Department of Chemical Engineering, Faculty of Engineering, Monash University, Clayton, Victoria 3800, Australia.
Nanotechnology. 2012 Mar 16;23(10):105602. doi: 10.1088/0957-4484/23/10/105602. Epub 2012 Feb 21.
Metallic nanoparticles that support surface plasmons are potential building units for future nanophotonic circuits, metamaterials, high-density optical data storage, etc. Many of these applications require the ability to 'dial-up' the desired plasmonic resonance modes and frequencies with high precision. Here, we demonstrate a thermal reshaping route that can be used to tailor longitudinal plasmon resonance energies of gold nanorods almost continuously from ~800 to ~560 nm. The longitudinal plasmon resonance wavelength exhibits an exponential decay function of the thermal annealing time at a given temperature. This correlates with the transmission electron microscopy characterization (TEM) which showed that the nanorod aspect ratio decreases exponentially with time, accompanying a gradual shape transformation from rod to sphere. The exponential decay half-time decreases with increasing annealing temperatures, with a value of 1.43 × 10(5) s at 50 °C down to 0.02 × 10(5) s at 100 °C. Our experimental results show that the shape transformation could be attributed to desorption of silver ions and side facet-binding Ag-Br-CTA ligands, which therefore promote the side growth leading to nanorod fattening. Compared to other synthetic methodologies to tune plasmonics, our thermal reshaping approach presents a straightforward paradigm for precisely tailoring plasmon resonance energy with a single parameter.
支持表面等离激元的金属纳米粒子是未来纳米光子电路、超材料、高密度光数据存储等的潜在构建单元。许多这些应用都需要能够以高精度“调整”所需的等离子体共振模式和频率的能力。在这里，我们展示了一种热整形方法，可以连续将金纳米棒的纵向等离子体共振能量从800nm 调谐到560nm。在给定温度下，纵向等离子体共振波长与热退火时间呈指数衰减关系。这与透射电子显微镜表征（TEM）相吻合，TEM 显示纳米棒的纵横比随时间呈指数下降，伴随着从棒状到球状的逐渐形状转变。指数衰减半衰期随退火温度的升高而降低，在 50°C 时为 1.43×10^5s，在 100°C 时降至 0.02×10^5s。我们的实验结果表明，形状转变可归因于银离子的解吸和侧面结合的 Ag-Br-CTA 配体，这促进了导致纳米棒变粗的侧面生长。与其他用于调整等离子体的合成方法相比，我们的热整形方法提供了一种通过单一参数精确调整等离子体共振能量的简单范例。
