Superbroadband Near Infrared Emission from Bismuth Doped High-Silica Nanocrystalline Zeolites
Superbroadband Near Infrared Emission from Bismuth Doped High-Silica Nanocrystalline Zeolites
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2009
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近年来，在传统玻璃材料中对铋相关的超宽带近红外光致发光（PL）进行了广泛的研究[16]。同时，不同的作者尝试性地将NIR发射归因于Bi、Bi、Bi的电子跃迁或分散在玻璃主体中的Bi原子簇，并且尚未得出最终结论[16]。与Bi掺杂玻璃的研究相比，很少关注Bi掺杂晶体的研究[7]。众所周知，晶体中活性离子的光谱比玻璃中的光谱更容易理解，因为晶体中存在一定数量的掺杂离子位点。因此，找到一种合适的晶体作为铋红外活性（BiIRA）中心的宿主可能为理解PL起源铺平道路。沸石作为主要由[SiO4]和[AlO4]结构单元组成的智能晶体材料，具有孔结构，这些使它们能够充当分子和离子的主体或作为纳米结构合成的模板[8]。最近，已经评估了它们作为稀土离子基质材料的潜力[9]。然而，由于通过非辐射振动失活的激发能的快速弛豫，发射器的效率在NIR区域中非常小。此外，所得样品不具有空气稳定性，通常将其保持在真空中以避免吸附配位水[9]。因此，寻找一种提高活性离子掺杂沸石近红外发光效率的方法是一个有趣的课题。在这封信中，我们报告了有效的超宽带近红外发射铋掺杂FAU型纳米晶沸石。该方法包括一个简单的离子交换过程和随后的高温退火在N2气氛条件下。我们还表明，发射强度和发光寿命可以很容易地定制通过改变退火温度。在稳态发光和时间分辨发光测量的基础上，详细讨论了发光的来源。
In recent years, extensive studies on bismuth related superbroadband near-infrared photoluminescence (PL) have been carried out in traditional glass materials [16]. Concurrently, different authors tentatively assigned the NIR emission to the electronic transition of Bi, Bi, Bi, or to cluster of Bi atoms dispersed in glass host, and the final conclusion has not been made yet [16]. In comparison with the studies of Bi doped glasses, little attention has been paid on the investigation of Bi doped crystals [7]. It is well known that spectroscopy of active ions is much more understandable in crystals than in glasses because there is a definite majority of sites for doping ions in crystal. Therefore, finding a suitable crystal as the host of bismuth infrared-active (BiIRA) centres may pave the way for understanding the PL origin. Zeolites, as smart crystalline materials mainly consisting of [SiO4] and [AlO4] structure units, possess pore structures and these enable them to act as hosts for molecules and ions or as templates for nanostructures synthesis [8]. Recently, their potential as host materials for rare-earth ions has been evaluated [9]. However, the efficiency of the emitters is very small in the NIR region due to the fast relaxation of the excitation energy through nonradiative vibrational deactivation. Moreover, the obtained samples were not air-stable, which were usually kept in vacuum to avoid the adsorption of coordinated water [9]. Thus, it is an interesting topic to find a strategy to increase the NIR PL efficiency in active ions doped zeolites. In this Letter, we report efficient superbroadband near infrared emission in bismuth doped FAU-type nanocrystalline zeolites. This method consists of a simple ion-exchange process and subsequent hightemperature annealing under N2 atmospheric condition. We also demonstrate that the emission intensity and luminescence lifetime can be easily tailored by changing the annealing temperature. Based on the measurement of steady-state and time-resolved luminescence, we discussed the luminescence origin in detail.