氧化鋅奈米線/銀微米片狀異質結構合成特性與其光觸媒分析

Synthesis and characterization of ZnO nanowires/Ag microplates heterostructures and their enhanced photocatalysis performance

張正偉(Cheng-Wei Chang)

指導教授 ： 嚴大任

國立清華大學/工學院/材料科學工程學系/碩士(2012年)

摘要

銀/氧化鋅異質結構為一種多樣的材料，可有效的增加電荷轉移且降低電子電洞對再復合效應。近年來，許多研究探討此一異質結構並提出如零維異質奈米顆粒(點對點)、一維樹枝狀銀線與氧化鋅奈米線(線對線)等不同形狀與結構。本篇論文設計一新穎銀與氧化鋅異質結構─氧化鋅奈米線陣列/二維銀片並探討其對光降解效益之影響。其中，一維規則氧化鋅奈米線陣列可形成抗反射層；二維維米銀片可形成二維的電子傳導層，增加異質結構在光觸媒的效益。利用競爭性的多元醇還原法先製備微米銀片，再利用水浴法以製備氧化鋅奈米線陣列形成新穎異質結構。實驗結果中，顯示單晶微奈米銀片可製備邊長至5奈米，且其平坦面為{111}，擁有高度方向性。另外，單晶氧化鋅奈米線陣列垂直向<0001>方向成長且直接長於微米銀片上。此一現象經由掃描式電子顯微鏡、X光粉末繞射儀、穿透式電子顯微鏡、與X光電子能譜儀證實存在氧化鋅奈米線與微米銀片為直接接觸且帶有電荷分離的效應。此效應有效傳導光激發電子自氧化鋅光觸媒於銀片上可以降低電子電洞對再復合效應，故有效增強光觸媒降解水中汙染物上的應用。利用假定汙染物亞甲基藍水溶液測試光降解效益，相較於純氧化鋅降解，發現當加入銀片的異質結構可以有效提升降解活性且遵循擬一級反應(pseudo first order reaction)，在使用微克等級的異質光觸媒條件下，其最佳光降解動力常數為6.60×10-3 min-1。

關鍵字

氧化鋅奈米線 ； 銀微米片 ； 光觸媒 ； 光降解

並列摘要

Ag/ZnO heterostructures are versatile materials capable of transferring interfacial charge transfer and suppressing electron-hole pairs recombination. Recently, great efforts have been made to prepare Ag/ZnO heterostructures with various morphologies such as clusters (particles-to-particles) and dendrites (wires-to-wires). We herein report a novel heterostructure of ZnO nanowire arrays growing on single crystalline polygonal Ag microplates which provides the merits of the antireflection layer for ZnO nanowire arrays and the 2D electrons transportation layer for Ag microplates. The Ag/ZnO heterostructure was fabricated by utilizing the rivalrous polyol reduction method and aqueous solution method. The experimental results showed that the edge length of single crystalline Ag microplates can reach up to 5 μm, and the Ag microplates are highly oriented with {111} facets as the basal planes. Arrays of single crystalline ZnO NWs were vertically assembled along <0001> direction attaching on the {111} facets of Ag microplates. It was confirmed by scanning electron microscope (SEM), transmittance electron microscope (TEM) and X–ray photoemission spectrum (XPS), revealing the direct contact and the charge transfer between Ag microplates and ZnO nanowires. Meanwhile, contacts of Ag/ZnO heterostructure form the charge separation, so enhance the photocatalytic activity by using the representative target pollutant–Methyl blue (MB). It shows the positive results of the heterostructure enhance the activities of MB photodegradation at the pseudo first order kinetic constant of 6.60×10-3 min-1 by means of employing micrograms of photocatalysts.

並列關鍵字

ZnO nanowires ； Ag microplates ； Photocatalysts ； Photodegradation

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