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Flotation process of micro-fine minerals have historically been hampered by slow flotation rate, poor selectivity, high reagent consumption, and low recovery. These disadvantages are mainly due to the large specific surface area attributed to the small-sized mineral particles. As such, research have revolved around enhancing their recovery by process intensification as one of the known effective methods. Micro/nanoparticles, on the other hand, possess many attributes, for instance, strong chemical activity, high reactivity, high surface free energy, and large adsorption capacity, all of which can contribute to improve the separation of micro-fine minerals. The mechanisms and preparation methods of nanoparticle collectors (NPCs) as well as ultrafine bubbles (UFBs) are described in this paper. Furthermore, the influences of NPCs and UFBs on the flotation of micro-fine minerals are also discussed. NPCs and UFBs are capable of providing hydrophobicity selectivity to the desired minerals to improve the flotation performance of mineral particles. This paper offers an overview of the underlying properties of NPCs and UFBs in intensifying flotation applications. [ABSTRACT FROM AUTHOR]

Here we report a new study on the boundary conditions for the flow of a simple liquid in a confined geometry obtained by measuring hydrodynamic drainage forces with colloid probe atomic force microscopy (AFM). In this work, we provide experimental data obtained using a best practice experimental protocol and fitted with a new theoretical calculation (Zhu, L.; Attard, P.; Neto, C. Langmuir2010, submitted for publication, preceding paper). We investigated the hydrodynamic forces acting on a silica colloid probe approaching a hydrophobized silicon surface in a single-component viscous Newtonian liquid (di-n-octylphthalate), a partially wetting system. The measured average slip lengths were in the range of 24−31 nm at approach velocities of between 10 and 80 μm/s. Using our experimental approach, the presence of nanoparticle contaminants in the system can be indentified, which is important because it has been shown that nanoparticles lead to a large apparent slip length. Under our stringent control of experimental conditions, the measurement of the slip length is reproducible and independent of the spring constant of the cantilever. [ABSTRACT FROM AUTHOR]

Nanofluids have attracted significant research interest for their promising application in enhanced oil recovery. One striking feature leading to the outstanding efficiency of nanofluids in enhanced oil recovery is the structure of nanoparticles, which induces oscillatory structural forces in the confined space between fluid–fluid interfaces or air–liquid and liquid–solid interfaces. To promote the understanding of the oscillatory structural forces and their application in enhanced oil recovery, we reviewed the origin and theory of the oscillatory structural forces, factors affecting their magnitude, and the experimental techniques demonstrating their impacts on enhanced oil recovery. We also reviewed the methods, where the benefits of nanofluids in enhanced oil recovery provided by the oscillatory structural forces are directly manifested. The oscillatory structural forces promote the wetting and spreading of nanofluids on solid surfaces, which ultimately enhances the separation of oil from the reservoir. Some imbibition tests demonstrated as much as 50% increased oil recovery, compared to the cases where the oscillatory structural forces were absent. [ABSTRACT FROM AUTHOR]

Background: Nanosuspensions, liquid dispersions with nanometer size distribution, are becoming trendy in pharmaceutical practice to formulate poorly water-soluble drugs and to enhance their bioavailability. Generally, nanosuspensions are produced in two main approaches; top-down or bottom-up. The former is based on size-reduction of large particles via milling or high pressure homogenization. The latter is focused on the mechanisms of nucleation and particle growth. Methods: In this review, the critical factors influencing the kinetics or dynamics of nucleation and growth are discussed. Subsequently, the mechanisms of nanosuspension instability as well as strategies for stabilization are elaborated. Furthermore, the effects of stabilizers on key parameters of instability as well as the process of choosing an appropriate stabilizer is discussed. Results: Steric and electrostatic stabilizations or combination of them is essential for nanosuspensions formulation to prevent coagulation. Accordingly, some characteristics of stabilizers play critical role on stability and optimization of nanosuspensions; i.e., HLB and concentration. Nevertheless, after reviewing various articles, it is ascertained that each formulation requires individual selection of surfactants according to the parameters of the particle surface and the medium. Conclusions: Based on the results, application of excipients such as stabilizers requires proper optimization of type and concentration. This implies that each formulation requires its own optimization process. [ABSTRACT FROM AUTHOR]

We explore present-day trends and challenges in nanomedicine. Creativity in the laboratories continues: the published literature on novel nanoparticles is now vast. Nanoagents are discussed here which are composed entirely of strongly photoluminescent materials, tunable to desired optical properties and of inherently low toxicity. We focus on “quantum nanoparticles” prepared from allotropes of carbon. The principles behind strong, tunable photoluminescence are quantum mechanical: we present them in simple outline. The major industries racing to develop these materials can offer significant technical guidance to nanomedicine, which could help to custom-design strongly signalling nanoagents specifically for stated clinical applications. Since such agents are small, they can be targeted easily, making active targeting possible. We consider it timely now to study the interactions nanoparticles undergo with tissue components in living animals and to learn to understand and overcome the numerous barriers the organism interposes between the blood and targets in or on parenchymal cells. As the near infra-red spectrum opens up, detection of glowing nanoparticles several centimeters deep in a living human subject becomes calculable and we present a simple way to do this. Finally, we discuss the slow-fuse and resource-inefficient entry of nanoparticles into clinical application. A first possible reason is failure to target across the body’s barriers, see above. Second, in the sparse translational landscape funding and support gaps yawn widely between academic research and subsequent development. We consider the agendas of the numerous “stakeholders” participating in this sad landscape and point to some faint glimmers of hope for the future. [ABSTRACT FROM AUTHOR]

Abstract: We report on the development of a supramolecular nanocarrier concept that allows for the encapsulation and separation of small apolar molecules from water. The nanocarriers consist of shell‐by‐shell‐coated nanoparticles such as TiO2 and ferromagnetic Fe3O4. The first ligand shell is provided by covalently bound hexadecyl phosphonic acid (PAC16) and the second shell by noncovalently assembled amphiphiles rendering the hybrid architecture soluble in water. Agitation of these constructs with water containing the hydrocarbons G1–G4, the fluorescent marker G5, the polychlorinated biphenyl PCB 77, or crude oil leads to a very efficient uptake (up to 411 %) of the apolar contaminant. In case of the hybrids containing a Fe3O4 core, straightforward phase separation by the action of an external magnet is provided. The load can easily be released by a final treatment with an organic solvent. [ABSTRACT FROM AUTHOR]

Dendritic Pt nanospheres of 20 nm diameter are synthesized by using a highly concentrated surfactant assembly within the large-sized cage-type mesopores of mesoporous silica (LP-FDU-12). After diluting the surfactant solution with ethanol, the lower viscosity leads to an improved penetration inside the mesopores. After Pt deposition followed by template removal, the arrangement of the Pt nanospheres is a replication from that of the mesopores in the original LP-FDU-12 template. Although it is well known that ordered LLCs can form on flat substrates, the confined space inside the mesopores hinders surfactant self-organization. Therefore, the Pt nanospheres possess a dendritic porous structure over the entire area. The distortion observed in some nanospheres is attributed to the close proximity existing between neighboring cage-type mesopores. This new type of nanoporous metal with a hierarchical architecture holds potential to enhance substance diffusivity/accessibility for further improvement of catalytic activity. [ABSTRACT FROM AUTHOR]

Mesoporous Pd@Pt nanoparticles possess high surface areas while still maintaining electroconductivity and low potential for agglomeration. By introducing L- or D-DOPA (3,4-dihydroxyphenylalanine) enantiomers during the synthesis of the mesoporous Pd@Pt nanoparticles, we can create a Pt shell that is sensitive to the chirality of the DOPA molecule. We demonstrate sensitive electrochemical detection of DOPA enantiomers. [ABSTRACT FROM AUTHOR]

The surface properties of a model membrane electrode assembly of a high-temperature proton-exchange-membrane fuel cell with a nanostructured PtAu working electrode were studied under operando conditions (polarization, humidified H2 atmosphere, 150 °C) using near-ambient-pressure photoelectron spectroscopy (NAP-XPS). NAP-XPS proved to be a powerful tool for the in situ investigation of the changes in the chemical composition, the segregation of the two metals, and the changes in their oxidation state. Nondestructive depth profiling revealed the influence of the polarization and the gas ambient on the distribution of the two metals in the near-surface region. The results suggest that the surface of the electrode is covered by a thin layer of gold, which is stable at potentials below the onset of surface-oxide formation. Anodic oxidation of the PtAu electrode pulls Pt to the surface, leading to intermixing of Pt and Au atoms and the formation of an interfacial alloy. [ABSTRACT FROM AUTHOR]

A review (350 references) is given to the interest of mesoporous materials for designing electrochemical sensors. After a brief summary of the implication of template-based ordered mesoporous materials in electrochemical science, the various types of inorganic and organic-inorganic hybrid mesostructures used to date in electroanalysis and the corresponding electrode configurations are described. The various sensor applications are then discussed on the basis of comprehensive tables and some representative illustrations. The main detection schemes developed in the field are (volt)amperometric sensing subsequent to preconcentration and electrocatalytic detection. [ABSTRACT FROM AUTHOR]

Kolloidale Pd@Pt ‐ Nanopartikel mit einheitlichen Mesoporen sind in einer Stufe durch langsame Reduktion von Metallspezies in stark saurer Lösung zugänglich. In diesem System wirken F127 ‐ Micellen direkt als Template für die Mesoporen des Produkts; die bessere Reduzierbarkeit der Pd ‐ Spezies führt zu den gewünschten Pd@Pt ‐ Kern ‐ Schale ‐ Nanokolloiden. [ABSTRACT FROM AUTHOR]

In this work, we report the facile formation of bimetallic nanoparticles of in the presence of the plant polyphenol ellagic acid (EA). It was found that EA formed micro-fibrillar assemblies, which aggregated into micro-bundles under aqueous conditions. Those micro-bundles acted as templates for the growth of nanoparticles, as well as bimetallic nanoparticles biomimetically. At higher concentrations of EA, it was observed that in addition to forming fibrous micro-bundles, columnar assemblies of EA were formed in the presence of the metal nanoparticles. The formation of the assemblies was found to be concentration dependent. It appears that upon binding to metal ions and subsequent formation of the nanoparticles, morphological changes occur in the case of EA assemblies. The morphological changes observed were probed by electron microscopy. Further, the ability of the materials to degrade the toxic aromatic nitro compound 2-methoxy-4-nitroaniline was explored, where 50% degradation was observed within 15 min, indicating that such hybrid materials may have potential applications in environmental remediation. [ABSTRACT FROM AUTHOR]

A coral-like macroporous Au electrode with electroplated Pt nanoparticles (hybrid macroporous Au-/nPts) coated with Nafion has been fabricated for the first time and used for highly selective and sensitive determination of dopamine (DA). The physically characterized results indicated that the electroplated Pt nanoparticles were dispersed uniformly on the macroporous Au electrode. The porosity and window pore size of the fabricated macroporous Au electrode were 50% and 100–300 nm, respectively. Also the electroplated Pt nanoparticles size was approximately 10–20 nm. The cyclic voltammograms results showed that the hybrid macroporous Au-/nPts exhibited a much larger surface activation area, a roughness factor (RF) of 2024.7, much higher than that of the macroporous Au electrode, which is 46.07. The electrochemical experimental results showed that the hybrid macroporous Au-/nPts coated with Nafion exhibited a dramatic electrocatalytic effect on the oxidation of DA. At 0.1 V, it responded linearly to DA concentrations ranging from 20 \muM to 160 \muM with a detection sensitivity of 90.9 \muA mM^-1 cm^-2. Furthermore, it showed wide detection ranging from 20 nM to 900 \muM. At the same time, the interference of ascorbic acid (AA) was effectively avoided because of the Nafion film coated on the surface of the hybrid electrode. [ABSTRACT FROM PUBLISHER]

The dynamics of fluid contained in a nano-cube has been studied by proposing theoretical model which is based on the microscopic consideration. The confinement affecting the movement at atomic level has been used to study the self-diffusion through Green Kubo relation. It is found that close to the walls, the dynamics of fluid slows down to an extent that it affects the flow of fluid even in the middle of the nanocube. Results are contrasted with the results obtained from similar considerations for fluid confined in rectangular nanotube. It is found that tendency of freezing near the wall is more in case of nanocube than in the rectangular nanotube. An empirical relation has also been proposed to explain the behaviour of wall mediated self-diffusion as a function of distance in either direction. [ABSTRACT FROM AUTHOR]

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A quartz crystal microbalance with dissipation monitoring (QCM-D) was used to study the adsorption of the layer formed by silica nanoparticles (SNP) and cellulose nanofibrils (NFC) together with cationic polyacrylamide (C-PAM) on cellulose surface, accompanied by use of atomic force microscope (AFM) to study the interactions between cellulose surfaces. The purpose was to understand the multilayer buildup compared to complex structure adsorption. The layer thickness and consequently also the repulsion between surfaces increased with each addition step during layer formation in the SNP-C-PAM systems, whereas the second addition of C-PAM decreased the repulsion in the case of NFC-C-PAM multilayer formation. An exceptionally high repulsion between surfaces was observed when nanofibrillar cellulose was added. This together with the extremely high dissipation values recorded with QCM-D indicated that nanofibrillar cellulose formed a loose and thick layer containing a lot of water. The multilayer systems formed fully and uniformly covered the surfaces. Silica nanoparticles were able to penetrate inside the loose C-PAM structure due to their small size. In contrast, NFC formed individual layers between C-PAM layers. The complex of C-PAM and SNP formed only a partly covered surface, leading to long-ranged pull-off force. This might explain the good flocculation properties reported for polyelectrolyte-nanoparticle systems. [ABSTRACT FROM AUTHOR]

This article discusses the adsorption of nanoparticles in a fluid interface. In order to account for this process, which is referred to as wetting, researchers need to analyze the interactions of vapor, liquid, and particle in a three phase contact region. The data for Lennard-Jones/spline fluids is studied by reference to the first-order mean spherical approximation and renormalization group transformation of the wetted nanoparticles. This data can be applied to problems involving the behavior and surface tension of nanoparticle-fluid systems.

Control over the structure of metals at the mesoscale (2-50 nm) is crucial for emerging applications such as energy conversion, sensing, and information processing. The self-assembly of nanoparticles with block copolymers provides a natural entry point to materials of this length scale. The field's historical development, relevant physical models, and recent results are presented. [ABSTRACT FROM AUTHOR]

The passage of individual molecules through nanosized pores in membranes is central to many processes in biology. Previously, experiments have been restricted to naturally occurring nanopores, but advances in technology now allow artificial solid-state nanopores to be fabricated in insulating membranes. By monitoring ion currents and forces as molecules pass through a solid-state nanopore, it is possible to investigate a wide range of phenomena involving DNA, RNA and proteins. The solid-state nanopore proves to be a surprisingly versatile new single-molecule tool for biophysics and biotechnology. [ABSTRACT FROM AUTHOR]

The paper is concerned with longitudinal and transverse waves propagating at a right angle to the layers of a nanocomposite material with initial (process-induced residual) stresses. The composite consists of alternating layers of two dissimilar materials. The materials are assumed nonlinearly elastic and described by the Murnaghan potential. For simulation of wave propagation, a problem is formulated within the framework of the three-dimensional linearized theory of elasticity for finite prestrains. It is established that the relative velocities of waves depend linearly on small prestresses. In some composite materials, however, the thicknesses of the layers may be in a ratio such that the wave velocities are independent of the prestress level [ABSTRACT FROM AUTHOR]

The size of (nano) particles is a key parameter used in controlling their function. The particle size is also important in order to understand their physical and chemical properties and regulate their number in health and safety issues. In this work, the geometric diameters of polystyrene spheres of nominal diameter 100 nm are measured using atomic force microscopy. The measurements are based on the apex height and on the average distance between neighbouring spheres when they form a close-packed monolayer on a flat mica substrate. The most important influence parameters for the determination of the geometric diameter are the lateral air gaps and deformation of the spheres. The lateral air gaps are caused by significant size variations of the individual spheres, and a correction is calculated based on the simulation of packing of spheres. The deformation of the spheres is caused mainly by capillary forces acting when they are in contact with each other or with the mica substrate. Based on calculated capillary forces and the literature values of the elastic properties of the polystyrene and mica, the deformation is estimated to be 2 nm with a standard uncertainty of 2 nm. The geometric diameter of the polystyrene spheres was measured with a combined standard uncertainty of [?]3 nm. The measured vertical diameter of 92.3 nm and the certified mobility equivalent diameter measured by differential mobility analysis (DMA) are marginally consistent at a confidence level of 95%. However, the measured lateral geometric diameter was 98.9 nm and is in good agreement with DMA. [ABSTRACT FROM AUTHOR]