Nanoparticles in wastewaters: hazards, fate and remediation

The increasing use of nanoparticleswill inevitably result in their release into the aquatic environment and thereby cause the exposure of living organisms. Due to their larger surface area, high ratio of particle number tomass, enhanced chemical reactivity, and potential for easier penetration of cells, nanoparticles may be more toxic than larger particles of the same substance. Some researchers have been showing some relations between nanoparticles and certain diseases. However, the doses, surface shapes, material toxicity and persistence of nanoparticles may all be factors in determining harmful biological effects. In order to better evaluate their risks, potential exposure route of nanoparticles has to be taken into consideration aswell. Finally, a brief summary of techniques for nanoparticle removal inwaters andwastewaters is presented, but it seems that no treatment can absolutely protect the public from exposure to a large-scale dissemination of nanomaterials

Ortho-Fluoro Effect on the C–C Bond Activation of Benzonitrile Using Zerovalent Nickel

The effect of fluoro substitution on the C–C bond activation of aromatic nitriles has been studied by reacting a variety of fluorinated benzonitriles with the nickel(0) fragment [Ni(dippe)] and by locating the reaction intermediates and transition-state structures on the potential energy surface by using density functional theory calculations with the [Ni(dmpe)] fragment (dippe = 1,2-bis(diisopropylphosphino)ethane, dmpe = 1,2-bis(dimethylphosphino)ethane). As in the previous reports, the reaction of fluorinated benzonitriles with the [Ni(dippe)] fragment initially formed an η2-nitrile complex, which then converted to the C–CN bond activation product. Thermodynamic parameters for the equilibrium between these complexes have been determined experimentally in both a polar (tetrahydrofuran) and a nonpolar (toluene) solvent for 3-fluoro- and 4-fluorobenzonitrile. The stability of the C–C bond activation products is shown to be strongly dependent on the number of ortho-F substituents (−6.6 kcal/mol per o-F) and only slightly dependent on the number of meta-F substituents (−1.8 kcal/mol per m-F)

Practical Works on Nanotechnology: Middle School to Undergraduate Students

Since its emergence a few decades ago, nanotechnology has been shown to be a perfect example of a crossroad between different fundamentals sciences. In the last 10 years, the continuous progress of classical top-down lithography and the use of alternative bottom-up elaboration methods has allowed new and smaller components to be created. Their combination has led to very complex and innovative architectures. At the same time, flexible, low-cost, and low-ecological-footprint devices have emerged. Thus, the diversity and multidisciplinary features present challenges in addressing these issues in educational programs

Silane and borane coordination on ruthenium complexes (structural and theoretical studies and catalytic applications)

L'activation de liaisons E-H (E = Si, B) par des complexes polyhydrures du ruthénium a fait l'objet d'études expérimentales et théoriques (DFT/B3LYP). Celles-ci ont permis la caractérisation de nouveaux complexes possédant des ligands s-H2, s-Si-H ou s-B-H. Leur comportement fluxionnel et leur réactivité sont soumis à l'influence des substituants sur le silicium et le bore (en particulier avec des chlorosilanes, dialkoxyboranes et dialkylboranes). Cette influence a aussi été observée au cours des réactions catalytiques d'hydrosilylation ou de silylation déshydrogénante, et d'hydroboration ou de borylation déshydrogénante d'alcènes catalysées par les complexes RuH2(h2-H2)2(PCy3)2 et RuH(C2H4)[(h3-C6H8)PCy2](PCy3).TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Silica nanoparticles separation from water: aggregation by cetyltrimethylammonium bromide (CTAB)

International audienceNanoparticles will inevitably be found in industrial and domestic wastes in the near future and as a consequence soon in water resources. Due to their ultra-small size, nanoparticles may not only have new hazards for environment and human health, but also cause low separation efficiency by classical water treatments processes. Thus, it would be an important challenge to develop a specific treatment with suitable additives for recovery of nanoparticles from waters. For this propose, this paper presents aggregation of silica nanoparticles (Klebosol 30R50 (75 nm) and 30R25 (30 nm)) by cationic surfactant cetyltrimethylammonium bromide (CTAB). Different mechanisms such as charge neutralization, ''depletion flocculation'' or ''volume-restriction'', and ''hydrophobic effect'' between hydrocarbon tails of CTAB have been proposed to explicate aggregation results. One important finding is that for different volume concentrations between 0.05% and 0.51% of 30R50 suspensions, the same critical coagulation concentration was observed at CTAB = 0.1 mM, suggesting the optimized quantity of CTAB during the separation process for nanoparticles of about 75 nm. Furthermore, very small quantities of CTAB (0.01 mM) can make 30R25 nanosilica aggregated due to the ''hydrophobic effect''. It is then possible to minimize the sludge and allow the separation process as ''greener'' as possible by studying this case. It has also shown that aggregation mechanisms can be different for very small particles so that a special attention has to be paid to the treatment of nanoparticles contained in water and wastewaters

Silica nanoparticle separation from water by aggregation with AlCl₃

Nanotechnology that is vigorously developed nowadays will inevitably let nanoparticles into water resources. Since these ultrasmall particles may have potential risks for human and animals, it is reasonable to consider urgently how to manage these polluted waters. The direct separation would be difficult due to their small size and high surface area, so AlCl₃ is added to modify surface physicochemical properities of nanosilica in order to produce aggregates. Early stages and long time equilibriumof nanosilica aggregation are explored. In the kinetics study (early stage), the influences of particle concentrations and particle sizes are studied and compared. The aggregation results at long time equilibrium are further investigated, which shows the charge neutralization effect could be overcome by other mechanisms. More than 99% of the turbidity can be removed from aggregation of nanosilica by AlCl₃ after sedimentation

New generation of magnetic and luminescent nanoparticles for in-vivo real-time imaging

International audienceA new generation of optimized contrast agents is emerging, based on metallic nanoparticles (NPs) and semiconductor nanocrystals (NCs) for respectively magnetic resonant imaging (MRI) and near-infra-red (NIR) fluorescent imaging techniques. Compared with established contrast agents such as iron oxide NPs or organic dyes, these NPs benefit from several advantages: their magnetic and optical properties can be tuned through size, shape and composition engineering, their efficiency can excess by several order of magnitude that one of contrast agents clinically used, their surface can be modified to incorporate specific targeting agents and antifolding polymers to increase the blood circulation time and the tumor recognition, they can possibly be integrated in complex architecture to yield multimodal imaging agents. In this review, we will report the materials of choice based on the understanding of the physics basics of NIR and MRI techniques and their corresponding syntheses as NPs. Surface engineering, water transfer, and specific targeting will be highlighted prior to their first use for in-vivo real-time imaging. Highly efficient NPs, safer in use and target specific are likely to be entering clinical applications in a near future

Nanoparticules de fer de taille contrôlée pour l'hyperthermie

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Efficient thread/page/parallelism autotuning for NUMA systems

Current multi-socket systems have complex memory hierarchies with significant Non-Uniform Memory Access (NUMA) effects: memory performance depends on the location of the data and the thread. This complexity means that thread- and data-mappings have a significant impact on performance. However, it is hard to find efficient data mappings and thread configurations due to the complex interactions between applications and systems. In this paper we explore the combined search space of thread mappings, data mappings, number of NUMA nodes, and degreeof-parallelism, per application phase, and across multiple systems. We show that there are significant performance benefits from optimizing this wide range of parameters together. However, such an optimization presents two challenges: accurately modeling the performance impact of configurations across applications and systems, and exploring the vast space of configurations. To overcome the modeling challenge, we use native execution of small, representative codelets, which reproduce the system and application interactions. To make the search practical, we build a search space by combining a range of state of the art thread- and data-mapping policies. Combining these two approaches results in a tractable search space that can be quickly and accurately evaluated without sacrificing significant performance. This search finds non-intuitive configurations that perform significantly better than previous works. With this approach we are able to achieve an average speedup of 1.97× on a four node NUMA syste

Iron Nanoparticle Growth in Organic Superstructures

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