Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
J Am Chem Soc. 2010 Jan 27;132(3):1041-50. doi: 10.1021/ja907253s.
Replacement of the native (as-synthesized) ligands of colloidal CdSe QDs with varying concentrations of a series of para-substituted anilines (R-An), where R ranges from strongly electron-withdrawing to strongly electron-donating, decreases the PL of the QDs. The molar ratio of R-An to QD ([R-An]:[QD]) at which the PL decreases by 50% shifts by 4 orders of magnitude over the series R-An. The model employed to describe the data combines a Freundlich binding isotherm (which reflects the dependence of the binding affinity of the amine headgroups of R-An on the substituent R) with a function that describes the response of the PL to R-An ligands once they are bound at their equilibrium surface coverage. The latter function includes as a parameter the rate constant, k(nr), for nonradiative decay of the exciton at a site to which an R-An ligand is coordinated. The value of this parameter reveals that the predominant mechanism of QD-ligand interaction is passivation of Cd(2+) surface sites through sigma-donation for R-An ligands with R = H, Br, OCF(3), and reductive quenching through photoinduced hole transfer for R = MeO, (Me)(2)N.
用一系列对位取代苯胺（R-An）的不同浓度替换胶体 CdSe QD 的原生（合成）配体，其中 R 的范围从强吸电子到强供电子，会降低 QD 的 PL。PL 降低 50%时的 R-An 与 QD 的摩尔比（[R-An]：[QD]）在 R-An 系列中变化了 4 个数量级。用于描述数据的模型将 Freundlich 结合等温线（反映了 R-An 的胺基头基团与取代基 R 的结合亲和力的依赖性）与描述 PL 对 R-An 配体的响应的函数相结合，一旦它们在其平衡表面覆盖率处结合。后一个函数包含一个参数，即激子在与 R-An 配体配位的位点上非辐射衰减的速率常数 k(nr)。该参数的值表明，QD-配体相互作用的主要机制是通过 sigma-供体对 R = H、Br、OCF(3)的 R-An 配体钝化 Cd(2+)表面位，以及通过光诱导空穴转移对 R = MeO、(Me)(2)N 进行还原猝灭。
