Nanoparticles nanosystems

In the recent literature the terms nanoparticles and nanosystems are used, in analogy to colloid and colloidal systems. The prefix nano indicates dimensions in the 1 to 100 nm range. This is above the atomic scale and, unless highly refined methods are used, below the resolution of a light microscope and thus also below the accuracy of optical microstructuring techniques. 

Figure 1 The size spectram showing nanoparticle and other nanosystems in die context of microparticulates and macrosystems. Also shown are the methods employed to measure the particle size and size distribution of this range of materials. Abbreviations MLV, muldlamellar vesicle SUV, single unilamellar vesicles. Source From Ref. 13.

In ocular delivery to the cul-de-sac of the eye, nanoparticles in suspension can prolong the action of the drug both by slow release and their slower escape by way of the punctae compared to a solution, and perhaps the adhesive qualities of some nanosystems (66) also assist. 

It is useful, for reasons which are apparent in relation to movement of nanoparticles in vivo, to divide nanosystems into two types, hard and soft, although there are obviously intermediate situations. Hard systems, for example, polymeric nanoparticles and nanocapsules, nanosuspensions or nanocrystals, dendrimers, and carbon nanotubes are neither flexible nor elastic. Hard systems can block capillaries and fenestrae that have dimensions similar to the particles, whereas soft systems can deform and reform to varying degrees. Erythrocytes and many liposomes fall into this category and are thus better able to navigate capillary beds and tissue extracellular spaces. Soft systems include nanoemulsions (microemulsions) and polymeric micelles. 

This is unfortunate because the theoretical advantage of nanosystems is their small size, allowing freer movement than microspheres in the circulation, including the lymph and in tissues. Flow rates are important not least in the determination of the possibility of nanoparticle interaction with endothelial receptors prior to internalization, or indeed in the decoupling of carriers and receptors due to shear forces. Flow of nanoparticles is a vital element in extravasation and in the enhanced permeation and retention (EPR) effect. What is the influence of nanoparticle size on particle flow in the circulation And, with the advent of CNTs in particular, what is the influence of shape on flow and fate CNTs certainly behave differently in the blood from spherical C60 fidlerenes. CNTs activate human platelets and induce them to aggregate, whereas their spherical analogues do not... 

Keywords. Fiquid crystals. Complex Fluids, Self-assembly, Mineral, Inorganic, Nanosystem, Nanoparticle, Nanotnbe, Nanowire, Nanorod, Anisotropy, NMR... 

We present experimental results on the ability of water-in-oil reverse micelles for synthesis and stabilization of Au, Agl and dye J-aggregate nanoparticles as well for selfassembling of hybrid nanosystem, consisting of semiconductor nanoparticles and dye J-aggregate. The preparation, spectral behaviour and properties of this nanoparticles are discussed. 

A hybrid nanosystem which consists of semiconductor nanoparticles and organic dye J-aggregate may be self-assembled in RMs (Fig. 5) [4], In this structure, the dye adsorbed to the nanoparticle surface operates as spectral sensitizer and nanocrystal size stabilizer simultaneously. The hybrid nanosystem of this kind may be a key element of solar cells. 

Note that for the structures consisting of a large number of nanoparticles, there can be a quantity of stable stationary and imstable forms of equilibrium. Accordingly, the stable and unstable nanostructures of composite materials can appear. The search and analysis of the parameters determining the formation of stable nanosystems is an urgent task. 

However, the available experimental data about degradation or dissolution of nanocatalysts need theoretical explanation on atomic and molecular levels in different models, with their specific reactions on nanoparticles and size effects in nanosystems. Unfortunately, modem theoretical approaches in simulations often lead to indefinite information about properties of nanoclusters, because of omitting quantum characters of interactions in such systems. 

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