具Au修飾的ZnSe•0.5(N2H4)奈米晶體之成長控制與其可見光催化特性研究

Abstract

本論文發展出一水熱反應程序，成功地製備出各種ZnSe•0.5(N2H4)奈米晶體，包含奈米線、奈米帶與奈米板結構。於實驗結果發現，聯胺與水的比例在此水熱反應系統中扮演著非常重要的角色，藉由調控此比例可直接控制產物的組成與形貌。產物ZnSe•0.5(N2H4)的化學組成與晶體結構，乃利用XRD、TGA、FTIR、XPS及TEM等分析來檢驗與確認。在各種結構樣品的比較中，ZnSe•0.5(N2H4)奈米線擁有相對較長的光激發載子生命週期，使其能夠表現出最佳的光催化分解rhodamine B染料分子的效率。而相較於相關商用品例如N-doped P-25 TiO2與ZnSe粉末，ZnSe•0.5(N2H4)奈米線於可見光下亦表現出較好的光催化能力，此結果顯示其可作為高效能光觸媒之潛力。經由表面修飾Au奈米粒子後，ZnSe•5(N2H4)奈米線之光催化活性可被進一步提升，此效能提升乃由於ZnSe•0.5(N2H4)/Au介面所帶來顯著的載子分離效果所致，載子分離之現象則可以時間解析螢光光譜分析來作定量描述。

ZnSe•0.5(N¬2H4) nanocrystals with various morphologies including nanowires, nanobelts and nanosheets were successfully prepared with a hydrothermal synthetic approach. It was found that the ratio of N2H4 to H2O employed in synthesis played an important role in nanocrystal growth, affecting the resultant composition and morphology of product. The chemical composition and crystallographic structure of ZnSe•0.5(N2H4) were examined and confirmed with XRD, TGA, FTIR, XPS and TEM analyses. With a relatively long exciton lifetime, ZnSe•0.5(N2H4) nanowires peformed much better in the photodegradation of rhodamine B than the other four counterpart products. As compared to the relevant commercial products like N-doped P-25 TiO2 and ZnSe powders, the as-synthesized ZnSe•0.5(N2H4) nanowires exhibited superior photocatalytic performance under visible light illumination, demonstrating their potential as an efficient photocatalyst in relevant redox reactions. A further enhancement in the photocatalytic activity can be achieved for ZnSe•0.5(N2H4) nanocrystals when Au nanoparticles were deposited on their surfaces. This improvement resulted from the pronounced charge carrier separation occurring at the interface of ZnSe•0.5(N2H4)/Au, which can be quantitatively interpreted with the time-resolved photoluminescence analysis.