Magnetic field-induced self-assembly of iron oxide nanocubes

Abstract

Self-assembly of inorganic nanoparticles has been studied extensively for particles having different sizes and compositions. However, relatively little attention has been devoted to how the shape and surface chemistry of magnetic nanoparticles affects their self-assembly properties. Here, we undertook a combined experiment-theory study aimed at better understanding of the self-assembly of cubic magnetite (Fe3O4) particles. We demonstrated that, depending on the experimental parameters, such as the direction of the magnetic field and nanoparticle density, a variety of superstructures can be obtained, including one-dimensional filaments and helices, as well as C-shaped assemblies described here for the first time. Furthermore, we functionalized the surfaces of the magnetic nanocubes with light-sensitive ligands. Using these modified nanoparticles, we were able to achieve orthogonal control of self-assembly using a magnetic field and light.

Nanoparticle Clusters: Assembly and Control Over Internal Order, Current Capabilities, and Future Potential

“…Secondly, arising from the inherent anisotropy of the NP-NP force field (even if only van der Waals interactions are present), new phenomena must be considered, e.g., torque and the absolute time scales of the particle reorientation vs particle lateral displacement (i.e., rotational vs translational diffusion). One illustrative example of the potential of anisotropic assemblies is a recent report by the Klajn group, [7,145] who noted that by preparing magnetic nanocubes, the favored particle orientations for the magnetic (corner to furthest corner) and van der Waals close packing (face to face) interactions differ. The frustration between these could then be controlled to determine the intermediate and long-range order in inter-facial assemblies.…”

“…The frustration between these could then be controlled to determine the intermediate and long-range order in inter-facial assemblies. In this way, belts or helices of cubes could be formed by controlling the external field (orientation and strength) and the cube-packing fraction [7,145] That example also raises the prospect of ordering NPCs into functional 2D or 3D arrays, which is a tremendously exciting possibility that we can only touch on here.…”

Irreversible Bleaching of Donor–Acceptor Stenhouse Adducts on the Surfaces of Magnetite Nanoparticles

“…In a relatively short time since the initial report on reversible photoswitching of DASAs, several creative applications have been reported . For example, Lee et al.…”

“…[4] In ar elativelys hort time since the initial report on reversible photoswitching of DASAs, [1] severalc reative applications have been reported. [5][6][7] For example, Lee et al showedt hat DASAfunctionalized polymers could be used as optical sensors for nerve gases, where the analytes bind to the amine function to form quaternary ammonium salts, thus inducing ad rastic color change (bleaching) of the sensor. [8] Importantly,t hese sensors could be reversibly activated by using light.…”

Highlights of the Faraday Discussion on Nanoparticle Synthesis and Assembly, Argonne, USA, April 2015

“…27 Compared to conventional electrochemical deposition of ions, nanoparticle deposition requires current more than an order of magnitude lower, and these low currents obviously serve to fabricate conductive junctions between the particles. 16 In these crystalline nanoparticles, there is an angle between the magnetic easy axis and the crystallographic axis. 17 (d) Reversible order-disorder transition in a bcc superlattice made of 1.67 nm octadecanethiol-ligated Au nanocrystals monitored by GISAXS.…”