Shape-induced superstructure formation in concentrated ferrofluids under applied magnetic fields.

The field-induced ordering of concentrated ferrofluids based on spherical and cuboidal maghemite nanoparticles is studied using small-angle neutron scattering, revealing a qualitative effect of the faceted shape on the interparticle interactions as shown in the structure factor and correlation lengths. Whereas a spatially disordered hard-sphere interaction potential with a short correlation length is found for ∼9 nm spherical nanoparticles, nanocubes of a comparable particle size exhibit a more pronounced interparticle interaction and the formation of linear arrangements. Analysis of the anisotropic two-dimensional pair distance correlation function gives insight into the real-space arrangement of the nanoparticles.

Strong size selectivity in the self-assembly of rounded nanocubes into 3D mesocrystals.

The self-assembly of nanoparticles into highly ordered crystals is largely influenced by variations in the size and shape of the constituent particles, with crystallization generally not observed if their polydispersity is too large. Here, we report on size selectivity in the self-assembly of rounded cubic maghemite nanoparticles into three-dimensional mesocrystals. Different X-ray scattering techniques are used to study and compare a nanoparticle dispersion that is used later for self-assembly, an ensemble of mesocrystals grown on a substrate, as well as an individual mesocrystal.

MicroRNA Detection through DNAzyme-Mediated Disintegration of Magnetic Nanoparticle Assemblies.

DNA-assembled nanoparticle superstructures offer numerous bioresponsive properties that can be utilized for point-of-care diagnostics. Functional DNA sequences such as deoxyribozymes (DNAzymes) provide novel bioresponsive strategies and further extend the application of DNA-assembled nanoparticle superstructures. In this work, we describe a microRNA detection biosensor that combines magnetic nanoparticle (MNP) assemblies with DNAzyme-assisted target recycling.

Ferromagnetic Resonance Biosensor for Homogeneous and Volumetric Detection of DNA.

The ability to detect and analyze the state of magnetic labels with high sensitivity is of crucial importance for developing magnetic biosensors. In this work, we demonstrate, for the first time, a ferromagnetic resonance (FMR) based homogeneous and volumetric biosensor for magnetic label detection. Two different isothermal amplification methods, i.

Colossal Anisotropy of the Dynamic Magnetic Susceptibility in Low-Dimensional Nanocube Assemblies.

One of the ultimate goals of nanocrystal self-assembly is to transform nanoscale building blocks into a material that displays enhanced properties relative to the sum of its parts. Herein, we demonstrate that 1D needle-shaped assemblies composed of FeO nanocubes display a significant augmentation of the magnetic susceptibility and dissipation as compared to 0D and 2D systems. The performance of the nanocube needles is highlighted by a colossal anisotropy factor defined as the ratio of the parallel to the perpendicular magnetization components.