利用半胱胺酸引導離子置入法製備具有光活性的硒化物奈米棒

Abstract

一維奈米異質結構因為其良好的電子傳輸特性，在過去幾十年一直是許多研究的重要目標。另一方面，由於奈米結構的大小、形狀與電子、光學、磁性等物理性質息息相關，可以廣泛應用在電學、光學、資料儲存或感測元件上。以半導體材料來說，硒(Se)具有獨特的物理和化學性質，在許多層面的應用上一直有著不錯的表現，其良好的光電轉換效率也適合應用在太陽能電池、光催化、整流器以及光感測等領域。從製程的角度來說，Se對於不同的金屬離子具有高度的反應性，因此許多研究嘗試借由離子交換等化學轉換的方式合成出不同的金屬硒化物。本研究利用半胱胺酸引導離子置入法的方式，只要改變加入不同的陽離子即可製備出各種不同的硒化物，包括Se/PbSe 核殼結構、Bi2Se3、CuSe與Cu2-xSe。首先我們成功地合成出單晶的Se奈米棒做為生長模板，接著加入半胱胺酸幫助和金屬離子形成錯合物，而能有利於接下來將金屬離子置入Se奈米棒，這個創新的手法是陽離子能成功置入Se晶體的關鍵。此方法不僅僅可以製造出不同的硒化物奈米棒，也保存了原本的Se奈米棒的型態，同時具有簡單及環保的優點，對於合成硒化物奈米棒結構的製程是一大突破。除此之外，我們也將這些有良好光敏特性的樣品做成電極並量測光電化學水分解的效能。在所有的樣品中，Se/PbSe奈米棒有最好的光電流表現，原因來自於其p-n接面以及有效的載子分離及轉移，這些特性造成了良好的光電轉換效果。除了Se/PbSe，我們所合成的硒化物奈米棒都有著不錯的光電流表現，代表它們具有顯著的潛力應用在光電化學系統。

In the past decade, extensive attention has been focused on the preparation of one-dimensional (1-D) nanoheterostructures because of the special, dimension-dependent physical and potential applications in electronics, optics, optoelectronics, sensors, catalysis. Selenium (Se) possesses many unique physical and chemical properties, making it a promising candidate in relevant optoelectronic and physicochemical applications. For example, its pronounced photoconductivity offers great potential in the fields of solar cells, photocatalysis, rectifiers and light sensing. In addition, Se exhibits high reactivity toward a variety of metal ions, which can be utilized to perform chemical transformation and obtain the corresponding metal selenides. In this work, a cysteine-complexation-directed ion-insertion process was developed to prepare a variety of metal selenides nanorods including core/shell Se/PbSe, Bi2Se3, CuSe, and Cu2-xSe structures. Single-crystalline Se nanorods were first prepared and used as the growth template. The success of the method relied on the complexation between cysteine molecules and metal ions, which facilitated the reaction of metal ions with Se nanorods and thus the delicate metal ion insertion. This method not only produced nanorods samples that preserved the morphology and crystallinity of the initial Se, but also was a facile and green process to obtain selenides nanorods which were difficult to be prepared with the general methods. The photoactivities of the samples were investigated by employing them as the photoelectrodes for photoelectrochemical water splitting. The resultant core/shell Se/PbSe nanorods were characterized by the p-n band alignment and vectorial charge transfer, both of which are beneficial for photoconverison applications. Among all the samples tested, Se/PbSe core/shell nanorods displayed the highest photocurrent generation as a result of the vectorial charge transfer, revealing their promising potentials in relevant photoelectrochemical processes.