Brzobohatý Oto, Šiler Martin, Trojek Jan, Chvátal Lukáš, Karásek Vítězslav, Paták Aleš, Pokorná Zuzana, Mika Filip, Zemánek Pavel
ASCR, Institute of Scientific Instruments, Královopolská 147, 612 64 Brno, Czech Republic.
Sci Rep. 2015 Jan 29;5:8106. doi: 10.1038/srep08106.
It was previously believed that larger metal nanoparticles behave as tiny mirrors that are pushed by the light beam radiative force along the direction of beam propagation, without a chance to be confined. However, several groups have recently reported successful optical trapping of gold and silver particles as large as 250 nm. We offer a possible explanation based on the fact that metal nanoparticles naturally occur in various non-spherical shapes and their optical properties differ significantly due to changes in localized plasmon excitation. We demonstrate experimentally and support theoretically three-dimensional confinement of large gold nanoparticles in an optical trap based on very low numerical aperture optics. We showed theoretically that the unique properties of gold nanoprisms allow an increase of trapping force by an order of magnitude at certain aspect ratios. These results pave the way to spatial manipulation of plasmonic nanoparticles using an optical fibre, with interesting applications in biology and medicine.
以前人们认为，较大的金属纳米颗粒就像微小的镜子，会被光束的辐射力沿着光束传播方向推动，没有被限制的机会。然而，最近有几个研究小组报告成功地实现了对直径达250纳米的金和银颗粒的光学捕获。我们基于金属纳米颗粒天然存在各种非球形形状这一事实提供了一种可能的解释，并且由于局域等离子体激元激发的变化，它们的光学性质有显著差异。我们通过实验证明并从理论上支持了基于非常低数值孔径光学器件在光学阱中对大金纳米颗粒的三维限制。我们从理论上表明，金纳米棱柱的独特性质在某些长宽比下可使捕获力提高一个数量级。这些结果为使用光纤对等离子体纳米颗粒进行空间操纵铺平了道路，在生物学和医学中有有趣的应用。
