摘要/Abstract

表面增强拉曼光谱（SERS）技术是一种基于贵金属纳米结构基底对被检测物进行高灵敏度检测的一种方法.具有特殊纳米结构的贵金属表面受到激光的照射时，金属表面的自由电子会受到极大的振荡，当入射光频率与振荡频率相近时，则会发生表面等离子体共振现象（SPR），使金属表面的局域电场强度极大增强，入射光强度和散射光强度都得到成倍的放大，从而使吸附在贵金属纳米结构表面的分子的拉曼散射信号得到有效的增强.使用NaBH₄还原-酸刻蚀模板法，制备了八面体Au/Ag复合纳米笼，其形貌规整，尺寸均匀约为600 nm，无Cu₂O模板的残留，Au元素均匀负载在Ag纳米笼上，质量分数约为16.8%；Au/Ag复合纳米笼的紫外可见吸收峰相对于Ag纳米笼发生了红移，更重要的是，Au和Ag元素协同赋予了复合纳米笼超高的SERS灵敏度和重复性，Au/Ag复合纳米笼实现了对罗丹明6G的痕量检测（5×10^-14 mol/L），通过时域有限差分法（FDTD）模拟证实：这主要归因于等离子共振作用产生的高电磁场强度；此外，Au元素的加入使Au/Ag复合纳米笼具有优异的抗氧化性和化学稳定性，即使在1%的H₂O₂溶液中浸泡3 h，仍然能够保持优异的SERS性能.八面体Au/Ag复合纳米笼有望成为一种具有应用前景的高灵敏度、高稳定性的SERS基底.
关键词: 模板法, Au/Ag复合纳米笼, 表面等离子体共振, 表面增强拉曼光谱, 化学稳定性
Surface-enhanced Raman spectroscopy (SERS) technology, based on noble metal nanostructures as substrate, is a highly sensitive method for the detected substance. When the surface of noble metal with special nanostructure is irradiated by laser, the free electrons on the metal surface will be greatly oscillated. While the frequency of the incident light is close to that of the oscillation, the surface plasmon resonance (SPR) will occur around the noble metal nanostructures material, greatly enhancing the local electric field intensity of the metal surface. The intensity of incident light and the scattering light will be also multiplied. As a result, the Raman scattering signals of molecules adsorbed on the surface of noble metal nanostructures will be effectively enhanced. In this paper, the octahedral Au/Ag composite nanocages were prepared by using NaBH₄ reduction-acid etching template method. The prepared octahedral Au/Ag composite nanocages are uniform in shape, with the size of about 600 nm, and there is no residual cuprous oxide template. The Au element is uniformly distributed on the Ag nanocages with the mass fraction about 16.8%. Compared with that of Ag nanocages, the UV-vis absorption peak of the Au/Ag composite nanocages is red-shifted. More importantly, the synergistical action of Au and Ag element endow the Au/Ag composite nanocages with ultra-high SERS sensitivity and reproducibility. The trace detection of R6G at an ultralow concentration of 5×10^-14 mol/L can be attributed to the high electromagnetic field intensity generated by the surface plasmon resonance, which was certificated by the finite difference time domain (FDTD) simulation method. Besides, the addition of the Au element provided the Au/Ag composite nanocages with excellent oxidation resistance and chemical stability. The excellent SERS performance can be kept even after soaking in 1% H₂O₂ solution for 3 h. The octahedral Au/Ag composite nanocages are a promising SERS substrate with high sensitivity and stability.
Key words: template method, Au/Ag composite nanocages, surface plasmon resonance, Surface-enhanced Raman spectroscopy (SERS), chemical stability


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