Analytical Sciences

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

Kanae ITO,* Koji YOSHIDA,* Shigeharu KITTAKA,** and Toshio YAMAGUCHI*,***

*Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Jonan, Fukuoka 814-0180, Japan
**Department of Chemistry, Faculty of Science, Okayama University of Science, 1-1 Ridaicho, Okayama 700-0005, Japan
***Advanced Materials Institute, Fukuoka University, 8-19-1 Nanakuma, Jonan, Fukuoka 814-0180, Japan

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.

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