Sensitivity of metal nanoparticle surface plasmon resonance to the dielectric environment
Sensitivity of metal nanoparticle surface plasmon resonance to the dielectric environment
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DOI：
10.1021/jp054227y
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发表时间：
2005-11-24
影响因子：
3.3
通讯作者：
Lazarides, AA
中科院分区：
文献类型：
--
作者：
Miller, MM;Lazarides, AA
金纳米颗粒光谱的电动力学模拟用于研究各种形状的纳米颗粒和各种结构的纳米壳的局域表面等离子体激元带位置对介质折射率 n 的敏感性。在尺寸小于130 nm的单电子组分纳米粒子中，偶极共振位置对体折射率的敏感性仅取决于共振波长以及金属和介质的介电性质。在金属介电函数的实部随波长线性变化且虚部较小且缓慢变化的频率范围内达到峰值的粒子等离子体激元中，峰值波长 lambda* 对折射率 n 的敏感性被发现是 lambda* 的线性递增函数，无论决定 lambda* 的粒子的结构特征如何。准静态理论用于推导小颗粒等离子体峰的折射率灵敏度的解析表达式。通过该分析，发现灵敏度对能带位置的依赖性是由粒子介电函数的实部 epsilon' 的波长依赖性决定的，并且发现灵敏度结果扩展到具有 epsilon'* = -2 chi n(2,) 形式的共振条件的所有粒子，其中 chi 是几何参数和其他常数的函数。因此，使用精确的计算方法对金纳米盘、纳米棒和空心纳米壳的偶极等离子体激元带观察到的灵敏度结果可以扩展到由其他金属组成的其他形状（例如六角形和切碎四面体）的颗粒以及高阶模式。该理论产生的体折射率灵敏度充当介电基底上的纳米粒子的灵敏度的上限以及纳米粒子对局部折射率变化（例如与生物分子传感相关的那些变化）的灵敏度。
Electrodynamic simulations of gold nanoparticle spectra were used to investigate the sensitivity of localized surface plasmon band position to the refractive index, n, of the medium for nanoparticles of various shapes and nanoshells of various structures. Among sing] e-component nanoparticles less than 130 nm in size, sensitivities of dipole resonance positions to bulk refractive index are found to depend only upon the wavelength of the resonance and the dielectric properties of the metal and the medium. Among particle plasmons that peak in the frequency range where the real part of the metal dielectric function varies linearly with wavelength and the imaginary part is small and slowly varying, the sensitivity of the peak wavelength, lambda*, to refractive index, n, is found to be a linearly increasing function of lambda*, regardless of the structural features of the particle that determine lambda*. Quasistatic theory is used to derive an analytical expression for the refractive index sensitivity of small particle plasmon peaks. Through this analysis, the dependence of sensitivity on band position is found to be determined by the wavelength dependence of the real part, epsilon', of the particle dielectric function, and the sensitivity results are found to extend to all particles with resonance conditions of the form, epsilon'* = -2 chi n(2,) where chi is a function of geometric parameters and other constants. The sensitivity results observed using accurate computational methods for dipolar plasmon bands of gold nanodisks, nanorods, and hollow nanoshells extend, therefore, to particles of other shapes (such as hexagonal and chopped tetrahedral), composed of other metals, and to higher-order modes. The bulk refractive index sensitivity yielded by the theory serves as an upper bound to sensitivities of nanoparticles on dielectric substrates and sensitivities of nanoparticles to local refractive index changes, such as those associated with biomolecule sensing.