INORGANIC NANOPARTICLES AS OPTICALLY EFFECTIVE ADDITIVES FOR POLYMERS

The transparency of polymer-particle composites can be markedly enhanced when nanoparticles are employed instead of larger particles, due to a reduction in light scattering. In addition, nanoparticles of metals (e.g., gold or silver) or semiconductors (e.g., TiO2, ZnO, or PbS) can exhibit intrinsic optical properties that may be of interest per se or in combination with the enhanced transparency caused by the nanoparticles. For such reasons, inorganic nanoparticles have found special interest in studies devoted to optical properties in composites that look back to a long history. For instance, the size-dependent color of gold nanoparticles has been used to color glass for centuries. More recently, inorganic nanoparticles were investigated with regard to optical effects in polymeric nanocomposites such as very high or very low refractive index, reversible color switching in elastomers via swelling processes, dichroism in oriented polymers, reversible photochromic behavior, or UV absorption in visually transparent materials.