pH-Dependent SERS by Semiconductor-Controlled Charge-Transfer Contribution

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• 作者：Wei Ji ; Yasutaka Kitahama ; Xiaoxia Han ; Xiangxin Xue ; Yukihiro Ozaki ; Bing Zhao
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：November 26, 2012
• 年：2012
• 卷：116
• 期：46
• 页码：24829-24836
• 全文大小：516K
• 年卷期：v.116,no.46(November 26, 2012)
• ISSN：1932-7455

文摘

With the explosive development of analysis and detecting techniques based on SERS, the further understanding and exploit of the chemical mechanism becomes particularly important. We investigated the contribution of semiconductor to surface-enhanced Raman scattering (SERS) in metal and semiconductor heterostructure consisting of Ag/4-mercaptophenol (MPH)/TiO₂. For this, we used the distinctive property, where the band edge position of an oxide semiconductor such as TiO₂ is sensitive to the pH value, to control the charge-transfer (CT) contribution. It was found that increasing the pH of the buffer solution negatively shifts the conduction band edge of TiO₂, thereby increasing the conductive band electron density at an equilibrium state. Thus, the relative band intensities of Ag/MPH/TiO₂ increase in the SERS spectrum, which is attributed to the Herzberg鈥揟eller contribution that occurs via CT. Moreover, because of the slower transport of cations from the pH buffer solution to the surface of TiO₂, which results from the space-charge limitation, there is a decay time that is associated with the pH-response process.