Optical Properties of Nanocomposites

Abstract

The optical characteristics of inorganic nanoparticles (NP) have been well known for quite a long time and this knowledge has been applied for the creation of optically functional materials based on these NPs and different polymers used as a processable matrix. Remarkable optical properties of certain polymer nanocomposites (NCs), such as absorption (ultraviolet [UV] and visible), transparency, color, high refractive index, fluorescence, luminescence, different nonlinear optical properties, etc. are the reasons for such large interest of various researchers from different disciplines all over the world in this type of material. In these materials, NPs improve optical properties, while a polymer matrix is used to stabilize the size and growth of NPs (Beecroft and Ober 1997). Polymer NCs, which show such intriguing optical properties, include NCs prepared from different polymers and metal NPs, metal oxide NPs, carbon-based NPs (fullerenes, graphene, and carbon nanotubes) or semiconductor nanocrystals (quantum dots), as well as NCs based on conjugated polymer matrices and different inorganic NPs. Since polymer NCs are prepared by synergistic combination of polymers and NPs, optical properties of these specific materials can be tailored by adequate selection of the organic and inorganic building blocks with desirable properties and by simply changing the portion of NPs introduced in the polymer matrix. This led to the rapid growth of the area of polymer NCs’ possible applications, such as for optical detectors, solar cells, in optical amplification, photovoltaics, biosensors, for waveguiding in integrated optical devices, as optical coatings, optical switches, high refractive index devices, for encapsulation of light emitting diodes (LEDs), as lens materials, etc. Linear and nonlinear optical properties of polymer NCs depend on the optical properties of the polymer matrix and applied NPs, as well as on other different parameters such as type, size, shape, surface characteristics, concentration, and spatial distribution of NPs in the matrix. Therefore, in order to fully understand optical properties of polymer NCs, it is necessary first to briefly describe the most important optical properties of its constituents, that is, polymers and NPs.