Irreversible adsorption of acidic, basic, and water gas molecules on calcium-deficient hydroxyapatite.

Hydroxyapatite [Ca10(PO4)6(OH)2, HAP] has P-OH Brønsted acidic sites, Ca2+ Lewis acidic sites, and OH- and O2- basic sites on which acidic and basic gas molecules can be selectively adsorbed, and has no micropore onto which various molecules adsorb regardless of the chemical properties of gas molecules. The interaction between the surface sites and acidic and basic gas and water molecules has been investigated by evaluating the adsorption properties of various molecules on the surfaces of calcium-deficient HAP. The specific adsorption sites were assessed by examining the reversible and irreversible adsorption of NH3, CO2, aldehydes, and water vapor on HAP at the temperature of 298 K, using two HAP samples with different Ca/P ratios, but similar structures and surface areas: Ca-deficient HAP with an extreme lower Ca/P ratio (named P-HAP) and one with a higher Ca/P ratio (named C-HAP).

Thermally Stimulated Light Reflection and Photoluminescence of BaTiO.

Perovskites have been attracting attention because of their considerable luminescence properties. A conventional perovskite such as BaTiO has no intrinsic photoluminescence. Doping with rare metals, nanocrystallization, and addition of organometallic halides induce significant photoluminescence and photovoltages.