Tvrdy Kevin, Kamat Prashant V
Radiation Laboratory, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA.
J Phys Chem A. 2009 Apr 23;113(16):3765-72. doi: 10.1021/jp808562x.
The photochemical behavior of CdSe quantum dots anchored to different surfaces was probed through their deposition on glass, SiO2, and TiO2 films. Following visible light irradiation under ambient conditions, CdSe quantum dots deposited on semiconducting TiO2 surface degraded, where no such degradation was observed when deposited on inert SiO2 surface or glass. Fluorescence decay and transient absorption experiments confirmed that charge injection from excited CdSe into TiO2 occurs with an apparent rate constant of 5.62 x 10(8) s(-1) and is the primary event responsible for photodegradation. In the presence of air, injected electrons are scavenged by surface adsorbed oxygen leaving behind reactive holes which induce anodic corrosion of CdSe quantum dots. In a vacuum environment, minimal CdSe degradation was observed as electron scavenging by oxygen is replaced with charge recombination between injected electrons and holes in CdSe nanocrystals. Spectroscopic measurements presented in this study highlight the role of both substrate and medium in dictating the photochemistry of CdSe quantum dots.
通过将CdSe量子点沉积在玻璃、SiO₂和TiO₂薄膜上来探究锚定在不同表面上的CdSe量子点的光化学行为。在环境条件下进行可见光照射后，沉积在半导体TiO₂表面的CdSe量子点发生降解，而沉积在惰性SiO₂表面或玻璃上时未观察到这种降解现象。荧光衰减和瞬态吸收实验证实，从激发的CdSe向TiO₂的电荷注入以5.62×10⁸ s⁻¹的表观速率常数发生，并且是导致光降解的主要事件。在有空气存在的情况下，注入的电子被表面吸附的氧清除，留下的反应性空穴会引发CdSe量子点的阳极腐蚀。在真空环境中，观察到CdSe的降解极少，因为氧对电子的清除被CdSe纳米晶体中注入的电子与空穴之间的电荷复合所取代。本研究中给出的光谱测量突出了底物和介质在决定CdSe量子点光化学过程中的作用。
