Colloidal stabilization of nanoparticles in concentrated suspensions.
TL;DR: This study synthesized dispersants with a molecular architecture that enables better control over the particle adlayer thickness that facilitates the fabrication of a wide range of products and intermediates in materials technology, cosmetics, pharmacy, and in all areas where concentrated nanoparticle suspensions are required.
Abstract: The stabilization of nanoparticles in concentrated aqueous suspensions is required in many manufacturing technologies and industrial products. Nanoparticles are commonly stabilized through the adsorption of a dispersant layer around the particle surface. The formation of a dispersant layer (adlayer) of appropriate thickness is crucial for the stabilization of suspensions containing high nanoparticle concentrations. Thick adlayers result in an excessive excluded volume around the particles, whereas thin adlayers lead to particle agglomeration. Both effects reduce the maximum concentration of nanoparticles in the suspension. However, conventional dispersants do not allow for a systematic control of the adlayer thickness on the particle surface. In this study, we synthesized dispersants with a molecular architecture that enables better control over the particle adlayer thickness. By tailoring the chemistry and length of these novel dispersants, we were able to prepare fluid suspensions (viscosity < 1 Pa.s at 100 s-1) with more than 40 vol % of 65-nm alumina particles in water, as opposed to the 30 vol % achieved with a state-of-the-art dispersing agent. This remarkably high concentration facilitates the fabrication of a wide range of products and intermediates in materials technology, cosmetics, pharmacy, and in all other areas where concentrated nanoparticle suspensions are required. On the basis of the proposed molecular architecture, one can also envisage other similar molecules that could be successfully applied for the functionalization of surfaces for biosensing, chromatography, medical imaging, drug delivery, and aqueous lubrication, among others.
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TL;DR: The state-of-the-art research in the area is described: the design and synthesis of catecholic molecules, their adsorption mechanisms and the stability of assemblies in solution, and their applications etc.
Abstract: The attachment strategy based on catecholic chemistry has been arousing renewed interest since the work on polymerized catecholic amine (polydopamine) (Messersmith et al., Science, 2007, 318, 426) was published. Catechols and their derived compounds can self-assemble on various inorganic and organic materials, including noble metals, metals, metal oxides, mica, silica, ceramics and even polymers. It opens a new route to the modification of various substrates and the preparation of functional composite materials by simple chemistry. However, there is still not a full review so far about the attachment chemistry despite the dramatically increasing number of publications. This critical review describes the state-of-the-art research in the area: the design and synthesis of catecholic molecules, their adsorption mechanisms and the stability of assemblies in solution, and their applications etc. Some perspectives on future development are raised (195 references).
1,039 citations
TL;DR: It is shown that catechols can be found either as simple molecular systems, forming part of supramolacular structures, coordinated to different metal ions or as macromolecules mostly arising from polymerization mechanisms through covalent bonds.
Abstract: Catechols are found in nature taking part in a remarkably broad scope of biochemical processes and functions. Though not exclusively, such versatility may be traced back to several properties uniquely found together in the o-dihydroxyaryl chemical function; namely, its ability to establish reversible equilibria at moderate redox potentials and pHs and to irreversibly cross-link through complex oxidation mechanisms; its excellent chelating properties, greatly exemplified by, but by no means exclusive, to the binding of Fe(3+); and the diverse modes of interaction of the vicinal hydroxyl groups with all kinds of surfaces of remarkably different chemical and physical nature. Thanks to this diversity, catechols can be found either as simple molecular systems, forming part of supramolacular structures, coordinated to different metal ions or as macromolecules mostly arising from polymerization mechanisms through covalent bonds. Such versatility has allowed catechols to participate in several natural processes and functions that range from the adhesive properties of marine organisms to the storage of some transition metal ions. As a result of such an astonishing range of functionalities, catechol-based systems have in recent years been subject to intense research, aimed at mimicking these natural systems in order to develop new functional materials and coatings. A comprehensive review of these studies is discussed in this paper.
613 citations
TL;DR: In marine systems, Me(O)NPs can absorb to micro-organisms with potential for trophic transfer following consumption, and their likely fate here is sedimentation following hetero-aggregation with natural organic matter and/or free anions, putting benthic, sediment-dwelling and filter feeding organisms most at risk.
335 citations
Cites background or methods from "Colloidal stabilization of nanopart..."
..., 2011), are employed to change the charge state of the particle, and to prevent agglomeration and aid dispersion in media of differing ionic strength (Bhatt and Tripathi, 2011) by providing a barrier to the agglomeration potential of van der Waals’ forces (Studart et al., 2007)....
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...…(Li et al., 2011), are employed to change the charge state of the particle, and to prevent agglomeration and aid dispersion in media of differing ionic strength (Bhatt and Tripathi, 2011) by providing a barrier to the agglomeration potential of van der Waals’ forces (Studart et al., 2007)....
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TL;DR: The relationship between the material properties and toxicity appears to be complex and diifficult to understand, which is partly due to incomplete characterization of the nanomaterial, and possibly due to experimental artefacts in the characterization of it and/or its interactions with living organisms.
Abstract: Metal oxide nanomaterials are widely used in practical applications and represent a class of nanomaterials with the highest global annual production. Many of those, such as TiO2 and ZnO, are generally considered non-toxic due to the lack of toxicity of the bulk material. However, these materials typically exhibit toxicity to bacteria and fungi, and there have been emerging concerns about their ecotoxicity effects. The understanding of the toxicity mechanisms is incomplete, with different studies often reporting contradictory results. The relationship between the material properties and toxicity appears to be complex and diifficult to understand, which is partly due to incomplete characterization of the nanomaterial, and possibly due to experimental artefacts in the characterization of the nanomaterial and/or its interactions with living organisms. This review discusses the comprehensive characterization of metal oxide nanomaterials and the mechanisms of their toxicity.
314 citations
TL;DR: In this paper, the authors summarized the literature from most recent articles on nanoparticles as a liquid fuel additive and discussed the effect of dispersion of several nanoparticles on the enhancement in the performance characteristics and reduction in emission of a CI engine fuelled with diesel-biodiesel blends.
311 citations
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TL;DR: In this article, a gas can condense to high density inside narrow, single-walled nanotubes (SWNTs) under conditions that do not induce adsorption within a standard mesoporous activated carbon.
Abstract: Pores of molecular dimensions can adsorb large quantities of gases owing to the enhanced density of the adsorbed material inside the pores1, a consequence of the attractive potential of the pore walls. Pederson and Broughton have suggested2 that carbon nanotubes, which have diameters of typically a few nanometres, should be able to draw up liquids by capillarity, and this effect has been seen for low-surface-tension liquids in large-diameter, multi-walled nanotubes3. Here we show that a gas can condense to high density inside narrow, single-walled nanotubes (SWNTs). Temperature-programmed desorption spectrosocopy shows that hydrogen will condense inside SWNTs under conditions that do not induce adsorption within a standard mesoporous activated carbon. The very high hydrogen uptake in these materials suggests that they might be effective as a hydrogen-storage material for fuel-cell electric vehicles.
3,558 citations
2,544 citations
TL;DR: A unified approach to the synthesis of a large variety of nanocrystals with different chemistries and properties and with low dispersity is reported, based on a general phase transfer and separation mechanism occurring at the interfaces of the liquid, solid and solution phases present during the synthesis.
Abstract: New strategies for materials fabrication are of fundamental importance in the advancement of science and technology. Organometallic and other organic solution phase synthetic routes have enabled the synthesis of functional inorganic quantum dots or nanocrystals. These nanomaterials form the building blocks for new bottom-up approaches to materials assembly for a range of uses; such materials also receive attention because of their intrinsic size-dependent properties and resulting applications. Here we report a unified approach to the synthesis of a large variety of nanocrystals with different chemistries and properties and with low dispersity; these include noble metal, magnetic/dielectric, semiconducting, rare-earth fluorescent, biomedical, organic optoelectronic semiconducting and conducting polymer nanoparticles. This strategy is based on a general phase transfer and separation mechanism occurring at the interfaces of the liquid, solid and solution phases present during the synthesis. We believe our methodology provides a simple and convenient route to a variety of building blocks for assembling materials with novel structure and function in nanotechnology.
2,418 citations
TL;DR: A cell labeling approach using short HIV-Tat peptides to derivatize superparamagnetic nanoparticles is developed, which efficiently internalized into hematopoietic and neural progenitor cells in quantities up to 10–30 pg of super paramagnetic iron per cell.
Abstract: The ability to track the distribution and differentiation of progenitor and stem cells by high-resolution in vivo imaging techniques would have significant clinical and research implications We have developed a cell labeling approach using short HIV-Tat peptides to derivatize superparamagnetic nanoparticles The particles are efficiently internalized into hematopoietic and neural progenitor cells in quantities up to 10-30 pg of superparamagnetic iron per cell Iron incorporation did not affect cell viability, differentiation, or proliferation of CD34+ cells Following intravenous injection into immunodeficient mice, 4% of magnetically CD34+ cells homed to bone marrow per gram of tissue, and single cells could be detected by magnetic resonance (MR) imaging in tissue samples In addition, magnetically labeled cells that had homed to bone marrow could be recovered by magnetic separation columns Localization and retrieval of cell populations in vivo enable detailed analysis of specific stem cell and organ interactions critical for advancing the therapeutic use of stem cells
1,788 citations
TL;DR: A review of spray pyrolysis processes in terms of the process parameters that enable the formation of particles with controlled morphology and composition can be found in this paper, where it is demonstrated that mixed metal oxide, nonoxide, and composite particles that are solid, hollow, porous, or fibrous can be produced by modifying the precursor characteristics, solution properties, and process parameters.
Abstract: A variety of spray pyrolysis (SP) techniques have been developed to directly produce ceramic powders from solutions. This paper reviews the current status of these processes in terms of the process parameters that enable the formation of particles with controlled morphology and composition. A model incorporating solute diffusion in the droplet and solvent evaporation from the droplet surface is presented to establish the critical parameters leading to solid particle formation. The model illustrates that solid particles can be obtained if solutes with high solubility and a large difference between the critical supersaturation and equilibrium concentration are used and if the process is designed to avoid solvent boiling. It is demonstrated that mixed metal oxide, non-oxide, and composite particles that are solid, hollow, porous, or fibrous can be produced by modifying the precursor characteristics, solution properties, and process parameters. The physical and chemical flexibility of SP processes offers numerous opportunities for the controlled synthesis of advanced ceramic powders and films. However, production rates are limited by the need to produce <5-[mu]m-diameter droplets and to avoid subsequent droplet coagulation. Developments in process controls, atomization, and system design are required for wider commercialization of SP-type processes.
1,061 citations