Luminescent diatom frustules: a review on the key research applications

For centuries, unicellular diatoms have fascinated scientists because of their intricate nanoporous cell wall architectures, known as frustules, made of amorphous silica. Siliceous frustules, with their highly symmetric nanopatterns, possess unique mechanical, optical, and photocatalytic properties. In particular, when excited by using sufficient energy, diatoms and their frustules exhibit strong luminescence properties. Considering the wide band gap of silica (~11 eV), a number of studies suggested the possible role of different defect states including oxygen deficiency centers, self trapped excitons, silanol groups, etc., as the origin of the observed luminescence. Recently, the potential of luminescent diatom frustules has been exploited in many novel optoelectronic, sensing, and biomedical applications. The wide availability of their fossil remains and the ease to cultivate them in artificial conditions also contribute to the use of diatoms for various applications. This chapter summarizes some of the most recent applications of luminescent diatom frustules in these fields.