Simultaneous Determination of the Adsorption Constant and the Photoinduced Electron Transfer Rate for a Cds Quantum Dot鈥揤iologen Complex

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• 作者：Adam J. Morris-Cohen ; Matthew T. Frederick ; Laura C. Cass ; Emily A. Weiss
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：July 6, 2011
• 年：2011
• 卷：133
• 期：26
• 页码：10146-10154
• 全文大小：956K
• 年卷期：v.133,no.26(July 6, 2011)
• ISSN：1520-5126

文摘

Transient absorption (TA) spectroscopy of solution-phase mixtures of colloidal CdS quantum dots (QDs) with acid-derivatized viologen molecules, N-[1-heptyl],N鈥?[3-carboxypropyl]-4,4鈥?bipyridinium dihexafluorophosphate (V²⁺), indicates electron transfer occurs from the conduction band of the QD to the LUMO of V²⁺ after photoexcitation of a band-edge exciton in the QD. Analysis of the magnitude of the ground state bleach of the QD as a function of the molar ratio QD:V²⁺ yields the QD鈥搇igand adsorption constant, K_a (4.4 脳 10⁴ M^鈥?) for V²⁺ ligands adsorbed in geometries conducive to electron transfer. The value of K_a, together with the measured rates of (i) formation of the V^{+鈥?/sup> electron transfer product and (ii) recovery of the ground state bleach of the QD, enables determination of the intrinsic rate constant for charge separation, k_CS,int 1.7 脳 1010 s鈥?, the rate for a single QD鈥揤2+ donor鈥揳cceptor pair. This analysis confirms previous reports that the number of ligands adsorbed to each QD is well-described by a Poisson distribution. This is the first report where the QD鈥搇igand charge transfer and binding equilibria are quantitatively investigated simultaneously with a single technique.}