Plasmon-induced modulation of the emission spectra of the fluorescent molecules near gold nanorods.
Plasmon-induced modulation of the emission spectra of the fluorescent molecules near gold nanorods.
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DOI：
10.1039/c1nr10544b
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发表时间：
2011-09
期刊：
影响因子：
6.7
通讯作者：
Lei Zhao;T. Ming;Huanjun Chen;Yao Liang;Jianfang Wang
中科院分区：
文献类型：
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作者：
Lei Zhao;T. Ming;Huanjun Chen;Yao Liang;Jianfang Wang
位于贵金属离子附近的荧光分子的激发和发射过程都可以与金属离子的局域表面等离子体共振强烈相互作用。虽然已经深入研究了这种等离子体-荧光团相互作用对荧光发射的强度、偏振和方向的影响，但是对发射光谱的等离子体效应几乎没有被探索。我们在单粒子水平上表明，Au纳米棒的局部表面等离子体共振可以强烈改变邻近荧光分子发射的光谱轮廓。荧光分子嵌入在均匀涂覆在每个Au纳米棒上的介观结构的二氧化硅壳中。纳米棒的纵向等离子体共振波长通过综合调谐纳米棒纵横比而有意地远离固有荧光发射峰值波长偏移。荧光分子的发射光谱被发现是显着调制。在等离子体共振波长处，除了固有荧光峰外，还出现了等离子体诱导的新荧光峰。随着Au纳米棒的尺寸增加，该等离子体激元诱导的荧光峰的强度增加。这种光谱调制可以通过描绘具有多个振动能级的荧光团的衰减过程来理解。具有特定共振能量的等离子体激元将增强具有近似等于等离子体激元能量的跃迁能量的能级之间的跃迁速率。这种等离子体增强的跃迁速率导致荧光发射的调制光谱分布。
Both the excitation and emission processes of a fluorescent molecule positioned near a noble metal nanocrystal can interact strongly with the localized surface plasmon resonance of the metal nanocrystal. While the effects of this plasmon-fluorophore interaction on the intensity, polarization, and direction of the fluorescence emission have been intensively investigated, the plasmonic effect on the emission spectrum has barely been explored. We show, on the single-particle level, that the localized surface plasmon resonance of Au nanorods can strongly alter the spectral profile of the emission from adjacent fluorescent molecules. The fluorescent molecules are embedded in a mesostructured silica shell that is uniformly coated on each Au nanorod. The longitudinal plasmon resonance wavelengths of the nanorods are deliberately shifted away from the intrinsic fluorescence emission peak wavelength by synthetically tuning the nanorod aspect ratio. The resultant emission spectra of the fluorescent molecules are found to be remarkably modulated. Besides the intrinsic fluorescence peak, a plasmon-induced new peak emerges at the plasmon resonance wavelength. The intensity of this plasmon-induced fluorescence peak increases as the size of the Au nanorod is increased. This spectral modulation can be understood by depicting the decay process of the fluorophore with multiple vibrational energy levels. The plasmon with a specific resonance energy will enhance the transition rate between the energy levels that have the transition energy approximately equal to the plasmon energy. This plasmon-enhanced transition rate results in a modulated spectral profile of the fluorescence emission.