利用反溶劑法製備金屬/半導體奈米異質結構

Abstract

在此研究計畫中，我們提出以一個對環境友善的反溶劑程序來製備各種金屬/ 半導體奈米異質結構，包含具金屬顆粒接枝之ZnO 奈米晶體與具金屬離子摻雜之 ZnO 奈米晶體。合成方法為將ZnO 粉末溶於深共熔離子液體，待注入含有金屬顆 粒或金屬離子的非良溶劑後，ZnO 因反溶劑程序而被析出與成長同時，會與事先置 入的金屬顆粒或金屬離子複合，進而形成具金屬顆粒接枝或具金屬離子摻雜之ZnO 奈米晶體。金屬顆粒的接枝可有效提升ZnO 奈米晶體之光誘發載子分離效果，進而 使其應用於光催化反應中時能表現較佳的效能，我們將比較不同金屬種類的導入 (Ag、Pd、Au)，對於ZnO 奈米晶體所帶來的載子分離效果與其光催化效能變化的 影響為何。至於金屬離子的摻雜，則是為了讓ZnO 奈米晶體之吸光波段擴增至可見 光區，使其於實作上能經由太陽光的照射來進行各種光催化反應，為了釐清金屬離 子摻雜對於半導體光觸媒活性的影響究竟為正面或負面，我們將探討不同金屬離子 種類的摻雜結果(Co2+、Ni2+、Cu2+)，以期能得到明確定論；此外，我們期待此些過 渡金屬離子摻雜之ZnO 奈米晶體，經照光與施以外加磁場後能產生顯著磁光效應， 進而改變載子傳輸路徑而增進其光催化反應效能。

In this project, we propose an environmentally benign antisolvent process for fabrication of various metal/semiconductor nanoheterostructures including metal particle-decorated ZnO nanocrystals and metal ion-doped ZnO nanocrystals. The method was based on the dissolution of ZnO powders in a deep eutectic ionic liquid, followed by the precipitation and growth of ZnO from ionic liquid upon introduction of a bad solvent. With the presence of metal particles (Ag, Pd, Au) or metal ions (Co2+, Ni2+, Cu2+) in the bad solvent, growth of ZnO in antisolvent process would be accompanied by metal decoration or ion doping, resulting in the formation of metal particle-decorated or metal ion-doped ZnO nanocrystals. Decoration of metal particles may promote effective charge carrier separation for ZnO nanocrystals to favor the subsequent photocatalysis. We will systematically investigate the influence of metal types on the charge separation efficiency and photocatalytic performance of ZnO. On the other hand, to enable response to visible light and thus practical energy harvesting from sunlight, metal ions are introduced into ZnO to invoke a dopant state within its bandgap. By comparing the results among various metal ion dopants, we may clarify the very critical but still controversial issue that whether the effect of metal ion doping on the photocatalytic activity of semiconductor photocatalyst is positive or not. Furthermore, a significant magneto-optical-like effect is anticipated to take place for those doped ZnO samples, which may affect the interfacial charge transfer process to further their photocatalytic performance.