Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Homi Bhabha National Instutute, Mumbai-400085, India.
Nanoscale. 2017 Jul 13;9(27):9723-9731. doi: 10.1039/c7nr02232h.
Semiconductor-metal hybrid nanostructures are recognized as great materials due to their high level of light-induced charge separation, which has direct relevance in photocatalysis and solar energy conversion. To understand the mechanism of charge separation processes, hybrid CdSe@CdS{Au} nano-heterostructures containing Au nanoparticles (NPs) with different sizes were synthesized, and the ultrafast charge-transfer dynamics were monitored using femtosecond transient absorption spectroscopy. Steady-state optical absorption studies suggest the formation of charge-transfer complexes between core shell nanocrystals (NCs) and Au NPs. Steady-state and time-resolved luminescence spectroscopy suggest electron transfer from the photo-excited CdSe@CdS core shell QDs NCs to the Au NPs within the heterostructure. The ultrafast interfacial electron-transfer dynamics in the heterostructures were monitored by femtosecond transient absorption spectroscopy. The results revealed that both hot and thermalized electrons are transferred from the core shell QDs to the metal NPs with time constants of 150 and 300 fs, respectively. Hot-electron transfer from QDs to Au NPs was found to take place predominantly in the heterostructures depending on the sizes of the metal NPs. The photo-degradation of rhodamin B in the presence of the CdSe@CdS{Au} heterostructures under visible-light radiation suggests that the hot electrons in the heterostructures play a major role in photocatalytic degradation.
半导体-金属杂化纳米结构因其具有高水平的光诱导电荷分离而被认为是一种很有前途的材料，这与光催化和太阳能转换直接相关。为了理解电荷分离过程的机制，合成了含有不同尺寸金纳米颗粒（NPs）的 CdSe@CdS{Au}纳米杂化异质结构，并使用飞秒瞬态吸收光谱监测了超快电荷转移动力学。稳态光吸收研究表明，在核壳纳米晶体（NCs）和 Au NPs 之间形成了电荷转移复合物。稳态和时间分辨荧光光谱表明，电子从光激发的 CdSe@CdS 核壳量子点 NCs 转移到异质结构中的 Au NPs。飞秒瞬态吸收光谱监测了异质结构中的超快界面电子转移动力学。结果表明，热电子和热化电子分别以 150 和 300 fs 的时间常数从核壳 QDs 转移到金属 NPs。发现 QDs 到 Au NPs 的热电子转移主要发生在异质结构中，这取决于金属 NPs 的尺寸。在可见光照下，CdSe@CdS{Au}杂化结构存在时罗丹明 B 的光降解表明，异质结构中的热电子在光催化降解中起着主要作用。
