Surface Modification of Silica Nanoparticles

Chandran SP, Hotha S, Prasad BLV (2008) Tunable surface modification of silica nanoparticles through click chtanistry. Curr Sci 95 1327-1333... 

Bagwe RP, Hilliard LR, Tan W (2006) Surface modification of silica nanoparticles to reduce aggregation and non-specific binding. Langmuir 22 4357 362... 

Rampazzo E, Brasola E, Marcuz S, Mancin F, Tecilla P, Tonellato U (2005) Surface modification of silica nanoparticles. A new strategy for the realization of self-organized fluorescence chemosensors. J Mater Chem 15 2687-2696... 

Surface modification of silica nanoparticles by silanes is a convenient way to modify the surface properties of colloidal silica dispersions in such a way that they become compatible with the various components in paint and coating formulations [27]. There are different types of silanes that can be used to modify the surface of sihca. In this review, we will focus on surface modification of silica by using alkoxysilanes with epoxy functional groups in an aqueous environment. Further, characterization techniques of silane-modified silica dispersions will be described. Examples of applications for silane-modified silica dispersions will also be discussed, as well as how silane-modified silica dispersions can improve the product properties of paints and coatings. 

Recently, the straightforward synthesis and easy modification of silica nanoparticles has been demonstrated, making them well suitable for biomedical applications such as bioseparation, cell recognition, bacterium and DNA detection, gene delivery, and so on. Silica nanoparticles are biologically inert, have very low toxicity, and are amenable to surface functionalization with a wide variety of molecules and functional groups [108-111]. In Table 7, the synthetic methods for preparation of silica nanoparticles in polymers are shown. 

The Stober method can be used to form core-shell silica nanoparticles when a presynthesized core is suspended in a water-alcohol mixture. The core can be a silica nanoparticle or other types of nanomaterials [46, 47]. If the core is a silica nanoparticle, before adding silicon alkoxide precursors, the hydroxysilicates hydrolyzed from precursors condense by the hydroxide groups on the surface of the silica cores to form additional layers. If the core is a colloid, surface modification of the core might be necessary. For example, a gold colloid core was modified by poly (vinylpyrrolidone) prior to a silica layer coating [46]. 

Dispersion stabilization with nanoparticles is also known. A recent example of a dispersion stabilized by nanoparticles was published by Tohver et al. This group used zirconia particles to stabilize an aqueous colloidal system of larger silica particles. The dispersion was stabilized by electrostatic stabilization and thus is essentially applicable only to aqueous systems. Surface modification of the particles changes the stabilization mechanism to steric stabilization, and dispersions in both aqueous and nonaqueous systems have been demonstrated. 

Our results revealed that silica nanoparticles may become slightly cytotoxic at high concentration even though they were nontoxic at low concentration. It has been reported that surface modification with aminosilanes increased the 50% lethal concentration of silica nanoparticles to Cos-1 cells to well above 1 mg/mL. By comparison, polylysine-modified silica showed cytotoxic effects (cell viability dropped to about 60% of control) to HNEl and HeLa cells at concentrations of 500 pg/mL or above. 

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... 

The chemical and physical modifications of inorganic nanoparticle and nanocarbon surfaces, therefore, have been extensively studied. The chemical modification of surfaces is permanent, but physical modification is temporary. We have pointed out that the dispersibility of silica nanoparticles and nanocarbons is extremely improved by surface grafting of polymers, namely, chemical binding of polymers, onto nanoparticle and nanocarbon surfaces (Tsubokawa, 1999 Tsubokawa, 2002 Tsubokawa, 2007). 

Efficient intracellular delivery of the anticancer drug camptothecin (CPT) by hollow silica/titania nanoparticles has been reported [114]. Monodispersed hollow nanoparticles (about 50 nm) were prepared by titania coating of Stober silica particles followed by silica dissolution and redeposition in an ammonia solution (Figure 11.13). Surface modification of these particles with an antibody herceptm, a... 

Improvements in the impact resistance of hybrid sol-gel silica coatings have been obtained after modifying the surface of silica nanoparticles obtained by the Stober method [74] with 3-methacryloxypropyltrimethoxysilane (3-MPS). The reaction of the —OH groups with —O—CH3 groups leads to organic surface modification (Figure 39.4). 

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