Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
ACS Nano. 2011 Jan 25;5(1):217-26. doi: 10.1021/nn102383s. Epub 2010 Dec 9.
Iron oxide cores of 35 nm are coated with gold nanoparticles so that individual particle motion can be tracked in real time through the plasmonic response using dark field optical microscopy. Although Brownian and viscous drag forces are pronounced for nanoparticles, we show that magnetic manipulation is possible using large magnetic field gradients. The trajectories are analyzed to separate contributions from the different types of forces. With field gradients up to 3000 T/m, forces as small as 1.5 fN are detected.
35nm 的氧化铁核被金纳米粒子包覆，这样就可以通过暗场光学显微镜利用等离子体激元响应实时跟踪单个粒子的运动。虽然纳米粒子的布朗运动和粘性阻力很显著，但我们表明，利用大的磁场梯度可以实现磁性操控。通过分析轨迹，可以分离出不同类型力的贡献。在高达 3000T/m 的磁场梯度下，可以检测到小至 1.5fN 的力。
