023
Received: 4 November 2018 / Revised: 21 December 2018 / Accepted: 29 January 2019 / Published: 1 February 2019
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Abstract
There is a big gap between idealized colloid science and the needs of a printing ink formulator. This often leads to formulations based on intuition and experience rather than good science. By bringing together the most relevant colloid and interface science with the [...] Read more.
There is a big gap between idealized colloid science and the needs of a printing ink formulator. This often leads to formulations based on intuition and experience rather than good science. By bringing together the most relevant colloid and interface science with the capabilities of modern apps, it is possible to bridge the gap between theory and reality to the benefit of both the colloid science community and those who need the science to improve their formulations. The process of making current science usable also exposes the limitations of available theories. This suggests a methodology for highlighting the grand challenges to the colloid science research community, including the challenge of making any new science more usable. Full article
(This article belongs to the Special Issue Colloids and Interfaces in Printing Technology)
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Open AccessArticle
The Methanol Adsorption in Microporous Alumina Agglomerates
Colloids Interfaces 2019, 3(1), 22; https://doi.org/10.3390/colloids3010022
Received: 11 January 2019 / Revised: 28 January 2019 / Accepted: 29 January 2019 / Published: 31 January 2019
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Abstract
We have studied theoretical and experimental methods of methanol adsorption in micropores of aluminum oxide agglomerates obtained by gas-dispersion synthesis. It is shown that the necessity to use strict equations based on the theory of volume filling of micropores, which implies a physical [...] Read more.
We have studied theoretical and experimental methods of methanol adsorption in micropores of aluminum oxide agglomerates obtained by gas-dispersion synthesis. It is shown that the necessity to use strict equations based on the theory of volume filling of micropores, which implies a physical and formal analogy between the volume filling of micropores and capillary condensation, for qualitative and quantitative description of adsorption equilibrium in open slit-like micropores. The applicability of the proposed equations for the description of adsorption equilibrium in such systems is demonstrated on the example of experimental methanol adsorption/desorption isotherm on the aluminum oxide, which possesses a microporous structure. Full article
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Open AccessArticle
Influence of Biodestructors on the Wear Resistance of Polyester Geotextile Materials
Colloids Interfaces 2019, 3(1), 21; https://doi.org/10.3390/colloids3010021
Received: 28 December 2018 / Revised: 17 January 2019 / Accepted: 29 January 2019 / Published: 31 January 2019
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Abstract
Changes in the structure and properties of geotextile nonwoven materials after microbiological load under natural conditions have been studied. Microbiological research of samples was conducted after testing for 12 and 24 months. The results of the research of physical and mechanical materials properties [...] Read more.
Changes in the structure and properties of geotextile nonwoven materials after microbiological load under natural conditions have been studied. Microbiological research of samples was conducted after testing for 12 and 24 months. The results of the research of physical and mechanical materials properties prove their sufficient resistance to the influence of biodestructors. Full article
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Open AccessArticle
Colloidal Stability of Positively Charged Dispersions of Styrene and Acrylic Copolymers in the Presence of TiO2 and CaCO3
Colloids Interfaces 2019, 3(1), 20; https://doi.org/10.3390/colloids3010020
Received: 28 December 2018 / Revised: 25 January 2019 / Accepted: 28 January 2019 / Published: 30 January 2019
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Abstract
Increasing antibiotic resistance of several pathogenic microorganisms calls for alternative approaches to prevent spreading of bacterial diseases. We propose to employ for this purpose coatings obtained from positively charged latex dispersions. In this contribution we characterize aqueous mixed dispersions containing TiO2 or [...] Read more.
Increasing antibiotic resistance of several pathogenic microorganisms calls for alternative approaches to prevent spreading of bacterial diseases. We propose to employ for this purpose coatings obtained from positively charged latex dispersions. In this contribution we characterize aqueous mixed dispersions containing TiO2 or CaCO3 and methyl methacrylate-ethyl acrylate or styrene-ethyl acrylate copolymers synthesized using a cationic surfactant, cetyltrimethylammonium bromide as an emulsifier. Particle size, electrokinetic (ζ) potential of the mixed dispersions and the resulting thin films, as well as antimicrobial properties of the latter are described. The TiO2 and CaCO3 dispersions were stabilised with polyethyleneimine (PEI) and optimum pH for the mixed dispersions were chosen on the basis of ζ-potential measurements. For TiO2, the maximum ζ = +35 mV was found at pH 7.5, and for CaCO3, pH was set at 8.2 (ζ = +38 mV), to prevent its dissolution. In most 1:1 mixtures of TiO2 or CaCO3 with the cetyltrimethylammonium bromide (CTAB)-stabilised latex dispersions, two distinct particles populations were observed, corresponding to the bare latex and bare TiO2 or CaCO3 fractions. Films made of the mixed dispersions remained positively charged and showed antimicrobial activity similar or reduced with respect to the bare polymer films. Full article
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Open AccessArticle
Sorption Properties of Polydivinylbenzene Polymers Towards Phenolic Compounds and Pharmaceuticals
Colloids Interfaces 2019, 3(1), 19; https://doi.org/10.3390/colloids3010019
Received: 21 December 2018 / Revised: 20 January 2019 / Accepted: 23 January 2019 / Published: 28 January 2019
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Abstract
Highly cross-linked polymers are commonly used in purification and separation techniques because of their many useful features. In order to better adjust their porosity to adsorption of specific compounds, methods like surface functionalization or imprinting are used. In this work, a series of [...] Read more.
Highly cross-linked polymers are commonly used in purification and separation techniques because of their many useful features. In order to better adjust their porosity to adsorption of specific compounds, methods like surface functionalization or imprinting are used. In this work, a series of highly cross-linked polydivinylbenzenes (pDVB) were prepared using a suspension method. Toluene was applied as a pore-forming diluent. Some part of toluene (1 mL) was replaced with phenol (F), 2,4,6-trichlorophenol (T) or their mixture (M) to prepare polymers with porosity more suitable for phenols sorption. Another approach was an introduction of sulfone groups onto the polymer surface (pDVB-SO3H). The physicochemical characteristics of the synthetized adsorbents included CHN, FTIR, DSC and porosimetric analyses. Afterwards, to evaluate sorption properties of the prepared adsorbents towards phenols, ibuprofen and salicylic acid the solid phase extraction (SPE) experiments were performed. The polymers had the specific surface areas of about 440–560 m2/g created mainly by mesopores with widths ca. 3.75 and 4.75–7.15 nm. Materials obtained with the addition of porosity modifiers (phenol, trichlorophenol, mixture) had more uniform porous structure and their sorption capacity toward phenols increased ca. 5%. Similar sorption capacities were obtained for ibuprofen. Salicylic acid had low affinity to the surface of the tested polymers. Full article
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Open AccessArticle
Influence of the Synthesis Method on the Structural Characteristics of Novel Hybrid Adsorbents Based on Bentonite
Colloids Interfaces 2019, 3(1), 18; https://doi.org/10.3390/colloids3010018
Received: 21 December 2018 / Revised: 18 January 2019 / Accepted: 24 January 2019 / Published: 28 January 2019
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Abstract
New hybrid composite materials were prepared by polymerization of resorcinol–formaldehyde resins in the presence of bentonite with various contents of polymer and water, and then exposed to pyrolysis in an inert atmosphere at 800 °C. The influence of the filler and synthesis method [...] Read more.
New hybrid composite materials were prepared by polymerization of resorcinol–formaldehyde resins in the presence of bentonite with various contents of polymer and water, and then exposed to pyrolysis in an inert atmosphere at 800 °C. The influence of the filler and synthesis method on the morphological, textural and structural characteristics has been described. The materials were characterized using low temperature nitrogen adsorption–desorption, small angle X-ray scattering, scanning electron microscopy, Raman spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA). The maximal values of the specific surface area of organo-bentonite and carbonized samples were 254 and 200 m2/g, respectively, which is much larger than that of the initial bentonite. The TGA and DSC experiments showed changes in the thermal stability of samples depending on their composition. The obtained data could provide a better understanding of the principles of preparing hybrid bentonite-containing composites that may provide an additional incentive to develop advanced technologies. Full article
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Open AccessArticle
Polymeric Nanocomposites of Iron–Oxide Nanoparticles (IONPs) Synthesized Using Terminalia chebula Leaf Extract for Enhanced Adsorption of Arsenic(V) from Water
Colloids Interfaces 2019, 3(1), 17; https://doi.org/10.3390/colloids3010017
Received: 18 October 2018 / Revised: 17 December 2018 / Accepted: 7 January 2019 / Published: 27 January 2019
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Abstract
This study demonstrates the ecofriendly synthesis of iron–oxide nanoparticles (IONPs) and their stabilization with polymers, i.e., chitosan (C) and polyvinyl alcohol (PVA)–alginate (PA), along with a further investigation for the removal of arsenic(As(V)) from water. IONPs with an average diameter of less than [...] Read more.
This study demonstrates the ecofriendly synthesis of iron–oxide nanoparticles (IONPs) and their stabilization with polymers, i.e., chitosan (C) and polyvinyl alcohol (PVA)–alginate (PA), along with a further investigation for the removal of arsenic(As(V)) from water. IONPs with an average diameter of less than 100 nm were prepared via a green synthesis process using an aqueous leaf extract of Terminalia chebula. Batch experiments were conducted to compare the removal efficiency of As(V) by these adsorbents. Factors such as pH and adsorbent dosages significantly affected the removal of arsenate As(V) by IONPs and polymer-supported reactive IONPs. Several adsorption kinetic models, such as pseudo first-order, and pseudo second-order Langmuir and Freundlich isotherms, were used to describe the adsorption of As(V). The removal of As(V) by IONPs follows the Langmuir adsorption isotherm. The highest monolayer saturation adsorption capacity as obtained from the Langmuir adsorption isotherm for IONPs was 28.57 mg/g. As(V) adsorption by polymer-supported IONPs best fit the Freundlich model, and maximum adsorption capacities of 34.4 mg/g and 40.3 mg/g were achieved for chitosan- and PVA–alginate-supported IONPs, respectively. However, among these absorbents, PVA–alginate-supported IONPs were found to be more effective than the other adsorbents in terms of adsorption, stability, and reusability. Full article
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Open AccessArticle
Conversion of D-Fructose into Ethyl Lactate Over a Supported SnO2–ZnO/Al2O3 Catalyst
Colloids Interfaces 2019, 3(1), 16; https://doi.org/10.3390/colloids3010016
Received: 17 December 2018 / Revised: 17 January 2019 / Accepted: 22 January 2019 / Published: 25 January 2019
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Abstract
The study is directed to the search of a simple effective catalyst for ethyl lactate obtained from fructose as renewable raw material. A series of SnO2-containing oxides prepared by impregnation of alumina were characterized by several techniques in order to determine [...] Read more.
The study is directed to the search of a simple effective catalyst for ethyl lactate obtained from fructose as renewable raw material. A series of SnO2-containing oxides prepared by impregnation of alumina were characterized by several techniques in order to determine their textural and acid-base properties. The transformation of a 13% fructose solution in 98% ethanol over SnO2/Al2O3 catalysts using autoclave rotated with 60 rpm at 160 °C for 3 h was studied. It was found that doping SnO2/Al2O3 samples with ZnO improves selectivity towards ethyl lactate. The supported SnO2-ZnO/Al2O3 catalyst provides 100% fructose conversion with 55% yield of ethyl lactate at 160 °C. A possible scheme of fructose transformation into ethyl lactate on L-acid IVSn4+ sites is discussed. Full article
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Open AccessArticle
Wettability of DPPC Monolayers Deposited from the Titanium Dioxide–Chitosan–Hyaluronic Acid Subphases on Glass
Colloids Interfaces 2019, 3(1), 15; https://doi.org/10.3390/colloids3010015
Received: 30 December 2018 / Revised: 17 January 2019 / Accepted: 18 January 2019 / Published: 23 January 2019
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Abstract
The investigations were carried out to determine wettability of the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers transferred from the liquid subphases containing chitosan (Ch), hyaluronic acid (HA), and/or titanium dioxide (TiO2) to a glass support by means of the Langmuir–Blodgett (LB) technique. [...] Read more.
The investigations were carried out to determine wettability of the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers transferred from the liquid subphases containing chitosan (Ch), hyaluronic acid (HA), and/or titanium dioxide (TiO2) to a glass support by means of the Langmuir–Blodgett (LB) technique. For comparative purposes, the analysis of the plates surfaces emerged from the analogous subphases without the phospholipid film was also made. Characterization of the DPPC monolayers was based on the contact angle measurements using three test liquids (water, formamide, diiodomethane) and a simulated body fluid (SBF) solution in which the concentration of ions was close to that of human plasma. After deposition of the DPPC monolayers on the glass plates, a significant increase in the contact angles of all the probe liquids was observed compared to the plates pulled out from the given subphase without floating DPPC. The presence of phospholipid monolayer increased the hydrophobic character of the surface due to orientation of its molecules with hydrocarbon chains towards the air. In addition, the components of the subphase attached along with DPPC to the glass support modify the surface polarity. The largest changes were observed in the presence of TiO2. Full article
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Open AccessArticle
Wetting and Spreading of Commercially Available Aqueous Surfactants on Porous Materials
Colloids Interfaces 2019, 3(1), 14; https://doi.org/10.3390/colloids3010014
Received: 5 December 2018 / Revised: 11 January 2019 / Accepted: 17 January 2019 / Published: 21 January 2019
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Abstract
The wetting properties of aqueous solutions of a commercially available surfactant at various concentrations on porous media are investigated using the KRUSS DSA100 shape analyzer and the ADVANCED software to process the data. Time evolution of both the contact angle and drop base [...] Read more.
The wetting properties of aqueous solutions of a commercially available surfactant at various concentrations on porous media are investigated using the KRUSS DSA100 shape analyzer and the ADVANCED software to process the data. Time evolution of both the contact angle and drop base diameter at each surfactant concentration after deposition were monitored. Three different porous substrates (sponges) were examined. The sponges used were a car sponge, dish sponge and audio sponge. The sponges were investigated both dry and at different degrees of saturation, that is, the amount of water absorbed into the sponge. It was found that pure distilled water droplets deposited on the dry porous media showed non-wetting. However, if droplets of surfactant solutions were deposited, then a change to a complete wetting case was found at all surfactant concentrations used. It has been observed that for all sponges, no matter the degree of saturation, they display a minimum contact angle after which the droplet is rapidly absorbed into the porous media. Full article
(This article belongs to the Special Issue Wetting on Micro/Nano-Scale: From Fundamentals to Application)
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Open AccessArticle
Adsorption and Decomposition of Peroxides on the Surfaces of Dispersed Oxides Fe2O3, Cr2O3 and V2O5
Colloids Interfaces 2019, 3(1), 13; https://doi.org/10.3390/colloids3010013
Received: 17 December 2018 / Revised: 12 January 2019 / Accepted: 16 January 2019 / Published: 17 January 2019
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Abstract
The adsorption of peroxides on dispersed oxides Fe2O3, Cr2O3 and V2O5 was studied. It is shown that the adsorption of peroxides is described by the Langmuir equation. The adsorption of benzoyl peroxide grows [...] Read more.
The adsorption of peroxides on dispersed oxides Fe2O3, Cr2O3 and V2O5 was studied. It is shown that the adsorption of peroxides is described by the Langmuir equation. The adsorption of benzoyl peroxide grows within Fe2O3 < Cr2O3 < V2O5. Adsorption-desorption equilibrium constants (K) for Cr2O3 and V2O5 are the same, but for Fe2O3 this value is 6 times higher. The decomposition of peroxides is observed in the solution and on the surface of adsorbents. The effective activation energy (E) of the thermal decomposition of peroxides in the studied systems is in the range of 80–140 kJ/mol. The activation energy of degradation of peroxides on the surface (Es) of the dispersed oxides studied is lower. The degradation reaction of peroxides on the surface of Fe2O3 and V2O5 has an oxidation-reducing nature, during which free radicals are produced. On the surface of Cr2O3, there is a heterolytic decay of peroxides. The parameters of the reaction of peroxides decomposition are found. The decomposition of peroxides in the presence of Fe2O3, Cr2O3 and V2O5 in styrene is accompanied by the formation of polystyrene both in the solution and on the surface of the adsorbent. Full article
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