Properties of Silica Nanoparticles

While the silicon-based sol-gel process usually results in amorphous silicon as a product, the metal-based sol-gel process often shows crystalline products. The metal oxide particles are often peptized, for example, with HNO3 to electrostatically stabilize their surface and get a more homogeneous and more stable dispersion [21b]. 

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Calero P, Martinez-Manez R, Sancenon F, Soto J (2008) Synthesis, characterisation and optical properties of silica nanoparticles coated with anthracene fluorophore and thiourea hydrogen-lxHiding subunits. Eur J Inorg Chem 5649-5658... 

Rahman, I.A., Vejayakumaran, P., Sipaut, C.S., Ismail, J., and Chee, C.K. (2009) Size-dependent physicochemical and optical properties of silica nanoparticles. Mater. Chem. Phys., 114 (1), 328-332. 

The size of silica nanoparticles affects their physical, chemical, electronic, and optical properties. Proper size of silica nanoparticles is crucial for design of silica-based nanomaterials. In Stober methods, the size of silica nanoparticles is adjusted by changing the type of organic solvent, the amount of silicon alkoxide, and the... 

One of the main features of silica nanoparticles is that the particle interior, and not only the surface, can be functionalized. In the previous examples, the silica nanoparticles act just as mere scaffolds where the two sensor components, the signaling dye and the receptor, are assembled. A careful analysis of the properties of silica gels, and particularly of their metal sorption ability, led us to imagine that the sensor scheme could be further simplified and the degree of self-organization increased. 

A great variety of oxides can be used as supports. These materials are chemically stable, but in some cases, interactions between the metallic particles and the support can occur. Thus, in the particular case of metal catalysts supported on some reducible oxides, the occurrence of so-called metal-support interaction effects has been reported. " " In order to minimize the metal-support interaction, stable oxides (not reducible), such as alumina or silica, are used. Moreover, the size-dependent electronic, structural, and chemical properties of metal nanoparticles on oxide supports are an important aspect of heterogeneous catalysis. " " ... 

We demonstrated that a naturally derived polysaccharide, chitosan, is capable of forming composite nanoparticles with silica. For encapsulated particles, we used silicification and biosilicification to encapsulate curcumin and analyzed the physicochemical properties of curcumin nanoparticles. It proved that encapsulated curcumin nanoparticles enhanced stability toward ultraviolet (UV) irradiation, antioxidation and antitumor activity, enhanced/added function, solubility, bioactivities/ bioavailability, and control release and overcame the immunobarrier. We present an in vitro study that examined the cytotoxicity of amorphous and composite silica nanoparticles to different cell lines. These bioactives include curcumin mdAntrodia cinnamomea. It is hoped that by examining the response of multiple cell lines to silica nanoparticles more basic information regarding the cytotoxicity as well as potential functions of silica in future oncological applications could become available. 

J, Ndmeth and 1, Ddkdny, The effect of nanoparticle growth on rheological properties of silica and silicate dispersions. Colloid Polym Sci., 278 211-219, 2000... 

Rahman lA, Padavettan V (2012) Synthesis of silica nanoparticles by sol-gel size-dependent properties, surface modification, and applications in silica-polymer nanocomposites—a review. J Nanomater 2012 1-15... 

A dielectric oxide layer such as silica is useful as shell material because of the stability it lends to the core and its optical transparency. The thickness and porosity of the shell are readily controlled. A dense shell also permits encapsulation of toxic luminescent semiconductor nanoparticles. The classic methods of Stober and Her for solution deposition of silica are adaptable for coating of nanocrystals with silica shells [864,865]. These methods rely on the pH and the concentration of the solution to control the rate of deposition. The natural affinity of silica to oxidic layers has been exploited to obtain silica coating on a family of iron oxide nanoparticles including hematite and magnetite [866-870]. The procedures are mostly adaptations of the Stober process. Oxide particles such as boehmite can also be coated with silica [871]. Such a deposition process is not readily extendable to grow shell layers on metals. The most successful method for silica encapsulation of metal nanoparticles is that due to Mulvaney and coworkers [872—875]. In this method, the smface of the nanoparticles is functionalized with aminopropyltrimethylsilane, a bifunctional molecule with a pendant silane group which is available for condensation of silica. The next step involves the slow deposition of silica in water followed by the fast deposition of silica in ethanol. Changes in the optical properties of metal nanoparticles with silica shells of different thicknesses were studied systematically [873 75]. This procedure was also extended to coat CdS and other luminescent semiconductor nanocrystals [542,876-879]. 

Li et al. [105] showed that in polymer-dispersed liquid films based on liquid crystals, a photopolymerizable acrylate matrix, and silica, the electro-optical properties could be controlled by the amount of silica nanoparticles. 

Ossiander T, Heinzl C, Gleich S et al (2014) Influcmce of the size and shape of silica nanoparticles on the properties and degradation of a PBI-based high... 

While PMMA is useful as a bone cement, it is not ideal for tissue engineering applications as it is nondegradable. Researchers incorporated the same type of silica nanoparticles into the biodegradable poly( -caprolactone) (PCL) and also observed apatite formation and favorable mechanical properties [47,48]. 

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]. 

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