Colloids Interfaces, Volume 1, Issue 1 (December 2017) – 10 articles

Fe₂O₃/ZSM-5 modified with Ce via citrate route (sol-gel approach) is applied for H₂S removal in 500–700 °C temperature range. The sulfidation activity of Fe₂O₃/ZSM-5 is appreciably promoted by introduction of Ce plausibly attributed to the synergy of Fe₂O₃ and CeO₂. 5Fe5Ce/ZSM-5 performs the optimal desulfurization behavior at 600 °C with sulfur capacity of 1020 μmol S/g, and the sulfidation process conforms to non-catalytic gas-solid redox reaction mechanism, which yields FeS₂, Ce₂S₃, and S. Fractal analysis is introduced to evaluate the surface porous structure and the adsorption capacity of the sorbent. Its surface fractal dimension is estimated by using Frenkel-Halsey-Hill (FHH) model. It considerably increases after sulfidation plausibly attributed to the formation of a few heterogeneous sulfides or elemental sulfur, which block or cover the surface pore structures of sorbents. Full article

The measured dynamic surface tension of a water drop in air saturated by heptane vapor shows a sharp decrease from about 60 mN m⁻¹ to 40 mN m⁻¹, and less after a certain adsorption time. The observed adsorption kinetics is analyzed by a theoretical model based on multilayer adsorption of alkanes from the vapor phase at the water surface. The model assumes a dependence of the kinetic coefficients of adsorption and desorption on the surface coverage and in equilibrium it reduces to the classical Brunauer–Emmett–Teller adsorption isotherm. The calculated time dependencies of adsorption and surface tension agree well with experimental data and predict a five-layer adsorption of heptane. Full article

Hybrid particles consisting of an organic polymer and silica or polyorganosiloxanes are interesting building blocks for nanocomposites. The synthesis of such particles typically requires multiple reaction steps involving the formation of polymer colloids and the subsequent deposition of silicon-containing material either inside or on the surface of these colloids, or vice versa. In 2014, we reported a facile method for the one-pot synthesis of sub-micron sized hybrid particles based on simultaneous sol-gel conversion of organotrimethoxysilanes and emulsion polymerization of a vinylic monomer, illustrated by the synthesis of polystyrene-polyphenylsiloxane particles from the monomers styrene and phenyltrimethoxysilane (Segers et al (2014). In this process, the required surface active species was formed in situ through hydrolytic conversion of phenyltrimethoxysilane to phenylsilanolate oligomers. Introduction of thiol groups in such hybrid particles should yield particles suited for functionalization with small metal nanoparticles, e.g., Au. Here, we present the synthesis of thiol-containing hybrid particles consisting of poly(3-mercaptopropyl)siloxane and polystyrene using the one-pot synthesis method based on simultaneous conversion of (3-mercaptopropyl)trimethoxysilane and styrene. We prepared particles from different volume ratios of (3-mercaptopropyl)trimethoxysilane and styrene, ranging from 1:99 to 80:20. The resulting spherical hybrid particles displayed different sizes, compositions, and architectures (including core-shell), which were studied in detail using scanning electron microscopy, thermogravimetric analysis, and scanning transmission electron microscopy combined with energy dispersive x-ray spectroscopy. The composition of these particles, and consequently the number of thiol groups available for further functionalization such as metal anchoring, was tunable. Full article

Currently, RNAi based approaches for cancer treatment involving short double stranded RNA molecules (siRNA) are under vigorous scrutinization. Due to numerous biological obstacles, siRNA delivery into target cells requires protective escort. On the other hand, combining of siRNA-mediated gene silencing and action of conventional chemotherapeutics can propose additional enhancement of anticancer activity. In the present study, we investigated a siRNA cocktail able to downregulate anti-apoptotic genes (BCL-xL, BCL-2, MCL-1) and the chemotherapeutic agent 5-fluorouracil (5-FU) to evaluate multi-target cytotoxic effect on human cervical carcinoma cells (HeLa cell line). Novel phosphorus containing dendrimers of 3rd and 4th generations (namely AE2G3 and AE2G4) with voluminous piperidine terminal cationic groups were designed and tested as siRNA carriers. Dendrimers of both generations showed remarkable ability to bind pro-apoptotic siRNAs and provided 80–100% siRNA uptake by HeLa cells in the serum containing medium, while the widespread transfection agent Lipofectamine showed only ~40% uptake. SiRNA cocktail (in low concentrations 50 and 100 nM) delivered by AE2G3 dendrimer caused almost complete elimination of cancer cells. We have discovered considerable increase of 5-FU cytotoxic effect by addition of AE2G3/siRNA cocktail complexes in low doses. Thus, we demonstrated the effectiveness of combined multi-target siRNA anticancer approach and described new highly effective serum stable nanomaterial vehicle for gene-based drugs. Full article

Understanding the organic–inorganic interphases of hybrid materials allows structure and properties control for obtaining new advanced materials. Lately, the use of ionic liquids (ILs) and poly(ionic liquids) (PILs) allowed structure control from the first sol-gel reaction steps due to their anisotropy and multiple bonding capacity. They also act as multifunctional compatibilizing agents that affect the interfacial interactions in a molecular structure-dependent manner. Thus, this review will explore the concepts and latest efforts to control silica morphology using processes such as the sol-gel, both in situ and ex situ of polymer matrices, pre-polymers or polymer precursors. It discusses how to control the polymer–filler interphase bonding, highlighting the last achievements in the interphase ionicity control and, consequently, how these affect the final nanocomposites providing materials with barrier, shape–memory and self-healing properties. Full article

The ability to control the assembly of nanoparticles on substrates used in plasmon-enhanced spectroscopy continues to drive research in the field of nanofabrication. Here we describe the use of fungi as soft biotemplates to fabricate nanostructured microtubules with gold and gold-silver nanoparticles with potential applications as sensors and biosensors. In the first step, spores of the filamentous fungus Cladosporium sphaerospermum were inoculated in a suspension of gold nanoparticles, forming stable microtubules of gold nanoparticles during fungus growth. These materials were exposed to a second suspension of silver nanoparticles, resulting in complexes multilayers structures of gold and silver nanoparticles, which were evaluated as substrates for surface-enhanced Raman scattering (SERS) using small amounts of thiophenol as probe molecules directly on the microtubules. Both gold and the gold-silver substrates provide the SERS effect. Full article

Polymer/surfactant mixtures have a wide range of industrial and technological applications, one of them being the use in microencapsulation and emulsion stabilization processes. These mixtures are able to form adsorption layers at the surface of oil droplets and so affect the emulsion stability, which depends on the polyelectrolyte/surfactant nature, concentrations ratio, method of the emulsification, etc. Polyelectrolytes alone show low surface activity in contrast to surfactants, which adsorb at the water/oil interface, making the droplets charged, but they are insufficient to stabilize emulsions. When an oppositely-charged polymer is added to the surfactant solution, a steric barrier is formed, which prevents coalescence and enhances the stability. The present review is devoted to the recent studies of the use of polymer/surfactant mixtures for the encapsulation of active ingredients and stabilization of single and double emulsions. Active ingredients are added to the oil phase prior to emulsification so that any subsequent dissolution of the core, like in other encapsulation protocols, can be omitted. By measuring the interfacial tension and dilational rheology it is possible to find optimum conditions for the emulsion formation and hence for encapsulation. Therefore, such systems have become a prominent approach for the encapsulation of active ingredients. Full article

The preparation of highly efficient and low-cost activated carbon from sawdust was achieved for the treatment of uranium-contaminated groundwater. The adsorption properties of the synthesized activated carbon, as well as their ability to be reused, were assessed. The obtained results demonstrated that sawdust activated carbon (SDAC) and its amine form (SDACA) had high affinity towards uranium ions at pH values of 4.5 and 5 for SDAC and SDACA, respectively. The experimental results showed that the maximum adsorption capacity of uranium was 57.34 and 76.7 mg/g for SDAC and SDACA, respectively. A maximum removal efficiency of 89.72% by SDAC and 99.55% by SDACA were obtained at a solid/liquid ratio of 8 mg/mL. The removal mechanism of uranium by SDAC and SDACA was suggested due to interaction with the amine and carboxylic groups. The validation of the method was verified through uranium separation from synthetic as well as from groundwater collected from water wells in the Wadi Naseib area, Southwestern Sinai, Egypt. Full article

In drop profile analysis tensiometry, the ratio of drop surfaces area S to volume V is large, i.e., S/V >> 1. In such a case, the concentration of a surfactant within the drop bulk decreases due to adsorption at the drop surface. In contrast, in bubble profile analysis tensiometry, we have S/V << 1 so that depletion due to adsorption is negligible. A protocol is presented to determine the correct adsorption parameters of surfactants from surface tension data measured by bubble and drop profile analysis tensiometry. The procedure is applied to experimental data measured for selected surfactants of different adsorption activities: C₁₀OH, CTAB, Tween 20, and the equimolar mixture SDS + DoTAB. The results show that for surfactants with higher surface activity, the differences between the surface tensions measured with the drops and bubbles profile analysis tensiometry, respectively, are larger, while for less surface-active surfactants, such as SDS, the results obtained from drop and bubble profile experiments are very close. The correction procedure is based on the same set of adsorption parameters used to fit both the experimental data obtained from drop-based measurements (which involve the depletion effects) and those data measured in a way that depletion effects are negligible. Full article