Color from colorless nanomaterials: Bragg reflectors made of nanoparticles

We report herein on a facile and reproducible approach to prepare mesoporous nanoparticle-based distributed Bragg reflectors (DBRs) from a diverse group of metal oxide nanoparticles including SiO2, TiO2, SnO2, and Sb:SnO2. The films prepared, regardless of the composition, and following dispersion and process engineering, demonstrate uniform color and high optical quality over large areas. Not only do the prepared NP DBRs possess high reflectivity but also significant mesoporosity, which opens up the opportunity for introduction of a variety of materials into the pores creating new opportunities in optical and optoelectronic devices. In addition, what also must be highlighted are the added-value properties to the above characteristic of the individual NP materials comprising the DBR such as the electrical conductivity and optical transparency of ATO or the photoconductivity of SnO2, which enable new opportunities in a broad range of fields.