Ameer Fathima S, Ranasinghe Meenakshi, Varahagiri Shilpa, Benza Donald W, Hu Longyu, Willett Daniel R, Wen Yimei, Bhattacharya Sriparna, Chumanov George, Rao Apparao M, Anker Jeffrey N
Department of Chemistry, Clemson University, Clemson SC 29634, USA.
Department of Mechanical Engineering, Clemson University, Clemson SC 29634, USA.
Nano Sel. 2021 Dec;2(12):2407-2418. doi: 10.1002/nano.202000278. Epub 2021 May 12.
The optical and chemical properties of gold and silver nanoparticles make them useful for many applications, including surface enhanced spectroscopy-based biosensors, photostable colorants, enhanced photovoltaics, and nanoscale optical elements. We report a simple technique to generate patterns of gold and silver nanoparticles with controlled shape and shape-dependent optical properties using metal stamps to impress them onto a glass substrate or flexible polymers. The pressure flattens the nanoparticles, converting initially spherical nanoparticles into discs with reduced height and increased diameter. This deformation causes their localized surface plasmon resonance wavelength to red-shift. Nanoparticles were characterized by electron microscopy, atomic force microscopy, and dark field optical scattering spectroscopy. The deformed nanoparticle patterns had a lateral resolution limited by the nanoparticle diameter (single particles are partly flattened only where they contact the stamp). The method also (i) transfers the stamp's topography, with smooth stamps generating flattened nanoparticles with uniform height, and small changes in stamp height are evident in the nanoparticle height and scattering wavelength, and (ii) allows facile removal of undeformed nanoparticles using scotch tape, and patterns of deformed nanoparticles can be transferred to a thin polymer-film. The patterning process is simple and inexpensive. It can be performed by hand for demonstrations or artistic applications, with controlled force for plasmonics research, and potentially automated on reel-to-reel presses for large scale production.
金和银纳米颗粒的光学和化学性质使其在许多应用中都很有用，包括基于表面增强光谱的生物传感器、光稳定着色剂、增强型光伏电池以及纳米级光学元件。我们报告了一种简单的技术，利用金属印章将金和银纳米颗粒压印到玻璃基板或柔性聚合物上，从而生成具有可控形状和形状依赖光学性质的纳米颗粒图案。压力使纳米颗粒变平，将最初的球形纳米颗粒转变为高度降低、直径增加的圆盘状。这种变形导致其局部表面等离子体共振波长发生红移。通过电子显微镜、原子力显微镜和暗场光学散射光谱对纳米颗粒进行了表征。变形的纳米颗粒图案的横向分辨率受纳米颗粒直径的限制（单个颗粒仅在与印章接触的地方部分变平）。该方法还（i）转移印章的形貌，光滑的印章会产生高度均匀的扁平纳米颗粒，印章高度的微小变化在纳米颗粒高度和散射波长中很明显，并且（ii）允许使用透明胶带轻松去除未变形的纳米颗粒，变形纳米颗粒的图案可以转移到薄聚合物薄膜上。图案化过程简单且成本低廉。它可以手动进行演示或艺术应用，也可以在等离子体研究中施加可控力，并且有可能在卷对卷压机上实现自动化大规模生产。
