Dipartimento di Chimica IFM, Università di Torino and NIS, Nanostructured Interfaces and Surfaces Centre of Excellence, Via P. Giuria 7, I-10125 Torino, Italy.
Phys Chem Chem Phys. 2011 Jan 7;13(1):136-43. doi: 10.1039/c0cp00143k. Epub 2010 Nov 1.
Nitrogen boron co-doped TiO(2) prepared via sol-gel synthesis and active under visible light, contains two types of paramagnetic extrinsic defects, both exhibiting a well resolved EPR spectrum. The first center is the well characterized [N(i)O]˙ species (i = interstitial) also present in N-doped TiO(2), while the second one involves both N and B. This latter center (labeled [NOB]˙) exhibits well resolved EPR spectra obtained using either (14)N or (15)N which show a high spin density in a N 2p orbital. The structure of the [NOB]˙ species is different from that previously proposed in the literature and is actually based on the presence of interstitial N and B atoms both bound to the same lattice oxygen ion. The interstitial B is also linked to two other lattice oxygen ions reproducing the trigonal planar structure typical of boron compounds. The energy level of the [NOB]˙ center lies near the edge of the valence band of TiO(2) and, as such, does not contribute to the visible light absorption. However, [NOB]˙ can easily trap one electron generating the NOB diamagnetic center which introduces a gap state at about 0.4 eV above the top of the valence band. This latter species can contribute to the visible light activity.
通过溶胶-凝胶合成制备的氮硼共掺杂 TiO(2) 在可见光下具有活性，包含两种类型的顺磁外部分子缺陷，都表现出很好的分辨 EPR 谱。第一个中心是特征明确的[N(i)O]˙物种（i = 间隙），也存在于 N 掺杂的 TiO(2)中，而第二个中心则涉及 N 和 B。后者中心（标记为[NOB]˙）表现出很好的分辨 EPR 谱，使用(14)N 或(15)N 都可以获得，它们在 N 2p 轨道上表现出高自旋密度。[NOB]˙物种的结构与文献中以前提出的结构不同，实际上基于同时与同一晶格氧离子结合的间隙 N 和 B 原子。间隙 B 还与两个其他晶格氧离子相连，再现了硼化合物的典型三角平面结构。[NOB]˙中心的能级位于 TiO(2)价带边缘附近，因此不会对可见光吸收有贡献。然而，[NOB]˙可以很容易地捕获一个电子，生成NOB抗磁性中心，在价带顶部上方约 0.4 eV 处引入一个间隙态。后者物种可以对可见光活性做出贡献。
