2017 Fiscal Year Annual Research Report
Near infrared plasmon-induced hole transfer in the heterostructured semiconductor nanocrystals
| Project/Area Number |
17J09073
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| Research Institution | Kyoto University |
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Principal Investigator |
廉 孜超 京都大学, 理学研究科, 特別研究員(DC2)
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| Project Period (FY) |
2017-04-26 – 2019-03-31
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| Keywords | Plasmonic hole transfer / Near-infrared light / Carrier dynamics / Hydrogen evolution |
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| Outline of Annual Research Achievements |
The progress of this research has gone well with our expectation. Direct observation of near-infrared plasmon-induced hot hole transfer was successfully made at a heterointerface in CdS/CuS heterostructured nanocrystals (HNCs). Different measurements to evaluate the optical and electrical structures of CuS NCs and CdS NCs with a suitable band alignment were performed and then we used time-resolved infrared spectroscopy to directly trace the plasmon-induced hot hole for observing the dynamics. A novel mechanism of plasmon-induced ‘transit’ charge transfer (PITCT) was proposed and the quenching experiments and a typical oxidation reaction were employed to support the mechanism. Further experiments are needed to demonstrate our hypothesis about hot hole transfer mechanism using the theoretical calculation. We also achieved the photocatalytic hydrogen evolution in the durian-shaped core@mesoporous-shell CdS/ZnSe NCs under visible light irradiation. They exhibited ultra-long-lived charge separation (> 6.2 ms) and efficient hole transfer confined in the ZnSe-shell for enhanced and stable photocatalytic hydrogen evolution. One paper was published on the second subject. (J. Phys. Chem. Lett. 2018, 9, 2212-2217.)
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The CdS/CuS HNCs were successfully prepared and fully characterized. Furthermore, the band energy structures were determined by optical bandgaps, MottSchottky methods. We found that the nature of plasmonic features was originated from its metallic features determined by the crystal structures. More importantly, the time-resolved infrared transient absorption spectroscopy was employed as a good technique to directly observe the dynamics of photo-induced carriers. The results provided us with opportunities to propose the mechanism of plasmon-induced “transit” charge transfer (PITCT). This is a novel mechanism in photocatalysis. The quenching experiments and photocatalytic activity of a typical oxidation reaction under NIR light irradiation supported this mechanism.
Next, durian-shaped CdS/ZnSe heterostructured semiconductor nanocrystals (d-CdS/ZnSe NCs) were successfully synthesized and the mechanism of formation processes were well investigated. The d-CdS/ZnSe NCs exhibited high activity for H2 evolution due to the ultra-long lived charge separation (> 6.2 ms) and efficient hole transfer confined in the mesoporous shell.
Thus, two important hole transfer mechanism were discovered by using unique HNCs in 2017.
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| Strategy for Future Research Activity |
In 2018, some experiments to enforce our mechanism will be performed in collaboration with theoretical scientists. Our collaborators now are doing this calculation to further explain the mechanism. Then, different phases of copper sulfide will be considered to use this mechanism for increasing the efficiency of hot hole injection. For example, CdS/Cu7S4 HNCs or CuS/CdS core/shell structures. The femtosecond transient absorption spectroscopy will give us the direct evidence to observe the carrier dynamics for application to H2 evolution, CO2 fixation, and pollutants degradation. To extend the topic of d-CdS/ZnSe NCs, we plan to prepare the CdS/ZnS nanocrystals to trace the photo-induced hole dynamics for photocatalytic H2 evolution under visible light irradiation.
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Research Products
(4 results)
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[Journal Article] Durian-Shaped CdS@ZnSe Core@Mesoporous-Shell Nanoparticles for Enhanced and Sustainable Photocatalytic Hydrogen Evolution2018
Author(s)
Lian, Z.; Sakamoto, M.; Kobayashi, Y.; Tamai, N.; Ma, J.; Sakurai, T.; Seki, S.; Nakagawa, T.; Lai, M.; Haruta, M.; Kurata, H.; Teranishi, T.
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Journal Title
The Journal of Physical Chemistry Letters
Volume: 9
Pages: 2212-2217
DOI
Peer Reviewed / Int'l Joint Research
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