Department of Chemistry, Northwestern University , 2145 Sheridan Rd., Evanston, Illinois 60208-3113, United States.
ACS Nano. 2016 Jun 28;10(6):6372-82. doi: 10.1021/acsnano.6b02814. Epub 2016 Jun 13.
This paper describes the enhancement of the rate of hole transfer from a photoexcited CdS quantum dot (QD), with radius R = 2.0 nm, to a molecular acceptor, phenothiazine (PTZ), by linking the donor and acceptor through a phenyldithiocarbamate (PTC) linker, which is known to lower the confinement energy of the excitonic hole. Upon adsorption of PTC, the bandgap of the QD decreases due to delocalization of the exciton, primarily the excitonic hole, into interfacial states of mixed QD/PTC character. This delocalization enables hole transfer from the QD to PTZ in <300 fs (within the instrument response of the laser system) when linked by PTC, but not when linked by a benzoate group, which has a similar length and conjugation as PTC but does not delocalize the excitonic hole. Comparison of the two systems was aided by quantification of the surface coverage of benzoate and PTC-linked PTZ by (1)H NMR. This work provides direct spectroscopic evidence of the enhancement of the rate of hole extraction from a colloidal QD through covalent linkage of a hole acceptor through an exciton-delocalizing ligand.
本文描述了通过将供体和受体通过苯并硫代氨基甲酸盐（PTC）连接体连接，从而增强半径为 2.0nm 的 CdS 量子点（QD）中光激发的空穴转移到分子受体吩噻嗪（PTZ）的速率，这种连接体已知会降低激子空穴的限制能量。在吸附 PTC 后，由于激子（主要是激子空穴）离域到具有混合 QD/PTC 特性的界面态，QD 的能带隙减小。这种离域使得当通过 PTC 连接时，空穴可以在<300fs（在激光系统的仪器响应范围内）内从 QD 转移到 PTZ，但当通过苯甲酸酯基团连接时则不行，苯甲酸酯基团具有与 PTC 相似的长度和共轭性，但不会离域激子空穴。通过（1）H NMR 对苯甲酸酯和 PTC 连接的 PTZ 的表面覆盖率进行定量，这两种系统的比较得到了辅助。这项工作提供了直接的光谱证据，证明通过激子离域配体将空穴受体通过共价键连接到胶体 QD 上，可以增强空穴提取的速率。
