**5.3 Optical nanomaterials**

At the moment, the most well-established applications for optical nanomaterials are in very low-tech applications such as sunscreen lotions and optical coatings, although many high-tech industrial solutions have recently emerged, including signal processing and photonic crystals for complex optical circuitry, as well as sensors for detecting and responding to chemical and biological challenges [6]. Several new companies have emerged to produce next-generation solar cells based on the nanoparticle principle, but they are still in the early stages of growth. Nanoparticles have also been shown to be useful in optical diagnostics, lightactivated treatments, as well as in optical communication initiatives [6]. **Table 5** illustrates graphical applications of nanostructures in optics.
