Shi Xiaowei, Ji Yinglu, Hou Shuai, Liu Wenqi, Zhang Hui, Wen Tao, Yan Jiao, Song Min, Hu Zhijian, Wu Xiaochun
State Key Laboratory for Powder Metallurgy, Central South University , Changsha 410006, PR China.
Langmuir. 2015 Feb 3;31(4):1537-46. doi: 10.1021/la503988e. Epub 2015 Jan 16.
Au@Cu2O core-shell nanostructures are fabricated to have a plasmon enhancement effect using Au nanorods (Au NRs) as a plasmon-tailorable core. By varying the concentration of Au NRs, we can tune the shell thickness in the range of 10-25 nm. The shell is composed of Cu2O nanocrystallites. Because of the thin shells, the extinction spectra at wavelength >500 nm are dominated by the Au core. However, the large dielectric constant of the shell causes an obvious red shift of the surface plasmon resonance (SPR) band of the Au nanorod. Besides, transverse octupolar SPR appears as a result of the anisotropy of the core and the high dielectric constant of the shell. The anisotropic geometry of the Au NR is found to support the octupolar resonances at smaller sizes than for their spherical counterpart. Theoretical simulations indicate that the transverse SPR bands are divided into two resonances, which are dipolar- and octupolar-dominant, respectively. The Cu2O shell degrades via a defect-mediated oxidative pathway, which is aggravated upon longitudinal SPR excitation. The SPR-mediated local field enhancement and resonance energy transfer are found to enhance the excitation of the defect states in the shell, thus providing a simple yet selective probing strategy for defect states.
以金纳米棒（Au NRs）作为可定制等离子体的核，制备了具有等离子体增强效应的金@氧化亚铜核壳纳米结构。通过改变Au NRs的浓度，我们可以将壳层厚度调节在10 - 25纳米范围内。壳层由氧化亚铜纳米微晶组成。由于壳层较薄，波长>500纳米处的消光光谱主要由金核主导。然而，壳层的大介电常数导致金纳米棒的表面等离子体共振（SPR）带明显红移。此外，由于核的各向异性和壳层的高介电常数，出现了横向八极SPR。发现Au NR的各向异性几何结构在比其球形对应物更小的尺寸下支持八极共振。理论模拟表明，横向SPR带分为两个共振，分别以偶极和八极为主。氧化亚铜壳层通过缺陷介导的氧化途径降解，在纵向SPR激发时会加剧。发现SPR介导的局部场增强和共振能量转移增强了壳层中缺陷态的激发，从而为缺陷态提供了一种简单而有选择性的探测策略。
