Metal/Semiconductor Nanohetrostructures: Interfacial Charge Transfer Dynamics and Their Photoconversion Applications

• Main Authors: Chen, Wei-Ta, 陳韋達
• Other Authors: Hsu, Yung-Jung
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/03604110684752726825

博士 === 國立交通大學 === 材料科學與工程學系所 === 102 === In this thesis, we investigated and presented the interfacial charge carrier dynamics for a series of metal/semiconductor nanoheterostructures including core-shell Au-CdS nanocrystals, core-shell Au-ZnS nanocrystals, core-satellite ZnS-Au nanoassemblies, and core-shell Au-Cd1-xZnxS nanocrystals. Due to the difference in band structures between Au and semiconductors (CdS, ZnS, and Cd1-xZnxS), the photoexcited electrons of semiconductor would preferentially transfer to Au, simultaneously leaving photogenerated holes at semiconductor domain to achieve charge separation. The electron-charging of Au in the nanoheterostructures can be revealed with time-resolved PL spectroscopy which quantitatively describes the electron transfer event between Au and semiconductors. The result of carrier dynamics measurement for the samples is further correlated with their performance evaluation in photoconversion processes, from which a direct correspondence is observed. To boost the electron transfer from CdS to Au, Zn is incorporated in the CdS shell of Au-CdS to form Au-Cd1-xZnxS nanocrystals. By introducing Zn dopants to enlarge the electron transfer driving force, Au-Cd1-xZnxS nanocrystals show one order of magnitude increase in electron transfer rate constant, demonstrating the possibility of improving the photoconversion efficiency for metal/semiconductor nanoheterostructures by means of composition. The present study gives rise to a new class of highly efficient metal/semiconductor nanoheterostructures which may effectively utilize the solar power. In addition, silver nanoclusters complexed with dihydrolipoic acid (DHLA) exhibit molecular-like excited state properties with well-defined absorption and emission features. The Ag8 clusters exhibit fluorescence maximum at 660 nm with a quantum yield of 4.62 %. By introducing MV2+ as a probe we have succeeded in elucidating the interfacial electro transfer dynamics of Ag nanoclusters. The formation of MV+. as the electron transfer product with a rate constant of 2.74 x 1010 s-1 confirms the ability of these metal clusters to participate in the photocatalytic reduction process. Basic understating of excited state processes in florescent metal clusters paves the way towards the devilment of biological probes, sensors and catalysts in energy conversion devices.