FemtoNanoOptics group, Université Lyon 1, CNRS, LASIM, 43 Bd du 11 Novembre, 69622 Villeurbanne, France.
ACS Nano. 2012 Aug 28;6(8):7034-43. doi: 10.1021/nn302089h. Epub 2012 Jul 19.
Hybrid nano-objects formed by two or more disparate materials are among the most promising and versatile nanosystems. A key parameter in their properties is interaction between their components. In this context we have investigated ultrafast charge separation in semiconductor-metal nanohybrids using a model system of gold-tipped CdS nanorods in a matchstick architecture. Experiments are performed using an optical time-resolved pump-probe technique, exciting either the semiconductor or the metal component of the particles, and probing the light-induced change of their optical response. Electron-hole pairs photoexcited in the semiconductor part of the nanohybrids are shown to undergo rapid charge separation with the electron transferred to the metal part on a sub-20 fs time scale. This ultrafast gold charging leads to a transient red-shift and broadening of the metal surface plasmon resonance, in agreement with results for free clusters but in contrast to observation for static charging of gold nanoparticles in liquid environments. Quantitative comparison with a theoretical model is in excellent agreement with the experimental results, confirming photoexcitation of one electron-hole pair per nanohybrid followed by ultrafast charge separation. The results also point to the utilization of such metal-semiconductor nanohybrids in light-harvesting applications and in photocatalysis.
由两种或两种以上不同材料形成的混合纳米物体是最有前途和多功能的纳米系统之一。它们性质的一个关键参数是它们组件之间的相互作用。在这方面，我们使用金尖的 CdS 纳米棒在火柴棒结构中的模型系统研究了半导体-金属纳米杂化物中的超快电荷分离。实验使用光时间分辨泵浦探测技术进行，激发颗粒的半导体或金属部分，并探测光诱导的光学响应变化。在纳米杂化物的半导体部分光激发的电子-空穴对被显示出经历快速电荷分离，电子在亚 20 fs 的时间尺度内转移到金属部分。这种超快的金充电导致金属表面等离子体共振的瞬态红移和展宽，与自由团簇的结果一致，但与在液体环境中静态充电的金纳米颗粒的观察结果相反。与理论模型的定量比较非常符合实验结果，证实了每个纳米杂化物光激发一个电子-空穴对，然后进行超快电荷分离。结果还指出了在光收集应用和光催化中利用这种金属-半导体纳米杂化物的可能性。
