The Derjaguin-Landau-Verwey-Overbeek (DLVO) theory sums the attractive van der Waals and repulsive electrostatic forces as a function of separation distance to predict the interaction between charged particles immersed in a liquid. In aqueous media, however, non-electrostatic polar (electron acceptor/electron donor or Lewis acid/base) forces between particles with high energy surfaces often are comparable to, or greater than, the components of DLVO theory. By means of contact angle measurements on smooth self-supporting clay films, the values of the polar surface forces (AB) and the van der Waals forces (LW) of hectorite were measured. Determinations of ζ were used to derive the electrostatic forces (EL). Calculations based on the values obtained for the EL, LW, and AB forces show that for smooth spheres with a radius of 1 µm in a ≥ 0.1 M NaCl solution a net attraction exists leading to flocculation. At NaCl concentrations of ≤ 0.01 M, a repulsion energy of about +500 to +1300 kT exists at separation distances ≤ 50 Å, preventing contact between particles, thus ensuring stability of the colloidal suspension. At these concentrations, theory predicts that small clay particles or edges of clay crystals having an effective radius of curvature ≤ 10 Å should be energetic enough to overcome the repulsion barrier which prevents flocculation. Experimentally, for NaCl solution concentrations of ≥ 0.1 M, suspensions of hectorite particles flocculated, whereas at concentrations of ≥ 0.01 M, the suspensions remained stable. These experimental results agree with the predictions made by summing all three forces, but contradict the calculations based on classical DLVO theory.

Aqueous suspensions of allophane show relatively high viscosity, presumably because of strong particle interaction between the unit particles. To test this hypothesis, we measured the particle weight and particle size of allophane during a dispersion using the light scattering method. The particle weight was more than several hundred times larger than that of the unit particle, and the size was 100–400 nm, whereas the Stokes’ diameter of the particles in the sample was less than 50 nm. Particle weight and size varied with the pH of the sample. Particle sizes were cross-checked by ultrafiltration through membrane filters. The experimental findings show that the unit particles of allophane within dilute dispersions appear to be associated like strings of beads, forming domains (primary floccules) about 100 nm in diameter. When these domains coagulate under certain conditions, they do not grow analogously but form clusters, such as secondary floccules, then precipitate. Formation of secondary flocculation of loose structure accounts for the maximum relative viscosity at the transition pH between dispersion and coagulation.

Fine kaolinite suspensions were mixed with unaged or aged FeCl3 in this experiment. The interaction between clay particles and Fe3+ hydrolysis products was studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The proportion of Fe adsorbed was measured and the electrical charge on the clay particles was determined by electrophoresis. The effect of this interaction on flocculation of clay suspensions was investigated in a series of sedimentation tests. The Fe3+ ions acted as counterions when their concentration was low and when unaged FeCl3 solution was used. Otherwise, their hydrolysis complexes acted as a bonding agent between kaolinite particles. The dispersion-flocculation behavior of kaolinite suspensions was found to be in agreement with the theory of Derjaguin, Landau, Verwey and Overbeek (DLVO), as the sedimentation behavior could be predicted from the data of zeta potentials (ζ).

The sedimentation behavior of a fine kaolinite, comprising a substantial proportion of colloidal particles as well as non-colloidal ones, has been studied when fresh FeCl3 or F2(SO4)3 electrolytes are added. The sedimentation behavior depends on the pH and the nature of electrolytes and can be explained qualitatively, in our study, by the theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO theory). Fe helps also to aggregate the kaolinite particles in flocs. Two extreme kinds of qualitative sedimentation have been observed: flocculation-sedimentation and accumulation-sedimentation. However, the transition between the two kinds of sedimentation is quite progressive. The present results are discussed in reference to the DLVO theory and the hydrolysis behavior of Fe electrolytes.

Iron oxide nanoparticles presenting colloidal stability in water were prepared through precipitation and then surface-functionalized with varying citric acid (CA) concentrations (0.10, 0.25, 0.50, and 0.70 g/mL). CA introduced functionality and minimized agglomeration. Iron oxide nanoparticles with colloidal stability in water at physiological pH were obtained after functionalization with 0.25–0.70 g/mL CA, whereas iron oxide nanoparticles without stability in water were obtained after functionalization with 0.10 g/mL CA. An electrode for glucose detection was fabricated by self-assembling colloidal-stable γ-Fe2O3 NP–CA in water on indium tin oxide (ITO) glass, followed by a glucose oxidase (GOx) and Nafion layer. The optimal functionalization of the γ-Fe2O3 NPs was obtained at a CA concentration of 0.25 g/mL. The electrochemical properties and electrocatalytic behavior of the modified electrode designated as Nafion/GOx/γ-Fe2O3 NP–0.25 CA/ITO were then evaluated. The electrode showed high sensitivity for glucose detection of 995.57 and 5.81 µA/(mM cm2) within the linear ranges of 0.1–5.0 µM and 5.0 µM–20.0 mM, respectively. The modified electrode also demonstrated a low limit of detection, good repeatability of 2.5% (n = 10), and sufficient reproducibility of 3.2% (n = 5).

The materials chosen to make thermal engines, spacecrafts, or human implants cannot fail in an unpredictable way to guarantee the users' well-being. These applications can benefit from the use of ceramics because of their temperature resistance, corrosion resistance, or hardness. Although parts based on ceramic matrix composites and zirconia are already in use, a more recent ceramic with a structure inspired from seashells provides an attractive combination of ease of processing, high strength, and high toughness. These nacre-like aluminas are made of aligned micron-sized monocrystalline platelets joined together by a mix of mineral secondary phase and nanoparticles. The review's first objective is to provide a picture of what these newly developed bioinspired ceramics are capable of within today's ceramic and nacre-inspired composites landscape. I will also extract from the results the links between process/microstructure/performance to better understand the potential of these materials in terms of toughness and strength increase. Finally, I will present the challenges that are ahead to eventually reproduce the exceptional fracture behavior observed in nacre.

Using evanescent wave (EW)–based optical detection methods coupled with video microscopy, we investigated in situ trajectories, diffusion, and interaction energies of ∼140 nm ceria particles near a glass surface at pH 3, 5, and 7. Trajectories of a single ceria particle in a 2D (x–y) plane were obtained by linking its time-sequenced positions. Diffusion coefficients of several single ceria particles were calculated from their respective mean-square displacement (MSD) versus time curves, and the results were interpreted based on the interaction potential energy curves obtained from Boltzmann statistics of the EW scattering intensity fluctuations of the particles. The types and characteristics of particle motions were determined by analyzing the MSD curves. Whereas both confined or subdiffusive and Brownian motions of the particles were observed at pH 7, only confined motion was seen at pH 3 and 5, and their corresponding diffusion coefficients are similar to those reported by several authors.

A liquid-state pyroelectric energy harvester is described and a remarkable capacity to convert a thermal gradient into electrical energy is demonstrated.

Increasing the sustainability of energy generation can be pursued by harvesting extremely low enthalpy sources: low temperature differences between cold and hot reservoirs are easily achieved in every industrial process, both at large and small scales, in plants as well as in small appliances, vehicles, natural environments, and human bodies. This paper presents the assessment and efficiency estimate of a liquid-state pyroelectric energy harvester, based on a colloid containing barium titanate nanoparticles and ferrofluid as a stabilizer. The liquid is set in motion by an external pump to control velocity, in a range similar to the one achieved by Rayleigh–Bénard convection, and the colloid reservoir is heated. The colloid is injected into a Fluorinated Ethylene Propylene pipe where titanium electrodes are placed to collect electrical charges generated by pyroelectricity on the surface of the nanoparticles, reaching 22.4% of the ideal Carnot efficiency of a thermal machine working on the same temperature drop. The maximum extracted electrical power per unit of volume is above 7 mW/m3 with a ΔT between electrodes of 3.9 K.

Boron nitride nanotubes (BNNTs) and hexagonal boron nitride platelets (h-BNs) have received considerable attention for aerospace insulation applications due to their exceptional chemical and thermal stability. Presently, making BN nanomaterials compatible with polymer and composite matrices is challenging. Due to their inert and highly stable structure, h-BN and BNNTs are difficult to covalently functionalize. In this work, we present a novel sonochemical technique that enables covalent attachment of fluoroalkoxy substituents to the surface of BN nanomaterials in a controlled and metered process. Covalent functionalization is confirmed via colloidal stability analysis, FT-IR, and x-ray photoelectron spectroscopy (XPS).

Ultrasonic sonochemistry and pulsed laser ablation in liquids (LAL) are modern techniques for materials synthesis that are in different ways linked to the formation and collapse of cavitation bubbles. We provide an overview of the physics of laser-induced and acoustically driven bubble oscillations and then describe how the high pressures and temperatures associated with ablation and bubble collapse, as well as emitted shock waves, take part in material synthesis inside and around the bubble. Emphasis is placed on the mechanisms of sonochemical synthesis and modification, and on a step-by-step account of the events from laser ablation through interaction of ablation products with the surrounding liquid up to the modification or aggregation of particles within the bubble. Both sonochemistry and LALs yield nanostructured materials and colloidal nanoparticles with unique properties. The synthesis process has been demonstrated to be scalable.

Noble metal (Ag, Au) nanoparticles (NPs) deposited on the surface of three-dimensional (3D) materials are promising 3D surface-enhanced Raman spectroscopy (SERS) substrates. In this work, the authors reported the preparation of 3D wax/silica/Ag(Au) colloidosomes by sulfonic acid group–terminated silica spheres (SiO2–SO3H) combined with a Pickering emulsion technique, as well as seed-mediated growth method of noble metal NPs. The presence of –SO3H group on the silica spheres not only improves significantly the quality of wax/silica colloidosomes (forming perfect silica shell around wax droplet) but also can adsorb metal precursor ions via electrostatic attraction for further growth of metal NPs. The size and coverage of Ag(Au) NPs on wax/silica droplets can be facilely tuned, and relevant wax/silica/Ag(Au) colloidosomes and silica/Ag(Au) Janus particles are obtained via this strategy. The obtained wax/silica/Ag colloidosomes as 3D SERS substrates exhibited excellent SERS enhancement ability and detection limit of 4-aminothiophenol reached 10−9 M.

In this paper, a colloidal solution of copper nanoparticles was prepared from a Cu ion aqueous solution with the protein casein surfactant by a liquid phase reduction method at low temperature below 373K. For the casein concentration ranging from 6g/L to 75g/L, the formation of copper nanoparticle colloid were observed. As a result, the peak was observed at the ranging of 450 to 650 nm corresponding to the copper nanoparticle colloid plasmon absorption. As the surfactant concentration increases, the absorption spectrum tends to blue-shift and the particle diameter decreases. Thus, it indicated that the optical property and particle diameter of copper nanoparticle colloidal solution will be controlled by the protein casein surfactant concentration.

Prior research into the liquid-phase exfoliation of graphite to produce few-layer graphene has focused primarily on the surface energy matching between graphite and solvent; however, the effect of other solvent properties, such as liquid viscosity, have not been systematically explored. In principle, a higher viscosity solvent should enable the production of graphene and other graphitic nanomaterials by liquid-phase exfoliation at lower shear rates than traditionally used organic solvents of low viscosity, such as N-methyl-2-pyrrolidone (NMP). Thus, at a given shear rate, more material should be exfoliated in the higher viscosity solvent. Hence, graphite suspensions in NMP, benzyl benzoate, and propylene glycol were exfoliated at various shear rates in a rheometer. Exfoliant concentrations were measured by ultraviolet- visual (UV-vis) spectroscopy and quality characterization was performed by Raman spectroscopy and scanning electron microscopy (SEM). Graphite exfoliation in the more viscous propylene glycol solvent resulted in a higher exfoliant concentration than in the less viscous NMP and benzyl benzoate solvents across all shear rates. Benzyl benzoate lowered exfoliant levels, likely due to a poor surface energy match, resulting in particle attraction and aggregation. Characterization showed that at least some of our material is few-layer graphene.

The generation of AuNPs was realized in presence of gold chloride (Au3+), and citrate solution as reducing agent. The production of AuNPs was proved by the color change in the solution; from yellow to red wine. Purified nanostructures synthesized at citrate/Au3+ molar ratio of 1.0/10.0 evidenced an absorption peak at 526 nm attributed to the localized surface Plasmon Resonance (LSPR) which suggested the formation of small gold nanoparticles (NPs). The decrease of citrate/Au3+ molar ratio at 1.0/3.0 provoked a growing of gold nanostructures, which was evidenced by a red shift in the SPR at 546nm. High Resolution Transmission Electron Microscopy technique evidenced the spherical form and sizes for both nanoparticles at the range 10-15 nm (small NPs) and 20-25 nm (big NPs), respectively. Electron Diffraction (ED) patterns for both sizes evidenced the (111), (200), (220), (311), and (222) reflections of face centered cubic (FCC) gold nanostructures. Studies of energy-dispersive X-ray Spectroscopy indicated peaks at 1.65, 2.12, 9.71, 11.58 and 13.38 keV for both nanostructures, which suggests the presence of gold into the crystalline structure of the nanoparticles. Interaction tests were carried out in presence of marine crustaceans and different concentrations of gold nanoparticles; including a control test. Both sizes evidenced to be toxic when the concentration and exposure time were increased.

In this study, 3 types of zwitterionic phospholipid biosurfactants LDP(S), CDP(S) and CTDP(S) were prepared from 3 different raw materials such as rapeseed oil, coconut oil and cottonseed oil respectively. The structure of the resulting phospholipid biosurfactants was elucidated by FT-IR, 1H NMR and 13C NMR spectroscopies and their interfacial properties have been examined such as CMC, static surface tension, wetting property, solution stability, and foam property. Interfacial property measurement and prescription test in cosmetic formulation prepared with the newly synthesized biosurfactants revealed that CDP(S) biosurfactant possesses excellent mildness and superior interfacial properties, indicating the potential applicability in cosmetic product formulations.

Room-temperature liquid metals, such as eutectic gallium–indium–tin (galinstan), dispersed in a polymer matrix present unique potential as conductors that may have minimal influence on the host polymer mechanical performance while providing enhanced electrical performance. Work described herein systematically evaluates the influence of uncured polydimethylsiloxane (PDMS) viscosity and galinstan loading on final dispersion viscosity and cured modulus. Dispersions of up to 80 vol% galinstan were obtained with relative permittivity values up to 170 that otherwise exhibited similar uncured rheological changes to a solid filler. Cured galinstan-in-PDMS dispersions, however, exhibited a reduced stiffness increase with respect to the host polymer relative to a solid filler. At a critical PDMS viscosity and metal, loading phase inversion to a conductive PDMS-in-metal dispersion was observed. It is anticipated that this work will enable the development of liquid metal polymer composites with independently controlled mechanical and electrical properties for a wide variety of stretchable electronic applications.