Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, USA.
Department of Physics and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43043, USA.
Nat Chem. 2018 Feb;10(2):225-230. doi: 10.1038/nchem.2906. Epub 2017 Dec 18.
The generation and transfer of triplet excitons across semiconductor nanomaterial-molecular interfaces will play an important role in emerging photonic and optoelectronic technologies, and understanding the rules that govern such phenomena is essential. The ability to cooperatively merge the photophysical properties of semiconductor quantum dots with those of well-understood and inexpensive molecular chromophores is therefore paramount. Here we show that 1-pyrenecarboxylic acid-functionalized CdSe quantum dots undergo thermally activated delayed photoluminescence. This phenomenon results from a near quantitative triplet-triplet energy transfer from the nanocrystals to 1-pyrenecarboxylic acid, producing a molecular triplet-state 'reservoir' that thermally repopulates the photoluminescent state of CdSe through endothermic reverse triplet-triplet energy transfer. The photoluminescence properties are systematically and predictably tuned through variation of the quantum dot-molecule energy gap, temperature and the triplet-excited-state lifetime of the molecular adsorbate. The concepts developed are likely to be applicable to semiconductor nanocrystals interfaced with molecular chromophores, enabling potential applications of their combined excited states.
半导体纳米材料-分子界面上的三重态激子的产生和转移将在新兴的光子学和光电技术中发挥重要作用，理解控制这种现象的规律至关重要。因此，能够协同地将半导体量子点的光物理性质与已知的廉价分子发色团的性质结合起来是至关重要的。在这里，我们表明 1-蒽甲酸功能化的 CdSe 量子点经历热激活延迟光致发光。这种现象是由于纳米晶体到 1-蒽甲酸的三重态-三重态能量转移几乎是定量的，产生了一个分子三重态“储库”，通过吸热的反向三重态-三重态能量转移，热重新填充 CdSe 的光致发光态。通过改变量子点-分子的能量隙、温度和分子吸附物的三重激发态寿命，系统地和可预测地调节了光致发光性质。所开发的概念可能适用于与分子发色团界面的半导体纳米晶体，从而能够应用它们的复合激发态。
