Assembly and Manipulation of Fe₃O₄/Coumarin Bifunctionalized Submicrometer Janus Particles

Abstract

Magnetic and fluorescent bifunctionalized Janus particles were fabricated via sequential particle embedding and surface modifications. The two hemispherical surfaces of a 500 nm silica particle were separately functionalized with Fe3O4 nanoparticles and coumarin dye molecules. The Fe3O4 hemisphere exhibited magnetically driven particle orientation and alignment, whereas the coumarin hemisphere served as an anisotropic emission indicator. The photoluminescence of these orientated and solidified Janus particles revealed anisotropic emission contrast as high as 40% between the magnet-aspect and the dye-aspect excitations. The dynamic anisotropic emission of the bifunctionalized Janus suspension under magnetic manipulation also revealed a nonsynchronized bulk correlation time that was much slower than that of an individual 500 nm particle. Under a static magnetic field, the suspended Janus particles assembled into a grape-like bunch, with random particle orientation. Unlike their microscale counterparts, the submicrometer magnetic Janus particles were less sensitive to gravity and more vulnerable to particle-particle interactions.

Forecastable and Guidable Bubble‐Propelled Microplate Motors for Cell Transport

“…The possibility of microplate motor guidance with magnetic particles is in line with recent works of others, reporting guided capsules, magnetically driven artificial bacteria flagella, Janus particles, pots, tubes, cell propulsion systems, as well as composite layered thin films . The cell–microplate agglomerates are not only able to be guided; they are also able to collide with a second cell.…”

A Simple and Scalable Route to Synthesize CoxCu1−xCo2O4@CoyCu1−yCo2O4 Yolk–Shell Microspheres, A High‐Performance Catalyst to Hydrolyze Ammonia Borane for Hydrogen Production

“…[6,7] In the field of heterogeneous catalysis, the superior performance of the catalysts with yolk-shell structures is believed to be highly associated with the freely movable core catalysts, and the hollow space between the core and shell, which provides a good environment for the catalytic reaction. [8] Various methods have been developed to prepare yolk-shell structured materials, including selective etching or dissolution, Ostwald ripening, the ship-in-bottle method, soft template assembly, galvanic replacement and the Kirkendall diffusion. [9][10][11] However, many steps are involved in most of these methods, which make them timeconsuming, tedious, and/or costly.…”

Hydrogel‐Based Janus Micromotors Capped with Functional Nanoparticles for Environmental Applications

“…In the field of nano/micromotors, the catalytic ability of Fe 3 O 4 NPs in H 2 O 2 is usually not utilized but the magnetic feature of Fe 3 O 4 NPs is the most common applied one. [ 37,81 ] With the application of a small magnetic field (strength ≈3 mT), Fe 3 O 4 Janus microspheres are oriented and their trajectories show a directionally deterministic motion (Figure 5b). By manipulating the orientation of a bar magnet, we can obtain complex trajectories and even write characters as demonstrated in Figure 5b where “F,” “D,” and “U” are written.…”