Hu Zhuang, Shu Yufei, Qin Haiyan, Hu Xiaofei, Peng Xiaogang
Key Laboratory of Excited-State Materials of Zhejiang Province and Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
J Am Chem Soc. 2021 Nov 10;143(44):18721-18732. doi: 10.1021/jacs.1c09363. Epub 2021 Oct 27.
With high-quality CdSe/CdS core/shell nanocrystals as the main model system and under a controlled atmosphere, responses of photoexcited semiconductor nanocrystals to two active species (water and/or oxygen) in an ambient environment are studied systematically. Under photoexcitation, although high-quality semiconductor nanocrystals in either thin solid films or various solutions have a near-unity photoluminescence quantum yield, there is still a small probability (∼10 per photon absorbed) to be photoreduced by the water molecules efficiently accumulated in the highly hydrophilic nanocrystal-ligands interface. The resulting negatively charged nanocrystals are the starting point of most photophysical variations, and the hydroxyl radical─key photo-oxidation product of water─plays the main role for initiating various photochemical processes. Depending on the supplementation of water to the interface, accessibility to oxygen, photoirradiation power, type of matrices, type of measurement schemes, and solubility of nanocrystals in the solution, various photophysical/photochemical phenomena─either reported or not reported in the literature─are reproducibly observed. Results confirm that photophysical properties and photochemical reactions can be well-correlated, offering a unified and unique basis for fundamental studies and the design of processing techniques in industry.
以高质量的CdSe/CdS核壳纳米晶体作为主要模型体系，在可控气氛下，系统研究了光激发半导体纳米晶体在环境气氛中对两种活性物质（水和/或氧气）的响应。在光激发下，尽管在固体薄膜或各种溶液中的高质量半导体纳米晶体具有接近单位的光致发光量子产率，但在高度亲水的纳米晶体-配体界面处有效积累的水分子仍有小概率（每吸收一个光子约为10%）将其光还原。产生的带负电荷的纳米晶体是大多数光物理变化的起始点，而羟基自由基（水的关键光氧化产物）在引发各种光化学过程中起主要作用。根据向界面补充水情况、氧气可及性、光辐照功率、基质类型、测量方案类型以及纳米晶体在溶液中的溶解度，可重复观察到文献中已报道或未报道的各种光物理/光化学现象。结果证实光物理性质和光化学反应可以很好地关联起来，为基础研究和工业加工技术设计提供了统一且独特的依据。
