Jeong Sohee, Achermann Marc, Nanda Jagjit, Ivanov Sergei, Klimov Victor I, Hollingsworth Jennifer A
C-PCS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
J Am Chem Soc. 2005 Jul 27;127(29):10126-7. doi: 10.1021/ja042591p.
We study the effect of thiols on the emission efficiency of aqueous CdSe/ZnS core/shell nanocrystal quantum dots (NQDs). We observe that the impact of thiol addition on emission quantum yields (QYs) is time-, concentration-, and pH-dependent. Further, we use a combination of time-resolved spectroscopic methods to determine the mechanism by which thiol addition can cause either increases or decreases in QYs. Specifically, through transient absorption measurements, we show that thiol addition can improve passivation of electron traps, increasing QYs at low thiol concentrations. Further, using nanosecond photoluminescence (PL), we observe that at higher thiol concentrations, hole traps are introduced that reduce PL QYs. Last, through a combination of pH-dependence and control studies (e.g., addition of 2-methyl thioethanol to an aqueous NQD solution and addition of dodecanethiol to a hexane NQD solution), we demonstrate that it is the ability of thiols in aqueous solution to generate thiolate that is the source of both favorable and adverse QY changes. Our results contribute to the understanding of the role of surface ligands, which is critical to the design of stable, high-quantum-yield, nonblinking NQDs.
我们研究了硫醇对水相CdSe/ZnS核壳纳米晶量子点（NQDs）发光效率的影响。我们观察到，添加硫醇对发射量子产率（QYs）的影响与时间、浓度和pH值有关。此外，我们结合使用时间分辨光谱方法来确定添加硫醇导致QYs增加或减少的机制。具体而言，通过瞬态吸收测量，我们表明添加硫醇可以改善电子陷阱的钝化，在低硫醇浓度下提高QYs。此外，使用纳秒光致发光（PL），我们观察到在较高硫醇浓度下，会引入空穴陷阱，从而降低PL QYs。最后，通过结合pH依赖性和对照研究（例如，向水相NQD溶液中添加2-甲基硫代乙醇以及向己烷NQD溶液中添加十二烷硫醇），我们证明水溶液中硫醇生成硫醇盐的能力是QYs发生有利和不利变化的根源。我们的结果有助于理解表面配体的作用，这对于设计稳定、高量子产率、不闪烁的NQDs至关重要。
