Quantum Plasmonics: Optical Monitoring of DNA-Mediated Charge Transfer in Plasmon Rulers.
Quantum Plasmonics: Optical Monitoring of DNA-Mediated Charge Transfer in Plasmon Rulers.
复制标题
DOI：
10.1002/adma.201503885
复制
发表时间：
2016-03-09
期刊：
影响因子：
--
通讯作者：
Reinhard BM
中科院分区：
文献类型：
--
作者：
Lerch S;Reinhard BM
金和银纳米粒子(NP)在电磁光谱的可见光范围内表现出独特的光学性质，其中入射光激发这些纳米结构中导带电子的相干集体电子振荡(等离子体)。[1]如果两个粒子彼此接近到大约一个NP直径(D)，单个NP的等离子体相互耦合，从而将NP之间的间隙中的电磁场限制和增强一个数量级。[2]NP之间依赖于距离的近场耦合导致远场光谱移动，[3]精确表征纳米粒子之间的距离相关等离子体激元耦合一直是密集的实验和理论研究的主题。[4]总的来说，可以区分两种不同的耦合模式。经典的电磁耦合是由电容耦合主导的，在电容耦合中，主要的纵向键偶极等离子体激元模式随着粒子间距的减小而不断红移。在这个区域中，一个直观的物理模型来近似与距离相关的等离子体激元共振波长λRES，是所谓的普适标度关系。[5，6]这个模型在很短的粒子间距下失效，其中经典的电磁耦合被破坏，因为纳米粒子之间的量子力学隧道效应减少了带隙两侧的电荷堆积。[7，8]结果是，随着S的减少，纵向键偶极等离子体激元模式的共振波长不再继续红移，而是停滞甚至蓝移。如果有足够的电流密度，还可以在比BDP更长的波长上检测到隧道电荷转移等离子体(TCTP)。[7，9，10]在量子等离子体区域中，等离子体驱动的NPs之间的电荷转移是当前发展新的非线性光谱、[11]传感器、[12]和潜在的催化剂的高度感兴趣的领域。
Gold and silver nanoparticles (NP) exhibit unique optical properties in the visible range of the electromagnetic spectrum where the incident light excites coherent collective electron oscillations (plasmons) of conduction band electrons in these nanoscale structures.[1] If two particles approach each other to approximately one NP diameter (D), the plasmons of the individual NPs couple, which confines and enhances the electromagnetic field in the gap between the NPs by orders of magnitude.[2] The distance dependent near-field coupling between the NPs leads to spectral shifts in the far-field,[3] and an accurate characterization of distance dependent plasmon coupling between NPs has been subject of intense experimental and theoretical research.[4] In general, two distinct coupling regimes can be differentiated. The classical electromagnetic coupling regime is dominated by capacitive coupling in which the dominating longitudinal bonding dipolar plasmon mode (BDP) continuously red-shifts with decreasing interparticle separation, S. An intuitive physical model to approximate the distance dependent plasmon resonance wavelength, λres, in this regime is the so-called universal scaling relationship.[5, 6] This model fails at very short interparticle separations where the classical electromagnetic coupling breaks down as quantum mechanical tunneling between the NPs reduces the charge pileup on both sides of the gap.[7, 8] As a consequence, the BDP resonance wavelength does not continue to red-shift with decreasing S but instead stagnates or even blue-shifts. Provided sufficient current density, a tunneling charge transfer plasmon (tCTP) can then also be detected at a significantly longer wavelength than the BDP.[7, 9, 10] The plasmon driven charge transfer between NPs in the quantum plasmonic regime is currently of high interest for developing new non-linear spectroscopies,[11] sensors,[12] and potentially catalysts.[13]