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Nanomaterials: A semiconductor with an enhanced signature(新型半导体纳米材料,让待检分子的拉曼信号放大)

Nanomaterials: A semiconductor with an enhanced signature(新型半导体纳米材料,让待检分子的拉曼信号放大)
Yufeng Shan, Zhihui Zheng, Jianjun Liu, Yong Yang, Zhiyuan Li, Zhengren Huang & Dongliang Jiang
npj Computational Materials
 3, Article number: 11 (2017)
Published online:15 March 2017
Abstract| Full Text | PDF OPEN

Abstract: Surface-enhanced Raman scattering technique, as a powerful tool to identify the molecular species, has been severely restricted to the noble metals. The surface-enhanced Raman scattering substrates based on semiconductors would overcome the shortcomings of metal substrates and promote development of surface-enhanced Raman scattering technique in surface science, spectroscopy, and biomedicine studies. However, the detection sensitivity and enhancement effects of semiconductor substrates are suffering from their weak activities. In this work, a semiconductor based on Nb2O5 is reported as a new candidate for highly sensitive surface-enhanced Raman scattering detection of dye molecules. The largest enhancement factor value greater than 107 was observed with the laser excitation at 633 and 780 nm for methylene blue detection. As far as literature review shows, this is in the rank of the highest sensitivity among semiconductor materials; even comparable to the metal nanostructure substrates with “hot spots”. The impressive surface-enhanced Raman scattering activities can be attributed to the chemical enhancement dominated by the photo-induced charge transfer, as well as the electromagnetic enhancement, which have been supported by the density-functional-theory and finite element method calculation results. The chemisorption of dye on Nb2O5 creates a new highest occupied molecular orbital and lowest unoccupied molecular orbital contributed by both fragments in the molecule-Nb2O5 system, which makes the charge transfer more feasible with longer excitation wavelength. In addition, the electromagnetic enhancement mechanism also accounts for two orders of magnitude enhancement in the overall enhancement factor value. This work has revealed Nb2O5 nanoparticles as a new semiconductor surface-enhanced Raman scattering substrate that is able to replace noble metals and shows great potentials applied in the fields of biology related. 

Editorial Summary   

中国科学家新近发现了一种能检测痕量生物小分子的新型半导体材料。来自中国科学院上海硅酸盐研究所的杨勇、黄政仁等,发现Nb2O5可以显著增强生物医药领域染料分子的拉曼信号。粗糙衬底上的纳米尺寸效应能增加光场,利用这种增强的光信号来检测特定分子的技术叫表面增强拉曼光谱(SERS)技术。但只有少数几种贵金属材料(如金、银)才能将信号强度提高到实用水平。杨勇等发现了一种目前SERS活性最强的半导体衬底材料,氧化铌纳米晶,可以高灵敏检测亚甲基蓝、甲基紫以及甲基蓝等染料分子。他们在检测亚甲基蓝染料时发现,在633780 nm光激发下,拉曼信号增强了107倍以上。   

A semiconductor that makes recognizing molecules easier is identified by researchers in China. Yong Yang and co-workers from the Shanghai Institute of Ceramics show that niobium pentoxide can strongly enhance the optical signature of the colored dyes used in biomedical applications. Nanometer-sized features on a rough surface can increase optical fields. This phenomenon can enhance the optical signature used to identify a specific molecule in a technique called surface-enhanced Raman spectroscopy (SERS).But only a few materials, notably noble metals such as gold and silver, have demonstrated useful levels of enhancement. Yang et al. find that niobium pentoxide nanoparticles can be used as a most-active SERS semiconductor substrate to detect the dyes methylene blue, methyl violet and methyl blue. They measured a SERS enhancement factor of over ten million using 633 and 780 nano meter light to detect methylene blue.

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