Preparation, properties and applications of near-infrared fluorescent silicate nanosheets.

The layered silicates Egyptian Blue (CaCuSi 4 O 10 , EB), Han Blue (BaCuSi 4 O 10 , HB) and Han Purple (BaCuSi 2 O 6 , HP) are known as historic pigments, but they also possess novel optoelectronic properties with great potential for fundamental research and technology. They fluoresce in the near-infrared (NIR) range and can be exfoliated into two-dimensional (2D) nanomaterials ( i.e. nanosheets, NS) which retain the photophysical properties of the bulk materials. These and other characteristics fuel the growing excitement of the scientific community about these materials. EB-, HB- and HP-NS have been used in various applications ranging from smart inks, energy storage, bioimaging, to phototherapy and more. In this review article, we report the fundamental properties of these low-dimensional silicate nanomaterials, discuss applications and outline perspectives for the future.