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

The layered silicates Egyptian Blue (CaCuSi₄O₁₀, EB), Han Blue (BaCuSi₄O₁₀, HB) and Han Purple (BaCuSi₂O₆, 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.