Surface enhance Raman scattering in aligned metal/semiconductor nanocrystals

我们通过测量拉曼散射光谱和光致发光光谱研究了半导体纳米晶体与金属纳米晶体之间的电子相互作用。首先，我们讨论了半导体纳米晶体的拉曼散射光谱形状。利用考虑动量守恒规则松弛的声子约束模型计算了拉曼散射光谱形状。我们使用的半导体纳米晶体有可能形成锌闪锌矿或纤锌矿晶体结构。假设纤锌矿结构的计算拉曼散射光谱更能解释实验光谱。这一结果与TEM图像得到的晶体结构一致。我们的发现表明，我们可以通过拉曼散射分析来确定纳米晶体的结构，而不需要使用TEM。接下来，我们制作了紧密堆积的半导体/金属混合纳米粒子单层，并同时测量了半导体纳米粒子的拉曼散射和光致发光光谱，以进一步研究半导体纳米粒子的拉曼散射和光致发光特性对金属纳米粒子表面等离子体激元的影响。透射电镜结果表明，成功制备了密实的半导体/金属纳米颗粒单层膜。随着金属纳米粒子比例的增加，PL强度急剧下降，而拉曼散射强度略有增加。时间分辨光致发光光谱表明，半导体纳米晶体中的光激发激子能量向金属纳米粒子转移。观察到的半导体-纳米粒子数密度对拉曼散射和光致发光强度的依赖关系可以用考虑电磁增强和能量传递影响的能量传递模型来解释。我们证明了同时测量拉曼散射和光致发光光谱是了解金属和半导体纳米结构之间相互作用的有用技术。少

We studied electronic interaction between semiconductor nanocrystals and metal nanocrystals by measuring Raman scattering and photoluminescence spectra. First, we discussed Raman scattering spectral shape of semiconductor nanocrystals. The Raman scattering spectral shape was calculated by a phonon confinement model considering the relaxation of the momentum conservation rule. The semiconductor nanocrystals we used had a possibility to farm zincblende or wurtzite crystal structure. The calculated Raman scattering spectra assuming wurtzite structure were more preferable to explain the experimental spectra. This result was consistent with the crystal structure obtained from TEM images. Our finding indicates that we can determine the nanocrystal structure from the Raman scattering analyses without using e. g. TEM.Next, we fabricated close-packed semiconductor/metal mixed nanoparticle monolayers and measured the Raman scattering and photoluminescence spectra simultaneously, in order to inve … More stigate the influence of the Raman scattering and photoluminescence properties of semiconductor nanoparticles on the surface plasmons of metal nanoparticles. The TEM images showed that close-packed semiconductor/metal nanoparticle monolayers were successfully fabricated. With an increase of the metal nanoparticle ratio, the PL intensity decreased dramatically, while the Raman scattering intensity increased slightly. The time-resolved photoluminescence spectra showed that the photo-excited exciton energy in semiconductor nanocrystals transferred to metal nanoparticles. The observed semiconductor-nanoparticle number density dependences of the Raman scattering and photoluminescence intensities were able to be explained by an energy transfer model which considered the effects of electromagnetic enhancement and energy transfer. We demonstrated that conducting simultaneous measurements of Raman scattering and photoluminescence spectra is a useful technique to understand the interaction between metal and semiconductor nanostructures. Less