Synthesis and second-harmonic generation studies of noncentrosymmetric gold nanostructures
Synthesis and second-harmonic generation studies of noncentrosymmetric gold nanostructures
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DOI：
10.1021/jp9845874
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发表时间：
1999-04-08
影响因子：
3.3
通讯作者：
Foss, CA
中科院分区：
文献类型：
--
作者：
Sandrock, ML;Pibel, CD;Foss, CA
采用改进的模板合成法在多孔阳极氧化铝薄膜中制备了非中心对称的金纳米颗粒结构。非中心对称结构由在单个主体氧化物孔内非常接近(约22+/-8 nm)的两个金粒子定义，其中一个的平均尺寸为a=37+/-6 nm和b=26+/-3，另一个的尺寸为a=27+/-5 nm和b=26+/-3 nm，其中a为轴向长度，b为准圆柱形结构的直径。金颗粒/多孔氧化铝薄膜复合材料的线UV/Vis偏振光谱显示出等离子体共振带，其入射角度与含有中心对称的金结构的复合材料相似，其中入射角是相对于表面法线定义的。入射波长为780 nm的二次谐波研究表明，含中心对称和非中心对称金纳米结构的复合材料在S偏振下的二次谐波强度较低，且与入射角无关。然而，在p-极化中，两种复合材料的倍频计数都随着theta的增加而增加，非中心对称结构显示出比中心对称结构更高的倍频信号。这些结果与长粒子轴偶极等离子体共振引起的局域场增强是一致的。
Noncentrosymmetric gold nanoparticle structures were prepared in porous anodic aluminum oxide films via a modified template synthesis procedure. The noncentrosymmetric structures are defined by two gold particles in close proximity (ca. 22 +/- 8 nm end to end) within a single host oxide pore, one having average dimensions of a = 37 +/- 6 nm and b = 26 +/- 3, and the other having dimensions of a = 27 +/- 5 nm and b = 26 +/- 3 nm, where a is the axial length and b is the diameter of the quasi-cylindrical structures. Linear UV/vis polarization spectra of the gold particle/porous alumina film composites show plasmon resonance bands whose a incidence angle dependence is similar to composites containing centrosymmetric gold structures, where the incidence angle is defined with respect to the surface normal. Second harmonic generation (SHG) studies using an incident wavelength of 780 nm indicate that SHG intensities under s-polarization are low and independent of incidence angle (theta) for composites containing centrosymmetric and noncentrosymmetric gold nanostructures. However, in p-polarization, both composites show an increase in SHG counts with theta, with the noncentrosymmetric structures showing a higher SHG signal than their centrosymmetric counterparts. These results are consistent with local-field enhancements arising from long particle axis dipolar plasmon resonances.