Applications of Nanocomposite Particles

Applications of Nanocomposite Particles

Several strategies are being pursued for creating nanoparticles containing multipleshell structures (for multifunctionality), with each shell composed of different materials.Template-based approaches are effective in this situation, for which an inner removabletemplate particle (silica, polymer beads) can be used to coat shells of othermaterials (e.g., a metal) via multi-step colloidal or vapor-phase assembly and can laterbe easily removed to create empty shells. These could even be filled with differentmaterials to produce multiple-shell composites [142]. Creating uniform coatings onparticle templates by colloidal self-assembly is based on the concept of self-assembledorganic molecular species. The two ends of the molecules to be joined have specificfunctional groups (e.g.. thiols, amines, carboxylic groups) that can be targeted for specificinteractions with the template and the clusters that are used to make the coatings.Uniform, dense packing of the molecules around the templates leads to close packing

of the clusters that form a porous but space-filled shell around the template (Figure). Noninteracting metal-coated magnetic particles (SiO2/Au, Fe3O4/Au, NiO/Co,etc.) or coated semiconducting particles (PbS/CdS) are examples of such composite particle structures.
These structures can have applications in magnetic recording, as multilayered catalyst materials, or in drug delivery. In such applications of drug delivery systems [143], for which a biocompatible outer layer and a drug-containing inner core are necessary, the multilayered particle approach will be crucial. As an alternative
to colloidal templating, structures such as PbS-coated CdS nanocomposite particles (a few nanometers in diameter) may be synthesized by ion displacement in inverse microemulsions and could be useful in nonlinear optical applications. The observed large refractive nonlinearity in these nanocomposite particles may be attributed to the optical Stark effect and to strong interfacial and internanoparticle interactions.
Asignatura: E.E.S
Saithrhu R. Gonzalez C.