Effect of Oxidation on Surface-Enhanced Raman Scattering Activity of Silver Nanoparticles: A Quantitative Correlation
Effect of Oxidation on Surface-Enhanced Raman Scattering Activity of Silver Nanoparticles: A Quantitative Correlation
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DOI：
10.1021/ac2005839
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发表时间：
2011-08-01
影响因子：
7.4
通讯作者：
Sukhishvili, Svetlana
中科院分区：
文献类型：
--
作者：
Han, Yun;Lupitskyy, Robert;Sukhishvili, Svetlana
我们定量研究，使用X射线光电子能谱（XPS），氧化的基板固定银纳米粒子（Ag NPs）在广泛的条件下，包括暴露于环境空气和控制臭氧环境下的紫外线照射，我们相关的银氧化程度与表面增强拉曼散射（Sers）增强因子（EF）。通过使用反式-1，2-双（4-吡啶基）乙烯（BPE）和硫氰酸钠作为模型分析物在532 nm的激发波长下评估原始和氧化的Ag NPs的SEAS活性。我们的研究表明，银纳米颗粒暴露于百万分之一（ppm）水平浓度的臭氧导致Ag 2 O的形成和SEAS EF的数量级减少。这种不利影响在Ag NP暴露于臭氧以十亿分之一（ppb）水平存在的环境条件下时也是显著的。相关的XPS和Sers的研究表明，形成只是一个亚单层的Ag 2 O是足以显着降低银纳米粒子的Sers EF。此外，等离子体吸收带的变化的研究指出，化学增强作为恶化的Sers信号的主要原因时，基板预暴露于环境空气中，并在基板预暴露于臭氧浓度升高的情况下，化学和电磁增强的变化的组合。最后，我们还发现紫外线照射和臭氧对银氧化具有协同效应，从而对银纳米颗粒的Sers增强产生不利影响，并且这种氧化效应是分析物依赖性的，这是由于各种分析物的化学增强和分子结合亲和力的固有差异。
We quantitatively studied, using X-ray photoelectron spectroscopy (XPS), oxidation of substrate-immobilized silver nanoparticles (Ag NPs) in a wide range of conditions, including exposure to ambient air and controlled ozone environment under UV irradiation, and we correlated the degree of silver oxidation with surface-enhanced Raman scattering (SERS) enhancement factors (EFs). The SEAS activity of pristine and oxidized Ag NPs was assessed by use of trans-1,2-bis(4-pyridyl)ethylene (BPE) and sodium thiocynate as, model analytes at the excitation wavelength of 532 nm. Our study showed that the exposure of Ag NPs to parts per million (ppm) level concentrations of ozone led to the formation of Ag2O and orders of magnitude reduction in SEAS EFs. Such an adverse effect was also notable upon exposure of Ag NPs under ambient conditions where ozone existed at parts per billion (ppb) level. The correlated XPS and SERS studies suggested that formation of just a submonolayer of Ag2O was sufficient to decrease markedly the SERS EF of Ag NPs. In addition, studies of changes in plasmon absorption bands pointed to the chemical enhancement as a major reason for deterioration of SERS signals when substrates were pre-exposed to ambient air, and to a combination of changes in chemical and electromagnetic enhancements in the case of substrate pre-exposure to elevated ozone concentrations. Finally, we also found UV irradiation and ozone had a synergistic effect on silver oxidation and thus a detrimental effect on SERS enhancement of Ag NPs and that such oxidation effects were analyte-dependent, as a result of inherent differences in chemical enhancements and molecular binding affinities for various analytes.