Silica based nanoparticles system

Silica Based Nanoparticles as Controlled Drug Release Systems... 

Dye-Doped Silica Nanoparticle Synthesis Using Nonionic Surfactant-Based Microemulsion Systems... 

A mesoporous silica nanosphere-based carrier system with chemically removable CdS nanoparticle caps for stimuli-responsive controlled release of neurotransmitters and drag molecules. 

Andrei J, Maria C, Aurcba M, Ran H, Zaharescu M. Influence of the silica based matrix on the formation of iron oxide nanoparticles in the Fe203-Si02 system, obtained by sol-gel method. J Mater Chem 2002 12 1401-7. 

S. Y., A mesoporous silica nanosphere-based carrier system with chemically removable CdS nanoparticle caps for stimuli-responsive controlled release of neurotransmitters and drug molecules. Journal of the American Chemical Society 125, (15), 4451 59, 2003. 

The mechanical properties of PA-based polymers can also be enhanced through the incorporation of inorganic micro- and nanofillers such as silica nanoparticles. Thus, the maximum value of stress at yield point (72 MPa) was observed in hybrid materials containing 10 wt% silica and the maximum stress at break point increased up to 66 MPa in PA-sUica hybrids containing 20 wt% silica (compared with 44 MPa for the silica-free PA system). Also, the tensile modulus was found to increase up to 2.59 GPa upon incorporation of 10 wt% silica within the polymeric matrix [268]. 

While almost all papers on nanocomposite aerogels containing metal oxide nanoparticles dispersed in an insulating matrix refer to silica-based systems, a few examples are also available for other matrices. 

Recently, rapid development of silica based nanocomposite materials has been reported. These materials can be used in many industries (e.g. automotive, electronic). Applications of silica nanoparticle reinforced polymer matrices highly depends on many parameters, for e.g. improved thermal [23], mechanical [24], chemical and physical properties. Generally, the addition of silica nanoparticles into the polymer mbbery matrix causes an increase in the glass transition temperature (Tg) and storage modulus, and also an increase in the thermal stability of the system [24-26]. 

The optical properties of nanoporous silica-based materials can be of interest for photonic applications. The doping of these systems with rare earth ions or semiconducting nanoparticles can lead to the development of improved optical amplifiers or displays. The sol-gel glass technique presents advantages for the preparation of such nanoporous vitreous oxides [421],... 

Polymer materials are ubiquitous in our daily life. They often consist of more than one species of polymers and, therefore, can be called multicomponent systems, for example, polymer blends and block copolymers. Because of the repulsive interaction between the constituent polymers, multicomponent polymer materials often show phase separation. Organic-inorganic composites are another class of polymer-based multicomponent materials that have attracted considerable interest from researchers because they often exhibit unexpected properties synergistically derived from the constituents. Nanometer-sized particulate fillers, for example, carbon black (CB) and silica (Si) nanoparticles, are known to form hybrids with organic polymers, which show a significant increase in their static and dynamic moduli, strength, and thermal and electrical conductivities. 

Silica Nanoparticles. The base-catalyzed hydrolysis of silicon aikoxides in microemulsions produces nanoparticles (20-39). Aqueous ammonia has been used primarily as the base, with AOT and nonionic polyoxyethylene ethers as the main surfactants. Figure 2.2.6 presents a flow diagram for the synthesis of pure silica (23-32) the microemulsion is first prepared and then the alkoxide is added. As can be seen from Table 2.2.1, the microemulsions include the systems AOT/ isooctane/water/ammonia, AOT/toluene/water/ammonia, NP-5/cyclohexane/water/ ammonia, and NP-4/heptane/water/ammonia. Typical reaction times are l -5 days. Various modified silica nanoparticles have also been prepared, including hydropho-... 

The experimental data of Espiard et al. (21,22), based on the AOT/ toluene/water/ammonia system, showed an increase in particle size with increase in R. This observation led the authors to conclude that the droplet size of the microemulsion water pool was a key determinant of particle size. The effect of R on particle size was also investigated for silica nanoparticles synthesized in AOT/ decane/water/ammonia microemulsions (31). No particles were observed below about R = 4. However, as R increased from 5 to 9.5, the particle size also increased, in agreement with the observations of Espiard et al. (21,22). As noted previously (see Figure 2.2.3), in this microemulsion system, free water pools do not become... 

Further progress in the development of sensing systems based on silica nanoparticles was achieved by doping with fluorescent probes. In these systems, the nanoparticles act as transporters delivering the probe across membranes into the cell, thus improving both performance and protection from matrix interferences.19-22 As we will see later, the possibility to confine several probes and dye molecules within the same particle also allows the design of more complex sensing schemes. 

In the previous several years, various nanoparticles have been assembled into pairs to fabricate polymer nanocomposites, such as clay/silica (45), clay/carbon black (43), CNTs/clay (41,42), and CNTs/Titanium (38). Polymer/CNTs/clay ternary composite is one of most important multiphase systems with interesting synergistic effect, where sodium based montmorillonite (MMT) are the most commonly used layered clay. In this chapter, we will select some typical examples to demonstrate the importance and synergies of using CNTs and clay together in the preparation of polymer nanocomposites. 

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