摘要
本文採用不同的光激螢光技巧來研究介孔矽質MCM-48材料在紅光螢光與藍綠光螢光的發光機制。在紅光螢光可以獲得兩個能量峰值1.9eV和2.16eV，這分別可以歸因於非橋氧電洞中心和與扭曲鍵相關的非橋氧電洞中心。我們發現光激螢光的強度經過快速熱退火處理後會增加，這個原因在於MCM-48表面氫鍵和單一矽氫氧基群的結合而導致非橋氧電洞中心濃度增加。當激發光源持續激發MCM-48時，光激螢光的強度會隨著時間而衰減。其主要的機制是起源於氧陰離子基和MCM-48表面產生鍵結。藍綠光螢光強度在經過快速熱退火處理後亦會增加。根據MCM-48的表面特性，這個增加可以解釋成二摺疊配位矽中心的產生。由經過快速熱退火處理之光激螢光和光激螢光激發光譜的研究後，我們推論MCM-48藍綠光部分之光激螢光的發生是由於二摺疊配位矽中心之三重態至單態的躍遷。
關鍵字
介孔材料並列摘要
Different photoluminescence (PL) techniques have been used to study the red and blue-green emission from mesoporous siliceous MCM-48. In the red emission, two PL bands were observed at 1.9 and 2.16 eV, which can be assigned to the non-bridging oxygen hole center (NBOHC) and the NBOHC associated with strained siloxane bridges, respectively. It is found that the PL intensity can be enhanced after rapid thermal annealing (RTA), and explained by the generation of NBOHC correlated with the hydrogen-bonded and single silanol groups on the MCM-48 surface. We also found the PL intensity of NBOHC in MCM-48 degrade with time during photoexcitation. The dominant mechanism of the PL degradation is suggested to be the combination of (O2—) anion radicals and the surface of MCM-48. The blue-green PL intensity can also be enhanced after rapid thermal annealing. According to the surface properties on the MCM-48, the enhancement can be explained by the generation of two-fold coordinated Si centers and NBOHCs associated with strain bonds. After the studies of the PL with RTA treatments and PLE, we suggest that the blue-green PL in MCM-48 is owing to a triplet-to-singlet transition of two-fold coordinated silicon centers.