Probing the Dependence of Electron Transfer on Size and Coverage in Carbon Nanotube鈥換uantum Dot Heterostructures

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• 作者：Lei Wang ; Jinkyu Han ; Yuqi Zhu ; Ruiping Zhou ; Cherno Jaye ; Haiqing Liu ; Zhuo-Qun Li ; Gordon T. Taylor ; Daniel A. Fischer ; Joerg Appenzeller ; Stanislaus S. Wong
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：November 25, 2015
• 年：2015
• 卷：119
• 期：47
• 页码：26327-26338
• 全文大小：580K
• ISSN：1932-7455

文摘

As a model system for understanding charge transfer in novel architectural designs for solar cells, double-walled carbon nanotube (DWNT)鈥揅dSe quantum dot (QD) (QDs with average diameters of 2.3, 3.0, and 4.1 nm) heterostructures have been fabricated. The individual nanoscale building blocks were successfully attached and combined using a hole-trapping thiol linker molecule, i.e., 4-mercaptophenol (MTH), through a facile, noncovalent 蟺鈥撓€ stacking attachment strategy. Transmission electron microscopy confirmed the attachment of QDs onto the external surfaces of the DWNTs. We herein demonstrate a meaningful and unique combination of near-edge X-ray absorption fine structure (NEXAFS) and Raman spectroscopies bolstered by complementary electrical transport measurements in order to elucidate the synergistic interactions between CdSe QDs and DWNTs, which are facilitated by the bridging MTH molecules that can scavenge photoinduced holes and potentially mediate electron redistribution between the conduction bands in CdSe QDs and the C 2p-derived states of the DWNTs. Specifically, we correlated evidence of charge transfer as manifested by (i) changes in the NEXAFS intensities of 蟺* resonance in the C K-edge and Cd M₃-edge spectra, (ii) a perceptible outer tube G-band downshift in frequency in Raman spectra, as well as (iii) alterations in the threshold characteristics present in transport data as a function of CdSe QD deposition onto the DWNT surface. In particular, the separate effects of (i) varying QD sizes and (ii) QD coverage densities on the electron transfer were independently studied.