Preparation of Nanorod Heterostructures Using One-Step Cation Exchange Method

• Main Authors: Chen, Meng-Yu, 陳孟渝
• Other Authors: Hsu, Yung-Jung
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/22488331392931211376

碩士 === 國立交通大學 === 材料科學與工程學系所 === 102 === The charge carriers generated from irradiated semiconductors are widely utilized in many photocatalytic reactions such as the elimination of environmental pollutants and hydrogen production from water splitting. To effectively carry out photocatalytic reactions, the band structure of semiconductors must be modulated to afford favorable charge transfer and achieve spatial charge separation. In this work, a novel one-step cation exchange method has been developed to prepare ZnO-decorated ZnSe nanorods (ZnSe–ZnO NRs). In a typical procedure, ZnSe NRs were prepared by conducting cation exchange reaction on Ag2Se NRs with Zn2+. With extra addition of H2O in the cation exchange process, formation of ZnSe nanorods would be accompanied by the deposition of ZnO nanocrystals, resulting in the formation of ZnSe–ZnO NRs. Through modulating the concentration of H2O added, the amount of ZnO nanocrystals decorated on ZnSe NRs could be readily controlled. Due to the staggered band offset, the photoexcited electrons of ZnSe would preferentially transfer to ZnO, simultaneously leaving photogenerated holes at ZnSe to achieve pronounced charge carrier separation. Time-resolved photoluminescence spectroscopy was used to quantitatively analyze the electron transfer from ZnSe to ZnO for the as-prepared ZnSe–ZnO NRs. A highest electron-transfer rate constant was observed for ZnSe–ZnO NRs with 0.8 vol% H2O, above which a reduced electron-transfer rate constant was recorded as a result of the consumption of charge carriers from the later-emerging electron-hole recombination process. The carrier dynamics results were fundamental consistent with those of performance evaluation in photocatalytic dye degradation, in which ZnSe–ZnO NRs with 0.8 vol% H2O exhibited the highest photocatalytic activity. On the other hand, by using L-cysteine as the reducing agent and Se nanorods as the growth template, we have developed an ion-insertion process to prepare a variety of functional selenide NRs that are difficult to be obtained from the typical methods, including CuSe and Bi2Se3.