微孔結晶における光電子ドナーとしての水素イオン
Satoru Matsuishi1, Katsuro Hayashi, Masahiro Hirano
1Frontier Collaborative Research Center, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan. satoru@lucid.msl.titech.ac.jp
Journal of the American Chemical Society
|September 8, 2005
まとめ
紫外線はC12A7結晶の水素イオンを分離し,原子水素と閉じ込められた電子を生成します. これらの電子は,水素が消失した後,材料の電気伝導性に寄与します.
科学分野:
- マテリアルサイエンス 材料科学
- 固体物理 固体物理学
- フォトケミストリーは,写真化学です.
背景:
- 12CaO.7Al2O3 (C12A7) 結晶は,イオンを収納できる亜ナノメートルのサイズのケージを持っています.
- 水素大気中の熱処理により,これらのケージに水素イオン (H-) が導入されます.
- 外部刺激下で捕獲された種の行動を理解することは,材料の開発において極めて重要です.
研究 の 目的:
- C12A7結晶における水素イオンの光解離を調査する.
- 結果となる原子水素 (H0) と閉じ込められた電子 (F+センター) を特徴付ける.
- 閉じ込められた電子がC12A7.7の電気的性質に及ぼす影響を調査する.
主な方法:
- 電子パラマグネティック共振 (EPR) スペクトロスコピーは,原子水素と閉じ込められた電子を検出および分析するために使用されました.
- 実験は,UV照明 (λ ≈ 330 nm) の下で冷凍温度 (4 K) で実施されました.
- 生成された種の安定性を観察するために,300 Kの解熱試験が行われました.
主要な成果:
- 水素処理されたC12A7のUV照明により,ほぼ1:1の比率で原子水素 (H0) と閉じ込められた電子 (F+センター) が生成されました.
- 観測された1:1比は,H- → H0 + e- (F+) の写真解離反応の直接的な証拠を提供します.
- 300 Kの熱で化すると,原子水素は完全に消滅し,約60%の閉じ込められた電子は残った.
結論:
- C12A7の水素イオンは,紫外線で原子水素と電子に効果的に解離することができる.
- 生き残った閉じ込められた電子は,ケージ間のジャンプを通じてC12A7の電気伝導性に寄与します.
- EPRスペクトルの超精細分裂は,原子水素がC12A7結晶構造内の間位点に閉じ込められていることを示唆しています.
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