磁性纳米颗粒的二维光操纵及团聚效应

我们利用暗场显微镜系统地研究了水剂磁性液体中Fe3O4磁性纳米颗粒在高度聚焦激光作用下的动力学过程.实验研究表明:当激光聚焦在样品池中间时,由于受到沿激光入射方向强散射力和吸收力的作用,磁性纳米颗粒会被排开至光斑的外围;当激光聚焦在样品池上表面时,在光力和样品池上玻片的共同作用下,磁性纳米颗粒会被捕获在样品池的上玻片的下表面并发生团聚效应;此外,我们还研究了不同激光功率作用下形成的磁性纳米团簇对入射白光的透过谱的影响,随着入射激光功率的增加,透过磁性液体的白光的透过率会急剧下降,而且透射谱的中心波长会随着入射激光功率的增加往长波方向移动.

Two-dimensional optical trapping and clustering of magnetic nanoparticles

The dynamics of Fe3O4 magnetic nanoparticles under the irradiation of a tightly focused laser beam was investigated by using a dark-field microscope. It was found that the magnetic nanoparticles were pushed away from the laser spot by the optical scattering force and the absorption force when the laser focus was located between the two cover slips of the sample cell. A depletion region of magnetic nanoparticles was formed in the laser spot. However, when the focus of the laser was located at the bottom of the upper cover slip of the sample cell, the magnetic nanoparticles could be trapped by the optical forces combined with the opposite force of the upper cover slip and formed magnetic clusters. In addition, the evolution of the incandescent light transmission spectrum of the magnetic fluid under the irradiation of the 532 nm laser with different powers was studied. It was observed that the intensity of the transmission spectrum of the incandescent light decreased and the peak wavelength of the transmission spectrum shifted towards the longer wavelength with the increase of the laser power.