X-ray excited optical luminescence from hexagonal boron nitride nanotubes : Electronic structures and the role of oxygen impurities

We report a study on the optical luminescence properties and the electronic structures of boron nitride nanotubes (BNNTs). BNNTs with natural B (80% ¹¹B and 20% ¹⁰B) and pure ¹⁰B are investigated in comparison with hexagonal BN crystals using X-ray absorption near-edge structures (XANES) and X-ray excited optical luminescence (XEOL). We find that the BNNT specimen synthesized with natural B contains more oxide impurities than that with pure ¹⁰B, resulting in significantly different behavior in optical luminescence. All BN samples with hexagonal structures are found to emit strong luminescence, but the emission spectra are strongly morphology- and structure-dependent. XEOL and XANES measurements were carried out at the B K-edge, N Kedge, and O K-edge in order to reveal the origin of different luminescence channels and the corresponding electronic structures in these BN materials. © 2011 American Chemical Society.