Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC, 27695, USA.
Leibniz-Institut für Polymerforschung Dresden e.V., Institute for Physical Chemistry and Polymer Physics, 01069, Dresden, Germany.
Adv Mater. 2022 Oct;34(40):e2203366. doi: 10.1002/adma.202203366. Epub 2022 Sep 1.
Plasmonic nanoparticles that can be manipulated with magnetic fields are of interest for advanced optical applications, diagnostics, imaging, and therapy. Alignment of gold nanorods yields strong polarization-dependent extinction, and use of magnetic fields is appealing because they act through space and can be quickly switched. In this work, cationic polyethyleneimine-functionalized superparamagnetic Fe O nanoparticles (NPs) are deposited on the surface of anionic gold nanorods coated with bovine serum albumin. The magnetic gold nanorods (MagGNRs) obtained through mixing maintain the distinct optical properties of plasmonic gold nanorods that are minimally perturbed by the magnetic overcoating. Magnetic alignment of the MagGNRs arising from magnetic dipolar interactions on the anisotropic gold nanorod core is comprehensively characterized, including structural characterization and enhancement (suppression) of the longitudinal surface plasmon resonance and suppression (enhancement) of the transverse surface plasmon resonance for light polarized parallel (orthogonal) to the magnetic field. The MagGNRs can also be driven in rotating magnetic fields to rotate at frequencies of at least 17 Hz. For suitably large gold nanorods (148 nm long) and Fe O NPs (13.4 nm diameter), significant alignment is possible even in modest (<500 Oe) magnetic fields. An analytical model provides a unified understanding of the magnetic alignment of MagGNRs.
可通过磁场操控的等离子体纳米粒子在先进的光学应用、诊断、成像和治疗方面具有重要意义。金纳米棒的取向产生强烈的偏振相关消光，而磁场的应用很有吸引力，因为它们通过空间作用，并且可以快速切换。在这项工作中，阳离子聚乙烯亚胺功能化的超顺磁性 Fe3O4纳米颗粒（NPs）沉积在涂有牛血清白蛋白的阴离子金纳米棒表面上。通过混合获得的磁性金纳米棒（MagGNRs）保持了等离子体金纳米棒的独特光学性质，这些性质受到磁性覆盖层的最小干扰。通过各向异性金纳米棒核的磁偶极相互作用引起的 MagGNRs 的磁性排列得到了全面表征，包括结构表征以及对平行（正交）于磁场的光的纵向表面等离子体共振的增强（抑制）和横向表面等离子体共振的抑制（增强）。MagGNRs 还可以在旋转磁场中以至少 17 Hz 的频率旋转。对于适当大的金纳米棒（148 nm 长）和 Fe3O4 NPs（13.4 nm 直径），即使在较小的磁场（<500 Oe）中也可以实现显著的取向。一个分析模型提供了对 MagGNRs 磁性排列的统一理解。
