Pore Size Dependent Behavior of Hydrated Ag⁺ Ions Confined in Mesoporous MCM-41 Materials under Synchrotron X-ray Irradiation

Abstract

The behavior of hydrated Ag⁺ ions in a 1.5 mol dm⁻³ AgNO₃ aqueous solution confined in mesoporous silica MCM-41 with different pore sizes was characterized by synchrotron X-ray absorption spectroscopy. The hydrated Ag⁺ ions are stabilized in 4-fold coordination down to 195 K in the pores (21 Å in diameter), whereas in the larger pores (28 Å) the hydrated Ag⁺ ions are reduced to Ag⁰ to form nano clusters with the Ag–Ag interactions of 2.80 Å.