Control of the valence state of copper ions through the addition of P₂O₅ in sol-gel silicate glass

The copper containing glass, particularly with rich Cu⁺ ions, is a promising material for antibacterial and luminescent. The valence control of Cu⁺/Cu²⁺ in melt-quenching glass has been widely investigated, but sol-gel method was rarely extended. Herein, the Cu⁺ rich silicate glass was successfully prepared by introducing the P₂O₅ as modifying agent in the sol-gel method fabricated phosphosilicate glasses, briefed as 10CaO-(90-x)SiO₂-xP₂O₅ (x = 0, 2.5, 5, 7.5, 10 mol%)- 5CuO. It is found that the high content of P₂O₅ will generates more Cu⁺ in the gel forming stage and result in a Cu⁺ rich glass. While, the content of Cu⁺ drops with excessive P₂O₅ additives in the prepared glass. The highest Cu⁺ content was obtained in glass with 7.5 mol% P₂O₅. Because phosphate glass network is looser than silica-oxygen glass network, which lead to copper ion in the phosphate cluster as a charge compensator is easier to be oxidized compared with in the Si–O network. Therefore, our study paved a new way for designing Cu⁺ rich glass by sol-gel method.