Highly Luminescent Copper(I) Halide Phosphors Encapsulated in Fumed Silica for Anti-Counterfeiting and Color-Converting Applications

Luminescent Cu(I) hybrid materials are currently receiving increasing attention due to their rich photophysical properties with promising phosphors applications. However, the complex synthesis processes usually involving chemotoxic organic solutions largely hinder their practical applications. Herein, the authors introduce the highly luminescent copper(I) halide phosphors encapsulated in fumed silica synthesized via aqueous mechanochemical process. By using different precursors, they obtain blue, green, and orange emission copper(I) halide phosphors with high photoluminescence quantum yields. The green emission is owing to the formation of the well-known 0D (18-crown-6)₂Na₂(H₂O)₃Cu₄I₆ (CNCI), while the blue and orange emissions are ascribed to the formation of the novel 1D (18-crown-6)₂Na₂(H₂O)₃Cu₂Cl₄ (CNCCl) and 0D (18-crown-6)₂Na₂(H₂O)₃Cu₄Br₆ (CNCBr) crystal structures, respectively. It is demonstrated that waterborne luminescent inks can be directly prepared from those phosphors via blending them with various waterborne polymers. The combination of three primary colors can lead to various spectra with multiple anti-counterfeiting functions. Further, such phosphors can also be embedded into polystyrene resin to form homogeneous luminescent composites, which can be used to prepare free-standing luminescent films and fabricate light-emitting diode (LED) with tunable emissions. This strategy opens a new avenue for the development of low-cost, highly luminescent phosphors.