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Clay-rich sandstone formations contain vast deposits of petroleum resources. Low salinity waterflooding presents a low-energy, low-environmental impact method to improve oil recovery from these systems. Fundamental mechanisms dictating improved oil recovery at low salinity conditions are not well-understood currently. This study investigates low salinity waterflooding at the pore-level to delineate fundamental mechanisms underlying oil recovery. Clay-functionalized, two-dimensional micromodels are used to provide direct visual observations of crude oil, brine, and clay particle interactions within the pore-space. Using this microvisual approach, establishment of initial reservoir conditions shows wettability evolution of the initially water-wet system towards a mixed-wet condition due to clay-particle interactions with the reservoir fluids, i.e., crude oil and brine. Pore-scale behavior during low salinity waterflooding shows spontaneous emulsification of the crude oil and brine. Specifically, the emulsions generated are Pickering type stabilized by the clay particles that were mobilized at salinities below the critical salt concentration (CSC). Spontaneous generation of the stable Pickering emulsions reduces mobility through preferential flow paths, thereby resulting in flow diversion of subsequent injection fluids to mobilize oil-filled pores. Leveraging the stability of the Pickering emulsions, a sequential salinity cycling method is developed to improve overall oil recovery by an additional 8% of the original oil in place. Flow diversion due to spontaneous Pickering emulsification in preferential flow paths observed here provides fundamental insight to the design and application of low energy-input, low environmental-impacts techniques in the field.

Ultrasmall heavy metal oxide nanoparticles are potential candidate materials for X-ray computed tomography (CT) contrast agents because they possess high X-ray attenuation powers owing to high X-ray attenuation coefficients of heavy metal atoms and high density of heavy metal atoms per nanoparticle. In this study, five kinds of polyacrylic acid (PAA)-coated ultrasmall heavy metal oxide (Bi2O3, Yb2O3, NaTaO3, Dy2O3, and Gd2O3) nanoparticles were synthesized and their X-ray attenuation properties were investigated. The estimated average particle diameters were 2.3 ± 0.1, 1.7 ± 0.1, 1.5 ± 0.1, 1.8 ± 0.1, and 1.9 ± 0.1 nm for PAA-coated ultrasmall Bi2O3, Yb2O3, NaTaO3, Dy2O3, and Gd2O3 nanoparticles, respectively. All of the nanoparticle suspension samples exhibited a high colloidal stability, a high biocompatibility, and X-ray attenuation powers which were stronger than that of a commercial iodine contrast agent Ultravist® at the same atomic concentration and much stronger, at the same number density. The effectiveness of the nanoparticle suspension samples as CT contrast agents was demonstrated by acquiring in vivo CT images by using one of the samples (i.e., PAA-coated ultrasmall Bi2O3 nanoparticles). After intravenous injection into the mouse tail vein, positive contrast enhancements in various organs were observed.

This work develops a process for fabricating particles composed of a quantum dot (QD) core, a SiO2 shell, and single-nanometer-sized Au nanoparticles (AuS) immobilized on the particle surface. The QD nanoparticles were silica-coated with a sol-gel process using tetraethyl orthosilicate (QD/SiO2). A colloidal solution of the AuS was prepared by reducing Au3+ with tetrakis(hydroxymethyl)phosphonium chloride in an aqueous solution. The QD/SiO2 particles were surface-modified with thiol groups by using (3-mercaptopropyl)trimethoxysilane (QD/SiO2/SH). The AuS nanoparticles were immobilized on the QD/SiO2/SH particle surface by adding a colloidal AuS solution to a colloidal QD/SiO2/SH solution (QD/SiO2/SH/AuS). The QD/SiO2/SH/AuS particles were surface-modified with thiol-terminated polyethylene glycol (PEG) (QD/SiO2/SH/AuS/PEG). Fluorescence images and computed tomography (CT) images could be obtained for the colloidal QD/SiO2/SH/AuS/PEG particle solution. The colloidal QD/SiO2/SH/AuS/PEG particle solution had a CT value per unit concentration of Au (M) of 6.68 × 103 HU/M. The circulation of the QD/SiO2/SH/AuS/PEG particles was confirmed in a mouse after injection of a colloidal particle solution into its blood vessels, and they accumulated in the heart. A portion of the QD/SiO2/SH/AuS/PEG particles accumulated in the liver and spleen and remained there.

Invert emulsion fluids stabilized by organoclays are important for applications in thixotropic fluids and petrochemical industry, especially in the field of oil extraction. Among these applications, improvement of the rheological properties of invert emulsion fluids at high temperatures lacks detailed study. In the current work, three different organoclays, including organo-sepiolite (OSEP), organo-hectorite (OSHCA) and organo-montmorillonite (OMMT) were prepared through chemical modification of unmodified clays using DODMAC. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that DODMAC is not only adsorbed on the surface of particles, but also inserted into the layers of OMMT and OSHCA. For OSEP particles, DODMAC can only be adsorbed on the surface of particles. Interestingly, the results of optical microscopy and rheology indicate that the OSHCA particle-stabilized invert emulsion fluid provides better rheological properties than the other two organoclays at high temperature. Such high rheological properties is ascribed to the weak flocculation of OSHCA particles. Due to its nonreactive Mg−OH surface groups, OSHCA maintains the rheology of high-temperature aged invert emulsions by reconstructing weak flocculation structure. On the other hand, on the particle surface of OMMT and OSEP, Al−OH may react with OH− under alkaline conditions, which will destroy the weak flocculation due to increased repulsion interaction. These results clearly shed light on the relationship between the performance of invert emulsion at high aged temperature and particle weak flocculation, and also are beneficial to the applications which need stable emulsion at high temperature.

Two diesel oil-in-water emulsions were formed by using positively charged alumina nanoparticles solely and negatively charged silica nanoparticls solely as emulsifier, respectively. The formal systems are typical Pickering emulsions in which alumina nanoparticles adsorb at oil/water interface endowing droplets very good stability, whereas the later systems are non-Pickering emulsions in which silica nanoparticles do not adsorb at oil/water interface but distribute in aqueous phase surrounding the droplets endowing droplets temporary stability. Trace amounts of anionic surface-active materials in the diesel oil are responsible for the formation of two different emulsions. In the Pickering emulsions they adsorb at alumina particle surface to endow particle surface activity via in situ hydrophobization, whereas in the non-Pickering emulsions they adsorb at oil/water interface constituting a novel emulsion co-stabilized by like charged surfactants and nanoparticles at very low concentrations. By addition of trace amount of extra anionic surfactant, such as 0.1 mM sodium dodecyl benzene sulfate (SDBS), the novel diesel oil-in-water emulsions with good temporary stability can be formed by using silica nanoparticles at a concentration as low as 0.01 wt%. The emulsions can be demulsified easily by addition of trace amount (0.06∼0.1 mM) of a cationic surfactant such as cetyltrimethylammonium bromide (CTAB), or a low concentration (0.6∼3.0 mM) of divalent electrolyte such as CaCl2, and therefore have potential applications in oil transportation. On the other hand the Pickering diesel oil-in-water emulsions are relatively difficult to demulsify, and suitable demulsification protocols need to be developed for their applications in oil transportation.

Thermosensitive N-isopropylacrylamide based cationic microgels (μG) were synthesized and complexed with anionic liposomes containing encapsulated antitumor antibiotic Doxorubicin (Dox). Compositions of the resulting complexes, in terms of a liposome-to-μG number ratio N, varied from N = 0.5 to a saturated complex with N = 30 where the surface of μG particles is fully covered with liposomes. The microgels collapse when heated from 25 up to 50 °C and the surface area of a microgel particle decreases. The thermo-induced contraction is accompanied with release of Dox from the μG-bound liposomes while a significant fraction of DOX is released for both the unsaturated and saturated complexes. Therefore, two mechanisms are hypothesized for the thermo-induced Dox release. The first one is due to temperature-induced conformational changes of polymer chains, subsequent rearrangements at liposome-microgel interface via liposome-microgel interaction. This mechanism can work for the complexes of any composition. The second process, namely a squeezing of liposomes via liposome-liposome interaction followed by Dox release can become significant for the saturated complex. The results we have obtained are of great interest for constructing multi-liposomal drug carriers, diagnostic systems and catalysts.

Colloidal inorganic nanoparticles featured with ultrasmall sizes and near-neutral surface wettability are considered as efficient emulsifiers to stabilize Pickering emulsions. Herein, we demonstrated that colloidal TiO2 nanoparticles synthesized by the well-established sol-gel approach using Ti(OC4H9)4 as precursor, could be directly used as an efficient Pickering emulsifier without any other additives. The sol-gel TiO2 nanoparticles showed near-neutral wettability at the oil-water interface (θow˜90°) derived from the surface residual butanol-related species as revealed by TGA/DTA and FT-IR analyses, which should be responsible for the formation of Pickering emulsion with ultrahigh stability. The Pickering emulsions stabilized by size-tunable TiO2 nanoparticles under various emulsification conditions were characterized by photography, optical microscopy and rheology measurements. The results suggested that the droplet sizes and rheology properties of the emulsion could be adjusted by tuning the TiO2 nanoparticle sizes. Moreover, as a potential application, we also demonstrated the simple fabrication of TiO2-coated silicone elastic hybrid microspheres through the Pickering emulsion templated polymerization. The present work demonstrated that sol-gel TiO2 nanoparticles could serve as efficient particle emulsifiers for achieving stable emulsions, and may also extend the wide application of colloidal TiO2 nanoparticles based on the Pickering emulsion platforms.

Producing stable particle-stabilised emulsions of small droplet sizes and high monodispersity via membrane emulsification approaches is hindered by the poor mixing environment during processing and the low diffusivity and minimal interfacial tension lowering capacity of colloidal particles. The present study investigates the co-stabilisation (particles and emulsifiers) of O/W emulsions formed by rotating membrane emulsification. Formulation aspects of the employed co-stabilisation strategy (type/concentration of emulsifiers and type/size of particles) were assessed at a fixed trans-membrane pressure (10 kPa) and rotational velocity (2000 rpm). Emulsion microstructure was shown to be affected by the occurrence of emulsifier/particle interactions. In formulations where these interactions are synergistic and emulsifier content is low, interfacial stabilisation is carried out by both species and resulting emulsions possess smaller droplet sizes, higher monodispersity indices and enhanced stability against coalescence, compared to systems stabilised by either of the two components alone. This work concludes that a carefully controlled co-stabilisation strategy can overcome the current challenges associated with the production of particle-stabilised emulsions via membrane emulsification methods.

Submicron-sized magnetic composite particles with low polydispersity were prepared to examine the relation between the magnetophoretic velocity and the clustering state of composite particles under application of magnetic field. Five different magnetic composite particles in a size range of 70–470 nm were employed to measure the magnetophoretic velocity. Since the smallest composite particles had colloidal stability insufficient to measure the magnetophoretic velocity, the rest of composite particles was observed with an optical microscope under a magnetic field. Magnetic composite particles larger than 300 nm formed pearl chains of magnetic composite particles under the magnetic field. The velocity of pearl chains was increased by the number of composite particles in a pearl chain. The ratio of the velocity of pearl chain to that of a single composite particle was employed to quantify the increase in magnetophoretic velocity with the clustering of composite particles. The velocity ratio for the large particles was in good agreement with the theoretical one correlated with the number of composite particles in a pearl chain. On the other hand, composite particles smaller than 200 nm formed random clusters of composite particles. Since a single small particle could not be directly observed with the optical microscope, the number of small composite particles in a cluster was estimated with an assumption that the small composite particles formed an ellipsoidal shape with a random filling factor of 0.64. Similarly to the large composite particles, the velocity ratio of random clusters composed of the small composite particles was also increased by clustering the small MCPs. Comparison of the velocity ratios between different composite particles indicated that the clusters of small particles have a tendency of exhibiting velocity ratios higher than that of large particles. A good correlation of the velocity ratio with the estimated number of composite particles in a cluster revealed that the number of composite particles is an important factor to quantify the magnetophoretic velocity of random clusters.

Vanadium dioxide (VO2) exhibits a good thermochromic property which can be used in a smart window. To improve its poor visible transparency, immobilization of the VO2 nanoparticles on the silica shell of hollow nanoparticles was proposed. In addition to improving the particle dispersibility of the VO2 and to reducing stress from repeated phase transitions of the VO2 between monoclinic and tetragonal, the hollow interior can reduce any undesirable oxidation of the VO2 to V3O7, V2O5, etc., along with the thermal decomposition behavior of organic compounds around the vanadium atom. The hollow silica nanoparticles with micropores (less than 2 nm) were prepared by a previously-reported template method. Through the pores, the vanadium precursor with a chelate ligand solution penetrates into the hollow interior. The vanadium intermediate formed by adding water was then captured by the silica shell. During the crystallization process under a nitrogen atmosphere, 10–30 nm of VO2 particles were immobilized on the silica shell with a high dispersibility by optimization of the vanadium precursor concentration, and ratios of vanadium/water and vanadium/hollow silica nanoparticles. The VO2/hollow silica nanoparticles in water exhibited a higher visible transparency than that of the commercial VO2. In addition, their thermochromic property in the infrared region was close to that of the commercial one.

We synthesized amino acid-type photo-cleavable surfactants composed of coumarin and glycine precursors and studied the photo-switchable interfacial properties, release of active ingredients, and colloidal stability of silica particles. Photo-cleavage of the surfactants reduced their interfacial activities at the squalane/water interface. Silica particles bearing aminoethylene groups on the surface were well dispersed in an aqueous solution of the photo-cleavable anionic surfactant. The surfactants form a bilayer on the silica particles by ion complexation of the amine and carboxylic groups, and the negative charge originating from the surfactant results in electrostatic repulsion, which contributes to the dispersion stability. Ultraviolet light irradiation caused flocculation of the silica particles and the release of the coumarin derivative and glycine into the medium through photo-induced isomerization and cyclization. The new photo-cleavable surfactant systems represented controlled multiple interfacial and colloidal properties upon photoirradiation.

In this paper, a fluorescent particulate stabilizer was developed for fluorescently labeling the oil-water interface of Pickering-emulsions. In this method, carbon nitride quantum dots (CNQDs) were selected to modify liquid paraffin emulsions, which were then stabilized by Laponite. This method avoids the adverse effect of dyes in studying the droplet interfaces of Pickering-emulsions. Our results indicated that the CNQDs are stable and monodispersed due to negative electrostatic repulsions, and no fluorescence quenching was found after the introduction of Laponite. The CNQDs obviously improved the particle wettability of Laponite to liquid paraffin, suggesting that they conferred increased particle hydrophobicity, which may in turn contribute higher stability to Pickering emulsions. With tunable wettability, CNQDs@Laponite nanoparticles standing at the oil-water interface may act as an identifiable, green-fluorescent interfacial film responsible for stabilizing and labelling oil-in-water Pickering emulsions. In addition, these results indicate an improved storage stability of Pickering emulsions compared with those stabilized by Laponite.

Cross-linked polymer particles containing centers of molecular recognition of toluene and prepared in the presence of luminophoric bromine-containing or hydroxyl-containing derivatives of 1,3-diphenyl-β-diketonate boron difluoride using styrene, methacrylic acid, ethylene glycol dimethacrylate and divinylbenzene are obtained for the first time. The influence of cross-linked particle characteristics (core particle diameter, core / shell particle diameter, shell thickness, particle size distribution) on the luminescent properties of their films is shown. The stability of bromine-containing or hydroxyl-containing derivatives of β-diketonate boron difluoride in different solvents (deuterotoluene, deuterochloroform) as well as at a temperature of 60 °C and in the presence of the initiator, α,α′-azoisobutyronitrile, that models the conditions of cross-linked polymer particle synthesis, is studied by 1H, 11В and 13C NMR spectroscopy. Furthermore, the sorption of ethanol by 3D-ordered structures based on the particles obtained is investigated by means of NMR spectroscopy and the changes of the luminescence spectra of such structures in the presence of toluene vapors are studied.

Spray-dried powders were produced from milk serum protein concentrate and lactose in varying ratios, and the rehydration characteristics of the powders were evaluated. The dissolution rate was estimated with a flow-cell based technique, and the external and internal distribution of the powder components were evaluated with X-ray photoelectron spectroscopy and confocal Raman microscopy, respectively. The surface of the powder particles is more or less covered by a thin protein layer. A phase segregation between protein and lactose is observed in the interior of the particle resulting in a protein rich layer in the vicinity of the surface. However, the protein layer in the vicinity of the particle surface tends to become thinner as the bulk protein concentration increases in the powders (from 10 to 60% w/w). The time for the spontaneous imbibition to occur show a linear correlation with the protein surface coverage. The dissolution rate of powders containing 0.1% w/w protein is around 60 times faster than for a powder containing 1% w/w protein but the dissolution rate of powders containing 1% and 100% w/w differ only by a factor of 2. Thus, it is suggested that the outer protein layer becomes denser at the interface as the protein content increases in the powders, thereby causing poorer rehydration characteristics of the powders (especially for low protein concentrations 0.1–1% w/w). This insight has relevance for the formulation of whey protein powders with improved rehydration characteristics.

Polystyrene (PS) microspheres are wrapped by reduced graphene oxide (rGO) nanosheets based on the thermodynamically driven heterocoagulation method, and in order to acquire PS/rGO@PtRuNPs composite particles, the resultant PS/rGO composite particles should be used as matrix to deposit Pt-Ru alloyed nanoparticles (PtRuNPs), taking unique advantages of both alloying effect and the 3D structure. A distinct 3D graphene/PtRu alloyed composite catalyst is fabricated by in-situ stacking of the ternary composite particles, which has double network channels for both electrons and reaction solution. The rGO sheets on the surface of the PS microspheres are interconnected interrelated with each other to construct a 3D network structure, while a interconnected gap among the spherical composite particles forms the other network for the reaction solution to spread into the composite catalyst. The influence of different Pt/Ru ratio on the catalytic activity for methanol oxidation is investigated, and under the obtained optimal Pt/Ru ratio, the most effective and economical noble metal consumption is further explored through changing the ratio of metal to graphene. As a result, the PS/rGO@PtRuNPs ternary composite catalyst has better catalytic activity than close-stacked rGO/PtRuNPs catalyst.

A foam with high stability for the efficient decontamination of radioactive materials has been prepared by using well-dispersed mesoporous silica nanoparticles (NPs). Three different types of silica NPs were tested: solvent-extracted mesoporous silica (SMS) NPs, calcined mesoporous silica (CMS) NPs, and commercial silica (M-5) NPs. The stability and decontamination efficiency of the foam prepared using SMS NPs was higher than those using other silica NPs. The liquid volume in the foam with the SMS NPs are 10–25 times greater than those containing the CMS and M-5 NPs. The stability of the decontamination foam consisting of SMS NPs is higher because of its higher viscosity; the SMS NPs sample contains a larger number of particles per unit volume and has smaller particle sizes than the CMS and M-5 NPs samples. To investigate the dispersion-agglomeration properties of the silica NPs, the size distributions of the silica NPs in the decontamination foam solutions were determined by using dynamic light scattering. The SMS NPs are smaller than the CMS and M-5 NPs in the decontamination foam solution. For stainless steel 304 and carbon steel specimens corroded with the radionuclide 60Co, decontamination foams containing SMS NPs were found to exhibit a decontamination efficiency 20–40% greater than those of the foams containing the other silica NPs. This superior efficiency arises because the foams prepared with SMS NPs exhibit improved stability and their liquid component can hold larger amounts of the decontamination agent.

The formation of zein/Tween-20 nanoparticles through the antisolvent precipitation method at various Tween-20 concentrations (CTween-20) has been investigated using dynamic light scattering, surface tension, fluorescence, and circular dichroism. When CTween-20 increases from 0 to 0.2 g/L, the particle sizes of zein/Tween-20 nanoparticles significantly decrease from 140 to 95 nm, followed by nearly constant values of 90–92 nm at CTween-20 = 0.2–4 g/L. Compared to Tween-20, zein/Tween-20 nanoparticles give smaller values of surface tension at CTween-20 = 0–2.8 g/L, and almost the same values at CTween-20 higher than 2.8 g/L. The values of fluorescence maximum intensity and α-helix content of zein molecules in zein/Tween-20 nanoparticles show pronouncedly different changes at CTween-20 = 0–0.2, 0.2–2.8, and 2.8–4 g/L. The formation of zein/Tween-20 nanoparticles is proposed to be induced by the aggregation of zein/Tween-20 complexes mainly driven by the hydrophobic force. Zein/Tween-20 complexes exhibit different structural properties at low, intermediate, and high Tween-20 concentrations.

The interfacial phenomena reflected by the thickness of oil films and the stability of oil-in-water emulsions were observed in the soft heterogeneous combination (SHC) flooding process, which were closely linked with the oil recovery. In this work, the effects of tetradecyl hydroxyl sulfo betaine (THSB) concentration and dispersed particle gel (DPG) concentration on the interfacial rheology were investigated; the adsorption performance at different temperatures, salinities and aging times were also systematically evaluated to determine the impact of external factors. The results show that three interactions appeared between the surfactant molecules and DPG particles. The adsorption process presents four stages. At a low THSB concentration and low DPG concentration, some DPG particles can adsorb on the interface together with the surfactant molecules, which markedly increase the adsorption film strength. When the THSB concentration increases, the surfactant molecules tend to interact with each other and aggregates of the surfactant molecules with DPG particles also appear, thereby damaging the compact film structure. As DPG particles are continuously added, the aggregates between particles enhance the strength of the adsorption film. Additionally, interfacial properties were maintained at high-temperatures, high-salinities and long aging times, which indicates the promising application of the SHC flooding system in reservoirs.

The formation of submicron polystyrene (PS) particles based on dewetting process during spin-coating was investigated. The surface morphologies on glass substrates were analyzed. The formation of particles was achieved using PS with relatively high molecular weight (Mw ≥ 3250). In addition, it was observed that the particle formation proceeded through sequential morphological changes in the order of initial wet thin film, secondary spinodal-decomposed structures, and eventual dewetted particles. One of the fabricated samples exhibited obvious optical resonance in the visible region based on the relationship between particle dimeters and optical wavelengths in the visible region. The optical resonance strongly depended on the ambient refractive index, which can be used for optical sensor-chips. Finally, a multi-functional biosensor-chip was demonstrated to detect glucose in water solutions.

We examined the dependence of the rheology of capillary suspensions on particle wettability using model ternary liquid/liquid/particle mixtures. Experiments were conducted using silica particles suspended in a majority liquid phase, to which a small minority of a second liquid was added. Silane modification was used to realize three different particle wettabilities ranging from particles being fully-wettable by the minority fluid, to being almost completely non-wettable by the minority liquid. In all three cases, the ternary suspensions showed solid-like behavior, with the yield stress and modulus decreasing as particles became less wettable towards the minority fluid. In all three cases, the minority liquid was found to induce particle aggregation into percolating networks which are responsible for the solid-like rheology. Our results suggest two reasons why the solid-like properties of such suspensions diminish as the particles become less wetting by the minority fluid: because particle network relies on multi-particle capillary clusters (rather than pair-wise meniscus binding), and because a certain fraction of particles become too non-wettable to participate in the network.

Precise control over particle composition and morphology is essential for the optimization of electroactive, multi-component transition metal oxides used as lithium-ion battery cathode materials. These transition metal oxide particles are often synthesized using precursors produced via coprecipitation reactions, in part due to the advantages provided by coprecipitation including scalability and homogeneous mixing of different transition metal ions. Understanding the kinetics of the nucleation and particle growth for each individual transition metal within a multicomponent blend solution is critical for rational and explicit control of particle composition, as well as to dictate the particle morphology. In this study, in-situ particle size distribution was measured during coprecipitation reactions using focused beam reflection. The transition metal concentrations were also in-situ tracked during the process which, in combination with the particle size information, provided detailed information on the reaction rate, reaction order, and mechanisms of particle nucleation and growth. This work is the first demonstration of application of such techniques to battery precursor particle synthesis, and provides insights into important observations during the coprecipitation process such as the change in the rate of coprecipitation of different transition metals when reacted in isolation or in a blend with other components. The techniques and analysis demonstrated in this paper could find application across many multicomponent transition metal coprecipitation systems important to various applications, including energy storage materials.

A series of sodium polyacrylate copolymers (i.e., poly acrylic acid-co-itaconic acid-co-2-acrylamide-2-methylpropanesulfonic acid or PSIA with different molecular weights and monomer molar ratios) were synthesized based on acrylic acid-co-itaconic acid (PAI) as water-based dispersants for ultrafine grinding of praseodymium-doped zirconium silicate (Pr-ZrSiO4). The particle size/size distribution, suspension rheology and dispersant adsorption were analyzed by laser particle size analysis, rheometry, Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG) and electrokinetic potential measurement, respectively. Compared to the dispersant PAI, the use of the dispersant PSIA1 with a greater molecular weight in the Pr-ZrSiO4 suspension ground for 45 min at pH values 7.0–8.0 can give a finer product with the narrower particle size distribution. The dispersant PSIA1 used in ultrafine grinding has a suitable viscosity of the suspension and generates more hydrogen bonds on the particle surface, and sulfonic acid group in the dispersant PSIA1 can provide a greater charge density than carboxylic acid groups in the dispersant PAI. In addition, the total potential energies between the particles in suspension with different copolymer dispersants at different pH values were also calculated. It is indicated that the effective ultrafine grinding of the particles is related to the total interparticle potential energy provided by the dispersant PSIA1 at pH 7.0–8.0.

Polymer-surfactant complex particles formed by dilution of shampoo play an important role in the sensory properties of shampoo, but their microscopic mechanism has not been clarified yet. This study clarifies the change mechanism influencing hair surface smoothness induced by this complex. The degrees of precipitation and adsorption of the polymer-surfactant complex particles are varied by changing the sodium chloride (NaCl) concentration in the shampoo formulation; hence, the relationships between the frictional and sensory properties during rinsing, the particle formation numbers in water, and the particle adsorption rate on the hair surface are investigated. The frictional property measurement and microscopic observation of human hair treated with the various shampoo solutions confirm that two different particle types, floating and adsorptive, are formed in water during the shampoo dilution process, both of which contribute to improving the hair smoothness. Then, NaCl is added to the basic shampoo composition to control the formation of these two particle types. The particle size distribution and chemical identification show formation of submicron-sized particles mainly consisting of cationized polymer in water with less than 0.20-wt % NaCl, which do not adsorb on the hair surface. For 0.75–3.00-wt.% NaCl, polymer-surfactant complex particles are formed, which easily adsorb on hair. Finally, we propose an optimal NaCl concentration of 0.75 wt.% to obtain excellent frictional properties. The result will contribute to the formulation of cosmetic products based on microscopic mechanism.

Controlling the development of the particle morphology during spray drying is of large importance to obtain high quality powders. During drying of skin-forming materials it is still unknown how the rheological properties of the skin develop as a function of time, moisture content and temperature. We here studied films prepared from whey protein – maltodextrin mixtures as a model system for spray drying. The rheological properties were assessed by oscillatory shear measurements at relevant high dry matter contents (66–82 w/w%). During drying, the films high in whey protein became brittle and had slower evaporation compared to films high in maltodextrin. Rheological analysis showed that for whey protein rich systems (with higher ratio than 25:75 WP:MD) the films were in structural arrest at the dry matter contents measured. Maltodextrin films on the other hand showed typical viscoelastic polymer behavior, although as little as 1% addition of whey protein altered its viscoelastic properties drastically. The viscoelastic properties could be related to vacuole formation during single droplet drying: samples that undergo structural arrest at a lower dry matter content (high in whey protein), form less and larger vacuoles compared to samples that undergo structural arrest only at high concentration (high in maltodextrin).

The present report compares the antibacterial properties of unique (sphere+rod)-shaped gold nanostar with its structural components, i.e., gold nanorods and nanosphere. Gold nanostars, nanorods, and nanospheres have been synthesized using literature reported protocols. Clinical isolates of gram-negative E. coli and gram-positive S. aureus bacteria have been used as model pathogens for the antibacterial studies. The antibacterial activities of the nanoparticles have been assessed using various techniques. To compare the antimicrobial activity of the nanoparticles, we have investigated the effects of varying gold concentrations of different nanoparticles on bacterial growth kinetics. The impacts of the leached/residual gold ions and the surface capping agent and charge have also been studied. Studies of the nanoparticle’s dose and exposure time show the highest antibacterial activity for nanostars and lowest for nanospheres for a given quantity of gold. Bradford’s Reagent Assay and confocal fluorescent microscopy studies confirm the trend of the particle-specific antibacterial activities. SEM/TEM and DNA extraction studies show the bactericidal activities involve a combination of effects like the destruction of cell membrane, fragmentation of bacterial DNA, internalization of particles, etc. To assess the antibacterial impacts of the amount of leached/residual gold ions, their concentrations have been determined by both inductively coupled plasma - optical emission (ICP-OES) and mass (ICP-MS) spectroscopic studies as well as the effects of the added gold ions have been studied. No discernible effects have been observed due to the variation in the leached/residual gold ions amount. The DCHF-DA fluorescence assay has been employed to determine the levels of reactive oxygen species (ROS) produced by different nanoparticle systems, which corresponds to the trend in antibacterial activities observed. The nature and magnitude of the surface charge have been determined by zeta potential measurements. Analyses of the impacts of various parameters/factors like gold ions, capping agents, surface charges, ROS levels, etc., show that the antibacterial activities of the gold nanoparticles of different morphology arise from both morphology-specific physical and chemical effects of the gold nanoparticles.

Polymer coating on fluorescent silica nanoparticles enables to tailor made nanocomposite with unique tunable properties. Combining the emission of a fluorescent probe and the surface chemistry of a polymer shell a wide range of applications can be cover. The changing in the conformation of polymer chains enables to modify the hydrophilicity of the functionalized particles. For this, zwitterionic polymers are optimal since the electrostatic interaction between charged groups determines the conformational regime of the chains and the colloidal stability of the particle. In this work, we propose a functionalization of Amino Fluorescent Silica Nanoparticles (Amino-NPF) with a zwitterionic polymer by ATRP method. Poly [2- (Methacryloyloxy) ethyl] dimethyl- (3-sulfopropyl) ammonium hydroxide (PDMAPS) was successfully grafted onto the Amino-NPF surface. In particular, we followed three routes with different amount of catalyst. Route 1 corresponds to non-Cu (II) in solution, while pathways 2 and 3 consist of an increment in the metal concentration, 10% and 60% relative to Cu (I), respectively. A very short reaction time, only 15 minutes, was employed to diminish or avoid radical-radical termination. The stability and dispersability of the obtained core-brush nanoparticles in different solvents was evaluated. We demonstrate that the Cu (II) to Cu (I) concentration ratio defines the conformation of the polymer chains and in turn the hydrophilic character of the particles.

Phytochemicals self-stabilized Pickering emulsion is expected to be a highly desirable oral self-delivery system. In this study, ursolic acid (UA), a representative pentacyclic triterpene, was reported for the first time that can be formed self-stabilized Pickering emulsion. That is, it is experimentally and theoretically proved that water-in-oil Pickering emulsion could be stabilized solely by UA. First, the morphology, wettability and interfacial properties of the UA particles were characterized. Then, the influence of variation with UA particle concentration (c) and water fraction (ϕ) on the droplet size and coalescence (and sedimentation) stability of UA stabilized emulsions were also studied. It was found that the formed emulsions performed excellent sediment stability except that under conditions where the UA particle concentration is low (c=1 wt%) or at low water fraction(ϕ=0.1). The viscoelastic properties of the emulsions could be improved with the increasing c or ϕ. Finally, The molecular dynamics simulation further verified that the UA particles are located at the oil-water interface and incompletely wrapped the water droplets to form a stable W/O Pickering emulsion. This work enriches the family of sustainable W/O Pickering stabilizers and provides a new strategy for the construction of a Carrier-Free Delivery System for pentacyclic triterpenes.

Due to its unique properties, raspberry-like colloidal particles (RCPs) have been widely used in various fields. However, a facile, scalable and robust approach of producing raspberry-like polymeric particles remains an ongoing challenge. Herein, raspberry-like poly(styrene-co-divinylbenzene) (PSD) polymeric particles were fabricated by one-step dispersion polymerization in the solvent mixture of ethanol and toluene. The morphologies of obtained polymeric particles could be easily tuned from spherical to raspberry-like structure by changing the composition of the solvent mixtures. A rational mechanism for the formation of raspberry-like polymeric particles was also proposed according to the morphological evolution under different copolymerization conditions. With the assitance of the immonilized PVP layer, the raspberry-like PSD colloidal particles can be further functionalized by depositing Ag nanoparticles on the particle surface. The antibacterial activity of raspberry-like PSD/Ag composite particles against E. coli was up to 99.99%. In addition, raspberry-like PSD/Ag composites can be further utilized to construct antibacterial superhydrophobic surface and liquid marbles.

Carbonaceous particles are accounted among the most common environmental pollutants. This makes necessary a careful examination of their potential impact on the physico-chemical properties of different biological films, e.g. tear film, skin, or lung surfactant. This work analyzes the interaction of three different types of carbonaceous particles with Langmuir monolayers of 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) spread at the water/vapor interface. This type of studies can be exploited as preliminary in vitro tests for evaluating the potential risks and hazards of this type of pollutants for human health, which requires to study the effect of the particles on the ability of lipid layers for reducing the surface tension under static and dynamics conditions. The obtained results have shown that the insertion of particles into lipid films leads to the emergence of excluded area-like effects which modify the interfacial cohesion and packing. This hinders partially the ability of the lipid films for reducing the surface tension, which may present important adverse effects for the normal physiological performance of lipid membranes, and in particular for the performance of lung surfactant layers. Furthermore, the analysis of the response of lipid layers including carbonaceous particles against mechanical stresses also evidenced that particle incorporation worsens the mechanical performance of lipid layers, which may alter both their functional and structural roles.

The effects of ion concentration on the deformation and coalescence of particle-stabilized oil droplets dispersed in water were investigated. We emulsified a mixture of oil and an aqueous solution of silica particles with various NaCl concentrations ranging from 0 M to 3 M. Oil droplets were spontaneously compressed by evaporation of the water phase. At low ion concentrations ( 0.1 M); however, they coalesced more readily and formed larger ellipsoidal droplets. The coalesced droplets did not relax to a spherical shape. We observed the formation of large aggregates of the silica particles in the water phase at high ion concentrations. This suggested that aggregates of particles adsorbed on the oil-water interfaces and this would be closely related to solid-like oil-water interfaces. In contrast, the particles were well dispersed in the water phase at low ion concentrations because of repulsive forces between the particles. Thus, the adsorbed particles on the oil-water interfaces did not form solid-like particulate shells and the interfaces remained liquid-like. We also confirmed that an increase or decrease in ion concentration, even after formation of particle-stabilized oil droplets, resulted in the same interface responses. The ion concentration affected adsorbed silica particles and was a dominant factor for the interfacial properties of particle-stabilized oil droplets in the water phase.

Sodium-ion batteries (SIBs) are pondered as an auspicious solution for energy storage sector owing to cost effectiveness and plenteous of sodium resources. In this article, the O3-type layered Na9/10Cr1/2Fe1/2O2 (O3-NCF) compound was made by simple solid state reaction. Rietveld refinement revealed that the prepared material possesses R-3 m space group of rhombohedral structure. Hexagonal shaped particle in O3-NCF was exposed from HR-TEM images. The as-prepared O3-NCF provided an initial reversible capacity of 129 mAh g−1 at 0.1 C, between 2 and 4 V and sustained with 89.30 mAh g−1 after 100 cycles. Therefore, the O3-NCF was as a favorable cathode material for SIBs.

Camptothecin (CPT) is a highly potent anticancer agent with low water solubility and high toxicity. Nitric oxide (NO) is a gaseous free-radical molecule with potential to enhance anticancer chemotherapy. In this study, we designed and fabricated hybrid colloidal particle carriers for simultaneous delivery of CPT and NO, aiming to produce augmented anticancer activities. The drug carrier contains two separate domains, where CPT is physically loaded in the PLGA particle and NO is chemically conjugated to the organosilica scaffold via S-nitrosothiol linkage. The fabrication involves preparation of CPT-loaded PLGA particles and deposition of S-nitroso-organosilica, leading to the formation of anisotropic, Janus-like colloidal particles. We prepared and characterized 3 formulations with various entrapment amounts of CPT and NO (CPT:NO molar ratio = 1:4, 1:15, and 1:200). The release study demonstrates successful co-delivery of CPT and NO. Moreover, the formulations show increased cytotoxicity with increasing NO loading against various cancer cell lines. In conclusion, our study demonstrates the feasibility of co-delivering CPT and NO using organic-inorganic composite particle carriers. The hybrid nanocarriers increase the versatility of colloidal anticancer drug delivery.

Considering the superior film-forming properties and excellent light-reflecting performances on (001) crystal plans of illite, such natural clay mineral could be a potential candidate for novel inorganic UV shielding materials by high-quality purification and particle refinement. In this article, ball milling and ultrasonic treatments were carried out and compared on deep purified illite. The changes of illite during these treatments were characterized by X-ray diffraction (XRD), special surface area (SSA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV–vis absorption spectrum, particles size distribution and the point of zero charge (PZC). The results show that compared with ball milling, sonicated illite displays larger particle size and higher surface roughness, since the micro flakes are slowly distorted and separated from original aggregated illite sheets. Further UV–vis transmittance and UV-aging tests reveal that better UV shielding performance of illite is achieved by suitable ball milling treatment, where the illite lamellar aggregates are vertically breaking down into smaller aggregates, and display 34% increased retention ratio of fabric strength than uncoated fabrics under UV irradiation.

The aim of this study was to compare the emulsifying capacity and stability of soybean oil-in-water (O/W) Pickering emulsions stabilized by different areca taro starches (native starch, OSA esterified starch, ball-milled starch, and compound modified starch with ball-milling and OSA), and investigate the stability mechanism of Pickering emulsions. It was found that the compound modified starch showed strong surface activity and high emulsion viscosity, resulted in the best emulsifying capacity and stability. It could be clearly seen that the starch particles adsorbed at the oil-water interface of droplets to form physical barriers, and the upper and middle emulsion phases were uniform and stable after storage for 30 d. Thus, the ball-milling combined with OSA modification can be used as a viable and effective method to produce better starch-based particle emulsifiers.

We here discuss the behaviour of a suspension composed of magnetic cubic particles on a material surface in order to apply the characteristics of a magnetic cubic particle suspension to the development of surface modification technology. A magnetic field is assumed to be applied in a direction parallel to the material surface and the cubic hematite particles are assumed to have a magnetic moment in the diagonal direction of the particle. Moreover, in the situation of a strong gravitational field, the cubic particles are assumed to be bound on the material surface with a face of each cubic particle in contact with the material or bottom surface plane. In a previous study we concentrated on the situation where half the ensemble particles have a magnetic moment pointing in the upward diagonal direction and the others in the downward diagonal direction relative to the material surface. We here expand the previous study to a variety of ensembles described by a ratio of the number of the magnetic moments aligning in these two directions. From quasi-2D Monte Carlo simulations, it is seen that the composition ratio of these cubic particles has a significant effect on the regime of the particle aggregates. That is, with decreasing composition ratio, the size of closely-packed aggregates becomes smaller, and thin linear clusters tend to be preferred in the situation of a strong magnetic field. Furthermore, a decrease in the composition ratio tends to dull the occurrence of regime change in particle aggregates for a change in the magnetic particle–particle interaction strength.

This work presents a concept for creating different chemistries along thin, micrometer sized fibers to be used as substrates for selective localization of nanoparticles. Glass fibers have been surface modified to introduce hydrophilic and hydrophobic regions along their length. Dynamic contact angle measurements using the Wilhelmy technique shows a marked change in the wetting behavior, confirming the transition in chemical functionality along the fiber. These fibers were then used as substrates to localize polystyrene nanoparticles from an aqueous dispersion at the air-water interface via a dip-coating method. Low contact angles and faster de-wetting allowed the particles to predominantly confine onto the hydrophilic regions of the glass fibers, indicating that both the fiber surface properties as well as the curvature of the fiber influences the profile of the particle carrying fluid meniscus. Our results also indicate a velocity-dependent particle deposition morphology and image quantification analysis revealed a significantly higher density of nanoparticles to be deposited at higher withdrawal velocities.

The main challenge of nanotechnologies for enhanced oil recovery (EOR) in carbonate reservoirs is to maintain the colloidal stability of nanoparticle dispersion (nanofluid) under the reservoir conditions with high salinity and high temperature. This study presents a nanofluid as an injection fluid for EOR under the extreme condition. The nanofluid was composed of surface-modified silica nanoparticles by a silane coupling agent (GPTMS, (3-Glycidoxypropyl)trimethoxysilane). The particle size distribution and particle aggregation were measured and observed to evaluate colloidal stability of the nanofluid by the light scattering and electron microscopy methods. As a result, the colloidal stability of the nanofluid was achieved at the salinity up to 20 wt% of base fluid at 90 °C, when the amount of GPTMS was 1 mmol/g. The wettability alteration test of carbonate rocks was carried out to validate the applicability of the nanofluid in the reservoir conditions. The results showed that the rock wettability of dolomite and limestone was effectively altered to neutral-wet and water-wet from strongly oil-wet, respectively, by the nanofluid with a small portion of particle concentration. Therefore, it is believed that the nanofluid can be an effective EOR agent in carbonate reservoirs.

The stability of carbon black nanoparticles (CB-NPs) was investigated in five different ecotoxicity test media for fish, daphnia, and algae (i.e., ISO Test water, Elendt M4 medium, OECD TG 201 medium, AAP medium, and Bold’s Basal Medium) in the presence and absence of Suwannee River Humic Acid (SRHA) as a function of time. Hydrodynamic size, particle sedimentation rate, and visual images of suspensions were analyzed for 96 h, and the SRHA concentration was varied from 0 to 10 mg/L. Zeta potential and water contact angle of CB-NP, and SRHA sorption to CB-NPs were also examined to complement stability analyses. CB-NPs always exhibited negative zeta potential regardless of media type and SRHA concentration, and became more negative in the presence of SRHA due to SRHA sorption. Moreover, CB-NPs were found to be hydrophobic in the absence of SRHA, whereas they became hydrophilic when SRHA was adsorbed. Stability test results showed that regardless of test media, the hydrodynamic size increased fast and the sedimentation rate was high in the absence of SRHA, indicating poor stability of the CB-NPs. Conversely, the presence of SRHA substantially increased the stability of CB-NPs over 96 h, regardless of the SRHA concentration and test media type. Stability trends in the presence and absence of SRHA were not consistent with predictions from classical Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. However, extended and modified DLVO theories, that also accounted for hydrophobic-attractive forces due to the inherent nature of CB-NPs and steric repulsive forces associated with the brush-like conformation of SRHA adsorbed to CB-NPs, better described CB-NPs’ stability in the absence and presence of SRHA, respectively.

Two-dimensional (2D) structured nanosheets of Polyaniline/Titanium dioxide (PANI/TiO2) composites were synthesized and characterized. Electrorheological (ER) fluids of as-synthesized composites dispersed in silicone oil were prepared, the ER performances were investigated. The results showed that the as-synthesized composites are 2D structured PANI coated TiO2 nanosheets with the thickness of 2.7 nm, the suspension of 5 wt% particle concentration shows very low off-field viscosity and enhanced ER performances. Rheological analysis and dielectric analysis indicated that 2D nanosheets composites presented good polarizability and polarization rate in silicone oil under external electric field, and the polarized particles can form chain, column even 3D network structures to resist the shear force, which contributed to enhanced ER performances.

The electrical conductivity of plastics can be improved by metal filler particles, but high metal loadings (several ten volume percent) are generally needed to realize percolating pathways that can conduct electricity. We explore the improvement of the electrical conductivity of polystyrene by simultaneously adding two different metal fillers: copper particles, and a lead/tin solder alloy. The essential idea is that during mixing, the solder can bind together the particles via numerous menisci and the resulting copper-solder aggregates can then form a percolating network – hence the term “bulk soldering”. We show that this approach can realize high conductivities at total metal loadings that are far lower than if the copper particles were used as the sole conductive filler. SEM confirms that the microstructure consists of copper particles bonded by the solder, and that such aggregates can percolate throughout the sample volume. Indeed at a total metal loading of 20 vol%, the mixing process can create an all-metal scaffold that remains free-standing even when continuous phase polystyrene is removed. We examine the effect of composition on the microstructure and conductivity, and show that there is an optimal solder:copper volume ratio of roughly 0.6 which gives the highest conductivity. High conductivity is achieved only if a flux is added during mixing. The flux removes the copper oxide layer on the copper particles, and hence ensure wetting of copper by solder. Finally we comment on the similarities and differences between these polystyrene/solder/copper mixtures versus other liquid/fluid/particle mixtures in which capillarity induces aggregation of particles.

Colloidosomes which are hollow structures made of a thin shell of colloidal particles are gaining significant attention because of possible applications in a number of fields such as agriculture, pharmacy, and food technology. Using the nanoindentation technique, we investigate the mechanical response of clay colloidosomes fabricated by drying clay particle stabilized oil-in-water emulsions. These emulsions form due to the synergistic stabilization of decane/water emulsions by a mixture of kaolinite and non-ionic surfactant SPAN-80. The use of colloidosomes in technological application often calls for estimation of mechanical response. In this work, the effect of load magnitude, loading rate and the diameter of the colloidosomes on the mechanical response is investigated. The magnitude of peak load and the rate of loading are varied from 20 μN to 200 μN and 2.5 μN/sec to 50 μN/sec respectively. The colloidosomes with diameters in the 8 μm to 16 μm range are investigated. The colloidosomes are found to be mechanically robust (do not rupture) below 140 μN and disintegrate or break above this load magnitude. The rate of loading is found to influence the slope of the load-displacement curve and the creep behavior, i.e., for a given peak load, the depth of penetration and hold displacement increase with increase in the loading rate. The indentation modulus and indentation hardness of colloidosomes of different diameters are found to be in the range of0.5-3.0 GPa and 15–40 MPa respectively.

Electro-responsive smart poly(glycidyl methacrylate) (PGMA)/graphene oxide (GO) composite particles were synthesized using Pickering emulsion polymerization, in which the GO sheets simultaneously performed two roles, as a shell in a core-shell structure and a solid Pickering emulsifier. While the morphology of the synthesized PGMA/GO particles was examined via both transmission electron microscopy and high-resolution scanning electron microscopy, their chemical structural bonding and thermal stability were examined using Fourier transform infrared spectroscopy and thermo gravimetric analysis, respectively. The electrorheological (ER) features of PGMA/GO particle-based ER fluids dispersed in a silicone oil were studied by a rotational rheometer with various electric fields supplied by a high-voltage power generator. The experimental flow curve of the shear stress fitted well with the Bingham fluid model. To obtain additional information about the relationship between their ER behaviors and dielectric properties, the dielectric spectra were examined using a LCR meter and found to fit well with the Cole-Cole equation.

Traditionally, experiments of pattern deposition are conducted using volatile suspensions or solutions in sessile drops. However, several recent studies on the pattern deposition of colloidal particles, bio-molecular films, and membranes employed volatile carrier liquids in micro-chambers or micro-channels with a rectangular perimeter. We show that the local rate of evaporation from a concave meniscus of liquid in a chamber increases in the vicinity of the contact line like X−1/2 for a vanishingly small three phase contact angle, where the contact line is positioned at X = 0. This result is a reminiscent of the local rate of evaporation of liquid from a convex sessile drop. Moreover, an increase in the magnitude of the contact angle reduces the singularity in the rate of evaporation near the contact line. We employ our findings to study the deposition of colloidal particles from a volatile liquid meniscus in the presence of particle coagulation and particle adsorption to the substrate of the chamber, while demonstrating the convective accumulation of particles near the pinned contact line.

Pyridyl functionalized siloxanes with various architectures were synthesized by addition of 4-amino-pyridine to epoxy-siloxanes. The polysiloxane precursors were prepared in house by combining ROP with hydrosilylation. Depending on the ratio between siloxane and polar functional groups, the pyridyl-modified compounds may be soluble in water, in organic solvents or both, exhibiting self assembling ability and particle stabilizing effect. Due to pyridyl groups, they act as ligands for 3d and 4f block metals. A particularly interesting application is concerned to their ability to transfer organic and inorganic molecules from water to the organic phase. This behavior was tested for silver clusters and for water soluble dyes and pH indicators. A possible end-use is foreseen for transparent colored polymers or removable/reusable pH indicators. The properties of the pyridyl-siloxanes can be tuned by synthesis. Thus, a lower content in siloxane groups leads to surface activity in water, while a higher amount of siloxane gives better phase transfer ability.

We consider the electroosmotic flow (EOF) around a chemically inert uncharged dielectric particle under an applied electric field. In presence of an applied external electric field, a dielectric particle could be polarized to create an inhomogeneous ζ-potential. The electrolyte permittivity is considered to vary with the ionic concentration. The existing studies consider either a perfectly conducting particle or dielectric particles under a thin Debye layer assumption. In the present case, the induced EOF is not only influenced by the applied electric field but also with the dielectric permittivity constant of the particle and Debye length. We have analyzed the EOF without invoking a thin layer or weak applied field assumptions. The governing nonlinear electrokinetic equations are solved numerically. The close agreement of the present computed solutions with the existing asymptotic analysis for limiting cases such as thin Debye layer for a dielectric particle and a conducting particle is encouraging. The surface conductivity, measured by the Dukhin number, found to become larger as the particle dielectric permittivity grows. The Dukhin number has a nonlinear dependence on the applied electric field. The dielectric decrement effects on the EOF have been addressed in the present analysis. It creates a reduction in the EOF around the particle. Our results show that when the Debye length is on the order of the particle size, the dependence of EOF on the applied electric field varies with the dielectric permittivity constant of the particle. However, a quadratic dependence of EOF on the applied field strength occurs at a thin Debye layer. Reduction in the Debye length creates an enhanced induced EOF.

Cholesteric liquid crystal (CLC) dispersion was prepared using the mixed emulsifiers composed of Tween 20 and Span 80. The effects of preparation parameters on mean particle size and particle size distribution of CLC dispersion were investigated, demonstrating that the CLC mixture was better dispersed and stabilized above the phase transition temperature, and keeping the HLB at 11.7, emulsifier amount at 1.0%, dispersing speed at 5000 rpm for 60 min, the CLC particle in the dispersion were spherical and had a reversible thermochromic property. This dispersion was then used in the preparation of temperature-response PVP/CLC fibers in a water-based system by electrospinning. Polarized optical microscopy and scanning electron microscopy image reveal that CLC particles were incorporated into the PVP/CLC fibers, protecting the CLC from leaking out. The PVP/CLC fibers exhibited an optical temperature response in the temperature range from 25 to 60 °C.

pH-Responsive Pickering foams were prepared by using negatively charged silica nanoparticles in combination with trace amount of dodecyl dimethyl carboxyl betaine as stabilizer. The foams are stable at pH ≤ 4.3 but unstable at pH ≥ 10 and can then be cycled between stable and unstable for many times by alternating the pH of the aqueous phase. It is shown that in acidic aqueous media the carboxyl betaine molecules are turned to cationic form which can adsorb at surfaces of the negatively charged silica nanoparticles with head-on configuration via electrostatic interaction, rendering particles surface activity by in situ hydrophobization, and the particles can then adsorb at air/water interface to stabilize the Pickering foams; whereas in neutral and alkaline aqueous media, the carboxyl betaine molecules are in zwitterionic form, which tend to desorb from particle surface due to weakening or removing of electrostatic interaction, triggering de-hydrophobization of the particles and defoaming of the systems. This principle makes it possible to construct stimuli-responsive aqueous foaming systems using commercial inorganic nanoparticles in combination with trace amount of conventional surfactants avoiding synthesis or preparation of complicated stimuli-responsive colloid particles.

Sol–gel processing is an important colloidal processing route for the synthesis of macroporous materials of tunable microstructure. More recently, methods that use particle stabilized foams or emulsions have been developed. However, such methods generally involve the use of an external surface active additives that bind the particles together during processing. In this work, we present a simple and scalable additive-free method for the fabrication of porous materials that are both macroporous and microporous in nature. In particular, we show that silica-alumina porous materials can be fabricated by processing oppositely charged nanoparticle gel emulsions which are a dispersion of oil droplets in a space spanning network of colloidal particles. The nanoparticle gel emulsions obtained are initially characterized by optical microscopy and oscillatory rheology. The water and oil in these emulsion gels are removed by drying and it is finally sintered at 1000 °C to obtain porous material. The pore size and their distribution in the three-dimensional porous material is characterized using scanning electron microscopy (SEM) and X-ray tomography. Microscopy observations revealed a homogeneous distribution of macro-pores of 20–40 μm in diameter along the width, breadth and thickness of the porous material with an average porosity of 40% measured from 2D X-ray computed tomography images. One of the important features of the porous materials thus fabricated is the presence of nanosized pores due to the inherent porosity of the nanoparticle gel as well as micron sized pores due to the oil droplets.

Information acquisition and fluid characterization of oil reservoirs are one of the most challenging and scientifically demanding areas in the oil exploration industry. Herein, we report a single-step solvothermal method for the synthesis of highly-stable hydrophilic and hydrophobic superparamagnetic iron oxide nanoparticles (SPIONs). The functionalization of SPIONs was achieved using polyethylene glycol (PEG-400) and oleylamine (OLA) for water/oil phases of the reservoir, respectively. For comparison, uncoated SPIONs were also prepared by coprecipitation. Stability of hydrophilic SPIONs was monitored in deionized (DI) water and artificial seawater (ASW), while stability of hydrophobic SPIONs was investigated in model oil (cyclohexane-hexadecane 1:1). Several physicochemical techniques were utilized to characterize the phase and functionalization of SPIONs. Transmission electron microscopy (TEM) images display the spherical shape nanoparticles (NPs) having particle diameters 11.6 ± 1.4, 12.7 ± 2.2, and 9.1 ± 3.0 nm for PEG-Fe3O4, OLA-Fe3O4, and Fe3O4, respectively. Spin-spin (T2) relaxation measurements were performed by an Acorn Area analyzer to demonstrate contrasting ability of the contrast agents. The transverse relaxivity (r2) values for PEG-Fe3O4 (66.7 mM−1 s−1) and OLA-Fe3O4 (49.0 mM−1 s−1) were 2.07 and 1.53 times higher than Fe3O4 (32.2 mM−1 s−1) NPs, respectively. The (i) enhanced NMR T2-relaxation with optimum SPIONs concentration, (ii) excellent relaxivity properties due to their ultra-small size, and (iii) long-term stability in various continuous phases, suggest them to be promising T2-contrast agents for oil reservoir applications.