Research Center for Exotic Nanocarbons (JST), Shinshu University, 4-17-1, Wakasato, Nagano-city 380-8553, Japan.
J Chem Phys. 2012 Feb 14;136(6):064505. doi: 10.1063/1.3682771.
We introduce a way to selectively probe local vibration modes at nanostructured asperities such as tips of carbon nanohorns. Our observations benefit from signal amplification in surface-enhanced Raman scattering (SERS) at sites near a silver surface. We observe nanohorn tip vibration modes in the range 200-500 cm(-1), which are obscured in regular Raman spectra. Ab initio density functional calculations assign modes in this frequency range to local vibrations at the nanohorn cap resembling the radial breathing mode of fullerenes. Careful interpretation of our SERS spectra indicates presence of caps with 5 or 6 pentagons, which are chemically the most active sites. Changes in the peak intensities and frequencies with time indicate that exposure to laser irradiation may cause structural rearrangements at the cap.
我们介绍了一种选择性探测纳米结构突起（如碳纳米角尖端）局部振动模式的方法。我们的观察得益于银表面附近的表面增强拉曼散射（SERS）中的信号放大。我们观察到纳米角尖端振动模式在 200-500cm(-1)范围内，这在常规拉曼光谱中被掩盖了。从头算密度泛函计算将该频率范围内的模式分配给纳米角帽的局部振动，类似于富勒烯的径向呼吸模式。对我们的 SERS 光谱的仔细解释表明存在具有 5 或 6 个五边形的帽，它们在化学上是最活跃的位点。随着时间的推移，峰强度和频率的变化表明，激光辐照可能导致帽的结构重排。
