Realization of red shift of absorption spectra using optical near-field effect
Realization of red shift of absorption spectra using optical near-field effect
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DOI：
10.1088/1361-6528/ab2092
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发表时间：
2019-08-23
期刊：
影响因子：
3.5
通讯作者：
Nobusada, Katsuyuki
中科院分区：
文献类型：
--
作者：
Yatsui, Takashi;Nakahira, Yusuke;Nobusada, Katsuyuki
在二氧化碳还原和水分解等许多应用中，需要紫外区域的高能光子来完成化学反应。然而，为了实现可持续发展，所利用的光子能量必须低于包括用于CO2还原的金属络合物、用于水分解的电极等材料的吸收限，因为从太阳接收到的可见光区域的能量低得多。在之前的工作中，我们已经证明，由于电场的空间不均匀性，光学近场（ONF）可以利用远低于吸收边的光子能量来实现化学反应。在本文中，我们证明ONF可以实现光催化还原金属络合物材料吸收光谱的红移。通过将金属络合物附着到具有纳米级突起的ZnO纳米晶体聚集体上，利用金属络合物的漫反射的吸收光谱可以向更长的波长移动10.6nm。基于包括 ONF 效应在内的第一原理计算程序的计算研究结果提供了金属配合物在较低光子能量下吸收增加的证据。由于近场辅助场的增加改善了金属络合物材料中的载流子激发，因此这种效应可能是普遍的，并且它可以适用于使用其他金属络合物材料的CO2还原，以及包括水分解在内的其他光激发过程。
In many applications such as CO2 reduction and water splitting, high-energy photons in the ultraviolet region are required to complete the chemical reactions. However, to realize sustainable development, the photon energies utilized must be lower than the absorption edge of the materials including the metal complex for CO2 reduction, the electrodes for water splitting, because of the huge amount of lower energy than the visible region received from the sun. In the previous works, we had demonstrated that optical near-fields (ONFs) could realize chemical reactions, by utilizing photon energies much lower than the absorption edge because of the spatial non-uniformity of the electric field. In this paper, we demonstrate that an ONF can realize the red shift of the absorption spectra of the metal-complex material for photocatalytic reduction. By attaching the metal complex to ZnO nano-crystalline aggregates with nano-scale protrusions, the absorption spectra by using diffuse reflection of the metal complex can be shifted to a longer wavelength by 10.6 nm. The results of computational studies based on a first-principles computational program including the ONF effect provide proof of the increase in the absorption of the metal complex at lower photon energies. Since the near-field assisted field increase improves the carrier excitation in the metal-complex materials, this effect may be universal and it could applicable to CO2 reduction using the other metal-complex materials, as well as to the other photo excitation process including water splitting.