Charge-Selective Surface-Enhanced Raman Scattering Using Silver and Gold Nanoparticles Deposited on Silicon鈥揅arbon Core鈥揝hell Nanowires

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• 作者：Sun Young Baik ; Yong Jae Cho ; Young Rok Lim ; Hyung Soon Im ; Dong Myung Jang ; Yoon Myung ; Jeunghee Park ; Hong Seok Kang
• 刊名：ACS Nano
• 出版年：2012
• 出版时间：March 27, 2012
• 年：2012
• 卷：6
• 期：3
• 页码：2459-2470
• 全文大小：1189K
• 年卷期：v.6,no.3(March 27, 2012)
• ISSN：1936-086X

文摘

The deposition of silver (Ag) or gold (Au) nanoparticles (NPs) on vertically aligned silicon鈥揷arbon (Si鈥揅) core鈥搒hell nanowires (NWs) produces sensitive substrates for surface-enhanced Raman spectroscopy (SERS). The undoped and 30% nitrogen (N)-doped graphitic layers of the C shell (avg thickness of 20 nm) induce a higher sensitivity toward negatively (鈭? and positively (+) charged dye molecules, respectively, showing remarkable charge selectivity. The Ag NPs exhibit higher charge selectivity than the Au NPs. The Ag NPs deposited on p- and n-type Si NWs also exhibit (鈭? and (+) charge selectivity, respectively, which is higher than that of the Au NPs. The X-ray photoelectron spectroscopy analysis indicates that the N-doped graphitic layers donate more electrons to the metal NPs than the undoped ones. More distinct electron transfer occurs to the Ag NPs than to the Au NPs. First principles calculations of the graphene鈥搈etal adducts suggest that the large electron transfer capacity of the N-doped graphitic layers is due to the formation of a N鈫扐g coordinate bond involving the lone pair electrons of the N atoms. We propose that the more (鈭? charged NPs on the N-doped graphitic layers prefer the adsorption of (+) charged dyes, enhancing the SERS intensity. The charge selectivity of the Si NW substrates can also be rationalized by the greater electron transfer from the n-type Si to the metal NPs.

Keywords:

surface-enhanced Raman scattering; charge selectivity; N-doped graphitic layers; silicon nanowires; silver nanoparticles; first principles calculations; electron transfer